Photo-curable resin composition for 3D printing

The present invention relates to photo-curable resin compositions for 3D printing comprising at least one ethylenically unsaturated, polymerizable compound and at least one photoinitiator system, comprising at least one photoinitiator G and at least one photosensitizer PS, selected from benzophenones, xanthones, thioxanthones and acridones. The invention moreover relates to a method for producing a three dimensional object by means of stereolithography or material jetting, using the photocurable resin composition and to the use of the

photocurable resin compositions for producing a three dimensional object by means of stereolithography or material jetting.

Stereolithography describes a method for 3D printing wherein a photocurable liquid is selectively coated into a thin layer upon a surface and exposed selectively and imagewise to actinic radiation, wherein the exposed liquid is cured to form a thin cured layer. Subsequently, new layers of the liquid photocurable resin are coated onto the previous, cured layer and exposed to radiation until a three dimensional object is formed. With the help of e.g. computer aided manufacturing or computer-aided design (CAM/CAD) software the light beam is used to draw a pre-programmed design or shape in the photocurable liquid.

Methods for preparing three-dimensional objects by means of stereolithography are e.g. described in WO 2016/071811 , EP-A 1 939 234 and WO 2007/031505.

Material jetting describes a method for 3D printing wherein fine droplets of a photocurable liquid are discharged from nozzles onto a base plate in a specified drawn pattern with the help of e.g. computer aided manufacturing or computer- aided design (CAM/CAD) software, followed by light irradiation to effect curing. Then, further fine droplets of the liquid photocurable resin are discharged thereon from the nozzles in a specified drawn pattern, producing a superimposed layer, followed again by light irradiation. The repetition of this operation finally leads to a fabricated 3D object. Methods for preparing three-dimensional objects by means of material jetting are e.g. described in WO 00/52624, JP-A 2002-067174 and JP-A 2010-155926.

The photocurable liquid typically contains one or more polymerizable compounds, and one or more photoinitiator compounds. Such photocurable resin compositions, comprising photoinitiators have been widely used for example as UV-curable inks, in coating materials, photoresists or for the production of three-dimensional objects. The use of phenylglyoxylates and derivatives thereof in photocurable resin compositions is also known.

US 2005/0228062 relates to photopolymerizable compositions comprising at least one ethylenically unsaturated photopolymerizable compound and as a

photoinitiator phenyl glyoxylate compounds of the general formula (I)

wherein

Y is for example C3-Ci2alkylenen, or C4-Ci2alkylene interrupted by one or more

-O- or NR2-, or

Y is a cyclic compound, for example phenylene or cyclohexylene; and

R1 is for example reactive group, for example OH, SH, -C(0)-0H, -C(0)-NH2, oroxiranyl.

US 2005/0228062 does not define the wavelength usable for curing purposes in detail. Further, the composition taught in US 2005/0228062 is still improvable with respect to curing efficancy. The photo-polymerizable compositions are irradiated with light with a wavelength in the range from 200 to 600 nm, for example with medium pressure mercury lamps. WO 2008/040650 describes UV-curable colored compositions comprising at least one ethylenically unsaturated photopolymerizable compound, at least one colorant and at least one curing agent of the phenylglyoxylate type. The composition taught in WO 2008/040650 is still improvable with respect to curing efficancy.

Furthermore, WO 2008/040650 does not define the wavelength usable for curing purposes in detail and the specific examples are focused on the use of

wavelengths clearly below 350 nm.

US 6,048,660 relates to photoinitiator compounds of the general formula (I)

wherein

Ri and R2 are for example a substituted or unsubstituted phenyl radical, and Y is for example a group

and to photocurable compositions comprising at least one ethylenically

unsaturated photopolymerizable compound, the photoinitiator and optionally a further photoinitiator. As a further photoinitiator, bis(2,4,6-trimethylbenzoyl)phenyl- phosphin oxide (Irgacure ^® 819) is used. However, known photoinitiators such as compounds of the phenylglyoxylate type are in general not able to absorb in the region between 375 to 450 nm and therefore cannot make full use of the advantages associated with the use of UV or blue emitting Light Emitting Diodes (LEDs) and Laser Diodes (LDs), especially of blue emitting LEDs and blue LDs, such as safe application, high cost efficiency, and easy handling. The composition taught in US 6,048,660 is still improvable with respect to curing efficancy.

Furthermore, US 6,048,660 does not define the wavelength usable for curing purposes in detail and the specific examples are focused on the use of medium pressure mercury lamps with light of wavelength in the range from 200 to 600 nm. WO 2014/060450 teaches hybrid photoinitiator compound of formula (I)

and the further residues are broadly defined. Further, WO 2014/060450 teaches the use of such hybrid photoinitiator compound forcuring purposes in a unspecific wavelength range including short wavelenghths below 350 nm. The composition taught in WO 2014/060450 is still improvable with respect to curing efficancy. WO 2018/119067 teaches ceramic dispersions that may include photoinitiators and oxetanes which are preferably, polyfluorated or sulfur-containing compounds. WO 2010/104603 teaches curable resins comprising variety of components. A broad variety of light sources are taught herein. The compositions taught in these documents are still improvable with respect to curing efficancy.

Thioxanthone-based compounds and acyl phosphine oxides instead are able to absorb in this spectral region. However, as for example described in

WO 2011/069947 those compounds are prone to yellowing upon exposure with light in said wavelength.

WO 2011/069947 describes carbazole based photoinitiator compounds of the general formula (I), wherein

at least one of R1 , R2 and R3 comprises a branched substituted or unsubstituted alkyl, alkenyl, alkynyl, aralkyl or alkaryl group.

It was one objective of the present invention to provide photocurable resin compositions which have an increased sensitivity towards UV, blue emitting LEDs and blue LDs and which do not comprise the disadvantages described, in particular an undesired yellowing behavior, of known photocurable resin

compositions.

It was further of interest to provide a photocurable resin composition for 3D printing which is curable at longer wavelength ranges, of preferably above 300 nm, preferably above 350 nm; in particular between 375 nm and 450 nm. The use of such wavelength ranges close to or within the deep blue range may allow the use of a broader range of light sources and may decrease undesired side reactions and bleaching. Further, it may ease handling with the irradiation as the irradiation is less dangerous for users. Surprisingly, it was found that a composition comprising an ethylenically

unsaturated compound and a photoinitiator system containing a photoinitiator and a photosensitizer as described herein provides high curing activity even at longer wavelength ranges above 350 nm. This object is solved by a photocurable resin composition for 3D printing, comprising:

a) at least one ethylenically unsaturated photopolymerizable compound, b) at least one photoinitiator system comprising,

b1 ) at least one at least one photoinitiator G, wherein the at least one

photoinitiator G is at least one photoinitiator G-1A of the general formula (la)

wherein

Z is R ¹ or R ⁷ ;

X is O, S, or NR ⁵ ;

Ch ¹ is Ar ¹ or Het ¹ ;

n is 1 to 4;

with the proviso that when n is 1 , Z is R ¹ ;

Ar ¹ is selected from the group consisting of phenyl, naphthyl, biphenyl, styryl, stilbenyl, diphenylacetylenyl, terphenylyl, anthracenyl, phenanthrenyl, pyrenyl or triphenylenyl; which is unsubstituted or substituted with one or more substituents selected from the group consisting of halogen; NO2; CN; OR ³ ; SR ⁴ ; NR ⁵ R ⁶ ; Ci-C2oalkyl and/or C2-C2oalkenyl, which are independently from each other unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Ci-C2oalkyl and/or

C2-C2oalkenyl, which are independently from each other

interrupted by one or more -0-, -S- , -NR ⁵ -, phenylene and/or naphthylene; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which are independently from each unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which are independently from each other interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl and/or naphthyl, which are independently from each other unsubstituted or substituted by one or more halogen, CN,

Ci-C2oalkyl, Cs-Cscycloalkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ; and/or

OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents, if present on adjacent ring atoms on Ar ¹ via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles; and/or

R ⁵ and R ⁶ form together with the N atom to which they are attached a 5- or 6-membered heterocycle;

Het ¹ is selected from the group consisting of furyl, thienyl, pyrrolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazole, imidazolyl, pyrazolyl, oxadiazolyl, thiadiazolyl, triazolyl, pyridyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazinyl, 2- or 3-benzofuryl, 2- or 3-benzothienyl, 2- or 3-indolyl, 2-benzoxazolyl, 2-benzothiazolyl, 2-benzoimidazolyl, 3-indazolyl, 2-, 3- or 4-quinolyl, 1-, 3- or 4-isoquinolyl,

3-phthalazinyl, 2- or 3-quinoxalinyl, pteridinyl, bithienyl, trithienyl, acridinyl, phenazinyl or purinyl; which is unsubstituted or substituted with one or more substituents selected from the group consisting of halogen, NO2, CN, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-C2oalkyl and/or C2-C2oalkenyl, which are independently from each other unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Ci-C2oalkyl and/or C2-C2oalkenyl, each of which is interrupted by one or more -0-,

-S- , -NR ⁵ -, phenylene and/or naphthylene; Cs-Cscycloalkyl and/or C3-C8cycloalkenyl, which are independently from each other unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, each of which is interrupted by one or more -0-, -S- and/or -NR ⁵ -;

phenyl and/or naphthyl, which are independently from each other unsubstituted or substituted by one or more halogen, CN, Ci-C2oalkyl, Cs-Cscycloalkyl, OR ³ , SR ⁴ NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ; and/or

OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents, if present on adjacent ring atoms on Het ¹ via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles; R ¹ is hydrogen; Ci-C2oalkyl or C2-C2oalkenyl, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Ci-C2oalkyl or C2-C2oalkenyl, which is interrupted by one or more -0-, -S-, -NRs-, phenylene and/or naphthylene; Cs-Cscycloalkyl or Cs-Cscycloalkeny, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Cs-Cscycloalkyl or

C3-C8cycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl or naphthyl, which is unsubstituted or substituted by one or more halogen, CN, Ci-C2oalkyl, OR ³ , SR ⁴ , NR ⁵ R ⁶ and/or -C(0)R ⁸ ;

R ³ is hydrogen; Ci-C2oalkyl or C2-C2oalkenyl, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Ci-C2oalkyl or C2-C2oalkenyl, which is interrupted by one or more -0-, -S-, -NRs-, phenylene and/or naphthylene; Cs-Cscycloalkyl or Cs-Cscycloalkenyl, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Cs-Cscycloalkyl or

Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl or naphthyl, which is unsubstituted or substituted by one or more by halogen, CN, Ci-C2oalkyl, OR ³ , SR ⁴ , NR ⁵ R ⁶ and/or -C(0)R ⁸ ;

R ⁴ is hydrogen; Ci-C2oalkyl or C2-C2oalkenyl, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Ci-C2oalkyl or C2-C2oalkenyl, which is interrupted by one or more -0-, -S-, -NR ⁵ -, phenylene and/or naphthylene; Cs-Cscycloalkyl or Cs-Cscycloalkenyl, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Cs-Cscycloalkyl or

Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl or naphthyl, which is unsubstituted or substituted by one or more by halogen, CN, Ci-C2oalkyl, OR ³ , SR ⁴ ,NR ⁵ R ⁶ and/or -C(0)R ⁸ ; R ⁵ , R ⁶ are independently of each other hydrogen; Ci-C2oalkyl or

C2-C2oalkenyl, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Ci-C2oalkyl or C2-C2oalkenyl, which is interrupted by one or more -0-, -S-, -NR ⁵ -, phenylene and/or naphthylene; Cs-Cscycloalkyl or C3-C8cycloalkenyl, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Cs-Cscycloalkyl or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl or naphthyl, which is unsubstituted or substituted by one or more by halogen, CN, Ci-C2oalkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ;

R ⁷ is Ci-C2oalkylene or Ci-C2oalkenylene, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-C2oalkylene or Ci-C2oalkenylene, which is interrupted by one or more -0-, -S-, -NR ⁵ -, phenylene and/or naphthylene;

C3-C8cycloalkylene or Cs-Cscycloalkenylene, which is

unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Cs-Cscycloalkylene or Cs-Cscycloalkenylene, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenylene or naphthylene, which is unsubstituted or substituted by one or more by halogen, Ci-C2oalkyl, OR ³ , SR ⁴ ,NR ⁵ R ⁶ and/or -C(0)R ⁸ ;

Re is OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-C2oalkyl or C2-C2oalkenyl, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Ci-C2oalkyl or C2-C2oalkenyl, which is interrupted by one or more -0-, -S-, -NR ⁵ -, phenylene and/or naphthylene; Cs-Cscycloalkyl or Cs-Cscycloalkeny, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Cs-Cscycloalkyl or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NRs-; phenyl, naphthyl, furanyl, thienyl, pyrroryl, benzofuranyl, benzothienyl, indoryl and/or benzoimidazoyl, which is unsubstituted or substituted by one or more halogen, CN,

Ci-C2oalkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ;

and/or

OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles;

and/or

R ⁵ and R ⁶ form together with the N atom to which they are attached a 5- or 6-membered heterocycle;

and/or

at least one photoinitiator G-1 B of the general formula (lb)

wherein

R ³ , R ⁴ , R ⁵ , R ⁶ , and R ⁸ have the meanings as defined above; and

m is 2 to 4;

Ch ² is Ar ² , Het ² or a group of the general formula B

wherein

each D is independently from each other Ci-C2oalkyl, which is

unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl or Ci-C2oalkyl or

C2-C2oalkenyl, which is interrupted by one or more -0-, -S-, -NR ⁵ -, phenylene and/or naphthylene;

p is 1 to 5;

Y is O, S or NR ⁵ ; R ² is hydrogen; Ci-C2oalkyl or C2-C2oalkenyl, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Ci-C2oalkyl or C2-C2oalkenyl, which is interrupted by one or more -0-, -S-, -NR ⁵ -, phenylene and/or naphthylene; Cs-Cscycloalkyl or Cs-Cscycloalkeny, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Cs-Cscycloalkyl or C3-C8cycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl or naphthyl, which is unsubstituted or substituted by one or more by halogen, CN, Ci-C2oalkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ;

Ar ² is phenylene, naphthylene, biphenylene, styrylene, stilbenylene, diphenylacetylenylene, terphenylene, anthracenylene,

phenanthrenylene, pyrenylene, triphenylene, diphenylmethylene, triphenylmethylene, tetraphenylmethylene or a group of the general formula (A)

wherein

V and W are independently from each other a direct bond, O, S or NR ⁵ ;

o is O or l ;

each of which is unsubstituted or substituted by one or more substituents selected from the group consisting of halogen, NO2, CN, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-C ₂ oalkyl and/or C ₂ -C2oalkenyl, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Ci-C2oalkyl and/or C2-C2oalkenyl, which is interrupted by one or more -0-, -S- , -NR ⁵ -, phenylene and/or naphthylene; Cs-Cscycloalkyl and/or

C3-C8cycloalkenyl, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl and/or naphthyl, which is unsubstituted or substituted by one or more halogen, CN, Ci-C2oalkyl,

Cs-Cscycloalkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ; and/or

OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents, if present at adjacent ring atoms on Ar ² via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles;

Het ² is furylene, thienylene, pyrrolylene, oxazolylene, isoxazolylene, thiazolylene, isothiazolylene, imidazolylene, pyrazolylene, oxadiazolylene, thiadiazolylene, triazolylene, pyridylene, pyrimidinylene, pyrazinylene, pyridazinylene, triazinylene, benzofurylene, benzothienylene, indolylene, benzoxazolylene, benzothiazolylene, benzoimidazolylene, indazolylen, quinolylene, isoquinolylene, phthalazinylene, quinoxalinylene, pteridinylene, bithienylene, trithienylene, acridinylene, phenazinylene, N,N-diphenylanilin or purinylene; each of which is unsubstituted or substituted by one or more halogen, NO2, CN, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-C2oalkyl and/or C2-C2oalkenyl, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Ci-C2oalkyl and/or C2-C2oalkenyl, which is interrupted by one or more -0-, -S- , -NR ⁵ -, phenylene and/or naphthylene; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which is unsubstituted or substituted by one or more halogen, CN, OR ³ ,

SR ⁴ and/or NR ⁵ R ⁶ ; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl and/or naphthyl, which is unsubstituted or substituted by one or more halogen, CN, Ci-C2oalkyl, Cs-Cscycloalkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ;

and/or

OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents if present at adjacent ring atoms on Het ² via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles; b2) at least one photosensitizer PS selected from the group consisting of benzophenone-based, xanthone-based, thioxanthone-based and acridone- based compounds.

Surprisingly, it has been found that the photocurable compositions according to the invention have good curing properties, especially at a wavelength from 375 to 450 nm (or a more specific wavelength as taught herein such as, e.g., from 375 to 440 nm, from 380 to 430 nm, from 390 to 420 nm, or from 400 to 410 nm). It has also been found that the compositions have an improved yellowing behavior.

In a preferred embodiment, the photopolymerizable composition is curable (and thus preferably irradiated with) light of a wavelength in the range from 300 to 500 nm, from 350 to 450 nm, from 360 to 410 nm, or from 375 to 450 nm. In a preferred embodiment, the photopolymerizable composition is curable (and thus preferably irradiated with) light of a wavelength in the range from 365 to 405 nm. In a preferred embodiment, the photopolymerizable composition is curable (and thus preferably irradiated with) light of a wavelength in the range from 360 to 380 nm, from 370 to 390 nm, from 380 to 400 nm, from 390 to 410 nm, from 375 to

440 nm, from 380 to 430 nm, from 390 to 420 nm, or from 400 to 410 nm. In a preferred embodiment, the photopolymerizable composition is curable (and thus preferably irradiated with) light of a wavelength of (approximately) 365 nm, (approximately) 385 nm, or (approximately) 405 nm.

In a preferred embodiment, at least 90% of the irradiation intensity (e.g, measurable in millijoule (mJ)) refers to light of a wavelengths of above 300 nm or above 350 nm. In other words, in a preferred embodiment, not more than 10% of the irradiation intensity (e.g., in mJ) result from light of a wavelengths of below 300 nm or of below 350 nm, in particular of below 375 nm. In a preferred embodiment, the photopolymerizable composition is (essentially) not irradiated with light of a wavelength of below 300 nm, below 350 nm, or below 360 nm. Detailed description of the invention

The residues and indices mentioned in the specification of the present application generally have the following preferred meanings, if said residues and indices are not further specified in the specific embodiments mentioned below:

Halogen is fluorine, chlorine, bromine or iodine, preferably fluorine or bromine.

The term“Ci-C2oalkyl” describes saturated linear or, where possible, branched hydrocarbon radicals having 1 to 20, preferably 1 to 12 carbon atoms

(“Ci-Ci2alkyl”). Examples are methyl, ethyl, n-propyl, isopropyl, n-butyl, sec. -butyl, isobutyl, tert. -butyl, n-pentyl, 2-pentyl, 3-pentyl, 2,2-dimethylpropyl,

1.1.3.3-tetramethylpentyl, n-hexyl, 1 -methylhexyl, 1 ,1 ,3,3,5,5-hexamethylhexyl, n-heptyl, isoheptyl, 1 ,1 ,3,3-tetramethylbutyl, 1 -methylheptyl, 3-methylheptyl, n-octyl, 1 ,1 ,3,3-tetramethylbutyl and 2-ethylhexyl, n-nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, or octadecyl. Ci-Ci2alkyl is typically methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, 2-pentyl, 3-pentyl, 2,2-dimethyl-propyl, n-hexyl, n-heptyl, n-octyl,

1.1.3.3-tetramethylbutyl and 2-ethylhexyl.

The term "C2-C2oalkenyl" as used herein relates to monounsaturated straight-chain or branched hydrocarbon radical having 2 to 20, preferably 2 to 12 carbon atoms ("C2-Ci2alkenyl"), and a double bond in any position. Examples are ethenyl, propenyl, isopropenyl ethenyl, 1 -propenyl, 2-propenyl, 1 -methylethenyl, 1 butenyl, 2-butenyl, 3-butenyl, 1 -methyl-1 -propenyl, 2-methyl-1 -propenyl, 1 -methyl-2- propenyl or 2-methyl-2-propenyl; C2-C6-alkenyl, such as ethenyl, 1 -propenyl, 2-propenyl, 1 -methylethenyl, 1 butenyl, 2-butenyl, 3-butenyl, 1 -methyl-1 -propenyl, 2-methyl-1 -propenyl, 1 -methyl-2-propenyl, 2-methyl-2-propenyl, 1 -pentenyl,

2-pentenyl, 3-pentenyl, 4-pentenyl, 1 methyl-1 -butenyl, 2 methyl 1 butenyl,

3-methyl-1 -butenyl, 1 -methyl-2-butenyl, 2 methyl-2-butenyl, 3 methyl-2-butenyl, 1-methyl-3-butenyl, 2-methyl-3-butenyl, 3 methyl-3-butenyl, 1 ,1 dimethyl-2- propenyl, 1 ,2-dimethyl-1 -propenyl, 1 ,2-dimethyl-2-propenyl, 1 ethyl 1 -propenyl, 1-ethyl-2-propenyl, 1 -hexenyl, 2-hexenyl, 3-hexenyl, 4 hexenyl, 5 hexenyl, 1 -methyl-1 -pentenyl, 2-methyl-1 -pentenyl, 3-methyl-1 -pentenyl, 4 methyl

1 pentenyl, 1 -methyl-2-pentenyl, 2-methyl-2-pentenyl, 3-methyl-2-pentenyl,

4 methyl-2-pentenyl, 1 -methyl-3-pentenyl, 2-methyl-3-pentenyl, 3-methyl-3- pentenyl, 4 methyl-3-pentenyl, 1 -methyl-4-pentenyl, 2-methyl-4-pentenyl,

3-methyl-4-pentenyl, 4 methyl-4-pentenyl, 1 ,1 -dimethyl-2-butenyl, 1 ,1 -dimethyl-3- butenyl, 1 ,2 dimethyl 1 butenyl, 1 ,2-dimethyl-2-butenyl, 1 ,2-dimethyl-3-butenyl,

1 ,3 dimethyl 1 -butenyl, 1 ,3 dimethyl-2-butenyl, 1 ,3-dimethyl-3-butenyl, 2,2 dimethyl 3-butenyl, 2,3 dimethyl-1 -butenyl, 2,3-dimethyl-2-butenyl, 2,3 dimethyl 3-butenyl,

3, 3-dimethyl-1 -butenyl, 3,3-dimethyl-2-butenyl, 1 ethyl 1 butenyl, 1-ethyl-2-butenyl, 1-ethyl-3-butenyl, 2-ethyl-1 -butenyl, 2 ethyl 2 butenyl, 2-ethyl-3-butenyl,

1 ,1 ,2-trimethyl-2-propenyl, 1 ethyl 1 methyl 2 propenyl, 1 -ethyl-2-methyl-1 - propenyl, 1 -ethyl-2-methyl-2-propenyl and the like, or C2-C8-alkenyl, such as the radicals mentioned for C2-C6-alkenyl and additionally 1 -heptenyl, 2-heptenyl, 3-heptenyl, 1 -octenyl, 2-octenyl, 3-octenyl, 4-octenyl and the positional isomers thereof.

The term "Cs-Cscycloalkyl" as used herein describes mono- or bicyclic

cycloaliphatic radicals having from 3 to 8 carbon atoms, preferably 5 or 6 carbon atoms. Examples of monocyclic radicals having 3 to 8 carbon atoms comprise cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclocotyl.

Examples of bicyclic radicals having 7 or 8 carbon atoms comprise

bicyclo[2.1.1]hexyl, bicyclo[2.2.1]heptyl, bicyclo[3.1.1 ]heptyl, bicyclo[2.2.1]heptyl, bicyclo[2.2.2]octyl and bicyclo[3.2.1]octyl.

The term“Cs-Cscyclalkenyl” as used herein describes mono- or bicyclic cyclic hydrocarbon radicals having from 3 to 8 carbon atoms and a double bond in any position. Examples of monocyclic radicals comprise cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, or cyclooctenyl. Examples of binocyclic radicals bicyclo[3.1 0]hex-2-enyl, 1 ,2,3,4,5,6-hexahydropentalenyl, or bicyclo[4.1 0]hept-3-enyl.

The term“Ci-C2oalkylene” as used herein describes divalent saturated linear or where possible, branched hydrocarbon radicals having 1 to 20, preferably 1 to 12 carbon atoms (“Ci-Ci2alkylene”). Examples are methylene, ethylene, n-propylene, isopropylene, n-butylene, sec. -butylene, isobutylene, tert.-butyenel, n-pentylene, 2-pentylene, 3-pentylene, 2,2-dimethylpropylene,

1.1 .3.3-tetramethylpentylene, n-hexylene, 1 -methylhexylene,

1 ,1 ,3,3,5,5-hexamethylhexylene, n-heptylene, isoheptylene,

1.1 .3.3-tetramethylbutylene, 1 -methylheptylene, 3-methylheptylene, n-octylene,

1.1 .3.3-tetramethylbutylene and 2-ethylhexylene, n-nonylene, decylene, undecylene, dodecylene, tridecylene, tetradecylene, pentadecylene,

hexadecylene, heptadecylene, or octadecylene.

The term“Ci-C2oalkenylene” as used herein as used herein describes divalent monounsaturated straight-chain or branched hydrocarbon radical having 1 to 20, preferably 1 to 12 carbon atoms (“Ci-Ci2alkenylen”). Examples are methenylene, ethenylene, n-propenylene, isopropenylene, n-butenylene, sec.-butenylene, isobutenylene, tert.-butenyenel, n-pentenylene, 2-pentenylene, 3-pentenylene, 2,2-dimethylpropenylene, 1 ,1 ,3,3-tetramethylpentenylene, n-hexenylene,

1 -methylhexenylene, 1 ,1 ,3,3,5,5-hexamethylhexenylene, n-heptenylene, isoheptenylene, 1 ,1 ,3,3-tetramethylbutenylene, 1 -methylheptenylene,

3-methylheptenylene, n-octenylene, 1 ,1 ,3,3-tetramethylbutenylene and

2-ethylhexenylene, n-nonenylene, decenylene, undecenylene, dodecenylene, tridecenylene, tetradecenylene, pentadecenylene, hexadecenylene,

heptadecenylene, or octadecenylene.

The term“Cs-Cscycloalkylene” as used herein describes divalent mono- or bicyclic cycloaliphatic radicals having from 3 to 8 carbon atoms, preferably 5 or 6 carbon atoms. Examples of monocyclic radicals having 3 to 8 carbon atoms comprise cyclopropylene, cyclobutylene, cyclopentylene, cyclohexylene , cycloheptylene and caclooctylene. Examples of bicyclic radicals having 7 or 8 carbon atoms comprise bicyclo[2.1 1 ]hexylene, bicyclo[2.2.1 ]heptylene, bicyclo[3.1 .1 ]heptylene, bicyclo[2.2.1]heptylene, bicyclo[2.2.2]octylene and bicyclo[3.2.1 ]octylene.

The term”C3-C8cycloalkenylene” as used herein describes divalent mono- or bicyclic hydrocarbon radicals having from 3 to 8 carbon atoms and a double bond in any position. Examples of monocyclic radicals comprise cyclopropenylene, cyclobutenylene, cyclopentenylene, cyclohexenylene, cycloheptenylene, or cyclooctenylene. Examples of binocyclic radicals bicyclo[3.1 0]hex-2-enylene, 1 ,2,3,4,5,6-hexahydropentenylene, or bicyclo[4.1 0]hept-3-enylene.

The term“5- or 6-membered heterocycle” as used herein describes an saturated, unsaturated or aromatic 5- or 6-membered ring comprising at least one

heteroatom selected from N, O and S. Examples are pyrrolidinyl, 3-pyrrolinyl, tetrahydrofuranyl, tetrahydrothiophenyl, pyrrolyl, furanyl, thiophenyl, piperidinyl, piperazinyl, tetrahydropyranyl, tetrahydrothiopyranyl, morpholinyl, and pyridinyl.

The invention relates to a photocurable resin composition comprising at least one photoinitiator G-1A of the general formula (la) and/or at least one photoinitiator G-2A of the general formula (lb),

(la) (lb) wherein

Ch ¹ , X, Z, Ch ² ; Y, R ² , m and n have the meanings as mentioned above. Preferred embodiments for the photoinitiator compounds G-1 A and G-1 B of formula (la) and (lb) are explained in the following.

Compounds G-1 A of the general formula (la)

In the general formula (la) X is O, S or NR ⁵ ; wherein R ⁵ have the meanings as defined above or the preferred meanings indicated below.

X is preferably O or S and particularly preferably O.

Z is R ¹ or R ⁷ , and

n is 1 to 4, under the proviso that when n is 1 ,

Z is R ¹ .

Accordingly, when n is 2, 3 or 4, Z is R ⁷ .

Thus, in one preferred embodiment of the compounds of formula (la) n is 1 , i.e. a monomeric compound, wherein Z is R ¹ with

R ¹ is hydrogen; Ci-C2oalkyl or C2-C2oalkenyl, which is unsubstituted or

substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Ci-C2oalkyl or C2-C2oalkenyl, which is interrupted by one or more -O-, -S-, -NR5-, phenylene and/or naphthylene; Cs-Cscycloalkyl or

Cs-Cscycloalkeny, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Cs-Cscycloalkyl or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl, which is unsubstituted or substituted by one or more halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ , NR ⁵ R ⁶ and/or -C(0)R;, preferably hydrogen; Ci-Ci2alkyl, which is

unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl ; Ci-Ci2alkyl, which is interrupted by one or more -0-, or phenylene; Cs-Cscycloalkyl, which is unsubstituted or substituted by one or more halogen, and/or OR ³ ; phenyl, which is unsubstituted or substituted by one or more halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and particularly preferably Ci-Csalkyl, which is unsubstituted or substituted by one or more OR ³ , NR ⁵ R ⁶ , or phenyl; Ci-Ci2alkyl, which is interrupted by one or more -0-, or phenylene; phenyl, which is unsubstituted, and even more preferred Ci-Ci2alkyl, which is unsubstituted or substituted by one or more OChb, N(Ci-C4alkyl)2, or phenyl; wherein R ³ R ⁴ , R ⁵ , R ⁶ and R ⁸ have the meanings as defined above or the preferred meanings indicated below.

In another preferred embodiment of the compounds of formula (la) n is 2, 3 or 4, preferably 2, i.e. a dimeric, trimeric or tetrameric, preferably dimeric compound, wherein Z is R ⁷ with

R ⁷ is Ci-C2oalkylene or Ci-C2oalkenylene, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-C2oalkylene or

Ci-C2oalkenylene, which is interrupted by one or more -0-, -S-, -NR ⁵ -, phenylene and/or naphthylene; Cs-Cscycloalkylene or

C3-C8cycloalkenylene, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Cs-Cscycloalkylene or

C3-C8cycloalkenylene, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenylene or naphthylene, which is unsubstituted or substituted by one or more by halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ , NR ⁵ R ⁶ and/or -C(0)R; more preferably Ci-Ci2alkylene, which is unsubstituted or substituted by one or more halogen, OR ³ ; Ci-C2oalkylene, which is interrupted by one or more -0-, and/or phenylene; Cs-Cscycloalkylene which is unsubstituted or substituted by one or more halogen, OR ³ ; Cs-Cscycloalkylene, which is interrupted by one or more -O- ; phenylene, which is unsubstituted or substituted by one or more by halogen, Ci-Ci2alkyl, and/or OR ³ ; and particularly preferably Ci-Ci2alkylene, or Ci-Ci2alkylene, which is

interrupted by one or more -0-, or phenylene. wherein R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁸ have the meanings as defined above or the preferred meaning indicated below. Ch ¹ in the general formula is Ar ¹ or Het ¹ .

Ar ¹ preferably is selected from the group consisting of phenyl, naphthyl,

biphenyl, styryl, stilbenyl, diphenylacetylenyl, terphenylyl, anthracenyl, phenanthrenyl, pyrenyl or triphenylenyl, more preferably selected from the group consisting of phenyl, naphthyl, biphenyl, styryl, terphenylyl, pyrenyl or triphenylenyl, and particularly preferably selected from the group consisting of phenyl and naphthyl.

Ar ¹ is unsubstituted or substituted with one or more substituents preferably selected from the group consisting of halogen; NO2, CN; OR ³ ; SR ⁴ ; NR ⁵ R ⁶ ; Ci-C2oalkyl and/or C2-C2oalkenyl, which are independently from each other unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ ,

NR ⁵ R ⁶ , phenyl and/or naphthyl; Ci-C2oalkyl and/or C2-C2oalkenyl, which are independently from each other interrupted by one or more -0-, -S-, -NR ⁵ -, phenylene and/or naphthylene; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which are independently from each unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Cs-Cscycloalkyl and/or

Cs-Cscycloalkenyl, which are independently from each other interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl and/or naphthyl, which are independently from each other unsubstituted or substituted by one or more halogen, CN, Ci-C2oalkyl, Cs-Cscycloalkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ;

and/or

OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents, if present on adjacent ring atoms, on Ar ¹ via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles;

and/or

R ⁵ and R ⁶ form together with the N atom to which they are attached a 5- or 6-membered heterocycle;

more preferably Ar ¹ is unsubstituted or substituted with one or more substituents selected from the group consisting of halogen; CN; OR ³ ; SR ⁴ ; NR ⁵ R ⁶ ; Ci-Ci2alkyl and/or C2-Ci2alkenyl, which are independently from each other unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Ci-Ci2alkyl and/or C2-Ci2alkenyl, which are

independently from each other interrupted by one or more -0-, -S- , -NR ⁵ -, phenylene; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which are

independently from each unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which are independently from each other interrupted by one or more -0-,

-S- and/or -NR ⁵ -; phenyl, which is independently from each other

unsubstituted or substituted by one or more halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ;

and/or

OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents, if present at adjacent ring atoms at Ar ¹ or with the ring carbon atoms of Ar ¹ via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles; and particularly preferably Ar ¹ unsubstituted or substituted with one or more substituents selected from the group consisting selected from halogen,

OR ³ , SR ⁴ , NR ⁵ NR ⁶ and/or Ci-Ci2alkyl, which is unsubstituted or substituted by one or more phenyl, and/or OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents, if present at adjacent ring atoms at Ar ¹ or with the ring carbon atoms of Ar ¹ via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles, preferably carbazolyl, or a morpholinyl. wherein R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁸ have the meanings as defined above or the preferred meanings indicated below.

Het ¹ is selected from the group consisting of furyl, thienyl, pyrrolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazole, imidazolyl, pyrazolyl, oxadiazolyl, thiadiazolyl, triazolyl, pyridyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazinyl,

2- or 3-benzofuryl, 2- or 3-benzothienyl, 2- or 3-indolyl, 2-benzoxazolyl,

2-benzothiazolyl, 2-benzoimidazolyl, 3-indazolyl, 2-, 3- or 4-quinolyl, 1 -,

3- or 4-isoquinolyl, 3-phthalazinyl, 2- or 3-quinoxalinyl, pteridinyl, bithienyl, trithienyl, acridinyl, phenazinyl or purinyl; more preferably from furyl, thienyl; pyrrolyl, bithienyl, trithienyl, and particularly preferably from furyl, thienyl; and pyrrolyl.

Het ¹ as defined above is unsubstituted or substituted with one or more

substituents preferably selected from the group consisting of halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-Ci2alkyl and/or C2-Ci2alkenyl, which are

independently from each other unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Ci-Ci2alkyl and/or C2-Ci2alkenyl, each of which is interrupted by one or more -0-, -S- , -NR ⁵ -, or phenylene;

C3-C8cycloalkyl and/or Cs-Cscycloalkenyl, which are independently from each other unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, each of which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl, which is independently from each other unsubstituted or substituted by one or more halogen, Ci-Ci ₂ alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ;

and/or

OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents, if present at adjacent ring atoms, on Het ¹ via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles;

more preferably unsubstituted or substituted with one or more substituents selected from the group consisting of halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-Ci2alkyl and/or C2-Ci2alkenyl, which are independently from each other unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Ci-Ci2alkyl and/or C2-Ci2alkenyl, each of which is interrupted by one or more -0-, -S- , -NR ⁵ -, phenylene; Cs-Cscycloalkyl and/or

Cs-Cscycloalkenyl, which are independently from each other unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ;

Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, each of which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl, which is independently from each other unsubstituted or substituted by one or more halogen,

Ci-Ci ₂ alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ,

and/or OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents on Het ¹ , if present at adjacent ring atoms, via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles;

and particularly preferably unsubstituted or substituted with one or more Ci-Ci2alkyl, wherein R ³ R ⁴ , R ⁵ , R ⁶ and R ⁸ have the meanings as defined above or the preferred meanings indicated below.

R ³ preferably is hydrogen; Ci-C2oalkyl or C2-C2oalkenyl, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ and/or phenyl; Ci-C2oalkyl or C2-C2oalkenyl, which is interrupted by one or more -0-, -S-, -NR5- and/or phenylene; Cs-Cscycloalkyl or Cs-Cscycloalkeny, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Cs-Cscycloalkyl or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl, which is unsubstituted or substituted by one or more by halogen, CN, Ci-Ci2alkyl, OR ³ , SR ⁴ ,NR ⁵ R ⁶ and/or -C(0)R; ore preferably hydrogen; Ci-Ci2alkyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ and/or phenyl; Ci-Ci2alkyl, which is interrupted by one or more -O and/or phenylene; Cs-Cscycloalkyl, which is unsubstituted or substituted by one or more halogen; phenyl, which is unsubstituted or substituted by one or more by halogen, Ci-Ci2alkyl, OR ³ ; and particularly preferably is Ci-Ci2alkyl or phenyl; wherein R ⁴ , R ⁵ , R ⁶ and R ⁸ have the meanings as defined above or the preferred meaning indicated below.

R ⁴ preferably is hydrogen; Ci-Ci2alkyl or C2-Ci2alkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , and/or phenyl; Ci-Ci2alkyl or C2-Ci2alkenyl, which is interrupted by one or more -0-, -S-, -NR ⁵ - and/or phenylene; Cs-Cscycloalkyl or Cs-Cscycloalkeny, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ ; Cs-Cscycloalkyl or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl or naphthyl, which is unsubstituted or substituted by one or more by halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ , NR ⁵ R ⁶ and/or -C(0)R; more preferably hydrogen; Ci-Ci2alkyl, which is

unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ and/or phenyl; Ci-Ci2alkyl , which is interrupted by one or more -0-, or phenylene; Cs-Cscycloalkyl, which is unsubstituted or substituted by one or more halogen; phenyl which is unsubstituted or substituted by one or more by halogen, Ci-Ci2alkyl, and/or OR ³ ; and particularly preferably is

Ci-Ci2alkyl or phenyl; wherein R ³ R ⁵ , R ⁶ and R ⁸ have the meanings as defined above or the preferred meaning indicated below.

R ⁵ , R ⁶ preferably - unless indicated otherwise - are independently of each other hydrogen; Ci-Ci2alkyl or C2-Ci2alkenyl, which is unsubstituted or

substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ and/or phenyl;

Ci-Ci2alkyl or C2-Ci2alkenyl, which is interrupted by one or more -0-, -S-, -NR ⁵ - and/or phenylene; Cs-Cscycloalkyl or Cs-Cscycloalkeny, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ ; Cs-Cscycloalkyl or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl or naphthyl, which is unsubstituted or substituted by one or more by halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ; more preferably independently of each other hydrogen; Ci-Ci2alkyl, which is unsubstituted or substituted by one or more halogen, OR ³ , and/or phenyl; Ci-Ci2alkyl, which is interrupted by one or more -0-, or phenylene; Cs-Cscycloalkyl, which is unsubstituted or substituted by one or more halogen phenyl, which is unsubstituted or substituted by one or more by halogen, Ci-Ci2alkyl, and/or OR ³ ; and/or -C(0)R ⁸ ; and particularly preferably are independently of each other Ci-Ci2alkyl; or form together with the N atom to which they are attached a 5- or 6-membred heterocycle, preferably morpholine; wherein R ³ , R ⁴ , and R ⁸ have the meanings as defined above or the preferred meaning indicated below.

Re preferably is OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-Ci2alkyl or C2-Ci2alkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Ci-Ci2alkyl or C2-Ci2alkenyl, which is interrupted by one or more -0-, -S-, -NR ⁵ -, phenylene and/or naphthylene; Cs-Cscycloalkyl or

Cs-Cscycloalkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ ; Cs-Cscycloalkyl or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NRs-; phenyl, naphthyl, furanyl, thienyl, pyrroryl, benzofuranyl, benzothienyl, indoryl and/or benzoimidazoyl, which is unsubstituted or substituted by one or more halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ;

and/or

OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles; and/or

R ⁵ and R ⁶ fomn together with the N atom to which they are attached a 5- or 6-membered heterocycle;

more preferably OR ³ and/or NR ⁵ R ⁶ ; Ci-Ci2alkyl, which is unsubstituted or substituted by one or more halogen, OR ³ , and/or phenyl; Ci-Ci2alkyl, which is interrupted by one or more -0-, and/or phenylene; Cs-Cscycloalkyl, which is unsubstituted or substituted by one or more halogen; phenyl, naphthyl, furanyl, thienyl, pyrroryl, benzofuranyl, benzothienyl, indoryl and/or benzoimidazoyl, which is unsubstituted or substituted by one or more halogen, Ci-Ci2alkyl, OR ³ , and/or NR ⁵ R ⁶ ;

and/or

R ⁵ and R ⁶ fomn together with the N atom to which they are attached a 5- or 6-membered heterocycle; and particularly preferably is phenyl,

unsubstituted or substituted by one more Ci-Ci2alkyl, wherein R ³ R ⁴ , R ⁵ , and R ⁶ have the meanings as defined above.

Compounds G-1 B of the general formula (lb)

In the general formula (lb) Y is O, S or NR ⁵ ; preferably O, wherein R ⁵ have the meanings as defined above. m is 2 to 4, preferably 2. The compounds of formula (lb) preferably are dimeric compounds.

Ch ² is Ar ² , Het ² or a group of the general formula (B)

wherein

each D is independently from each other Ci-C2oalkyl, which is

unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl or Ci-C2oalkyl or C2-C2oalkenyl, which is interrupted by one or more -0-, -S-, -NR ⁵ -, phenylene and/or naphthylene;

p is 1 to 5;

Ar ² is preferably selected from phenylene, naphthylene, biphenylene, styrylene, stilbenylene, diphenylacetylenylene, terphenylene, anthracenylene, phenanthrenylene, pyrenylene, triphenylene, diphenylmethylene, triphenylmethylene, tetraphenylmethylene or a group of the general formula (A)

wherein V and W are independently from each other a direct bond, O, S or NR ⁵ ; and o is 0 or 1 , more preferably Ar ² is diphenylmethylene, phenylene,

biphenylene, or naphthylene; or a group of the general

formula (A), wherein V is a direct bond, o is 1 and W is O, S or NR ⁵ , or wherein o is 0 and W is O, S or NR ⁵ , wherein R ⁵ have the meanings as defined above. The group of the general formula (A) is a linking moiety between two three or four units of the formula ( )

(P

The units of formula ( ) are connected to the group of the general formula (A) via the‘-location which are attached to at least one fused phenyl ring of the group (A).

In one preferred embodiment all units of formula ( ) present in the particular compound, i.e. 2, 3, or 4, can be attached to the same phenyl ring. In another preferred embodiment, every phenyl ring of group A is connected with at least one unit of the formula ( ).

More preferred are compounds, wherein every phenyl ring of the group (A) is connected with one unit of formula ( ), particularly preferred are compounds of the following formulae (l*-1 a) and (l*-1 b)

( -1 a) ( ^{M b} )

Ar ² is unsubstituted or substituted by one or more substituents preferably

selected from the group consisting of halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-Ci2alkyl and/or C2-Ci2alkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Ci-Ci2alkyl and/or

C2-Ci2alkenyl, which is interrupted by one or more -0-, -S- , -NR ⁵ -, phenylene; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; C3-C8cycloalkyl and/or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl, which is unsubstituted or substituted by one or more halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ; and/or OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents on Ar ² via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles;

more preferably unsubstituted or substituted by one or more Ci-Ci2alkyl, which is unsubstituted or substituted by one or more phenyl; or Ci-Ci2alkyl , which is interrupted by one or more phenylene; or phenyl.,

wherein R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁸ have the meanings as defined above.

Het ² is preferably selected from the group consisting of furyl, thienyl, pyrrolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazole, imidazolyl, pyrazolyl, oxadiazolyl, thiadiazolyl, triazolyl, pyridyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazinyl,

2- or 3-benzofuryl, 2- or 3-benzothienyl, 2- or 3-indolyl, 2-benzoxazolyl,

2-benzothiazolyl, 2-benzoimidazolyl, 3-indazolyl, 2-, 3- or 4-quinolyl, 1 -,

3- or 4-isoquinolyl, 3-phthalazinyl, 2- or 3-quinoxalinyl, pteridinyl, bithienyl, trithienyl, acridinyl, phenazinyl or purinyl , more preferably bithienyl, or trithienyl.

Het ² is unsubstituted or substituted with one or more substituents preferably

selected from the group consisting of halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-Ci2alkyl and/or C2-Ci2alkenyl, which are independently from each other unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Ci-Ci2alkyl and/or C2-Ci2alkenyl, each of which is interrupted by one or more -0-, -S- , -NR ⁵ -, phenylene; Cs-Cscycloalkyl and/or

Cs-Cscycloalkenyl, which are independently from each other unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ;

Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, each of which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl, which is independently from each other unsubstituted or substituted by one or more halogen,

Ci-Ci ₂ alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ;

and/or OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other, substituents, if present at adjacent ring atoms, on Het ¹ via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles;

more preferably unsubstituted or substituted by one or more Ci-Ci2alkyl, which is unsubstituted or substituted by one or more phenyl; or Ci-Ci2alkyl, which is interrupted by one or more phenylene; or phenyl,

wherein R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁸ have the meanings as defined above.

The group of the general formula (B) preferably is represented by

wherein

D is Ci-C2oalkyl, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl or Ci-C2oalkyl or

C2-C2oalkenyl, which is interrupted by one or more -0-, -S-, -NR ⁵ -, phenylene and/or naphthylene; more preferably Ci-C2oalkyl, which is unsubstituted; or Ci-C2oalkyl, which is interrupted by one or more -0-; and

P is 1 ,

wherein R ³ , R ⁴ , R ⁵ , and R ⁶ have the meanings as defined above.

R ² is preferably hydrogen; Ci-C2oalkyl or C2-C2oalkenyl, which is

unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Ci-C2oalkyl or C2-C2oalkenyl, which is interrupted by one or more -0-, -S-, -NR ⁵ -, phenylene and/or naphthylene; Cs-Cscycloalkyl or C3-C8cycloalkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Cs-Cscycloalkyl or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl, which is unsubstituted or substituted by one or more by halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; more preferably Ci-Ci2alkyl, or phenyl,

wherein R ³ , R ⁴ , R ⁵ , and R ⁶ and have the meanings as defined above.

The group of the general formula (B) is a linking moiety between two three or four units of the formula ( )

The units of formula ( ) are connected to the group of the general formula (B) via the‘-location which are attached to at least one phenyl ring of the group (B).

In one preferred embodiment all units of formula ( ) present in the particular compound, i.e. 2, 3, or 4, can be attached to the same phenyl ring. In another preferred embodiment, every phenyl ring of group (B) is connected with at least one unit of the formula ( ).

More preferred are compounds, wherein every phenyl ring of the group (B) is connected with one unit of formula ( ), particularly preferred are compounds of the following formula ( -2)

In a preferred embodiment the invention relates to a photocurable resin

composition as described above wherein the at least one photoinitiator is a photoinitiator G-1A of the general formula (la), wherein Z, X and n have the meanings as defined above and

wherein

Ch ¹ is Ar ¹ or Het ¹ ;

Ar ¹ is selected from the group consisting of phenyl, naphthyl, biphenyl, styryl, stilbenyl, diphenylacetylenyl, terphenylyl, anthracenyl, phenanthrenyl, pyrenyl or triphenylenyl; which is unsubstituted or substituted with one or more substituents selected from the group consisting of halogen; NO2; CN; OR ³ ; SR ⁴ ; NR ⁵ R ⁶ ; Ci-Ci2alkyl and/or C2-Ci2alkenyl, which are

independently from each other unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Ci-Ci2alkyl and/or C2-Ci2alkenyl, which are independently from each other interrupted by one or more -0-,

-S- , -NR ⁵ -, phenylene; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which are independently from each unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which are independently from each other interrupted by one or more -0-,

-S- and/or -NR ⁵ -; phenyl, which is independently from each other

unsubstituted or substituted by one or more halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ;

and/or

OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents, if present at adjacent ring atoms at Ar ¹ via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles;

Het ¹ is selected from the group consisting of furyl, thienyl, pyrrolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazole, imidazolyl, pyrazolyl, oxadiazolyl, thiadiazolyl, triazolyl, pyridyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazinyl,

2- or 3-benzofuryl, 2- or 3-benzothienyl, 2- or 3-indolyl, 2-benzoxazolyl,

2-benzothiazolyl, 2-benzoimidazolyl, 3-indazolyl, 2-, 3- or 4-quinolyl, 1 -,

3- or 4-isoquinolyl, 3-phthalazinyl, 2- or 3-quinoxalinyl, pteridinyl, bithienyl, trithienyl, acridinyl, phenazinyl or purinyl; which is unsubstituted or substituted with one or more substituents selected from the group

consisting of halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-Ci2alkyl and/or

C2-Ci2alkenyl, which are independently from each other unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Ci-Ci2alkyl and/or C2-Ci2alkenyl, each of which is interrupted by one or more -0-, -S- , -NR ⁵ -, phenylene; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which are independently from each other unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, each of which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl, which is independently from each other unsubstituted or substituted by one or more halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ; and/or

OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other , substituents, if present at adjacent ring atoms, on Het ¹ via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles;

R ¹ is hydrogen; Ci-C2oalkyl or C2-C2oalkenyl, which is unsubstituted or

substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Ci-C2oalkyl or C2-C2oalkenyl, which is interrupted by one or more -0-, -S-, -NR5-, phenylene and/or naphthylene; Cs-Cscycloalkyl or

C3-C8cycloalkeny, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Cs-Cscycloalkyl or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl, which is unsubstituted or substituted by one or more halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ , NR ⁵ R ⁶ and/or -C(0)R;

R ³ is hydrogen; Ci-C2oalkyl or C2-C2oalkenyl, which is unsubstituted or

substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ and/or phenyl; Ci-C2oalkyl or C2-C2oalkenyl, which is interrupted by one or more -0-, -S-, -NR5- and/or phenylene; Cs-Cscycloalkyl or Cs-Cscycloalkeny, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Cs-Cscycloalkyl or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl, which is unsubstituted or substituted by one or more by halogen, CN, Ci-Ci2alkyl, OR ³ , SR ⁴ ,NR ⁵ R ⁶ and/or -C(0)R;

R ⁴ is hydrogen; Ci-Ci2alkyl or C2-Ci2alkenyl, which is unsubstituted or

substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , and/or phenyl;

Ci-Ci2alkyl or C2-Ci2alkenyl, which is interrupted by one or more -0-, -S-, -NR ⁵ - and/or phenylene; Cs-Cscycloalkyl or Cs-Cscycloalkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ ; Cs-Cscycloalkyl or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl or naphthyl, which is unsubstituted or substituted by one or more by halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ , NR ⁵ R ⁶ and/or -C(0)R; R ⁵ , R ⁶ are independently of each other hydrogen; Ci-Ci2alkyl or C2-Ci2alkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ and/or phenyl; Ci-Ci2alkyl or C2-Ci2alkenyl, which is interrupted by one or more -0-, -S-, -NR ⁵ - and/or phenylene; Cs-Cscycloalkyl or

C3-C8cycloalkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ ; Cs-Cscycloalkyl or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl or naphthyl, which is unsubstituted or substituted by one or more by halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ;

R ⁷ is Ci-C2oalkylene or Ci-C2oalkenylene, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-C2oalkylene or Ci-C2oalkenylene, which is interrupted by one or more -0-, -S-, -NR ⁵ -, phenylene and/or naphthylene; Cs-Cscycloalkylene or

C3-C8cycloalkenylene, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Cs-Cscycloalkylene or

C3-C8cycloalkenylene, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenylene or naphthylene, which is unsubstituted or substituted by one or more by halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ , NR ⁵ R ⁶ and/or -C(0)R;

Re is OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-Ci2alkyl or C2-Ci2alkenyl, which is

unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Ci-Ci2alkyl or C2-Ci2alkenyl, which is interrupted by one or more -0-, -S-, -NR ⁵ -, phenylene and/or naphthylene; Cs-Cscycloalkyl or

Cs-Cscycloalkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ ; Cs-Cscycloalkyl or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NRs-; phenyl, naphthyl, furanyl, thienyl, pyrroryl, benzofuranyl, benzothienyl, indoryl and/or benzoimidazoyl, which is unsubstituted or substituted by one or more halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ;

and/or

OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles; and/or R ⁵ and R ⁶ form together with the N atom to which they are attached a 5- or

6-membered heterocycle;

under the proviso that when n is 1 , Z is R ¹ ;

and/or at least one photoinitiator G-1 B of the general formula (lb), wherein

R ³ , R ⁴ , R ⁵ , R ⁶ , and R ⁸ have the meanings as defined above; and

Ch ² is Ar ² or Het ² or a group of the general formula (B)

wherein

D is Ci-C2oalkyl, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl or Ci-C2oalkyl or

C2-C2oalkenyl, which is interrupted by one or more -0-, -S-, -NR ⁵ -, phenylene and/or naphthylene;

P is 1 ;

R ² is hydrogen; Ci-C2oalkyl or C2-C2oalkenyl, which is unsubstituted or

substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Ci-C2oalkyl or C2-C2oalkenyl, which is interrupted by one or more -0-, -S-, -NR ⁵ -, phenylene and/or naphthylene; Cs-Cscycloalkyl or

C3-C8cycloalkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Cs-Cscycloalkyl or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl, which is unsubstituted or substituted by one or more by halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ;

Ar ² is phenylene, naphthylene, biphenylene, styrylene, stilbenylene,

diphenylacetylenylene, terphenylene, anthracenylene, phenanthrenylene, pyrenylene, triphenylene, diphenylmethylene, triphenylmethylene, tetraphenylmethylene or a group of the general formula (A) wherein

V and W are independently from each other a direct bond, O, S or NR ⁵ ; o is O or l ;

each of which is unsubstituted or substituted by one or more substituents selected from the group consisting of halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-Ci2alkyl and/or C2-Ci2alkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Ci-Ci2alkyl and/or

C2-Ci2alkenyl, which is interrupted by one or more -0-, -S- , -NR ⁵ -, phenylene; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ;

Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl, which is unsubstituted or substituted by one or more halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ; and/or

OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents on Ar ² via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles;

Het ² is furylene, thienylene, pyrrolylene, oxazolylene, isoxazolylene, thiazolylene, isothiazolylene, imidazolylene, pyrazolylene, oxadiazolylene,

thiadiazolylene, triazolylene, pyridylene, pyrimidinylene, pyrazinylene, pyridazinylene, triazinylene, benzofurylene, benzothienylene, indolylene, benzoxazolylene, benzothiazolylene, benzoimidazolylene, indazolylen, quinolylene, isoquinolylene, phthalazinylene, quinoxalinylene, pteridinylene, bithienylene, trithienylene, acridinylene, phenazinylene or purinylene; each of which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-Ci2alkyl and/or C2-Ci2alkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Ci-Ci2alkyl and/or C2-Ci2alkenyl, which is interrupted by one or more -0-, -S- , -NR ⁵ -, phenylene; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; C3-C8cycloalkyl and/or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl, which is unsubstituted or substituted by one or more halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ; and/or

OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents on Het ² , if present at adjacent ring atoms, via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles;

and

wherein m, and Y have the meanings as defined above.

In a further embodiment of the invention the photocurable resin composition comprises at least one photoinitiator G-1A of the general formula (la), wherein Z, X and n have the meanings as defined above and wherein

Ch ¹ is Ar ¹ or Het ¹ ;

Ar ¹ is selected from the group consisting of phenyl, naphthyl, biphenyl, styryl, stilbenyl, diphenylacetylenyl, terphenylyl, anthracenyl, phenanthrenyl, pyrenyl or triphenylenyl; which is unsubstituted or substituted with one or more substituents selected from the group consisting of halogen; NO2; CN; OR ³ ; SR ⁴ ; NR ⁵ R ⁶ ; Ci-Ci2alkyl and/or C2-Ci2alkenyl, which are

independently from each other unsubstituted or substituted by one or more halogen, CN, OR ³ ,

SR ⁴ , NR ⁵ R ⁶ , phenyl; Ci-Ci2alkyl and/or C2-Ci2alkenyl, which are

independently from each other interrupted by one or more -0-, -S- , -NR ⁵ -, phenylene; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which are

independently from each unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which are independently from each other interrupted by one or more -0-,

-S- and/or -NR ⁵ -; phenyl, which is independently from each other

unsubstituted or substituted by one or more halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ;

and/or OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents on Ar ¹ , if present at adjacent ring atoms, via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles;

Het ¹ is selected from the group consisting of furyl, thienyl, pyrrolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazole, imidazolyl, pyrazolyl, oxadiazolyl, thiadiazolyl, triazolyl, pyridyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazinyl,

2- or 3-benzofuryl, 2- or 3-benzothienyl, 2- or 3-indolyl, 2-benzoxazolyl,

2-benzothiazolyl, 2-benzoimidazolyl, 3-indazolyl, 2-, 3- or 4-quinolyl, 1 -,

3- or 4-isoquinolyl, 3-phthalazinyl, 2- or 3-quinoxalinyl, pteridinyl, bithienyl, trithienyl, acridinyl, phenazinyl or purinyl; which is unsubstituted or substituted with one or more substituents selected from the group

consisting of halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-Ci2alkyl and/or

C2-Ci2alkenyl, which are independently from each other unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Ci-Ci2alkyl and/or C2-Ci2alkenyl, each of which is interrupted by one or more -0-, -S- , -NR ⁵ -, phenylene; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which are independently from each other unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, each of which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl, which is independently from each other unsubstituted or substituted by one or more halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ , and/or

OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents on Het ¹ , if present at adjacent ring atoms, via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles;

R ¹ is hydrogen; Ci-Ci2alkyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl ; Ci-Ci2alkyl, which is interrupted by one or more -0-, or phenylene; Cs-Cscycloalkyl, which is unsubstituted or substituted by one or more halogen, and/or OR ³ ; phenyl, which is

unsubstituted or substituted by one or more halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ;

R ³ is hydrogen; Ci-Ci2alkyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ and/or phenyl; Ci-Ci2alkyl, which is interrupted by one or more -O and/or phenylene; Cs-Cscycloalkyl, which is unsubstituted or substituted by one or more halogen; phenyl, which is unsubstituted or substituted by one or more by halogen, Ci-Ci2alkyl, OR ³ ;

R ⁴ is hydrogen; Ci-Ci2alkyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ and/or phenyl; Ci-Ci2alkyl, which is interrupted by one or more -0-, or phenylene; Cs-Cscycloalkyl, which is unsubstituted or substituted by one or more halogen; phenyl which is unsubstituted or substituted by one or more by halogen, Ci-Ci2alkyl, and/or OR ³ ;

R ⁵ , R ⁶ are independently of each other hydrogen; Ci-Ci2alkyl, which is

unsubstituted or substituted by one or more halogen, OR ³ , and/or phenyl; Ci-Ci2alkyl, which is interrupted by one or more -0-, or phenylene;

Cs-Cscycloalkyl, which is unsubstituted or substituted by one or more halogen phenyl, which is unsubstituted or substituted by one or more by halogen, Ci-Ci2alkyl, and/or OR ³ ; and/or -C(0)R ⁸ ;

R ⁷ is Ci-Ci2alkylene, which is unsubstituted or substituted by one or more

halogen, OR ³ ; Ci-C2oalkylene, which is interrupted by one or more -0-, and/or phenylene; Cs-Cscycloalkylene which is unsubstituted or substituted by one or more halogen, OR ³ ; Cs-Cscycloalkylene, which is interrupted by one or more -O- ; phenylene, which is unsubstituted or substituted by one or more by halogen, Ci-Ci2alkyl, and/or OR ³ ;

Re is OR ³ and/or NR ⁵ R ⁶ ; Ci-Ci2alkyl, which is unsubstituted or substituted by one or more halogen, OR ³ , and/or phenyl; Ci-Ci2alkyl, which is interrupted by one or more -0-, and/or phenylene; Cs-Cscycloalkyl, which is

unsubstituted or substituted by one or more halogen; phenyl, naphthyl, furanyl, thienyl, pyrroryl, benzofuranyl, benzothienyl, indoryl and/or benzoimidazoyl, which is unsubstituted or substituted by one or more halogen, Ci-Ci2alkyl, OR ³ , and/or NR ⁵ R ⁶ ;

and/or

R ⁵ and R ⁶ form together with the N atom to which they are attached a 5- or

6-membered heterocycle;

with the proviso that when n is 1 , Z is R ¹ ;

and/or at least one photoinitiator G-1 B of the general formula (lb), wherein Y and m have the meanings as defined above, and

wherein

Ch ² is A r ² or Het ² or a group of the general formula (B)

wherein

D is Ci-C2oalkyl, which is unsubstituted; or Ci-C2oalkyl, which is interrupted by one or more -0-;

P is 1 ;

R ² is hydrogen; Ci-C2oalkyl or C2-C2oalkenyl, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Ci-C2oalkyl or C2-C2oalkenyl, which is interrupted by one or more -0-, -S-, -NR ⁵ -, phenylene and/or naphthylene; Cs-Cscycloalkyl or Cs-Cscycloalkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Cs-Cscycloalkyl or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl, which is unsubstituted or substituted by one or more by halogen, Ci-Ci ₂ alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ;

Ar ² is phenylene, naphthylene, biphenylene, styrylene, stilbenylene, diphenylacetylenylene, terphenylene, anthracenylene, phenanthrenylene, pyrenylene, triphenylene, diphenylmethylene, triphenylmethylene, tetraphenylmethylene or a group of the general formula (A)

or a group of the general formula (A) wherein V and W are independently from each other a direct bond, O, S or NR ⁵ ; o is O or l ;

each of which is unsubstituted or substituted by one or more substituents selected from the group consisting of halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-Ci2alkyl and/or C2-Ci2alkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Ci-Ci2alkyl and/or

C2-Ci2alkenyl, which is interrupted by one or more -O-, -S- , -NR ⁵ -, phenylene; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ;

Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which is interrupted by one or more -O-, -S- and/or -NR ⁵ -; phenyl, which is unsubstituted or substituted by one or more halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ; and/or

OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents on Ar ² , if present at adjacent ring atoms, via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles;

Het ² is furylene, thienylene, pyrrolylene, oxazolylene, isoxazolylene, thiazolylene, isothiazolylene, imidazolylene, pyrazolylene, oxadiazolylene,

thiadiazolylene, triazolylene, pyridylene, pyrimidinylene, pyrazinylene, pyridazinylene, triazinylene, benzofurylene, benzothienylene, indolylene, benzoxazolylene, benzothiazolylene, benzoimidazolylene, indazolylen, quinolylene, isoquinolylene, phthalazinylene, quinoxalinylene, pteridinylene, bithienylene, trithienylene, acridinylene, phenazinylene or purinylene; each of which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-Ci2alkyl and/or C2-Ci2alkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl; Ci-Ci2alkyl and/or C2-Ci2alkenyl, which is interrupted by one or more -0-, -S- , -NR ⁵ -, phenylene; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which is unsubstituted or substituted by one or more halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ;

Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl, which is unsubstituted or substituted by one or more halogen, Ci-Ci2alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ; and/or OR3, SR ⁴ , and/or NR ⁵ R ⁶ form together with other substituents on Het ² , if present at adjacent ring atoms, via the radicals R ³ , R ⁴ , R ⁵ and/or R ⁶ one or more 5- or 6-membered heterocycles.

In a preferred embodiment of the invention the photocurable resin composition comprises at least one photoinitiator G-1A of the general formula (la), wherein the radicals and indices have the following meanings: n is 1 to 4;

Z is R ¹ or R ⁷ ;

X is O, S or NR ⁵ ;

R ¹ Ci-Ci2alkyl, which is unsubstituted or substituted by one or more OR ³ ,

NR ⁵ R ⁶ , or phenyl; Ci-Ci2alkyl, which is interrupted by one or more -O-, or phenylene; phenyl, which is unsubstituted;

Ch ¹ is Ar ¹ or Het ¹ ;

Ar ¹ is phenyl, naphthyl, or biphenyl, which is unsubstituted or substituted by one or more substituents selected from OR ³ , SR ⁴ , NR ⁵ NR ⁶ , C(0)R ⁸ and/or Ci-Ci2alkenyl, which is unsubstituted or substituted by one or more phenyl;

Het ¹ furyl, thienyl; pyrrolyl, which is unsubstituted or substituted with one or more Ci-Ci2alkyl;

R ³ is Ci-Ci2alkyl or phenyl;

R ⁴ is Ci-Ci2alkyl or phenyl; each unsubstituted or substituted by -C(0)R ⁸ ;

R ⁵ , R ⁶ are independently of each other Ci-Ci2alkyl; or form together with the N atom to which they are attached a 5- or 6-membred heterocycle, preferably morpholinyl;

R ⁷ is Ci-Ci2alkylene, or Ci-Ci2alkylene, which is interrupted by one or more -O-;

R ⁸ is phenyl, unsubstituted or substituted by one or more Ci-Ci2alkyl; and/or at least one photoinitiator G-1 B of the general formula (lb), wherein the radicals and indices have the following meanings: m is 2 to 4; Ch ² is Ar ² or Het ² ;

Y is O;

Ar ² is diphenylmethylene, phenylene, biphenylene, naphthylene,

triphenylmethylene, or tetraphenylmethylene;

Het ² is a group (A) of the general formula (A) wherein

V and W are independently from each other a direct bond, O, S or NR ⁵ ; o is O or l ;

R ² is Ci-Ci2alkyl, or phenyl; and

R ⁵ is Ci-Ci2alkyl.

Preferred compounds G-1A of the general formula (la) are summarized in the list below:

Preferred compounds G-1 B of the general formula (lb) are summarized in table 1 in regard of the radicals and indices Ch ² , Y, R ² and m:

Particularly preferred photoinitiator compounds G-1A are the following:

( G-1A-3) ( G-1A-4)

(G-1A-16) (G-1A-19)

(G-1A-24) (G-1A-25)

(G-1A-51 )

In another preferred embodiment the photoinitiator G-1 A is a compound of formula (G-1A-1 ), (G-1A-2), (G-1A-3), (G-1A-4), (G-1A-5), (G-1A-7), (G-1A-8), (G-1A-10), (G-1A-11 ), (G-1A-13), (G-1A-14), (G-1A-19), (G-1A-21 ), (G-1A-23), (G-1A-24), (G-1A-25), (G-1A-32), (G-1A-33), (G-1A-38), (G-1A-39), (G-1A-40), (G-1A-46),

(G-1A-47), (G-1A-49), or (G-1 -A-50).

Particularly preferred photoinitiator compounds G-1 B are the following:

(G-1 B-4) (G-1 B-6)

(G-1 B-14) (G-1 B-15)

In another preferred embodiment the photoinitiator G-1 B is a compound of formula (G-1 B-6). In one preferred embodiment of the invention the photocurable composition comprises one kind of the at least one photoinitiator G.

In another preferred embodiment the photocurable composition comprises a mixture of two or more different photoinitiators G. Suitable mixtures are mixtures of two or more different photoinitiators G-1A, or mixtures of two or more different photoinitiators G-1 B, or mixtures of one or more photoinitiators G-1 A and one or more photoinitiators G-1 B. Photosensitizer PS

The photocurable composition according to the invention comprises at least one photoinitiator system comprising at least one photoinitiator G as described above and at least one photosensitizer PS selected from the group consisting of benzophenone-based, xanthon-based, thioxanthone-based, and acridone-based compounds.

Photosensitizers are known in the art as compounds which are added to

photocurable resin compositions in order to broaden or to shift the spectral sensitivity.

Suitable photosensitizers PS for the purpose of the present invention are compounds which absorbs light in the range from 375 to 450 nm (or a more specific wavelength as taught herein such as, e.g. from 375 to 440 nm, from 380 to 430 nm, from 390 to 420 nm, or from 400 to 410 nm).

The at least one photosensitizer PS is selected from the group consisting of benzophenone-based, xanthon-based, thioxanthone-based, and acridone-based compounds.

The term’’benzophenone-based compounds” for the purpose of the present invention relates to compounds comprising as a parent compound benzophenone, wherein optionally one or more, up to the maximum number of hydrogen atoms, i.e. 10, are substituted with radicals different from hydrogen. Suitable substituents are all substituents which lead to a benzophenone-based compound which absorbs light in the preferred range of 375 to 450 nm (or a more specific wavelength as taught herein such as, e.g. from 375 to 440 nm, from 380 to

430 nm, from 390 to 420 nm, or from 400 to 410 nm). The same applies for the “xanthon-based”,“thioxanthone-based, and“acridone-based compounds” as used herein accordingly. In a preferred embodiment the photocurable composition according to the invention comprises at least one photosensitizer PS, wherein the at least one photosensitizer PS is a compound of the formula (I la) and/or (Mb)

wherein

D ^x is O or S;

E is a direct bond, CH2, O, S or NR ⁵

R9, Rl0, Rl1, Rl2, Rl3, Rl4, Rl5, Rl6, Rl7, Rl8, Rl9, R20, R21 , R22, R23, R24, R25, R26 are independently from each other hydrogen, halogen, NO2, CN, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-C2oalkyl and/or C2-C2oalkenyl, which is unsubstituted or substituted by one or more halogen, CN, OR ³ , SR ⁴ , NR ⁵ R ⁶ , phenyl and/or naphthyl; Ci-C2oalkyl and/or C2-C2oalkenyl, which is interrupted by one or more -0-, -S- , -NR5-, phenylene and/or naphthylene; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which is unsubstituted or substituted by one or more halogen, CN, R ⁸ , OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Cs-Cscycloalkyl and/or Cs-Cscycloalkenyl, which is interrupted by one or more -0-, -S- and/or -NR ⁵ -; phenyl and/or naphthyl, which is unsubstituted or substituted by one or more halogen, CN, Ci-C2oalkyl, Cs-Cscycloalkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ; and/or

Rs and Re form together with the N atom to which they are attached a 5- or 6-membered heterocycle; and/or

two of R ⁹ R ¹⁰ , R ^{1 1} , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹ , R ²² , R ²³ ,

R ²⁴ , R ²⁵ and/or R ²⁶ if present at adjacent carbon atoms together form a 5- or

6-membered carbocycle or heterocycle; and

wherein R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁸ is has the meaning as defined above. In the compounds of formula (I la) from 0 to 8 hydrogen atoms can be substituted with a radical different from hydrogen, preferably the number of substituents different from hydrogen is from 0 to 4, preferably from 0 to 2, and also preferably 1 to 3.

In the compounds of formula (Mb) from 0 to 10 hydrogen atoms can be substituted with a radical different from hydrogen, preferably the number of substituents different from hydrogen is from 0 to 4, preferably 1 or 2.

Compositions are preferred, wherein the at least one photosensitizer PS is a compound of the formula (lla) or (Mb), wherein the radicals and indices have the following meanings:

D ^x is O;

E is S or NR ⁵ ;

Rg, Rio, R1 1 , R12, R13, RM, RIS, Rie, R ¹⁷ , R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ and/or R ²⁶ are independently from each other hydrogen, halogen, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; Ci-Ci2alkyl, which is unsubstituted or substituted by one or more halogen, and/or OR ³ ; Ci-Ci2alkyl, which is interrupted by one or more -O; C3-C8cycloalkyl , which is unsubstituted or substituted by one or more halogen; Cs-Cscycloalkyl, which is interrupted by one or more -O- ; phenyl naphthyl, which is unsubstituted or substituted by one or more halogen, Ci-Ci ₂ alkyl, OR ³ , SR ⁴ and/or NR ⁵ R ⁶ ; and/or -C(0)R ⁸ ;

and wherein R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁸ is has the meaning as defined above.

In one preferred embodiment the photocurable composition according to the invention comprises at least one photosensitizer PS wherein the at least one photosensitizer PS is a compound of the formula (lla) wherein the radicals and indices have the following meanings:

D ^x is O;

E is S or NR ⁵ ;

wherein R ⁹ R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , and/or

R ¹⁶ are independently of each other hydrogen, halogen, OR ³ , and/or

Ci-Ci2alkyl;

R ³ is Ci-Ci2alkyl;

R ⁵ is Ci-Ci2alkyl. wherein preferably 4 to 8, more preferably 5 to 7 of the radicals R ⁹ R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , and/or R ¹⁶ are hydrogen;

and/or a compound of formula (Mb), wherein the radicals and indices have the following meanings:

D ^x is O,

R ¹⁷ , R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ and/or

R ²⁶ are independently of each other hydrogen, NR ⁵ R ⁶ , Ci-Ci2alkyl; wherein preferably 6 to 10, more preferably 7 to 9 of the radicals R ¹⁷ , R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ and/or R ²⁶ are hydrogen;

wherein

R ⁵ , R ⁶ are independently of each other hydrogen, Ci-Ci2alkyl, or form together with the N atom to which they are attached a 5- or 6-membered heterocycle.

In a preferred embodiment, the photosensitizers PS for the purpose of the present invention are compounds which absorbs light in the range from 300 to 500 nm, from 350 to 450 nm, from 375 to 440 nm, from 380 to 430 nm, from 390 to

420 nm, or from 400 to 410 nm. In a preferred embodiment, the photosensitizers PS for the purpose of the present invention are compounds which absorbs light in the range from 365 to 405 nm. In a preferred embodiment, the photosensitizers PS for the purpose of the present invention are compounds which absorbs light in the range from 360 to 380 nm, from 370 to 390 nm, from 380 to 400 nm, from 390 to 410 nm, or from 400 to 420 nm. In a preferred embodiment, the photosensitizers PS for the purpose of the present invention are compounds which absorbs light in the range of (approximately) 365 nm, (approximately) 385 nm or (approximately) 405 nm. In a preferred embodiment, photosensitizers PS for the purpose of the present invention are compounds which absorbs light in the range from 375 to 450 nm.

Particularly preferred photosensitizers PS of the general formula (lla) are the following:

(PS-7)

Particularly preferred photosensitizers PS of the general formula (lib) are the following:

Particularly preferred photosensitizer PS are compounds (PS-1 ), (PS-2), (PS-4), (PS-11 ) and (PS-13).

The composition of the invention may comprise one photosensitizer PS or a mixture of two or more thereof, preferably the composition comprises one photosensitizer PS. As mentioned above the at least one photosensitizer PS absorbs light in a wavelength preferably in the range from 375 to 450 nm (or a more specific wavelength as taught herein such as, e.g. from 375 to 440 nm, from 380 to

430 nm, from 390 to 420 nm, or from 400 to 410 nm). Accordingly, the present photocurable resin composition is curable with light having a wavelength in the range from 375 to 450 nm (or a more specific wavelength as taught herein such as, e.g. from 375 to 440 nm, from 380 to 430 nm, from 390 to 420 nm, or from 400 to 410 nm), for example originating from UV and blue emitting LEDs and blue LD.

As used herein, the terms“blue” or“blue-emitting” may be understood in the broadest sense as emitting light in the blue range, typically also including the near UV range. For instance blue emission may be in the range of from 300 to 500 nm, in particular in the range from 375 to 450 nm (or a more specific wavelength as taught herein such as, e.g. from 375 to 440 nm, from 380 to 430 nm, from 390 to 420 nm, or from 400 to 410 nm).

Ethylenically unsaturated photopolymerizable compound

The photocurable composition according to the invention comprises at least one ethylenically unsaturated photopolymerizable compound.

The at least one ethylenically unsaturated photopolymerizable compound is capable of causing a polymerization reaction and/or a crosslinking reaction by irradiation with actinic radiation in the presence of the at least one photoinitiator for radical polymerization, preferably in the presence of the at least one photoinitiator system according to the invention.

The at least one ethylenically unsaturated compound comprises one or more olefinic double bonds, for example, one, two, three, four, five or six double bonds.

In a preferred embodiment of the invention, the ethylenically unsaturated compound is not a compound of formula (la) or (lb) (radical photoinitiator G). In a preferred embodiment of the invention, ethylenically unsaturated compound is not a photosensitizer PS. In a preferred embodiment of the invention, the ethylenically unsaturated compound is not an epoxide. In a preferred embodiment of the invention the at least one ethylenically

unsaturated photopolymerizable compound is selected from acrylates,

methacrylates, vinylethers, styrenes, and organosiloxanes, or a mixture of two or more thereof.

(Meth)acrylates

In the present invention, the term“(meth)acrylic acid” encompasses both acrylic acid and methacrylic acid. Likewise, the term“(meth)acrylate” encompasses both acrylate and methacrylate.

Suitable (meth)acrylates for the purpose of the invention are (meth)acrylates containing one double bond, for example alkyl or hydroxyalkyl (meth)acrylates, for example methyl, ethyl, butyl, 2-ethylhexyl or 2-hydroxyethyl and isobornyl

(meth)acrylate.

Further preferred (meth)acrylates include urethane (meth)acrylates, polyester (meth)acrylates, epoxy (meth)acrylates and (meth)acrylic esters of alcohols.

Epoxy (meth)acrylates for the purpose of the invention are reaction products of at least one epoxy compound and and at least one (meth)acrylic acid.

Suitable epoxy-compounds are selected from aromatic epoxy compounds, alicyclic epoxy compounds and/or an aliphatic epoxy compounds, preferably aromatic epoxy compounds. Preferred aromatic epoxy compounds are aromatic glycidyl ether, preferably glycidyl ether of a bisphenol compound, preferably bisphenol A or bisphenol F.

Particularly suitable epoxy (meth)acrylates are for example epoxy

di(meth)acrylates as described in WO 2016/071811 A1 obtained by the reaction of 1 mol of a diepoxy compound with 2 mol of (meth)acrylic acid, represented by the following general formula (Xll-ii): E ^N -{C(FI)(0FI)-CFI ₂ -0-C0-C(R ³ⁱⁱ )=CFI ₂ } ₂ (Xll-ii) wherein

R ³ⁱⁱ represents a hydrogen atom or a methyl group, and E" represents a diepoxy compound residue (group after removing two epoxy groups from diepoxy compound).

In the above general formula (Xll-ii), the diepoxy compound residue E" may be any of an aromatic diepoxy compound residue, an aliphatic diepoxy compound residue, and an alicyclic diepoxy compound residue.

Non-limiting examples of the di(meth)acrylate compound (Xll-ii) include a di(meth)acrylate compound obtained by reacting 1 mol of a diepoxy compound composed of one, or two or more aromatic diepoxy compound(s), alicyclic diepoxy compound(s), and aliphatic diepoxy compound(s) with 2 mol of (meth)acrylic acid, and a di(meth)acrylate compound obtained by reacting 1 mol of an aromatic diepoxy compound with 2 mol of (meth)acrylic acid is preferably used in view of availability, mechanical properties and compatibility with the human body.

Specific examples thereof include a di(meth)acrylate compound obtained by reacting 1 mol of diglycidyl ether of a bisphenol-based compound such as bisphenol A or bisphenol F with 2 mol of (meth)acrylic acid, a di(meth)acrylate compound obtained by reacting 1 mol of diglycidyl ether, which is obtained by reacting an alkylene oxide adduct of a bisphenol-based compound such as bisphenol A or bisphenol F with an epoxydating agent such as epichlorohydrin, with 2 mol of (meth)acrylic acid, a di(meth)acrylate compound obtained by reacting 1 mol of a novolake type diepoxy compound with 2 mol of (meth)acrylic acid, and the like, and one, or two or more di(meth)acrylate compound(s) can be used.

Of these di(meth)acrylate compounds, a dimethacrylate compound obtained by reacting 1 mol of diglycidyl ether, which is obtained by reacting a bisphenol A compound with epichlorohydrin, with 2 mol of methacrylic acid is preferably used as the epoxy-based di(meth)acrylate compound (Xll-ii). Suitable (meth)acrylic esters of alcohols are (meth)acrylates obtained by the reaction of an aromatic alcohol, aliphatic alcohol, alicyclic alcohol having one or more, preferably at least two, hydroxyl groups in the molecule, and/or the alkylene oxide adduct thereof, with (meth)acrylic acid.

Suitable alcohols are aromatic, aliphatic and cycloaliphatic polyols, preferably aliphatic polyols, preferably comprising at least two hydroxyl groups.

Examples of aromatic polyols are hydroquinone, 4,4'-dihydroxydiphenyl,

2,2-di(4-hydroxyphenyl)propane, and also novolaks and resols. Other suitable polyols are polymers and copolymers containing hydroxyl groups in the polymer chain or in side groups, examples being polyvinyl alcohol and copolymers thereof or polyhydroxyalkyl methacrylates or copolymers thereof. Further polyols which are suitable are oli-goesters having hydroxyl end groups.

Examples of aliphatic and cycloaliphatic polyols are alkylenediols having preferably 2 to 12 C atoms, such as ethylene glycol, 1 ,2- or 1 ,3-propanediol,

1 ,2-, 1 ,3- or 1 ,4-butanediol, pentanediol, hexanediol, octanediol, dodecanediol, diethylene glycol, triethylene glcyol, polyethylene glycols having molecular weights of preferably from 200 to 1500, 1 ,3-cyclopentanediol, 1 ,2-, 1 ,3- or

1 ,4-cyclohexanediol, 1 ,4-dihydroxymethylcyclohexane,

4,8-bis(hydroxymethyl)tricyclo[5.2.1.0 ² ' ⁶ ]decane, glycerol,

tris( -hydroxyethyl)amine, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol and sorbitol.

The polyols may be partially or completely esterified with (meth)acrylic acid, and in partial esters the free hydroxyl groups may be modified, for example etherified or esterified with other carboxylic acids different from (meth)acrylic acid, such as crotonic acid, itaconic acid, cinnamic acid, and unsaturated fatty acids such as linolenic acid or oleic acid. Examples of preferred esters are: trimethylolpropane triacrylate, trimethylolethane triacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, tetramethylene glycol dimethacrylate, triethylene glycol dimethacrylate,

tetraethylene glycol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol diacrylate, dipentaerythritol triacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, tricyclo[5.2.1.0 ² · ⁶ ] decane dimethanol diacrylate, tripentaerythritol octaacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, dipentaerythritol dimethacrylate, dipentaerythritol

tetramethacrylate, tripentaerythritol octamethacrylate, pentaerythritol diitaconate, dipentaerythritol tris-itaconate, dipentaerythritol pentaitaconate, dipentaerythritol hexaitaconate, ethylene glycol diacrylate, 1 ,3-butanediol diacrylate,

1 ,3-butanediol dimethacrylate, 1 ,4-butanediol diitaconate, sorbitol triacrylate, sorbitol tetraacrylate, pentaerythritol-modified triacrylate, sorbitol tetra methacry- late, sorbitol pentaacrylate, sorbitol hexaacrylate, oligoester acrylates and methacrylates, glycerol diacrylate and triacrylate, 1 ,4-cyclohexane diacrylate, bisacrylates and bismethacrylates of polyethylene glycol with a molecular weight of from 200 to 1500, or mixtures thereof.

Preferred are (meth)acrylate esters of alcohols, obtained from (meth)acrylates having one (meth)acrylic group in one molecule and a polyhydric alcohol.

Suitable polyester (meth)acrylates for the purpose of the invention are

condensation products of polyesterols (polyhydrofunctional polyesters) and

(meth)acrylic acids or anhydrides thereof. Raw material for polyesterols are polyols and polycarboxyl ic acids or anhydrides.

Examples for polyols are ethylene glycol, 1 ,2-propane diol, diethylene glycol,

1.4-butane diol, 1 ,6-hexanediol, neopentylglycol, trimethylpentanediol,

1.4-cyclohexane dimethanol, treyclodecanedimethanol, trimethylolopropane, glycerol, hydroxpivalic acidneopentylglycol ester, pentaerythritol.

Examples for carboxylic acids, esters and anhydrides are phthalic anhydride isophthalic acid, therephthalic acid and their lower alkyl ester derivatives, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, hexahydroterephthalic acid, 5-tert-butyl isophthalic acid, adipic acid azelaic acid, sebacic acid, decane dicarboxylic acid and their lower alkyl ester derivatives, dimerised fatty acids, trimellitic anhydride, pyromellitic anhydride.

Polyesteracrylates can be further modified for example chlorinated or fluorinated, amine modified or can be functionalized for further crosslinking or reaction with acid or hydroxyl groups. The polyester acrylate in context with the current invention is a material with a medium molecular weight ranging from 500 to 6000, preferred are products with a molecular weight from 500 to 3000, more specific from 700 to 2000. The functionality of the polyester acrylate ranges from 1 to 8, preferred are tetra to hexafunctional types.

Commercial examples for polyester acrylates are EBECRYL 436, EBECRYL 438, EBECRYL 446, EBECRYL 450, EBECRYL 505, EBECRYL 524, EBECRYL 525, EBECRYL 584, EBECRYL 586, EBECRYL 657, EBECRYL 770, EBECRYL 800, EBECRYL 810, EBECRYL 811 , EBECRYL 812, EBECRYL 830, EBECRYL 851 , EBECRYL 852, EBECRYL 870, EBECRYL 880, EBECRYL 1657, EBECRYL 2047, EBECRYL 531 , Laromer PE 55 F, Laro-mer PE 56 F, Laromer PE 44 F, Laromer LR 8800, Laromer LR 8981 , Photomer 5018, Pho-tomer 5029, Jagalux UV 1 100, Jagalux UV 1200, Jagalux UV 1300, Setacure AP 578, Seta-cure AP 576, Setacure AP 578, Setacure AP 579, Syntaalat UV 190, Synocure AC-1007, Synocure AC-1309, Craynor CN 292. Further examples of commercially available polyester acrylate binders can be found in Karsten "Lackrohstoff-Tabellen" 10. edition, Vincentz Verlag Hannover, 2000, ISBN 3-87870-561 -1.

Preferred are EBECRYL 800, EBECRYL 810, EBECRYL 830, EBECRYL 885.

Vinylethers

In another preferred embodiment the at least one ethylenically unsaturated photopolymerizable compound is at least one vinyl ether. Suitable vinyl ether for the purpose of the invention are alkyl vinyl ether, preferably methyl vinylether, ethyl vinylether, isobutyl vinylether, or the like.

Styrene

In another preferred embodiment the at least one ethylenically unsaturated photopolymerizable compound is at least one styrene, wherein the at least one styrene is preferably styrene or alpha-methyl styrene, particularly preferably styrene.

Urethane (meth)acrylates

In another preferred embodiment the at least one ethylenically unsaturated photopolymerizable compound is at least one urethan (meth)acrylate.

Suitable urethan (meth)acrylates for the purpose of the inventionen are described in WO2016/071811.

Preferred urethane (meth)acrylates are urethane-based di(meth)acrylates obtainable by the reaction of 1 mol of an organic diisocyanate and 2 mol of hydroxyalkyl (meth)acrylate and are represented by the following formula (Xll-i)

D ⁱ -{NH-C0-0-R ²ⁱ -0-C0-C(R ¹ⁱ )=CH ₂ }2 (Xll-i) wherein

R ¹ⁱ represents a hydrogen atom or a methyl group, R ²ⁱ represents an alkylene group, and D' represents an organic diisocyanate compound residue (group after removing two isocyanate groups from organic diisocyanate

compound); and

In the above general formula (A-1 a), the organic diisocyanate compound residue D' may be any of an aromatic diisocyanate compound residue, an aliphatic diisocyanate compound residue, and an alicyclic diisocyanate compound residue. Examples of the urethane-based di(meth)acrylate-based compounds of formula (XI li) include, but are not limited to, urethane di(meth)acrylates obtained by the reaction of 1 mol of an organic diisocyanate compound composed of one, or two or more aliphatic diisocyanate compound(s) such as hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, isophorone diisocyanate,

hydrogenated diphenylmethane diisocyanate, hydrogenated m-xylylene

diisocyanate, and hydrogenated toluene diisocyanate, and aromatic diisocyanates such as diphenylmethane diisocyanate, toluene diisocyanate, and xylylene diisocyanate with 2 mol of a hydroxyalkyl ester whose (meth)acrylic acid has 2 to 6 carbon atoms, such as hydroxyethyl (meth)acrylate, hydroxypropyl

(meth)acrylate, hydroxybutyl (meth)acrylate, hydroxypentyl (meth)acrylate and hydroxyhexyl (meth)acrylate [(meth)acrylic acid ester obtained by the reaction of

1 mol of an alkylenediol having 2 to 6 carbon atoms with 1 mol of (meth)acrylic acid.

More specific examples thereof include urethane di(meth)acrylate obtained by reacting 1 mol of 2,2,4-trimethylhexamethylene diisocyanate with 2 mol of hydroxyethyl (meth)acrylate, urethane di(meth)acrylate obtained by reacting 1 mol of isophorone diisocyanate with 2 mol of hydroxyethyl (meth)acrylate, urethane di(meth)acrylate obtained by reacting 1 mol of hydrogenated diphenylmethane diisocyanate with 2 mol of hydroxyethyl (meth)acrylate, urethane di(meth)acrylate obtained by reacting 1 mol of 2,2,4- trimethylhexamethylene diisocyanate with

2 mol of hydroxypropyl (meth)acrylate, urethane di(meth)acrylate obtained by reacting 1 mol of isophorone diisocyanate with 2 mol of hydroxypropyl

(meth)acrylate, urethane di(meth)acrylate obtained by reacting 1 mol of

2,2,4-trimethylhexamethylene diisocyanate with 2 mol of hydroxyethyl

(meth)acrylate, urethane di(meth)acrylate obtained by reacting 1 mol of

diphenylmethane diisocyanate with 2 mol of hydroxyethyl (meth)acrylate, urethane di(meth)acrylate obtained by reacting 1 mol of diphenylmethane diisocyanate with 2 mol of hydroxypropyl (meth)acrylate, urethane di(meth)acrylate obtained by reacting 1 mol of toluene diisocyanate with 2 mol of hydroxyethyl (meth)acrylate, urethane di(meth)acrylate obtained by reacting 1 mol of toluene diisocyanate with 2 mol of hydroxypropyl (meth)acrylate, and the like, and one, or two or more urethane di(meth)acrylate(s) can be used.

Of these compounds, urethane dimethacrylate obtained by reacting 1 mol of 2,2,4-trimethylhexamethylene diisocyanate with 2 mol of hydroxyethyl

methacrylate, so-called UDMA, is preferably used as the urethane-based di(meth)acrylate compound (Xlli).

Further suitable ethylenically unsaturated photopolymerizable compounds

Further suitable examples for ethylenically unsaturated photopolymerizable compound are esters of the above mentioned alcohols and polyols, preferably polyol and ethylenically unsaturated carboxylic acids different from (meth)acrylic acid.

Preferred unsaturated carboxylic acids are crotonic acid, itaconic acid, cinnamic acid, and unsaturated fatty acids such as linolenic acid or oleic acid.

Organosiloxanes

Examples of organosiloxane are: alkenyl-containing organopolysiloxane, mercapto-containing organopolysiloxane and alkenyl-containing MQ resin, for example, disclosed in US 6,013,693, US 5,877,228, US 8,293,810 and

EP 1 757 979.

Organosiloxanes that may be used in the present invention include, but are not limited to, acrylamide-functional organopolysiloxane, see for example Japanese Patent Publication Number Sho 57-52371 and EP 0 400 785; an

organopolysiloxane having at least 2 mercaptoalkyl groups in each molecule and an organopolysiloxane having at least 2 alkenyl groups in each molecule,

(US 4,707,503); an alkenyl-functional organopolysiloxane; an acrylic-functional or methacrylic-functional organopolysiloxane; and an organopolysiloxane having at least 2 alkenyl groups in each molecule and an organopolysiloxane having at least 2 silicon-bonded hydrogen atoms in each molecule. Preferred for use in the present invention are acrylamide-functional organopolysiloxane and an

organopolysiloxane having at least 2 mercaptoalkyl groups in each molecule and an organopolysiloxane having at least 2 alkenyl groups in each molecule.

Examples for mercaptoalkyl-functional organopolysiloxanes dimethyl(3- mercaptopropyl)siloxy-endblocked dimethylpolysiloxane, dimethyl(3- mercaptopropyl)siloxy-endblocked dimethylsiloxanemethylphenylsiloxane copolymer, dimethyl(3-mercaptopropyl)siloxy-endblocked

dimethylsiloxanediphenylsiloxane copolymer, methyl(3-mercaptopropyl)siloxane- dimethylsiloxane copolymer, methyl(3-mercaptopropyl)siloxane- methylphenylsiloxane copolymer, methyl(3-mercaptopropyl)siloxane- diphenylsiloxane copolymer, 3-mercaptopropyl(phenyl)siloxane-dimethylsiloxane copolymer, and 3-mercaptopropyl(phenyl)siloxane-diphenylsiloxane copolymer. The aforesaid organopolysiloxanes may be used alone or as mixtures of two or more thereof.

The alkenyl-functional organopolysiloxane is exemplified by, but not limited to, dimethylvinylsiloxy-endblocked dimethylpolysiloxane dimethylvinylsiloxy- endblocked dimethylsiloxanemethylphenylsiloxane copolymer, dimethylvinylsiloxy- endblocked dimethylsiloxane-diphenylsiloxane copolymer, dimethylvinylsiloxy- endblocked dimethylsiloxanemethylvinylsiloxane copolymer, dimethylvinylsiloxy- endblocked dimethylsiloxanephenylvinylsiloxane copolymer, dimethylvinylsiloxy- endblocked methylvinylpolysiloxane, methylvinylsiloxane-dimethylsiloxane copolymer, methylvinylsiloxane-methylphenylsiloxane copolymer,

methylvinylsiloxane-diphenylsiloxane copolymer, phenylvinylsiloxane- dimethylsiloxane copolymer, and phenylvinylsiloxane-diphenylsiloxane copolymer. The aforesaid organopolysiloxanes may be used alone or as mixtures of two or more thereof.

MQ resins are organopolysiloxane resins of three-dimensional network structure essentially containing triorganosiloxy units (i.e., monofunctional siloxane units MesSiO) and S1O4/2 units as described for example in US 8,293,810 and

EP 1 757 979.

In one preferred embodiment of the invention, the photocurable composition comprises one kind of the at least one ethylenically unsaturated

photopolymerizable compound.

In another preferred embodiment, the photocurable composition comprises two or more different ethylenically unsaturated photopolymerizable compounds, e.g. two, three, four or five different ethylenically unsaturated photopolymerizable

compounds.

Accordingly, the photocurable composition comprises two or more ethylenically unsaturated compounds selected from (meth)acrylates, vinylethers, styrenes, and organosiloxanes, particularly preferably a mixture of two or more (meth)acrylates, particularly preferably two or more esters of (meth)acrylic acid and polyols, e.g. a mixture of tricyclo[5.2.1.0 ^{2 6} ] decane dimethanol diacrylate and dipentaerythritol hexaacrylate.

Depending on the choice of the particular ethylenically unsaturated compound(s) the photocurable resin composition is liquid, or solid, preferred are liquid photocurable resin compositions. Preferably, the at least one ethylenically unsaturated compound(s) the photocurable resin composition are selected in that the photocurable resin composition is liquid.

Diluent

In one embodiment of the invention the composition according to the invention may comprise one or more diluents. As described above the photocurable resin composition is liquid or solid, preferably liquid. In embodiments, wherein the photocurable resin composition is solid, it may be - depending on the particular application of the resin - necessary to add a diluent in a sufficient amount to obtain a liquid photocurable resin composition. Suitable diluents are for example water, methanol, ethanol, n-propanol,

isopropanol, or a mixture of two or more thereof, preferably water. The amount of the diluent is selected depending on the nature of the diluent the particular ethylenically unsaturated compound(s) and is typically up to 14.5 wt.-%, also preferred up to 9.9 wt.-%, also preferred up to 4.8 wt.-% and also preferred up to 2.7 wt.-%, based on the total amount of the photocurable resin composition according to the invention.

However, in a preferred embodiment the composition of the invention does not comprise any diluent.

Further additives

The present photocurable resin composition may comprise one or more additives, for example binders, diluents, film forming components, colorants, e.g. pigments or dyes. In addition, additives customary in the art, such as, for example, defoaming agents, a filler, a flame-retardant, thermal inhibitors, light stabilizers, UV absorber, curing depth control agents, blowing agents, leveling agents, rheology modifiers, dispersants, optical brightners, waxes, and other initiators as co-initiator, e.g.

thermal-radical initiators, other photo-radical initiators, photo-acid generators or photo-base generators, or other photo-sensitizers can be used.

These additives are in general known for the skilled person in the field of photocurable resins.

Examples for suitable dispersants are for example as described in

WO 2011/069947

Examples for suitable colorants are dyes, pigments or a combination thereof.

Organic and/or inorganic pigments may be used. Suitable binders are for example binder described on US 6,048,660. The choice of binder is made depending on the field of application and on properties required for this field, such as the capacity for development in aqueous and organic solvent systems, adhesion to substrates and sensitivity to oxygen.

Examples of suitable binders are polymers having a molecular weight of about 5000 to 2000000, preferably 10000 to 1000000. Examples are: homo- and copolymers of acrylates and methacrylates, for example copolymers of methyl methacrylate/ethyl acrylate/methacrylic acid, poly(alkyl methacrylates), poly(alkyl acrylates); cellulose esters and cellulose ethers, such as cellulose acetate, cellulose acetobutyrate, methylcellulose, ethylcellulose; polyvinylbutyral, polyvinylformal, cyclized rubber, polyethers such as polyethylene oxide,

polypropylene oxide and polytetrahydrofuran; polystyrene, polycarbonate, polyurethane, chlorinated polyolefins, polyvinyl chloride, vinyl chloride/vinylidene copolymers, copolymers of vinylidene chloride with acrylonitrile, methyl

methacrylate and vinyl acetate, polyvinyl acetate, copoly(ethylene/vinyl acetate), polymers such as polycaprolactam and poly(hexamethylenadipamide), and polyesters such as poly(ethylene glycol terephtalate) and poly(hexamethylene glycol succinate) and polyimides.

The at least one ethylenically unsaturated photopolymerizable compound according to the present invention can also be used as a mixture with non- photopolymerizable, film-forming components. These may, for example, be physically drying polymers or solutions thereof in organic solvents, for instance nitrocellulose or cellulose acetobutyrate. They may also, however, be chemically and/or thermally curable (heat-curable) resins, examples being polyisocyanates, polyepoxides and melamine resins, as well as polyimide precursors. The use of heat-curable resins at the same time is important for use in systems known as hybrid systems, which in a first stage are photopolymerized and in a second stage are crosslinked by means of thermal aftertreatment.

Examples for further additives are thermal inhibitors, which are intended to prevent premature polymerization, examples being hydroquinone, hydroquinine derivatives, p-methoxyphenol, .beta.-naphthol or sterically hindered phenols, such as 2,6-di-tert-butyl-p-cresol. In order to increase the stability on storage in the dark it is possible, for example, to use copper compounds, such as copper

naphthenate, stearate or octoate, phosphorus compounds, for example

triphenylphosphine, tributylphosphine, triethyl phosphite, triphenyl phosphite or tribenzyl phosphite, quaternary ammonium compounds, for example

tetramethylammonium chloride or trimethylbenzylammonium chloride, or hydroxylamine derivatives, for example N-diethylhydroxylamine. To exclude atmospheric oxygen during the polymerization it is possible to add paraffin or similar wax-like substances which, being of inadequate solubility in the polymer, migrate to the surface in the beginning of polymerization and form a transparent surface layer which prevents the ingress of air. It is also possible to apply an oxygen-impermeable layer. Light stabilizers which can be added in a small quantity are UV absorbers, for example those of the hydroxyphenylbenzotriazole, hydroxyphenyl-benzophenone, oxalamide or hydroxyphenyl-s-triazine type. These compounds can be used individually or in mixtures, with or without sterically hindered amines (HALS).

Examples of such UV absorbers and light stabilizers are

1. 2-(2'-hydroxyphenyl)benzotriazoles for example 2-(2'-hydroxy-5'- methylphenyl)benzo-triazole, 2-(3',5'-di-tert-butyl-2'- hydroxyphenyl)benzotriazole, 2-(5'-tert-butyl-2'- hydroxyphenyl)benzotriazole, 2-(2'-hydroxy-5'-(1 ,1 ,3,3- tetramethylbutyl)phenyl)benzotriazole, 2-(3',5'-di-tert-butyl-2'- hydroxyphenyl)-5-chlorobenzotriazole, 2-(3'-tert-butyl-2'-hydroxy-5'- methylphenyl)-5-chlorobenzotriazole, 2-(3'-sec-butyl-5'-tert-butyl-2'- hydroxyphenyl)benzotrizole, 2-(2'-hydroxy-4'-octoxyphenyl)benzotriazole, 2-(3',5'-di-tert-amyl-2'-hydroxyphenyl)benzotriazole, 2-(3',5'-bis- (. alpha.,. alpha. -dimethylbenzyl)-2'-hydroxyphenyl)-benzotriaz ole, mixture of 2-(3'-tert-butyl-2'-hydroxy-5'-(2-octyloxycarbonylethyl)phen yl)-5-chlorobe nzotriazole, 2-(3'-tert-butyl-5'-[2-(2-ethyl-hexyl-oxy)carbonylethyl]-2'- hydroxyphenyl) -5-chlorobenzotriazole, 2-(3'-tert-butyl-2'-hydroxy-5'-(2- methoxycarbonylethyl)phenyl)-5-chloroben zotriazole, 2-(3'-tert-butyl-2'- hydroxy-5'-(2-methoxycarbonylethyl)phenyl)-benzotriazo le, 2-(3'-tert-butyl- 2'-hydroxy-5'-(2-octyloxycarbonylethyl)phenyl)benzotriazo le, 2-(3'-tert-butyl- 5'-[2-(2-ethylhexybxy)carbonylethyl]-2'-hydroxyphenyl)ben zotriazole, 2-(3'-dodecyl-2'-hydroxy-5'-methylphenyl)benzotriazole, and 2-(3'-tert-butyl- 2'-hydroxy-5'-(2-isooctyloxycarbonylethyl)phenylbenzotria zole,

2,2'-methylenebis[4-(1 ,1 ,3,3-tetramethylbutyl)-6-benzotriazol-2-yl-phenol] ; transesterification product of 2-[3'-tert-butyl-5'-(2-methoxycarbonylethyl)-2'- hydroxy-phenyl]-benzotriaz ole with polyethylene glycol 300;

[R-CH2 CH2 -COO(CH2)3 ]2 - where R=3'-tert-butyl-4'-hydroxy-5'-2H- benzotriazol-2-yl-phenyl .

2. Esters of substituted or unsubstituted benzoicacids, for example

4-tert-butylphenyl salicylate, phenyl salicylate, octylphenyl salicylate, dibenzoylresorcinol, bis(4-tert-butylbenzoy)resorcinol, benzoylresorcinol,

2.4-di-tert-butylphenyl 3,5-di-tert-butyl-4-hydroxybenzoate, hexadecyl

3.5-di-tert-butyl-4-hydroxybenzoate, octadecyl 3,5-di-tert-butyl-4- hydroxybenzoate, and 2-methyl-4,6-di-tert-butylphenyl 3,5-di-tert-butyl-4- hydroxybenzoate.

3. Acrylates, for example isooctyl or ethyl . alpha. -cyano-. beta., .beta. -diphenyl acrylate, methyl . alpha. -carbomethoxycinnamate, butyl or methyl .alpha. - cyano-. beta.,. beta. -methyl-p-methoxycinnamate, methyl .alpha. - carboxymethoxy-p-methoxycinnamate and N-(. beta. -carbomethoxy-. beta. - cyanovinyl)-2-methylindoline.

4. Sterically hindered amines, for example bis-(2,2,6,6-tetramethylpiperidyl) sebacate, bis-(2,2,6,6-tetramethylpiperidyl) succinate, bis-(1 , 2, 2,6,6- pentamethylpiperidyl) sebacate, bis-(1 ,2,2,6,6-pentamethylpiperidyl) n-butyl-3,5-di-tert-butyl-4-hydroxybenzylmalonate, condensation product of 1 -hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid, condensation product of N,N'-bis-(2,2,6,6-tetramethyl-4-piperidyl)hexa- methylenediamine and 4-tert-octylamino-2,6-dichloro-1 ,3,5-s-triazine, tris-(2,2,6,6-tetramethyl-4-piperidyl) nitrilotriacetate, tetrakis-(2,2,6,6- tetramethyl-4-piperidyl)-1 ,2,3,4-butane tetraoate, 1 ,1 '-(1 ,2- ethandiyl)bis(3,3,5,5-tetramethyl-piperazinone), 4-benzoyl-2, 2,6,6- tetramethylpiperidine, 4-stearyloxy-2,2,6,6-tetramethylpiperidine, bis-(1 ,2,2,6,6-pentamethylpiperidyl) 2-n-butyl-2-(2-hydroxy-3,5-di-tert- butylbenzyl) malonate, 3-n-octyl-7,7,9,9-tetramethyl-1 ,3,8-triazaspiro- [4.5]decane-2,4-dione, bis-(1 -octyloxy-2,2,6,6-tetramethylpiperidyl) sebacate, bis-(1 -octyloxy-2,2,6,6-tetramethylpiperidyl) succinate, condensation product of N,N'-bis-(2,2,6,6-tetramethyl-4- piperidyl)hexamethylenediannine and 4-morpholino-2,6-dichloro-1 ,3,5- triazine, condensation product of 2-chloro-4, 6-di-(4-n-butylamino-2, 2,6,6- tetramethylpiperidyl)-1 ,3,5-triazi ne and 1 ,2-bis-(3-aminopropyl- amino)ethane, condensation product of 2-chloro-4,6-di-(4-n-butylamino- 1 ,2,2,6,6-pentamethylpiperidyl)-1 ,3,5-tria zine and 1 ,2-bis-(3- aminopropylamino)ethane, 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1 ,3,8- triazaspiro[4.5]decane-2,4-di one, 3-dodecyl-1 -(2,2,6,6-tetramethyl-4- piperidyl)pyrrolidine-2,5-dione and 3-dodecyl-1 -(1 , 2,2,6, 6-penta-methyl-4- piperidyl)-pyrrolidine-2,5-dione. Oxalamides, for example 4,4'-dioctyloxyoxanilide, 2,2'-diethoxyoxanilide, 2,2'-dioctyloxy-5,5'-di-tert-butyloxanilide, 2,2'-didodecyloxy-5,5'di-tert- butyloxanilide, 2-ethoxy-2'-ethyl-oxanilide, N,N'-bis-(3- dimethylaminopropyl)oxalamide, 2-ethoxy-5-tert-butyl-2'-ethyloxanilide and its mixture with 2-ethoxy-2'-ethyl-5,4'-di-tert-butyloxanilide, mixtures of o- and p-methoxy- and of o- and p-ethoxy-disubstituted oxanalides. 2-(2-Hydroxyphenyl)-1 ,3,5-triazines, for example 2,4,6-tris(2-hydroxy-4- octyloxyphenyl)-1 ,3,5-triazine, 2-(2-hydroxy-4-octyloxyphenyl)-4,6-bis-(2,4- dimethylphenyl)-1 ,3,5-triazine , 2-(2,4-dihydroxyphenyl)-4,6-bis(2,4- dimethylphenyl)-1 ,3,5-triazine, 2,4-bis(2-hydroxy-4-propyloxy-phenyl)-6- (2,4-dimethylphenyl)-1 ,3,5-triazin e, 2-(2-hydroxy-4-octyloxyphenyl)-4,6- bis(4-methylphenyl)-1 ,3,5-triazine, 2-(2-hydroxy-4-dodecyloxyphenyl)-4,6- bis(2,4-dimethylphenyl)-1 ,3,5-triazin e, 2-[2-hydroxy-4-(2-hydroxy-3- butyloxy-propyloxy)phenyl]-4,6-bis(2,4-dimethy lphenyl)-1 ,3,5-triazine, 2-[2-hydroxy-4-(2-hydroxy-3-octyloxy-propyloxy)phenyl]-4,6-b is(2,4-dimethy lphenyl)-1 ,3,5-triazine, 2-[4-dodecyl/tridecyl-oxy-(2-hydroxypropyl)oxy-2- hydroxy-phenyl]-4,6-bis(2 ,4-dimethylphenyl)-1 ,3,5-triazine.

7. Phosphites and phosphonites, for example triphenyl phosphite, diphenyl alkyl phosphites, phenyl dialkyl phosphites, tris(nonylphenyl) phosphite, trilauryl phosphite, trioctadecyl phosphite, distearyl pentaerythrityl diphosphite, tris-(2,4-di-tert-butylphenyl) phosphite, diisodecyl

pentaerythrityl diphosphite, bis-(2,4-di-tert-butylphenyl) pentaerythrityl diphosphite, bis-(2,6-di-tert-butyl-4-methylphenyl) pentaerythrityl

diphosphite, bis-isodecyloxy pentaerythrityl diphosphite, bis-(2,4-di-tert- butyl-6-methylphenyl) pentaerythrityl diphosphite, bis-(2,4,6-tri-tert- butylphenyl) pentaerythrityl diphosphite, tristearyl sorbityl triphosphite, tetrakis-(2,4-di-tert-butylphenyl)-4,4'-biphenylene diphosphonite,

6-isooctyloxy-2,4,8,10-tetra-tert-butyl-12H-dibenzo[d,g]-1 ,3,2-dioxaphosph ocine, 6-fluoro-2,4,8,10-tetra-tert-butyl-12-methyl-dibenzo[d,g]-1 ,3,2- dioxaphosp hocine, bis-(2,4-di-tert-butyl-6-methylphenyl) methyl phosphite and bis(2,4-di-tert-butyl-6-methylphenyl) ethyl phosphite.

Those additives as well as the amount of the different additives can be selected from the skilled person in the art in dependence of the used starting materias and the intended use. In a typical embodiment the photopolymerizable resin

composition comprises up to 14.5 wt.-%, also preferred up to 9.9 wt.-%, also preferred up to 4.8 wt.-% and also preferred up to 2.7 wt.-%, based on the total amount of the photocurable resin composition according to the invention.

The photopolymerizable resin composition of the invention comprises preferably from 0.05 to 15 wt.-%, preferably from 0.1 to 10 wt.-%, more preferably 0.2 to 5 wt.-% and particularly preferably from 0.3 to 3 wt.-% of the photoinitiator system, based on the total weight of the composition. In another preferred embedment of the invention comprises

a) 85.00 to 99.95 wt.-%, preferably from 90.00 to 99.9 wt.-%, preferably 95.00 to 99.80 wt.-%, preferably 97.00 to 99.70 wt.-% of the at least one

ethylenically unsaturated photopolymerizable compound; and

b) 0.05 to 15.00 wt.-%, preferably from 0.10 to 10.00 wt.-%, preferably 0.20 to 5.00 wt.-% and particularly preferably from 0.30 to 3.0 wt.-% of the photoinitiator system,

based on the total weight of the composition, preferably based on the the sum of the at least one ethylenically unsaturated photopolymerizable compound and the photoinitiator system.

In a preferred embodiment the photocurable resin composition of the invention comprises a photoinitiator system, wherein the photoinitiator system comprises

(a) from 50 to 99 wt.-%, preferably 70 to 97 wt.-%, more preferably 80 to

95 wt.-% of the at least one photoinitiator G-1 A of the general formula (la) and/or the at least one photoinitiator G-1 B of the general formula (lb); and

(b) from 1 to 50 wt.-%, preferably, 3 to 30 wt.-%, more preferably 5 to 20 wt.-% of at least one photosensitizer PS of the formula (lla) or (lib),

wherein the given amounts are based on the total amount of the photoinitiator system.

In a further aspect, the present invention relates to a method for the preparation of the photocurable resin composition according to the invention, comprising the step of mixing

a) the at least one unsaturated photopolymerizable compound,

b) the at least one at least one photoinitiator G, wherein the at least one

photoinitiator G is at least one photoinitiator G-1 A of the general formula (la) or at least one photoinitiator G-1 B of the general formula (lb), and

c) the at least one photosensitizer PS, and

d) optionally one or more diluent; and

e) optionally further additives;

until a homogenous composition is obtained. The term“homogenous mixture” for the purpose of the invention relates to a mixture wherein the single components of the mixture cannot be differentiated from each other anymore. In other words, all components of the mixture are present in the same phase.

The temporal sequence of the addition of the single components, i.e. the at least one unsaturated photopolymerizable compound, the at least one photoinitiator and the at least one photosensitizer, and the optional compounds is not critical.

The photocurable composition of the invention can - in general - be used for a multitude of purposes. In one preferred embodiment however, the photocurable composition is used in a method for 3D printing by 3D stereolithography.

Accordingly, in a further aspect of the invention a method for producing a three dimensional object by means of stereolithography is provided, comprising the steps of

a) providing the photocurable resin composition according to the invention; b) imagewise irradiation of a first liquid layer of the photocurable resin with light to form a cured layer;

c) forming a further liquid layer on the cured layer;

d) imagewise irradiation of the further liquid layer of the photocurable resin with light to form a further cured layer;

e) multiple repetitions of steps c) and d) wherein by stacking of the cured

layers a three dimensional object is obtained;

wherein the light has a wavelength from 375 to 450 nm (or a more specific wavelength as taught herein such as, e.g. from 375 to 440 nm, from 380 to 430 nm, from 390 to 420 nm, or from 400 to 410 nm) and is operated by a control system.

Optionally, it is possible to apply heat and/or light to the object to complete the curing as a post curing process. In principle, any known stereolithographic method and apparatus can be used. Methods for producing three dimensional objects by means of stereolithography are known to the skilled person in the art and for example described in

EP 1 939 234, WO 2016/071811 , and WO 2007/031505. Stereolithography equipment is commercially available from various manufacturers. Typically, the liquid photocurable resin composition according to the invention is placed in a shaping contained, which comprises a light permeable bottom.

Afterwards imagewise irradiation of a first liquid layer of the photocurable resin with light is conducted, wherein a first cured layer is formed. Imagewise irradiation in this context means that the composition is irradiated with light in a

predetermined shape pattern through the light permeable bottom to obtain a cured layer having the desired shape. Subsequently, new layers of the liquid

photocurable resin are coated onto the previous, cured layer and exposed to radiation until a three dimensional object is formed.

With the help of a control system, for example a computer aided manufacturing or computer-aided design (CAM/CAD) software the light is controlled to draw a pre- programmed design or shape in the photocurable liquid.

The light used in the method according to the invention has a wavelength from 375 to 450 nm (or a more specific wavelength as taught herein such as, e.g. from 375 to 440 nm, from 380 to 430 nm, from 390 to 420 nm, or from 400 to 410 nm) and is preferably originating from UV, blue emitting LED or blue LD, preferably from UV or blue emitting LED with a Digital Light Processing (DLP) unit or a Liquid Crystal (LC) panel, or UV or blue LD with Galvanometer mirror or X-Y plotter.

In principle any stereolithography machine that uses 375 to 450 nm (or a more specific wavelength as taught herein such as, e.g. from 375 to 440 nm, from 380 to 430 nm, from 390 to 420 nm, or from 400 to 410 nm) light may be used to carry out the inventive process. Commercially available stereolithograpy 3D printers are, for example, Vida and Vida HD by EnvisionTEC and M1 and M2 by Carbon (UV-LED with DLP), DigitalWax 009J by DWS and Value3D MagiX ML-200 by MUTOH (blue LED with DLP), DentaForm by Structo (blue LED with LC panel), VECTOR 3SP by EnvisionTEC (UV-LD with Galvanometer mirror), Form 2 by Formlabs and DigitalWax 030X by DWS (blue LD with Galvanometer mirror) and DigitalWax 008J by DWS (blue LD scanned by X-Y plotter). Thus, in a preferred embodiment of the method according to the invention the irradiation in step b) and c) is conducted by means of imagewise irradiation of UV or blue emitting LEDs or UV or blue LDs.

Accordingly, in a preferred embodiment, the light originates from a light source selected from the group consisting of a light-emitting diode (LED), a liquid crystal (LC) light source, and a laser diode (LD).

In another preferred embodiment of the invention, the photocurable composition of the present invention is used in a method for 3D printing by material jetting.

In principle, any known material jetting method and apparatus can be used.

Methods for producing three dimensional objects by means of material jetting are known to the skilled person in the art and for example described in

WO 2000/52624, JP-A 2002-067174 and JP-A_2010-155926. Material jetting equipment is commercially available from various manufacturers, for example, Objet 30 by Stratasys and AGILISTA-3200 by KEYENCE.

In a further aspect of the invention a method for producing a three dimensional object by means of material jetting is provided, comprising the steps of

(a) applying a first layer of the photocurable composition according to the

invention onto a base plate in a specific drawn pattern;

(b) curing of the first layer of the photocurable composition by irradiation with light;

(c) applying a further layer of the photocurable composition in a specific drawn pattern;

(d) curing of the further layer of the photocurable composition by irradiation with light; e) multiple repetitions of steps c) and d) wherein by stacking of the cured layers a three dimensional object is obtained;

wherein the light has a wavelength from 375 to 450 nm (or a more specific wavelength as taught herein such as, e.g. from 375 to 440 nm, from 380 to

430 nm, from 390 to 420 nm, or from 400 to 410 nm).

In step a) of the inventive method typically fine droplets of the liquid photocurable composition are discharged from nozzles onto a base plate in a specified drawn pattern with the help of e.g. computer aided manufacturing or computer-aided design (CAM/CAD) software, followed by light irradiation to effect curing in step b). Then, further fine droplets of the liquid photocurable resin are discharged thereon from the nozzles in a specified drawn pattern, producing a superimposed layer in step c), followed again by light irradiation according to step d). Multiple repetitions of steps c) and d) finally leads to a fabricated 3D object. In a preferred

embodiment of the method according to the invention the curing steps are conducted by light having a wavelength from 375 to 450 nm (or a more specific wavelength as taught herein such as, e.g. from 375 to 440 nm, from 380 to

430 nm, from 390 to 420 nm, or from 400 to 410 nm), preferably originating form UV or blue emitting LEDs.

Optionally, it is possible to apply heat and/or light to the object to complete the curing as a post curing process.

Use of the invention

The composition according to the invention can be used in general in all application wherein the photocurable resin composition is suitable and applicable. Examples are the use for producing pigmented and non-pigmented paints and varnishes, powder coatings, printing inks, printing plates, adhesives, pressure sensitive adhesives, dental compositions, gel coats, photoresists, electroplating resists, etch resists, both liquid and dry films, solder resists, resists to manufacture color filters, resists to generate structures in the manufacturing processes of plasma-display panels, electroluminescence displays and LCD, spacers for LCD, for holographic data storage (HDS), as composition for encapsulating electrical and electronic components, for producing magnetic recording materials, micromechanical parts, waveguides, optical switches, plating masks, etch masks, colour proofing systems, glass fibre cable coat ings, screen printing stencils, for producing three-dimensional objects by means of stereo-lithography or material jetting, as image recording material, for holographic recordings, microelectronic circuits, decolorizing materials, decolorizing materials for image recording materials, for image recording materials using microcapsules, as a photoresist material for a UV and visible laser direct imaging system, as a photoresist material used for forming dielectric layers in a sequential build-up layer of a printed circuit board.

In a preferred embodiment of the invention the photocurable resin composition is used for producing a three dimensional object by means of stereolithography or material jetting. Three dimensional objects for the purpose of the invention are not limited but, for example, a toy, a medical instrument, an electronic part, an automotive part, a motorcycle part, a train part, an aircraft part, an other industrial part, a dental material such as an artificial tooth and a dental corrective devices, a jewelry, a hearing aid, an earpiece, a positive die for lost wax mold to produce thereof, and a prototype for design verification or performance check for development and manufacture of industrial products.

The following examples are included for illustrative purposes only and do not limit the scope of the claims. Unless otherwise stated, all parts and percentages are by weight. In the examples, all experiments are carried out under following or similar test conditions in a yellow room at 25 degree C unless otherwise indicated. Examples

A. Compound Examples 1. Photoinitiator

In the examples the photoinitiator compounds summarized in Table 1 have been used, wherein the numbering of the compounds in Table 1 corresponds to the numbering of the particular compounds in the general description:

Table 1 : Used photoinitiator compounds

The used photoinitiator compounds and photosensitizers were purchased from chemical suppliers, e.g. Aldrich, Tokyo Chemical Industry; otherwise they were prepared according the following synthesis methods or will be prepared by alternative organic reactions which are not limited. a) Synthesis of example G-1 A-3

In a 500ml reactor with Dean-Stark apparatus 4.00 g (26.6 mmol) of phenylglyoxylic acid, 2.47 g (24.2 mmol) of 1 -Hexanol, 0.33 g (1.92 mmol) of p-toluenesulfonic acid monohydride and 250 ml of toluene were placed. The mixture was stirred at reflux for 24 hours. After the reaction was completed, the reaction mixture was concentrated under reduced pressure, then the crude product was purified by column chromatography on silica gel with heptane/ethylacetate=20/1 to 1/1 as eluent. 5.25 g of G-1 A-3 was obtained as colorless oil (92.7% yield).

The structure is confirmed by the 1 H-NMR spectrum (CDCb) d [ppm]: 8.00 (dd, 2H), 7.66 (td, 1 H), 7.51 (td, 2H), 4.39 (t, 2H), 0.9-1.78 (m, 11 H). b) Synthesis of example G-1 A-25

In 250ml 2-neck flask 5.00 g (26.8 mmol) of diphenylsulfide, 3.66 g

(26.8 mmol) of ethylchloroglyoxylate, 3.58 g (26.8 mmol) of

aluminumthchloride and 60 ml of dichloromethane were placed. The mixture was stirred at 0°C to room temperature for 3 hours. After the reaction was completed, the reaction mixture was poured into cold water, and the organic layer was washed with saturated NaHCOsaq, and brine. The organic layer was dried over MgS04, concentrated under reduced pressure, then the crude product was purified by column chromatography on silica gel with heptane/ethylacetate= 1/4 as eluent. 2.10 g of G-1 A-25 was obtained as pale yellow oil (27.3% yield).

The structure is confirmed by the 1 H-NMR spectrum (CDCh) d [ppm]: 7.86 (d, 2H), 7.53 (m, 2H), 7.43 (m, 3H), 7.19 (d, 2H), 4.42 (q, 2H), 1.39 (t, 3H).

Other used photoinitiator compounds have been prepared according to the exemplary described methods given for G-1A-3 and G-1A-25.

2. Photosensitizers PS

In the examples the photosensitizers PS summarized in Table 2 have been used, wherein the numbering of the compounds in Table 2 correspond to the numbering of the particular compounds in the general description: Table 2: Used photosensitizers PS

Synthesis of example PS-13

In 250ml 4-neck flask 8.05 g (48.1 mmol) of carbazole, 5.00 g (22.9 mmol) of 4, 4 ^' -difluorobenzophenone, 6.43 g (57.3 mmol) of t-BuOK and 100 ml of dimethylacetamide were placed. The mixture was stirred at 100-120°C for 8 hours. After the reaction was completed, the reaction mixture was poured into cold water. The generated yellow solid was washed with H2O, EtOH and TBME, then the solid was dried under reduced pressure. 7.00 g of PS-13 was obtained as a pale yellow solid (59.8% yield).

The structure is confirmed by the 1 H-NMR spectrum (CDCb) d [ppm]: 8.19(d, 4H), 8.16(d, 4H), 7.80(d, 4H), 7.56(d, 4H), 7.46(t, 4H), 7.34(t, 4H)

B. Application examples

1. Working Examples: Preparation of photocurable resin and light exposure The following substances are introduced into a 20 ml amber screw bottle and applied to sonication at 40 degree C for 15 minutes then kept at 25 degree C for overnight: Table 3: Amounts of used components in photocurable resin

0.13 g of the photocurable resin is charged on a hole of hole slide glass

(Matsunami Glass Ind., Ltd). Light exposure is carried out by using a LED exposure source equipped with 405nm, 385nm and 365nm LED lamp units (UVT300-C, Micro Square Inc.) wherein the exposure power is adjusted to be 10 mW/cm ² by use of a light power meter (UV-M03A, ORC MANUFACTURING Co., Ltd.) and the exposed energy is controlled by an exposure timer of

UVT300-C. The exposed slide glass is kept for 20 hours in dark then the color of the cured resin is assessed under white light (LED viewer pro 4x5, FUJI FILM) by eye observation. The results are summarized in Table 4.

Table 4: Color of cured photosensitive resins, light exposure: 405 nm at

100 mJ

2. Comparative examples: Preparation of photosensitive resin and light exposure Comparative experiments are carried out in the same manner as the Working Examples Example but using following commercially available photoinitiators.

Irgacure 184 1 -Hydroxy-cyclohexyl-phenyl-ketone, BASF SE

Irgacure 651 2,2-Dimethoxy-1 ,2-diphenylethan-1 -one, BASF SE

Irgacure 819 Bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide, BASF SE

The amounts of the used components are summarized in Table 5 (resin composition comprising photosensitizer) and Table 6 (resin composition comprising no photosensitizer). Table 5: Used components in compositions comprising a photosensitizer

Table 6: Used components in compositions comprising no photosensitizer

The results are summarized in Table 7:

Table 7: Color of photosensitive resins after exposure to light with 405 nm at

100 mJ

As can be seen from the results summarized in table 7, resin compositions comprising only a photoinitiator compound according to the invention

(Comparative Examples C1 to C14) without an additional photosensitizer are not curable with light having a wavelength of 405 nm. The same applies for

Comparative Examples C15 and C17, comprising only commercially available photoinitiator compound.

Only Comparative Example C19, i.e. Irgacure 819-containing-resin is photocurable in absence of a photosensitizer, however, the obtained cured film is yellow. The same applies for Comparative Example C20, comprising Irgacure 819 and a photoinitiator PS-4.