This application claims priority to a Korean patent application No. 10- 2015-0102683 filed on July 20, 2015, the whole content of this application being incorporated herein by reference for all purposes.

TECHNICAL FIELD

The present invention relates to novel colorant compounds based on triarylmethane substructure, and methods for preparing the same. The present invention also concerns colorant compositions for color filter comprising the same, and display devices equipped with such color filter. BACKGROUND OF THE INVENTION

Color filters are widely used in various applications, particularly used in display devices, such as liquid crystal display (LCD) and organic light-emitting display (OLED) and the like. Due to rapid progression of the display

technologies, further improvement of the color filter, especially in terms of brightness, contrast ratio, and color reproduciability, is required in the art.

When forming the color filter, a color composition having a colorant material comprising a pigment and/or a dye is often used. Pigment usually shows better stability against heat and/or environment, but an achievable brightness is often insufficient compared with dye. On the other hand, when dye is used as the color filter colorant, satisfactory brightness of the color filter may be attained, but its stability, especially thermal stability, and/or contrast ratio are often insufficient.

Particularly, a dyestuff having a triarylmethane structure is believed to be a good candidate for the color filter application. However, its stability, especially thermal stability, is not high enough to endure high-temperature process(es) of color filter fabrication. PCT International patent application publication No. WO 2012/144521 Al suggests a colorant dispersion liquid, a colored resin composition for use in color filters, a color filter formed using said colored resin composition for use in color filters; and a liquid crystal display device and an organic light-emitting display device that have said color filter. In particular, it discloses the colorant dispersion liquid containing a colorant of the dimerized triarylmethane structure having the chemical formula below.

DESCRIPTION OF THE INVENTION

The purpose of the present invention is to provide a novel compound comprising triarylmethane substructure with an excellent thermal stability. Another purpose is to provide a colorant compound, especially a blue colorant compound, which endures high-temperature process of color filter fabrication in display application as well as exhibits sufficient brightness and/or contrast ratio.

Indeed, it has been surprisingly found by the present inventors that the compounds of the present invention show outstanding thermal stability. It has also been found that the compounds according to the present invention can be advantageously used for the formation of color filter having excellent brightness and/or contrast ratio.

In the present invention, "alkyl groups" is understood to denote in particular a straight chain, branched chain, or cyclic hydrocarbon groups usually having from 1 to 20 carbon atoms. Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, neopentyl, hexyl, cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. Some or all of the hydrogen atoms of the alkyl group may or may not be substituted with other groups, such as halogen atom, amino groups or hydroxyl groups. In the present invention, "alkoxy groups" is understood to denote in particular a straight chain, branched chain, or cyclic hydrocarbon group usually having from 1 to 20 carbon atoms, preferably from 1 to 8 carbon atoms, singularly bonded to oxygen (Alk-O-).

In the present invention, "aryl groups" is understood to denote in particular any functional group or substituent derived from an aromatic ring. In particular, the aryl groups can have 6 to 20 carbon atoms (preferably 6 to 12 due to its easiness of synthesis at a low cost) in which some or all of the hydrogen atoms of the aryl group may or may not be substituted with other groups, especially halogen atom, alkyl groups, alkoxy groups, aryl groups, aryloxy groups, thioalkoxy groups, heterocycles, amino groups or hydroxyl groups. The aryl groups are preferably optionally substituted phenyl groups, naphthyl groups, anthryl group and phenanthryl group.

In the present invention, "heterocycles" is understood to denote in particular a cyclic compound, which has at least one heteroatom as a member of its one or more rings. Frequent heteroatoms within the ring include sulfur, oxygen and nitrogen. The heterocycles can be either saturated or unsaturated, aromatic or non-aromatic, and may be 3-membered, 4-membered, 5-membered, 6-membered or 7-membered ring. The heterocycles can be further fused with other one or more ring systems. Examples of the heterocycles include pyrrolidines, oxolanes, thiolanes, pyrroles, furans, thiophenes, piperidines, oxanes, thianes, pyridines, pyrans, pyrazoles, imidazoles, and thiopyrans, and their derivatives. The heterocycles can further be substituted by other groups, such as alkyl groups, alkoxy groups, aryl groups, thioalkoxy groups, amino groups or aryloxy groups as defined above.

In the present invention, "halogenated" is understood to denote in particular at least one of the hydrogen atoms of the following chemical group has been replaced by a halogen atom, preferably selected from fluorine and chlorine, more preferably fluorine. If all of the hydrogen atoms have been replaced by halogen atoms, the halogenated chemical group is perhalogenated. For instance, "halogenated alkyl groups" include (per)fluorinated alkyl groups such as (per)fluorinated methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl or tert-butyl; and for instance -CF ₃ , -C ₂ F ₅ , heptafluoroisopropyl (-CF(CF ₃ ) ₂ ), hexafluoroisopropyl (-CH(CF ₃ ) ₂ ) or -CF ₂ (CF ₂ ) ₄ CF ₃ .

In the present invention, "millbase composition" is understood to denote in particular an intermediate composition which comprises at least a part of components to be included in a final composition for forming a color filter. The final composition for forming a color filter can be formulated by combining the millbase composition with other components. In the present invention, the millbase composition often comprises at least colorant components to be included in the final composition for forming a color filter.

One aspect of the present invention concerns a compound having the formula (I) below:

In the present invention, X is independently oxygen atom, -NH-, or sulfur atom. Especially, X is preferably sulfur atom.

In the present invention, Rl 1 is independently selected from the group consisting of hydrogen atom, alkyl groups, and aryl groups. The alkyl groups and aryl groups may be substituted with other groups. It is preferred that the alkyl groups have 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms. The alkyl groups may be substituted with one or more halogen atoms, in particular with fluorine atom, or with amino group. The aryl groups may be substituted with one or more halogen atoms, such as fluorine atom, optionally fluorinated alkyl groups having 1 to 4 carbon atoms, optionally fluorinated alkoxy groups having 1 to 4 carbon atoms, and hydroxyl group. Preferably, Rl 1 is independently selected from the aryl groups substituted with alkyl group or halogen atom. Particular examples of Rl 1 includes halogenated benzenes, such as fluorinated benzenes and chlorinated benzenes, alkyl-substituted benzenes, and alkoxy-substituted benzenes, but the present invention is not limited thereto.

In the present invention, R21 is independently selected from the group consisting of hydrogen atom, alkyl groups, and aryl groups. The alkyl groups and aryl groups may be substituted with other groups. It is preferred that the alkyl groups have 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms. The alkyl groups may be substituted with one or more halogen atoms, in particular with fluorine atom, or with amino group. The aryl groups may be substituted with one or more halogen atoms, such as fluorine atom, optionally fluorinated alkyl groups having 1 to 4 carbon atoms, optionally fluorinated alkoxy groups having 1 to 4 carbon atoms, and hydroxyl group. Preferably, R21 is independently selected from the aryl groups substituted with alkyl group or halogen atom. Particular examples of R21 includes halogenated benzenes, such as fluorinated benzenes and chlorinated benzenes, alkyl-substituted benzenes, and alkoxy-substituted benzenes, but the present invention is not limited thereto.

In the present invention, each R31, R32, R33, R34, R35, R36, R37, and R38 is independently selected from the group consisting of hydrogen atom, halogen atom, alkyl groups, alkoxy groups, cyano group, nitro group, sulfonyl group, and hydroxyl group. The alkyl groups and alkoxy groups may be substituted with other groups. R34 and R35 may be bound together to form -0-, -NH-, -S-, or -SO ² -. It is preferred that R31 to R38 are hydrogen atom.

In the present invention, each R41, R42, R43, and R44 is independently selected from the group consisting of hydrogen atom, alkyl groups, and aryl groups. The alkyl groups and aryl groups may be substituted with other groups. Examples thereof include optionally substituted alkyl groups having 1 to 10 carbon atoms, such as ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, pentyl group, hexyl group, 2-ethylhexyl group, 2-methoxyethyl group, 2-ethoxyethyl group, 2-cyanoethyl group, and 2,2,2- trifluoroethyl group, but the present invention is not limited thereto. A fluorine- containing groups, in particular an alkyl group or an aryl group substituted by at least one fluorine atom, may be used in the present invention. Each R41 and R42, or R43 and R44 may be bound together to form a ring structure. Such ring structure may comprise one or more heteroatoms, such as nitrogen, sulfur and oxygen. Examples of the ring comprise the following structure, but the present invention is not limited thereto:

It is preferred that R41 to R44 are ethyl group. In the present invention, L denotes a linking group to connect two or more same or different triarylmethane substructures. L has valency of "n" which is understood to stand for the number of triarylmethane substructures in the molecule. The linking group "L" in the present invention comprises at least one aromatic ring. Such aromatic rings can be further substituted by substituents. The nitrogen atom of the amine group of the heterocycle substructure in the formula (I) can be connected to any atom in the substituent of the aromatic ring of the L or be directly connected to the atom which constitutes the aromatic ring of the L. Examples of the aromatic ring include hydrocarbon-based aromatic rings, such as benzene ring, naphthalene ring, tetralin ring, indene ring, fluorene ring, anthracene ring, phenanthrene ring, biphenyl, and terphenyl, and

heterocyclic aromatic rings, including 5-membered rings, such as furan, thiophene, pyrrole, oxazole, thiazole, imidazole, and pyrazole; 6-membered rings, such as pyran, pyridine, pyridazine, pyrimidine, and pyrazine; and fused rings, such as benzofuran, thionaphthene, indole, carbazole, cumarine, quinoline, isoquinoline, acridine, quinazoline, and quinoxaline; but the present invention is not limited thereto. Such aromatic ring may be further substituted by any substituents. Examples of such substituents include halogen atoms, such as fluorine atom, chlorine atom, and bromine atom, alkyl groups, carboxyl group, and amino groups, but the present invention is not limited thereto. Preferably, "L" comprises hydrocarbon-based aromatic rings with 6 to 14 carbon atoms. More preferably, "L" comprises benzene group, or naphthalene group, particularly benzene group. Particular examples of "L" include the following structures, but the present invention is not limited thereto:

In the present invention, "n" stands for the number of triarylmethane substructures, and as such, is an integer of 2 or more, "n" is often no more than 4, more preferably no more than 3. It is particularly preferred when "n" is 2.

In the present invention, "a" stands for the valency of the counter-anion "An," and thus, is an integer of 1 or more, "a" may be an integer of 1. "a" is preferably an integer of 2 or more, more preferably 2 or 3, most preferably 2.

In the present invention, "m" stands for the number of cationic part, "b" stands for the number of anionic part, and as such, each is an integer of 1 or more, "m" and "b" can be suitably selected depending on the number of cationic triarylmethane substructures ("n") and the valency of the counter-anion ("a"). Between the "n", "m", "a", and "b", the following Equation 1 should be met: n x m = a x b (Equation 1) In the present invention, "An" denotes any counter-anion. Type of the counter-anion is not particularly limited in the present invention, and can be organic anions, or inorganic anions. For the examples of such counter-anion, reference can be made to Japanese patent application publication No. JP 2014- 108975 A, of which disclosure is incorporated herein by reference by its entirety. In the present invention, An ^a" is preferably selected from the group consisting of halides, borate anions, carboxylate anions, sulfate anions, sulfonate anions, sulfonimide anions, phosphate anions, and any combination thereof. The anionic compounds comprising at least one sulfonate group, especially those comprising two or more sulfonate groups, are particularly preferred in the present invention. In a particular embodiment of the present invention, the counter-anion (An) may comprise anionic dye or pigment compounds which comprise at least one anionic functional group, such as carboxylate group, sulfate group, phosphate group, and sulfonate group. Examples of the dyes and the pigments can be found in PCT international patent application publication No. WO 2012/144521 Al and

Japanese patent application publication No. JP 2014-108975 A. Without wishing to be bound by any particular theory, by the selection of the anionic dye or pigment compounds as the counter-anion (An), thermal stability of the compound of the present invention is believed to be able to be further improved at least partially due to the increase of its molecular weight.

The compound of the present invention preferably comprises the divalent cation having the formula (II- 1) or (Π-2) below:

(II-l)

(II-2)

In the formulae (II-l) and (II-2) above, each X, Rl 1, R21, R31 to R38, and R41 to R44 have the same meaning as defined in the above.

In the present invention, each R51, R52, R53, and R54 is independently selected from the group consisting of hydrogen atom, halogen atom, alkyl groups, alkoxy groups, cyano group, nitro group, sulfonyl group, and hydroxyl group. The alkyl groups and aryl groups may be substituted with other groups.

Examples thereof include optionally substituted alkyl groups having 1 to 10 carbon atoms, such as ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, pentyl group, hexyl group, 2-ethylhexyl group, 2-methoxyethyl group, 2-ethoxyethyl group, 2-cyanoethyl group, and 2,2,2- trifluoroehtyl group, but the present invention is not limited thereto.

Another aspect of the present invention concerns a method of preparing the compound of the present invention. Such a method includes reacting the compound of formula (III) and the compound of formula (IV) below:

In the formulae (III) and (IV), each X, L, Rl 1, R21, R31 to R38, R41 to R44, and "n" has the same meaning as defined in the above. The desired counter-anion may be introduced as necessary.

For further details of the method of preparing the compound, reference can be made to the following Examples.

The compound of the present invention is advantageously used as a blue colorant, of which use can be optionally combined with at least one further dye or pigment. Therefore, further aspect of the present invention provides a colorant material comprising the compound according to the invention, and optionally at least another dye or pigment. Examples of the dyes and of the pigments can be found in PCT international patent application publication No. WO 2012/144521 Al and Japanese patent application publication No. JP 2014- 108975 A, respectively, both are incorporated herein by reference by their entireties. In particular, the compound of the present invention can be used as a colorant material in combination with a blue pigment, such as ε-type copper phthalocyanine particles or a violet pigment such as pigment violent(PV)-23, the pigment optionally containing at least one sulfonate group.

The compound of the present invention can be suitably used for the formation of color filter. Accordingly, still further aspect of the present invention concerns a composition for forming color filter, comprising the compound or the colorant material according to the invention. The composition may optionally comprise at least one component selected from the group consisting of a pigment, a dye, a binder, a dispersion aid or dispersant, a polymerizable monomer, a solvent, an inhibitor, a polymerization initiator, and any combination thereof.

Further details of the above-mentioned components, including pigment, dye, binder, dispersion aid/dispersant, polymerizable monomer, solvent, inhibitor, and initiator, can be found for instance in the disclosures of WO 2012/144521, JP 2014-108975 A, and PCT international patent application publication No. WO 2013/050431, of which disclosure is incorporated herein by reference by its entirety.

In the present invention, the composition for forming color filter may be a millbase composition for color filter. The millbase composition preferably comprises (A) a colorant material; (B) a solvent; and (C) a binder, wherein the colorant material (A) comprises the compound of the invention or the colorant material of the present invention.

The present invention also relates to a color filter comprising the

compound or the colorant material of the present invention. Such color filters may be prepared by lithographic methods, especially through the following steps: combining the millbase composition according to the present invention with other additional components to form a composition for forming color filter, applying the composition for forming color filter on a substrate, drying, exposing and developing. The color filters are applicable for preparation of display devices, such as a liquid crystal display device, a light-emitting display device, or a solid-state image sensing device such as a charge coupled device (CCD) and the like.

The present invention therefore also relates to the use of the compound of the present invention as a colorant, preferably as a blue colorant, and to the use of the compound or of the colorant material of the present invention for preparation of color filters, and in particular for forming the blue portion of color filters.

Still further aspect of the present invention concerns the compound having the formula (III) below :

In the formula (III), each X, L, Rl 1, R21, and "n" has the same meaning as defined in the above.

Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

The following examples are intended to describe the invention in further detail without the intention to limit it.

Example

Example 1-1 : Preparation of Compound 1

1 α,α'-dibromo-p-xylene (5 g, 18.65 mmol) and o-toluidine (4.2 g, 39.18 mmol) were dissolved in 250 ml of acetone, and stirred at 50 °C. After completion of the reaction, extraction was conducted with adding 100 ml of H ₂ 0 and 100 ml of DCM. The organic layer was dried with MgSC^ and filtered. After concentration under reduced pressure, the residue was subjected to Si0 ₂ column treatment (Hex:EA=40: l) to obtain the Compound 1.

Example 1-2: Preparation of Compound 2

Potassium thiocyanate (3.37 g, 34.76 mmol) was dissolved in 300 ml of acetone, and the temperature was cooled down to 0 °C. Benzoyl chloride (3.67 ml, 31.6 mmol) was added drop-wise. The mixture was stirred for 1.5 hours at room temperature, and then, cooled down to 0 °C again. The Compound 1 (10 g, 31.6 mmol) dissolved in 30 ml of acetone was added drop-wise. It was stirred for 2 hours at room temperature. After completion of the reaction, 200 ml of H ₂ 0 was added. 200 ml of EA was added, and extraction was conducted two times. The organic layer was dried with MgSC^ and filtered. After

concentration under reduced pressure, the Compound 2 was obtained.

Example 1-3: Preparation of Compound 3

The Compound 2 (15 g, 23.33 mmol) was dissolved in 150 ml of 2N NaOH, and refluxed for 15 hours. After completion of the reaction, the temperature was cooled down to room temperature. After adding 150 ml of DCM, extraction was conducted two times. The organic layer was dried with MgS04 and filtered. After concentration under reduced pressure, the Compound 3 was obtained.

Example 1-4: Preparation of Compound 4

4 The Compound 3 (5 g, 11.5 mmol), 2-chloroacetophenone (1.78 g, 11.5 mmol), and sodium bicarbonate (2.41 g, 28.75 mmol) were dissolved in 100 ml of ACN, and the temperature was increased to 60 °C. After stirring for 3 hours, the temperature was cooled down to room temperature. After adding 100 ml of DCM and 200 ml of H ₂ 0, extraction was conducted. The organic layer was dried with MgSC^ and filtered. After concentration under reduced pressure, the residue was subjected to Si0 ₂ column treatment (Hex:EA=40: l) to obtain the Compound 4.

The Compound 4 (7 g, 11.02 mmol) and 4,4'- bis(diethylamino)benzophenone (3.93 g, 12.12 mmol) were dissolved in 150 ml of toluene (anh.), and POCI ₃ (5.13 ml, 55.1 mmol) was added. The temperature was raised to 100 °C, and stirring was done for 15 hours. After completion of the reaction, the temperature was cooled down to room temperature. The temperature was further cooled down to 4 °C in ice-bath, and 10 ml of IPA was slowly added drop-wise for quenching. 50 ml of H ₂ 0 was slowly added, 100 ml of DCM was added, and extraction was conducted three times. The organic layer was dried with MgSC^ and filtered. After concentration under reduced pressure, the residue was subjected to Si0 ₂ column (DCM:EA:MeOH=5:5: l) to obtain the Compound 5.

The Compound 5 (5 g, 3.78 mmol) and bis(trifluoromethane)sulfonimide lithium salt (2.71 g, 9.46 mmol) were dissolved in 100 ml of MeOH, and stirred for 2 hours at room temperature. 500 ml of H ₂ 0 was slowly added drop-wise to the mixture under stirring. The produced solid was filtered, and washed with 50 ml of H ₂ 0 three times to obtain the Compound 6.

Example 2 (Comparative): Preparation of Compound 7

The following Compound 7 was synthesized in accordance with the Production Example 1 of WO 2012/144521 A2.

Compound 7

Example 3: Preparation of colorant millbase 1

8 g of the Compound 6 obtained from Example 1-6, and 92 g of propylene glycol mono methyl ether acetate(PGMEA) were introduced to bead mill, and ground for 4 to 6 hours at 40 °C using zirconia bead (size: 0.05-2 mm) to obtain the colorant millbase 1.

Example 4 (Comparative): Preparation of colorant millbase 2

8 g of the Compound 7 obtained from Example 2, and 92 g of PGMEA were introduced to bead mill, and ground for 4 to 6 hours at 40 °C using zirconia bead (size: 0.05-2 mm) to obtain the colorant millbase 2.

Performance tests

(1) Preparation of the film for the measurement of brightness and contrast ratio: The colorant millbase was coated on a glass substrate (EAGLE -XG FUSION GLASS available from Corning) via spin coating (200-300 rpm for 15 sec.) to form a film of thickness about 2 micron and pre-baked at 90 °C for 90 seconds. Thereafter, the film was subjected to a post baking at 230 °C for 20 min.

(2) Measurement of brightness: Spectroscopy was performed on the film by using Otsuka Photal MCPD 3000 colorimeter to obtain x and y color coordinates (x, y) and brightness (Y).

(3) Measurement of contrast ratio: Contrast was measured with a contrast tester Tsubosaka CT-1 (30,000:1) after the post baking process. [Table 1 : Result of brightness and contrast ratio]

(4) Preparation of the film for the measurement of heat resistance: The colorant millbase was coated on a glass substrate (EAGLE -XG FUSION GLASS available from Corning) via spin coating (200-300 rpm for 15 sec.) to form a film of thickness about 2 micron and pre-baked at 90 °C for 90 seconds. Then, the film was exposed to light irradiation (UV irradiation) with an intensity of 40 mJ/cm ² for 2 seconds and then developed with KOH solution. Thereafter, the film was subjected to a post baking at 230 °C for 20 min.

(5) Heat resistance test: The film obtained from (4) was introduced to oven and baked at the temperature of 240 °C for 40 min. The baking at the temperature of 240 °C for 40 min. was repeated two more times. ΔΥ, Δχ, Ay, and Δ E*ab were measured by comparing the respective value before and after each baking at 240 °C for 40 min.

[Table 2: Result of heat resistance test]

As shown in the above, the compound according to the present invention exhibit greatly improved heat resistance (AE*ab) over the comparative compound. Moreover, the compound according to the invention shows higher brightness as well as contrast ratio than then comparative compound.