Field of the Invention - The invention relates to a substrate which has coated to at least a portion thereof, at least one release agent, wherein the release agent forms a definite geometric pattern.

0 Background of the Invention

Silicone release agents are well known in the art. Numerous silicones are commercially available, as are liners coated with a layer of silicone. However, these silicones have various drawbacks including controlling the 5 amount of release desirable. Frequently, silicones provides what is known in the art as "premium release", meaning that they exhibit extremely low release values, i.e., 4-60 g/cm of width. These low values are not always desirable, especially for release coatings to be used on _Q the back surfaces of adhesive tapes. This type of back surface coating is known as "low adhesion backsize" or LAB. A controlled release having exhibiting values of from 60 to about 500 g/cm of width to the adhesive is desired, so that the tape will not prematurely unwind. Silicones are 5 available in both solvent curable, and uv-curable systems. Many nonsilicone polymers such as urethanes are used as LABs because of their higher release force than the silicones. Various modifications of silicones have been attempted for use in adhesive tapes, such as binding them 0 with polymers having higher releases, as in U.S. Pat. Nos. 3,3288,482, 3,527,659 and the like.

Pattern release coatings have been of interest for many years for the goal of controlling release in silicones. In DE-PS 8 55 746, the idea of making a release 5 coating which formed a pattern was disclosed. However, no method for accomplishing the pattern coating was disclosed,

nor exemplified. Likewise, UK Patent Application GB 2,209,148 A, published May 4, 1989, discloses a two-layer self-adhesive label having a self-adhesive base which provides a non-adherent area. The nonadherent area is c described as printed with a pattern UV cured release panel. However, no method for making such a pattern is disclosed or claimed.

In U.S. Pat. No. 3,503,782, a differential release paper is made by applying a full coating of a first

2_ _Q release agent, and a second partial coating of a differing release agent. It is stated that the second coating may be provided in the form of a pattern. In this manner, the surface is provided with a variable release force. However, this requires the complete coating of the surface with one

15 release agent, typically requiring several processing steps and waste of a certain amount of silicone release agent which is under area covered by the second agent.

In DE 3727 078 Al, Beiersdorf, published February 23, 1989, it is disclosed that the problems of making and

20 using this type of coating have never been resolved. It is disclosed in this publication that two layer screen-printed silicone release coatings may be made on a substrate by priming the substrate with a commercial primer, known to have a low release value. Primers disclosed include

25 iεocyanatelinked polyvinyl acetate, and solutions of chromostearate complexes mixed with polyvinyl alcohol. The silicone may then be overcoated onto the primer. The silicone is coated using a screen with a sieve size of 10-450 mesh, and typically covers 20-80% of the surface of

30 the primer.

Thus, all of the patterned release liners for which methods of manufacture are disclosed above, have ^" required the use of a primer, or second fully coated layer of release agent. ^" 35 Processes are also known for pattern printing of other compounds onto substrates, i.e., adheεives. In U.S. Pat. No. 3,741,786, pressure-sensitive adhesive transfer tapes are disclosed having a plurality of substantially

non-contiguous raised pressure-sensitive adhesive segments. This construction is disclosed to allow the pressure- sensitive segments to be transferred.

An objective of the present invention is to provide a release article having a patterned coating for use with adhesive tapes and other applications which does not require the use of a primer with the silicone release agent.

Another objective of the present invetnion is to provide a plurality of articles having smooth controlled release varying from about 100 g/cm to well over 500 g/cm.

Summary of the Invention The invention provides a primerless release article comprising a film substrate, having coated on at least a portion thereof, at least one layer of a printable silicone release agent, wherein said agent forms a definite geometric pattern consisting of discrete islands and bridges, said islands having dimensions of from about 0.25 mm by 0.25 mm to about 4 mm by 4 mm, said bridges forming a grid, each bridge having a width of from about 0.25 mm to about 1.0 mm.

More specifically, the invention provides two different types of primerless release articles, one being the negative of the other.

The invention provides one type of primerless release article comprising a film substrate, and coated on at least a portion thereof, at least one layer of a printable silicone release agent, wherein said agent forms a definite geometric pattern consisting of discrete coated islands and uncoated bridges, said coated islands having dimensions of from about 0.25 mm by 0.25 mm to about 4 mm by 4 mm,, said uncoated bridges forming a grid, each bridge having a width of from about 0.25 mm to about 1.00 mm. The invention also provides a a second type of primerless release article comprising a film substrate, and coated on at least a portion thereof, at least one layer of

a printable silicone release agent, wherein said agent forms a definite geometric pattern consisting of discrete uncoated islands and coated bridges, said uncoated islands having dimensions of from about 0.25 mm by 0.25 mm to about c 4 mm by 4 mm, said coated bridges forming a grid, each bridge having a width of from about 0.25 mm to about 1.0 mm.

As used herein, the ensuing terms have the correlative meanings. 0 1. The term "island" means a discrete area having a defined geometric shape.

2. The term "bridge" means a discrete columnar area which may intersect with other bridges to form a grid pattern. 5 3. The term "grid" means a pattern of interconnected bridges emanating from differing points, forming and surrounding roughly equivalent geometric islands.

0 Description of the Drawings

FIG; 1 shows a release article of the invention. The surface of the substrate 1, is coated with a silicone release agent in a pattern characterized by coated areas, or islands 2, each island having an edge area of 3 mm and 5 uncoated bridges 3 forming a grid, each bridge having a width of 1 mm. The total percentage of the surface area which is siliconized is 56%.

FIG. 2 shows another release article of the invention. The surface of the substrate 1, is coated with 0 a silicone release agent in a pattern characterized by coated areas 2 and uncoated bridges 3 forming a grid. The islands are similar in size to those of Fig. 1, the bridges have a width of 0.5 mm, narrower than those of Figure 1. The total percentage of the surface area which is 5 siliconized is 72%.

FIG. 3 shows another release article of the invention. The surface of the substrate 1, is coated with a silicone release agent in a pattern characterized by coated areas 2 and uncoated bridges 3, forming a grid. This pattern is characterized by smaller islands than Figures 1 and 2, each island having an edge area of 2 mm, and each bridge width being 0.5 mm. The total percentage of the surface area which is siliconized is 64%.

FIG. 4 shows a second type of release article of the invention. The surface of the substrate 1, is coated by a silicone release agent in a pattern characterized by uncoated islands 3, each uncoated island having an edge area of 1 mm and coated bridges forming a grid 2, each bridge having a ^' width of 0.75 mm. The total percentage of the surface area which is siliconized is 33%.

FIG. 5 shows another release article of the invention. The surface of the substrate 1, is coated with a silicone release agent in a pattern characterized by coated islands 2 and uncoated bridges 3, forming a grid. This pattern is characterized by smaller islands than Figures 1 and 2, each island having a edge area of 2 mm, and each bridge width being 0.75 mm. The total percentage of the surface area which is siliconized is 53%.

FIG. 6 shows another release article of the invention. The surface of the substrate 1, is coated with a silicone release agent in a pattern characterized by coated islands 2 and uncoated bridges 3, forming a grid. This pattern is characterized by square islands having an edge area of 1.75 mm, and each bridge width being 0.75 mm. The total percentage of the surface area which is siliconized is 49%.

Detailed Description of the Invention Release articles of the invention are particular- ly useful when release force values in excess of 100 g/cm are desired.

Silicone release agents useful in articles of the invention include a wide variety of organopolysiloxanes. The compositions are preferably, but not necessarily, high molecular weight silicone polymers or copolymers. Some useful examples include both ultraviolet radiation cured and solvent cured silicones such as polyorganoεiloxaneε, including polydimethylsiloxanes, epoxypolysiloxaneε, and the like.

In preferred articles, a solvent-free crosεlink- able silicone system is used, such the epoxy functional diorganopolysiloxanes, in which up to 20% of the groups are epoxy functional groupε as described in U.S. Pat. 4,547,431. Also useful are the radiation curable coatings described in U.S. Patent No. 4,576,999 wherein there is diεclosed precrosεlinking polyorganoεiloxane containing unitε of

G

-Si-0

where R is C ₍₁ _ _{3 )} alkyl and G is independently C _{3 )} alkyl, an epoxy-functional organic radical of.2 to 20 carbon atoms, or an acrylic functional radical of 2-20 carbon atoms with at least one unit being epoxy or acrylic functional.

Also useful are epoxy substituted polysiloxaneε having the formula

AR ₂ SiO(R ₂ SiO) _χ (RQSiO) SiR ₂ A

wherein R ₂ is a onovalent hydrocarbon or halogenated hydrocarbon group having from 1 to 10 carbon atoms, A is R or Q, and Q is a group with the formula

-R _l0 (C ₂ H ₄ 0) _a (C ₃ H ₆ 0) _b CH CH ₂

R is an alkylene group having from 3 to 5 carbon atoms, a has an average value of 0 to 300 and b has an average value of 0 to 30, a + b has an average value of 2 to 60, x has an average value of 1 to 500, and y has an average value of 0 to 100, and each molecule containε at leaεt one Q group. Also useful are combinations of vinyl endblocked diorganopolysiloxaneε in which from 3 to 30 mole percent of the nonterminal siloxane units and at least 50 mole percent of the remaining organic radicals on the siloxane units are methyl radicals, and organopolysiloxaneε which have at leaεt 3 Si-bonded hydrogen atomε per molecule aε diεclosed in U.S. Pat. 4,208,504. The release agent exhibits a definite geometric pattern consisting of discrete islands and bridges on the substrate, wherein the islandε have di enεionε of from about 0.25 mm by 0.25 mm to about 4 mm by 4 mm, and the uncoated bridges form a grid, each bridge having a width of from about 0.25 mm to about 1.0 mm. In preferred articles of the invention, the iεlandε have dimensions of from about 0.50 mm by 0.50 mm to about 3 mm by 3 mm. Where a high tack adhesive is used, the bridges must be no wider than 0.75 mm, preferably from about 0.25 mm to about 0.50 mm. The islands present in the pattern, whether coated areas, or uncoated areas, may be square, circular, triangular, elliptic, rhombic, or other defined geometric shape. The bridges then form a related grid. For example, where the islandε are circular, the bridgeε are narrow between adjacent circles, and the intersection of the bridgeε iε enlarged; where the iεlandε are εquare, the bridges form diagonally opposed equal lines.

The particular geometric εhape used depends on the release values desired for the releaεe article, the nature of the adhesive which it will contact, and the type of substrate, Useful substrates are films, preferred subεtrateε are thermosplastic films such as polyolefins, foils or other εuitable nonporouε tape backings.

The printing of the release coat or coats may be carried out in a single printing step by any suitable printing technique. The pattern is coated on a roll-coater having a plurality of transfer rolls equiped with feed devices which meter the release agent in accurately defined weights onto the outer roll surface of the coater roll. The coater rolls are fitted with an embossed outer surface corresponding to the pattern to be printed onto the substrate. The solvent-free systems, e.g. uv-curable materials are especially print-technology applicable.

Articles of the invention are useful for rolled adhesive tape, for abrasive articles, and for bandages for transcutaneous administration of a microemulsion medicament. Such a device contains an abεorbant material placed in a stamped out reservoir which interεectε a piece of closed-cell polyethylene foam. The medicament is contained in the absorbant material. The polyethylene foam piece is covered by a protective polyester foil for storage. This foil is coated with the patterned silicone coating of the invention.

The following tests have been used for evaluating articles of the invention. All weight, ratios, and percentageε herein are by weight unleεs otherwise specifically noted.

Gloεεary of Terms

1. Tape X - A εtandard preεεure-εenεitive adheεive tape having an acrylic preεεure-senεitive adheεive aε diεclosed in U.S. Patent No. Re 24,906, i.e.,

a 95.5:4.5 isooctyl acrylate: acrylic acid adhesive coated onto a 0.5 mm polyester film.

2. Tape Y - A solvent based rubber resin pressure εenεitive adhesive tape having 35% Kraton™ 1107, available from Shell Chemical Company, 16.5% Wingtack™ 10, available from Goodyear Chemical Company; and 46.51 Wingtack™ Plus, available from Goodyear Chemical Company, dispersed in a solvent mixture of 4:1 toluene:heptane, and coated onto a 90 mm cast polypropylene film. 3. Tape Z - A solvent based rubber resin pressure sensitive adhesive having 33% Kraton™ 1107; 44% Escorez™ 1310, available from Exxon Chemical Company; 22% Zonarez™ A25, available from Arizona Chemical and 1% Irganox™ 1076 Antioxidant, available from Ciba Geigy, dispersed in a mixture of 4:1 toluene:heptane and coated onto a polyethylene coated paper.

Test Methods

Release Value Test Procedure

A pressure-sensitive adhesive tape is presεed against the surface of a release coated substrate using two pasεeε of a 2 Kg rubber roller to produce a laminate. The laminate was cut into 25 mm X 250 mm strips and attached, substrate side down, to a smooth stainless steel panel. The release value is the force, in grams, required to pull the pressure-sensitive adhesive tape with adhesive adhered thereto away from the releaεe coated substrate at an angle of 180° and a pulling speed of 300 mm/min.

Heat Aged Release Value Teεt

A laminate of a presεure-εenεitive adheεive tape and releaεe coated εubεtrate was prepared as deεcribed above and heated in an oven at 70°C under a conεtant load of 20 gramε per square centimeter for 20 h^urs. After thiε time, the laminate waε removed from t'ιe oven, allowed to cool for at leaεt 10 minuteε at room tenperature, and within 2 hours after removal from the oven, the force

required to pull the pressure sensitive tape with adhesive adhered thereto away from the release coated substrate was measured as deεcribed above in the teεt for Releaεe Value.

_c Readhesion Test

A 25 X 250 mm strip of pressure sensitive tape, as removed from the release coated substrate, was pressed to the surface of a bright annealed stainless steel panel using two passes of a 2 Kg rubber roller. The readhesion 0 value is the force, in Newtons/25 mm, required to pull the tape from the panel surface at an angle of 180° and a stripping speed of 300 m/min.

Examples 5

Example 1 An epoxy silicone having an epoxy equivalent weight of 865 is prepared as described in U.S. Patent No. 4,822,687, and coated onto an 0.085 mm cast polypropylene o film in an island having 1 mm x 1 mm islands and separated by bridges of.0.375 mm. The silicone is cured as described in the reference. The sample was tested - according to the test methods for Releaεe Value, Heat-Aged Release Value, and Readhesion, described above and the 5 test results are summarized in Table 1.

Examples 2-10 Examples 2-10 were prepared as described in Example 1 except that the island and bridge sizes were 0 changed as indicated in Table 1 .

Examples 12-14 Examples 12-14 were made as deεcribed in Example 1 with iεland and bridge εizeε aε shown in Table 1. Teεt 5 Tape Y was used in the Release Value Test.

Exampleε 115-17 Exampleε 15-17 were made as using an epoxy silicone having an Epoxy Equivalent Weight of 445. The epoxy silicone was made as described in U.S. Pat. o. 4,822,687. The island size and bridge widths are shown in Table 1.

Examples 18-30 Examples 18-30 were made by coating Wacker- Chemie "VP-1530", available from Wacker-Chemie GmbH in the island sizes and bridge width as indicated in Table 1 and cured under UV light.

Examples 31-32 Examples 31-32 were made by coating Wacker

Dehasive™ 920, available from Wacker-Chemie GmbH in the island sizes and bridge width as indicated in Table 1 and heat cured.

Exampleε 33-35

Exampleε 33-35 were made as in Example 1 except that the island was coated as a grid with the island sizes, indicating the uncoated islands and the bridge sizeε indicating the width of the coated bridgeε forming the grid.

Example 36 Example 36 was made as in Example 33 except that the silicone was coated onto a 0.040 mm biaxially oriented polypropylene film.

TABLE I

Heat Aged Readhe- Release Release sion Islands bridge Silicone/ Test Value Value Value

Ex Size-mm mm Substrate Tape g/25mm g/25mm N/25mm

|\3 I

349 12 . 1

19 1X1 0.500 C Z 126 648 11.5

20 1X1 0.625 C Z 81 360 12.0

21 2X2 0.375 C Z 17 138 15.3

22 2X2 0.500 C Z 41 211 15.4

23 2X2 0.625 C Z 64 392 11.5

24 3X3 0.375 C Z 12 87 15.9

25 3X3 0.500 C Z 18 109 14.9

26 3X3 0.625 C Z 32 161 13.7

27 Comparative* C Z 15 18 17.5

28 2X2 0.750 C #5336 495 804

29 1.75X1.75 0.750 C #5336 532 968

30 Comparative* C #5336 72 91

31 2X2 0.750 D #5337 1196 1826** 40.5

32 Comparative* D #5337 740 208** 47.2 33*** 1X1 0.750 A X 41.8 54.3 10.3 34***.75x.75 0.750 A X 12.5 114 15.3 35*** 1X1 0.750 A Z 253

36*** 1X1 0.750 E Z 177

A - Epoxysiloxane with an Epoxy Equivalent Weight of 865 coated onto 0.085mm thick cast polypropylene

B - Epoxysiloxane with an Epoxy Equivalent Weight of 445

coated onto 0.089mm thick cast polypropylene

Y - Test Tape Y.

C - Wacker-Chemie "VP-1530" coated onto 0.085mm thick cast polypropylene film. Z - Test Tape Z. #5336 - Foam Tape #5336 available from 3M Company, St.

Paul, MN. #5337 - Foam Tape #5337 available from 3M Company, St.

Paul, MN. D - Wacker Dehasive™ 920 thermally cured silicone coated onto

0.085 mm cast polypropylene film. E - Epoxysiloxane with an Epoxy Equivalent Weight of 865 coated onto 0.040 thick biaxially oriented polypropylene film. * - Comparative is fully coated with silicone ** - Heat Aged Release Value Test is conducted as described above except that the samples were aged for 7 days at 70°C. *** _ Grid pattern in which the pattern size indicates the islands which are uncoated and the brideges form the grid which is silicone coated.