JP7707576B2 - Release layer forming composition and release layer - Google Patents

Description

The present invention relates to a composition for forming a release layer and a release layer, and more specifically, to a composition for forming a release layer that is cured by irradiation with light and a release layer obtained by photocuring the composition.

In recent years, electronic devices are being required to be thin and lightweight, as well as flexible. This has created a demand for lightweight, flexible plastic substrates to replace the conventional heavy, fragile, and inflexible glass substrates.

In particular, new generation displays require the development of active matrix type full color TFT display panels using lightweight flexible plastic substrates (hereinafter also referred to as resin substrates). In addition, for touch panel displays, materials that can accommodate flexibility, such as transparent electrodes and resin substrates for touch panels used in combination with display panels, have been developed. As for transparent electrodes, other transparent electrode materials have been proposed in place of the conventionally used ITO, such as transparent conductive polymers that can be bent, such as PEDOT, metal nanowires, and mixtures thereof (Patent Documents 1 to 4).

Meanwhile, the substrate for touch panel films has also changed from glass to sheets made of plastics such as polyethylene terephthalate (PET), polyimide, cycloolefin, and acrylic, and transparent flexible touch screen panels that have flexibility have been developed (Patent Documents 5 to 7).

In general, flexible touch screen panels are produced by creating a release (adhesive) layer on a support substrate such as a glass substrate, and then creating a device made of a resin substrate or the like on top of the release (adhesive) layer and peeling it off to ensure stable productivity and peelability (Patent Document 8).

As the release layer, for example, a curable resin compound containing a specific polymer and a crosslinking agent has been described (Patent Documents 9 to 10). While these release layers can be easily peeled off from the support substrate, they peel off at the interface between the support substrate and the release layer, so the release layer remains on the device side and may adversely affect the device fabrication process and transparency.

International Publication No. 2012/147235 JP 2009-283410 A Special Publication No. 2010-507199 JP 2009-205924 A International Publication No. 2017/002664 International Publication No. 2016/160338 JP 2015-166145 A JP 2016-531358 A International Publication No. 2018/033995 International Publication No. 2019/159248

The present invention has been made in consideration of the above circumstances, and aims to provide a photocurable composition for forming a release layer that can form a device composed of a resin substrate or the like on a release layer and that provides a release layer that can be easily peeled off at the interface between the release layer and the device composed of the resin substrate or the like.

As a result of extensive research into achieving the above object, the present inventors have discovered that (A) a composition for forming a release layer containing a polymer that is cured by irradiation with light can form a device composed of a resin substrate or the like on the release layer by irradiation with light, and can reproducibly provide a release layer that peels easily at the interface between the release layer and the device composed of a resin substrate or the like, thereby completing the present invention.

That is, the present invention provides
1. A composition for forming a release layer, comprising (A) a polymer that is cured by irradiation with light;
2. The composition for forming a release layer according to 1, wherein the polymer (A) that is cured by irradiation with light is a polymer having a structural moiety that undergoes photodimerization.
3. The composition for forming a release layer according to 1 or 2, wherein the structural moiety that is photodimerizable is a cinnamoyl group.
4. (A) The composition for forming a release layer according to any one of 1 to 3, wherein the polymer cured by irradiation with light is a polymer obtained by using a monomer having a structural moiety that undergoes photodimerization;
5. The release layer-forming composition according to any one of 1 to 4, wherein the polymer (A) that is cured by irradiation with light is a polymer obtained by using a monomer selected from the group consisting of an acrylic acid ester compound, a methacrylic acid ester compound, a maleimide compound, an acrylamide compound, acrylonitrile, maleic anhydride, a styrene compound, and a vinyl compound;
6. The polymer (A) that is cured by irradiation with light is a polymer obtained by using a monomer having a structural moiety that can be photodimerized and a monomer not having a structural moiety that can be photodimerized,
6. The composition for forming a release layer according to 4 or 5, wherein the content of the monomer having a structural moiety that can be photodimerized is 1 to 50 mol % relative to 100 mol % of all monomer units, and the content of the monomer not having a structural moiety that can be photodimerized is 50 to 99 mol % relative to 100 mol % of all monomer units;
7. The composition for forming a release layer according to 6, wherein the monomer not having a structural moiety that can be photodimerized is a monomer having an alicyclic hydrocarbon group.
8. A release layer obtained by photocuring any one of the release layer-forming compositions according to 1 to 7.
9. A laminate in which a resin layer having a light transmittance of 80% or more at a wavelength of 400 nm is laminated on the release layer of 8.
10. The laminate of 9, wherein the resin layer is a thermosetting film containing an epoxy compound.
11. A method for producing a laminate by applying the release layer-forming composition according to any one of 1 to 7 onto a substrate and then exposing the substrate to light,
12. A step of applying the composition for forming a release layer according to any one of 1 to 7 to a substrate and exposing the composition to light to form a release layer;
The present invention provides a method for producing a resin substrate, the method including the steps of: forming a resin substrate having a light transmittance of 80% or more at a wavelength of 400 nm on the release layer; and peeling the resin substrate with a peeling force of 1.0 N/25 mm or less.

By using the release layer forming composition of the present invention, a device composed of a resin substrate or the like can be formed on the release layer, and a release layer that easily peels off at the interface between the release layer and the device composed of the resin substrate or the like can be reproducibly obtained by light irradiation. In addition, in the manufacturing process of a flexible electronic device, it becomes possible to separate the resin substrate together with the circuits formed thereon from the base without damaging the resin substrate formed on the base or the circuits formed thereon. Therefore, the release layer forming composition of the present invention can contribute to speeding up the manufacturing process of flexible electronic devices equipped with resin substrates and improving the yield.

The present invention will be described in further detail below.
[Composition for forming release layer]
The composition for forming a release layer of the present invention is characterized by containing (A) a polymer that is cured by irradiation with light.
[1] Component (A) The component (A) in the composition for forming a release layer of the present invention is a polymer that is cured by irradiation with light.
The polymer that is cured by irradiation with light is preferably a polymer having a structural moiety that undergoes photodimerization.
Examples of the structural moiety that undergoes photodimerization include a cinnamoyl group, a chalcone group, a coumarin group, and an anthracene group, with a cinnamoyl group being preferred due to its high photodimerization reactivity.
Suitable cinnamoyl groups and substituents containing a cinnamoyl structure include structures represented by the following formula [1] or [2]. In this specification, a cinnamoyl group in which the benzene ring is a naphthalene ring is also included in the "cinnamoyl group" and "substituent containing a cinnamoyl structure".

In the above formula [1], X ¹ represents an alkyl group having 1 to 18 carbon atoms, a phenyl group, or a biphenyl group.
In the above formula [2], ^X2 represents a hydrogen atom, a cyano group, an alkyl group having 1 to 18 carbon atoms, a phenyl group, a biphenyl group, or a cyclohexyl group;
In ^X1 and ^X2 , the phenyl group and the biphenyl group may be substituted with a halogen atom or a cyano group, and ^X1 and ^X2 may be a group in which a plurality of alkyl groups having 1 to 18 carbon atoms, phenyl groups, biphenyl groups and cyclohexyl groups are bonded via one or more bonds selected from a covalent bond, an ether bond, an ester bond, an amide bond, a urea bond, a urethane bond, an amino bond, a carbonyl bond and a combination thereof.
In the above formulas [1] and [2], A represents any one of the following formulas [A1], [A2], [A3], [A4], [A5] and [A6].

In the above formulas [A1] to [A6], R ¹ to R ⁸ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogen atom, a trifluoromethyl group, or a cyano group.
The alkyl group having 1 to 4 carbon atoms may be straight-chain, branched or cyclic, and specific examples thereof include methyl, ethyl, n-propyl, i-propyl, n-butyl and t-butyl groups.
The alkyl group in the alkoxy group having 1 to 4 carbon atoms may be straight-chain, branched, or cyclic, and specific examples thereof include methoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, and t-butoxy groups.
Examples of halogen atoms include fluorine, chlorine, bromine and iodine atoms.

Methods for introducing such a photodimerizable structural portion into a polymer include, but are not limited to, polymerizing a monomer having a photodimerizable structural portion.

Examples of monomers having a structural moiety that undergoes photodimerization include acrylic ester compounds, methacrylic ester compounds, maleimide compounds, acrylamide compounds, acrylonitrile, maleic anhydride, styrene compounds, vinyl compounds, and the like, each having a structural moiety that undergoes photodimerization. Of these, acrylic ester compounds and methacrylic ester compounds having a structural moiety that undergoes photodimerization, preferably a structure represented by the above formula [1] or [2], are preferred.
Suitable examples of the monomer having a photodimerizable structural moiety include compounds represented by the following formulae M1-1 to M1-13, but are not limited thereto.
The monomer having a photodimerizable structural moiety may be used alone or in combination of two or more kinds.

(In the formula, ^M1 is a hydrogen atom or a methyl group, s1 represents the number of methylene groups and is a natural number from 2 to 9, and R is methoxy or ethoxy.)

The polymer that hardens upon irradiation with light (A) component in the composition for forming a release layer of the present invention may contain a monomer that has a structural moiety that undergoes photodimerization (structural unit (a)) as well as a monomer that does not have a structural moiety that undergoes photodimerization (structural unit (b)).
The monomer of the structural unit (b) is not particularly limited as long as it is copolymerizable with the structural unit (a), and examples thereof include an acrylic acid ester compound, a methacrylic acid ester compound, a maleimide compound, an acrylamide compound, acrylonitrile, maleic anhydride, a styrene compound, and a vinyl compound.

Specific examples of acrylic acid ester compounds include methyl acrylate, ethyl acrylate, isopropyl acrylate, benzyl acrylate, naphthyl acrylate, anthryl acrylate, anthryl methyl acrylate, phenyl acrylate, glycidyl acrylate, 2,2,2-trifluoroethyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isobornyl acrylate, 2-methoxyethyl acrylate, methoxytriethylene glycol acrylate, 2-ethoxyethyl acrylate, tetrahydrofurfuryl acrylate, 3-methoxybutyl acrylate, 2-methyl-2-adamantyl acrylate, 2-propyl-2-adamantyl acrylate, 8-methyl-8-tricyclodecyl acrylate, 8-ethyl-8-tricyclodecyl acrylate, and the like.

Specific examples of methacrylic acid ester compounds include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, benzyl methacrylate, naphthyl methacrylate, anthryl methacrylate, anthryl methyl methacrylate, phenyl methacrylate, glycidyl methacrylate, 2,2,2-trifluoroethyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, 2-methoxyethyl methacrylate, methoxytriethylene glycol methacrylate, 2-ethoxyethyl methacrylate, tetrahydrofurfuryl methacrylate, 3-methoxybutyl methacrylate, stearyl methacrylate, adamantyl methacrylate, 2-methyl-2-adamantyl methacrylate, γ-butyrolactone methacrylate, 2-propyl-2-adamantyl methacrylate, 8-methyl-8-tricyclodecyl methacrylate, 8-ethyl-8-tricyclodecyl methacrylate, etc.

Specific examples of the vinyl compound include methyl vinyl ether, benzyl vinyl ether, vinyl naphthalene, vinyl carbazole, allyl glycidyl ether, 3-ethenyl-7-oxabicyclo[4.1.0]heptane, 1,2-epoxy-5-hexene, and 1,7-octadiene monoepoxide.
Specific examples of the styrene compound include styrene, methylstyrene, chlorostyrene, and bromostyrene.
Specific examples of the maleimide compound include maleimide, N-methylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide.

In particular, from the viewpoint of the heat resistance and hydrophobicity of the resulting release layer, the monomer of the structural unit (b) is preferably a monomer having an alicyclic hydrocarbon group, and more preferably a (meth)acrylic acid ester having an alicyclic hydrocarbon group having a carbon number of 6 to 20. Examples of the alicyclic hydrocarbon group include a cyclohexyl group, a t-butylcyclohexyl group, an isobornyl group, a dicyclopentanyl group, a dicyclopentenyl group, and an adamantyl group.
Specific examples of monomers having an alicyclic hydrocarbon group include isobornyl methacrylate, isobornyl acrylate, dicyclopentanyl methacrylate, dicyclopentanyl acrylate, dicyclopentenyl methacrylate, dicyclopentenyl acrylate, adamantyl methacrylate, cyclohexyl methacrylate, and t-butylcyclohexyl methacrylate.
The monomers of the structural unit (b) may be used singly or in combination of two or more kinds of the same kind.

(A) In a polymer obtained using a monomer (structural unit (a)) having a structural portion that undergoes photodimerization, the content of the monomer of structural unit (a) is preferably 1 to 70 mol%, more preferably 3 to 50 mol%, and even more preferably 5 to 30 mol%, relative to 100 mol% of all monomer units. If the content of the monomer of structural unit (a) of the crosslinking agent is too low, the solvent resistance and heat resistance of the release layer may decrease, and the release properties may decrease. On the other hand, if the content is too high, a reaction with the resin substrate on the release layer may proceed, and the release properties may decrease.

The method for obtaining the polymer used in the composition for forming a release layer of the present invention is not particularly limited, but an example thereof includes a method in which a monomer of the structural unit (a), a monomer of the structural unit (b), and a polymerization initiator are reacted in a solvent at a temperature of 50 to 110° C.
In this polymerization reaction, a solvent capable of dissolving the monomer of the structural unit (a), the monomer of the structural unit (b), the polymerization initiator, etc. may be used. Specific examples of such a solvent include those listed in the section [Solvent] below.

The obtained polymer is usually in the form of a solution dissolved in a solvent, and in the present invention, the powdered polymer removed from the solvent may be used as component (A), or the obtained polymer solution may be used as component (A) as it is. Also, the powdered polymer removed from the solvent may be redissolved in a solvent to use as component (A).
In addition, as a method for extracting the polymer from the polymer solution obtained as described above, for example, the polymer solution is mixed with a poor solvent such as hexane, diethyl ether, water, etc. under stirring to reprecipitate the polymer, and the resulting precipitate is filtered and washed, and then dried at normal pressure or reduced pressure, at room temperature or under heating to obtain a powder. By such an operation, not only the solvent but also the polymerization initiator and unreacted monomers coexisting with the polymer can be removed, and as a result, a purified polymer powder can be obtained. If the polymer cannot be sufficiently purified by one operation, the obtained powder can be redissolved in a solvent and the above operation can be repeated.

In addition, in the release layer forming composition of the present invention, a single type of polymer or a mixture of multiple types of polymers may be used as the polymer of component (A).

[2] Other Additives The release layer-forming composition of the present invention may contain other additives as necessary, so long as the effects of the present invention are not impaired.
Examples of other additives include surfactants, silane coupling agents, rheology modifiers, pigments, dyes, storage stabilizers, antifoaming agents, and antioxidants.
In particular, from the viewpoint of improving the coatability onto a substrate, the release layer-forming composition of the present invention preferably contains a surfactant.
As the surfactant, known surfactants such as nonionic surfactants, fluorine-based surfactants, and silicone-based surfactants can be used.

Specific examples of nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether, and polyoxyethylene oleyl ether; polyoxyethylene alkylaryl ethers such as polyoxyethylene octylphenyl ether and polyoxyethylene nonylphenyl ether; polyoxyethylene-polyoxypropylene block copolymers; sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan trioleate, and sorbitan tristearate; and polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan trioleate, and polyoxyethylene sorbitan tristearate.

Specific examples of fluorine-based surfactants include EFTOP (registered trademark) EF301, EF303, and EF352 (manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.), Megafac (registered trademark) F171, F173, F554, F559, F563, R-30, R-40, R-40-LM, and DS-21 (manufactured by DIC Corporation), Fluorad FC430 and FC431 (manufactured by 3M), Asahiguard (registered trademark) AG710, Surflon (registered trademark) S-382, SC101, SC102, SC103, SC104, SC105, and SC106 (manufactured by Asahi Glass Co., Ltd.).
A specific example of the silicone surfactant is organosiloxane polymer KP341 (manufactured by Shin-Etsu Chemical Co., Ltd.).

These surfactants may be used alone or in combination of two or more.
When a surfactant is used, the amount used is preferably from 0.0001 to 1 part by mass, and more preferably from 0.001 to 0.5 parts by mass, based on 100 parts by mass of the polymer (A).

[3] Solvent The release layer-forming composition of the present invention may contain a solvent.
The solvent is not particularly limited in type, structure, etc., so long as it has the ability to dissolve component (A), component (B) used as necessary, and/or other additives. In the present invention, glycol ether-based solvents having 3 to 20 carbon atoms, ester-based solvents having 3 to 20 carbon atoms, ketone-based solvents having 3 to 20 carbon atoms, and amide-based solvents having 3 to 20 carbon atoms are preferred.

Specific examples of glycol ether solvents include propylene glycol monomethyl ether (PGME), propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monoethyl ether, and propylene glycol monopropyl ether.
Specific examples of the ester solvent include ethyl lactate, γ-butyrolactone, methyl 2-hydroxyisobutyrate, and ethyl 2-hydroxyisobutyrate.
Specific examples of the ketone solvent include methyl ethyl ketone, cyclohexanone, cyclopentanone, and benzophenone.
Specific examples of the amide solvent include N-methylpyrrolidone, N,N-dimethylacetamide, and 3-methoxy-N,N-dimethylpropanamide.
The solvent may be used alone or in combination of two or more.

The content of the solvent is preferably such that the solids concentration in the composition for forming a release layer of the present invention is 0.1 to 40% by mass, more preferably 0.5 to 20% by mass, and even more preferably 0.5 to 10% by mass. The solids are a collective term for all components of the composition for forming a release layer other than the solvent.

The method for preparing the composition for forming a release layer of the present invention is not particularly limited, and examples thereof include a method in which other additives are mixed, as necessary, in a predetermined ratio with a solution of component (A) dissolved in a solvent to prepare a homogeneous solution, and a method in which other additives are further added and mixed, as necessary, at an appropriate stage of the above preparation method.
The prepared solution of the composition for forming the release layer is preferably filtered using a filter having a pore size of about 0.2 μm before use.

The viscosity of the release layer-forming composition of the present invention is appropriately set taking into consideration the thickness of the release layer to be produced, but when the objective is to reproducibly obtain a film having a thickness of about 0.01 to 5 μm, the viscosity is usually preferably about 1 to 5,000 mPa·s at 25°C, and more preferably about 1 to 2,000 mPa·s.

The viscosity can be measured using a commercially available viscometer for measuring the viscosity of liquids, for example, by referring to the procedure described in JIS K7117-2, at a composition temperature of 25°C. Preferably, a cone-plate type rotational viscometer is used as the viscometer, and preferably the same type of viscometer is used with a standard cone rotor of 1°34' x R24, and the measurement is performed at a composition temperature of 25°C. An example of such a rotational viscometer is the TVE-25L manufactured by Toki Sangyo Co., Ltd.

[Release layer]
The release layer can be obtained by a method including a heating step in which the composition for forming a release layer of the present invention described above is applied onto a substrate to form a coating film, followed by an exposure step in which light such as ultraviolet light is irradiated after the heating step.
In this case, the heating time cannot be generally specified because it varies depending on the temperature, but is usually 1 minute to 5 hours. A preferred example of the heating mode is a method of heating at 50 to 150°C for 1 minute to 1 hour. As long as the maximum heating temperature is within the above range, a step of heating at a temperature lower than that may be included.

The conditions for irradiation with ultraviolet light or the like are not limited as long as the component (A) is photocured. For example, ultraviolet light can be irradiated at about 500 to 2,000 mJ/cm ² .

When the release layer of the present invention is formed on a substrate, the release layer may be formed on a part of the substrate surface or on the entire substrate surface. The form of forming the release layer on a part of the substrate surface includes a form in which the release layer is formed only on a predetermined area of the substrate surface, and a form in which the release layer is formed on the entire substrate surface in a pattern such as a dot pattern or a line and space pattern.
In the present invention, the substrate refers to a substrate on whose surface the release layer-forming composition of the present invention is applied and which is used in the manufacture of flexible electronic devices and the like.

When irradiating with ultraviolet light or other light, a mask having a predetermined pattern is attached, ultraviolet light or other light is irradiated, and the unexposed areas are washed out, and a release layer can be formed in a pattern such as a line and space pattern by developing with an alkaline developer or the like.

Examples of the substrate (base material) include glass, metal (such as a silicon wafer), and slate. Glass is particularly preferred because the release layer obtained from the release layer-forming composition of the present invention has sufficient adhesion to the substrate. The substrate surface may be composed of a single material, or may be composed of two or more materials. The substrate surface may be composed of two or more materials in a manner in which a certain area of the substrate surface is composed of a certain material and the remaining surface is composed of another material, or in which a material in a pattern such as a dot pattern or a line and space pattern is present in the other material over the entire substrate surface.

The coating method is not particularly limited, but examples include cast coating, spin coating, blade coating, dip coating, roll coating, bar coating, die coating, inkjet printing, and printing methods (relief printing, intaglio printing, planographic printing, screen printing, etc.).

Examples of the heating device include a hot plate, an oven, etc. The heating atmosphere may be air or an inert gas, and may be normal pressure or reduced pressure.
Examples of devices used for light irradiation include high-pressure mercury lamps and metal halide lamps.

The thickness of the release layer is usually about 0.01 to 50 μm, and from the viewpoint of productivity, it is preferably about 0.01 to 20 μm, and more preferably about 0.01 to 5 μm. The thickness of the coating film before heating is adjusted to achieve the desired thickness.

The release layer of the present invention has good releasability for the resin substrate provided thereon. Therefore, the release layer of the present invention can be suitably used in the manufacturing process of a flexible electronic device to peel the resin substrate of the device together with the circuits and the like formed on the resin substrate from the base without damaging the resin substrate.

An example of a method for manufacturing a flexible electronic device using the release layer of the present invention is described below. First, a release layer is formed on a glass substrate by the above-mentioned method using the release layer-forming composition of the present invention. A resin substrate-forming solution for forming a resin substrate is applied onto this release layer, and the resulting coating is baked to form a resin substrate fixed to the glass substrate via the release layer of the present invention.

The baking temperature of the coating film is set appropriately depending on the type of resin, etc., but in the present invention, the maximum temperature during baking is preferably 200 to 250°C, more preferably 210 to 250°C, and even more preferably 220 to 240°C. By setting the maximum temperature during baking in this range when producing the resin substrate, the peelability between the release layer and the resin substrate can be further improved. In this case, too, as long as the maximum temperature is within the above range, a step of baking at a temperature lower than that may be included.

The resin substrate is preferably formed so as to completely cover the release layer and has an area larger than that of the release layer. Examples of the resin substrate include a resin substrate made of an acrylic polymer and a resin substrate made of a cycloolefin polymer. The resin substrate may be formed in a conventional manner. In addition, the resin substrate preferably has a light transmittance of 80% or more at a wavelength of 400 nm.

Next, a desired circuit is formed as necessary on the resin substrate fixed to the base via the release layer of the present invention, and then, for example, the resin substrate is cut along the release layer, and the resin substrate together with the circuit is peeled off from the release layer to separate the resin substrate from the base. At this time, a part of the base may be cut together with the release layer.
By using the release layer of the present invention, the resin substrate can be peeled off from the release layer with a peeling force of 1.0 N/25 mm or less.

The present invention will be described in more detail below with reference to synthesis examples, preparation examples, examples, and comparative examples, but the present invention is not limited to the following examples.

The abbreviations used in the following examples have the following meanings.
[Polymer raw materials]
ADMA: 2-adamantyl methacrylate DCPMA: dicyclopentanyl methacrylate AIBN: azobisisobutyronitrile

Cin1: a compound represented by the following formula

Cin2: a compound represented by the following formula

〔solvent〕
CHN: Cyclohexanone

[Measurement of molecular weight of polymer]
The molecular weight of the acrylic copolymer in the synthesis examples was measured as follows using a room temperature gel permeation chromatography (GPC) apparatus (GPC-101) manufactured by Shodex Co., Ltd. and columns (KD-803, KD-805) manufactured by Shodex Co., Ltd. The number average molecular weight (hereinafter referred to as Mn) and weight average molecular weight (hereinafter referred to as Mw) below are expressed in terms of polystyrene.
Column temperature: 40°C
Eluent: tetrahydrofuran Flow rate: 1.0 mL/min Standard sample for creating calibration curve: Standard polystyrene (molecular weight: about 197,000, 55,100, 12,800, 3,950, 1,260, 580) manufactured by Showa Denko K.K.

(1) Synthesis of component (A) [Synthesis Example 1]
3.50g (15.89mmol) of ADMA as a non-crosslinkable monomer, 1.38g (3.97mmol) of Cin1 as a crosslinkable monomer, and 0.10g (0.60mmol) of AIBN as a polymerization catalyst were dissolved in 50.0g of THF, and reacted for 20 hours under heating and reflux to obtain an acrylic copolymer solution. The acrylic copolymer solution was gradually dropped into 500.0g of hexane to precipitate a solid, which was then filtered and dried under reduced pressure to obtain an acrylic polymer (PA-1). The Mw of the obtained acrylic copolymer was 15,000.

[Synthesis Examples 2 to 6]
Polymers (PA-2) to (PA-6) were obtained in the same manner as in Synthesis Example 1, except that the types and amounts of raw material compounds were as shown in Table 1 below. The Mw of the obtained polymers is shown in Table 1.

(2) Preparation of resin substrate forming composition [Preparation Example 1] Preparation of resin substrate forming composition F1 10 g of Zeonor (registered trademark) 1020R (a cycloolefin polymer manufactured by Zeon Corporation) and 3 g of Epolead (registered trademark) GT401 (manufactured by Daicel Corporation) were added to an eggplant flask containing 100 g of carbon tetrachloride as a solvent. The solution was stirred for 24 hours under a nitrogen atmosphere to dissolve, thereby preparing resin substrate forming composition F1.

(3) Preparation of release layer forming composition [Example 1-1]
CHN was added to 100 parts by mass of the polymer (PA-1) obtained in Synthesis Example 1 as the component (A) to prepare a release layer-forming composition (A-1) having a solid content concentration of 5.0% by mass.

[Examples 1-2 to 1-5, Comparative Example 1-1]
Release layer-forming compositions A-2 to A-12 were prepared in the same manner as in Example 1-1, except that the types and amounts of each component were as shown in Table 2.

(4) Preparation of release layer and resin substrate [Example 2-1]
The composition A-1 for forming a release layer prepared in Example 1-1 was applied onto a glass substrate (Corning Eagle XG, 100 mm x 100 mm x 0.7 mm, the same applies below) as a base using a spin coater (conditions: rotation speed 2,000 rpm for about 30 seconds). The resulting coating film was heated at 100°C for 2 minutes using a hot plate, and then irradiated with ultraviolet light at 2,000 mJ/ ^cm2 using a high-pressure mercury lamp to form a release layer with a thickness of about 0.1 μm on the glass substrate, thereby obtaining a glass substrate with a release layer.
Then, using a spin coater (conditions: rotation speed 200 rpm for about 15 seconds), the composition F1 for forming a resin substrate was applied onto the release layer (resin thin film) on the glass substrate. The resulting coating film was heated at 80° C. for 2 minutes using a hot plate, and then heated at 230° C. for 30 minutes using a hot plate to form a resin substrate with a thickness of about 3 μm on the release layer, thereby obtaining a resin substrate and a glass substrate with a release layer.

[Examples 2-2 to 2-5, Comparative Example 2-1]
The same procedure as in Example 2-1 was carried out except that (A-2) to (A-6) were used as the release layer-forming compositions, to obtain resin substrates and glass substrates with release layers of Examples 2-2 to 2-5 and Comparative Example 2-1.

[Comparative Example 2-2]
The same procedure as in Example 2-1 was carried out except that ultraviolet light was not irradiated using a high pressure mercury lamp, to obtain a resin substrate/a glass substrate with a release layer of Comparative Example 2-2.

[Evaluation of peel strength]
The resin substrate and the glass substrate with the peelable layer obtained above were cut into strips of 25 mm x 50 mm using a cutter. After sticking Cellotape (registered trademark) (CT-24, manufactured by Nichiban Co., Ltd.), the tape was peeled off at a peeling angle of 90° and a peeling speed of 300 mm/min using an Autograph AGS-X500N (manufactured by Shimadzu Corporation) to measure the peeling force. Those that could not be peeled off were deemed to be unpeelable. The evaluation results were recorded as "peeling force", and the results are summarized in Table 3.

[Evaluation of peeled interface]
The thickness of the peeling layer remaining on the glass substrate after the evaluation of the peeling force was measured using a stylus-type film thickness meter. The thickness was compared with the thickness when the peeling layer was formed, and the peeling interface was determined. The evaluation result was determined as "peeling interface", and when the remaining film ratio (remaining film ratio (%) = peeling layer film thickness after peeling / peeling layer film thickness when the peeling layer was formed x 100) was 90% or more, it was determined as the peeling layer/resin interface, when it was 10% or more but less than 90%, it was determined as the cohesive failure of the peeling layer, and when it was less than 10%, it was determined as the glass substrate/peeling layer interface. The evaluation results are summarized in Table 3.

As shown in Table 3, the release layers of each Example exhibited low peel strength and were found to have excellent release properties. It was also confirmed that the release layers of the Examples peeled off at the interface between the release layer and the resin substrate. On the other hand, it was found that the films of Comparative Examples 2-1 and 2-2 did not function as release layers.

Claims (10)

A release layer-forming composition for forming a release layer that is interposed between a base and a resin substrate and that peels off at an interface with the resin substrate, comprising:
(A) contains a polymer that is cured by irradiation with light,
the polymer is a polymer obtained by using a monomer having a structural moiety that undergoes photodimerization,
A composition for forming a peeling layer, characterized in that the monomer having a structural portion that can be photodimerized is one or more selected from acrylic acid ester compounds and methacrylic acid ester compounds having a substituent containing a cinnamoyl group or a cinnamoyl structure represented by the following formula [1] or formula [2].
[In formula [1], X ¹ represents an alkyl group having 1 to 18 carbon atoms, a phenyl group, or a biphenyl group,
In formula [2], ^X2 represents a hydrogen atom, a cyano group, an alkyl group having 1 to 18 carbon atoms, a phenyl group, a biphenyl group, or a cyclohexyl group;
In formula [1] and formula [2], A represents any one of the following formulas [A1], [A2], [A3], [A4], [A5] and [A6].
(In formulas [A1] to [A6], R ¹ to R ⁸ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogen atom, a trifluoromethyl group, or a cyano group.) The composition for forming a release layer according to claim 1, wherein in the formulas [1] and [2], A represents the formula [A1]. The release layer forming composition according to claim 1 or 2, wherein the monomer having a structural moiety that undergoes photodimerization is one or more selected from acrylic acid ester compounds and methacrylic acid ester compounds having a substituent containing a cinnamoyl group or a cinnamoyl structure represented by formula [1]. the polymer (A) that is cured by irradiation with light is a polymer obtained by using a monomer having a photodimerizable structural moiety and a monomer not having a photodimerizable structural moiety,
A composition for forming a peeling layer according to any one of claims 1 to 3, wherein the content of the monomer having the structural moiety that can be photodimerized is 1 to 50 mol % relative to 100 mol % of all monomer units, and the content of the monomer not having the structural moiety that can be photodimerized is 50 to 99 mol % relative to 100 mol % of all monomer units. The release layer forming composition according to claim 4, wherein the monomer that does not have a structural moiety that undergoes photodimerization is a monomer that has an alicyclic hydrocarbon group. A release layer formed by photocuring the release layer-forming composition according to any one of claims 1 to 5. A laminate in which a resin layer having a light transmittance of 80% or more at a wavelength of 400 nm is laminated on the release layer according to claim 6. The laminate according to claim 7, wherein the resin layer is a thermosetting film containing an epoxy compound. A method for producing a laminate in which a release layer is formed by applying the release layer-forming composition according to any one of claims 1 to 5 onto a substrate and then exposing the substrate to light. A step of applying the composition for forming a release layer according to any one of claims 1 to 5 to a substrate and exposing the composition to light to form a release layer;
forming a resin substrate having a light transmittance of 80% or more at a wavelength of 400 nm on the release layer; and peeling the resin substrate with a peeling force of 1.0 N/25 mm or less.