TW202248381A - Adhesive sheet, reinforcement film, and device manufacturing method - Google Patents

Abstract

An adhesive sheet (2) is obtained by forming, into a layered configuration, an adhesive composition that contains an acrylic base polymer and a polyfunctional (meth)acrylate having four or more (meth)acryloyl groups in one molecule as a photocuring agent. Relative to the total amount of constituent monomer components, the acrylic base polymer contains at least 70 wt% of (meth)acrylic acid alkyl esters, which are chain alkyls with the alkyl group having at least 6 carbons. The content in the adhesive composition of polyfunctional (meth)acrylate having four or more functional groups is preferably at least 7 parts by weight relative to 100 parts by weight of the acrylic base polymer.

Description

Adhesive sheet, reinforcing film, and manufacturing method of device

The present invention relates to an adhesive sheet containing a photocurable adhesive composition, and a reinforcing film provided with the adhesive sheet on a film substrate. Furthermore, the present invention relates to a method of manufacturing a device with a reinforcing film that bonds a reinforcing film to the surface of an adherend.

Sometimes an adhesive film is attached to the surface of an optical device such as a display or an electronic device to protect the surface or impart impact resistance. Such an adhesive film is usually fixed and laminated with an adhesive layer (adhesive sheet) on the main surface of the film substrate, and is bonded to the surface of the device through the adhesive sheet.

In the state before the device is assembled, processed, transported, etc., damage or breakage of the adherend can be suppressed by temporarily adhering the adhesive film to the surface of the device or device component parts. Patent Document 1 discloses a reinforcing film provided with an adhesive sheet comprising a photocurable adhesive composition on a film substrate.

The reinforcing film can be peeled off from the adherend due to the low adhesiveness of the adhesive immediately after it is attached to the adherend. Therefore, secondary processing can be performed from the adherend, and the reinforcing film can be selectively peeled and removed from the portion of the adherend that does not require reinforcement. The adhesive of the reinforcement film is firmly bonded to the adherend by photohardening, so the film substrate is permanently attached to the surface of the adherend, and can be used as a reinforcing material responsible for surface protection of the device. [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2020-41113

[Problem to be solved by the invention]

In recent years, the borderless display has progressed continuously, and a configuration in which an optical sensor such as a fingerprint sensor is arranged in the display area of the display has been proposed. For example, by arranging an optical sensor on the back of an organic EL (Electroluminescence, electroluminescence) panel as a display element, a configuration with an optical sensor in the display area can be realized.

It has been pointed out that in this configuration, when the screen is viewed in a bright place, components such as an optical sensor arranged on the back surface of the image display panel are visually recognized (recognized). Visibility (recognition) of the optical sensor from the front of the display can be reduced by arranging a high-haze adhesive sheet on the back of the image display panel (between the image display panel and the optical sensor). On the other hand, the adhesive sheet preferably has a low haze in consideration of the convenience of optical inspection by visual inspection or inspection equipment in the manufacturing process of the device.

In view of the above circumstances, an object of the present invention is to provide an adhesive sheet having a high haze in a final product assembled into a device without lowering the inspection property in the manufacturing steps of the device. [Technical means to solve the problem]

One aspect of the present invention is an adhesive sheet obtained by forming a photocurable adhesive composition in a layered form. The adhesive composition contains an acrylic base polymer and a photocuring agent, and may further contain a photopolymerization initiator.

The acrylic base polymer contains at least 70% by weight of an alkyl (meth)acrylate based on the total amount of monomer components, and the alkyl group in the alkyl (meth)acrylate is one with 6 or more carbon atoms. chain alkyl. The photocuring agent contains polyfunctional (meth)acrylate having 4 or more (meth)acryl groups in 1 molecule.

The content of the tetrafunctional or higher polyfunctional (meth)acrylate in the adhesive composition is preferably 7 parts by weight or more relative to 100 parts by weight of the acrylic base polymer.

The difference H ₁ -H ₀ between the haze H ₁ after photocuring and the haze H ₀ before photocuring of the adhesive sheet is preferably 1.0% or more. The haze H0 of the adhesive sheet before photocuring is preferably less than 6%, and may be less than ₅ %. The haze H1 _of the adhesive sheet after photocuring is preferably 3% or more, and may be 5% or more or 6% or more.

Still another aspect of the present invention is a reinforcing film obtained by fixedly laminating the above-mentioned adhesive sheet on one main surface of the film substrate. A device with a reinforcing film can be formed by temporarily adhering the sheet of the reinforcing film to the surface of the adherend, and then photocuring the adhesive sheet. The adherend may also be an organic EL panel. [Effect of Invention]

The above-mentioned adhesive sheet has a low haze before photohardening, so even in the state of being attached to the adherend, the accuracy of optical inspection by visual inspection or photography can be ensured. In addition, the adhesive sheet has a high haze after light hardening, so it is difficult to visually recognize (identify) from the outer surface of the device to components such as optical sensors arranged on the back side of the adhesive sheet.

FIG. 1 is a cross-sectional view of an adhesive sheet with a release film, in which release films 51 and 52 are temporarily attached to both sides of the adhesive sheet 2 . 2 is a cross-sectional view of a reinforcement film in which an adhesive sheet 2 is fixedly laminated on one main surface of a film substrate 1 and a release film 52 is temporarily adhered to the adhesive sheet 2 . The adhesive sheet 2 is obtained by forming a photocurable adhesive composition in a layered form, and is hardened by irradiation with active light rays such as ultraviolet rays to increase the bonding strength with the adherend.

FIG. 3 is a cross-sectional view showing a state where the reinforcing film 10 is attached to the surface of the device 20 . The release film 51 is removed by peeling off the surface of the adhesive sheet 2 of the reinforcing film shown in FIG. Film 10. In this state, the adhesive sheet 2 is in a state where the reinforcing film 10 (adhesive sheet 2 ) is temporarily adhered to the device 20 before photocuring. By photocuring the adhesive sheet 2 , the adhesive force at the interface between the device 20 and the adhesive sheet 2 is improved, and the reinforcing film 10 is fixed to the surface of the device 20 .

"Fixed" refers to the state where two layers of laminated layers are firmly connected, and it is impossible or difficult to peel off at the interface between the two. "Temporary adhesion" refers to the state in which the adhesive force between the two laminated layers is small and can be easily peeled off at the interface between the two.

The adhesive sheet shown in FIG. 1 is in a state where release films 51 and 52 are temporarily attached to both sides of the adhesive sheet 2 , and the release films 51 and 52 can be easily peeled off from the surface of the adhesive sheet 2 . In the reinforcing film shown in FIG. 2 , the film substrate 1 is fixed to the adhesive sheet 2 , and the release film 51 is temporarily adhered to the adhesive sheet 2 . When the film substrate 1 and the release film 51 are peeled off, peeling occurs at the interface between the adhesive sheet 2 and the release film 51 , and the adhesive sheet 2 remains fixed on the film substrate 1 . No adhesive remains on the peeled release film 51 .

The device with a reinforcing film shown in FIG. 3 is in a state where the device 20 and the adhesive sheet 2 are temporarily adhered before the adhesive sheet 2 is photohardened. When the film substrate 1 and the device 20 are peeled off, peeling occurs at the interface between the adhesive sheet 2 and the device 20, so that the state where the adhesive sheet 2 is fixed on the film substrate 1 is maintained. After the adhesive sheet 2 is light-cured, the adhesive force between the adhesive sheet 2 and the device 20 is increased, and it is in a fixed state, so it is difficult to peel the film base material 1 from the device 20. When both are peeled off, the adhesive sheet 2 remains Coagulation failure occurs.

[adhesive sheet] The adhesive sheet 2 contains a photocurable composition containing a base polymer and a photocuring agent. The adhesive sheet 2 has low adhesive force with the adherend such as devices or device parts before photocuring, so it can be peeled off from the adherend. The adhesive sheet 2 is excellent in adhesion reliability because the adhesive force with the adherend is improved by photocuring.

Photocurable adhesives hardly harden in the general storage environment, and harden by the irradiation of active light such as ultraviolet rays. Therefore, the reinforcing film formed by adhesive sheet 2 fixedly laminated on the film substrate 1 has the following advantages: the hardening time point of the adhesive sheet 2 can be set arbitrarily, and the preparation time of the steps can be flexibly handled.

The thickness of the adhesive sheet 2 is, for example, about 1 to 300 μm. There is a tendency that the adhesiveness with an adherend improves so much that the thickness of the adhesive sheet 2 is large. On the other hand, when the thickness of the adhesive sheet 2 is too large, the fluidity before photocuring may be high and handling may be difficult. Therefore, the thickness of the adhesive sheet 2 is preferably 3-100 μm, more preferably 5-50 μm, further preferably 6-40 μm, especially preferably 8-30 μm. From the viewpoint of thinning, the thickness of the adhesive sheet 2 may be 25 μm or less, 20 μm or less, or 18 μm or less.

The total light transmittance of the adhesive sheet used in optical devices such as displays is preferably at least 80%, more preferably at least 85%, and still more preferably at least 90%.

When the haze of the adhesive sheet is high, when optical inspection is performed by visual inspection or photography in the manufacturing process of the device, light scattering on the adhesive sheet may hinder the inspection and reduce inspection accuracy. Therefore, from the viewpoint of ensuring inspection accuracy, the haze of the adhesive sheet is preferably less than 6%, and may be 5% or less, 4% or less, or 3% or less. On the other hand, since the haze of the adhesive sheet is high in the final product such as a display, it is possible to prevent the user from seeing (recognizing) components such as optical sensors arranged on the back side of the adhesive sheet. From this point of view, the haze of the adhesive sheet is preferably 3% or more, more preferably 5% or more, further preferably 6% or more, and may be 7% or more, 8% or more, 9% or more, or 10% or more. %above.

The adhesive sheet of the present invention has a low haze before photohardening, and the haze increases after photohardening. Therefore, by performing optical inspection before photocuring the adhesive sheet, the accuracy of optical inspection can be improved. In addition, in the final product obtained by photocuring the adhesive sheet, the haze of the adhesive sheet is high, so it is difficult for the user of the device to recognize the optical sensor and the like arranged on the back.

The increase in haze of the adhesive sheet caused by photohardening, that is, the difference H ₁ -H ₀ between the H ₁ of the adhesive sheet after photohardening and the haze H ₀ of the adhesive sheet before photohardening is preferably 1.0 % or more, more preferably 1.5% or more, and may be 2.0% or more, 2.5% or more, 3.0% or more, 4.0% or more or 5.0% or more. The upper limit of the haze increase amount is not particularly limited, but generally, it may be 30% or less, 20% or less, or 15% or less.

＜Adhesive composition＞ The adhesive composition constituting the adhesive sheet 2 contains a base polymer and a photocuring agent, and has photocurability. As described below, by making the adhesive composition contain a specific base polymer and a photocuring agent, an adhesive sheet having a large increase in haze due to photocuring can be obtained. From the viewpoint of improving the efficiency of photocuring, the adhesive composition (photocurable composition) constituting the adhesive sheet 2 preferably contains a photopolymerization initiator.

(base polymer) The base polymer is the main component of the adhesive composition, and is the main factor determining the properties of the adhesive sheet such as the adhesive force. The adhesive composition preferably contains an acrylic polymer as a base polymer from the viewpoint of easy control of the adhesive force, and more than 50% by weight of the adhesive composition is preferably an acrylic polymer.

The acrylic base polymer contains an alkyl (meth)acrylate as a main monomer component. In addition, in this specification, "(meth)acrylic acid" means acrylic acid and/or methacrylic acid.

As the alkyl (meth)acrylate, a C _1-22 alkyl (meth)acrylate having 1 to 22 alkyl carbon atoms is preferably used. In the alkyl (meth)acrylate, the alkyl group may have a branch or may have a cyclic alkyl group.

The acrylic base polymer preferably contains at least 70% by weight of an alkyl (meth)acrylate based on the total amount of monomer components, and the alkyl group in the alkyl (meth)acrylate has the number of carbon atoms A chain alkyl group of 6 or more. The higher the ratio of alkyl (meth)acrylates (hereinafter referred to as "alkyl (meth)acrylates with C6 or more") having a chained alkyl group having 6 or more carbon atoms, the better the photocured adhesive sheet will be. The higher the haze of the material tends to be. The amount of the C6 or higher alkyl (meth)acrylate is more preferably 75% by weight or more, more preferably 80% by weight or more, and may be 85% by weight or more, or 90% by weight or more with respect to the total amount of constituent monomer components , 93% by weight or more or 95% by weight or more.

The upper limit of the amount of C6 or more alkyl (meth)acrylate is not particularly limited. As described below, in order to introduce crosslinking points into the acrylic base polymer, it is preferable to use a hydroxyl group-containing monomer or a carboxyl group-containing monomer. The amount of base (meth)acrylate is preferably 99.5% by weight or less, more preferably 99% by weight or less, and may be 98% by weight or less or 97% by weight or less.

The chain alkyl group of C6 or more alkyl (meth)acrylate may be a straight chain or may have a branch. Specific examples of alkyl (meth)acrylates with C6 or more include: hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (meth)acrylate ) octyl acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, (meth)acrylate base) undecyl acrylate, dodecyl (meth)acrylate, isotridecyl (meth)acrylate, tetradecyl (meth)acrylate, isodecayl (meth)acrylate Tetradecyl ester, Pentadecyl (meth)acrylate, Hexadecyl (meth)acrylate, Heptadecyl (meth)acrylate, Octadecyl (meth)acrylate, ( Isostearyl methacrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, behenyl acrylate, etc.

From the viewpoint of lowering the glass transition temperature of the acrylic base polymer and making the adhesive sheet moderately flexible, the carbon number of the chain alkyl group in the alkyl (meth)acrylate of C6 or more is preferably 9 or less. Specific examples of low Tg C6 or higher alkyl (meth)acrylates include: 2-ethylhexyl acrylate (Tg: -70°C), n-hexyl acrylate (Tg: -65°C), n-hexyl acrylate Octyl acrylate (Tg: -65°C), isononyl acrylate (Tg: -60°C), n-nonyl acrylate (Tg: -58°C), isooctyl acrylate (Tg: -58°C), etc.

As mentioned above, the chain alkyl group in C6 or more alkyl (meth)acrylate may have a branch. It is considered that when the carbon number of the alkyl group is large or the alkyl group has a branched structure, the molecular volume is large, so it is easy to light-cure the adhesive with a light-hardening agent with a large functional group. Larger phase domains are formed, and the haze increases significantly.

The monomer components of the acrylic base polymer can contain more than two kinds of C6 or more alkyl (meth)acrylates, and can also contain C _6-9 alkyl (meth)acrylates and C ₁₀ (meth)acrylates _-22 Alkyl esters.

The monomer components of the acrylic base polymer may contain not only C6 or more alkyl (meth)acrylates, but also alkyl (meth)acrylates having an alkyl group with 5 or less carbon atoms, or a cyclic Alkyl (meth)acrylates.

Specific examples of alkyl (meth)acrylates having an alkyl group having 5 or less carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, Isobutyl (meth)acrylate, second butyl (meth)acrylate, third butyl (meth)acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, (meth) Neopentyl acrylate, etc.

Specific examples of alkyl (meth)acrylates having an alicyclic alkyl group include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, and cycloheptyl (meth)acrylate. Cycloalkyl (meth)acrylates such as cyclooctyl (meth)acrylate; (meth)acrylates with bicyclic aliphatic hydrocarbon rings such as iso(meth)acrylate; (meth)acrylic acid Dicyclopentyl, Dicyclopentyloxyethyl (meth)acrylate, Tricyclopentyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-methyl (meth)acrylate (Meth)acrylates having an aliphatic hydrocarbon ring having three or more rings, such as 2-adamantyl ester and 2-ethyl-2-adamantyl (meth)acrylate.

The acrylic base polymer preferably contains a monomer component having a crosslinkable functional group as a copolymerization component in addition to the above-mentioned alkyl (meth)acrylate. The monomer having a crosslinkable functional group may, for example, be a hydroxyl group-containing monomer or a carboxyl group-containing monomer. The acrylic base polymer may have both a hydroxyl group-containing monomer and a carboxyl group-containing monomer as a copolymerization component, or may have only any one. The introduction of a crosslinked structure into the acrylic base polymer tends to improve the cohesive force, and the peelability of the adhesive sheet 2 before photocuring from the adherend tends to improve.

Examples of hydroxyl-containing monomers include: 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxy (meth)acrylate Hydroxyhexyl, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, 4-(hydroxymethyl)cyclo(meth)acrylate Hexyl Methyl Etc. Examples of carboxyl group-containing monomers include: (meth)acrylic acid, 2-carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, butene Acid etc.

In the acrylic base polymer, the total amount of the hydroxyl group-containing monomer and the carboxyl group-containing monomer is preferably 0.5 to 20% by weight, more preferably 1 to 15% by weight, and may be 1.5 to 10% by weight.

The acrylic base polymer may contain N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperidone, etc. 𠯤, vinyl pyrrole, vinyl pyrrole, vinyl imidazole, vinyl azole, vinyl morpholine, N-acryloyl morpholine, N-vinyl carboxylic acid amides, N-vinyl caprolactam and other nitrogen-containing monomers.

The acrylic base polymer may contain monomer components other than the above. In the acrylic base polymer, as monomer components, vinyl ester monomers, aromatic vinyl monomers, epoxy group-containing monomers, vinyl ether monomers, sulfo group-containing monomers, phosphoric acid group-containing monomers, etc. Monomers, monomers containing acid anhydride groups, etc.

An acrylic polymer as a base polymer can be obtained by polymerizing the above-mentioned monomer components using various known methods such as solution polymerization, emulsion polymerization, and bulk polymerization. The solution polymerization method is preferable from the standpoint of the balance of properties such as adhesive force and holding force of the adhesive, and cost. As a solvent for solution polymerization, ethyl acetate, toluene, methyl ethyl ketone and the like can be used. The solution concentration is usually about 20 to 80% by weight. As a polymerization initiator, various well-known substances, such as an azo system and a peroxide system, can be used. To adjust the molecular weight, chain transfer agents can be used. The reaction temperature is usually about 50 to 80°C, and the reaction time is usually about 1 to 8 hours.

The weight average molecular weight of the acrylic base polymer is preferably from 100,000 to 2 million, more preferably from 200,000 to 1.5 million, and still more preferably from 300,000 to 1 million. In addition, when introducing a crosslinked structure into an acrylic base polymer, the molecular weight of a base polymer means the molecular weight before introducing a crosslinked structure.

(crosslinking agent) Introducing a cross-linked structure into the acrylic base polymer is preferable from the viewpoint of making the adhesive have moderate cohesion and adhesive force, and ensuring the peelability of the adhesive sheet before photocuring from the adherend. . For example, a crosslinked structure is introduced by adding a crosslinking agent to a solution obtained by polymerizing an acrylic base polymer, and heating as necessary. The crosslinking agent may, for example, be an isocyanate crosslinking agent, an epoxy crosslinking agent, an azoline crosslinking agent, an aziridine crosslinking agent, a carbodiimide crosslinking agent, a metal chelate Cross-linking agent, etc. These crosslinking agents react with functional groups such as hydroxyl and carboxyl introduced into the acrylic base polymer to form a crosslinking structure. Isocyanate-based crosslinking agents and epoxy-based crosslinking agents are preferred because they have high reactivity with the hydroxyl group or carboxyl group of the acrylic base polymer and are easy to introduce a crosslinked structure.

As an isocyanate type crosslinking agent, the polyisocyanate which has 2 or more isocyanate groups in 1 molecule can be used. Examples of the polyisocyanate-based crosslinking agent include: lower aliphatic polyisocyanates such as butyl diisocyanate and hexamethylene diisocyanate; cyclopentyl diisocyanate, cyclohexylene diisocyanate, isophorone Alicyclic isocyanate such as diisocyanate; Aromatic isocyanate such as 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate; Trimethylolpropane/toluene diisocyanate Trimer adducts (for example, "Coronate L" manufactured by Tosoh), trimethylolpropane/hexamethylene diisocyanate trimer adducts (for example, "Coronate HL" manufactured by Tosoh), Trimethylolpropane adduct of xylylene diisocyanate (for example, "Takenate D110N" manufactured by Mitsui Chemicals, isocyanurate form of hexamethylene diisocyanate (for example, "Coronate HX" manufactured by Tosoh) ”) and other isocyanate adducts, etc.

As an epoxy crosslinking agent, the polyfunctional epoxy compound which has 2 or more epoxy groups in 1 molecule can be used. The epoxy-type crosslinking agent may have 3 or more or 4 or more epoxy groups in 1 molecule. The epoxy group of the epoxy-based crosslinking agent may also be a glycidyl group. Examples of epoxy-based crosslinking agents include: N,N,N',N'-tetraglycidyl-m-xylylenediamine, diglycidylaniline, 1,3-bis(N,N-di Glycidylaminomethyl) cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol di Glycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trihydroxy Methyl propane polyglycidyl ether, diglycidyl adipate, diglycidyl phthalate, triglycidyl-tris(2-hydroxyethyl)isocyanurate, resorcinol diglycidyl Glyceryl ether, bisphenol S diglycidyl ether, etc. As the epoxy-based crosslinking agent, commercially available items such as "Denacol" manufactured by Nagase Kasei, "Tetrad X" and "Tetrad C" manufactured by Mitsubishi Gas Chemical can also be used.

The usage-amount of a crosslinking agent can be adjusted suitably according to the composition, molecular weight, etc. of an acrylic base polymer. With respect to 100 parts by weight of the acrylic base polymer, the amount of crosslinking agent used is about 0.03 to 2 parts by weight, preferably 0.05 to 1 part by weight, more preferably 0.08 to 0.8 parts by weight, or 0.1 to 0.5 parts by weight share.

In order to promote the formation of the cross-linked structure, a cross-linking catalyst can also be used. As a crosslinking catalyst, organometallic compounds, such as an organometallic complex (chelate compound), the compound of a metal and an alkoxy group, and the compound of a metal and an acyloxy group; and a tertiary amine etc. are mentioned. In particular, an organometallic compound is preferable from the viewpoint of suppressing the progress of the crosslinking reaction in a solution state at room temperature to secure the pot life of the adhesive composition. The metal of the organometallic compound may, for example, be iron, tin, aluminum, zirconium, zinc, titanium, lead or cobalt. The usage-amount of a crosslinking catalyst is generally 0.5 weight part or less with respect to 100 weight part of acrylic base polymers.

(light hardener) The adhesive composition constituting the adhesive sheet 2 also contains a photocuring agent in addition to the acrylic base polymer. When the adhesive sheet 2 containing the photocurable adhesive composition is photocured after being bonded to an adherend, the adhesive force with the adherend is enhanced.

As a light hardening agent, the polyfunctional (meth)acrylate which has 4 or more (meth)acryloyl groups in 1 molecule can be used. Polyfunctional (meth)acrylates are typically esters of polyhydric alcohols and (meth)acrylic acid. From the viewpoint of compatibility with the acrylic base polymer, the molecular weight of the photocuring agent is preferably 2,000 or less, more preferably 1,000 or less, and may be 800 or 600 or less. From the point of view of making the adhesive after light hardening moderately cohesive and thereby improving adhesion, the functional group equivalent weight of the light hardener (that is, the molecular weight of each (meth)acryl group) is preferably 60-200, more preferably Preferably it is 70-150, and it can also be 75-130 or 80-120.

Specific examples of tetrafunctional or higher polyfunctional (meth)acrylates include: tetramethylolmethane tetra(meth)acrylate, di-trimethylolpropane tetra(meth)acrylate, di - Trimethylolpropane penta(meth)acrylate, di-trimethylolpropane hexa(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, propane Oxidized pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and the like. A polyfunctional (meth)acrylate can also use 2 or more types together.

Since the multifunctional (meth)acrylate shows moderate compatibility with the acrylic base polymer and has a small refractive index difference with the acrylic base polymer, it can reduce the fogging of the adhesive sheet before photohardening Spend. Also, by using a polyfunctional (meth)acrylate with four or more functions as a light hardener, there is a tendency for the haze of the adhesive sheet after light curing to increase, and the more the amount of the polyfunctional (meth)acrylate The larger the amount, the larger the haze increase H ₁ -H ₀ of the adhesive sheet due to photohardening tends to be.

With respect to 100 parts by weight of the acrylic base polymer, the amount of the tetrafunctional or higher polyfunctional (meth)acrylate in the adhesive composition is preferably 7 parts by weight or more, more preferably 8 parts by weight or more, and even more preferably It is 10 parts by weight or more, and may be 13 parts by weight or more, or 15 parts by weight or more. The amount of the tetrafunctional or more functional (meth)acrylate in the adhesive composition is not particularly limited, but if the amount of the photohardener is too large, the haze of the adhesive sheet before photohardening may increase . Also, when the amount of the photocuring agent is too large, the adhesion and flexibility of the adhesive sheet after photocuring may be insufficient. Therefore, with respect to 100 parts by weight of the acrylic base polymer, the amount of the tetrafunctional or higher polyfunctional (meth)acrylate in the adhesive composition is preferably 40 parts by weight or less, more preferably 35 parts by weight or less, and further It is preferably 30 parts by weight or less, and may be 25 parts by weight or less.

In the adhesive composition, as a photohardening agent, in addition to polyfunctional (meth)acrylates containing more than four functions, (meth)acrylates below three functions, or other photocurable monomers or Oligomer. When the adhesive composition contains polyfunctional (meth)acrylates with four or more functions as light hardeners, the total amount of light hardeners (polyfunctional (tetrafunctional or more) The total of (meth)acrylate and other photocuring agents) is preferably 40 parts by weight or less, and may be 30 parts by weight or less or 25 parts by weight or less. With respect to 100 parts by weight of the acrylic base polymer, the content of light hardeners other than polyfunctional (meth)acrylates with four or more functions is preferably 15 parts by weight or less, more preferably 10 parts by weight or less, and may be 5 parts by weight or less, 3 parts by weight or less, and 1 part by weight or less.

(photopolymerization initiator) The adhesive composition preferably contains a photopolymerization initiator. The photopolymerization initiator generates active species by the irradiation of active light, thereby promoting the hardening reaction of the photohardener. When using a polyfunctional (meth)acrylate as a photocuring agent, it is preferable to use a photoradical polymerization initiator. As the photoradical polymerization initiator, it is preferably a photoradical generator that is cleaved by visible light or ultraviolet light with a wavelength shorter than 450 nm to generate free radicals, such as hydroxyketones, benzoyl dimethyl acetal Ketones, amino ketones, acyl phosphine oxides, benzophenones, trichloromethyl-containing trioxane derivatives, etc. A photoinitiator may be used individually, and may mix and use 2 or more types.

The content of the photopolymerization initiator in the adhesive composition is about 0.001-5 parts by weight, or 0.01-3 parts by weight or 0.03-1 part by weight relative to 100 parts by weight of the acrylic base polymer.

(Oligomer) The adhesive composition may contain oligomers in addition to the acrylic base polymer. For example, the adhesive composition may contain an acrylic oligomer in addition to the acrylic base polymer. As an oligomer, what has a weight average molecular weight of about 1000-30000 can be used. The acrylic oligomer contains an alkyl (meth)acrylate as a main constituent monomer component. From the viewpoint of improving the adhesive force of the adhesive sheet 2 after photocuring, the glass transition temperature of the acrylic oligomer is preferably 40°C or higher, more preferably 50°C or higher. The oligomer may contain a crosslinkable functional group similarly to the acrylic base polymer.

The content of the oligomer in the adhesive composition is not particularly limited. When the adhesive composition contains an acrylic oligomer in addition to the acrylic base polymer, from the viewpoint of adjusting the adhesive force to an appropriate range, it is less than 100 parts by weight of the acrylic base polymer. The amount of the polymer is preferably 0.1-20 parts by weight, more preferably 0.3-10 parts by weight, and still more preferably 0.5-5 parts by weight.

(other additives) In addition to the components exemplified above, the adhesive composition may also contain a silane coupling agent, an adhesiveness-imparting agent, a plasticizer, a softener, an anti-deterioration agent, a filler, and a coloring agent within a range that does not impair the characteristics of the present invention. , UV absorbers, antioxidants, surfactants, antistatic agents and other additives.

＜Formation of Adhesive Sheet＞ By roll coating, contact roll coating, gravure coating, reverse coating, roll brush coating, spray coating, dip roll coating, rod coating, knife coating, air knife coating, curtain coating Coating, lip coating, die coating, etc., the above-mentioned adhesive composition is applied to the base material, and the solvent is dried and removed if necessary, thereby forming an adhesive sheet. As a drying method, an appropriate method can be suitably adopted. The heating and drying temperature is preferably from 40°C to 200°C, more preferably from 50°C to 180°C, further preferably from 70°C to 170°C. The drying time is preferably from 5 seconds to 20 minutes, more preferably from 5 seconds to 15 minutes, and still more preferably from 10 seconds to 10 minutes.

When the adhesive composition contains a crosslinking agent, it is preferable to perform crosslinking by heating or aging simultaneously with or after solvent drying. The heating temperature and heating time can be appropriately set according to the type of cross-linking agent used, and the cross-linking is usually carried out by heating in the range of 20°C to 160°C for about 1 minute to 7 days. The heating for drying and removing the solvent can also be used as the heating for crosslinking.

By introducing a crosslinked structure into the acrylic base polymer, the gel fraction increases, and the storage modulus of the adhesive sheet 2 tends to increase. And there is a tendency as follows: the higher the gel fraction of the adhesive before photohardening, the harder the adhesive is, and when the reinforcing film is peeled off from the adherend due to secondary processing, etc., the paste in the adherend can be suppressed residual. The gel fraction of the adhesive sheet 2 before photocuring (that is, the gel fraction of the photocurable composition constituting the adhesive sheet) is preferably 25% or more, more preferably 30% or more, and may be 35% above, above 40%, or above 45%. On the other hand, when the gel fraction is too large, the adhesive force and flexibility may decrease. Therefore, the gel fraction of the adhesive sheet 2 before photocuring is preferably 80% or less, and may be 75% or less or 70% or less.

The gel fraction can be obtained as the insoluble fraction in solvents such as ethyl acetate. Specifically, after immersing the adhesive sheet in ethyl acetate at 23°C for 7 days, the ratio of the insoluble fraction to that before immersion was determined. Calculate the gel fraction in the form of the weight fraction of the sample (unit: weight %). Generally speaking, the gel fraction of a polymer is equal to the degree of cross-linking, and the more cross-linking parts in the polymer, the greater the gel fraction.

The base material used for formation of an adhesive sheet is not specifically limited. For example, by coating the adhesive composition on the release film 51, and performing solvent removal and crosslinking as necessary, and attaching the release film 52, as shown in FIG. Adhesive sheet. It is also possible to attach a release film 52 to the adhesive sheet 2 and then carry out cross-linking.

As the release films 51 and 52, plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films can be preferably used. The thickness of the release film is usually 3-200 μm, preferably about 10-100 μm. For the contact surfaces of the release films 51, 52 and the adhesive sheet 2, it is preferable to use silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based release agents, or silicon oxide powder. Release treatment. Regarding the release films 51 and 52 , antistatic treatment may be performed on either one or both of the release-treated surface and the non-treated surface. By applying antistatic treatment to the release film, static electricity can be suppressed when the release film is peeled off from the adhesive sheet.

[reinforcing film] The above-mentioned adhesive sheet is used for bonding various members. In one embodiment, the adhesive sheet 2 is used for bonding the flexible plastic film substrate to the surface of various devices or their constituent members. Appropriate rigidity is imparted by attaching a flexible plastic film to the surface of the device or its constituent parts, so it can expect effects such as improved operability and damage prevention for thin-thick members.

When the film substrate 1 is attached to the device or its constituent members via the adhesive sheet 2, as shown in FIG. After bonding the adhesive sheet 2 of the reinforcing film 10 to the device or its constituent members, the adhesive sheet 2 is photocured.

＜Film substrate＞ As the film substrate 1 of the reinforcing film 10, a flexible plastic film can be used. In order to fix the film substrate 1 and the adhesive sheet 2, it is preferable that the adhesive sheet 2 attachment surface of the film substrate 1 is not subjected to release treatment.

The thickness of the film substrate 1 is, for example, about 4 to 500 μm. From the viewpoint of reinforcing the device by imparting rigidity and mitigating impact, the thickness of the film substrate 1 is preferably at least 12 μm, more preferably at least 20 μm, and may be at least 30 μm, at least 40 μm, or Above 45 μm. The thickness of the film substrate 1 is preferably 300 μm or less, more preferably 200 μm or less, from the viewpoint of making the reinforcing film flexible and improving handleability.

As the plastic material constituting the film substrate 1, polyester resin, polyolefin resin, cyclic polyolefin resin, polyamide resin, polyimide resin, polyetheretherketone, polyether Polyarylate-based resins, aromatic polyamide-based resins, etc. In the reinforcing film for optical devices such as displays, the film substrate 1 is preferably a transparent film. Also, when the adhesive sheet 2 is photocured by irradiating active light from the film base 1 side, the film base 1 is preferably transparent to the active light used for curing the adhesive. In terms of both mechanical strength and transparency, polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate can be preferably used. Polyimide, transparent aromatic polyamide, polyether ether ketone. When irradiating active rays from the adherend side, it is only necessary that the adherend is transparent to the actinic rays, and the film substrate 1 may be opaque to the actinic rays.

The surface of the film substrate 1 may be provided with functional coatings such as an easy-adhesive layer, an easy-slip layer, a release layer, an antistatic layer, a hard coat layer, and an anti-reflection layer. Furthermore, in order to fix the film substrate 1 and the adhesive sheet 2 , it is preferable that no release layer is provided on the surface of the film substrate 1 where the adhesive sheet 2 is attached.

＜Production of Reinforcement Membrane＞ A reinforced film can be obtained by laminating the photocurable adhesive sheet 2 on the film substrate 1 . The adhesive sheet 2 may be directly formed on the film substrate 1 , or the adhesive sheet formed on the release film may be transferred onto the film substrate 1 . For example, the release film 52 temporarily attached to one side of the adhesive sheet 2 can be peeled off from the adhesive sheet with a release film shown in FIG. 1 , and the film substrate 1 can be attached to the adhesive sheet 2 As shown in FIG. 2 , an adhesive sheet 2 is fixedly laminated on the film substrate 1 and a release film is temporarily attached to the adhesive sheet 2 .

[Device with reinforcement film] The above-mentioned reinforcing film of the present invention is used by being attached to a device or a device component. The adherend to which the reinforcing film is bonded is not particularly limited, and examples thereof include various electronic devices, optical devices, and their constituent parts.

In one embodiment, the adherend to which the reinforcing film is bonded is an organic EL panel. The organic EL panel may be any of a top emission type and a bottom emission type. A top emission type organic EL panel has a structure in which an anode (metal electrode), an organic light-emitting layer, and a cathode (transparent electrode) are sequentially provided on a substrate, and light is extracted from the cathode side. The bottom emission type organic EL panel is configured by sequentially including a cathode, an organic light-emitting layer, and an anode on a transparent substrate, and extracting light from the transparent substrate side. By using a flexible heat-resistant film such as a polyimide film as a substrate of an organic EL panel, thinning and flexibility can be realized.

The reinforcement film can be attached to the entire adherend, or selectively attached only to the part to be reinforced (reinforcement target area). Also, after bonding the reinforcing film to the entire portion to be reinforced (reinforcement target area) and the non-reinforcement target area (non-reinforcement target area), the reinforcing film attached to the non-reinforcement target area may be cut and removed. Before the adhesive is photohardened, the reinforcing film is in a state of temporarily adhering to the surface of the adherend, so the reinforcing film can be peeled off from the surface of the adherend. It is also possible to attach the reinforcement film to the reinforcement target area and the non-reinforcement target area, selectively irradiate the reinforcement target area with light to light-cure the adhesive, and then selectively peel off and remove the non-reinforcement target area where the adhesive has not hardened The reinforcement film.

Appropriate rigidity is imparted by laminating a reinforcing film, so it can be expected to improve operability and prevent damage to thin members such as organic EL panels using flexible substrates. For example, a reinforcing film may be attached to the flexible substrate on the back surface (the surface opposite to the light extraction side) of the organic EL panel. A reinforcement film can also be pasted on the light extraction surface of the organic EL panel. The reinforcing film can also be pasted outside the substrate of the organic EL panel, for example, the reinforcing film can be pasted on the sealing material that seals the organic light-emitting layer and the electrodes.

In the manufacturing process of the device, when attaching the reinforcing film to the semi-finished product, the reinforcing film can be attached to the large-sized semi-finished product that has not been cut into the product size. The reinforcement film can also be laminated roll-to-roll on the parent roll of the device manufactured by the roll-to-roll process. Before pasting the reinforcement film, the surface of the adherend can be activated for the purpose of cleaning. The surface activation treatment may, for example, be plasma treatment, corona treatment or glow discharge treatment.

From the standpoint of peeling from the adherend and preventing peeling during storage or handling, the adhesive force between the adhesive sheet 2 and the adherend before photocuring is preferably about 0.005 to 1 N/25 mm. Regarding the adhesive force, the adhesive force was determined by a peeling test with a tensile speed of 300 mm/min and a peeling angle of 180° using a polyimide film as an adherend. Unless otherwise specified, the adhesive strength is measured at 25°C.

As mentioned above, the haze of the adhesive sheet 2 before photocuring is preferably less than 6%, and may be 5% or less, 4% or less, or 3% or less. By reducing the haze of the adhesive sheet 2 before photocuring, even after bonding the reinforcing film to the adherend, it does not prevent the organic EL panel from the film base 1 side by visual inspection or photography. Optical inspection of adherends can maintain inspection accuracy.

After attaching the reinforcing film to the adherend and performing an optical inspection or removing the reinforcing film from the non-reinforcing target area as necessary, the adhesive sheet 2 is irradiated with active light to light-harden the adhesive. The actinic ray may, for example, be ultraviolet rays, visible light, infrared rays, X-rays, α-rays, β-rays, or γ-rays. The active light rays are preferably ultraviolet rays, since hardening of the adhesive in a storage state can be suppressed and hardening can be facilitated. The irradiation intensity and irradiation time of the active light can be appropriately set according to the composition and thickness of the adhesive. Irradiation of active light to the adhesive sheet 2 may be performed from either one of the film substrate 1 side and the adherend side, or may be irradiated from both sides.

The adhesive force of the adhesive sheet 2 to an adherend increases with light hardening. The adhesive force between the adhesive sheet 2 and the adherend after photocuring is preferably 2 N/25 mm or more, more preferably 2.5 N/25 mm or more. The adhesive force between the adhesive sheet 2 and the adherend after photocuring is preferably more than 5 times the adhesive force between the adhesive sheet 2 and the adherend before photocuring.

As mentioned above, the haze of the adhesive sheet 2 increases by photocuring. The haze of the adhesive sheet 2 after photocuring is preferably 3% or more, more preferably 5% or more, further preferably 6% or more, and may be 7% or more, 8% or more, 9% or more, or 10% above. The haze increase H ₁ -H ₀ of the adhesive sheet caused by photohardening is preferably 1.0% or more, more preferably 1.5% or more, and may be 2.0% or more, 2.5% or more, 3.0% or more, or 4.0% Above or above 5.0%, may also be below 30%, below 20%, or below 15%.

As described above, by attaching the reinforcing film, moderate rigidity is given to the adherend, and the stress is relaxed and dispersed, so various abnormalities that may occur in the manufacturing process can be suppressed, and the production efficiency can be improved, and the yield rate can be improved. In addition, since the reinforcing film can be peeled off from the adherend before the adhesive is photohardened, it is possible to carry out secondary processing when lamination or poor bonding occurs, and it is also possible to selectively remove the reinforcing film from the non-reinforcing target area Wait for processing. Furthermore, the haze of the adhesive sheet is low before photohardening, so even in the state where the reinforcing film is pasted, the accuracy of inspection by visual inspection or photography can be ensured.

In the use of the completed device, even when the device is dropped, heavy goods are placed on the device, and a flying object collides with the device and is suddenly loaded with an external force, by affixing a reinforcing film, it can Prevent damage to the device. In addition, since the reinforcing film is firmly attached to the device after photocuring the adhesive, the reinforcing film is not easily peeled off even if it is used for a long time, and the reliability is excellent. In addition, since the adhesive sheet is highly fogged by photohardening, it is difficult to visually recognize the optical sensor placed on the back of the reinforcement film from the outer surface of the device, and it can also be preferably used for displaying on a display. Image display devices equipped with optical sensors such as fingerprint sensors in the area. [Example]

Hereinafter, examples and comparative examples related to the adhesive sheet are given and further described, but the present invention is not limited to these examples.

[Example 1] ＜Preparation of Adhesive Composition＞ Into the reaction vessel equipped with thermometer, stirrer, reflux cooling pipe and nitrogen introduction pipe, drop 96.2 parts by weight of 2-ethylhexyl acrylate (2EHA) and 3.8 parts by weight of 2-hydroxyethyl acrylate (2HEA) as monomers, 0.2 parts by weight of azobisisobutyronitrile (AIBN) as a polymerization initiator and 156 parts by weight of ethyl acetate as a solvent were blown with nitrogen, and nitrogen replacement was carried out for about 1 hour while stirring. Then, it heated to 60 degreeC, it was made to react for 7 hours, and the solution of the acrylic-type polymer whose weight average molecular weight (Mw) was 600,000 was obtained.

To the above-mentioned acrylic polymer solution (100 parts by weight of polymer), 0.1 part by weight of hexamethylene diisocyanate isocyanurate ("Coronate HX" manufactured by Tosoh) was added as a crosslinking agent. 0.02 parts by weight of iron acetylacetonate ("triacetylacetonate iron" manufactured by Nippon Chemical Industry Co., Ltd.) as a joint catalyst, dipentaerythritol polyacrylate (a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate) as a light hardener ; "NK Ester A-DPH" manufactured by Shin Nakamura Chemical Industry) 10 parts by weight, and 2,2-dimethoxy-1,2-diphenylethane-1-one (IGM Resins "Omnirad651") 0.1 parts by weight, and uniformly mixed to obtain an adhesive composition.

＜Production of Adhesive Sheet＞ The above-mentioned adhesive composition was coated on a silicone release-treated polyethylene terephthalate film (heavy release film) with a thickness of 75 μm so that the thickness after drying was 20 μm. After drying at 130°C for 1 minute to remove the solvent, attach the release-treated surface of a polyethylene terephthalate film (light release film) with a thickness of 50 μm that has been treated with silicone release to the surface of the adhesive Coated side. Thereafter, aging treatment was carried out for 4 days in an atmosphere of 25° C. to make it cross-linked, and an adhesive sheet with a release film temporarily adhered on both sides was obtained.

[Examples 2-7, Comparative Examples 1-7] The adhesive composition was prepared in the same manner as in Example 1, and an adhesive sheet was produced, except that the composition of the monomer of the acrylic polymer, the type and the addition amount of the light hardener were changed as shown in Table 1.

[Example 8, Comparative Examples 8 and 9] The monomer composition of the acrylic polymer, the type and amount of light hardener were changed as shown in Table 1. Also, 0.1 parts by weight of N,N,N',N'-tetraglycidyl-m-xylylenediamine (tetrafunctional epoxy compound, "Tetrad C" manufactured by Mitsubishi Gas Chemical) belonging to a tetrafunctional epoxy compound was added As a cross-linking agent instead of isocyanate-based cross-linking agent, without adding a cross-linking catalyst. Except these changes, the adhesive composition was prepared in the same manner as Example 1, and the adhesive sheet was produced.

[Evaluation] <Haze before photohardening> Peel off the release film (light release film) on one side of the adhesive sheet of the examples and comparative examples, attach the adhesive sheet to the glass plate, and then peel off the other release film The film (heavy release film) was peeled off to prepare a sample for haze measurement. Using a haze meter ("NDH-5000" manufactured by Nippon Denshoku Industries), light was irradiated from the surface of the adhesive sheet side, and the haze H0 of the adhesive sheet before _{photohardening} was measured according to JIS K7136.

<Haze after light hardening> Peel off the light-release film from the adhesive sheets of the examples and comparative examples, and attach the adhesive sheet to the glass plate, then peel off the surface of the film side by its own weight, and use an LED with a wavelength of 365 nm (light -emitting diode (light emitting diode) light source, irradiating 2000 mJ/cm ² of ultraviolet rays to make the adhesive composition photoharden. Thereafter, the heavy release film was peeled off, light was irradiated from the surface of the adhesive sheet side, and the haze H1 _of the adhesive sheet before photohardening was measured.

Table 1 shows the composition of the acrylic polymer in the adhesive composition of Examples and Comparative Examples, the type and amount of photocuring agent added, and the haze of the adhesive sheet before and after photocuring. In Table 1, the polymer composition is the weight ratio of the constituent monomers, and the amount of the photocuring agent is the added amount relative to 100 parts by weight of the solid content of the acrylic polymer. The details of the monomer and light hardener are as follows.

＜Single＞ 2EHA 2-ethylhexyl acrylate BA Butyl Acrylate 2HEA 2-Hydroxyethyl Acrylate 4HBA 4-Hydroxybutyl Acrylate AA Acrylic ＜Light hardener＞ DPH dipentaerythritol polyacrylate (refractive index: 1.489, viscosity: 7500 mPa s (25°C)) TMMT Pentaerythritol tetraacrylate (refractive index: 1.480, viscosity: 215 mPa s (40°C)) HDN 1,6-Hexanediol Diacrylate (Refractive Index: 1.456, Viscosity: 6 mPa·s(25℃)) DCP tricyclodecane dimethanol diacrylate (refractive index: 1.503, viscosity: 135 mPa s (25°C)) TMPT Trimethylolpropane triacrylate (refractive index: 1.474, viscosity: 105 mPa s (25°C))

[Table 1] Adhesive Composition Haze (%) polymer composition light hardener H ₀ H ₁ H ₁ -H ₀ 2EHA BA 2HEA 4HBA AAA type quantity Example 1 96.2 - 3.8 - - DPH 10 2.0 3.4 1.4 Example 2 96.2 - 3.8 - - DPH 20 3.2 10.8 7.6 Example 3 96.2 - 3.8 - - TMMT 10 1.1 3.0 1.9 Example 4 96.2 - 3.8 - - TMMT 20 3.7 7.2 3.5 Example 5 90.9 - - 9.1 - DPH 20 5.3 8.1 2.8 Example 6 98.5 - - 1.5 - DPH 20 4.7 16.0 11.3 Example 7 72.7 18.2 - 9.1 - DPH 20 4.8 6.5 1.7 Example 8 96.2 - - - 3.8 DPH 20 4.0 12.4 8.5 Comparative example 1 96.2 - 3.8 - - HDN 20 0.7 1.0 0.3 Comparative example 2 96.2 - 3.8 - - DCP 20 0.8 1.2 0.4 Comparative example 3 96.2 - 3.8 - - TMPT 20 0.7 1.0 0.3 Comparative example 4 96.2 - 3.8 - - DPH 1 0.7 1.2 0.5 Comparative Example 5 96.2 - 3.8 - - DPH 5 0.9 1.3 0.4 Comparative example 6 96.2 - 3.8 - - TMMT 5 0.7 1.3 0.5 Comparative Example 7 63.6 27.3 - 9.1 - DPH 20 3.5 4.2 0.7 Comparative Example 8 - 95.0 - - 5.0 DPH 20 0.7 1.1 0.4 Comparative Example 9 - 95.0 - - 5.0 TMMT 20 0.7 1.0 0.4

In Examples 1 to 8 in which polyfunctional acrylates with four or more functions were used as light hardeners, the haze increase H ₁ -H ₀ caused by light hardening of the adhesive sheet was 1% or more. In contrast, In Comparative Examples 1 and 2 using a difunctional acrylate and Comparative Example 3 using a trifunctional acrylate, H ₁ -H ₀ did not reach 1%. In Comparative Examples 4-6 in which the amount of acrylates with four or more functions was less, H ₁ -H ₀ did not reach 1%. According to the comparison between Example 1 and Example 2, and the comparison between Example 3 and Example 4, it can be seen that the more the content of multifunctional acrylates with four or more functions in the adhesive composition is, the more the adhesion caused by photohardening will be. The greater the haze rise of the sheet is.

According to the comparison of Example 2, Example 7 and Comparative Example 7, it can be seen that the higher the ratio of 2EHA (C8 alkyl acrylate) in the monomer components constituting the acrylic polymer, the higher the haze caused by photohardening greater tendency. In the comparison between Example 5 and Example 6, the same tendency can also be seen. According to the comparison of Example 8 and Comparative Examples 8 and 9, it can be seen that when using acrylic acid belonging to carboxyl-containing monomers as the comonomer component of the acrylic polymer, and using an epoxy crosslinking agent, due to the use of Alkyl (meth)acrylate with a large carbon number alkyl group is the main monomer component of the base polymer, and the haze increase caused by photohardening is also relatively large.

1: Membrane substrate 2: Adhesive sheet 10: Reinforcing film 20: Adhered body (organic EL panel) 51: Release film 52: Release film 100: Device with reinforced membrane

Fig. 1 is a cross-sectional view showing a laminated structure of an adhesive sheet provided with a release film on both sides. Fig. 2 is a cross-sectional view showing a laminated structure of a reinforcing film. Fig. 3 is a cross-sectional view showing an example of a laminated structure of a device bonded with a reinforcing film.

2: Adhesive sheet

51: Release film

52: Release film

Claims (8)

An adhesive sheet obtained by forming a photocurable adhesive composition containing an acrylic base polymer and a photocuring agent into a layered form. Regarding the above adhesive composition, in the above acrylic base polymer, The amount of alkyl (meth)acrylate is 70% by weight or more relative to the total amount of monomer components, and the alkyl group in the alkyl (meth)acrylate is a chain alkyl group with 6 or more carbon atoms. The light curing agent contains a polyfunctional (meth)acrylate having 4 or more (meth)acryl groups in one molecule, and contains 7 parts by weight or more of the above-mentioned polyfunctional (meth)acrylate with respect to 100 parts by weight of the acrylic base polymer. (meth)acrylate, and the difference H ₁ -H ₀ between the haze H ₁ after photocuring and the haze H ₀ before photocuring is 1.0% or more. The adhesive sheet according to claim 1, wherein the adhesive composition further contains a photopolymerization initiator. The adhesive sheet according to claim 1 or 2, wherein the acrylic base polymer contains at least one monomer component selected from the group consisting of hydroxyl-containing monomers and carboxyl-containing monomers, and the acrylic base polymer A crosslinked structure is introduced into the polymer. The adhesive sheet according to any one of Claims 1 to 3, whose haze H0 before photohardening is ₅ % or less. As the adhesive sheet according to any one of Claims ₁ to 4, the haze H1 after photohardening is 6% or more. A reinforced film, which is obtained by adhering and laminating the adhesive sheet according to any one of claims 1 to 5 on one of the main surfaces of the film substrate. A method of manufacturing a device, which is a method of manufacturing a device with a reinforcing film attached to its surface, and is After temporarily adhering the above-mentioned adhesive sheet of the reinforcing film as in claim 6 to the surface of the adherend, The above-mentioned adhesive sheet was subjected to photocuring. The manufacturing method of the device according to claim 7, wherein the above-mentioned adherend is an organic EL panel.

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