JP2020200464A - Adhesive sheet for sticking to optical member - Google Patents

Abstract

To provide an adhesive sheet for sticking to an optical member, whereby, an adhesive sheet is stuck to e.g. a display that displays a black screen, its designability can be improved, and its ultraviolet transmittance is kept low.SOLUTION: An adhesive sheet for sticking to an optical member 11 contains an acrylic polymer, a colorant and an ultraviolet absorber, wherein the colorant contains at least one selected from metal oxide and carbon black, the acrylic polymer having an acid value of 50 mgKOH/g or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to an adhesive sheet for bonding optical members.

Conventionally, a display device such as a liquid crystal display (LCD) and an input device used in combination with a display device such as a touch panel have been widely used. In the manufacture of these display devices and input devices, transparent adhesive sheets are used for bonding optical members.

For example, Patent Document 1 describes a double-sided adhesive composed of a laminate including a flexible base material layer, a first black layer and a second black layer, and a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer. The sheet is disclosed. In such a case, the adhesive sheet used for laminating the black layer may be required to have a design property that does not impair the black appearance.

By the way, as a means for imparting a black appearance to the pressure-sensitive adhesive sheet, a method of adding a pigment to the pressure-sensitive adhesive sheet is also known. For example, Patent Document 2 discloses a black foil-like pressure-sensitive adhesive containing a pressure-sensitive adhesive component, a black pigment, and a styrene-maleic acid resin.

Japanese Unexamined Patent Publication No. 2005-060435 Japanese Unexamined Patent Publication No. 2013-32430

As described above, a black adhesive sheet obtained by coloring a base material or an adhesive is known, but such an adhesive sheet is not supposed to be bonded to a display surface, and the design of the adhesive sheet No consideration was given to sex. Further, since the conventional black adhesive sheet has a high ultraviolet transmittance, there is a case where a black adhesive sheet having a low ultraviolet transmittance is required for bonding to a display surface.

Therefore, in order to solve the problems of the prior art, the present inventors are an adhesive sheet capable of enhancing the design when the black screen is attached to a display or the like, and the ultraviolet transmittance is increased. We proceeded with the study for the purpose of providing an adhesive sheet that was kept low.

As a result of diligent studies to solve the above problems, the present inventors have made a pressure-sensitive adhesive sheet containing an acrylic polymer, a colorant containing at least one selected from metal oxides and carbon black, and ultraviolet absorption. By blending the agent, when an adhesive sheet is attached to a display or the like displaying a black screen, an adhesive sheet that can enhance the design of the adhesive sheet and has a low ultraviolet transmittance can be obtained. I found it.
Specifically, the present invention has the following configuration.

一般式（１）において、Ｒ^１は、水素原子、ハロゲン原子、炭素数１〜４のアルコキシ基、ニトロ基またはシアノ基を表し、Ｒ^２は、水素原子または炭素数１〜８のアルキル基を表し、Ｒ^３は、アルキル基系構造体を表す；

一般式（２）において、Ｒ^４、Ｒ^５およびＲ^６は、水素原子、水酸基、アルキル基系構造体またはハロゲン原子であって、Ｒ^４、Ｒ^５およびＲ^６のすべてが水素原子であることはない。
［８］ 厚みが１０〜５０００μｍである［１］〜［７］のいずれかに記載の光学部材貼合用粘着シート。 [1] Contains an acrylic polymer, a colorant and an ultraviolet absorber,
An adhesive sheet for bonding optical members containing at least one colorant selected from metal oxide and carbon black.
[2] The pressure-sensitive adhesive sheet for bonding optical members according to [1], wherein the colorant is a metal oxide.
[3] The pressure-sensitive adhesive sheet for attaching an optical member according to [1] or [2], wherein the acid value of the acrylic polymer is 50 mgKOH / g or less.
[4] The adhesive sheet for attaching an optical member according to any one of [1] to [3], which has a total light transmittance of 40 to 80%.
[5] The adhesive sheet for bonding optical members according to any one of [1] to [4], which has a haze of 0.5 to 15%.
[6] The pressure-sensitive adhesive sheet for bonding optical members according to any one of [1] to [5], wherein the primary average particle size of the colorant is 0.1 to 15 μm.
[7] The adhesive sheet for attaching optical members according to any one of [1] to [6], wherein the ultraviolet absorber is represented by the following general formula (1) or (2);

In the general formula (1), R ¹ represents a hydrogen atom, a halogen atom, an alkoxy group having 1 to 4 carbon atoms, a nitro group or a cyano group, and R ² represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Represented, R ³ represents an alkyl group structure;

In the general formula (2), R ⁴ , R ⁵ and R ⁶ are hydrogen atoms, hydroxyl groups, alkyl group structures or halogen atoms, and all of R ⁴ , R ⁵ and R ⁶ are hydrogen atoms. There is no.
[8] The adhesive sheet for bonding optical members according to any one of [1] to [7], which has a thickness of 10 to 5000 μm.

According to the present invention, it is an adhesive sheet for attaching an optical member that can enhance the design when it is attached to a display or the like displaying a black screen, and is an adhesive for attaching an optical member having a low ultraviolet transmittance. You can get a sheet.

FIG. 1 is a schematic view showing a cross section of an adhesive sheet having a release sheet.

Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be based on typical embodiments or specific examples, but the present invention is not limited to such embodiments. In this specification, the numerical range represented by using "~" means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.

(Adhesive sheet)
The present invention relates to an adhesive sheet used for bonding optical members. The pressure-sensitive adhesive sheet of the present invention contains an acrylic polymer, a colorant and an ultraviolet absorber, and the colorant contains at least one selected from metal oxides and carbon black.

Since the adhesive sheet for attaching optical members of the present invention (hereinafter, also referred to as an adhesive sheet) has the above-mentioned structure, it is possible to enhance its design when it is attached to a display or the like displaying a black screen. it can. Specifically, when the adhesive sheet of the present invention is attached to a display displaying a black screen, the degree of black color development (preferability of the degree of blackness) of the display can be increased, so that the display and the display are provided. The design of the display device can be enhanced. Further, even if the display is in a state where the black screen is not displayed, the degree of blackness of the display is increased by attaching the adhesive sheet, so that the sense of unity with the surroundings is emphasized and the design is enhanced. Further, the adhesive sheet of the present invention can suppress the ultraviolet transmittance to a low level. Therefore, deterioration of the adherend to which the adhesive sheet is attached due to ultraviolet rays can be suppressed.

Further, the adhesive sheet for attaching an optical member of the present invention has high visibility, and even when the adhesive sheet for attaching an optical member is attached to the visible surface side of a display, for example, the characters displayed in the display are prevented from blurring. As described above, the adhesive sheet for bonding optical members of the present invention has succeeded in increasing the degree of black color development of the display or the like but not deteriorating the visibility of the display or the like.

The total light transmittance of the pressure-sensitive adhesive sheet is preferably 40% or more. The total light transmittance of the pressure-sensitive adhesive sheet is preferably 80% or less, more preferably 75% or less, and even more preferably 70% or less. By setting the total light transmittance of the adhesive sheet within the above range, it is possible to increase the degree of black color development of the display or the like.

The haze of the adhesive sheet is preferably 0.5% or more. The haze of the pressure-sensitive adhesive sheet is preferably 30% or less, more preferably 25% or less, further preferably 20% or less, and particularly preferably 15% or less. By setting the haze of the adhesive sheet within the above range, visibility can be maintained while increasing the degree of black color development of the display or the like.

The thickness of the pressure-sensitive adhesive sheet is preferably 10 μm or more, more preferably 20 μm or more, and further preferably 50 μm or more. The thickness of the pressure-sensitive adhesive sheet is preferably 5000 μm or less, more preferably 3000 μm or less, and even more preferably 1000 μm or less. By making the thickness of the adhesive sheet equal to or less than the above upper limit value, it is possible to prevent water vapor from entering from the end portion and improve the durability. On the other hand, the handling of the adhesive sheet can be facilitated by setting the thickness of the adhesive sheet to the above lower limit value or more.

The pressure-sensitive adhesive sheet of the present invention may be a single-layer pressure-sensitive adhesive sheet. Further, the pressure-sensitive adhesive sheet may be a single-sided pressure-sensitive adhesive sheet having a base material (preferably a transparent base material) on one side, or a double-sided pressure-sensitive adhesive sheet. The double-sided adhesive sheet includes a single-layer adhesive sheet composed of an adhesive layer, a multi-layer adhesive sheet in which a plurality of adhesive layers are laminated, and a multi-layer adhesive in which another adhesive layer is laminated between the adhesive layers. A multi-layered pressure-sensitive adhesive sheet in which a support is laminated between a sheet, a pressure-sensitive adhesive layer and a pressure-sensitive adhesive layer, and a multi-layered pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is laminated on one side of the support and another pressure-sensitive adhesive layer is laminated on the other side. Can be mentioned. When the double-sided adhesive sheet has a support, it is preferable to use a transparent support as the support. As the support, a general film used in the optical field can be used as in the case of the transparent substrate. Since such a double-sided pressure-sensitive adhesive sheet is also excellent in transparency of the pressure-sensitive adhesive sheet as a whole, it can be suitably used for bonding optical members to each other.

As shown in FIG. 1, the present invention may relate to an adhesive sheet with a release sheet having a release sheet 12a and a release sheet 12b on both surfaces of the adhesive sheet 11. The release sheet is a releaseable laminated sheet having a release sheet base material and a release agent layer provided on one side of the release sheet base material, or a polyolefin film such as a polyethylene film or polypropylene film as a low polarity base material. Can be mentioned.

Papers and polymer films are used as the base material for the release sheet in the releaseable laminated sheet. In optical applications, polymer films are preferably used to prevent foreign matter from entering. As the release agent constituting the release agent layer, for example, a general-purpose addition type or condensation type silicone type release agent or a long-chain alkyl group-containing compound is used. In particular, an addition type silicone release agent having high reactivity is preferably used.
Specific examples of the silicone-based release agent include BY24-4527 and SD-7220 manufactured by Toray Dow Corning Silicone, and KS-3600, KS-774, and X62-2600 manufactured by Shin-Etsu Chemical Co., Ltd. Can be mentioned. Further, it contains a silicone resin which is an organic silicon compound having an SiO ₂ units and _{(CH 3) 3 SiO 1/2} units or _{CH 2 = CH (CH 3)} SiO 1/2 units in the silicone-based release agent preferable. Specific examples of the silicone resin include BY24-843, SD-7292, SHR-1404, etc. manufactured by Toray Dow Corning Silicone Co., Ltd., KS-3800, X92-183, etc. manufactured by Shin-Etsu Chemical Co., Ltd.
A commercially available product may be used as the peelable laminated sheet. Examples include a heavy separator film, which is a release-treated polyethylene terephthalate film manufactured by Teijin DuPont Film Co., Ltd., and a light separator film, which is a release-treated polyethylene terephthalate film manufactured by Teijin DuPont Film Co., Ltd. it can.

When the pressure-sensitive adhesive sheet of the present invention is a double-sided pressure-sensitive adhesive sheet, it is preferable to have a pair of release sheets having different peeling forces. That is, it is preferable that the release sheet has different peelability between one release sheet and the other release sheet in order to facilitate peeling. When the peelability from one side and the peelability from the other side are different, it becomes easy to peel off only the release sheet having the higher peelability first.

The gel fraction of the pressure-sensitive adhesive sheet of the present invention is preferably 30 to 100%, more preferably 40 to 100%, and even more preferably 50 to 100%.

(Acrylic polymer)
The acrylic polymer is not particularly limited as long as it has an acrylic monomer unit. For example, a non-crosslinkable (meth) acrylic acid ester unit (a1) and an acrylic monomer unit having a crosslinkable functional group are used. It is preferable that it contains (a2). In addition, in this specification and claims, a "unit" is a repeating unit (monomer unit) constituting a polymer.

The non-crosslinkable (meth) acrylic acid ester unit (a1) is a repeating unit derived from the (meth) acrylic acid alkyl ester. Examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylic acid, ethyl (meth) acrylic acid, propyl (meth) acrylic acid, isopropyl (meth) acrylic acid, n-butyl (meth) acrylic acid, and (meth). Isobutyl acrylate, t-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, ( Isooctyl acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-undecyl (meth) acrylate, (meth) Examples thereof include n-dodecyl acrylate, stearyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, cyclohexyl (meth) acrylate, and benzyl (meth) acrylate. One of these may be used alone, or two or more thereof may be used in combination.
Among the above (meth) acrylic acid alkyl esters, since the adhesiveness is high, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate At least one selected from is preferable.

The acrylic monomer unit (a2) having a crosslinkable functional group is selected from a carboxy group-containing monomer unit, a hydroxy group-containing monomer unit, an amino group-containing monomer unit and a glycidyl group-containing monomer unit. It is preferable that it is at least one kind. That is, the acrylic polymer preferably has at least one crosslinkable functional group selected from a carboxy group, a hydroxy group, an amino group, an amide group, a glycidyl group and an isocyanate group.
Examples of the carboxy group-containing monomer unit include acrylic acid and methacrylic acid.
The hydroxy group-containing monomer unit is a repeating unit derived from the hydroxy group-containing monomer. Examples of the hydroxy group-containing monomer include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxypropyl (meth) acrylate. Examples thereof include (meth) acrylic acid [(mono, di or poly) alkylene glycol] such as mono (meth) acrylic acid mono (diethylene glycol), and (meth) acrylic acid lactone such as (meth) acrylic acid monocaprolactone.
Examples of the amino group-containing monomer unit include repeating units derived from amino group-containing monomers such as (meth) acrylamide and allylamine.
Examples of the glycidyl group-containing monomer unit include repeating units derived from a glycidyl group-containing monomer such as glycidyl (meth) acrylate.

The content of the acrylic monomer unit (a2) having a crosslinkable functional group in the acrylic polymer is preferably 0.01 to 40% by mass, more preferably 0.5 to 35% by mass. By setting the content of the acrylic monomer unit (a2) having a crosslinkable functional group within the above range, it becomes easy to control the crosslinkability and adhesiveness of the acrylic polymer.

The acrylic polymer may further contain units derived from alkoxyalkyl group-containing (meth) acrylates. The alkoxyalkyl group-containing (meth) acrylate is an alkoxyalkyl (meth) acrylate. As the alkoxyalkyl (meth) acrylate, for example, an alkoxyalkyl (meth) acrylate having an alkoxy group having 1 to 12 carbon atoms and an alkylene group bonded to the alkoxy group having 1 to 18 carbon atoms is preferable. The alkoxy group preferably has 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms, and particularly preferably 1 or 2 carbon atoms. The alkylene group bonded to the alkoxy group preferably has 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, further preferably 1 to 4 carbon atoms, and particularly preferably 1 to 3 carbon atoms. preferable.

Examples of such alkoxyalkyl (meth) acrylates include 2-methoxymethyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxymethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, Examples thereof include 3-methoxypropyl (meth) acrylate, 3-ethoxypropyl (meth) acrylate, 4-methoxybutyl (meth) acrylate, and 4-ethoxybutyl (meth) acrylate.

The acrylic polymer may further contain units derived from the nitrogen-containing monomer. The nitrogen-containing monomer is a monomer containing a nitrogen element in one molecule. Examples of the nitrogen-containing monomer include dimethylacrylamide, diethylacrylamide, acryloylmorpholine, hydroxyethylacrylamide, methylolacrylamide, methoxymethylacrylamide, ethoxymethylacrylamide, dimethylaminoethylacrylamide, N-vinylcaprolactam, and N-vinyl-2-. Examples thereof include pyrrolidone, dimethylaminoethyl (meth) acrylate, and N-vinylformamide. Among them, the nitrogen-containing monomer is preferably at least one selected from an acrylamide derivative, an amino group-containing monomer and a nitrogen-containing heterocyclic ring-containing monomer, and more preferably an acrylamide derivative. The acrylamide derivative is more preferably at least one selected from dimethylacrylamide, diethylacrylamide and acryloylmorpholine, and particularly preferably dimethylacrylamide.

The acrylic polymer may have other monomer units, if desired. The other monomer may be a monomer copolymerizable with the above-mentioned acrylic monomer, and examples thereof include (meth) acrylonitrile, vinyl acetate, styrene, vinyl chloride, vinylpyrrolidone, and vinylpyridine. The content of the other monomer unit in the acrylic polymer is preferably 20% by mass or less, and more preferably 15% by mass or less.

The acid value of the acrylic polymer is preferably 50 mgKOH / g or less, more preferably 40 mgKOH / g or less, further preferably 30 mgKOH / g or less, still more preferably 20 mgKOH / g or less. It is even more preferably 10 mgKOH / g or less, and particularly preferably 5 mgKOH / g or less. The acid value of the acrylic polymer may be 0 mgKOH / g. By setting the acid value of the acrylic polymer within the above range, the pressure-sensitive adhesive sheet of the present invention has excellent color loss resistance. Specifically, by setting the acid value of the acrylic polymer within the above range, it is possible to suppress an increase in the total light transmittance even when the pressure-sensitive adhesive sheet is left under high temperature and high humidity conditions for a long time. it can. The total light transmittance before and after the pressure-sensitive adhesive sheet is placed in an environment of 85 ° C. and a relative humidity of 85% for 240 hours is measured, and the amount of change in the total light transmittance calculated from the value is preferably less than 10%. Further, the total light transmittance after the pressure-sensitive adhesive sheet is placed in an environment of 85 ° C. and a relative humidity of 85% for 240 hours is preferably less than 85%. The amount of change in the total light transmittance is calculated by the following formula.
Amount of change (%) = (total light transmittance of the sample before treatment)-(total light transmittance of the sample after treatment)

The acid value of the acrylic polymer is measured according to JIS K 0070 (1992). Specifically, first, about 2 g of a sample is precisely weighed in a 100 ml Erlenmeyer flask with a precision balance, and 10 ml of a mixed solvent of ethanol / diethyl ether = 1/1 (weight ratio) is added thereto to dissolve the sample. Further, add 1 to 3 drops of a phenolphthalein ethanol solution as an indicator to this container, and stir sufficiently until the sample becomes uniform. This is titrated with a 0.1N potassium hydroxide-ethanol solution, and the end point of neutralization is when the indicator has a light red color for 30 seconds. The value obtained from the result using the following calculation formula (1) is used as the acid value of the sample.
Acid value (mgKOH / g) = [B × f × 5.611] / S (1)
In the calculation formula (1), B is the amount (ml) of the 0.1N potassium hydroxide-ethanol solution used, f is the factor of the 0.1N potassium hydroxide-ethanol solution, and S is the sample sample. The amount collected (g).

The weight average molecular weight of the acrylic polymer is preferably 100,000 to 2 million, more preferably 200,000 to 1.5 million. The weight average molecular weight of the acrylic polymer is a value before cross-linking with a cross-linking agent described later. The weight average molecular weight is a value measured by size exclusion chromatography (SEC) and determined based on polystyrene. As the acrylic polymer, a commercially available one may be used, or one synthesized by a known method may be used.

(Colorant)
The pressure-sensitive adhesive sheet of the present invention contains at least one colorant selected from metal oxides and carbon black. The colorant is preferably a black pigment, and particularly preferably a metal oxide. By using a metal oxide as the colorant, the visibility of the pressure-sensitive adhesive sheet can be enhanced more effectively. In addition to the metal oxide and carbon black, the colorant may contain other colorants. Examples of other colorants include aniline black and activated carbon.

Metal oxides include copper oxide, iron tetraoxide, manganese dioxide, titanium oxide, zinc oxide, zirconium oxide, barium titanate, potassium titanate, iron titanate, copper-chromium oxide, copper-manganese oxide, Examples thereof include copper-iron-manganese oxide, copper-chromium-manganese oxide, copper-iron-chromine oxide, titanium black and the like. Above all, the metal oxide is more preferably a metal oxide whose metal type is selected from copper, iron and manganese. By selecting the above type as the colorant, the color stability becomes good.

The colorant is fine particles, and the primary average particle size of the colorant is preferably 0.1 μm or more. The primary average particle size of the colorant is preferably 15 μm or less, more preferably 12 μm or less, further preferably 10 μm or less, and particularly preferably 5 μm or less. By setting the primary average particle size of the colorant within the above range, the visibility of the pressure-sensitive adhesive sheet can be improved more effectively.

The content of the colorant is preferably 0.01 part by mass or more, more preferably 0.1 part by mass or more, and 0.2 part by mass or more with respect to 100 parts by mass of the acrylic polymer. Is more preferable. The content of the colorant is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, based on 100 parts by mass of the acrylic polymer.

The colorant is preferably mixed with the acrylic polymer in a state of being dispersed in the dispersed resin. Examples of the dispersion resin include polyester resin, urethane resin, acrylic resin, and polyether resin.

(UV absorber)
The pressure-sensitive adhesive sheet of the present invention contains an ultraviolet absorber. The ultraviolet absorber can be selected from those having a maximum absorption wavelength in the ultraviolet region. In the present invention, it is particularly preferable to use an ultraviolet absorber having a maximum absorption wavelength at a wavelength of 350 nm or more. Examples of the ultraviolet absorber having a maximum absorption wavelength at a wavelength of 350 nm or more include a compound represented by the following general formula (1) or (2).

In the above formula, R ¹ represents a hydrogen atom, a halogen atom, an alkoxy group having 1 to 4 carbon atoms, a nitro group or a cyano group, and R ² represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Reference numeral ³ represents an alkyl group structure.

In the above equation, R ⁴ , R ⁵ and R ⁶ are hydrogen atoms, hydroxyl groups, alkyl group structures or halogen atoms, and not all of R ⁴ , R ⁵ and R ⁶ are hydrogen atoms. The alkyl group-based structure is a concept including a substituent mainly composed of an alkyl group such as a substituted or unsubstituted alkyl group or a substituted or unsubstituted alkoxy group.

Among them, an ultraviolet absorber which improves compatibility by introducing an alkyl group having a large molecular weight into the aromatic ring of the basic skeleton and exhibits liquid or oily at 23 ° C. can be particularly preferably used. Here, showing liquidity or oiliness at 23 ° C. means a state in which the ultraviolet absorber alone is fluid even without a diluting solvent.

As the ultraviolet absorber, a commercially available product can be used. Examples of commercially available products include triazine-based UV absorbers (Tinubin 477) and benzotriazole-based UV absorbers (Tinubin 109, Tinubin 384-2, Tinubin PS) manufactured by BASF Japan Ltd.

The content of the ultraviolet absorber is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 8 parts by mass, and 1 to 6 parts by mass with respect to 100 parts by mass of the acrylic polymer. It is more preferable to have. The content of the ultraviolet absorber in the present invention is preferably adjusted to an amount such that the ultraviolet transmittance at a wavelength of 380 nm is less than 10%. That is, the ultraviolet transmittance of the pressure-sensitive adhesive sheet of the present invention at a wavelength of 380 nm is preferably less than 10%. The ultraviolet absorber may be used alone or in combination of two or more, and when two or more of them are used in combination, the total mass is preferably within the above range.

(Crosslinking agent)
The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive sheet of the present invention may contain a cross-linking agent. The cross-linking agent can be appropriately selected in consideration of the reactivity of the acrylic polymer with the cross-linking functional group. For example, it can be selected from known cross-linking agents such as isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds and butylated melamine compounds. Among these, it is preferable to use an isocyanate compound or an epoxy compound because the hydroxy group-containing (meth) acrylate can be easily crosslinked. That is, the cross-linking agent is preferably at least one selected from a bifunctional or higher functional epoxy compound and a bifunctional or higher functional isocyanate compound, and more preferably a bifunctional or higher functional isocyanate compound.

Examples of the isocyanate compound include tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and the like. Examples of commercially available products include tolylene diisocyanate compounds (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate L), xylylene diisocyanate compounds (manufactured by Mitsui Chemicals, Inc., Takenate D-110N) and the like.
Examples of the epoxy compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, and 1,6-hexanediol di. Glycidyl ether, tetraglycidyl xylene diamine, 1,3-bis (N, N-diglycidyl aminomethyl) cyclohexane, trimethylolpropan polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, etc. Can be mentioned.
Examples of commercially available products include 1,3-bis (N, N-diglycidylaminomethyl) benzene (Mitsubishi Gas Chemical Company, Ltd., TETRAD-X) and 1,3-bis (N, N-diglycidylaminomethyl). ) Cyclohexane (Mitsubishi Gas Chemical Company, Inc., TETRAD-C) and the like.

The content of the cross-linking agent in the pressure-sensitive adhesive composition is appropriately selected according to the desired adhesiveness and the like, but is preferably 0.01 to 5 parts by mass, preferably 0.1 to 100 parts by mass of the acrylic polymer. ~ 3 parts by mass is more preferable. By setting the content of the cross-linking agent within the above range, the workability can be further improved. As the cross-linking agent, one type may be used alone or two or more types may be used in combination, and when two or more types are used in combination, the total mass is preferably within the above range.

(solvent)
The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive sheet of the present invention may contain a solvent. In this case, the solvent is used to improve the coating suitability of the pressure-sensitive adhesive composition. Solvents include, for example, hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane and methylcyclohexane; halogenated hydrocarbons such as dichloromethane, trichloroethane, trichloroethylene, tetrachloroethylene and dichloropropane; methanol, ethanol, Alcohols such as propanol, isopropyl alcohol, butanol, isobutyl alcohol, diacetone alcohol; ethers such as diethyl ether, diisopropyl ether, dioxane, tetrahydrofuran; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone; methyl acetate , Ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, ethyl butyrate, etc .; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene Examples thereof include polyols such as glycol monomethyl ether acetone and derivatives thereof.

The content of the solvent in the pressure-sensitive adhesive composition is not particularly limited, but is preferably 25 to 500 parts by mass, more preferably 30 to 400 parts by mass with respect to 100 parts by mass of the acrylic polymer.
The content of the solvent is preferably 10 to 90% by mass, more preferably 20 to 80% by mass, based on the total mass of the pressure-sensitive adhesive composition. One type of solvent may be used alone, two or more types may be used in combination, and when two or more types are used in combination, the total mass is preferably within the above range.

(Other ingredients)
The pressure-sensitive adhesive sheet may contain components other than the above as long as the effects of the present invention are not impaired. Examples of other components include components known as additives for adhesives. For example, a plasticizer, an antioxidant, a metal corrosion inhibitor, a tackifier, a silane coupling agent, a light stabilizer such as a hindered amine compound, and the like can be selected as necessary. In addition, dyes and pigments may be added for the purpose of coloring.
Examples of the plasticizer include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, and benzoate. Examples thereof include carboxylic acid vinyl esters such as vinyl acid acid and styrene.
Examples of the antioxidant include phenol-based antioxidants, amine-based antioxidants, lactone-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and the like. One type of these antioxidants may be used alone, or two or more types may be used in combination.
As the metal corrosion inhibitor, a benzodiazole-based resin can be mentioned as a preferable example because of the compatibility and high effect of the pressure-sensitive adhesive.
Examples of the tackifier include rosin-based resin, terpene-based resin, terpene phenol-based resin, Kumaron inden-based resin, styrene-based resin, xylene-based resin, phenol-based resin, and petroleum resin.
Examples of the silane coupling agent include a mercaptoalkoxysilane compound (for example, a mercapto group-substituted alkoxy oligomer).

<Manufacturing method of adhesive sheet>
The method for producing an adhesive sheet of the present invention preferably includes a step of applying an adhesive composition on a release sheet to form a coating film.

The coating of the pressure-sensitive adhesive composition can be carried out using a known coating device. Examples of the coating device include a blade coater, an air knife coater, a roll coater, a bar coater, a gravure coater, a micro gravure coater, a rod blade coater, a lip coater, a die coater, a curtain coater and the like.

The method for producing the pressure-sensitive adhesive sheet preferably includes a step of heating the coating film. In this case, a known heating device such as a heating furnace or an infrared lamp can be used to heat the coating film formed by applying the pressure-sensitive adhesive composition.
The agent for producing the pressure-sensitive adhesive sheet may be subjected to an aging treatment in which the pressure-sensitive adhesive sheet is allowed to stand at a constant temperature for a certain period of time after the solvent is removed after coating. The aging treatment can be performed, for example, by allowing it to stand at 23 ° C. for 7 days.

<Use of adhesive sheet>
The adhesive sheet of the present invention is used for bonding optical members. Examples of the optical member include a shatterproof film attached to each constituent member of an optical product such as a touch panel and an image display device, and a cover lens on the outermost layer. Above all, it is preferable to use it for sticking to the adhesive sheet touch panel of the present invention. Examples of the constituent members of the touch panel include an ITO film in which an ITO film is provided on a transparent resin film, an ITO glass in which an ITO film is provided on the surface of a glass plate, and a transparent conductive film in which a transparent resin film is coated with a conductive polymer. Examples include hard coat films and fingerprint resistant films. Examples of the constituent members of the image display device include an antireflection film, an alignment film, a polarizing film, a retardation film, and a luminance improving film used in a liquid crystal display device.
Examples of the material used for these members include glass, polycarbonate, polyethylene terephthalate, polymethylmethacrylate, polyethylene naphthalate, cycloolefin polymer, triacetyl cellulose, polyimide, cellulose acylate and the like.

The present invention may relate to a laminate in which the above-mentioned pressure-sensitive adhesive sheet and the above-mentioned optical member are laminated. When the laminate is manufactured, it includes a step of attaching the adhesive sheet to the optical member. In the bonding step, it is preferable to bond the adhesive sheet to the optical member using a hand roller or the like. Further, in order to improve the adhesion between the adhesive sheet and the optical member, for example, an autoclave treatment may be performed under the conditions of 20 to 100 ° C. and 1 to 10 atm.

The features of the present invention will be described in more detail with reference to Examples and Comparative Examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as limiting by the specific examples shown below.

<Synthesis of acrylic polymer A>
Acrylic polymer A was prepared by solution polymerization in ethyl acetate. Butyl acrylate (BA) and 2-hydroxyethyl acrylate (2HEA) were blended so as to have a mass ratio of 70:30, and AIBN (azobisisobutyronitrile) was dissolved in the solution as a radical polymerization initiator. The solution was heated to 60 ° C. and subjected to random copolymerization to obtain an acrylic polymer A. The solution viscosity of the 35% by mass solution of the acrylic polymer A at 23 ° C. was 6,400 mPa · s. The acid value of the acrylic polymer A was 0.0 mgKOH / g.

<Synthesis of acrylic polymer B>
Acrylic polymer B was prepared by solution polymerization in ethyl acetate. Butyl acrylate (BA), 2-ethylhexyl methacrylate (2EHMA), ethyl acrylate (EA), 2-hydroxyethyl methacrylate (2HEMA) and acrylic acid (AA) in a mass ratio of 85: 5: 4: 4: 2. AIBN (azobisisobutyronitrile) was dissolved in the solution as a radical polymerization initiator. The solution was heated to 60 ° C. and subjected to random copolymerization to obtain an acrylic polymer B. The solution viscosity of the 35% by mass solution of the acrylic polymer B at 23 ° C. was 3,650 mPa · s. The acid value of the acrylic polymer B was 1.6 mgKOH / g.

<Synthesis of acrylic polymer C>
Acrylic polymer C was prepared by solution polymerization in ethyl acetate. Butyl acrylate (BA), methyl acrylate (MA), methyl methacrylate (MMA) and acrylic acid are blended in a mass ratio of 87: 1: 4: 8 and AIBN (azobisisobutyro) is used as a radical polymerization initiator. Butyl) was dissolved in the solution. The solution was heated to 60 ° C. and subjected to random copolymerization to obtain an acrylic polymer C. The solution viscosity of the 35% by mass solution of the acrylic polymer C at 23 ° C. was 4,200 mPa · s. The acid value of the acrylic polymer C was 60.0 mgKOH / g.

(Example 1)
0.5 parts by mass of an isocyanate-based cross-linking agent (Coronate L-55E manufactured by Toso Co., Ltd.) as a cross-linking agent and a triazine-based UV absorber as an ultraviolet absorber ((BASF Japan)) with respect to 100 parts by mass of the acrylic polymer A. Add 2 parts by mass of Chinubin 477) manufactured by Dainichi Seika Co., Ltd. and 0.06 parts by mass of copper, iron and manganese oxide pigments (TM Black 3550 manufactured by Dainichi Seika Kogyo Co., Ltd.) as colorants. Ethyl acetate was added as a solvent so that the solid content concentration was 35% by mass to obtain a pressure-sensitive adhesive composition.

The pressure-sensitive adhesive composition was applied onto a first release sheet (heavy separator film, Teijin DuPont Film Co., Ltd., release-treated polyethylene terephthalate film). The coating was performed using a doctor blade YD type manufactured by Yoshimitsu Seiki Co., Ltd. so that the thickness after drying was 25 μm. Then, it was dried at 100 ° C. for 3 minutes with a hot air dryer to remove the solvent, and an adhesive sheet was formed.
A second release sheet (light separator film, manufactured by Teijin DuPont Film Co., Ltd.), which has been subjected to a mold release treatment that is more peelable than the first release sheet, is attached to one side of this adhesive sheet, and the adhesive with the release sheet is attached. An adhesive sheet of Example 1 which is a sheet was obtained.

(Example 2)
An adhesive composition and an adhesive sheet with a release sheet were obtained in the same manner as in Example 1 except that the amount of the colorant added was changed to 0.22 parts by mass.

(Example 3)
A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 1 except that the colorant was changed to carbon black (multi-rack A 903 black manufactured by Toyo Color Co., Ltd.) by 0.1 parts by mass. It was.

(Example 4)
0.5 parts by mass of an isocyanate-based cross-linking agent (Coronate L-55E manufactured by Toso Co., Ltd.) as a cross-linking agent and a triazine-based UV absorber as an ultraviolet absorber ((BASF Japan)) with respect to 100 parts by mass of the acrylic polymer B. Add 2 parts by mass of Chinubin 477) manufactured by Dainichi Seika Co., Ltd. and 0.2 parts by mass of copper, iron, and manganese oxide pigments (TM Black 3550 manufactured by Dainichi Seika Kogyo Co., Ltd.) as colorants. Ethyl acetate was added as a solvent so that the solid content concentration was 35% by mass to obtain a pressure-sensitive adhesive composition.

(Example 5)
0.5 parts by mass of an isocyanate-based cross-linking agent (Coronate L-55E manufactured by Toso Co., Ltd.) as a cross-linking agent and a triazine-based ultraviolet absorber as an ultraviolet absorber ((BASF Japan)) with respect to 100 parts by mass of the acrylic polymer C. Add 2 parts by mass of Chinubin 477) manufactured by Dainichi Seika Co., Ltd. and 0.16 parts by mass of copper, iron and manganese oxide pigments (TM Black 3550 manufactured by Dainichi Seika Kogyo Co., Ltd.) as colorants. Ethyl acetate was added as a solvent so that the solid content concentration was 35% by mass to obtain a pressure-sensitive adhesive composition.

(Comparative Example 1)
An adhesive composition and an adhesive sheet with a release sheet were obtained in the same manner as in Example 1 except that no colorant was added.

(Comparative Example 2)
A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 1 except that no ultraviolet absorber was added and the amount of the colorant added was changed to 0.14 parts by mass.

(Evaluation)
<Optical characteristics>
The light peeling separator, which is the second peeling sheet, was peeled off, and a PET film (Cosmo Shine A4300 # 100 manufactured by Toyobo Co., Ltd.) was laminated using a hand roller in place of the peeled separator to prepare a laminated film. The laminated film was cut into a size of 50 mm in width and 50 mm in length, and the first release sheet was peeled off. Next, the exposed adhesive surface was attached to a slide glass (manufactured by Matsunami Glass Co., Ltd., S9112) using a hand roller. In this state, it was held in an autoclave under the conditions of 40 ° C. and 5 atm for 30 minutes to be brought into close contact with the glass plate.
The total light transmittance and haze of the obtained laminate were measured using an integrating sphere type light transmittance measuring device (NDH-5000, manufactured by Nippon Denshoku Kogyo Co., Ltd.) in accordance with JIS K 7150. This measurement was performed three times, and the average value was taken as the measured value.

<Gel fraction>
The adhesive sheet was cut to a size of 100 mm × 60 mm to prepare a sample for measurement. About 0.1 g of the pressure-sensitive adhesive sheet of the measurement sample was collected in a sample bottle, 30 ml of ethyl acetate was added, and the mixture was shaken for 24 hours. Then, the contents of this sample bottle were filtered off with a 150 mesh stainless steel wire mesh, and the residue on the wire mesh was dried at 100 ° C. for 1 hour to measure the dry mass (g). From the obtained dry mass, the gel fraction was calculated by the following formula 1.
Gel fraction (mass%) = (dry mass / collected mass of adhesive sheet) x 100 ... Equation 1

<Design>
A sample was prepared in the same manner as the optical characteristic measurement, and evaluated by placing it on a display displaying a black screen.
○: It looked blacker than when nothing was put on it ×: No change

<Visibility>
A sample was prepared in the same manner as the optical characteristic measurement, and evaluated by placing it on a display displaying characters.
○: No bleeding or blurring △: Bleeding or blurring is seen ×: Bleeding or blurring is seen and the characters cannot be read

<Color loss>
A sample was prepared in the same manner as in the measurement of the optical characteristics, placed in an environment of 85 ° C. and a relative humidity of 85%, and the total light transmittance was measured after 240 hours. The amount of change was calculated by the following formula based on the total light transmittance of the sample before being placed in an environment of 85 ° C. and 85% relative humidity, and evaluated by the following evaluation criteria.
Amount of change (%) = (total light transmittance of the sample before treatment)-(total light transmittance of the sample after treatment)
◯: The amount of change in total light transmittance is less than ± 10%, and the total light transmittance after treatment is less than 85% Δ: The amount of change in total light transmittance is 10% or more, and the total light transmittance after treatment is Less than 85% ×: The amount of change in the total light transmittance is 10% or more, and the total light transmittance after treatment is 85% or more.

<UV cut>
An adhesive sheet using a transparent film as a base material was cut into a size of 50 mm × 50 mm, the light release separator was peeled off, and the adhesive sheet was attached to a slide glass (manufactured by Matsunami Glass Co., Ltd., S9112). In this state, hold it in an autoclave under the conditions of 40 ° C. and 5 atm for 30 minutes to bring it into close contact with a glass plate, and then peel off the heavy-release separator and write a self-recording spectrophotometer (model: UV-3100PC, manufactured by Shimadzu Corporation). The spectral transmittance at a wavelength of 380 nm was measured and evaluated according to the following evaluation criteria.
◯: Spectral transmittance at wavelength 380 nm is less than 10% ×: Spectral transmittance at wavelength 380 nm is 10% or more

MO: Metal oxide CB: Carbon black

1 Adhesive sheet with release sheet 11 Adhesive sheet 12a Release sheet 12b Release sheet

Claims (8)

Contains acrylic polymers, colorants and UV absorbers
An adhesive sheet for bonding optical members, wherein the colorant contains at least one selected from metal oxide and carbon black. The pressure-sensitive adhesive sheet for bonding optical members according to claim 1, wherein the colorant is a metal oxide. The pressure-sensitive adhesive sheet for attaching an optical member according to claim 1 or 2, wherein the acid value of the acrylic polymer is 50 mgKOH / g or less. The adhesive sheet for bonding optical members according to any one of claims 1 to 3, wherein the total light transmittance is 40 to 80%. The adhesive sheet for attaching optical members according to any one of claims 1 to 4, wherein the haze is 0.5 to 15%. The pressure-sensitive adhesive sheet for attaching an optical member according to any one of claims 1 to 5, wherein the primary average particle size of the colorant is 0.1 to 15 μm. The adhesive sheet for attaching an optical member according to any one of claims 1 to 6, wherein the ultraviolet absorber is represented by the following general formula (1) or (2).

In the general formula (1), R ¹ represents a hydrogen atom, a halogen atom, an alkoxy group having 1 to 4 carbon atoms, a nitro group or a cyano group, and R ² represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Represented, R ³ represents an alkyl group structure;

In the general formula (2), R ⁴ , R ⁵ and R ⁶ are hydrogen atoms, hydroxyl groups, alkyl group structures or halogen atoms, and all of R ⁴ , R ⁵ and R ⁶ are hydrogen atoms. There is no. The adhesive sheet for bonding optical members according to any one of claims 1 to 7, which has a thickness of 10 to 5000 μm.

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