JP2011032350A - Acrylic adhesive composition and adhesive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acrylic adhesive composition which little deteriorates transparency and visibility under high temperature and high humidity, even when used for non-carrier type adhesive films adhered to the surfaces of panel substrates, and hardly leaves a paste, and to provide an adhesive film using the adhesive composition. <P>SOLUTION: This acrylic adhesive composition comprising a specific acrylic copolymer (A) and a cross-linking agent (B) is characterized in that 0.05 to 1.6 pts.mass of a metal chelate-based cross-linking agent and 0.05 to 0.2 pt.mass of an epoxy group-having cross-linking agent as cross-linking agents (A) are compounded with 100 pts.mass of the acrylic copolymer (A). The non-carrier type adhesive film 10 is produced by disposing peeling films 12, 13 having surfaces 12a, 13a subjected to peeling treatments on both the sides of an adhesive layer 11 comprising the acrylic adhesive composition. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an adhesive film suitably used for attaching an antireflection film to the surface of a flat panel display, and an acrylic adhesive composition suitably used for forming an adhesive layer of the adhesive film. Related to things.

In recent years, flat panel displays such as liquid crystal displays and plasma display panels are widely used as display devices. In many cases, an optical surface film such as an antireflection film or a protective film is attached to the surface of these flat panel displays. Moreover, these surface films are often stuck on the surface of a touch panel or the like.
Thus, when sticking a surface film on the surface of a target object (panel base material) such as a flat panel display or a touch panel, conventionally, as shown in FIG. A surface film-integrated pressure-sensitive adhesive film 20 on which a layer 22 is formed has been frequently used. A release film 23 is usually provided on the side of the adhesive layer 22 that does not contact the surface film 21.

  However, as shown in FIG. 3B, when such a surface film-integrated pressure-sensitive adhesive film 20 is attached to the panel base material 30 and placed under a high temperature and high humidity, it is generated from the panel base material 30. Due to outgas and the like, whitening occurs due to bubbles (swelling) in the vicinity of the interface between the adhesive layer 22 and the surface film 21, and the visibility of the flat panel display or touch panel as the panel base material 30 is reduced. There was a case. Moreover, although the polycarbonate which is excellent in transparency is often used for the panel base material 30 used for applications such as a flat panel display and a touch panel, especially the polycarbonate is likely to generate outgas, and therefore the problem of reduced visibility. Was remarkable.

Against this backdrop, for example, Patent Document 1 discloses a surface film-integrated pressure-sensitive adhesive sheet for display, and according to this, it is said that a decrease in transparency and visibility can be suppressed.
This display pressure-sensitive adhesive sheet is obtained by forming a pressure-sensitive adhesive layer by applying a specific pressure-sensitive adhesive composition to a surface film (transparent resin film), followed by crosslinking reaction. As a specific pressure-sensitive adhesive composition, an example of Patent Document 1 discloses a composition containing an acrylic pressure-sensitive adhesive polymer, a low molecular weight polymer, and an epoxy compound-based crosslinking agent.

On the other hand, in addition to such a surface film-integrated pressure-sensitive adhesive film 20, as shown in FIG. 1, a pressure-sensitive adhesive film 10 that does not include a surface film has also been developed.
This adhesive film 10 is called, for example, a non-carrier film or the like, and a release film 12 in which surfaces (surfaces on the side in contact with the adhesive layer 11, that is, a release surface) 12 a and 13 a are peeled on both surfaces of the adhesive layer 11, 13 is a so-called double-sided separator-attached film. Here, the release films 12 and 13 are subjected to release treatment by applying a release component such as a silicone resin to the surfaces 12a and 13a of a base film such as polyethylene terephthalate (PET).

  When the non-carrier-type adhesive film 10 as shown in FIG. 1 is used to attach a surface film 21 such as an antireflection film or a protective film to the surface of the panel substrate 30, one side of the adhesive layer 11 is usually used. The release film 12 on the side is peeled off, and a surface film 21 is first stuck on the exposed adhesive layer 11 as shown in FIG. Thereafter, the other release film 13 is peeled off, and the surface of the panel substrate 30 is brought into close contact with the exposed adhesive layer 11 as shown in FIG.

JP 2002-327160 A

According to the inventor's study, when the pressure-sensitive adhesive composition described in Patent Document 1 is used to produce a surface film-integrated pressure-sensitive adhesive film 20 and this is adhered to the surface of the panel substrate 30. The effect of suppressing the decrease in transparency and visibility of the pressure-sensitive adhesive film 20 under high temperature and high humidity was once recognized. However, when this pressure-sensitive adhesive composition is used to produce a non-carrier type pressure-sensitive adhesive film 10 as shown in FIG. 1 and the surface film 21 is attached to the surface of the panel substrate 30 as shown in FIG. Under the high temperature and high humidity, bubbles were generated and whitening occurred, and the transparency and visibility were significantly reduced.
That is, when the pressure-sensitive adhesive composition described in Patent Document 1 is used for the pressure-sensitive adhesive layer 22 of the surface film-integrated pressure-sensitive adhesive film 20, an effect is obtained with respect to a decrease in transparency and visibility. However, when it was used for the adhesive layer 11 of the non-carrier type adhesive film 10, such an effect was not obtained.

  In addition, the adhesive layer of an adhesive film that is attached to a panel substrate such as a flat panel display or a touch panel is required to be easily peelable without being left behind after being once attached to the panel substrate. It has been. However, conventionally, a non-carrier type pressure-sensitive adhesive film has not been found that has reduced transparency and visibility under high temperature and high humidity, and is less likely to remain glue.

  The present invention has been made in view of the above circumstances, and even when used for a non-carrier-type pressure-sensitive adhesive film adhered to the surface of a panel substrate, a decrease in transparency and visibility under high temperature and high humidity is suppressed. It is an object of the present invention to provide an acrylic pressure-sensitive adhesive composition that hardly causes adhesive residue and an adhesive film using the same.

  When the present inventor diligently studied, the adhesion between the pressure-sensitive adhesive layer of the non-carrier type pressure-sensitive adhesive film and the surface film adhered to the pressure-sensitive adhesive layer is determined by the pressure-sensitive adhesive layer and the surface film in the surface-film integrated pressure-sensitive adhesive film. I thought that it was lower than the adhesion of. And when a non-carrier type adhesive film is used, since the adhesion between the adhesive layer and the surface film is low in this way, when the surface film is attached to the surface of the panel substrate using this, Found that the transparency and visibility are likely to be significantly reduced under high temperature and high humidity.

The reason why the adhesion between the adhesion layer of the non-carrier type adhesion film and the surface film adhered to the adhesion layer is lower than the adhesion between the adhesion layer and the surface film in the surface film integrated adhesion film is It can be considered as follows.
That is, when using a non-carrier type adhesive film and sticking the surface film to the surface of the panel substrate, first, the release film on one side of the adhesive film is peeled off to expose the adhesive layer. At this time, by peeling off the release film, the exposed surface of the adhesive layer tends to be wavy uneven. When the surface of the pressure-sensitive adhesive layer is uneven, the contact area between the surface of the pressure-sensitive adhesive layer and the surface film provided thereon becomes small, and these adhesions are likely to be lowered.
Furthermore, since a release film is provided on the non-carrier type adhesive layer, a release component such as a silicone resin applied to the surface of the release film easily moves to the adhesive layer. As a result, the adhesiveness of the adhesive layer is lowered, and the adhesiveness between the surface of the adhesive layer and the surface film provided thereon is further reduced. In particular, PET, which is frequently used as a material for a surface film, tends to have insufficient adhesion to an acrylic pressure-sensitive adhesive, compared to polycarbonate, which is frequently used as a material for a panel substrate.
On the other hand, in the case of a pressure-sensitive adhesive film integrated with a surface film, the surface film is often directly adhered to the pressure-sensitive adhesive layer, so that the adhesion between the pressure-sensitive adhesive layer and the surface film is very good.

And if the adhesiveness between the adhesive layer of the non-carrier type adhesive film and the surface film adhered to the adhesive layer is low in this way, the transparency and visibility decrease easily under high temperature and high humidity. The reason is considered as follows.
That is, when outgas is generated from a panel substrate such as polycarbonate, the outgas passes through the adhesive layer adhered to the surface of the panel substrate with good adhesion and reaches the interface between the adhesive layer and the surface film. Therefore, it is considered that many fine bubbles are formed. At this time, if the adhesion between the adhesive layer and the surface film is low, a large number of fine bubbles are easily combined with each other, and as a result, large bubbles are considered to be formed.
On the other hand, in the case of the adhesive film integrated with the surface film, the adhesion between the adhesive layer and the surface film is high, so the outgas reaches the interface between the adhesive layer and the surface film and forms a large number of fine bubbles there. Even so, it is difficult for the bubbles to easily merge. Therefore, it is considered that large bubbles are not easily formed.
When large bubbles are present, the transparency and visibility are likely to be significantly deteriorated as compared with the case where many fine bubbles are present.

Therefore, the inventor of the present application has studied a pressure-sensitive adhesive composition that can adhere well to a surface film and hardly cause adhesive residue even when a pressure-sensitive adhesive layer of a non-carrier type pressure-sensitive adhesive film is formed.
As a result, according to the acrylic pressure-sensitive adhesive composition in which a metal chelate crosslinking agent and a crosslinking agent having an epoxy group are used in combination as a crosslinking agent, and a specific amount thereof is blended with a specific acrylic copolymer (A). Thus, the present inventors have found that the above problems can be solved, and have completed the present invention.

The acrylic pressure-sensitive adhesive composition of the present invention comprises a monomer mixture (a) comprising (meth) acrylic acid ester and a carboxyl group-containing monomer and a hydroxyl group-containing monomer copolymerizable with the (meth) acrylic acid ester. An acrylic pressure-sensitive adhesive composition containing a polymerized acrylic copolymer (A) having a weight average molecular weight of 500,000 to 2,000,000 and a crosslinking agent (B), wherein the acrylic copolymer (A) is 100 masses. The metal chelate crosslinking agent 0.05 to 1.6 parts by mass and the crosslinking agent 0.05 to 0.2 parts by mass having an epoxy group were blended as the crosslinking agent (B). Features.
In the acrylic pressure-sensitive adhesive composition of the present invention, the copolymer (C) obtained by copolymerizing a monomer mixture (c) containing cyclohexyl methacrylate and (meth) acrylic acid alkyl ester is the acrylic copolymer (A). It is preferable that 1-40 mass parts is mix | blended with respect to 100 mass parts.
The copolymer (C) is preferably a copolymer having a weight average molecular weight of 2000 to 30000 obtained by copolymerizing the monomer mixture (c) containing 40 to 80% by mass of the cyclohexyl methacrylate.
The pressure-sensitive adhesive film of the present invention is characterized in that a release film whose surface is peeled is provided on both sides of the pressure-sensitive adhesive layer made of the acrylic pressure-sensitive adhesive composition.

  According to the present invention, even when used for a non-carrier-type adhesive film adhered to the surface of a panel substrate, the transparency and visibility under high temperature and humidity are suppressed, and the adhesive remains less likely to remain. -Based adhesive composition and an adhesive film using the same can be provided.

It is a longitudinal cross-sectional view which shows the adhesive film of this invention. It is sectional drawing explaining a mode that a surface film is stuck on the surface of a panel base material using the adhesive film of FIG. 1, the state (a) which affixed the surface film on the adhesive film of FIG. It is the state (b) which stuck the base material. It is sectional drawing which shows the state which affixed the adhesive film of (a) surface film integrated adhesive film, and the adhesive film of (b) and (a) on the surface of a panel base material.

Hereinafter, the present invention will be described in detail.
[Acrylic adhesive composition]
The acrylic pressure-sensitive adhesive composition of the present invention contains an acrylic copolymer (A) and a crosslinking agent (B).
The acrylic copolymer (A) was obtained by copolymerizing a monomer mixture (a) containing (meth) acrylic acid ester and a carboxyl group-containing monomer and a hydroxyl group-containing monomer copolymerizable with the (meth) acrylic acid ester. The weight average molecular weight is 500,000 to 2,000,000.
In addition, (meth) acrylic acid means acrylic acid and methacrylic acid.

Here, as (meth) acrylic acid ester, (meth) acrylic acid methyl, (meth) acrylic acid n-propyl, (meth) acrylic acid isopropyl, (meth) acrylic acid t-butyl, (meth) acrylic acid n- Examples thereof include butyl, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isononyl (meth) acrylate, dodecyl (meth) acrylate, and the like.
As carboxyl group-containing monomers copolymerizable with (meth) acrylic acid esters, (meth) acrylic acid, β-carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, crotonic acid, maleic acid , Fumaric acid and the like may be mentioned, and two or more may be used in combination.
Examples of the hydroxyl group-containing monomer copolymerizable with (meth) acrylic acid ester include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, (meta ) 8-hydroxyoctyl acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) .methyl acrylate and the like. Also good.

  Among these, as a preferable monomer mixture (a), since a crosslinking reaction sufficiently proceeds and high adhesive force is easily obtained, it contains n-butyl (meth) acrylate as a (meth) acrylate ester and contains a carboxyl group. A mixture containing acrylic acid as a monomer and 2-hydroxyethyl (meth) acrylate as a hydroxyl group-containing monomer may be mentioned.

  The mass ratio of the (meth) acrylic acid ester, the carboxyl group-containing monomer, and the hydroxyl group-containing monomer in the monomer mixture (a) is 85 to 99% by mass of (meth) acrylic acid ester and carboxyl, from the viewpoint of adhesive strength and the like. 0.1-10 mass% of group containing monomers and 0.1-5 mass% of hydroxyl group containing monomers are preferable.

  The acrylic copolymer (A) obtained by copolymerizing the monomer mixture (a) has a weight average molecular weight of 500,000 to 2,000,000. Here, when the weight average molecular weight is less than 500,000, the acrylic copolymer has a small cohesive force. Therefore, when a non-carrier type adhesive film is produced from an acrylic adhesive composition containing the same, and a surface film such as an antireflection film is stuck on a substrate such as a panel substrate, the cohesive failure inside the adhesive layer As a result, bubbles grow, and the transparency and visibility under high temperature and high humidity decrease greatly. Moreover, when the surface film once stuck on the substrate is peeled off, the adhesive layer remains on the substrate surface, so-called “glue residue” is likely to occur. On the other hand, when it exceeds 2 million, the production of the acrylic copolymer itself becomes difficult. A more preferable weight average molecular weight is 800,000 to 1,500,000.

  The acrylic copolymer (A) is produced by a conventionally known polymerization method such as solution polymerization, bulk polymerization, emulsion polymerization or suspension polymerization using a polymerization initiator such as benzoyl peroxide or azobisisobutyronitrile. it can.

In the acrylic pressure-sensitive adhesive composition of the present invention, a metal chelate-based crosslinking agent and a crosslinking agent having an epoxy group are used in combination as the crosslinking agent (B).
When a non-carrier type pressure-sensitive adhesive film is produced using an acrylic pressure-sensitive adhesive composition by using a metal chelate-based cross-linking agent and a cross-linking agent having an epoxy group, and a surface film is stuck on a substrate In addition, the adhesion between the adhesive layer and the surface film can be sufficiently enhanced. As a result, coalescence of bubbles at these interfaces can be suppressed under high temperature and high humidity, and deterioration of transparency and visibility can be suppressed. Moreover, it is possible to make it difficult for adhesive residue to occur.

Among the cross-linking agents (B), the metal chelate-based cross-linking agent has an effect of further promoting the cross-linking reaction on the surface of the adhesive layer. As a result, even if a release film is provided on this surface, it is possible to prevent the release component containing, for example, a silicone resin from the release film from being transferred to the adhesive layer. When the peeling component migrates to the adhesive layer, the adhesive strength of the adhesive layer decreases, so by preventing such migration, the adhesion between the adhesive layer and the surface film is sufficiently enhanced, and bubbles at these interfaces The coalescence of each other can be suppressed, and the decrease in transparency and visibility can be suppressed.
On the other hand, the crosslinking agent having an epoxy group acts to advance the crosslinking reaction of the entire adhesive layer such as the inside of the adhesive layer, and to increase the adhesive force of the entire adhesive layer made of the acrylic copolymer (A).
In particular, when the surface film is made of PET, the adhesion between the surface film and the pressure-sensitive adhesive layer made of the acrylic pressure-sensitive adhesive composition tends to be insufficient, and thus the metal chelate-based cross-linking agent and the cross-linking agent having an epoxy group as described above. By using together, sufficient adhesion can be secured even when the surface film is made of PET.
Moreover, adhesive residue can also be suppressed by controlling these usage-amounts.

Examples of the metal chelate-based crosslinking agent include those in which a polyvalent metal is covalently or coordinately bonded to an organic compound. Examples of the polyvalent metal atom include Al, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, Ti, and the like. . Among these, Al, Zr, and Ti are preferable. In particular, Al is preferred because it is not colored and has good transparency.
In addition, examples of the atom in the organic compound that is covalently or coordinately bonded include an oxygen atom, and examples of the organic compound include alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, and ketone compounds.
Specifically, aluminum trisacetylacetonate that is particularly stable and easy to handle is preferably used. Moreover, as a metal chelate type crosslinking agent, you may use 2 or more types of compounds together.

  As the crosslinking agent containing an epoxy group, 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane is preferably used because the acrylic copolymer (A) can be sufficiently crosslinked. In addition, for example, N, N, N, N′-tetraglycidyl-m-xylenediamine, bisphenol A-epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin Triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diglycidyl amine and the like may be used, and two or more kinds may be used in combination.

  The compounding amount of the crosslinking agent (B) is 0.05 to 1.6 parts by mass of the metal chelate-based crosslinking agent and 100 to 100 parts by mass (solid content) of the acrylic copolymer (A). An agent is 0.05-0.2 mass part. More preferably, the metal chelate crosslinking agent is 0.05 to 0.8 parts by mass, and the epoxy group-containing crosslinking agent is 0.05 to 0.15 parts by mass.

  When the compounding amount of the metal chelate crosslinking agent is less than the above range, it is difficult to prevent the release component from the release film from being transferred to the adhesive layer. Moreover, the adhesive force as the whole adhesion layer becomes inadequate that the compounding quantity of the crosslinking agent which has an epoxy group is less than the said range. As a result, in any case, these cannot be brought into close contact to the extent that the coalescence of bubbles at the interface between the adhesive layer and the surface film is suppressed. On the other hand, when the compounding amount of the metal chelate-based crosslinking agent exceeds the above range, the crosslinking reaction on the surface of the adhesive layer proceeds excessively, and when the compounding amount of the crosslinking agent containing an epoxy group exceeds the above range, the entire adhesive layer As a result, the pressure-sensitive adhesive layer is liable to leave adhesive residue in any case.

The acrylic pressure-sensitive adhesive composition of the present invention preferably further contains a copolymer (C).
The copolymer (C) acts as a tackifier (tackifier), and is a copolymer of a monomer mixture (c) containing cyclohexyl methacrylate and an alkyl (meth) acrylate. By mix | blending this, the acrylic adhesive composition obtained can form the adhesion layer which is more excellent in adhesiveness with a surface film.
Examples of the alkyl (meth) acrylate ester include methyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, benzyl (meth) acrylate, phenoxymethyl (meth) acrylate, Examples thereof include phenoxyethyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and dicyclopentanyl (meth) acrylate, and two or more kinds may be used in combination.
Moreover, other monomers, such as 2-hydroxyethyl methacrylate and methacrylic acid, may be contained in the monomer mixture (c) in the range of 10% by mass or less.

In particular, as a preferable copolymer (C), a copolymer obtained by copolymerizing a monomer mixture (c) containing 40 to 80% by mass of cyclohexyl methacrylate and having a mass average molecular weight of 2000 to 30000. Is mentioned.
Such a copolymer (C) has good compatibility with the acrylic copolymer (A), and therefore, the transparency of the adhesive layer can be ensured. Here, when the amount of cyclohexyl methacrylate in the monomer mixture (c) is out of the range of 40 to 80% by mass, the compatibility with the acrylic copolymer (A) is lowered and the transparency of the adhesive layer is affected. And may not be suitable for use on panel substrates. On the other hand, if the weight average molecular weight is less than 2000, the production itself is difficult, and the cohesive force of the adhesive layer is reduced. On the other hand, when it exceeds 30000, the compatibility with the acrylic copolymer (A) decreases, and the transparency of the adhesive layer tends to be affected.

  The copolymer (C) is preferably blended in an amount of 1 to 40 parts by mass (solid content) with respect to 100 parts by mass (solid content) of the acrylic copolymer (A). Here, if the blending amount of the copolymer (C) is less than the above range, it is difficult to obtain the blending effect. If the blending amount exceeds the above range, the compatibility with the acrylic copolymer (A) decreases, and the adhesive May affect layer transparency.

  The copolymer (C) can be produced by a conventionally known polymerization method such as solution polymerization, bulk polymerization, emulsion polymerization or suspension polymerization using a polymerization initiator such as benzoyl peroxide or azobisisobutyronitrile. .

  The acrylic pressure-sensitive adhesive composition of the present invention comprises the acrylic copolymer (A), a crosslinking agent (B), an optional component copolymer (C), and, if necessary, an ultraviolet absorber, It can be produced by mixing additives such as antioxidants, antiseptics, antifungal agents, plasticizers, antifoaming agents, wettability adjusting agents and the like. In addition, the acrylic pressure-sensitive adhesive composition usually contains a solvent derived from the production process of the acrylic copolymer (A) or the copolymer (C), but an appropriate solvent is further added to form an adhesive layer. It may be diluted so as to have a viscosity suitable for the treatment.

[Adhesive film]
The acrylic pressure-sensitive adhesive composition of the present invention can be used for various applications. For example, it can be used for the pressure-sensitive adhesive layer 22 of the surface film-integrated pressure-sensitive adhesive film 20 as shown in FIG. As shown in FIG. 2, the adhesive layer 11 is suitably used for a non-carrier type adhesive film 10 in which release films 12 and 13 whose surfaces have been subjected to a release treatment are provided on both surfaces. Since the non-carrier type adhesive film 10 is not provided with a surface film in advance, the type of the surface film to be attached can be selected each time according to demand. Therefore, there is a great merit in terms of inventory management. On the other hand, as described above, the non-carrier type adhesive film is easier to form large bubbles at the interface between the adhesive layer and the surface film under high temperature and high humidity than the one with the surface film integrated type. There is a tendency that the decrease in the property tends to be remarkable. In that respect, according to the acrylic pressure-sensitive adhesive composition of the present invention, even when the pressure-sensitive adhesive layer 11 of the non-carrier type pressure-sensitive adhesive film 10 is formed, a decrease in transparency and visibility under high temperature and high humidity can be suppressed. The rest is unlikely to occur.

When manufacturing the non-carrier type pressure-sensitive adhesive film 10, first, a release film 12 having a surface 12a peel-treated is prepared, and an acrylic pressure-sensitive adhesive composition is applied to the surface 12a. Then, the applied acrylic pressure-sensitive adhesive composition is heated at 80 to 130 ° C. to remove and dry the solvent, and the crosslinking reaction is advanced to form the pressure-sensitive adhesive layer 11. Although there is no restriction | limiting in particular in the thickness of the adhesion layer 11, The range of 25-150 micrometers is preferable here.
Then, another non-carrier type pressure-sensitive adhesive film 10 is formed on the pressure-sensitive adhesive layer 11 by placing another release film 13 having a surface 13a peel-treated so that the surface 13a is in contact with the pressure-sensitive adhesive layer 11 and bonding them together. Can be manufactured.

  Here, as the release films 12 and 13, polyolefins such as polyethylene and polypropylene, PET subjected to release treatment, and the like are used. In particular, those in which a release component containing a silicone resin or the like is applied to the surfaces 12a and 13a of a base film made of PET are preferably used. The thickness of the release films 12 and 13 is usually about 20 to 125 μm.

  When the non-carrier type adhesive film 10 as shown in FIG. 1 manufactured in this way is used to attach a surface film 21 such as an antireflection film or a protective film to the surface of a panel substrate 30 such as a flat panel display or a touch panel. For this, the release film 12 on one side of the pressure-sensitive adhesive layer 11 is peeled off, and a surface film 21 is first stuck on the exposed pressure-sensitive adhesive layer 11 as shown in FIG. Thereafter, the other release film 13 is peeled off, and the surface of the panel substrate 30 may be brought into close contact with the exposed adhesive layer 11 as shown in FIG.

  Thus, in the panel base material 30 to which the surface film 21 was stuck by the adhesion layer 11 which consists of an acrylic adhesive composition of this invention, the adhesiveness of the adhesion layer 11 and the surface film 21 is very excellent. Therefore, even when this panel base material 30 is placed under high temperature and high humidity, outgas is generated from the panel base material, and many fine bubbles are formed at these interfaces, many fine bubbles are combined. Is unlikely to occur. Therefore, it is possible to suppress a decrease in transparency and visibility. In addition, such an adhesive layer 11 has sufficient adhesiveness but hardly causes adhesive residue. Therefore, for example, the surface film can be replaced well.

The acrylic pressure-sensitive adhesive composition of the present invention is suitable for attaching a surface film such as an antireflection film or a protective film. For example, a polarizer film, a retardation film, an optical compensation film, a brightness enhancement film, a conductive film, etc. It may be used when an optical film such as an optical plate, a prism sheet, an electromagnetic wave shielding film, or a near-infrared absorbing film is attached, and is not limited. Also, PET is often used as these materials. For example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polybutylene. A terephthalate film, a polyurethane film, an ethylene-vinyl acetate copolymer film or the like may be used without any limitation.
As the base material, polycarbonate is often used from the viewpoint of transparency, for example, cellulose resin such as triacetyl cellulose, polyester resin, polyethersulfone resin, polysulfone resin, polyamide resin, polyimide resin, A polyolefin resin, a (meth) acrylic resin, a cyclic polyolefin resin (norbornene resin), a polyarylate resin, a polystyrene resin, a polyvinyl alcohol resin, or the like may be used without any limitation.

Hereinafter, the present invention will be described with specific examples.
[Acrylic copolymer (A)]
Each monomer mixture (a) shown in Table 1 was copolymerized as follows to produce acrylic copolymers (A1) to (A3).

(1) Production of acrylic copolymer (A1) n-butyl acrylate (BA: butyl acrylate) 98 parts by mass, acrylic acid 1 part by mass, 2-hydroxylethyl acrylate (2HEA: 2-hydroxyethyl acrylate) 1 part Parts, 100 parts by mass of ethyl acetate, and 0.1 parts by mass of benzoyl peroxide were placed in a reaction vessel. Next, the air in the reaction vessel was replaced with nitrogen gas, and the reaction solution in the reaction vessel was heated to 75 ° C. and stirred for 12 hours in a nitrogen atmosphere under stirring.
After the reaction, the solution in the reaction vessel was diluted with ethyl acetate and adjusted to a solid content of 25% by mass to obtain a solution of an acrylic copolymer (A1) having a viscosity of 5000 mPa · s and a weight average molecular weight of 1,000,000.
The weight average molecular weight was measured by a gel permeation chromatograph method and was a numerical value in terms of polystyrene.

(2) Production of acrylic copolymer (A2) n-butyl acrylate 98 parts by mass, acrylic acid 1 part by mass, 2-hydroxylethyl acrylate (2HEA: 2-hydroxyethyl acrylate) 1 part by mass, toluene 100 parts by mass, 0.3 parts by mass of azobisisobutyronitrile was put in a reaction vessel. Next, the air in the reaction vessel was replaced with nitrogen gas, and the reaction solution in the reaction vessel was heated to 75 ° C. and stirred for 12 hours in a nitrogen atmosphere under stirring.
After the reaction, the liquid in the reaction vessel was diluted with ethyl acetate and adjusted to a solid content of 25% by mass to obtain a solution of an acrylic copolymer (A2) having a viscosity of 1000 mPa · s and a weight average molecular weight of 400,000.

(3) Production of acrylic copolymer (A3) 100 parts by mass of n-butyl acrylate, 100 parts by mass of ethyl acetate, and 0.1 part by mass of benzoyl peroxide were placed in a reaction vessel. Next, the air in the reaction vessel was replaced with nitrogen gas, and the reaction solution in the reaction vessel was heated to 75 ° C. and stirred for 12 hours in a nitrogen atmosphere under stirring.
After the reaction, the solution in the reaction vessel was diluted with ethyl acetate and adjusted to a solid content of 25% by mass to obtain a solution of an acrylic copolymer (A3) having a viscosity of 4000 mPa · s and a weight average molecular weight of 1,000,000.

[Copolymer (C)]
Each monomer mixture (c) shown in Table 2 was copolymerized as follows to produce copolymers (C1) to (C6).
(4) Production of copolymer (C1) 80 parts by mass of cyclohexyl methacrylate (CHMA), 20 parts by mass of methyl methacrylate (MMA), 100 parts by mass of toluene, and 10 parts by mass of azobisisobutyronitrile are put in a reaction vessel. It was. Next, the air in the reaction vessel was replaced with nitrogen gas, and the reaction solution in the reaction vessel was heated to 100 ° C. and allowed to react for 5 hours under stirring in a nitrogen atmosphere.
After the reaction, the liquid in the reaction vessel was diluted with toluene and adjusted to a solid content of 30% by mass to obtain a solution of an acrylic copolymer (C1) having a viscosity of 200 mPa · s and a weight average molecular weight of 4000.

(5) Production of copolymer (C2) 30 mass% solid content, in the same manner as in the production of copolymer (C1) except that 40 parts by mass of cyclohexyl methacrylate and 60 parts by mass of methyl methacrylate were used. A solution of an acrylic copolymer (C2) having a viscosity of 300 mPa · s and a weight average molecular weight of 4000 was obtained.

(6) Production of copolymer (C3) The solid content was 30% by mass in the same manner as in the production of the copolymer (C1) except that 20 parts by mass of cyclohexyl methacrylate and 80 parts by mass of methyl methacrylate were used. A solution of an acrylic copolymer (C3) having a viscosity of 400 mPa · s and a weight average molecular weight of 4000 was obtained.

(7) Production of copolymer (C4) 80 parts by mass of cyclohexyl methacrylate, 20 parts by mass of methyl methacrylate, 100 parts by mass of toluene, and 1 part by mass of azobisisobutyronitrile were put in a reaction vessel. Then, the air in the reaction vessel was replaced with nitrogen gas, and the reaction solution in the reaction vessel was heated to 90 ° C. and stirred for 5 hours in a nitrogen atmosphere under stirring.
After the reaction, the liquid in the reaction vessel was diluted with toluene and adjusted to a solid content of 30% by mass to obtain a solution of an acrylic copolymer (C4) having a viscosity of 800 mPa · s and a weight average molecular weight of 30,000.

(8) Production of copolymer (C5) Instead of reducing methyl methacrylate to 17 parts by mass, 3 parts by mass of 2-hydroxyethyl methacrylate (HEMA) was used. Other than that was carried out similarly to manufacture of the said copolymer (C1), and obtained the solution of the acrylic copolymer (C5) of solid content 30 mass%, viscosity 200mPa * s, and weight average molecular weight 4000.

(9) Production of copolymer (C6) Instead of 2-hydroxyethyl methacrylate, 3 parts by mass of methacrylic acid (MAA) was used. Other than that was carried out similarly to manufacture of the said copolymer (C5), and obtained the solution of the acrylic copolymer (C6) of solid content 30 mass%, a viscosity of 300 mPa * s, and the weight average molecular weight 4000.

[Example 1]
An acrylic pressure-sensitive adhesive composition was produced according to the formulation shown in Table 3. The numerical value in a table | surface is a mass part of solid content.
The crosslinking agent (B) has an epoxy group using aluminum trisacetylacetonate (indicated in the table as aluminum chelate A (W)) manufactured by Kawaken Fine Chemical Co., Ltd. as a metal chelate crosslinking agent. As the cross-linking agent, 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane (indicated in the table as TETRAD-C) manufactured by Mitsubishi Gas Chemical Co., Ltd. was used.
Next, the thickness (formed pressure-sensitive adhesive layer formed) after drying the manufactured acrylic pressure-sensitive adhesive composition on the release surface of a light-release type release PET film (thickness 38 μm) that was release-treated with a release component containing a silicone resin The thickness of the adhesive layer was 50 μm, and the solvent was removed at 100 ° C., followed by drying and a crosslinking reaction to form an adhesive layer.
Next, a heavy release type release PET film (thickness: 38 μm) which has been subjected to release treatment with a release component containing a silicone resin is bonded onto the adhesive layer so that the release surface side is in contact with the adhesive layer, and at 23 ° C. and 50% RH. The film was left for 7 days to obtain a non-carrier type pressure-sensitive adhesive film in which a release film whose surface (peeled surface) was peeled was provided on both sides of the pressure-sensitive adhesive layer. In addition, light peeling and heavy peeling are the grades of ease of peeling, and light peeling means that it is easy to peel rather than heavy peeling.

The following evaluation was performed about the obtained adhesive film. The results are shown in Table 3.
(1) Bubble resistance After cutting an adhesive film into 50 mm x 50 mm, the light peeling type peeling PET was peeled off and the surface film made from optical PET was stuck. Thereafter, this was left at 23 ° C. and 50% RH for 24 hours. Thereafter, the heavy release type peeled PET was peeled off, bonded to a polycarbonate substrate having a thickness of 1 mm, and allowed to stand for 24 hours.
Thus, the laminated body by which the surface film made from PET for optics was stuck on the base-material surface through the adhesion layer was obtained.
This laminate was allowed to stand at 80 ° C. and 95% RH for 48 hours, and then allowed to stand at 23 ° C. and 50% RH for 24 hours, and the state of bubble formation on the surface of the laminate was observed with a loupe.
The bubble resistance was evaluated in the following four stages.
A: Bubbles having a diameter of 0.5 mm or more are not observed.
○: Slight bubbles with a diameter of 0.5 mm or more are observed.
Δ: Bubbles having a diameter of 0.5 mm or more are partially observed.
X: Bubbles having a diameter of 0.5 mm or more are observed on almost the entire surface.

(2) Evaluation method of adhesive residue The pressure-sensitive adhesive film was cut into 25 mm × 100 mm, and then a laminate was produced under the same conditions as in the evaluation of bubble resistance. Then, the adhesive film was peeled off under the conditions of a peeling angle of 180 ° and a peeling speed of 300 mm / min in an atmosphere of 23 ° C. and 50% RH, and the adhesive residue on the substrate side was visually confirmed.
○: No glue residue △: Slight glue residue ×: There is glue residue on the entire surface

(3) Transparency of pressure-sensitive adhesive layer After the pressure-sensitive adhesive film was cut to 50 mm × 50 mm, the light-peeling type peeled PET was peeled off, and an optical PET surface film was attached. Thereafter, this was left at 23 ° C. and 50% RH for 24 hours. Thereafter, the heavy peeled PET was peeled off, bonded to a glass plate having a thickness of 2 mm, and allowed to stand for 24 hours to obtain a laminate for evaluating transparency.
Next, the haze value (cloudiness) is measured with a haze meter (manufactured by Murakami Color Research Laboratory, HM-65W) for a PET surface film for optics, a glass plate, and a laminate for transparency evaluation. Thus, the haze value of the adhesive layer was calculated.
Haze value of adhesive layer = (Haze value of laminate for transparency evaluation) − (Haze value of optical PET surface film + Haze value of glass plate)
The haze value of the obtained adhesive layer was evaluated in the following three stages.
○: Haze value 0.1-0.5
Δ: Haze value 0.6 to 0.9
X: Haze value 1 or more

[Examples 2 to 13, Comparative Examples 1 to 10]
An acrylic pressure-sensitive adhesive composition was produced according to the formulation shown in Tables 3 and 4.
And the adhesive film and the laminated body were manufactured like Example 1, and evaluated similarly.
The results are shown in Tables 3 and 4.

10 (Non-carrier type) Adhesive film 11 Adhesive layer 12, 13 Release film

Claims (4)

The weight average molecular weight obtained by copolymerizing a monomer mixture (a) containing (meth) acrylic acid ester and a carboxyl group-containing monomer and a hydroxyl group-containing monomer copolymerizable with the (meth) acrylic acid ester is 500,000 to 2,000,000. Acrylic copolymer (A) of
An acrylic pressure-sensitive adhesive composition containing a crosslinking agent (B),
With respect to 100 parts by mass of the acrylic copolymer (A), 0.05 to 1.6 parts by mass of a metal chelate crosslinking agent as the crosslinking agent (B) and 0.05 to 0. An acrylic pressure-sensitive adhesive composition containing 2 parts by mass.   A copolymer (C) obtained by copolymerizing a monomer mixture (c) containing cyclohexyl methacrylate and an alkyl (meth) acrylate is 1 to 40 parts by mass with respect to 100 parts by mass of the acrylic copolymer (A). The acrylic pressure-sensitive adhesive composition according to claim 1, which is blended.   The copolymer (C) is a copolymer having a weight average molecular weight of 2000 to 30000 obtained by copolymerizing the monomer mixture (c) containing 40 to 80% by mass of the cyclohexyl methacrylate. 2. The acrylic pressure-sensitive adhesive composition according to 2.   A pressure-sensitive adhesive film comprising a release film having a surface peel-treated on both sides of an pressure-sensitive adhesive layer made of the acrylic pressure-sensitive adhesive composition according to claim 1.

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