JP2011209379A - Adhesive composition for optical filter, adhesive, and adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition for optical filters, an adhesive, and an adhesive sheet that can suppress the reduction in gel fraction in an obtained adhesive even when adhesive composition containing a crosslinking agent and hydroxyl group containing additive is stored at room temperature (23°C).SOLUTION: The adhesive composition for optical filters includes acrylic polymer (A) containing hydroxyl group, a crosslinking agent (B) where the crosslinking reaction with the acrylic polymer (A) does not progress at 23°C and starts to progress during heating of 80°C or higher, and a hydroxyl group-containing additive (C).

Description

  The present invention relates to a pressure-sensitive adhesive composition for optical filters, a pressure-sensitive adhesive (a material obtained by crosslinking a pressure-sensitive adhesive composition), and a pressure-sensitive adhesive sheet used for display panels and the like.

  A plasma display panel (PDP) emits ultraviolet light by generating a plasma from a mixed gas of neon and xenon sealed in a cell and exciting a phosphor coated on the cell wall. However, near infrared rays, neon light, electromagnetic waves, etc. are simultaneously generated in addition to the necessary visible light. Near-infrared rays are used for remote controls and the like, and cause malfunctions of other electrical devices. Moreover, since neon light shows orange, it will destroy the color tone of a display. Furthermore, electromagnetic waves may adversely affect the human body. Therefore, in the PDP, an optical filter is usually used on the front surface in order to prevent these near infrared rays, neon light, electromagnetic waves and the like from leaking to the outside.

  Conventional optical filters have a structure in which films having various performances as described above are laminated via an adhesive with glass as a support, but recently, for the purpose of simplifying the optical filter structure, We are trying to give the adhesive the functions that film has so far. Therefore, it is necessary to add an additive that had not been previously required to the pressure-sensitive adhesive.

  Here, the acrylic pressure-sensitive adhesive is generally obtained from a pressure-sensitive adhesive composition obtained by adding a crosslinking agent to an acrylic polymer, and exhibits cohesion by utilizing a crosslinking reaction between the acrylic polymer and the crosslinking agent. In order to impart functions such as a light absorption function to the PDP optical filter adhesive as described above, additives have been added to the adhesive composition in addition to the acrylic polymer and the crosslinking agent (patents) References 1, 2).

JP 2008-266439 A JP 2009-35615 A

  Usually, as an additive added to the adhesive composition for an optical filter of PDP, a substance having no functional group that is reactive with a crosslinking agent at room temperature is mainly used. This is because the reaction between the crosslinking agent and the additive progresses during storage at room temperature, and is inherently expected in a pressure-sensitive adhesive obtained by adding an additive exhibiting reactivity with the crosslinking agent to the adhesive composition. This is because the crosslinking reaction between the acrylic polymer and the crosslinking agent becomes insufficient, and the gel fraction that affects the adhesive properties of the pressure-sensitive adhesive is problematic.

  A method widely used for crosslinking utilizes a reaction that generates a urethane bond, uses an isocyanate compound having two or more isocyanate groups as functional groups in one molecule as a crosslinking agent, and contains a hydroxyl group, a carboxyl group, or the like. In this method, an acrylic polymer and an isocyanate compound are reacted to crosslink. In this case, an additive mainly composed of a hydroxyl group-containing compound such as a dye and a rust inhibitor reacts with the isocyanate compound at room temperature, so that it has been difficult to add to the adhesive composition for the above reason.

  However, in order to give the pressure-sensitive adhesive a new function, it is necessary to add a hydroxyl group-containing additive such as a dye that reacts with an isocyanate compound at room temperature and a rust inhibitor to the pressure-sensitive adhesive composition. Moreover, when the additive which has a novel function is soluble only in an alcohol solvent, it is necessary to add an alcohol solvent as a hydroxyl-containing additive to an adhesive composition.

  The present invention has been made in view of such a situation, and even when a pressure-sensitive adhesive composition containing a crosslinking agent and a hydroxyl group-containing additive is stored at room temperature (23 ° C.), the resulting pressure-sensitive adhesive has a gel content. It aims at providing the adhesive composition for optical filters, an adhesive, and an adhesive sheet which can suppress the fall of a rate.

  In order to achieve the above-described object, first, the present invention is such that the crosslinking reaction between the acrylic polymer (A) containing a hydroxyl group and the acrylic polymer (A) does not proceed at 23 ° C. A pressure-sensitive adhesive composition for an optical filter comprising: a crosslinking agent (B) that initiates and proceeds with a crosslinking reaction with the acrylic polymer (A) during heating, and a hydroxyl group-containing additive (C). Provided (Invention 1)

  According to the said invention (invention 1), when an adhesive composition is preserve | saved at 23 degreeC, a crosslinking agent (B) and a hydroxyl-containing additive (C) do not react easily, and it is acrylic by heating at 80 degreeC or more. Since the cross-linking reaction (original cross-linking reaction) between the system polymer (A) and the cross-linking agent (B) proceeds sufficiently, it is possible to suppress a decrease in gel fraction with the obtained pressure-sensitive adhesive. Further, since the crosslinking agent (B) and the hydroxyl group-containing additive (C) are difficult to react during storage, those reaction products hardly occur during storage, and thus are caused by the reaction product. The change of the total light transmittance and haze value in the obtained adhesive can be suppressed.

  In the said invention (invention 1), the said crosslinking agent (B) has an ester group as a functional group which carries out a crosslinking reaction with the said acrylic polymer (A) (invention 2), or crosslinks with the said acrylic polymer (A). It is preferable that it is a blocked isocyanate compound (invention 3) which has an isocyanate group as a functional group to react and is formed by blocking the isocyanate group with a protective group.

  In the said invention (invention 1-3), it is preferable that the said hydroxyl-containing additive (C) is an alcohol solvent (invention 4).

  2ndly, this invention provides the adhesive for optical filters formed by bridge | crosslinking the said adhesive composition for optical filters (invention 1-4) (invention 5).

  3rdly, this invention is an adhesive sheet for optical filters provided with the base material and the adhesive layer, Comprising: The said adhesive layer consists of the said adhesive for optical filters (invention 5), It is characterized by the above-mentioned. An adhesive sheet for optical filters is provided (Invention 6).

  In the said invention (invention 1), it is preferable that the said base material is an optical member (invention 7).

  Fourthly, the present invention is an adhesive sheet for an optical filter comprising two release sheets and an adhesive layer sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets, The pressure-sensitive adhesive layer is composed of the pressure-sensitive adhesive for optical filters (Invention 5).

  The pressure-sensitive adhesive sheet for optical filters according to the above inventions (Inventions 6 to 8) is preferably used for a plasma display panel (Invention 9).

  According to the present invention, when the adhesive composition is stored at 23 ° C., the crosslinking agent and the hydroxyl group-containing additive hardly react, and the crosslinking reaction between the acrylic polymer and the crosslinking agent is caused by heating at 80 ° C. or higher. Since it progresses sufficiently, it is possible to suppress a decrease in gel fraction with the resulting pressure-sensitive adhesive. Moreover, the change of the total light transmittance and haze value in the adhesive obtained by the product of the crosslinking agent and the hydroxyl group containing additive which reacted during storage can also be suppressed.

It is sectional drawing of the adhesive sheet for optical filters which concerns on the 1st Embodiment of this invention. It is sectional drawing of the adhesive sheet for optical filters which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows an example of an optical filter.

Hereinafter, embodiments of the present invention will be described.
[Adhesive composition for optical filters]
The adhesive composition for optical filters according to the present embodiment (hereinafter, “for optical filters” may be omitted) is
An acrylic polymer (A) containing a hydroxyl group;
At 23 ° C., the crosslinking agent (B) that does not proceed with the crosslinking reaction with the acrylic polymer (A) but starts the crosslinking reaction with the acrylic polymer (A) when heated at 80 ° C. or higher, and
A hydroxyl group-containing additive (C).

  The acrylic polymer (A) in the present embodiment has a hydroxyl group, which is a functional group necessary for the reaction with the crosslinking agent (B). A specific example of the acrylic polymer (A) is preferably a (meth) acrylic acid ester copolymer containing a hydroxyl group. In addition, in this specification, (meth) acrylic acid ester means both acrylic acid ester and methacrylic acid ester. The same applies to other similar terms.

  The (meth) acrylic acid ester-based copolymer containing a hydroxyl group includes a (meth) acrylic acid ester having 1 to 20 carbon atoms in the alkyl group of the ester moiety and a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer). And a copolymer with other monomers used as desired.

  Examples of the (meth) acrylic acid ester having 1 to 20 carbon atoms in the alkyl group of the ester moiety include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and (meth) acrylic acid. Butyl, pentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, (meth) acryl Examples include dodecyl acid, myristyl (meth) acrylate, palmityl (meth) acrylate, and stearyl (meth) acrylate. These may be used alone or in combination of two or more.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, (meth And (meth) acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylate. These may be used alone or in combination of two or more.

  Examples of the other monomer include non-crosslinkable acrylamide such as acrylamide and methacrylamide, styrene, and vinyl acetate. In addition, a monomer having a crosslinkable functional group other than a hydroxyl group, such as a carboxyl group or an amino group, can be used as long as the effect of the present invention is not hindered. These may be used alone or in combination of two or more.

  Here, the (meth) acrylic acid ester-based copolymer containing a hydroxyl group preferably contains 0.1 to 30% by mass, particularly preferably 0.2 to 10% by mass, of the hydroxyl group-containing monomer. . By containing the hydroxyl group-containing monomer in the above range, the degree of crosslinking of the obtained pressure-sensitive adhesive becomes preferable for an optical filter. On the other hand, when the content of the hydroxyl group-containing monomer is less than 0.1% by mass, the resulting pressure-sensitive adhesive is not sufficiently crosslinked, which may result in poor durability. When the content of the hydroxyl group-containing monomer exceeds 30% by mass, the resulting pressure-sensitive adhesive is excessively cross-linked, which may reduce bonding suitability to the adherend.

  There is no restriction | limiting in particular about the copolymerization form of the (meth) acrylic acid ester type copolymer containing a hydroxyl group, Any of a random, a block, and a graft copolymer may be sufficient.

  The mass average molecular weight of the acrylic polymer (A) is preferably 50,000 to 2,000,000, and more preferably 200,000 to 1,200,000. In addition, the mass mean molecular weight in this specification is the value of polystyrene conversion measured by the gel permeation chromatography (GPC) method. When the weight average molecular weight is within the above range, the resulting pressure-sensitive adhesive has sufficient adhesion to the adherend and adhesion durability under high heat / humid heat conditions, and can suppress floating and peeling. it can.

  In this embodiment, said acrylic polymer (A) may be used individually by 1 type, and may be used in combination of 2 or more type.

  In the present embodiment, the crosslinking agent (B) does not proceed with the crosslinking reaction with the acrylic polymer (A) at 23 ° C., but starts the crosslinking reaction with the acrylic polymer (A) when heated at 80 ° C. or higher. To do.

  The reason why the crosslinking reaction with the acrylic polymer (A) does not proceed at 23 ° C. (ordinary temperature) is that the reaction between the hydroxyl group-containing additive (C) and the crosslinking agent (B) proceeds when the reaction proceeds at ordinary temperature. This is because the cross-linking reaction between the original acrylic polymer (A) and the cross-linking agent (B) becomes insufficient, and the gel fraction of the pressure-sensitive adhesive decreases.

  In addition, the reason that the crosslinking reaction with the acrylic polymer (A) starts and proceeds when heated at 80 ° C. or higher is to prevent the adhesive composition from being crosslinked in a natural environment, and to prevent the acrylic polymer (A ) And the crosslinking agent (B) by an appropriate and sufficient crosslinking reaction to obtain a pressure-sensitive adhesive having the originally desired characteristics. In addition, it is preferable that the upper limit of heating temperature is about 130 degreeC. If heating temperature is 130 degrees C or less, when an adhesive composition is apply | coated to film base materials, such as a PET film, and it heats, the expansion-contraction and thermal deformation of a film base material can be suppressed.

  As the crosslinking agent (B), preferably, firstly, an ester group-containing compound (B1) having an ester group as a functional group, and secondly, a block in which an isocyanate group as a functional group is blocked by a protective group. An isocyanate compound (B2) is mentioned.

  The ester group-containing compound (B1) crosslinks the acrylic polymer (A) using a transesterification reaction, and the ester group of the ester group-containing compound (B1) and the hydroxyl group of the acrylic polymer (A) by heating. React with each other to effect crosslinking. The transesterification reaction is an equilibrium reaction, and the alcohol, which is a by-product of the reaction, volatilizes by heating, so that the transesterification reaction is further shifted toward the progress of crosslinking.

  This ester group-containing compound (B1) is a compound having two or more ester groups in one molecule. Examples of the ester group include an alkyl ester group having 1 to 20 carbon atoms such as a methyl ester group and an ethyl ester group; an aryl ester group such as a benzyl ester group, among which a methyl ester group and an ethyl ester group are preferable. When the ester group is a methyl ester group or an ethyl ester group, the by-product becomes methanol or ethanol having a relatively low boiling point, and these by-products are likely to volatilize, so that the reaction proceeds with high efficiency.

  According to the ester group-containing compound (B1), since the transesterification reaction does not proceed at around 23 ° C., even if the adhesive composition contains the hydroxyl group-containing additive (C), the hydroxyl group-containing additive ( The reaction with C) does not proceed. Therefore, the adhesive which suppressed the fall of the gel fraction resulting from reaction with a crosslinking agent (B) at the time of preserve | saving an adhesive composition at 23 degreeC and a hydroxyl-containing additive (C) can be obtained.

  Specific examples of the ester group-containing compound (B1) include Coronate 2555 manufactured by Nippon Polyurethane Industry Co., Ltd., MF-K60X manufactured by Asahi Kasei Co., Ltd. and K6000 manufactured by Asahi Kasei Co., Ltd.

  The blocked isocyanate compound (B2) is a compound having two or more isocyanate groups in one molecule, and these isocyanate groups are blocked by a protective group. Examples of protective groups include alkoxy groups, phenoxy groups, active methylene compound residues, mercaptan compound residues, acid amide compound residues, amino groups, imidazole compound residues, imino groups, oxime compound residues, And lactam compound residues.

  The said protective group is a group induced | guided | derived from a blocking agent, and a blocked isocyanate compound (B2) can be obtained by processing the isocyanate group of a crosslinking agent by the well-known blocking method using the said blocking agent.

  Examples of the blocking agent include alcohol compounds such as methanol, ethanol, propanol, butanol, methyl cellosolve, butyl cellosolve, phenyl cellosolve, methyl carbitol, benzyl alcohol, cyclohexanol, and furfuryl alcohol; phenol, cresol, xylenol, p Phenol compounds such as ethylphenol, o-isopropylphenol, p-tert-butylphenol, p-tert-octylphenol, nonylphenol, α-naphthol, β-naphthol, p-nitrophenol, p-chlorophenol; dimethyl malonate; Active methylene compounds such as diethyl malonate, acetylacetone and ethyl acetoacetate; butyl mercaptan, dodecyl mercaptan, thiophenol, etc. Mercaptan compounds; acid amide compounds such as acetanilide, acetanisidide, acetylamide and benzamide; amine compounds such as diphenylamine, aniline and carbazole; imidazole compounds such as imidazole, 2-ethylimidazole and 2-ethyl-4-methylimidazole ; Imine compounds such as ethyleneimine; oxime compounds such as formaldoxime, acetoaldoxime, methyl ethyl ketoxime, cyclohexanone oxime; lactam compounds such as ε-caprolactam, δ-valerolactam, β-propiolactam, etc. It is done. Among these, alcohol compounds, phenol compounds, active methylene compounds, oxime compounds, lactam compounds, and the like are preferably used, and particularly, active methylene compounds in which a protecting group is removed with a relatively small amount of heat are preferably used. .

  According to the blocked isocyanate compound (B2), since the isocyanate group is blocked by a protecting group at around 23 ° C., even if the adhesive composition contains the hydroxyl group-containing additive (C), the hydroxyl group-containing compound is contained at room temperature. The reaction with the additive (C) does not proceed. Therefore, the adhesive which suppressed the fall of the gel fraction resulting from reaction with a crosslinking agent (B) at the time of preserve | saving an adhesive composition at 23 degreeC and a hydroxyl-containing additive (C) can be obtained.

  Further, in the blocked isocyanate compound (B2), the protective group is removed from the isocyanate group by heating at 80 ° C. or higher, and the reaction between the isocyanate group and the hydroxyl group of the acrylic polymer (A) starts. proceed.

  Preferable specific examples of the blocked isocyanate compound (B2) include TPA-B80E manufactured by Asahi Kasei Co., Ltd., MF-B60X manufactured by Asahi Kasei Co., Ltd., and E402-B80T manufactured by Asahi Kasei Co., Ltd.

  The said crosslinking agent (B) may be used individually by 1 type, and may be used in combination of 2 or more type. Moreover, the compounding quantity of a crosslinking agent (B) is 0.01-20 mass parts normally with respect to 100 mass parts of acrylic polymers (A), Preferably, it is 0.1-10 mass parts.

  Examples of the hydroxyl group-containing additive (C) include an alcohol solvent (C2) in addition to the additive (C1) that imparts a predetermined function to the optical filter. As an additive (C1), a pigment | dye, a rust preventive agent, etc. are mentioned, for example.

  The dye is used for adjusting the color tone of the optical filter. Examples of the dye include a metal complex compound having a hydroxyl group, a cyanine compound, a phthalocyanine compound, a naphthalocyanine compound, a porphyrin compound, a pyromethene compound, an azo compound, a squarylium compound, an imonium compound, and a dithiol compound. And triphenylmethane-based compounds, but are not limited to these, and any compound having a hydroxyl group may be used. These pigments may be used alone or in combination of two or more.

  The antirust agent suppresses a change in transmittance due to the interaction between the metal mesh and the additive, the interaction between the metal mesh and the adhesive, or the like when the adhesive comes into contact with the metal mesh of the electromagnetic wave shielding film. Examples of the rust preventive include azole compounds having a hydroxyl group, triazole compounds, benzotriazole compounds, thiazole compounds, benzothiazole compounds, imidazole compounds, benzimidazole compounds, phosphorus compounds, amine compounds, Examples thereof include nitrite compounds, surfactants, silane coupling agents, and the like, but are not limited thereto, and any compounds having a hydroxyl group may be used. These rust inhibitors may be used alone or in combination of two or more.

  The said additive (C1) may be used individually by 1 type, and may be used in combination of 2 or more type. Moreover, although the compounding quantity of the additive (C1) in an adhesive composition is based also on the kind, it is 0.0001-20 mass% normally, Preferably, it is 0.01-10 mass%.

  The alcohol-based solvent (C2) is an additive that is added to the adhesive composition (including but not limited to the additive (C1)) is soluble only in the alcohol-based solvent. It is effective to dissolve. That is, according to this alcohol solvent (C2), even if an additive that is soluble only in an alcohol solvent is added to the adhesive composition, the additive remains undissolved in the adhesive layer. Becomes a foreign object.

  Additives that are soluble only in alcohol solvents include, for example, ultraviolet absorbers, near infrared absorbers, and neon light absorbers in addition to the dyes and rust inhibitors described above.

  As alcohol solvent (C2), a C1-C5 alkyl alcohol is preferable. Since these are easy to volatilize when heated, the transesterification reaction can proceed efficiently when the ester group-containing compound (B1) is used as the crosslinking agent (B). Specific examples of the alcohol solvent (C2) include methanol, ethanol, isopropyl alcohol, and the like.

  When the pressure-sensitive adhesive composition according to this embodiment contains an alcohol solvent (C2), the nonvolatile content concentration is preferably 5 to 50% by mass, and particularly preferably 10 to 40% by mass. When the non-volatile content concentration is in this range, the adhesive composition can be used as it is as a coating solution and can be applied by various coating methods.

  The pressure-sensitive adhesive composition according to the present embodiment contains, in addition to the above-described components, components used in a normal pressure-sensitive adhesive composition for optical filters, for example, an ultraviolet absorber, a near-infrared absorber, a neon light absorber, and the like. You may do it. Moreover, pigment | dyes other than the said additive (C1), a rust preventive agent, etc. may be contained, and solvents other than the said alcohol solvent (C2) may be contained as a solvent.

  In the adhesive composition described above, the reaction between the crosslinking agent (B) and the hydroxyl group-containing additive (C) does not proceed in the state of being stored at room temperature (23 ° C.), and the heating is performed at 80 ° C. or higher. Since the crosslinking reaction between the acrylic polymer (A) and the crosslinking agent (B) proceeds sufficiently, the crosslinking agent (B) and the hydroxyl group-containing additive (C) when the adhesive composition is stored at room temperature. A decrease in gel fraction due to the reaction is suppressed. Moreover, the change of the total light transmittance and haze resulting from the product of the crosslinking agent (B) and the hydroxyl group-containing additive (C) reacted during storage are also suppressed.

[Adhesive for optical filters]
The pressure-sensitive adhesive for optical filters according to this embodiment is obtained by crosslinking the pressure-sensitive adhesive composition for optical filters. In order to crosslink the pressure-sensitive adhesive composition for optical filters, a heat treatment is performed.

  When performing heat processing, it is preferable that heating temperature is 80-130 degreeC, and it is especially preferable that it is 90-120 degreeC. The heating time is preferably 10 seconds to 60 minutes, particularly preferably 30 seconds to 30 minutes.

  By the heat treatment, the crosslinking reaction between the acrylic polymer (A) and the crosslinking agent (B) starts and proceeds. Thereby, the shape as an adhesive layer will be maintained favorable.

The gel fraction (I) of the pressure-sensitive adhesive obtained by heating immediately after preparing the pressure-sensitive adhesive composition, and the pressure-sensitive adhesive obtained by heating after preparing the pressure-sensitive adhesive composition and storing it at room temperature (23 ° C.) for 24 hours The gel fraction reduction rate (%) calculated from the gel fraction (II) (see the following formula) is preferably less than 40%, particularly preferably less than 20%, and less than 4%. More preferably it is. By satisfying this numerical value, a decrease in the gel fraction in the pressure-sensitive adhesive caused by the reaction between the crosslinking agent (B) and the hydroxyl group-containing additive (C) when the pressure-sensitive adhesive composition is stored at room temperature is suppressed. Is shown.
Gel fraction reduction rate (%) = (1-gel fraction of adhesive (II) (%) / gel fraction (I) (%)) × 100

The total light transmittance of the obtained pressure-sensitive adhesive is preferably 95% or more, and particularly preferably 98% or more. Moreover, the total light transmittance (I) of the pressure-sensitive adhesive obtained by heating immediately after preparing the pressure-sensitive adhesive composition and the pressure-sensitive adhesive composition were prepared and heated after being stored at room temperature (23 ° C.) for 24 hours. The total light transmittance change (%) (see the following formula) calculated from the total light transmittance (II) of the pressure-sensitive adhesive is preferably 1% or less, and particularly preferably 0.1% or less. By satisfying this numerical value, there is a change in the total light transmittance in the pressure-sensitive adhesive resulting from the reaction product of the crosslinking agent (B) and the hydroxyl group-containing additive (C) when the pressure-sensitive adhesive composition is stored at room temperature. Shown to be suppressed. Thereby, when it uses as a display member, it becomes an adhesive by which the total light transmittance as an optical physical property is not influenced by the elapsed time from adhesive composition preparation to heating.
Total light transmittance change (%) = total light transmittance (I) (%) − total light transmittance (II) (%)

The haze value of the obtained pressure-sensitive adhesive is preferably 3% or less, and particularly preferably 1% or less. Further, the pressure-sensitive adhesive obtained by heating immediately after preparing the pressure-sensitive adhesive composition and the pressure-sensitive adhesive obtained by heating after preparing the pressure-sensitive adhesive composition and storing it at room temperature (23 ° C.) for 24 hours. The haze value change (%) (see the following formula) calculated from the haze value (II) is preferably 1% or less, particularly preferably 0.2% or less. By satisfying this numerical value, the change in haze value in the pressure-sensitive adhesive caused by the reaction product of the crosslinking agent (B) and the hydroxyl group-containing additive (C) when the pressure-sensitive adhesive composition is stored at room temperature is suppressed. Is shown. Thereby, when using as a display member, it becomes an adhesive whose haze value as an optical physical property is not influenced by the elapsed time from adhesive composition preparation to heating.
Haze value change (%) = Haze value (II) (%) − Haze value (I) (%)

  The adhesive described above can be preferably used for an optical filter used for a plasma display panel or the like. For example, a metal mesh film (an electromagnetic shielding film having a metal mesh) and another film (for example, a contrast improving film) It is suitable for bonding. In this pressure-sensitive adhesive, a decrease in gel fraction is suppressed, and changes in total light transmittance and haze value are also suppressed. Therefore, the pressure-sensitive adhesive is suitable for optical filters.

[Optical filter adhesive sheet]
As shown in FIG. 1, the optical filter pressure-sensitive adhesive sheet 1 </ b> A according to the first embodiment includes, in order from the bottom, a release sheet 12, a pressure-sensitive adhesive layer 11 laminated on the release surface of the release sheet 12, and a pressure-sensitive adhesive layer. 11 and a base material 13 laminated on the substrate 11.

  Further, as shown in FIG. 2, the optical filter adhesive sheet 1B according to the second embodiment is in contact with the two release sheets 12a and 12b and the release surfaces of the two release sheets 12a and 12b. The adhesive layer 11 is sandwiched between the two release sheets 12a and 12b. In addition, the release surface of the release sheet in this specification refers to a surface having peelability in the release sheet, and includes both a surface that has been subjected to a release treatment and a surface that exhibits peelability without being subjected to a release treatment. .

  In any of the pressure-sensitive adhesive sheets 1A and 1B, the pressure-sensitive adhesive layer 11 is made of a pressure-sensitive adhesive formed by crosslinking the above-described pressure-sensitive adhesive composition.

  The thickness of the pressure-sensitive adhesive layer 11 is appropriately determined according to the purpose of use of the pressure-sensitive adhesive sheets 1A and 1B, but is usually in the range of 5 to 100 μm, preferably 10 to 60 μm. For example, the pressure-sensitive adhesive layer 11 is attached to a metal mesh. When used as an agent layer, it is preferably 10 to 50 μm, particularly preferably 15 to 40 μm.

  There is no restriction | limiting in particular as the base material 13, What was used as a base material of the normal adhesive sheet for optical filters can be used. For example, in addition to a desired optical member, glass; metal foil such as aluminum and copper; polyester film such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, triacetyl cellulose film, polyurethane film, polyurethane acrylate film, polyethylene film, polypropylene Film, polyvinyl chloride film, polyvinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film, acrylic resin film, norbornene resin film, cycloolefin resin film, liquid crystal polymer film, etc. A plastic film; and a laminate of two or more of these. The plastic film may be uniaxially stretched or biaxially stretched.

  Examples of the optical member include an electromagnetic wave shielding film having a metal mesh, a contrast improving film, an antireflection film, an antiglare film, and a color tone correction film.

  Although the thickness of the base material 13 changes with kinds, for example in the case of an optical member, it is 10-500 micrometers normally, Preferably it is 50-300 micrometers.

  As the release sheets 12, 12a, 12b, for example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, Polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene / (meth) acrylic acid copolymer film, ethylene / (meth) acrylic acid ester copolymer film, polystyrene film, polycarbonate film, polyimide film Fluorine resin film, liquid crystal polymer film, etc. are used. These crosslinked films are also used. Furthermore, these laminated films may be sufficient.

  The release surface of the release sheet (particularly the surface in contact with the pressure-sensitive adhesive layer 11) is preferably subjected to a release treatment. Examples of the release agent used for the release treatment include alkyd, silicone, fluorine, unsaturated polyester, polyolefin, and wax release agents.

  Although there is no restriction | limiting in particular about the thickness of the peeling sheets 12, 12a, 12b, Usually, it is about 20-150 micrometers.

  In order to manufacture the pressure-sensitive adhesive sheet 1A, after applying a coating solution containing the pressure-sensitive adhesive composition and, if desired, a solvent to the release surface of the release sheet 12, heat treatment is performed to form the pressure-sensitive adhesive layer 11 The base material 13 is laminated on the pressure-sensitive adhesive layer 11. In addition, after the pressure-sensitive adhesive layer 11 is first formed on the substrate 13, the release surface of the release sheet 12 may be laminated on the pressure-sensitive adhesive layer 11. The conditions for the heat treatment are as described above. The concentration / viscosity of the coating solution is not particularly limited as long as it can be coated, and can be appropriately selected according to the situation.

  Moreover, in order to manufacture the said adhesive sheet 1B, the coating solution containing the said adhesive composition and the solvent depending on necessity is apply | coated to the peeling surface of one peeling sheet 12a (or 12b), and it heat-processes. After forming the pressure-sensitive adhesive layer 11, the release surface of the other release sheet 12 b (or 12 a) is superimposed on the pressure-sensitive adhesive layer 11.

  As a method for applying the coating solution, for example, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like can be used.

  Examples of the solvent include alcohols such as methanol, ethanol, propanol, butanol and 1-methoxy-2-propanol; aliphatic hydrocarbons such as hexane, heptane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; Halogenated hydrocarbons such as ethylene chloride; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; cellosolv solvents such as ethyl cellosolve are used. These solvents can be used alone or in combination of two or more. Among these, it is preferable to use alcohol or a mixture of alcohol and ketone (particularly methyl ethyl ketone). In this case, alcohol corresponds also to a hydroxyl-containing additive (C).

  Here, for example, a method for manufacturing an optical filter 4 for a plasma display panel, which includes an electromagnetic wave shielding film 2 having a metal mesh 21 and a contrast enhancement film 3 as shown in FIG. 3, will be described.

  When using the adhesive sheet 1A, the contrast improving film 3 is used as the base material 13 of the adhesive sheet 1A, the release sheet 12 of the adhesive sheet 1A is peeled off, and the exposed adhesive layer 11 and the electromagnetic wave shielding film 2 are removed. Or the electromagnetic wave shielding film 2 is used as the base material 13 of the pressure-sensitive adhesive sheet 1A, the release sheet 12 of the pressure-sensitive adhesive sheet 1A is peeled off, and the exposed pressure-sensitive adhesive layer 11 and the contrast improving film 3 are bonded. .

  When the pressure-sensitive adhesive sheet 1B is used, one release sheet 12a (or 12b) of the pressure-sensitive adhesive sheet 1B is peeled off, the exposed pressure-sensitive adhesive layer 11 and the contrast improving film 3 are bonded, and then the other release sheet. 12b (or 12a) is peeled off and the exposed adhesive layer 11 and the electromagnetic wave shielding film 2 are bonded together, or one release sheet 12a (or 12b) of the adhesive sheet 1B is peeled off to expose the adhesive The layer 11 and the electromagnetic wave shielding film 2 are bonded together, then the other release sheet 12b (or 12a) is peeled off, and the exposed pressure-sensitive adhesive layer 11 and the contrast improving film 3 are bonded together.

  In the pressure-sensitive adhesive layer 11 of the above pressure-sensitive adhesive sheets 1A and 1B, a decrease in gel fraction is suppressed, and changes in total light transmittance and haze value are also suppressed. As an optical filter for a plasma display panel It is suitable.

  The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  For example, the release sheet 12 of the adhesive sheet 1A may be omitted, or one of the release sheets 12a and 12b in the adhesive sheet 1B may be omitted.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further more concretely, the scope of the present invention is not limited to these Examples etc.

[Example 1]
An acrylic acid ester copolymer (mass average molecular weight) was obtained by copolymerizing 68.5 parts by mass of n-butyl acrylate, 30 parts by mass of methyl acrylate, 1 part by mass of 2-hydroxyethyl acrylate, and 0.5 parts by mass of acrylamide. : 800,000, solid concentration: 29% by mass, hereinafter referred to as “acrylic polymer (a)”).

  1001 parts by mass of the acrylic polymer (a), 0.51 parts by mass of a crosslinking agent having an ester group capable of transesterification (manufactured by Nippon Polyurethane Industry Co., Ltd., product name: Coronate 2555, solid content concentration: 90% by mass), 0.006 parts by mass of a pigment (color tone adjusting agent, orazole pink) soluble only in an alcohol-based solvent and 20 parts by mass of ethanol as a hydroxyl group-containing additive are mixed, and methyl ethyl ketone (MEK) has a nonvolatile content concentration of 21 masses. % To obtain an adhesive composition [1].

  The adhesive composition [1] was dried on the release-treated surface of a release film (product of Lintec Corporation, product name: SP-PET38T103-1, thickness: 38 μm) obtained by releasing one side of a polyethylene terephthalate film with a silicone resin. It apply | coated using the knife coater so that latter thickness might be set to 25 micrometers, and it heated at 120 degreeC for 30 minute (s), and formed the adhesive layer.

  Next, the release treatment surface of a release film (product name: SP-PET 381031, thickness: 38 μm) obtained by peeling one side of the polyethylene terephthalate film with a silicone resin is bonded to the pressure-sensitive adhesive layer. Was used as an adhesive sheet for optical filters.

[Example 2]
100 parts by mass of the acrylic polymer (a) obtained in Example 1 has a crosslinker having an ester group capable of transesterification (product name: MF-K60X, solid content concentration: 60% by mass, manufactured by Asahi Kasei Co., Ltd.) 0 .82 parts by mass, a pigment soluble only in an alcohol solvent (same as above) 0.006 parts by mass, and 20 parts by mass of ethanol as a hydroxyl group-containing additive are mixed, and methyl ethyl ketone (MEK) has a nonvolatile content concentration of 21% by mass. It added so that it might become, and adhesive composition [2] was obtained.

  An adhesive sheet for an optical filter was prepared in the same manner as in Example 1 except that the adhesive composition [2] was used instead of the adhesive composition [1] and the heating conditions were 100 ° C. and 30 minutes. .

Example 3
1002 parts by mass of the acrylic polymer (a) obtained in Example 1 has an ester group capable of transesterification (a product made by Asahi Kasei Co., Ltd., product name: K6000, solid content concentration: 60% by mass) 0.82 Part by mass, 0.006 part by mass of a pigment soluble only in an alcohol solvent (same as above), and 20 parts by mass of ethanol as a hydroxyl group-containing additive are mixed, and methyl ethyl ketone (MEK) has a nonvolatile content concentration of 21% by mass. Thus, an adhesive composition [3] was obtained.

  A pressure-sensitive adhesive sheet for an optical filter was prepared in the same manner as in Example 1 except that the pressure-sensitive adhesive composition [3] was used instead of the pressure-sensitive adhesive composition [1] and the heating conditions were 100 ° C. and 30 minutes. .

Example 4
To 100 parts by mass of the acrylic polymer (a) obtained in Example 1, 0.43 parts by mass of a block isocyanate-based crosslinking agent (manufactured by Asahi Kasei Co., Ltd., product name: TPA-B80E, solid content concentration: 80% by mass), alcohol 0.006 parts by mass of a pigment soluble in only a solvent (same as above) and 20 parts by mass of ethanol as a hydroxyl group-containing additive are added, and methyl ethyl ketone (MEK) is added so that the nonvolatile content concentration is 21% by mass. Thus, an adhesive composition [4] was obtained.

  A pressure-sensitive adhesive sheet for an optical filter was prepared in the same manner as in Example 1 except that the pressure-sensitive adhesive composition [4] was used instead of the pressure-sensitive adhesive composition [1] and the heating conditions were 130 ° C. and 60 minutes. .

Example 5
To 100 parts by mass of the acrylic polymer (a) obtained in Example 1, 0.66 parts by mass of a blocked isocyanate crosslinking agent (manufactured by Asahi Kasei Corporation, product name: MF-B60X, solid content concentration: 60% by mass), alcohol 0.006 parts by mass of a pigment soluble in only a solvent (same as above) and 20 parts by mass of ethanol as a hydroxyl group-containing additive are added, and methyl ethyl ketone (MEK) is added so that the nonvolatile content concentration is 21% by mass. Thus, an adhesive composition [5] was obtained.

  A pressure-sensitive adhesive sheet for an optical filter was prepared in the same manner as in Example 1 except that the pressure-sensitive adhesive composition [5] was used instead of the pressure-sensitive adhesive composition [1] and the heating conditions were 130 ° C. and 60 minutes. .

Example 6
To 100 parts by mass of the acrylic polymer (a) obtained in Example 1, 0.89 parts by mass of a blocked isocyanate crosslinking agent (manufactured by Asahi Kasei Co., Ltd., product name: E402-B80T, solid content concentration: 80% by mass), alcohol 0.006 parts by mass of a pigment soluble in only a solvent (same as above) and 20 parts by mass of ethanol as a hydroxyl group-containing additive are added, and methyl ethyl ketone (MEK) is added so that the nonvolatile content concentration is 21% by mass. Thus, an adhesive composition [6] was obtained.

  A pressure-sensitive adhesive sheet for an optical filter was prepared in the same manner as in Example 1 except that the pressure-sensitive adhesive composition [6] was used instead of the pressure-sensitive adhesive composition [1] and the heating conditions were 130 ° C. and 60 minutes. .

[Comparative Example 1]
To 100 parts by mass of the acrylic polymer (a) obtained in Example 1, xylylene diisocyanate trifunctional adduct (manufactured by Soken Chemical Co., Ltd., product name: TD-75, solid content concentration: 75% by mass) 45 parts by mass, 0.006 parts by mass of a pigment soluble only in an alcohol solvent (same as above), and 20 parts by mass of ethanol as a hydroxyl group-containing additive, and methyl ethyl ketone (MEK) with a nonvolatile content concentration of 21% by mass It added so that adhesive composition [7] might be obtained.

  An adhesive sheet for an optical filter was prepared in the same manner as in Example 1 except that the adhesive composition [7] was used instead of the adhesive composition [1] and the heating conditions were 100 ° C. and 30 minutes. .

[Test Example 1] (Gel fraction measurement)
0.2 g of the pressure-sensitive adhesive in the pressure-sensitive adhesive layer obtained in Examples or Comparative Examples was weighed and sandwiched between # 200 meshes insoluble in a solvent, and this was used as a sample. The sample was heated to reflux at 85 ° C. using a Soxhlet extractor at atmospheric pressure for 16 hours so that the sample always touched the distilled ethyl acetate. The sample obtained after refluxing was dried by leaving it in an oven at 100 ° C. for 3 hours, and the mass of the sample was measured. The gel fraction of the pressure-sensitive adhesive was calculated by the following formula. The results are shown in Table 1.
Gel fraction (%) = (Adhesive mass remaining after reflux and drying / Adhesive mass before reflux) × 100

[Test Example 2] (Calculation of gel fraction reduction rate)
In Examples or Comparative Examples, the pressure-sensitive adhesive gel fraction (I) of the pressure-sensitive adhesive layer obtained by heating immediately after preparation of the pressure-sensitive adhesive composition (within 1 minute) and the pressure-sensitive adhesive composition were prepared at room temperature ( From the gel fraction (II) of the pressure-sensitive adhesive in the pressure-sensitive adhesive layer obtained after storage at 23 ° C. for 24 hours, the gel fraction reduction rate (%) was calculated by the following formula. The results are shown in Table 1.
Gel fraction reduction rate (%) = (1-gel fraction of adhesive (II) (%) / gel fraction (I) (%)) × 100

[Test Example 3] (Measurement of total light transmittance)
The pressure-sensitive adhesive layer obtained in Examples or Comparative Examples was bonded to glass, and this was used as a measurement sample. After measuring the background with glass, the sample for measurement described above was totally transmitted using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name: NDH-2000) according to JIS K7361-1: 1997. The rate (%) was measured. The results are shown in Table 1.

[Test Example 4] (Calculation of total light transmittance change)
In Examples or Comparative Examples, the total light transmittance (I) of the pressure-sensitive adhesive layer obtained by heating immediately after the pressure-sensitive adhesive composition was prepared (within 1 minute) and the pressure-sensitive adhesive composition were prepared at room temperature. From the total light transmittance (II) of the pressure-sensitive adhesive of the pressure-sensitive adhesive layer obtained by heating at 23 ° C. for 24 hours, the total light transmittance change (%) was calculated by the following formula. The results are shown in Table 1.
Total light transmittance change (%) = total light transmittance (I) (%) − total light transmittance (II) (%)

[Test Example 5] (Measurement of haze value)
The pressure-sensitive adhesive layer obtained in Examples or Comparative Examples was bonded to glass, and this was used as a measurement sample. After measuring the background with glass, the haze value (%) of the above measurement sample was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name: NDH-2000) according to JIS K7136: 2000. Was measured. The results are shown in Table 1.

[Test Example 6] (Calculation of change in haze value)
In the examples or comparative examples, the haze value (I) of the pressure-sensitive adhesive layer obtained by heating immediately after the pressure-sensitive adhesive composition was prepared (within 1 minute) and the pressure-sensitive adhesive composition were prepared at room temperature (23 The haze value change (%) was calculated from the following formula from the haze value (II) of the pressure-sensitive adhesive layer obtained by heating after storage at 24 ° C. for 24 hours. The results are shown in Table 1.
Haze value change (%) = Haze value (II) (%) − Haze value (I) (%)

  From Table 1, in Comparative Example 1, ethanol and an isocyanate group reacted in the pressure-sensitive adhesive composition, whereby a decrease in gel fraction was observed in the obtained pressure-sensitive adhesive. On the other hand, in the adhesive obtained in the Example, it turns out that this gel fraction fall could be suppressed.

  In Comparative Example 1, ethanol and an isocyanate group react in the adhesive composition, and due to the product, changes in total light transmittance and changes in haze value are observed in the obtained adhesive. It was. On the other hand, in the example in which the reaction between the crosslinking agent and ethanol hardly occurs, there was no change in total light transmittance and no change in haze value in the obtained pressure-sensitive adhesive, which was improved as compared with Comparative Example 1. As a result.

  The pressure-sensitive adhesive composition, pressure-sensitive adhesive, and pressure-sensitive adhesive sheet for an optical filter of the present invention are particularly suitable for an optical filter (front filter) of a plasma display panel.

DESCRIPTION OF SYMBOLS 1A, 1B ... Adhesive sheet 11 ... Adhesive layer 12, 12a, 12b ... Release sheet 13 ... Base material 2 ... Electromagnetic wave shielding film 21 ... Metal mesh 3 ... Contrast improvement film 4 ... Optical filter

Claims (9)

An acrylic polymer (A) containing a hydroxyl group;
At 23 ° C., a crosslinking agent (B) that does not proceed with a crosslinking reaction with the acrylic polymer (A) but starts a crosslinking reaction with the acrylic polymer (A) when heated at 80 ° C. or higher, and
A pressure-sensitive adhesive composition for an optical filter comprising a hydroxyl group-containing additive (C).   The pressure-sensitive adhesive composition for optical filters according to claim 1, wherein the crosslinking agent (B) has an ester group as a functional group that undergoes a crosslinking reaction with the acrylic polymer (A).   The crosslinking agent (B) is a blocked isocyanate compound having an isocyanate group as a functional group that undergoes a crosslinking reaction with the acrylic polymer (A), and the isocyanate group is blocked by a protective group. Item 2. The pressure-sensitive adhesive composition for optical filters according to Item 1.   The pressure-sensitive adhesive composition for optical filters according to claim 1, wherein the hydroxyl group-containing additive (C) is an alcohol solvent.   The adhesive for optical filters formed by bridge | crosslinking the adhesive composition for optical filters in any one of Claims 1-4. A pressure-sensitive adhesive sheet for an optical filter comprising a base material and a pressure-sensitive adhesive layer,
The said adhesive layer consists of an adhesive for optical filters of Claim 5, The adhesive sheet for optical filters characterized by the above-mentioned.   The pressure-sensitive adhesive sheet for optical filters according to claim 6, wherein the substrate is an optical member. Two release sheets,
An adhesive sheet for an optical filter comprising an adhesive layer sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets,
The said adhesive layer consists of an adhesive for optical filters of Claim 5, The adhesive sheet for optical filters characterized by the above-mentioned.   The pressure-sensitive adhesive sheet for optical filters according to any one of claims 6 to 8, which is used for a plasma display panel.

Images