JP6209076B2 - Adhesive composition, polarizing plate with adhesive, and display device - Google Patents

Description

  The present invention relates to an adhesive composition, a polarizing plate with an adhesive, and a display device.

  In recent years, as a display device for displaying an image, such as a liquid crystal display device and organic electroluminescence, devices of various display methods are widely used. Among these, the liquid crystal display device is generally sandwiched between two supporting substrates such as a glass plate and includes a liquid crystal cell including a liquid crystal component oriented in a predetermined direction, a polarizing plate, a retardation film, a brightness enhancement film, and the like. The optical film is bonded to the optical film. An adhesive is used when laminating optical films or sticking an optical film to a liquid crystal cell.

  The polarizing plate used for the liquid crystal display device is disposed so that the stretching axes of the two stretched polarizing films intersect each other. In a severe environment such as high temperature and high humidity, the polarizing film easily undergoes dimensional changes accompanying expansion and contraction, and stress is generated in the polarizing plate. When the generated stress is not relaxed by the adhesive disposed between the polarizing plate and the liquid crystal cell, the residual stress is unevenly generated in the polarizing plate. As a result, the two polarizing plates arranged so that the extension axes of the polarizing film intersect each other on the front and back surfaces of the display panel are shifted in phase, and light is emitted from the four periphery of the display unit of the liquid crystal display device. Unevenness called “white spots” occurs, which leaks and becomes white.

The occurrence of the white spots described above varies depending on the size of the display panel.
In general, in a small display panel, a relatively soft adhesive (soft type adhesive) is used to relieve the generated stress in order to prevent white spots from occurring (see, for example, Patent Document 1). . This soft-type pressure-sensitive adhesive easily adheres to the processing blade and tends to be inferior in punching suitability, and is not suitable for manufacturing a large display panel.
On the other hand, in a large display panel, in order to prevent the occurrence of white spots, a relatively hard adhesive (hard type adhesive) is used to suppress the generation of stress. When this hard type adhesive is applied to a small display panel, stress due to shrinkage or the like tends to concentrate on the edge, and the above-mentioned white spots tend to appear remarkably around the panel.

  In addition, from the viewpoint of improving the workability when affixing to an adherend, the pressure-sensitive adhesive is required to have an appropriate tackiness. The pressure-sensitive adhesive having an appropriate tackiness can be temporarily fixed to the adherend. If the tackiness of the pressure-sensitive adhesive is weak, the pressure-sensitive adhesive may be peeled off at the time of temporary fixing, and workability is deteriorated.

JP-A-10-279907

As mentioned above, soft-type adhesives are said to be suitable for small display panels, but even if the current soft-type adhesives are used for small display panels, the occurrence of white spots is sufficiently prevented. Is difficult. The same applies to a large display panel, and even if the current hard-type adhesive is used for a large display panel, it is difficult to sufficiently prevent the occurrence of white spots.
Furthermore, the fact is that the adhesive that can sufficiently prevent the occurrence of white spots even when used for both a small display panel and a large display panel has not yet been proposed. It is necessary to use different adhesives for large display panels.
Furthermore, from the viewpoint of workability, an appropriate tackiness is required for the pressure-sensitive adhesive.

  Therefore, an object of the present invention is to have moderate tackiness, prevent white spots from occurring more than before, and have white spots even when used for both large display panels and small display panels. It is providing the adhesive composition which can prevent generation | occurrence | production. Moreover, the objective of this invention is providing the polarizing plate with an adhesive and a display apparatus with which an image with few white spots is displayed.

  In the process leading to the present invention, the pressure-sensitive adhesive composition becomes harder than before by using an isocyanate compound at a higher content than the conventional acrylic copolymer having a carboxyl group. The present inventors have found that not only the white spots of the image can be improved but also the generation of stress can be suppressed even in a small display panel. Furthermore, in order to improve the tackiness by obtaining knowledge that the tackiness tends to decrease when the isocyanate compound is used at a higher content than before, terpene phenol tackifiers are particularly effective. The present invention has been achieved based on such findings.

Specific means for achieving the above object are as follows.
<1> An acrylic copolymer having a carboxyl group, an isocyanate compound, and a terpene phenol tackifier, and the content of the isocyanate compound is 100 parts by mass of the acrylic copolymer having a carboxyl group. The adhesive composition which is 10 mass parts-50 mass parts with respect to it.

<2> The pressure-sensitive adhesive composition according to <1>, wherein the terpene phenol tackifier has a softening point of 130 ° C to 145 ° C.

<3> The content of the terpene phenol tackifier is 2 parts by mass to 10 parts by mass with respect to 100 parts by mass of the acrylic copolymer having the carboxyl group, according to <1> or <2>. Adhesive composition.

<4> The acrylic copolymer having a carboxyl group includes any one of the above <1> to <3> containing 0.1% by mass to 5% by mass of a structural unit derived from an acrylic monomer having a carboxyl group. The pressure-sensitive adhesive composition according to item.

<5> The pressure-sensitive adhesive composition according to any one of <1> to <4>, wherein the isocyanate compound includes a tolylene diisocyanate compound.

<6> Polarizer,
An adhesive layer provided on the polarizer and formed by the adhesive composition according to any one of <1> to <5>;
A polarizing plate with an adhesive.

<7> a display panel for displaying images;
The polarizing plate with the adhesive according to <6>, which is disposed on at least one surface of the display panel,
A display device comprising:

  According to the present invention, it has an appropriate tackiness, can prevent the occurrence of white spots as compared with the prior art, and can generate white spots even when used for both large and small display panels. An adhesive composition that can be prevented is provided. Moreover, according to this invention, the polarizing plate with an adhesive and display apparatus which can display an image with few white spots are provided.

  Hereinafter, the pressure-sensitive adhesive composition of the present invention, a polarizing plate with a pressure-sensitive adhesive using the same, and a display device will be described in detail.

<Adhesive composition>
The pressure-sensitive adhesive composition of the present invention includes an acrylic copolymer having a carboxyl group, an isocyanate compound, and a terpene phenol tackifier, and the content of the isocyanate compound is an acrylic copolymer having the carboxyl group. It is 10-50 mass parts with respect to 100 mass parts of polymers.

  In addition to the acrylic copolymer having a carboxyl group and the isocyanate compound, the pressure-sensitive adhesive composition of the present invention further contains other components such as other crosslinking agents and silane coupling agents as necessary. You may go out.

  In the conventional pressure-sensitive adhesive composition, the content of the isocyanate compound is suppressed to about 5 parts by mass at the most with respect to 100 parts by mass of the acrylic copolymer. However, in the present invention, the isocyanate compound is positively contained at a high content of 10 to 50 parts by mass with respect to 100 parts by mass of the acrylic copolymer having a carboxyl group. As a result, it is possible to prevent the occurrence of white spots as compared with the prior art, and to obtain a pressure-sensitive adhesive composition that can prevent white spots from occurring even when used for both large and small display panels. It is done.

  Since the pressure-sensitive adhesive composition of the present invention is excellent in preventing white spots, it can be suitably used for a large display panel of 19 inches or more (that is, a large display device) and less than 19 inches (further 10). It can also be suitably used for a small display panel (that is, a small display device) of less than an inch). In other words, according to the present invention, there is no need to make a pressure-sensitive adhesive composition whose composition is changed according to the size of the display panel.

Moreover, when an isocyanate compound is contained at a high content of 10 to 50 parts by mass with respect to 100 parts by mass of an acrylic copolymer having a carboxyl group, the tackiness tends to decrease. By including a terpene phenol tackifier here, a decrease in tackiness can be effectively suppressed, and an adhesive composition excellent in workability can be obtained.
Each component is described in detail below.

(Acrylic copolymer having a carboxyl group)
The pressure-sensitive adhesive composition of the present invention contains an acrylic copolymer having a carboxyl group (hereinafter sometimes abbreviated as “acrylic copolymer”). The acrylic copolymer having a carboxyl group has a structural unit derived from an acrylic monomer having a carboxyl group, and may further have a structural unit derived from another monomer.

  Examples of the acrylic monomer having a carboxyl group include acrylic acid (AA), methacrylic acid (MAA), ω-carboxy-polycaprolactone mono (meth) acrylate, succinic acid monohydroxyethyl (meth) acrylate, and maleic acid monohydroxyethyl. (Meth) acrylate, monohydroxyethyl fumarate (meth) acrylate, monohydroxyethyl phthalate (meth) acrylate, 1,2-dicarboxycyclohexane monohydroxyethyl (meth) acrylate, (meth) acrylic acid dimer, etc. . These may be used alone or in combination of two or more. Among them, acrylic acid is preferable because it has high reactivity with other monomers during the copolymerization reaction and can reduce unreacted monomers.

  The content ratio of the structural unit derived from the acrylic monomer having a carboxyl group in the acrylic copolymer is preferably 0.1% by mass to 5% by mass, more preferably 1% by mass to 5% by mass, and 1% by mass to 3 mass% is still more preferable. When the content ratio is 0.1% by mass or more, crosslinking with an isocyanate compound described later is effectively performed, and when it is 5% by mass or less, the pot life can be suppressed from being shortened.

Examples of other monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, n-octyl (meth) acrylate, Isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, stearyl (meth) acrylate, Examples thereof include monomers having no functional group such as phenoxyethyl (meth) acrylate and benzyl (meth) acrylate. These may be used alone or in combination of two or more.
Among these, alkyl (meth) acrylates having an alkyl group having 1 to 4 carbon atoms and phenoxyethyl (meth) acrylate are preferable in terms of easy adjustment of cohesive force and adhesive force of the pressure-sensitive adhesive, and those having 1 to 4 carbon atoms. Alkyl acrylates having an alkyl group and phenoxyethyl acrylate are more preferable, and n-butyl acrylate is used as a main component, methyl acrylate and n-butyl acrylate are used in combination, or n-butyl acrylate is used as a main component, and phenoxyethyl is used. It is more preferable to use acrylate and n-butyl acrylate together, or to use methyl acrylate, phenoxyethyl acrylate, and n-butyl acrylate together with n-butyl acrylate as a main component.

  The content of the structural unit derived from n-butyl acrylate (BA) in the acrylic copolymer is preferably 75% by mass to 95% by mass, and more preferably 80% by mass to 95% by mass. 80% by mass to 90% by mass is more preferable.

  As another monomer, when methyl acrylate (MA) and / or phenoxyethyl acrylate (PHEA) and n-butyl acrylate (BA) are used in combination, the mass ratio of MA and / or PHEA to BA ((MA + PHEA) / BA ) Is preferably 0.01 to 1, more preferably 0.1 to 1, and still more preferably 0.1 to 0.7. When the mass ratio of MA and / or PHEA is 0.01 or more, the polarity of the resin is high, and even if a large amount of isocyanate compound is contained, it is easy to mix, and when it is 1 or less, tackiness is easily maintained. There is a tendency.

  The total content of structural units derived from MA and / or PHEA and BA in the acrylic copolymer is preferably 95% by mass to 99.9% by mass, more preferably 95% by mass to 99% by mass, A mass% to 98 mass% is more preferable.

As another monomer, it is preferable to further use a monomer having a functional group other than a carboxyl group. Further, other monomers having a functional group other than a carboxyl group that can be used in combination include monomers having a hydroxyl group such as 2-hydroxyethyl acrylate (2HEA) and 4-hydroxybutyl acrylate (4HBA), N, N-dimethylacrylamide (DMAA). Monomer having an amide group such as 4-hydroxybutyl acrylate glycidyl ether (4HBAGE), glycidyl methacrylate (GMA) and the like, and a monomer having a hydroxyl group is preferable from the viewpoint of cohesive strength. 2-hydroxyethyl acrylate is preferred.
In the acrylic copolymer, the total amount of structural units derived from other monomers having a functional group other than a carboxyl group is preferably 1% by mass or less, more preferably 0.5% by mass or less, More preferably, it is 0.2 mass% or less.

  A particularly preferred acrylic copolymer is a copolymer containing at least a structural unit derived from acrylic acid, n-butyl acrylate, methyl acrylate and / or phenoxyethyl acrylate, specifically, AA / BA / MA copolymer, AA / BA / MA / 2HEA copolymer, AA / BA / MA / PHEA copolymer, AA / BA / 2HEA / PHEA copolymer, AA / BA / MA / 2HEA / A copolymer of PHEA may be mentioned.

  The weight average molecular weight of the acrylic copolymer is preferably 300,000 to 2,000,000, more preferably 500,000 to 2,000,000, and 700,000 to 1,800,000. More preferably, it is 000.

In the present specification, the weight average molecular weight (Mw) of the acrylic copolymer is a value measured by the following method. That is, it is measured according to the following (1) to (3).
(1) An acrylic copolymer solution is coated on a release sheet (release sheet) and dried at 100 ° C. for 2 minutes to obtain a film-like acrylic copolymer.
(2) The film-like acrylic copolymer obtained in (1) is dissolved in tetrahydrofuran so that the solid content is 0.2% by mass.
(3) Under the following conditions, the weight average molecular weight (Mw) of the (meth) acrylic copolymer is measured using gel permeation chromatography (GPC).
<Conditions>
・ GPC: HLC-8220 GPC [manufactured by Tosoh Corporation]
・ Column: TSK-GEL GMHXL (4 used)
-Mobile phase solvent: Tetrahydrofuran-Standard sample: Standard polystyrene-Flow rate: 0.6 ml / min
-Column temperature: 40 ° C

  The glass transition temperature (Tg) of the acrylic copolymer is preferably in the range of −50 ° C. to −30 ° C., more preferably in the range of −48 ° C. to −40 ° C. When the Tg is −50 ° C. or higher, the elastic modulus can be adjusted, and the durability and the whiteout property are excellent. Moreover, when Tg is −30 ° C. or lower, the tackiness and bonding suitability are excellent without significantly impairing the viscosity.

In this specification, the glass transition temperature (Tg) of the acrylic copolymer is a molar average glass transition temperature determined by the following calculation. _{Tg 1,} Tg 2 of the following formulas, ... and Tg _n, the components 1, the glass transition temperature of the components 2, ... and component n respectively homopolymers, absolute temperature (° K). m ₁ , m ₂ ,... and _mn are the mole fractions of the respective components.

[Calculation formula of glass transition temperature (Tg)]

  The “glass transition temperature (Tg) of the homopolymer” referred to herein includes L.P. E. The glass transition temperature of the monomer described in Nielsen, translated by Shigeharu Onoki, “Mechanical properties of polymers”, pages 11 to 35, is applied.

  The content of the acrylic copolymer in the pressure-sensitive adhesive composition is preferably in the range of 50% by mass to 74% by mass and more preferably in the range of 54% by mass to 69% by mass with respect to the total solid content. When the content of the acrylic copolymer is within the above range, the pressure-sensitive adhesive is given hardness, the generation of stress is suppressed, and the occurrence of white spots is effectively suppressed.

  The polymerization method of the acrylic copolymer in the present invention is not particularly limited, and methods such as solution polymerization, emulsion polymerization, and suspension polymerization can be applied. Solution polymerization is preferred because the treatment process is relatively simple and can be performed in a short time.

  In solution polymerization, a predetermined organic solvent, a monomer, a polymerization initiator, and a chain transfer agent used as needed are generally charged in a polymerization tank, and the number is stirred in a nitrogen stream or under reflux of the organic solvent. The reaction is heated for an hour. The polymerization initiator is not particularly limited, and for example, an azo compound can be used.

(Isocyanate compound)
The pressure-sensitive adhesive composition of the present invention contains at least one isocyanate compound. The isocyanate compound is contained in an amount of 10 to 50 parts by mass with respect to 100 parts by mass of the acrylic copolymer having a carboxyl group. When the isocyanate compound is contained in such an amount, white spots are prevented regardless of the size of the display panel. When the content of the isocyanate compound is 10 parts by mass or more, white spots can be prevented from occurring more than before, and white spots can be prevented from occurring even when used for both large and small display panels. It becomes possible. When the content of the isocyanate compound is 50 parts by mass or less, white turbidity caused by carbon dioxide generated by the reaction of the isocyanate is suppressed, and the appearance is improved. In addition, when the content of the isocyanate compound is increased to about 10 parts by mass, the tackiness tends to decrease, but by including a terpene phenol-based tackifier described later, an adhesive composition excellent in tackiness and Become.

  It is preferable that content of the isocyanate compound in an adhesive composition is 15 mass parts-50 mass parts with respect to 100 mass parts of total amounts of the acryl-type copolymer which has a carboxyl group, and 20 mass parts-45. It is more preferable that it is a mass part, and it is further more preferable that it is 30 mass parts-40 mass parts.

  A preferred example of the isocyanate compound is a tolylene diisocyanate compound. As the tolylene diisocyanate compound, a tolylene diisocyanate compound derived from tolylene diisocyanate such as a dimer or trimer of tolylene diisocyanate or an adduct of tolylene diisocyanate and a polyol such as trimethylolpropane may be used. it can. These may be used alone or in combination of two or more.

  As the tolylene diisocyanate compound, a commercially available product may be used. As an example of a commercially available product, “Coronate L” (trade name) manufactured by Nippon Polyurethane Industry Co., Ltd. can be suitably used.

(Terpene phenolic tackifier)
The pressure-sensitive adhesive composition of the present invention contains a terpene phenol tackifier. The terpene phenol tackifier is a resin obtained by copolymerizing a terpene monomer and a phenol compound. The terpene phenol-based tackifier is easy to mix even in a pressure-sensitive adhesive composition containing more isocyanate compound than before, and can effectively exhibit tackiness.

  The terpene phenol tackifier preferably has a softening point of 130 ° C. to 145 ° C., more preferably 130 ° C. to 140 ° C., from the viewpoint of mixing properties in the pressure-sensitive adhesive composition.

  The softening point of the terpene phenol tackifier is a value measured based on the softening point test method (ring and ball method) defined in JIS K 2207 (2006 version).

  A terpene phenol type tackifier may be used individually by 1 type, and may be used in combination of 2 or more type. Examples of terpene phenol tackifiers include copolymers of monocyclic monoterpenes such as α-pinene, β-pinene and dipentene (limonene) with phenolic compounds such as phenol, cresol and bisphenol A. Can do.

  As the terpene phenol-based tackifier, commercially available products may be used. Examples of commercially available products include “YS Polystar TH130” (trade name, softening point 130 ° C.), “YS Polystar U115” (Yasuhara Chemical Co., Ltd.) Product name, softening point 115 ° C), "YS Polystar T145" (trade name, softening point 145 ° C), "YS Polystar T140" (trade name, softening point 140 ° C), "YS Polystar T130" (trade name, softening point) 130 ° C.), “YS Polystar T115” (trade name, softening point 115 ° C.), “YS Polystar 2130” (trade name, softening point 130 ° C.), “YS Polystar 2115” (trade name, softening point 115 ° C.), “ “YS Polystar S145” (trade name, softening point 145 ° C.), “YS Polystar N125” (trade name, softening point 125 ° C.), “My “IAce G150” (trade name, softening point 150 ° C.), “Mighty Ace G125” (trade name, softening point 125 ° C.), “Mighty Ace K125” (trade name, softening point 125 ° C.), “Arakawa Chemical Industries Ltd.” “Tamanol 901” (trade name, softening point: 130 ° C.) can be preferably used.

  The content of the terpene phenolic tackifier in the pressure-sensitive adhesive composition is preferably 2 parts by mass to 10 parts by mass with respect to 100 parts by mass of the total amount of the acrylic copolymer having a carboxyl group. It is more preferable that it is 8 parts by mass. When the content of the terpene phenol tackifier is 10 parts by mass or less, stress suppression tends to be more exhibited.

(Silane coupling agent)
The pressure-sensitive adhesive composition of the present invention may contain a silane coupling agent. When the pressure-sensitive adhesive composition contains a silane coupling agent, even if a display device (for example, a liquid crystal display device) incorporating a polarizing plate is exposed to a high-temperature and high-humidity environment, There is a tendency that the gap is difficult to peel off.

  Examples of the silane coupling agent include polymerizable unsaturated group-containing silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-mercapto. Mercapto group-containing silane compounds such as propyltriethoxysilane and 3-mercaptopropyldimethoxymethylsilane, and epoxies such as 3-glycidoxypropyltrimethoxysilane and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane Silane compounds having a structure, such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, and N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane Amino group-containing silane compound, and tris - (3-trimethoxysilylpropyl) isocyanurate. These may be used alone or in combination of two or more.

  A commercially available silane coupling agent may be used, and “KBM-403” (trade name) manufactured by Shin-Etsu Chemical Co., Ltd. can be suitably used as an example of a commercially available product.

  As content of the silane coupling agent in an adhesive composition, the range of 0.01 mass part-2.0 mass parts is preferable with respect to 100 mass parts of total amounts of an acryl-type copolymer. When the content of the silane coupling agent is within the above range, the durability of the pressure-sensitive adhesive layer can be further improved.

  In addition to the above components, the pressure-sensitive adhesive composition of the present invention may further contain various additives such as ultraviolet absorbers, solvents and the like.

<Polarizing plate with adhesive>
The polarizing plate with the pressure-sensitive adhesive of the present invention has at least a polarizer and a pressure-sensitive adhesive layer provided on the polarizer and formed of the pressure-sensitive adhesive composition of the present invention described above.

  In general, for example, a polyvinyl alcohol (PVA) film is used as the polarizer. The polarizer can be used as a polarizing plate having, for example, a three-layer structure (for example, TAC / polarizer / TAC) held between protective sheets such as triacetyl cellulose (TAC).

  For example, an adhesive layer is provided by applying the adhesive composition of the present invention described above to at least one surface of a polarizing plate having a three-layer structure of TAC / polarizer / TAC. Is produced. In this case, the pressure-sensitive adhesive composition may be applied on the polarizing plate, but is preferably applied on a protective sheet (peeling sheet) that is peeled off during use. Specifically, the pressure-sensitive adhesive composition of the present invention is coated on a protective sheet (release sheet), dried, and a pressure-sensitive adhesive layer is formed on the protective sheet to produce a pressure-sensitive adhesive sheet. A pressure-sensitive adhesive-attached polarizing plate is produced by transferring and curing the agent layer on the polarizing plate. The application of the pressure-sensitive adhesive composition can be suitably performed by a coating method such as a dipping method, a coating method, or an ink jet method using a liquid pressure-sensitive adhesive composition. Among these, the application method is preferable.

  The pressure-sensitive adhesive composition applied on the protective sheet (release sheet) is preferably dried at 70 ° C. to 120 ° C. under drying conditions of about 1 minute to 3 minutes using a hot air dryer or the like.

Furthermore, from the viewpoint of protecting the contact surface with the adherend, a protective sheet (peeling sheet) for protecting the exposed surface is provided in close contact with the exposed surface of the adhesive layer provided on the polarizing plate. It is preferable. As this protective sheet, a synthetic resin sheet such as polyester subjected to a release treatment with a release agent such as a fluororesin, paraffin wax, or silicone is suitable so that it can be easily peeled off from the adhesive layer. Used for. When pasting on a glass plate or the like of a display panel, the protective sheet is peeled off, and the exposed surface of the pressure-sensitive adhesive layer is adhered to the glass plate or the like.
Moreover, you may further provide the surface protection sheet which protects the surface (exposed surface) of the side in which the adhesive layer of a polarizing plate is not provided. As the surface protective sheet, a protective film or the like that is adhesively processed on one side of a PET film is preferably used.

  The thickness of the pressure-sensitive adhesive layer is not particularly limited, and is preferably 1 μm to 100 μm, more preferably 5 μm to 50 μm, and still more preferably 15 μm to 30 μm in terms of the thickness after drying.

The polarizing plate with the pressure-sensitive adhesive of the present invention is applicable even when the size of the laminated liquid crystal cell is 19 inches wide (260 mm × 415 mm) or more. When the size of the liquid crystal cell is 19 inches wide (260 mm × 415 mm) or more, expansion and contraction due to the influence of heat and humidity of the polarizing plate are increased. Therefore, in the conventional polarizing plate with an adhesive, since the stress is not sufficiently suppressed when exposed to high temperature and high humidity, it occurs around the bezel when the light source of a large display device (for example, a liquid crystal display device) is turned on. It is difficult to suppress the occurrence of “white spots”. In contrast, the pressure-sensitive adhesive polarizing plate of the present invention has a structure in which the copolymer resin design and the type and amount of the cross-linking agent are appropriate, so that stress suppression is possible even when exposed to high temperature and high humidity. Is sufficient for a liquid crystal cell having a size of 19 inches wide (260 mm × 415 mm) or more. Further, even when applied to a small display device (liquid crystal display device) of less than 19 inches (or less than 10 inches), occurrence of white spots can be suppressed by appropriate stress relaxation.
Moreover, in the adhesive sheet which provided the conventional adhesive composition, the part which is less than the size of one polarizing plate was discarded. On the other hand, since the pressure-sensitive adhesive composition of the present invention does not need to be used depending on the size of the polarizing plate, it is used for a small-size polarizing plate even in a portion that is less than the size of the large-sized polarizing plate. The adhesive sheet can be used without waste.

<Display device>
The display device of the present invention is configured by providing a display panel for displaying an image and the above-described polarizing plate with an adhesive of the present invention disposed on at least one surface of the display panel. Examples of the display panel include a liquid crystal display panel in which a liquid crystal compound is sealed, an organic electroluminescence display panel, and the like.

  As an example of the display device of the present invention, the polarizing plate with the pressure-sensitive adhesive of the present invention is disposed on both surfaces of the liquid crystal display panel so that the pressure-sensitive adhesive layer is in contact with the surface of the liquid crystal display panel (for example, the surface of the glass plate). And a liquid crystal display device having a structure (polarizing plate / adhesive layer / liquid crystal display panel / adhesive layer / polarizing plate structure) in which polarizing plates are bonded to both surfaces of the liquid crystal display panel via an adhesive layer. Can do.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof.

(Production Example B)
In a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, n-butyl acrylate (BA) 90.25 parts by mass, methyl acrylate (MA) 9.5 parts by mass, 2-hydroxy Ethyl acrylate (2HEA) 0.15 parts by mass, acrylic acid (AA) 0.1 parts by mass, ethyl acetate (EAc) 110 parts by mass, and azobisdimethylvaleronitrile (ABVN) 0.1 parts by mass were mixed. Thereafter, the inside of the reactor was purged with nitrogen. Thereafter, while stirring the obtained mixture, the mixture in the reactor was heated to 65 ° C. and held for 8 hours to carry out the polymerization reaction. After completion of the polymerization reaction, the reaction mixture was diluted with ethyl acetate to adjust the solid content to 27.0% by mass. Thus, a solution of resin B (acrylic copolymer) which is a BA / MA / 2HEA / AA copolymer was obtained.

(Production Examples C to J, A)
Except that the monomer composition and blending ratio (parts by mass) were changed as shown in Table 1 below, the solutions for resins C to J (acrylic copolymers) and comparative examples were the same as in Production Example B. A solution of Resin A was obtained.

Example 1
-Preparation of adhesive composition-
As the acrylic copolymer, 370.4 parts by mass of the resin B solution (100 parts by mass as the solid content of the resin B), which is the BA / MA / 2HEA / AA copolymer obtained in Production Example B, and isocyanate 40 parts by weight of Coronate L as a compound (an isocyanate compound manufactured by Nippon Polyurethane Industry Co., Ltd., 30 parts by weight as an active ingredient of an isocyanate compound) and YS Polystar TH130 (manufactured by Yashara Chemical Co., Ltd., softening point 130 ° C.) as a terpene phenol tackifier 5 parts by mass and 0.1 parts by mass of KBM-403 as a silane coupling agent were sufficiently stirred and mixed to obtain an adhesive composition.

-Production of optical film sample-
The pressure-sensitive adhesive composition was applied to the release agent-treated surface of the release film surface-treated with the silicone-based release agent so that the coating amount after drying was 25 g / cm ² . Next, this was dried at 100 ° C. for 90 seconds with a hot-air circulating dryer to form an adhesive layer on the release film. Subsequently, a polarizing plate (which has a laminated structure of TAC film / PVA film / TAC film by laminating cellulose triacetate (TAC) films on both sides of a polarizer mainly composed of polyvinyl alcohol (PVA) film); thickness of about 190 μm ] And the surface of the pressure-sensitive adhesive layer were overlapped and bonded together, and pressed through a pressure nip roll. After pressure bonding, the film was cured for 10 days under an environmental condition of 23 ° C. and 65% RH, and a pressure-sensitive adhesive polarizing plate having a laminate structure of release film / pressure-sensitive adhesive layer / polarizing plate was produced as an optical film sample.

-Evaluation-
The following evaluation was performed using the polarizing plate with an adhesive produced above. The evaluation results are shown in Table 2 below.

(1) Durability (4.3 inches)
54 mm × 96 mm (long side) test piece (4.3 inches) obtained by cutting the pressure-sensitive adhesive polarizing plate prepared in “Preparation of optical film sample” so that the long side is 45 ° with respect to the absorption axis. Was prepared, and the release film was peeled from the test piece. By sticking the surface of the pressure-sensitive adhesive layer exposed by peeling to one surface of a 0.7 mm-thick alkali-free glass plate (# 1737, manufactured by Corning), the test piece is stacked on the glass plate, and a laminator is used. The laminate was pasted. Next, this laminate was subjected to autoclave treatment (50 ° C., 5 kg / cm ² , 20 minutes), and allowed to stand at 23 ° C. and 65% RH for 24 hours. Then, it was left for 500 hours in a Dry environment (80 ° C., 0% RH) under high temperature and low humidity conditions or a WET environment (60 ° C., 90% RH) under high temperature and high humidity conditions. Alternatively, high temperature and low temperature were repeated (300 cycles of -40 ° C. for 30 minutes and 85 ° C. for 30 minutes as one cycle), and the mixture was put into an H / S environment.
After the standing time had elapsed, the state of foaming, floating and peeling was visually observed and evaluated according to the following evaluation criteria.

<Evaluation criteria>
A: Foaming, floating, and peeling were not observed at all.
B: Although foaming, floating, and peeling were slightly observed, it was within an allowable range.
C: Foaming, floating, and peeling were noticeable.

(2) White spot (2-1) White spot phenomenon (small size: 7 inches)
Two test pieces were prepared by changing the size of the test piece in “(1) Durability (4.3 inches)” to 88 mm × 156 mm (7.0 inches), and a non-alkali glass plate having a thickness of 0.7 mm. A test sample was prepared by pasting both sides of # 1737 (manufactured by Corning) so that the polarization axes were orthogonal to each other. Next, this test sample was subjected to autoclaving (50 ° C., 5 kg / m ² , 20 minutes), and allowed to stand for 24 hours at 23 ° C. and 50% RH. Then, it was left for 500 hours in a dry environment (70 ° C., 0% RH). After standing, each was placed on the backlight of a liquid crystal monitor under the conditions of 23 ° C. and 50% RH, and the white spots were visually observed.

<Evaluation criteria>
A: No white spots were observed at all.
B: Almost no white spots were observed.
C: Some white spots were recognized, but were within an allowable range.
D: Large white spots were recognized.

(2-2) White spot phenomenon (Large size: 19 inches)
In “(2-1) White spot phenomenon (7 inches)”, except that the size of the test piece obtained by cutting the polarizing plate with adhesive was changed to 240 mm × 427 mm (19 inches), “(2 -1) Evaluation was made in the same manner as the “white spot phenomenon (small size: 7 inches)”.

(3) Appearance An autoclave treatment (50 ° C., 5 kg / cm ² , 20 minutes) was applied to the laminate prepared in the same manner as “(1) Durability (4.3 inches)”, and 23 ° C., 65% It was left for 24 hours under the condition of RH. The appearance after standing was visually observed and evaluated according to the following evaluation criteria.

<Evaluation criteria>
A: Foaming was not recognized.
B: Foamed.

(4) Tackiness (probe tack)
Using a probe tack tester TAC-1000 (Resca Co., Ltd.), the test was performed under the conditions of a load of 200 gf / cm ² , a speed of 5 mm / min, and a contact time of 0.1 sec.

<Evaluation criteria>
A: 80 (gf) or more and excellent workability.
B: It is less than 80 (gf) and is inferior in workability.

(Examples 2 to 21, Comparative Examples 1 to 6)
In Example 1, the type of acrylic copolymer, the content ratio (parts by mass) of the acrylic copolymer and the isocyanate compound, or the type or content ratio (parts by mass) of tackifier is as shown in Table 2 below. A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that the pressure-sensitive adhesive composition was used, and a polarizing plate with a pressure-sensitive adhesive was prepared and evaluated. In Table 2, “not evaluated” indicates that foaming was observed and evaluation was not possible.

The tackifier used is as follows.
YS Polystar TH130: Yasuhara Chemical Co., Ltd., softening point 130 ° C., terpene phenol type YS Polystar T140: Yasuhara Chemical Co., Ltd., softening point 140 ° C., Terpene phenol type YS Polystar T115: Yasuhara Chemical Co., Ltd., softening point 115 ° C. , Terpenephenol-based pine crystal D-6011: manufactured by Arakawa Chemical Industries, Ltd., rosin-based

  As shown in Table 2, in the examples, regardless of the DRY environment, the WET environment, and the H / S environment, the occurrence of foaming, floating, and peeling was suppressed, and good durability was obtained. Moreover, in the Example, generation | occurrence | production of the white spot was able to be suppressed effectively irrespective of the size of the test piece. Moreover, there was no entrainment of the foam which is easy to occur at the time of bonding, and the favorable tack property was shown.

Claims (7)

  The acrylic copolymer having a carboxyl group, an isocyanate compound, and a terpene phenol tackifier, the content of the isocyanate compound being 10 parts by mass with respect to 100 parts by mass of the acrylic copolymer having the carboxyl group The adhesive composition which is a mass part-50 mass parts.   The pressure-sensitive adhesive composition according to claim 1, wherein the terpene phenol tackifier has a softening point of 130C to 145C.   The pressure-sensitive adhesive composition according to claim 1 or 2, wherein a content of the terpene phenol tackifier is 2 parts by mass to 10 parts by mass with respect to 100 parts by mass of the acrylic copolymer having the carboxyl group. .   The acrylic copolymer having a carboxyl group contains 0.1% by mass to 5% by mass of a structural unit derived from an acrylic monomer having a carboxyl group. Adhesive composition.   The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the isocyanate compound contains a tolylene diisocyanate compound. A polarizer,
A pressure-sensitive adhesive layer provided on the polarizer and formed by the pressure-sensitive adhesive composition according to any one of claims 1 to 5,
A polarizing plate with an adhesive. A display panel for displaying images,
The polarizing plate with an adhesive according to claim 6, which is disposed on at least one surface of the display panel;
A display device comprising: