KR102246370B1 - Pressure-sensitive adhesive composition, polarizer with pressure-sensitive adhesive, and display device - Google Patents

Abstract

A pressure-sensitive adhesive composition comprising an acrylic copolymer having a carboxyl group, an isocyanate compound, and a terpenephenol-based tackifier, wherein the content of the isocyanate compound is 10 parts by mass to 50 parts by mass based on 100 parts by mass of the acrylic copolymer having a carboxyl group.

Description

Pressure-sensitive adhesive composition, polarizer with pressure-sensitive adhesive, and display device TECHNICAL FIELD

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

Recently, as a display device for displaying an image, such as a liquid crystal display device and organic electroluminescence, devices of various display systems have been widely used. Among them, a liquid crystal display device is generally a structure in which a liquid crystal cell containing a liquid crystal component that is sandwiched between two supporting substrates such as a glass plate and oriented in a predetermined direction, and an optical film such as a polarizing plate, a retardation film, and a brightness enhancing film are bonded to each other. Have. At the time of lamination of optical films and adhesion of optical films to liquid crystal cells, a pressure-sensitive adhesive is used.

The polarizing plates used in the liquid crystal display are arranged so that the stretching axes of the two stretched polarizing films cross each other. In harsh environments such as high temperature and high humidity, the polarizing film is liable to change in dimensions due to expansion, contraction, etc., and stress is generated in the polarizing plate. When this generated stress is not relieved by the pressure-sensitive adhesive disposed between the polarizing plate and the liquid crystal cell, residual stress is unevenly generated in the polarizing plate. As a result, the two polarizing plates arranged so that the stretching axes of the polarizing film intersect each other on the front and rear surfaces of the display panel are out of phase, and light leaks from the four peripheries of the display portion of the liquid crystal display and becomes white. A stain called occurs.

The above-described gray hair has different occurrence frequency, occurrence pattern, and the like according to the size of the display panel.

In general, in a small display panel, a relatively soft pressure-sensitive adhesive (soft-type pressure-sensitive adhesive) is used to alleviate the stress generated in order to prevent the occurrence of gray hair (for example, see Japanese Laid-Open Patent Publication No. Hei 10-279907). This soft-type adhesive is not suitable for manufacturing large-sized display panels because it tends to adhere to the processing blade and thus has poor punching processing aptitude.

Meanwhile, in a large display panel, a relatively hard adhesive (hard type adhesive) is used to suppress the occurrence of stress in order to prevent the occurrence of gray hair. When this hard-type pressure-sensitive adhesive is applied to a small display panel, stress due to shrinkage or the like tends to be concentrated on the short side of the display panel, and the gray hair tends to appear remarkably around the display panel.

In addition, from the viewpoint of enhancing workability when sticking to an adherend, an appropriate tackiness is required for the pressure-sensitive adhesive. A pressure-sensitive adhesive having an appropriate adhesive property can be temporarily fixed to the adherend. If the pressure-sensitive adhesive is weak, the pressure-sensitive adhesive may peel off and fall off during temporary setting, resulting in poor workability.

As described above, a soft-type adhesive is said to be suitable for a small display panel, but it is difficult to sufficiently prevent the occurrence of gray hair even when a soft-type adhesive is currently used for a small display panel. The same applies to large-sized display panels, and it is difficult to sufficiently prevent the occurrence of gray hair even when a hard-type adhesive is currently used for large-sized display panels.

Furthermore, even if it is used for both a small display panel and a large display panel, there is still no proposal for an adhesive that can sufficiently prevent the occurrence of gray hair, and it is necessary to use a separate adhesive for a small display panel and a large display panel.

In addition, from the viewpoint of workability, appropriate adhesiveness is required for the adhesive.

An object of the present invention is to provide a pressure-sensitive adhesive composition capable of preventing the occurrence of gray hair, which has adequate adhesiveness, and can prevent the occurrence of gray hair, even when used in both a large display panel and a small display panel. In addition, an object of the present invention is to provide a polarizing plate with an adhesive and a display device in which an image with less gray hair is displayed.

In the process of reaching the present invention, by using an isocyanate compound in a higher content than the conventional acrylic copolymer having a carboxyl group, the pressure-sensitive adhesive composition becomes harder than the conventional one, thereby improving the gray hair of the large display panel as well as the stress reduction in the small display panel. The knowledge was obtained that the outbreak can be suppressed. Furthermore, we obtained the knowledge that the tackiness tends to decrease when the isocyanate compound is used in a higher content than the conventional one, and to improve tackiness, we found that terpenephenol tackifiers are particularly effective. The invention has been accomplished.

Specific means for achieving the above object are as follows.

<1> A pressure-sensitive adhesive composition comprising an acrylic copolymer having a carboxyl group, an isocyanate compound, and a terpenephenol-based tackifier, wherein the content of the isocyanate compound is 10 parts by mass to 50 parts by mass based on 100 parts by mass of the acrylic copolymer having a carboxyl group.

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

<3> The pressure-sensitive adhesive composition according to <1> or <2>, wherein the content of the terpenephenol-based tackifier is 2 parts by mass to 10 parts by mass based on 100 parts by mass of the acrylic copolymer having a carboxyl group.

<4> The pressure-sensitive adhesive composition according to any one of <1> to <3>, wherein 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.

<5> The acrylic copolymer having a carboxyl group is a constitution derived from at least one monomer selected from the group consisting of alkyl (meth)acrylate and phenoxy ethyl (meth)acrylate having an alkyl group having 1 to 4 carbon atoms The pressure-sensitive adhesive composition according to any one of the above <1> to <4> containing a unit.

<6> The acrylic copolymer having a carboxyl group is a constitutional unit derived from acrylic acid, a constitutional unit derived from n-butyl acrylate, and a constitution derived from at least one monomer selected from methyl acrylate and phenoxy ethyl acrylate. The pressure-sensitive adhesive composition according to any one of the above <1> to <5> containing a unit.

<7> The pressure-sensitive adhesive composition according to <6>, wherein the acrylic copolymer having a carboxyl group further contains a structural unit derived from 2-hydroxyethyl acrylate.

<8> The adhesive composition in any one of said <1>-<7> in which the said isocyanate compound contains a tolylene diisocyanate compound.

<9> with a polarizer,

A polarizing plate with an adhesive provided on the polarizer and having a pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive composition according to any one of the above <1> to <8>.

<10> a display panel displaying an image,

A display device comprising the polarizing plate with an adhesive according to <9>, disposed on at least one surface of the display panel.

According to the present invention, there is provided a pressure-sensitive adhesive composition capable of preventing the occurrence of gray hair, which has adequate adhesiveness, and is capable of preventing the occurrence of gray hair, even when used in both a large display panel and a small display panel. Further, according to the present invention, a polarizing plate and a display device with an adhesive capable of displaying an image with less gray hair are provided.

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

<Adhesive composition>

The pressure-sensitive adhesive composition of the present invention comprises an acrylic copolymer having a carboxyl group, an isocyanate compound, and a terpenephenol-based tackifier, and the content of the isocyanate compound is 10 parts by mass to 50 parts by mass based on 100 parts by mass of the acrylic copolymer having a carboxyl group. to be.

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

In the conventional pressure-sensitive adhesive composition, the content of the isocyanate compound is suppressed to about 5 parts by mass, even if it is as high as 100 parts by mass of the acrylic copolymer. However, in the present invention, the isocyanate compound is actively contained in a high content of 10 parts by mass to 50 parts by mass per 100 parts by mass of the acrylic copolymer having a carboxyl group. Accordingly, a pressure-sensitive adhesive composition capable of preventing the occurrence of gray hair can be obtained compared to the prior art, and even when used in both a large display panel and a small display panel, gray hair can be prevented.

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

In addition, when the isocyanate compound is contained in a high content of 10 parts by mass to 50 parts by mass based on 100 parts by mass of the acrylic copolymer having a carboxyl group, the tackiness tends to decrease. By containing a terpenephenol-based tackifier here, a decrease in adhesiveness can be effectively suppressed and a pressure-sensitive adhesive composition excellent in workability is 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.

As an acrylic monomer having a carboxyl group, for example, acrylic acid (AA), methacrylic acid (MAA), ω-carboxy-polycaprolactone mono (meth)acrylate, succinic acid monohydroxyethyl (meth)acrylate, maleic acid monohydro Roxy ethyl (meth) acrylate, fumaric acid monohydroxy ethyl (meth) acrylate, phthalic acid monohydroxy ethyl (meth) acrylate, 1,2-dicarboxycyclohexane monohydroxy ethyl (meth) acrylate, (meth) ) Acrylic acid dimers, etc. are mentioned. These acrylic monomers having a carboxyl group may be used alone or in combination of two or more. Among them, acrylic acid is preferable as an acrylic monomer having a carboxyl group from the viewpoint of high reactivity with other monomers during the copolymerization reaction and the ability to 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% by mass 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, it is possible to suppress shortening of the pot life.

As other monomers, for example, 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, phenoxy ethyl (meth) acrylate, benzyl (meth) acrylate, and other monomers that do not have a functional group. These monomers may be used alone or in combination of two or more.

Among them, at least one selected from the group consisting of alkyl (meth)acrylates and phenoxyethyl (meth)acrylates having an alkyl group having 1 to 4 carbon atoms as other monomers from the viewpoint of easy adjustment of the cohesiveness and adhesion of the pressure-sensitive adhesive. It is preferably a species monomer, more preferably at least one monomer selected from the group consisting of alkyl acrylates and phenoxy ethyl acrylates having an alkyl group having 1 to 4 carbon atoms, and n-butyl acrylate is the main component Methyl acrylate and n-butyl acrylate are used as the main component, phenoxy ethyl acrylate and n-butyl acrylate are used as the main component, or n-butyl acrylate is used as the main component It is more preferable to use methyl acrylate, phenoxy ethyl acrylate, and n-butyl acrylate in combination.

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

When using methyl acrylate (MA) and/or phenoxy ethyl acrylate (PHEA) and n-butyl acrylate (BA) as other monomers, 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 increased, and even if a large amount of the isocyanate compound is included, it is easy to mix, and when it is 1 or less, the adhesiveness tends to be easily maintained.

The total content of the 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, and 95% by mass to 98% by mass Is more preferred.

It is preferable that the pressure-sensitive adhesive composition of the present invention further uses a monomer having a functional group other than a carboxyl group as another monomer. Other monomers having a functional group other than a carboxyl group that can be used further include a monomer having a hydroxyl group such as 2-hydroxy ethyl acrylate (2HEA) and 4-hydroxy butyl acrylate (4HBA), and N,N-dimethylacrylamide. Monomers having an amide group such as (DMAA), monomers having an epoxy group such as 4-hydroxy butyl acrylate glycidyl ether (4HBAGE), and glycidyl methacrylate (GMA). From the viewpoint of cohesive strength A monomer having a hydroxyl group is preferred, and 2-hydroxy ethylacrylate is particularly preferred.

The total amount of structural units derived from other monomers having a functional group other than a carboxyl group in the acrylic copolymer is preferably 1% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.2% by mass or less.

Particularly preferred acrylic copolymers are copolymers containing at least structural units derived from acrylic acid, n-butyl acrylate, methyl acrylate and/or phenoxy ethyl acrylate, specifically AA/BA/MA copolymers, AA/BA/MA/2HEA copolymer, AA/BA/MA/PHEA copolymer, AA/BA/2HEA/PHEA copolymer, AA/BA/MA/2HEA/PHEA copolymer etc. are 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 still more preferably 700,000 to 1,800,000.

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) The acrylic copolymer solution is applied onto a release sheet (release sheet) and dried at 100° C. for 2 minutes to obtain a film-shaped acrylic copolymer.

(2) The film-like acrylic copolymer obtained in the above (1) is dissolved in tetrahydrofuran to a solid content of 0.2% by mass.

(3) The weight average molecular weight (Mw) of the (meth)acrylic copolymer is measured using gel permeation chromatography (GPC) under the following conditions.

<condition>

·GPC: HLC-8220 GPC [manufactured by Tosoh Corporation]

·Column: TSK-GEL GMHXL (use 4)

Mobile phase solvent: tetrahydrofuran

Standard sample: standard polystyrene

Flow rate: 0.6ml/min

·Column temperature: 40℃

The glass transition temperature (Tg) of the acrylic copolymer is preferably in the range of -50°C to -30°C, and more preferably in the range of -48°C to -40°C. When Tg is -50°C or higher, the elastic modulus can be adjusted, and durability and whiteness are excellent. Moreover, when Tg is -30 degreeC or less, adhesiveness and bonding suitability are excellent without extremely impairing 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. In the following formula, Tg ₁ , Tg ₂ , ... And Tg _n is component 1, component 2, ... And the glass transition temperature of the homopolymer of each of the components n, calculated in terms of absolute temperature (°K). m ₁ , m ₂ ,… And m _n is the mole fraction of each component.

[Calculation formula of glass transition temperature (Tg)]

In addition, the glass transition temperature of the monomer described in pages 11 to 35 of “The Mechanical Properties of Polymers” by L.E. Nielsen's, Shigeharu Onogi station is applied to the "glass transition temperature (Tg) of a single polymer" here.

The content rate 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 based on the total solid content. When the content of the acrylic copolymer is within the above range, hardness is imparted to the pressure-sensitive adhesive to suppress the occurrence of stress and effectively suppress the occurrence of gray hair.

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 preferable as a polymerization method of the acrylic copolymer 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 necessary are placed in a polymerization tank, and the mixture is heated and reacted for several hours while stirring in a nitrogen stream or under reflux of the organic solvent. It does not specifically limit as said polymerization initiator, For example, an azo compound can be used.

(Isocyanate compound)

The pressure-sensitive adhesive composition of the present invention contains at least one type of isocyanate compound. The isocyanate compound is contained in an amount of 10 to 50 parts by mass per 100 parts by mass of the acrylic copolymer having a carboxyl group. When the isocyanate compound is contained in such an amount, gray hair is prevented regardless of the size of the display panel. When the content of the isocyanate compound is 10 parts by mass or more, the occurrence of gray hair can be prevented compared to the prior art, and even when used in both a large display panel and a small display panel, it becomes possible to prevent the occurrence of gray hair. When the content of the isocyanate compound is 50 parts by mass or less, cloudiness due to carbon dioxide generated in the reaction of the isocyanate compound is suppressed and the appearance is improved. Further, if the content of the isocyanate compound is increased to about 10 parts by mass, the tackiness tends to decrease, but by containing a terpenephenol-based tackifier described later, a pressure-sensitive adhesive composition having excellent tackiness is obtained.

The content of the isocyanate compound in the pressure-sensitive adhesive composition is preferably 15 parts by mass to 50 parts by mass, more preferably 20 parts by mass to 45 parts by mass, and more preferably 30 parts by mass to 40 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 to disown.

As an isocyanate compound, a tolylene diisocyanate compound is mentioned suitably. 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 a polyol such as tolylene diisocyanate and trimethylolpropane, can be used. have. These tolylene diisocyanate compounds may be used alone or in combination of two or more.

As for the tolylene diisocyanate compound, a commercially available product may be used. As a commercially available product of the tolylene diisocyanate compound, "Colonate L" (brand name) manufactured by Japan Polyurethane Industries Co., Ltd. can be suitably used.

(Terpenephenol Tackifier)

The pressure-sensitive adhesive composition of the present invention contains a terpenephenol-based tackifier. Terpenephenol-based tackifier is a resin obtained by copolymerizing a terpene monomer and a phenol compound. Terpenephenol-based tackifier is easy to mix even in a pressure-sensitive adhesive composition containing more isocyanate compounds than conventional, and can effectively exhibit adhesiveness.

The terpenephenol-based tackifier has a softening point of preferably 130°C to 145°C, and more preferably 130°C to 140°C from the viewpoint of mixability in the pressure-sensitive adhesive composition.

The softening point of the terpenephenol-based tackifier is a value measured based on the softening point test method (ring ball method) specified in JIS K 2207 (2006 edition).

Terpenephenol-based tackifiers may be used alone or in combination of two or more. Examples of terpenephenol-based tackifiers include copolymers of monocyclic monoterpenes such as α-pinene, β-pinene, and dipentene (limonene) and phenol compounds such as phenol, cresol, and bisphenol A.

Terpenephenol-based tachyfire may be used commercially available products. As a commercial product of terpenephenol-based tackifier, Yasuhara Chemical Co., Ltd.'s "YS Polyster TH130" (brand name, softening point 130°C), "YS Polyster U115" (brand name, softening point 115°C), and "YS Polyster T145" (brand name, softening point 115°C), Softening Point 145°C), “YS Polyester T140” (brand name, softening point 140°C), “YS Polyester T130” (brand name, softening point 130°C), “YS Polyester T115” (brand name, softening point 115°C), “YS Police 2130” (brand name, softening point 130℃), “YS Polyster 2115” (brand name, softening point 115℃), “YS Polyster S145” (brand name, softening point 145℃), “YS Polyster N125” (brand name, softening point 125 ℃), “Mighty Ace G150” (brand name, softening point 150°C), “Mighty Ace G125” (brand name, softening point 125°C), “Mighty Ace K125” (brand name, softening point 125°C), “Tamanol” from Arakawa Chemical Industry Co., Ltd. 901” (brand name, softening point: 130°C) can be used suitably.

The content of the terpenephenol-based tackifier in the pressure-sensitive adhesive composition is preferably 2 parts by mass to 10 parts by mass, and more preferably 3 parts by mass to 8 parts by mass with respect to 100 parts by mass of the total amount of the acrylic copolymer having a carboxyl group. When the content of the terpenephenol-based tackifier is 10 parts by mass or less, stress suppression tends to be exhibited more.

(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, there is a tendency that the gap between the pressure-sensitive adhesive layer and the polarizing plate or liquid crystal cell tends to be difficult to peel off even when the display device (for example, a liquid crystal display device) in which the polarizing plate is assembled is exposed under a high-temperature, high-humidity environment. .

Examples of the silane coupling agent include silane compounds containing polymerizable unsaturated groups such as vinyl trimethoxysilane, vinyl triethoxysilane, and 3-methacryloxypropyl trimethoxysilane, 3-mercaptopropyl trimethoxysilane, 3 -Mercapto group-containing silane compounds such as mercaptopropyl triethoxysilane and 3-mercaptopropyl dimethoxymethylsilane, 3-glycidoxypropyl trimethoxysilane, 2-(3,4-epoxycyclohexyl) Silane compounds having an epoxy structure such as ethyl trimethoxysilane, 3-aminopropyl trimethoxysilane, N-(2-aminoethyl)-3-aminopropyl trimethoxysilane, N-(2-aminoethyl)- Amino group-containing silane compounds, such as 3-aminopropylmethyl dimethoxysilane, tris-(3-trimethoxysilylpropyl) isocyanurate, etc. are mentioned. These silane coupling agents may be used alone or in combination of two or more.

The silane coupling agent may use a commercially available product. As a commercial product of the silane coupling agent, "KBM-403" (brand name) manufactured by Shin-Etsu Chemical Industries, Ltd. can be suitably used.

The content of the silane coupling agent in the pressure-sensitive adhesive composition is preferably in the range of 0.01 parts by mass to 2.0 parts by mass with respect to 100 parts by mass of the total amount of the acrylic copolymer having a carboxyl group. 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 the pressure-sensitive adhesive composition of the present invention, in addition to the above components, various additives such as an ultraviolet absorber, a solvent, and the like can be appropriately blended.

<Polarizing plate with adhesive>

The polarizing plate with an 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.

As a polarizer, for example, a polyvinyl alcohol (PVA) film or the like is generally used. The polarizer can be used as a polarizing plate composed of, for example, a three-layer structure (eg, TAC/polarizer/TAC) held between protective sheets such as triacetylcellulose (TAC).

For example, a polarizing plate with a pressure-sensitive adhesive is produced by providing a pressure-sensitive adhesive layer by applying the pressure-sensitive adhesive composition of the present invention to at least one surface of a three-layered polarizing plate of TAC/polarizer/TAC. In this case, although the pressure-sensitive adhesive composition may be provided on the polarizing plate, it is preferably applied on a protective sheet (release sheet) to be peeled off at the time of use. Specifically, the pressure-sensitive adhesive composition of the present invention is coated on a protective sheet (release sheet) and dried to form a pressure-sensitive adhesive layer on the protective sheet to form a pressure-sensitive adhesive sheet, and then the pressure-sensitive adhesive layer is transferred onto a polarizing plate and cured to attach the pressure-sensitive adhesive. A polarizing plate is produced. The application of the pressure-sensitive adhesive composition can be suitably performed by a coating method such as an immersion method, a coating method, or an ink jet method using a liquid pressure-sensitive adhesive composition. Among them, the application of the pressure-sensitive adhesive composition is preferably applied by a coating method.

The pressure-sensitive adhesive composition applied on the protective sheet (peeling 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.

In addition, it is preferable to provide a protective sheet (release sheet) for protecting the exposed surface in close contact with the exposed surface of the adhesive layer provided on the polarizing plate from the viewpoint of protecting the contact surface to the adherend. As this protective sheet, a synthetic resin sheet such as polyester, which has undergone a release treatment with a release agent such as fluorine-based resin, paraffin wax, or silicone, is suitably used so that peeling between the adhesive layer and the adhesive layer can be easily performed. When attaching to a glass plate of a display panel, the protective sheet is peeled off, and the surface of the exposed pressure-sensitive adhesive layer is brought into close contact with the glass plate.

Further, on the surface of the polarizing plate on the side where the pressure-sensitive adhesive layer is not provided (exposed surface), a surface protection sheet for protecting the surface may be further provided. As the surface protection sheet, a protective film or the like applied to one side of the PET film is suitably used.

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

The polarizing plate with a pressure-sensitive adhesive of the present invention can be applied even when the size of the laminated liquid crystal cell is 19 inches wide (260 mm×415 mm) or more. If the size of the liquid crystal cell is 19 inches wide (260 mm × 415 mm) or more, expansion and contraction of the polarizing plate due to the influence of heat and humidity increases. Therefore, in the conventional polarizing plate with adhesive, stress suppression is not sufficient when exposed to high temperature and high humidity. Therefore, it is possible to suppress the occurrence of "white hair" around the bezel when the light source of a large display device (for example, a liquid crystal display device) is turned on. Is difficult. In contrast, since the polarizing plate with an adhesive of the present invention has a composition in which the resin design of the copolymer and the type and amount of the crosslinking agent are appropriate, stress suppression is sufficient even when exposed to high temperature and high humidity, and has a size of 19 inches wide (260 mm × 415 mm) or more. It is also suitable for liquid crystal cells of. Further, even when applied to a small display device (liquid crystal display device) of less than 19 inches (and further less than 10 inches), occurrence of gray hair is suppressed by appropriate stress relaxation properties.

In addition, in the pressure-sensitive adhesive sheet provided with the conventional pressure-sensitive adhesive composition, portions that do not reach the size of one polarizing plate were discarded. On the other hand, since the pressure-sensitive adhesive composition of the present invention does not need to be divided according to the size of the polarizing plate, it can be used for a small-sized polarizing plate even if it does not reach the size of a large-sized polarizing plate, so that the pressure-sensitive 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 a polarizing plate provided with the pressure-sensitive adhesive of the present invention disposed on at least one side of the display panel. Examples of the display panel include a liquid crystal display panel encapsulated with a liquid crystal compound, an organic electroluminescent display panel, and the like.

As an example of the display device of the present invention, polarizing plates with an adhesive of the present invention are disposed on both sides of a liquid crystal display panel so that the adhesive layer contacts the surface of the liquid crystal display panel (for example, the surface of the glass plate), and through the adhesive layer. A liquid crystal display device including a structure in which polarizing plates are adhered to both surfaces of a liquid crystal display panel (structure of a polarizing plate/adhesive layer/liquid crystal display panel/adhesive layer/polarizing plate) is exemplified.

Example

Hereinafter, the present invention will be described in more detail by examples, but the present invention is not limited to the following examples unless it goes beyond the gist of the present invention.

(Production Example B)

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

(Production Examples C to J, A)

A solution of resins C to J (acrylic copolymer) and a solution of resin A for a comparative example were obtained in the same manner as in Production Example B except that the composition and compounding ratio (parts by mass) of the monomers were changed as shown in Table 1 below.

(Example 1)

-Preparation of adhesive composition-

370.4 parts by mass of a solution of Resin B, a BA/MA/2HEA/AA copolymer obtained in Preparation Example B as an acrylic copolymer (100 parts by mass as a solid content of Resin B), and 40 parts by mass of colonate L as an isocyanate compound (Japan Poly. An isocyanate-based compound manufactured by Urethane Industries, 30 parts by mass as an active ingredient of an isocyanate compound), 5 parts by mass of YS polyester TH130 (Yasuhara Chemical Co., Ltd. product, softening point 130°C) as a terpenephenol-based tackifier, and as a silane coupling agent 0.1 parts by mass of KBM-403 was sufficiently stirred and mixed to obtain a pressure-sensitive adhesive composition.

-Production of optical film samples-

A pressure-sensitive adhesive composition was applied to the release agent-treated surface of the release film surface-treated with a silicone-based release agent so that the coating amount after drying was 25 g/cm 2. Next, the applied pressure-sensitive adhesive composition was dried at 100° C. for 90 seconds with a hot air circulation dryer to form a pressure-sensitive adhesive layer on the release film. Next, a polarizing plate [having a laminated structure of a TAC film/PVA film/TAC film by laminating a cellulose triacetate (TAC) film on both sides of a polarizer mainly comprising a polyvinyl alcohol (PVA) film; The back surface having a thickness of about 190 µm] and the surface of the pressure-sensitive adhesive layer were superimposed and bonded, passed through a pressure nip roll, and pressed to obtain a bonded body. This bonded body was cured for 10 days under an environmental condition of 23°C and 65%RH to prepare a polarizing plate with a pressure-sensitive adhesive having a laminated structure of a release film/adhesive layer/polarizing plate 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)

A 54 mm x 96 mm (long side) test piece (4.3 inches) was prepared by cutting the polarizing plate with an adhesive prepared in the above ``production of an optical film sample'' so that the long side was 45° with respect to the absorption axis, and the peeling film was peeled from the test piece. I did. The surface of the pressure-sensitive adhesive layer exposed by peeling was brought into close contact with one side of an alkali-free glass plate (#1737, manufactured by Corning) having a thickness of 0.7 mm, so that the test piece was stacked on the glass plate and attached using a laminator to obtain a laminate. Next, the laminate was subjected to an autoclave treatment (50°C, 5 kg/cm 2, 20 minutes) and left to stand for 24 hours under conditions of 23°C and 65% RH. The durability test of leaving the laminate in a dry environment (80℃, 0%RH) under high temperature and low humidity conditions for 500 hours, and a durability test by leaving it in a WET environment (60℃, 90%RH) under high temperature and humidity conditions for 500 hours. And durability tests in which high and low temperatures were repeated (-40°C for 30 minutes, 85°C for 30 minutes as one cycle and 300 cycles) to be put into the H/S environment, respectively.

After the end of the durability test, the foaming, lifting and peeling conditions were visually observed and evaluated according to the following evaluation criteria.

<Evaluation criteria>

A: Foaming, lifting and peeling were not recognized at all.

B: At least one of foaming, lifting, and peeling was slightly recognized, but it was an acceptable range.

C: At least one of foaming, lifting and peeling was remarkably recognized.

(2) white hair

(2-1) White hair phenomenon (small: 7 inches)

Prepare two test pieces in which the size of the test piece in ``(1) Durability (4.3 inch)'' was changed to 88 mm × 156 mm (7.0 inch), and on both sides of an alkali-free glass plate (#1737, manufactured by Corning) having a thickness of 0.7 mm. A test sample was prepared by attaching the polarization axes to be orthogonal to each other. Next, this test sample was subjected to autoclave treatment (50°C, 5kg/m2, 20 minutes) and left for 24 hours under conditions of 23°C and 50%RH, and then 500 hours in a dry environment (70°C, 0%RH). Left unattended. The test sample after this left to stand was placed on the backlight of a liquid crystal monitor under conditions of 23°C and 50%RH, and the state of gray hair was visually observed, and evaluated according to the following evaluation criteria.

<Evaluation criteria>

A: No white hair was recognized.

B: Hardly any gray hair was recognized.

C: Gray hair was slightly recognized, but it was an allowable range.

D: Gray hair was greatly recognized.

(2-2) White hair phenomenon (large size: 19 inches)

Except for changing the size of the specimen obtained by cutting the polarizing plate with an adhesive in the above ``(2-1) gray hair development (7 inches)'' to 240 mm x 427 mm (19 inches), ``(2-1) gray hair development (small: 7 inches) )”.

(3) Appearance

The laminate prepared in the same manner as in the above "(1) durability (4.3 inches)" was subjected to autoclave treatment (50°C, 5 kg/cm 2, 20 minutes) and allowed to stand for 24 hours under conditions of 23°C and 65% RH. The appearance of the laminate after standing was observed visually and evaluated according to the following evaluation criteria.

<Evaluation criteria>

A: Foaming was not recognized.

B: Foaming was recognized.

(4) Adhesiveness (probe tag)

The following evaluation criteria were performed by measuring the probe tack value of the pressure-sensitive adhesive composition under the conditions of a load of 200 gf/cm 2 (1961.33 mN/cm 2), a speed of 5 mm/min, and a contact time of 0.1 sec using a probe tack tester TAC-1000 (Rescar, Inc.) It was evaluated according to.

<Evaluation criteria>

A: The probe tack value is 80gf (784.532mN) or more, and has excellent workability.

B: The probe tack value is less than 80 gf (784.532 mN), and workability is inferior.

(Examples 2 to 21 and Comparative Examples 1 to 6)

Example 1, except that the type of the 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 the tackifier were changed as shown in Table 2 below. In the same manner, an adhesive composition was prepared, and a polarizing plate with an adhesive was produced using this adhesive composition, and evaluation was performed. In addition, in Table 2, "not evaluated" indicates that it was not possible to evaluate because foaming was recognized.

The used tackifier is as follows.

YS Polyster TH130: manufactured by Yasuhara Chemical Co., Ltd., softening point 130℃, terpenephenol type

YS Polyster T140: manufactured by Yasuhara Chemical Co., Ltd., softening point 140°C, terpenephenol type

YS Polyster T115: manufactured by Yasuhara Chemical Co., Ltd., softening point 115°C, terpenephenol type

Fine Crystal D-6011: manufactured by Arakawa Chemical Industries, Ltd., rosin-based

As shown in Table 2, in the Examples, foaming, lifting and peeling were suppressed regardless of the DRY environment, the WET environment, and the H/S environment, thereby obtaining good durability. In addition, in the examples, it was possible to effectively suppress the occurrence of gray hair regardless of the size of the test piece. In addition, in the examples, bubbles that tend to occur during bonding were not curled up and exhibited good adhesiveness.

Claims (10)

An acrylic copolymer having a carboxyl group, an isocyanate compound, and a terpenephenol-based tackifier, and the content of the isocyanate compound is 10 parts by mass to 50 parts by mass based on 100 parts by mass of the acrylic copolymer having a carboxyl group,
The pressure-sensitive adhesive composition in which the content of the terpenephenol-based tackifier is 2 parts by mass to 10 parts by mass based on 100 parts by mass of the acrylic copolymer having a carboxyl group. The method according to claim 1,
A pressure-sensitive adhesive composition having a softening point of 130°C to 145°C of the terpenephenol-based tackifier. delete The method according to claim 1 or 2,
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. The method according to claim 1 or 2,
The acrylic copolymer having a carboxyl group contains a structural unit derived from at least one monomer selected from the group consisting of alkyl (meth)acrylate and phenoxyethyl (meth)acrylate having an alkyl group having 1 to 4 carbon atoms. The pressure-sensitive adhesive composition. The method according to claim 1 or 2,
The acrylic copolymer having a carboxyl group contains a constitutional unit derived from acrylic acid, a constitutional unit derived from n-butyl acrylate, and a constitutional unit derived from at least one monomer selected from methyl acrylate and phenoxy ethyl acrylate. The pressure-sensitive adhesive composition. The method of claim 6,
The acrylic copolymer having a carboxyl group further contains a structural unit derived from 2-hydroxy ethyl acrylate. The method according to claim 1 or 2,
The pressure-sensitive adhesive composition wherein the isocyanate compound includes a tolylene diisocyanate compound. With polarizer,
A polarizing plate with an adhesive provided on the polarizer and having an adhesive layer formed of the adhesive composition according to claim 1 or 2. A display panel that displays an image;
A display device comprising the polarizing plate with an adhesive according to claim 9 disposed on at least one surface of the display panel.