JP2022179186A - Manufacturing method of pressure sensitive adhesive sheet, manufacturing method of optical laminate, and manufacturing method of picture display unit - Google Patents

Abstract

To provide a manufacturing method of a pressure sensitive adhesive sheet appropriate for manufacturing a pressure sensitive adhesive sheet with durability and transparency thereof secured, as well as capable of preventing a change in a dimension of an optical film included in an optical laminate.SOLUTION: Provided is a manufacturing method including: heating a coating film of an adhesive composition including a (meth)acrylic polymer (A) as a primary component and further including an isocyanate-based cross-linking agent (B); and forming a pressure sensitive adhesive sheet from the coating film. Assuming a self-polymerization body (C) of the cross-linking agent (B), a distance Ra in Hansen solubility parameter (HSP) between the (meth)acrylic polymer (A) and the self-polymerization body (C) is 15 or less. A condition of the heating satisfies an expression (1) or (2) below, in which x and y are temperature (°C) and duration (sec.) of the heating, respectively: x≤120 (1); or x>120 and y≤-2.17x+365.83 (2).SELECTED DRAWING: Figure 7

Description

The present invention relates to a method for producing an adhesive sheet, a method for producing an optical laminate, and a method for producing an image display device.

2. Description of the Related Art In recent years, image display devices typified by liquid crystal display devices and electroluminescence (EL) display devices (eg, organic EL display devices and inorganic EL display devices) have rapidly spread. These various image display devices usually have a laminated structure of an image forming layer such as a liquid crystal layer and an EL light emitting layer, and an optical laminate including an optical film and an adhesive sheet. The pressure-sensitive adhesive sheet is mainly used for bonding between films included in the optical layered body and bonding between the image forming layer and the optical layered body. Examples of the optical film are a polarizing plate, a retardation film, and a polarizing plate with a retardation film in which the polarizing plate and the retardation film are integrated. Patent Documents 1 and 2 disclose an example of an optical layered body.

JP 2008-031214 A JP 2009-98665 A

Excessive changes in the dimensions of the optical film due to temperature changes cause light leakage and color unevenness in image display devices. Light leakage and color unevenness are particularly likely to occur in a relatively large-sized image display device using a polarizing plate with a retardation film. In addition, image display devices designed with a narrow bezel (narrow bezel) are becoming popular, and suppression of dimensional change is becoming more and more important. In order to suppress the dimensional change, it is conceivable to increase the elastic modulus of the pressure-sensitive adhesive sheet included in the optical layered body. However, if the elastic modulus is simply increased, the durability of the pressure-sensitive adhesive sheet may be lowered and it may not be able to follow changes in dimensions, and the transparency desired for an optical pressure-sensitive adhesive sheet may be impaired.

An object of the present invention is to provide a method for producing a pressure-sensitive adhesive sheet that is suitable for producing a pressure-sensitive adhesive sheet that can suppress changes in the dimensions of an optical film included in an optical laminate and that ensures durability and transparency. .

The present invention
Heating a coating film of a pressure-sensitive adhesive composition containing a (meth)acrylic polymer (A) as a main component and further containing an isocyanate cross-linking agent (B) to form a pressure-sensitive adhesive sheet from the coating film. including
Assuming the self-polymer (C) of the isocyanate-based cross-linking agent (B), the Hansen solubility parameter (HSP) between the (meth)acrylic polymer (A) and the self-polymer (C) the distance Ra is 15 or less,
The heating conditions satisfy the following formula (1) or (2),
A method for producing an adhesive sheet,
I will provide a.
x≦120 (1)
x>120 and y≦−2.17x+365.83 (2)
However, x and y are the temperature (° C.) and time (seconds) of the heating, respectively.

In another aspect, the invention provides a
A method for producing an optical laminate including an adhesive sheet and an optical film,
The adhesive sheet is formed by the method for producing an adhesive sheet of the present invention,
a method for manufacturing an optical laminate,
I will provide a.

In another aspect, the invention provides a
A method for manufacturing an image display device comprising an optical laminate including an adhesive sheet and an optical film,
The adhesive sheet is formed by the method for producing an adhesive sheet of the present invention,
a method for manufacturing an image display device;
I will provide a.

The manufacturing method according to the present invention is suitable for manufacturing a pressure-sensitive adhesive sheet that can suppress changes in the dimensions of the optical film contained in the optical layered body and that also ensures durability and transparency.

FIG. 1 is a cross-sectional view schematically showing an example of a pressure-sensitive adhesive sheet obtained by the production method of the present invention. FIG. 2 is a cross-sectional view schematically showing an example of an optical layered body provided with an adhesive sheet obtained by the production method of the present invention. FIG. 3 is a cross-sectional view schematically showing an example of an optical layered body provided with an adhesive sheet obtained by the production method of the present invention. FIG. 4 is a cross-sectional view schematically showing an example of an optical layered body provided with a pressure-sensitive adhesive sheet obtained by the production method of the present invention. FIG. 5 is a cross-sectional view schematically showing an example of an optical layered body provided with an adhesive sheet obtained by the production method of the present invention. FIG. 6 is a cross-sectional view schematically showing an example of an image display device provided with an adhesive sheet obtained by the production method of the present invention. FIG. 7 is a graph showing the production conditions (main heating temperature and time) of pressure-sensitive adhesive sheets produced in Examples and Comparative Examples, and the results of comprehensive evaluation.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments shown below.

As used herein, "(meth)acryl" means acryl and methacryl. Moreover, "(meth)acrylate" means acrylate and methacrylate.

[Method for producing adhesive sheet]
In the production method of the present embodiment, the coating film of the pressure-sensitive adhesive composition (I) containing the (meth)acrylic polymer (A) as a main component and further containing the isocyanate cross-linking agent (B) is heated and applied. Forming an adhesive sheet from the membrane. Hereinafter, the heating of the coating film is referred to as main heating. In the main heating, mainly the adhesive composition (I) contained in the coating film is thermally crosslinked and cured. The pressure-sensitive adhesive composition (I) containing the isocyanate-based cross-linking agent (B) is suitable for forming a pressure-sensitive adhesive sheet with ensured durability.

Assuming the self-polymer (C) of the isocyanate-based cross-linking agent (B), the distance Ra of the Hansen solubility parameter (HSP) between the (meth)acrylic polymer (A) and the self-polymer (C) is , 15 or less. The isocyanate-based cross-linking agent (B) may react with each other due to heat during the formation of the pressure-sensitive adhesive sheet to form a self-polymer of the cross-linking agent (B). The formation of the self-polymer increases the cohesive force of the adhesive sheet, thereby contributing to the formation of the adhesive sheet that can suppress the dimensional change of the optical film. However, when the compatibility between the (meth)acrylic polymer (A) and the self-polymer is low, the durability and transparency of the pressure-sensitive adhesive sheet tend to deteriorate. A possible reason for the decrease is that self-polymer-rich independent domains tend to occur inside the pressure-sensitive adhesive sheet. The formation of the above domains can cause whitening of the PSA sheet due to scattering and reflection of light at the interface of the domains, and when the PSA sheet is deformed by an external force, voids ( voids) and the like. According to the studies of the present inventors, the compatibility of the (meth)acrylic polymer (A) with the isocyanate cross-linking agent (B) and its self-polymer becomes high when the distance Ra is 15 or less.

The distance Ra may be 14.5 or less, 14 or less, 13.5 or less, 13 or less, 12.5 or less, or even 12 or less. The lower limit of the distance Ra is, for example, 6 or more.

The Hansen Solubility Parameter (HSP) is the solubility parameter introduced by Hildebrand divided into three components: the dispersion term δD, the polarization term δP and the hydrogen bonding term δH. δD indicates the energy derived from the intermolecular dispersion force. δP indicates the energy derived from intermolecular polar forces. δH indicates energy derived from intermolecular hydrogen bonding force. The unit of each component is usually MPa ^1/2 . The three components define a point (vector) in a three-dimensional space known as Hansen's space. The distance Ra is defined by points (D _A , P _A , H _A ) corresponding to the (meth)acrylic polymer (A) and points (D _C , P _C , H _C ) and can be calculated by the formula: {4×(δD _A −δD _B ) ² +(δP _A −δP _B ) ² +(δH _A −δH _B ) ² } ^1/2 . Details of the Hansen Solubility Parameters are disclosed in "Hansen Solubility Parameters; A Users Handbook" (CRC Press, 2007). δD, δP and δH of the polymer can be determined by calculation using known software such as HSPiP (version 5) based on the constituent units possessed by the polymer and the content of such units in the polymer. More specifically, δD, δP and δH of each structural unit are individually calculated, and the weighted average value obtained by weighting the calculated δD, δP and δH by the content of the unit is used as the δD, δH of the polymer. δP and δH. However, the calculation is performed at a temperature of 23°C. Note that the calculated values of .delta.D, .delta.P and .delta.H may differ slightly depending on the software used. However, the difference is usually negligible in determining Ra. Hansen Solubility Parameters for crosslinkers are calculated only for those that form self-polymers.

The self-polymer (C) assumed in the calculation of the distance Ra is a single polymer composed of structural units derived from the isocyanate-based cross-linking agent (B). However, the self-polymer of the cross-linking agent (B) actually contained in the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition (I) contains structural units other than the structural units derived from the cross-linking agent (B). sometimes

The main heating condition satisfies the following formula (1) or (2). However, x and y are the heating temperature (° C.) and time (seconds) in the main heating, respectively. Equation (2) means that if the heating temperature x exceeds 120° C., the heating time y should be limited within a predetermined time. The heating temperature x can be defined as the highest temperature to which the coating film is exposed. or when the set temperature changes over time, it can be defined as the highest set temperature to which the coating film is exposed in the heating device). The heating time y can be defined as the time the coating film is exposed to a temperature above 120°C. When using a heating device, for example, the time the coating film is located in a space set to a temperature exceeding 120 ° C., or the time for the coating film to pass through a section set to a temperature exceeding 120 ° C. Time y may be defined. When there are a plurality of intervals set at a temperature exceeding 120° C., the total time spent passing through the intervals can be defined as time y. When the set temperature changes over time, the time during which the set temperature exceeds 120° C. can be calculated as the time y. The same applies to the temperature p and time q of preheating, which will be described later.
x≦120 (1)
x>120 and y≦−2.17x+365.83 (2)

According to studies by the present inventors, the isocyanate-based cross-linking agent (B) in a monomeric state deteriorates in solubility at high temperatures and tends to gradually aggregate inside the coating film. Therefore, the higher the temperature x and the longer the time y, the more likely the independent domains are formed on the pressure-sensitive adhesive sheet, and the size and density of the formed domains tend to increase. On the other hand, when the temperature x is below a certain level, the formation of oligomers such as dimers and trimers preferentially progresses due to self-polymerization of the cross-linking agent (B), and aggregation is suppressed. The main heating under conditions satisfying the above formula (1) or (2) is suitable for suppressing aggregation of the cross-linking agent (B).

The lower limit of the temperature x is, for example, 80° C. or higher, and may be 85° C. or higher, or even 90° C. or higher. The upper limit of the temperature x is, for example, 165° C. or lower, and may be 160° C. or lower. The upper limit of the temperature x under the condition satisfying formula (1) may be 115° C. or less, 110° C. or less, 105° C. or less, 100° C. or less, 95° C. or less, or even 90° C. or less. The main heating temperature x may be maintained constant throughout the main heating or may be varied during the main heating.

The lower limit of the time y is, for example, 10 seconds or more, and may be 20 seconds or more, 30 seconds or more, 35 seconds or more, 40 seconds or more, 40 seconds or more, 45 seconds or more, or even 50 seconds or more. The upper limit of time y is, for example, 300 seconds or less, and may be 180 seconds or less, or even less than 180 seconds. The upper limit of the time y under the conditions satisfying formula (2) is 100 seconds or less, 95 seconds or less, 90 seconds or less, 85 seconds or less, 80 seconds or less, 75 seconds or less, 70 seconds or less, 65 seconds or less, and It may be 60 seconds or less.

The main heating conditions may satisfy the formula: y≦−2.17x+345.83 when x>120. Heating that satisfies the above formula has a more limited time y than heating that satisfies formula (2).

The conditions for the main heating may satisfy y≦80 and further y≦60 when x>120.

The main heating conditions may satisfy y < 180 when x ≤ 120, y ≤ 160, y ≤ 140, y ≤ 120, y ≤ 110, y ≤ 100, y < 100, y ≤ 95, and may satisfy y≦90.

In the production method of the present embodiment, before the main heating is performed on the coating film of the pressure-sensitive adhesive composition (I), the coating film is prepared under the heating conditions of temperature p (° C.) and time q (seconds). Preliminary heating may also be included. The preheating temperature p is lower than the main heating temperature x. Preheating mainly proceeds with drying of the coating film and removal of the solvent in the case of the solvent-based adhesive composition (I). Removal of the solvent can contribute to suppression of aggregation of the isocyanate-based cross-linking agent (B). In addition, the preheating suppresses the melting of the isocyanate-based cross-linking agent (B) and promotes the reaction with a compound having a hydroxy group, typically water, to some extent to generate an oligomer of the cross-linking agent (B). can contribute to

The main heating temperature x (° C.) and the preheating temperature p (° C.) may satisfy the formula: x−p≦55. xp is 50° C. or less, 45° C. or less, 40° C. or less, 35° C. or less, 30° C. or less, less than 30° C., 25° C. or less, 20° C. or less, 15° C. or less, or even 10° C. or less. good. The lower limit of xp is above 0°C, and may be 5°C or higher, or even 10°C or higher. A small difference between the temperature x and the temperature p can contribute to suppressing shrinkage of the coating film caused by rapid temperature changes.

The temperature p is, for example, 50°C or higher and lower than 80°C. The lower limit of the temperature p may be 55° C. or higher, 60° C. or higher, 65° C. or higher, or even 70° C. or higher. The upper limit of the temperature p may be 75° C. or lower. The preheating temperature p may be kept constant throughout the preheating or may be varied during the preheating.

The time q is, for example, 5 seconds or more, and may be 10 seconds or more, 15 seconds or more, 20 seconds or more, 25 seconds or more, 30 seconds or more, 35 seconds or more, 40 seconds or more, or even 45 seconds or more. The upper limit of the time q is, for example, 180 seconds or less, and may be 120 seconds or less, 115 seconds or less, or even 110 seconds or less.

When the pressure-sensitive adhesive composition (I) is a solvent type, the time q is 30% or less, preferably 25% or less, more preferably 25% or less, based on the content of the solvent contained in the coating film before preheating. The content may be set to 20% or less.

Even if the time q is represented by q/(q+y), which is the ratio of the preheating time to the total time of preheating and main heating, and satisfies 0.2 ≤ q/(q+y) ≤ 0.6 good. The lower limit of q/(q+y) may be 0.25 or more, or even 0.3 or more. The upper limit of q/(q+y) may be 0.55 or less, 0.5 or less, 0.45 or less, or even 0.4 or less.

Preheating may be performed after a predetermined time r has elapsed from the formation of the coating film. Securing the time r between the formation of the coating film and the start of preheating can contribute to efficient removal of the solvent contained in the coating film. The time r is, for example, 5 to 180 seconds, may be 5 to 120 seconds, or 10 to 60 seconds. During the time r, the coating film is in an unheated atmosphere, for example, in an atmosphere of 20 to 30.degree.

Preheating and main heating may be performed continuously. As a more specific example, one heating device is divided into a preheating section and a main heating section, and the temperatures x and p of each section are set independently, and the preheating section to the main heating section are set. The coating film may be continuously transported to.

The coating film to be subjected to heating can be formed, for example, by applying the pressure-sensitive adhesive composition (I) or a mixture of the pressure-sensitive adhesive composition (I) and a solvent to a substrate film. The base film is typically a resin film or metal film. The base film may be a film (release film) whose coating surface has been subjected to release treatment. In one example of the release film, the coated surface is subjected to release treatment with a silicone compound. Moreover, the base film may be an optical film, and in this case, an optical laminate including the pressure-sensitive adhesive sheet and the optical film can be formed.

A known method can be employed for application to the substrate film. Coating is, for example, roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, extrusion coating using a die coater, or the like. can be implemented by

Compositions and mixtures applied to the base film preferably have a viscosity suitable for handling and application.

[Adhesive composition (I)]
The pressure-sensitive adhesive composition (I) of the present embodiment contains a (meth)acrylic polymer (A) and a cross-linking agent (B). The (meth)acrylic polymer (A) is contained in the pressure-sensitive adhesive composition (I) as a main component. In other words, the pressure-sensitive adhesive composition (I) is an acrylic pressure-sensitive adhesive composition. A main component means the component with the largest content rate also in a composition. The content of the main component is, for example, 50% by weight or more, and may be 60% by weight or more, 70% by weight or more, 73% by weight or more, or even 75% by weight or more.

((Meth) acrylic polymer (A))
The (meth)acrylic polymer (A) preferably has, as a main unit, a structural unit derived from the (meth)acrylic monomer (A1) having an alkyl group having 1 to 30 carbon atoms in the side chain. The alkyl group may be linear or branched. The (meth)acrylic polymer (A) may have one or more structural units derived from the (meth)acrylic monomer (A1). Examples of (meth) acrylic monomers (A1) include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate. , isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate ( Lauryl (meth)acrylate), n-tridecyl (meth)acrylate and n-tetradecyl (meth)acrylate. As used herein, the term "main unit" refers to the total structural units of the polymer, for example 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, and still more preferably 80% by weight or more. means unit.

The (meth)acrylic polymer (A) may have structural units derived from the (meth)acrylic monomer (A1) having a long-chain alkyl group in the side chain. An example of said monomer (A1) is n-dodecyl (meth)acrylate (lauryl (meth)acrylate). As used herein, the term "long-chain alkyl group" means an alkyl group having 6 to 30 carbon atoms.

The (meth)acrylic polymer (A) is a structural unit derived from the (meth)acrylic monomer (A1) having a glass transition temperature (Tg) in the range of −70 to −20° C. when homopolymerized. may have An example of said monomer (A1) is n-butyl acrylate.

The (meth)acrylic polymer (A) may have structural units other than the structural unit derived from the (meth)acrylic monomer (A1). The structural unit is derived from the monomer (A2) copolymerizable with the (meth)acrylic monomer (A1). The (meth)acrylic polymer (A) may have one or more of these structural units.

Examples of monomers (A2) are aromatic ring-containing monomers. The aromatic ring-containing monomer may be an aromatic ring-containing (meth)acrylic monomer. Examples of aromatic ring-containing monomers include phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, ethylene oxide-modified nonylphenol (meth) acrylate, hydroxyethylated β- naphthol (meth)acrylate and biphenyl (meth)acrylate. The content of structural units derived from aromatic ring-containing monomers in the (meth)acrylic polymer (A) is, for example, 0 to 50% by weight, 1 to 30% by weight, 5 to 25% by weight, 8 to 20% by weight. % by weight, 10-18% by weight, 11-17% by weight, or even 12-16% by weight. Having a structural unit derived from an aromatic ring-containing monomer in the (meth)acrylic polymer (A) is a phase between the (meth)acrylic polymer (A), the cross-linking agent (B), and its self-polymer. It can contribute to the improvement of solubility.

Another example of monomer (A2) is a hydroxyl-containing monomer. The hydroxyl group-containing monomer may be a hydroxyl group-containing (meth)acrylic monomer. Examples of hydroxyl-containing monomers are 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl ( hydroxyalkyl (meth)acrylates such as meth)acrylates, 10-hydroxydecyl (meth)acrylate and 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methylacrylate. In addition, the hydroxyl group can react with various cross-linking agents. From the viewpoint of improving the uniformity of the crosslinked structure to be formed, the content of structural units derived from hydroxyl group-containing monomers in the (meth)acrylic polymer (A) may be 1% by weight or less. It may be 5% by weight or less, further 0.1% by weight or less, or 0% by weight (without including the structural unit).

The monomer (A2) may be a carboxyl group-containing monomer, an amino group-containing monomer, or an amide group-containing monomer. Examples of carboxyl group-containing monomers are (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid and crotonic acid. Examples of amino group-containing monomers are N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate. Examples of amide group-containing monomers are (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropylacrylamide, N-methyl(meth)acrylamide, N- Butyl (meth)acrylamide, N-hexyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methylol-N-propane (meth)acrylamide, aminomethyl (meth)acrylamide, aminoethyl (meth)acrylamide, mercaptomethyl (Meth) acrylamide-based monomers such as mercaptoethyl (meth) acrylamide; and N-vinyl group-containing lactam monomers such as N-vinylpyrrolidone and N-vinyl-ε-caprolactam. When the (meth)acrylic polymer (A) has a structural unit derived from a carboxyl group-containing monomer, particularly acrylic acid, for example, the self-polymerization property of the isocyanate cross-linking agent (B) can be enhanced. Improvement of the self-polymerization of the cross-linking agent (B) can contribute to suppression of peeling of the pressure-sensitive adhesive sheet in a humidified environment, and stabilization of physical properties of the pressure-sensitive adhesive sheet in a system having a high content of the cross-linking agent (B). .

Monomer (A2) may be a polyfunctional monomer. Examples of multifunctional monomers are hexanediol di(meth)acrylate (1,6-hexanediol di(meth)acrylate), butanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (Poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri( polyfunctional acrylates such as meth)acrylates, tetramethylolmethane tri(meth)acrylates, allyl (meth)acrylates, vinyl (meth)acrylates, epoxy acrylates, polyester acrylates and urethane acrylates; and divinylbenzene. Polyfunctional acrylates are preferably 1,6-hexanediol diacrylate and dipentaerythritol hexa(meth)acrylate.

The total content of structural units derived from the carboxyl group-containing monomer, amino group-containing monomer, amide group-containing monomer and polyfunctional monomer in the (meth)acrylic polymer (A) is preferably is 20% by weight or less, more preferably 10% by weight or less, and still more preferably 8% by weight or less. When the (meth)acrylic polymer (A) has the structural unit, the total content is, for example, 0.01% by weight or more, and may be 0.05% by weight or more. The (meth)acrylic polymer (A) may not contain structural units derived from polyfunctional monomers.

Examples of other monomers (A2) include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, and 3-methoxy (meth)acrylate. Alkoxyalkyl (meth)acrylates such as propyl, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate and 4-ethoxybutyl (meth)acrylate; glycidyl (meth)acrylate and ( Epoxy group-containing monomers such as methyl glycidyl acrylate; sulfonic acid group-containing monomers such as sodium vinyl sulfonate; phosphoric acid group-containing monomers; cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate and (meth)acrylic acid esters having an alicyclic hydrocarbon group such as isobornyl (meth)acrylate; vinyl esters such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene and vinyltoluene; ethylene, propylene olefins, such as butadiene, isoprene and isobutylene, or dienes; vinyl ethers, such as vinyl alkyl ether; and vinyl chloride.

The total content of structural units derived from the other monomer (A2) in the (meth)acrylic polymer (A) is, for example, 30% by weight or less, and may be 10% by weight or less, or 0 % by weight (not including the structural unit).

The (meth)acrylic polymer (A) can be formed by polymerizing one or more of the above monomers by a known method. A monomer and a partial polymer of the monomer may be polymerized. Polymerization can be carried out, for example, by solution polymerization, emulsion polymerization, bulk polymerization, thermal polymerization, or active energy ray polymerization. Solution polymerization and active energy ray polymerization are preferred because they can form a pressure-sensitive adhesive sheet with excellent optical transparency. Polymerization is preferably carried out while avoiding contact of the monomer and/or partial polymer with oxygen. Polymerization in shutdown can be employed. The (meth)acrylic polymer (A) to be formed may be in any form such as a random copolymer, a block copolymer, or a graft copolymer.

The polymerization system forming the (meth)acrylic polymer (A) may contain one or more polymerization initiators. The type of polymerization initiator can be selected depending on the polymerization reaction, and may be, for example, a thermal polymerization initiator or a photopolymerization initiator.

Solvents used for solution polymerization include esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as methylcyclohexane; and ketones such as methyl ethyl ketone and methyl isobutyl ketone. However, the solvent is not limited to the above examples. The solvent may be a mixed solvent of two or more solvents.

Polymerization initiators used for solution polymerization are, for example, azo polymerization initiators, peroxide polymerization initiators, and redox polymerization initiators. Peroxide polymerization initiators are, for example, dibenzoyl peroxide and t-butyl permaleate. Among them, the azo polymerization initiator disclosed in JP-A-2002-69411 is preferable. The azo polymerization initiator, for example, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis (2-methylpropion acid) dimethyl, 4,4'-azobis-4-cyanovaleric acid. However, the polymerization initiator is not limited to the above examples. The amount of the azo polymerization initiator used is, for example, 0.05 to 0.5 parts by weight, and may be 0.1 to 0.3 parts by weight, per 100 parts by weight of the total amount of the monomers.

Active energy rays used for active energy ray polymerization include, for example, ionizing radiation such as α rays, β rays, γ rays, neutron beams and electron beams, and ultraviolet rays. The active energy rays are preferably ultraviolet rays. Polymerization by irradiation with ultraviolet rays is also called photopolymerization. A polymerization system for active energy ray polymerization typically contains a photopolymerization initiator. Polymerization conditions for active energy polymerization are not limited as long as the (meth)acrylic polymer (A) is formed.

Photopolymerization initiators include, for example, benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, and photoactive oxime-based photopolymerization initiators. , a benzoin-based photopolymerization initiator, a benzyl-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, a ketal-based photopolymerization initiator, and a thioxanthone-based photopolymerization initiator. However, the photopolymerization initiator is not limited to the above examples.

Benzoin ether-based photopolymerization initiators include, for example, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethan-1-one, anisolemethyl is ether. Acetophenone-based photopolymerization initiators include, for example, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenylketone, 4-phenoxydichloroacetophenone, 4-(t-butyl)dichloro Acetophenone. Examples of α-ketol photopolymerization initiators are 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. The aromatic sulfonyl chloride photopolymerization initiator is, for example, 2-naphthalenesulfonyl chloride. A photoactive oxime-based photopolymerization initiator is, for example, 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. A benzoin-based photopolymerization initiator is, for example, benzoin. A benzylic photopolymerization initiator is, for example, benzyl. Examples of benzophenone-based photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α-hydroxycyclohexylphenyl ketone. A ketal photopolymerization initiator is, for example, benzyl dimethyl ketal. Thioxanthone-based photopolymerization initiators are, for example, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone.

The amount of the photopolymerization initiator used is, for example, 0.01 to 1 part by weight, and may be 0.05 to 0.5 part by weight, per 100 parts by weight of the total amount of the monomers.

The weight average molecular weight (Mw) of the (meth)acrylic polymer (A) is, for example, 1,000,000 to 2,800,000, and from the viewpoint of the durability and heat resistance of the pressure-sensitive adhesive sheet, it is 1,200,000 or more, further 1,400,000 or more. may be The weight average molecular weight (Mw) of polymers and oligomers in this specification is a value (converted to polystyrene) based on GPC (gel permeation chromatography) measurement.

The content of the (meth)acrylic polymer (A) in the pressure-sensitive adhesive composition (I) is, for example, 50% by weight or more, 60% by weight or more, 70% by weight or more, and further 80% by weight in terms of solid content. or more. The upper limit of the content is, for example, 99% by weight or less, and may be 97% by weight or less, 95% by weight or less, 93% by weight or less, or even 90% by weight or less.

(Isocyanate-based cross-linking agent (B))
The isocyanate-based cross-linking agent (B) contains an isocyanate group as a cross-linking reactive group. Cross-linking agent (B) is typically a polyfunctional cross-linking agent having two or more cross-linking reactive groups per molecule. The cross-linking agent (B) may be a tri- or higher functional cross-linking agent having 3 or more cross-linking reactive groups per molecule. The upper limit of the number of cross-linking reactive groups per molecule is 5, for example.

The isocyanate-based cross-linking agent (B) may be an aromatic isocyanate compound, an alicyclic isocyanate compound, or an aliphatic isocyanate compound.

Examples of aromatic isocyanate compounds that can be used for the cross-linking agent (B) include phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2′-diphenylmethane diisocyanate, and 4,4′-diphenylmethane. diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate and 1,5-naphthalene diisocyanate, xylylene diisocyanate.

Examples of alicyclic isocyanate compounds that can be used as the cross-linking agent (B) include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xyloxy diisocyanate, hydrogenated tolylene diisocyanate and hydrogenated tetramethylxylylene diisocyanate.

Examples of aliphatic isocyanate compounds that can be used as the cross-linking agent (B) include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, and dodecamethylene diisocyanate. and 2,4,4-trimethylhexamethylene diisocyanate.

The cross-linking agent (B) may be a derivative of the above isocyanate compound. Examples of derivatives include multimers (dimers, trimers, pentamers, etc.), adducts (adducts) obtained by adding polyhydric alcohols such as trimethylolpropane, urea modified products, and biuret modified products. , allophanate-modified, isocyanurate-modified, carbodiimide-modified, and urethane prepolymers obtained by addition to polyether polyol, polyester polyol, acrylic polyol, polybutadiene polyol, polyisoprene polyol, and the like.

The cross-linking agent (B) is preferably an aromatic isocyanate compound or a derivative thereof, more preferably tolylene diisocyanate or a derivative thereof (in other words, a tolylene diisocyanate-based (TDI-based) cross-linking agent). TDI-based cross-linking agents are superior to xylylene diisocyanate and its derivatives (in other words, xylylene diisocyanate-based (XDI-based) cross-linking agents) in terms of reaction uniformity. An example of a TDI-based cross-linking agent is an adduct of tolylene diisocyanate and a polyfunctional alcohol, and a more specific example is a trimethylolpropane/tolylene diisocyanate trimer adduct.

Commercially available products can be used as the cross-linking agent (B). Examples of commercially available products include Millionate MT, Millionate MTL, Millionate MR-200, Millionate MR-400, Coronate L, Coronate HL and Coronate HX (manufactured by Tosoh; all trade names), Takenate D-102 and Takenate D. -103, Takenate D-110N, Takenate D-120N, Takenate D-140N, Takenate D-160N, Takenate D-165N, Takenate D-170HN, Takenate D-178N, Takenate 500 and Takenate 600 (manufactured by Mitsui Chemicals; Both are trade names). As the cross-linking agent (B), Coronate L, Takenate D-102 and Takenate D-103 (all of which are trimethylolpropane/tolylene diisocyanate trimer adducts) can be preferably used.

The amount of the cross-linking agent (B) in the pressure-sensitive adhesive composition (I) is, for example, 1.5 parts by weight or more, 2 parts by weight or more with respect to 100 parts by weight of the (meth) acrylic polymer (A), and may be 2.5 parts by weight or more. The upper limit of the blending amount is, for example, 25 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, 12 parts by weight or less, 10 parts by weight or less, 7 parts by weight or less, 5 parts by weight or less, and further 4 parts by weight or less. may be

The pressure-sensitive adhesive composition (I) may contain one or more cross-linking agents (B).

((meth)acrylic oligomer)
The pressure-sensitive adhesive composition (I) may further contain a (meth)acrylic oligomer (D).

The (meth)acrylic oligomer (D) can have the same composition as the (meth)acrylic polymer (A) described above, except that the weight average molecular weight (Mw) is different. The weight average molecular weight (Mw) of the (meth)acrylic oligomer (D) is, for example, 1000 or more, and may be 2000 or more, 3000 or more, or even 4000 or more. The upper limit of the weight average molecular weight (Mw) of the (meth)acrylic oligomer is, for example, 30,000 or less, and may be 15,000 or less, 10,000 or less, or even 7,000 or less.

The (meth)acrylic oligomer (D) has, for example, one or more structural units derived from the following monomers: methyl (meth)acrylate, ethyl (meth)acrylate, propyl ( meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, Alkyl (meth)acrylates such as isodecyl (meth)acrylate, undecyl (meth)acrylate and dodecyl (meth)acrylate; (meth)acrylates such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate and dicyclopentanyl (meth)acrylate Esters of acrylic acid and alicyclic alcohols; aromatic ring-containing (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate; and (meth)acrylates obtained from terpene compound derivative alcohols.

The (meth)acrylic oligomer (D) preferably has structural units derived from a (meth)acrylic monomer having a relatively bulky structure. In this case, the adhesiveness of the adhesive sheet can be further enhanced. Examples of the acrylic monomer include alkyl (meth)acrylates having a branched alkyl group such as isobutyl (meth)acrylate and t-butyl (meth)acrylate; cyclohexyl (meth)acrylate and isobornyl (meth)acrylate. and esters of (meth)acrylic acid and alicyclic alcohols such as dicyclopentanyl (meth)acrylate; aromatic ring-containing (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate. The monomer preferably has a cyclic structure, more preferably two or more cyclic structures. In addition, when the (meth)acrylic oligomer (D) is polymerized and/or the pressure-sensitive adhesive sheet is formed when UV irradiation is performed, the progress of polymerization and/or formation is hardly inhibited. It preferably does not have an unsaturated bond, and for example, an alkyl (meth)acrylate having an alkyl group with a branched structure, or an ester of (meth)acrylic acid and an alicyclic alcohol can be used.

Specific examples of the (meth)acrylic oligomer (D) include a copolymer of butyl acrylate, methyl acrylate and acrylic acid, a copolymer of cyclohexyl methacrylate and isobutyl methacrylate, and a copolymer of cyclohexyl methacrylate and isobornyl methacrylate. Copolymers of cyclohexyl methacrylate and acryloylmorpholine, copolymers of cyclohexyl methacrylate and diethylacrylamide, copolymers of 1-adamantyl acrylate and methyl methacrylate, copolymers of dicyclopentanyl methacrylate and isobornyl methacrylate. Polymer, copolymer of methyl methacrylate and at least one selected from dicyclopentanyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, isobornyl acrylate and cyclopentanyl methacrylate, homopolymer of dicyclopentanyl acrylate , a homopolymer of 1-adamantyl methacrylate and a homopolymer of 1-adamantyl acrylate.

For the polymerization of the (meth)acrylic oligomer (D), the above-described polymerization method for the (meth)acrylic polymer (A) can be employed.

When the pressure-sensitive adhesive composition (I) contains the (meth)acrylic oligomer (D), the amount thereof is, for example, 70 parts by weight or less with respect to 100 parts by weight of the (meth)acrylic polymer (A), It may be 50 parts by weight or less, or even 40 parts by weight or less. The lower limit of the amount to be blended is, for example, 1 part by weight or more, 2 parts by weight or more, and may be 3 parts by weight or more with respect to 100 parts by weight of the (meth)acrylic polymer (A). The pressure-sensitive adhesive composition (I) may not contain the (meth)acrylic oligomer (D).

(Additive)
The pressure-sensitive adhesive composition (I) may contain other additives. Examples of additives include cross-linking agents other than the isocyanate-based cross-linking agent (B), silane coupling agents, colorants such as pigments and dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, Rework improver, softener, antioxidant, anti-aging agent, light stabilizer, UV absorber, polymerization inhibitor, antistatic agent (ionic compound such as alkali metal salt, ionic liquid, ionic solid, etc.), inorganic filler materials, organic fillers, powders such as metal powders, particles, and foil-like materials. The additive can be blended in an amount of, for example, 10 parts by weight or less, preferably 5 parts by weight or less, and more preferably 1 part by weight or less per 100 parts by weight of the (meth)acrylic polymer (A).

Examples of cross-linking agents other than isocyanate-based cross-linking agents (B) are peroxide-based cross-linking agents, epoxy-based cross-linking agents, imine-based cross-linking agents and polyfunctional metal chelates. When the pressure-sensitive adhesive composition (I) contains a cross-linking agent other than the isocyanate-based cross-linking agent (B), the total amount of the compounded amount is 0.1 to 0.1 to 100 parts by weight of the (meth)acrylic polymer (A). 5 parts by weight is preferred, and 0.1 to 3 parts by weight, 0.1 to 2 parts by weight and 0.1 to 1 part by weight, in that order, are more preferred. The pressure-sensitive adhesive composition (I) may not contain a cross-linking agent other than the isocyanate-based cross-linking agent (B), such as an epoxy-based cross-linking agent.

Examples of silane coupling agents are 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane and 2-(3,4-epoxycyclohexyl)ethyl Epoxy group-containing silane coupling agents such as trimethoxysilane; 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3 -dimethylbutylidene)propylamine and amino group-containing silane coupling agents such as N-phenyl-γ-aminopropyltrimethoxysilane; ) acrylic group-containing silane coupling agents; and isocyanate group-containing silane coupling agents such as 3-isocyanatopropyltriethoxysilane.

When the pressure-sensitive adhesive composition (I) contains a silane coupling agent, the amount is, for example, 5 parts by weight or less, 3 parts by weight or less, relative to 100 parts by weight of the (meth)acrylic polymer (A), It may be 1 part by weight or less, 0.5 parts by weight or less, 0.2 parts by weight or less, 0.1 parts by weight or less, or even 0.05 parts by weight or less. The adhesive composition (I) may not contain a silane coupling agent.

Types of the pressure-sensitive adhesive composition (I) are, for example, emulsion type and solvent type (solution type). The pressure-sensitive adhesive composition (I) may be solvent-based from the viewpoint of forming a pressure-sensitive adhesive sheet with superior durability. The solvent-based pressure-sensitive adhesive composition (I) may not contain a photocuring agent such as an ultraviolet curing agent.

[Adhesive sheet]
An example of the pressure-sensitive adhesive sheet obtained by the manufacturing method of this embodiment is shown in FIG. The pressure-sensitive adhesive sheet 1 in FIG. 1 is formed from the pressure-sensitive adhesive composition (I). The adhesive sheet 1 contains, for example, a crosslinked product of (meth)acrylic polymer (A). In the production method of this embodiment, a pressure-sensitive adhesive sheet having the following properties may be formed.

The thickness of the adhesive sheet 1 is, for example, 1 to 200 μm, and may be 5 to 150 μm, 10 to 100 μm, 10 to 75 μm, 10 to 50 μm, 10 to 40 μm, 10 to 30 μm, and further 10 to 20 μm. .

The storage elastic modulus G′ (25° C.) of the pressure-sensitive adhesive sheet 1 is, for example, 0.15 MPa or more, and may be 0.16 MPa or more, 0.17 MPa or more, or further 0.18 MPa or more. The upper limit of the storage modulus G′ (25° C.) is, for example, 5 MPa or less, 3.0 MPa or less, 2.5 MPa or less, 2.0 MPa or less, 1.5 MPa or less, 1.0 MPa or less, 0.8 MPa or less, 0 .6 MPa or less, 0.5 MPa or less, or even less than 0.5 MPa. The PSA sheet 1 having a storage elastic modulus G' within the above range is particularly suitable for suppressing dimensional changes of the optical film.

The storage elastic modulus (25° C.) of PSA Sheet 1 can be evaluated by the following method. First, a sample for measurement made of the material constituting the adhesive sheet 1 is prepared. The shape of the measurement sample is disc-shaped. The measurement sample has a bottom diameter of 8 mm and a thickness of 2 mm. A sample for measurement may be obtained by punching a disc-shaped laminate from a laminate in which a plurality of pressure-sensitive adhesive sheets 1 are laminated. Next, a dynamic viscoelasticity measurement is performed on the measurement sample. For dynamic viscoelasticity measurement, for example, ARES-G2 manufactured by TA Instruments can be used. From the results of the dynamic viscoelasticity measurement, the storage elastic modulus G' of the pressure-sensitive adhesive sheet 1 at 25°C can be specified. The conditions for the dynamic viscoelasticity measurement are as follows.
・Measurement conditions Frequency: 1Hz
Deformation mode: Torsion Measurement temperature: -70°C to 150°C
Heating rate: 5°C/min

The gel fraction of the adhesive sheet 1 is, for example, 60% or more, 65% or more, and may be 70% or more. The upper limit of the gel fraction is, for example, 99% or less, and may be 98% or less, or even 95% or less. The adhesive sheet 1 having a gel fraction within the above range is particularly suitable for suppressing dimensional changes of the optical film.

The gel fraction of the adhesive sheet 1 can be evaluated by the following method. First, about 0.2 g is scraped from Adhesive Sheet 1 to obtain a small piece. Next, the obtained small piece is wrapped with an expanded porous membrane of polytetrafluoroethylene (NTF1122 manufactured by Nitto Denko, average pore size 0.2 μm) and tied with a kite string to obtain a test piece. Next, the weight A of the obtained test piece is measured. Weight A is the sum of the weights of the adhesive sheet piece, the stretched porous membrane and the kite string. The total weight B of the stretched porous membrane and the kite string used is measured in advance. Next, the test piece is immersed in a container with an internal volume of 50 mL filled with ethyl acetate and allowed to stand at 23° C. for one week. After standing still, the test piece is taken out from the container, dried for 2 hours in a dryer set at 130° C., and then the weight C of the test piece is measured. From the measured weight A, weight B and weight C, the gel fraction of the pressure-sensitive adhesive sheet 1 is calculated by the formula: gel fraction (% by weight) = (C - B) / (A - B) x 100 (%). .

The haze of the adhesive sheet 1 is, for example, 1% or less when the thickness is 75 μm, and is 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, or 0.5% or less. , less than 0.5%, less than 0.45%, less than 0.43%, less than 0.4%, or even less than 0.37%. The lower limit of haze is, for example, 0.1% or more, and may be 0.2% or more. However, the haze is a value measured by the following method. The degree of whitening of the pressure-sensitive adhesive sheet 1 can be evaluated by the haze. The haze of the pressure-sensitive adhesive sheet 1 can be measured according to Japanese Industrial Standards (former Japanese Industrial Standards; JIS) K7136:1981.

Ten 1.5 μm square evaluation regions were arbitrarily set on the cross-sectional image of the pressure-sensitive adhesive sheet 1, and an island-shaped region having a minor axis of 100 nm or more was defined as the first domain. The number of evaluation regions present may be 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, or even 0. As used herein, the term "domain" means an island-like region of a sea-island structure that the adhesive sheet 1 may have. Further, the minor axis of the domain can be defined as the length of the shortest imaginary line segment that passes through the center of gravity of the domain and has the perimeter of the domain at both ends on the cross-sectional image. can. It is preferable that the respective evaluation regions set in the cross-sectional images do not overlap each other. A cross-sectional image can be obtained, for example, with a transmission electron microscope (TEM). The magnification of the acquired cross-sectional image is, for example, 10,000 to 30,000 times. The pressure-sensitive adhesive sheet 1 in which the domains are in the above-described state is particularly suitable for suppressing changes in the dimensions of the optical film while ensuring transparency.

When 10 evaluation areas of 1.5 μm square are arbitrarily set on the cross-sectional image of the pressure-sensitive adhesive sheet 1, for all the first domains observed in the 10 evaluation areas, adjacent first domains may be 300 nm or more, 500 nm or more, or even 800 nm or more. A large shortest distance means that the density of the domains in the pressure-sensitive adhesive sheet 1 is low. The distance between domains adjacent to each other can be defined as the distance between outer peripheries.

Ten 1.5 μm-square evaluation regions were arbitrarily set on the cross-sectional image of the pressure-sensitive adhesive sheet 1, and an island-shaped region having a minor axis of 50 nm or more and less than 100 nm was defined as a second domain. The number of evaluation areas with 10 or less domains may be 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, or even 10. According to studies by the present inventors, the second domain can affect the durability and transparency of the pressure-sensitive adhesive sheet 1, though not to the extent that the first domain does.

Ten 1.5 μm square evaluation regions are arbitrarily set on the cross-sectional image of the pressure-sensitive adhesive sheet 1, and when an island-shaped region having a minor axis of 50 nm or more and less than 100 nm is defined as a second domain, the ten evaluation regions are evaluated. For all the second domains observed in the evaluation area of , the shortest distance between adjacent second domains may be 150 nm or more, 175 nm or more, or even 200 nm or more.

Ten 1.5 μm square evaluation regions are arbitrarily set on the cross-sectional image of the pressure-sensitive adhesive sheet 1, and when an island-shaped region having a minor axis of 50 nm or more and less than 100 nm is defined as a second domain, the ten evaluation regions are evaluated. Of all the second domains observed in the evaluation area, the ratio (number ratio) of the second domains having the shortest distance between adjacent second domains of 100 nm or more is 50% or more. 60% or more, or even 70% or more.

The state of domains in the adhesive sheet 1 can be evaluated, for example, by image analysis of a cross-sectional image. Various software such as ImageJ can be used for image analysis.

The state of the domains in the adhesive sheet 1 changes based on the manufacturing conditions of the adhesive sheet 1 (including the heating conditions described above). In addition, the state of the domain includes the composition of the pressure-sensitive adhesive composition (I), the composition and properties (e.g., glass transition temperature) of the (meth)acrylic polymer (A), the type and amount of the cross-linking agent (B), and the addition of It may vary based on the type and amount of the agent.

The first domain and/or the second domain may contain a polymer of the isocyanate cross-linking agent (B). Examples of polymers are self-polymers of the crosslinker (B).

The adhesive sheet 1 can be used for optical applications, for example. The pressure-sensitive adhesive sheet 1 may be used for optical laminates and/or image display devices. The pressure-sensitive adhesive sheet 1 is suitable for use in image display devices, such as an image display device with a narrow frame and an image display device with a relatively large screen size, for which suppression of dimensional change in the optical film is particularly required. . By using these in image display devices, for example, peeling of the film included in the optical layered body is suppressed.

[Method for producing optical laminate and optical laminate]
The method for manufacturing an optical layered body of the present embodiment is a method for manufacturing an optical layered body including an adhesive sheet and an optical film, and includes forming an adhesive sheet by the method for manufacturing an adhesive sheet described above. The optical laminate can be produced, for example, by forming a pressure-sensitive adhesive sheet on a substrate film, which is an optical film, by the production method described above. A pressure-sensitive adhesive sheet may be formed on a transfer sheet such as a release sheet by the above manufacturing method, and the formed pressure-sensitive adhesive sheet may be transferred onto an optical film.

FIG. 2 shows an example of the optical layered body obtained by the manufacturing method of this embodiment. The optical layered body 10A of FIG. 2 includes an adhesive sheet 1 and an optical film 2. As shown in FIG. The adhesive sheet 1 and the optical film 2 are laminated together. 10 A of optical laminated bodies can be used as an optical film with an adhesive sheet.

Examples of the optical film 2 are polarizing plates, retardation films, and laminated films containing polarizing plates and/or retardation films. However, the optical film 2 is not limited to the above examples. The optical film 2 may contain a film made of glass.

A polarizing plate includes a polarizer. A polarizer protective film may be bonded to at least one surface of the polarizer. Any pressure-sensitive adhesive or adhesive can be used for joining the polarizer and the polarizer protective film. The adhesive sheet 1 may be used for bonding. A polarizer is typically a polyvinyl alcohol (PVA) film in which iodine is oriented by stretching such as stretching in air (dry stretching) or stretching in boric acid solution.

A retardation film is a film having birefringence in the in-plane direction and/or the thickness direction. A retardation film is, for example, a stretched resin film or a film in which a liquid crystal material is oriented and fixed.

The retardation film includes a λ / 4 plate, a λ / 2 plate, an antireflection retardation film (see, for example, paragraphs 0221, 0222, 0228 of JP-A-2012-133303), a viewing angle compensation retardation film (for example, JP-A-2012-133303, paragraphs 0225 and 0226), obliquely oriented retardation film for viewing angle compensation (eg, JP-A-2012-13303, paragraph 0227). The retardation film is not limited to the above examples as long as it has birefringence in the in-plane direction and/or the thickness direction. The retardation value of the retardation film, the arrangement angle, the three-dimensional birefringence, whether it is a single layer or a multilayer, and the like are not limited. A known film can be used as the retardation film.

The thickness of the optical film 2 is, for example, 1-200 μm. The thickness of the optical film 2, which is a polarizing plate, is, for example, 1 to 150 μm, and may be 100 μm or less, 75 μm or less, 50 μm or less, 20 μm or less, or even 15 μm or less. The lower limit of the thickness may be 10 μm or more, 20 μm or more, 50 μm or more, 75 μm or more, or even 100 μm or more.

The optical film 2 may be a single layer or a laminated film composed of two or more layers. When the optical film 2 is a laminated film, the adhesive sheet 1 may be used for joining the layers.

Another example of the optical laminate obtained by the manufacturing method of this embodiment is shown in FIG. The optical layered body 10B of FIG. 3 has a layered structure in which a separator 3, an adhesive sheet 1 and an optical film 2 are layered in this order. By peeling off the separator 3, the optical laminate 10B can be used as an optical film with an adhesive sheet.

Separator 3 is typically a resin film. Examples of the resin forming the separator 3 are polyester such as polyethylene terephthalate (PET), polyolefin such as polyethylene and polypropylene, polycarbonate, acrylic, polystyrene, polyamide, and polyimide. A peeling treatment may be performed on the surface of the separator 3 that is in contact with the adhesive sheet 1 . The release treatment is, for example, treatment with a silicone compound. However, the separator 3 is not limited to the above example. The separator 3 is peeled off when the optical layered body 10B is used, for example, when attached to the image forming layer.

Another example of the optical laminate obtained by the manufacturing method of this embodiment is shown in FIG. The optical layered body 10C of FIG. 4 has a laminated structure in which a separator 3, an adhesive sheet 1, a retardation film 2A, an interlayer adhesive 4 and a polarizing plate 2B are laminated in this order. After peeling off the separator 3, the optical layered body 10C can be used by attaching it to, for example, an image forming layer.

A known adhesive can be used for the interlayer adhesive 4 . The adhesive sheet 1 may be used as the interlayer adhesive 4 .

Another example of the optical laminate obtained by the manufacturing method of this embodiment is shown in FIG. The optical layered body 10D of FIG. 5 has a laminated structure in which a separator 3, an adhesive sheet 1, a retardation film 2A, an interlayer adhesive 4, a polarizing plate 2B and a protective film 5 are laminated in this order. After peeling off the separator 3, the optical layered body 10D can be used by attaching it to, for example, an image forming layer.

The protective film 5 has a function of protecting the outermost optical film 2 (polarizing plate 2B) during distribution and storage of the optical layered body 10D and when the optical layered body 10D is incorporated in an image display device. Moreover, it may be the protective film 5 that functions as a window to an external space when incorporated in the image display device. Protective film 5 is typically a resin film. The resin constituting the protective film 5 is, for example, polyester such as PET, polyolefin such as polyethylene and polypropylene, acrylic, cycloolefin, polyimide, and polyamide, preferably polyester. However, the protective film 5 is not limited to the above examples. The protective film 5 may be a glass film or a laminated film containing a glass film. The protective film 5 may be subjected to surface treatments such as antiglare, antireflection, and antistatic.

The protective film 5 may be bonded to the optical film 2 with any adhesive. Bonding with the adhesive sheet 1 is also possible.

The optical layered body can have any configuration as long as it includes the pressure-sensitive adhesive sheet formed by the method for producing the pressure-sensitive adhesive sheet described above.

The optical layered body obtained by the production method of the present embodiment can be distributed and stored, for example, as a wound body obtained by winding a band-shaped optical layered body, or as a sheet-shaped optical layered body.

The optical layered body obtained by the production method of the present embodiment is typically used in an image display device. The image display device is, for example, an EL display such as a liquid crystal display, an organic EL display and an inorganic EL display.

[Manufacturing method of image display device and image display device]
A method for manufacturing an image display device of the present embodiment is a method for manufacturing an image display device having an optical laminate including an adhesive sheet and an optical film, and includes forming an adhesive sheet by the method for manufacturing an adhesive sheet described above. . The image display device can be manufactured using, for example, the pressure-sensitive adhesive sheet formed by the method for manufacturing the pressure-sensitive adhesive sheet and/or the optical layered body formed by the method for manufacturing the optical layered body.

An example of an image display device obtained by the manufacturing method of this embodiment is shown in FIG. The image display device 11 in FIG. 6 includes a substrate 7, an image forming layer (for example, an organic EL layer or a liquid crystal layer) 6, an adhesive sheet 1, a retardation film 2A, an interlayer adhesive 4, a polarizing plate 2B and a protective film 5 in this order. It has a laminated structure. The image display device 11 has the optical laminates 10A, 10B, 10C, and 10D shown in FIGS. 2 to 5 (excluding the separator 3). The substrate 7 and the image forming layer 6 may have the same configurations as those of the substrate and the image forming layer provided in a known image display device.

The image display device 11 in FIG. 6 may be an organic EL display or a liquid crystal display. However, the image display device 11 is not limited to this example. The image display device 11 may be an electroluminescence (EL) display, a plasma display (PD), a field emission display (FED: Field Emission Display), or the like. The image display device 11 may be used for home appliance use, vehicle use, public information display (PID) use, and the like.

The image display device may have any configuration as long as it includes the pressure-sensitive adhesive sheet formed by the method for manufacturing the pressure-sensitive adhesive sheet and/or the optical layered body formed by the method for manufacturing the optical layered body.

EXAMPLES The present invention will be described in more detail below with reference to examples. The invention is not limited to the examples shown below.

First, evaluation methods for the (meth)acrylic polymers and pressure-sensitive adhesive sheets produced in Examples and Comparative Examples are described.

[Weight average molecular weight (Mw)]
The weight average molecular weight (Mw) of the (meth)acrylic polymer was evaluated by GPC under the following conditions.
・ Analyzer: Acquity APC manufactured by Waters
・Column: G7000HXL+GMHXL+GMHXL manufactured by Tosoh
・Column temperature: 40°C
・Eluent: tetrahydrofuran (acid added)
・Flow rate: 0.8 mL/min ・Injection volume: 100 μL
・Detector: Differential refractometer (RI)
・ Standard sample: Polystyrene (PS) manufactured by Agilent

[Distance Ra]
The distance Ra was calculated by the method described above. HSPiP (version 5) was used as software.

[Storage elastic modulus G' (25°C)]
The storage elastic modulus G' (25°C) of the pressure-sensitive adhesive sheet was evaluated by the method described above. However, a sample for measurement was prepared by punching out a laminate obtained by stacking the produced pressure-sensitive adhesive sheets into a disc shape. ARES-G2 manufactured by TA Instruments was used for the dynamic viscoelasticity measurement of the measurement sample.

[Whitening]
The degree of whitening of the adhesive sheet was evaluated as follows based on the haze measurement of the adhesive sheet. It can be determined that the smaller the haze, the smaller the degree of whitening. The haze of the pressure-sensitive adhesive sheet was measured in an atmosphere of 25° C. using a haze meter HZ-V3 manufactured by Suga Test Instruments in accordance with JIS K7136:1981. Measurement is performed by attaching 5 layers (adhesive sheet thickness: 15 μm) or 3 layers (adhesive sheet thickness: 25 μm) to a slide glass S012140 (thickness 1.3 mm) manufactured by Matsunami Glass Industry. It was carried out in a combined state (total thickness of 75 μm in each case). For the pressure-sensitive adhesive sheet of Example 21 having a thickness of 35 μm, the measured value V in the state where two layers were laminated (total thickness of 70 μm) was converted to a value corresponding to a total thickness of 75 μm by the formula: V × 75/ 70 converted.
A: Measured haze is less than 0.37% B: Measured haze is 0.37% or more and less than 0.43% C: Measured haze is 0.43% or more and less than 0.50% D: Measured Haze is 0.50% or more

[Domain Status]
The state of the domains of the adhesive sheet was evaluated by the above evaluation method for the cross-sectional image of the adhesive sheet. The cross-sectional image was acquired by a TEM (HT7820 manufactured by Hitachi, Ltd.; acceleration voltage: 100 kV) at a magnification of 20,000. A sample to be subjected to TEM was prepared by subjecting the adhesive sheet to be evaluated to a heavy metal staining treatment with RuO ₄ , embedding it in resin, and then cutting it into a thickness of about 100 nm by an ultra-thin section method. Ten evaluation regions were set on the cross-sectional image so as not to overlap each other. Evaluation of condition was performed by image analysis on cross-sectional images, and ImageJ was used for image analysis. States 1-5 of the domains evaluated and the evaluation criteria for each state are as follows.

(State 1: number of evaluation regions in which the first domain exists)
A: the number of evaluation areas is 0
B: The number of evaluation areas is 1 to 2
C: The number of evaluation areas is 3 to 5
D: The number of evaluation areas is 6 or more

(State 2: Shortest distance between adjacent first domains for all first domains)
A: The shortest distance is 300 nm or more D: The shortest distance is less than 300 nm

(State 3: Shortest distance between adjacent second domains for all second domains)
A: The shortest distance is 200 nm or more C: The shortest distance is 150 nm or more and less than 200 nm D: The shortest distance is less than 150 nm

(State 4: the number of evaluation regions in which the number of second domains is 10 or less)
A: The number of evaluation areas is 3 or more D: The number of evaluation areas is 1 to 2

(State 5: Percentage of domains whose shortest distance between adjacent second domains is 100 nm or more among all second domains)
A: 50% or more D: less than 50%

[Humidification durability]
Humidification durability (corresponding to an accelerated durability test) of the PSA sheet was evaluated by the following method. First, a pressure-sensitive adhesive sheet-attached circularly polarizing plate having the pressure-sensitive adhesive sheets prepared in Examples and Comparative Examples on one exposed surface was formed. Next, a circularly polarizing plate was fixed to the surface of a glass plate (Eagle XG manufactured by Corning) via the adhesive sheet. Fixing of the circularly polarizing plate was performed in an atmosphere of 23° C. and 50% RH. Next, after treatment in an autoclave at 50 ° C. and 5 atmospheres (absolute pressure) for 15 minutes, it was left to stand until it cooled to 23 ° C., and after stabilizing the bonding of the circularly polarizing plate to the glass plate, it was heated at 60 ° C. and 95 ° C. It was left for 500 hours in a heated and humidified atmosphere of % RH. After standing, the atmosphere was returned to 23° C. and 50% RH, and the circularly polarizing plate was visually checked for peeling from the glass plate and bubbles between the glass plate and the circularly polarizing plate. Humidification durability was evaluated as follows.
A: No change in appearance such as foaming or peeling is observed.
B: Single peeling or foaming is slightly observed at the edge, but within a practically acceptable range.
C: Slight continuous peeling or foaming is observed at the edge, but within a practically acceptable range.
D: Significant peeling or foaming is observed at the edge, which is problematic in practice.

The method for forming the pressure-sensitive adhesive sheet-attached circularly polarizing plate used for evaluating the durability to humidification is described below.

<Preparation of polarizing plate P1>
(Production of polarizer)
A long polyvinyl alcohol (PVA) resin film (manufactured by Kuraray, product name “PE3000”, thickness 30 μm) is uniaxially stretched in the longitudinal direction using a roll stretching machine (total stretching ratio 5.9 times) at the same time. , swelling, dyeing, cross-linking, washing and drying were sequentially performed on the resin film to prepare a polarizer having a thickness of 12 μm. In the swelling treatment, the resin film was stretched 2.2 times while being treated with pure water at 20°C. In the dyeing treatment, the resin film was stretched 1.4 times while being treated with an aqueous solution containing iodine and potassium iodide at a weight ratio of 1:7 at 30°C. The iodine concentration in the aqueous solution was adjusted so that the single transmittance of the polarizer to be produced was 45.0%. A two-step process was employed for the cross-linking treatment. In the first-stage cross-linking treatment, the resin film was stretched 1.2 times while being treated with an aqueous solution of boric acid and potassium iodide at 40°C. The content of boric acid in the aqueous solution used for the first-stage cross-linking treatment was 5.0% by weight, and the content of potassium iodide was 3.0% by weight. In the second-stage cross-linking treatment, the resin film was stretched 1.6 times while being treated with an aqueous solution of boric acid and potassium iodide at 65°C. The content of boric acid in the aqueous solution used in the second-stage cross-linking treatment was 4.3% by weight, and the content of potassium iodide was 5.0% by weight. A potassium iodide aqueous solution at 20° C. was used for the cleaning treatment. The content of potassium iodide in the aqueous solution used for the cleaning treatment was 2.6% by weight. The drying treatment was performed under drying conditions of 70° C. and 5 minutes.

(Preparation of polarizing plate P1)
A triacetyl cellulose (TAC) film (manufactured by Konica Minolta, product name “KC2UA”, thickness 25 μm) was attached to each main surface of the polarizer prepared above with a polyvinyl alcohol-based adhesive. However, in the TAC film attached to one main surface, a hard coat (7 μm thick) was formed on the main surface opposite to the polarizer side. Thus, a polarizing plate P1 having a structure of protective layer with hard coat/polarizer/protective layer (no hard coat) was obtained.

<Preparation of retardation film R1>
(Preparation of first retardation film)
Isosorbide (ISB) 26.2 parts by weight, 9,9-[4-(2-hydroxyethoxy)phenyl]fluorene (BHEPF) 100.5 parts by weight, 1,4-cyclohexanedimethanol (1,4-CHDM) 10 .7 parts by weight, 105.1 parts by weight of diphenyl carbonate (DPC), and 0.591 parts by weight of cesium carbonate (0.2% by weight aqueous solution) as a catalyst were charged into a reaction vessel and dissolved under a nitrogen atmosphere ( about 15 minutes). At this time, the temperature of the heat medium in the reaction vessel was set at 150° C., and stirring was carried out as necessary. Next, the pressure inside the reaction vessel was reduced to 13.3 kPa, and the temperature of the heat medium was raised to 190° C. in 1 hour. Phenol generated as the temperature of the heat medium increased was discharged out of the reaction vessel (the same applies hereinafter). Next, after maintaining the temperature in the reaction vessel at 190° C. for 15 minutes, the pressure in the reaction vessel was changed to 6.67 kPa, and the temperature of the heat medium was raised to 230° C. in 15 minutes. When the stirring torque of the stirrer provided in the reaction vessel increased, the temperature of the heat medium was raised to 250° C. in 8 minutes, and the pressure in the reaction vessel was reduced to 0.200 kPa or less. After reaching a predetermined stirring torque, the reaction was terminated, and the produced reaction product was extruded into water and pelletized. Thus, a polycarbonate resin having a composition of BHEPF/ISB/1,4-CHDM=47.4 mol %/37.1 mol %/15.5 mol % was obtained. The obtained polycarbonate resin had a glass transition temperature of 136.6° C. and a reduced viscosity of 0.395 dL/g.

After vacuum drying the prepared polycarbonate resin pellets at 80 ° C. for 5 hours, a single screw extruder (manufactured by Isuzu Kakoki, screw diameter 25 mm, cylinder set temperature 220 ° C.), T die (width 200 mm, set temperature 220 ° C.), chill roll A long resin film having a thickness of 120 μm was obtained using a film forming apparatus equipped with a set temperature of 120 to 130° C. and a winder. Next, the obtained resin film was stretched in the width direction with a tenter stretching machine at a stretching temperature of 137 to 139° C. and a stretching ratio of 2.5 to obtain a first retardation film.

(Production of second retardation film)
20 parts by weight of a side chain type liquid crystal polymer (weight average molecular weight 5000) represented by the following chemical formula (I) (where 65 and 35 are mol% of each structural unit), a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF) , trade name “Paliocolor LC242”) 80 parts by weight, and a photopolymerization initiator (manufactured by Ciba Specialty Chemicals, trade name “Irgacure 907”) 5 parts by weight are dissolved in 200 parts by weight of cyclopentanone to form a liquid crystal coating liquid. prepared. Next, the surface of a norbornene-based resin film (manufactured by Nippon Zeon, trade name “Zeonex”), which is a base film, is coated with the prepared liquid crystal coating liquid using a bar coater, and then heated at 80 ° C. for 4 minutes. By drying, the liquid crystal contained in the coating film was oriented. Next, the coating film was cured by irradiation with ultraviolet rays to form a liquid crystal solidified layer (thickness: 0.58 μm) as a second retardation film on the substrate film. The in-plane retardation Re of the liquid crystal solidified layer for light with a wavelength of 550 nm is 0 nm, and the thickness direction retardation Rth is -71 nm (nx = 1.5326, ny = 1.5326, nz = 1.6550). The solidified layer exhibited refractive index properties of nz>nx=ny.

(Preparation of retardation film R1)
One surface of the first retardation film prepared above and the liquid crystal solidified layer of the second retardation film were pasted together via an adhesive to prepare a retardation film R1.

<Preparation of circularly polarizing plate with adhesive sheet>
(Production of interlayer adhesive)
79.9 parts by weight of butyl acrylate, 15 parts by weight of benzyl acrylate, 5 parts by weight of acrylic acid and 0.5 parts by weight of 4-hydroxybutyl acrylate were placed in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. A monomer mixture containing 1 part by weight was charged. Next, 0.1 part by weight of 2,2'-azoisobutyronitrile as a polymerization initiator was added to 100 parts by weight of the monomer mixture together with ethyl acetate, and nitrogen gas was introduced while gently stirring. After the inside of the flask was replaced with nitrogen, the polymerization reaction was allowed to proceed for 7 hours while maintaining the liquid temperature in the flask around 55°C. Next, ethyl acetate was added to the resulting reaction solution to adjust the solid content concentration to 30% by weight to obtain a solution of a (meth)acrylic polymer used as an interlaminar pressure-sensitive adhesive. The weight average molecular weight of the obtained polymer was 2,200,000.

Next, a trimethylolpropane/tolylene diisocyanate trimer adduct (manufactured by Tosoh, trade name "Coronate L") was added to the solution of the obtained (meth)acrylic polymer with respect to 100 parts by weight of the solid content of the solution. ) 0.5 parts by weight, 0.1 parts by weight of benzoyl peroxide which is a peroxide cross-linking agent, epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403) 0.2 parts by weight, And a polyether compound having a reactive silyl group (manufactured by Kaneka, Silyl SAT10) 0.5 parts by weight is mixed, and an adhesive composition used as an interlayer adhesive for bonding the polarizing plate P1 and the retardation film R1 The product PSA1 was obtained.

(Preparation of polarizing plate with interlayer pressure-sensitive adhesive layer)
The pressure-sensitive adhesive composition PSA1 prepared above is applied to the release surface of a polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., MRF38) having a thickness of 38 μm, which is a release film having a silicone-treated release surface. It was coated so that the thickness of the layer after drying was 12 μm, and dried at 155° C. for 1 minute to form an interlayer pressure-sensitive adhesive layer. Next, the formed interlayer pressure-sensitive adhesive layer was transferred to the protective layer (no hard coat) side of the polarizing plate P1 to obtain a polarizing plate with an interlayer pressure-sensitive adhesive layer.

(Preparation of circularly polarizing plate with adhesive sheet)
On the second retardation film side of the retardation film R1 (the norbornene-based resin film used as the base film when producing the second retardation film is peeled off), each pressure-sensitive adhesive sheet prepared in Examples and Comparative Examples was transferred from the release film and pasted. Next, the polarizing plate with an interlayer pressure-sensitive adhesive layer prepared above was attached to the first retardation film side of the retardation film R1 via the interlayer pressure-sensitive adhesive layer to obtain a circularly polarizing plate with an pressure-sensitive adhesive sheet. The attachment of the retardation film R1 and the polarizing plate with an interlayer pressure-sensitive adhesive layer is performed by adjusting the angle formed by the slow axis of the first retardation film and the absorption axis of the polarizer when viewed from the side of the first retardation film. was 45 degrees counterclockwise.

[Condensation marks (appearance)]
After the main heating, the surface of the release film and the coating film (adhesive sheet) was visually checked for traces of droplets, and dew condensation traces that could occur during the production of the adhesive sheet were evaluated as follows.
A: Traces of droplets are not seen.
B: Traces of droplets are slightly observed, but at a practically acceptable level.
C: Traces of droplets are observed, which is problematic in practice.

[Extent of residue]
The content of residual monomers and residual solvent contained in the adhesive sheet formed on the release sheet was determined, and the degree of residue was evaluated as follows. Incidentally, ppm is on a weight basis.
A: The content of residual monomers and the content of residual solvents are both less than the measurement limits B: The total content of residual monomers and residual solvents is above the measurement limits and 50 ppm or less C: The total content of residual monomers and residual solvents is more than 50 ppm and less than or equal to 100 ppm D: the total content of residual monomers and residual solvents is more than 100 ppm

(Method for measuring residual monomer)
About 0.1 g of the adhesive sheet was collected in a screw tube, 5 mL of acetone was added, and the mixture was shaken overnight. Thereafter, the content of the screw tube was filtered through a membrane filter (average pore size 0.45 μm), and 1 μL of the obtained filtrate was injected into gas chromatography (GC) to determine the content of residual monomers. GC measurement conditions are shown below.
GC device: Agilent Technologies, 6890N
Column: Agilent Technologies, HP-1 (0.250 mmφ × 30 m, df = 1.0 μm)
Column temperature: After holding at 40°C for 1 minute, the temperature was raised to 60°C (rate of 5°C/min), then to 140°C (rate of 10°C/min), and further to 300°C. (rate 20°C/min), held at 300°C for 10 minutes Column flow rate: 2 mL/min (He)
Column pressure: constant flow mode (136 kPa)
Inlet temperature: 200°C
Injection volume: 1 μL
Injection method: split (10:1)
Detector: Flame Ionization Detector (FID)
Detector temperature: 250°C

(Method for measuring residual solvent)
About 0.02 g of the adhesive sheet was collected and sealed in a headspace vial with a volume of 20 mL. Next, the vial containing the adhesive sheet is heated at 150 ° C. for 30 minutes with a head space sampler (HSS), 1 mL of the gas phase in the vial after heating is injected into the GC, and the content of the residual solvent is measured. asked. HSS conditions and GC measurement conditions are shown below.
· HSS conditions HSS device: Agilent Technologies, G1888
Heating temperature: 150°C
Heating time: 30 minutes Pressurization time: 0.20 minutes Loop fill time: 0.20 minutes Loop equilibration time: 0.05 minutes Injection time: 0.50 minutes Sample loop temperature: 160°C
Transfer line temperature: 200°C
・GC measurement conditions (residual solvent)
GC device: Agilent Technologies, 6890N
Column: Agilent Technologies, HP-1 (0.250 mmφ × 30 m, df = 1.0 μm)
Column temperature: maintained at 40°C for 3 minutes, then heated to 120°C (rate 10°C/min), then heated to 300°C (rate 20°C/min) and held at 300°C for 10 minutes Column Flow rate: 1 mL/min (He)
Column pressure: constant flow mode (81 kPa)
Inlet temperature: 250°C
Injection volume: 1 mL
Injection method: split (20:1)
Detector: FID
Detector temperature: 250°C

[Comprehensive evaluation]
A comprehensive evaluation of the durability and transparency of the pressure-sensitive adhesive sheets was carried out as follows.
A: The evaluation of humidification durability is A, and the evaluation of whitening is A to C.
B: The evaluation of humidification durability is B, and the evaluation of whitening is A to C.
C: The evaluation of humidification durability is C, and the evaluation of whitening is A to C.
D: At least one evaluation is D out of humidification durability and whitening.

Next, the method for producing each pressure-sensitive adhesive sheet of Examples and Comparative Examples will be described.

The correspondence between the abbreviations or names shown in the following description and the compounds is as follows.
BA: n-butyl acrylate BzA: benzyl acrylate AA: acrylic acid HBA: 4-hydroxybutyl acrylate AIBN: 2,2'-azobisisobutyronitrile C/L: trimethylolpropane/tolylene diisocyanate trimer addition Material (isocyanate-based cross-linking agent; manufactured by Tosoh, Coronate L)
TetradC: 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane (polyfunctional epoxy-based cross-linking agent; manufactured by Mitsubishi Gas Chemical Co., Ltd., Tetrad C)
KBM403: 3-glycidoxypropyltriethoxysilane (silane coupling agent; manufactured by Shin-Etsu Chemical Co., Ltd., KBM403)

[Preparation of (meth)acrylic polymer (A)]
(Synthesis example 1)
94.9 parts by weight of BA, 5.0 parts by weight of AA, and 0.1 part by weight of HBA were charged into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. Next, 0.1 part by weight of AIBN as a polymerization initiator was added to 100 parts by weight of a mixture of BA, AA and HBA, and nitrogen gas was introduced while gently stirring to replace the inside of the flask with nitrogen. The polymerization reaction was allowed to proceed for 7 hours while maintaining the temperature of the liquid in the vicinity of 55°C. Next, ethyl acetate was added to the resulting reaction solution to adjust the solid content concentration to 12% by weight to obtain a solution of (meth)acrylic polymer (A-1). The (meth)acrylic polymer (A-1) had a weight average molecular weight (Mw) of 2,200,000. Regarding HSP, δD, δP and δH of the (meth)acrylic polymer (A-1) were 16.75 MPa ^1/2 , 3.49 MPa ^1/2 and 5.38 MPa ^1/2 respectively.

(Synthesis example 2)
A (meth)acrylic polymer (meth)acrylic polymer ( A-2) solution was obtained. The (meth)acrylic polymer (A-2) had a weight average molecular weight (Mw) of 2,200,000. Regarding HSP, δD, δP and δH of the (meth)acrylic polymer (A-2) were 17.05 MPa ^1/2 , 3.49 MPa ^1/2 and 5.43 MPa ^1/2 respectively.

(Synthesis Example 3)
A (meth)acrylic polymer (meth)acrylic polymer ( A-3) solution was obtained. The (meth)acrylic polymer (A-3) had a weight average molecular weight (Mw) of 2,300,000. Regarding HSP, δD, δP and δH of the (meth)acrylic polymer (A-3) were 17.15 MPa ^1/2 , 3.49 MPa ^1/2 and 5.44 MPa ^1/2 respectively.

The weight-average molecular weight (Mw) and HSP distance Ra of the monomers and polymerization initiators used in Synthesis Examples 1 to 3 and the charged amounts thereof and the obtained polymers are summarized in Table 1 below. δD, δP and δH of the C/L self-polymer were 20.50 MPa ^1/2 , 12.40 MPa ^1/2 and 9.60 MPa ^1/2 respectively.

[Preparation of adhesive composition and adhesive sheet]
(Production Examples 1 to 8)
As shown in Table 2 below, 100 parts by weight of the solid content of the (meth)acrylic polymer (A) was mixed with a crosslinking agent and the like to obtain a solvent-type pressure-sensitive adhesive composition. Note that Tetrad-C did not form a self-polymer.

Next, the pressure-sensitive adhesive composition prepared in each production example was applied to the release surface of a 38 μm-thick PET film (manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., MRF38), which is a release film having a silicone-treated release surface. After coating to form a coating film and leaving it until preheating in an environment of 23 ° C. (leaving time r), preheating and preheating in an air circulation constant temperature oven while conveying the base film and the coating film. The main heating was continuously performed to form adhesive sheets of Examples 1 to 25 and Comparative Examples 1 to 5 having a predetermined thickness. Table 3 below shows the standing time r and the conditions of preheating and main heating. The temperatures for preheating and main heating are set temperatures for the preheating section and main heating section in the oven, respectively. The preheating time and main heating time are the times during which the base film and the coating film pass through the preheating section and the main heating section, respectively.

Table 4 below shows the evaluation results of the pressure-sensitive adhesive sheets produced. FIG. 7 shows the temperature and time of main heating and the results of comprehensive evaluation of the produced pressure-sensitive adhesive sheet. Domain states 1 to 5 in Table 4 are as follows.
State 1: Number of evaluation regions in which the first domain exists State 2: For every first domain, the shortest distance between neighboring first domains State 3: For every second domain, the neighboring Shortest distance between second domains State 4: Number of evaluation regions with 10 or less second domains State 5: Between adjacent second domains among all second domains Percentage of domains whose shortest distance is 100 nm or more

As shown in Table 4, the pressure-sensitive adhesive sheets of Examples were suitable for suppressing dimensional change and were excellent in transparency and durability as compared with the pressure-sensitive adhesive sheets of Comparative Examples.

According to the production method of the present invention, for example, an optical laminate and/or an optical pressure-sensitive adhesive sheet for use in an image display device can be formed.

REFERENCE SIGNS LIST 1 adhesive sheet 2 optical film 10A, 10B, 10C, 10D optical laminate 11 image display device

Claims (18)

Heating a coating film of a pressure-sensitive adhesive composition containing a (meth)acrylic polymer (A) as a main component and further containing an isocyanate cross-linking agent (B) to form a pressure-sensitive adhesive sheet from the coating film. including
Assuming the self-polymer (C) of the isocyanate-based cross-linking agent (B), the Hansen solubility parameter (HSP) between the (meth)acrylic polymer (A) and the self-polymer (C) the distance Ra is 15 or less,
The heating conditions satisfy the following formula (1) or (2),
A method for manufacturing an adhesive sheet.
x≦120 (1)
x>120 and y≦−2.17x+365.83 (2)
However, x and y are the temperature (° C.) and time (seconds) of the heating, respectively. 2. The method for producing a pressure-sensitive adhesive sheet according to claim 1, wherein the heating condition satisfies y<180 when x≦120. 2. The method for producing a pressure-sensitive adhesive sheet according to claim 1, wherein the heating condition satisfies y<100 when x≦120. The method for producing a pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the heating temperature x is 80°C or higher. Further comprising preheating the coating film under heating conditions of temperature p (° C.) and time q (seconds) prior to the heating of the coating film,
The method for producing a pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the preheating temperature p is lower than the heating temperature x. 6. The method for producing a pressure-sensitive adhesive sheet according to claim 5, wherein the heating temperature x and the preheating temperature p satisfy the formula: xp≦55. The method for producing a pressure-sensitive adhesive sheet according to claim 5 or 6, wherein the preheating temperature p is 50°C or higher and lower than 80°C. The method for producing a pressure-sensitive adhesive sheet according to any one of claims 5 to 7, wherein the preheating time q is 40 seconds or longer. The preheating time q is represented by q/(q+y), which is the ratio of the preheating time q to the total of the preheating time q and the heating time y, and 0.2 ≤ q/( q+y)≦0. 9. The method for producing a pressure-sensitive adhesive sheet according to any one of claims 5 to 8, which satisfies 6. The method for producing a pressure-sensitive adhesive sheet according to any one of claims 1 to 9, wherein the pressure-sensitive adhesive sheet has a storage elastic modulus G' (25°C) of 0.15 MPa or more. The method for producing a pressure-sensitive adhesive sheet according to any one of claims 1 to 10, wherein the pressure-sensitive adhesive sheet has a haze of 1% or less. Claims 1 to 11, wherein the amount of the isocyanate-based cross-linking agent (B) in the pressure-sensitive adhesive composition is 1.5 parts by weight or more with respect to 100 parts by weight of the (meth)acrylic polymer (A). A method for producing a pressure-sensitive adhesive sheet according to any one of the above. The method for producing a pressure-sensitive adhesive sheet according to any one of claims 1 to 12, wherein the isocyanate-based cross-linking agent (B) is tolylene diisocyanate-based. The method for producing a pressure-sensitive adhesive sheet according to any one of claims 1 to 13, wherein the (meth)acrylic polymer (A) contains structural units derived from aromatic ring-containing monomers. The production of the pressure-sensitive adhesive sheet according to any one of claims 1 to 14, wherein the (meth)acrylic polymer (A) contains 1% by weight or less of structural units derived from a hydroxyl group-containing monomer. Method. The method for producing a pressure-sensitive adhesive sheet according to any one of claims 1 to 15, wherein the pressure-sensitive adhesive composition is solvent-based. A method for producing an optical laminate including an adhesive sheet and an optical film,
The adhesive sheet is formed by the method for producing an adhesive sheet according to any one of claims 1 to 16,
A method for manufacturing an optical laminate. A method for manufacturing an image display device comprising an optical laminate including an adhesive sheet and an optical film,
The adhesive sheet is formed by the method for producing an adhesive sheet according to any one of claims 1 to 16,
A method for manufacturing an image display device.

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