KR20240070613A - Optical laminates, adhesive sheets and image display devices - Google Patents

Abstract

The present invention provides an optical laminate including an adhesive sheet having a sufficient gel fraction and improved durability. The optical laminate of the present invention includes an adhesive sheet with a gel fraction of 70% or more and an optical film. The maximum value of the frequency in the histogram created by the test method below is 1400 or more. Test method: Using an atomic force microscope, the elastic modulus is measured in a range of 500 nm in length x 500 nm in width on the surface of the adhesive sheet so that the number of measurement points is 65536, and the elastic modulus is measured with a class width of 0.1 MPa. Create a histogram.

Description

Optical laminates, adhesive sheets and image display devices

The present invention relates to optical laminates, adhesive sheets, and image display devices.

In recent years, image display devices typified by liquid crystal displays and electroluminescence (EL) display devices (for example, organic EL display devices and inorganic EL display devices) have become rapidly popular. These various image display devices usually have a laminated structure of an optical laminated body including an image forming layer such as a liquid crystal layer and an EL emitting layer, and an optical film and an adhesive sheet. The adhesive sheet is mainly used for bonding between films included in an optical laminate or for bonding an image forming layer and an optical laminate. Examples of optical films include a polarizing plate, a retardation film, and a polarizing plate including a retardation film in which the polarizing plate and the retardation film are integrated. Patent Document 1 discloses an example of an optical laminated body.

Japanese Patent Publication No. 2008-031214

Excessive changes in the dimensions of the optical film due to temperature changes cause light leakage and color unevenness in the image display device. Light leakage and color unevenness are particularly likely to occur in image display devices having a relatively large size and using a polarizing plate provided with a retardation film. In addition, image display devices with narrow frames (bezels) designed (reduced frame width) are becoming widespread, and suppressing dimensional changes is becoming increasingly important. In order to suppress dimensional changes, it is conceivable to increase the elastic modulus of the adhesive sheet included in the optical laminate. As one of the methods for increasing the elastic modulus of the adhesive sheet, it is considered to increase the gel fraction of the adhesive sheet. However, simply increasing the elastic modulus may reduce the durability of the adhesive sheet and make it unable to keep up with changes in dimensions.

Therefore, the purpose of the present invention is to provide an optical laminate including a pressure-sensitive adhesive sheet with a sufficient gel fraction and improved durability.

The present invention,

Comprising an adhesive sheet having a gel fraction of 70% or more and an optical film,

An optical laminate having a maximum frequency of 1400 or more in a histogram prepared by the following test method is provided.

Test method: Using an atomic force microscope, the elastic modulus is measured so that the number of measurement points is 65536 in a range of 500 nm in length x 500 nm in width on the surface of the adhesive sheet, and the above-described elasticity has a rank width of 0.1 MPa. Create a histogram of elastic modulus.

In addition, the present invention,

It is an adhesive sheet with a gel fraction of 70% or more,

An adhesive sheet is provided wherein the maximum frequency in a histogram prepared by the following test method is 1400 or more.

Test method: Using an atomic force microscope, the elastic modulus is measured so that the number of measurement points is 65536 in a range of 500 nm in length x 500 nm in width on the surface of the adhesive sheet, and the above-described elasticity has a rank width of 0.1 MPa. Create a histogram of elastic modulus.

In addition, the present invention,

An optical laminate comprising the above-mentioned adhesive sheet and an optical film is provided.

In addition, the present invention,

An image display device provided with the above optical laminate is provided.

Also, the present invention.

It is an adhesive sheet with a gel fraction of 70% or more,

An adhesive sheet is provided, wherein the coefficient of variation of elastic modulus measured by the following test method is less than 0.08.

Test method: Using an atomic force microscope, the elastic modulus is measured so that the number of measurement points is 65536 over a range of 500 nm in length x 500 nm in width on the surface of the adhesive sheet.

According to the present invention, an optical laminate including a pressure-sensitive adhesive sheet having a sufficient gel fraction and improved durability can be provided.

1 is a cross-sectional view schematically showing an example of the optical laminate of the present invention.
Figure 2 is a cross-sectional view schematically showing an example of the adhesive sheet of the present invention.
FIG. 3A is a diagram showing an example of an atomic force microscope image of the surface of an adhesive sheet.
FIG. 3B is a diagram showing an example of a histogram of elastic modulus measured with an atomic force microscope.
Figure 4 is a cross-sectional view schematically showing an example of the optical laminated body of the present invention.
Figure 5 is a cross-sectional view schematically showing an example of the optical laminate of the present invention.
Figure 6 is a cross-sectional view schematically showing an example of the optical laminate of the present invention.
Fig. 7 is a cross-sectional view schematically showing an example of the image display device of the present invention.

Although the present invention will be described in detail below, the present invention is not limited to the following embodiments and can be implemented with any modification without departing from the gist of the present invention.

(Embodiment of optical laminate)

An example of the optical laminated body of this embodiment is shown in FIG. 1. The optical laminate 10A in FIG. 1 includes an adhesive sheet 1 and an optical film 2. The adhesive sheet 1 and the optical film 2 are laminated on each other. The optical laminate 10A can be used as an optical film provided with an adhesive sheet.

(adhesive sheet)

The adhesive sheet 1 has a gel fraction of 70% or more. Additionally, the maximum frequency value F _max in the histogram created by the test method below is 1400 or more.

Test method: Using an atomic force microscope (AFM), the elastic modulus is measured so that the number of measurement points is 2 ¹⁶ (65536) over a range of 500 nm in length x 500 nm in width on the surface of the adhesive sheet 1. , create a histogram of elastic modulus with a class width of 0.1 MPa.

The gel fraction of the adhesive sheet 1 can be specified by the following method. First, as a measurement sample, an adhesive sheet 1 (e.g., FIG. 2) that has been produced for at least one week is prepared. This adhesive sheet 1 is, for example, stored in an environment of 23°C and 55%RH for one week or more after production. When the pressure-sensitive adhesive sheet 1 is formed of a pressure-sensitive adhesive composition containing a crosslinking agent, the reaction by the crosslinking agent has sufficiently progressed when more than one week has elapsed since production. In other words, the reaction with the cross-linking agent was completed. Completion of the reaction with the crosslinking agent can be confirmed by, for example, Fourier transform infrared spectroscopy (FT-IR). Next, a part of the adhesive sheet 1 is scraped off to obtain small pieces. Next, the obtained small pieces are surrounded by a stretched porous polytetrafluoroethylene film and tied into a twisted yarn. Thereby, a test piece is obtained. Next, the total weight of the small pieces, stretched porous membrane, and yarn of the adhesive sheet 1 (weight A) is measured. In addition, the total of the stretched porous membrane and yarn used is defined as weight B. Next, the test piece is immersed in a container filled with ethyl acetate and left to stand at 23°C for one week. After standing, the test piece is taken out from the container, dried in a dryer set at 130°C for 2 hours, and then the weight C of the test piece is measured. Based on the formula below, the gel fraction of the pressure-sensitive adhesive sheet 1 can be calculated from weight A, weight B, and weight C.

Gel fraction (% by weight) = (C-B)/(A-B) × 100

The gel fraction of the adhesive sheet 1 is 70% or more, preferably 80% or more, more preferably 90% or more, further preferably 94% or more, especially preferably 95% or more, and Depending on the condition, it may be 96% or more, 97% or more, 98% or more, or 100%. The adhesive sheet 1 with a gel fraction of 70% or more tends to have excellent processability and process stability, and is easy to suppress the occurrence of concavities, for example, during storage. This adhesive sheet 1 is also suitable for suppressing changes in the dimensions of the optical film.

The maximum value of the frequency, F _max , can be specified in detail by the following method. First, as a measurement sample, an adhesive sheet 1 (e.g., FIG. 2) that has been produced for at least one week is prepared. Next, the adhesive sheet 1 is cut into a rectangle to make a test piece. At this time, the thickness of the test piece is adjusted to about 100 nm. The surface of the obtained test piece can be regarded as the surface of the adhesive sheet 1. Next, the test piece is placed on a substrate such as a Si wafer. Using AFM, the elastic modulus is measured so that the number of measurement points is 65536 over a range of 500 nm in length x 500 nm in width on the surface of the test piece. At this time, the spacing between adjacent measurement points is adjusted to approximately 2 nm. The measurement of elastic modulus is performed, for example, over the entire range of 500 nm in length x 500 nm in width on the surface of the test piece. The elastic modulus of a test piece can be determined by vibrating the cantilever probe of the AFM on the surface of the test piece and measuring the repulsive force generated between the test piece and the probe. As AFM, for example, MFP-3D-SA manufactured by Oxford Instruments can be used. As a cantilever, for example, OMCL-AC240TS (spring constant 3 N/m) manufactured by Olympus can be used. Details of the measurement conditions for elastic modulus are as follows.

·Measuring conditions

Measurement mode: AM-FM viscoelastic mapping

Measurement range: 500㎚ vertical × 500㎚ horizontal

Scan rate: 3Hz

Set point: 0.8V

Target Amplitude: 2V

Measurement temperature: 25℃

By the above measurement, data on the elastic modulus can be obtained for a plurality of positions on the surface of the test piece. By mapping this data, an AFM image as shown in Fig. 3A can be obtained. In this AFM image, color visual information is provided to each pixel based on the elastic modulus value. The size of one pixel in an AFM image corresponds to the size of the cantilever probe. The number of pixels constituting the AFM image corresponds to the number of measurement points.

Next, a histogram of elastic modulus with a class width of 0.1 MPa is created (FIG. 3b). In this histogram, the horizontal axis represents the elastic modulus, and the vertical axis represents the frequency (number of measurement points). As shown in FIG. 3B, for example, one peak P exists in the histogram. Peak P is typically unimodal. The frequency corresponding to the peak of this peak P can be regarded as the maximum value F _max . Additionally, a histogram may have multiple peaks or multimodal peaks. However, in this case, the maximum frequency F _max tends to be less than 1400.

The maximum value F _max is preferably 1600 or more, more preferably 1800 or more, may be 2000 or more, may be 2200 or more, may be 2400 or more, and may be 2600 or more. The upper limit of the maximum value F _max is not particularly limited and is, for example, 3500.

The maximum value F _max can be used as an index of the variation in elastic modulus in the adhesive sheet 1. It can be said that the larger the maximum value F _max is, the more suppressed the variation in elastic modulus is in the adhesive sheet 1. According to examination by the present inventors, durability tends to be improved in the adhesive sheet 1 which has a sufficient gel fraction, a maximum value of F _max of 1400 or more, and fluctuations in elastic modulus are suppressed. Additionally, fluctuations in elastic modulus generally tend to occur significantly in adhesive sheets with a high gel fraction due to fluctuations in the concentration of materials (polymers, etc.) constituting the adhesive sheet.

In the above histogram, the elastic modulus G _max corresponding to the maximum value F _max corresponds to the mode value. The elastic modulus G _max is not particularly limited and is, for example, in the range of 10 to 100 MPa.

In addition, in the above histogram, the ratio R of the total frequency T of the frequency included in the range of ±2.0 MPa from the elastic modulus G _max (MPa) corresponding to the maximum value F _max to the total frequency is not particularly limited, For example, it is 70% or more, preferably 75% or more, more preferably 80% or more, even more preferably 85% or more, may be 90% or more, and may be 95% or more. The upper limit of the ratio R is not particularly limited and is, for example, 99%.

In the ratio R, the total frequency corresponds to the integral value of all peaks P, for example, and corresponds to the total number of measurement points by AFM. The total value T corresponds to the integrated value of the peak P in the range from G _max -2.0 MPa to G _max +2.0 MPa. Additionally, in a histogram, the integrated value of peak P means the area of peak P. Therefore, in this specification, the ratio R may be referred to as “area ratio.”

The half width of peak P is not particularly limited, and may be, for example, 4.0 MPa or less, 3.5 MPa or less, or 3.0 MPa or less. The lower limit of the half width of peak P is not particularly limited and is, for example, 1.0 MPa.

For peak P, the peak width at the position of frequency 5 is not particularly limited, and is, for example, 15 MPa or less, preferably 10 MPa or less, may be 9 MPa or less, and may be 8 MPa or less. The lower limit of the peak width is not particularly limited and is, for example, 5 MPa.

In this embodiment, it is preferable that the coefficient of variation of the elastic modulus measured by the test method below is less than 0.08. In addition, the elastic modulus can be measured in detail by the method described above for the maximum value of the frequency F _max .

Test method: Using an atomic force microscope (AFM), the elastic modulus is measured so that the number of measurement points is 65536 over a range of 500 nm in length x 500 nm in width on the surface of the adhesive sheet 1.

It can be said that the smaller the coefficient of variation of the elastic modulus is, the more suppressed the variation of the elastic modulus is in the adhesive sheet 1. The coefficient of variation of the elastic modulus is more preferably 0.078 or less, further preferably 0.075 or less, may be 0.073 or less, and may be 0.07 or less. The lower limit of the coefficient of variation of elastic modulus is not particularly limited. The coefficient of variation of the elastic modulus may be 0.02 or more, 0.035 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.065 or more, or 0.067 or more. Additionally, the coefficient of variation of elastic modulus means the ratio of the standard deviation to the average value of elastic modulus.

The storage modulus G' of the adhesive sheet 1 at 25°C is not particularly limited, and is, for example, 0.1 MPa or more, preferably 0.15 MPa or more, more preferably 0.2 MPa or more, and even more preferably is 0.5 MPa or more, particularly preferably 0.8 MPa or more, and may be 1.0 MPa or more. The upper limit of the storage elastic modulus G' of the adhesive sheet 1 at 25°C is not particularly limited and is, for example, 5 MPa. The adhesive sheet 1 with a storage modulus G' of 0.1 MPa or more, especially 0.15 MPa or more, is suitable for suppressing changes in the dimensions of the optical film. According to the adhesive sheet 1 having a storage elastic modulus G' of 0.1 MPa or more, especially 1.0 MPa or more, there is a tendency to sufficiently suppress changes in appearance when, for example, an optical laminate is bonded to an image forming layer or the like.

The storage elastic modulus G' of the adhesive sheet 1 at 25°C can be specified by the following method. First, prepare a sample for measurement made of the material constituting the adhesive sheet 1. The shape of the sample for measurement is disk-shaped. The sample for measurement has a bottom diameter of 8 mm and a thickness of 2 mm. The sample for measurement may be a laminate in which a plurality of adhesive sheets 1 are laminated and punched into a disk shape. Next, 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 modulus G' of the adhesive sheet 1 at 25°C can be specified. In addition, the conditions for dynamic viscoelasticity measurement are as follows.

·Measuring conditions

Frequency: 1Hz

Deformation Mode: Torsion

Measurement temperature: -70℃ to 150℃

Temperature increase rate: 5℃/min

The adhesive sheet 1 preferably has high transparency. The haze of the adhesive sheet 1 is, for example, 1.0% or less, preferably 0.8% or less, and more preferably 0.6% or less. The lower limit of the haze of the adhesive sheet 1 is not particularly limited and is, for example, 0.1%. In this specification, the haze of the adhesive sheet 1 is a value at a thickness of 25 μm, and can be measured based on Japanese Industrial Standards (formerly Japanese Industrial Standards; JIS) K7136:1981.

The adhesive force of the adhesive sheet 1 is, for example, 0.5 N/25 mm or more, preferably 2 N/25 mm or more, and more preferably 5 N/25 mm or more. The upper limit of the adhesive force of the adhesive sheet 1 is, for example, 10 N/25 mm from the viewpoint of reworkability. The adhesive force of the adhesive sheet 1 can be measured by the following method. First, the adhesive sheet 1 is cut to 25 mm in width x 150 mm in length to make a test piece. Next, the stainless steel test plate and the evaluation sheet are overlapped through the adhesive sheet 1, and a 2 kg roller is rotated once to press them together. The evaluation sheet has a size of 30 mm in width x 150 mm in length, and is not particularly limited as long as it does not peel off from the adhesive sheet 1 during the test. As an evaluation sheet, for example, an ITO film (125 Tetrite OES (manufactured by Oike Kogyo Co., Ltd.), etc.) can be used. Next, using a commercially available tensile tester, the peeling force was measured when the adhesive sheet 1 was peeled off from the stainless steel test plate at a peeling angle of 180° and a tensile speed of 300 mm/min while holding the evaluation sheet. The average value is specified as the adhesive force of the adhesive sheet 1. Additionally, the above test is conducted under an atmosphere of 23°C.

The press-fit hardness of the adhesive sheet 1 at 25°C is preferably adjusted to an appropriate range. The indentation hardness is determined by numerically processing the displacement-load hysteresis curve obtained by pressing a diamond Berkovich type (triangular pyramid) probe perpendicularly to the surface of the adhesive sheet 1 using software (triboscan) in the measuring device unit. can do. In detail, the indentation hardness is measured by a single indentation method at 25°C using a nanoindenter (Triboindenter TI-950 manufactured by Hysitron Inc.) under the conditions of an indentation speed of 500 nm/sec and an indentation depth of 3000 nm.

The thickness of the adhesive sheet 1 is not particularly limited, and may be, for example, 1 to 200 μm, 5 to 150 μm, or further 10 to 100 μm.

The composition of the adhesive sheet 1 is not particularly limited as long as the gel fraction and maximum value F _max are within the above-mentioned ranges, but it preferably contains two or more types of polymers. As an example, the pressure-sensitive adhesive sheet 1 is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic polymer (A) and a crosslinking agent (B). Examples of the crosslinking agent (B) include isocyanate-based crosslinking agents and polyfunctional (meth)acrylate-based crosslinking agents. The pressure-sensitive adhesive sheet (1) formed from this pressure-sensitive adhesive composition may contain a crosslinked product of a (meth)acrylic polymer (A) and a polymer (C) containing as a main component a structural unit derived from a crosslinking agent (B). In this specification, “main component” means the structural unit contained in the largest amount by weight among all structural units constituting the polymer. In the polymer (C), the content of the structural unit derived from the crosslinking agent (B) is, for example, 70% by weight or more, and preferably 90% by weight or more. Polymer (C), for example, consists substantially only of structural units derived from the crosslinking agent (B). In the adhesive sheet 1, the cross-linked product of the (meth)acrylic polymer (A) and the polymer (C) may form an interpenetrating network (IPN) structure or a semi-interpenetrating network (semi-IPN) structure. This IPN structure (or semi-IPN structure) is suitable for increasing the elastic modulus of the adhesive sheet 1 and improving durability.

[(meth)acrylic polymer (A)]

The (meth)acrylic polymer (A) can function as a base polymer for an acrylic adhesive. Acrylic adhesives have excellent optical transparency, have adhesive properties such as appropriate wettability, cohesiveness, and adhesiveness, and tend to have excellent weather resistance, heat resistance, etc. The (meth)acrylic polymer (A) contains, for example, a structural unit derived from alkyl (meth)acrylate as a main component. In this specification, “(meth)acrylate” means acrylate and/or methacrylate.

The number of carbon atoms of the alkyl group contained in the alkyl (meth)acrylate for forming the main skeleton of the (meth)acrylic polymer (A) is not particularly limited and is, for example, 1 to 30. This alkyl group may be linear, branched, or cyclic. Examples of alkyl groups include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, amyl group, hexyl group, cyclohexyl group, heptyl group, 2-ethylhexyl group, isooctyl group, nonyl group, and de. Examples include syl group, isodecyl group, dodecyl group, isomyristyl group, lauryl group, tridecyl group, pentadecyl group, hexadecyl group, heptadecyl group, and octadecyl group. Alkyl (meth)acrylates can be used individually or in combination. It is preferable that the average carbon number of the alkyl group is 3 to 9. Alkyl (meth)acrylate is preferably butylacrylate.

In the (meth)acrylic polymer (A), the content of the structural unit derived from alkyl (meth)acrylate is preferably, for example, 50% by weight or more from the viewpoint of improving the adhesiveness of the adhesive sheet 1. is 60% by weight or more, more preferably 70% by weight or more, and even more preferably 80% by weight or more.

As the monomer constituting the (meth)acrylic polymer (A), in addition to alkyl (meth)acrylate, at least one copolymerization monomer selected from the group consisting of aromatic ring-containing monomers, amide group-containing monomers, carboxyl group-containing monomers, and hydroxyl group-containing monomers. can be mentioned. Copolymerization monomers can be used individually or in combination.

The (meth)acrylic polymer (A) preferably contains structural units derived from aromatic ring-containing monomers. An aromatic ring-containing monomer is a compound that contains an aromatic ring structure in its structure and also contains a polymerizable unsaturated double bond such as a (meth)acryloyl group or vinyl group. Examples of aromatic rings include benzene rings, naphthalene rings, and biphenyl rings. The aromatic ring-containing monomer is preferably aromatic ring-containing (meth)acrylate.

Examples of aromatic ring-containing (meth)acrylates include benzyl (meth)acrylate, phenyl (meth)acrylate, o-phenylphenol (meth)acrylate, phenoxy (meth)acrylate, and phenoxyethyl (meth)acrylate. ) Acrylate, phenoxypropyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, ethylene oxide modified nonylphenol (meth)acrylate, ethylene oxide modified cresol (meth)acrylate, phenol ethylene oxide modified (meth)acrylate ) Acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, methoxybenzyl (meth)acrylate, chlorobenzyl (meth)acrylate, cresyl (meth)acrylate, polystyryl (meth) Things having a benzene ring, such as acrylate; Hydroxyethylated β-naphthol acrylate, 2-naphthoethyl (meth)acrylate, 2-naphthoxyethyl acrylate, 2-(4-methoxy-1-naphthoxy)ethyl (meth)acrylate, etc. Having a naphthalene ring; Those having a biphenyl ring, such as biphenyl (meth)acrylate, can be mentioned. Among these, from the viewpoint of improving the adhesive properties and durability of the adhesive sheet 1, benzyl (meth)acrylate and phenoxyethyl (meth)acrylate are preferable, and benzyl acrylate is more preferable.

The (meth)acrylic polymer (A) may contain structural units derived from an amide group-containing monomer. An amide group-containing monomer is a compound that contains an amide group in its structure and also contains a polymerizable unsaturated double bond such as a (meth)acryloyl group or vinyl group. Examples of amide group-containing monomers include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropylacrylamide, and N-methyl(meth)acrylamide. ) Acrylamide, N-butyl (meth)acrylamide, N-hexyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methylol-N-propane (meth)acrylamide, aminomethyl (meth)acrylamide ) Acrylamide-based monomers such as acrylamide, aminoethyl (meth)acrylamide, mercaptomethyl (meth)acrylamide, and mercaptoethyl (meth)acrylamide; N-acryloyl heterocyclic monomers such as N-(meth)acryloylmorpholine, N-(meth)acryloylpiperidine, and N-(meth)acryloylpyrrolidine; and N-vinyl group-containing lactam monomers such as N-vinylpyrrolidone and N-vinyl-ε-caprolactam. Among these, from the viewpoint of improving the durability of the adhesive sheet 1, an N-vinyl group-containing lactam monomer is preferable.

The (meth)acrylic polymer (A) may contain a structural unit derived from a carboxyl group-containing monomer. A carboxyl group-containing monomer is a compound that contains a carboxyl group in its structure and also contains a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Examples of the carboxyl group-containing monomer include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Among these, acrylic acid is preferable from the viewpoint of copolymerization, cost, and improving the adhesive properties of the adhesive sheet 1. By having the (meth)acrylic polymer (A) having a structural unit derived from a carboxyl group-containing monomer, especially acrylic acid, for example, the self-polymerization of the crosslinking agent (B), especially the isocyanate-based crosslinking agent, can be increased. The improvement of the self-polymerization of the crosslinking agent (B) is particularly useful for suppressing peeling of the adhesive sheet (1) in a humidified environment and stabilizing the physical properties of the adhesive sheet (1) in systems with a high content of the crosslinking agent (B). You can contribute.

The (meth)acrylic polymer (A) may contain a structural unit derived from a hydroxyl group-containing monomer. A hydroxyl group-containing monomer is a compound that contains a hydroxyl group in its structure and also contains a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate. hydroxyl group-containing alkyl (meth)acrylates such as ester, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate; Hydroxyl group-containing cycloalkyl (meth)acrylates such as (4-hydroxymethylcyclohexyl)-methyl acrylate can be mentioned. Among these, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferable.

Among copolymerization monomers, from the viewpoint of adhesiveness, durability, etc., aromatic ring-containing monomers and carboxyl group-containing monomers are preferably used, and aromatic ring-containing monomers are especially preferably used. The (meth)acrylic polymer (A) containing a structural unit derived from a carboxyl group-containing monomer tends to promote the reaction between, for example, isocyanate-based crosslinking agents by introducing water molecules in the surrounding atmosphere. The aromatic ring-containing monomer tends to improve the compatibility of the (meth)acrylic polymer (A) and the polymer (C) and improve the durability of the optical laminate in a high temperature and high humidity environment.

In the (meth)acrylic polymer (A), the content of the structural unit derived from the copolymerization monomer is not particularly limited, and is, for example, 0 to 40% by weight, may be 0.1 to 30% by weight, or 0.1 to 20% by weight. % is also acceptable.

In the (meth)acrylic polymer (A), the content of the structural unit derived from the aromatic ring-containing monomer is not particularly limited, and is, for example, 3 to 25% by weight, more preferably 22% by weight or less, and 20% by weight or less. Weight% or less is more preferable. This content rate is more preferably 8% by weight or more, and even more preferably 12% by weight or more.

In the (meth)acrylic polymer (A), the content of the structural unit derived from the amide group-containing monomer is not particularly limited, and is, for example, 0.1 to 10% by weight, more preferably 0.2 to 8% by weight, 0.6 to 6% by weight is more preferable.

In the (meth)acrylic polymer (A), the content of the structural unit derived from the carboxyl group-containing monomer is not particularly limited, and is, for example, 0.1 to 25% by weight, and more preferably 3% by weight or more. From the viewpoint of suppressing the reaction with the isocyanate-based crosslinking agent, this content is preferably 20% by weight or less, and more preferably 10% by weight or less.

In addition, in the (meth)acrylic polymer (A), it is preferable that the content of structural units derived from copolymerized monomers having active hydrogen highly reactive with isocyanate-based crosslinking agents, for example, hydroxyl group-containing monomers, is low. In the (meth)acrylic polymer (A), the content of structural units derived from hydroxyl group-containing monomers is, for example, 1% by weight or less, more preferably 0.5% by weight or less, and even more preferably 0.2% by weight or less. The (meth)acrylic polymer (A) does not have to substantially contain structural units derived from hydroxyl group-containing monomers.

As the monomer component, in addition to the alkyl (meth)acrylate and the above copolymerized monomers, for the purpose of improving the adhesiveness and heat resistance of the adhesive sheet 1, an unsaturated double bond such as a (meth)acryloyl group or vinyl group is used. Other copolymerizable monomers having polymerizable functional groups can be used. Other copolymerization monomers can be used individually or in combination.

Examples of other copolymerization monomers include acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; Caprolactone adduct of acrylic acid; monomers containing sulfonic acid groups such as allylsulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, and sulfopropyl (meth)acrylate; Phosphate group-containing monomers such as 2-hydroxyethyl acryloyl phosphate; Alkylaminoalkyl (meth)acrylates such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; Alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, N-(meth)acryloyl-8-oxyoctamethylene succinimide, etc. succinimide monomer; Maleimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; N-methyl itaconimide, N-ethyl itaconimide, N-butyl itaconimide, N-octyl itaconimide, N-2-ethylhexyl itaconimide, N-cyclohexyl itaconimide Itaconimide monomers such as mead and N-lauryl itaconimide; Vinyl monomers such as vinyl acetate and vinyl propionate; Cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; Epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate; Glycol-based (meth)acrylates such as polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate; (meth)acrylate monomers such as tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, silicone (meth)acrylate, and 2-methoxyethyl acrylate; 3-Acryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8 -Vinyloctyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane, 10-acryloyloxydecyltrimethoxysilane, 10-methacryloyloxydecyltriethoxysilane, 10-acryloyloxydecyltriethoxysilane and silane-based monomers containing silicon atoms such as monooxydecyltriethoxysilane.

In addition, other copolymerization monomers include, for example, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and bisphenol A diglycidyl ether. Di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythate Examples include polyfunctional monomers having two or more unsaturated double bonds, such as ritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and caprolactone-modified dipentaerythritol hexa(meth)acrylate.

When using other copolymerization monomers as monomer components, the content of structural units derived from other copolymerization monomers in the (meth)acrylic polymer (A) is preferably 10% by weight or less, and more preferably 7% by weight or less. And, it is more preferable that it is 5% by weight or less.

The weight average molecular weight of the (meth)acrylic polymer (A) is usually 300,000 to 4 million. From the viewpoint of durability, the weight average molecular weight of the (meth)acrylic polymer (A) is preferably 300,000 to 3 million, and more preferably 400,000 to 2.2 million. A weight average molecular weight of 300,000 or more is preferable from the viewpoint of heat resistance. If the weight average molecular weight is 4 million or less, the adhesive sheet 1 has difficulty becoming hard and peeling tends to be difficult to occur. The weight average molecular weight (Mw)/number average molecular weight (Mn), which means molecular weight distribution, is preferably 1.8 to 10, more preferably 1.8 to 7, and even more preferably 1.8 to 5. It is preferable that the molecular weight distribution (Mw/Mn) is 10 or less in terms of durability. The weight average molecular weight and molecular weight distribution (Mw/Mn) are measured by GPC (gel permeation chromatography) and obtained from the values calculated by polystyrene conversion.

The (meth)acrylic polymer (A) can be formed by polymerizing one or two or more types of monomers described above by a known method. You may polymerize a monomer and a partially polymerized product of the monomer. Polymerization can be performed, 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 by avoiding contact between the monomer and/or partial polymer and oxygen, for example, polymerization in an inert gas atmosphere such as nitrogen, or polymerization in a state where oxygen is blocked by a resin film, etc. can be employed. The (meth)acrylic polymer (A) to be formed may be 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 type or two or more types of polymerization initiators. The type of polymerization initiator can be selected through polymerization reaction, and may be, for example, a thermal polymerization initiator or a photo polymerization initiator.

Solvents used in solution polymerization include, for example, 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 cyclohexane and methylcyclohexane; 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 in solution polymerization include, for example, azo-based polymerization initiators, peroxide-based polymerization initiators, and redox-based polymerization initiators. Peroxide-based polymerization initiators include, for example, dibenzoyl peroxide and t-butyl permaleate. Among them, the azo-based polymerization initiator disclosed in Japanese Patent Application Laid-Open No. 2002-69411 is preferable. The azo-based polymerization initiator is, for example, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2- Methyl propionic 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, based on 100 parts by weight of the total amount of monomers.

Active energy rays used in 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 ray is preferably ultraviolet rays. Polymerization by irradiation of ultraviolet rays is also called photopolymerization. The polymerization system of active energy ray polymerization typically contains a photopolymerization initiator. The polymerization conditions for active energy ray 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, photoactive oxime-based photopolymerization initiators, and benzoin-based photopolymerization initiators. They are a 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, anisole methyl ether. Acetophenone-based photopolymerization initiators include, for example, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, It is 4-(t-butyl)dichloroacetophenone. The α-ketol-based photopolymerization initiator is, for example, 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. The aromatic sulfonyl chloride-based 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. The benzoin-based photopolymerization initiator is, for example, benzoin. The benzyl-based photopolymerization initiator is, for example, benzyl. Benzophenone-based photopolymerization initiators include, for example, benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α-hydroxycyclohexylphenyl ketone. The ketal-based photopolymerization initiator is, for example, benzyldimethylketal. Thioxanthone-based photopolymerization initiators include, for example, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, and 2,4-dioxanthone. These are isopropylthioxanthone 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 parts by weight, based on 100 parts by weight of the total amount of monomers.

The content of the (meth)acrylic polymer (A) in the adhesive composition is, in terms of solids ratio, for example, 50% by weight or more, and may be 60% by weight or more, 70% by weight or more, and further may be 80% by weight or more. The upper limit of the content rate 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, and further 90% by weight or less.

[Cross-linking agent (B)]

The crosslinking agent (B) is typically a polyfunctional crosslinking agent having two or more crosslinking reactive groups per molecule. The crosslinking agent (B) may be a trifunctional or higher crosslinking agent having 3 or more crosslinking reactive groups per molecule. The upper limit of the number of crosslinking reactive groups per molecule is, for example, 5.

The crosslinking agent (B) preferably has good compatibility with the (meth)acrylic polymer (A). By using a crosslinking agent (B) that has good compatibility with the (meth)acrylic polymer (A), clouding of the adhesive sheet 1 can be easily suppressed after the adhesive sheet 1 is produced. For example, as described later, when an isocyanate-based crosslinking agent is used as the crosslinking agent (B), the adhesive composition tends to exhibit a lower critical solution temperature (LCST type) phase separation behavior. In this case, if the crosslinking agent (B) and the (meth)acrylic polymer (A) have good compatibility, clouding of the adhesive sheet 1 can be suppressed even if the adhesive composition is dried at a relatively high temperature. That is, the range of drying temperature applicable to the adhesive composition tends to be wide. In particular, when the (meth)acrylic polymer (A) contains structural units derived from aromatic ring-containing monomers or structural units derived from monomers with relatively small molecular weights such as methyl acrylate and ethyl acrylate, (meth) The compatibility between the acrylic polymer (A) and the crosslinking agent (B) tends to be good.

The crosslinking agent (B) includes, for example, at least one selected from the group consisting of an isocyanate-based crosslinking agent and a polyfunctional (meth)acrylate-based crosslinking agent, and preferably includes an isocyanate-based crosslinking agent. Isocyanate-based crosslinking agents are suitable for solvent-based adhesive compositions. A multifunctional (meth)acrylate-based crosslinking agent is suitable for an active energy ray-curable adhesive composition.

As an isocyanate-based crosslinking agent, a compound (isocyanate compound) having at least two isocyanate groups can be used. It is preferable that the number of isocyanate groups contained in the isocyanate compound is 3 or more. The upper limit of the number of isocyanate groups is not particularly limited and is, for example, 5. Examples of the isocyanate compound include aromatic isocyanate compounds, alicyclic isocyanate compounds, and aliphatic isocyanate compounds. It is preferable that the isocyanate-based crosslinking agent can self-polymerize by reacting with water.

Examples of aromatic isocyanate compounds include phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, Examples include 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, and xylylene diisocyanate.

Examples of alicyclic isocyanate compounds include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogen. Added xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated tetramethylxylylene diisocyanate, etc. are mentioned.

As aliphatic isocyanate compounds, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2,4 , 4-trimethylhexamethylene diisocyanate, etc. are mentioned.

Examples of the isocyanate-based crosslinking agent include polymers (dimers, trimers, pentamers, etc.) of the above isocyanate compounds, adducts obtained by addition to polyhydric alcohols such as trimethylolpropane, urea-modified products, biuret-modified products, and allophanate-modified products. , isocyanurate modified products, carbodiimide modified products, polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, etc., and urethane prepolymers obtained by addition. From the viewpoint of compatibility with the (meth)acrylic polymer (A), it is preferable that the isocyanate-based crosslinking agent contains a long-chain alkyl group.

Preferred examples of the isocyanate-based crosslinking agent are aromatic isocyanate compounds and their derivatives, and specifically, tolylene diisocyanate-based (TDI-based) crosslinking agents (tolylene diisocyanate and its derivatives) and diphenylmethane diisocyanate-based (MDI-based) crosslinking agents (di phenylmethane diisocyanate and its derivatives). However, the isocyanate-based crosslinking agent may be a hexamethylene diisocyanate-based (HDI-based) crosslinking agent (hexamethylene diisocyanate and its derivatives). It is particularly preferable that the isocyanate-based crosslinking agent is a TDI-based crosslinking agent. Compared to HDI-based crosslinking agents, TDI-based crosslinking agents and MDI-based crosslinking agents are more likely to cause reactions between crosslinking agents, and are therefore suitable for producing the pressure-sensitive adhesive sheet (1) having an IPN structure.

The isocyanate-based crosslinking agent is a TDI-based crosslinking agent, and preferably contains an adduct of a polyhydric alcohol and tolylene diisocyanate, or an isocyanurate modified form of tolylene diisocyanate. Specific examples of the adduct of polyhydric alcohol and tolylene diisocyanate include trimethylolpropane/tolylene diisocyanate trimer adduct.

Commercially available isocyanate-based crosslinking agents include, for example, those manufactured by Mitsui Chemicals under the brand names “Takenate D-101E,” “Takenate D-262,” “Takenate D-110N,” “Takenate D-120N,” and “Takenate D-101E.” “Takenate D-140N”, “Takenate D-160N”, “Takenate D-165N”, “Takenate D-170HN”, “Takenate D-178N”, “Takenate 500”, “Takenate 600”, Product names made by Tosoh Corporation: “Millionate MT”, “Millionate MTL”, “Millionate MR-200”, “Millionate MR-400”, “Coronate L”, “Coronate HL”, “Coronate” Nate HX” and the like, and preferably Takenate D-101E and Takenate D-262.

The isocyanate-based crosslinking agent may be used individually by one type or may be used in mixture of two or more types.

As a polyfunctional (meth)acrylate-based crosslinking agent, a compound (polyfunctional (meth)acrylate compound) having at least two (meth)acryloyl groups can be used. Examples of the polyfunctional (meth)acrylate compound include polyalkylene glycol di(meth)acrylates such as polypropylene glycol di(meth)acrylate and polyethylene glycol di(meth)acrylate; Alkyldiol di(meth)acrylates such as 1,6-hexanediol di(meth)acrylate and neopentyl glycol di(meth)acrylate; (meth)acrylic acid adducts of diglycidyl ether compounds such as bisphenol A diglycidyl ether di(meth)acrylate; Trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate Compounds having three or more (meth)acryloyl groups, such as latex, are included, and polypropylene glycol di(meth)acrylate is preferable.

Examples of commercially available polyfunctional (meth)acrylate-based crosslinking agents include the brand name “APG-400” manufactured by Shinnakamura Chemical Co., Ltd.

The polyfunctional (meth)acrylate-based crosslinking agent may be used individually as one of the above-mentioned agents, or may be used in mixture of two or more types.

The crosslinking agent (B) is not limited to isocyanate-based crosslinking agents and polyfunctional (meth)acrylate-based crosslinking agents. Other examples of the crosslinking agent (B) include peroxide-based crosslinking agents, epoxy-based crosslinking agents, imine-based crosslinking agents, and multifunctional metal chelates. You may use a mixture of two or more types of these crosslinking agents. For example, a polyfunctional (meth)acrylate-based crosslinking agent and an epoxy-based crosslinking agent may be mixed and used.

The compounding amount of the crosslinking agent (B) is, for example, 2 parts by weight or more, preferably 3 parts by weight or more, more preferably 5 parts by weight or more, with respect to 100 parts by weight of the (meth)acrylic polymer (A). Preferably it is 8 parts by weight or more, particularly preferably 10 parts by weight or more, and may be 12 parts by weight or more. The compounding amount of the crosslinking agent (B) is, for example, 30 parts by weight or less, preferably 25 parts by weight or less, and may be less than 20 parts by weight, based on 100 parts by weight of the (meth)acrylic polymer (A).

As an example, when the crosslinking agent (B) is an adduct of trimethylolpropane and an isocyanate compound containing a long-chain alkyl group, the compounding amount is preferably about 10 parts by weight based on 100 parts by weight of the (meth)acrylic polymer (A). When the crosslinking agent (B) is an isocyanurate modified form of an isocyanate compound containing a long-chain alkyl group, the mixing amount is preferably about 5 parts by weight based on 100 parts by weight of the (meth)acrylic polymer (A). When the crosslinking agent (B) is a bifunctional (meth)acrylate-based crosslinking agent, the mixing amount is preferably about 20 parts by weight based on 100 parts by weight of the (meth)acrylic polymer (A). When the crosslinking agent (B) is a tetrafunctional (meth)acrylate-based crosslinking agent, the compounding amount is preferably about 10 parts by weight based on 100 parts by weight of the (meth)acrylic polymer (A). When the crosslinking agent (B) is a hexafunctional (meth)acrylate-based crosslinking agent, the mixing amount is preferably about 7 parts by weight based on 100 parts by weight of the (meth)acrylic polymer (A). However, the compounding amount of the crosslinking agent (B) is not limited to the above, and can be adjusted appropriately depending on the molecular weight and structure of the crosslinking agent (B).

In the pressure-sensitive adhesive composition, if the blending amount of the crosslinking agent (B) relative to 100 parts by weight of the (meth)acrylic polymer (A) is large, such as 2 parts by weight or more, when producing the pressure-sensitive adhesive sheet (1), the crosslinking agents (B) react with each other. , a polymer (C) containing a structural unit derived from the crosslinking agent (B) as a main component may be formed. The polymer (C) is suitable for suppressing dimensional changes in the adhesive sheet (1) by providing sufficient cohesion to the adhesive sheet (1). In other words, polymer (C) is suitable for suppressing display unevenness and light leakage in an image display device. Additionally, the combination of (meth)acrylic polymer (A) and polymer (C) is suitable for improving the durability of the adhesive sheet 1 under a high temperature and high humidity environment, etc.

[Other ingredients]

The adhesive composition may further contain a (meth)acrylic oligomer.

The (meth)acrylic oligomer may 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 is, for example, 1000 or more, and may be 2000 or more, 3000 or more, and further may be 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, and further may be 7,000 or less.

(meth)acrylic oligomers have, for example, one or two or more types of 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 alkyl (meth)acrylates such as acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohol, such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclofentanyl (meth)acrylate; 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 preferably has structural units derived from a (meth)acrylic monomer having a relatively bulky structure. In this case, the adhesiveness of the adhesive sheet 1 can be further improved. Examples of the acrylic monomer include alkyl (meth)acrylates having an alkyl group with a branched structure, such as isobutyl (meth)acrylate and t-butyl (meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohol, such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclofentanyl (meth)acrylate; These are aromatic ring-containing (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate. The monomer preferably has a cyclic structure, and more preferably has two or more cyclic structures. In addition, when irradiation of ultraviolet rays is performed during polymerization of a (meth)acrylic oligomer and/or during formation of an adhesive sheet, the progress of polymerization and/or formation is difficult to inhibit, and the monomer does not have an unsaturated bond. It is preferable, and for example, an alkyl (meth)acrylate having an alkyl group having a branched structure, or an ester of (meth)acrylic acid and an alicyclic alcohol can be used.

Specific examples of (meth)acrylic oligomers include copolymers of butylacrylate, methyl acrylate, and acrylic acid, copolymers of cyclohexyl methacrylate and isobutyl methacrylate, and cyclohexyl methacrylate and isobornyl methacrylate. Copolymer of cyclohexyl methacrylate and acryloylmorpholine, copolymer of cyclohexyl methacrylate and diethylacrylamide, copolymer of 1-adamantyl acrylate and methyl methacrylate, DC A copolymer of chloropentanyl methacrylate and isobornyl methacrylate, dicyclopentanyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, isobornyl acrylate and cyclofentanyl methacrylate. It is a copolymer of at least one type of methyl methacrylate, a homopolymer of dicyclopentanyl acrylate, a homopolymer of 1-adamantyl methacrylate, and a homopolymer of 1-adamantyl acrylate.

To polymerize the (meth)acrylic oligomer, the method for polymerizing the (meth)acrylic polymer (A) described above can be adopted.

When the adhesive composition contains a (meth)acrylic oligomer, the mixing amount is, for example, 70 parts by weight or less, 50 parts by weight or less, and even 40 parts by weight or less, based on 100 parts by weight of the (meth)acrylic polymer (A). do. The lower limit of the compounding amount is, for example, 1 part by weight or more, and may be 2 parts by weight or more, and further may be 3 parts by weight or more, based on 100 parts by weight of the (meth)acrylic polymer (A). The adhesive composition does not need to contain a (meth)acrylic oligomer.

The adhesive composition may further contain known additives. Additives include, for example, silane coupling agents, polyfunctional alcohols, solvents, colorants, powders such as pigments, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, rework enhancers, and softeners. , antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, antistatic agents (alkali metal salts of ionic compounds, ionic liquids, ionic solids, etc.), inorganic or organic fillers, metal powders, particles, thin substances, etc. I can hear it. Additionally, within a controllable range, a redox system to which a reducing agent is added may be employed. These additives can be used 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, based on 100 parts by weight of the (meth)acrylic polymer (A).

Specific examples of silane coupling agents include, for example, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4- epoxy group-containing silane coupling agents such as epoxycyclohexyl)ethyltrimethoxysilane; 3-Aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, N -Amino group-containing silane coupling agents such as phenyl-γ-aminopropyltrimethoxysilane; (meth)acrylic group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane; and silane coupling agents containing isocyanate groups such as 3-isocyanate propyltriethoxysilane.

When the adhesive composition contains a silane coupling agent, the compounding amount is, for example, 5 parts by weight or less, 3 parts by weight or less, 1 part by weight or less, and 0.5 parts by weight, based on 100 parts by weight of the (meth)acrylic polymer (A). Hereinafter, it may be 0.2 part by weight or less, 0.1 part by weight or less, and further 0.05 part by weight or less. The adhesive composition does not need to contain a silane coupling agent.

The adhesive composition may contain polyfunctional alcohol. The molecular weight of the polyfunctional alcohol is, for example, 240 or less, 230 or less, 220 or less, 210 or less, 200 or less, 190 or less, 180 or less, 170 or less, 160 or less, and may also be 150 or less. The lower limit of the molecular weight is, for example, 60 or more, and may be 80 or more, 90 or more, and further may be 100 or more.

Examples of polyfunctional alcohols include alkylene glycols such as ethylene glycol and propylene glycol, and polymers thereof; Ether glycols such as diethylene glycol and polymers thereof; trimethylolethane; trimethylolpropane; glycerin; And sugar alcohols such as pentaerythritol and sorbitol. The polyfunctional alcohol is preferably trimethylolpropane, glycerin, diethylene glycol and polymers thereof, and is more preferably trimethylolpropane.

Polyfunctional alcohol may be trifunctional or more. Examples of trifunctional polyfunctional alcohols are trimethylolpropane and glycerin.

The polyfunctional alcohol does not need to have a reactive group other than a hydroxyl group that is reactive with the crosslinking agent (B). The reactive group is, for example, at least one selected from an amino group, a carboxyl group, and an epoxy group, and is especially an amino group.

The compounding amount of the polyfunctional alcohol in the adhesive composition is, for example, 0.5 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the (meth)acrylic polymer (A). The upper limit of the mixing amount may be 15 parts by weight or less, 10 parts by weight or less, 8 parts by weight or less, 5 parts by weight or less, 4 parts by weight or less, and further 3 parts by weight or less.

Types of the adhesive composition include, for example, emulsion type, solvent type (solution type), active energy ray curing type (photo curing type), and heat melt type (hot melt type). From the viewpoint of being able to form the adhesive sheet 1 with excellent durability, the adhesive composition may be of a solvent type or an active energy ray curable type, or may be of a solvent type. The solvent-type adhesive composition does not need to contain a photocuring agent such as an ultraviolet curing agent.

The adhesive sheet 1 can be produced from the adhesive composition by the following method. For the solvent type, for example, an adhesive composition or a mixture of an adhesive composition and a solvent is applied to a base film to form a coating film, and the formed coating film is dried to form the adhesive sheet 1. The pressure-sensitive adhesive composition is thermally cured by heat during drying. For the active energy ray curing type (photo curing type), for example, a monomer (group) that becomes the (meth)acrylic polymer (A) by polymerization, a crosslinking agent (B), and, if necessary, a partial polymerization of the monomer (group), A mixture of polymerization initiator, oligomer, additive, and solvent is applied to the base film, and the formed coating film is irradiated with active energy rays to form the adhesive sheet 1. Before irradiation with active energy rays, the coating film may be dried to remove the solvent. The base film may be a film (release liner) whose application surface has been subjected to a release treatment.

The adhesive sheet 1 formed on the base film can be transferred to any layer. Additionally, the base film may be an optical film, and in this case, an optical laminated body containing the adhesive sheet 1 and the optical film is obtained.

For application to the base film, a known method can be adopted. Application includes, for example, roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, extrusion by die coater, etc. It can be done by court.

Solvent-type pressure-sensitive adhesive compositions, especially pressure-sensitive adhesive compositions containing an isocyanate-based crosslinking agent, tend to exhibit lower critical solution temperature (LCST) phase separation behavior. Therefore, when using a solvent-type adhesive composition, the drying temperature of the coating film is preferably, for example, 200°C or lower, and may be 160°C or lower, 150°C or lower, 130°C or lower, 120°C or lower, and even 100°C or lower. do. When the drying temperature is 130°C or lower, the reaction rate of the cross-linking agent (B), especially the isocyanate-based cross-linking agent, can be appropriately adjusted, and the compatibility of the (meth)acrylic polymer (A) and the polymer (C) is maintained well, resulting in adhesion. There is a tendency to reduce fluctuations in the elastic modulus of the sheet 1. The lower limit of the drying temperature of the coating film is not particularly limited, and is, for example, 40°C, and may be 60°C. The drying time of the coating film can be adjusted appropriately depending on the drying temperature, etc., and may be, for example, 5 seconds to 20 minutes, 5 seconds to 10 minutes, or even 10 seconds to 5 minutes. When the drying temperature is set high, it is preferable to set the drying time short from the viewpoint of reducing fluctuations in the elastic modulus of the adhesive sheet 1. Drying of the coating film is preferably performed in an environment with relatively high humidity. As a result, the reaction of the crosslinking agent (B), especially the isocyanate-based crosslinking agent, in the coating film tends to proceed quickly and uniformly. The relative humidity at the drying temperature of the coating film is, for example, 0%RH or more, and may be 5%RH or more, 10%RH or more, 20%RH or more, and further may be 30%RH or more.

Active energy ray-curable adhesive compositions, especially adhesive compositions containing a polyfunctional (meth)acrylate-based crosslinking agent, tend to exhibit upper critical solution temperature (UCST) phase separation behavior. Therefore, when using an active energy ray-curable adhesive composition, a drying treatment may also be performed simultaneously with irradiating the coating film with active energy rays, or before and after irradiating the active energy rays. The drying temperature of the coating film is preferably, for example, 60°C or higher, and may be 80°C or higher, 100°C or higher, 110°C or higher, and further 120°C or higher. By setting the drying temperature of the coating film high, the compatibility of the (meth)acrylic polymer (A) and the polymer (C), especially the polymer (C) containing structural units derived from a polyfunctional (meth)acrylate crosslinking agent, is improved. By maintaining it well, there is a tendency to reduce fluctuations in the elastic modulus of the adhesive sheet 1. The upper limit of the drying temperature of the coating film is not particularly limited, and is, for example, 200°C. The drying time of the coating film can be adjusted appropriately depending on the drying temperature, etc., and may be, for example, 5 seconds to 20 minutes, 5 seconds to 10 minutes, or even 10 seconds to 5 minutes.

(optical film)

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

A polarizing plate is, for example, a laminate containing a polarizer and a transparent protective film. The transparent protective film is disposed, for example, in contact with the main surface (surface with the largest area) of the layered polarizer. The polarizer may be disposed between two transparent protective films.

The polarizer is not particularly limited, and various types of polarizers can be used. As a polarizer, for example, a dichroic substance such as iodine or a dichroic dye is adsorbed on a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, or an ethylene-vinyl acetate copolymer-based partially saponified film, and 1 axially stretched; and polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochloric acid-treated polyvinyl chloride. Among these, a polarizer made of a polyvinyl alcohol-based film and a dichroic substance such as iodine is preferable, and an iodine-based polarizer containing iodine and/or iodine ions is more preferable. The thickness of the polarizer is not particularly limited, but is generally about 5 to 80 μm.

A polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine and stretching it uniaxially can be produced, for example, by immersing polyvinyl alcohol in an aqueous solution of iodine, dyeing it, and stretching it to 3 to 7 times the original length. If necessary, polyvinyl alcohol may be immersed in an aqueous solution of potassium iodide or the like containing boric acid, zinc sulfate, zinc chloride, etc. Additionally, if necessary, before dyeing, the polyvinyl alcohol-based film may be immersed in water and washed. By washing the polyvinyl alcohol-based film with water, surface contamination and anti-blocking agents of the polyvinyl alcohol-based film can be cleaned, and swelling of the polyvinyl alcohol-based film also has the effect of suppressing the occurrence of uneven dyeing. Stretching of the polyvinyl alcohol-based film may be performed after dyeing with iodine, may be performed while dyeing, or may be performed before dyeing with iodine. Stretching may be performed in an aqueous solution such as boric acid or potassium iodide or in a water bath.

As a polarizer, a thin polarizer with a thickness of 10 μm or less can also be used. From the viewpoint of thinning, it is preferable that the thickness of the polarizer is 1 to 7 μm. Such a thin polarizer has little thickness unevenness, is excellent in visibility, and has excellent durability due to little dimensional change, and is preferable because it can further reduce the thickness of the polarizing plate.

As a thin polarizer, representative examples include Japanese Patent Application Laid-Open No. 51-069644, Japanese Patent Application Laid-Open No. 2000-338329, International Publication No. 2010/100917, Japanese Patent No. 4751481, and Japanese Patent Application Laid-Open No. 2012- A thin polarizer described in Publication No. 073563 can be mentioned. These thin polarizers can be obtained by a manufacturing method including a step of stretching a polyvinyl alcohol-based resin (hereinafter also referred to as PVA-based resin) layer and a resin substrate for stretching in the state of a laminate, and a dyeing step. With this manufacturing method, since the PVA-based resin layer is supported by the resin base material for stretching, problems such as breakage due to stretching can be suppressed even if the PVA-based resin layer is thin.

Among manufacturing methods that include a process of stretching and dyeing in the state of a laminate, stretching can be performed at a high magnification and polarization performance can be improved, International Publication No. 2010/100917, Japanese Patent No. 4751481, Japan. A manufacturing method including the step of stretching in an aqueous boric acid solution described in Patent Publication No. 2012-073563 is preferable, and in particular, before stretching in an aqueous boric acid solution described in Japanese Patent Publication No. 4751481 or Japanese Patent Publication No. 2012-073563. A manufacturing method including an auxiliary air stretching process is preferred.

As a material for forming the transparent protective film provided on one or both sides of the polarizer, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier, isotropy, etc. is used. Specific examples of such thermoplastic resins include cellulose resins such as triacetylcellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, and (meth)acrylic. Resins, cyclic polyolefin resins (norbornene-based resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The material of the transparent protective film may be a thermosetting resin such as (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone, or an ultraviolet curable resin. When a polarizing plate has two transparent protective films, the materials of the two transparent protective films may be the same or different from each other. For example, a transparent protective film made of a thermoplastic resin is bonded to one main surface of the polarizer via an adhesive, and a transparent protective film made of a thermosetting resin or an ultraviolet curable resin is bonded to the other main surface of the polarizer. It may be joined. The transparent protective film may contain one or more types of arbitrary additives. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, discoloration inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, colorants, etc. The content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, further preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. %am. When the content of the thermoplastic resin in the transparent protective film is 50% by weight or more, the high transparency that the thermoplastic resin originally possesses tends to be sufficiently exhibited.

The thickness of the transparent protective film can be determined as appropriate, but is generally about 10 to 200 μm in terms of workability such as strength and handleability, and thinness.

The polarizer and the transparent protective film are usually in close contact through a water-based adhesive or the like. Examples of water-based adhesives include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl latex, water-based polyurethane, and water-based polyester. Adhesives other than the above adhesives include ultraviolet curing adhesives and electron beam curing adhesives. The adhesive for electron beam curable polarizing plates exhibits suitable adhesion to various transparent protective films. The adhesive may contain a metal compound filler.

In a polarizing plate, instead of a transparent protective film, a retardation film or the like may be formed on the polarizer. On the transparent protective film, another transparent protective film can be provided, a retardation film, etc. can be provided.

With respect to the transparent protective film, a hard coat layer may be provided on the surface opposing the surface to which the polarizer is adhered, and treatment for the purposes of anti-reflection, anti-sticking, diffusion, anti-glare, etc. may be performed.

As the retardation film, one obtained by stretching a polymer film or one obtained by aligning and fixing a liquid crystal material can be used. The retardation film has birefringence, for example in-plane and/or in the thickness direction.

Examples of the retardation film include a retardation film for anti-reflection (see Japanese Patent Application Laid-Open No. 2012-133303 [0221], [0222], and [0228]), and a retardation film for viewing angle compensation (see Japanese Patent Application Laid-Open No. 2012-133303 [0225]). , [0226]), and an oblique orientation retardation film for viewing angle compensation (see Japanese Patent Laid-Open No. 2012-133303 [0227]).

As the retardation film, as long as it substantially has the above functions, for example, the retardation value, arrangement angle, three-dimensional birefringence, whether it is a single layer or a multilayer, etc. are not particularly limited, and a known retardation film can be used.

The thickness of the retardation film is preferably 20 μm or less, more preferably 10 μm or less, further preferably 1 to 9 μm, and particularly preferably 3 to 8 μm.

The retardation film is composed of two layers, for example, a quarter wave plate and a half wave plate in which liquid crystal material is aligned and fixed.

Another example of the optical laminated body of this embodiment is shown in FIG. 4. The optical laminate 10B in FIG. 4 has a laminated structure in which a release liner 3, an adhesive sheet 1, and an optical film 2 are laminated in this order. The optical laminate 10B can be used as an optical film with an adhesive sheet by peeling off the release liner 3.

Constitutive materials of the release liner 3 include, for example, plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester film, porous materials such as paper, cloth, and nonwoven fabric, nets, foam sheets, metal foil, and these. Suitable thin-walled materials such as laminated materials may be used, but plastic films are preferably used because they have excellent surface smoothness.

The plastic film is not particularly limited as long as it is a film that can protect the adhesive sheet 1, and examples include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, Examples include vinyl chloride copolymer film, polyethylene terephthalate film, polybutylene terephthalate film, polyurethane film, and ethylene-vinyl acetate copolymer film.

The thickness of the release liner 3 is usually about 5 to 200 μm, and preferably about 5 to 100 μm. If necessary, the release liner 3 is subjected to mold release and antifouling treatment using a silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based mold release agent, silica powder, etc., or antistatic treatment such as coating type, kneading type, or vapor deposition type. It's okay. In particular, by appropriately performing a release treatment such as silicone treatment, long-chain alkyl treatment, or fluorine treatment on the surface of the release liner 3, the peelability from the adhesive sheet 1 can be further improved.

Additionally, as described above, the release film used when producing the adhesive sheet 1 may be used as the release liner 3.

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

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

Another example of the optical laminated body of this embodiment is shown in FIG. 6. The optical laminate 10D in FIG. 6 includes a release liner 3, an adhesive sheet 1, a retardation film 2A, an interlayer adhesive 4, a polarizer 2B, and a protective film 5 laminated in this order. It has a layered structure. The optical laminate 10D can be used by peeling off the release liner 3 and then attaching it to, for example, an image forming layer.

The protective film 5 is the outermost layer of the optical film 2 (polarizing plate 2B) during distribution and storage of the optical laminate 10D and when the optical laminate 10D is built into the image display device. It has the function of protecting. Additionally, the protective film 5 may function as a window to external space when built into an image display device. The 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, with polyester being preferred. However, the protective film 5 is not limited to the above example. 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 treatment such as anti-glare, anti-reflection, anti-static, etc.

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

The optical laminated body of this embodiment can be distributed and stored, for example, as a rolled product obtained by winding a strip-shaped optical laminated body or as a sheet-shaped optical laminated body.

The optical laminated body of this embodiment is typically used in an image display device. Image display devices are, for example, EL displays such as liquid crystal displays, organic EL displays, and inorganic EL displays.

(Embodiment of image display device)

An example of the image display device of this embodiment is shown in FIG. 7. The image display device 11 in FIG. 7 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, It has a laminated structure in which the polarizing plate 2B and the protective film 5 are laminated in this order. The image display device 11 has the optical laminated body 10B, 10C, or 10D of FIGS. 4 to 6 (however, the release liner 3 is excluded). The substrate 7 and the image forming layer 6 may have the same configuration as the substrate and image forming layer provided in a known image display device.

The image display device 11 in FIG. 7 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), or the like. The image display device 11 can be used for home appliances, vehicle-mounted applications, public information display (PID) applications, etc.

The image display device of this embodiment can have any configuration as long as it is provided with the optical laminated body of this embodiment.

Example

Hereinafter, the present invention will be explained in more detail through examples. The present invention is not limited to the examples shown below.

[(meth)acrylic polymer A1]

A four-neck flask equipped with a stirring blade, thermometer, nitrogen gas introduction tube, and condenser contained 81.9 parts by weight of butylacrylate, 4.8 parts by weight of acrylic acid, 0.1 parts by weight of 4-hydroxybutylacrylate, and 13.2 parts by weight of benzyl acrylate. The monomer mixture was added. Additionally, with respect to 100 parts by weight of the monomer mixture, 0.1 part by weight of 2,2'-azobisisobutyronitrile (AIBN) was added along with ethyl acetate as a polymerization initiator, and nitrogen gas was introduced while gently stirring to replace nitrogen. , the liquid temperature in the flask was maintained at around 55°C, and the polymerization reaction was performed for 7 hours. After that, ethyl acetate was added to the obtained reaction liquid, the solid content concentration was adjusted to 30% by weight, and a solution of (meth)acrylic polymer A1 was obtained.

[(meth)acrylic polymer A2]

A monomer mixture containing 94.9 parts by weight of butylacrylate, 5.0 parts by weight of acrylic acid, and 0.1 part by weight of 4-hydroxybutylacrylate was added to a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas introduction tube, and condenser. Next, 0.1 part by weight of AIBN was added as a polymerization initiator to 100 parts by weight of the monomer mixture, nitrogen gas was introduced while gently stirring to purge the inside of the flask with nitrogen, and the liquid temperature in the flask was maintained at around 55°C to carry out the polymerization reaction. was carried out for 7 hours. Next, ethyl acetate was added to the obtained reaction liquid to adjust the solid content concentration to 12% by weight, and a solution of (meth)acrylic polymer A2 was obtained.

The abbreviations in Table 1 are as follows.

BA: n-butylacrylate

AA: Acrylic acid

HBA: 4-hydroxybutylacrylate

BzA: Benzyl acrylate

AIBN: Azo-based polymerization initiator, 2,2'-azobisisobutyronitrile (manufactured by Kishida Chemical)

[Production of adhesive sheet]

(Examples 1 to 3 and Comparative Examples 1 to 2)

A (meth)acrylic polymer and a crosslinking agent were mixed to obtain the composition shown in Table 2 below to obtain a solvent-type adhesive composition. Next, the adhesive composition was applied to the surface of the PET film as the base film (release liner) so that the thickness of the adhesive sheet after drying was 25 μm. A fountain coater was used to apply the adhesive composition. The obtained coating film was dried for 1 minute in an air circulation type constant temperature oven set to the drying temperature shown in Table 2 to form adhesive sheets of Examples 1 to 3 and Comparative Examples 1 to 2.

(Example 4)

A (meth)acrylic polymer, crosslinking agent, and additives were mixed to obtain the composition shown in Table 2 below, and an active energy ray-curable adhesive composition was obtained. Next, the adhesive composition was applied to the surface of the PET film, which was the base film (release liner), so that the thickness of the adhesive sheet was 25 μm. A fountain coater was used to apply the adhesive composition. A release liner was also bonded to the surface of the obtained coating film. After drying the coating film at 130°C, it was irradiated with ultraviolet rays under the conditions of an illumination intensity of 4 mW/cm2 and a light quantity of 1200 mJ/cm2. As a result, curing of the coating film progressed, and the adhesive sheet of Example 4 was obtained.

The abbreviations in Table 2 are as follows.

D262: Isocyanurate modified form of tolylene diisocyanate (manufactured by Mitsui Chemicals, brand name: Takenate D-262)

D101E: Trimethylolpropane/tolylene diisocyanate adduct (manufactured by Mitsui Chemicals, brand name: Takenate D-101E)

APG400: Polypropylene glycol diacrylate (manufactured by Shinnakamura Chemical Co., Ltd., brand name: APG-400)

Tetrad C: 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane (multifunctional epoxy-based crosslinker; Mitsubishi Gas Chemical Co., Ltd., Tetrad C)

Omnirad 651: Photopolymerization initiator, 2,2-dimethoxy-1,2-diphenylethan-1-one (manufactured by IGM Resins B.V.)

[evaluation]

<Weight average molecular weight (Mw) of (meth)acrylic polymer>

The weight average molecular weight (Mw) of the obtained (meth)acrylic polymer was measured by GPC (gel permeation chromatography).

·Analysis device: HLC-8120GPC, manufactured by Tosoh Corporation

Column: Tosoh Corporation, G7000H _XL +GMH _XL +GMH _XL

·Column size: 7.8㎜ϕ×30㎝ each, 90㎝ in total

·Column temperature: 40℃

·Flow rate: 0.8ml/min

·Injection volume: 100μl

·Eluent: Tetrahydrofuran

Detector: Differential refractometer (RI)

·Standard sample: polystyrene

<Thickness>

The thickness of the adhesive sheet, etc. was measured using a dial gauge (manufactured by Mitutoyo).

<Gel fraction>

Evaluation of the gel fraction of the produced adhesive sheet was performed by the method described above. The weight of the small piece obtained by scraping off part of the adhesive sheet was about 0.2 g. NTF1122 (average pore diameter 0.2 μm) manufactured by Nitto Denko was used as the stretched porous polytetrafluoroethylene film.

<Adhesion>

The adhesive strength of the produced adhesive sheet was evaluated by the method described above. An Autograph AG-IS manufactured by Shimadzu Seisakusho was used as the tensile tester.

<Haize>

The haze of the produced adhesive sheet was measured in an atmosphere of 25°C using a haze meter HZ-V3 manufactured by Suga Shikenki in accordance with JIS K7136:1981. The measurement was conducted with the adhesive sheet to be evaluated laminated on slide glass S012140 (thickness 1.3 mm) manufactured by Matsunami Glass Industries.

<Storage modulus G'>

The storage elastic modulus G' of the adhesive sheet at 25°C was evaluated by the method described above. Dynamic viscoelasticity measurement was performed using “ARES-G2” manufactured by TA Instruments.

<Atomic force microscopy measurement>

By the above-described method, the elastic modulus was measured using AFM so that the number of measurement points was 65536 over a range of 500 nm in length and 500 nm in width on the surface of the adhesive sheet. As AFM, MFP-3D-SA manufactured by Oxford Instruments was used. As a cantilever, OMCL-AC240TS (spring constant 3 N/m) manufactured by Olympus was used. A histogram of elastic modulus with a class width of 0.1 MPa was created, and the maximum frequency value, F _max , etc. was specified. Additionally, the average value and standard deviation of the elastic modulus were calculated, and the coefficient of variation was specified.

<Humidification durability>

The humidification durability (corresponding to an accelerated durability test) of the adhesive sheet was evaluated by the following method. First, a circularly polarizing plate was formed having each of the adhesive sheets produced in Examples and Comparative Examples on one exposed surface. As a circularly polarizing plate provided with an adhesive sheet, a sample with a size of 100 mm in length and 40 mm in width was prepared. Next, the circularly polarizing plate was fixed to the surface of a glass plate (Eagle XG, manufactured by Corning) via the adhesive sheet. Fixation of the circularly polarizing plate was carried out in an atmosphere of 23°C and 50%RH. Next, it was treated in an autoclave at 50°C and 5 atm (absolute pressure) for 15 minutes, left until cooled to 23°C to stabilize the bonding of the circularly polarizing plate to the glass plate, and then placed in an autoclave at 60°C and 95%RH. It was left in a heated and humidified atmosphere for 500 hours. After leaving, it was returned to an atmosphere of 23°C and 50%RH, it was visually confirmed that the circularly polarizing plate did not peel off from the glass plate, or foaming occurred between the glass plate and the circularly polarizing plate, and the humidification durability was evaluated as follows.

A: No changes in appearance such as foaming or peeling are observed.

C: Significant peeling or foaming is observed at the ends, which poses a problem in practical terms.

Hereinafter, a method of forming a circularly polarizing plate provided with an adhesive sheet used for evaluation of humidification durability is shown.

<Production of polarizer P1>

(Production of polarizer)

A long polyvinyl alcohol (PVA)-based resin film (manufactured by Kuraray, product name "PE3000", thickness 30 ㎛) is stretched uniaxially in the longitudinal direction (total stretching ratio 5.9 times) using a roll stretching machine, while simultaneously stretching the resin. Each treatment of swelling, dyeing, crosslinking, washing, and drying was sequentially performed on the film to produce a polarizer with 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 at 30°C containing iodine and potassium iodide in a weight ratio of 1:7. 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 adopted for the cross-linking treatment. In the first stage crosslinking 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 boric acid content in the aqueous solution used in the first step crosslinking treatment was 5.0% by weight, and the potassium iodide content was 3.0% by weight. In the second stage crosslinking 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 boric acid content in the aqueous solution used in the second step crosslinking treatment was 4.3% by weight, and the potassium iodide content was 5.0% by weight. For the washing treatment, an aqueous potassium iodide solution at 20°C was used. The content of potassium iodide in the aqueous solution used in the washing treatment was 2.6% by weight. Drying treatment was performed under drying conditions at 70°C and 5 minutes.

(Production of polarizer P1)

A triacetylcellulose (TAC) film (made by Konica Minolta, product name “KC2UA”, thickness 25 μm) was bonded to each main surface of the above-produced polarizer using a polyvinyl alcohol-based adhesive. However, in the TAC film bonded to one main surface, a hard coat (7 μm thick) was formed on the main surface opposite to the polarizer side. In this way, polarizing plate P1 having the structure of protective layer with hard coat/polarizer/protective layer (without hard coat) was obtained.

<Production of phase contrast film R1>

(Production of the first retardation film)

26.2 parts by weight of isosorbide (ISB), 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 added to a reaction vessel and dissolved in a nitrogen atmosphere (about 15 minutes). At this time, the temperature of the heating medium in the reaction vessel was set to 150°C, and stirring was performed as necessary. Next, the pressure inside the reaction vessel was reduced to 13.3 kPa, and the heating medium temperature was raised to 190°C in 1 hour. The phenol generated with the increase in the temperature of the heating medium was discharged out of the reaction vessel (the same applies hereinafter). Next, the temperature in the reaction vessel was maintained at 190°C for 15 minutes, and then the pressure in the reaction vessel was changed to 6.67 kPa, and the heating medium temperature was raised to 230°C in 15 minutes. When the stirring torque of the stirrer equipped with the reaction vessel increased, the temperature of the heating medium was raised to 250°C in 8 minutes, and the pressure within the reaction vessel was set to 0.200 kPa or less. After reaching a predetermined stirring torque, the reaction was terminated, and the resulting reactant was extruded into water and pelletized. In this way, a polycarbonate resin having a composition of BHEPF/ISB/1,4-CHDM=47.4 mol%/37.1 mol%/15.5 mol% was obtained. The glass transition temperature of the obtained polycarbonate resin was 136.6°C, and the reduced viscosity was 0.395 dL/g.

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

(Production of the second retardation film)

20 parts by weight of a side-chain liquid crystal polymer (weight average molecular weight 5000) represented by the following 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) , 80 parts by weight of brand name "PaliocolorLC242"), and 5 parts by weight of a photopolymerization initiator (manufactured by Chiba Specialty Chemicals, brand name "Irgacure 907") were dissolved in 200 parts by weight of cyclopentanone to prepare a liquid crystal coating liquid. Next, the prepared liquid crystal coating liquid was applied to the surface of the base film, a norbornene-based resin film (manufactured by Nippon Zeon, brand name “Zeonex”) using a bar coater, and then heated and dried at 80°C for 4 minutes. The liquid crystal contained in the coating film was oriented. Next, the coating film was cured by irradiation of ultraviolet rays, and a liquid crystal solidified layer (thickness 0.58 μm) as a second retardation film was formed on the base film. The in-plane phase difference Re of the liquid crystal frozen layer for light with a wavelength of 550 nm is 0 nm, the phase difference Rth in the thickness direction is -71 nm (nx = 1.5326, ny = 1.5326, nz = 1.6550), and the liquid crystal frozen layer is nz>nx. = showed refractive index characteristics of ny.

(Production of phase contrast film R1)

One side of the first retardation film produced above and the liquid crystal solidified layer of the second retardation film were bonded through an adhesive to produce retardation film R1.

<Production of circular polarizer with adhesive sheet>

(Production of interlayer adhesive)

A four-necked flask equipped with a stirring blade, thermometer, nitrogen gas introduction tube, and condenser contained 79.9 parts by weight of butylacrylate, 15 parts by weight of benzyl acrylate, 5 parts by weight of acrylic acid, and 0.1 part by weight of 4-hydroxybutylacrylate. A monomer mixture was added. Next, 0.1 part by weight of 2,2'-azoisobutyronitrile as a polymerization initiator was added with ethyl acetate to 100 parts by weight of the monomer mixture, and nitrogen gas was introduced while gently stirring to purge the flask with nitrogen. , the liquid temperature in the flask was maintained at around 55°C, and the polymerization reaction proceeded for 7 hours. Next, ethyl acetate was added to the obtained reaction liquid to adjust the solid content concentration to 30% by weight to obtain a solution of the (meth)acrylic polymer used in the interlayer adhesive. The weight average molecular weight of the obtained polymer was 2.2 million.

Next, to the solution of the obtained (meth)acrylic polymer, 0.5 parts by weight of trimethylolpropane/tolylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, brand name "Coronate L") and peroxide, based on 100 parts by weight of solid content of the solution. 0.1 parts by weight of benzoyl peroxide as a crosslinking agent, 0.2 parts by weight of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., brand name “KBM-403”), and 0.5 parts by weight of a polyether compound having a reactive silyl group (Kaneka Co., Ltd., Cyryl SAT10). Parts by weight were mixed to obtain an adhesive composition PSA1 used as an interlayer adhesive for bonding the polarizer P1 and the retardation film R1.

(Production of a polarizing plate with an interlayer adhesive layer)

After drying, the prepared adhesive composition PSA1 was applied to the peeling surface of a 38-μm-thick polyethylene terephthalate (PET) film (Mitsubishi Chemical Polyester Film, MRF38), which is a peeling liner whose peeling surface was treated with silicone. It was applied to a layer thickness of 12 μm and dried at 155°C for 1 minute to form an interlayer adhesive layer. Next, the formed interlayer adhesive layer was transferred to the protective layer (without hard coat) side of the polarizing plate P1, and a polarizing plate provided with an interlayer adhesive layer was obtained.

(Production of a circularly polarizing plate with an adhesive sheet)

Each of the adhesive sheets produced in the Examples and Comparative Examples was transferred from the release liner to 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 was peeled off). Attached. Next, the polarizing plate provided with the interlayer adhesive layer produced above was attached to the first retardation film side of retardation film R1 through the interlayer adhesive layer, thereby obtaining a circularly polarizing plate provided with an adhesive sheet. The attachment of the polarizing plate including the retardation film R1 and the interlayer adhesive layer was performed so that the angle between the slow axis of the first retardation film and the absorption axis of the polarizer was 45 degrees counterclockwise when viewed from the side of the first retardation film.

As can be seen from Table 3, the adhesive sheet of the example in which the gel fraction was 70% or more and the maximum frequency F _max in the histogram of the elastic modulus was 1400 or more had improved durability compared to the adhesive sheet in the comparative example. .

The adhesive composition of the present invention can be suitably used in the production of adhesive sheets included in image display devices such as EL displays and liquid crystal displays.

Claims (15)

Comprising an adhesive sheet having a gel fraction of 70% or more and an optical film,
An optical laminate in which the maximum value of the frequency in a histogram prepared by the following test method is 1400 or more.
Test method: Using an atomic force microscope, the elastic modulus is measured so that the number of measurement points is 65536 in a range of 500 nm in length x 500 nm in width on the surface of the adhesive sheet, and the above-described elasticity has a rank width of 0.1 MPa. Create a histogram of elastic modulus. It is an adhesive sheet with a gel fraction of 70% or more,
An adhesive sheet in which the maximum frequency in a histogram created by the test method below is 1400 or more.
Test method: Using an atomic force microscope, the elastic modulus is measured so that the number of measurement points is 65536 in a range of 500 nm in length × 500 nm in width on the surface of the adhesive sheet, and the above-described elasticity has a rank width of 0.1 MPa. Create a histogram of elastic modulus. According to paragraph 2,
In the histogram, the elastic modulus G _max corresponding to the maximum value is within the range of 10 to 100 MPa. According to paragraph 2 or 3,
An adhesive sheet, wherein the coefficient of variation of the elastic modulus measured by the test method is less than 0.08. According to any one of claims 2 to 4,
An adhesive sheet, wherein the coefficient of variation of the elastic modulus measured by the test method is 0.035 or more. According to any one of claims 2 to 5,
In the histogram, the ratio of the sum of the frequencies included in the range of ±2.0 MPa from the elastic modulus G _max (MPa) corresponding to the maximum value to the total frequency is 70% or more. According to any one of claims 2 to 6,
An adhesive sheet having a storage modulus G' at 25°C of 0.1 MPa or more. According to any one of claims 2 to 7,
An adhesive sheet having a haze of 1.0% or less. According to any one of claims 2 to 8,
An adhesive sheet formed from an adhesive composition containing a (meth)acrylic polymer (A) and a crosslinking agent (B). According to clause 9,
The crosslinking agent (B) is an adhesive sheet containing at least one selected from the group consisting of an isocyanate-based crosslinking agent and a polyfunctional (meth)acrylate-based crosslinking agent. According to claim 9 or 10,
A pressure-sensitive adhesive sheet, wherein the amount of the crosslinking agent (B) in the pressure-sensitive adhesive composition is 2 parts by weight or more based on 100 parts by weight of the (meth)acrylic polymer (A). According to any one of claims 9 to 11,
The adhesive composition is a solvent-based or active energy ray-curable adhesive sheet. An optical laminate comprising the adhesive sheet according to any one of claims 2 to 12 and an optical film. An image display device comprising the optical laminated body according to claim 13. It is an adhesive sheet with a gel fraction of 70% or more,
An adhesive sheet, wherein the coefficient of variation of elastic modulus measured by the following test method is less than 0.08.
Test method: Using an atomic force microscope, the elastic modulus is measured so that the number of measurement points is 65536 over a range of 500 nm in length x 500 nm in width on the surface of the adhesive sheet.

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