Polymer, tackifying agent, adhesive composition, adhesive sheet, optical laminate and picture display unit

Abstract

To provide a polymer usable for an adhesive composition, the polymer suitable for a use to an optical laminate or a picture display unit, while suitable for manufacturing an adhesive sheet with improved adhesive strength.SOLUTION: A polymer has a weight-average molecular weight of 1500 to 30000, a glass-transition temperature of 30°C or lower, and a refractive index of 1.51 or more. The polymer may have δH (hydrogen bond term of Hansen solubility parameter) of 5.15 or less. The polymer includes a constitutional unit derived from a monomer b having a double bond-containing ring.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polymer, a tackifier, a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, an optical laminate, and an image display device. [Background technology]

[0002] In recent years, image display devices, such as liquid crystal display devices and electroluminescence (EL) display devices (e.g., organic EL display devices and inorganic EL display devices), have rapidly become popular. Image display devices generally include an optical laminate containing optical substrates such as a polarizing film and a retardation film. In an optical laminate containing multiple optical substrates, a bonding layer is usually disposed between adjacent optical substrates to bond them together. One example of the bonding layer is a pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition.

[0003] Patent Document 1 discloses an example of a pressure-sensitive adhesive sheet. In Patent Document 1, the pressure-sensitive adhesive sheet is produced from a thermosetting pressure-sensitive adhesive composition. In addition to the thermosetting pressure-sensitive adhesive composition, a photocurable pressure-sensitive adhesive composition that can be used to produce a pressure-sensitive adhesive sheet by utilizing light is also known. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-14376 Summary of the Invention [Problem to be solved by the invention]

[0005] The use of a pressure-sensitive adhesive sheet having a high refractive index is advantageous for improving the surface brightness of an image display device. However, according to the studies of the present inventors, there is room for improvement in the adhesive strength of a high refractive index pressure-sensitive adhesive sheet.

[0006] An object of the present invention is to provide a polymer that can be used in a pressure-sensitive adhesive composition, which is suitable for use in optical laminates and image display devices, and is also suitable for producing pressure-sensitive adhesive sheets with improved adhesive strength. [Means for solving the problem]

[0007] [1] The polymer according to an embodiment of the present invention is It has a weight average molecular weight of 1,500 to 30,000, a glass transition temperature of 30°C or lower, and a refractive index of 1.51 or higher. [2] The polymer according to the above item [1] may have a ΔH of 5.15 or less, where ΔH is the hydrogen bond term of the Hansen solubility parameter (HSP). [3] The color of the polymer according to [1] or [2] above is CIE1976 L defined in JIS Z8781-4:2013. * ,a * ,b * Color space chromaticity b * The absolute value of may be 1.1 or less. [4] The weight average molecular weight of the polymer according to any one of [1] to [3] above may be 2,400 to 16,000. [5] The polymer according to any one of [1] to [4] above may contain a structural unit derived from a monomer b having a double bond-containing ring. [6] In the polymer according to the above item [5], the double bond-containing ring may be an aromatic ring. [7] In the polymer according to the above [5] or [6], the monomer b may have two or more of the double bond-containing rings in its side chain. [8] In the polymer according to any one of [5] to [7] above, the monomer b may have, in its side chain, a structure in which a first double bond-containing ring and a second double bond-containing ring included in the two or more double bond-containing rings are bonded via a linking group. [9] In the polymer according to any one of the above items [5] to [8], the monomer b may be phenoxybenzyl acrylate.

[10] The polymer according to any one of [5] to [9] above may have a content of the structural units derived from the monomer b of 50% by weight or more.

[11] A tackifier according to an embodiment of the present invention comprises the polymer according to any one of [1] to

[10] above.

[12] A tackifier according to an embodiment of the present invention comprises a polymer having a weight-average molecular weight of 1,500 to 30,000, the polymer comprising a structural unit derived from a monomer b having a double bond-containing ring, and the monomer b having two or more of the double bond-containing rings in its side chain.

[13] A pressure-sensitive adhesive composition according to an embodiment of the present invention is a photocurable pressure-sensitive adhesive composition comprising a monomer component M and the polymer described in any one of [1] to

[10] above, or the tackifier described in

[11] or

[12] above.

[14] A pressure-sensitive adhesive sheet according to an embodiment of the present invention is a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition described in

[13] above.

[15] An optical laminate according to an embodiment of the present invention comprises the pressure-sensitive adhesive sheet according to

[14] above and an optical film.

[16] An image display device according to an embodiment of the present invention includes the optical laminate described in

[15] above. [Effects of the Invention]

[0008] According to an embodiment of the present invention, it is possible to provide a polymer that can be used in a pressure-sensitive adhesive composition, and that is suitable for use in optical laminates and image display devices, and also suitable for producing pressure-sensitive adhesive sheets with improved adhesive strength. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention. [Figure 2] 1 is a schematic diagram illustrating an example of a method for forming a pressure-sensitive adhesive sheet from the pressure-sensitive adhesive composition of the present invention. [Figure 3] 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. [Figure 4]1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. [Figure 5] 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. [Figure 6] 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. [Figure 7] 1 is a schematic cross-sectional view of an image display device according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Terminology] In this specification, when the expression "weight" appears, it may be read as "mass," which is the commonly used SI unit for indicating weight, and vice versa.

[0011] In this specification, the expression "(meth)acrylic" means "acrylic and / or methacrylic", the expression "(meth)acrylate" means "acrylate and / or methacrylate", the expression "(meth)allyl" means "allyl and / or methallyl", and the expression "(meth)acrolein" means "acrolein and / or methacrolein".

[0012] In this specification, when the term "100 parts by weight of monomer component M" is used as a standard for the content of various components in a pressure-sensitive adhesive composition, it means the total amount of the monomer component M that is not partially polymerized and is contained in the pressure-sensitive adhesive composition, and the monomer component M that is consumed in forming a partially polymerized product that may be contained in the pressure-sensitive adhesive composition.

[0013] In this specification, when the reference is made to "100 parts by weight of the total of monomer component M and inorganic particles" as a standard for the content of various components in a pressure-sensitive adhesive composition, this refers to the total amount of non-partially polymerized monomer component M contained in the pressure-sensitive adhesive composition, monomer component M consumed in forming a partially polymerized product that may be contained in the pressure-sensitive adhesive composition, and inorganic particles.

[0014] <<1. Polymer B>> A polymer according to an embodiment of the present invention (hereinafter referred to as "polymer B") has (I) a weight-average molecular weight of 1,500 to 30,000, (II) a glass transition temperature of 30° C. or lower, and (III) a refractive index of 1.51 or higher. Polymer B can be used, for example, as an additive in a pressure-sensitive adhesive composition.

[0015] ≪1-1. Properties of Polymer B≫ <1-1-a. Weight average molecular weight> Polymer B has a weight-average molecular weight (hereinafter referred to as "Mw") of 1500 to 30,000. An Mw of 1500 to 30,000 can contribute to improving the adhesive strength of the pressure-sensitive adhesive sheet. An Mw of 1500 to 30,000 can also contribute to improving compatibility with the pressure-sensitive adhesive composition and thereby ensuring the optical properties of the pressure-sensitive adhesive sheet, for example, suppressing an increase in haze caused by the addition of polymer B. Pressure-sensitive adhesive sheets with suppressed haze are suitable for use in optical laminates and image display devices.

[0016] Mw may be 25,000 or less, 20,000 or less, 18,000 or less, 16,000 or less, 15,000 or less, 13,000 or less, 10,000 or less, 8,000 or less, or even 6,000 or less. Mw may be 1,500 or more, 2,000 or more, 2,400 or more, 2,500 or more, 3,000 or more, 3,500 or more, or even 4,000 or more. Mw may be 2,000 to 16,000, 2,400 to 16,000, or even 4,000 to 16,000.

[0017] The Mw of polymer B can be determined as a polystyrene equivalent value by gel permeation chromatography (GPC). However, when evaluating the Mw and other properties described herein, the solvent content in polymer B is set to less than 0.1% by weight by sufficient drying. Drying may be performed using heat, reduced pressure, or electromagnetic radiation.

[0018] <1-1-b. Glass transition temperature> Polymer B has a glass transition temperature (hereinafter referred to as "Tg") of 30°C or less. A Tg of 30°C or less can contribute to improving the adhesive strength of the pressure-sensitive adhesive sheet. A Tg of 30°C or less can also contribute to improving compatibility with the pressure-sensitive adhesive composition and thereby ensuring the optical properties of the pressure-sensitive adhesive sheet, for example, suppressing an increase in haze due to the addition of polymer B.

[0019] The Tg may be 50° C. or lower, 45° C. or lower, 40° C. or lower, 35° C. or lower, 30° C. or lower, 25° C. or lower, 20° C. or lower, 15° C. or lower, 10° C. or lower, 8° C. or lower, 5° C. or lower, 2° C. or lower, 1° C. or lower, 0° C. or lower, −1° C. or lower, −2° C. or lower, −3° C. or lower, −4° C. or lower, −5° C. or lower, or even −6° C. or lower. The lower limit of the Tg may be, for example, −50° C. or higher, −45° C. or higher, −40° C. or higher, −35° C. or higher, −30° C. or higher, −25° C. or higher, −20° C. or higher, −15° C. or higher, or even −10° C. or higher.

[0020] The Tg of polymer B can be determined by differential scanning calorimetry (DSC). The specific measurement method is as follows: First, the object to be measured (polymer B) and a reference (standard substance) are prepared and sealed in an aluminum sample pan. Next, DSC measurement of the object to be measured is performed using a differential scanning calorimeter (e.g., Q2000 manufactured by TA Instruments). Three cycles of measurement are performed, with the heating and cooling rates during the measurement being 10°C / min. The measurement is also performed within a range of at least ±70°C based on the temperature at which the baseline shifts. During the heating process of each cycle, the midpoint temperature between the inflection point on the low-side and the inflection point on the high-side of the baseline shift is determined, and this temperature is taken as the Tg of the object to be measured in each cycle. The average of the Tg values ​​in the second and third cycles is determined as the Tg of polymer B.

[0021] <1-1-c. Refractive index> Polymer B has a refractive index of 1.51 or more. A refractive index of 1.51 or more can contribute to improving the refractive index of the pressure-sensitive adhesive sheet. A refractive index of 1.51 or more can also contribute to ensuring the optical properties of the pressure-sensitive adhesive sheet, for example, suppressing an increase in haze caused by adding polymer B to a pressure-sensitive adhesive composition with a high refractive index.

[0022] The refractive index may be 1.52 or more, 1.53 or more, 1.54 or more, 1.55 or more, 1.56 or more, 1.57 or more, 1.58 or more, 1.59 or more, or even 1.595 or more. The upper limit of the refractive index is, for example, 3.00 or less, and may be 2.50 or less, 2.00 or less, 1.90 or less, 1.80 or less, 1.70 or less, 1.69 or less, 1.68 or less, 1.67 or less, 1.66 or less, 1.65 or less, 1.64 or less, 1.63 or less, 1.62 or less, 1.61 or less, or even 1.60 or less.

[0023] The refractive index of polymer B can be measured using an Abbe refractometer at a wavelength of 589 nm and a temperature of 25°C. The Abbe refractometer may be a DR-M4 model manufactured by ATAGO or an equivalent (e.g., DR-M2 model). As described above, the evaluation sample of polymer B is prepared by reducing the solvent content to less than 0.1% by vacuum drying or other methods. The sample is dropped onto a smooth glass substrate to form a laminate of glass and polymer B, and the surface of the polymer B is then brought into contact with the prism, which is the measurement unit of the Abbe refractometer. The sample is then left at room temperature for approximately 10 minutes to allow a clear interface between the prism and polymer B to form, and measurement is then performed at 25°C. If the Tg of polymer B is high and it is difficult to form a clear interface between the prism and polymer B, the interface may be formed by heating to approximately 50°C. In this case, measurement is performed after the temperature returns to 25°C.

[0024] <1-1-d. Hansen Solubility Parameter (HSP)> The δH of polymer B may be 5.15 or less, where δH is the hydrogen bond term of the Hansen solubility parameter (HSP). Suppressing δH to 5.15 or less can contribute to suppressing gelation when forming a pressure-sensitive adhesive sheet from a pressure-sensitive adhesive composition containing polymer B.

[0025] ΔH may be 5.10 or less, 5.05 or less, 5.00 or less, 4.95 or less, 4.90 or less, 4.85 or less, 4.80 or less, 4.75 or less, 4.70 or less, or even 4.65 or less. The lower limit of ΔH is, for example, 3.70 or more, and may be 3.80 or more, 3.90 or more, 4.00 or more, 4.10 or more, 4.20 or more, or even 4.30 or more.

[0026] The Hansen solubility parameter (HSP) is a solubility parameter introduced by Hildebrand, divided into three components: the dispersion term δD, the polarization term δP, and the hydrogen bonding term δH. δD represents the energy derived from the dispersion force between molecules. δP represents the energy derived from the polar force between molecules. δH represents the energy derived from the hydrogen bonding force between molecules. The units of each component are usually MPa. 1 / 2 The above three components define a point (vector) in a three-dimensional space known as Hansen space. Details of the Hansen solubility parameters are disclosed in "Hansen Solubility Parameters; A Users Handbook (CRC Press, 2007)." The δD, δP, and δH of polymer B can be determined by calculation using known software such as HSPiP (version 5) based on the structural units contained in polymer B and the content of those units in polymer B. More specifically, the δD, δP, and δH of each structural unit can be calculated individually, and the calculated δD, δP, and δH can be weighted by the content of those units to obtain weighted average values, which can then be used as the δD, δP, and δH of polymer B. However, the calculations are performed at a temperature of 23°C.

[0027] The ΔP of Polymer B may be 3.15 or more, 3.20 or more, 3.30 or more, 3.40 or more, 3.50 or more, 3.60 or more, 3.70 or more, or even 3.80 or more. The upper limit of ΔP is, for example, 5.00 or less, and may be 4.90 or less, 4.80 or less, 4.70 or less, 4.60 or less, 4.50 or less, 4.40 or less, 4.30 or less, 4.20 or less, 4.10 or less, 4.00 or less, or even 3.90 or less. As described above, ΔP is the polarization term of the HSP.

[0028] The δD of polymer B may be 17.85 or more, 17.90 or more, 18.00 or more, 18.10 or more, 18.20 or more, 18.30 or more, 18.40 or more, 18.50 or more, 18.60 or more, or even 18.65 or more. The upper limit of δD is, for example, 20.00 or less, and may be 19.75 or less, 19.50 or less, 19.25 or less, 19.00 or less, 18.90 or less, or even 18.80 or less, or 18.70 or less.

[0029] <1-1-e.Chromaticity> The color of polymer B is CIE1976 L defined in Japanese Industrial Standard (JIS) Z8781-4:2013. * ,a * ,b * Color space chromaticity b * The absolute value of chromaticity b may be 1.1 or less. * The absolute value of chromaticity b may be 1.0 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, or even 0.3 or less. * The lower limit of the absolute value of is 0 (zero), and it may be 0.05 or more, 0.1 or more, or even 0.2 or more.

[0030] The chromaticity of polymer B can be determined as follows. First, a non-alkali glass plate (thickness 0.7-0.8 mm, total light transmittance 92%, chromaticity b *Two sheets of glass (0.20) are prepared. Next, polyimide tape (50 μm thick) is attached to one side of one alkali-free glass plate in a frame-like shape. This attachment creates an area surrounded on all four sides by the polyimide tape. Polymer B to be evaluated is then heated to a flowable state, and an appropriate amount is placed in the area. Polymer B is then spread using another alkali-free glass sheet, creating a test piece in which polymer B is sandwiched between the two alkali-free glass sheets in a 50 μm-thick sheet shape. After cooling the test piece to room temperature, the light transmittance of the test piece for light with wavelengths from 300 nm to 800 nm is measured using an analytical device such as a spectrophotometer (e.g., Hitachi High-Tech's UV-Visible-Near-Infrared Spectrophotometer UH4150) in a measurement environment of 23°C. From the spectral data obtained by the measurement, chromaticity b is calculated using analysis software (e.g., Hitachi High-Tech's UV Solutions color calculation program). * The absolute value of chromaticity b * When specifying the absolute value, reference data (blank data) measured without placing a sample in the analyzer is used as the standard.

[0031] 1-2. Composition of Polymer B <1-2-a. Monomer b having a double bond-containing ring> Polymer B preferably contains a structural unit derived from monomer b having a double bond-containing ring. Polymer B containing a structural unit derived from monomer b can contribute to improving the refractive index of the pressure-sensitive adhesive sheet. Polymer B may contain structural units derived from one or more types of monomer b.

[0032] In this specification, the double bond-containing ring refers to a ring in which at least one of the bonds constituting the ring is a double bond. Examples of the double bond include a carbon-carbon double bond, a carbon-heteroatom double bond, and a heteroatom-heteroatom double bond. Examples of the heteroatom include nitrogen, sulfur, and oxygen.

[0033] The number of double bonds in the double bond-containing ring is not particularly limited and may be, for example, 1 to 10, or 2 to 5. When the double bond-containing ring contains two or more double bonds, these double bonds may be conjugated or non-conjugated. The double bond-containing ring is preferably an aromatic ring.

[0034] The double bond-containing ring may be a carbocyclic ring. Examples of the carbocyclic ring include a benzene ring (which may be a benzene ring constituting a part of a biphenyl structure or a fluorene structure), a naphthalene ring, an indene ring, an azulene ring, an anthracene ring, and a phenanthrene ring. The double bond-containing ring may be a heterocyclic ring. Examples of the heterocyclic ring include a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazine ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring, an oxazole ring, an isoxazole ring, a thiazole ring, and a thiophene ring. Examples of heteroatoms that may be contained in the heterocyclic ring as ring-constituting atoms include at least one selected from the group consisting of nitrogen, sulfur, and oxygen. The heteroatom may be either or both of nitrogen and sulfur. The double bond-containing ring may be a fused ring. An example of the monomer b has a structure in which one or more carbocyclic rings and one or more heterocyclic rings are fused, such as a dinaphthothiophene structure.

[0035] The double bond-containing ring may have one or more substituents (excluding ethylenically unsaturated groups, which will be described later) on the ring-constituting atoms, or may have no substituents. Examples of the substituents include alkyl groups, alkoxy groups, aryloxy groups, hydroxyl groups, halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, etc.), hydroxyalkyl groups, hydroxyalkyloxy groups, and glycidyloxy groups. However, the substituents are not limited to the above examples. The substituents may contain carbon atoms, and in such cases, the number of carbon atoms contained in the substituent is, for example, 1 to 4, 1 to 3, or even 1 to 2. One example of the double bond-containing ring has no substituents on the ring-constituting atoms. Another example of the double bond-containing ring has one or more substituents selected from the group consisting of alkyl groups, alkoxy groups, and halogen atoms (e.g., bromine atoms) on the ring-constituting atoms.

[0036] In the monomer b, the number of double bond-containing rings contained in one molecule is, for example, 1, and may be 2 or more. The upper limit of the number of double bond-containing rings is not particularly limited and is, for example, 16 or less. The upper limit may be 12 or less, 8 or less, 6 or less, 5 or less, 4 or less, 3 or less, or even 2 or less.

[0037] In the monomer b, the double bond-containing ring is preferably located in a side chain. In other words, the monomer b preferably has at least one double bond-containing ring and at least one ethylenically unsaturated group in one molecule. As the monomer b, a compound containing one ethylenically unsaturated group in one molecule (in other words, a monofunctional monomer) is preferably used. The monomer b may have two or more double bond-containing rings in its side chain.

[0038] Monomer b may have a structure in its side chain in which a first double bond-containing ring and a second double bond-containing ring contained in two or more double bond-containing rings are bonded via a linking group. Polymer B containing a structural unit derived from monomer b having such a structure in its side chain tends to be less likely to crystallize. If crystallization occurs, mixing of polymer B into the pressure-sensitive adhesive composition may be hindered.

[0039] The linking group that may be present between the first double bond-containing ring and the second double bond-containing ring may contain atoms such as P, Ge, Te, Se, N, S, and Si, and these atoms may be bonded to an oxygen atom. However, the linking group does not necessarily contain the above atoms. Examples of linking groups include an oxy group (-O-), a thiooxy group (-S-), an oxyalkylene group (e.g., -O-(CH2)), and the like. n -; n is 1 to 3, preferably 1), a thiooxyalkylene group (e.g., -S-(CH2) n -; n is 1 to 3, preferably 1), a straight-chain alkylene group (-(CH2) n-; n is 1 to 6, preferably 1 to 3), and the above-mentioned oxyalkylene group, the above-mentioned thiooxyalkylene group, and the above-mentioned straight-chain alkylene group in which the alkylene group is partially or completely halogenated. The linking group may contain one or more types selected from the group consisting of an oxy group, a thiooxy group, an oxyalkylene group, and a straight-chain alkylene group. The linking group may contain an oxy group.

[0040] Examples of the ethylenically unsaturated group are a (meth)acryloyl group, a vinyl group, and a (meth)allyl group. From the viewpoint of polymerization reactivity, a (meth)acryloyl group is preferred, and from the viewpoint of flexibility and adhesiveness, an acryloyl group is more preferred. In other words, monomer b preferably contains a (meth)acrylic monomer having a double bond-containing ring, and more preferably contains an acrylic monomer having a double bond-containing ring. Examples of the (meth)acrylic monomer having a double bond-containing ring include aromatic ring-containing (meth)acrylates. Specific examples of aromatic ring-containing (meth)acrylates will be described later.

[0041] The double bond-containing ring and the ethylenically unsaturated group may be bonded directly or via a linking group. Examples of linking groups that may be present between the double bond-containing ring and the ethylenically unsaturated group include one or more selected from the group consisting of alkylene groups, oxyalkylene groups, poly(oxyalkylene) groups, phenyl groups, alkylphenyl groups, alkoxyphenyl groups, groups in which one or more hydrogen atoms in these groups have been substituted with hydroxyl groups (e.g., hydroxyalkylene groups), oxy groups (-O-), and thiooxy groups (-S-). In one example of Monomer b, the double bond-containing ring and the ethylenically unsaturated group are bonded directly. In another example of Monomer b, the double bond-containing ring and the ethylenically unsaturated group are bonded via a linking group selected from the group consisting of alkylene groups, oxyalkylene groups, and poly(oxyalkylene) groups. The number of carbon atoms in the alkylene group and oxyalkylene group that may be included in the linking group is, for example, 1 to 4, and may be 1 to 3, or even 1 to 2. The number of repeating oxyalkylene units in the poly(oxyalkylene) group that can be contained in the linking group is, for example, 1 to 8, and may be 1 to 6, 1 to 4, 1 to 3, 2 to 3, or even 1 to 2, 2, or 1.

[0042] Specific examples of the monomer b are aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds. The aromatic ring-containing (meth)acrylates and aromatic ring-containing vinyl compounds may be used alone or in combination of two or more.

[0043] Monomer b may contain two or more aromatic rings (preferably carbon rings) in one molecule. A monomer having two or more aromatic rings and at least one ethylenically unsaturated group in one molecule (aromatic ring-containing monomer) is particularly suitable for increasing the refractive index of the pressure-sensitive adhesive sheet. The two or more aromatic rings may be located on the side chain of monomer b.

[0044] Examples of the aromatic ring-containing monomer include a monomer having a structure in which two or more non-fused aromatic rings are bonded via a linking group, a monomer having a structure in which two or more non-fused aromatic rings are directly bonded, a monomer having a fused ring, a monomer having a fluorene structure, a monomer having a dinaphthothiophene structure, and a monomer having a dibenzothiophene structure. The aromatic ring-containing monomer may have the above structure in its side chain. Among these, a monomer having a structure in which two or more non-fused aromatic rings are bonded via a linking group in its side chain (for example, phenoxybenzyl (meth)acrylate, which will be described later) is preferably used.

[0045] Examples of linking groups that may be present between two or more non-fused aromatic rings are the same as the examples of linking groups that may be present between the first double bond-containing ring and the second double bond-containing ring.

[0046] Examples of monomers having a structure in which two or more non-fused aromatic rings are directly bonded include biphenyl structure-containing (meth)acrylates, triphenyl structure-containing (meth)acrylates, and vinyl group-containing biphenyls. Specific examples include o-phenylphenol (meth)acrylate, biphenyl (meth)acrylate, and biphenylmethyl (meth)acrylate.

[0047] Examples of monomers having a condensed ring include naphthalene ring-containing (meth)acrylates, anthracene ring-containing (meth)acrylates, vinyl group-containing naphthalenes, and vinyl group-containing anthracenes. Specific examples include 1-naphthylmethyl (meth)acrylate (also known as 1-naphthalenemethyl (meth)acrylate), hydroxyethylated β-naphthol acrylate, 2-naphthoethyl (meth)acrylate, 2-naphthoxyethyl acrylate, and 2-(4-methoxy-1-naphthoxy)ethyl (meth)acrylate.

[0048] Examples of monomers having a fluorene structure include 9,9-bis(4-hydroxyphenyl)fluorene(meth)acrylate and 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene(meth)acrylate. Note that, since monomers having a fluorene structure have a structure in which two benzene rings are directly bonded, they are included in the concept of monomers having a structure in which two or more non-fused aromatic rings are directly bonded.

[0049] Examples of the monomer having a dinaphthothiophene structure are (meth)acryloyl group-containing dinaphthothiophene, vinyl group-containing dinaphthothiophene, and (meth)allyl group-containing dinaphthothiophene. Specific examples include (meth)acryloyloxymethyl dinaphthothiophene (e.g., a compound having a structure in which a CHCH(R)C(O)OCH group is bonded to the 5th or 6th position of the dinaphthothiophene ring; R is a hydrogen atom or a methyl group), (meth)acryloyloxyethyl dinaphthothiophene (e.g., a compound having a structure in which a CHCH(R)C(O)OCH(CH) group or a CHCH(R)C(O)OCHCH group is bonded to the 5th or 6th position of the dinaphthothiophene ring; R is a hydrogen atom or a methyl group), vinyl dinaphthothiophene (e.g., a compound having a structure in which a vinyl group is bonded to the 5th or 6th position of the naphthothiophene ring), and (meth)allyloxy dinaphthothiophene. Incidentally, a monomer having a dinaphthothiophene structure is included in the concept of a monomer having a fused ring because it has a naphthalene structure and also has a structure in which a thiophene ring and two naphthalene structures are fused together.

[0050] Examples of monomers having a dibenzothiophene structure include (meth)acryloyl group-containing dibenzothiophenes and vinyl group-containing dibenzothiophenes. Note that, since monomers having a dibenzothiophene structure have a structure in which a thiophene ring and two benzene rings are fused, they are included in the concept of monomers having fused rings. Neither the dinaphthothiophene structure nor the dibenzothiophene structure corresponds to a structure in which two or more non-fused aromatic rings are directly bonded.

[0051] Monomer b may be a monomer having one aromatic ring (preferably a carbon ring) and at least one ethylenically unsaturated group in one molecule (aromatic ring-single-containing monomer).

[0052] Examples of aromatic ring-containing monomers include carbon aromatic ring-containing (meth)acrylates such as benzyl (meth)acrylate, methoxybenzyl (meth)acrylate, phenyl (meth)acrylate, ethoxylated phenol (meth)acrylate, phenoxypropyl (meth)acrylate, phenoxybutyl (meth)acrylate, cresyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and chlorobenzyl (meth)acrylate; 2-(4,6-dibromo-2-s-butylphenoxy)ethyl (meth)acrylate, 2-(4,6-dibromo-2-isopropylphenoxy)ethyl (meth)acrylate, and 6-(4 Bromine-substituted aromatic ring-containing (meth)acrylates such as 2,6-dibromo-4-nonylphenyl acrylate, 2,6-dibromo-4-dodecylphenyl acrylate; carbon-containing aromatic ring-containing vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, and tert-butylstyrene; and compounds having a vinyl substituent on a heteroaromatic ring such as N-vinylpyridine, N-vinylpyrimidine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, and N-vinyloxazole.

[0053] Monomer b may have a structure in which an oxyethylene chain is interposed between the ethylenically unsaturated group and the double bond-containing ring in the various monomers b described above. Monomers having such a structure can be understood as ethoxylated products of the original monomers. The number of repeating oxyethylene units (-CHCHO-) in the oxyethylene chain is, for example, 1 to 8, and may be 1 to 6, 1 to 4, 1 to 3, or even 1 to 2, or even 1. Examples of monomer b that is an ethoxylated product include ethoxylated o-phenylphenol (meth)acrylate, ethoxylated nonylphenol (meth)acrylate, ethoxylated cresol (meth)acrylate, phenoxyethyl (meth)acrylate, and phenoxydiethylene glycol (meth)acrylate.

[0054] Monomer b may include a high refractive index monomer. In this specification, the high refractive index monomer refers to a monomer having a refractive index of 1.51 or more, 1.53 or more, 1.55 or more, 1.56 or more, 1.57 or more, 1.58 or more, 1.59 or more, 1.60 or more, 1.61 or more, 1.62 or more, 1.63 or more, 1.64 or more, 1.65 or more, 1.66 or more, 1.67 or more, 1.68 or more, or even 1.69 or more. The upper limit of the refractive index of the high refractive index monomer is not particularly limited, and may be, for example, 3.00 or less, 2.50 or less, 2.00 or less, 1.90 or less, 1.80 or less, or even 1.70 or less. The high refractive index monomer may be used alone or in combination of two or more.

[0055] The refractive index of the monomer can be measured using an Abbe refractometer at a wavelength of 589 nm and a temperature of 25°C. The Abbe refractometer may be a DR-M4 model manufactured by ATAGO or an equivalent (e.g., DR-M2 model). If the nominal value of the refractive index at 25°C is provided by the monomer manufacturer, this nominal value can be used as the refractive index.

[0056] Examples of high refractive index monomers are phenoxybenzyl acrylate (refractive index 1.566), 1-naphthylmethyl acrylate (refractive index 1.595), ethoxylated o-phenylphenol acrylate (refractive index 1.578 when the number of repeating oxyethylene units is 1), benzyl acrylate (refractive index 1.519), phenoxyethyl acrylate (refractive index 1.517), and phenoxydiethylene glycol acrylate (refractive index 1.510). ), 6-acryloyloxymethyldinaphthothiophene (refractive index 1.75), 6-methacryloyloxymethyldinaphthothiophene (refractive index 1.726), 5-acryloyloxyethyldinaphthothiophene (refractive index 1.786), 6-acryloyloxyethyldinaphthothiophene (refractive index 1.722), 6-vinyldinaphthothiophene (refractive index 1.802), and 5-vinyldinaphthothiophene (refractive index 1.793). However, the high refractive index monomer is not limited to the above examples. It is preferable that monomer b contains phenoxybenzyl acrylate as a high refractive index monomer.

[0057] The content of the structural units derived from monomer b in polymer B is, for example, 10% by weight or more, and may be 30% by weight or more, 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, 97% by weight or more, 98% by weight or more, 99% by weight or more, or even 100% by weight. In some cases, the content may be 10% by weight or less, 5% by weight or less, or even 1% by weight or less. Polymer B may not contain any structural units derived from monomer b.

[0058] <1-2-b. Other Monomers> Polymer B may contain structural units derived from monomer c other than monomer b. An example of monomer c is a hydroxyl group-containing monomer. The hydroxyl group-containing monomer has at least one hydroxyl group and at least one ethylenically unsaturated group in one molecule. Polymer B may contain structural units derived from one or more hydroxyl group-containing monomers.

[0059] Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer b. The hydroxyl group-containing monomer may be a (meth)acrylic monomer.

[0060] Examples of the hydroxyl group-containing monomer are 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl acrylate. The hydroxyl group-containing monomer is preferably 4-hydroxybutyl (meth)acrylate.

[0061] The content of structural units derived from hydroxyl group-containing monomers in polymer B is, for example, 25% by weight or less, and may be 20% by weight or less, 15% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, less than 5% by weight, 4% by weight or less, 3% by weight or less, 2% by weight or less, or even 1% by weight or less. The lower limit of the content is, for example, 0.01% by weight or more, 0.1% by weight or more, or even 0.5% by weight or more. Polymer B may not contain structural units derived from hydroxyl group-containing monomers.

[0062] Polymer B contains structural units derived from hydroxyl group-containing monomers, and the content of structural units derived from hydroxyl group-containing monomers in polymer B may be less than 5% by weight, or may be 4% by weight or less, 3% by weight or less, 2% by weight or less, or even 1% by weight or less.

[0063] Another example of the monomer c is a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms on the side chain. The number of carbon atoms in the alkyl group may be 7 or less, 6 or less, 5 or less, or even 4 or less. The alkyl group may be linear or branched. The polymer B may contain structural units derived from one or more types of (meth)acrylic acid alkyl esters.

[0064] Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate (lauryl (meth)acrylate), n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, and octadecyl (meth)acrylate. The (meth)acrylic acid alkyl ester may be n-butyl (meth)acrylate.

[0065] The content of structural units derived from a (meth)acrylic acid alkyl ester in polymer B may be, for example, 50% by weight or less, 40% by weight or less, 30% by weight or less, 25% by weight or less, 20% by weight or less, 15% by weight or less, 10% by weight or less, 7% by weight or less, 5% by weight or less, or even 4% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. In some cases, the lower limit of the content may be 50% by weight or more. Polymer B may not contain structural units derived from a (meth)acrylic acid alkyl ester.

[0066] Another example of the monomer c is an aliphatic ring-containing monomer. The aliphatic ring-containing monomer has at least one aliphatic ring and at least one ethylenically unsaturated group in one molecule. Polymer B may contain structural units derived from one or more aliphatic ring-containing monomers.

[0067] Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer b. The aliphatic ring-containing monomer may be a (meth)acrylic monomer.

[0068] Examples of the aliphatic ring-containing monomer include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, cyclooctyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, tricyclopentanyl (meth)acrylate, and adamantyl (meth)acrylate.

[0069] The content of the structural units derived from the alicyclic-containing monomer in the polymer B is, for example, 50% by weight or less, and may be 40% by weight or less, 30% by weight or less, 25% by weight or less, 20% by weight or less, 15% by weight or less, 10% by weight or less, 7% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, or even 2% by weight or less. The lower limit of the content is, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. In some cases, the lower limit of the content may be 50% by weight or more, 80% by weight or more, or even 90% by weight or more. The polymer B may not contain any structural units derived from the alicyclic-containing monomer.

[0070] Polymer B may have a structural unit derived from a monomer having an acidic group. Another example of monomer c is a carboxyl group-containing monomer. The carboxyl group-containing monomer has at least one carboxyl group and at least one ethylenically unsaturated group in one molecule. Monomer component M may contain one or more carboxyl group-containing monomers. Polymer B may contain a structural unit derived from one or more carboxyl group-containing monomers.

[0071] Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer b. The carboxyl group-containing monomer may be a (meth)acrylic monomer.

[0072] The content of structural units derived from carboxyl group-containing monomers in polymer B is, for example, 10% by weight or less, and may be 7% by weight or less, 5% by weight or less, 3% by weight or less, or even 1% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. It is preferable that polymer B does not contain structural units derived from carboxyl group-containing monomers.

[0073] Polymer B contains structural units derived from carboxyl group-containing monomers, and the content of structural units derived from carboxyl group-containing monomers in Polymer B may be less than 1% by weight.

[0074] Another example of the monomer c is a nitrogen atom-containing monomer. The nitrogen atom-containing monomer refers to a monomer having at least one nitrogen atom in the molecule (per molecule).

[0075] Examples of the nitrogen atom-containing monomer include N-vinyl cyclic amide, (meth)acrylamide, etc. Polymer B may contain structural units derived from one or more nitrogen atom-containing monomers.

[0076] Examples of N-vinyl cyclic amides include N-vinyl-2-pyrrolidone (NVP), N-vinyl-2-piperidone, N-vinyl-2-caprolactam, N-vinyl-3-morpholinone, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, and vinylmethyloxazolidinone. Examples of (meth)acrylamides include (meth)acrylamide, N-alkyl(meth)acrylamide, and N,N-dialkyl(meth)acrylamide. Examples of (meth)acrylamides include various N-hydroxyalkyl(meth)acrylamides and N-alkoxyalkyl(meth)acrylamides.

[0077] Examples of nitrogen atom-containing monomers other than N-vinyl cyclic amides and (meth)acrylamides include amino group-containing monomers such as aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; cyano group-containing monomers such as acrylonitrile and methacrylonitrile; (meth)acryloylmorpholine, N-vinylpiperazine, N-vinylpyrrole, N-vinylimidazole, N-vinylpyrazine, N-vinylmorpholine, N-vinylpyrazole, vinylpyridine, vinylpyrimidine, vinyloxazole, vinylisoxazole, vinylthiazole, vinylisothiazole, vinylpyridazine, (meth)acryloylpyrrolidone, (meth)acryloylpyrrolidine, (meth)acryloylpiperidine, N-methylvinyl heterocycle-containing monomers such as N-isopropylpyrrolidone; maleimide-based monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide-based monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-laurylitaconimide, and N-cyclohexylitaconimide; imide group-containing monomers such as succinimide-based monomers of N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyoctamethylenesuccinimide; and isocyanate group-containing monomers such as 2-(meth)acryloyloxyethylisocyanate.

[0078] The content of the constitutional units derived from the nitrogen atom-containing monomer in polymer B is, for example, 25% by weight or less, and may be 20% by weight or less, 15% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, or even 1% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.1% by weight or more, or even 0.5% by weight or more. Polymer B may not contain constitutional units derived from the nitrogen atom-containing monomer.

[0079] Another example of monomer c is an ether group-containing monomer. The ether group-containing monomer has at least one ether group and at least one ethylenically unsaturated group in one molecule. Polymer B may contain structural units derived from one or more ether group-containing monomers.

[0080] Examples of the ethylenically unsaturated group are the same as those mentioned above in the description of monomer b. The ether group-containing monomer may be a (meth)acrylic monomer.

[0081] Examples of the ether group-containing monomer are 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, and methoxydipropylene glycol (meth)acrylate. The ether group-containing monomer is preferably 2-(2-ethoxyethoxy)ethyl acrylate (CBA).

[0082] The content of the structural units derived from the ether group-containing monomer in polymer B is, for example, 40% by weight or less, and may be 30% by weight or less, 25% by weight or less, 20% by weight or less, 15% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, or even 1% by weight or less. The lower limit of the content is, for example, 0.01% by weight or more, 0.1% by weight or more, or even 0.5% by weight or more. Polymer B may not contain any structural units derived from the ether group-containing monomer.

[0083] 1-3. Preparation of Polymer B Polymer B can be produced by known polymerization methods such as solution polymerization, radiation polymerization, bulk polymerization, emulsion polymerization, and various radical polymerizations such as polymerization under supercritical conditions. Radiation that can be used for radiation polymerization includes electron beams, UV rays, and microwaves. The resulting polymer B may be any of a random copolymer, a block copolymer, a graft copolymer, and the like.

[0084] <1-4. Uses of Polymer B> Polymer B can be used as a tackifier by being added to a pressure-sensitive adhesive composition, but the uses of Polymer B are not limited to the above examples.

[0085] 2. Tackifier 2-1. First tackifier The first tackifier according to the embodiment of the present invention comprises a polymer B. The polymer B contained in the first tackifier, including preferred examples, is as described above. The first tackifier may comprise one or more types of polymer B.

[0086] 2-2. Second tackifier A second tackifier according to an embodiment of the present invention comprises a polymer C having an Mw of 1,500 to 30,000. The polymer C comprises a structural unit derived from a monomer b having a double bond-containing ring. The monomer b has two or more double bond-containing rings in its side chain. The second tackifier may comprise one or more types of polymer C.

[0087] The range of Mw that polymer C can have is the same as the range of Mw that polymer B can have. Examples of constituent units derived from monomer b that polymer C can contain are the same as the examples of constituent units derived from monomer b having two or more double bond-containing rings in its side chain that polymer B can contain. For example, monomer b for polymer C may have a structure in its side chain in which a first double bond-containing ring and a second double bond-containing ring contained in the two or more double bond-containing rings are linked via a linking group. Furthermore, monomer b for polymer C may be phenoxybenzyl acrylate.

[0088] The range in which the content of the structural units derived from monomer b in polymer C can take is the same as the range in which the content of the structural units derived from monomer b in polymer B can take.

[0089] Polymer C may contain a constituent unit derived from a monomer c other than monomer b. Examples of monomer c and the ranges that can be taken for the content of each constituent unit derived from monomer c in polymer C are the same as the examples of monomer c for polymer B and the ranges that can be taken for the content of each constituent unit derived from monomer c in polymer B, respectively.

[0090] 2-3. Uses of tackifiers The first tackifier and the second tackifier can be added to a pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition is, for example, a photocurable type. The pressure-sensitive adhesive composition is, for example, an acrylic pressure-sensitive adhesive composition. However, the uses of the first tackifier and the second tackifier are not limited to the above examples. Furthermore, the types of pressure-sensitive adhesive compositions to which the first tackifier and the second tackifier can be added are not limited to the above examples.

[0091] <<3. Pressure-sensitive adhesive composition>> A pressure-sensitive adhesive composition according to an embodiment of the present invention (hereinafter referred to as "pressure-sensitive adhesive composition A") comprises a monomer component M, a polymer B, and a first tackifier or a second tackifier. A portion of the monomer component M may be partially polymerized. The pressure-sensitive adhesive composition A is a photocurable pressure-sensitive adhesive composition that forms a pressure-sensitive adhesive sheet by irradiation with light. Note that being a photocurable pressure-sensitive adhesive composition is particularly preferable in terms of environmental protection and sustainability, as it can reduce the amount of energy required to form a pressure-sensitive adhesive sheet compared to a thermosetting pressure-sensitive adhesive composition that mainly uses heat to form a pressure-sensitive adhesive sheet.

[0092] 3-1. Polymer B, First Tackifier, and Second Tackifier The polymer B, first tackifier, and second tackifier that may be contained in the PSA composition A are as described above. The PSA composition A may contain one or more types of polymer B. The PSA composition A may contain one or more types of first tackifiers. The PSA composition A may contain one or more types of second tackifiers.

[0093] The content of polymer B in pressure-sensitive adhesive composition A is, for example, 0.1 parts by weight or more, and may be 0.5 parts by weight or more, 1.0 parts by weight or more, 2.0 parts by weight or more, 3.0 parts by weight or more, 4.0 parts by weight or more, 5.0 parts by weight or more, 6.0 parts by weight or more, 7.0 parts by weight or more, 8.0 parts by weight or more, 9.0 parts by weight or more, 10.0 parts by weight or more, 15 parts by weight or more, 20 parts by weight or more, 25 parts by weight or more, 30 parts by weight or more, 35 parts by weight or more, or even 40 parts by weight or more, relative to 100 parts by weight of monomer component M. The upper limit of the content is, for example, 60 parts by weight or less, 55 parts by weight or less, 50 parts by weight or less, or even 45 parts by weight or less.

[0094] When the pressure-sensitive adhesive composition A contains inorganic particles (described below), the content of the polymer B relative to 100 parts by weight of the total of the monomer component M and the inorganic particles (specifically, a mixture of the inorganic particles and the dispersant) may be 0.1 parts by weight or more, 0.5 parts by weight or more, 1 part by weight or more, 2 parts by weight or more, 3 parts by weight or more, 4 parts by weight or more, 5 parts by weight or more, 6 parts by weight or more, 7 parts by weight or more, 8 parts by weight or more, 9 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, or even 20 parts by weight or more. The upper limit of the content may be 50 parts by weight or less, 40 parts by weight or less, 35 parts by weight or less, or even 30 parts by weight or less. The content may be 1 to 30 parts by weight, or even 2 to 30 parts by weight.

[0095] The ranges within which the contents of the first tackifier and the second tackifier in the pressure-sensitive adhesive composition A can fall are the same as the ranges within which the content of the polymer B in the pressure-sensitive adhesive composition A can fall.

[0096] 3-2. Monomer component M <3-2-a. Monomer a having a double bond-containing ring> Monomer component M may contain a monomer a having a double bond-containing ring. Monomer a is a component suitable for improving the refractive index of the pressure-sensitive adhesive sheet.

[0097] Examples of monomer a are the same as the examples of monomer b. Monomer a may be the same as or different from monomer b.

[0098] In the monomer a, the double bond-containing ring is preferably an aromatic ring. The monomer a may contain two or more aromatic rings (preferably carbon rings) in one molecule, and preferably contains a monomer having two or more aromatic rings and at least one ethylenically unsaturated group in one molecule (a monomer containing multiple aromatic rings). The monomer a may have a structure in its side chain in which a first double bond-containing ring and a second double bond-containing ring contained in two or more double bond-containing rings are bonded via a linking group. It is particularly preferable that the monomer a contains phenoxybenzyl acrylate.

[0099] The content of monomer a in monomer component M is, for example, 30% by weight or more, and may be 50% by weight or more, 60% by weight or more, 65% by weight or more, 70% by weight or more, more than 70% by weight, 75% by weight or more, 80% by weight or more, 85% by weight or more, 87% by weight or more, 90% by weight or more, 91% by weight or more, 92% by weight or more, 93% by weight or more, 94% by weight or more, 95% by weight or more, 96% by weight or more, 97% by weight or more, 98% by weight or more, or even 99% by weight or more. The upper limit of the content is, for example, 100% by weight, and may be 98% by weight or less, 97% by weight or less, 96% by weight or less, 95% by weight or less, 93% by weight or less, 90% by weight or less, less than 90% by weight, 85% by weight or less, 80% by weight or less, 75% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 25% by weight or less, 10% by weight or less, or even 5% by weight or less.

[0100] When the pressure-sensitive adhesive composition A contains inorganic particles described below, the content of monomer a relative to 100 parts by weight of the total of monomer component M and inorganic particles (more specifically, a mixture of inorganic particles and a dispersant) may be 10 parts by weight or more, 20 parts by weight or more, 30 parts by weight or more, 35 parts by weight or more, 36 parts by weight or more, 37 parts by weight or more, 38 parts by weight or more, 39 parts by weight or more, 40 parts by weight or more, 41 parts by weight or more, 42 parts by weight or more, 43 parts by weight or more, 44 parts by weight or more, 45 parts by weight or more, 46 parts by weight or more, 47 parts by weight or more, 48 parts by weight or more, 49 parts by weight or more, 50 parts by weight or more, 51 parts by weight or more, 52 parts by weight or more, 53 parts by weight or more, 54 parts by weight or more, 55 parts by weight or more, 56 parts by weight or more, 57 parts by weight or more, 58 parts by weight or more, or even 59 parts by weight or more. The upper limit of the content may be 90 parts by weight or less, 80 parts by weight or less, 70 parts by weight or less, or even 60 parts by weight or less. The content may be 40 to 60 parts by weight.

[0101] <3-2-b. Other Monomers> The monomer component M may contain a monomer d other than the monomer a. Examples of the monomer d are the same as the examples of the monomer c. The monomer component M may not contain the monomer d.

[0102] An example of monomer d is a hydroxyl group-containing monomer. The content of the hydroxyl group-containing monomer in the monomer component M is, for example, 25% by weight or less, and may be 20% by weight or less, 15% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, or even 2% by weight or less. The lower limit of the content is, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. The monomer component M may not contain a hydroxyl group-containing monomer.

[0103] Another example of monomer d is a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms in the side chain. The content of the (meth)acrylic acid alkyl ester in monomer component M is, for example, 25% by weight or less, and may be 20% by weight or less, 15% by weight or less, 10% by weight or less, 7% by weight or less, 5% by weight or less, or even 4% by weight or less. The lower limit of the content is, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. Monomer component M may not contain a (meth)acrylic acid alkyl ester.

[0104] Another example of monomer d is an aliphatic ring-containing monomer. The content of the aliphatic ring-containing monomer in the monomer component M is, for example, 25% by weight or less, and may be 20% by weight or less, 15% by weight or less, 10% by weight or less, 7% by weight or less, 5% by weight or less, or even 4% by weight or less. The lower limit of the content is, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. The monomer component M may not contain an aliphatic ring-containing monomer.

[0105] Another example of the monomer d is a carboxyl group-containing monomer. The content of the carboxyl group-containing monomer in the monomer component M is, for example, 10% by weight or less, and may be 7% by weight or less, 5% by weight or less, 3% by weight or less, or even 1% by weight or less. The lower limit of the content is, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. It is preferable that the monomer component M does not contain a carboxyl group-containing monomer.

[0106] When the pressure-sensitive adhesive composition A contains inorganic particles described below, the content of monomer d relative to 100 parts by weight of the total of monomer component M and inorganic particles (specifically, a mixture of inorganic particles and a dispersant) may be 30 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less, 8 parts by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, or even 1.5 parts by weight or less. The lower limit of the content may be 0.01 parts by weight or more, 0.1 parts by weight or more, 0.5 parts by weight or more, or even 1 part by weight or more.

[0107] When the pressure-sensitive adhesive composition A contains inorganic particles described below, the content of the monomer component M relative to 100 parts by weight of the total of the monomer component M and the inorganic particles (more specifically, a mixture of the inorganic particles and the dispersant) may be 10 parts by weight or more, 20 parts by weight or more, 30 parts by weight or more, 35 parts by weight or more, 36 parts by weight or more, 37 parts by weight or more, 38 parts by weight or more, 39 parts by weight or more, 40 parts by weight or more, 41 parts by weight or more, 42 parts by weight or more, 43 parts by weight or more, 44 parts by weight or more, 45 parts by weight or more, 46 parts by weight or more, 47 parts by weight or more, 48 parts by weight or more, 49 parts by weight or more, 50 parts by weight or more, 51 parts by weight or more, 52 parts by weight or more, 53 parts by weight or more, 54 parts by weight or more, 55 parts by weight or more, 56 parts by weight or more, 57 parts by weight or more, 58 parts by weight or more, 59 parts by weight or more, or even 60 parts by weight or more. The upper limit of the content may be 90 parts by weight or less, 80 parts by weight or less, 70 parts by weight or less, or even 60 parts by weight or less. The content may be 40 to 60 parts by weight.

[0108] ≪3-3.Partial polymer≫ The pressure-sensitive adhesive composition A may contain a partial polymer of the monomer component M. The partial polymer may be either a homopolymer or a copolymer. The partial polymer can contribute to the stable formation of a coating layer, which will be described later, by appropriately increasing the viscosity of the pressure-sensitive adhesive composition A. Note that the pressure-sensitive adhesive composition A does not necessarily contain a partial polymer.

[0109] The weight-average molecular weight of the partial polymer may be, for example, greater than 30,000, 50,000 or more, 100,000 or more, 500,000 or more, or even 1,000,000 or more. The upper limit of the weight-average molecular weight is not particularly limited, and may be, for example, 3,000,000 or less, or 2,000,000 or less. The weight-average molecular weight is determined by measuring using GPC (gel permeation chromatography) and calculating the value in terms of polystyrene.

[0110] ≪3-4. Photopolymerization initiator≫ The pressure-sensitive adhesive composition A usually contains a photopolymerization initiator. The photopolymerization initiator may be a photoradical generator that generates radicals when exposed to visible light and / or ultraviolet light with a wavelength shorter than 450 nm.

[0111] Examples of photopolymerization initiators include benzoin ethers such as benzoin methyl ether, benzoin isopropyl ether, and benzil dimethyl ketal; substituted benzoin ethers such as anisole methyl ether; substituted acetophenones such as 2,2-diethoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone; α-hydroxyalkylphenones such as 1-hydroxycyclohexyl-phenyl ketone; substituted alpha-ketols such as 2-methyl-2-hydroxypropiophenone; aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride; photoactive oximes such as 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime; and benzophenone compounds such as benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, and 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone. Thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and 2,4-diethylthioxanthone; 2,4,6-trichloro-s-triazine, 2-phenyl-4,6-bis(trichloromethyl)-s-triazine, 2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, and 2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine triazine-based compounds such as 2-piperonyl-4,6-bis(trichloromethyl)-s-triazine, 2,4-bis(trichloromethyl)-6-styryl-s-triazine, 2-(naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxy-naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2,4-trichloromethyl-(piperonyl)-6-triazine, and 2,4-trichloromethyl-(4'-methoxystyryl)-6-triazine;Oxime ester compounds such as 1,2-octanedione, 1-[4-(phenylthio)-, 2-(O-benzoyloxime)], O-(acetyl)-N-(1-phenyl-2-oxo-2-(4'-methoxy-naphthyl)ethylidene)hydroxylamine; phosphine compounds such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; quinone compounds such as 9,10-phenanthrenequinone, camphorquinone, and ethylanthraquinone; borate compounds; carbazole compounds; imidazole compounds; and titanocene compounds. The pressure-sensitive adhesive composition A may contain one or more photopolymerization initiators.

[0112] Specific examples of the photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethan-1-one (Omnirad 651, manufactured by IGM Resins), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, manufactured by IGM Resins), and 1-hydroxycyclohexyl phenyl ketone (Omnirad 184, manufactured by IGM Resins).

[0113] The content of the photopolymerization initiator in the pressure-sensitive adhesive composition A is, for example, 0.02 to 10 parts by weight, or may be 0.05 to 5 parts by weight, 0.1 to 3 parts by weight, or even 0.2 to 2 parts by weight, relative to 100 parts by weight of the monomer component M.

[0114] When the pressure-sensitive adhesive composition A contains inorganic particles described below, the content of the photopolymerization initiator relative to a total of 100 parts by weight of the monomer component M and the inorganic particles (more specifically, a mixture of the inorganic particles and the dispersant) may be 0.02 to 10 parts by weight, 0.05 to 5 parts by weight, 0.1 to 3 parts by weight, or even 0.2 to 2 parts by weight.

[0115] ≪3-5. Inorganic particles≫ The pressure-sensitive adhesive composition A may contain inorganic particles. The inorganic particles can contribute to improving the refractive index of the pressure-sensitive adhesive sheet. The inorganic particles are preferably in a dispersed state in the pressure-sensitive adhesive composition A.

[0116] The inorganic particles can be selected from, for example, metal compound particles and metal particles, one or more types depending on the desired purpose, such as improving the refractive index. The metal compound particles may be metal oxide particles. Examples of materials constituting the metal oxide particles include titanium oxide, zirconium oxide, cerium oxide, aluminum oxide, zinc oxide, tin oxide, copper oxide, barium titanate, and niobium oxide. The metal oxide particles can be used alone or in combination of two or more types. The inorganic particles preferably contain zirconium oxide, and may be zirconium oxide particles composed essentially of zirconium oxide alone. The zirconium oxide particles can contribute to increasing the refractive index of the pressure-sensitive adhesive sheet.

[0117] The material constituting the metal compound particles may be a metal hydroxide such as aluminum hydroxide, boehmite, magnesium hydroxide, calcium hydroxide, zinc hydroxide, iron hydroxide, copper hydroxide, barium hydroxide, basic magnesium carbonate, hydrotalcite, or a hydrated metal compound. Examples of the material constituting the metal particles are iron, zinc, tungsten, and platinum.

[0118] The material of the inorganic particles may be a high-entropy alloy in which multiple types of elements are mixed.

[0119] The inorganic particles may be surface-treated. One example of the surface treatment is hydrophobization. In this specification, it is preferable that the inorganic particles do not include carbon black particles.

[0120] The inorganic particles may contain a high refractive index material. The refractive index of the high refractive index material is, for example, 1.60 or more, and may be 1.70 or more, 1.80 or more, or even 2.00 or more. The upper limit of the refractive index of the high refractive index material is not particularly limited and may be, for example, 3.00 or less, 2.80 or less, 2.50 or less, or even 2.20 or less. The refractive index of the material contained in the inorganic particles can be determined as the refractive index measured for a monolayer film of the material using a commercially available spectroscopic ellipsometer at 23°C and 549 nm. The spectroscopic ellipsometer may be, for example, an "EC-400" (manufactured by J.A. Woolam) or an equivalent.

[0121] The inorganic particles may be nanoparticles having an average particle size of less than 1 μm. The average particle size of the inorganic particles may be 100 nm or less. The average particle size may be 70 nm or less, 50 nm or less, 30 nm or less, 20 nm or less, 15 nm or less, 10 nm or less, 7 nm or less, 5 nm or less, or even 4 nm or less. The lower limit of the average particle size may be, for example, 1 nm or more, 1.5 nm or more, 2 nm or more, or even 2.5 nm or more. The average particle size can be specified as the median diameter (D50) in the particle size distribution measured by dynamic light scattering.

[0122] The content of the inorganic particles relative to 100 parts by weight of the total of the monomer component M and the inorganic particles (specifically, a mixture of the inorganic particles and the dispersant) is, for example, 10 parts by weight or more, 20 parts by weight or more, 30 parts by weight or more, 35 parts by weight or more, 36 parts by weight or more, 37 parts by weight or more, 38 parts by weight or more, 39 parts by weight or more, 40 parts by weight or more, 41 parts by weight or more, 42 parts by weight or more, 43 parts by weight or more, 44 parts by weight or more, 45 parts by weight or more, 46 parts by weight or more, 47 parts by weight or more, 48 parts by weight or more, 49 parts by weight or more, 50 parts by weight or more, 51 parts by weight or more, 52 parts by weight or more, 53 parts by weight or more, 54 parts by weight or more, 55 parts by weight or more, 56 parts by weight or more, 57 parts by weight or more, 58 parts by weight or more, 59 parts by weight or more, or even 60 parts by weight or more. The upper limit of the content is, for example, 90 parts by weight or less, 80 parts by weight or less, 70 parts by weight or less, or even 60 parts by weight or less. The content is preferably 40 to 60 parts by weight.

[0123] <3-6. Dispersants> The PSA composition A may contain a dispersant for inorganic particles. The dispersant is a component for sufficiently dispersing the inorganic particles in the PSA composition A. The dispersant is preferably in contact with the surfaces of the inorganic particles, and more preferably coats the surfaces of the inorganic particles.

[0124] An example of a dispersant is a compound having a hydrophilic portion and a hydrophobic portion in one molecule. The hydrophilic portion and the hydrophobic portion of the dispersant are presumed to exhibit relatively high affinity for the inorganic particles and the monomer component M, respectively. The dispersant may or may not have a polymerizable functional group such as an ethylenically unsaturated group.

[0125] The hydrophilic portion of the dispersant preferably has a hydrophilic group, such as an ether group or an ester group.

[0126] The hydrophilic portion of the dispersant preferably has a functional group F that exhibits adsorptivity or reactivity with inorganic particles. Examples of the functional group F include at least one selected from the group consisting of alkaline groups and acidic groups. Specific examples of the functional group F include a hydroxy group, a carboxy group, a nitrogen atom-containing group, a sulfur atom-containing group, a phosphorus atom-containing group, and a silicon atom-containing group. The number of functional groups F contained in one molecule of the dispersant may be 1, or 2 or more (for example, about 2 to 5). The types of the two or more functional groups F present in one molecule may be the same or different from each other.

[0127] The hydrophilic portion of the dispersant may have a chain structure, or may have a composite structure of a chain structure and a cyclic structure. The dispersant may have, for example, a structure in which a functional group F and a hydrophobic portion are linked via a chain structure; a structure in which a functional group F is attached to a side chain of a chain structure whose one end is linked to the hydrophobic portion; or a structure in which a chain structure whose other end is linked to the hydrophobic portion does not have a functional group F (for example, the other end of the chain structure is open). The dispersant may have two or more of the above structures.

[0128] The dispersant may be an aliphatic compound, for example, represented by the following formula (1): [ka]

[0129] In formula (1), R is an alkyl group, preferably an alkyl group having 1 to 3 carbon atoms, and more preferably an ethyl group. m is 1 to 10, preferably 2 to 8, and more preferably 3 to 7. n is 5 to 20, and preferably 8 to 12.

[0130] The dispersant may be an aromatic compound having an aromatic ring. Examples of the aromatic ring are the same as those mentioned above in the description of the monomers a and b.

[0131] The dispersant may be selected from known surfactants. Examples of surfactants include anionic surfactants (carboxylic acid type, phosphate ester type, sulfate ester type, sulfonic acid type, etc.), nonionic surfactants, cationic surfactants, and amphoteric surfactants. The surfactant that can be used as the dispersant is preferably an anionic surfactant.

[0132] The content of the dispersant relative to 100 parts by weight of the inorganic particles is, for example, 0.1 parts by weight or more, or may be 0.5 parts by weight or more, or even 1.0 part by weight or more. The upper limit of the content is, for example, 30 parts by weight or less, or may be 20 parts by weight or less.

[0133] 3-7. Crosslinking Agents The pressure-sensitive adhesive composition A may contain a crosslinking agent. An example of the crosslinking agent is a polyfunctional monomer having two or more polymerizable functional groups in one molecule. The polyfunctional monomer may be a (meth)acrylic monomer. Examples of the polyfunctional monomer are a monomer having two or more C=C bonds in one molecule, and a monomer having one or more C=C bonds and one or more polymerizable functional groups such as epoxy groups, aziridine groups, oxazoline groups, hydrazine groups, methylol groups, etc. in one molecule. The polyfunctional monomer is preferably a monomer having two or more C=C bonds in one molecule.

[0134] Examples of polyfunctional monomers include (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol diacrylate (N Polyfunctional acrylates (such as ester compounds of polyhydric alcohols and (meth)acrylic acid) such as dimethyl acrylate (DDA), 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and tetramethylolmethane tri(meth)acrylate; allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl di(meth)acrylate, and hexyl di(meth)acrylate. The polyfunctional monomer is preferably a polyfunctional acrylate, more preferably trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, or dipentaerythritol hexa(meth)acrylate.

[0135] The content of the crosslinking agent in the pressure-sensitive adhesive composition A is, for example, 5 parts by weight or less, and may be 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or even 0.5 parts by weight or less, per 100 parts by weight of the monomer component M. The lower limit of the content may be, for example, 0.01 part by weight or more, or even 0.05 part by weight or more.

[0136] When the pressure-sensitive adhesive composition A contains inorganic particles, the content of the crosslinking agent relative to 100 parts by weight of the total of the monomer component M and the inorganic particles (specifically, a mixture of the inorganic particles and the dispersant) may be, for example, 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or even 0.5 parts by weight or less. The lower limit of the content may be, for example, 0.01 parts by weight or more, 0.03 parts by weight or more, or even 0.05 parts by weight or more.

[0137] <3-8. Silane coupling agents> The pressure-sensitive adhesive composition A may contain a silane coupling agent. Specific examples of the silane coupling agent include epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino group-containing silane coupling agents such as 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, and N-phenyl-γ-aminopropyltrimethoxysilane; (meth)acrylic group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane; and isocyanate group-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane.

[0138] The content of the silane coupling agent in the pressure-sensitive adhesive composition A is, for example, 3 parts by weight or less, and may be 2 parts by weight or less, 1 part by weight or less, or even 0.5 parts by weight or less, per 100 parts by weight of the monomer component M. The lower limit of the content may be, for example, 0.1 parts by weight or more, or even 0.2 parts by weight or more. The pressure-sensitive adhesive composition A may not contain a silane coupling agent.

[0139] When the pressure-sensitive adhesive composition A contains inorganic particles, the content of the silane coupling agent relative to 100 parts by weight of the total of the monomer component M and the inorganic particles (specifically, a mixture of the inorganic particles and the dispersant) is, for example, 5 parts by weight or less, and may be 3 parts by weight or less, 1 part by weight or less, 0.8 parts by weight or less, 0.5 parts by weight or less, 0.4 parts by weight or less, 0.3 parts by weight or less, 0.2 parts by weight or less, or even 0.1 parts by weight or less. The lower limit of the content is, for example, 0.01 parts by weight or more, and may also be 0.05 parts by weight or more.

[0140] ≪3-9. Antioxidants≫ The PSA composition A may contain an antioxidant. Examples of the antioxidant include phenol-based antioxidants, hindered phenol-based antioxidants, amine-based antioxidants, and phosphite-based antioxidants.

[0141] Examples of the phenolic antioxidant include monophenolic antioxidants, bisphenolic antioxidants, and polymeric phenolic antioxidants. Examples of the monophenolic antioxidant include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, and stearin-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate. Examples of the bisphenol antioxidant are 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), and 3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]2,4,8,10-tetraoxaspiro[5,5]undecane. Examples of polymeric phenolic antioxidants include 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, bis[3,3'-bis-(4'-hydroxy-3'-t-butylphenyl)butyric acid]glycol ester, 1,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-S-triazine-2,4,6-(1H,3H,5H)trione, and tocopherol.

[0142] The hindered phenol-based antioxidant may have a structure in which a tertiary butyl group is bonded to at least one carbon atom adjacent to a carbon atom on an aromatic ring to which a phenolic OH group is bonded. Examples of hindered phenolic antioxidants include dibutylhydroxytoluene (BHT); and Irganox1010, Irganox1010FF, Irganox1035, Irganox1035FF, Irganox1076, Irganox1076FD, Irganox1076DWJ, Irganox1098, Irganox1135, Irganox1330, Irganox1726, Irganox1425WL, Irganox1520L, Irganox245, Irganox245FF, Irganox259, Irganox3114, Irganox565, and Irganox295 (all of which are trade names manufactured by BASF).

[0143] The amine antioxidant is preferably a hindered amine antioxidant. The hindered amine antioxidant may have at least one hindered piperazine group in one molecule. Examples of the hindered amine antioxidant include ADK STAB LA-63, ADK STAB LA-63P, ADK STAB LA-52, and ADK STAB LA-57 (all of which are trade names, manufactured by ADEKA Corporation).

[0144] Examples of the phosphite antioxidants are triphenyl phosphite, diphenyl isodecyl phosphite, and phenyl diisodecyl phosphite; and Adeka STAB 2112, Adeka STAB 2112RG, Adeka STAB 1178, and Adeka STAB 3010 (all of which are trade names, manufactured by ADEKA Corporation).

[0145] The content of the antioxidant in the pressure-sensitive adhesive composition A is, for example, 5 parts by weight or less, and may be 3 parts by weight or less, 1 part by weight or less, 0.8 parts by weight or less, or even 0.5 parts by weight or less, per 100 parts by weight of the monomer component M. The lower limit of the content may be, for example, 0.01 parts by weight or more, or even 0.05 parts by weight or more. The pressure-sensitive adhesive composition A may not contain an antioxidant.

[0146] When the pressure-sensitive adhesive composition A contains inorganic particles, the content of the antioxidant relative to 100 parts by weight of the total of the monomer component M and the inorganic particles (specifically, a mixture of the inorganic particles and the dispersant) is, for example, 5 parts by weight or less, or may be 3 parts by weight or less, 1 part by weight or less, 0.8 parts by weight or less, or even 0.5 parts by weight or less. The lower limit of the content is, for example, 0.01 parts by weight or more, or may be 0.05 parts by weight or more.

[0147] ≪3-10. UV absorbers≫ The pressure-sensitive adhesive composition A may contain an ultraviolet absorber (UVA). Examples of UVA include triazine-based UVA, benzotriazole-based UVA, benzophenone-based UVA, oxybenzophenone-based UVA, salicylic acid ester-based UVA, and cyanoacrylate-based UVA. Each UVA is a compound having a triazine skeleton, a benzotriazole skeleton, a benzophenone skeleton, an oxybenzophenone skeleton, a salicylic acid ester structure, and a cyanoacrylate structure, respectively. The UVA is preferably a triazine-based or benzotriazole-based UVA, and more preferably a benzotriazole-based UVA.

[0148] Examples of triazine-based UVAs include 2,4-bis-[{4-(4-ethylhexyloxy)-4-hydroxy}-phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine (Tinosorb S, manufactured by BASF), 2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine (TINUVIN460, manufactured by BASF), reaction product of 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-hydroxyphenyl with [(C10-C16 (mainly C12-C13) alkyloxy)methyl]oxirane (TINUVIN400, manufactured by BASF), and 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-[3-(dodecyloxy)methyl]oxirane. )-2-hydroxypropoxy]phenol), reaction products of 2-(2,4-dihydroxyphenyl)-4,6-bis-(2,4-dimethylphenyl)-1,3,5-triazine with (2-ethylhexyl)-glycidic acid ester (TINUVIN 405, BASF), 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-phenol (TINUVIN 1577, BASF), 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]-phenol (ADK STAB LA46 (manufactured by ADEKA), and 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine (TINUVIN479 (manufactured by BASF)).

[0149] Examples of benzotriazole-based UVAs include 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (TINUVIN 928, manufactured by BASF), 2-(2H-1,2,3-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (TINUVIN 571, manufactured by BASF), 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole (TINUVIN PS, manufactured by BASF), ester compound of benzenepropanoic acid and 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy(C7-9 branched and linear alkyl) (TINUVIN 384-2, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (TINUVIN 900, manufactured by BASF), reaction product of methyl-3-(3-(2H-benzotriazol-2-yl)-5-t-butyl-4-hydroxyphenyl)propionate / polyethylene glycol 300 (TINUVIN 1130, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-p-cresol (TINUVIN P, manufactured by BASF), 2(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (TINUVIN234, manufactured by BASF), 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-(tert-butyl)phenol (TINUVIN326, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (TINUVIN328, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (TINUVIN234, manufactured by BASF), 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-(tert-butyl)phenol (TINUVIN326, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (TINUVIN328, manufactured by BASF), -yl)-4-(1,1,3,3-tetramethylbutyl)phenol (TINUVIN329, manufactured by BASF), reaction products of methyl 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate with polyethylene glycol 300 (TINUVIN213, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (TINUVIN571, manufactured by BASF), 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimido-methyl)-5-methylphenyl]benzotriazole (Sumisorb 250, manufactured by Sumitomo Chemical Co., Ltd.).

[0150] The content of UVA in the pressure-sensitive adhesive composition A is, for example, 10 parts by weight or less, and may be 5 parts by weight or less, 3 parts by weight or less, or even 2 parts by weight or less, relative to 100 parts by weight of the monomer component M. The lower limit of the content may be, for example, 0.1 parts by weight or more, 0.5 parts by weight or more, or even 1 part by weight or more. The pressure-sensitive adhesive composition A may not contain UVA.

[0151] When the PSA composition A contains inorganic particles, the content of UVA relative to 100 parts by weight of the total of the monomer component M and the inorganic particles (specifically, a mixture of the inorganic particles and the dispersant) is, for example, 10 parts by weight or less, or may be 5 parts by weight or less, 3 parts by weight or less, or even 2 parts by weight or less. The lower limit of the content is, for example, 0.1 parts by weight or more, or may be 0.5 parts by weight or more, or even 1 part by weight or more.

[0152] 3-11. Solvents The content of the solvent in the PSA composition A is, for example, 5 wt % or less, and may be 4 wt % or less, 3 wt % or less, 2 wt % or less, 1 wt % or less, or even 0.5 wt % or less. The PSA composition A may be substantially free of solvent. "Substantially free of solvent" means that solvents derived from additives and the like are allowed at a content of, for example, 0.1 wt % or less, preferably 0.05 wt % or less, and more preferably 0.01 wt % or less.

[0153] 3-12. Additives The PSA composition A may contain additives other than those described above. Examples of the additives include a chain transfer agent, a viscosity modifier, a tackifier, a plasticizer, a softener, an antioxidant, a filler, a colorant, a surfactant, and an antistatic agent.

[0154] 3-13. Physical Properties The viscosity of the pressure-sensitive adhesive composition A is preferably 5 to 150 poise at 25° C. The pressure-sensitive adhesive composition A having a viscosity in the above range is particularly suitable for forming a coating layer, which will be described later.

[0155] ≪3-14. Manufacturing Method≫ The pressure-sensitive adhesive composition A can be prepared by mixing the various components. The pressure-sensitive adhesive composition A containing inorganic particles may be prepared by the following method. First, a dispersion in which inorganic particles are dispersed in a solvent is prepared. This dispersion is mixed with a dispersant and at least some of the monomers contained in the monomer component M. The solvent is removed from the resulting mixture to prepare a dispersion containing inorganic particles, a dispersant, and a monomer. The method for removing the solvent from the mixture is not particularly limited, and methods such as removal under reduced pressure can be used. Next, the remaining monomers, polymer B, a photopolymerization initiator, etc. are added to the dispersion and mixed. In this way, the pressure-sensitive adhesive composition A containing inorganic particles can be prepared.

[0156] ≪≪4. Adhesive sheet≫≫ <4-1. Adhesive sheet> An example of a pressure-sensitive adhesive sheet according to an embodiment of the present invention is shown in Fig. 1. The pressure-sensitive adhesive sheet 1 in Fig. 1 is formed from a pressure-sensitive adhesive composition A. The pressure-sensitive adhesive sheet 1 contains a polymer B derived from the pressure-sensitive adhesive composition A.

[0157] The polymerization rate of the monomer component M in the pressure-sensitive adhesive sheet 1 is preferably 90% or more, and may be 95% or more, 98% or more, or even 99% or more.

[0158] The gel fraction of the pressure-sensitive adhesive sheet 1 is, for example, 50% or more, and may be 75% or more, 80% or more, 85% or more, or even 90% or more.

[0159] The refractive index of the pressure-sensitive adhesive sheet 1 is, for example, 1.55 or more, and may be 1.56 or more, 1.57 or more, 1.58 or more, 1.59 or more, 1.60 or more, 1.61 or more, 1.62 or more, 1.63 or more, 1.64 or more, 1.645 or more, or even 1.65 or more. The upper limit of the refractive index is, for example, 1.80 or less, and may be 1.79 or less, 1.78 or less, 1.77 or less, 1.76 or less, 1.75 or less, 1.74 or less, 1.73 or less, 1.72 or less, 1.71 or less, 1.70 or less, 1.69 or less, 1.68 or less, 1.67 or less, or even 1.66 or less. In some cases, the upper limit of the refractive index may be 1.65 or less, 1.64 or less, or even 1.63 or less. A preferred example of the refractive index of the pressure-sensitive adhesive sheet 1 is 1.63 to 1.66. Another preferred example of the refractive index of the pressure-sensitive adhesive sheet 1 is 1.60 to 1.63. The optical laminate may be provided with optical substrates having high refractive indexes. Using a high-refractive-index pressure-sensitive adhesive sheet 1 to bond high-refractive-index optical substrates is advantageous in reducing reflected light at the interface between the optical substrate and the pressure-sensitive adhesive sheet.

[0160] In this specification, the refractive index of the adhesive sheet 1 refers to the refractive index of the surface of the adhesive sheet 1. The refractive index of the adhesive sheet 1 can be measured using a prism coupler under conditions of a measurement temperature of 25°C and a measurement wavelength of 594 nm. For adhesive sheets 1 with a thickness of less than 20 μm, measurement in the optical propagation mode is generally suitable. For adhesive sheets 1 with a thickness of 20 μm or more, measurement in the critical angle mode is generally suitable. A commercially available measuring device can be used as the prism coupler, for example, a Model 2010 / M prism coupler manufactured by Metricon or an equivalent can be used.

[0161] The haze of the pressure-sensitive adhesive sheet 1 is, for example, 5.0% or less, and may be 3.0% or less, less than 3.0%, 2.5% or less, 2.0% or less, 1.7% or less, 1.5% or less, 1.2% or less, 1.0% or less, 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, or even 0.2% or less. The lower limit of the haze is not particularly limited and may be 0.1% or more. A pressure-sensitive adhesive sheet 1 with low haze is particularly suitable for use in optical laminates.

[0162] In this specification, haze refers to the ratio of diffuse transmitted light to total transmitted light when visible light is irradiated onto the pressure-sensitive adhesive sheet 1, which is the object to be measured. Haze can be calculated using the following formula: In the following formula, Th is haze (%), Td is scattered light transmittance, and Tt is total light transmittance. Th(%)=Td / Tt×100

[0163] The chromaticity of the adhesive sheet 1 is CIE1976 L defined in JIS Z8781-4:2013. * ,a * ,b * Color space chromaticity b * The absolute value of chromaticity b may be 2.0 or less. * The absolute value of chromaticity b may be 1.7 or less, 1.5 or less, 1.2 or less, 1.0 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, or even 0.5 or less. * The lower limit of the absolute value of chromaticity b of the pressure-sensitive adhesive sheet 1 is, for example, 0 or more, and may be 0.1 or more. * can be evaluated using a commercially available colorimeter capable of measurements in accordance with JIS Z8781-4:2013.

[0164] The content of acidic groups (particularly COOH groups) in polymer B contained in pressure-sensitive adhesive sheet 1 is, for example, 0.1 wt % or less, 0.01 wt % or less, or even 0.001 wt % or less. Polymer B preferably contains substantially no acidic groups. The acidic group content can be measured, for example, by the following method. First, a sol component (non-crosslinked component) contained in pressure-sensitive adhesive sheet 1 is extracted using a solvent (e.g., toluene). A component (polymer B) having a weight-average molecular weight of 1,500 to 30,000 is separated using preparative gel permeation chromatography (GPC). This component is dried in an oven at 130°C for 2 hours to remove the solvent. The acidic group content can be determined by evaluating the dried component using infrared spectroscopy.

[0165] The adhesive sheet 1 preferably has an adhesive strength to alkali-free glass of 0.5 N / 25 mm or more, and may be 0.7 N / 25 mm or more, 0.8 N / 25 mm or more, 1.0 N / 25 mm or more, 1.2 N / 25 mm or more, 1.5 N / 25 mm or more, 1.7 N / 25 mm or more, 2.0 N / 25 mm or more, 2.2 N / 25 mm or more, 2.5 N / 25 mm or more, 2.7 N / 25 mm or more, 3.0 N / 25 mm or more, 3.5 N / 25 mm or more, 4.0 N / 25 mm or more, 4.5 N / 25 mm or more, 5.0 N / 25 mm or more, 6.0 N / 25 mm or more, 7.0 N / 25 mm or more, 8.0 N / 25 mm or more, 9.0 N / 25 mm or more, or even 10.0 N / 25 mm or more. The upper limit of the adhesive strength is, for example, 50.0 N / 25 mm or less, and may be 40.0 N / 25 mm or less, 30.0 N / 25 mm or less, 25.0 N / 25 mm or less, or even 20.0 N / 25 mm or less. In some cases, the upper limit of the adhesive strength may be 10.0 N / 25 mm or less, 5.0 N / 25 mm or less, or even 4.0 N / 25 mm or less. A preferred example of the adhesive strength is 1.0 to 4.0 N / 25 mm. Another preferred example of the adhesive strength is 3.0 to 25.0 N / 25 mm.

[0166] The adhesive strength can be measured by the following method. First, a laminate including a pressure-sensitive adhesive sheet 1 and a substrate is prepared under a measurement environment of 23°C and 50% RH. The substrate is not particularly limited as long as it supports the pressure-sensitive adhesive sheet 1 and does not affect the measurement results of the adhesive strength. As an example, the substrate may be a polyethylene terephthalate film. Next, the laminate is cut into a strip of 100 mm length x 25 mm width to prepare a test piece. Next, the test piece is placed on alkali-free glass via the pressure-sensitive adhesive sheet 1, and they are pressed together by moving a 2 kg roller back and forth once. The alkali-free glass is glass that is substantially free of alkali components (alkali metal oxides). Specifically, the weight ratio of the alkali components in the glass is, for example, 1000 ppm or less, and even 500 ppm or less. The alkali-free glass is, for example, in the form of a plate, having a thickness of 0.5 mm or more.

[0167] After leaving the test piece in the above environment for 30 minutes, it was placed in a pressure degassing apparatus (autoclave) and autoclaved for 30 minutes at a temperature of 50°C and a pressure of 0.5 MPa. It was then left for 24 hours in an atmosphere of 23°C and 50% RH. Next, using a universal tension and compression tester, the test piece was peeled from the alkali-free glass at a peel rate of 300 mm / min and a peel angle of 180°. The force (peel strength) required to peel the test piece from the alkali-free glass was determined as the adhesive strength.

[0168] The thickness of the pressure-sensitive adhesive sheet 1 is, for example, 500 μm or less, and may be 250 μm or less, 150 μm or less, 100 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, or even 20 μm or less. The lower limit of the thickness of the pressure-sensitive adhesive sheet 1 is, for example, 2 μm or more, and may be 5 μm or more. In some cases, the lower limit of the thickness of the pressure-sensitive adhesive sheet 1 may be 20 μm or more, or may be 30 μm or more. A preferred example of the thickness of the pressure-sensitive adhesive sheet 1 is 2 to 30 μm. Another preferred example of the thickness of the pressure-sensitive adhesive sheet 1 is 30 to 100 μm.

[0169] ≪4-2. Manufacturing Method≫ The PSA sheet 1 can be formed from the PSA composition A by, for example, irradiating light 14 onto a first laminate 10 comprising, in this order, a base sheet 11, a coating layer 12 containing the PSA composition A, and a release liner 13 (see FIG. 2). The coating layer 12 is cured by irradiation with light 14 to form the PSA sheet 1. Irradiation with light 14 is typically carried out from the side of the base sheet 11. In this case, the light 14 passes through the base sheet 11 and reaches the coating layer 12, curing the coating layer 12. However, irradiation with light 14 may also be carried out from the side of the release liner 13, or from both the side of the release liner 13 and the side of the base sheet 11.

[0170] The formed pressure-sensitive adhesive sheet 1 is sandwiched between the base sheet 11 and the release liner 13 until the release liner 13 is peeled off, and constitutes a part of the second laminate 17. By peeling the release liner 13 from the second laminate 17, a third laminate 15 including the base sheet 11 and the pressure-sensitive adhesive sheet 1 is obtained. In the third laminate 15, the surface of the pressure-sensitive adhesive sheet 1 is exposed to the outside. An optical film can be laminated onto the exposed surface of the pressure-sensitive adhesive sheet 1 directly or via another layer.

[0171] The light 14 is, for example, visible light or ultraviolet light having a wavelength shorter than 450 nm. The light may include light having a wavelength in the same region as the absorption wavelength of the photopolymerization initiator contained in the pressure-sensitive adhesive composition A. Light having a wavelength of 300 nm or less may be irradiated by filtering out short-wavelength light using a filter or the like. Filtering out short-wavelength light is suitable for suppressing deterioration of the base sheet 11 and / or release liner 13 due to the light 14. The light source 18 of the light 14 is, for example, a light irradiation device equipped with an ultraviolet irradiation lamp. Examples of ultraviolet irradiation lamps include ultraviolet LEDs, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, microwave-excited mercury lamps, black light lamps, chemical lamps, germicidal lamps, low-pressure discharge mercury lamps, and excimer lasers. Two or more ultraviolet irradiation lamps may be combined.

[0172] The illuminance of the light 14 irradiated onto the first laminate 10 (specifically, the coating layer 12) is, for example, 2.0 to 30 mW / cm 2 The illuminance is 2.5mW / cm 2 More than 3.0mW / cm 2 More than 3.5mW / cm 2 More than 4.0mW / cm 2 More than 5.0mW / cm 2 More than 6.0mW / cm 2 More than 7.0mW / cm 2 More than 8.0mW / cm 2 More than 9.0mW / cm 2 or more, and even 10mW / cm 2 The upper limit of the illuminance may be, for example, 25 mW / cm 2less than 20 mW / cm 2 It may be the following:

[0173] The time for irradiating the first laminate 10 (specifically, the coating layer 12) with light 14 is, for example, 10 to 1000 seconds, and may be 60 seconds or more, 100 seconds or more, 150 seconds or more, or even 200 seconds or more. The upper limit of the time is, for example, 800 seconds or less, and may be 600 seconds or less, 500 seconds or less, 400 seconds or less, 300 seconds or less, or even 250 seconds or less. Irradiation with light 14 may be continuous or intermittent.

[0174] The integrated light amount of the light 14 on the first laminate 10 (specifically, the coating layer 12) is, for example, 25 mJ / cm 2 2 or more, 100 mJ / cm 2 More than 500mJ / cm 2 More than 1000mJ / cm 2 More than 2000mJ / cm 2 More than 2500mJ / cm 2 More than 3000mJ / cm 2 More than 5000mJ / cm 2 More than 7500mJ / cm 2 or more, even 10,000 mJ / cm 2 The upper limit of the cumulative light amount is not particularly limited, and may be, for example, 30,000 mJ / cm 2 or more. 2 Less than 25,000 mJ / cm 2 Below, 20000mJ / cm 2 Below that, even 18000mJ / cm 2 It may be the following:

[0175] The light 14 may be irradiated onto the first laminate 10 in multiple stages. The illuminance and / or integrated light amount of the light 14 in each stage may be the same or different from each other. Furthermore, the light source in each stage may be the same or different from each other.

[0176] An example of the substrate of the release liner 13 (hereinafter referred to as "liner substrate") is a resin film. Examples of resins that can be contained in the liner substrate include polyesters such as polyethylene terephthalate and polyethylene naphthalate, acetate resins, polyethersulfone, polycarbonate, polyamide, polyimide, polyolefin, (meth)acrylic resins, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl alcohol, polyarylate, and polyphenylene sulfide. The resin is preferably a polyester such as polyethylene terephthalate.

[0177] The release liner 13 may include a layer other than the liner substrate. The release liner 13 may include a release layer. The release liner 13 includes, for example, a liner substrate and a release layer formed on one surface of the liner substrate. This release liner 13 can be used so that the release layer faces the coating layer 12. The release layer is typically a cured layer of a release agent composition containing a release agent. Various release agents can be used as the release agent, such as silicone-based release agents, fluorine-based release agents, long-chain alkyl-based release agents, fatty acid amide-based release agents, and silica powder.

[0178] The release liner 13 may be in the form of a sheet or a continuous piece.

[0179] An example of the base sheet 11 is a resin film. Examples of the resin contained in the base sheet 11 are the same as the examples of the resin that can be contained in the liner base material.

[0180] The thickness of the base sheet 11 is, for example, 10 to 200 μm, and may be 25 to 150 μm.

[0181] The base sheet 11 may have a release layer on the surface on the side of the coating layer 12. Examples of the release layer that may be provided on the base sheet 11 are the same as the examples of the release layer that may be provided on the release liner 13. Both the release liner 13 and the base sheet 11 may have a release layer.

[0182] For the base sheet 11, a sheet having a greater peel strength from the adhesive sheet 1 than the release liner 13 can usually be selected.

[0183] The base sheet 11 may be in the form of a sheet or a continuous sheet.

[0184] The first laminate 10 can be formed, for example, by forming a coating layer 12 on a base sheet 11 (or a release liner 13) and then placing the release liner 13 (or base sheet 11) on the formed coating layer 12. Alternatively, the first laminate 10 may be formed by applying the photocurable composition in a poured manner into the space between the base sheet 11 and the release liner 13, which are held at a predetermined distance so that their main surfaces face each other.

[0185] The coating layer 12 can be formed by various coating methods such as roll coating, kiss roll coating, gravure coating, reverse coating, roll brush, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating.

[0186] The thickness of coating layer 12 can be adjusted depending on the desired thickness of pressure-sensitive adhesive sheet 1, and may be, for example, 500 μm or less, 250 μm or less, 150 μm or less, 100 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, or even 20 μm or less. The lower limit of the thickness of coating layer 12 is, for example, 2 μm or more, and may be 5 μm or more.

[0187] The first laminate 10 may include a long base sheet 11, a long coating layer 12, and a long release liner 13, in other words, it may be long. The long first laminate 10 can be obtained, for example, by forming the coating layer 12 between the base sheet 11 and the release liner 13 while conveying them after they have been unwound from a roll.

[0188] ≪≪5. Optical laminate≫≫ An example of an optical laminate according to an embodiment of the present invention is shown in Fig. 3. The optical laminate 20A in Fig. 3 includes an adhesive sheet 1 and an optical film 2. The adhesive sheet 1 and the optical film 2 are laminated together. The optical laminate 20A can be used as an optical film with an adhesive sheet.

[0189] Examples of the optical film 2 include a polarizing film, a retardation film, and a laminated film including a polarizing film and / or a retardation film. However, the optical film 2 is not limited to the above examples. The optical film 2 may also include a glass film.

[0190] The optical film 2 may be a polarizing film, and the pressure-sensitive adhesive sheet 1 may be in contact with the optical film 2 .

[0191] The polarizing film includes a polarizer. The polarizing film typically includes a polarizer and a protective film (transparent protective film). The protective film is disposed, for example, in contact with the main surface (the surface having the largest area) of the polarizer. The polarizer may be disposed between two protective films. The protective film may be disposed on at least one surface of the polarizer.

[0192] The polarizer is not particularly limited, and examples include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films, which are uniaxially stretched after adsorbing a dichroic substance such as iodine or a dichroic dye; and oriented polyene films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. Polarizers typically consist of a polyvinyl alcohol film (including partially saponified ethylene-vinyl acetate copolymer films) and a dichroic substance such as iodine.

[0193] The thickness of the polarizer is not particularly limited and may be, for example, 80 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, or even 20 μm or less. The lower limit of the polarizer thickness is not particularly limited and may be, for example, 1 μm or more, 5 μm or more, 10 μm or more, or even 15 μm or more. A thin polarizer (for example, a thickness of 20 μm or less) is suppressed in dimensional change and can contribute to improving the durability of the optical laminate, particularly durability at high temperatures.

[0194] The material for the protective film may be, for example, a thermoplastic resin that is excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, etc. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins (norbornene-based resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The material for the protective film may be a thermosetting resin or an ultraviolet-curable resin such as a (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone-based resin. When the polarizing film has two protective films, the materials of the two protective films may be the same or different. For example, a protective film made of a thermoplastic resin may be bonded to one main surface of a polarizer via an adhesive, and a protective film made of a thermosetting resin or an ultraviolet-curable resin may be bonded to the other main surface of the polarizer. The protective film may contain one or more optional additives, such as ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, color inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and colorants.

[0195] The thickness of the protective film can be determined as appropriate, but is generally about 10 to 200 μm in terms of strength, workability such as handling, thinness, and the like.

[0196] The polarizer and the protective film are usually adhered to each other via an aqueous adhesive or the like. Examples of aqueous adhesives include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl latex, aqueous polyurethane, and aqueous polyester. Examples of adhesives other than the above-mentioned adhesives include ultraviolet-curable adhesives and electron beam-curable adhesives. Electron beam-curable polarizing film adhesives exhibit suitable adhesiveness to various protective films. The adhesive may contain a metal compound filler.

[0197] In the polarizing film, a retardation film or the like can be formed on the polarizer instead of the protective film. Another protective film or a retardation film or the like can be further provided on the protective film.

[0198] The protective film may have a hard coat layer on the surface opposite to the surface bonded to the polarizer, and may also be subjected to treatments for purposes such as anti-reflection, anti-sticking, diffusion, and anti-glare.

[0199] The polarizing film may be a circular polarizing film.

[0200] The thickness of the polarizing film is, for example, 500 μm or less, and may be 300 μm or less, 200 μm or less, 100 μm or less, or even 60 μm or less. The lower limit of the thickness may be, for example, 10 μm or more, 25 μm or more, or even 40 μm or more.

[0201] A retardation film is a film having birefringence in the in-plane direction and / or the thickness direction, and is, for example, a stretched resin film or a film in which a liquid crystal material is oriented and fixed.

[0202] The retardation film may be a λ / 4 plate, a λ / 2 plate, an anti-reflection retardation film (see, for example, paragraphs 0221, 0222, and 0228 of JP 2012-133303 A), a viewing angle compensation retardation film (see, for example, paragraphs 0225 and 0226 of JP 2012-133303 A), or an obliquely oriented viewing angle compensation retardation film (see, for example, paragraph 0227 of JP 2012-133303 A). The retardation film is not limited to the above examples, as long as it has birefringence in the in-plane direction and / or the thickness direction. The retardation value, arrangement angle, three-dimensional birefringence, whether the retardation film is single-layer or multi-layer, and the like are also not limited. Known films can be used as the retardation film.

[0203] The optical film 2 has a thickness of, for example, 1 to 200 μm.

[0204] The optical film 2 may be a single layer or a laminated film composed of two or more layers. When the optical film 2 is a laminated film, the pressure-sensitive adhesive sheet 1 may be used to bond the layers together.

[0205] Another example of an optical laminate according to an embodiment of the present invention is shown in Figure 4. Optical laminate 20B in Figure 4 has a layered structure in which a release liner 3, a pressure-sensitive adhesive sheet 1, and an optical film 2 are layered in this order. By peeling off release liner 3, optical laminate 20B can be used as an optical film with a pressure-sensitive adhesive sheet.

[0206] The release liner 3 is typically a resin film. Examples of resins that can be used to form the release liner 3 include polyesters such as polyethylene terephthalate (PET), polyolefins such as polyethylene and polypropylene, polycarbonate, acrylic, polystyrene, polyamide, and polyimide. The surface of the release liner 3 that comes into contact with the pressure-sensitive adhesive sheet 1 may be subjected to a release treatment. The release treatment may be, for example, a treatment using a silicone compound. However, the release liner 3 is not limited to the above examples. The release liner 3 is peeled off when the optical laminate 20B is used, for example, when it is attached to the image-forming layer.

[0207] Another example of an optical laminate according to an embodiment of the present invention is shown in Fig. 5. Optical laminate 20C in Fig. 5 has a layered structure in which a release liner 3, a pressure-sensitive adhesive sheet 4, a retardation film 2B, a pressure-sensitive adhesive sheet 1, and a polarizing film 2A are layered in this order. After peeling off release liner 3, optical laminate 20C can be used by being attached to, for example, an image-forming layer.

[0208] A known adhesive sheet can be used for the adhesive sheet 4. The adhesive sheet 1 may also be used for the adhesive sheet 4.

[0209] Another example of an optical laminate according to an embodiment of the present invention is shown in Fig. 6. Optical laminate 20D in Fig. 6 has a layered structure in which a release liner 3, a pressure-sensitive adhesive sheet 4, a retardation film 2B, a pressure-sensitive adhesive sheet 1, a polarizing film 2A, and a protective film 5 are layered in this order. After peeling off release liner 3, optical laminate 20D can be used by being attached to, for example, an image-forming layer.

[0210] The protective film 5 has the function of protecting the optical film 2 (polarizing film 2A), which is the outermost layer, during distribution and storage of the optical laminate 20D and when the optical laminate 20D is incorporated into an image display device. The protective film 5 may also function as a window to the external space when incorporated into an image display device. The protective film 5 is typically a resin film. Examples of resins constituting the protective film 5 include polyesters such as PET, polyolefins such as polyethylene and polypropylene, acrylics, cycloolefins, polyimides, and polyamides, with polyesters being preferred. However, the protective film 5 is not limited to the above examples. The protective film 5 may also be a glass film or a laminated film including a glass film. The protective film 5 may be subjected to surface treatments such as anti-glare, anti-reflection, and anti-static.

[0211] The protective film 5 may be bonded to the optical film 2 with any adhesive. Bonding with an adhesive sheet 1 is also possible.

[0212] The optical laminate may have any configuration as long as it includes the pressure-sensitive adhesive sheet 1 and the optical film 2.

[0213] The pressure-sensitive adhesive sheet 1 can be disposed between any layers included in the optical laminate. In other words, the pressure-sensitive adhesive sheet 1 may be a so-called interlayer pressure-sensitive adhesive layer.

[0214] The optical laminate according to the embodiment of the present invention can be distributed and stored, for example, as a rolled body obtained by rolling up a strip-shaped optical laminate, or as a sheet-shaped optical laminate.

[0215] The optical laminate according to the embodiment of the present invention is typically used in image display devices, such as liquid crystal displays, organic EL displays, and inorganic EL displays.

[0216] ≪≪6. Image display device≫≫ An example of an image display device according to an embodiment of the present invention is shown in Fig. 7. The image display device 21 in Fig. 7 has a layered structure in which a substrate 7, an image-forming layer (e.g., an organic EL layer or a liquid crystal layer) 6, an adhesive sheet 4, a retardation film 2B, an adhesive sheet 1, a polarizing film 2A, and a protective film 5 are layered in this order. The image display device 21 has the optical laminate 20D of Fig. 6 (excluding the release liner 3). The image display device 21 may have the optical laminates 20A, 20B, and 20C of Figs. 3 to 5 instead of the optical laminate 20D. The substrate 7 and the image-forming layer 6 may have the same configurations as the substrate and the image-forming layer, respectively, of known image display devices.

[0217] The image display device 21 in Fig. 7 may be an organic EL display or a liquid crystal display. However, the image display device 21 is not limited to this example. The image display device 21 may also be an electroluminescence (EL) display, a plasma display (PD), a field emission display (FED), or the like. The image display device 21 may be used for home appliances, in-vehicle applications, public information displays (PID), and the like.

[0218] The image display device 21 may have any configuration as long as it includes the pressure-sensitive adhesive sheet 1 and / or the optical laminate 20. [Example]

[0219] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples in any way.

[0220] <Synthesis of Polymer B1> A four-neck flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser was charged with 99 parts by weight of POB-A, 1 part by weight of 4-hydroxybutyl acrylate (4HBA), 0.30 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator, 3 parts by weight of 1-thioglycerol as a chain transfer agent, and 300 parts by weight of ethyl acetate. The mixture was maintained at 70°C and stirred gently while introducing nitrogen gas. After sufficient nitrogen substitution for at least 1 hour, the liquid temperature in the flask was maintained at 72-74°C and the polymerization reaction was carried out for 6 hours to prepare a solution of polymer B1. The solution was then heated at 90°C for 12 hours, followed by 3 hours of reduced pressure treatment at 120°C to remove the ethyl acetate. This yielded a thoroughly dried polymer B1, with the amount of ethyl acetate detected by gas chromatography being less than 0.1 parts by weight.

[0221] <Synthesis of Polymers B2 to B16> Except for changing the types and contents of the monomer, polymerization initiator, and chain transfer agent as shown in Table 1, thoroughly dried polymers B2 to B16 were synthesized in the same manner as for polymer B1.

[0222] [Mw of polymer B] The Mw of the obtained polymer B was measured by GPC (gel permeation chromatography). The measurement equipment and conditions were as follows. The measurement equipment and conditions were different for the nitrogen-containing composition and the nitrogen-free composition. (Nitrogen-containing composition) Analytical equipment: Agilent 1200 Column: Tosoh TSKgel SuperAWM-H + superAW4000 + superAW2500 Column temperature: 40℃ Eluent: DMF (salt added) ·Flow rate: 0.4mL / min ·Injection volume: 40μL Detector: Refractive index (RI) Standard sample: Agilent, polystyrene (PS) (Nitrogen-free composition) Analytical equipment: Waters, Alliance Column: Tosoh TSKgel SuperHZM-H x 2 Column temperature: 40℃ ·Eluent:THF ·Flow rate: 0.2mL / min ·Injection volume: 30μL Detector: Refractive index (RI) Standard sample: Agilent, polystyrene (PS)

[0223] [Table 1]

[0224] The abbreviations in Table 1 are as follows: POB-A: Phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical, product name "Light Acrylate POB-A") 4HBA: 4-hydroxybutyl acrylate ACMO: acryloylmorpholine BA: n-butyl acrylate CHMA: Cyclohexyl methacrylate IBXMA: Isobornyl methacrylate CBA: 2-(2-ethoxyethoxy)ethyl acrylate NVP: N-vinylpyrrolidone St: styrene AIBN: Azo polymerization initiator, 2,2'-azobisisobutyronitrile (Kishida Chemical Co., Ltd.)

[0225] [Tg of polymer B] The Tg of Polymer B was measured by DSC using the method described above. The differential scanning calorimeter used was a Q2000 manufactured by TA Instruments. The sample amount of Polymer B used in the DSC measurement was approximately 5 mg.

[0226] [Refractive index of polymer B] The refractive index of Polymer B was measured by the above-mentioned method using an Abbe refractometer (manufactured by ATAGO, Model DR-M4) at a measurement wavelength of 589 nm and a measurement temperature of 25°C.

[0227] [HSP of polymer B] The HSP (ΔD, ΔP, ΔH) of polymer B was determined by calculation using HSPiP (version 5) based on the structural units contained in polymer B and the contents of those units in polymer B.

[0228] [Color of polymer B b * Absolute value of Chromaticity b of polymer B * The absolute value of (|b * |) was measured using the method described above. The analytical device used was a Hitachi High-Tech UV-Visible-Near-Infrared Spectrophotometer UH4150. The analytical software used was Hitachi High-Tech UV Solutions.

[0229] The evaluation results of the properties of the polymers B1 to B16 are shown in Table 2 below.

[0230] [Table 2]

[0231] <Preparation of Dispersion D1> [Synthesis of dispersant d1] To 1.0 mol of propionic acid, 8.0 mol of ε-caprolactone, 0.2 mol of p-toluenesulfonic acid monohydrate, and 2.2 mol of pure water were added, and the mixture was stirred at 80°C for 8 hours. Next, stirring was continued for another 2 hours while dehydrating under reduced pressure (30 kPa). Next, the propionic acid remaining in the reaction system was distilled off, and the mixture was subjected to a purification step (washed with water three times) and a drying step to obtain dispersant d1 (a compound represented by the above formula (1) in which R is an ethyl group, m is 5, and n is 10).

[0232] [Preparation of Dispersion D1] 5 parts by weight of the above-mentioned dispersant d1 and 45 parts by weight of phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical Industry Co., Ltd., trade name "Light Acrylate POB-A"; hereinafter referred to as "POB-A") were added to and mixed with 167 parts by weight of a methanol dispersion of zirconium oxide particles (manufactured by Sakai Chemical Industry Co., Ltd., grade name "SZR-GM," average particle diameter (D50) based on dynamic light scattering: approximately 10 nm, zirconium oxide particle concentration: 30% by weight). Next, the solvent was removed under reduced pressure using a rotary evaporator to obtain Dispersion D1, a dispersion of zirconium oxide particles. Dispersion D1 contained zirconium oxide particles / Dispersant d1 / POB-A in a weight ratio of 50 / 5 / 45.

[0233] <Preparation of Dispersion D2> [Synthesis of dispersant d2] 415 g (1 mol) of tristyrenated phenol and 1 g (0.018 mol) of potassium hydroxide were charged into an autoclave and mixed uniformly. The resulting reaction system was heated to 130°C, and 352 g (8 mol) of ethylene oxide (EO) was added dropwise. After the dropwise addition was completed, the temperature was maintained at 130°C and the pressure was maintained at 0.1 MPa, and the mixture was aged for 1 hour to obtain an EO 8 mol adduct of tristyrenated phenol. Next, 767 g (1 mol) of the resulting EO 8 mol adduct of tristyrenated phenol and 152 g (1.3 mol) of sodium monochloroacetate were added to the reactor and stirred until uniform. Next, the reaction system was heated to 60°C and 52 g of sodium hydroxide was added, followed by heating to 80°C and aging for 3 hours. After aging, the mixture was cooled to 50°C, and 117 g (1.2 mol) of 98 wt% sulfuric acid was added dropwise at the same temperature to obtain a white suspension. The resulting suspension was washed with distilled water, and the solvent was removed by distillation under reduced pressure to obtain dispersant d2.

[0234] To 100 parts by weight of a methanol dispersion of zirconium oxide particles (manufactured by Sakai Chemical Industry Co., Ltd., grade name "SZR-M", average particle size (D50) based on dynamic light scattering: 3 nm, zirconium oxide particle concentration: 30 wt %), 1.5 parts by weight of the above-mentioned dispersant d2 and 28.5 parts by weight of POB-A were added and mixed. Next, the solvent was removed under reduced pressure using a rotary evaporator to obtain Dispersion D2, a dispersion of zirconium oxide particles. Dispersion D2 contained zirconium oxide particles / Dispersant d2 / POB-A in a weight ratio of 50 / 2.5 / 47.5.

[0235] <Example 1 of Addition to Pressure-Sensitive Adhesive Composition Containing Inorganic Particles> Example 1 100 parts by weight of Dispersion D1 was mixed with 10 parts by weight of Polymer B1, 0.05 parts by weight of 1,2-diphenylethan-1-one (manufactured by IGM Resins, trade name "Omnirad651") as a photopolymerization initiator, and 0.05 parts by weight of 1-hydroxycyclohexylphenylketone (manufactured by IGM Resins, trade name "Omnirad184"), 0.5 parts by weight of Irganox1010 (manufactured by BASF) as an antioxidant, 0.3 parts by weight of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Silicones, trade name "KBM-403") as a silane coupling agent, and 0.05 parts by weight of 1,9-nonanediol diacrylate (NDDA) as a crosslinking agent. This gave the adhesive composition of Example 1.

[0236] (Examples 2 to 13 and Comparative Examples 1 and 2) Pressure-sensitive adhesive compositions of Examples 2 to 13 and Comparative Examples 1 and 2 were obtained in the same manner as in Example 1, except that the type of dispersion, the type of polymer B, and the content of polymer B were changed as shown in Table 3.

[0237] (Reference example 1) An adhesive composition of Reference Example 1 was obtained in the same manner as in Example 1, except that Polymer B was not mixed.

[0238] <Evaluation> Using each of the pressure-sensitive adhesive compositions of Examples 1 to 13, Comparative Examples 1 and 2, and Reference Example 1, pressure-sensitive adhesive sheets for evaluation were produced by the following method.

[0239] [Preparation of release liner] A silicone-based release agent composition was prepared by mixing 30 parts by weight of an addition reaction curable silicone (LTC761 containing a hexenyl group-containing polyorganosiloxane, a 30 wt% toluene solution, manufactured by Dow Corning Toray Co., Ltd.), 0.9 parts by weight of a release control agent (BY24-850 containing an unreactive silicone resin, manufactured by Dow Corning Toray Co., Ltd.), 2 parts by weight of a curing catalyst (SRX212 containing a platinum catalyst, manufactured by Dow Corning Toray Co., Ltd.), and a toluene / hexane mixed solvent (volume ratio 1:1) as a diluent. The silicone solids concentration in the release agent composition was 1.0 wt%. Next, the release agent composition was applied to one side of a liner substrate (Lumirror XD500P polyester film, 75 μm thick) using a wire bar and heated at 130°C for 1 minute to prepare a release liner with a release layer (60 nm thick) on one side.

[0240] [Preparation of adhesive sheet] The adhesive composition was applied to one side of a substrate sheet (PET separator, Mitsubishi Plastics, MRF38) using an applicator to form a coating layer. Next, the release liner described above was placed on top of the formed coating layer to obtain a first laminate. The release liner was placed so that the release layer was in contact with the coating layer.

[0241] Next, an illuminance of 9 mW / cm was applied from the side of the base sheet of the first laminate. 2 and cumulative light intensity of 714 mJ / cm 2 The adhesive was irradiated with ultraviolet light for 10 seconds. An LED was used as the light source. The peak wavelength of the irradiated light was 340 nm. This photocured the coating layer, yielding a pressure-sensitive adhesive sheet (20 μm thick) sandwiched between the base sheet and release liner. The illuminance of the light was measured using an illuminance meter (UD-T3040T2, manufactured by Topcon Technohouse Co., Ltd.) near the surface of the base sheet where the ultraviolet light was incident.

[0242] Thereafter, following the above operation, an illuminance of 18 mW / cm was applied from the side of the base sheet of the first laminate. 2 and cumulative light intensity 667mJ / cm 2The adhesive sheet was irradiated with ultraviolet light for 10 seconds. A metal halide lamp was used as the light source. This removed any uncured monomer and unreacted initiator remaining on the adhesive sheet. The illuminance of the light was measured using an illuminance meter (U0-T36T2, manufactured by Topcon Technohouse Co., Ltd.) near the ultraviolet light incident surface of the substrate sheet.

[0243] [Refractive index evaluation] For each of the pressure-sensitive adhesive sheets produced, the release liner was peeled off to expose the surface, and the refractive index was measured in critical angle mode using a prism coupler (manufactured by Metricon, model "2010M") at a measurement temperature of 25°C and a measurement wavelength of 594 nm.

[0244] [Hayes's Review] For each pressure-sensitive adhesive sheet produced, the base sheet and release liner were peeled off, and an alkali-free glass plate (0.7 to 0.8 mm thick, total light transmittance 92%, haze 0.06%) was attached to each exposed surface to obtain a test specimen in which the pressure-sensitive adhesive sheet was sandwiched between two alkali-free glass plates. This test specimen was then left in an environment of 23°C and 50% RH for 30 minutes, after which it was placed in a pressure-degassing apparatus (autoclave) and autoclaved for 30 minutes at a temperature of 50°C and a pressure of 0.5 MPa. It was then left in an atmosphere of 23°C and 50% RH for 24 hours. The haze of the test specimen was then measured using a spectroscopic haze meter (HSP-150vis, manufactured by Murakami Color Research Laboratory) at 23°C.

[0245] [chromaticity b * Evaluation For each pressure-sensitive adhesive sheet produced, the base sheet and release liner were peeled off to expose each surface, and a non-alkali glass plate (thickness 0.7 to 0.8 mm, total light transmittance 92%, chromaticity b *0.20) was bonded together to obtain a test piece in which the adhesive sheet was sandwiched between two alkali-free glass plates. This test piece was left in an environment of 23°C and 50% RH for 30 minutes, then placed in a pressure degassing apparatus (autoclave) and autoclaved for 30 minutes at a temperature of 50°C and a pressure of 0.5 MPa. Next, it was left in an atmosphere of 23°C and 50% RH for 24 hours. Next, in a measurement environment of 23°C, the transmittance of the above test piece for light with wavelengths from 300 nm to 800 nm was measured using a UV-Visible-Near-Infrared Spectrophotometer (Hitachi High-Tech, UH4150). Chromaticity b was calculated from the obtained spectral data using a color calculation program (Hitachi High-Tech, UV Solutions). * The absolute value of the chromaticity b * The values ​​were based on reference data (blank data) measured without placing a sample in the measurement chamber of the ultraviolet-visible-near-infrared spectrophotometer.

[0246] [Adhesion strength evaluation] Under a measurement environment of 23°C and 50% RH, the release liner was peeled from each of the prepared PSA sheets, and a polyethylene terephthalate film (50 μm thick) was attached and backed. The resulting laminate was cut into a 100 mm long x 25 mm wide strip to prepare a test piece. The substrate sheet was peeled from the test piece, and placed on alkali-free glass (manufactured by Corning Incorporated, product name "EG-XG", thickness 0.7 mm), and the two were pressed together by moving a 2 kg roller back and forth once.

[0247] After leaving the test piece in the above environment for 30 minutes, it was placed in a pressure degassing apparatus (autoclave) and autoclaved for 30 minutes at a temperature of 50°C and a pressure of 0.5 MPa. It was then left for 24 hours in an atmosphere of 23°C and 50% RH. Next, using a universal tension and compression tester (Shimadzu Corporation, Autograph SHIMAZU AGX-V 50N), the test piece was peeled from the alkali-free glass at a peel rate of 300 mm / min and a peel angle of 180°. The force (peel strength) required to peel the test piece from the alkali-free glass was determined as the adhesive strength.

[0248] [Refractive Index Difference Between Polymer B and Base Composition] The refractive index of the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition of Reference Example 1 was defined as the "refractive index of the base composition," and the refractive index difference between the refractive index of Polymer B and the refractive index of the base composition was determined for each of the pressure-sensitive adhesive sheets of Examples 1 to 12 and Comparative Examples 1 and 2.

[0249] [Table 3]

[0250] The abbreviations in Table 3 are as follows: POB-A: Phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical, product name "Light Acrylate POB-A")

[0251] <Example 2 of Addition to Pressure-Sensitive Adhesive Composition Containing Inorganic Particles> Example 14 Phenoxybenzyl acrylate (POB-A) and 4-hydroxybutyl acrylate (4HBA) were mixed with Dispersion D1 to obtain a mixture containing zirconium oxide particles, Dispersant d1, POB-A, and 4HBA in the amounts shown in Table 4. 100 parts by weight of this mixture was mixed with 10 parts by weight of polymer B11, 0.6 parts by weight of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (manufactured by IGM Resins, trade name "Omnirad819") as a photopolymerization initiator, 2.5 parts by weight of TINUVIN384-2 (manufactured by BASF) as a UVA, 0.5 parts by weight of Irganox1010 (manufactured by BASF) as an antioxidant, 0.5 parts by weight of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Silicones, trade name "KBM-403") as a silane coupling agent, and 0.03 parts by weight of 1,9-nonanediol diacrylate (NDDA) as a crosslinking agent. This gave the adhesive composition of Example 14.

[0252] (Examples 15 to 20) The pressure-sensitive adhesive compositions of Examples 15 to 20 were obtained in the same manner as in Example 14, except that the composition of the mixture, the type of additive, and the content of the additive were changed as shown in Table 4.

[0253] (Reference example 2) An adhesive composition of Reference Example 2 was obtained in the same manner as in the adhesive composition of Example 14, except that Polymer B was not mixed.

[0254] <Evaluation> Each of the pressure-sensitive adhesive compositions of Examples 14 to 20 and Reference Example 2 was used to prepare a pressure-sensitive adhesive sheet for evaluation by the following method. The adhesive strength, refractive index, haze, and chromaticity b were measured using the prepared pressure-sensitive adhesive sheet by the same method as in Example 1. * The following evaluation was conducted.

[0255] The adhesive composition was applied to one side of a substrate sheet (PET separator, Mitsubishi Plastics, MRF38) using an applicator to form a coating layer. Next, the release liner described above was placed on top of the formed coating layer to obtain a first laminate. The release liner was placed so that the release layer was in contact with the coating layer.

[0256] Next, an illuminance of 9 mW / cm was applied from the side of the base sheet of the first laminate. 2 and cumulative light intensity of 1467mJ / cm 2 At the same time, ultraviolet light from a black light source was irradiated from the release liner side of the first laminate at an illuminance of 9 mW / cm. 2 and cumulative light intensity of 714 mJ / cm 2 The coating was exposed to light from an LED (peak wavelength 340 nm) for 10 seconds. This photocured the coating layer, yielding a pressure-sensitive adhesive sheet (50 μm thick) sandwiched between the base sheet and release liner. The illuminance of the ultraviolet light from the black light source was measured using an illuminance meter (U0-T36T2, manufactured by Topcon Technohouse) near the surface of the base sheet where the ultraviolet light was incident. The illuminance of the light from the LED was measured using an illuminance meter (UD-T3040T2, manufactured by Topcon Technohouse) near the surface of the release liner where the ultraviolet light was incident.

[0257] Thereafter, following the above operation, an illuminance of 18 mW / cm was applied from the side of the base sheet of the first laminate. 2and cumulative light intensity 667mJ / cm 2 The adhesive sheet was irradiated with ultraviolet light for 10 seconds. A metal halide lamp was used as the light source. This removed any uncured monomer and unreacted initiator remaining on the adhesive sheet. The illuminance of the light was measured using an illuminance meter (U0-T36T2, manufactured by Topcon Technohouse Co., Ltd.) near the ultraviolet light incident surface of the substrate sheet.

[0258] [Refractive Index Difference Between Polymer B and Base Composition] The refractive index of the adhesive sheet formed from the adhesive composition of Reference Example 2 was defined as the "refractive index of the base composition," and the refractive index difference between the refractive index of Polymer B and the refractive index of the base composition was determined for each of the adhesive sheets of Examples 14 to 20.

[0259] The evaluation results for each property are shown in Table 5.

[0260] [Table 4]

[0261] The abbreviations in Table 4 are as follows: POB-A: Phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical, product name "Light Acrylate POB-A") 4HBA: 4-hydroxybutyl acrylate Omni.819: bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (manufactured by IGM Resins, trade name "Omnirad 819") Tinuvin 384-2: Benzotriazole-based UVA (manufactured by BASF, trade name "Tinuvin 384-2") Tinuvin 405: Triazine UVA (manufactured by BASF, product name "Tinuvin 405") Tinuvin 571: Benzotriazole-based UVA (manufactured by BASF, trade name "Tinuvin 571") NDDA: 1,9-nonanediol diacrylate Irganox 1010: tetrakis[3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionic acid]pentaerythritol (manufactured by BASF) KBM403: 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Silicones Co., Ltd., product name "KBM-403")

[0262] [Table 5]

[0263] <Example of addition to adhesive composition containing no inorganic particles> Example 21 100 parts by weight of the partial polymer of POB-A was mixed with 3 parts by weight of polymer B1, 0.05 parts by weight of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (manufactured by IGM Resins, trade name "Omnirad 819") and 0.05 parts by weight of 1,2-diphenylethan-1-one (manufactured by IGM Resins, trade name "Omnirad 651") as photopolymerization initiators, 0.5 parts by weight of Irganox 1010 (manufactured by BASF) as an antioxidant, 0.3 parts by weight of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Silicones, trade name "KBM-403") as a silane coupling agent, and 0.020 parts by weight of 1,9-nonanediol diacrylate (NDDA) as a crosslinker. This gave the adhesive composition of Example 21.

[0264] (Reference example 3) An adhesive composition of Reference Example 3 was obtained in the same manner as in the adhesive composition of Example 21, except that Polymer B was not mixed.

[0265] The compositions of the pressure-sensitive adhesive compositions of Example 21 and Reference Example 3 are shown in Table 6.

[0266] <Evaluation> Using each of the pressure-sensitive adhesive compositions of Example 21 and Reference Example 3, pressure-sensitive adhesive sheets for evaluation were prepared in the same manner as in Example 14. Furthermore, the adhesive strength, refractive index, haze and chromaticity b were measured using the prepared pressure-sensitive adhesive sheets in the same manner as in Example 1.* The following evaluation was conducted.

[0267] [Refractive Index Difference Between Polymer B and Base Composition] The refractive index of the adhesive sheet formed from the adhesive composition of Reference Example 3 was defined as the "refractive index of the base composition," and the refractive index difference between the refractive index of Polymer B and the refractive index of the base composition was determined for the adhesive sheet of Example 21.

[0268] The evaluation results are shown in Table 7.

[0269] [Table 6]

[0270] The abbreviations in Table 6 are as follows: POB-A: Phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical, product name "Light Acrylate POB-A") Omni.819: bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (manufactured by IGM Resins, trade name "Omnirad 819") Omni.651: 1,2-diphenylethan-1-one (manufactured by IGM Resins, trade name "Omnirad651") NDDA: 1,9-nonanediol diacrylate Irganox 1010: tetrakis[3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionic acid]pentaerythritol (manufactured by BASF) KBM403: 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Silicones Co., Ltd., product name "KBM-403")

[0271] [Table 7]

[0272] As can be seen from Tables 1 to 7, Polymer B, which has an Mw of 1,500 to 30,000, a Tg of 30°C or less, and a refractive index of 1.51 or more, was suitable for producing a pressure-sensitive adhesive sheet with a high refractive index and improved adhesive strength. [Industrial Applicability]

[0273] The polymer of the present invention can be used, for example, in a photocurable pressure-sensitive adhesive composition. [Explanation of symbols]

[0274] 1 adhesive sheet 2 Optical Film 2A Polarizing Film 2B retardation film 3 Release liner 4 adhesive sheets 5 Protective film 6. Image forming layer 7. Circuit Board 20A, 20B, 20C, 20D Optical laminate 21 Image display device

Claims

1. having a weight average molecular weight of 1,500 to 30,000, a glass transition temperature of 30°C or less, and a refractive index of 1.51 or more; Polymers.

2. 2. The polymer according to claim 1, wherein the δH of the polymer is 5.15 or less. Here, δH is the hydrogen bond term of the Hansen solubility parameter (HSP).

3. The color of the polymer is determined according to CIE1976 L as specified in JIS Z8781-4:2013. * , a * , b * Color space chromaticity b * 2. The polymer according to claim 1, wherein the absolute value of

4. 2. The polymer according to claim 1, wherein the weight average molecular weight of the polymer is 2,400 to 16,000.

5. The polymer according to claim 1 , which comprises a structural unit derived from a monomer b having a double bond-containing ring.

6. The polymer according to claim 5 , wherein the double bond-containing ring is an aromatic ring.

7. The polymer according to claim 5 , wherein the monomer b has two or more of the double bond-containing rings in a side chain.

8. The polymer according to claim 7, wherein the monomer b has, in a side chain, a structure in which a first double bond-containing ring and a second double bond-containing ring contained in the two or more double bond-containing rings are bonded via a linking group.

9. The polymer according to claim 5 , wherein the monomer b is phenoxybenzyl acrylate.

10. The polymer according to claim 5 , wherein the content of the structural units derived from the monomer b in the polymer is 50% by weight or more.

11. A tackifier comprising the polymer according to any one of claims 1 to 10.

12. A polymer having a weight average molecular weight of 1,500 to 30,000, the polymer contains a structural unit derived from a monomer b having a double bond-containing ring, The monomer b has two or more of the double bond-containing rings in a side chain. Tackifier.

13. a monomer component M; The polymer according to any one of claims 1 to 10, or the tackifier according to claim 12, A photocurable pressure-sensitive adhesive composition.

14. A pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition according to claim 13.

15. An optical laminate comprising the pressure-sensitive adhesive sheet according to claim 14 and an optical film.

16. An image display device comprising the optical laminate according to claim 15.

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