Adhesive layer, method for producing the same, adhesive sheet, optical film with an adhesive layer, and image display device

Abstract

To provide a pressure-sensitive adhesive layer having good adhesion and capable of effectively suppressing internal reflection even when applied to optical members having a low refractive index, such as anti-reflection films, light diffusion films, prism films, light guide films, lens films, Fresnel lenses, lenticular lenses, or microlens films, and a method for producing the same. [Solution] An adhesive layer having a first surface and a second surface opposite the first surface, wherein the adhesive layer has a base formed throughout the entire adhesive layer from an adhesive composition containing a base polymer, the first surface having a first refractive index based on the adhesive composition, while the second refractive index of the second surface is lower than the first refractive index of the first surface.

Description

Technical Field

[0001] The present invention relates to an adhesive layer and a method for manufacturing the same. The present invention also relates to an adhesive sheet having the adhesive layer and an optical film with an adhesive layer. Further, the present invention relates to an image display device using these.

Background Art

[0002] For example, a display device such as a liquid crystal display device or an organic EL display device uses an adhesive composition to bond a polarizing film, a retardation film, a transparent cover member such as a cover glass, and various other optical films to other optical films. In this way, an optical film laminate having two optical films is formed by disposing an adhesive layer between the two optical films. The optical film laminate having such a configuration is arranged in the display device such that, for example, the side of the optical film is the viewing side. In this configuration, when external light enters from the optical film on the viewing side, there is a problem that the incident light is reflected at the interface between the adhesive layer and the optical film on the non-viewing side and returns to the viewing side. This problem becomes particularly prominent when the incident angle of the external light is shallow.

[0003] On the other hand, it has been proposed to use, for example, a light-diffusing adhesive composition containing light-diffusing fine particles with a (meth)acrylic polymer as a base polymer in the backlight unit of an image display device (Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The above problems are considered to be caused by the difference in refractive index between the adhesive layer and the adherend. For example, between the adhesive layer and an optical member (such as an antireflection film, a light diffusion film, a light guide film, a prism film, a lens film, a Fresnel lens or a lenticular lens or a microlens film) using a material with a low refractive index such as a fluororesin, a polysiloxane, low refractive index inorganic particles, a porous material, a hollow material, etc., problems with visibility occur due to the influence of internal reflection of incident light at the interface. Since the problem is considered to be due to the lower refractive index of the optical film compared to the adhesive layer, it is conceivable to solve the above problem by using an adhesive layer with a low refractive index. For example, as a method of forming an adhesive layer with a low refractive index using an acrylic adhesive, it is conceivable to use fluoroalkyl acrylate (refractive index around 1.38) as a monomer unit in a general acrylic polymer (refractive index usually 1.47 to 1.52) which is a base polymer. However, an adhesive layer with a low refractive index using a base polymer containing the fluoroalkyl acrylate as a monomer unit has a high surface tension and it is difficult to ensure adhesion. Thus, it has been extremely difficult to create an adhesive layer with a low refractive index (for example, refractive index of 1.40 or less) while ensuring the adhesion of the adhesive layer.

[0006] On the other hand, although the adhesive layer formed from the light diffusion adhesive composition of Patent Document 1 has a light diffusion function, it is difficult to sufficiently ensure adhesion with an optical film or the like because light diffusion fine particles are dispersed throughout the adhesive layer.

[0007] An object of the present invention is to provide an adhesive layer capable of effectively suppressing internal reflection and having good adhesion, and a method for producing the same, even when applied to an optical member with a low refractive index such as an antireflection film, a light diffusion film, a lens film, a Fresnel lens or a lenticular lens or a microlens film.

[0008] The present invention also aims to provide an adhesive sheet having the adhesive layer, further to provide an optical film with an adhesive layer having the adhesive layer, and still further to provide an image display device having the adhesive layer or the optical film with an adhesive layer.

Means for Solving the Problems

[0009] As a result of intensive studies to solve the above problems, the present inventors have found an adhesive layer and the like shown below, and have completed the present invention.

[0010] That is, the present invention relates to an adhesive layer having a first surface and a second surface on the opposite side of the first surface, the adhesive layer forms a base of the entire adhesive layer with an adhesive composition containing a base polymer, the first surface has a first refractive index based on the adhesive composition, while the second refractive index of the second surface is lower than the first refractive index of the first surface.

[0011] In the adhesive layer, the difference between the first refractive index of the first surface and the second refractive index of the second surface is preferably 0.02 to 0.45.

[0012] In the adhesive layer, the second refractive index of the second surface is preferably 1.45 or less.

[0013] As the adhesive layer, an embodiment in which a low refractive index material having a refractive index lower than that of the base polymer is dispersed on the second surface side can be adopted.

[0014] In the adhesive layer, the thickness of the region where the low refractive index material is dispersed is preferably 600 nm or less in the thickness direction from the second surface side in the adhesive layer.

[0015] In the adhesive layer, it is preferable that the refractive index of the base polymer is 1.40 to 1.55 and the refractive index of the low refractive index material is 1.10 to 1.45. Further, it is preferable that the difference between the refractive index of the base polymer and the refractive index of the low refractive index material is 0.07 to 0.45.

[0016] Examples of the low refractive index material include particles having an average particle diameter of 10 nm to 150 nm.

[0017] Examples of the low refractive index material include at least one inorganic particle selected from the group consisting of MgF2, CaF2, and Na3AlF6, porous silica particles, hollow nanosilica particles, and at least one particle selected from the group consisting of hollow polymer particles.

[0018] It is preferable that the adhesive layer has a total light transmittance of 85% or more.

[0019] It is preferable that the adhesive layer has a reflectance of 0.5 to 3.5% on the second surface.

[0020] It is preferable that the difference in reflectance between the first surface and the second surface of the adhesive layer is 0.1 to 3.5%.

[0021] It is preferable that the adhesive layer has a gel fraction of 30 to 95% by weight.

[0022] It is preferable that the adhesive layer has a storage elastic modulus G' of 0.05 to 0.50 MPa at 25°C.

[0023] It is preferable that the adhesive layer has a tanδ peak value of -5 to -50°C during dynamic viscoelasticity measurement at 1 Hz.

[0024] Further, the present invention relates to a method for producing the adhesive layer, Step (1) of forming a base adhesive layer with an adhesive composition containing a base polymer on a support, Step (2) of preparing a dispersion in which a low refractive index material having a refractive index lower than that of the base polymer is dispersed, On the second surface of the base adhesive layer, which is opposite to the first surface on the support side, applying the dispersion or solution, and allowing the low refractive index material contained in the dispersion or solution to penetrate in the thickness direction from the second surface of the base adhesive layer (step (3)), and Step (4) of drying the adhesive layer into which the low refractive index material has penetrated, relates to a method for producing an adhesive layer, characterized by including the above steps.

[0025] The present invention also relates to an adhesive sheet characterized by having the adhesive layer and a support on one or both sides of the adhesive layer.

[0026] The present invention also relates to an optical film with an adhesive layer having an adhesive layer provided on one or both sides of the optical film, wherein the adhesive layer on one or both sides is the adhesive layer, and the first surface side of the adhesive layer is provided on the optical film, and relates to an optical film with an adhesive layer.

[0027] In the optical film with an adhesive layer, a polarizing film is preferably used as the optical film.

[0028] The present invention also relates to an optical laminate characterized by having the optical film with an adhesive layer and a low refractive index optical member bonded to the adhesive layer of the optical film with an adhesive layer.

[0029] The present invention also relates to an image display device characterized by having the adhesive layer, the optical film with an adhesive layer, or the optical laminate.

Advantages of the Invention

[0030] Unlike the diffusion adhesive layer in which fine particles are uniformly diffused in the adhesive layer, the adhesive layer of the present invention has different refractive indices on both sides of a single-layer adhesive layer having a first surface and a second surface. On the side of the first surface, it has a first refractive index based on the adhesive composition that forms the base of the entire adhesive layer, and on the other side of the second surface, it has a second refractive index lower than the first refractive index of the first surface. Thus, since the adhesive layer of the present invention has an adhesive surface controlled to a low refractive index rather than the refractive index based on the adhesive layer, it can adjust the refractive index difference from an optical member (for example, an antireflection film, a light diffusion film, a light guide film, a prism film, a lens film, a Fresnel lens or a lenticular lens or a microlens film, etc.) formed of a low refractive index material. As a result, reflection at the interface between the adhesive layer and the optical member can be suppressed, and it can contribute to an improvement in light extraction efficiency. When the second surface of the adhesive layer of the present invention is applied to a surface uneven portion such as a microlens, the adhesive layer can protect the surface uneven shape by filling the surface uneven portion, and compared with the case where a void layer is provided in the surface uneven portion, the voids can be filled without impairing the light extraction efficiency, and damage and shape breakage due to vibration during handling and transportation can be suppressed. Further, although the second surface of the adhesive layer of the present invention has a refractive index adjustment region adjusted to a low refractive index, it has a high total light transmittance and can form a low refractive index region without increasing the haze value. Further, on the first surface of the adhesive layer of the present invention, since the adhesive layer maintains its original adhesive force, the adhesion to a general optical film (for example, a polarizing film, etc.) is also good. On the other hand, since the adhesive composition forms the base on the second surface of the adhesive layer controlled to a low refractive index, the adhesion to an optical film formed of a low refractive index material can be ensured.

Brief Description of the Drawings

[0031]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0032] Hereinafter, the pressure-sensitive adhesive layer and the like of the present invention will be described with reference to the drawings.

[0033] <Pressure-sensitive adhesive layer> As shown in FIG. 1, the pressure-sensitive adhesive layer 1 of the present invention has a first surface f1 and a second surface f2 on the opposite side of the first surface f1. Further, in the pressure-sensitive adhesive layer 1, a base (matrix) 1a of the entire pressure-sensitive adhesive layer 1 is formed by a pressure-sensitive adhesive composition containing a base polymer. The first surface f1 has a first refractive index n1, and the second refractive index n2 of the second surface f2 is designed to be lower than the first refractive index n1. In FIG. 1, in the base 1a, on the side of the second surface f2, a low refractive index material 2 having a refractive index lower than that of the base polymer is dispersed (Unevenly distributed) is exemplified.

[0034] The first refractive index n1 of the first surface f1 corresponds to the refractive index of the pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition forming the base 1a in the pressure-sensitive adhesive layer 1 of the present invention. Therefore, the first refractive index n1 is determined by the pressure-sensitive adhesive composition forming the base 1a. Since the refractive index of the base polymer is substantially the same as the refractive index of the base 1a of the entire pressure-sensitive adhesive layer 1, the first refractive index n1 of the first surface f1 is generally determined by the refractive index of the base polymer. The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer will be described later. For example, the refractive index of a pressure-sensitive adhesive layer formed by a typical acrylic pressure-sensitive adhesive is generally about 1.47 to 1.52. The refractive index of a pressure-sensitive adhesive layer formed by a silicone-based pressure-sensitive adhesive is generally about 1.40.

[0035] On the other hand, the second refractive index n2 of the second surface f2 is not particularly limited as long as n1 > n2 is satisfied in relation to the first refractive index n1 on the first surface f1 side, and is appropriately determined in consideration of the refractive index of the low refractive index optical film serving as the adherend. However, if the difference (n1 - n2) between the first refractive index n1 and the second refractive index n2 becomes too large, internal reflection in the adhesive layer 1 may occur. Therefore, it is preferable to adjust the difference (n1 - n2) to be 0.02 to 0.45. The difference (n1 - n2) is more preferably 0.03 to 0.35, and even more preferably 0.03 to 0.25.

[0036] The second refractive index n2 of the second surface f2 is preferably 1.45 or less, more preferably 1.4 or less, even more preferably 1.35 or less, and even more preferably 1.3 or less, from the viewpoint of effectively suppressing internal reflection. If the second refractive index n2 is 1.4 or less, it is also possible to use the second surface side of the adhesive layer 1 of the present invention as an alternative to the air layer. On the other hand, the second refractive index n2 is preferably 1.25 or more, more preferably 1.28 or more, from the viewpoint of maintaining the adhesive force. The range of the second refractive index n2 is lower than the lower limit value of the refractive index of the adhesive layer formed by a typical acrylic adhesive (generally about 1.47 to 1.52).

[0037] In the adhesive layer 1, as shown in FIG. 1, when the low refractive index material 2 is dispersed on the second surface f2 side, the refractive index of the base polymer in the adhesive composition forming the base 1a is 1.40 to 1.55, and in the base 1a, the refractive index of the low refractive index material 2 dispersed on the second surface f2 side is preferably 1.10 to 1.45. The difference between the refractive index of the base polymer and the refractive index of the low refractive index material 2 is preferably 0.07 to 0.45. The refractive index of the base polymer is more preferably 1.40 to 1.52, and even more preferably 1.40 to 1.50. The refractive index of the low refractive index material 2 is more preferably 1.14 to 1.42, and even more preferably 1.18 to 1.40. The difference between the refractive index of the base polymer and the refractive index of the low refractive index material 2 is more preferably 0.07 to 0.35, and even more preferably 0.10 to 0.30. Although the lower the refractive index of the low refractive index material 2, the lower the refractive index can be reduced with a lower addition amount, on the other hand, since the difference between the refractive index of the base polymer (adhesive layer 1a) and the refractive index of the low refractive index material 2 tends to increase and scattering (haze) is likely to occur, it is preferable to adjust so that the refractive index difference does not become too large. The refractive index can be shown as the refractive index value of the D line measured in an environment of 23 ° C by spectroscopic ellipsometry for the case where the material is a single-layer film.

[0038] As the low refractive index material 2, particles having an average particle diameter of 10 nm to 150 nm can be used. Particles having an average particle diameter within the above range are preferable for suppressing the haze of the adhesive layer 1 and maintaining a high total light transmittance even when dispersed on the second surface f2 side of the adhesive layer 1. The average particle diameter is preferably 20 nm to 100 nm, and more preferably 20 nm to 90 nm. The average particle diameter of the particles is a value measured by a particle size distribution diameter measuring device using the dynamic light scattering method.

[0039] Examples of the low refractive index material 2 include MgF2 (refractive index 1.38), CaF2 (refractive index 1.43: fluorite), Na3AlF (refractive index 1.34: sodium hexafluoroaluminate (cryolite)), and the like. These materials (for example, particles) can be used alone or in combination of two or more.

[0040] In addition, as the low refractive index material 2, for example, hollow particles can be used. The hollow particles can be either inorganic particles or polymer particles. Since the hollow particles have a low refractive index void space inside the particles, the refractive index of the hollow particles is lower than the refractive index of the components forming the hollow particles. For example, although the refractive index of silica is 1.46, hollow nanosilica particles (refractive index 1.24, trade name: Throughia 5320, particle size 75 nm, manufactured by Nichiai Catalyst Kasei Co., Ltd.) and porous silica particles can be used as the low refractive index material. In addition, hollow polymer fine particles (refractive index 1.32, trade name: Tech Polymer NH product number XX - 255AA, particle size 80 nm, hollow ratio 39%, manufactured by Sekisui Chemical Co., Ltd.) can be exemplified. When the hollow particles are provided in the low refractive surface treatment layer, there are problems with strength and scratch resistance because they are hollow materials. However, the hollow particles (low refractive index material 2) in the present invention are in a form added (impregnated) into the adhesive layer 1, so they can be applied without considering the problems of strength and scratch resistance.

[0041] In addition, as the low refractive index material 2, an oligomer containing a fluoroalkyl group, an oligomer of a polysiloxane resin, or the like can be used.

[0042] The thickness of the adhesive layer 1 is not particularly limited, but is usually 5 μm to 500 μm, preferably 10 μm to 400 μm, and more preferably 10 μm to 350 μm. In FIG. 1, the region where the low refractive index material 2 is dispersed in the adhesive layer 1 is represented by a thickness T from the second surface f2 side. The thickness T is appropriately designed according to the thickness of the adhesive layer, but is usually preferably 600 nm or less, more preferably 300 nm or less, and even more preferably 200 nm or less. Note that the thickness T is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more in order to effectively suppress internal reflection when applied to an optical film having a low refractive index.

[0043] In the adhesive layer 1, the region where the low refractive index material 2 related to the thickness T is dispersed has an irregular uneven shape in relation to the base (matrix) 1a. In the present invention, the thickness T is determined by averaging the measured values of the depths of the uneven shapes.

[0044] The low refractive index material 2 is distributed on the side of the second surface f2 in an individual dispersed state or in a state where a part thereof is aggregated. The boundary between the region where the low refractive index material 2 is dispersed and the base 1a where the low refractive index material 2 is not dispersed has an irregular uneven shape as described in relation to FIG. 1. However, in measuring the thickness T, at each measurement position, the depth range in which 90% of the low refractive index material 2 exists is taken as the measured value of the thickness T at that measurement position, and the measured values at a plurality of measurement positions are averaged.

[0045] Figure 2 is a plan view showing the state of the second surface f2 of the adhesive layer 1. As shown in Figure 2, it has a sea-island structure in which the low refractive index material 2 is dispersed in an island shape on the base 1a, and there are portions of the base 1a and portions of the low refractive index material 2. The area ratio of the low refractive index material 2 on the second surface f2 is preferably in the range of 30 to 99%. The area ratio is the ratio of the area occupied by the low refractive index material 2 to the total area of the square region in a square region with a side length of 10 μm to 200 μm. Measurements are made for a plurality of square regions, and the area ratio is obtained by averaging the measured values.

[0046] In addition, the ratio of the low refractive index material 2 in the adhesive layer 1 is not particularly limited as long as the first refractive index n1 on the first surface f1 side and the second refractive index n2 of the second surface f2 satisfy the relationship n1 > n2.

[0047] The total light transmittance of the entire adhesive layer 1 of the present invention is preferably 85% or more, more preferably 88% or more, and even more preferably 90% or more. The higher the total light transmittance of the adhesive layer 1, the better. Also, the haze value is preferably 1.5% or less, more preferably 1% or less, and even more preferably 0.8% or less. The lower the haze value of the adhesive layer 1, the better. The total light transmittance and haze value of the entire adhesive layer 1 are values measured in accordance with JIS K7361.

[0048] Also, the reflectance of the second surface of the adhesive layer 1 of the present invention is preferably 0.5 to 3.5%. The reflectance of the second surface of the adhesive layer 1 of the present invention is lower than the reflectance of the first surface, and in relation to the low refractive index material, internal reflection can be controlled to be small. The reflectance of the second surface is preferably 0.5 to 3.0%, and more preferably 0.5 to 2.5%. Also, the difference in reflectance between the first surface and the second surface of the adhesive layer 1 of the present invention is preferably 0.1 to 3.5%.

[0049] Incidentally, in the above description of the adhesive layer 1 of the present invention, it is premised that the second refractive index n2 of the second surface f2 is designed to be lower than the first refractive index n1. However, the adhesive layer 1 of the present invention can be regarded as an invention characterized in that the reflectance of the second surface f2 is lower than the reflectance of the first surface f1, in addition to being able to be specified by the relationship between the refractive indices of both surfaces.

[0050] Also, the gel fraction of the adhesive layer 1 of the present invention is preferably 30 to 95% by weight. The gel fraction is preferably 30 to 90% by weight, more preferably 35 to 90% by weight, and even more preferably 40 to 90% by weight. When the gel fraction of the adhesive layer 1 is within the above range, it has stress relaxation properties and is a preferable aspect for ensuring followability to unevenness. Incidentally, the gel fraction relates to the base 1a in the adhesive layer 1 and does not include the low refractive index material 2.

[0051] <Measurement of Gel Fraction of Adhesive Layer> Approximately 0.2 g was scraped from the adhesive layer (before penetration of the low refractive index material) and designated as sample 1. After wrapping the sample 1 with a Teflon (registered trademark) film having a diameter of 0.2 μm (product name “NTF1122”, manufactured by Nitto Denko Corporation), it was tied with kite string, and this was designated as sample 2. The weight of sample 2 before being subjected to the following test was measured, and this was designated as weight A. Incidentally, the weight A is the total weight of sample 1 (adhesive layer), the Teflon (registered trademark) film, and the kite string. Also, the total weight of the Teflon (registered trademark) film and the kite string was designated as weight B. Next, the sample 2 was placed in a 50 ml container filled with ethyl acetate and left standing at 23° C. for 1 week. Then, the sample 2 was taken out from the container, dried in a dryer at 130° C. for 2 hours to remove ethyl acetate, and then the weight of sample 2 was measured. The weight of sample 2 after being subjected to the test was measured, and this was designated as weight C. Then, the gel fraction (% by weight) was calculated from the following formula. Gel fraction (% by weight) = (C - B) / (A - B) × 100

[0052] Also, the adhesive layer 1 of the present invention preferably has a storage elastic modulus G' of 0.05 to 0.50 MPa at 25°C. The storage elastic modulus G' is preferably 0.06 to 0.45 MPa, more preferably 0.07 to 0.40 MPa, and still more preferably 0.08 to 0.35 MPa. When the storage elastic modulus G' of the adhesive layer 1 is within the above range, it is a preferable aspect in terms of protecting a thin-type image display device (such as an LCD or OLED terminal) and ensuring dimensional stability during cutting.

[0053] Also, the adhesive layer 1 of the present invention preferably has a tanδ peak value (glass transition temperature) of -5 to -50°C during dynamic viscoelasticity measurement at 1 Hz. The tanδ peak value is preferably -7 to -50°C, more preferably -9 to -45°C, and still more preferably -10 to -40°C. When the tanδ peak value of the adhesive layer 1 is within the above range, it is a preferable aspect in terms of ensuring resistance to dropping impact of an image display device (such as a mobile terminal).

[0054] <Measurement of the storage elastic modulus G' and tanδ peak value of the adhesive layer> A plurality of adhesive layers were laminated to prepare a test sample with a thickness of about 2 mm. This test sample was punched into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and dynamic viscoelasticity measurement was performed using an "Advanced Rheometric Expansion System (ARES)" manufactured by Rheometric Scientific under the following conditions. From the measurement results, the storage elastic modulus G' and tanδ peak value of the adhesive layer at 25°C were read. (Measurement conditions) Frequency: 1 Hz Deformation mode: Torsion Measurement temperature: -70°C to 150°C Heating rate: 5°C / min

[0055] Next, the manufacturing method of the adhesive layer of the present invention will be described with reference to FIG. 3.

[0056] First, as step (1), a base adhesive layer 1' is formed on a support S with an adhesive composition containing a base polymer. The base adhesive layer 1' forms a base 1a in the resulting adhesive layer 1. In the base adhesive layer 1', the side on the support 1 side is the first surface f1', and the opposite side is the second surface f2'. The method for forming the base adhesive layer 1' is not particularly limited and can be formed by a method usually used in this field. Specifically, the adhesive composition is applied to one side of the support S, and the coating film formed from the adhesive composition is dried to form it, or it can be formed by irradiating active energy rays such as ultraviolet rays.

[0057] The support S is not particularly limited, and for example, various base materials such as a release film, a transparent resin film base material, etc. can be used.

[0058] Examples of the constituent materials of the release film include resin films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester film, porous materials such as paper, cloth, and non-woven fabric, nets, foamed sheets, metal foils, and appropriate thin sheets such as laminates thereof. However, a resin film is preferably used from the viewpoint of excellent surface smoothness. The release film can be subjected to release and antifouling treatment or antistatic treatment as necessary.

[0059] On the other hand, as step (2), a dispersion liquid 10 in which a low refractive index material 2 having a refractive index lower than that of the base polymer used in the adhesive composition is dispersed is prepared (not shown). As the dispersion medium used for the dispersion liquid, one that can disperse the low refractive index material 2 and can penetrate into the base adhesive layer 1' is used, and it is appropriately selected according to the type of the low refractive index material and the type of the adhesive composition forming the base adhesive layer. The concentration of the low refractive index material in the dispersion medium is preferably adjusted to, for example, 0.1 to 10% by weight.

[0060] Examples of the dispersion medium include alcohols such as methanol, ethanol, isopropyl alcohol, 1-propanol, n-butanol, 2-butanol, cyclohexanol, t-butyl alcohol, glycerin, ethylene glycol, 2-methyl-2,4-pentanediol, phenol, and parachlorophenol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pentanone, 2-hexanone, and 2-heptanone; ethers such as diethyl ether, tetrahydrofuran, dioxane, and anisole; esters such as ethyl acetate, butyl acetate, and methyl lactate; aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as n-hexane and cyclohexane; amides such as dimethylformamide and dimethylacetamide; and cellosolves such as methyl cellosolve, ethyl cellosolve, and methyl cellosolve acetate. These dispersion media can be used alone or in combination of two or more. Note that the above solvents are merely examples, and the solvents used in the present invention are not limited thereto.

[0061] Next, as step (3), the dispersion liquid 10 is applied to the second surface f2' of the base adhesive layer 1', and the low refractive index material 2 contained in the dispersion liquid 10 is allowed to penetrate in the thickness direction from the second surface f2' of the base adhesive layer 1'. (3)-1 in FIG. 3 shows the state immediately after the dispersion liquid 10 is applied to the base adhesive layer 1', and (3)-2 shows the state where the low refractive index material 2 has penetrated into the base adhesive layer 1'. The side of the second surface f2' of the base adhesive layer 1' is swollen by the dispersion medium of the dispersion liquid 10, and in this process, the low refractive index material 2 in the dispersion liquid 10 penetrates into the base adhesive layer 1'.

[0062] Next, as step (4), the base adhesive layer 1' into which the low refractive index material 2 has penetrated is dried. By the drying process, the dispersion medium of the dispersion liquid 10 that has penetrated into the base adhesive layer 1' is evaporated, and the adhesive layer 1 shown in FIG. 1 can be obtained. This state is shown in (4) of FIG. 3. The conditions of the drying process are determined according to the type of the dispersion medium.

[0063] The region (thickness T) where the low refractive index material 2 is dispersed in the adhesive layer 1 is determined by the relationship between the adhesive composition forming the base adhesive layer 1' and the dispersion medium of the dispersion liquid 10. The dispersion medium can be appropriately selected so that the penetration depth becomes the above-described value. Further, the coating amount of the dispersion liquid is appropriately set so as to obtain a desired thickness T.

[0064] As the coating method of the above dispersion liquid, for example, an appropriate method 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, die coater, etc. can be used. The thickness T can be controlled by the coating method of the dispersion liquid, the concentration of the dispersion liquid, the coating amount, etc.

[0065] <Adhesive composition> An adhesive composition containing a base polymer that forms the base (matrix) 1a of the adhesive layer 1 of the present invention will be described.

[0066] As the adhesive composition, a transparent material having adhesiveness that can be used for optical applications is preferably used. As the adhesive composition, for example, it can be appropriately selected and used from acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. From the viewpoints of transparency, processability, durability, etc., it is preferable to use an acrylic adhesive. A base polymer corresponding to the type of the adhesive composition is used. In the present invention, it is preferably an acrylic adhesive containing a (meth)acrylic polymer as a base polymer.

[0067] The acrylic adhesive can include, for example, a partial polymer of a monomer component containing an alkyl (meth)acrylate and / or a (meth)acrylic polymer obtained from the monomer component. The base polymer of the acrylic adhesive includes a partial polymer of a monomer component containing an alkyl (meth)acrylate and / or a (meth)acrylic polymer obtained from the monomer component.

[0068] Examples of the alkyl (meth)acrylate include the aforementioned linear or branched alkyl (meth)acrylates having 1 to 24 carbon atoms. Among these, alkyl (meth)acrylates having 1 to 9 carbon atoms are preferred, and alkyl (meth)acrylates having a branch with 4 to 9 carbon atoms can be preferably exemplified. The alkyl (meth)acrylate is preferred in terms of the ease of achieving a balance in adhesive properties. Specific examples of the alkyl (meth)acrylate having a branch with 4 to 9 carbon atoms include n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, etc. These can be used alone or in combination of two or more.

[0069] In the present invention, the alkyl (meth)acrylate having an alkyl group with 1 to 24 carbon atoms at the ester terminal is preferably 40% by weight or more, more preferably 50% by weight or more, and even more preferably 60% by weight or more based on the total amount of the monofunctional monomer components forming the (meth)acrylic polymer.

[0070] The monomer component can contain, as a monofunctional monomer component, a copolymerization monomer other than the alkyl (meth)acrylate. The copolymerization monomer can be used as the remainder of the alkyl (meth)acrylate in the monomer component.

[0071] As the copolymerizable monomer, for example, a cyclic nitrogen-containing monomer can be included. As the cyclic nitrogen-containing monomer, those having a polymerizable functional group having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group and having a cyclic nitrogen structure can be used without particular limitation. The cyclic nitrogen structure preferably has a nitrogen atom in the cyclic structure. Examples of the cyclic nitrogen-containing monomer include lactam-based vinyl monomers such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, and methylvinylpyrrolidone; vinyl-based monomers having a nitrogen-containing heterocyclic ring such as vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, and vinylmorpholine. Further, (meth)acrylic monomers containing a heterocyclic ring such as a morpholine ring, a piperidine ring, a pyrrolidine ring, and a piperazine ring can be mentioned. Specifically, N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, N-acryloylpyrrolidine, and the like can be mentioned. Among the cyclic nitrogen-containing monomers, lactam-based vinyl monomers are preferred.

[0072] In the present invention, the cyclic nitrogen-containing monomer is preferably 0.5 to 50% by weight, more preferably 0.5 to 40% by weight, and even more preferably 0.5 to 30% by weight based on the total amount of the monofunctional monomer components forming the (meth)acrylic polymer.

[0073] Among the monomer components used in the present invention, as the monofunctional monomer component, a hydroxyl group-containing monomer can be included. As the hydroxyl group-containing monomer, those having a polymerizable functional group having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group and having a hydroxyl group can be used without particular limitation. Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate; and hydroxyalkyl cycloalkane (meth)acrylates such as (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. In addition, hydroxyethyl (meth)acrylamide, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, and the like can be mentioned. These can be used alone or in combination. Among these, hydroxyalkyl (meth)acrylate is preferred.

[0074] In the present invention, the hydroxyl group-containing monomer is preferably 1% by weight or more, more preferably 2% by weight or more, and even more preferably 3% by weight or more based on the total amount of the monofunctional monomer components forming the (meth)acrylic polymer, from the viewpoint of enhancing the adhesive strength and cohesive strength. On the other hand, if the amount of the hydroxyl group-containing monomer becomes too large, the adhesive layer may become hard and the adhesive strength may decrease, and the viscosity of the adhesive composition may become too high or gelation may occur. Therefore, the hydroxyl group-containing monomer is preferably 30% by weight or less, more preferably 27% by weight or less, and even more preferably 25% by weight or less based on the total amount of the monofunctional monomer components forming the (meth)acrylic polymer.

[0075] In addition, the monomer components for forming the (meth)acrylic polymer can contain other functional group-containing monomers as monofunctional monomers. Examples thereof include carboxyl group-containing monomers and monomers having a cyclic ether group.

[0076] As the carboxyl group-containing monomer, those having a polymerizable functional group having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group and having a carboxyl group can be used without particular limitation. Examples of the carboxyl group-containing monomer include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, etc. These can be used alone or in combination. For itaconic acid and maleic acid, their anhydrides can be used. Among these, acrylic acid and methacrylic acid are preferred, and acrylic acid is particularly preferred. Note that a carboxyl group-containing monomer can be arbitrarily used as the monomer component used for producing the (meth)acrylic polymer of the present invention. On the other hand, it is not necessary to use a carboxyl group-containing monomer.

[0077] As the monomer having a cyclic ether group, those having a polymerizable functional group having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group and having a cyclic ether group such as an epoxy group or an oxetane group can be used without particular limitation. Examples of the epoxy group-containing monomer include glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, etc. Examples of the oxetane group-containing monomer include 3-oxetanylmethyl (meth)acrylate, 3-methyl-oxetanylmethyl (meth)acrylate, 3-ethyl-oxetanylmethyl (meth)acrylate, 3-butyl-oxetanylmethyl (meth)acrylate, 3-hexyl-oxetanylmethyl (meth)acrylate, etc. These can be used alone or in combination.

[0078] In the present invention, the carboxyl group-containing monomer and the monomer having a cyclic ether group are preferably 30% by weight or less, more preferably 27% by weight or less, and even more preferably 25% by weight or less based on the total amount of the monofunctional monomer components forming the (meth)acrylic polymer.

[0079] In the monomer components forming the (meth)acrylic polymer of the present invention, examples of the copolymerizable monomer include, for example, CH2=C(R 1 )COOR 2 (wherein R 1 is hydrogen or a methyl group, and R 2 represents a substituted alkyl group having 1 to 3 carbon atoms or a cyclic cycloalkyl group.)

[0080] Here, as the substituent of the substituted alkyl group having 1 to 3 carbon atoms for R 2 , it is preferably an aryl group having 3 to 8 carbon atoms or an aryloxy group having 3 to 8 carbon atoms. The aryl group is preferably a phenyl group although not limited.

[0081] Examples of such a monomer represented by CH2=C(R 1 )COOR 2 include phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and the like. These can be used alone or in combination.

[0082] In the present invention, the (meth)acrylate represented by CH2=C(R 1 )COOR 2 can be used in an amount of 50% by weight or less, preferably 45% by weight or less, more preferably 40% by weight or less, and even more preferably 35% by weight or less based on the total amount of the monofunctional monomer components forming the (meth)acrylic polymer.

[0083] As other copolymerizable monomers, vinyl acetate, vinyl propionate, styrene, α-methylstyrene; glycol-based acrylate monomers such as polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate; acrylate-based monomers such as tetrahydrofurfuryl (meth)acrylate, fluoro (meth)acrylate, silicone (meth)acrylate, and 2-methoxyethyl acrylate; amide group-containing monomers, amino group-containing monomers, imide group-containing monomers, N-acryloylmorpholine, vinyl ether monomers, etc. can also be used. Further, monomers having a cyclic structure such as terpene (meth)acrylate and dicyclopentanyl (meth)acrylate can be used as the copolymerizable monomers.

[0084] Furthermore, silane-based monomers containing silicon atoms and the like can be mentioned. Examples of silane-based monomers include 3-acryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane, 10-acryloyloxydecyltrimethoxysilane, 10-methacryloyloxydecyltriethoxysilane, 10-acryloyloxydecyltriethoxysilane, and the like.

[0085] In addition to the monofunctional monomers exemplified above, the monomer component forming the (meth)acrylic polymer of the present invention can contain polyfunctional monomers as necessary in order to adjust the cohesive force of the adhesive composition.

[0086] A polyfunctional monomer is a monomer having at least two polymerizable functional groups having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group. For example, esters of polyhydric alcohols such as (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, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate and (meth)acrylic acid; allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl di(meth)acrylate, hexyl di(meth)acrylate and the like. Among these, trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, and dipentaerythritol hexa(meth)acrylate can be preferably used. The polyfunctional monomer can be used alone or in combination of two or more.

[0087] The amount of the polyfunctional monomer used varies depending on its molecular weight, the number of functional groups, etc., but it is preferably used in an amount of 3 parts by weight or less, more preferably 2 parts by weight or less, and even more preferably 1 part by weight or less based on 100 parts by weight in total of the monofunctional monomers. The lower limit is not particularly limited, but it is preferably 0 parts by weight or more, and more preferably 0.001 parts by weight or more. By using the polyfunctional monomer in the above range, the adhesive strength can be improved.

[0088] The production of the (meth)acrylic polymer can be appropriately selected from known production methods such as solution polymerization, radiation polymerization such as ultraviolet (UV) polymerization, bulk polymerization, and various radical polymerizations such as emulsion polymerization. Further, the obtained (meth)acrylic polymer may be any of a random copolymer, a block copolymer, a graft copolymer, etc.

[0089] In the present invention, a partial polymer of the monomer component can also be preferably used.

[0090] The production of the (meth)acrylic polymer can be appropriately selected from known production methods such as solution polymerization, radiation polymerization such as ultraviolet (UV) polymerization, bulk polymerization, and various radical polymerizations such as emulsion polymerization. Further, the obtained (meth)acrylic polymer may be any of a random copolymer, a block copolymer, a graft copolymer, etc.

[0091] When the (meth)acrylic polymer is produced by radical polymerization, a polymerization initiator, a chain transfer agent, an emulsifier, etc. used in radical polymerization can be appropriately added to the monomer component to carry out the polymerization. The polymerization initiator, chain transfer agent, emulsifier, etc. used in the radical polymerization are not particularly limited and can be appropriately selected and used. Note that the weight average molecular weight of the (meth)acrylic polymer can be controlled by the amount of the polymerization initiator and chain transfer agent used and the reaction conditions, and the amount used is appropriately adjusted according to these types.

[0092] For example, in solution polymerization, etc., as the polymerization solvent, for example, ethyl acetate, toluene, etc. are used. As a specific example of solution polymerization, the reaction is carried out under an inert gas stream such as nitrogen, a polymerization initiator is added, and usually, it is carried out under reaction conditions of about 50 to 70 °C for about 5 to 30 hours.

[0093] When the (meth)acrylic polymer is produced by radiation polymerization, it can be produced by irradiating the monomer component with radiation such as an electron beam or ultraviolet (UV) to carry out polymerization. When carrying out ultraviolet polymerization, it is preferable to contain a photoinitiator in the monomer component because of advantages such as being able to shorten the polymerization time.

[0094] (Silane coupling agent) Furthermore, the pressure-sensitive adhesive composition of the present invention can contain a silane coupling agent. The blending amount of the silane coupling agent is preferably 1 part by weight or less, more preferably 0.01 to 1 part by weight, and even more preferably 0.02 to 0.6 part by weight with respect to 100 parts by weight of the base polymer (for example, the above-mentioned (meth)acrylic polymer).

[0095] (Crosslinking agent) The pressure-sensitive adhesive composition of the present invention can contain a crosslinking agent. Examples of the crosslinking agent include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, silicone-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, silane-based crosslinking agents, alkyl etherified melamine-based crosslinking agents, metal chelate-based crosslinking agents, and crosslinking agents such as peroxides. The crosslinking agent can be used alone or in combination of two or more. Among these, isocyanate-based crosslinking agents are preferably used.

[0096] The above crosslinking agent may be used alone or in combination of two or more, but the total content is preferably 5 parts by weight or less, more preferably 0.01 to 5 parts by weight, even more preferably 0.01 to 4 parts by weight, and particularly preferably 0.02 to 3 parts by weight with respect to 100 parts by weight of the monofunctional monomer component forming the (meth)acrylic polymer.

[0097] (Other additives) In addition to the above components, the pressure-sensitive adhesive composition of the present invention may contain appropriate additives according to the use. For example, viscosity modifiers, release modifiers, tackifiers (for example, those that are solid, semi-solid, or liquid at room temperature and composed of rosin derivative resins, polyterpene resins, petroleum resins, oil-soluble phenolic resins, etc.), plasticizers, softeners, pigments, colorants (pigments, dyes, etc.), pH adjusters (acids or bases), rust inhibitors, anti-aging agents, antioxidants, light stabilizers, ultraviolet absorbers, etc. can be mentioned.

[0098] The pressure-sensitive adhesive sheet of the present invention has the pressure-sensitive adhesive layer 1 and a support on one or both sides of the pressure-sensitive adhesive layer 1. FIG. 4 shows the case where the support 3a is provided on the first surface f1 of the pressure-sensitive adhesive layer 1 and the support 3b is provided on the second surface f2. As the supports 3a and 3b, the same supports as the support S used in the pressure-sensitive adhesive layer 1 shown in FIG. 3 can be used. Further, the support 3a can be used as it is the support S used in the manufacturing method of the pressure-sensitive adhesive layer 1 shown in FIG. 3. The support 3b can be appropriately provided on the second surface f2 of the pressure-sensitive adhesive layer 1 after manufacturing the pressure-sensitive adhesive layer 1 by the manufacturing method shown in FIG. 3.

[0099] The optical film A with a pressure-sensitive adhesive layer of the present invention has an optical film 4 and a pressure-sensitive adhesive layer 1 provided on one or both sides of the optical film 4. The pressure-sensitive adhesive layer 1 is provided on either one or both sides of the optical film 4. The first surface f1 side of the pressure-sensitive adhesive layer 1 is provided on the optical film 4. When the pressure-sensitive adhesive layer 1 is provided on one side of the optical film 4, a normal pressure-sensitive adhesive layer can also be provided on the other side. FIG. 5 shows the case where the pressure-sensitive adhesive layer 1 is provided only on one side of the optical film 4. FIG. 5 shows the case where the support 3b is provided on the second surface f2 of the pressure-sensitive adhesive layer 1.

[0100] <Optical film> As the optical film, for example, those used for forming an image display device such as a liquid crystal display device are used, and the type thereof is not particularly limited. For example, a polarizing film can be mentioned as the optical film. As the polarizing film, those having a transparent protective film on one or both sides of the polarizer are generally used.

[0101] <Polarizing film> Examples of the polarizing film include those having a transparent protective film on at least one surface of the polarizer.

[0102] The polarizer is not particularly limited, and various types can be used. Examples of the polarizer include those obtained by adsorbing a dichroic substance such as iodine or a dichroic dye on a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, or an ethylene-vinyl acetate copolymer-based partially saponified film, and then uniaxially stretching it; and polyene-based oriented films such as a dehydrated product of polyvinyl alcohol or a dehydrochlorinated product of polyvinyl chloride. Among these, a polarizer composed of a polyvinyl alcohol-based film and a dichroic substance such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm.

[0103] A polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine and uniaxially stretching it can be prepared, for example, by dyeing a polyvinyl alcohol-based film by immersing it in an aqueous solution of iodine and stretching it to 3 to 7 times its original length. It can also be immersed in an aqueous solution such as potassium iodide which may contain boric acid, zinc sulfate, zinc chloride, etc. as required. Further, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed before dyeing. By washing the polyvinyl alcohol-based film, not only can the dirt on the surface of the polyvinyl alcohol-based film and the blocking inhibitor be washed away, but also the unevenness such as uneven dyeing can be prevented by swelling the polyvinyl alcohol-based film. The stretching may be performed after dyeing with iodine, during dyeing, or after stretching and then dyeing with iodine. Stretching can also be performed in an aqueous solution or a water bath containing boric acid, potassium iodide, etc.

[0104] In the present invention, a thin polarizer with a thickness of 10 μm or less can also be used. From the viewpoint of thinning, the thickness is preferably 1 to 7 μm. Such a thin polarizer has less thickness unevenness, excellent visibility, little dimensional change, excellent durability, and can be thinned in terms of the thickness as a polarizing film, which is preferable.

[0105] Examples of the thin polarizer include a thin polarizing film described in JP-A-51-069644, JP-A-2000-338329, WO 2010 / 100917 pamphlet, Japanese Patent No. 4751481, or JP-A-2012-073563. These thin polarizing films can be obtained by a production method including a step of stretching a polyvinyl alcohol-based resin (hereinafter also referred to as a PVA-based resin) layer and a stretching resin substrate in a laminated state and a step of dyeing. According to this production method, even if the PVA-based resin layer is thin, it can be stretched without problems such as breakage due to stretching because it is supported by the stretching resin substrate.

[0106] Among the production methods including a step of stretching and a step of dyeing in a laminated state, as the thin polarizer, those obtained by a production method including a step of stretching in an aqueous boric acid solution as described in WO 2010 / 100917 pamphlet, Japanese Patent No. 4751481, or JP-A-2012-073563 are preferable in that they can be stretched at a high magnification and the polarization performance can be improved. In particular, those obtained by a production method including an auxiliary step of stretching in air before stretching in an aqueous boric acid solution as described in Japanese Patent No. 4751481 or JP-A-2012-073563 are preferable.

[0107] As materials for forming the transparent protective film, for example, thermoplastic resins excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, etc. are used. 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 resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. Note that on one side of the polarizer, the transparent protective film is bonded by an adhesive layer, while on the other side, as the transparent protective film, thermosetting resins such as (meth)acrylic, urethane, acrylic urethane, epoxy, silicone, etc. or ultraviolet curable resins can be used. The transparent protective film may contain one or more arbitrary appropriate additives. Examples of the additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, colorants, etc. The content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. When the content of the thermoplastic resin in the transparent protective film is 50% by weight or less, there is a possibility that the high transparency and the like inherent in the thermoplastic resin cannot be sufficiently exhibited.

[0108] The thickness of the transparent protective film can be appropriately determined, but generally it is about 1 to 500 μm from the viewpoints of workability such as strength and handleability, and thin film properties.

[0109] On the surface of the transparent protective film that does not bond the polarizer, functional layers such as a hard coat layer, an antireflection layer, and an anti-sticking layer can be formed, or a treatment for the purpose of diffusion or antiglare may be applied.

[0110] The adhesive used for bonding the polarizer and the transparent protective film is not particularly limited as long as it is optically transparent, and various forms such as aqueous, solvent-based, hot-melt, radical-curable, and cation-curable types can be used. However, an aqueous adhesive or a radical-curable adhesive is preferred.

[0111] Examples of the optical film include those that can be used as an optical layer for forming a liquid crystal display device, such as a reflector, an anti-transmission plate, a retardation film (including wavelength plates such as 1 / 2 and 1 / 4), a visual compensation film, and a brightness enhancement film. These can be used alone as an optical film, or can be laminated on the polarizing film and used in one or more layers in practical use. A retardation film can also be used as the transparent protective film. The retardation film can be appropriately used according to the purpose, such as those obtained by stretching and shrinking a polymer film or those in which a liquid crystal material is oriented and fixed.

[0112] The optical film obtained by laminating the optical layer on the polarizing film can also be formed by sequentially laminating them separately in the manufacturing process of a liquid crystal display device or the like. However, the optical film laminated in advance has advantages such as excellent quality stability and assembly work, and can improve the manufacturing process of a liquid crystal display device or the like. Appropriate adhesion means such as an adhesive layer can be used for lamination. When bonding the polarizing film and other optical layers, their optical axes can be set at appropriate arrangement angles according to the intended retardation characteristics and the like.

[0113] The optical laminate B of the present invention has an optical member 5 with a low refractive index, which is bonded to the pressure-sensitive adhesive layer 1 of the optical film A with a pressure-sensitive adhesive layer and the optical film A with a pressure-sensitive adhesive layer. The optical member 5 is provided on the second surface f2 side of the pressure-sensitive adhesive layer 1. The optical laminate B shown in FIG. 6 is exemplified when the optical member 5 is bonded to the pressure-sensitive adhesive layer 1 after peeling the support 3b (for example, a release film) from the optical film A with a pressure-sensitive adhesive layer shown in FIG. 5. Examples of the optical member 5 include an antireflection film, a light diffusion film, a prism film, a light guide film, a lens film, a Fresnel lens, a lenticular lens, or a microlens film.

[0114] The pressure-sensitive adhesive layer-containing optical film or optical laminate of the present invention can be preferably used for forming various image display devices such as liquid crystal display devices. The formation of a liquid crystal display device can be carried out in accordance with the prior art. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a display panel such as a liquid crystal cell, a pressure-sensitive adhesive layer-containing optical film or an optical laminate, and an illumination system as necessary and incorporating a drive circuit. In the present invention, there is no particular limitation except for using the pressure-sensitive adhesive layer-containing optical film or optical laminate according to the present invention, and it can be in accordance with the prior art. For the liquid crystal cell, any type such as a TN type, an STN type, a π type, a VA type, an IPS type, etc. can be used.

[0115] It is possible to form an appropriate liquid crystal display device such as a liquid crystal display device in which a pressure-sensitive adhesive layer-containing optical film or an optical laminate is disposed on one or both sides of a display panel such as a liquid crystal cell, or a liquid crystal display device using a backlight or a reflector in an illumination system. In that case, the pressure-sensitive adhesive layer-containing optical film or optical laminate according to the present invention can be installed on one or both sides of a display panel such as a liquid crystal cell. When providing optical films on both sides, they may be the same or different. Further, when forming a liquid crystal display device, appropriate components such as a diffusion layer, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusion sheet, and a backlight can be disposed in one or two or more layers at appropriate positions.

Example

[0116] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by these examples. In addition, parts and % in each example are all based on weight. All room temperature standing conditions not specifically specified below are 23°C and 65% RH.

[0117] (Release film) A polyester film (trade name: Diafoil MRF, manufactured by Mitsubishi Rayon Co., Ltd.) with a thickness of 38 μm having one side peel-treated with silicone was used.

[0118] Comparative Example 1 (Preparation of Adhesive Composition (A)) 41 parts by weight of 2-ethylhexyl acrylate (2EHA), 41 parts by weight of isostearyl acrylate (ISTA), 14 parts by weight of N-vinyl-2-pyrrolidone (NVP), 4 parts by weight of N-2-hydroxybutyl acrylate (4HBA), 0.035 parts by weight of two kinds of photoinitiators (trade name: Irgacure 184, manufactured by BASF), and 0.035 parts by weight of a photoinitiator (trade name: Irgacure 651, manufactured by BASF) were charged into a four-necked flask to prepare a monomer mixture. Next, this monomer mixture was exposed to ultraviolet rays under a nitrogen atmosphere to be partially photopolymerized, thereby obtaining a partial polymer (acrylic polymer syrup) having a polymerization rate of about 10% by weight. To 100 parts by weight of the thus obtained acrylic polymer syrup, 0.025 parts by weight of trimethylolpropane triacrylate (TMPTA) and 0.3 part of a silane coupling agent (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) were added, and then these were uniformly mixed to prepare an adhesive composition (A).

[0119] (Production of Adhesive Layer (A)) The adhesive composition (A) was applied onto the release-treated surface of a release film so that the thickness after the formation of the adhesive layer became 100 μm to form a coating layer. Next, another release film was coated on the surface of the coating layer such that the release-treated surface faced the coating layer side. Thereafter, ultraviolet irradiation was performed under the conditions of illuminance: 6.5 mW / cm 2 , light amount: 2000 mJ / cm 2 , peak wavelength: 350 nm to photocure the coating layer to form an adhesive layer (A), and an adhesive sheet (substrate-less type, thickness of adhesive layer: 100 μm) provided with release films on both surfaces of the adhesive layer (A) was produced. The refractive index (n D ) of the D line measured at 23°C by an Abbe refractometer of the adhesive layer (A) was 1.48, and the gel fraction was 67%.

[0120] Comparative Example 2 (Preparation of Adhesive Composition (B)) 76 parts by weight of 2-ethylhexyl acrylate (2EHA), N-vinyl-2-pyrrolidone (NVP) 18 parts by weight, and 16 parts by weight of 2-hydroxyethyl acrylate (HEA) were added to the monomer mixture. As a photopolymerization initiator, 0.050 parts by weight of 1-hydroxycyclohexyl phenyl ketone (trade name: Irgacure 184, having an absorption band at wavelengths of 200 to 370 nm, manufactured by BASF) and 0.050 parts by weight of 2,2-dimethoxy-1,2-diphenylethane-1-one (trade name: Irgacure 651, having an absorption band at wavelengths of 200 to 380 nm, manufactured by BASF) were blended. Then, ultraviolet rays were irradiated until the viscosity (measurement conditions: BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30 °C) reached about 20 Pa·s to obtain a prepolymer composition (polymerization rate: 9%) in which a part of the above monomer components was polymerized. Next, 0.060 parts by weight of hexanediol diacrylate (HDDA) and 0.3 parts by weight of a silane coupling agent (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) were added to the prepolymer composition and mixed to obtain an adhesive composition (b).

[0121] (Preparation of Adhesive Composition (B)) To the adhesive composition (b) obtained above (assuming 100 parts by weight of the monomer components forming the acrylic polymer), 0.8 parts by weight (solid content weight) of 2,4-bis -[{4-(4-ethylhexyloxy)-4-hydroxy}-phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine (trade name: Tinosorb S, absorption maximum wavelength of the absorption spectrum: 346 nm, manufactured by BASF Japan) dissolved in butyl acrylate to a solid content of 15% and 0.3 parts by weight of bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (trade name: Irgacure 819, having an absorption band at wavelengths of 200 to 450 nm, manufactured by BASF Japan) were added and stirred to obtain an adhesive composition (B).

[0122] (Manufacture of Adhesive Layer (B)) The pressure-sensitive adhesive composition (B) was applied onto the release-treated surface of a release film so that the thickness after forming the pressure-sensitive adhesive layer would be 150 μm to form a coating layer. Next, another release film was coated on the surface of the coating layer with the release-treated surface facing the coating layer side. Thereafter, ultraviolet irradiation was performed under the conditions of illuminance: 6.5 mW / cm 2 , light quantity: 2000 mJ / cm 2 , peak wavelength: 350 nm to photocure the coating layer to form a pressure-sensitive adhesive layer (B), and a pressure-sensitive adhesive sheet (substrate-less type, thickness of the pressure-sensitive adhesive layer: 150 μm) provided with release films on both sides of the pressure-sensitive adhesive layer (B) was produced. The refractive index (n D ) of the D line measured at 23°C by an Abbe refractometer of the pressure-sensitive adhesive layer (B) was 1.49, and the gel fraction was 88%.

[0123] Comparative Example 3 (Preparation of the pressure-sensitive adhesive composition (C)) Into a separable flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen gas introduction tube, 95 parts by weight of butyl acrylate (BA), 5 parts by weight of acrylic acid (AA), 0.2 part by weight of azobisisobutyronitrile as a polymerization initiator, and 233 parts by weight of ethyl acetate were charged. Thereafter, nitrogen gas was passed, and nitrogen substitution was performed for about 1 hour while stirring. Thereafter, the flask was heated to 60°C and reacted for 7 hours to obtain an acrylic polymer having a weight average molecular weight (Mw) of 1.1 million. To the above acrylic polymer solution (assuming 100 parts by weight of solid content), 0.8 part by weight of trimethylolpropane triisocyanate (trade name: Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) and 0.1 part by weight of a silane coupling agent (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) were added as an isocyanate-based crosslinking agent to prepare a pressure-sensitive adhesive composition (C: solution).

[0124] (Manufacture of the pressure-sensitive adhesive layer (C)) The pressure-sensitive adhesive composition (C: solution) was applied onto the release-treated surface of a release film such that the thickness after drying would be 23 μm, and then dried at 100°C for 3 minutes to remove the solvent, thereby obtaining a pressure-sensitive adhesive layer (C). Thereafter, crosslinking treatment was performed by heating at 50°C for 48 hours. The exposed surface of the obtained pressure-sensitive adhesive layer (C) was covered with another release film such that the release-treated surface faced the exposed surface side, thereby producing a pressure-sensitive adhesive sheet (substrate-free type, thickness of pressure-sensitive adhesive layer: 23 μm) having release films provided on both surfaces of the pressure-sensitive adhesive layer (C). The refractive index (n D ) of the D line measured at 23°C by an Abbe refractometer for the pressure-sensitive adhesive layer (C) was 1.47, and the gel fraction was 82%.

[0125] Comparative Example 4 (Preparation of pressure-sensitive adhesive composition (D)) Into a separable flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen gas introduction tube, 99 parts by weight of butyl acrylate (BA), 1 part by weight of 4-hydroxybutyl acrylate (4HBA) as monomer components, 0.2 part by weight of azobisisobutyronitrile as a polymerization initiator, and ethyl acetate as a polymerization solvent were charged so that the solid content would be 30% by weight. Thereafter, nitrogen gas was passed, and nitrogen substitution was performed for about 1 hour while stirring. Then, the flask was heated to 60°C and reacted for 7 hours to obtain an acrylic polymer having a weight average molecular weight (Mw) of 1.1 million. To the solution (100 parts by solid content) of this acrylic polymer, 0.11 part of trimethylolpropane xylylene diisocyanate ("Takenate D110N" manufactured by Mitsui Chemicals, Inc.) as an isocyanate-based crosslinking agent and 0.1 part of a silane coupling agent ("KBM-403" manufactured by Shin-Etsu Chemical Co., Ltd.) were added to prepare a pressure-sensitive adhesive composition (D: solution).

[0126] (Manufacture of pressure-sensitive adhesive layer (D)) The pressure-sensitive adhesive composition (D: solution) was applied onto the release-treated surface of a release film so that the thickness after drying was 20 μm, and then dried at 120°C for 3 minutes to remove the solvent, thereby obtaining a pressure-sensitive adhesive layer (D). Thereafter, crosslinking treatment was performed by heating at 50°C for 48 hours. The exposed surface of the obtained pressure-sensitive adhesive layer (D) was covered with another release film such that the release-treated surface faced the exposed surface side, thereby producing a pressure-sensitive adhesive sheet (substrate-free type, thickness of pressure-sensitive adhesive layer: 23 μm) provided with release films on both sides of the pressure-sensitive adhesive layer (D). The refractive index (n D ) of the D line measured at 23°C by an Abbe refractometer for the pressure-sensitive adhesive layer (D) was 1.47, and the gel fraction was 75%.

[0127] Example 1 (Preparation of Dispersion Containing Low Refractive Index Particles) As a dispersion containing low refractive index particles, hollow nanosilica particles (hollow particles, refractive index: 1.24, average primary particle diameter: 75 nm, trade name: Throughia 5320, manufactured by Nippon Shokubai Catalysts & Chemicals, Ltd.) were diluted with a dispersion medium (methyl ethyl ketone / methyl isobutyl ketone = 9 / 1: volume ratio) to prepare a dispersion having a particle concentration of 1.5% by weight.

[0128] (Manufacture of Pressure-Sensitive Adhesive Layer with Adjusted Refractive Index) One of the release films of the pressure-sensitive adhesive sheet obtained in Comparative Example 1 was peeled off. The above dispersion was applied onto the surface of the exposed pressure-sensitive adhesive layer (A) using a bar coater RDS No. 3 so that the thickness of the refractive index adjustment region was about 20 nm to 150 nm, and then dried in a drying oven at 110°C for 180 seconds. Next, a new second release film was laminated onto the surface of the pressure-sensitive adhesive layer (A) in which the hollow nanosilica particles were dispersed to obtain a pressure-sensitive adhesive sheet. Note that the release film on the opposite side with respect to the second release film was the first release film.

[0129] Examples 2 to 8 In Example 1, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer with an adjusted refractive index was produced in the same manner as in Example 1, except that the type of the pressure-sensitive adhesive layer and the type of the dispersion (type of low refractive index particles, its average particle diameter, type of dispersion medium, particle concentration) were changed as shown in Table 1. In addition, when the target thickness of the refractive index adjustment region after drying is more than 150 to about 300 nm, a bar coater RDS No. 5 was used, and when the target thickness of the refractive index adjustment region after drying is about 20 to 150 nm, a bar coater RDS No. 3 was used.

[0130] (Evaluation) Table 1 shows the results of the following evaluations on the pressure-sensitive adhesive layers (pressure-sensitive adhesive sheets) obtained in the examples and comparative examples.

[0131] <Measurement of average surface refractive index> The average surface refractive index of the pressure-sensitive adhesive layer (on the refractive index adjustment region side: the second surface) obtained in the example was measured for the refractive index at the sodium D line (589 nm) using a spectroscopic ellipsometer (EC-400, manufactured by JA. Woolam). From the pressure-sensitive adhesive sheets obtained in the examples and comparative examples, the release films on both sides were peeled off, and the average refractive index of the surface (the second surface) where the dispersion liquid was applied was measured with a blackboard adhered to the surface (the first surface) where the dispersion liquid was not applied. For the pressure-sensitive adhesive sheets of the comparative examples, the average refractive index of the surface of the pressure-sensitive adhesive layer was measured with both release films peeled off and a blackboard adhered to one surface. The pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets of the comparative examples have the same refractive index on both sides.

[0132] <Measurement of the thickness of the refractive index adjustment region> The cross-section in the depth direction of the pressure-sensitive adhesive layer was adjusted, and TEM observation was performed. The thickness of the refractive index adjustment region was measured from the obtained TEM image (direct magnification 3000 to 30000 times). The thickness of the refractive index adjustment region was defined as the average value of the unevenness of the interface between the region where the particles are dispersed and the region where the particles are not dispersed in the pressure-sensitive adhesive layer. When it is difficult to distinguish the interface, the surface TEM image was subjected to binary image processing with image processing software (ImageJ), and the thickness of the depth of the region where 90% (area) of the particles exist was used.

[0133] <Total light transmittance, haze> From the adhesive sheet obtained in the example, the second release film (on the second surface side of the adhesive layer) was peeled off and bonded to a slide glass (product name: White Polishing No. 1, thickness: 0.8 to 1.0 mm, total light transmittance: 92%, haze: 0.2%, manufactured by Matsunami Glass Industry Co., Ltd.). Further, the other first release film was peeled off to prepare a test piece having a layer structure of an adhesive layer (the refractive index adjustment region is on the slide glass side) / slide glass. On the other hand, in the adhesive layer of the comparative example, one release film was peeled off, bonded to the same slide glass as above, and further, the other release film was peeled off to prepare a test piece having a layer structure of an adhesive layer / slide glass. The total light transmittance and haze value in the visible light region of the above test piece were measured using a haze meter (device name: HM-150, manufactured by Murakami Color Research Laboratory Co., Ltd.).

[0134] <Adhesiveness> Sheet pieces measuring 100 mm in length and 20 mm in width were cut out from the pressure-sensitive adhesive sheets obtained in the examples and comparative examples. Next, from the sheet pieces obtained from the pressure-sensitive adhesive sheets of the examples, after peeling off the first release film (the side where the dispersion was not applied in the pressure-sensitive adhesive layer), a PET film (product name: Lumirror S-10, thickness: 25 μm, manufactured by Toray Industries, Inc.) was attached (lined) to the pressure-sensitive adhesive layer surface. Next, the second release film was peeled off, and it was pressure-bonded to a glass plate (product name: Soda-lime glass #0050, manufactured by Matsunami Glass Industry Co., Ltd.) as a test plate under the pressure-bonding conditions of a 2 kg roller and one reciprocation to prepare a sample composed of the test plate / pressure-sensitive adhesive layer (the first surface is the PET side) / PET film. On the other hand, for the sheet pieces obtained from the pressure-sensitive adhesive sheets of the comparative examples, after peeling off one release film, a PET film similar to the above was attached to the pressure-sensitive adhesive layer surface, and then the other release film was peeled off, and a sample was prepared using the same test plate as above. The obtained samples were subjected to autoclave treatment (50 °C, 0.5 MPa, 15 minutes), and then allowed to cool for 30 minutes in an atmosphere of 23 °C and 50% R.H. After cooling, using a tensile testing machine (device name: Autograph AG-IS, manufactured by Shimadzu Corporation), in accordance with JIS Z0237, in an atmosphere of 23 °C and 50% R.H., at a tensile speed of 300 mm / min and a peeling angle of 180°, the pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer / PET film) was peeled off from the test plate, and the 180° peel adhesion (N / 20 mm) was measured.

[0135] <Measurement of surface reflectance> The surface (second surface) on the side where the dispersion of the pressure-sensitive adhesive layer obtained in the example was applied was used as the reflectance measurement surface. The first release film (the side where the dispersion was not applied in the pressure-sensitive adhesive layer) was peeled off from the pressure-sensitive adhesive sheet obtained in the example, and a black acrylic plate (product name "CLAREX", manufactured by Nitto Denko Corporation) was bonded. Then, the second release film (the side where the dispersion was applied in the pressure-sensitive adhesive layer) was peeled off, and the peeled surface was used as a sample for measuring the surface reflectance. On the other hand, for the pressure-sensitive adhesive layer obtained in the comparative example, after peeling one release film from the pressure-sensitive adhesive sheet, it was bonded to the same black acrylic plate as above, and then the other release film was peeled off, and the peeled surface was used as a sample for measuring the surface reflectance. The surface reflectance (Y value) was measured with a reflection-type spectrophotometer (U4100, manufactured by Hitachi High-Technologies Corporation).

[0136] <Measurement of Internal Reflection Suppression Ratio (Effect of Improving Transmittance)> After peeling the second release film (the side where the dispersion was applied in the pressure-sensitive adhesive layer) from the pressure-sensitive adhesive sheet obtained in the example, the low refractive index layer side of the laminated film having a low refractive index layer with a refractive index of 1.36 formed on a triacetyl cellulose film was bonded to the pressure-sensitive adhesive layer surface so that the low refractive index adjustment region of the pressure-sensitive adhesive layer was in contact with the low refractive index layer on the laminated film. Next, the first release film was peeled off, and a slide glass (product name: White Polished No. 1, thickness: 0.8 to 1.0 mm, total light transmittance: 92%, haze: 0.2%, manufactured by Matsunami Glass Industry Co., Ltd.) was bonded to the pressure-sensitive adhesive layer surface. Thus, a test piece having a layer structure of triacetyl cellulose film / low refractive index layer / pressure-sensitive adhesive layer (the second surface is the low refractive index layer side) / slide glass was produced. On the other hand, for the pressure-sensitive adhesive layer obtained in the comparative example, after peeling one release film from the pressure-sensitive adhesive sheet, a test piece having a layer structure of triacetyl cellulose film / low refractive index layer / pressure-sensitive adhesive layer / slide glass was produced in the same manner as above.

[0137] The internal reflection suppression rate (the effect of improving transmittance) was calculated based on the following formula by measuring the transmittance of the test piece fabricated above. Note that the "transmittance (%) when there are no particles" in the following formula is the reflectance of the test piece of the comparative example. That is, the internal reflection suppression effect (the effect of improving transmittance) is an index indicating to what extent the internal reflectance can be reduced by having a refractive index adjustment layer. Internal reflection suppression rate (%) = "Transmittance (%)" - "Transmittance (%) when there are no particles"

[0138]

Table 1

[0139] In Table 1, (X1) Hollow silica nanoparticles: refractive index 1.24 (product name: Throughia 5320, particle size 75 nm, manufactured by Nichiai Catalyst Kasei Co., Ltd.), (X2) Hollow polymer microparticles: refractive index 1.32 (product name: Tech Polymer NH product number XX - 255AA, particle size 80 nm, manufactured by Sekisui Chemical Co., Ltd.), (X3) Hollow polymer microparticles: refractive index 1.33 (product name: Tech Polymer NH product number XX - 260AA, particle size 60 nm, manufactured by Sekisui Chemical Co., Ltd.), (Y1) MgF2: 1.38, average primary particle size: 40 nm, manufactured by CIK Nanotech Co., Ltd. (Y2) Na3AlF6: 1.34, average primary particle size: 50 nm, manufactured by CIK Nanotech Co., Ltd., MEK / MIBK Methyl ethyl ketone / Methyl isobutyl ketone = 9 / 1 (volume ratio), Ethanol / MIBK Ethanol / Methyl isobutyl ketone = 9 / 1 (volume ratio), IPA Isopropyl alcohol, are shown.

Explanation of symbols

[0140] 1 ··· Adhesive layer 1a ··· Base (matrix) of the entire adhesive layer 2 ··· Low refractive index material f1 ··· First surface of the adhesive layer f2 ··· The second surface of the adhesive layer T ··· The thickness of the refractive index adjustment region S ··· Support 3a ··· Support 3b ··· Support 4 ··· Optical film 5 ··· Low refractive index optical member 10 ··· Dispersion liquid

Claims

1. A single-layer adhesive layer having a first surface and a second surface on the opposite side of the first surface, The adhesive layer forms the base of the entire adhesive layer with an adhesive composition containing a base polymer, The first surface has a first refractive index based on the adhesive composition, while the second refractive index of the second surface is lower than the first refractive index of the first surface, In the adhesive layer, a low refractive index material having a refractive index lower than that of the base polymer is dispersed on the second surface side, The thickness of the region where the low refractive index material is dispersed is 600 nm or less in the thickness direction from the second surface side in the adhesive layer, The refractive index of the base polymer is 1.40 to 1.55, and the refractive index of the low refractive index material is 1.10 to 1.45, An adhesive layer for an optical film, characterized in that the difference between the refractive index of the base polymer and the refractive index of the low refractive index material is 0.07 to 0.

45.

2. The adhesive layer for an optical film according to claim 1, characterized in that the difference between the first refractive index of the first surface and the second refractive index of the second surface is 0.02 to 0.

45.

3. The adhesive layer for an optical film according to claim 1 or 2, characterized in that the second refractive index of the second surface is 1.45 or less.

4. The adhesive layer for an optical film according to any one of claims 1 to 3, characterized in that the low refractive index material is particles having an average particle diameter of 10 nm to 150 nm.

5. The low refractive index material is MgF ２ , CaF ２ and Na ３ AlF ６ At least one particle selected from the group consisting of at least one inorganic particle, porous silica particles, hollow nanosilica particles, and hollow polymer particles selected from the group consisting of. The adhesive layer for an optical film according to any one of claims 1 to 4, characterized in that it is at least one particle.

6. The pressure-sensitive adhesive layer for an optical film according to any one of claims 1 to 5, characterized in that the total light transmittance is 85% or more.

7. The pressure-sensitive adhesive layer for an optical film according to any one of claims 1 to 6, characterized in that the reflectance of the second surface is 0.5 to 3.5%.

8. The pressure-sensitive adhesive layer for an optical film according to any one of claims 1 to 7, characterized in that the difference in reflectance between the first surface and the second surface is 0.1 to 3.5%.

9. The pressure-sensitive adhesive layer for an optical film according to any one of claims 1 to 8, characterized in that the gel fraction is 30 to 95% by weight.

10. The pressure-sensitive adhesive layer for an optical film according to any one of claims 1 to 9, characterized in that the storage elastic modulus G' at 25°C is 0.05 to 0.50 MPa.

11. The pressure-sensitive adhesive layer for an optical film according to any one of claims 1 to 10, characterized in that the tanδ peak value during the dynamic viscoelasticity measurement at 1 Hz is -5 to -50°C.

12. A method for producing a pressure-sensitive adhesive layer for an optical film according to any one of claims 1 to 11, comprising: Step (1) of forming a base pressure-sensitive adhesive layer on a support with an adhesive composition containing a base polymer; Step (2) of preparing a dispersion in which a low refractive index material having a refractive index lower than that of the base polymer is dispersed; Step (3) of applying the dispersion to the second surface on the opposite side of the first surface on the support side of the base pressure-sensitive adhesive layer, and allowing the low refractive index material contained in the dispersion to penetrate in the thickness direction from the second surface of the base pressure-sensitive adhesive layer; and Step (4) of drying the pressure-sensitive adhesive layer into which the low refractive index material has penetrated. A method for producing a pressure-sensitive adhesive layer for an optical film, characterized by including the above steps.

13. An adhesive sheet comprising an adhesive layer for an optical film according to any one of claims 1 to 11 and having a support on one or both sides of the adhesive layer.

14. An optical film with an adhesive layer having an adhesive layer provided on one or both sides of the optical film, wherein the adhesive layer on one or both sides is the adhesive layer according to any one of claims 1 to 11, and the first surface side of the adhesive layer is provided on the optical film. An optical film with an adhesive layer characterized by this.

15. The optical film with an adhesive layer according to claim 14, wherein the optical film is a polarizing film.

16. An optical laminate comprising the optical film with an adhesive layer according to claim 14 or 15 and having a low refractive index optical member bonded to the adhesive layer of the optical film with an adhesive layer.

17. An image display device comprising the adhesive layer according to any one of claims 1 to 11, the optical film with an adhesive layer according to claim 14 or 15, or the optical laminate according to claim 16.

Images