Polarization film having adhesive layer and picture display unit

Abstract

To provide a polarization film having an adhesive layer capable of preventing a single body transmissivity of a polarization film from deteriorating under a high temperature environment, and also to provide a picture display unit using the polarization film having an adhesive layer.SOLUTION: A polarization film having an adhesive layer is a polarization film including a polarization membrane and a first transparent protective film, and includes a first adhesive layer disposed on a first transparent protective film side of the polarization film. The polarization membrane has film thickness of 20 μm or less. The first adhesive layer is used in bonding a front transparent member arranged on a visible side of the picture display unit. A difference ((A)-(B)) is 1.0 wt.% or more between saturation moisture percentage (A) at 80°C, 85%R.H., and saturation moisture percentage (B) at 25°C, 50%R.H. The saturation moisture percentage (A) is 1.5 wt.% to 3.0 wt.%, inclusive. The polarization film having an adhesive layer has a thickness of 150 μm to 600 μm, inclusive.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polarizing film with a pressure-sensitive adhesive layer and an image display device. [Background technology]

[0002] Liquid crystal display devices and organic electroluminescence (EL) display devices are widely used as various image display devices such as mobile phones, smartphones, car navigation devices, personal computer monitors, and televisions. Dyed polyvinyl alcohol films (containing dichroic substances such as iodine and dichroic dyes) are used as the polarizing films for these various image display devices because they have both high transmittance and high polarization. The polarizing films are usually used as polarizing films (polarizing plates) with protective films such as triacetyl cellulose attached to one or both sides of the polarizing film using an adhesive.

[0003] In the various image display devices described above, a front transparent plate (also referred to as a "cover window" or "window layer") such as a transparent resin plate or a glass plate may be provided on the viewing side of the image display panel in order to prevent damage to the image display panel due to impact from the outer surface, etc. In addition, devices equipped with a touch panel on the viewing side of the image display panel have become widespread in recent years.

[0004] Furthermore, as a method for disposing a front transparent member such as a front transparent plate or a touch panel on the front surface of an image display panel, an "interlayer filling structure" has been proposed in which the image display panel and the front transparent member are bonded together via an adhesive layer. An adhesive layer may also be provided between the touch panel and the front transparent plate. In an interlayer filling structure, the gap between the members is filled with the adhesive layer, thereby reducing the refractive index difference at the interface and suppressing the deterioration of visibility due to reflection or scattering. Furthermore, since the interlayer filling structure bonds and fixes the members together with the adhesive layer, it has the advantage of being less likely to peel off due to impacts such as being dropped, compared to when the front transparent member is fixed only to the housing.

[0005] Among the various image display devices, in-vehicle displays such as car navigation systems require high-temperature durability. For example, Patent Documents 1-3 describe that when an image display device in which an image display cell and a front transparent member are interlayer-filled with an adhesive is subjected to a long-term high-temperature durability test required for in-vehicle displays, the polyvinyl alcohol constituting the polarizing film undergoes polyenation in a high-temperature environment, resulting in a decrease in the single-unit transmittance of the in-plane central portion of the polarizing film constituting the image display panel. In particular, it has been pointed out that the polyenation is promoted by moisture contained in the polarizing film, and that the decrease in single-unit transmittance tends to be more pronounced as the in-plane size of the polarizing film increases. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-75998 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-102353 [Patent Document 3] Japanese Patent Application Publication No. 2018-101117 Summary of the Invention [Problem to be solved by the invention]

[0007] The above-mentioned Patent Document 1 discloses that a polarizing film can be provided that can suppress a decrease in single-unit transmittance in a high-temperature environment by using an adhesive layer (adhesive sheet) that is used to bond the polarizing film to a front transparent member placed on the viewing side of the image display device and has specific parameters; Patent Document 2 discloses that a polarizing film can be provided that can suppress a decrease in single-unit transmittance in a high-temperature environment by using a transparent protective film that has a specific saturated water absorption amount; and Patent Document 3 discloses that a polarizing film can be provided that can suppress a decrease in single-unit transmittance in a high-temperature environment by using an adhesive layer (adhesive sheet) that is used to bond the polarizing film to a transparent resin plate placed on the viewing side of the image display device and has a specific storage modulus. However, the present inventors have found that these properties can be improved by means other than those mentioned above.

[0008] In view of the above-mentioned circumstances, the present invention aims to provide a polarizing film with an adhesive layer that can suppress a decrease in the single transmittance of the polarizing film in a high-temperature environment, and an image display device using the polarizing film with an adhesive layer. [Means for solving the problem]

[0009] Specifically, the present invention relates to a polarizing film with an adhesive layer, which comprises a polarizing film and a first transparent protective film, and which has a first adhesive layer provided on the first transparent protective film side of the polarizing film, wherein the polarizing film has a thickness of 20 μm or less, and the first adhesive layer is used to attach a front transparent member to be placed on the viewing side of an image display device, and the difference ((A) - (B)) between the saturated moisture content (A) at 80°C and 85% RH and the saturated moisture content (B) at 25°C and 50% RH is 1.0 wt % or more.

[0010] The present invention also relates to a polarizing film with an adhesive layer, which comprises a polarizing film and a first transparent protective film, and which has a first adhesive layer provided on the first transparent protective film side of the polarizing film, wherein the polarizing film has a thickness of 20 μm or less, and the first adhesive layer is used to attach a front transparent member to be placed on the viewing side of an image display device, and the adhesive layer-attached polarizing film has a ratio ((A) / (B)) of saturated moisture content (A) at 80°C and 85% RH to saturated moisture content (B) at 25°C and 50% RH of 2.5 or less.

[0011] The present invention also relates to an image display device having an image display cell and the above-mentioned front transparent member, with the above-mentioned pressure-sensitive adhesive layer-attached polarizing film bonded to the front transparent member. [Effects of the Invention]

[0012] Although the details of the mechanism of action of the effect of the pressure-sensitive adhesive layer-attached polarizing film of the present invention are partially unknown, it is presumed as follows: However, the present invention does not need to be interpreted as being limited to this mechanism of action.

[0013] The polarizing film with a pressure-sensitive adhesive layer of the present invention is a polarizing film having a polarizing film and a first transparent protective film, and has a first pressure-sensitive adhesive layer provided on the first transparent protective film side of the polarizing film, wherein the polarizing film has a thickness of 20 μm or less, and the first pressure-sensitive adhesive layer is used to attach a front transparent member to be placed on the viewing side of an image display device, and the difference ((A) - (B)) between the saturated moisture content (A) at 80°C and 85% RH and the saturated moisture content (B) at 25°C and 50% RH is 1.0 wt % or more. A pressure-sensitive adhesive layer in which the difference ((A) - (B)) between the saturated moisture content (A) and the saturated moisture content (B) is a certain level or more, i.e., a pressure-sensitive adhesive layer in which the difference between the saturated moisture content at high temperature and the saturated moisture content at around room temperature is a certain level or more, can sufficiently absorb moisture released from a polarizing film having a polarizing membrane with a film thickness of 20 μm or less when a polarizing film with a pressure-sensitive adhesive layer in an image display device is exposed to an environment ranging from around room temperature to a high temperature, and therefore can prevent diffusion of moisture within the image display device, and is presumed to be able to suppress a decrease in the single-unit transmittance of the polarizing film due to polyenization in a high-temperature environment.

[0014] Furthermore, the pressure-sensitive adhesive layer-attached polarizing film of the present invention may be a polarizing film having a polarizing film and a first transparent protective film, the polarizing film having a first pressure-sensitive adhesive layer provided on the first transparent protective film side of the polarizing film, the polarizing film having a thickness of 20 μm or less, the first pressure-sensitive adhesive layer being used to attach a front transparent member to be placed on the viewing side of an image display device, and the ratio ((A) / (B)) of the saturated moisture content (A) at 80°C and 85% RH to the saturated moisture content (B) at 25°C and 50% RH may be 2.5 or less. A pressure-sensitive adhesive layer in which the ratio ((A) / (B)) of saturated moisture content (A) to saturated moisture content (B) is a certain level or less, i.e., a pressure-sensitive adhesive layer in which the ratio of saturated moisture content at high temperature to saturated moisture content at around room temperature is a certain level or less, can sufficiently absorb moisture released from a polarizing film having a polarizing membrane with a film thickness of 20 μm or less when a polarizing film with a pressure-sensitive adhesive layer in an image display device is exposed to an environment ranging from around room temperature to a high temperature, and therefore can prevent diffusion of moisture within the image display device, and is therefore presumably able to suppress a decrease in the single transmittance of the polarizing film due to polyenization in a high-temperature environment.

[0015] In the above Patent Documents 1 to 3, it is pointed out that the larger the in-plane size of the polarizing film due to polyenation in a high-temperature environment, the more significant the decrease in the single transmittance of the polarizing film tends to be. 2 There is no evidence that polyenization in a high-temperature environment can be suppressed even when a polarizing film (such as the above) is used. Furthermore, the above patent documents do not pay attention to the fact that, even when a polarizing film with such a large in-plane size is used, the difference or ratio between the thickness of the polarizing film and the saturated moisture content in the first pressure-sensitive adhesive layer (the viewer-side pressure-sensitive adhesive layer) is important for suppressing polyenization in a high-temperature environment. On the other hand, the pressure-sensitive adhesive layer-attached polarizing film of the present invention is useful because, by using a polarizing film with a thickness of 20 μm or less and the first pressure-sensitive adhesive layer, a decrease in the single transmittance of the polarizing film due to polyenization in a high-temperature environment can be suppressed even when the in-plane size of the polarizing film is large. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic cross-sectional view showing an example of the configuration of a polarizing film with a pressure-sensitive adhesive layer. [Figure 2] FIG. 1 is a schematic cross-sectional view showing an example of the configuration of an image display device using a polarizing film with a pressure-sensitive adhesive layer. DETAILED DESCRIPTION OF THE INVENTION

[0017] 1 is a schematic cross-sectional view showing an example of the configuration of a polarizing film with a pressure-sensitive adhesive layer of the present invention. Polarizing film 10 includes at least a polarizing film 11 and a first transparent protective film 12, and polarizing film 100 with a pressure-sensitive adhesive layer includes a first pressure-sensitive adhesive layer 20 on the side of polarizing film 10 facing first transparent protective film 12. Polarizing film 10 may also include a second transparent protective film and a second pressure-sensitive adhesive layer 30 on the side of polarizing film 10 opposite the side having first transparent protective film 12. If necessary, separators 45 and 46 may be releasably attached to first pressure-sensitive adhesive layer 20 and second pressure-sensitive adhesive layer 30, respectively.

[0018] 2 is a schematic cross-sectional view showing an example of the configuration of an image display device using the polarizing film with a pressure-sensitive adhesive layer of the present invention. In the image display device 110, a front transparent member 70 and a polarizing film 10 are bonded together via a first pressure-sensitive adhesive layer 20, and an image display cell 90 and the polarizing film 10 are bonded together via a second pressure-sensitive adhesive layer 30. The front transparent member 70 may have a printed step 72 on the periphery of the front transparent plate 71.

[0019] The pressure-sensitive adhesive layer 20 is a so-called "interlayer filler" that not only bonds the polarizing film 10 to the front transparent member 70, but also functions to reduce the difference in refractive index at the interface and suppress deterioration of visibility due to reflection or scattering of light. The interlayer filler also acts as a cushioning layer against impacts and pressures from the outer surface of the image display cell 90, such as a liquid crystal cell.

[0020] <Polarizing film with adhesive layer (polarizing film with adhesive layer and one-sided protection)> The polarizing film with an adhesive layer of the present invention (single-sided protected polarizing film with an adhesive layer) is a polarizing film having a polarizing film and a first transparent protective film, and has a first adhesive layer provided on the first transparent protective film side of the polarizing film.

[0021] <Polarizing film> The polarizing film of the present invention is an iodine-based polarizing film formed by adsorbing and orienting iodine on a polyvinyl alcohol-based film, and has a thickness of 20 μm or less. When the polarizing film of the present invention has a thickness of more than 20 μm, the amount of moisture contained in the polarizing film tends to be large, and therefore, the polarizing film tends to have a large in-plane size (for example, an in-plane size of 300 cm) in a high-temperature environment (for example, 95° C., 500 hours). 2 This is undesirable because it is not possible to prevent a decrease in the single transmittance of the polarizing film having the polarizing layer.

[0022] The polyvinyl alcohol-based film can be any film that is translucent in the visible light region and disperses and adsorbs iodine. Examples of materials for the polyvinyl alcohol-based film include polyvinyl alcohol and its derivatives. Examples of polyvinyl alcohol derivatives include polyvinyl formal, polyvinyl acetal; olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, and their alkyl esters, modified with acrylamide, etc. The polyvinyl alcohol preferably has an average degree of polymerization of approximately 100 to 10,000, more preferably approximately 1,000 to 10,000, and even more preferably approximately 1,500 to 4,500. The polyvinyl alcohol preferably has a saponification degree of approximately 80 to 100 mol%, more preferably approximately 95 mol% to 99.95 mol%. The average degree of polymerization and the saponification degree can be determined in accordance with JIS K 6726.

[0023] The polarizing film can be produced by a known method, and is usually obtained by dyeing a polyvinyl alcohol-based film with iodine and stretching it. In particular, a thin polarizing film having a thickness of 10 μm or less can be produced by a known method for producing a thin polarizing film, which includes a step of stretching a laminate of a polyvinyl alcohol-based resin layer and a resin substrate for stretching, and a step of dyeing the laminate with iodine.

[0024] In the polarizing film with a pressure-sensitive adhesive layer, the in-plane size of the polarizing film is not particularly limited. However, in the polarizing film with a pressure-sensitive adhesive layer of the present invention, even when the in-plane size of the polarizing film is large, the in-plane size of the polarizing film is preferably 150 cm or less, from the viewpoint of being able to suppress a decrease in the single-unit transmittance due to polyenation in a high-temperature environment. 2 It may be more than 300cm 2 It may be more than 600cm 2 It may be more than 900cm 2 The in-plane size of a polarizing film is usually the same as the in-plane size of a polarizing membrane.

[0025] <First transparent protective film> The first transparent protective film of the present invention is not particularly limited, and various transparent protective films used in polarizing films can be used. Examples of materials that can be used to form the first transparent protective film include thermoplastic resins that are excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, etc. Examples of thermoplastic resins include cellulose ester resins such as triacetyl cellulose, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins such as nylon and aromatic polyamide, polyimide resins, polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers, (meth)acrylic resins, cyclic polyolefin resins (norbornene resins) having a cyclo- or norbornene structure, polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The first transparent protective film may be a cured layer formed from a thermosetting resin or an ultraviolet-curable resin, such as a (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone resin. Among these, cellulose ester resins, polycarbonate resins, (meth)acrylic resins, cyclic polyolefin resins, and polyester resins are preferred.

[0026] The thickness of the first transparent protective film can be determined as appropriate, but generally, from the standpoint of workability such as strength and handling, thinness, etc., it is preferably about 1 to 500 μm, more preferably about 1 to 300 μm, and even more preferably about 5 to 100 μm.

[0027] The first transparent protective film has a moisture permeability of 100 g / m from the viewpoint of diffusing moisture in the polarizing film to the outside of the system and suppressing a decrease in the single transmittance of the polarizing film due to polyenation. 2 24 hours or more is preferable, and 200 g / m 2 24 hours or more is preferable, and 300 g / m 2It is more preferable that the moisture permeability is 1600 g / m or more from the viewpoint of improving the humidity durability of the polarizing film. 2 24 hours or less is preferable, 1300 g / m 2 The moisture permeability can be calculated according to the moisture permeability test (cup method) of JIS Z0208 by cutting a sample to a diameter of 60 mm, placing it in a moisture permeability cup containing approximately 15 g of calcium chloride, placing it in an incubator at a temperature of 40°C and a humidity of 90% RH, and measuring the increase in weight of the calcium chloride before and after leaving it for 24 hours.

[0028] The polarizing film and the first transparent protective film are usually bonded together via an adhesive layer. The adhesive layer can be formed from various adhesives commonly used in polarizing films, such as isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl latex-based adhesives, and water-based polyesters. These adhesives are usually used as aqueous solutions and contain 0.5 to 60% by weight of solids. Other examples of the adhesive include active energy ray-curable adhesives such as ultraviolet-curable adhesives and electron beam-curable adhesives. Examples of the active energy ray-curable adhesives include (meth)acrylate-based adhesives. Examples of the curable component in the (meth)acrylate-based adhesive include compounds having a (meth)acryloyl group and compounds having a vinyl group. Furthermore, compounds having an epoxy group or an oxetanyl group can also be used as cationic polymerization-curable adhesives. The epoxy group-containing compound is not particularly limited as long as it has at least two epoxy groups in its molecule, and various commonly known curable epoxy compounds can be used. The thickness of the adhesive layer is not particularly limited, and when an aqueous adhesive or the like is used, it is preferably about 30 to 5000 nm, and more preferably about 100 to 1000 nm; when an ultraviolet-curable adhesive, an electron beam-curable adhesive, or the like is used, it is preferably about 0.1 to 100 μm, and more preferably about 0.5 to 10 μm.

[0029] <First adhesive layer (visible-side adhesive layer)> The first pressure-sensitive adhesive layer of the present invention is used to attach a front transparent member to be placed on the viewing side of an image display device, and has a difference ((A) - (B)) between the saturated moisture content (A) at 80°C and 85% RH and the saturated moisture content (B) at 25°C and 50% RH of 1.0 wt % or more. Alternatively, the first pressure-sensitive adhesive layer of the present invention is used to attach a front transparent member to be placed on the viewing side of an image display device, and has a ratio ((A) / (B)) of the saturated moisture content (A) at 80°C and 85% RH to the saturated moisture content (B) at 25°C and 50% RH of 2.5 or less. The first pressure-sensitive adhesive layer is a pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive.

[0030] The first adhesive layer typically has a thickness of 50 μm or more, from the viewpoint of being used to attach a front transparent member to be placed on the viewing side of an image display device. However, from the viewpoint of preventing the generation of bubbles due to foreign matter in a high-temperature environment (e.g., 95°C, 500 hours), from the viewpoint of increasing the amount of water absorption, and from the viewpoint of level difference absorption, the thickness is preferably 150 μm or more, and more preferably 200 μm or more. From the viewpoint of productivity, etc., the thickness is preferably 600 μm or less, more preferably 500 μm or less, and even more preferably 400 μm or less.

[0031] Examples of the front transparent member arranged on the viewing side of the image display device include a front transparent plate (also referred to as a "cover window," a "window layer," etc.) and a touch panel. A transparent plate having appropriate mechanical strength and thickness is used as the front transparent plate. Examples of such transparent plates include transparent resin plates such as acrylic resins and polycarbonate resins, and glass plates. Examples of the touch panel include various touch panels such as resistive, capacitive, optical, and ultrasonic touch panels, as well as glass or transparent resin plates equipped with touch sensor functions. When a capacitive touch panel is used as the front transparent member, it is preferable to provide a front transparent plate made of glass or a transparent resin plate on the viewing side of the touch panel.

[0032] The first pressure-sensitive adhesive layer has a difference ((A) - (B)) between the saturated moisture content (A) at 80°C and 85% RH and the saturated moisture content (B) at 25°C and 50% RH of 1.0% by weight or more. If the difference ((A) - (B)) between the saturated moisture content (A) and the saturated moisture content (B) of the first pressure-sensitive adhesive layer is less than 1.0% by weight, this is not preferred because it will not be possible to suppress a decrease in the single-piece transmittance of the polarized film in a high-temperature environment (e.g., 95°C for 500 hours). The difference ((A) - (B)) between the saturated moisture content (A) and the saturated moisture content (B) of the first pressure-sensitive adhesive layer is preferably 1.1% by weight or more, more preferably 1.3% by weight or more, and from the viewpoint of a change in dielectric constant in a humid environment, is preferably 5.0% by weight or less, more preferably 4.0% by weight or less. Alternatively, the first pressure-sensitive adhesive layer has a ratio ((A) / (B)) of the saturated moisture content (A) at 80°C and 85% RH to the saturated moisture content (B) at 25°C and 50% RH of 2.5 or less. If the ratio ((A) / (B)) of the saturated moisture content (A) to the saturated moisture content (B) of the first pressure-sensitive adhesive layer exceeds 2.5, it is not preferable because it is not possible to suppress a decrease in the single-piece transmittance of the polarizing film in a high-temperature environment (e.g., 95°C, 500 hours). From the viewpoint of humidification cloudiness, the ratio ((A) / (B)) of the saturated moisture content (A) to the saturated moisture content (B) of the first pressure-sensitive adhesive layer is preferably 1.0 or more, more preferably 2.0 or more, and is preferably 2.4 or less. If the saturated moisture content is too low, the adhesive will not be able to absorb enough moisture, and if the saturated moisture content is too high, the amount of moisture absorbed will increase, causing components in the adhesive layer to bleed out and have adverse effects. Therefore, the saturated moisture content (A) is preferably about 1.5 to 3.0% by weight, and more preferably about 2.0 to 2.5% by weight, and the saturated moisture content (B) is preferably about 0 to 3.0% by weight, and more preferably about 0.5 to 2.0% by weight.

[0033] The first pressure-sensitive adhesive layer preferably has high transparency. The first pressure-sensitive adhesive layer preferably has a haze value of 1% or less and a total light transmittance of 90% or more. The haze value and the total light transmittance are measured using a haze meter in accordance with JIS K7136.

[0034] The adhesive (adhesive composition) forming the first adhesive layer is not limited as long as it satisfies the above-mentioned difference in saturated moisture content, but an acrylic adhesive containing an acrylic polymer as a base polymer is preferred because it has excellent optical transparency, exhibits adhesive properties such as moderate wettability, cohesiveness and adhesiveness, and is also excellent in weather resistance and heat resistance.

[0035] The acrylic polymer has a main skeleton of a (meth)acrylic acid alkyl ester monomer unit. In this specification, "(meth)acrylic" means acrylic and / or methacrylic. When the base polymer is a copolymer, the arrangement of the constituent monomers may be random or block.

[0036] Examples of the (meth)acrylic acid alkyl ester include (meth)acrylic acid alkyl esters having an alkyl group having 1 to 20 carbon atoms. The alkyl group may be a linear or branched alkyl group, or a cyclic cycloalkyl group. From the viewpoint of easily controlling the difference ((A)-(B)) between the saturated moisture content (A) and the saturated moisture content (B) in the pressure-sensitive adhesive layer to 1.0 wt % or more, or easily controlling the ratio ((A) / (B)) of the saturated moisture content (A) to the saturated moisture content (B) to 2.5 or less, it is preferable to use a (meth)acrylic acid alkyl ester having a linear or branched alkyl group having 8 or less carbon atoms, more preferably a (meth)acrylic acid alkyl ester having a linear or branched alkyl group having 6 or less carbon atoms, and even more preferably a (meth)acrylic acid alkyl ester having a linear or branched alkyl group having 4 or less carbon atoms. The (meth)acrylic acid alkyl esters may be used alone or in combination of two or more.

[0037] Furthermore, from the viewpoint of easily controlling the difference ((A)-(B)) between the saturated moisture content (A) and the saturated moisture content (B) in the pressure-sensitive adhesive layer to 1.0% by weight or more, or from the viewpoint of easily controlling the ratio ((A) / (B)) of the saturated moisture content (A) to the saturated moisture content (B) to 2.5 or less, it is preferable to use a (meth)acrylic acid alkyl ester having a linear or branched alkyl group in combination with a (meth)acrylic acid alkyl ester having a cyclic cycloalkyl group. In this case, the weight ratio of the (meth)acrylic acid alkyl ester having a linear or branched alkyl group to the (meth)acrylic acid alkyl ester having a cyclic cycloalkyl group ((meth)acrylic acid alkyl ester having a linear or branched alkyl group / (meth)acrylic acid alkyl ester having a cyclic cycloalkyl group) is preferably 70 / 30 to 95 / 5, more preferably 80 / 20 to 92 / 8.

[0038] The proportion of the (meth)acrylic acid alkyl ester is preferably 40% by weight or more, more preferably 50% by weight or more, and even more preferably 60% by weight or more, of the total monomer components constituting the acrylic polymer.

[0039] In addition to the (meth)acrylic acid alkyl ester, the acrylic polymer preferably contains a polar monomer, from the viewpoint of easily controlling the difference ((A)-(B)) between the saturated moisture content (A) and the saturated moisture content (B) in the pressure-sensitive adhesive layer to 1.0% by weight or more, or from the viewpoint of easily controlling the ratio ((A) / (B)) of the saturated moisture content (A) to the saturated moisture content (B) to 2.5 or less. Examples of polar monomers include nitrogen-containing monomers such as N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, (meth)acryloylmorpholine, N-vinylcarboxylic acid amides, and N-vinylcaprolactam; and hydroxyl group-containing monomers such as hydroxyl group-containing (meth)acrylic acid esters such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl acrylate. The hydroxyl group-containing monomers are particularly preferred as polar monomers. The polar monomers can be used alone or in combination of two or more.

[0040] The proportion of the polar monomer is preferably 15% by weight or more, more preferably 20% by weight or more, and even more preferably 30% by weight or more, of the total monomer components constituting the acrylic polymer, and is preferably 60% by weight or less, more preferably 50% by weight or less, and even more preferably 40% by weight or less.

[0041] In addition to the above-exemplified monomers, other copolymerizable monomers may be used as the monomer components constituting the acrylic polymer, as long as the effects of the present invention are not impaired. Examples of the other copolymerizable monomers include amino group-containing monomers, epoxy group-containing monomers, and aromatic vinyl monomers.

[0042] The total proportion of the (meth)acrylic acid alkyl ester and the polar monomer is preferably 70% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, and even more preferably 95% by weight or more, of the total monomer components constituting the acrylic polymer.

[0043] The acrylic polymer can be prepared by polymerizing the above-mentioned monomer components by a known polymerization method. Examples of the polymerization method for the acrylic polymer include solution polymerization, emulsion polymerization, bulk polymerization, and polymerization by irradiation with active energy rays (active energy ray polymerization). In terms of transparency, water resistance, cost, etc., the solution polymerization method or the active energy ray polymerization method is preferred.

[0044] When preparing the acrylic polymer, a polymerization initiator such as a photopolymerization initiator or a thermal polymerization initiator may be used depending on the type of polymerization reaction. The molecular weight of the acrylic polymer can be adjusted appropriately. In order to provide the pressure-sensitive adhesive layer with appropriate viscoelasticity and adhesiveness, the weight-average molecular weight of the acrylic polymer, calculated as polystyrene, is preferably about 50,000 to 2,000,000, and more preferably about 100,000 to 1,500,000.

[0045] The proportion of the acrylic polymer in the solid content of the acrylic pressure-sensitive adhesive is preferably 70% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, and even more preferably 95% by weight or more.

[0046] The pressure-sensitive adhesive layer may have a crosslinked structure, if necessary. The crosslinked structure can be formed, for example, by adding a crosslinking agent to the pressure-sensitive adhesive. Examples of commonly used crosslinking agents that can be used include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, and metal chelate-based crosslinking agents. The content of the crosslinking agent is typically 10 parts by weight or less, preferably 5 parts by weight or less, and more preferably 3 parts by weight or less, per 100 parts by weight of the acrylic polymer, from the viewpoints that the flexibility (fluidity) of the pressure-sensitive adhesive may be reduced, thereby reducing adhesion to the adherend, or that air bubbles may be introduced or display unevenness may occur due to printing unevenness on the front transparent member. The crosslinking agents may be used alone or in combination of two or more.

[0047] A silane coupling agent may be added to the pressure-sensitive adhesive to adjust the adhesive strength. When the silane coupling agent is used, the amount of the silane coupling agent is usually about 0.01 to 5 parts by weight, and preferably about 0.03 to 2 parts by weight, per 100 parts by weight of the acrylic polymer. The silane coupling agents may be used alone or in combination of two or more.

[0048] The pressure-sensitive adhesive may contain a hygroscopic substance from the viewpoint of controlling the difference ((A)-(B)) between the saturated moisture content (A) and the saturated moisture content (B) in the pressure-sensitive adhesive layer or the ratio ((A) / (B)) of the saturated moisture content (A) to the saturated moisture content (B). Examples of the hygroscopic substance include zeolite.

[0049] If necessary, a tackifier may be added to the pressure-sensitive adhesive, such as a terpene-based tackifier, a styrene-based tackifier, a phenol-based tackifier, a rosin-based tackifier, an epoxy-based tackifier, a dicyclopentadiene-based tackifier, a polyamide-based tackifier, a ketone-based tackifier, or an elastomer-based tackifier.

[0050] The adhesive may contain additives such as plasticizers, softeners, anti-degradants, fillers, colorants, ultraviolet absorbers, antioxidants, surfactants, and antistatic agents, as long as the properties of the adhesive are not impaired.

[0051] The pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive. The pressure-sensitive adhesive may be a pressure-sensitive adhesive composition having any form, such as an emulsion type, a solvent type (solution type), an active energy ray-curable type, or a hot melt type (hot melt type). Preferred examples of the pressure-sensitive adhesive include a solvent-type pressure-sensitive adhesive and an active energy ray-curable (photo-curable) pressure-sensitive adhesive. Preferred examples of the solvent-type pressure-sensitive adhesive include a pressure-sensitive adhesive containing the (meth)acrylic polymer as an essential component. Preferred examples of the active energy ray-curable pressure-sensitive adhesive include a pressure-sensitive adhesive containing, as an essential component, a mixture (monomer mixture) of monomer components constituting the (meth)acrylic polymer or a partially polymerized product thereof. From the viewpoints of controlling the curing timing, productivity, etc., the pressure-sensitive adhesive is preferably an active energy ray-curable (photo-curable) pressure-sensitive adhesive.

[0052] The active energy ray-curable (photocurable) pressure-sensitive adhesive contains a photocurable component in addition to a mixture (monomer mixture) of monomer components constituting the (meth)acrylic polymer or a partial polymer thereof. For example, a polyfunctional polymerizable compound having two or more polymerizable functional groups per molecule is preferably used. Examples of the polyfunctional polymerizable compound include a compound having two or more C=C bonds per molecule, and a compound having one C=C bond and a polymerizable functional group such as epoxy, aziridine, oxazoline, hydrazine, or methylol. From the viewpoints of flexibility and adhesiveness, the blending ratio of the photocurable component is preferably 7 parts by weight or less, more preferably 5 parts by weight or less, and even more preferably 3 parts by weight or less, per 100 parts by weight of the total monomer components constituting the acrylic polymer.

[0053] Examples of methods for forming the pressure-sensitive adhesive layer include a method of applying the solvent-based pressure-sensitive adhesive to a separator or the like and drying and removing the polymerization solvent or the like to form a pressure-sensitive adhesive layer; a method of applying the solvent-based pressure-sensitive adhesive to a polarizing film or the like and drying and removing the polymerization solvent or the like to form a pressure-sensitive adhesive layer on the polarizing film or the like; and a method of applying an active energy ray-curable pressure-sensitive adhesive to a separator or the like and forming the pressure-sensitive adhesive by irradiating it with active energy rays.

[0054] <Polarizing film with adhesive layer (double-sided protective polarizing film with adhesive layer)> The polarizing film with an adhesive layer (double-sided protected polarizing film with an adhesive layer) of the present invention has a polarizing film having a second transparent protective film, and the second transparent protective film is provided on the side of the polarizing film opposite to the side having the first transparent protective film.

[0055] <Second transparent protective film> The second transparent protective film of the present invention is not particularly limited, and may be the same as the first transparent protective film described above. However, the second transparent protective film should have a moisture permeability of 1 g / m or less from the viewpoint of production efficiency in the drying process after laminating the polarizing film and the transparent protective film. 2 24 hours or more is preferable, and 5g / m 2 24 hours or more is more preferable, and 10 g / m 2 24 hours or more is more preferable, and from the viewpoint of allowing the first pressure-sensitive adhesive layer to absorb moisture in the polarizing film in a high-temperature environment, the moisture permeability is preferably 200 g / m 2 24 hours or less is preferable, and 180 g / m 2 24 hours or less is more preferable, and 150 g / m 2 It is more preferable that the time is 24 hours or less. The polarizing film and the second transparent protective film are usually attached to each other via the adhesive layer.

[0056] The first transparent protective film and / or the second transparent protective film may be a retardation plate having a front retardation of 40 nm or more and / or a thickness retardation of 80 nm or more. The front retardation is usually controlled to be in the range of 40 to 200 nm, and the thickness retardation is usually controlled to be in the range of 80 to 300 nm. When a retardation plate is used as the transparent protective film, the retardation plate also functions as the transparent protective film, thereby enabling a thinner film to be achieved.

[0057] Examples of the retardation plate include a birefringent film obtained by uniaxially or biaxially stretching a polymer material, an oriented film of a liquid crystal polymer, and an oriented layer of a liquid crystal polymer supported by a film. The thickness of the retardation plate is not particularly limited, but is generally about 20 to 150 μm. The retardation plate may be used by being attached to a transparent protective film that does not have a retardation.

[0058] The first transparent protective film and / or the second transparent protective film may contain any suitable additive such as an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a color inhibitor, a flame retardant, an antistatic agent, a pigment, or a colorant.

[0059] The surface of the first transparent protective film and / or the second transparent protective film that is not bonded to the polarizing film may be provided with a functional layer such as a hard coat layer, an anti-reflection layer, an anti-sticking layer, a diffusion layer, an anti-glare layer, etc. The functional layer such as the hard coat layer, the anti-reflection layer, the anti-sticking layer, the diffusion layer, or the anti-glare layer may be provided on the protective film itself, or may be provided separately from the protective film.

[0060] The first transparent protective film and / or the second transparent protective film and the polarizing film, or the polarizing film and the functional layer, may be laminated via an intervening layer such as a surface modification treatment layer, an easy-adhesive layer, a blocking layer, or a refractive index adjustment layer.

[0061] Examples of the surface modification treatment for forming the surface modification layer include corona treatment, plasma treatment, primer treatment, and saponification treatment.

[0062] Examples of the easy-adhesion adhesive that forms the easy-adhesion layer include forming materials containing various resins having a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a silicone-based resin, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, or the like.

[0063] The blocking layer has the function of preventing impurities such as oligomers and ions eluted from a transparent protective film, etc., from migrating (penetrating) into the polarizing film. The blocking layer may be any layer as long as it is transparent and can prevent impurities from eluting from a transparent protective film, etc. Examples of materials for forming the blocking layer include urethane prepolymer-based forming materials, cyanoacrylate-based forming materials, and epoxy-based forming materials.

[0064] The refractive index adjusting layer is a layer provided to suppress a decrease in transmittance due to reflection between layers having different refractive indices, such as the transparent protective film and a polarizing film, etc. Examples of refractive index adjusting materials that form the refractive index adjusting layer include forming agents containing various resins such as silica-based, acrylic-based, acrylic-styrene-based, and melamine-based resins and additives.

[0065] <Second adhesive layer (cell-side adhesive layer)> The polarizing film with an adhesive layer (double-sided protected polarizing film with an adhesive layer) of the present invention has a polarizing film having a second adhesive layer, and the second adhesive layer is provided on the side of the polarizing film having a second transparent protective film.

[0066] The adhesive (adhesive composition) forming the second adhesive layer can be any of various adhesives used in polarizing films, and can be appropriately selected and used based on a polymer such as an acrylic polymer, a silicone polymer, polyester, polyurethane, polyamide, polyvinyl ether, vinyl acetate / vinyl chloride copolymer, modified polyolefin, epoxy polymer, fluorine polymer, or rubber-based polymer such as natural rubber or synthetic rubber. In particular, acrylic adhesives containing an acrylic polymer as a base polymer are preferably used because they have excellent optical transparency, exhibit appropriate adhesive properties such as wettability, cohesiveness, and adhesion, and are also excellent in weather resistance and heat resistance.

[0067] The thickness of the second pressure-sensitive adhesive layer is not particularly limited, but from the viewpoints of adhesiveness, handling, etc., it is preferably about 3 μm to 35 μm, more preferably 5 μm to 32 μm, and even more preferably 10 μm to 30 μm.

[0068] The first pressure-sensitive adhesive layer and / or the second pressure-sensitive adhesive layer preferably have a low content of organic acid monomers (free organic acids) such as (meth)acrylic acid. By reducing the organic acid monomer content in the first pressure-sensitive adhesive layer, a decrease in the single transmittance of the polarizing plate due to polyenation is suppressed. The content of (meth)acrylic acid monomers in the pressure-sensitive adhesive layer is preferably 100 ppm or less, more preferably 70 ppm or less, and even more preferably 50 ppm or less. The organic acid monomer content in the pressure-sensitive adhesive layer is determined by immersing the pressure-sensitive adhesive layer in pure water, heating at 100°C for 45 minutes, and quantifying the acid monomers extracted into the water using ion chromatography.

[0069] Generally, the presence of unreacted residual monomers is unavoidable in thermosetting or photocurable polymers. Therefore, in order to reduce the acid monomer content in the pressure-sensitive adhesive layer, it is preferable to reduce the amount of organic acid monomer components such as (meth)acrylic acid in the monomer components constituting the base polymer. It is preferable that the base polymer does not substantially contain organic acid monomers (carboxy group-containing monomers) as monomer units. Of the total monomer components constituting the acrylic polymer, the carboxy group-containing monomer is preferably 0.5 wt% or less, more preferably 0.1 wt% or less, and even more preferably 0.05 wt% or less.

[0070] A separator is releasably attached to the first pressure-sensitive adhesive layer and / or the second pressure-sensitive adhesive layer, as required. Suitable separator materials include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films. The substrate used in forming the pressure-sensitive adhesive layer (applying the pressure-sensitive adhesive) may be used as the separator for the pressure-sensitive adhesive layer. By appropriately subjecting the surface of the separator to a release treatment such as silicone treatment, long-chain alkyl treatment, or fluorine treatment, the releasability from the pressure-sensitive adhesive layer can be improved when used in practice.

[0071] <Image display device> The image display device of the present invention has an image display cell and the front transparent member, and the polarizing film with the pressure-sensitive adhesive layer is attached to the front transparent member.

[0072] Examples of the image display cell include a liquid crystal cell and an organic EL cell. The liquid crystal cell may be, for example, a reflective liquid crystal cell that uses external light, a transmissive liquid crystal cell that uses light from a light source such as a backlight, or a semi-transmissive semi-reflective liquid crystal cell that uses both external light and light from the light source. When the liquid crystal cell uses light from a light source, the image display device (liquid crystal display device) has a polarizing film disposed on the opposite side of the image display cell (liquid crystal cell) from the viewing side, and further has a light source disposed thereon. The polarizing film on the light source side and the liquid crystal cell are preferably bonded together via an appropriate adhesive layer. The liquid crystal cell may be driven in any mode, such as VA mode, IPS mode, TN mode, STN mode, or bend orientation (π type).

[0073] The organic EL cell preferably has a light-emitting body (organic electroluminescence light-emitting body) formed by sequentially laminating a transparent electrode, an organic light-emitting layer, and a metal electrode on a transparent substrate. The organic light-emitting layer is a laminate of various organic thin films, and various layer configurations can be adopted, such as a laminate of a hole-injection layer made of a triphenylamine derivative or the like and a light-emitting layer made of a fluorescent organic solid such as anthracene, a laminate of such a light-emitting layer and an electron-injection layer made of a perylene derivative or the like, or a laminate of a hole-injection layer, a light-emitting layer, and an electron-injection layer.

[0074] The pressure-sensitive adhesive layer-attached polarizing film of the present invention is excellent in suppressing a decrease in the single-unit transmittance due to polyenization of the polarizing film in a high-temperature environment, and is therefore suitable for use in in-vehicle image display devices such as car navigation devices and rear monitors. [Example]

[0075] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0076] <Preparation of First Pressure-Sensitive Adhesive Layer> <Adhesive layer A> A monomer mixture consisting of 60 parts by weight of butyl acrylate (BA), 6 parts by weight of cyclohexyl acrylate (CHA), 26 parts by weight of 4-hydroxybutyl acrylate (4HBA), and 8 parts by weight of hydroxyethyl acrylate (HEA) was added to a four-neck flask with 0.09 parts by weight of 2,2-dimethoxy-1,2-diphenyl-1-one (trade name "Irgacure 651", manufactured by BASF Japan) and 0.09 parts by weight of 1-hydroxy-cyclohexyl-phenyl-ketone (trade name "Irgacure 184", manufactured by BASF Japan). The mixture was exposed to ultraviolet light in a nitrogen atmosphere to partially photopolymerize, yielding a partially polymerized product (monomer syrup) with a polymerization rate of approximately 10%. To 100 parts by weight of this partial polymer, 0.12 parts by weight of dipentaerythritol hexaacrylate ("KAYARAD DPHA" manufactured by Nippon Kayaku Co., Ltd.) as a polyfunctional polymerizable compound and 0.3 parts by weight of 3-glycidoxypropyltrimethoxysilane ("KBM-403" manufactured by Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent were added and mixed uniformly to prepare a pressure-sensitive adhesive (pressure-sensitive adhesive composition). The resulting pressure-sensitive adhesive was applied to the release-treated surface of a separator (a polyethylene terephthalate film with a release treatment on one side, 38 μm thick, product name "MRF38" manufactured by Mitsubishi Plastics, Inc.) to form a coating layer, and then a similar separator was placed on top of the coating layer. Next, the adhesive was illuminated with a black light at an intensity of 5 mW / cm. 2 of ultraviolet rays, with an accumulated light intensity of 3600mJ / cm 2 Polymerization was continued until irradiation was complete, producing a first pressure-sensitive adhesive layer with separators on both sides. The thickness of the first pressure-sensitive adhesive layer was set to the thickness shown in Table 1 by adjusting the coating amount.

[0077] <Adhesive layer B> A monomer mixture consisting of 67 parts by weight of 2-ethylhexyl acrylate (2EHA), 15 parts by weight of N-vinyl-2-pyrrolidone (NVP), 3 parts by weight of 2-hydroxyethyl acrylate (HEA), and 15 parts by weight of 4-hydroxybutyl acrylate (4HBA) was added to a four-neck flask with 0.035 parts by weight of 2,2-dimethoxy-1,2-diphenyl-1-one (trade name "Irgacure 651", manufactured by BASF Japan) and 0.035 parts by weight of 1-hydroxy-cyclohexyl-phenyl-ketone (trade name "Irgacure 184", manufactured by BASF Japan). The mixture was exposed to ultraviolet light under a nitrogen atmosphere to partially photopolymerize, yielding a partially polymerized product (monomer syrup) with a polymerization rate of approximately 10%. To 100 parts by weight of this partial polymer, 0.3 parts by weight of 1,6-hexanediol diacrylate ("NK Ester A-HD-N" manufactured by Shin-Nakamura Chemical Co., Ltd.) as a polyfunctional polymerizable compound and 0.3 parts by weight of 3-glycidoxypropyltrimethoxysilane ("KBM-403" manufactured by Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent were added and mixed uniformly to prepare a pressure-sensitive adhesive (pressure-sensitive adhesive composition). The resulting pressure-sensitive adhesive was applied to the release-treated surface of a separator (a polyethylene terephthalate film with a release treatment on one side, 38 μm thick, product name "MRF38" manufactured by Mitsubishi Plastics, Inc.) to form a coating layer, and a similar separator was then placed on top of the coating layer. Subsequently, the adhesive was illuminated with a black light at an intensity of 5 mW / cm. 2 of ultraviolet rays, with an accumulated light intensity of 3600mJ / cm 2 Polymerization was continued until irradiation was complete, producing a first pressure-sensitive adhesive layer with separators on both sides. The thickness of the first pressure-sensitive adhesive layer was set to the thickness shown in Table 1 by adjusting the coating amount.

[0078] <Adhesive layer C> A monomer mixture consisting of 40 parts by weight of 2-ethylhexyl acrylate (2EHA), 40 parts by weight of isostearyl acrylate (ISTA), 18 parts by weight of N-vinyl-2-pyrrolidone (NVP), and 2 parts by weight of 4-hydroxybutyl acrylate (4HBA) was added to a four-neck flask with 0.05 parts by weight of 2,2-dimethoxy-1,2-diphenyl-1-one (trade name "Irgacure 651", manufactured by BASF Japan) and 0.05 parts by weight of 1-hydroxy-cyclohexyl-phenyl-ketone (trade name "Irgacure 184", manufactured by BASF Japan). The mixture was exposed to ultraviolet light under a nitrogen atmosphere to partially photopolymerize, yielding a partially polymerized product (monomer syrup) with a polymerization rate of approximately 10%. To 100 parts by weight of this partial polymer, 0.02 parts by weight of trimethylolpropane triacrylate ("TMP3A" manufactured by Osaka Organic Chemical Industry Co., Ltd.) as a polyfunctional polymerizable compound and 0.3 parts by weight of 3-glycidoxypropyltrimethoxysilane ("KBM-403" manufactured by Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent were added and mixed uniformly to prepare a pressure-sensitive adhesive (pressure-sensitive adhesive composition). The resulting pressure-sensitive adhesive was applied to the release-treated surface of a separator (a polyethylene terephthalate film with a release treatment on one side, 38 μm thick, product name "MRF38" manufactured by Mitsubishi Plastics, Inc.) to form a coating layer, and then a similar separator was placed on top of the coating layer. Subsequently, the adhesive was illuminated with a black light at an intensity of 5 mW / cm. 2 of ultraviolet rays, with an accumulated light intensity of 3600mJ / cm 2 Polymerization was continued until irradiation was complete, producing a first pressure-sensitive adhesive layer with separators on both sides. The thickness of the first pressure-sensitive adhesive layer was set to the thickness shown in Table 1 by adjusting the coating amount.

[0079] Example 1 <Preparation of polarizing film> <Polarizing film A> A polyvinyl alcohol film with an average degree of polymerization of 2,400, a degree of saponification of 99.9 mol%, and a thickness of 45 μm was prepared. The polyvinyl alcohol film was immersed in a 20°C swelling bath (water bath) for 30 seconds between rolls with different peripheral speed ratios, where it was stretched 2.2 times in the conveying direction while swelling (swelling step). Subsequently, it was immersed in a 30°C dye bath (an aqueous solution containing 0.1 wt% iodine and 0.9 wt% potassium iodide) for 30 seconds, where it was dyed and stretched 3.3 times in the conveying direction relative to the original polyvinyl alcohol film (a polyvinyl alcohol film that was not stretched in the conveying direction at all) (dyeing step). The dyed polyvinyl alcohol film was then immersed in a 40°C crosslinking bath (an aqueous solution containing 3.0 wt% boric acid and 3.0 wt% potassium iodide) for 28 seconds, where it was stretched 3.6 times in the conveying direction relative to the original polyvinyl alcohol film (crosslinking step). The resulting polyvinyl alcohol film was then immersed in a 61°C stretching bath (aqueous solution containing 4.0% by weight of boric acid and 5.0% by weight of potassium iodide) for 60 seconds to be stretched 6.0 times in the conveying direction relative to the original polyvinyl alcohol film (stretching step). The film was then immersed in a 20°C washing bath (aqueous solution containing 2.0% by weight of potassium iodide) for 10 seconds (washing step). The washed polyvinyl alcohol film was dried at 40°C for 30 seconds to produce a polarizing film. The iodine content, as determined by the following measurement method, was 2.8% by weight. The polarizing film had a thickness of 18 μm.

[0080] [Method for measuring iodine concentration (wt%) in polarizing film] The iodine concentration (wt %) of the polarizing film was determined using a fluorescent X-ray analyzer (manufactured by Rigaku Corporation, trade name "ZSX-PRIMUS IV", measurement diameter: ψ20 mm) according to the following formula. Iodine concentration (wt%) = 14.474 × (fluorescent X-ray intensity) / (film thickness) (kcps / μm). The coefficient used to calculate the concentration varies depending on the measuring device, but this coefficient can be determined using an appropriate calibration curve.

[0081] <Preparation of polarizing film with adhesive layer> The adhesive used was an aqueous solution containing an acetoacetyl group-containing polyvinyl alcohol resin (average polymerization degree 1,200, saponification degree 98.5 mol%, acetoacetylation degree 5 mol%) and methylol melamine in a weight ratio of 3:1. Using this adhesive, a 30 μm-thick transparent protective film (made by Nippon Shokubai, moisture permeability 125 g / (m)) made of a (meth)acrylic resin (modified acrylic polymer having a lactone ring structure) was attached as a second transparent protective film to one side (image display cell side) of the polarizing film obtained above. 2 On the other side (viewing side), a 49 μm thick transparent protective film (moisture permeability 300 g / (m)) was used as the first transparent protective film. The first transparent protective film was a triacetyl cellulose film (manufactured by Fujifilm, product name "TJ40UL") coated with HC. 2 The polarized film was laminated using a roll laminator and then heated and dried in an oven (at 90°C for 10 minutes) to produce a polarized film in which transparent protective films were laminated on both sides of the polarized film. The single transmittance of the polarized film was 41.7%. Next, the separator of the first pressure-sensitive adhesive layer having separators on both sides thereof obtained above was peeled off, and the pressure-sensitive adhesive layer was laminated onto the first transparent protective film of the obtained polarized film to produce a polarized film with a pressure-sensitive adhesive layer.

[0082] [Method for measuring saturated moisture content] The first pressure-sensitive adhesive layer obtained above was cut into a 1 cm x 1 cm piece, the separator removed, and attached to aluminum foil to prepare an evaluation sample. Using a moisture adsorption / desorption analyzer (IGA-Sorp, manufactured by Hiden), the sample was left in a 95°C, 0% RH environment until no weight change was observed, and the weight (W1) of the sample was measured after complete removal of moisture. The sample was then left in an 80°C, 85% RH environment, and weight change was observed. When the sample's weight no longer changed (saturated state), its weight (W2) was measured. The saturated moisture content (A) was measured using the following formula. The saturated moisture content (B) at 25°C, 50% RH was measured in the same manner, and the difference (A - B) was calculated. The results are shown in Table 1.

number

[0083] [Evaluation of single-piece transmittance under high temperature environment (1)] The polarizing film with the adhesive layer obtained above was cut into a 20 × 15 cm sheet (within-plane size of 300 cm) so that the absorption axis of the polarizing film was the long side. 2 ), and a glass plate (pseudo-image display cell) was bonded to the surface of the second transparent protective film of the polarizing film via a 20 μm-thick acrylic adhesive layer as a second adhesive layer. The separator was then peeled off and the glass plate (front transparent member) was bonded to the other glass plate via the first adhesive layer, to produce a laminate (pseudo-image display device). The resulting laminate was left to stand in a hot air oven at 95°C for 500 hours, and the single-unit transmittance (ΔTs) was measured before and after heating. The single-unit transmittance was measured using a spectrophotometer (Murakami Color Research Laboratory, product name "DOT-3") and evaluated according to the following criteria. The single-unit transmittance was the Y value corrected for luminosity using a 2-degree visual field (light source C) according to JIS Z8701-1982. The measurement wavelength was 380 to 700 nm (10 nm intervals). The results are shown in Table 1. ΔTs(%)=Ts 500 -Ts0 Here, Ts0 is the single transmittance of the laminate before heating, and Ts 500 is the single transmittance of the laminate after heating for 500 hours. ◎: ΔTs (%) is 0% or more and 5% or less. ○: ΔTs (%) is -1% or more and less than 0%. △: ΔTs (%) is -2% or more and less than -1%. ×: ΔTs (%) is less than −2% or more than 5%.

[0084] [Evaluation of single-piece transmittance under high temperature environment (2)] The same procedure as in [Evaluation of single-unit transmittance in a high-temperature environment (1)] above was carried out, except that instead of leaving the sample in a hot air oven at 95°C for 500 hours, the sample was left in a hot air oven at 95°C for 1000 hours, and the single-unit transmittance was evaluated according to the following criteria. ΔTs(%)=Ts 1000 -Ts0 Here, Ts0 is the single transmittance of the laminate before heating, and Ts 1000 is the single transmittance of the laminate after heating for 1000 hours. ◎: ΔTs (%) is 0% or more and 5% or less. ○: ΔTs (%) is -1% or more and less than 0%. △: ΔTs (%) is -2% or more and less than -1%. ×: ΔTs (%) is less than −2% or more than 5%.

[0085] [Evaluation of air bubbles caused by foreign matter] In the above-mentioned <Preparation of Polarizing Film with Adhesive Layer>, pseudo foreign matter (glass) having an average particle size of 150 μm was mixed onto the first transparent protective film of the obtained polarizing film, and the first adhesive layer was attached to prepare a polarizing film with an adhesive layer. The obtained polarizing film with an adhesive layer was cut into a 20 × 15 cm square (in-plane size 300 cm) so that the absorption axis of the polarizing film was the long side. 2 ), and a glass plate (pseudo-image display cell) was bonded to the surface of the second transparent protective film of the polarizing film via a 20 μm-thick acrylic adhesive layer as a second adhesive layer, and then bonded to another glass plate (front transparent member) via the first adhesive layer from which the separator had been peeled off, to produce a laminate (pseudo-image display device).The resulting laminate was left to stand in a hot air oven at 95°C for 500 hours, and then evaluated for bubble generation due to foreign matter according to the following criteria.The results are shown in Table 1. ◯: No bubbles are generated. △: The bubbles are less than 100 μm. ×: Bubble growth is 100 μm or more.

[0086] [Haze value measurement] The release films on both sides of the first pressure-sensitive adhesive layer with separators on both sides prepared as described above were peeled off and the layer was attached to a glass slide (product name: White Polish No. 1, thickness: 0.8-1.0 mm, total light transmittance: 92%, haze: 0.2%, manufactured by Matsunami Glass Industry Co., Ltd.) to prepare a test specimen with a layer structure of glass slide / pressure-sensitive adhesive layer / glass slide. The test specimen was left in an environment of 85°C and 85% RH for 1000 hours, and the haze values ​​in the visible light range at the initial (X) and after leaving (Y) were measured using a haze meter (device name: HM-150, manufactured by Murakami Color Research Institute Co., Ltd.). The results are shown in Table 1. The first pressure-sensitive adhesive layer of the present invention preferably has an initial haze value of 1.5 or less, more preferably 1.0 or less, before being left in an environment of 85°C and 85% RH for 1000 hours; the haze value after being left in an environment of 85°C and 85% RH for 1000 hours is preferably 3.0 or less, more preferably 2.0 or less; and the difference in haze value before and after being left in an environment of 85°C and 85% RH for 1000 hours is preferably 1.5 or less, more preferably 1.0 or less.

[0087] <Examples 2-9 and Comparative Examples 1-4> In Examples 2-9 and Comparative Examples 1-4, the same procedures as in Example 1 were carried out and the above evaluations were carried out, except that the type (thickness) of the polarizing film, the in-plane size of the polarizing film, and the type and thickness of the first adhesive layer were changed to the values ​​shown in Table 1. The results are shown in Table 1. 2 is 15cm x 10cm, and the in-plane size is 600cm 2 is 30cm x 20cm, and the in-plane size is 900cm 2 The size of the polarizing film is 50 cm x 18 cm. The preparation of polarizing film B is described below.

[0088] <Preparation of polarizing film> <Polarizing film B> A polarizing film and a polarizing film were produced in the same manner as in Example 1, except that a 75 μm-thick polyvinyl alcohol film was immersed in a 35°C swelling bath (water bath) between rolls with different peripheral speed ratios for 30 seconds to swell and stretched 2.2 times in the conveying direction (swelling step), and the iodine concentration of the dye bath was adjusted so that the iodine concentration of the final polarizing film was 2.5 wt %. The thickness of the resulting polarizing film was 28 μm. The single transmittance of the resulting polarizing film was 41.7%.

[0089] [Table 1]

[0090] The pressure-sensitive adhesive layer-attached polarizing films of Examples 1-9 had polarizing film thicknesses of 20 μm or less, the first pressure-sensitive adhesive layer was used to attach a front transparent member disposed on the viewing side of an image display device, and the difference ((A)-(B)) between the saturated moisture content (A) at 80°C and 85% RH and the saturated moisture content (B) at 25°C and 50% RH was 1.0 wt % or more, or the ratio ((A) / (B)) between the saturated moisture content (A) at 80°C and 85% RH and the saturated moisture content (B) at 25°C and 50% RH was 2.5 or less. Therefore, the results of the evaluation (1) of the single-piece transmittance under a high-temperature environment were excellent or good, and thus the pressure-sensitive adhesive layer-attached polarizing films of Examples 1-3 and 5-8 showed particularly good results in the evaluation (2) of the single-piece transmittance under a high-temperature environment, because they were excellent or good.

[0091] On the other hand, the polarized film with a pressure-sensitive adhesive layer of Comparative Example 1-2 had a difference in saturated moisture content ((A) - (B)) of 0.8 wt %, and therefore showed a poor result of △ or × in the evaluation (1) of the single-piece transmittance under a high-temperature environment. Also, the polarized film with a pressure-sensitive adhesive layer of Comparative Example 3-4 had a polarizing film thickness of 28 μm, and therefore showed a poor result of △ or × in the evaluation (1) of the single-piece transmittance under a high-temperature environment. [Explanation of symbols]

[0092] 10: Polarizing film 11: Polarizing film 12: First transparent protective film 13: Second transparent protective film 20: First adhesive layer 30: Second adhesive layer 45,46: Separator 70: Front transparent member 71: Front transparent plate 72: Printing step 90: Image display cell 100: Polarized film with adhesive layer 110: Image display device

Claims

1. A polarizing film having a polarizing membrane and a first transparent protective film, the polarizing film having a first pressure-sensitive adhesive layer provided on the first transparent protective film side of the polarizing film, The polarizing film has a film thickness of 20 μm or less, the first pressure-sensitive adhesive layer is used to bond a front transparent member disposed on the viewing side of an image display device, and the difference ((A) - (B)) between the saturated moisture content (A) at 80°C and 85% RH and the saturated moisture content (B) at 25°C and 50% RH is 1.0% by weight or more, the saturated moisture content (A) is 1.5% by weight or more and 3.0% by weight or less, and the thickness of the pressure-sensitive adhesive layer-attached polarizing film is 150 μm or more and 600 μm or less.

2. The first transparent protective film has a moisture permeability of 100 g / m ２ The polarizing film with a pressure-sensitive adhesive layer according to claim 1, characterized in that the shelf life is 24 hours or more.

3. the polarizing film has a second transparent protective film, 3. The polarizing film with a pressure-sensitive adhesive layer according to claim 1, wherein the second transparent protective film is provided on the side of the polarizing film opposite to the side having the first transparent protective film.

4. the polarizing film has a second pressure-sensitive adhesive layer, 4. The polarizing film with a pressure-sensitive adhesive layer according to claim 3, wherein the second pressure-sensitive adhesive layer is provided on the side of the polarizing film having the second transparent protective film.

5. 5. The polarizing film with a pressure-sensitive adhesive layer according to claim 4, wherein the second pressure-sensitive adhesive layer has a thickness of 3 μm or more and 35 μm or less.

6. The polarizing film has an in-plane size of 300 cm ２ The pressure-sensitive adhesive layer-attached polarizing film according to any one of claims 1 to 5, characterized in that:

7. an image display cell and the front transparent member; An image display device, comprising the front transparent member to which the polarizing film with the pressure-sensitive adhesive layer according to any one of claims 1 to 6 is attached.

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