TW202311045A - Polarization plate and polarization plate with retardation layer capable of reducing light transmittance T380 to 3.5% or less at a wavelength of 380 nm - Google Patents

Abstract

The objective of the present invention is to provide a polarization plate and a polarization plate with retardation layer. The polarization plate reduces light transmittance T380 at a wavelength of 380 nm to 3.5% or less and also suppresses warpage in a high temperature environment. The solution is that the polarization plate according to the present invention has a light transmittance T380 that is 3.5% or less at a wavelength of 380 nm, and satisfies the following formula (1): [Formula 1] 16≤Th/W (1). In formula (1), Th represents the thickness ([mu]m) of the polarization plate, and W represents a warpage value (mm) measured using the following heating warpage test. The heating warpage test: the polarization plate is cut into a size of 70 mm×150 mm as a test specimen, and the test specimen is attached using an adhesive layer to a test glass plate. The test specimen is heated at 85 DEG C for 25 hours, and is then left to stand at room temperature (23 DEG C) for 1 hour or more to measure the warpage height of the test specimen.

Description

Polarizing plate and polarizing plate with retardation layer

The invention relates to a polarizing plate and a polarizing plate with a retardation layer.

In recent years, image display devices represented by liquid crystal display devices and electroluminescent (EL) display devices (such as organic EL display devices and inorganic EL display devices) are rapidly becoming popular. A polarizer is typically used in an image display device. It is known that in order to protect an image display element (especially an OLED element) from ultraviolet rays, it is known that ultraviolet absorption is imparted to the polarizing plate (for example, patent document 1). However, the polarizing plate described in Patent Document 1 has a problem that warpage easily occurs in a high-temperature environment. Current Technical Literature patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2011-203400

The present invention is made to solve the above-mentioned conventional problems, and its main purpose is to provide a polarizing plate and a polarizing plate with a retardation layer, the polarizing plate can reduce the light transmittance T ₃₈₀ at a wavelength of 380nm to below 3.5%, and At the same time, it can suppress warpage under high temperature environment.

式(1)中，Th表示前述偏光板之厚度(μm)，W表示利用下述加熱翹曲試驗測定之翹曲值(mm)； 加熱翹曲試驗： 將偏光板裁切成70mm×150mm之尺寸作成試驗試樣，並將試驗試樣利用黏著劑層貼合於試驗用玻璃板後，將試驗試樣在85℃下加熱24小時，接著在室溫(23℃)下靜置1小時以上後，測定試驗試樣之翹曲高度。 [2]如上述[1]之偏光板，亦可具備有：偏光件；第1保護層，其係配置於該偏光件之視辨側；及第2保護層，其係配置於該偏光件之與視辨側相反側。該第2保護層亦可含有樹脂與紫外線吸收劑。 [3]如上述[2]之偏光板中，上述第2保護層之厚度亦可為10μm以下。 [4]如上述[2]或[3]之偏光板中，上述第1保護層之厚度亦可為40μm以下。 [5]如上述[2]~[4]中任一項之偏光板中，上述第2保護層亦可為在有機溶劑中分散及/或溶解有上述樹脂及上述紫外線吸收劑之液體的塗佈膜的固化層。 [6]如上述[2]~[5]中任一項之偏光板中，相對於上述樹脂100質量份，上述紫外線吸收劑之含有比率亦可為1質量份以上。 [7]本發明另一面向之附相位差層之偏光板，具備有：如上述[1]~[6]中任一項之偏光板；與相位差層，其係配置於上述偏光板之與視辨側相反側。 Means for solving the problems [1] The light transmittance T ₃₈₀ of the polarizing plate according to the embodiment of the present invention at a wavelength of 380 nm is 3.5% or less, and satisfies the following formula (1); [Mathematical formula 1]

In formula (1), Th represents the thickness (μm) of the aforementioned polarizing plate, W represents the warpage value (mm) measured by the following heating warpage test; heating warpage test: cut the polarizing plate into 70mm×150mm Dimensions Prepare a test sample and attach the test sample to the test glass plate with an adhesive layer, heat the test sample at 85°C for 24 hours, and then let it stand at room temperature (23°C) for more than 1 hour Afterwards, the warpage height of the test sample was measured. [2] The polarizing plate according to the above [1] may further include: a polarizer; a first protective layer arranged on the viewing side of the polarizer; and a second protective layer arranged on the polarizer It is the side opposite to the visual perception side. The second protective layer may also contain a resin and an ultraviolet absorber. [3] In the polarizing plate according to the above [2], the thickness of the second protective layer may be 10 μm or less. [4] In the polarizing plate according to the above [2] or [3], the thickness of the first protective layer may be 40 μm or less. [5] In the polarizing plate according to any one of the above [2] to [4], the above-mentioned second protective layer may be a liquid coating in which the above-mentioned resin and the above-mentioned ultraviolet absorber are dispersed and/or dissolved in an organic solvent. Cured layer of cloth membrane. [6] In the polarizing plate according to any one of the above [2] to [5], the content ratio of the ultraviolet absorber may be 1 part by mass or more with respect to 100 parts by mass of the resin. [7] Another aspect of the present invention is a polarizing plate with a retardation layer, comprising: the polarizing plate according to any one of the above [1] to [6]; and a retardation layer disposed on the polarizing plate The side opposite to the visual side.

Effects of the Invention According to the embodiment of the present invention, the light transmittance T ₃₈₀ at a wavelength of 380 nm can be reduced, and at the same time, warping in a high-temperature environment can be suppressed.

Hereinafter, representative embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

(Definition of terms and symbols) Definitions of terms and symbols in this manual are as follows. (1) Refractive index (nx, ny, nz) "nx" is the refractive index in the direction where the in-plane refractive index is the largest (that is, the direction of the slow axis), "ny" is the refractive index in the direction that is perpendicular to the slow axis in the plane (that is, the direction of the fast axis), " nz" is the refractive index in the thickness direction. (2) In-plane retardation (Re) "Re(λ)" is the in-plane retardation measured with light of wavelength λnm at 23°C. For example, "Re(550)" is an in-plane retardation measured at 23° C. with light having a wavelength of 550 nm. Re(λ) can be obtained by the formula: Re=(nx-ny)×d when the thickness of the layer (thin film) is defined as d(nm). (3) Phase difference in the thickness direction (Rth) "Rth(λ)" is the retardation in the thickness direction measured at 23° C. with light having a wavelength of λnm. For example, "Rth(550)" is the retardation in the thickness direction measured at 23° C. with light having a wavelength of 550 nm. Rth(λ) can be obtained by the formula: Rth=(nx-nz)×d when the thickness of the layer (thin film) is set as d(nm). (4) angle When an angle is mentioned in this specification, unless otherwise specified, the angle includes angles in both clockwise and counterclockwise directions.

[數學式3]

[數學式4]

(式(1)~(3)中，Th表示偏光板1之厚度(μm)，W表示利用下述加熱翹曲試驗測定之翹曲值(mm)) 加熱翹曲試驗： 將偏光板裁切成70mm×150mm之尺寸作成試驗試樣，並將該試驗試樣利用黏著劑層貼合於試驗用玻璃板後，將試驗試樣在85℃下進行24小時加熱，接著在室溫(23℃)下靜置1小時以上後，測定試驗試樣之翹曲高度。此外，關於加熱翹曲試驗的詳情，將於後述實施例中說明。 偏光板滿足上述式(1)時，可將偏光板之光透射率T ₃₈₀降低至如上述、且同時可抑制偏光板在高溫環境下之翹曲。 A. Overall Configuration of Polarizing Plate FIG. 1 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention. The light transmittance T ₃₈₀ of the polarizing plate 1 in the illustrated example at a wavelength of 380nm is 3.50% or less, preferably 2.00% or less, more preferably 1.85% or less, more preferably 1.50% or less, especially preferably 1.00% or less, especially It should be less than 0.80%. The polarizing plate 1 satisfies the following formula (1), preferably satisfies the following formula (2), particularly preferably satisfies the following formula (3). [mathematical formula 2]

[mathematical formula 3]

[mathematical formula 4]

(In formulas (1) to (3), Th represents the thickness (μm) of the polarizing plate 1, and W represents the warpage value (mm) measured by the following heating warpage test.) Heating warpage test: cut the polarizer Make a test sample with a size of 70mm×150mm, and attach the test sample to the test glass plate with an adhesive layer, heat the test sample at 85°C for 24 hours, and then heat it at room temperature (23°C ) for more than 1 hour, measure the warpage height of the test sample. In addition, the detail of a heat warpage test is demonstrated in the Example mentioned later. When the polarizing plate satisfies the above formula (1), the light transmittance T ₃₈₀ of the polarizing plate can be reduced to the above-mentioned level, and at the same time, the warping of the polarizing plate in a high temperature environment can be suppressed.

In one embodiment of the present invention, the polarizer 1 is provided with: a polarizer 2; a first protective layer 3 disposed on the viewing side of the polarizer 2; and a second protective layer 4 disposed on the polarizer 2 The side opposite to the visual side. The second protective layer 4 contains a resin and an ultraviolet absorber. With respect to 100 parts by mass of the resin, the content ratio of the ultraviolet absorber is, for example, not less than 1 part by mass, preferably not less than 3 parts by mass, more preferably not less than 5 parts by mass, and for example not more than 20 parts by mass, preferably not more than 15 parts by mass, More preferably, it is 12 mass parts or less. When the content ratio of the ultraviolet absorber is within the above range, the light transmittance T ₃₈₀ of the polarizing plate can be lowered stably. The first protective layer 3 is attached on the viewing side of the polarizer 2 using any appropriate adhesive layer 5a. The second protective layer 4 represents an upper side that is pasted on the opposite side of the polarizer 2 to the viewing side by using any appropriate adhesive layer 5b. That is, the polarizing plate 1 may be formed of the first protective layer 3 , the adhesive layer 5 a , the polarizer 2 , the adhesive layer 5 b , and the second protective layer 4 . Each of the adhesive layer 5 a and the adhesive layer 5 b is typically formed of an ultraviolet curing adhesive. The adhesive layer 5a and/or the adhesive layer 5b may also be an adhesive layer.

The thickness of the polarizing plate 1 is, for example, 30 μm or more, preferably 40 μm or more, and for example, 65 μm or less, preferably 50 μm or less. When the thickness of the polarizing plate is not more than the above-mentioned upper limit, the thickness of the polarizing plate can be reduced, and warpage in a high-temperature environment can be stably suppressed. In one embodiment, the thickness of the second protective layer 4 is smaller than that of the first protective layer 3 . The upper limit of the thickness of the second protective layer 4 is, for example, 20 μm or less, preferably 15 μm or less, more preferably 10 μm or less, more preferably 8 μm or less, particularly preferably 5 μm or less. The lower limit of the thickness of the second protective layer 4 is typically at least 0.5 μm, preferably at least 1 μm, more preferably at least 3 μm. When the thickness of the second protective layer is not more than the above-mentioned upper limit, the thickness of the polarizing plate can be reduced, and the warping of the polarizing plate in a high-temperature environment can be further suppressed. When the thickness of the second protective layer is more than the above lower limit, the light transmittance T ₃₈₀ of the polarizing plate can be further stably reduced. The upper limit of the thickness of the first protective layer 3 is, for example, 45 μm or less, preferably 40 μm or less. The lower limit of the thickness of the first protective layer 3 is typically at least 20 μm, preferably at least 30 μm. In addition, when surface treatment is given to the 1st protective layer 3, the thickness of the 1st protective layer 3 is the thickness including the thickness of a surface treatment layer. The surface treatment layer will be described later. When the thickness of the first protective layer is not more than the above-mentioned upper limit, the thickness of the polarizing plate can be further reduced, and the warping of the polarizing plate in a high-temperature environment can be further suppressed. When the thickness of the first protective layer is not less than the above lower limit, the polarizer can be stably protected. The thickness of the polarizer 2 is, for example, 1 μm or more, preferably 3 μm or more, and for example, 15 μm or less, preferably 12 μm or less, more preferably 10 μm or less, particularly preferably 8 μm or less. The respective thicknesses of the adhesive layer 5 a and the adhesive layer 5 b are, for example, 0.5 μm or more, preferably 1 μm or more, and for example, 10 μm or less, preferably 5 μm or less.

In one embodiment of the present invention, the second protective layer 4 is a cured layer of a coating film containing an organic solvent solution of a resin and an ultraviolet absorber. The cured layer of the coating film is formed, for example, by applying the above-mentioned organic solvent solution to the substrate and then drying the coating film. Therefore, even if the thickness of the cured layer of the coating film is within the range of the thickness of the above-mentioned second protective layer (especially less than 10 μm, especially 3 μm to 5 μm), since it is supported by the base material, it can still be used when manufacturing a polarizing plate. Stable delivery. On the other hand, extrusion molding has also been studied as a method of manufacturing the second protective layer, but when the second protective layer is an extrusion-molded product, if the thickness of the second protective layer is within the above range, stable molding of the second protective layer is possible. And/or when delivery becomes difficult.

B. Overall composition of polarizing plate with adhesive layer Fig. 2 is a schematic cross-sectional view of a polarizing plate with an adhesive layer attached to another aspect of the present invention. The polarizing plate 11 with an adhesive layer includes: the above-mentioned polarizing plate 1; More specifically, the adhesive layer 6 a is arranged on the opposite side of the polarizer 2 with respect to the second protective layer 4 , and is provided on the surface of the second protective layer 4 . The adhesive layer 6a represents that the upper line is formed of an adhesive described later. The polarizing plate 11 with an adhesive layer can be attached to an image display panel equipped with an image display element by using the adhesive layer 6a.

C. Overall composition of polarizing plate with retardation layer 3 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to yet another aspect of the present invention. The polarizing plate with retardation layer 10 includes: the above-mentioned polarizing plate 1; and the first retardation layer 7 disposed on the opposite side of the polarizing plate 1 from the viewing side. Also, the polarizing plate 10 with a retardation layer may be further provided with a second retardation layer 8, and the second retardation layer 8 is disposed on the opposite side of the first retardation layer 7 to the viewing side (relative to the first retardation layer 7). The retardation layer 7 is arranged on the opposite side of the polarizing plate 1). If it is a polarizing plate with a retardation layer, it can have the desired optical compensation function. The first retardation layer 7 is typically bonded to the second protective layer 4 by using any appropriate adhesive layer 6b. The adhesive layer 6b represents that the upper line is formed of an adhesive described later. The adhesive layer 6b may also be an adhesive layer. Typically, the second retardation layer 8 is bonded to the first retardation layer 7 using any appropriate adhesive layer 5c. The adhesive layer 5c represents that the upper part is formed of an ultraviolet curable adhesive. The adhesive layer 5c may also be an adhesive layer. In addition, the polarizing plate 10 with a retardation layer may further include the above-mentioned adhesive layer 6a. In the polarizing plate 10 with a retardation layer, the adhesive layer 6 a is arranged on the side opposite to the viewing side of the second retardation layer 8 and is provided on the second retardation layer 8 .

Hereinafter, the constituent elements of the polarizing plate and the polarizing plate with an adhesive layer will be described.

D. Polarizer Any appropriate polarizer can be used as the polarizer 2 . For example, the resin film forming the polarizing plate 2 may be a single-layer resin film, or may be a laminate of two or more layers.

As a specific example of a polarizer composed of a single-layer resin film, a PVA-based resin film subjected to dyeing treatment with iodine and stretching treatment (typically uniaxial stretching) is mentioned. The above-mentioned dyeing with iodine is performed, for example, by immersing a PVA-based film in an iodine aqueous solution. The elongation ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. Elongation can be performed after dyeing or while dyeing. In addition, dyeing may be performed after stretching. Swelling treatment, crosslinking treatment, washing treatment, drying treatment, etc. are performed on the PVA-based resin film as necessary. For example, by immersing the PVA-based resin film in water for washing before dyeing, not only can the dirt and anti-adhesive agent on the surface of the PVA-based film be cleaned, but also the PVA-based resin film can be swollen to prevent uneven dyeing.

Specific examples of a polarizer using a laminate include: a polarizer using a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer using A polarizer obtained by coating a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate. A polarizer obtained by using a laminate of a resin base material and a PVA-based resin layer coated and formed on the resin base material can be produced, for example, by applying a PVA-based resin solution to the resin base material and making it drying to form a PVA resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA resin layer; stretching and dyeing the laminate to make the PVA resin layer into a polarizer. In one embodiment of the present invention, it is preferable to form a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin on one side of the resin substrate. The extension means that the upper system includes immersing the laminate in an aqueous solution of boric acid and extending it. Furthermore, stretching may include stretching the laminate in air at a high temperature (for example, 95° C. or higher) before stretching in a boric acid aqueous solution, if necessary. Furthermore, in one embodiment of the present invention, it is preferable to subject the laminate to drying shrinkage treatment in which the laminate is heated while being transported in the longitudinal direction to shrink the laminate by 2% or more in the width direction. Typically, the manufacturing method of this embodiment includes sequentially performing aerial assisted stretching treatment, dyeing treatment, underwater stretching treatment, and drying shrinkage treatment on the laminate. By introducing auxiliary stretching, even when PVA is coated on a thermoplastic resin, the crystallinity of PVA can be improved, and high optical characteristics can be achieved. Also, by improving the orientation of PVA in advance at the same time, it is possible to prevent problems such as decrease in orientation or dissolution of PVA when immersed in water in the subsequent dyeing step or stretching step, and achieve high optical characteristics. Furthermore, when the PVA-based resin layer is immersed in a liquid, the disorder of orientation and the decrease in orientation of polyvinyl alcohol molecules can be suppressed more than when the PVA-based resin layer does not contain a halide. Thereby, the optical characteristics of the polarizer obtained through the processing step of immersing the laminate in liquid, such as dyeing treatment and underwater stretching treatment, can be improved. Furthermore, the optical characteristics can be improved by shrinking the laminate in the width direction by drying shrinkage treatment. The laminate of the obtained resin substrate/polarizer can be used directly (that is, the resin substrate can be used as the first protective layer of the polarizer), or the resin substrate can be peeled off from the laminate of the resin substrate/polarizer, And use any suitable protective layer that meets the purpose of the release area layer. The details of the manufacturing method of the polarizer are described in, for example, Japanese Patent Laid-Open No. 2012-73580 and Japanese Patent No. 6470455. In this specification, all the descriptions of these publications are incorporated by reference.

The polarizer 2 is preferably composed of a polarizer obtained by using a laminate of a resin base material and a PVA-based resin layer coated and formed on the resin base material. A polarizer obtained by stripping.

The polarizer 2 preferably exhibits absorption dichroism at any wavelength between 380 nm and 780 nm. The single transmittance of the polarizer 2 is, for example, 41.5%-46.0%, preferably 43.0%-46.0%, more preferably 44.5%-46.0%. The degree of polarization of the polarizer 2 is preferably above 97.0%, more preferably above 99.0%, more preferably above 99.9%.

E. The first protective layer The first protective layer 3 is disposed on one side in the thickness direction of the polarizer 2 . The first protective layer 3 is formed of any appropriate film that can be used as a protective layer of the polarizer 2 . Specific examples of the material used as the main component of the film include cellulose-based resins such as cellulose triacetate (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyamide-based resins, etc. Transparent resins such as imide-based, polyether-based, polystyrene-based, polystyrene-based, polynorolefin-based, polyolefin-based, (meth)acrylic-based, and acetate-based. In addition, thermosetting resins such as (meth)acrylic, urethane, (meth)acrylate urethane, epoxy, polysiloxane, etc., or ultraviolet curable resins, etc. . In addition, "(meth)acrylic resin" means an acrylic resin and/or a methacrylic resin. In addition, glassy polymers, such as a siloxane polymer, are mentioned, for example. Moreover, the polymer film described in Unexamined-Japanese-Patent No. 2001-343529 (WO01/37007) can also be used. As the material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain can be used, for example, Alternating copolymers composed of isobutylene and N-methylmaleimide and acrylonitrile. Resin composition of styrene copolymer. The above-mentioned materials which become the main components of the film can be used alone or in combination. The polymer film can be, for example, an extruded product of the above-mentioned resin composition.

The first protective layer 3 preferably contains a cellulose-based resin, more preferably cellulose triacetate. In one embodiment of the present invention, the first protective layer 3 is disposed on the outermost surface of the polarizing plate 1 on the viewing side. Surface treatment such as hard coating treatment, anti-reflection treatment, anti-adhesion treatment, anti-glare treatment, etc. may be performed on the first protective layer 3 as required. Among the above-mentioned surface treatments, hard coating treatment is preferably mentioned. That is, the first protective layer 3 preferably includes a base material formed of the above materials and a hard coat layer disposed on the base material. The hard coat layer can impart excellent pencil hardness to the polarizing plate 1 .

F. Second protective layer The second protective layer 4 is arranged on the opposite side of the first protective layer 3 with respect to the polarizer 2 . The second protective layer 4 contains a resin and an ultraviolet absorber as described above. Examples of the resin contained in the second protective layer 4 include cellulose-based materials such as cellulose triacetate (TAC), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and the like. Polyester series; polyolefin (PO) series such as polyethylene (PE) and polypropylene (PP); polyamide (PA) series; (meth)acrylic series; polystyrene (PS) series; polyoxymethylene (polyoxymethylene) series Acetal, POM) series; Polyurethane (PU) series; Cycloolefin series. As the resin contained in the second protective layer 4, cycloolefin-based resins and (meth)acrylic resins are preferable, olefin-based resins and polymethylmethacrylate (PMMA) resins are more preferable, and polymethylmethacrylate (PMMA) resins are more preferable. Lifting and lowering olefinic resin. Specific examples of the northene-based resin include "cycloolefin-based resin obtained by hydrogenating a ring-opening polymer of a northene-based monomer" described in JP-A-2006-208925. Commercially available products of the cycloolefin-based resins include, for example, the product name "ARTON" manufactured by JSR Corporation, the product name "ZEONEX" manufactured by Zeon Corporation, the product name "APEL" manufactured by Mitsui Chemicals, Polyplastics Co., Ltd.'s product name "TOPAS". Commercially available polymethyl methacrylate (PMMA) resins include, for example, Mitsubishi Chemical Corporation's product name "ACRY PELLET", KURARAY CO., LTD's product name "PARAPET", Sumitomo Chemical Corporation's product "Sumipex" and "Delpet" manufactured by Asahi Kasei Co., Ltd.

Any suitable ultraviolet absorber can be used as the ultraviolet absorber contained in the second protective layer 4 . As the ultraviolet absorber, for example, a benzotriazole-based ultraviolet absorber, a triazole-based ultraviolet absorber, and a benzophenone-based ultraviolet absorber may be mentioned. The ultraviolet absorbers can be used alone or in combination. Among the ultraviolet absorbers, three types of ultraviolet absorbers are preferably mentioned. The content ratio of the ultraviolet absorber in the second protective layer 4 is as described in the above item A.

As described above, the second protective layer 4 is preferably a cured layer of a coating film in which a resin and an ultraviolet absorber are dispersed and/or dissolved in an organic solvent. The liquid is preferably an organic solvent solution in which the resin and the ultraviolet absorber will dissolve. In other words, the second protective layer is preferably a dry coating film (coating film) comprising a resin dispersible and/or soluble in an organic solvent and a UV absorber, preferably a resin soluble in an organic solvent and a UV absorber. The coating film (coating film) is dried. In order to form the cured layer of the coating film as the second protective layer 4, first, the above-mentioned resin and ultraviolet absorber are added to an organic solvent to prepare the above-mentioned liquid. Examples of organic solvents include aliphatic hydrocarbons such as isooctane, heptane, hexane, and isohexane; alicyclic hydrocarbons such as methylcyclohexane and ethylcyclohexane; aromatic hydrocarbons such as primary xylene and toluene; acetone, acetylacetone, methyl isobutyl ketone (MIBK), methyl ethyl ketone ( MEK), cyclohexanone, cyclopentanone and other ketones; butyl acetate, ethyl acetate, methyl acetate, propylene glycol monomethyl ether acetate and other esters; 1-methoxy-2-propanol, iso Alcohols such as propanol (IPA); halogenated aliphatic hydrocarbons such as methylene chloride; halogenated aromatic hydrocarbons such as 1,2,4-trichlorobenzene; terpenes such as limonene. Organic solvents may be used alone or in combination. Among the organic solvents, cyclopentylmethyl ether and ethyl acetate are preferably mentioned. The organic solvent is appropriately selected according to the type of resin used. When the resin is a cycloolefin-based resin (northylene-based resin), cyclopentyl methyl ether is preferably selected, and when the resin is a (meth)acrylic resin (PMMA resin), ethyl acetate is preferably selected. The density|concentration of the resin in the said liquid is 1 mass % or more and 20 mass % or less, for example. The addition amount of the ultraviolet absorber in the above-mentioned liquid is the same as the content ratio of the ultraviolet absorber described in the above item A. Next, after coating the liquid (preferably an organic solvent solution) on any suitable substrate (such as a PET substrate), it is dried at any suitable temperature and time. Thereby, the cured layer which is the coating film of a 2nd protective layer is formed on a base material. Thereafter, after bonding the cured layer (second protective layer 4) of the coating film to the surface of the polarizer 2 (the surface opposite to the first protective layer) using the adhesive layer 5b, Layer (second protective layer 4) peeled off the base material.

G. Adhesive layer Each of the adhesive layer 6 a and the adhesive layer 6 b is formed of an adhesive (pressure-sensitive adhesive). In addition, the adhesive forming the adhesive layer can also be used to bond the test sample and the test glass plate in the above-mentioned heating warpage test. The adhesive represents an upper line containing a (meth)acrylic polymer as a base polymer. The (meth)acrylic polymer is a polymer containing a monomer component (raw material monomer) mainly composed of an alkyl (meth)acrylate. Alkyl (meth)acrylate is preferably at least 50% by mass of all monomer components used as raw materials for (meth)acrylic polymers, and the remainder of monomers other than alkyl (meth)acrylate Can be set arbitrarily. In addition, (meth)acrylate means acrylate and/or methacrylate.

Examples of the alkyl (meth)acrylate constituting the main skeleton of the (meth)acrylic polymer include linear or branched alkyl groups having 1 to 18 carbon atoms. Alkyl (meth)acrylates may be used alone or in combination. The average carbon number of the alkyl group is preferably 3-10.

The (meth)acrylic polymer may contain, in addition to structural units derived from alkyl (meth)acrylates, structural units derived from comonomers polymerizable with alkyl (meth)acrylates. That is, the monomer component used as a raw material of a (meth)acrylic-type polymer may contain a comonomer other than an alkyl (meth)acrylate.

Examples of comonomers include carboxyl group-containing monomers, hydroxyl group-containing monomers, amine group-containing monomers, amide group-containing monomers, cyclopolymerizable monomers, epoxy group-containing monomers, and sulfonic acid group-containing monomers. Monomers containing phosphoric acid groups, polyfunctional acrylates, (meth)acrylates with alicyclic hydrocarbon groups, (meth)acrylates with aromatic hydrocarbon groups, vinyl esters, aromatic vinyl compounds, dienes Classes, vinyl ethers, vinyl chloride, etc.

Among the above-mentioned comonomers, reactive group-containing monomers having a reactive group capable of reacting with a crosslinking agent described later are preferably used, and carboxyl group-containing monomers and hydroxyl group-containing monomers are more preferably used. When the adhesive contains a crosslinking agent described later, the reactive group-containing monomer becomes a reaction point with the crosslinking agent. Carboxyl group-containing monomers and hydroxyl group-containing monomers are rich in reactivity with intermolecular crosslinking agents, so they can be suitably used to improve the cohesiveness or heat resistance of the obtained adhesive layer. In addition, the carboxyl group-containing monomer is preferable in terms of both durability and reworkability, while the hydroxyl group-containing monomer is preferable in terms of improving reworkability. A comonomer can be used individually or in combination among the raw material monomers of a (meth)acrylic-type polymer.

As a carboxyl group-containing monomer, (meth)acrylic acid is mentioned preferably, and acrylic acid is mentioned more preferably. When using a carboxyl group-containing monomer as a raw material monomer, the content of the carboxyl group-containing monomer is usually 0.01 mass % or more and 10 mass % or less in all monomer components used as a raw material of a (meth)acrylic polymer.

As a hydroxyl group-containing monomer, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferable, and 4-hydroxybutyl (meth)acrylate is more preferable. When a hydroxyl group-containing monomer is used as a raw material monomer, the content of the hydroxyl group-containing monomer is usually 0.01 mass % or more and 10 mass % or less in all monomer components used as a raw material of a (meth)acrylic polymer.

The weight average molecular weight Mw of the (meth)acrylic polymer is, for example, 200,000 to 3 million, preferably 1 million to 2.5 million, more preferably 1.2 million to 2.5 million. When the weight average molecular weight Mw is within the above range, an adhesive layer excellent in durability (especially heat resistance) can be obtained. When the weight average molecular weight Mw exceeds 3 million, the viscosity may increase and/or gelation may occur during polymer polymerization.

The adhesive may contain a crosslinking agent. As a crosslinking agent, an organic crosslinking agent, a polyfunctional metal chelate compound, etc. can be used. As an organic type crosslinking agent, an isocyanate type crosslinking agent, a peroxide type crosslinking agent, an epoxy type crosslinking agent, an imine type crosslinking agent is mentioned, for example. Multifunctional metal chelates are covalently bonded or coordinately bonded between polyvalent metals and organic compounds. The crosslinking agents can be used alone or in combination. The cross-linking agent preferably includes an isocyanate-based cross-linking agent and a peroxide-based cross-linking agent. When a crosslinking agent is blended into the adhesive, the blending amount of the crosslinking agent is usually 0.01 to 15 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer (base polymer).

The adhesive may contain a silane coupling agent containing reactive functional groups. In the silane coupling agent containing reactive functional groups, the reactive functional groups are typically functional groups other than acid anhydride groups. Silane coupling agents containing reactive functional groups can be used alone or in combination. When a silane coupling agent containing a reactive functional group is blended into the adhesive, the blending amount of the silane coupling agent containing a reactive functional group is usually 0.001 parts by mass or more relative to 100 parts by mass of the (meth)acrylic polymer And 5 parts by mass or less.

H. The first retardation layer and the second retardation layer Each of the first retardation layer 7 and the second retardation layer 8 may be composed of any retardation film having appropriate optical and/or mechanical characteristics according to the purpose. The first retardation layer 7 typically shows the relationship of nx>ny≧nz. In addition, "ny=nz" here includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. The first retardation layer 7 can function as a so-called λ/4 plate. The in-plane retardation Re(550) of the first retardation layer 7 is, for example, 100 nm to 200 nm, preferably 130 nm to 150 nm. The angle formed by the slow axis of the first retardation layer 7 and the absorption axis of the polarizer 2 is preferably 40° to 50°, more preferably 42° to 48°, more preferably 44° to 46°, and especially preferably about 45°. The second retardation layer 8 typically exhibits a refractive index characteristic of nz>nx=ny. In addition, "nx=ny" here includes not only the case where nx and ny are completely equal, but also the case where they are substantially equal. The retardation Rth(550) in the thickness direction of the second retardation layer 8 is preferably -50nm~-300nm, more preferably -100nm~-180nm.

I. Image display device The polarizing plate, the polarizing plate with an adhesive layer, and the polarizing plate with a retardation layer described in items A to H above can be applied to image display devices. Therefore, an embodiment of the present invention also includes an image display device using any one of a polarizing plate, a polarizing plate with an adhesive layer, and a polarizing plate with a retardation layer. Representative examples of image display devices include liquid crystal display devices and organic EL display devices. The image display device according to the embodiment of the present invention is typically equipped with the polarizing plate described in the above items A to F on the viewing side. The image display device includes an image display panel. The image display panel includes image display elements. In addition, an image display device may be called an optical display device, an image display panel may be called an optical display panel, and an image display element may be called an optical display element.

Example Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by these examples. In addition, the measuring method of each characteristic is as follows.

(1) Heating warpage test The acrylic adhesive obtained in Production Example 1 was coated on the silicone-treated surface of a release film (PET film, manufactured by Mitsubishi Polyester Film Co., Ltd., MRF38), and dried in an air-circulating constant temperature oven set at a predetermined temperature. , an adhesive layer (adhesive sheet) having a thickness of 15 μm was formed. Next, the adhesive layer was transferred from the release film to the surface of the second protective layer of the polarizing plate obtained in Examples and Comparative Examples. Thereafter, the polarizing plate provided with the adhesive layer (polarizing plate with an adhesive layer) was cut into a size of 70 mm×150 mm to prepare a test sample. In the test sample, the direction of the absorption axis of the polarizer is parallel to the long side direction of the test sample. Next, the test sample was bonded to a glass plate for a test (manufactured by Matsunami Glass Co., Ltd.) through an adhesive layer. The test glass plate has a size of 80 mm×170 mm, and the thickness of the test glass plate is 0.2 mm. Next, the test sample bonded to the test glass plate was put into an oven, heated at 85°C for 24 hours, and then left to stand at room temperature (23°C) at 55%RH for 1 hour. When the shape of the test sample was observed with the glass plate for the test facing the lower side, it was a concave shape (U-shaped) opened upward. Thereafter, the warpage height of the test sample was measured. Specifically, the test sample is placed on the horizontal surface in such a way that the test glass plate is in contact with the horizontal surface, and the horizontal surface and the bottom surface of the test glass plate (the surface facing the horizontal surface) to which the test sample is attached are measured using a ruler. ) between the short edges of the vertical direction, as the warpage height of the test specimen. The results are shown in Table 1.

(2) Measurement of light transmittance T ₃₈₀ The polarizing plates obtained in each of the examples and each of the comparative examples were mounted on a spectrophotometer (trade name "LPF-200", manufactured by Otsuka Electronics Co., Ltd.), and incident light was applied to the first protective layer. The light transmittance T ₃₈₀ at a wavelength of 380 nm was measured by means of normal incidence. The results are shown in Table 1.

[manufacturing example 1] In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a cooler, 75.1 parts of butyl acrylate, 19 parts of benzyl acrylate, 4.8 parts of acrylic acid, and 0.1 part of 2-hydroxyethyl acrylate were used as polymerization initiators. Feed 0.1 part of 2,2'-azobisisobutyronitrile together with 100 g of ethyl acetate, introduce nitrogen gas while stirring slowly to replace nitrogen, then keep the liquid temperature in the flask at around 55°C and carry out polymerization reaction for 8 hours. A solution containing an acrylic polymer having a weight average molecular weight of 2,200,000 was obtained. With respect to 100 parts of solid content of the obtained acrylic polymer solution, 3 parts of an isocyanate crosslinking agent (manufactured by Tosoh Corporation, CORONATE L), 0.2 parts of a peroxide crosslinking agent (benzoyl peroxide), and A silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., KBM403) was used as 0.075 parts to obtain an acrylic adhesive of a solution (solid content: 11% by mass) of the acrylic adhesive composition.

[Example 1~7] 1. Production of polarizer As the thermoplastic resin substrate, a long amorphous isophthalic acid copolymerized polyethylene terephthalate film (thickness: 100 μm) with a Tg of about 75°C is used. Halo processing. PVA-based resin mixed with polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mole%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER") at a ratio of 9:1 13 mass parts of potassium iodide was added to 100 mass parts, and the resultant was dissolved in water to prepare a PVA aqueous solution (coating liquid). The above-mentioned PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60° C. to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate. The obtained laminate was uniaxially stretched to 2.4 times in the longitudinal direction (longitudinal direction) in an oven at 130°C (in-air assisted stretching treatment). Next, the laminated body was immersed for 30 seconds in an insoluble bath (an aqueous solution of boric acid obtained by mixing 4 parts by mass of boric acid with respect to 100 parts by mass of water) at a liquid temperature of 40° C. (insoluble treatment). Next, adjust the concentration and immerse for 60 seconds in a dyeing bath (iodine aqueous solution obtained by mixing iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by mass of water) at a liquid temperature of 30°C to make the final polarized light The single transmittance (Ts) of the piece becomes the desired value (dyeing treatment). Next, it was immersed for 30 seconds in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by mass of potassium iodide and 5 parts by mass of boric acid with respect to 100 parts by mass of water) at a liquid temperature of 40° C. (crosslinking treatment). Thereafter, the laminate was immersed in a boric acid aqueous solution (boric acid concentration 4% by mass, potassium iodide concentration 5% by mass) at a liquid temperature of 70°C, and uniaxially stretched in the longitudinal direction (longitudinal direction) between rollers with different circumferential speeds, The total stretching ratio was set to 5.5 times (underwater stretching treatment). Then, the laminated body was immersed in the cleaning bath (the aqueous solution which mixed 4 mass parts of potassium iodide with respect to 100 mass parts of water) of 20 degreeC of liquid temperature (cleaning process). Thereafter, while drying in an oven maintained at approximately 90° C., it was brought into contact with a heating roll made of SUS maintained at a surface temperature of approximately 75° C. (drying shrinkage treatment). In the manner described above, a polarizer having a thickness of about 5 μm was formed on the resin substrate.

2. Attachment of the first protective layer A TAC film (thickness: 32 μm) with a hard coat layer (HC) as the first protective layer was bonded to the surface of the obtained polarizer (the surface opposite to the resin substrate) using a UV-curable adhesive. Specifically, it was applied so that the thickness of the ultraviolet curable adhesive layer was about 2.0 μm, and bonded using a roll press. Thereafter, UV light is irradiated from the TAC film side to harden the adhesive. Next, the resin substrate is peeled off. 3. Production of the second protective layer Cycloolefin-based resin (trade name ARTON, manufactured by JSR Corporation) was dissolved in cyclopentyl methyl ether to prepare a cycloolefin-based resin organic solvent solution (concentration: 10% by mass). Next, an ultraviolet absorber (UVA, trade name ADK STAB LA-F70, manufactured by ADEKA Co., Ltd.) was added to the organic solvent solution in an amount as shown in Table 1 with respect to 100 parts by mass of the cycloolefin resin to prepare Produce the organic solvent solution of cycloolefin resin and UVA. Next, using an applicator, this organic solvent solution was applied on a PET substrate so that the thickness after drying became the value shown in Table 1, and dried at 110° C. for 3 minutes. Thus, a cured layer (UVA-COP/PET) of a coating film of a cycloolefin-based resin and an organic solvent solution of UVA as a second protective layer was produced. Next, the second protective layer was bonded to the surface of the polarizer (the surface opposite to the first protective layer) using an ultraviolet curing adhesive. Specifically, it was applied so that the thickness of the ultraviolet curable adhesive layer became about 2.0 μm, and it was bonded using a roll press. Thereafter, UV rays are irradiated from the second protective layer side to cure the adhesive. Next, the PET substrate was peeled off from the second protective layer. In the above manner, a polarizing plate having a composition of first protective layer (HC/TAC film)/polarizer/second protective layer (UVA-COP) was obtained.

[Example 8] Except that the second protective layer (UVA-COP) is changed to the second protective layer (UVA-PMMA) made in the following manner, in the same manner as in Example 1, a film with the first protective layer (HC/TAC) is obtained. )/polarizer/the second protective layer (UVA-PMMA) of the composition of the polarizing plate. ＜Creation of the second protective layer＞ PMMA resin (trade name NeoCryl B-728, manufactured by DSM COATING RESINS) was dissolved in ethyl acetate to prepare an organic solvent solution of PMMA resin (concentration: 10% by mass). Next, an ultraviolet absorber (UVA, trade name ADK STAB LA-F70, manufactured by ADEKA Co., Ltd.) was added to the organic solvent solution in such a manner as to be added in parts shown in Table 1 with respect to 100 parts by mass of the PMMA resin, to prepare a PMMA resin And UVA organic solvent solution. Next, using an applicator, this organic solvent solution was applied on a PET substrate so that the thickness after drying became the value shown in Table 1, and dried at 60° C. for 3 minutes. Thereby, the cured layer (UVA-PMMA/PET) of the coating film of PMMA resin and UVA organic solvent solution as a 2nd protective layer was produced.

[Comparative example 1] A polarizing plate was obtained in the same manner as in Example 1 except that no ultraviolet absorber (UVA) was used. That is, in the polarizing plate of Comparative Example 1, the second protective layer did not contain UVA.

[Comparative example 2] Instead of the cured layer of the coating film of the organic solvent solution of cycloolefin resin and UVA, a cycloolefin resin film (trade name G+, manufactured by Zeon Corporation) with a thickness of 25 μm prepared by extrusion was used. In the same manner as in Example 1, a polarizing plate was obtained.

[Table 1]

[Evaluation] It is evident from Table 1 that by adjusting the thickness of the second protective layer and setting the thickness Th (μm) of the polarizing plate/the warpage value (mm) of the heating warpage test to 10 or more, it is possible to obtain a product that can The light transmittance T ₃₈₀ is reduced to less than 3.5%, and at the same time, it can suppress the warpage of the polarizing plate under high temperature environment.

Industrial availability The polarizing plate and the polarizing plate with a retardation layer of the present invention can be suitably used in image display devices (typically liquid crystal display devices, organic EL display devices).

1: polarizer 2: Polarizer 3: The first protective layer 4: The second protective layer 5a, 5b, 5c: Adhesive layer 6a, 6b: Adhesive layer 7: The first retardation layer 8: The second retardation layer 10: Polarizing plate with retardation layer 11: Polarizing plate with adhesive layer

Fig. 1 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention. Fig. 2 is a schematic cross-sectional view of a polarizing plate with an adhesive layer attached to another aspect of the present invention. 3 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to yet another aspect of the present invention.

1: polarizer

2: Polarizer

3: The first protective layer

4: The second protective layer

5a, 5b: Adhesive layer

Claims (7)

A polarizing plate, whose light transmittance T ₃₈₀ at a wavelength of 380nm is 3.5% or less, and the aforementioned polarizing plate satisfies the following formula (1):

In the formula (1), Th represents the thickness (μm) of the aforementioned polarizing plate, and W represents the warpage value (mm) measured by the following heating warpage test; Heating warpage test: Cut the polarizing plate into 70mm×150mm Dimensions Make a test sample, and stick the test sample to the test glass plate through the adhesive layer, heat the test sample at 85°C for 24 hours, and then let it stand at room temperature (23°C) for more than 1 hour Afterwards, the warpage height of the test sample was measured. As the polarizing plate of claim 1, it has: Polarizer; The first protective layer is disposed on the viewing side of the aforementioned polarizer; and The second protective layer is disposed on the opposite side of the aforementioned polarizer to the viewing side; The aforementioned second protective layer contains a resin and an ultraviolet absorber. The polarizing plate according to claim 2, wherein the thickness of the second protective layer is 10 μm or less. The polarizing plate according to claim 3, wherein the thickness of the first protective layer is 40 μm or less. The polarizing plate according to claim 2, wherein the second protective layer is a cured layer of a coating film in which the resin and the ultraviolet absorber are dispersed and/or dissolved in an organic solvent. The polarizing plate according to claim 2, wherein the content ratio of the ultraviolet absorber is 1 part by mass or more with respect to 100 parts by mass of the resin. A polarizing plate with a retardation layer, comprising: The polarizing plate according to any one of claims 1 to 6; and The retardation layer is disposed on the opposite side of the aforementioned polarizer to the viewing side.

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