JP2005331718A - Polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate having photochromic characteristic whose photochromic characteristic is not deteriorated when curved surface processing is performed so that the polarizing plate may have lens shape in order to serve as a lens for sunglasses or goggles, and which does not cause trouble such as discoloration or the lowering of transmittance. <P>SOLUTION: In the polarizing plate where a protective layer is stuck to at least one surface of a polarizing thin film through an adhesive layer having the photochromic characteristic, the protective layer is composed of polyester resin obtained by polycondensing dicarboxylic acid components composed of one kind or two or more kinds of terephthalic acid components selected from a group composed of terephthalic acid and terephthalic acid derivative and glycol components containing ≥40 mole% 1,4-cyclohexanedimethanol, or composition composed of polyester resin (a) and polycarbonate resin (b), and the weight ratio of (a) and (b) is 60/40 to 80/20. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polarizing plate, and more particularly to a polarizing plate having photochromic properties and being used for anti-glare sunglasses, goggles and the like by being curved.

  The polarizing plate is composed of a polarizing element and a protective layer that protects the polarizing element, and exhibits excellent anti-glare properties. Therefore, the polarizing plate is used as a lens such as sunglasses or goggles. In particular, as a protective layer, a polarizing plate using a polycarbonate sheet excellent in impact resistance and heat resistance (see, for example, Patent Document 1) has recently been favorably used.

It has been proposed that this polarizing plate is further provided with photochromic performance that reversibly changes its color depending on the presence or absence of light irradiation. That is, the polarizing layer and the polycarbonate layer are a laminated body having both a polarizing property and a photochromic property, which are laminated through a resin layer having a photochromic property and an adhesive layer (see Patent Document 2).
Japanese Patent Laid-Open No. 03-039903 JP 2002-062423 A

  However, in the above laminate, when the laminate is heated and processed into a lens-like curved surface for use in sunglasses, goggles, etc., the photochromic compound deteriorates due to the high temperature during the processing, and the photochromic compound light is generated by the generated impurities. There is a problem that the characteristics are adversely affected and sufficient photochromic performance cannot be obtained after processing. In addition, another problem is caused such that the dye of the polarizing layer is discolored due to thermal decomposition or the like during processing under heating, or the transmittance is changed to deteriorate the properties as a polarizing plate.

  It is an object of the present invention to provide a polarizing plate having photochromic characteristics, which does not cause deterioration in photochromic characteristics even when processed into a curved surface into a lens shape, and does not cause problems such as discoloration and decrease in transmittance. .

  The present inventor has found that the use of a polyester-based resin as a protective layer of a polarizing plate solves problems such as deterioration in photochromic properties. That is, the present invention provides a polarizing plate in which a protective layer is attached to at least one surface of a polarizing thin film via an adhesive layer having photochromic properties, and the protective layer is selected from the group consisting of terephthalic acid and terephthalic acid derivatives. Characterized in that it comprises a polyester resin obtained by polycondensation of a dicarboxylic acid component comprising one or more terephthalic acid components and a glycol component containing 40 mol% or more of 1,4-cyclohexanedimethanol. The gist of the polarizing plate is as follows.

  Further, the present invention provides a polarizing plate in which a protective layer is attached to at least one surface of the polarizing thin film via an adhesive layer having photochromic properties, and the protective layer is selected from the group consisting of terephthalic acid and terephthalic acid derivatives. Polyester resin (a) and polycarbonate resin obtained by polycondensation of a dicarboxylic acid component composed of one or more terephthalic acid components and a glycol component containing 40 mol% or more of 1,4-cyclohexanedimethanol A gist is a polarizing plate comprising (b) and comprising a composition having a weight ratio of (a) to (b) of 60/40 to 80/20.

  As described above, the polarizing plate of the present invention comprises a polarizing thin film and a protective layer attached via an adhesive layer having photochromic properties, and the protective layer is a composition of a polyester resin or a polyester resin and a polycarbonate resin. In addition, it has photochromic properties in combination with polarization properties, and is used for sunglasses, goggles, etc., so even if it is curved into a lens shape, there will be no deterioration in photochromic properties, and it will not cause problems such as discoloration and transmittance reduction .

  As the protective layer constituting the polarizing plate of the present invention, one made of a polyester resin or one made of a composition of a polyester resin and a polycarbonate resin is used. By using a polyester resin, there is no decrease in photochromic properties even when curved into a lens shape, and considering the heat resistance and impact resistance required for sunglasses etc., as a protective layer, polyester resin and polycarbonate resin It is more preferable to use this composition.

  The polyester resin of the present invention is obtained by polycondensation of a dicarboxylic acid component and a glycol component. As a glycol component, it is necessary to make 1,4-cyclohexanedimethanol 40 mol% or more, that is, the ratio of 1,4-cyclohexanedimethanol to the whole glycol component needs to be 40 mol% or more. If it is less than 40 mol%, the transparency is lowered, the compatibility with the polycarbonate resin is also lowered, and the mechanical strength such as impact strength is lowered. In particular, the proportion of 1,4-cyclohexanedimethanol in the entire glycol component is preferably 50 mol% or more. In this case, the refractive index of the polyester resin obtained is very close to the refractive index of the polycarbonate resin. Thus, excellent transparency can be obtained, and the compatibility between both resins is very good, so that excellent impact resistance can be ensured. In addition, although 1,4-cyclohexanedimethanol has two types of isomers of cis type and trans type, any of them may be used. Examples of the glycol component used in combination with 1,4-cyclohexanedimethanol include ethylene glycol and propylene glycol. However, ethylene glycol is particularly preferable because of its good physical property balance, wide industrial production, and low cost. It is. Of course, 100% 1,4-cyclohexanedimethanol may be used as the glycol component.

  Moreover, as a dicarboxylic acid component, what has as a main component the 1 type, or 2 or more types of terephthalic acid type component chosen from the group which consists of a terephthalic acid and a terephthalic acid derivative is used. In particular, the proportion of the terephthalic acid component in the entire dicarboxylic acid component is preferably 95 mol% or more. If it is less than 95 mol%, the mechanical strength, heat resistance, and chemical resistance decrease, which is not preferable. For example, when more than 5 mol% of isophthalic acid, which is widely used as a dicarboxylic acid component, is used in combination, the mechanical strength, heat resistance, and chemical resistance are significantly reduced. It is particularly preferable that the terephthalic acid component is 97 mol% or more based on the entire dicarboxylic acid component. Examples of the terephthalic acid derivative include dimethyl terephthalate and diethyl terephthalate. Among them, dimethyl terephthalate is preferable.

  In the present invention, when the composition of the polyester resin (a) and the polycarbonate resin (b) is used as the protective layer, the weight ratio (a) / (b) of these resins is in the range of 60/40 to 80/20. It is necessary to become. When the weight ratio of the polycarbonate resin exceeds 40, it is not preferable because foaming due to the influence of residual moisture in the polycarbonate resin may occur when the polarizing plate is processed into a curved surface in a lens shape. In addition, if the weight ratio of the polycarbonate resin is less than 20, the heat resistance is inferior. For example, if the polarizing plate is used for sunglasses and left in an automobile, it is exposed to a temperature environment that far exceeds the outside air temperature and causes problems such as deformation. There is a problem that occurs.

  The protective layer of the present invention is in the form of a sheet obtained by molding the resin composition. As the molding method, for example, a molding method known in plastic processing technology such as extrusion molding, calendar molding, cast molding, injection molding, or the like can be used. However, since the rainbow pattern and the variation in the degree of polarization occur due to the bonding with the polarizing thin film, it is better to control the retardation value (birefringence of the protective layer sheet × thickness of the protective layer sheet). Specifically, it is preferable to control the retardation value to at least 300 nm or less or 2000 nm or more, and it is desirable to control the retardation value to 100 nm or less or 3000 nm or more. As an example of this control method, a method of forming a sheet so that the retardation value does not increase as much as possible by a casting method, a method of reducing a retardation value by annealing or pressing after forming a sheet, a retardation value by stretching a sheet, etc. The method of raising

  The adhesive layer of the present invention has photochromic properties and is obtained by dissolving a compound exhibiting photochromic performance in an adhesive. Examples of the adhesive include acrylic adhesives, epoxy adhesives, polyurethane adhesives, olefin adhesives, etc., but can sufficiently bond the polarizing thin film and the protective layer, and have optical properties. It is excellent in see-through feeling, does not turn yellow over time, and may be anything as long as it does not cause defects such as peeling, cracking, and whitening during thermoforming, but considering the workability and changes over time, polyurethane adhesive It is preferable to use an agent. The thickness of the adhesive layer is preferably in the range of 5 μm to 100 μm, and desirably 10 μm to 50 μm. When the thickness is less than 5 μm, sufficient adhesive strength cannot be obtained. On the other hand, when the thickness exceeds 100 μm, the adhesive strength is sufficient, but the productivity, economy, and processability deteriorate. The ratio of the photochromic compound to the adhesive is preferably 0.01 to 0.5 parts by weight, and preferably 0.05 to 0.2 parts by weight with respect to 100 parts by weight of the adhesive. . When the photochromic compound is less than 0.01 parts by weight, contrast and response speed are poor, and sufficient photochromic characteristics cannot be obtained. On the other hand, when it exceeds 0.5 parts by weight, the contrast and response speed are sufficient, but it is not economical. It is also possible to add an ultraviolet absorber to the adhesive layer so as to have an ultraviolet cutting ability.

  As a compound which shows photochromic performance, if it has compatibility with the said adhesive agent, it will not specifically limit. Azobenzene compounds, thioindigo compounds, dithizone metal complexes, spiropyran compounds, spirooxazine compounds, fulgide compounds, dihydropyrene compounds, spirothiopyran compounds, 1,4-2H-oxazine-triphenylmethane compounds, viologen compounds And chromene compounds, fulgimide compounds, and the like. Among these, one or a mixture of two or more are used depending on the color at the time of color development.

  The polarizing thin film of the present invention is not particularly limited as long as it exhibits a polarizing function. For example, a dichroic dye such as iodine or a dichroic dye is adsorbed on a polymer film such as a polyvinyl alcohol film. Examples of dichroic dyes include chloratin fast red, congo red, brilliant blue 6B, benzoperpurine, chlorazole black BH, direct blue 2B, diamine green, chrysophenone, and Sirius yellow. , Direct first red, acid black and the like.

  The polarizing thin film can be produced, for example, as follows. An aqueous solution in which an additive such as metal ions or boric acid is dissolved after the polymer film is immersed in an aqueous solution in which iodine or a dichroic pigment is dissolved, and the iodine or dichroic pigment is adsorbed on the polymer film. This is a method of stretching in one direction while immersed in the inside.

  The polarizing plate of the present invention is produced, for example, by bonding the polarizing thin film produced as described above and a protective layer through an adhesive mixed with a photochromic compound in advance and press-bonding. Further, the polarizing plate is curved into a lens shape by vacuum molding, press molding or the like, and used for sunglasses, goggles and the like.

  In order to use the polarizing plate of the present invention as sunglasses or goggles, it is preferable to have a structure capable of cutting off ultraviolet rays, and an ultraviolet absorber is added to the protective layer or the adhesive layer, or an ultraviolet absorbing substance or the like is formed on the surface of the protective layer. It is desirable to perform surface treatment with. The surface treatment method here is not particularly limited, and examples thereof include coating, sputtering, laminating, pressing, and transfer. Further, in order to prevent the polarizing plate from being damaged, the surface may be subjected to a curing treatment, or depending on the application, the surface may be subjected to an antifogging treatment or an antireflection treatment.

Next, specific examples of the present invention will be described.
<Example 1>
"PCTG 5445" manufactured by Eastman Chemical Co. (obtained by polycondensation of a dicarboxylic acid component having a terephthalic acid ratio of 99 mol% or more and a glycol component having a 1,4-cyclohexanedimethanol ratio of 50 mol%. The sheet having a thickness of 0.45 mm was manufactured using a vent type extruder.

    On the other hand, while stretching a polyvinyl alcohol film (“Kuraray Vinylon # 7500” manufactured by Kuraray) in a water bath, CI Direct Black 17 (C.I. 27700), C.I. I. Direct Orange 39 (C.I. 40215), C.I. I. After dyeing with direct dye 81 (C.I. 28160) mixed dyeing solution, treating with boric acid, washing with water and drying, a polarizing thin film having a transmittance of 35.8% and a polarization degree of 95.4% is obtained. It was.

  Further, the photochromic compound 1 ′, 3 ′, 3′-trimethylspiro (2H-1-benzopyran-2,2′-indoline) 2.0 parts by weight with respect to 100 parts by weight of the one-component moisture-curable polyurethane adhesive. Were mixed and mixed uniformly.

  The photochromic compound containing adhesive was apply | coated to the single side | surface of the polarizing thin film obtained as mentioned above, and the protective layer of the polyester resin was bonded together. Next, a one-part moisture-curing polyurethane adhesive is applied to the other surface of the polarizing thin film, and after a solvent is volatilized, a polyester resin protective layer is bonded to obtain a polarizing plate having a thickness of about 0.95 mm. It was. A polarizing lens was obtained by molding this polarizing plate into a curved surface using a 6-curve spherical metal mold.

The following evaluation was performed about the obtained polarizing plate and polarizing lens, and the result is shown in Table 1.
<Photochromic properties>
The transmittance before and after irradiating the polarizing lens with light having a peak intensity of 364 nm for 1 minute was measured (measurement device manufactured by Murakami Color Research Laboratory: HM-100), and the difference is shown in Table 1.
<Transmissivity>
Based on JIS K7105 (plastic optical property test method), the transmittance before and after curved surface molding was measured (measurement device manufactured by Murakami Color Research Laboratory Co., Ltd .: using HM-100), and the difference is shown in Table 1. .
<Color difference>
Based on JIS Z8730 (color display method—color difference of object color), the color difference before and after the curved surface molding is calculated, and the difference is shown in Table 1.

<Examples 2 to 4, Comparative Example 1>
A polarizing plate and a polarizing lens obtained in the same manner as in Example 1 except that the following were used as the protective layer were evaluated, and the results are shown in Table 1.
<Protective layer>
“PCTG 5445” manufactured by Eastman Chemical Co., Ltd. and polycarbonate resin (“Iupilon E-2000” manufactured by Mitsubishi Engineering Plastics Co., Ltd.) were mixed at the blending ratio shown in Table 1, and this was used using a vent type extruder. A sheet having a thickness of 0.45 mm was produced by stretching 1.1 times during take-up.

  As is clear from Table 1, the polarizing plates of Examples 1 to 4 of the present invention have no deterioration in performance of photochromic characteristics even after being curved into a lens shape, and there are no problems such as discoloration and reduction in transmittance. On the other hand, in Comparative Example 1 that deviates from the scope of the present invention, the photochromic characteristics are lowered, and the degree of discoloration or transmittance is also large.

Claims (2)

  In a polarizing plate in which a protective layer is attached to at least one surface of a polarizing thin film via an adhesive layer having photochromic properties, the protective layer is one or two selected from the group consisting of terephthalic acid and terephthalic acid derivatives A polarizing plate comprising a polyester resin obtained by polycondensation of a dicarboxylic acid component comprising the above terephthalic acid component and a glycol component containing 40 mol% or more of 1,4-cyclohexanedimethanol.   In a polarizing plate in which a protective layer is attached to at least one surface of a polarizing thin film via an adhesive layer having photochromic properties, the protective layer is one or two selected from the group consisting of terephthalic acid and terephthalic acid derivatives It consists of a polyester resin (a) and a polycarbonate resin (b) obtained by polycondensing a dicarboxylic acid component comprising the above terephthalic acid component and a glycol component containing 40 mol% or more of 1,4-cyclohexanedimethanol. A polarizing plate comprising a composition having a weight ratio of (a) and (b) of 60/40 to 80/20.