JP3368524B2 - Polarizer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing plate for a liquid crystal display. 2. Description of the Related Art In order to visualize a display pattern, a liquid crystal display device uses upper and lower polarizing plates for the purpose of controlling the vibration direction of light. The polarizing plate generally has a structure in which both surfaces of a polarizing film are laminated with a transparent resin film, particularly a cellulose acetate-based film, and the polarizing plate is used by being adhered to a liquid crystal display device with an adhesive. On the other hand, as the liquid crystal display device is used in various places, it is required to be thinner and lighter, and the polarizing plate used in the liquid crystal display device is also required to be thinner and lighter. . However, there is a limit in pursuing a thinner and lighter polarizing plate with a conventional configuration. Originally, a polyvinyl alcohol-based polarizing film itself has polarizing performance, but it is indispensable to provide a protective layer due to poor mechanical properties and optical durability. It is very effective if it can be omitted. However, since a polarizing plate having a protective layer on only one side has an asymmetrical structure on the front and back sides, the orientation direction of the polarizing film is particularly very warped. Is a problem. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a polarizing plate which achieves both thinness, light weight, and durability. That is, according to the present invention, a protective layer (2) made of a transparent synthetic resin film is provided on the adhesive surface of a synthetic resin film (1) having an adhesive layer on one side, and an adhesive layer (3) is provided thereon.
Is a polarizing plate in which a polyvinyl alcohol-based polarizing film (4), an adhesive layer (5), and a release film (6) are sequentially laminated through the film. Hereinafter, the present invention will be described in detail. The present invention will be described below with reference to FIG. 1 and FIG. FIG. 1 is a sectional view of the configuration of the polarizing plate of the present invention. (1) a synthetic resin film with a single-sided adhesive layer,
(2) is a protective layer made of a transparent synthetic resin film, (3)
Is an adhesive layer, (4) is a polyvinyl alcohol-based polarizing film, (5) is an adhesive layer, and (6) is a release film. The polarizing plate in the present invention is formed by sequentially laminating (1) to (6). The synthetic resin forming the synthetic resin film (1) with a single-sided adhesive layer is used for a usual polarizing plate, that is, for protecting the surface from being scratched when the polarizing plate is bonded to a liquid crystal display device. In addition to the purpose of being peeled off at the time of use, in the polarizing plate of the present invention, it is indispensable to prevent warping of the orientation direction of the polarizing film toward the polarizing film due to the asymmetry. The most common material is polyethylene. A polymer obtained by copolymerizing vinyl acetate with vinyl acetate based on polyethylene and imparting tackiness or an acrylic pressure-sensitive adhesive layer formed into a film by single-layer or multilayer extrusion or an inflation method is suitably used. Other examples include a film obtained by adhesively processing a polyester-based or polyamide-based film. Adhesive strength is 1 gf / 25 against the polarizing plate
mm or more is generally used. [0010] Dyes, pigments, lubricants, antioxidants, ultraviolet absorbers, tackifiers and the like can be added as additional components in the film according to the purpose. In order to suppress the warping of the polarizing plate, it is necessary to have a certain residual shrinkage stress after lamination. For this purpose, the tensile strength is 500 gf / 10 mm or more and the tensile elongation is 100%.
When the above film is used and the film is bonded to the protective layer of the polarizing film, the film has a tensile strength of 0.1%.
A tension of 01 to 0.5 is applied, and lamination is performed such that the direction of the tension is parallel to the orientation direction of the polarizing film (4). 0.0
If it is smaller than 1, it is not enough to correct the original warpage,
If it exceeds 0.5, the warpage on the synthetic resin film (1) side will increase. FIG. 2 is a diagram showing the direction of the tension of the synthetic resin film (1) with a single-sided adhesive layer and the orientation of the polarizing film (4) at the time of bonding. The synthetic resin forming the transparent synthetic resin film layer (2) is not particularly limited as long as the required transparency, strength and durability can be satisfied. Examples thereof include polyester, polycarbonate, polyarylate, and the like. Examples thereof include polysulfone, polyether sulfone, polyether ether ketone, polymethyl methacrylate, polystyrene, polyolefin, polyvinyl chloride, cellulose triacetate, and cellulose diacetate. The thickness can be set according to the purpose,
There is no particular limitation as long as the mechanical strength during use is obtained, and it is generally about 5 μm to 100 μm. The adhesive layer (3) is a layer responsible for bonding the transparent synthetic resin film layer (2) and the polyvinyl alcohol-based polarizing film (4). Has the desired adhesive properties,
There is no particular limitation as long as it satisfies the durability during use. For example, a polyvinyl alcohol-based adhesive may be used. The polyvinyl alcohol-based polarizing film (4) is a film having polarization performance by adsorbing and orienting iodine and a dichroic dye on the polyvinyl alcohol-based film, and is formed by a generally known method. Manufactured. The pressure-sensitive adhesive layer (5) is a layer for actually bonding to a liquid crystal display device, does not attack the polyvinyl alcohol-based polarizing film (4), does not float or peel off during use, and has a desired adhesive strength. There is no particular limitation as long as it has durability. In general, acrylic, silicon,
Adhesives such as rubber, urethane and epoxy are used. The peeling film (6) protects the pressure-sensitive adhesive layer (5) until the polarizing plate is actually bonded to the liquid crystal display device, and is used after being peeled off at the time of bonding. It is not particularly limited as long as it has a peeling force suitable for the above. For example, a structure in which a silicone-based or fluorine-based release agent layer is provided on a polyester-based base film is generally used. According to the present invention, the asymmetrical structure of the protective layer on only one side eliminates the warpage up to the time of bonding, and has the same durability and handling properties as those using a conventional polarizing plate. However, when it is attached to a liquid crystal display device, it can be made thinner, which is very useful for reducing the weight and thickness of mobile phones, mobile information terminals, and the like, which are currently being developed. Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto. The evaluation method is as follows. (1) Tensile strength and tensile elongation: Measured using a tensile tester (Shimadzu Autograph AGS-D) according to JIS-K-6781. (2) Light transmittance and degree of polarization: The synthetic resin film with one-sided adhesive and the release film were peeled off, and the spectrophotometer (UV-2200 manufactured by Shimadzu Corporation) was used in accordance with the Japan Electronics Machinery Standards (EIAJ) LD-201-1983. It measured using. (3) Warp: The polarizing plate is perpendicular to the orientation of the polarizing film.
A sample cut into a square having a side of 100 mm was prepared so as to be parallel, and the sample was allowed to stand in a horizontal position, and the warpage was measured to the mm unit with a JIS Class 1 steel measure. At that time, the upward warpage when the release film (6) side was the lower surface was indicated by +, and the upward warpage when the opposite surface was the upper surface was indicated by-. (4) Durability: A square polarizing plate having a side of 28 mm is peeled off from a release film, and a synthetic resin film having one-sided adhesive is peeled off, and is adhered to a glass plate having a side of 30 mm and a thickness of 1 mm.
The sample was placed in a thermostat at a temperature of 80 ° C. and observed for change in appearance after 500 hours, and the light transmittance and the degree of polarization were measured and evaluated. Reference Example 1 Preparation of Polyvinyl Alcohol-Based Polarizing Film (4) A polyvinyl alcohol film having a thickness of 80 μm and a saponification degree of 99.7% was uniaxially stretched (stretching ratio: 5 times), and the tension was maintained. It was immersed in an aqueous solution of iodine and potassium iodide, then treated with an aqueous solution of boric acid, washed with water and dried to obtain a polyvinyl alcohol-based polarizing film (4). Example 1 The polarizing film (4) obtained in Reference Example 1 (thickness: 18 μm)
The transparent synthetic resin film (2) has a thickness of 80 μm.
Triacetyl cellulose film (Fuji TAC UV
80) was bonded using a 5% by weight aqueous solution of polyvinyl alcohol (Kuraray Povar 217) as an adhesive (3), and dried at 60 ° C. for 20 minutes. An acrylic pressure-sensitive adhesive (5) is applied to the polarizing film side of this film so as to have a thickness of 25 μm, and a silicone-based release agent is applied thereon, and a 25 μm-thick PET film (Toray Miller)
(6) was pasted. On the transparent resin film side, tensile strength 627 gf / 10 mm, tensile elongation 283%, thickness 60μ
m, a polyethylene film with a single-sided adhesive layer (Sekisui Protect Tape 622AX) (1) is chucked in a flow direction with a tensile tester (Shimadzu Autograph AGS-D),
The film was pulled so as to have a tension of 50 gf / 10 mm, and the adhesive surface was bonded so as to be parallel to the orientation direction of the polarizing film. At this time, the tension applied to the polyethylene film is 0.08 of the tensile strength of the polyethylene film. The evaluation results are shown in Tables 1 and 2. Comparative Example 1 A polarizing plate was produced in the same manner as in Example 1 except that the polyethylene film (1) having a single-sided adhesive layer was not bonded. Table 1 shows the evaluation results. Comparative Example 2 Example 1 was repeated except that the tension applied when laminating the polyethylene film having a single-sided adhesive layer was 5 gf / 10 mm.
A polarizing plate was produced in the same manner as described above. At this time, the tension applied to the polyethylene film is 0.008 of the tensile strength of the polyethylene film. Table 1 shows the evaluation results. Comparative Example 3 A polarizing plate was produced in the same manner as in Example 1 except that the tension applied when laminating the polyethylene film having a single-sided adhesive layer was 400 gf / 10 mm. At this time, the tension applied to the polyethylene film is 0.638, which is the tensile strength of the polyethylene film. Table 1 shows the evaluation results.
Shown in Comparative Example 4 The same material as in Example 1 was used, but an 80 μm-thick triacetyl cellulose film (Fuji TAC UV80) was attached to both sides of the polarizing film, and an acrylic adhesive was applied to one side. It was applied so as to have a thickness of 25 μm, and a 25 μm-thick PET film (Toray Miller Mill) coated with a silicone release agent was laminated thereon. On the other side, tensile strength 6
27 gf / 10 mm, tensile elongation 283%, thickness 60 μm
A polyethylene film (Sekisui Protect Tape 622AX) with an adhesive layer on one side is chucked in a flow direction with a tensile tester (Shimadzu Autograph AGS-D), and 50 gf
The film was pulled so as to have a tension of / 10 mm, and the pressure-sensitive adhesive surface was bonded so as to be parallel to the orientation direction of the polarizing film. At this time,
The tension applied to the polyethylene film is 0.08 of the tensile strength of the polyethylene film. The evaluation results are shown in Tables 1 and 2. [Table 1] *: Thickness derived from the polarizing plate when bonded to the liquid crystal display device (value excluding the synthetic resin film (1) and the release film (6), which are excluded when bonding). (Light transmittance change) = (Initial light transmittance)-(Light transmittance after test) (Polarization change) = (Initial polarization)-(Polarization after test)

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a configuration of a polarizing plate of the present invention. FIG. 2 is a diagram showing a direction of tension of a synthetic resin film with a single-sided adhesive layer (1) and an orientation direction of a polarizing film (4) at the time of bonding. [Description of Signs] (1) Synthetic resin film with single-sided adhesive layer (2) Protective layer made of transparent synthetic resin film (3) Adhesive layer (4) Polyvinyl alcohol-based polarizing film (5) Adhesive layer (6) Peeling the film

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B 5/30

Claims (1)

(57) Claims 1. A protective layer (2) made of a transparent synthetic resin film is provided on the adhesive surface of a synthetic resin film (1) having an adhesive layer on one side, and an adhesive layer is provided thereon. A polarizing plate obtained by sequentially laminating a polyvinyl alcohol-based polarizing film (4), an adhesive layer (5), and a release film (6) via (3)
A synthetic resin film having an adhesive layer on one side
(1) Tensile strength of 500 gf / 10 mm or more, tensile elongation
Synthetic tree with a degree of 100% or more and an adhesive layer on one side
Transparent synthetic resin for polarizing film (4)
When bonding to the protective layer (2) made of a film,
The resin film (1) has a tensile strength of 0.01 to 0.5.
Of the polarizing film (4)
A polarizing plate laminated so that the orientation directions are parallel.