JP2007163570A - Polarizing plate for lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate for a lens which is constituted of a polarizing thin film and a protection layer and is used for an antiglare sunglass or the like, which is excellent in shock resistance and heat resistance and further has high polarizing performance and which does not have adverse influence on productivity or profitability when utilized as the lens. <P>SOLUTION: Polycarbonate resin sheets are adhered as the protection layers onto both surfaces of the polarizing thin film. The polycarbonate resin sheet has a retardation value of ≥2,000nm and is stretched under an atmosphere of 140 to 180°C at least between a distance of twice sheet width or more. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is a polarizing plate in which a polycarbonate resin sheet is adhered as a protective layer to a polarizing thin film, which is processed into a lens shape such as a spherical shape, for lenses used for anti-glare sunglasses, goggles, etc. It relates to a polarizing plate.

  The polarizing plate is used for anti-glare such as sunglasses and goggles because it exhibits excellent anti-glare properties in addition to liquid crystal display. As such a polarizing plate, a cellulose-based sheet such as triacetyl cellulose or an acrylic sheet is conventionally used as a protective layer on one or both sides of a polarizing thin film formed by adsorbing and orienting a dichroic dye to a polymer film. What was integrated by sticking is used.

  However, a polarizing plate using a cellulose-based sheet or an acrylic sheet as a protective layer is very dangerous when performing sports or the like because it has low impact resistance and is easily damaged. Alternatively, a cellulose sheet having a protective layer has a problem that sufficient heat resistance cannot be obtained. Therefore, a polarizing plate using a polycarbonate resin sheet excellent in impact resistance and heat resistance has recently been favorably used as the protective layer (see, for example, Patent Document 1), and this polarizing plate is formed into a lens shape by thermoforming. Are processed into a spherical surface, or after being subjected to spherical processing, a polycarbonate resin is laminated and integrated by injection to provide sunglasses or the like.

  However, when a polycarbonate resin sheet is used as a protective layer for a polarizing thin film, there is a problem that colored interference fringes are generated. This problem is solved by using a polycarbonate resin sheet having specific birefringence. . In other words, when a polycarbonate resin sheet is obtained by extrusion molding or the like, the retardation value (product of the birefringence and thickness of the sheet) is controlled by stretching in one direction while heating. And a method of taking up the take-up roll at a speed higher than that of the cooling roll (Patent Document 2).

  On the other hand, the polarizing thin film is obtained by stretching a polymer film adsorbed with a dichroic dye in one direction in a state of being immersed in an aqueous solution in which boric acid or the like is dissolved. When a polarizing plate is obtained by sticking the polycarbonate resin sheet as a protective layer to the polarizing thin film, the polarizing thin film and the polycarbonate resin sheet are attached so that the respective stretching directions are matched. By doing so, a polarizing plate having high polarization performance can be obtained.

Here, in the stretching of the polycarbonate resin sheet, the method as in Patent Document 2 is stretched in a very limited range immediately after leaving the final cooling roll, so that the end in the width direction of the sheet is neck-in. Thus, it is stretched in an oblique direction as compared with the central portion. Therefore, in the polarizing plate in which the polycarbonate resin sheet and the polarizing thin film are adhered, particularly in the case where the end of the sheet is adhered, the stretching direction of the polarizing thin film and the stretching direction of the polycarbonate resin sheet are shifted. As a result, the light absorption axis of the polarizing thin film itself and the absorption axis of the polarizing plate with the protective layer are shifted from each other. As a result, problems such as a sense of incongruity and a decrease in apparent polarization performance due to the deviation of the axis occur. Of course, if only the central part of the polycarbonate resin sheet is used, this problem is solved, but the productivity and profitability are significantly hindered.
JP 03-039033 A JP 09-005683 A

  The present invention solves the above problems, and provides a polarizing plate for a lens that has excellent impact resistance and heat resistance, and at the same time has high polarization performance, and does not adversely affect productivity or profitability when used as a lens. With the goal.

  The present invention is a polarizing plate for a lens in which a protective layer made of a polycarbonate resin sheet having a retardation value of 2000 nm or more is attached to both surfaces of a polarizing thin film, and the sheet is in an atmosphere of 140 to 180 ° C., The gist of the present invention is a polarizing plate for a lens, which is stretched at least at a distance of at least twice the sheet width.

  As described above, the polarizing plate for lenses of the present invention is obtained by sticking a polycarbonate resin sheet having a retardation value of 2000 nm or more to a polarizing thin film as a protective layer, and is excellent in impact resistance and heat resistance. In addition, the protective layer is subjected to a stretching treatment at a distance of at least twice the sheet width in an atmosphere of 140 to 180 ° C., so that at the end in the width direction of the sheet due to neck-in due to stretching. The orientation in the oblique direction was corrected, and the light absorption axis of the polarizing thin film coincided with the absorption axis of the polarizing plate with a protective layer applied, regardless of where the sheet was used. A polarizing plate can be obtained, and in the anti-glare sunglasses using this polarizing plate, problems such as a sense of incongruity due to the difference in appearance on the left and right and a decrease in polarizing performance are solved. Further, when this polarizing plate is used as a lens, it is not necessary to pay attention to the position where it is used, and it does not adversely affect productivity or profitability.

  The polarizing thin film of the present invention is not particularly limited as long as it is a thin film exhibiting a polarizing function. For example, a dichroic dye such as a dichroic dye is applied to a polymer film such as a polyvinyl alcohol film from the viewpoint of heat resistance. And the like that are adsorbed and oriented. Examples of the dichroic dye include azo dyes and anthraquinone dyes, and specifically include chloratin fast red, congo red, brilliant blue 6B, benzoperpurine, chlorazole black BH, direct blue 2B, and diamine green. , Chrysophenone, Sirius yellow, direct first red, acid black and the like.

  The polarizing thin film can be manufactured, for example, as follows. The polymer film is immersed in an aqueous solution in which the dichroic dye is dissolved. After the dichroic dye is adsorbed on the polymer film, the polymer film is immersed in an aqueous solution in which additives such as metal ions and boric acid are dissolved. In the state, it can be manufactured by stretching in one direction.

  A protective layer made of a polycarbonate resin sheet is attached to both surfaces of the polarizing thin film. The polycarbonate resin is not particularly limited, and a known resin can be used, and this resin can be used as a protective layer by forming a sheet shape by extrusion molding or the like. The retardation value of this polycarbonate resin sheet needs to be 2000 nm or more. This is because if it is less than this value, there is a problem that colored interference fringes are generated. The retardation value can be controlled to a desired value by stretching in one direction when the polycarbonate resin is formed into a sheet shape.

  Furthermore, the polycarbonate resin sheet needs to be stretched at a distance of at least twice the sheet width in an atmosphere of 140 to 180 ° C. As described above, the polycarbonate resin sheet is stretched in one direction in order to set the retardation value to a specific range. At that time, the end portion in the width direction of the sheet is inclined in the oblique direction as compared with the center portion by neck-in. Stretched. Then, by extending | stretching a sheet | seat while maintaining more than a glass transition temperature in a heating furnace etc., the extending | stretching of the diagonal direction in an edge part is corrected, and it becomes the same extending | stretching direction in all the parts of a sheet | seat. The stretching distance is at least twice the sheet width. If it is less than this, the stretching in the oblique direction is not sufficiently corrected. Moreover, this extending | stretching process is performed in 140-180 degreeC atmosphere. If it is less than 140 ° C., the stretching in the oblique direction is not corrected even if the distance between the stretching is increased. On the other hand, if the temperature exceeds 180 ° C., wrinkles occur due to thermal shrinkage and softening of the sheet, and a sheet having a good appearance cannot be obtained. In addition, this extending | stretching process may be implemented immediately after taking out the polishing roll at the time of extrusion molding, and may be implemented offline after once shape | molding in a sheet | seat shape.

  The polarizing plate for lenses of the present invention is produced by applying an adhesive to the polarizing thin film produced as described above or a polycarbonate resin sheet, and bonding and pressure-bonding the adhesive. Examples of the adhesive used include acrylic adhesives, epoxy adhesives, polyurethane adhesives, and olefin adhesives.

  Next, specific examples of the present invention will be described.

<Preparation of polarizing thin film>
Polyvinyl alcohol film (trade name: “Kuraray Vinylon # 7500”, manufactured by Kuraray Co., Ltd.) in which a dichroic dye is dissolved (brilliant blue 6B concentration is 0.4 g / L, benzoperpurine concentration is 0.2 g) / L, the concentration of chlorazole black BH was 0.1 g / L), and stained at 40 ° C. for 10 minutes. This dyed film was immersed in an aqueous solution in which nickel acetate tetrahydrate (0.4 g / L) and boric acid (40 g / L) were dissolved at 40 ° C. for 20 minutes, and about 2 uniaxially in this solution. The film was stretched twice, then washed with water and dried to obtain a polarizing thin film.

<Production of polycarbonate resin sheet>
Polycarbonate resin (trade name: “Iupilon E-2000”, manufactured by Mitsubishi Engineering Plastics) was T-die extruded. A polishing roll temperature of 180 ° C., a distance of 5 m between the polishing roll and the take-up roll, and a thickness of 0.4 mm by stretching under the condition that the speed difference between the polishing roll and the take-up roll is adjusted to 1.3 times. A roll sheet having a sheet width of 700 mm and a retardation value of 3400 to 3800 nm was obtained. The retardation value was measured at 10 locations on the sheet using an automatic birefringence meter (manufactured by KS-SYSTEMS), and the range (the smallest value to the largest value) was shown.

<Example 1>
The above polycarbonate sheet having a width of 700 mm is heated and stretched in a heating furnace having a furnace length of 5.5 m and a furnace temperature of 170 ° C. under conditions of an initial speed of 1.0 m / min and a take-off speed of a drying furnace outlet of 1.3 m / min. The roll sheet having a thickness of 0.385 mm, a width of 550 mm, and a retardation value of 3600 to 4000 nm was obtained. The obtained sheet was bonded to both surfaces of the above polarizing thin film with a one-component moisture-curable polyurethane adhesive containing ethyl acetate to obtain a polarizing plate.

<Example 2>
Except for performing the furnace temperature at 150 ° C., a heat-stretching treatment was performed under the same conditions as in Example 1 to obtain a roll sheet having a thickness of 0.39 mm, a width of 670 mm, and a retardation value of 4000 to 4400 nm. The obtained sheet was bonded to both surfaces of the above polarizing thin film with a one-component moisture-curable polyurethane adhesive containing ethyl acetate to obtain a polarizing plate.

<Comparative Example 1>
Without heating and stretching the polycarbonate resin sheet, a polarizing plate was obtained by laminating both surfaces of the polarizing thin film with a one-component moisture-curable polyurethane adhesive containing ethyl acetate. In the production of the polycarbonate resin sheet, heating is not performed between the polishing roll and the take-up roll, and the film is stretched using preheating due to the resin being heated before the polishing roll. The stretching distance under an atmosphere of 180 ° C. was about 500 to 1000 mm.

<Comparative example 2>
A heat-stretching treatment was performed under the same conditions as in Example 1 except that the furnace temperature was 135 ° C., and a roll sheet having a thickness of 0.40 mm, a width of 680 mm, and a retardation value of 3000 nm to 3500 nm was obtained. The obtained sheet was bonded to both surfaces of the above polarizing thin film with a one-component moisture-curable polyurethane adhesive containing ethyl acetate to obtain a polarizing plate.

  The light absorption axis angle of each polarizing plate obtained as described above was evaluated. In other words, with the Rema measuring instrument Type PA2 (manufactured by Rema), the absorption axis angle was measured at 10 points in the polycarbonate resin sheet width direction, and the maximum value and the minimum value were within ± 2 °. The case where the maximum value or the minimum value exceeded ± 2 ° was defined as “x”. The results are shown in Table 1.

Claims (1)

  A polarizing plate for a lens in which a protective layer made of a polycarbonate resin sheet having a retardation value of 2000 nm or more is attached to both surfaces of a polarizing thin film, and the sheet has at least a sheet width in an atmosphere of 140 to 180 ° C. A polarizing plate for a lens, which is stretched at a distance of 2 times or more.