JPH10253825A - Manufacture of elliptically polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an elliptically polarizing plate excellent in uniformity of a phase difference characteristic over the whole surface and not generating an irregular color on a display surface by blowing air against a back face of a mutually sticking surface of a phase difference plate under specific wind pressure, and press-fitting and sticking the phase different plate to the polarizing plate. SOLUTION: First of all, a polarizing plate 1 is placed on a plane 3, and is preferably attracted and fixed to the plane 3 by reduced pressure or the like to improve positioning accuracy. A phase difference plate 2 is arranged in a mutually sticking position with the polarizing plate 1 by separating a protective sheet. In that case, it is desirable that in order to be easily put in a non-tensile force condition, this is delivered as a doubly winding body 20, and an end part is put in a free end condition. A mutually sticking surface is press-fitted to a back face of a mutually sticking surface of the phase difference plate 2 stuck to the polarizing plate 1 while blowing air under wind pressure of 10 to 1000g/cm<2> . It is desirable that blowing is started from an end part to start mutual sticking and air is blown in a linear shape while successively moving so as to follow a line where the polarizing plate 1 and the phase difference plate 2 contact with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an elliptically polarizing plate in which a polarizing plate and a retardation plate are bonded together via an adhesive layer.

[0002]

2. Description of the Related Art In recent years, a high contrast liquid crystal display device utilizing the birefringence of a super twisted nematic (STN) liquid crystal has been generally used.
However, a display device using this liquid crystal element has a
There is a problem that the display surface is colored due to elliptically polarized light based on the birefringence of the N liquid crystal. Therefore, an elliptically polarizing plate in which a retardation plate is bonded to a polarizing plate via an adhesive layer is generally used.

A retardation plate is obtained by stretching polycarbonate, polyarylate, or the like. However, due to the stress applied when the retardation plate is bonded to a polarizing plate, variations in the valley value, which is the optical characteristic of the retardation compensator, in the product plane are caused. And there is a problem that color unevenness occurs on the display surface.

[0004] For this reason, various bonding methods for uniforming the valley value in the product surface have been conventionally proposed. For example, Japanese Patent Application Laid-Open No. HEI 4-123008 discloses that a polarizing plate and a retardation plate having a size equal to or larger than the product size are bonded in advance by pressing with a roll, and the edge of the laminate is cut off to obtain a product size. A method for obtaining an elliptically polarizing plate is described. According to this method, unnecessary materials are consumed wastefully to obtain a product.

Japanese Unexamined Patent Publication (Kokai) No. 6-71757 discloses that when a retardation film having an adhesive layer and a polarizing plate film are bonded to each other, a retardation film placed on a lower support member with the adhesive layer on the upper side. A method is described in which the lower support member is moved along the lower surface of the upper support member and bonded to the lower support member while the end portion is pressed against the end portion of the polarizing plate film sucked and held on the lower surface of the upper support member.

The method described in Japanese Patent Application Laid-Open No. Hei 6-71757 is intended to bond two films without applying tensile stress. However, also in this method, since the bonding operation is performed by a bonding roll, a certain level of tension acts on the phase difference plate, so that the stress applied to the phase difference plate cannot be ignored.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional problems, and provides an elliptically polarizing plate which is excellent in the uniformity of the retardation characteristics over the entire surface and does not cause color unevenness on the display surface. The aim is to provide a method.

[0008]

The method of manufacturing an elliptically polarizing plate according to the present invention is directed to a method of manufacturing an elliptically polarizing plate in which a polarizing plate and a retardation plate are bonded via an adhesive layer. The method is characterized in that a phase difference plate is pressed and bonded to a polarizing plate by blowing air at a wind pressure of 10 to 1000 g / cm ² on the back surface of the surface.

The present inventors have studied the causes of color unevenness in STN display devices. As a result, variations in the valley value in the plane of an elliptically polarizing plate, which is one of display elements, are one of the major causes, and most of them are. Has been found to occur when a polarizing plate and a retardation plate are bonded together. Furthermore, in order to laminate a polarizing plate and a retardation plate using a pressure roll as in a conventional laminating method, it is necessary to apply a constant tension to the retardation plate. It was also found that the valley value of the phase difference plate was shifted.

In order to carry out the method of the present invention, it is preferable that a polarizing plate is first placed on a flat surface, and it is adsorbed and fixed to the flat surface by decompression or the like in order to improve positioning accuracy. The retardation plate peels off the protective sheet and is arranged at a position where the retardation plate is bonded to the polarizing plate. At this time, the retardation plate may be in a single-wafer state, but it is preferable that the phase difference plate be a wound body in order to facilitate a non-tension state, and that the end part be a free end by being fed out. .

The bonding surface is pressed against the back surface of the bonding surface of the phase difference plate bonded to the polarizing plate while blowing air at a wind pressure of 10 to 1000 g / cm ² . If the wind pressure is lower than 10 g / cm ^2, sufficient adhesion between the polarizing plate and the retardation plate cannot be obtained, and reliability such as durability cannot be obtained. On the other hand, if the wind pressure is higher than 1000 g / cm ² , tension is generated on the retardation plate during bonding, and there is a problem that the valley value varies. Therefore, the wind pressure is in the above range.

When the polarizing plate and the retardation plate are bonded together, the bonding is started from one end so that no air bubbles remain between them, and no tension is generated on the phase difference plate toward the other end. It is preferable to bond them sequentially while loosening. Therefore, air blowing should be started from the end where the polarizing plate and the phase difference plate start to be bonded, and sprayed linearly while sequentially moving so as to follow the line where the polarizing plate and the phase difference plate are in contact. preferable.

Furthermore, it is preferable to spray uniformly in the width direction of the line where the polarizing plate and the phase difference plate are in contact with each other. The blowing direction of the air is not particularly limited, but it is preferable that the air be blown at a right angle to the retardation plate at the portion to be bonded.

The temperature of the air is preferably higher than the normal temperature in order to ensure the bonding reliability. However, if the air temperature is higher than the glass transition temperature of the phase difference plate, the valley value of the phase difference plate greatly changes. It is necessary that the glass transition temperature does not exceed.

According to the method for producing an elliptically polarizing plate of the present invention,
Compared with the pasting method using a pressure roll, a retardation plate can be bonded to a polarizing plate with almost no tension applied to the retardation plate. Therefore, it is possible to obtain an optically uniform elliptically polarizing plate with very little variation in the valley value.

[0016]

Embodiments of the present invention will be described below. 1) Preparation of polarizing plate pressure-sensitive adhesive sheet and retardation plate pressure-sensitive adhesive sheet A transparent iodine-based pressure-sensitive adhesive layer formed by coating a transparent acrylic pressure-sensitive adhesive on a 38 μm-thick release paper so as to have a thickness of 25 μm after drying is coated on a commercially available iodine-based pressure-sensitive adhesive layer. Was transferred to a polarizing plate to obtain a polarizing plate adhesive sheet (not shown). The pressure-sensitive adhesive layer formed in the same manner as described above was transferred to a polycarbonate having a valley value of 560 nm obtained by stretching polycarbonate to obtain a phase difference plate pressure-sensitive adhesive sheet (not shown). The release paper was not peeled off, but was wound up in a curl shape with the adhesive layer inside.

2) Preparation for Lamination FIG. 1 is a plan view of the pressure-sensitive adhesive sheet 1 for a polarizing plate, where a = 100.
mm, b = 200 mm. p indicates the stretching direction, and α is 45 degrees. FIG. 2 is a side view showing an embodiment of the manufacturing method according to the present invention, and a polarizing plate pressure-sensitive adhesive sheet 1 is temporarily fixed on a flat base 3 with a pressure-sensitive adhesive layer facing upward. 20
Is a rolled sheet of the pressure-sensitive adhesive sheet 2. 4
Denotes an air blowing device, which can reciprocate between one end and the other end of the polarizing plate adhesive sheet 1.

(Examples 1 to 3) The short side a of the polarizing plate pressure-sensitive adhesive sheet 1 and the longitudinal end portion of the phase difference plate pressure-sensitive adhesive sheet 2 on the non-laminated surface of the pressure-sensitive adhesive sheet 2 are overlapped. The air of the wind pressure and temperature shown in Table 1 is blown linearly in the width direction of the retardation plate and substantially perpendicularly to the polarizing plate pressure-sensitive adhesive sheet 1 by the air blowing device 4 while relaxing the air blower 2 so as not to apply tension. The air blowing device 4 was moved in the direction of the arrow A while being sprayed on the contact portion with the retardation plate pressure-sensitive adhesive sheet 2 and bonded.

(Comparative Examples 1 to 3) Table 1 shows the wind pressure and temperature of air.
A polarizing plate and a retardation plate were bonded together in the same manner as in Example 1 except that the conditions were as shown in FIG.

Comparative Example 4 Lamination was performed using only a conventional pressure roll without blowing air.

Performance Evaluation (1) Measurement of valley value The valley value of the completed elliptically polarizing plate 5 was 9 as shown in FIG.
, And the difference between the maximum value and the minimum value was expressed (the measuring device was manufactured by Otsuka Electronics Co., Ltd.
Model "RETS-2000" is used). (2) Durability The completed elliptically polarizing plate was attached to a glass cell (trade name “ASAHI AS” manufactured by Asahi Glass Co., Ltd.), allowed to elapse for 10 minutes in an autoclave at 50 ° C. and 5 atm, and then placed in an oven at 90 ° C. And left for 500 hours, and then taken out and the attached state was visually observed. Table 1 shows the above results.

[0022]

[Table 1]

All of the products obtained in Examples 1 to 3 of the present invention have smaller variations in valley value and better durability than those of Comparative Example 4 using a conventional pressure roll. However, although the variation of the valley value is small in Comparative Example 1,
Since the wind pressure was too low, separation between the retardation plate and the polarizing plate occurred. In the case of Comparative Example 2, the wind pressure was too high, and in the case of Comparative Example 3, the air temperature was too high, so that the variability of the valley value was large.

[0024]

As described above, the method for producing an elliptically polarizing plate of the present invention has the above-mentioned structure, and the obtained elliptically polarizing plate can have excellent uniformity of retardation characteristics over the entire surface. By using this, a liquid crystal display device in which color unevenness does not occur on the display surface can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view showing a polarizing plate adhesive sheet.

FIG. 2 is a side view showing an embodiment of the method for producing an elliptically polarizing plate of the present invention.

FIG. 3 is a plan view of the elliptically polarizing plate showing a measurement position of a valley value.

[Explanation of symbols]

 1: Adhesive sheet for polarizing plate 2: Adhesive sheet for retardation plate 3: Flat table 4: Air blowing device 5: Elliptical polarizing plate 20: Wound body 50: Measurement position of valley value

Claims (1)

[Claims] 1. A method for manufacturing an elliptically polarizing plate in which a polarizing plate and a retardation plate are bonded via an adhesive layer, wherein air is applied to the back surface of the bonding surface of the retardation plate at a wind pressure of 10 to 1000 g / cm ^2. A method for manufacturing an elliptically polarizing plate, wherein the retardation plate is pressure-bonded to the polarizing plate by spraying.