JPH10206631A - Manufacture of elliptic polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stick a phase different plate and a polarizing plate together without applying nonuniform stress to the phase difference plate by inserting a spacer so as to be brought into close contact with the starting end or the tail end in the inserting direction of a polarizing plate sheet-fed body to pressurizing rollers. SOLUTION: A polarizing film is cut out at an angle θ to its optical axis, and is formed as a polarizing plate sheet-fed body 2. A long size phase difference film 1 is sent out in the mutually sticking direction, and a die separable film 5 covering its upper surface is torn off, and a pressure sensitive adhesive layer 6 is exposed. A spacer 4 is arranged on it, and the polarizing plate sheet- fed body 2 is arranged so that its side (b) and the side (a) of the polarizing plate sheet-fed body 2 are brought into close contact with each other. The sheet-fed body 2 is stuck on the film 1 by being inserted into pressurizing rollers 3 in a condition of being mutually superposed through the pressure sensitive adhesive layer 6 so that these optical axes form a prescribed angle θ. When plural sheet-fed bodies 2 are stuck together, they are stuck together by arranging the spacer 4 on the tail end of the last sheet-fed body 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing an elliptically polarizing plate. More specifically, the present invention relates to a method for producing an elliptically polarizing plate comprising a composite pressure-sensitive adhesive sheet of a polarizing plate and a retardation plate which has been subjected to pressure-sensitive adhesive bonding before being bonded and fixed to a glass substrate for liquid crystal panels.

[0002]

2. Description of the Related Art Liquid crystal display panels are used in large quantities as display devices for OA equipment and the like. In particular, large-sized liquid crystal display panels often use STN (super twisted nematic) type liquid crystal display panels. Recently, STN-type liquid crystal display panels are often used for medium-sized and small-sized display panels such as notebook personal computers and word processors.

By the way, since the STN liquid crystal display panel utilizes birefringence, light passing through the liquid crystal cell becomes elliptically polarized light, and there is a problem that the display color is colored. In order to prevent coloring by returning elliptically polarized light to linearly polarized light, a method of interposing a retardation plate between a liquid crystal cell and a polarizing plate has been proposed.

[0004] A lamination of a retardation plate and a polarizing plate is called an elliptically polarizing plate, and the manufacturing method is such that an adhesive is interposed between the retardation plate and the polarizing plate so that the optical axes of each other form a predetermined angle. Laminate and press together with rolls. In general, a long polarizing film obtained by stretching is cut at regular intervals so as to form a predetermined angle θ with respect to the stretching axis to obtain a parallelogram-shaped polarizing plate sheet, while being stretched. The elongated retardation film is used to slow its slow axis (usually coincides with the stretching axis).
Prepare a parallelogram shaped phase difference plate sheet obtained by cutting at regular intervals so as to form a predetermined angle θ with respect to, one of them is placed on a support member, this stretching axis and the other An elliptically polarizing plate is manufactured by applying pressure from above and below with a pressure roll in a superposed state via an adhesive so that the stretching axis forms a predetermined angle θ.

[0005] The retardation of a stretched film is controlled by the stretching ratio and thickness of the film. However, the retardation film, once stretched, is subjected to stress due to the subsequent transfer of an adhesive or lamination with a polarizing plate. And the phase difference changes.

For this reason, for example, in Japanese Patent Application Laid-Open Nos. 4-29029 and 6-71757, one of two films is used in a laminating step of a film having an adhesive layer formed on at least one laminating surface. The two films are stuck together by a pressure roll so that no stress is applied by a method of holding by suction.

[0007] However, in these conventional techniques, both the polarizing plate and the retardation plate must be cut to a predetermined size and stored, and the optical axes at the time of lamination must be adjusted. It is necessary to overlap them so as to form a predetermined angle, and there is a problem in accuracy when the cutting angles are not the same. In addition, this method is not desirable in terms of yield and cost, and there is a problem that the material cannot be used effectively. Further, depending on the insertion angle of the film with respect to the rotation axis of the pressure roll, the linear pressure received by the film is not uniform over the entire surface, so that the retardation plate is distorted and the phase difference value is prevented from changing. Did not.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has been described in connection with a case where a retardation plate and a polarizing plate used for optical compensation are bonded together. An object of the present invention is to provide an effective method of manufacturing an elliptically polarizing plate which can be bonded without applying uneven stress and which is excellent in quality.

[0009]

As described above, in the step of bonding the phase difference plate and the polarizing plate, the stress applied to the phase difference plate changes the phase difference value of the phase difference plate. Since a uniform stress causes unevenness of the phase difference, it is necessary to reduce the stress as much as possible.

Therefore, in the present invention, one of the retardation film and the polarizing film is prepared as a long film, and the other is prepared as a single sheet cut at a predetermined angle θ with respect to the optical axis. At the same time, as shown in FIG. 1, the other sheet 2 is pressed on the long film 1 via the adhesive layer 6 so that their optical axes form a predetermined angle θ. The rolls 3 are continuously inserted and bonded so as to be substantially perpendicular to the rotation axis thereof. At this time, the predetermined angle θ
When the insertion direction is not a right angle, the insertion direction and the optical axis of the sheet 2 become oblique, and the side a of the sheet 2 becomes oblique with respect to the pressure roll 3, and is not formed on the retardation plate. In order to prevent a uniform stress from being applied, the spacer 4 is inserted in close contact with the starting end or the end of the sheet 2 in the direction of insertion into the pressure roll 3. FIG. 1 shows a retardation film stretched in a longitudinal uniaxial direction, that is, a longitudinal direction, as a long film 1 and a polarizing plate as a single sheet 2 for convenience.

In the present invention, by inserting spacers before and after the sheet, the occurrence of phase difference unevenness due to stress distortion applied to the phase difference plate during pressure bonding can be reduced as much as possible. An elliptically polarizing plate capable of optical compensation can be obtained.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is intended to prevent a non-uniform stress from being applied to a retardation plate when laminating a retardation plate comprising a uniaxially or biaxially stretched film and a polarizing plate used for optical compensation. As a result of intensive study for the purpose of doing, especially when bonding the retardation plate and the polarizing plate via the adhesive layer, the angle between the slow axis of the retardation plate and the stretching axis of the polarizing plate is not a predetermined angle In the case of θ (0 <θ <180 °), for example, a trapezoidal spacer as shown in FIG. 2A is attached to the pressure roll of a sheet-like body composed of either a retardation plate or a polarizing plate. By inserting at the beginning or end in the insertion direction, unevenness of stress at the time of bonding is reduced, phase difference unevenness due to distortion does not occur in the phase difference plate, and the elliptically polarizing plate achieving the intended optical compensation Can be obtained. In the following description, for the sake of convenience, the retardation plate will be described as a long body and the polarizing plate will be described as a single-leaf body, but this is merely intended to not complicate the description, and the polarizing plate will be described as a long body. ,
It does not depart from the technical scope of the present invention even if the retardation plate is a single-wafer body.

As shown in FIG. 2 (a), the shape of the spacer is such that the angle θ1 between the side c and the side d is parallel and the side b forms the side d with the predetermined angle with a tolerance of about ± 10 °. The angle is set approximately equal to θ. The length of the side b is set to be substantially equal to or slightly longer than the side a of the polarizing plate sheet 2. As long as the angle θ1 and the length of the side b satisfy the above conditions,
The shape of the spacer is not particularly limited, and may be, for example, as shown in (b) to (d) of FIG.

The best effect of the present invention can be obtained when the thickness of the spacer is substantially the same as the thickness of the polarizing plate sheet so that the stress applied to the retardation film is uniform over the entire surface of the polarizing plate. . In addition, the material of the spacer is not particularly limited, and the polarizing plate sheet itself may be used as the spacer. In this case, since the lamination is performed continuously, the most efficient manufacturing method is used in terms of product efficiency. I can say.

The polarizing plate used in the present invention is not particularly limited, but usually comprises a polarizing film having a polarizing function and a protective film for protecting the polarizing film. Here, as the polarizing film, vinyl alcohol-based polymer / iodine-based, vinyl alcohol-based polymer / dichroic dye-based, vinyl alcohol-based / polyene-based, polyvinyl halide / polyene-based, polyacrylonitrile / polyene-based, (Meth) acrylate / polyene-based, polycarbonate-based and the like. As a protective film for protecting them, a transparent sheet of light isotropic such as cellulose triacetate, polycarbonate, polymethyl methacrylate and the like can be given. The elongated body obtained by stretching the polymer film is cut into a parallelogram as described above to obtain a polarizing plate.

As the retardation plate, a polyvinyl alcohol-based, polycarbonate-based, acrylic-based, polyester-based film, or the like is used in terms of transparency, heat resistance, optical homogeneity, workability, and the like. A long body obtained by stretching these polymer films uniaxially or biaxially is used as it is, or is slit into an appropriate width in accordance with the shape of a polarizing plate and used for bonding. These may be subjected to corona treatment on both surfaces or one surface of the retardation plate as necessary in order to improve the adhesion to the pressure-sensitive adhesive layer.

The pressure-sensitive adhesive is preferably an acrylic one in terms of light transmittance and durability, etc., and is used by dissolving it with a solvent and adding a isocyanate-based curing agent.

The elliptically polarizing plate is obtained by laminating a retardation plate and a polarizing plate with an adhesive therebetween. Then, in order to fix the plate to a glass plate, the retardation plate is opposite to the surface to be laminated to the polarizing plate. An adhesive layer is also formed on the side surface. In order to obtain such a configuration, a retardation plate having a pressure-sensitive adhesive layer formed on both surfaces and a polarizing plate having no pressure-sensitive adhesive layer formed on either surface are bonded together, or a pressure-sensitive adhesive layer is formed on one surface. Is bonded to the opposite surface (non-adhesive surface) of the retardation plate on which the adhesive layer is formed and the adhesive surface of the polarizing plate having an adhesive layer formed on one surface.

As a method of forming the pressure-sensitive adhesive layer on the retardation plate or the polarizing plate, the pressure-sensitive adhesive layer formed on the release film and having a thickness of 5
To 50 μm, preferably 20 to 40 μm of an adhesive layer,
If necessary, a method of transferring the image to a retardation plate or a polarizing plate may be used.

As the release film, use is made of one having a base material such as kraft paper, glassine paper, parchment paper, polyethylene terephthalate (PET) film, an anchor coat if necessary, and a release treatment with silicone. Can be

As a specific method of laminating the retardation plate and the polarizing plate obtained as described above, as shown in FIG. 1, a long retardation film 1 is fed in the laminating direction, The release film 5 covering the upper surface of the pressure-sensitive adhesive sheet 1 is peeled off to expose the pressure-sensitive adhesive layer 6, the spacer 4 is disposed thereon, and the polarizing plate sheet 2 is placed so that the side b and the side a are in close contact with each other. Are arranged, and pressure is applied from above and below with a pressure roll 3 to bond them. When a plurality of polarizing plates are to be bonded, a new polarizing plate leaf 2 is successively arranged in close contact with the polarizing plate leaf 2, and the required number of polarizing plate leafs 2 are placed on the retardation film. Paste with 1. At the end of the last polarizing plate sheet 2, the spacer 4 is arranged and bonded so that the side a and the side b are close to each other, and the bonding step is completed. Thereafter, the retardation film 1 is cut and cut into individual elliptically polarizing plates.

[0022]

EXAMPLES Examples of the present invention will be described below together with comparative examples to specifically explain the effects of the present invention.

(Example) First, a corona treatment is applied to both surfaces of a retardation film made of a polycarbonate film uniaxially stretched to a retardation value of 560 nm in order to increase the adhesion to the pressure-sensitive adhesive layer. Next, an acrylic base polymer containing butyl acrylate formed on the release film as a main component and having a carboxyl group and a hydroxyl group as a functional group is crosslinked with an isocyanate-based crosslinking agent to impart cohesiveness. An acrylic pressure-sensitive adhesive layer having a thickness of 30 μm was transferred to both surfaces of the retardation film to obtain a retardation film in which a pressure-sensitive adhesive layer covered with a release film was formed on both surfaces. Slitting was performed so that the width of the retardation film after the adhesive processing was 495 mm.

As a polarizing plate, a three-layer film having a width of 450 mm and a thickness of 180 μm, in which both sides of a film obtained by stretching polyvinyl alcohol and further adsorbing iodine were sandwiched by a cellulose triacetate film as a protective film, was used. . This polarizing plate was cut using a cutter at a cutting interval of 700 mm so that the angle formed with the stretching axis direction of the film was 45 °, to obtain a parallelogram-shaped sheet of polarizing plate.

The above retardation film and a sheet of polarizing plate were laminated using a laminating machine. Specifically, the release film on the upper surface side of the retardation film placed on a flat surface is peeled off from the end to expose the adhesive layer, and a sheet of a polarizing plate is further placed on the two parallel plates. 2 formed by cutting out of 2 sides
Align four sides of the retardation film so that they overlap with both sides of the retardation film, and put them in close contact with each other in the direction of insertion into the pressure roll. The leaves were stuck together.

After bonding as described above, the retardation film was cut and cut for each sheet of the polarizing plate, and J1 to J4 were attached in the order in which the sample numbers were inserted. Of these, the polarizing plate sheets of the two sample sheets J1 and J4 at both ends were used as spacers. Therefore, the sample sheet obtained as an example is in the center J2.
And J3.

With respect to the sample sheets J2 and J3 having the cross-sectional structure of the polarizing plate / adhesive layer / retardation plate / adhesive layer / release film obtained as described above, the in-plane retardation in the parallelogram shape was obtained. As shown in FIG. 3, the valley value was measured at a total of 135 points including 9 points in the width direction and 15 points in the length direction. Table 1 shows the measurement results.

(Comparative Example) Using a retardation film and a sheet of polarizing plate prepared in the same manner as in the example, the two sheets of polarizing plate were not closely contacted in the laminating direction at a distance of 1000 mm. Except that it was placed above, it was bonded in the same manner as in the example. The sample numbers of the two sheets were designated as H1 and H2 in the order of insertion. The valley values of these sample sheets were measured in the same manner as in the examples. The results of the measurement are also shown in Table 1.

[0029]

[Table 1]

As can be seen from Table 1, although the average value of the valley value is almost the same between the example and the comparative example, the maximum value of the valley value is smaller in the example than in the comparative example, and the range showing the variance of the valley value. R is also 10 in comparison with the range R of the comparative example.
nm small. From these results, it can be seen that variations in the valley value can be reduced by inserting the polarizing plate sheet cut at the same angle as a spacer before and after the polarizing plate sheet.

The variation in the valley value in the comparative example is large because the spacers are not inserted as in the comparative example, and the polarizer sheets are spaced apart from each other with the space between the adjacent polarizer sheets. This is because, when they are laminated, the retardation film is distorted, thereby increasing the valley value, and several such points appear as singular points. On the other hand, when the method according to the embodiment is used, there is no singular point where the valley value increases, and the variation in the valley value can be reduced.

From these results, by using the bonding method of the present invention, it is possible to obtain an elliptically polarizing plate having a cross-sectional structure of polarizing plate / adhesive layer / retardation plate / adhesive layer / release film obtained after bonding. Variation in phase difference can be reduced.

[0033]

As described above, according to the present invention, when manufacturing a elliptically polarizing plate by laminating a retardation plate and a polarizing plate used for optical compensation, uneven stress is applied to the retardation plate. It is possible to manufacture an elliptically polarizing plate excellent in quality by being able to be bonded without such a problem, and also to provide a continuous and efficient method for manufacturing an elliptically polarizing plate by using a sheet itself as a spacer. Can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of an embodiment of the present invention.

FIG. 2 is a plan view illustrating a shape example of a spacer.

FIG. 3 is an explanatory diagram showing measurement points of a valley value of an elliptically polarizing plate.

[Description of sign]

 Reference Signs List 1 retardation film 2 sheet of polarizing plate 3 pressure roll 4 spacer 5 release film 6 adhesive layer

Claims (2)

[Claims] 1. A sheet material obtained by cutting one of a long body of a retardation film and a polarizing film, and the other film at a predetermined angle θ (0 <θ <180 °) with respect to the optical axis thereof. Are superimposed such that their optical axes form a predetermined angle θ, and are continuously inserted and stuck so that the longitudinal direction of the long body is substantially orthogonal to the rotation axis of the pressure roll, and the elliptically polarizing plate is laminated. A manufacturing method of an elliptically polarizing plate, wherein a spacer is inserted in close contact with a start end or an end of the sheet in a direction of insertion into a pressure roll. 2. The method for producing an elliptically polarizing plate according to claim 1, wherein a spacer is made of the sheet.