JPH02120805A - Production of elliptically polarizing plate - Google Patents

Abstract

PURPOSE:To obtain an elliptically polarizing plate having excellent durability and to prevent the generation of floating and foaming even in high-temp. environment by providing tacky adhesive layers to both of the polarizing plate and the phase difference plate and adhering these plates. CONSTITUTION:The tacky adhesive layers 2, 3, 5 are respectively provided to, for example, the polarizing plate 1 and the phase difference plate 4 and the tacky adhesive layers are adhered to each other, by which the elliptical polarizing plate is formed. Namely, the phase difference plate 4 and the polarizing plate 1 are adhered via the tacky adhesive layers 2, 3 in the state of providing the tacky adhesive layer 5 in the tacky adhesive layer 2 provided to the polarizing plate 1, the tacky adhesive layer 3 provided to the phase difference plate 4 and the tacky adhesive layer 5 for adhering the elliptical polarizing plate 6 to a display panel 7. The elliptical polarizing plate having the excellent durability is obtd. in this way and the generation of floating and foaming of the elliptically polarizing plate is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a birefringent liquid crystal display in which a polarizing plate and a retardation plate are bonded together through adhesive layers provided on each to improve durability. This invention relates to a method of manufacturing an elliptically polarizing plate used for preventing coloring.

Background of the invention STN (Super Twisted Nemat)
ic) Larger screens for personal computers, Watt processors, etc. have been achieved using high contrast liquid crystal displays that utilize the birefringence of K1 products. Such displays are based on the birefringence of STN liquid crystal (elliptically polarized light, and the display through a polarizing plate is generally colored green or yellow. Therefore, by compensating for the phase difference due to the birefringence of STN liquid crystal, A method has been taken to cancel the coloring by returning the light to linearly polarized light.As a means to do so, a method using a retardation plate made of a multi-fold film has been proposed.This method is called the FTN method. This enables black and white display using a single-layer cell, and eliminates the bulkiness and weight of the previous D-8TN system in which separate liquid crystal cells were stacked on top of each other.

FIG. 3 shows an example of the configuration of an FTN type display.

(2) A display panel includes a polarizing plate 8, a retardation plate 4, and a birefringent liquid crystal cell 7, with the polarizing plate 1 side being the viewing side.

When the polarizing plate 1 and the retardation plate 4 are fixed to the display panel 7, they are bonded in advance to form an elliptically polarized plate 6, and the adhesive layer 5 provided on the outer surface of the retardation plate 4 is used.

Prior Art and Problems Conventionally, in the manufacture of such an elliptically polarizing plate, as shown in FIG. 2, an adhesive layer 2 is provided on only one side of a polarizing plate 10, and the adhesive layer 2 is bonded to a retardation plate 4 through this.

However, the elliptical polarizing plate obtained by this method has a problem of poor durability and, for example, floating or foaming in an atmosphere at a temperature of about 70°C. Lifting and foaming of the elliptically polarizing plate makes it impossible to see the displayed content, which is fatal.

Means for Solving the Problems The present invention overcomes the above problems by providing adhesive layers on both the polarizing plate and the retardation plate and adhering them through the adhesive layers.

That is, the present invention provides a method for producing an elliptically polarizing plate, which is characterized in that a polarizing plate made of a polarizing film and a retardation plate made of a birefringent film are adhered via adhesive layers provided on each. It is.

By providing an adhesive layer on both the working polarizing plate and the retardation plate and adhering them through this, it is possible to create an elliptically polarizing plate with excellent durability, and no floating or foaming occurs even in a high temperature atmosphere of 80°C. This can be prevented.

Example In the present invention, an elliptically polarizing plate is formed by providing an adhesive layer on each of a polarizing plate and a retardation plate, and bonding the adhesive layers to each other. FIG. 1 shows an example of the process. 2 is an adhesive layer provided on the polarizing plate 1, and 3 is an adhesive layer provided on the retardation plate 4.

Note that 5 is an adhesive layer for adhering the elliptically polarizing plate 6 to the display panel 7. In the rotation, the retardation plate 4 and the polarizing plate 1 are bonded together via the adhesive layer 2.degree.3 with the adhesive layer 5 previously provided. In the present invention, an adhesive layer 5 may be attached to the outer surface of the retardation plate 4 after the polarizing plate 1 and the retardation plate 4 are bonded together via the adhesive layer 2.3. Note that during storage or distribution of the elliptically polarizing plate, it is common to protect the adhesive layer 5 by attaching a separator to it.

The polarizing plate used in the present invention is formed of a polarizing film. Further, the retardation plate is formed of a birefringent film. As a result, a light, thin, and large-sized elliptically polarizing plate suitable for liquid crystal displays can be easily obtained. There are no particular limitations on the polarizing film and birefringent film to be used. A polarizing film can be obtained, for example, by treating a hydrophilic film such as a stretched polyvinyl alcohol film with a dichroic dye such as iodine, or by appropriately treating a plastic film to orient the polyene. A birefringent film can be obtained, for example, by stretching a plastic film. Note that the retardation plate used may be composed of a laminate of two or more types of birefringent films.

The adhesive used for forming the adhesive layer and an acrylic adhesive having excellent dh1 transparency are preferably used. of course,
It is not limited to this. Further, it is preferable to use a material that does not require drying treatment at high temperatures and does not change the polarization characteristics of the polarizing plate or the birefringence characteristics of the retardation plate. In view of the fact that no drying process is required, it is preferable to use a coating that can be coated without a solvent using an appropriate coating machine such as a squeeze coater. From the viewpoint of preventing deterioration of polarizing plates, etc., a method of transferring an adhesive layer provided on a separator can also be preferably applied. The thickness of the adhesive layer provided may be determined as appropriate. It is generally set in the range of 1 to 500.

By the way, a polarizing plate made by dyeing polyvinyl alcohol-based stretched film with iodine (transmittance 45%, polarization degree 9)
An adhesive layer made of an acrylic adhesive is provided on one side of the film (4%), and a retardation plate made of a birefringent film made of stretched polycarbonate film (retardation 580
An adhesive layer made of the same (acrylic adhesive) is provided on both sides of the polarizing plate and the retardation plate is attached to the retardation plate through the adhesive layer.
They were adhered using a laminator heated to 0.degree. C. to obtain an elliptically polarizing plate. At that time, the adhesive layer of the outer retardation plate was protected with a separator.

On the other hand, an elliptically polarizing plate was obtained by a conventional method using the same polarizing plate, retardation plate, and adhesive. That is, the adhesive layer provided on the polarizing plate was directly adhered to the exposed surface of the retardation plate (FIG. 2).

The two types of elliptically polarizing plates (Example and Conventional Example) obtained above were adhered to a liquid crystal display (Fig. 3) and left in an atmosphere of 60°C, 70°C or 80°C for 100 hours to cause them to float and foam. I investigated the situation.

The above results are shown in the table.

Note that when the adhesive layer 3 was provided only on the retardation plate 4 and the polarizing plate 1 was directly adhered thereto, no lifting or foaming occurred even at 70°C, which was superior to the previous method.

The elliptically polarizing plate of the present invention cancels coloring due to phase difference in a display using a birefringent liquid crystal cell such as an STN liquid crystal cell, and is preferably used for forming an FTN black and white display with excellent contrast. Cancellation of coloring is achieved by using a retardation plate that compensates for the retardation due to birefringence of the liquid crystal cell, including the wavelength-dependent birefringence.

Effects of the Invention According to the present invention, an elliptically polarizing plate having excellent durability can be obtained. As a result, it is possible to prevent the fatal problem of not being able to see the displayed content on the display due to floating or foaming of the elliptically polarizing plate.

[Brief explanation of drawings]

FIG. 1 is an explanatory sectional view of a process example of the embodiment, FIG. 2 is an explanatory sectional view of a conventional example, and FIG. 3 is a sectional view of an application example of an elliptically polarizing plate. 1: Polarizing plate made of polarizing film 2. 3, 5: Adhesive layer 4, Retardation plate made of birefringent film 6: Elliptical polarizing plate 7: Display panel 8 Polarizing plate patent applicant Nitto Denko Corporation

Claims (1)

[Claims] 1. A method for manufacturing an elliptically polarizing plate, which comprises adhering a polarizing plate made of a polarizing film and a retardation plate made of a birefringent film via adhesive layers provided on each.