JPH06342105A - Manufacture of phase plate for liquid crystal display - Google Patents

Abstract

PURPOSE:To provide the manufacture of a phase plate for the liquid crystal display, with which the peeling of the upperside polarizing plate laminated on the upper surface of the phase plate at the interface between them and bubbles in the pressure sensitive adhesive layers are prevented from being generated under high temp. and high humidity conditions by including a stage for performing a plasma treatment on one surface of an oriented film and a stage for providing both surfaces of the oriented film with the pressure sensitive adhesive layers. CONSTITUTION:In the first stage, at least one surface of the oriented film 1 consisting of a uniaxially oriented hydrophobic plastic film is plasma-treated with e.g. a parallel electrode plasma-generating device. At this time, a tightly sealed space is provided in the bell jar 11 and evacuated to a reduced pressure and the reduced pressure is kept constant at the time of performing the plasma treatment. At the same time, the oriented film 1 is mounted on the lower electrode of the two electrodes 12 arranged parallel to each other and a voltage from the high-frequency power source 13 is applied between the two electrodes 12 to generate a plasma atmosphere. Then a gas is supplied into the space between the electrodes 12 in the plasma atmosphere through the gas supply line 14 to plasma-treating the surface of the oriented film 1. In the second stage, both surfaces of the plasma-treated oriented film 1 are provided with the pressure sensitive adhesive layers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a retardation plate for a liquid crystal display using a liquid crystal cell.

[0002]

2. Description of the Related Art Generally known liquid crystal displays are
As shown in FIG. 4, the liquid crystal cell 4 is used in a form in which an upper polarizing film 3a and a lower polarizing film 3b are attached to the upper and lower surfaces of the liquid crystal cell 4 with pressure-sensitive adhesive layers 2 interposed therebetween. However, in the liquid crystal display having such a structure, the display is in a slightly colored state due to secondary refraction of light by the polarizing plate film, or the difference in shade between the image and the background, that is, the so-called contrast is not sufficiently obtained. There was a problem.

Therefore, in order to solve the above problem, FIG.
As shown in, it is considered to provide a retardation plate made of a stretched film 1 such as a polycarbonate resin as an optical correction plate between the upper polarizing film 3a and the liquid crystal cell 4. That is, the upper polarizing plate film 3a provided with the pressure sensitive adhesive layer 2 is laminated with the stretched film 1 to form a composite, which is attached to one surface of the liquid crystal cell 4 via the pressure sensitive adhesive layer 2. By attaching the retardation film, the retardation plate is interposed between the upper polarizing plate film and the liquid crystal cell.

However, in the conventional liquid crystal display provided with a retardation plate, peeling or air bubbles are generated between the retardation plate and the upper polarizing plate film under the conditions of high temperature and high humidity for conducting a characteristic test such as heat resistance and humidity resistance. As a result, there is a problem that sufficient characteristics such as image quality cannot be obtained.

In order to solve such a problem, Japanese Patent Laid-Open No. Hei 3
In No. 129322, a retardation plate having a specific resin layer on the surface and a pressure-sensitive adhesive layer on the other surface is proposed.
In the high temperature and high humidity atmosphere, the problem of peeling and bubbles between the retardation plate and the upper polarizing plate could not be completely solved.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a phase difference in which peeling does not occur between the retardation plate and the upper polarizing plate under high temperature and high humidity conditions, and bubbles are not generated in the adhesive layer. It is an object to provide a method for manufacturing a plate.

[0007]

The present invention comprises (A) a step of subjecting at least one surface of a stretched film made of a hydrophobic plastic to plasma treatment, and (B) a pressure-sensitive adhesive layer on both sides of the stretched film. And a method of manufacturing a retardation plate for a liquid crystal display.

That is, the first step of the method for producing a retardation plate for a liquid crystal display of the present invention is polycarbonate,
At least one surface of a stretched film made of a uniaxially stretched hydrophobic plastic such as vinylidene chloride, cellulose triacetate, or polystyrene is subjected to plasma treatment by, for example, a parallel electrode plasma apparatus as shown in FIG.

The bell jar 11 shown in FIG. 1 is a closed space, and the stretched film 1 is placed on the lower electrode plates of two electrode plates 12 which are depressurized and maintained at a constant pressure during plasma processing and arranged in parallel with each other. Place and place a voltage between the electrodes by the high frequency power supply 13 to create a plasma atmosphere,
Gas is supplied to the plasma atmosphere from the gas supply passage 14 under the plasma atmosphere to plasma-treat the surface of the stretched film. Reference numeral 15 is a column for supporting the upper electrode plate, and 16 is an exhaust port for exhausting gas in the bell jar.

The apparatus and electrodes used for the plasma treatment are not particularly limited. The discharge method is also not limited, and any of DC discharge, low frequency discharge, high frequency discharge, microwave discharge, etc. may be used.

The plasma processing gas of the present invention is oxygen gas,
At least one selected from nitrogen gas, argon gas, hydrogen gas, dry air, ammonia gas, and helium gas.

In the present invention, for example, a high frequency power source (1
(3.56MHz), the output is 0.1W /
Within the range of cm ^{2 to 20} W / cm ² , particularly preferably 0.1.
It is desirable to set in the range of up to 2.0 W / cm ² . If it is 20 W / cm ² or more, the output of the plasma treatment is too strong and the stretched film deteriorates.
^When it is ² or less, plasma is not generated, which is not preferable.

Further, in the present invention, it is desirable that the pressure during the plasma treatment is set within the range of 0.01 to 10 Torr, particularly preferably within the range of 0.05 to 2 Torr. If the plasma treatment is performed at 0.01 Torr or less, the plasma treatment effect is small and plasma is not generated at 10 Torr or more, which is not preferable.

Further, in the present invention, it is desirable that the plasma treatment time is set within the range of 0.5 seconds to 10 minutes, particularly preferably within the range of 10 seconds to 5 minutes. If the plasma treatment is performed for 0.5 seconds or less, the plasma treatment effect is small and 1
If the plasma treatment is performed for 0 minutes or more, the stretched film deteriorates, which is not preferable.

In the present invention, the stretched film may be plasma-treated on one side or both sides of the film. When processing on one side, it is preferable to set the conditions so that the rear surface of the film can also be modified by the plasma treatment.

Next, in the second step of the present invention, pressure-sensitive adhesive layers are provided on both sides of the plasma-treated stretched film. The method for providing the pressure-sensitive adhesive layer is a roll coating method, a blade coating method, a spray coating method, which is a coating liquid prepared by dispersing or dissolving the following materials for forming the pressure-sensitive adhesive layer in water or a suitable solvent. The stretched film is applied and dried by a coating method such as an air knife coating method and a Mayer bar coating method.

In the pressure-sensitive adhesive layer in the present invention, for example, butyl acrylate as a monomer component, or 2
-Acrylic pressure-sensitive adhesives, rubber-based adhesives, silicone-based adhesives, etc., which contain ethylhexyl acrylate as a main component and have a carboxyl group, a hydroxyl group, or an amino group introduced as a functional group, but are not limited to these is not.

The thickness of the pressure-sensitive adhesive layer is 5 to 50 μm.
m, preferably about 10 to 30 μm. In the production method of the present invention, it is preferable to laminate a release sheet on the pressure-sensitive adhesive layer constituting the obtained retardation plate in order to protect the layer.

As shown in FIG. 2, the retardation plate for liquid crystal display obtained by the present invention has a stretched film 1 having a plasma treated surface 5 on one side and a pressure sensitive adhesive layer 2 on both sides. Or, as shown in FIG. 3, the stretched film 1 has plasma-treated surfaces 5 on both sides,
The pressure sensitive adhesive layer 2 is provided on both sides.

[0020]

EXAMPLES The present invention will be described in more detail by way of examples.

Example 1 One side of a stretched film made of a hydrophobic plastic of polycarbonate uniaxially stretched to a thickness of 85 μm was subjected to plasma treatment using the apparatus shown in FIG. The plasma treatment was performed using a high frequency power source with an argon flow rate of 20 cc / min and 13.56 MHz under the conditions of 1 W / cm ² , 0.1 Torr and a treatment time of 30 seconds.

Next, an acrylic pressure-sensitive adhesive (manufactured by Toyo Ink Co., trade name: BPS-5127) as a pressure-sensitive adhesive is applied to both sides of the plasma-treated film so as to have a film thickness of 35 μm, and dried. A pressure sensitive adhesive layer was provided, and a retardation plate for a liquid crystal display according to the present invention was produced.

Comparative Example 1 A retardation plate for a liquid crystal display was produced in the same manner as in Example 1 except that a stretched film that was not subjected to plasma treatment was used.

Using the retardation plates obtained in Example 1 and Comparative Example 1 above, the characteristics were evaluated in the following manner.

(1) Evaluation of Adhesive Interface with Polarizing Plate One side of the retardation plate of Example 1 and Comparative Example 1 had a film thickness of 180 μ having a three-layer structure of cellulose triacetate / polyvinyl alcohol / cellulose triacetate.
The m polarizing plate was laminated at room temperature under normal pressure using a table laminator. Next, on the opposite side of the retardation plate, which is laminated with the polarizing plate, soda glass is laminated under the same conditions as,
This was used as a test sample. The above test sample was (A) 50 at 70 ° C in a dry state.
The condition of the pressure-sensitive adhesive layer was visually evaluated after maintaining the conditions for 0 hours (B) in an environment of 60 ° C. and 90% RH for 500 hours.

As shown in Table 1, when the retardation plate produced by the production method of the present invention is used, peeling and air bubbles do not occur at high temperature and high humidity at the adhesive interface with the polarizing plate, and thus a stretched film is obtained. It was confirmed that the effect of plasma treatment was sufficient.

[0027]

[Table 1]

(2) Evaluation of Peel Strength A polyethylene terephthalate (PET) film was placed on one surface of each of the retardation plates of Example 1 and Comparative Example 1 at room temperature,
Laminated using a table laminator under normal pressure. Next, the opposite surface side of the retardation plate bonded to the PET film was bonded in the same manner as the soda glass, and this was used as a test sample. The 180 ° peel strength between the PET film and the retardation plate of the above test sample was measured at a peel rate of 100 mm / mi.
Under the conditions of n, the measurement was performed under each atmosphere of (A) 25 ° C. and (B) 80 ° C.

The results are shown in Table 2, and it was confirmed that excellent peeling strength was obtained when the retardation plate according to the manufacturing method of the present invention was used.

[0030]

[Table 2]

[0031]

In the production method of the present invention, the wettability of the surface of the stretched film constituting the retardation plate is improved by plasma-treating the stretched film, and the pressure-sensitive adhesive layer under high temperature and high humidity. It was possible to improve the adhesiveness with. That is, it is a manufacturing method capable of providing an excellent retardation plate in which peeling and air bubbles do not occur between the stretched film and the pressure-sensitive adhesive layer.

[Brief description of drawings]

FIG. 1 shows an example of an apparatus for manufacturing a retardation plate for a liquid crystal display according to the present invention.

FIG. 2 is a schematic sectional view of an example of a retardation plate for a liquid crystal display obtained by the present invention.

FIG. 3 is another schematic cross-sectional view of the retardation plate for a liquid crystal display obtained by the present invention.

FIG. 4 is a schematic sectional view of a liquid crystal display.

FIG. 5 is a schematic sectional view of a liquid crystal display having a retardation plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stretched film 2 Pressure-sensitive adhesive layer 3a, 3b Polarizing plate 4 Liquid crystal cell 11 Bell jar 12 Parallel electrode plate 13 High frequency power supply 14 Gas supply path 15 Strut 16 Exhaust port

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[Procedure amendment]

[Submission date] February 24, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

In the present invention, the stretched film may be plasma-treated on one side or both sides of the film. When processing one surface, masking should be done so that the back surface is not affected. In the case of treating both sides, one side is treated first and the other side is treated, or both sides are treated by setting conditions so that the rear surface of the film is modified by the plasma treatment. However, the method is not limited thereto.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuji Tanaka 3-1, Sobamachi, Shizuoka City, Shizuoka Prefecture

Claims (1)

[Claims] 1. A process comprising: (A) subjecting at least one surface of a stretched film made of a hydrophobic plastic to plasma treatment; and (B) providing a pressure-sensitive adhesive layer on both sides of the stretched film. A method of manufacturing a retardation plate for a liquid crystal display, comprising: