JP2000035567A - Plastic substrate for liquid crystal element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plastic substrate for a liquid crystal element which can construct a liquid crystal element with high reliability as an optical device. SOLUTION: In a liquid crystal display element 20 formed by interposing a liquid crystal layer 27 between a pair of substrates 29a, 29b, inorganic gas barrier films 23a, 23b are formed on at least one surface of a pair of plastic substrates 21a, 21b and hard coat layers 22a, 22b are laminated and formed on the inorganic gas barrier films 23a, 23b. ITO films 24a, 24b and alignment films 25a, 25b are formed on the one surface of the plastic substrates 21a, 21b on which the inorganic gas barrier films are formed. the substrates 29a, 29b are stuck together so that the surfaces of the substrates 29a, 29b on which ITO films 24a, 24b are formed, are opposite to each other and the liquid crystal layer 27 is formed and sealed with a sealant 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic substrate constituting a liquid crystal element with a liquid crystal layer interposed therebetween.
In particular, the present invention relates to a plastic substrate for a liquid crystal element on which an inorganic gas barrier film is formed.

[0002]

2. Description of the Related Art In order to reduce the thickness and weight of a liquid crystal display element and improve the processability of the substrate, attempts have been made to form a substrate of the liquid crystal display element using a plastic material instead of glass. However, the gas permeability of the plastic substrate is higher than that of the glass substrate, so that the gas transmitted from the outside becomes bubbles in the liquid crystal layer, resulting in display failure of the liquid crystal display element.

For this reason, as disclosed in Japanese Patent Application Laid-Open No. 3-138617, a gas barrier film of a metal oxide or metal nitride such as Si or Ti having a light transmitting property is sputtered on the surface of a plastic substrate of a liquid crystal display element. There has been proposed a structure formed by a method or the like to suppress gas permeability of a plastic substrate.

FIG. 3 is a sectional view showing the structure of a conventional liquid crystal display device 10. As shown in FIG. The liquid crystal display element 10 includes a pair of substrates 1
A liquid crystal layer 7 is sealed between 1a and 11b and sealed by a sealing material 6 to be formed. The pair of substrates 11a, 1
1b, hard coat films 2a and 2b are formed on both surfaces of plastic substrates 1a and 1b, and gas barrier films 3a and 3b made of an amorphous metal oxide or metal nitride such as Si or Ti are formed on the hard coat films 2a and 2b. Transparent electrodes 4a and 4b such as ITO (indium tin oxide) and alignment films 5a and 5b are formed on the surfaces to be formed.

[0005]

When the plastic substrates 1a and 1b are subjected to film processing in the above-described order and, for example, SiO ₂ is selected as the gas barrier films 3a and 3b,
The SiO ₂ films 3a, 3b and the ITO films 4a,
4b can be formed continuously in the same apparatus by a sputtering method. Therefore, in order to keep the manufacturing cost low, film processing is conventionally performed on the plastic substrates 1a and 1b as shown in FIG.

However, the thickness of the above-mentioned ITO films 4a and 4b is 700 to 2000 、, and the thickness of the SiO ₂ films 3 a and 3 b is 600 to 1000 、. May occur. Therefore, when minute foreign matter enters the liquid crystal layer 7 or the like in the process of manufacturing the liquid crystal display element, the ITO films 4a, 4b
The gas barrier films 3a and 3b in the portions where no gas is formed come into direct contact with the foreign matter, and the gas barrier films 3a and 3b are pressed by a process such as pressing the bonded substrate.
b will cause cracks. As a result, the gas that has passed through the plastic substrates 1a and 1b is cracked by the liquid crystal layer 7
There is a problem in that the liquid crystal layer penetrates into the liquid crystal layer to generate air bubbles in the liquid crystal layer 7 of the liquid crystal display element 10, resulting in poor reliability as an optical device.

An object of the present invention is to solve the above problems and to provide a plastic substrate for a liquid crystal element capable of forming a highly reliable liquid crystal element as an optical device.

[0008]

In order to achieve the above object, a plastic substrate for a liquid crystal element according to the present invention is a plastic substrate for a liquid crystal element on which an inorganic gas barrier film is formed. It is characterized in that a coat layer is formed.

According to the plastic substrate for a liquid crystal element of the present invention, a plastic substrate on which a liquid crystal element is formed with a liquid crystal layer interposed is provided with an inorganic gas barrier film for preventing gas permeation of the plastic substrate. Further, a hard coat layer for protecting the inorganic gas barrier film is provided thereon. The inorganic gas barrier film formed thereunder is protected by the hard coat layer, and it is possible to prevent the inorganic gas barrier film from being damaged by fine foreign matter in the outside air in the process of manufacturing the liquid crystal element.

Therefore, the reliability of the inorganic gas barrier film in preventing gas permeation can be improved, and the reliability of the liquid crystal element as an optical device can be improved.

[0011]

FIG. 1 is a sectional view showing the structure of a liquid crystal display device 20 according to one embodiment of the present invention, and FIG.
13 is a cross-sectional view showing another example of the substrate 29 shown in FIG. As shown in FIG. 1, the liquid crystal display element 20 is formed by injecting a liquid crystal layer 27 between a pair of plastic substrates 29 a and 29 b that have been subjected to a film treatment, and sealing with a sealant 26. The substrate 29a has a size of 300 mm × 324 mm and a thickness of 0.4 mm.
An inorganic gas barrier film 23a made of a SiO _x film is formed to a thickness of about 600 ° on one surface of an acrylic plastic substrate 21a having a thickness of 2 mm by sputtering. Thereafter, the substrate 21a is coated with a hard coat agent mixed with Si particles based on a siloxane-based material by a dipping method, and sintered to form a hard coat film 22a having a thickness of 1.5 to 2 nm.
Are formed on both surfaces of the plastic substrate 21a. The hard coat film 22a is formed of an inorganic gas barrier film 2 serving as a base.
3a and the plastic substrate 21a are protected, and the adhesion of the ITO film 24a formed on the hard coat film 22a by the sputtering method is improved.

Further, an ITO film 24a is formed by sputtering on the hard coat film 22a on the side of the plastic substrate 21a on which the inorganic gas barrier film 23a is formed. An electrode pattern is formed on the ITO film 24a using a known method such as etching. Further, after an alignment film 25a is formed by laminating it, the alignment film 25a is subjected to an alignment treatment such as rubbing. Further, as in the liquid crystal display element 20a shown in FIG. 2, the substrate 29a may have an inorganic gas barrier film 23a made of SiO _x formed on both surfaces of the plastic substrate 21a. The substrate 29b is similar to the substrate 29a.

[0013] The liquid crystal display device 20,20a formed in the manner described above, the inorganic gas barrier layer 2 made of SiO _x
Accelerated tests were performed on both the substrates 3a and 23b formed on one side and the substrates formed on both sides of the plastic substrates 21a and 21b. In the accelerated test,
The liquid crystal display elements 20 and 20a are stored in an energized state and a non-energized state in an environment of a temperature of 40 ° C. and 95%, a temperature of 60 ° C. and 95%, and a temperature of 70 ° C. and 95%, respectively. In any of the above cases, no bubbles were generated in the liquid crystal layer 27 in the liquid crystal display elements 20 and 20a until 1000 hours. Further, the temperature is 50 ° C. and the pressure is 5 kgf.
/ Cm ² for 12 hours, the liquid crystal layer 27
No air bubbles were found inside.

As described above, according to the present embodiment, the liquid crystal display elements 20 and 20a are provided with a pair of plastic substrates 21a and 21a.
Inorganic gas barrier film 23a made of SiO _x on the surface opposite interposed at least the liquid crystal layer 27 of 21b, 23b
Are formed, and the inorganic gas barrier films 23a, 23
b and the hard coat films 22a and 22b
a, 21b are formed on both surfaces. As a result, the inorganic gas barrier films 23a and 23b formed on the plastic substrates 21a and 21b are covered with the hard coat films 22a and 22b, so that the inorganic gas barrier films 23a and 23b come into contact with minute foreign substances in the outside air in the manufacturing process. 23b
Can be prevented from being damaged. Therefore, as a result, the reliability of preventing gas permeation of the inorganic gas barrier films 23a and 23b can be improved, and the display reliability of the liquid crystal display devices 20 and 20a can be improved.

Although the present embodiment has been described by taking a liquid crystal display element as an example, the present invention may be applied to a liquid crystal element used for an optical compensator in which an ITO film as a transparent electrode is not formed.

[0016]

As described above, according to the plastic substrate for a liquid crystal element of the present invention, a hard coat layer is formed by laminating an inorganic gas barrier film on a plastic substrate having a liquid crystal layer interposed therebetween. Thus, it is possible to prevent the occurrence of minute scratches on the inorganic gas barrier film. As a result, the reliability of the inorganic gas barrier film in preventing gas permeation can be improved, and the reliability of the liquid crystal element as an optical device can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a liquid crystal display element 20 according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view showing another example of the substrates 29a and 29b shown in FIG.

FIG. 3 is a cross-sectional view showing a configuration of a conventional liquid crystal display element 10.

[Explanation of symbols]

 20, 20a Liquid crystal display element 21a, 21b Plastic substrate 22a, 22b Hard coat film 23a, 23b Inorganic gas barrier film 24a, 24b ITO film (transparent electrode) 25a, 25b Alignment film 26a, 26b Seal material 27a, 27b Liquid crystal layer 29a, 29b substrate

Claims (1)

[Claims] 1. A plastic substrate for a liquid crystal element on which an inorganic gas barrier film is formed, wherein a hard coat layer for protecting the inorganic gas barrier film is formed.