JPH06208108A - Liquid crystal display element and manufacture thereof - Google Patents

Abstract

PURPOSE:To achieve thinning and weight reduction by providing a base plate whose elongation under a high-temperature high-humidity condition is larger than the elongation of a polarization plate, so that the warping of a plastic-film base plate on the opposite side of a liquid crystal can be restrained even under a high-temperature high-humidity condition, and also the cell gap can be evened and color spots can be hardly caused. CONSTITUTION:When a base plate 2 warps toward the liquid crystal 3 side, the gap between base plates 1 is restrained by gap agents 4, so that the evenness of the cell gap can be maintained. On the other hand, when the base plate 2 warps toward the opposite side of the liquid crystal 3, the unevenness of the cell gap is caused, and also the strain becomes large. Accordingly, by providing a base plate 1 whose elongation under a high-temperature high-humidity condition is larger than the elongation of a polarization plate 5, the elongation of the polarization plate 5 under a high- temperature high-humidity condition is made smaller than or equal to the elongation of the base plate 1. Thus, the warping of the base plate 1 toward the opposite side of the liquid crystal 3 that has been caused under a high-temperature high-humidity condition can be changed to the warping toward the liquid crystal 3 side or the warping can be eliminated, so that the warping can be restrained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a method for manufacturing the same, and more particularly, it can be applied to a liquid crystal display device using a plastic film substrate, and in particular, a thick reinforcing plate is provided. The present invention relates to a liquid crystal display element capable of suppressing the warp of a plastic film substrate on the side opposite to the liquid crystal side even under high temperature and high humidity, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In a conventional liquid crystal display element, a gap agent is sandwiched between upper and lower substrates made of a plastic film on which ITO electrodes and the like are sandwiched and bonded with a sealant, and a liquid crystal is injected between the upper and lower substrates. In addition, it is known that the injection port is sealed with a sealant. Since this liquid crystal display element is composed of a plastic film substrate,
It has the advantages that it is thinner and lighter than an element composed of a glass substrate, and that it can be bent easily.

[0003]

However, in the conventional liquid crystal display element as described above, since the substrate is made of a plastic film, it is particularly exposed to high temperature and high humidity (for example, reliability under high temperature and high humidity). At the time of the test), there is a problem that the plastic substrate is apt to be deformed such as warped or distorted, which makes the cell gap non-uniform and easily causes color spots. In this conventional liquid crystal display element, since the gap agent is provided between the upper and lower substrates as described above, warpage of the plastic film substrate toward the liquid crystal side can be suppressed, but it is opposite to the liquid crystal side of the plastic film substrate. The warp to the side could not be suppressed.

Therefore, as a conventional liquid crystal display device which solves the above problem, there has been proposed a device in which a plastic film reinforcing plate is provided on the surface of the plastic film substrate opposite to the liquid crystal side. However, this method has an advantage that the above problem can be solved by making the reinforcing plate a thick plate, but the advantages of using a plastic film substrate, such as thinness and lightness, are impaired. There was a problem of being lost.

Therefore, according to the present invention, the warp of the plastic film substrate on the side opposite to the liquid crystal side can be suppressed even under high temperature and high humidity without providing a thick reinforcing plate, and the cell gap is made uniform to cause color spots. It is an object of the present invention to provide a liquid crystal display device which can be made difficult and can be made thin and lightweight, and a manufacturing method thereof.

[0006]

The invention according to claim 1 is
A liquid crystal display device in which a liquid crystal is sealed between upper and lower substrates made of a plastic film to form a liquid crystal cell, and a polarizing plate is attached to the substrate surface of the liquid crystal cell on the side opposite to the side in which the liquid crystal is sealed. In the above, the substrate is provided such that the elongation under high temperature and high humidity is equal to or larger than the elongation of the polarizing plate. Under high temperature and high humidity according to the present invention, room temperature ~
Including the conditions of 80 ° C. and 60 to 95% RH.

According to a second aspect of the present invention, liquid crystal is sealed between upper and lower substrates made of a plastic film to form a liquid crystal cell, and the substrate surface of the liquid crystal cell opposite to the side where the liquid crystal is sealed. In the method for producing a liquid crystal display device in which the polarizing plate is adhered to, the method includes a step of adhering to the substrate of the liquid crystal cell a polarizing plate treated so that the elongation under high temperature and high humidity is smaller than the elongation of the substrate. It is characterized by that.

According to a third aspect of the present invention, in the above-mentioned second aspect of the invention, the treatment is performed by exposing the polarizing plate to high humidity and expanding the substrate more than elongation of the substrate under high temperature and high humidity. It is characterized by performing. According to a fourth aspect of the present invention, liquid crystal is sealed between upper and lower substrates made of a plastic film to form a liquid crystal cell, and a polarizing plate is provided on the substrate surface of the liquid crystal cell on the side opposite to the side where the liquid crystal is sealed. In the method of manufacturing a liquid crystal display element, which is attached,
The method is characterized by including the step of attaching the polarizing plate to the substrate of the liquid crystal cell which is treated so that the elongation under high temperature and high humidity is larger than that of the polarizing plate.

According to a fifth aspect of the present invention, in the above-mentioned fourth aspect of the invention, the treatment is performed by exposing the liquid crystal cell to low humidity to cause contraction rather than elongation of the polarizing plate under high temperature and high humidity. It is characterized by that.

[0010]

As a result of repeating various experiments while thinking and making mistakes, the inventors of the present invention found that the cell gap nonuniformity or distortion of the liquid crystal panel generated under high temperature and high humidity at the time of the reliability test was different from that of the substrate and the polarizing plate. We paid attention to the fact that it was largely influenced by the treatment of 1), and the main cause was due to the difference in the dimensional change amount between the polarizing plate and the substrate which occurred under high temperature and high humidity. For example, when a polarizing plate and a substrate are attached to each other, if the stretching of the polarizing plate is larger than that of the substrate, a concave curl is formed with the substrate facing upward, and the substrate warps on the side opposite to the liquid crystal side. On the other hand, if the elongation of the substrate is larger than that of the polarizing plate, a convex curl with the substrate facing up,
The substrate warps on the liquid crystal side. Hereinafter, a specific description will be given with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a liquid crystal display device for explaining the principle of the present invention. In FIG. 1, 1 is a plastic film substrate, 2 is a sealant formed around the plastic film substrate 1, and 3 is a liquid crystal sealed between the plastic film substrates 1 via a gap agent 4, Reference numeral 5 denotes a polarizing plate attached to the surface of the plastic film substrate 1 opposite to the liquid crystal 3 side. If the substrate 2 warps to the liquid crystal 3 side (in the case of convex curl),
As shown in (a), since the gap between the substrates 1 is suppressed by the gap agent 4, the cell gap is kept uniform. On the other hand, the substrate 2 warps on the side opposite to the liquid crystal 3 side (concave curl).
Then, as shown in FIG. 1B, the cell gap becomes non-uniform, and the strain increases. As a result, the plastic film liquid crystal panel, when exposed to high temperature and high humidity,
Since both the polarizing plate 5 and the substrate 2 have large dimensional changes due to temperature and humidity, they are controlled as will be described later to prevent concave curl even under high temperature and high humidity as shown in FIG. 1 (b). A highly reliable liquid crystal display device could be obtained. The operation of the present invention will be described below for each claim.

According to the first aspect of the present invention, since the substrate is provided such that the elongation under high temperature and high humidity is equal to or larger than the elongation of the polarizing plate, the elongation of the polarizing plate under high temperature and high humidity can be improved. It may be less than the elongation, or each elongation may be equal. Therefore, it is possible to suppress the warp of the substrate on the side opposite to the liquid crystal side, which has occurred under high temperature and high humidity in the past, by eliminating the warp or warpage of the substrate to the liquid crystal side. However, the cell gap can be kept uniform, and a highly reliable liquid crystal panel in which color spots hardly occur can be obtained. Moreover, since a thin and lightweight polarizing plate can be used instead of providing a thick plastic film reinforcing plate as in the related art, thinning and weight reduction can be realized. The warp of the polarizing plate and the substrate toward the liquid crystal side can be suppressed by the gap agent interposed between the substrates as described above.

According to a second aspect of the present invention, since a polarizing plate treated so that its elongation under high temperature and high humidity is smaller than that of the substrate is attached to the substrate of the liquid crystal cell, the above-mentioned invention is adopted. Similarly to the invention described above, the elongation of the polarizing plate under high temperature and high humidity can be made smaller than that of the substrate, and the warp of the substrate on the side opposite to the liquid crystal side that has conventionally occurred under high temperature and high humidity is determined by the polarizing plate. It can be suppressed by the warp of the substrate to the liquid crystal side. Therefore, the same effect as that of the invention described in claim 1 can be obtained.

According to the invention of claim 3, after exposing the polarizing plate to high humidity to expand it more than the elongation of the substrate under high temperature and high humidity,
Since it is attached to the substrate of the liquid crystal cell to configure the structure, the above-mentioned claim 2
Similar to the invention described above, the elongation of the polarizing plate under high temperature and high humidity can be made smaller than that of the substrate, and the same effect as that of the invention of claim 2 can be efficiently obtained. In the invention according to claim 4, the polarizing plate is attached to the substrate of the liquid crystal cell which is treated so that the elongation under high temperature and high humidity is larger than the elongation of the polarizing plate. Similar to the invention, the elongation of the substrate under high temperature and high humidity can be made larger than that of the polarizing plate, and the warp of the substrate on the side opposite to the liquid crystal side that has conventionally occurred under high temperature and high humidity can be used for the polarizing plate and the substrate. Can be suppressed by the warp of the liquid crystal to the liquid crystal side. Therefore, the same effect as that of the invention described in claim 1 can be obtained.

According to the invention of claim 5, the liquid crystal cell is exposed to low humidity to shrink more than the expansion of the polarizing plate under high temperature and high humidity, and then the polarizing plate is attached to the substrate of the liquid crystal cell.
Similar to the invention described in claim 4, the elongation of the substrate under high temperature and high humidity can be made larger than that of the polarizing plate, and the same effect as that of the invention described in claim 4 can be efficiently obtained. .

[0016]

【Example】

(Example 1) Polyether sulfone (PE
S) The film used was a solvent resistant coat and a gas barrier coat. An ITO electrode is formed on this substrate, and this I
An oriented polyimide film was provided so as to cover the TO electrode. Then, a gap agent made of glass beads was sandwiched between the upper and lower substrates and bonded with an epoxy sealant. Next, liquid crystal was injected into this through an injection port, and the injection port was closed with an epoxy-based sealant to form a liquid crystal cell. Polyethylene terephthalate (PET) is used as the substrate of this liquid crystal cell.
A -2 color dye type polarizing plate was attached. When this liquid crystal panel was left in a high temperature and high humidity environment of 40 ° C. and 90% RH, no abnormality such as color spots or large distortion was observed on the liquid crystal panel even after 1000 hours.

In this example, the PES film used has a larger elongation at high temperature and high humidity than PET used for the polarizing plate. Any other substrate or polarizing plate may be used as long as the substrate and the polarizing plate satisfying this relationship are combined, and for example, a PET substrate and a PET polarizing plate having the same elongation may be used. (Example 2) Next, a polarizing plate in which a polyvinyl alcohol (PVA) -iodine type polarizer, which is commonly used, is sandwiched between cellulose type films is used. Since this polarizing plate has a large elongation under high temperature and high humidity, when formed into a panel in the same manner as in Example 1, the uniform cell gap cannot be maintained under high temperature and high humidity. Therefore, the polarizing plate was left in a high humidity environment of room temperature 95% RH for 100 hours, and then the high temperature and high humidity (40 ° C.
After being expanded more than the elongation of the substrate of 90% RH), it was attached to the substrate of the liquid crystal cell. The other panel forming steps were performed in the same manner as in Example 1 above. When this liquid crystal panel was left in an environment of 40 ° C. and 90% RH, no abnormality such as color spots or large distortion was observed even after 500 hours had passed.

(Embodiment 3) Next, the liquid crystal cell after the injection port is sealed, which is manufactured by the same panelizing process as that of Embodiment 1, is left for 100 hours in a low humidity at room temperature of 10% RH or less,
After shrinking the polarizing plate under high temperature and high humidity (40 ° C., 90% RH) more than the elongation, the same polarizing plate as that of Example 2 (which was placed under normal temperature and normal humidity) was attached. Then, when this liquid crystal panel was left in an environment of 40 ° C. and 90% RH,
After 500 hours, no abnormality such as color spots or large distortion was observed on the liquid crystal panel.

The low-humidity treatment of the cells may be carried out by leaving it under a reduced pressure atmosphere. In this case, the same effect as that of the third embodiment can be obtained and the process time can be further shortened.

[0020]

According to the present invention, the warp of the plastic film substrate on the side opposite to the liquid crystal side can be suppressed even under high temperature and high humidity without providing a thick reinforcing plate, and the cell gap can be made uniform. There is an effect that it is possible to make the unevenness less likely to occur and to realize thinning and weight reduction.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of a liquid crystal display element for explaining the principle of the present invention.

[Explanation of symbols]

 1 plastic film substrate 2 sealant 3 liquid crystal 4 gap member 5 polarizing plate

Claims (5)

[Claims] 1. A liquid crystal cell is formed by enclosing a liquid crystal between upper and lower substrates made of a plastic film, and a polarizing plate is attached to the substrate surface of the liquid crystal cell on the side opposite to the side in which the liquid crystal is enclosed. In the liquid crystal display element, the liquid crystal display element is provided with a substrate whose elongation under high temperature and high humidity is equal to or larger than that of the polarizing plate. 2. A liquid crystal cell is formed by enclosing a liquid crystal between upper and lower substrates made of a plastic film, and the polarizing plate is attached to the substrate surface of the liquid crystal cell opposite to the side in which the liquid crystal is enclosed. In the method for producing a liquid crystal display element, the liquid crystal comprising a step of attaching a polarizing plate treated so that the elongation under high temperature and high humidity is smaller than the elongation of the substrate to the substrate of the liquid crystal cell. Display element manufacturing method. 3. The liquid crystal display device according to claim 2, wherein the treatment is performed by exposing the polarizing plate to high humidity to expand the substrate more than the elongation of the substrate under high temperature and high humidity. Production method. 4. A liquid crystal is formed between upper and lower substrates made of a plastic film to form a liquid crystal cell, and a polarizing plate is attached to the substrate surface of the liquid crystal cell opposite to the side where the liquid crystal is enclosed. In the method of manufacturing a liquid crystal display element,
A method for producing a liquid crystal display element, which comprises a step of attaching the polarizing plate to a substrate of a liquid crystal cell which is treated so that its elongation under high temperature and high humidity is larger than that of the polarizing plate. 5. The manufacturing of a liquid crystal display device according to claim 4, wherein the treatment is performed by exposing the liquid crystal cell to low humidity to cause the liquid crystal cell to contract more than the elongation of the polarizing plate under high temperature and high humidity. Method.