JPH1054977A - Liquid crystal panel and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the uniformity of a panel gap and to obtain the good uniformity of a display. SOLUTION: A transparent adhesive 8 is applied over the entire part of the rear surface of a first substrate having plural pixel electrodes 2 and a transparent substrate 9 is adhered by the transparent adhesive 8 over the entire part of the rear surface of the first substrate 1. At this time, the first substrate 1, the adhesive 8 and the transparent substrate 9 having nearly the same refractive indices are used so as to prevent the reflection on each other. The first substrate 1 and a second substrate 4 having counter electrodes 3 facing the plural pixel electrodes 2 and color filters are disposed to face each other apart a prescribed interval and both substrates are stuck to each other by sealants in the outer peripheral parts of both substrates. Liquid crystals 7 are sealed between the first substrate 1 and the second substrate 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal panel and a method for manufacturing the same.

[0002]

2. Description of the Related Art In general, a liquid crystal panel is required to have a uniform distance between two opposing substrates (hereinafter referred to as a panel gap) in order to obtain good display.

First, the configuration of a conventional liquid crystal panel will be described with reference to FIG. FIG. 4A is a schematic sectional view of a conventional liquid crystal panel, and FIG. 4B is a schematic plan view thereof. As shown in FIG. 4A, T
A pixel electrode 2 such as FT is formed, and a second substrate 4 provided with a counter electrode 3 and a color filter (not shown)
The substrates 1 are opposed to each other at a predetermined distance, and the outer peripheral portions of both substrates are bonded together with a sealant 6 having spacer bead balls 5. Liquid crystal 7 is injected between the first substrate 1 and the second substrate 4 through an injection port (not shown), and the injection port is closed to complete a liquid crystal panel.

[0004]

In recent years, in a liquid crystal panel, a polysilicon TF is used as a pixel electrode 2.
Since a T element is used, an expensive substrate such as a quartz substrate is used as the first substrate 1, and the thickness of the quartz substrate has tended to be reduced due to the need to reduce costs. However, there is an increasing need to increase the display area.

In the above liquid crystal panel, if the first substrate 1 is made thinner and the display area is made wider, the first substrate 1 warps or deforms. There is a problem that it is difficult to make the gap uniform. Also, when the thermal expansion coefficients of both substrates are different, even if the panel gap is uniform when the completed liquid crystal panel is installed at room temperature, the substrate changes when the liquid crystal panel is installed in a high or low temperature, and the panel changes. There is a problem that the uniformity of the gap is lost.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a display panel capable of enhancing the uniformity of a panel gap and obtaining good display uniformity, and a method of manufacturing the same. And

[0007]

According to a first aspect of the present invention, there is provided a first substrate having a plurality of pixel electrodes, and a second substrate having a counter electrode facing the plurality of pixel electrodes. And a liquid crystal panel in which liquid crystal is sealed between the first substrate and the second substrate at a predetermined interval, and at least the first substrate is provided on the back surface of the first substrate. A transparent substrate having a refractive index substantially the same as the refractive index of the substrate is provided. According to this configuration, it is possible to suppress the warpage of the substrate and local deformation of the substrate, and it is possible to increase the uniformity of the panel gap.

According to a third aspect of the present invention, in the liquid crystal panel according to the first or second aspect, the transparent substrate has a thermal expansion coefficient that is smaller than that of the substrate provided with the transparent substrate. It is characterized by being substantially the same. According to this configuration, even if heat is applied during the manufacturing process of the liquid crystal panel or heat is applied after the completion of the liquid crystal panel, a high uniformity of the panel gap can be maintained.

According to a fourth aspect of the present invention, an adhesive having a refractive index substantially equal to that of the first substrate is applied to the entire back surface of the first substrate having a plurality of pixel electrodes, and 1
A transparent substrate having a refractive index substantially the same as that of the first substrate is adhered on the back surface of the substrate with the adhesive, and a second substrate having a counter electrode facing the first substrate and the plurality of pixel electrodes is provided.
And a liquid crystal is sealed between the first substrate and the second substrate. According to this manufacturing method, when the pixel electrode is formed on the first substrate, the first substrate is provided with the transparent substrate made of a highly rigid material on the back surface, so that the warpage of the first substrate is reduced. Can be. In addition, when the two substrates are bonded to each other, when the two substrates are pressed using a rigid plate, the first substrate is provided with a transparent substrate, so that local deformation of the first substrate due to foreign matter or the like is suppressed. In addition, when both substrates are pressurized with gas, warpage of the first substrate due to wind pressure can be suppressed.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view of a liquid crystal panel according to an embodiment of the present invention. In FIG. 1, components having the same configuration as the conventional one are denoted by the same reference numerals.

In FIG. 1, a plurality of pixel electrodes 2, for example, a high-temperature polysilicon TFT are provided on a first substrate 1 made of a quartz glass substrate having a thickness of 0.6 mm.
A transparent adhesive 8 such as an acrylic adhesive is applied to the entire back surface of the first substrate 1, and a transparent substrate 9 made of a borosilicate glass substrate having a thickness of about 0.5 mm to 10 mm is applied to the entire back surface of the first substrate 1. With a transparent adhesive 8. Here, the first substrate 1, the adhesive 8, and the transparent substrate 9 have substantially the same refractive index so as not to reflect each other. The refractive index of the quartz glass substrate as the first substrate 1 is 1.46, and therefore, the refractive indices of the transparent adhesive 8 and the transparent substrate 9 are 1.4.
It is desirable to use 6 ± 1. A first substrate 1,
A plurality of pixel electrodes 2 and a second substrate 4 having a color filter (not shown) opposed to the plurality of pixel electrodes 2, for example, a borosilicate glass substrate having a thickness of 1.1 mm are opposed to each other at a predetermined interval; A liquid crystal 7 is sealed between the first substrate 1 and the second substrate 4 by bonding the two substrates to the outer peripheral portions of the two substrates with a sealant 6 mixed with a spacer bead ball 5.

Here, a film substrate can be used as the first substrate 1, and a transparent resin substrate made of a material having high rigidity and light weight, such as an acrylic resin substrate, can be used as the transparent substrate 9. Alternatively, an inexpensive substrate can be used. Further, as the transparent adhesive 8, an epoxy resin-based adhesive, a silicone-based adhesive, or the like can be used in addition to the acrylic adhesive. Further, a double-sided pressure-sensitive adhesive sheet or the like may be used instead of the adhesive.

FIGS. 2A to 2C show process diagrams in a method for manufacturing a liquid crystal panel according to the present invention.

As shown in FIG. 2A, a pixel electrode 2 such as a TFT element is formed on a first substrate 1. Then, FIG.
As shown in (b), a transparent adhesive 8 is applied to the entire back surface of the first substrate 1, and a transparent substrate 9 made of a material having high rigidity is applied to the entire back surface of the first substrate 1 with the transparent adhesive 8. Glue. Here, the first substrate 1, the transparent adhesive 8 and the transparent substrate 9 having substantially the same refractive index are used so as not to reflect each other.

Here, it is necessary to reduce the warpage of the first substrate 1 in order to ensure the uniformity of the panel gap. However, warpage of the first substrate 1 generally increases after the pixel electrodes 2 are formed due to stress generated when the pixel electrodes 2 are formed on the first substrate 1. For example, when a high-temperature polysilicon TFT is formed as a pixel electrode 2 on a quartz glass substrate having a thickness of 0.6 mm and a thickness of 125 mm ² , a transparent substrate 9 is formed.
Is not provided, after the pixel electrode 2 is formed, the first substrate 1 is warped about 12 μm to 22 μm, generally about 17 μm, whereas when the transparent substrate 9 is provided, The warpage can be suppressed to about 2 μm, that is, from about 1 μm to about 3 μm.

Next, as shown in FIG.
And a second substrate 4 having a counter electrode 3 and a color filter (not shown) are opposed to each other at a predetermined interval. The two substrates are bonded together with a sealant 6 having spacer bead balls 5 arranged on the outer peripheral portion of the substrate 4. Then, the liquid crystal 7
Is injected through a liquid crystal injection port (not shown), and the liquid crystal panel is completed by closing the injection port. Alternatively, after the sealing agent 6 is disposed on the outer peripheral portion of the first substrate 1 or the second substrate 4, the liquid crystal 7 is dropped on the substrate on which the sealing agent 6 is disposed, and then the first substrate 1 and the second substrate 4 to complete the liquid crystal panel.

Here, when the first substrate 1 and the second substrate 4 are bonded together, the two substrates are usually pressed with a rigid plate,
Alternatively, bonding is performed by applying wind pressure with a gas, at which time a pressure of about 1 kg / cm ² is required. In a conventional manufacturing process of a liquid crystal panel not including the transparent substrate 9, when a foreign object enters between the rigid plate and the first substrate 1 when pressing both substrates using the rigid plate,
If deformation by pressure is easier for the substrate than for foreign matter,
The panel gap changes locally, and the uniformity of the panel gap is greatly impaired. The ease of deformation of a substrate, that is, Young's modulus, is generally proportional to the square of the thickness of the substrate.

According to the present invention, since the first substrate 1 is provided with the transparent substrate 9 made of a material having high rigidity, it is possible to suppress the above-mentioned local change of the gap due to the foreign matter. In addition, when pressure is applied with gas, stress is applied to the substrates by wind pressure at the time of bonding, but since the first substrate 1 is provided with the transparent substrate 9, the first substrate 1 does not warp, A uniform panel gap can be obtained between the first substrate 1 and the second substrate 4.

When the first substrate 1 provided with the transparent substrate 9 and the second substrate 4 are bonded and hardened with the sealant 6, if heating is necessary, the uniformity of the panel gap is ensured. In addition, it is desirable that the second substrate 4 and the transparent substrate 9 have the same thermal expansion coefficient.

When the first substrate 1 having the transparent substrate 9 and the second substrate 4 are made of materials having different coefficients of thermal expansion, if the sealing agent 6 does not need to be heated when adhesively hardened. It is desirable to use an ultraviolet curable acrylic adhesive having high adhesive strength.

When manufacturing a liquid crystal panel of the high-temperature polysilicon TFT system, when forming the pixel electrode 2, about 1000
It is necessary to use quartz glass as the first substrate 1 because it has a heat treatment step of ° C. On the other hand, the second substrate 4
Since it does not have a heat treatment step at 300 ° C. or higher, borosilicate glass, which is relatively inexpensive, can be generally used. The thermal expansion coefficients of quartz glass and borosilicate glass are 5.3 × 10 ⁻⁷ / K and 46 × 10 ⁻⁷ / K, respectively. Therefore, in the liquid crystal panel after bonding, the amount of expansion and contraction of the two glass substrates due to heat is different by about 8 times. Furthermore, when the completed liquid crystal panel is placed in a high or low temperature, the amount of expansion and contraction of both substrates becomes different. In addition, since only the outer peripheral portions of both substrates are adhered with the sealant 6, both substrates change non-uniformly, and as a result, the uniformity of the panel gap is impaired.

However, according to the present invention, since the transparent substrate 9 having the same thermal expansion coefficient as the second substrate 4 is provided on the back surface of the first substrate 1, the first substrate 1 In addition, the difference in the amount of expansion and contraction of the second substrate 4 can be reduced, and the change in the panel gap can be suppressed.

In the above embodiment, the case where the transparent substrate 9 is provided on the first substrate 1 has been described.
Even if the transparent substrate 9 is bonded to the second substrate 4 or both the first substrate 1 and the second substrate 4, the same effect as described above can be obtained.

In the above embodiment, the TFT
Although the type liquid crystal panel has been described, it is needless to say that the present invention can be applied to a simple matrix type liquid crystal panel, an MIM type liquid crystal panel, and the like.

FIG. 3 is a schematic diagram of an optical system when an image of the liquid crystal panel of the present invention is projected on a screen. The display image on the liquid crystal panel is focused on the screen 11 through the projection lens 10. When the foreign matter 12 adheres to the surface of the transparent substrate 9 in the liquid crystal panel of the present invention, the screen 1 has a thickness corresponding to the thickness of the first substrate 1 and the transparent substrate 9.
Since the focus of the foreign matter 12 is focused on a position deviated from 1, the foreign matter 12 is recognized as a dot spot in image quality. As the difference between the focus position of the foreign matter 12 and the position of the screen 11 increases, the spot-like stain increases and the contrast decreases at the same time, making it difficult to recognize. When projecting a 1.3-inch diagonal liquid crystal panel onto a 40-inch screen, when the total thickness of the first substrate 1 and the transparent substrate 9 is 5 mm or more, spot-like spots due to foreign matter 12 of 1 mm or less appear on the screen. Not recognized.

By providing a non-reflective coating on the surface of the transparent substrate 9 opposite to the bonding surface, the transmittance of the liquid crystal panel is improved, and the pixel electrode 2 due to light reflected on the surface is improved.
Can be prevented from malfunctioning.

[0028]

As described above, according to the liquid crystal panel of the present invention, a first substrate having a plurality of pixel electrodes and a second substrate having a counter electrode facing the plurality of pixel electrodes are provided in a predetermined manner. A liquid crystal display panel in which liquid crystal is sealed between the first substrate and the second substrate with a gap provided therebetween, and at least a refractive index of the first substrate is provided on a back surface of the first substrate. Since it is provided with a transparent substrate having substantially the same refractive index as the above, warpage and local deformation of the substrate are suppressed,
The uniformity of the panel gap can be increased, and good display quality can be obtained.

According to the method of manufacturing a liquid crystal panel of the present invention, a transparent substrate made of a highly rigid material is provided on the back surface of the first substrate when forming the pixel electrode on the first substrate. Warpage of the first substrate can be reduced, and uniformity of the panel gap can be ensured. In addition, when the two substrates are bonded to each other, when the two substrates are pressed using a rigid plate, the first substrate is provided with a transparent substrate, so that local deformation of the first substrate due to foreign matter or the like is suppressed. When both substrates are pressurized with gas, the first
Of the substrate can be suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a liquid crystal panel according to an embodiment of the present invention.

FIG. 2 is a process chart of a liquid crystal panel in one embodiment of the present invention.

FIG. 3 is a schematic diagram of an optical system when projected by the liquid crystal panel of the present invention.

4A is a cross-sectional view of a conventional liquid crystal panel, and FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 first substrate 2 pixel electrode 3 counter electrode 4 second substrate 7 liquid crystal 8 transparent adhesive 9 transparent substrate

Claims (5)

[Claims] A first substrate having a plurality of pixel electrodes;
A liquid crystal panel in which liquid crystal is sealed between the first substrate and the second substrate, with the plurality of pixel electrodes facing a second substrate having a counter electrode facing the same at a predetermined interval. A liquid crystal panel comprising a transparent substrate having a refractive index substantially equal to the refractive index of the first substrate, at least on the back surface of the first substrate. 2. The liquid crystal panel according to claim 1, wherein said transparent substrate is made of borosilicate glass or acrylic resin. 3. The liquid crystal panel according to claim 1, wherein the transparent substrate has substantially the same thermal expansion coefficient as a substrate facing the substrate provided with the transparent substrate. panel. 4. An adhesive having a refractive index substantially the same as that of the first substrate is applied to the entire back surface of the first substrate having a plurality of pixel electrodes, and the first substrate is provided on the back surface of the first substrate. A transparent substrate having a refractive index substantially the same as that of the first substrate is bonded with the adhesive, and a predetermined distance is provided between the first substrate and a second substrate having a counter electrode facing the plurality of pixel electrodes. Liquid crystal sealing between the first substrate and the second substrate. 5. A double-sided pressure-sensitive adhesive sheet having a refractive index substantially the same as that of the first substrate is provided on the entire back surface of the first substrate having a plurality of pixel electrodes, and the first substrate is provided on the back surface of the first substrate.
5. The method for manufacturing a liquid crystal panel according to claim 4, wherein a transparent substrate having a refractive index substantially the same as that of said substrate is bonded by said double-sided pressure-sensitive adhesive sheet.