JPS62192725A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To maintain a uniform cell spacing over a wide temp. range and to prevent the generation of foam in the low temp. stage by forming a region where spacer materials do not exist so that the spacing between a pair of substrates is made narrower in said region than the region where the spacer materials exist. CONSTITUTION:A pair of the substrates 1A, 1B provided with electrodes are disposed with the spacer materials 2 therebetween in such a manner that the electrode surfaces face each other. The periphery thereof is sealed with a sealant 3 to form a cell. A liquid crystal 5 is injected into the cell through an injection port 4 and the injection port is sealed by a sealant. The spacer materials are not disposed in the region A on the left side of the figure and said region is so formed that the cell spacing tA of the region A is narrower than the cell spacing tB of the region B where the spacer materials exist at approximately the intermediate temp. of the service temp. region of the liquid crystal display element. The inside of the cell is thereby sealed in the reduced pressure state even if the substrates having poor flatness are used. Deflection is thus corrected and the uniform cell spacing in the display part is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display element, and particularly to a liquid crystal display element in which the cell gap is kept constant with high precision over a wide temperature range.

[Prior art] In a liquid crystal display device that utilizes the birefringence of liquid crystal, the display characteristics respond extremely sensitively to changes in the cell gap, and the uniformity of the cell gap requires an accuracy of ±1 to 2%. . In order to achieve this accuracy, not only the flatness of the glass substrate used in the cell but also the particle size accuracy of the spacer material are important factors.

Conventionally, for this purpose, high-precision glass fiber was used as a spacer material and the inside of the cell was kept in a weakly depressurized state, but the lack of elasticity of the spacer material led to zero
When exposed to low temperatures ranging from ℃ to -30℃, liquid crystal material cat 1
Because the shrinkage of the glass substrate was greater than that of the glass substrate, the interior of the cell was under a strong vacuum, which tended to eventually generate bubbles. In order to avoid this problem, a method has been used in which elastic plastic balls are used as spacer materials to create a slightly reduced pressure inside the cell. In other words, due to the contraction of the liquid crystal material, the inside of the cell becomes depressurized in the same way as when glass fiber is used, but the pressure deforms the spacer material and the cell gap becomes smaller, reducing the degree of depressurization inside the cell. Since the bubbles are smaller than they would be if they had been used, the generation of bubbles can be prevented.

However, using elastic spacer materials is not suitable for high-precision cell gap control.
In other words, if the density of the spacer material spread inside the cell is uneven.

In areas where the density of the spacer material is low, deformation of the spacer material tends to be large, resulting in a low gap, and conversely, in areas with high density, the deformation is small, resulting in a high gap. In addition, irregular deflection of the glass substrate causes a distribution in the pressure applied to the spacer material in the cell, so even if the spacer material distribution is uniform, the spacer material deforms greatly in areas of high pressure, causing low pressure. There was a problem in that the areas where the pressure was low, which became gaps, were less deformed, resulting in high gaps. On the other hand, a problem that occurs with both glass fiber spacers and plastic ball spacers is that cells with 40
The cell gap increases due to expansion of the liquid crystal material when heated above .degree. C., resulting in noticeable color changes and color unevenness in the background color.

Problems to be Solved by the Invention] As mentioned above, the conventional technology achieves a highly accurate cell gap,
Moreover, no bubbles are generated at low temperatures, and there is no method for preventing the cell gap from increasing due to expansion of the liquid crystal at high temperatures.

Alternatively, in order to prevent the generation of bubbles at low temperatures, it was necessary to sacrifice the cell gap accuracy at room temperature.

In the present invention, even when using a substrate with poor flatness (a glass substrate with irregular flexure), the flexure is corrected by sealing the inside of the cell under reduced pressure, resulting in a uniform display area. The object is to provide a new method in which cell spacing is achieved, and furthermore, the cell spacing is kept constant over a wide temperature range and the problem of foaming at low temperatures is also solved.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and consists of a pair of substrates provided with electrodes, a spacer material placed between the substrates, and electrode surfaces facing each other. In a liquid crystal display element whose periphery is at least sealed with a sealant and a liquid crystal is sealed inside, an area where no spacer material is present is formed in a surface surrounded by the sealant other than the area used for display, and A liquid crystal is sealed inside under reduced pressure so that the gap between the pair of substrates is narrower in the region where the spacer material is not present than in the region where the spacer material is present. It is a liquid crystal display element.

FIG. 1 is a plan view of a basic example of the liquid crystal display element of the present invention, with the upper substrate and sealant removed for clarity.

Further, FIG. 2 is a sectional view of the liquid crystal display element of FIG. 1.

This liquid crystal display element is made by arranging a pair of substrates IA and IB with electrodes (not shown) and a spacer material 2 so that the electrode surfaces face each other, and sealing the periphery with a sealing material 3 to form a cell. This is a liquid crystal display element in which liquid crystal 5 is injected through an injection port 4 and the injection port is sealed with a sealing material (not shown), and no spacer material is disposed in the area A on the left side of the figure. At a temperature approximately in the middle of the operating temperature range of this liquid crystal display element, the cell gap t^ in the region A is made narrower than the cell gap t8 in the region B where the spacer material is present.

The substrate used in the present invention may be any substrate made of glass, plastic, etc. on which electrodes are formed.

At least one of them is transparent. Further, an undercoat layer made of 5i02, Al2O3, polyimide, polyamide, etc., a color filter layer, a polarizing layer, etc. may be provided between this substrate and the electrode, and SiO2, Al2O3, etc. may be provided on the electrode.
, an alignment film made of polyimide, polyamide, etc., a single layer of color filter, etc., two layers of electrodes, a combination of fully bent wiring, a transistor, a diode, a nonlinear resistance element, etc. may be provided.

Known spacer materials such as glass fiber, alumina particles, and plastic particles can be used as the spacer material placed between the substrates, but by using a combination of hard inorganic spacer materials and elastic organic spacer materials, it is possible to This is preferable because it reduces foaming.

In addition, this spacer material may be simply sprinkled, but it is also possible to apply an alignment film material after spraying, to mix it with the alignment film material and print at the same time, or to spray the spacer material before the alignment film material hardens. Alternatively, the spacer material may be bonded to one of the substrates by bonding the spacer material to one of the substrates. By doing this, it is possible to prevent the spacer material from moving. It is preferable that the spacer material in the area where the spacer material is needed is not lost due to outflow.

To seal this liquid crystal display element under reduced pressure, the liquid crystal may be sucked out by reducing the pressure from the injection port after the liquid crystal is injected, or the liquid crystal may flow out by applying pressure to the area where no spacer material is present. The cell gap tA in the region A where no spacer material is present may be made narrower than the cell gap t8 in the region B where the spacer material is present.

The present invention provides an area in which no spacer material is sprayed in a part of the liquid crystal display element, and fills the liquid crystal in a reduced pressure state, thereby making the cell gap in this area smaller than the cell gap in the display area, allowing it to expand due to temperature changes. The purpose is to absorb the volume change of the shrunken liquid crystal in this region and to alleviate the change in the cell gap in the display section.

Area A where this spacer material does not exist is 5 of the display area.
It is appropriate to have an area in the range of ~20%, but if the area is too small, there will be little effect, and if it is too large, the entire cell will become large compared to the area required for display, which is preferable from the point of view of design and cost. Therefore, it is generally desirable to set the area to around 10%. Although this area can be provided anywhere on the liquid crystal display element, the cell gap becomes smaller due to the reduced pressure during liquid crystal injection using the vacuum injection method. Therefore, it is desirable to avoid the injection port side from the viewpoint of not causing a decrease in the liquid crystal injection speed.

As an area where this spacer material does not exist, an arrangement as shown in FIG. 3 can be considered.

Furthermore, in order to clearly distinguish one display area and to prevent destruction of the spacer material due to concentration of pressure near the boundary between the display area where spacer material is used and the area where spacer material is not used, a seal is placed at the boundary between both areas. It is desirable to provide pillars made of material in the form of dots, lines, etc. outside the periphery, and these must have a shape that does not impede the flow of liquid crystal within the cell due to temperature changes. Furthermore, it is also possible to prevent the spacer material from flowing into areas where no spacer material is used due to the flow of liquid crystal within the cell caused by temperature changes or the like.

FIG. 3 simply shows the plane of the liquid crystal display element, the sealing material and the spacer material are both omitted, and the explanation will be made assuming that the injection port is provided on the right side of FIG. 5. (1) is an example in which a spacer material-free region 11 is provided on the opposite side of the injection port, and (2) is an example in which a spacer material-free region 12 is provided on one side adjacent to the injection port. (3) is an example in which a spacer material-free region 13 is provided on both sides adjacent to the injection port, and (4) is an example in which a spacer material-free region 14 is provided on all sides other than the injection port. be.

This area where there is no spacer material is an area where the cell gap of the liquid crystal display element changes greatly, so it is formed in an area where there is no display pattern. 1. It has a rectangular display area like a normal dot matrix display or LCTV. The objects are arranged as shown in FIGS. 3 (1) to (4) as described above.

However, depending on the display pattern, the arrangement is not necessarily limited to these four ways; for example, a clock.

For displaying radar images, etc., as shown in (5), the three corners other than the injection port are used as the area 15 where no spacer material exists, or when there is no right display pattern near the center of the cell in composite display, (6) ), it is also possible to provide an area in which no spacer material exists in the island 111iB near the center in addition to the peripheral area 18A.

The example shown in FIG. 3(1) has the same structure as the examples shown in FIGS. 1 and 2, and will be explained in more detail below based on this example.

In the present invention, the area A where this spacer material does not exist is
Since the inside of the cell is in a reduced pressure state, the gap tA is narrower than the cell gap tB in the region B where the spacer material, which is the display portion, exists. This gap (ta-ta) may be set appropriately depending on the operating temperature range of the liquid crystal display element, the size of the area where no spacer material is present, the material and thickness of the substrate, etc. Temperature t^/lo
= about 0.3 to 0.8, more preferably about 0.4 to 0.7.

As a result, even at low temperatures, the cell gap in the area without this spacer material is further reduced, and when an organic spacer material with gamma strength is also used, the area where the spacer material is present, which is the indicated part. However, the cell gap is slightly reduced to prevent foaming. This reduction in the cell gap in the display area usually tends to cause defects such as color unevenness, but if the spacer material and density are uniform, the color unevenness is hardly noticeable and the background color of the entire cell changes uniformly. However, the appearance of the display does not necessarily deteriorate, and it is less likely to be a disadvantage than the inability to display due to foaming. This prevention of foaming caused by low temperatures produces a similar effect in conventional liquid crystal display elements that simply provide an area where no spacer material exists, but damage to the cell seal and substrate damage occurs at high temperatures, which will be explained next. However, the effect of preventing color unevenness does not occur.

The liquid crystal display element of the present invention does not only suffer from poor foaming at low temperatures as described above, but also is less prone to defects such as uncontrollable cell gaps, peeling of seals, peeling of sealing material, and cracking of substrates due to expansion of liquid crystals at high temperatures. It is something. This is a temperature in the middle of the operating temperature range, generally about room temperature, and the inside of the cell is in a reduced pressure state, and the cell gap t^ in the area where no spacer material is present is above the intercell gap in the area where the spacer material is present. However, when the liquid crystal expands due to high temperatures, the cell gap that had been narrowed expands to compensate for this expansion, causing strong pressure to be applied to the sealing material and the sealing material, and causing the cell gap to expand. It is less likely to cause color unevenness due to spreading and loss of the effect of the spacer material.

This color unevenness at high temperatures is different in nature from the uniform color change of the background color at low temperatures, and is quite unsightly.

This is because the shrinkage of the cell gap is uniformly suppressed by the spacer material at low temperatures, so even if the cell gap narrows, the entire display area narrows almost uniformly, and the display performance deteriorates due to a uniform deviation from the original set cell gap. However, when the cell swells at high temperatures, the gap between the cells does not spread uniformly, and the cell substrate wavers, forming gaps in the spacer material in narrow areas, and bulging in wide areas. The gap becomes much wider than this, and since the cell gap does not spread uniformly, color unevenness becomes much more noticeable than when the temperature is low, and the display appearance deteriorates significantly.

The optimal value of the width of area A where this spacer material does not exist is:
It varies depending on the material and thickness of the board, and is determined accordingly.
Generally, in the case of a hard material such as glass, it is difficult to bend, so it needs to be wider than a material such as plastic, and in the case of the same material, the thinner it is, the easier it is to bend, so it needs to be narrower. However, if this width is made too wide, disadvantages such as a reduction in the display area and contact between the two substrates are likely to occur, so it may be determined by experiments or calculations as appropriate.

For example 1. Approximately a dozen ff for a glass substrate with a thickness of l+III
It is suitable to have a width of about 1 liter, and depending on the display area, the range of the area where no spacer material exists is shown in Fig. 3 (
By changing from 1) to (2), (3), and (4), the area of the area where the spacer material does not exist is made to be about 5 to 20% of the area of the area where the spacer material exists. Bye.

[Effect] The operation of the present invention will be explained using FIG. 2.

Liquid crystal materials usually change in volume by about 1% for a 10°C change in temperature.
Change. Therefore, expansion of the liquid crystal due to temperature rise usually increases the cell gap, and the spacer material becomes loose, which impairs the uniformity of the cell gap. Therefore, the increase in the liquid crystal volume is due to the return of the glass substrate in the adjustment area where no spacer material is present, and the internal volume of the cell increases. Therefore, the uniformity of the cell gap in the display section is not impaired.

On the other hand, when the liquid crystal shrinks due to a drop in temperature, the glass substrate in the adjustment region further flexes, thereby reducing the internal volume of the cell and reducing the degree of reduced pressure within the cell, thereby preventing the generation of bubbles. If a cell does not have an adjustment region, which is a region without spacer material, and a spacer material with no elasticity is used, the spacer material will maintain the cell gap, and the internal volume of the cell will hardly change.In other words, the liquid crystal material The contraction of the will result in the generation of vacuum bubbles. In addition, when an elastic spacer material is used, the spacer material deforms due to contraction of the liquid crystal material and the cell gap becomes smaller, which alleviates the degree of vacuum pressure inside the cell and prevents the generation of vacuum bubbles. uniformity becomes worse.

In the present invention, the shrinkage and expansion of the liquid crystal is absorbed by reducing and increasing the cell gap in the adjustment area, which is the area without spacer material, so that the cell gap in the area where the spacer material is present deteriorates uniformity over a wide temperature range. It also exhibits excellent properties never seen before in that it does not generate bubbles at low temperatures.

[Examples] Example 1 In a 180° twisted birefringence mode liquid crystal display cell with internal dimensions of 110×905 m, a spacer-free adjustment region with a width of 17 mm was provided on the opposite side of the inlet. Spacers were sprayed only on the display area using a mask. High-precision glass fiber (average particle size: 7 cm) was used as the spacer material. The thickness of both glass plates is 1
．． A 1 mm glass substrate was used. When liquid crystal was injected into this cell using the vacuum method, the average cell gap at the 0 display area was 8.9.
pm, the gap in the center of the regulatory region is approximately 3 l ■
Cell cutting was carried out by applying pressure so that At room temperature, this liquid crystal cell showed a uniform background color and good display characteristics.

Even when this liquid crystal cell was cooled to 0°C, no bubbles were generated and the background color was uniform even though it was a birefringent mode cell.
The cell gap was maintained accurately and uniformly. Even when the sample was further cooled to -20°C, no bubbles were observed.

On the other hand, as a comparative example, spacers were placed on the entire surface,
A cell was manufactured by sealing the cell while pressurizing the cell surface so that the cell gaps were uniform. When the cell of this comparative example was cooled, bubbles were generated in the display area at 0° C., and the bubbles remained for a while even after the cell was returned to room temperature.

When the cell of the present invention was left in an atmosphere of 50° C. and operated, it was found that no background color unevenness occurred and the cell gap at room temperature was maintained in the display section. On the other hand, when the cell of the comparative example was similarly operated at 50° C., since it was used in birefringence mode, an increase in the cell gap and uneven background color appeared due to variations, and the appearance deteriorated.

Example 2 Same as Example 1, but a mixture of high-precision glass fiber (average particle size 7 ALm) and elastic organic particulate spacer (average 11 diameter 7.5 pm) in l:9 ratio was used as the spacer material. to form cells.

In this liquid crystal cell, no bubbles were observed up to -30°C, and the background color was uniform at room temperature and high temperature as in Example 1.

Example 3 In the same manner as in Example 2, a peripheral sealing material was printed using the same material as the peripheral sealing material on the boundary between the adjustment area where no spacer material was present and the display area where the spacer material was present and had a width of 17ti+ on the opposite side of the injection port. At the same time, eight broken-line struts each having a width of 1 mm and a length of 5 mm were formed to produce a cell. Compared to Example 1, in this cell, the spacer material is less likely to flow toward the adjustment area, and even during cooling, color unevenness does not occur due to a reduction in the cell gap in the display area that is in contact with the adjustment area, resulting in a better appearance. It was good.

[Effects of the invention] By sealing the inside of the cell under reduced pressure, it is possible to correct the poor flatness of the glass substrate used at room temperature, and furthermore, by providing an area where no spacer material exists, the cell in this area can be Make the gap narrower than the cell gap of the display section. in particular.

By more actively sealing the cell under reduced pressure, the corrected flatness can be maintained even at high temperatures.

In addition, even on the low temperature side, the relaxation region still has the ability to absorb the volume change of the shrunken liquid crystal material, so it is possible to prevent the inside of the cell from entering a strongly reduced pressure state, thereby preventing foaming. be able to.

[Brief explanation of drawings]

FIG. 1 is an explanatory plan view of a typical example of a liquid crystal display element according to the present invention. FIG. 2 is a sectional view of FIG. 1. FIG. 3 is an explanatory plan view showing a region where no spacer material exists. IA, IB: Substrate 2 Varnish spacer material 3: Sealing material

Claims (3)

[Claims] (1) In a liquid crystal display element in which a spacer material is placed between a pair of substrates provided with electrodes, the electrode surfaces are made to face each other, the periphery is sealed with a sealant, and a liquid crystal is sealed inside. A region in which no spacer material is present is formed in a portion other than the region used for display within the plane surrounded by the region, and a liquid crystal is sealed inside under a reduced pressure state so that the gap between the pair of substrates is filled with the spacer material. A liquid crystal display element characterized in that a region without spacer material is narrower than a region where spacer material is present. (2) The liquid crystal display element according to claim 1, wherein the spacer material is a combination of an inorganic spacer material and an organic elastic spacer material. (3) The liquid crystal display element according to claim 1, wherein the spacer material is an inorganic spacer material.