JPH07270805A - Liquid crystal display device and production thereof - Google Patents

Abstract

PURPOSE:To obtain an electric field effect type liquid crystal display device having a high contrast and in which a gap unevenness and a bright unevenness are not present and which is capable of a large capacity display having high uniformity of a display. CONSTITUTION:In a liquid crystal display device provided with a liquid crystal layer held between one pair of substrates 1, 1 having electrodes disposed to face oppositely and in which at least one of them is a transparent electrode, oriented films orienting and controlling liquid crystal molecules on the surfaces of substrates to a prescribed direction, spacers giving a constant gap between substrates 1, 1, a control means changing the transmitting light quantities of liquid crystal by impressing voltages between electrodes and a driving circuit generating a prescribed voltage wave form, this divice is the liquid crystal display device in which a spacer consists of a core part 3 and a buffer layer part 2 and the elastic modulus of the core part 3 is made to be higher than that of buffer layer part 2. Thus, the liquid crystal display device having the high contrast and in which the gap unevenness and the bright unevenness are not present and which is capable of a large capacity display having high uniformity of a display is obtained.

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 capable of high-capacity display with high contrast and high uniformity of display without gap unevenness or brightness unevenness.

[0002]

2. Description of the Related Art In a liquid crystal display device capable of displaying a large capacity, vertical alignment treatment is performed on the surface of spacer beads as a means for preventing a liquid crystal alignment defect around the spacer, which is a cause of display unevenness, and obtaining a uniform gap. And a method of performing a parallel alignment treatment in a mixed manner have been proposed (Toshiba Corporation, Japanese Patent Laid-Open No. 3-6).
9917 publication).

[0003]

A liquid crystal display device capable of displaying a large capacity has a super twisted nematic type (STN type) and a thin film transistor type (T type).
There are two types, FT type), and improvement of image quality is an important issue for both types, and therefore reduction of various display unevenness is essential. The above-mentioned conventional technique has a vertical alignment treatment and a parallel alignment treatment mixed on the surface of the spacer beads, and has the effect of preventing the expansion of the alignment defect region which is the cause of display unevenness, but it is necessary to completely remove the alignment defect region. There is a problem that the movement of the spacer cannot be suppressed.

The display unevenness due to the spacers has two causes, that is, defective alignment of liquid crystal molecules around the spacers and movement of the spacers, which appear as a composite. The movement of the spacer caused unevenness of the gap, light leakage due to spacer aggregation, damage to the panel, and generation of filamentous domains. In addition, poor alignment of liquid crystal molecules around the spacer caused a decrease in contrast ratio due to light leakage, streak-like unevenness due to the mixture of two types of domains, and thread-like domains due to spacer movement. Therefore, the reduction of the display unevenness due to the spacer cannot be sufficiently solved by the countermeasure against the alignment defect.

The present invention solves this problem, and an object thereof is to provide a liquid crystal display device capable of high-capacity display with high contrast and high uniformity of display without gap unevenness or brightness unevenness. .

[0006]

[Means for Solving the Problems] In order to solve the above problems and achieve the above object, the present invention uses the following means. [Means 1] A pair of substrates having electrodes, at least one of which is transparent and opposed to each other, a liquid crystal layer sandwiched between the substrates, an alignment film for controlling alignment of liquid crystal molecules on a substrate surface in a predetermined direction, and a space between the substrates. In a liquid crystal display device including a spacer that provides a constant gap, a control unit that applies a voltage between the electrodes to change the amount of transmitted light of the liquid crystal, and a drive circuit that generates a predetermined voltage waveform, the spacer includes a core portion and a buffer. A liquid crystal display device comprising a layer portion, wherein the elastic modulus of the core portion is higher than that of the buffer layer portion.

[Means 2] A pair of substrates, which have electrodes and are opposed to each other, at least one of which is transparent, a liquid crystal layer sandwiched between the substrates, an alignment film for controlling the alignment of liquid crystal molecules on the substrate surface in a predetermined direction, Spacers that provide a constant gap between substrates,
In a liquid crystal display device comprising a control means for changing the amount of transmitted light of the liquid crystal by applying a voltage between the electrodes and a drive circuit for generating a predetermined voltage waveform, the spacer comprises a core portion and a buffer layer portion, A liquid crystal display device, characterized in that the elastic modulus of a portion is higher than that of the buffer layer portion, and liquid crystal molecules in contact with the buffer layer portion are vertically aligned.

[Means 3] The thickness of the spacer described in the means 1 or 2 is changed by applying a pressure,
And, the rate of change of thickness with respect to a given pressure has three or more stages, and the panel is pressed with a pressure slightly higher than the inflection point of the first rate of change and the second rate of change, and the liquid crystal is sealed. A liquid crystal display device characterized by being provided.

[Means 4] The diameter of the core portion of the spacer according to the means 1 or 2 is d _c , the thickness of the buffer layer portion is t _b , and the total diameter of the core portion and the buffer layer portion is _{d t (= d c + 2t} b), when the thickness of the liquid crystal layer in a state in which liquid crystal is sealed and the d, d is less than 1.2 times greater than 0.8 times the d _c, and d _c And d are smaller than d _t , a liquid crystal display device.

[Means 5] A liquid crystal display characterized in that the deformation rate of the buffer layer section is 1.05 or more when the deformation rate of the core portion of the spacer according to the means 1 or 2 is 1. apparatus.

[Means 6] A liquid crystal display characterized in that, when the thickness or diameter of the core portion of the spacer according to means 4 is 1, the thickness of the buffer layer portion is 0.3 or less. apparatus.

[Means 7] A liquid crystal display characterized in that the elastic modulus of the buffer layer portion is 0.5 or less, where the elastic modulus of the core portion of the spacers according to the means 1 and 2 is 1. apparatus.

[Means 8] A liquid crystal display device, wherein the core portion of the spacer according to means 1 or 2 is made of an inorganic material.

[Means 9] A liquid crystal display device, wherein the buffer layer of the spacer according to the means 1 or 2 is made of an organic material having a long-chain alkyl group.

[Means 10] A liquid crystal display device characterized in that the surface of the buffer layer of the spacer according to the means 1 or 2 is coated with an organic material having a long-chain alkyl group.

[Means 11] As a value of the elastic modulus of the core portion of the spacer described in the means 1 or 2, the compressive displacement is 5 kg / cm ² or more and 80 kg / when the core portion has a diameter of 10%. A liquid crystal display device having a size of not more than cm ² .

[Means 12] As a value of the elastic modulus of the buffer layer portion of the spacer according to the means 1 or 2, the compressive elastic modulus is 10 kg / cm ² or less when the compressive displacement is 10% of the thickness of the buffer layer. And a liquid crystal display device.

[Means 13] A pair of substrates having electrodes, at least one of which is transparent and opposed to each other, a liquid crystal layer sandwiched between the substrates, an alignment film for controlling alignment of liquid crystal molecules on the substrate surface in a predetermined direction, In a liquid crystal display device including a spacer that provides a constant gap between substrates, a control unit that applies a voltage between the electrodes to change the amount of transmitted light of the liquid crystal, and a drive circuit that generates a predetermined voltage waveform, the spacer is a core. And a buffer layer portion, wherein the core portion has a compressive fracture elastic strength higher than that of the buffer layer portion, and liquid crystal molecules in contact with the buffer layer portion are vertically aligned. Liquid crystal display device.

[Means 14] The compressive fracture elastic strength of the core portion of the spacer according to the means 13 is 8 kg / mm ² or more 2
A liquid crystal display device characterized by being 4 kg / mm ² or less.

[Means 15] The compressive fracture elastic strength of the buffer layer portion of the spacer according to the means 13 is 10 kg /
A liquid crystal display device characterized by being less than or equal to mm ² .

[Means 16] The liquid crystal layer according to the means 1, 2 or 13 has a helical structure having a dielectric anisotropy and a twist angle, and the twist angle is 180 degrees or more 360.
And the product d · Δn of the thickness d of the liquid crystal layer and the refractive index anisotropy Δn is between 0.2 μm and 1.2 μm, and the thickness d of the liquid crystal layer is 3.0 μm or more. The liquid crystal display device, wherein the refractive index anisotropy Δn is 1.3 or less.

[Means 17] A liquid crystal display device characterized in that the spacer according to the means 16 is a transmissive display device having a light shielding property.

[Means 18] A liquid crystal display device characterized in that the spacer according to the means 16 is a transparent or white display device.

[Means 19] A pair of transparent substrates having electrodes, at least one of which is transparent, a liquid crystal layer sandwiched between the substrates, an alignment film for controlling the alignment of liquid crystal molecules on the substrate surface in a predetermined direction, A spacer that provides a constant gap between the substrates, a control unit that applies a voltage between the electrodes to change the amount of transmitted light of the liquid crystal, and a drive circuit that generates a predetermined voltage waveform, and the spacer includes a core portion and a buffer layer portion. A method of manufacturing a liquid crystal display device, wherein the elastic modulus of the core portion is higher than that of the buffer layer portion, and liquid crystal molecules in contact with the buffer layer portion are vertically aligned. A method for manufacturing a liquid crystal display device, wherein the core portion is coated with an organic material by an air suspension coating method.

[Means 20] A pair of substrates having electrodes, at least one of which is transparent and opposed to each other, a liquid crystal layer sandwiched between the substrates, an alignment film for controlling alignment of liquid crystal molecules on the substrate surface in a predetermined direction, A spacer that provides a constant gap between the substrates, a control unit that applies a voltage between the electrodes to change the amount of transmitted light of the liquid crystal, and a drive circuit that generates a predetermined voltage waveform, and the spacer includes a core portion and a buffer layer portion. The method of manufacturing a liquid crystal display device, wherein the elastic modulus of the core portion is higher than that of the buffer layer portion, and liquid crystal molecules in contact with the buffer layer portion are vertically aligned. A liquid characterized in that the surface of the buffer layer is coated with a long-chain alkyl group by polymerizing a monomer having a long-chain alkyl group in the final step, which is formed by two or more steps of polymerization. Method for manufacturing a display device.

[Means 21] A pair of substrates having electrodes, at least one of which is transparent and opposed to each other, a liquid crystal layer sandwiched between the substrates, an alignment film for controlling alignment of liquid crystal molecules on the substrate surface in a predetermined direction, A spacer that provides a constant gap between the substrates, a control unit that applies a voltage between the electrodes to change the amount of transmitted light of the liquid crystal, and a drive circuit that generates a predetermined voltage waveform, and the spacer includes a core portion and a buffer layer portion. A method for manufacturing a liquid crystal display device, wherein the elastic modulus of the core portion is higher than that of the buffer layer portion, and liquid crystal molecules in contact with the buffer layer portion are vertically aligned. A method for manufacturing a liquid crystal display device, wherein the surface of the buffer layer is subjected to vertical alignment treatment by immersing in a long-chain alkylsilane coupling solution.

[0027]

The operation of the present invention will be described with reference to FIGS. 1, 2 and 3.

1 and 3 are schematic cross-sectional views of the element structure of the liquid crystal display device of the present invention, and FIG. 2 is a view showing the structure of the spacer used in the present invention. In FIG. 1, a liquid crystal layer is held by a substrate having two electrodes, and the thickness of the liquid crystal layer is determined by a spacer. Here, as the spacer, as shown in FIG. 2, a spacer in which a soft resin (buffer layer portion) is coated around a spacer (core portion) having a hard central portion is sprayed as a solution in which water or alcohol is added, or nitrogen is sprayed. Or mixed with compressed air and dispersed on the substrate by dry spraying.

Here, assuming that the diameter of the core portion of the spacer shown in FIG. 2 is d _c , the thickness of the buffer layer is t _b , and the total diameter of the spacer is d _t (d _t = d _c + 2t _b ), the liquid crystal is When not enclosed, the spacer has a concentric structure.
As shown in FIG. 3B, the thickness of the display portion is larger than the thickness of the sealant portion, and the cell gap is non-uniform. on the other hand,
As shown in FIGS. 1 and 3A, the device structure after encapsulating the liquid crystal is d <d _t , d _c <d _t , when the buffer layer is compressed.
The relationship of 0.8 × d _c <d <1.2 × d _c is established, the spacer of the display portion is deformed to have the same thickness as the spacer in the sealant, and the liquid crystal element obtains a uniform cell gap. Moreover, since the contact area of the spacer with the substrate is increased, the movement can be suppressed.

Further, by performing a surface treatment so that the liquid crystal molecules are vertically aligned on the surface of the buffer layer, the area of the alignment defect region around the spacer can be reduced.

The operation of enhancing the uniformity of the display, which is the object of the present invention, which has a high contrast and has no gap unevenness or brightness unevenness will be described below.

(1) Prevention of Spacer Movement FIG. 4 shows the present invention, and FIG. 5 shows the amount of deformation of the pressure applied to the conventional spacer and the thickness of the spacer.

In the conventional spacer, the plastic spacer indicated by the broken line in the figure is deformed by a relatively small pressure. Therefore, the contact area of the spacer with the substrate increases and it becomes difficult to move. However, since the spacer is easily deformed, the gap in the panel is likely to be nonuniform, leading to display unevenness. Further, the silica (glass) spacer shown by the solid line in the figure is unlikely to be deformed,
It was easy to get a uniform gap, but because it was hard, the panel was scratched and streaky unevenness occurred.

However, if a spacer having a hard central portion and a soft resin coating therearound is used, a uniform gap is obtained and the panel is not scratched. This is because, when pressure is applied to the spacer as shown in FIG. 4, the rate of change of the spacer has three or more stages. In the first step, that is, in the range (a) in the figure, the spacer has a soft surface and is easily deformed by a slight overload, and the 10% compression elastic modulus is as low as 1 to 10 kg / cm ² . In the second stage, as shown in the range (b) in the figure, since the amount of deformation of the spacer exceeds the thickness of the buffer layer, deformation is less likely to occur due to the effect of the hard spacer in the core portion, and the 10% compression elastic modulus is 5 to 5. It is a high value of 80 kg / cm ² . In the third stage, as shown in the range (c) of the figure, the spacer is a region which is hardly deformed even if pressure is applied, and the spacer is broken when a pressure higher than the compressive breaking strength is applied.

To obtain a uniform cell gap, FIG.
The pressure immediately after changing from the range (a) to the range (b) shown in Fig. 5, the range (b ') in the figure, that is, 0.8 x d _c <d <1.2 x
It is advisable to assemble the liquid crystal panel with a pressure such as d _c .

The liquid crystal cell is shown in FIG.
As shown in (b), the thickness of the display portion is larger than the thickness of the sealant portion, and the cell gap is non-uniform. Since the liquid crystal is put in a decompression container in the step of enclosing the liquid crystal, pressure is applied to the spacer due to the pressure difference between the inside and outside of the cell. In addition, there may be a step of pressurizing the liquid crystal cell after encapsulation, which also applies pressure to the spacer. At that time, the spacer may move and damage the panel, or the spacer may aggregate on the non-electrode portion or the like. However, when a spacer having a hard central portion and a soft resin coating therearound is used in the present invention, the surface of the spacer is soft, so that the panel is not scratched. Further, the buffer layer of the spacer is largely deformed by the pressure and pressed against the substrate, so that the contact area with the substrate increases and it becomes difficult to move. Further, since the central portion is made of a medium having a high elastic modulus such as a glass spacer, a pressure within a certain range is applied, so that 0.8 × d _c <d <1.2 × d _c , and the thickness is ± 0.1. It is also possible to obtain a uniform gap within 05 μm. In the case of the STN type liquid crystal display device, for example, a liquid crystal having a birefringence of Δn = 0.133 is used and a cell thickness d = 6.4 μm.
Then, the product Δnd of Δn and d is 0.85 μm, and the white display bright state transmittance is about 25%. However, if d = 6.0, Δnd is 0.80 μm and the white display bright state transmittance is about 20%. %
Fall to. Therefore, in order to suppress the variation of the transmittance within ± 1%, it is necessary to control the cell thickness within ± 0.05 μm, but the present invention satisfies this value. At this time, the shape of the spacer is preferably spherical, but may be rectangular parallelepiped or columnar. The variation in the thickness of the buffer layer may be larger than the variation in the thickness of the hard core portion unless it is extremely large. When the thickness or diameter of the core part is 1, 0.0
A range of 5 to 0.5 is desirable. That is, since the diameter of the core portion is usually 3 to 7 μm, 0.05 to 2.0 μm is preferable. The buffer layer is formed by coating an organic material having a long-chain alkyl group on the surface by an air suspension coating method or a flow coating method, or by two or more steps of polymerization, and by a final step of the polymerization, a long-chain alkyl group. It can be obtained by coating the surface of the buffer layer with an organic material having, and as the resin of the material, polymethyl acrylate, polyvinylidene fluoride, polydivinylbenzene, etc. are suitable. Compressive elastic modulus at 10% is 1 to 10 kg / cm ² , or compressive fracture strength is 5 to 1
The resin of 5 kg / mm ² is not limited to these, and can be used without any problem. A spherical spacer made of silica is suitable as the material of the core part, but the elastic modulus is larger than that of the buffer layer, and the thickness is 10% of the particle diameter due to compression displacement.
A spacer made of plastic such as polydivinylbenzene may be used as long as the compression elastic modulus at that time is 5 to 80 kg / cm ² or the compressive fracture strength per spacer is in the range of 8 to 24 kg / mm ² . When the ratio of the thickness of the spacers before and after enclosing the liquid crystal is the deformation rate, the deformation rate of the core part is 1
In this case, the deformation rate of the buffer layer portion should be 1.05 or more.

As another method of obtaining a uniform cell gap and not damaging the panel or moving the spacer, at least two kinds of spacers having different thicknesses are used, and the compression elastic modulus of the spacer having the smallest thickness is set. There is a method to make it higher than other spacers. The spacer having the smallest thickness holds the gap, and the thick spacer deforms to have the same thickness as the spacer having the smallest thickness. At this time, since the small spacers may move, it is important to make the amount of dispersion per unit area smaller than the amount of dispersion of other spacer groups. The number of spacers dispersed to obtain a uniform gap needs to be about 50 to 150 per square mm, but if spacers with a compression elastic modulus of 7 kg / cm ² or more are used, even about 20 per square mm. A uniform gap is obtained. Also, when two types of spacers are used, the smaller spacers move but the dispersion number
By reducing the number to about one-half, the probability of movement is reduced, and the uniformity of display is improved.

(2) Prevention of misalignment around spacers Another cause of display unevenness due to spacers is misalignment of liquid crystal molecules around the spacers. FIG. 6 shows an enlarged plan view of one pixel of the display portion of the STN type liquid crystal display device.
Is a normal alignment, and the alignment is the same in the vicinity of the spacer and in the part without the spacer, but in FIGS. 7 and 7 ', the alignment state of the liquid crystal molecules in the vicinity of the spacer is different from that of the other part without the spacer ( Light is scattered. Especially in the case of dark (black) display, this misalignment causes leakage light and causes a reduction in the contrast ratio. Further, when the number of dispersions of the spacer per unit area is large, the amount of this leaked light is also increased and the contrast ratio is decreased.

First, in order to reduce the amount of leaked light, it is necessary to obtain a uniform gap with a small number of spacers. For example, a spacer having a hard central portion and covered with a soft resin may be used, or at least two different thicknesses may be used. It is effective to use different kinds of spacers. At this time, the number of dispersions is about 20 to 50 per square mm, which is less than half of the conventional value.

Next, means for reducing the amount of leaked light will be described. FIG. 7 is a schematic view of the alignment of liquid crystal molecules around the spacer that causes alignment failure, (a) is a cell cross-sectional view,
(b) is a cell plan view. In the figure, liquid crystal molecules 5
Is parallel to the surface of the spacer 4 and vertical to the substrate 1. In the state where no voltage is applied, the liquid crystal molecules in the normal part are aligned parallel to the substrate, but in the vicinity of the spacer, unlike the normal part, the liquid crystal molecules are aligned perpendicular to the substrate and parallel to the spacer surface. Therefore, when the normal portion displays black, light leaks in the vicinity of the spacer and the contrast decreases. Further, when the liquid crystal molecules are aligned parallel to each other on the spacer surface, there is another alignment pattern on the optical axis. Figure 8
A sectional view is shown in (a) and a plan view is shown in (b). In the figure, the liquid crystal molecules are aligned parallel to the spacer surface and also to the substrate. If the alignment defect of FIG. 7 is type 1 and the alignment defect of FIG. 8 is type 2, type 1 causes a large alignment defect region as shown in 7 of FIG. 6, but type 2 has a smaller region than type 1. , 7'in FIG.
The degree is as shown in. However, since type 1 and type 2 occur with the same probability, display unevenness such as streaks is likely to occur especially when both types are mixed.

In order to prevent this, liquid crystal molecules may be aligned vertically with respect to the spacer surface. 9A and 9B are schematic views showing the alignment of liquid crystal molecules around the spacer, where FIG. 9A is a cell sectional view and FIG. 9B is a cell plan view. In the orientation shown in the figure, the orientation is the same in the vicinity of the spacer and in other regions in the state where no voltage is applied, and leakage light is reduced. Further, since there is only one type of alignment pattern of the optical axis of the molecules on the spacer surface, the occurrence of display unevenness is small. In order to achieve vertical alignment, the spacer is treated on the surface of the buffer layer with a surfactant such as a long-chain alkylsilane coupling agent, or a long-chain alkyl chain ((CH ₂ ) _n , or (CF ₂ ) The buffer layer may be formed of a material having _n ). A means for observing the alignment state of liquid crystal molecules in the vicinity of the spacer is observed by a polarization microscope, and when the rubbing axis and the polarization axis are aligned with each other and a crossed Nicol is formed, a stripe-shaped dark pattern parallel to the rubbing axis is observed. The vertical alignment is observed when the cross-shaped pattern is observed, and the parallel alignment is observed when a cross-shaped pattern is observed.

In order to further reduce the leakage light and increase the contrast, the spacer may have a light shielding structure. This is particularly effective in the case of a transmissive display, and the same effect can be obtained if a cold cathode tube, a hot cathode tube, or an electroluminescence is used as a light source.

Further, as shown in FIG. 10A, when there is an alignment defect around the spacer and two or more spacers are aggregated, the alignment defect region grows as the spacer moves as shown in FIG. 10B. It looks like a string is pulled, and the uniformity of the display is significantly reduced. (This kind of misalignment is called a thread-like domain.) In order to suppress this thread-like domain, a spacer in which the central portion is hard and a soft resin is coated around the same is used, and two kinds of spacers having different thicknesses are used. It is effective to suppress the movement of the spacer by hardening the spacer having a small thickness, and to perform the vertical alignment treatment on the surface of the buffer layer of the spacer to reduce the alignment defect in the vicinity of the spacer.

In addition, a buffer layer of a soft resin or the like having an elastic modulus smaller than that of the core is formed around the core of the spacer, and a surface treatment is performed so that liquid crystal molecules are vertically aligned on the surface of the buffer layer. By providing a uniform gap, it is possible to obtain a function of preventing alignment defects around the spacer and preventing the spacer from moving.

[0045]

EXAMPLES The present invention will be specifically described with reference to examples.

Example 1 A perspective view of the element structure of the present invention is shown in FIG. As the substrate, two glass substrates having a thickness of 1.1 mm, the surface of which is polished and ITO (indium tin oxide) transparent electrodes are formed by a sputtering method are used. A nematic liquid crystal composition having a positive dielectric constant anisotropy Δε of 4.5 and a birefringence Δn of 0.133 (589 nm, 20 ° C.) is sandwiched between these substrates. A polyimide-based orientation control film (RN422 manufactured by Nissan Chemical Industries, Ltd.) applied on the surface of the substrate was applied by a spinner, followed by baking at 250 ° C. for 30 minutes and rubbing treatment to obtain a pretilt angle of 3.5 degrees (rotating crystal method. Measured by). The rubbing directions on the upper and lower substrates were set so that the twist angle (twist angle) of the liquid crystal molecules was 240 degrees in order to perform time-division driving. Here, the twist angle is defined by the rubbing direction and the type and amount of the optically active substance added to the nematic liquid crystal. The twist angle is limited to the maximum value because the lighting state near the threshold value is the orientation that scatters light, the upper limit is 360 degrees, the lower limit is limited by the contrast, and 180 degrees is the limit. In this example, the twist angle was set to 240 degrees because the object of the present invention is to provide a liquid crystal element capable of displaying black and white so that the contrast can be sufficiently satisfied even when the number of scanning lines is 200 or more.

In this embodiment, for example, a G1220DU (polarization degree 99.95%) manufactured by Nitto Denko Corporation is used as a polarizing plate in order to adopt a normally closed system in which a dark display is obtained when no voltage is applied, and the polarization axis of the lower polarizing plate 17 is used. The angle between the (or absorption axis) 18 and the rubbing direction 15 of the lower electrode substrate 16 is preferably in the range of 30 degrees to 60 degrees (or 120 degrees to 150 degrees) in consideration of the contrast ratio, brightness and color. In this embodiment, the angle is 135 degrees.

The angle at which the absorption axis 18 of the lower polarizing plate 17 and the absorption axis 10 of the upper polarizing plate 9 intersect is set to about 90 degrees. In this embodiment, one triacetyl cellulose (TAC) film is used as the birefringent polymer film 11 for displaying black and white, and the substrate 13 or 16 is used.
However, it may be arranged between the substrate 13 and the liquid crystal layer 8 or between the substrate 15 and the liquid crystal layer 8.

The organic polymer film 11 is attached to the substrate 1
One each between 3 or 16 and the polarizing plate 9 or 17,
Alternatively, two sheets may be arranged for each. In this case, it is desirable that the retardation of each polymer film be lower than that of one polymer film on one side. In addition to the TAC film, a structure using a birefringent plastic stretched film such as polycarbonate (PC), polyvinyl alcohol (PVA), polyether sulfone (PES), and polyethylene terephthalate (PET) is also possible, and is limited to the TAC film. It is not something that will be done.

In the present embodiment, Δnd was set to 0.82 μm in order to achieve both high contrast and high transmittance.
Since it is 0.133, the cell thickness was set to 6 μm. To obtain this cell thickness, spacers were dispersed in the sealing material and in the display area, respectively. The epoxy thermosetting sealant contains silica spherical spacer SW6.0 (thickness: 6) manufactured by Catalyst Kasei Co., Ltd.
μm, compression elastic modulus 40 kg / cm ² ) were mixed and applied to the substrate by screen printing. Further, the same silica spacer was used for the display part as a spacer whose surface was coated with polymethyl acrylate resin (compressive elastic modulus 2.5 kg / cm ² ) by an air suspension coating method. The compression modulus was measured with a micro compression tester manufactured by Shimadzu Corporation.

A method of forming the resin-coated spacer will be described below. As a fluidized bed granulation coating apparatus used for the air suspension coating method, a flow coater FLO-1 type manufactured by Freund Sangyo Co., Ltd. was used, and the silica spacer was placed in a stirring container, and the air pressure was 1.5 kg / cm ² , and the air amount was 35,000.
The mixture was stirred at cm ³ / min, and a 10% toluene solution of methyl polyacrylate was added as a coating solution thereto at a flow rate of 20 cm ^3.
Sprayed for 30 seconds / minute. Then, it was dried at 150 ° C. for 30 minutes while stirring with the air pressure. As a result, a resin film having a thickness of 0.4 μm was formed on the surface of the silica spacer having a diameter of 6 μm. The particle diameter and the buffer layer thickness were measured with a polarizing microscope micrometer.

In the dispersion method, the spacer is 0.2 wt% in pure water.
% Dispersion was performed with a mixing sprayer, and the average number of dispersion was 20 to 50 per 1 mm 2. It is desirable that the number of spacers dispersed is small so that the contrast is not deteriorated.
A uniform cell thickness cannot be obtained with an average of 20 or less per mm. The surface of the spacer of this embodiment is made of a soft resin, but the central part is made of hard silica, so that a uniform cell thickness can be obtained with a small amount of dispersion.

After spraying the spacers, the two substrates were laminated and thermoset to form a liquid crystal cell. Then, the liquid crystal is sealed in a vacuum container, and the press (Hitachi Chemical Co., Ltd .: MDP-29 type) 1
Pressure was applied at 50 ° C. and 2000 kgf for 120 minutes, and the sealing port was hardened with an ultraviolet curable resin.

The cell thickness at this time was measured with a polarization microscopic analyzer U6000 manufactured by Hitachi, Ltd., and it was 6.0 μm in the vicinity of the sealant before filling the liquid crystal, and 6.8 μm in the center of the display.
However, after encapsulating the liquid crystal, 6.0μ near the sealant.
m, and 6.05 μm in the central part of the display part, and a substantially uniform cell thickness was obtained. Since the pressure was applied to the substrate, the spacer of the display unit was held down by the substrate and the probability of movement was low. Pulse width 20 μs, amplitude 40 V, pulse interval 5 ms
When the voltage waveform of 1 was applied, only 4 spacers moved on average per 1 mm2.

The maximum contrast ratio (ratio of transmittance of white display and black display) in the panel is 10: 1 when measured with a brightness meter PR-1980A manufactured by Photo Research Co., and the minimum contrast ratio is 9: 1. The unevenness was small.

[Comparative Example 1] Micropearl SP- manufactured by Sekisui Fine Chemical Co., Ltd. as a spacer dispersed in the display section.
206 was used, and other configurations were the same as those in Example 1.
The spacer is a spherical spacer bead made of a polymer material, but the compression elastic modulus is 4.8 kg / cm ² , which is lower than the compression elastic modulus of 40 kg / cm ² of the silica spacer, and is the same pressure as in Example 1 because it is soft. When the panel was assembled by applying pressure, the cell thickness of the panel display portion became smaller than that in the vicinity of the sealant.

At this time, the cell thickness was 6.0 μm in the vicinity of the sealant before filling the liquid crystal and 6.4 μm in the central part of the display part, but after filling the liquid crystal, 6.0 μm in the vicinity of the sealant, central part of the display part. Then, it was 5.8 μm. Therefore, the maximum contrast ratio in the panel was 10: 1, but the minimum contrast ratio was 5: 1. When a voltage waveform having a pulse width of 20 μs, an amplitude of 40 V and a pulse interval of 5 ms was applied, an average of 20 spacers moved per square mm.

[Embodiment 2] In Embodiment 1, the spacer is surface-treated so that the liquid crystal molecules are vertically aligned on the surface of the spacer dispersed in the display portion, and the other structures are the same as those in Embodiment 1. . As a surface treatment agent, LP-8T manufactured by Shin-Etsu Chemical Co., Ltd. was used, dissolved in isopropyl alcohol at 1.4%, the spacer was added at 0.5%, ultrasonic cleaning was performed, and the spacer was taken out from the solution.
Rinsing was performed in isopropyl alcohol, dried and then dispersed.

Since the liquid crystal molecules are vertically aligned on the spacer surface, alignment defects around the spacer are eliminated, the amount of leaked light is reduced, and the contrast ratio of one pixel is improved from 10: 1 to 20: 1.

Comparative Example 2 Sekisui Fine Chemical Co., Ltd. Micropearl SP-
206 was used, and other configurations were the same as those in the second embodiment.
By vertically aligning the surface of the spacer, the defective alignment region around the spacer was reduced, and the contrast ratio of one pixel was improved from 10: 1 to 18: 1. However, since the spacer is a spherical spacer bead made of a polymer material and is softer than the silica spacer, when the panel is assembled by applying the same pressure as in Example 1, the cell thickness of the panel display portion is smaller than that near the sealant. It got smaller.

At this time, the cell thickness was 6.0 μm in the vicinity of the sealant before filling the liquid crystal and 6.4 μm in the central part of the display part, but 6.0 μm in the vicinity of the sealant after encapsulating the liquid crystal, central part of the display part. Then, it was 5.8 μm. Therefore, the maximum contrast ratio in the panel was 20: 1, but the minimum contrast ratio was 10: 1. Also, the pulse width is 20 μs,
When a voltage waveform with an amplitude of 40 V and a pulse interval of 5 ms was applied, an average of 20 spacers moved per square mm as in Comparative Example 1.

[Embodiment 3] In Embodiment 2, Micropearl SP manufactured by Sekisui Fine Chemical Co., Ltd. is provided in the core portion of the spacer.
-206 is used (thickness 6.0μm, compression modulus 4.8kg / c
m ² , compressive fracture strength 11 kg / mm ² ), and other configurations were the same as in Example 2. At this time, the cell thickness was 6.0 μm in the vicinity of the sealant before filling the liquid crystal and 6.8 μm in the central part of the display part, but after filling the liquid crystal was 6.0 μm in the vicinity of the sealant and 6.0 μm in the central part of the display part. The thickness was 1 μm, and a substantially uniform cell thickness was obtained. Also, since pressure was applied to the substrate, the spacers in the display section were suppressed by the substrate and became difficult to move. When a voltage waveform with a pulse width of 20 μs, an amplitude of 40 V, and a pulse interval of 5 ms was applied, an average of 6 spacers per 1 mm 2 was obtained. The spacer has moved.

The maximum contrast ratio in the panel is 2
The display contrast was small at 0: 1 and the minimum contrast ratio was 16: 1.

[Example 4] In Example 2, a glass fiber spacer (compressive elastic modulus 60 kg /
cm ² ) and other configurations were the same as in Example 2.
Sumitomo Optical Glass Co., Ltd. (thickness 6.0 μm, length 30 μm) was used as the glass fiber spacers, and the average number of dispersion was 1 to 5 silica fiber spacers per square mm.

The cell thickness at this time was 6.0 μm in the vicinity of the sealant before filling the liquid crystal and 6.8 μm in the central part of the display portion, but after filling the liquid crystal, 6.0 μm in the vicinity of the sealant, central portion of the display part. Was 6.05 μm, and a substantially uniform cell thickness was obtained. Further, since the pressure was applied to the substrate, the spacer of the display portion was held by the substrate and did not move.
Since the number of dispersed spacers was small, the average contrast ratio of 100 pixels was improved from 10: 1 to 20: 1.

[Embodiment 5] In Embodiment 2, spacers having a light-shielding property are used as the spacers dispersed in the display portion.
The other structure was the same as that of the second embodiment. As a means for providing a light-shielding property, a black pigment dye, CuO, Fe ₃ O ₄ was added to the buffer layer. This further improved the contrast ratio to 30: 1. In addition, this embodiment is a transmissive display device. Although a cold cathode tube was used as the backlight, the same effect was obtained by using a hot cathode tube or electroluminescence.

[Embodiment 6] In Embodiment 1, a reflection plate is used instead of the light source, and the angle at which the absorption axis 18 of the lower polarizing plate 17 and the absorption axis 10 of the upper polarizing plate 9 intersect is approximately 0 degrees. did. The other structure was the same as that of the first embodiment. NPF-G3228M made by Nitto Denko integrated with a polarizing plate as a reflector
(Single transmittance 46.5%, polarization degree 95%) was used. Especially since the spacer is transparent or white, the white transmittance is 42
%was gotten.

Example 7 In Example 1, as a spacer buffer layer, a material having a side chain of a styrenedivinylbenzene copolymer and having an alkyl chain C _n H _{2n + 1} -group (n is 6 or more) was used. Used to coat the core by suspension polymerization. Here, the material of the buffer layer is not particularly limited as long as it is polymethylmethacrylate, benzoguanamine melamine formaldehyde condensation polymer, styrene polymer, sulfone polymer, or conjugated polymer.

Liquid crystal molecules are vertically aligned by the alkyl chains on the surface of the buffer layer. However, n is 5 or less, or 1
When it is 5 or more, the liquid crystal molecules are aligned in parallel. Since the liquid crystal molecules are vertically aligned on the spacer surface, alignment defects around the spacer are eliminated, the amount of leaked light is reduced, and the contrast ratio of one pixel is 20: 1.

[Embodiment 8] In Embodiment 2, as a surface treatment method for spacers, C _n H _{2n + 1} COOH (n = 6 to
15) is dissolved in 0.2% by weight in ethyl alcohol, 0.5% of the spacer is added and ultrasonic cleaning is performed, and the spacer is taken out from the solution, washed in ethyl alcohol and dried, and the spacer is placed on the substrate. It was sprayed by dry dispersion with nitrogen gas.

By this surface treatment, the liquid crystal molecules are vertically aligned on the spacer surface, the alignment defect around the spacer is eliminated, the amount of leaked light is reduced, and the contrast ratio of one pixel is changed from 10: 1 to 20: 1. Improved.

[Embodiment 9] In Embodiment 1, two kinds of spacers, plastic spacers and silica spacers, were used as the spacers dispersed in the display portion, and the other structures were the same as those in Embodiment 2. The plastic spacer is Sekisui Fine Chemical's Micropearl SP-20.
625, the thickness is 6.25 μm, and the compression elastic modulus is 4.8.
It is kg / cm ² . The silica spacer has a thickness of 6.0μ
The silica spherical spacer SW6.0 manufactured by Catalyst Kasei Co., Ltd. was used. The average number of dispersed silica spherical spacers per square mm is 10 to 20, and the number of plastic spacers is 1.
The average was 50 to 100 per square mm.

At this time, the cell thickness was 6.0 μm in the vicinity of the sealant before filling the liquid crystal and 6.4 μm in the central part of the display portion, but 6.0 μm in the vicinity of the sealant after encapsulating the liquid crystal, and in the central portion of the display part. Then, 6.10 μm was obtained. Also, when the deformation of the plastic spacer on the panel plane was observed with a polarization microscope, it was 6.25 μm before the liquid crystal was sealed, but it was 6.4 μm after the liquid crystal was sealed. That is, the diameter of the spherical spacer seen from the panel cross section has decreased,
It can be seen that the diameter when viewed from the plane was large and the spacer was crushed. In addition, applying the same waveform as in Comparative Example 1,
When the movement of the spacers was observed, an average of 3 spacers per square mm was moved. Further, the maximum contrast ratio in the panel was 20: 1 and the minimum contrast ratio was 16: 1, and the display unevenness was small.

[Embodiment 10] In Embodiment 9, two kinds of spacers made of the same material and different in thickness and elastic modulus are used as spacers dispersed in the display section.
The other structure was the same as that of the third embodiment. One is Sekisui Fine Chemical's Micropearl SP-206 (thickness 6.0 μm, compression modulus 4.8 kg / cm ² ), the other is Kao Luna Pearl YS-383 (thickness 6.2 μm. , And the compression modulus was 3.5 kg / cm ² ) and the ratio of the number of dispersions per square mm was 1: 5.

At this time, the cell thickness was 6.0 μm in the vicinity of the sealant before filling the liquid crystal and 6.4 μm in the central part of the display portion, but 6.0 μm in the vicinity of the sealant after encapsulating the liquid crystal, central part of the display portion. Then, 6.12 μm was obtained. At this time, the maximum contrast ratio in the panel was 20: 1 and the minimum contrast ratio was 16: 1.

[0076]

According to the present invention, the contrast is high,
Further, it is possible to obtain a liquid crystal display device capable of high-capacity display with high uniformity of display without gap unevenness or brightness unevenness.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a liquid crystal display device of the present invention.

FIG. 2 is a schematic diagram of a spacer of the present invention.

FIG. 3 is a cross-sectional view of a liquid crystal display device of the present invention.

FIG. 4 is a diagram showing the relationship between the applied weight and the amount of change of the spacer of the present invention.

FIG. 5 is a diagram showing a relationship between a weight applied by a conventional spacer and a change amount.

FIG. 6 is an enlarged plan view of a pixel portion of a conventional liquid crystal display device.

FIG. 7 is a schematic view showing an alignment state of liquid crystal molecules near a conventional spacer.

FIG. 8 is a schematic diagram showing an alignment state of liquid crystal molecules near a conventional spacer.

FIG. 9 is a schematic diagram showing an alignment state of liquid crystal molecules in the vicinity of a spacer of the present invention.

FIG. 10 is a schematic diagram showing a state of poor alignment of liquid crystal molecules near the spacer.

FIG. 11 is a perspective view of a liquid crystal display device of the present invention.

[Explanation of symbols]

1 ... Substrate, 2 ... Buffer layer, 3 ... Core part, 4 ... Sealing agent, 5 ... Spacer, 6 ... Normal orientation part, 7 ... Abnormal orientation part,
8 ... Liquid crystal molecule, 9 ... Upper polarizing plate, 10 ... Upper polarizing plate absorption axis direction, 11 ... Birefringent medium, 12 ... Fast axis direction of retardation plate, 13 ... Upper electrode substrate, 14 ... Upper rubbing axis, 15
... lower rubbing axis, 16 ... lower electrode substrate, 17 ... lower polarizing plate, 18 ... lower polarizing plate absorption axis direction, 19 ... backlight, 20 ... pixel, 21 ... non-electrode part.

Claims (21)

[Claims] 1. A pair of substrates, which have electrodes and are opposed to each other, at least one of which is transparent, a liquid crystal layer sandwiched between the substrates, an alignment film for controlling alignment of liquid crystal molecules on a substrate surface in a predetermined direction,
In a liquid crystal display device including a spacer that provides a constant gap between substrates, a control unit that applies a voltage between the electrodes to change the amount of transmitted light of the liquid crystal, and a drive circuit that generates a predetermined voltage waveform, the spacer is a core. And a buffer layer portion, wherein the elastic modulus of the core portion is higher than the elastic modulus of the buffer layer portion. 2. A pair of substrates, which have electrodes and are opposed to each other, at least one of which is transparent, a liquid crystal layer sandwiched between the substrates, an alignment film for controlling alignment of liquid crystal molecules on a substrate surface in a predetermined direction,
In a liquid crystal display device including a spacer that provides a constant gap between substrates, a control unit that applies a voltage between the electrodes to change the amount of transmitted light of the liquid crystal, and a drive circuit that generates a predetermined voltage waveform, the spacer is a core. And a buffer layer portion, the elastic modulus of the core portion is higher than that of the buffer layer portion, and liquid crystal molecules in contact with the buffer layer portion are vertically aligned. . 3. The thickness of the spacer according to claim 1 or 2 is changed by applying a pressure, and the rate of change of the thickness with respect to the applied pressure has three or more stages, and A liquid crystal display device, wherein the panel is pressed with a pressure slightly higher than an inflection point of the rate of change and the second rate of change, and liquid crystal is sealed. 4. The diameter of the core portion of the spacer according to claim 1 or 2 is d _c , the thickness of the buffer layer portion is t _b , and the total diameter of the core portion and the buffer layer portion is d.
_{t (= d c + 2t b} ), when the thickness of the liquid crystal layer in a state in which liquid crystal is sealed and the d, d is less than 1.2 times greater than 0.8 times the d _c, and the d _c A liquid crystal display device characterized in that d is smaller than d _t . 5. A liquid crystal display device, wherein the deformation rate of the buffer layer section is 1.05 or more, where the deformation rate of the core section of the spacer according to claim 1 or 2 is 1. . 6. The liquid crystal display device according to claim 4, wherein the thickness of the buffer layer portion is 0.3 or less when the thickness or diameter of the core portion of the spacer is 1. . 7. A liquid crystal display device, wherein the elastic modulus of the buffer layer portion is 0.5 or less, where the elastic modulus of the core portion of the spacer according to claim 1 or 2 is 1. . 8. A liquid crystal display device, wherein the core portion of the spacer according to claim 1 or 2 is made of an inorganic material. 9. A liquid crystal display device, wherein the buffer layer of the spacer according to claim 1 or 2 is made of an organic material having a long-chain alkyl group. 10. A liquid crystal display device, wherein the surface of the buffer layer of the spacer according to claim 1 or 2 is coated with an organic material having a long-chain alkyl group. 11. The elastic modulus of the core portion of the spacer according to claim 1 or 2, wherein the compressive displacement is 5 kg / cm ² or more and 80 kg when the core portion has a diameter of 10%.
A liquid crystal display device characterized by being less than / cm ² . 12. The compressive elastic modulus as a value of the elastic modulus of the buffer layer portion of the spacer according to claim 1 or 2 when the compressive displacement is 10% of the thickness of the buffer layer, the compressive elastic modulus is 10 kg.
/ Cm ² or less, a liquid crystal display device. 13. A pair of substrates, which have electrodes and are opposed to each other and at least one of which is transparent, a liquid crystal layer sandwiched between the substrates,
An alignment film that controls the alignment of liquid crystal molecules on the surface of the substrate in a predetermined direction, a spacer that gives a constant gap between the substrates, a control means that applies a voltage between the electrodes to change the amount of transmitted light of the liquid crystal, and a predetermined voltage waveform. In a liquid crystal display device having a driving circuit for generating the spacer, the spacer includes a core portion and a buffer layer portion, and the compressive fracture elastic strength of the core portion is higher than the compressive fracture elastic strength of the buffer layer portion and the buffer layer A liquid crystal display device characterized in that liquid crystal molecules in contact with the part are vertically aligned. 14. The compressive fracture elastic strength of the core portion of the spacer according to claim 13 is 8 kg / mm ² or more and 24 kg / m.
A liquid crystal display device characterized by being m ² or less. 15. A liquid crystal display device according to claim 13, wherein the compressive fracture elastic strength of the buffer layer portion of the spacer is 10 kg / mm ² or less. 16. The liquid crystal layer according to claim 1, wherein the liquid crystal layer has a spiral structure having a dielectric anisotropy and a twist angle, and the twist angle is 180 degrees or more and 360 degrees or less. And the product d · Δn of the thickness d of the liquid crystal layer and the refractive index anisotropy Δn is between 0.2 μm and 1.2 μm, and the thickness d of the liquid crystal layer is 3.0 μm or more, the refractive index A liquid crystal display device having an anisotropy Δn of 1.3 or less. 17. A liquid crystal display device, wherein the spacer according to claim 16 is a transmissive display device having a light shielding property. 18. A liquid crystal display device, wherein the spacer according to claim 16 is a transparent or white display device. 19. A pair of substrates, which have electrodes and are opposed to each other, at least one of which is transparent, a liquid crystal layer sandwiched between the substrates,
An alignment film that controls the alignment of liquid crystal molecules on the surface of the substrate in a predetermined direction, a spacer that gives a constant gap between the substrates, a control means that applies a voltage between the electrodes to change the amount of transmitted light of the liquid crystal, and a predetermined voltage waveform. The spacer includes a core portion and a buffer layer portion, the elastic modulus of the core portion is higher than that of the buffer layer portion, and liquid crystal molecules in contact with the buffer layer portion are vertically aligned. A method for producing a liquid crystal display device, wherein the core portion of the spacer is coated with an organic material by an air suspension coating method. 20. A pair of substrates, which have electrodes and are opposed to each other and at least one of which is transparent, a liquid crystal layer sandwiched between the substrates,
An alignment film that controls the alignment of liquid crystal molecules on the surface of the substrate in a predetermined direction, a spacer that gives a constant gap between the substrates, a control means that applies a voltage between the electrodes to change the amount of transmitted light of the liquid crystal, and a predetermined voltage waveform. The spacer includes a core portion and a buffer layer portion, the elastic modulus of the core portion is higher than that of the buffer layer portion, and liquid crystal molecules in contact with the buffer layer portion are vertically aligned. The method of manufacturing a liquid crystal display device, wherein the spacer is formed by polymerization in two or more steps, and the surface of the buffer layer is formed by polymerizing a monomer having a long chain alkyl group in the final step. A method for manufacturing a liquid crystal display device, characterized in that the liquid crystal display device is coated with a base. 21. A pair of substrates, which have electrodes and are opposed to each other, at least one of which is transparent, a liquid crystal layer sandwiched between the substrates,
An alignment film that controls the alignment of liquid crystal molecules on the surface of the substrate in a predetermined direction, a spacer that gives a constant gap between the substrates, a control means that applies a voltage between the electrodes to change the amount of transmitted light of the liquid crystal, and a predetermined voltage waveform. The spacer includes a core portion and a buffer layer portion, the elastic modulus of the core portion is higher than that of the buffer layer portion, and liquid crystal molecules in contact with the buffer layer portion are vertically aligned. A method for manufacturing a liquid crystal display device, wherein the surface of the buffer layer is vertically aligned by immersing the spacer in a long-chain alkylsilane coupling solution. Method.