JP2003280002A - Liquid crystal display - Google Patents

Abstract

(57) [Problem] To provide a liquid crystal display device in which a foaming phenomenon from a liquid crystal material is reduced or the phenomenon is not generated, and a display performance is further improved. A transparent electrode and an alignment film are formed on a substrate, and one member is manufactured. As for the other member, the substrate 5
A transparent electrode 4 and an alignment film 3 are formed thereon. Two types of spacer groups are scattered between the one member and the other member to be uniformly dispersed. When the present invention uses two types of spacer groups, both of them are an aggregate composed of a number of spacers having a variation in particle size so that both have a peak in the particle size distribution. This is for adjusting the gap between the substrates so as to make the gap between the substrates between the member and the other member equal. The average particle size of the other spacer group 2 is smaller than the average particle size of the one spacer group 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to improvement of a dispersion state in a spacer for adjusting a gap between substrates for aligning a gap between substrates.

[0002]

2. Description of the Related Art A conventional liquid crystal display device, in particular, a portion relating to a spacer will be described with reference to FIGS. FIG. 5 is a diagram showing a state in which spacers are dispersed on the substrate, and FIG. 6 is a schematic sectional view of an STN type liquid crystal display device obtained by the subsequent steps.

Reference numeral 5 is a glass substrate, on which transparent electrodes 4 made of a transparent conductive film (for example, ITO) are formed in a stripe shape, and made of polyimide synthetic resin or the like and rubbed on the transparent electrodes 4. A pair of members having a structure in which the alignment film 3 described above is coated is formed, the spacers 1 made of a synthetic resin material or the like are scattered on one of the members, and the spacers 1 are dispersed on the alignment film 3.

Then, by bonding the other member through the seal member 7, a liquid crystal display device having a structure as shown in FIG. 6 can be obtained. Actually, the substrate 5 is opposed so that both transparent electrodes 4 are orthogonal to each other and the orthogonal portions are arranged in a matrix. The portion of this matrix arrangement becomes the display area.

According to this device, after that, a super twist nematic liquid crystal material is further injected, and both members are made to face each other via the liquid crystal layer 6 having a twist angle of 160 to 300 degrees of liquid crystal molecules. .

Further, in the liquid crystal display device having such a structure, in order to perform further color display, a color filter is formed to obtain a color liquid crystal display device.

According to the liquid crystal display device having the above-mentioned structure, the pair of members are bonded to each other through the spacer 1 so that pressure is applied to the spacer 1 and distortion occurs even if it is initially spherical. ing. This state is shown in FIG.

According to the figure, 1 is the initial spacer shape, and 2 is the state of the spacer inserted in the apparatus, which is slightly deformed and distorted.

According to the liquid crystal display device having the above structure, the spacer 1 is for adjusting the inter-substrate gap for aligning the inter-substrate gap between the two members, whereby the liquid crystal layer 6 is formed.
Thickness is uniform over the display surface.

Therefore, in order to make the gap adjustment between the substrates more effective, it is preferable to increase the number of spacers. That is, the narrower the CV value, which is a variation coefficient indicating the uniformity of the spacers, or the larger the number of sprays, the more advantageous it becomes.

[0011]

However, in the liquid crystal display device having the above-mentioned structure, when the operating environment is low, the liquid crystal layer 6 contracts and the liquid crystal material foams.

In order to solve such a problem, there has been proposed a technique for controlling foaming by providing a member for applying an external force so that the pressure inside the apparatus is always higher than the atmospheric pressure (Japanese Patent Laid-Open No. 2002-6326). No.). However, according to this device, there is a problem that the structure is complicated, and it is larger and thicker.

The present inventor has conducted extensive studies in view of the above circumstances, and as a result, disperses at least two kinds of spacer groups consisting of a large number of spacers having particle size variations so as to have a peak in the particle size distribution. Then, one of the spacer groups is for adjusting the gap between the substrates, and the other spacer group has an average particle size smaller than the average particle size of the one spacer group. I found it.

Therefore, the present invention has been completed based on the above findings, and the purpose thereof is to adjust the spacer group to reduce or eliminate the phenomenon of foaming from the liquid crystal material and further improve the display performance. An object is to provide an improved liquid crystal display device.

[0015]

A liquid crystal display device according to the present invention includes one member in which a plurality of transparent electrodes are arranged in a stripe pattern on a substrate, and one transparent electrode group and an alignment film are sequentially stacked, and another member. Another transparent electrode group in which a plurality of transparent electrodes are arranged in a stripe pattern on the substrate and the other member in which an alignment film is sequentially laminated are made to intersect the transparent electrodes of the one transparent electrode group and the other transparent electrode group at right angles. So as to form a display area, the liquid crystal layer is opposed to the liquid crystal layer, a sealing member is arranged around the liquid crystal layer, and the liquid crystal layer is fixed so that the particle size distribution has a peak. In a device configuration in which a spacer group including a large number of spacers provided is dispersed in at least two kinds, one spacer group is for adjusting the inter-substrate gap for aligning the inter-substrate gap between one member and the other member. ,other The spacer group is characterized by its average particle diameter is smaller than the average particle size of one of the spacer groups.

In another liquid crystal display device of the present invention, the ratio a / b of the particle diameter a corresponding to the peak of one spacer group and the particle diameter b corresponding to the peak of the other spacer group is 1.02 to 1.02.
It is characterized by being 1.07.

Still another liquid crystal display device of the present invention is characterized in that a ratio A / B between the density A of one spacer group and the density B of the other spacer group is 0.5 to 2.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a liquid crystal display device of the present invention will be described with reference to FIGS. The same parts as those in the conventional liquid crystal display device shown in FIGS. 5 and 6 are designated by the same reference numerals.

Basically, the liquid crystal display device has the same structure as that of the liquid crystal display device shown in FIGS. 5 and 6, but is characterized by the spacer group used therein.

FIG. 1 is a view showing a state in which spacers according to the present invention are dispersed on a substrate, and FIG. 2 is a schematic cross-sectional view of an STN type liquid crystal display device obtained by the subsequent steps.

Transparent electrodes 4 made of a transparent conductive film (for example, ITO) are arranged in stripes on a substrate 5 made of a glass material or a plastics material, and the one transparent electrode group is provided. A polyimide synthetic resin or the like is coated on these transparent electrodes 4, and a rubbing treatment is performed on the resin to form an alignment film 3 to prepare one member.

As for the other member, the transparent electrodes 4 made of a transparent conductive film (for example, ITO) are arranged in a stripe pattern on the substrate 5 made of a glass material or a plastic material, and the other transparent electrode group is provided. A polyimide synthetic resin or the like is coated on the transparent electrode 4, and the alignment film 3 is formed by rubbing the resin.

As shown in FIG. 1, two kinds of spacer groups are scattered on the alignment film 3 of the one member or the other member and are uniformly dispersed.

These spacer groups are made of a synthetic resin such as dinibiylbenzene and acryl and have a substantially spherical shape.

Then, by bonding one member or the other member through the seal member 7, a liquid crystal display device having a structure as shown in FIG. 2 can be obtained.

In this bonding step, both transparent electrodes 4 are orthogonal to each other, and the orthogonal portions are opposed to each other so as to be arranged in a matrix, and the matrix arrangement portion becomes a display area.

Subsequent to the above bonding step, a super twist nematic liquid crystal material is injected so that the twist angle of the liquid crystal molecules is 1 or less.
Both members are opposed to each other with a liquid crystal layer 6 of 60 to 300 degrees interposed therebetween.

For further color display, a color liquid crystal display device is formed by forming color filters.
For example, a color filter composed of three colors is formed by depositing colored layers of three colors of red (R), green (G), and blue (B) on the substrate 5. Further, a light-shielding film made of black resin or a light-shielding metal is provided at a predetermined portion between the colored layers.

The above-mentioned two kinds of spacer groups are almost spherical if they are only scattered, but by the subsequent bonding step, as shown in FIG. 3, distortion occurs and they are crushed. It becomes a state.

When the present invention uses two kinds of spacer groups, it is an aggregate consisting of a large number of spacers, both of which have particle size distributions having peaks in the particle size distribution, and FIG. As shown in FIG. 2, one spacer group 1 is for adjusting the inter-substrate gap for aligning the inter-substrate gap between one member and the other member, and the other spacer group 2 has an average particle size of one. Spacer group 1
The feature is that it is smaller than the average particle size of.

This point will be described below. As described above, the narrower the CV value, which is the coefficient of variation showing the uniformity of the spacers, or the larger the number of dispersions, the more effective the gap adjustment between substrates becomes. Therefore, one spacer group 1 is used. This achieves display uniformity.

The CV value represents the particle size distribution of the spacer, and the smaller the value, the smaller the distribution. CV =
(Σ / D) × 100.

Regarding one of the spacer groups 1 for adjusting the gap between the substrates as described above, in contrast to the foaming phenomenon at a low temperature,
Often works at a disadvantage. It is considered that this is because the contraction of the spacer cannot follow the contraction of the liquid crystal layer 6.

Therefore, for the spacers dispersed between the substrates, the wider the particle size distribution or the smaller the number of dispersed particles, the more advantageous it is to the foaming phenomenon.

More specifically, when the number of spacers in which the original spherical shape is uniformly crushed increases, a foaming phenomenon tends to occur along with this, which is disadvantageous. Therefore, if the particle size distribution is wide, those having a large size are mainly crushed, and the other spacers have a small crush amount. Moreover, since the number of sprays is small, the absolute number of crushes is small.

The present inventor further uses the other spacer group 2, but by making the average particle size smaller than the average particle size of the one spacer group 1, it is advantageous for the foaming phenomenon. We have discovered and completed the present invention.

That is, one spacer group 1 having a large diameter is mainly crushed to determine the cell gap. Then, the other spacer group 2 is hardly crushed and the display uniformity is maintained. By using the other spacer group 2 as described above, the number of spacers in which the original spherical shape is uniformly crushed is reduced, and thus the occurrence of the foaming phenomenon is reduced.

FIG. 4 shows the distribution of the one spacer group 1 and the other spacer group 2 as described above. The horizontal axis of the figure is the particle size (spacer diameter) and is the number of spacers.

For reference, the conventional distribution is shown in FIG. According to the figure, the peak distributions of one spacer group 1 and the other spacer group 2 are shown. Further, the peak shown in the approximate center of both peaks has a common function of the peaks of these spacer groups 1 and 2, and the spacer group of such a peak shown in the center may be arranged.

Next, examples will be described.

(Example 1) The liquid crystal display device of this example is obtained by forming a color filter for color display on the liquid crystal display device shown in FIG. This device is shown in FIG. The same parts as those of the liquid crystal display device shown in FIG. 2 are designated by the same reference numerals.

As shown in FIG. 8, a color filter 9 is formed on the substrate 5, and a smoothing film 8 is further provided.

In the color liquid crystal display device having such a constitution, the display uniformity and the low temperature foaming resistance were evaluated by using the spacer group under the four conditions A to D. As shown in Table 1. The results were obtained.

The spacer group used in this example has an average diameter of 6.5 μm in both the present invention and the comparative example. Hereinafter, the same applies to other examples.

For the spacer group of condition A, a mixture with one spacer group 1 for adjusting the inter-substrate gap and the other spacer group 2 is used as in the present invention (the number of peaks is 2 in Table 1). is there). The spacer groups under the conditions B to D are one type of conventional spacer group (the number of peaks is 1 in Table 1), and the CV value is changed between them.

For each liquid crystal display device having these conditions,
The display uniformity on the display screen was evaluated. Furthermore, these liquid crystal display devices were installed in a low temperature environment, and the presence or absence of foaming of the liquid crystal material was examined. These evaluation results were classified into three categories, ○, △, and ×.

In the display uniformity, ∘ indicates that good display performance without display unevenness was obtained, Δ indicates slight display unevenness and poor practicality, and x indicates display unevenness. This is the case when the occurrence becomes remarkable.

In the presence or absence of foaming of the liquid crystal material (low temperature foaming resistance), the mark ◯ means that there was no foaming phenomenon, and Δ
The mark indicates the case where a little foaming was confirmed, and the mark x indicates the case where the foaming occurred remarkably.

[0049]

[Table 1]

As is clear from the table, according to the condition A of the present invention, good display performance without display unevenness was obtained, and there was no foaming phenomenon at all.

Further, as is clear from the conditions B to D, C
When the V value is small, the display uniformity is good, but on the other hand, the low temperature foaming resistance is low.

(Example 2) In the liquid crystal display device shown in FIG. 8, by using the spacer groups under seven conditions, that is, by further using the spacer groups represented by the conditions E to H, uniform display is achieved. When the properties and low temperature foaming resistance were evaluated, the results shown in Table 2 were obtained.

In this example, the ratio a / b of the particle diameter a corresponding to the peak of one spacer group 1 and the particle diameter b corresponding to the peak of the other spacer group 2 is 1.02 to 1.08. There are four variations within the range.

Regarding conditions A and E to H, one of
The density A of the spacer group 1 and the density B of the other spacer group 2
The ratio A / B of 1 is set to 1. In addition, this density is the number /
mm ²Is.

[0055]

[Table 2]

As is clear from this table, the particle diameter a corresponding to the peak of one spacer group 1 and the other spacer group 2
Ratio a / b with the particle size b corresponding to the peak of
Under conditions A, E, F, and G of 1.07, good display performance without display unevenness was obtained, and there was no bubbling phenomenon. It is preferable to set the ratio a / b to 1.04 to 1.06.

(Example 3) In the liquid crystal display device shown in FIG. 8, by using the spacer group under seven conditions, that is, by further using the spacer group shown by the conditions I to L, uniform display is achieved. When the properties and low temperature foaming resistance were evaluated, the results shown in Table 3 were obtained.

In this example, the ratio A / B between the density A of one spacer group 1 and the density B of the other spacer group 2 is changed in five ways within the range of 0.5 to 2. Also,
Ratio a / b of particle size a corresponding to the peak of one spacer group 1 and particle size b corresponding to the peak of the other spacer group 2
Is set to 1.04.

[0059]

[Table 3]

As is apparent from this table, setting the ratio A / B within the range of 0.5 to 2 provided good display performance without display unevenness and did not cause a bubbling phenomenon. The ratio A / B is preferably 0.75 to 1.5.

The present invention is not limited to the above embodiment, and various modifications and improvements may be made without departing from the scope of the present invention.

For example, according to the above-described embodiment, two kinds of spacer groups, each of which is composed of a large number of spacers in which the particle diameters are varied so that the particle diameter distribution has a peak, are used. You may use 4 or more types.

[0063]

As described above, according to the liquid crystal display device of the present invention, there are at least two types of spacer groups each including a large number of spacers having different particle diameters so that the liquid crystal layer has a peak in the particle diameter distribution. In the device configuration in which the spacers are dispersed by means of one spacer group, one spacer group is for adjusting the inter-substrate gap for aligning the inter-substrate gap between one member and the other member, and the other spacer group has an average particle size of one spacer group. By being smaller than the average particle size of the group, it was possible to provide a liquid crystal display device in which the phenomenon of foaming from the liquid crystal material was reduced or the occurrence of such phenomenon was eliminated and the display performance was further improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a state in which spacers are dispersed on a substrate in a liquid crystal display device of the present invention.

FIG. 2 is a schematic sectional view of an STN type liquid crystal display device of the present invention.

FIG. 3 is a state diagram showing distortion of a spacer.

FIG. 4 is a distribution diagram of one spacer group and the other spacer group according to the present invention.

FIG. 5 is a diagram showing a state in which spacers are dispersed on a substrate in a conventional liquid crystal display device.

FIG. 6 is a schematic cross-sectional view of a conventional STN type liquid crystal display device.

FIG. 7 is a distribution diagram of a conventional spacer group.

FIG. 8 is a schematic sectional view of an STN type color liquid crystal display device of an example.

[Explanation of symbols]

1 ... One spacer group 2 ... the other spacer group 3 ... Alignment film 4 ... Transparent electrode 5 ... Glass substrate 6 ... Liquid crystal layer 7 ... Seal member 9 ... Color filter

Claims (3)

[Claims] 1. A member in which a plurality of transparent electrodes are arranged in a stripe pattern on a substrate and a transparent electrode group and an alignment film are sequentially laminated, and a plurality of transparent electrodes are arranged in a stripe pattern on another substrate. The other member in which the other transparent electrode group and the alignment film are sequentially laminated, so that both the transparent electrodes of the one transparent electrode group and the other transparent electrode group are orthogonal to each other to form a display area,
A spacer composed of a large number of spacers which are opposed to each other with a liquid crystal layer in between, a sealing member is arranged around the liquid crystal layer and fixed, and further, the liquid crystal layer has a variation in particle diameter so as to have a peak in particle diameter distribution. A liquid crystal display device in which at least two types of groups are dispersed, one spacer group is for adjusting the inter-substrate gap for aligning the inter-substrate gap between one member and the other member, and the other spacer group. Is a liquid crystal display device characterized in that its average particle size is smaller than that of one spacer group. 2. The ratio a / b of the particle diameter a corresponding to the peak of one spacer group and the particle diameter b corresponding to the peak of the other spacer group is 1.02 to 1.07. The liquid crystal display device according to claim 1. 3. The liquid crystal display device according to claim 1, wherein the ratio A / B of the density A of one spacer group and the density B of the other spacer group is 0.5 to 2.