GB2324618A - Liquid crystal display element - Google Patents

Abstract

A liquid crystal display is provided with spacers 6 and an alignment control film 5a, the alignment control film having dispersed therein fine particles of an organic resin. The resin promotes adhesion between the alignment layer and the substrates 10 and 20 and may be thermosetting or uv curable. The particles may be present in amounts which are in the range 0.5% to 7% by volume. Such an arrangement improves the shock resistance of ferroelectric liquid crystal displays.

Description

Liquid Crvstal Display Element and Method of Manufacturina Same The present invention relates to a liquid crystal display element and to a method of manufacturing this liquid crystal display element, and in particular to a structure and manufacturing method for providing a liquid crystal display element having uniform cell thickness, sufficient shock stability, and good display quality.

Conventionally, liquid crystal display elements comprised of a pair of substrates each having at least electrodes, assembled together such that the surfaces thereof provided with electrodes face inward, with a gap therebetween filled with liquid crystal, are well-known.

In this kind of liquid crystal display element, change of the width of the space between the facing substrates (the cell gap) due to substrate deformation caused by external pressure, etc. may lead to problems such as disturbance of alignment and change of threshold voltage due to leakage of current between electrodes of the opposite substrates, thus making good display impossible.

A well-known method of resolving this kind of problem is to provide spacers between the substrates, which maintain a uniform gap therebetween. Generally, in providing spacers, one of two methods is adopted: (1) distributing spherical particles between the substrates; or (2) forming walls of pillar-shaped members made of an organic or inorganic material.

Recently, ferroelectric liquid crystal has attracted notice as a liquid crystal material. Ferroelectric liquid crystal has superior properties such as spontaneous polarisation, which enables the liquid crystal to respond rapidly, and in-plane switching, which frees it from dependence on viewing angle. However, a problem with ferroelectric liquid crystal is that it is vulnerable to external impact. Since the order of ferroelectric liquid crystal molecules is closer to a crystalline structure, the molecules do not return to their original order if this order is disturbed by external pressure.

For this reason, in a liquid crystal display element using ferroelectric liquid crystal, spacers provided by method (2) above are suitable. Specific examples of method (2) are a method in which an alignment control film of the polyimide type or completely imidised polyamic acid type is provided, after which spacers are provided thereon; and a method in which spacers and then an alignment control film are provided, rubbing processing is performed on the alignment control film, and then the substrates are assembled together.

However, the foregoing methods (1) and (2) have the following respective problems.

With method (1), the spacers move (flow) during liquid crystal injection after assembling of the substrates, and during use due to temperature changes and depending on the position in which the liquid crystal display element is installed. Thus control of the arrangement of the spacers is difficult, and they do not necessarily maintain a uniform distribution. Further, air bubbles may arise between the two substrates due to substrate shrinkage and seasonal or daily temperature changes. Consequently, the cell gap cannot be uniformly fixed, and this leads to impairment of display quality, such as uneven display. In addition, since the liquid crystal flows more than with method (2), a drawback with this method is that the liquid crystal display element has low shock stability.

Again, with method (2), the spacers have little or no adhesive force for attaching the two substrates together, so that the substrates held together by the spacers are likely to become detached. When the point of attachment of the two substrates is the alignment control film, and it is made of an imide compound, the foregoing detachment is due to the almost complete lack of adhesive force of the compound (resin) itself. Again, when the point of attachment of the two substrates is between the alignment control film and a resin forming the spacers, and the resin itself has adhesive force, the two substrates are attached, but soon become detached. Again, when the spacers are made of an organic or inorganic resin having no adhesive force, the two substrates will not be attached.

In this way, when adhesive force is insufficient, the cell gap loses its uniformity, and as a result display quality is impaired. Further, when adhesive force is insufficient, unnecessary gaps arise between the two substrates, and the liquid crystal easily moves through these gaps, resulting in marked impairment of the liquid crystal display element's shock stability against external pressure.

One object of the present invention is to provide a liquid crystal display element having sufficient shock stability and good display quality, by fixed attachment of two substrates so as to have a uniform cell gap.

Another object of the present invention is to provide a liquid crystal display element which has high shock stability against external pressure, by preventing spherical spacers from moving.

According to a first aspect of the present invention there is provided a liquid crystal display element comprising a pair of substrates, at least one of which is transparent, spacers, which maintain a uniform gap between the two substrates, and liquid crystal filling the gap between the two substrates; in which at least one of the two substrates is provided with an alignment control film made of a material which includes an organic resin.

With the foregoing structure, the spacers maintain a fixed distance between the substrates, i.e., a fixed cell gap. These spacers may be spherical, or they may have another shape. In the case of spherical spacers, with conventional structures, due to the temperature changes, installation position, etc. discussed above, the spacers flow, and a uniform distribution cannot be maintained. With the structure of the present invention, in contrast, by including of an organic resin in the alignment control film, it is given an adhesive property, and, in a structure where the spacers and the alignment control film come into contact, the spacers are attached and fixed to the alignment control film which has an adhesive property.

Again, in a structure where both substrates are provided with alignment control films, which come into contact with each other at points, since at least one of the alignment control films has an adhesive property, the two alignment control films can be attached together.

Accordingly, the spacers do not move due to temperature changes or installation position, and, as a result, a uniform cell gap can be obtained. Further, since the structural hardness of the substrates is improved, shock stability against external pressure is also improved. In this way, by giving an alignment control film an adhesive property by including an organic resin therein, superior cell gap uniformity and shock stability, and display quality which is free of unevenness, can be realised.

According to a second aspect of the present invention there is provided a liquid crystal display element comprising a pair of substrates, at least one of which is transparent, spacers, which maintain a uniform gap between the two substrates, and liquid crystal filling the gap between the two substrates; in which at least one of the two substrates is provided with an alignment control film, on the surface of which an organic resin is dispersed.

With the foregoing structure, since an organic resin is dispersed on the surface of an alignment control film, the spacers can be fixed to the alignment control film.

In other words, since the organic resin, which is adhesive, attaches the alignment control film and the spacers, the spacers can be fixed to the surface of the alignment control film. In order to give an organic resin an adhesive property, it is necessary to apply, for example, heat or ultraviolet light to a particular resin.

By means of a method which gives a resin an adhesive property or strengthens an already present adhesive property using its thermal or optical characteristics, stronger adhesion can be obtained.

Again, in a structure where both substrates are provided with alignment control films, which come into contact with each other at points, since an organic resin is dispersed on the surface of at least one of the alignment control films, the two alignment control films can be attached together.

Accordingly, the spacers do not move due to temperature changes or installation position, and, as a result, a uniform cell gap can be obtained. Further, since the structural hardness of the substrates is improved, shock stability against external pressure is also improved. In this way, by giving an alignment control film an adhesive property by dispersing an organic resin on the surface thereof, superior cell gap uniformity and shock stability, and display quality which is free of unevenness, can be realised.

The present invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 shows a schematic cross-sectional view of the structure of a liquid crystal element according to Examples 1, 5, 6, 7, 8, and 9 of the present invention; Figure 2 schematically shows the structure of a liquid crystal element according to Example 1 at each step in a manufacturing method thereof; Figure 3 shows a schematic cross-sectional view of the structure of a liquid crystal element according to Example 2 of the present invention; Figure 4 schematically shows the structure of the liquid crystal element shown in Figure 3 at each step in a manufacturing method thereof; Figure 5 shows a schematic cross-sectional view of the structure of a liquid crystal element according to Example 3 of the present invention; Figure 6 shows a schematic cross-sectional view of the structure of a liquid crystal element according to Example 4 of the present invention; Figure 7 shows the structure of a particle of an organic resin to be included in or dispersed on an alignment control film, and showing the states of inclusion of this particle in, and dispersing of this particle on, the alignment control film; and Figure 8 schematically shows a step for including particles of organic resin in or dispersing such particles on the alignment control film, and a step for assembling of the two substrates.

Example 1 The following will explain an example of the present invention with reference to Figures 1 and 2.

Figure 1 is a cross-sectional view showing the schematic structure of a liquid crystal display element according to the present Example. This liquid crystal display element is provided with two substrates 10 and 20, and is structured so that these two substrates are assembled together opposite one another, and the gap therebetween is filled with a liquid crystal 7. A ferroelectric liquid crystal is used for the liquid crystal 7.

The substrate 10 includes an insulating substrate la, a plurality of electrodes 2a arranged so as to be mutually parallel, and light masking sections 3a.

Further, wall-shaped spacers 6 are provided along the light masking sections 3a. Then, so as to cover the foregoing members, an insulating film 4a and an alignment control film Sa are provided, in that order.

The substrate 20 is made up of an insulating substrate ib, a plurality of electrodes 2b arranged so as to be mutually parallel, and an insulating film 4b, and, laminated onto the surface of the insulating film 4b, an alignment control film 5b.

The insulating substrates la and lb are made of a transparent material such as glass or plastic. Indium tin oxide (ITO) is the material typically used for the electrodes 2a and 2b, but there is no need to be limited to this material. When the present liquid crystal display element is structured as a transmission-type liquid crystal display element, it is sufficient if the material used is transparent. Again, when it is structured as a reflection-type liquid crystal display element, either the electrodes 2a or the electrodes 2b need not be transparent.

The light masking sections 3a are made, for example, of a film of Si, but, provided the material used is opaque, various inorganic materials, organic resins, etc., may be used.

Further, as discussed below, an organic resin is included in the alignment control film 5a, so as to give it an adhesive property. By this means, the alignment control film Sa firmly adheres to each of the substrates 10 and 20, and attaches the substrates 10 and 20 together.

Next, the manufacturing process of the liquid crystal display element according to the present Example will be explained with reference to Figure 2.

First, a film of ITO 1000A in thickness is provided on the surface of the insulating substrate la made of glass, etc. by means of sputtering. Then photo-resist is spin-coated onto the surface of this ITO film, and the electrodes 2a are patterned by means of photolithography. Here, if the photo-resist is retained instead of removing it, photo-resist 8a remains on each patterned electrode 2a, as shown in Figure 2(a).

Thereafter, a film of Si 1000A in thickness is formed on the entire surface of the substrate, and, by means of the lift-off method, light masking sections 3a are formed between each pair of electrodes 2a, as shown in Figure 2(b).

Here, Si was used as the material for the light masking sections 3a, and the lift-off method was used for patterning thereof, but other materials and methods may also be used. For example, when an organic material or an easily-etched inorganic material is used as the material for the light masking sections 3a, it is possible either to pattern the light masking sections 3a after patterning of the electrodes 2a, or, conversely, to pattern the electrodes 2a after patterning of the light masking sections 3a.

Next, an ultraviolet curable resin is spin-coated onto the surface of the electrodes 2a and the light masking sections 3a such that its thickness after the baking to be described below will be 1.5cm. Next, this ultraviolet curable resin is patterned in stripes, so as not to overlap with the electrodes 2a, using a photomask. Thereafter, by baking at 2000C for 1 hour, spacers 6 are formed in the shape of walls on the light masking sections 3a, adjacent to the electrodes 2a, as shown in Figure 2(c).

For the ultraviolet curable resin used as the material for the spacers 6, the Shin-Nittetsu Chemical product V259-PA, for example, may be used, but similar ultraviolet curable resins manufactured by other companies may also be used. Alternatively, depending on the combination with the photo-resist, an inorganic material or an organic resin may also be used.

Again, the spacers 6 in the present Example were provided in the shape of stripes on the light masking sections 3a, so as not to overlap with the electrodes 2a, but the spacers 6 are not limited to this shape. For example, the spacers 6 may be in the form of a plurality of round or square pillars provided intermittently in the longitudinal direction of the electrodes 2a.

Next, an insulating material is spin-coated onto the substrate provided with the spacers 6, forming an insulating film 4a with a uniform surface, as shown in Figure 2(d). The insulating material may be, for example, the Nissan Chemical Industries, Ltd. product A2014, etc.

Next, an alignment control film material to be discussed below is spin-coated onto the surface of the insulating film 4a, and baked at a predetermined temperature (hereinafter, this temperature will be referred to as the "film formation temperature"). Then, by performing rubbing alignment processing of the coated film, the alignment control film 5a is provided, as shown in Figure 2(e). In order to increase the adhesion of the two substrates 10 and 20, a predetermined organic resin, as discussed below, is included in the alignment control film 5a.

By means of the foregoing steps, the substrate 10 is completed.

With regard to the substrate 20, on the insulating substrate lb are provided the electrodes 2b, light masking sections (not shown), the insulating film 4b, and the alignment control film 5b, in that order, by steps equivalent to those performed for the substrate 10.

Incidentally, in the present Example, spin-coating was used to coat onto the substrate the materials for the insulating films 4a and 4b, the alignment control films 5a and 5b, and the spacers 6. In addition to this method, however, roll coating or printing, for example, may also be used to form coats of these materials.

Next, the substrates 10 and 20 are placed opposite one another such that the rubbing directions of the alignment control films 5a and Sb are the same, and are assembled together and attached by baking at a predetermined temperature (hereinafter this temperature will be referred to as the "assembly temperature").

Thereafter, the gap between the two substrates 10 and 20 is filled with ferroelectric liquid crystal as the liquid crystal 7, thus completing a liquid crystal display element according to the present Example.

Incidentally, in the foregoing process, the spacers 6 were provided only on the substrate 10 side, but there is no need to be limited to this arrangement. Both the substrate 10 and the substrate 20 may be provided with spacers 6, and then assembled together.

In a liquid crystal display element (liquid crystal cell) prepared according to the foregoing process, cell thickness was uniform with a precision of within O.lym.

In addition, in the pixel display section, uniform alignment and switching characteristics were also obtained.

A variety of liquid crystal display elements were prepared by varying the conditions at the time of preparing the cell, such as the quantity of the organic resin included in the alignment control film 5a, the film formation temperature and assembly temperature, whether ultraviolet light was projected, etc. Then the characteristics of each liquid crystal cell, such as adhesion, were evaluated. These various cells will be explained below.

In order to confirm the effect of inclusion of the resin, as a Comparative Example, a cell equivalent to that of the present Example was prepared, except that resin was not included in the alignment control film Sa.

In preparing the Comparative Example, the film formation temperature of the alignment control film 5a was 1200C, and the assembly temperature was 1800C. For the liquid crystal 7, the Merck Ltd. product SCE8, which is a ferroelectric liquid crystal, was used. The characteristics of the Comparative Example prepared in this manner are as shown in Table 1.

Table 1

ADHESION | MEMORY ANGLE j ALIGNMENT | SHOCK STABILITY NOT EVIDENT ~ 15.60 GOOD 2.0Kg/cm In contrast, in the present Example, cells were prepared with resin included in the alignment control film Sa at various concentrations by volume. For the liquid crystal 7, the foregoing SCE8 was used in each case. For the alignment film Sa, a polyimide type alignment control film, specifically, the Japan Synthetic Rubber product AL5417, was used. The resin included was a thermo/ultraviolet curable resin, specifically, the Shin-Nittetsu Chemical product V259-PA. Experimental cells were prepared with six types of alignment control film 5a, including quantities of 0.05%, 0.1%, 1%, 3%, 5%, and 7% (concentration by volume), respectively.

Using the foregoing experimental cells, adhesion and other characteristics of each cell were evaluated with film formation temperatures of 1200C, 1500C, and 1800C, and with assembly temperatures of room temperature (250C) , 1200C, and 1800C. An experiment was also performed concerning the relationship between adhesion and projection or non-projection of ultraviolet light.

Here, alignment was quantified by measuring memory angle, which is a characteristic of ferroelectric liquid crystal, and alignment was evaluated chiefly by considering changes in memory angle. The following explains the results of the various evaluations.

(1) Quantity of Resin and Adhesion With a film formation temperature of the alignment control film 5a of 1200C and an assembly temperature of 1800C, the relationships between the quantity of resin included and adhesion and alignment, respectively, were investigated. The results are shown in Table 2.

Table 2

RESIN RESIN ADHESION MEMORY ALIGNMENT SHOCK QUANTITY ANGLE STABILITY 0.01% NONE EVIDENT 15.90 GOOD 2.OKg/cm2 EVIDENT, BUT 16.00 GOOD 2.5Kg/cm2 WEAK 1% STRONG 16.30 GOOD 15Kg/cm2 3% STRONG 14.90 SOMEWHAT BLUISH 15Kg/cm2 5% STRONG 13.60 SOMEWHAT BLUISH 15Kg/cm2 STRONG 12.40 In comparison with the Comparative Example, adhesion became evident with inclusion of 0.1k resin, and adhesion was stronger the greater the quantity of resin included.

It can be seen that structural hardness also increased in accompaniment therewith. With regard to alignment, memory angle decreased, and alignment deteriorated, with increase of the quantity of resin included. In the present Example, the optimum quantity of resin is 1%, in which case a liquid crystal display element can be provided in which alignment is not influenced, but which has superior structural hardness.

(2) Film Formation Temperature, Assembly Temperature, and Adhesion With 1% resin included, cells were prepared under various film formation temperatures and assembly temperatures, and adhesion was investigated in each cell. The results are shown in Table 3.

Table 3

FILM ASSEMBLY ADHESION MEMORY ALIGN- SHOCK FORMATION TEMPERATURE ANGLE - MENT STABILITY TEMPERATURE 1200C 250C EVIDENT, 15.70 GOOD 5Kg/cm2 BUT WEAK 1200C 1200C STRONG 15.50 GOOD 15Kg/cm2 1200C 1800C STRONG 16.30 GOOD 15Kg/cm2 1500C 1800C STRONG 16.00 GOOD 15Kg/cm2 1800C 250C EVIDENT, 16.00 GOOD 2Kg/cm2 BUT WEAK 1800C 1200C EVIDENT, 16.1 GOOD 4Kg/cm2 BUT WEAK 1800C ~ 180 C ~ STRONG 16.2 GOOD 10Kg/cm2 From the foregoing results, it can be seen that strong adhesion can be realised by setting the assembly temperature at the same or higher than the film formation temperature. Further, since the resin used in the present Example is a thermo/ultraviolet curable resin, stronger adhesion can be obtained if there is a difference between the film formation temperature and the assembly temperature.

(3) Ultraviolet Projection and Adhesion With inclusion of 1% resin, and a film formation temperature of 1200C, the substrates 10 and 20 were assembled at room temperature, and 1000mJ ultraviolet light (G and I rays) was projected thereon. Adhesion was weak without projection of ultraviolet light, but was strengthened by projection thereof.

The foregoing Example and Comparative Example confirmed that two alignment control films not originally having an adhesive property can be attached by giving at least one of the alignment control films an adhesive property by including a resin therein. This enables a liquid crystal display element having a uniform cell gap and high structural hardness.

As discussed above, with the liquid crystal display element according to the present Example, by including an organic resin in at least the alignment control film 5a, the substrates 10 and 20 can be strongly attached together, and thus a liquid crystal display element can be obtained which has a uniform cell gap, sufficient shock stability, and good display quality.

Further, the spacers 6 are provided on at least one of the substrates 10 and 20 in the form of pillars or walls, and the substrates 10 and 20 are assembled together by attachment of the alignment control film Sa, which is provided so as to cover the spacers 6, to the opposite alignment control film 5b. With this structure, the substrates 10 and 20 are assembled together with the spacers 6 maintaining a uniform interval therebetween.

Further, since the points of contact between the two substrates 10 and 20 are the alignment control films Sa and 5b, the adhesive property of the substrates 10 and 20 is determined by the adhesion of the alignment control films Sa and 5b.

Accordingly, since an organic resin is included in the alignment control film Sa, as discussed above, a liquid crystal display element can be manufactured which has superior adhesion between the substrates 10 and 20.

In addition, with the foregoing structure, control of the cell gap is also easy.

The foregoing manufacturing method includes a first step, in which the spacers 6 are provided on the insulating substrate la in the form of pillars or walls, and a second step, in which the alignment control film Sa is provided so as to cover the spacers 6 and the insulating substrate la. With this method, prior to the first step, in which the spacers 6 are provided on the insulating substrate la, electrodes 2a, light masking sections 3a, etc. may first be provided, as needed, on the insulating substrate la. Thereafter, in the second step, the alignment control film Sa is provided so as to cover the insulating substrate la provided with the spacers 6 and, as necessary, with the electrodes 2a, etc.

Again, as shown in Figures 2(d) and 2(e), prior to providing the alignment control film Sa, an insulating film 4a may be provided so as to cover the insulating substrate la, after which the alignment control film 5a is provided.

In this way, since the spacers 6 are provided before the alignment control film Sa, contamination or damage of the alignment control film 5a by solvents used in the step for providing the spacers 6 can be prevented.

Consequently, a liquid crystal display element can be provided which has good display quality which is free of unevenness. Accordingly, by strongly attaching the alignment control films 5a and 5b of the substrates 10 and 20, a liquid crystal display element can be realised which has a uniform cell gap and superior structural hardness. This is also the case in Example 2 to be explained below.

Moreover, in cases when a baking step is used in forming the spacers 6 and the alignment control film 5a, a spacer material requiring a baking temperature higher than that of the alignment control film Sa may be used.

This has the advantage of broadening the scope of spacer materials which may be used.

Further, the foregoing manufacturing method includes a first baking step, for baking the alignment control film Sa when forming the alignment control film Sa on the insulating substrate la, and a second baking step, for baking the alignment control film 5a when assembling the two substrates 10 and 20. With this method, the first baking is performed at the time of formation of the alignment control film 5a, then, as necessary, rubbing processing, etc. of the alignment control film 5a is performed, and thereafter the second baking is performed during the assembly step. Accordingly, the alignment control film Sa can be given an adhesive property.

Possible adhesive modes which may be used to give the alignment control film Sa an adhesive property are (1) adhesion by chemical bonding of opposing contact surfaces in accordance with a polymerising reaction of reaction groups; (2) adhesion by bonding of opposing contact surfaces in accordance with intermolecular force by means of hydroxyl groups or hydrogen groups of an organic resin which are unreacted or are included internally therein; and (3) adhesion by fusing of opposing contact surfaces. The two-step baking process makes use of these adhesive modes to give the substrates 10 and 20 sufficient adhesion, and thus a liquid crystal display element with superior cell gap uniformity and display quality can be provided. The tw points, and thus a liquid crystal display element with stronger adhesive property can be obtained.

The temperatures of the foregoing two-step baking process may be set so as to obtain a suitable adhesive strength, based on the characteristics of the resin used.

Accordingly, various processes are possible, such as one in which the first baking temperature is lower than the second, one in which the first baking temperature is higher than the second, and one in which the two are equal.

Incidentally, the present Example uses ferroelectric liquid crystal for the liquid crystal 7 because ferroelectric liquid crystal is capable of rapid response due to spontaneous polarisation and memory. Accordingly, it is possible to display, for example, high-capacity, high-definition images. A problem with ferroelectric liquid crystal is that, since the order of its molecules is more crystalline than that of, say, nematic liquid crystal, it is vulnerable to impact, i.e., molecules whose order is disturbed by external pressure do not easily return to their original order. However, with the foregoing structure, since a sufficient substrate hardness is realised, this problem is resolved. As a result, a liquid crystal display element can be provided which fully exploits the superior characteristics of ferroelectric liquid crystal. This also applies to each of the following Examples.

Example 2 The following will explain another example of the present invention with reference to Figures 3 and 4. For ease of explanation, members equivalent to those shown in the Figures pertaining to the foregoing Example will be given the same reference symbols, and explanation thereof will be omitted.

Figure 3 is a cross-sectional view schematically showing the structure of a liquid crystal display element according to the present Example.

The present liquid crystal display element is provided with a substrate 11 instead of the substrate 10 explained in Example 1 above. The substrate 11 is provided with an insulating substrate lla, electrodes 12a, and light masking sections 13a equivalent to the insulating substrate la, electrodes 2a, and light masking sections 3a explained in Example 1 above. Further, an insulating film 14a is provided so as to cover the electrodes 12a and the light masking sections 13a. Next, spacers 16 are provided on the insulating film 14a, and then an alignment control film 15a is provided so as to cover the insulating film 14a and the spacers 16.

The following will explain a method of manufacturing the liquid crystal display element according to the present Example.

First, by steps equivalent to those of Example 1, the electrodes 12a and the light masking sections 13a are provided on the insulating substrate lla. The structure of the liquid crystal display element upon completion of these steps is as shown in Figure 4(a).

Next, an insulating film material is spin-coated onto the surface of the electrodes 12a and the light masking sections 13a, and baked at 2000C. By this means, an insulating film 14a with a uniform surface is provided, as shown in Figure 4(b). For the insulating film material, the Nissan Chemical Industries, Ltd.

product A2014, for example, may be used.

Next, an ultraviolet curable resin is spin-coated onto the surface of the insulating layer 14a such that its thickness after the baking to be described below will be 1.5cm. Next, this ultraviolet curable resin is patterned in stripes, so as not to overlap with the electrodes 12a, using a photo-mask. Thereafter, by baking at 2000C for 1 hour, spacers 16 are formed in the shape of walls on the light masking sections 13a, parallel to the electrodes 12a, as shown in Figure 4(c).

For the ultraviolet curable resin used as the material for the spacers 16, the Shin-Nittetsu Chemical product V259-PA, for example, may be used, but similar ultraviolet curable resins manufactured by other companies may also be used. Alternatively, depending on the combination with the photo-resist, an inorganic material or an organic resin may also be used.

Again, the spacers 16 in the present Example were provided in the shape of stripes on the light masking sections 13a, so as not to overlap with the electrodes 12a, but the spacers 16 are not limited to this shape.

For example, the spacers 16 may be in the form of a plurality of round or square pillars provided intermittently in the longitudinal direction of the electrodes 12a.

Next, an alignment control film material equivalent to that used in Example 1 is spin-coated onto the substrate on which the spacers 16 have been formed as above, and baked at one of the suitable film formation temperatures explained in Example 1. Then, by performing rubbing alignment processing of the coated film, the alignment control film 15a is provided, as shown in Figure 4(d).

As in the case of Example 1, in order to increase the adhesion of the two substrates 11 and 20 by giving the alignment control film 15a an adhesive property, a suitable quantity of a predetermined organic resin is included therein.

By means of the foregoing steps, the substrate 11 is completed, and, by assembling together the two substrates 11 and 20 by steps equivalent to those of Example 1, and injecting the liquid crystal 7 into the gap therebetween, the liquid crystal display element is completed.

As discussed above, the liquid crystal display element according to the present Example differs from that of Example 1 in that the insulating film 14a is provided before the spacers 16. However, both Examples are equivalent in that the two substrates are attached by adhesion of the two alignment control films.

For this reason, with respect to adhesion of the two substrates 11 and 20 in the present Example, effects equivalent to those of Example 1 can be obtained by including an organic resin in at least the alignment control film 15a. As a result, effects equivalent to those of Example 1 with respect to cell gap uniformity, good display quality, and shock stability can also be obtained. Upon preparing a liquid crystal display element according to the present Example and actually investigating, in the same manner as in Example 1, the effects of inclusion of the organic resin in the alignment control film 15a, the effects obtained with respect to adhesion, etc. were equivalent to those of Example 1.

Example 3 The following will explain a further example of the present invention with reference to Figure 5. For ease of explanation, members equivalent to those shown in the Figures pertaining to the foregoing Examples will be given the same reference symbols, and explanation thereof will be omitted.

Figure 5 is a cross-sectional view schematically showing the structure of a liquid crystal display element according to the present Example.

The present liquid crystal display element is provided with a substrate 30 instead of the substrate 10 explained in Example 1 above. The substrate 30 is provided with an insulating substrate 31a, electrodes 32a, and light masking sections 33a equivalent to the insulating substrate la, electrodes 2a, and light masking sections 3a explained in Example 1 above.

Further, an insulating film 34a and an alignment control film 35a are laminated in that order on the electrodes 32a and the light masking sections 33a so as to cover these respective members. Next, wall-shaped spacers 36 are provided on the alignment control film 35a in the form of stripes, so as not to overlap with the electrodes 32a.

The following will explain a method of manufacturing the liquid crystal display element according to the present Example.

First, by steps equivalent to those of Example 1, the electrodes 32a and the light masking sections 33a are provided on the insulating substrate 31a. Next, by spincoating an insulating film material onto the surface of the electrodes 32a and the light masking sections 33a, an insulating film 34a with a uniform surface is provided.

Next, an alignment control film 35a is formed on the insulting film 34a.

In the alignment control film 35a is included 1% by volume of the Shin-Nittetsu Chemical product V259-PA, which is a thermo/ultraviolet curable resin. The baking temperature of the alignment control film 35a may be the same as the baking temperature to be used when forming the spacers 36, as discussed below. Here, since the spacers 36 are to be baked at 2000C, the alignment control film 35a is also baked at 2000C.

Next, an ultraviolet curable resin is spin-coated onto the surface of the alignment control film 35a such that its thickness after the baking to be described below will be 1.5cm. Next, this ultraviolet curable resin is patterned in stripes, so as not to overlap with the electrodes 32a, using a photo-mask. Thereafter, by baking at 2000C for 1 hour, the spacers 36 are formed.

For the ultraviolet curable resin used as the material for the spacers 36, the Shin-Nittetsu Chemical product V259-PA, for example, may be used, but similar ultraviolet curable resins manufactured by other companies may also be used. Alternatively, depending on the combination with the photo-resist, an inorganic material or an organic resin may also be used.

Again, the spacers 36 in the present Example were provided in the shape of stripes, so as not to overlap with the electrodes 32a, but the spacers 36 are not limited to this shape. For example, the spacers 36 may be in the form of a plurality of round or square pillars provided intermittently in the longitudinal direction of the electrodes 32a.

With regard to the substrate 20, on the insulating substrate 1b are provided the electrodes 2b, light masking sections (not shown), the insulating film 4b, and the alignment control film 5b, in that order. After spincoating of the alignment control film Sb, it is baked at either of two baking temperatures, 120"C and 2000C.

Further, as with the alignment control film 35a, 1% by volume of the ultraviolet curable resin V259-PA is included in the alignment control film 5b.

Then, after performing rubbing alignment processing of the alignment control films 35a and 5b, the substrates 30 and 20 are attached by assembling under an applied pressure of 1Kg/cm2 and baking at 2000C. For the liquid crystal 7, SCE8 is then injected into the gap therebetween, thus completing the liquid crystal display element.

As discussed above, the liquid crystal display element according to the present Example differs from those of Examples 1 and 2 in that the spacers 36 are provided after the alignment control film 35a, and the lower substrate 30 and the upper substrate 20 are attached by adhesion of the spacers 36 and the alignment film 5b.

Upon preparing liquid crystal display elements according to the present Example by the foregoing steps, and investigating the adhesion of the substrates 30 and 20, strong adhesion was evident, whether the baking temperature of the alignment control film Sb was 1200C or 2000C.

When, for comparative purposes, a liquid crystal display element was prepared by the same process as that of the present Example, except that the alignment control films did not include resin, the two substrates were found to have some adhesion, but it was weaker than in the present Example, and there were areas where the substrates easily became detached.

This indicates that, since acrylic resin was used as the material for the spacers 36 (this resin itself having an adhesive s ive property), there was some adhesion even without including a resin in the alignment control film 5b, but that Stronger adhesion can be obtained by, as in the present Example, including a resin in the alignment control film 5b.

Further, for comparative purposes, a liquid crystal display element was prepared by the same process as that of the present Example, except that an inorganic material was used for the spacers, and a polyimide-type alignment control film was used, and the difference in adhesion with the inclusion or non-inclusion of resin was investigated. As a result, it was found that the spacers adhered when resin was included, but did not adhere when resin was not included.

As discussed above, in the present Example, the spacers 36 are provided in the form of pillars or walls on the substrate 30, and the two substrates 20 and 30 are attached together by adhesion of the upper surfaces of the spacers 36 to the alignment control film Sb. With this structure, the substrates 20 and 30 are assembled with the spacers 6 maintaining a uniform interval therebetween. Further, since the points of contact between the two substrates 20 and 30 are the alignment control film 5b and the upper surfaces of the spacers 36, the adhesive property of the substrates 20 and 30 is determined by the adhesion of these members.

Since, as discussed above, an organic resin is also included in the alignment control film 5b, the adhesion between the substrates 20 and 30 is improved, and thus a liquid crystal display element with good display quality and shock stability can be realised. In addition, with the foregoing structure, control of the cell gap is also easy.

The foregoing manufacturing method includes a first step, in which the alignment control film 35a is provided on the insulating substrate 31a, and a second step, in which the spacers 36 are provided in the form of pillars or walls on the alignment control film 35a. With this method, prior to the second step, in which the spacers 36 are provided on the alignment control film 35a, electrodes 32a, light masking sections 33a, and the insulating layer 34a may first be provided, as needed, on the insulating substrate 31a.

With the foregoing method, the points of adhesion of the substrates 20 and 30 are between the spacers 36 and the surface of the alignment control film 5b which includes the organic resin. An alignment control film 5b which does not include an organic resin usually has little or no adhesive property (for example, a polyimidetype alignment control film), and in such cases the adhesion of the substrates 20 and 30 depends solely on the adhesion of the material forming the spacers 36 which come into contact with the alignment control film Sb.

Since inorganic spacer materials have almost no adhesive property, when the spacers are made of such materials, the substrates 20 and 30 cannot be attached. Again, even most organic spacer materials have insufficient adhesion, and the substrates 20 and 30 cannot be sufficiently attached.

In the present Example, in contrast, since the alignment control film 5b is given adhesion, the substrates 20 and 30 can be attached regardless of the spacer material. Again, with alignment control film and spacer materials which already have an adhesive property, adhesion thereof is made Stronger. In this way, with the foregoing method, the substrates 20 and 30 are sufficiently attached, and thus a liquid crystal display element with superior cell gap control, display quality, and shock stability can be manufactured. As a result, a liquid crystal display element with a uniform cell gap and superior structural hardness can be obtained.

Example 4 The following will explain a further example of the present invention with reference to Figure 6. For ease of explanation, members equivalent to those shown in the Figures pertaining to the foregoing Examples will be given the same reference symbols, and explanation thereof will be omitted.

Figure 6 is a cross-sectional view schematically showing the structure of a liquid crystal display element according to the present Example.

The present liquid crystal display element is provided with spherical spacers 9 instead of the spacers 6 explained in Example 1 above. In a substrate 40, on an insulating substrate 41a, transparent electrodes 42a and light masking sections 43a are provided, as in Example 1 above, and on the surface thereof, an insulating film 44a and an alignment control film 45a are provided, in that order.

With regard to the substrate 20, on the insulating substrate lb are provided the electrodes 2b, light masking sections (not shown), the insulating film 4b, and the alignment control film 5b, in that order.

1% by volume of the ultraviolet curable resin V259 PA is included in the alignment control films Sb and 45a.

Baking of the alignment control films 5b and 45a is performed at a film formation temperature of 1200C.

Then, after uniformly distributing spherical spacers 9 having a diameter of 1.5 m on one of the substrates 20 and 40, and printing a thermosetting sealant outside the pixel areas, the substrates 20 and 40 are assembled.

Thereafter, the substrates 20 and 40 are heat pressed under an applied pressure of 1Kg/cm2 and at a temperature of 1800C for 1 hour. Finally, a ferroelectric liquid crystal (SCE8) is injected into the gap between the substrates 20 and 40, thus completing the liquid crystal display element according to the present Example.

Further, for comparative purposes, a liquid crystal display element having the same structure as that of the present Example, except that a resin was not included in the alignment control films, was prepared, and the characteristics of the two liquid crystal display elements were compared. The results are shown in Table 4.

Table 4

INCLUSION OF MEMORY ALIGNMENT SHOCK NOTE RESIN ANGLE STABILITY YES YES 16.30 GOOD 3Kg/cm2 SPACERS ARE FIXED NO 16.2 GOOD 0.6Kg/cm SPACERS MOVE As the foregoing results show, the alignment control films are given an adhesive property by including resin therein, and thus, since the spacers 9 are fixed between the alignment control films 5b and 45a, structural hardness is increased. Again, when observing the behaviour of the spacers at the time of injection of the liquid crystal, in the element in which resin was not included in the alignment control films, it was found that some spacers moved, giving rise to places where uniformity of spacer distribution was disturbed. In such places, since the cell gap was not uniform, uneven display occurred.

Further, during liquid crystal injection, a liquid crystal cell in which the substrates 20 and 40 are not attached by means of the spacers may, depending on the duration of injection, bulge, making it impossible to obtain a desired cell gap, which may in turn result in an overly thick cell. A liquid crystal cell with resin included in the alignment control films, in contrast, was able to ensure a uniform cell gap, and obtain display quality which was free of unevenness.

Example 5 A liquid crystal display element according to the present Example has the same schematic structure as the liquid crystal display element explained in Example 1 and shown in Figure 1.

In other words, the lower substrate 10 is made up of the insulating substrate la, on which are provided the electrodes 2a and the light masking sections 3a, on which, in turn, are provided the spacers 6, and then, so as to cover these other members, the insulating film 4a and the alignment control film 5a are laminated thereon, in that order.

However, in the present Example, a thermoplastic resin is included in the alignment control film Sa.

Specifically, Japan Synthetic Rubber product AL5417 is used for the alignment control film 5a, in which is included 1% by volume of the TECHNO ALPHA product staystik 383G as the thermoplastic resin.

Under the foregoing conditions, inclusion of about 1% by volume of thermoplastic resin is appropriate.

However, the appropriate quantity to include will vary depending on the resin used and the type of alignment control film, liquid crystal, etc. Consequently, an optimum quantity should be determined according to the resin to be included.

The resin is an adhesive of the thermoplastic type, and has an adhesive temperature (softening point) within a range from 1600C to 2750C.

In the manufacturing method according to the present Example, after baking the alignment control film Sa at 1200C and performing rubbing processing thereon, the substrates 10 and 20 are heat pressed under an applied pressure of 1Kg/cm2 at 1800C for 1 hour, and then, still in a pressed state, are allowed to cool gradually. Here, the heat pressing temperature (1800C) is suitable for the present adhesive resin, and does not influence the other elements composing the liquid crystal element.

When the resin was not included in the alignment control film Sa, there was no adhesion when the substrates 10 and 20 were assembled, but by including the resin in the alignment control film 5a as in the present Example, a liquid crystal display element having adhesion and superior structural hardness can be obtained.

Then the ferroelectric liquid crystal SCE8 is vacuum injected at around 1000C, its phase transition temperature to the isotropic phase. At this temperature, the foregoing thermoplastic resin is not softened at the time of injection of the liquid crystal. As a result, a liquid crystal display element with good alignment, a uniform cell gap, and superior structural hardness can be realised.

Next, a liquid crystal display element was prepared which was pressed with uneven force by inserting an uneven plate at the time of heat pressing. In this case, since the pressing force was not uniform, some areas did not adhere, and a liquid crystal element with non-uniform cell gap was obtained. However, by performing a second heat pressing of this liquid crystal display element under the same conditions, but with uniform force applied throughout, the cell gap was made uniform.

When using thermosetting resin, once adhered and set, the adhesion cannot be corrected. However, the foregoing confirmed that, with thermoplastic resin, it was possible to make corrections in the substrate assembly step by re-application of heat.

The thermoplastic resin used as the organic resin in the present Example has a softening point higher than or equal to the isotropic phase transition temperature of the ferroelectric liquid crystal, but lower than or equal to the softening point of the material used for the spacers 6. Thermoplastic resin is a resin which softens under application of heat. Making use of this characteristic, the temperature at the time of the substrate assembly step is raised to the softening point of the resin. Due to softening of the resin, the points of contact become fused, and if cooled gradually thereafter, the resin returns to its original hardness, resulting in adhesion.

The advantage of using thermoplastic resin is that assembly can be redone if adhesion is incomplete due to any insufficiency in the various conditions (temperature, pressure, duration of pressing, etc.) at the time of the substrate assembly step. In other words, with resin of the thermosetting type, once the resin is polymerised and hardened, it will not return to its original softness and state of crosslinking. With a thermoplastic resin, however, even in the event of defective substrate assembly, the resin can be re-softened by reheating, and the substrate assembly step can be performed again. In short, the resin can be given adhesion by softening by heating, and, making use of its thermoplastic characteristics, substrate assembly can be performed repeatedly. This is extremely advantageous in improving the yield.

However, with this type of resin, if the softening point is too low, the liquid crystal and the resin become mixed during heating at the time of injection of the liquid crystal, which has a detrimental influence on the characteristics of the liquid crystal. Again, if the softening point of the resin is higher than those of the spacers and other structural elements of the liquid crystal display element, the other structural elements soften before the resin, and the liquid crystal display element cannot be manufactured. Accordingly, a condition for inclusion of the resin in the alignment control film is that its softening point is preferably higher than or equal to the isotropic phase transition temperature of the liquid crystal to be injected, but lower than or equal to the softening point of the spacer material. By using a thermoplastic resin meeting this condition and specifying the assembly temperature, a liquid crystal display element with a uniform cell gap and high structural hardness can be provided.

Example 6 A liquid crystal display element according to the present Example has the same schematic structure as the liquid crystal display element explained in Example 1 and shown in Figure 1. However, in the present Example, a mixture of two types of organic resin, thermo/ultraviolet curable resin and thermoplastic resin, is included in the alignment control film 5a. Specifically, the abovementioned AL5417 is used for the alignment control film Sa, in which is included 1 by volume of a mixture of equal quantities of the above-mentioned thermo/ultraviolet setting resin V259-PA and the above-mentioned thermoplastic resin staystik 383G.

Under the foregoing conditions, inclusion of about 1% by volume of the mixture of thermo/ultraviolet curable resin and thermoplastic resin is suitable. However, a suitable quantity to include will vary depending on the resins used and the type of alignment control film, liquid crystal, etc. Consequently, an optimum quantity should be determined according to the resins to be included.

In the manufacturing method according to the present Example, after baking the alignment control film 5a at 1200C and performing rubbing processing thereon, the substrates 10 and 20 are heat pressed under an applied pressure of 1Kg/cm2 at 1800C for 1 hour, and then, still in a pressed state, are allowed to cool gradually.

Then the ferroelectric liquid crystal SCE8 is vacuum injected at around 1000C, its phase transition temperature to the isotropic phase. Because of the effects of adhesion by thermosetting and adhesion by fusing due to thermoplasticity, a liquid crystal display element prepared in this way has stronger adhesion than one prepared using only one resin.

Next, a liquid crystal display element was prepared which was 'pressed with uneven force by inserting an uneven plate at the time of heat pressing. In this case, since the pressing force was not uniform, some areas did not adhere, and a liquid crystal element with non-uniform cell gap was obtained. However, by performing a second heat pressing of this liquid crystal display element under the same conditions, but with uniform force applied throughout, the cell gap was made uniform.

In the present Example, the thermosetting resin used as organic resin is a resin in which application of heat promotes a hardening reaction, and the resin hardens according to the polymerisation degree and cross-linking.

If, making use of these characteristics, the baking temperature at the time of forming the alignment control film 5a is set to a lower temperature than the baking temperature at the time of attaching the substrates 10 and 20, the thermosetting resin is still insufficiently hardened when the substrates 10 and 20 are brought together, and the resin thus becomes fused to the substrates 10 and 20. Then, by baking in the substrate assembly step, the hardening reaction of the resin between the substrates 10 and 20 progresses, and strong adhesion is obtained. In other words, the promotion of the resin's hardening reaction by the application of heat is utilised for adhesion. As a result, a liquid crystal display element can be manufactured which has a uniform cell gap and strong structural hardness.

Further, when only a thermosetting resin was included, assembly could not be redone, but when a thermoplastic resin was also included, it was confirmed that reattachment (remaking) was possible. In this way, the inclusion of two types of resin made it possible to add another effect to the effect obtained by inclusion of one resin alone, and was conducive to manufacture of a liquid crystal element with even better cell gap uniformity. With regard to the combination of resins included, the optimum combination and blending ratio may be determined giving consideration to the functions of the resins and the desired adhesion, productivity, etc.

In the present Example, the organic resin included in the alignment control film 5a is a mixture of two or more types of resin having different characteristics. By this means, the merits of each resin are exploited to obtain an advantageous effect. For example, if the resins included are a thermosetting resin and an ultraviolet curable resin, desired adhesion can be obtained by adjusting adhesion by heating and adhesion by projection of ultraviolet light. With a structure of this kind, if, for example, there are restrictions on the temperature or duration with which heat may be applied, or the quantity of ultraviolet light which may be projected, sufficient adhesion may be obtained under these restricted conditions by adjusting the blending ratios of the thermosetting resin and the ultraviolet curable resin. By making the best use of the merits of each resin, the scope of manufacturing methods is broadened, and manufacturing methods suited to various requirements can be provided.

In addition, the foregoing mixture may also be included in the alignment control film Sb, or may be dispersed on the alignment control film Sa or on both alignment control films 5a and 5b.

When the resin included in or dispersed on the alignment film(s) is a mixture of a thermosetting resin and a thermoplastic resin, even if uneven pressing or uneven heating during assembly by thermosetting results in non-uniform hardening, the areas not uniformly attached can be attached by reheating, using the resoftening effect of the thermoplastic resin. In other words, assembly defects which arise with assembly using thermosetting resin alone can be resolved by blending a thermoplastic resin with the thermosetting resin, and this is effective in improving the yield.

In this way, if two or more resins with different characteristics are included in or dispersed on the alignment control film(s), effects can be obtained such as improving adhesion, and mitigating or eliminating defects or deficiencies arising with use of one resin alone, and thus a liquid crystal display element with high precision can be obtained.

The foregoing discussed two examples of blends of resins, but there is no limitation to these blends. For example, a blend of three or more resins, or a blend of thermosetting resins of the same type but having different setting temperatures, are possible. In short, the optimum blend is one able to attain the most effective adhesion under conditions limited by the manufacturing process of the liquid crystal display element.

Incidentally, the polymerisation of many ultraviolet curable resins, as with thermo/ultraviolet curable resins, is made more complete by the application of heat.

With this type of resin, it is preferable to apply heat during the substrate assembly step. In this way, by using an ultraviolet curable resin, a liquid crystal display element can be provided which has a uniform cell gap and strong structural hardness.

In the present Example, the ultraviolet curable resin used as organic resin is a resin in which projection of ultraviolet light promotes a hardening reaction, and the resin hardens according to the polymerisation degree and crosslinking. If these characteristics are made use of, the hardening reaction progresses by the projection of ultraviolet light, and accordingly adhesion can be obtained at the time of attaching the substrates 10 and 20 even without the application of heat. In other words, the promotion of the resin's hardening reaction by the projection of ultraviolet light is utilised for adhesion. Accordingly, ultraviolet curable resins are effective in structures in which the repeated application of heat may deform substrates or structural elements, change alignment control film characteristics, etc.

Example 7 A liquid crystal display element according to the present Example has the same schematic structure as the liquid crystal display element explained in Example 1 and shown in Figure 1. However, in the present Example, a soluble polyimide type material is used for the alignment control film 5a, and a predetermined quantity of fine particles of acrylic resin is included therein.

Specifically, the above-mentioned AL5417, which is a soluble polyimide type material not having an adhesive property itself, is used for the alignment control film Sa, in which is included 10% by volume of fine particles of acrylic resin having particle diameters of O.lym to 0.2m and a softening point of 1500C.

In the manufacturing method according to the present Example, after applying the alignment control film 5a, it is baked at 1200C, and then, after performing rubbing processing thereof, the substrates 10 and 20 are heat pressed under an applied pressure of lKg/cm2 at 1800C for 1 hour. Then the ferroelectric liquid crystal SCE8 is injected.

When using spin-coating to apply the alignment control film 5a with the fine particles included therein, if an excessive quantity is included, or dispersion is incomplete, there are cases when uneven coating may arise. No problems arose under the conditions of the present Example, but dispersal method and coating method should be chosen according to the material and the quantity to be included thereof; there is no limitation to the methods explained above. To give some major examples, dispersal by ultrasonic dispersal, and application by roll coating or printing, are possible.

Again, the resin used here is an acrylic resin, but, provided the resin used has an adhesive property, it need not be limited to this. Major examples include epoxy resins, etc. Neither is the proportion of resin included limited to the 10k included here; the resin may be included in a proportion suitable to the necessary adhesion, alignment, etc.

Again, the resin particle diameters indicated above are appropriate from the point of view of alignment and coating, but, since the influence on alignment differs according to the resin used, an appropriate particle diameter should be selected according to the type of alignment control film, type of liquid crystal to be injected, etc.

In the foregoing manufacturing process, the pressing temperature of 1800C at the time of substrate assembly is a temperature sufficient to soften the fine particles, and thus, at this temperature, the two substrates were attached by the fine particles. Further, inclusion of the resin as discussed above had no adverse influence on the structural elements of the liquid crystal display element, and good alignment was obtained. In this way, the alignment control film 5a, which had no adhesive property when the fine particles was not included, was given an adhesive property by including the fine particles therein, and thus a liquid crystal display element with superior structural hardness was obtained.

As discussed above, in the present Example, easily handled fine particles are used for the organic resin for obtaining 'adhesion, and these fine particles are dispersed on the surface of the alignment control film 5a (and/or the alignment control film 5b). By this means, the two alignment control films (as in Example 1), or the spacers and an alignment control film (as in Example 2) can be simply and certainly attached, or existing adhesion therebetween can be increased.

Example 8 A liquid crystal display element according to the present Example has the same schematic structure as the liquid crystal display element explained in Example 1 and shown in Figure 1. However, in the present Example, the alignment control film 5a is provided as follows. A soluble polyimide type material is used for the alignment control film 5a; specifically, the above-mentioned AL5417, which is a soluble polyimide type material not having an adhesive property itself.

After applying the alignment control film 5a by spin-coating, it is prebaked on a hot-plate at 800C for 1 minute, thus vaporising the solvent. Then, fine particles of acrylic resin (particle diameter O.lym to 0.2cm; softening point 1500C) are dispersed over the surface of the alignment control film Sa, so that their density on the surface thereof is 5k, using a dry spacer dispersal device.

Next, the alignment control film 5a is baked at 1200C. By this baking, the fine particles dispersed on the surface of the alignment control film 5a are fixed thereon. Thereafter, rubbing processing is performed, and the substrates 10 and 20 are heat pressed under an applied pressure of 1Kg/cm2 at 1800C for 1 hour. Then a ferroelectric liquid crystal (SCE8) is injected.

In the foregoing process, rubbing processing is performed after dispersal of the fine particles, but it is also possible to perform rubbing processing before dispersing the fine particles on the alignment control film 5a. Moreover, the baking temperature during formation of the alignment control film Sa, the pressing temperature during assembly of the substrates, etc. are not limited to the examples indicated above; conditions may be set according to the fine particles and alignment control film material used, in order to obtain suitable adhesion.

Upon preparing a liquid crystal display element according to the foregoing process, the substrates 10 and 20 were attached due to the effect of the fine particles, and alignment was also good. In this way, it was possible to obtain an adhesive property by dispersing fine particles on the alignment control film 5a, and thus to obtain a liquid crystal display element with superior structural hardness.

In order to apply the present Example to the liquid crystal display element of Example 2, fine particles are also dispersed on the alignment control film 5b.

As discussed above, in the present Example, easily handled fine particles are used for the organic resin for obtaining adhesion, and these fine particles are dispersed on the surface of the alignment control film 5a (and/or the alignment control film 5b). By this means, the two alignment control films (as in Example 1), or the spacers and an alignment control film (as in Example 2) can be simply and certainly attached, or existing adhesion therebetween can be increased.

Example 9 The following will explain a further example of the present invention with reference to Figures 1, 7, and 8.

A liquid crystal display element according to the present Example has the same schematic structure as the liquid crystal display element explained in Example 1 and shown in Figure 1. However, in the present Example, a predetermined quantity of fine particles 51 of organic resin having a two-layer structure, as shown in Figure 7(a), are included in the alignment control film 5b.

A soluble polyimide type material is used for the alignment control film Sb; specifically, AL5417, which is a soluble polyimide type material not having an adhesive property itself.

Further, in the alignment control film 5b are included 10% by volume of fine particles 51 of acrylic resin having the two-layer structure shown in Figure 7(a). The fine particles 51 have particle diameters of 0.lem to 0.2m and a softening point of 1500C. Further, the softening point of the inner resin 51a is 1000C, and that of the outer resin Slb is 200"C.

The alignment control film 5b, which includes the foregoing fine particles 51, is applied by spin-coating, prebaked on a hot-plate at 800C, baked at 1200C, and then undergoes rubbing processing. Thereafter, the substrates 10 and 20 are heat pressed under conditions of 1Kg/cm2, 1800C, 1 hour.

As discussed in Example 7 above with regard to inclusion of a resin, it is important how uniformly the resin is included in the solvent. However, there is no need to be limited to the conditions discussed above; the methods of selecting, including, and coating the resin discussed in Example 7 above may also be used.

Then a ferroelectric liquid crystal (SCE8) is injected. In a liquid crystal display element prepared in this way, the substrates 10 and 20 were firmly attached, and the liquid crystal display element had superior structural hardness and good alignment.

Further, when, as above, the two-layer fine particles 51 are included in the alignment control film Sb, during substrate assembly, the outer resin 51b, which has not yet softened, protects and contains the inner resin 51a, which has melted.

Accordingly, when assembling the substrates 10 and 20, as shown in Figure 8, in the areas which come into contact with the wall-shaped spacers 6, the pressure applied breaks the shell formed by the outer resin 51b, and the softened inner resin 51a, which has an adhesive property, flows out, thus attaching the substrates 10 and 20. In the pixel areas where there are no spacers 6, on the other hand, no pressure is applied, the fine particles 51 (resin) externally maintain their shape, and the inner resin 51a does not flow out. As a result, the resin does not spread over the alignment control film 5b, and alignment is not disturbed. In other words, with this method, since the adhesion of the resin affects only the points of contact, a sufficient adhesive quality can be secured, but without detrimental effects to alignment.

Incidentally, in the present Example, the fine particles 51 were introduced in the alignment control film 5b, as shown in state A in Figure 7(b), but the fine particles 51 may also be dispersed on the surface of the alignment control layer Sb, as shown in state B in Figure 7(b).

As discussed above, the present Example uses fine particles which include an inner resin 51a and an outer resin 51b which covers the inner resin 51a, in which the inner resin 51a has a softening point which is lower than that of the outer resin 51b; specifically, fine particles having the two-layer structure shown in Figure 7(a).

Here, if the softening point of the inner resin 51a is Ta, and that of the outer resin 51b is Tb, then Ta < Tb.

Including these fine particles in, or dispersing them on the surface of, the alignment control film 5b, the two substrates 10 and 20 are assembled with, for example, the wall-shaped spacers 6 therebetween. If the temperature T at this time is set to Ta < T < Tb, then at temperature T, the inner resin Sla has softened, but the outer resin Slb has not. For that reason, the fine particles 51 externally maintain their original shape. If the substrates 10 and 20 are assembled under these conditions, as is schematically shown in Figure 8, in the areas corresponding to the wall-shaped spacers 6, pressure causes the outer resin 51b to break, and the inner resin 51a flows out, causing the spacers 6 and the alignment control film 5b to adhere. In the areas not corresponding to the spacers 6, however, since no pressure is applied to the outer resin 51b, the particles 51 maintain their original shape.

As discussed above, the advantage of using this type of fine particle is that the softened inner resin Sla does not spread over the areas of the alignment control film 5b not in contact with the spacers 6. When dispersing fine particles on the pixel surface, depending on the type and dispersal ratio of the resin, the resin may spread over the alignment control film 5b during substrate assembly, and may impair the effects of the alignment control film Sb, which has undergone alignment processing. In contrast, by using a resin, like the foregoing, with a two-layer structure, the resin does not spread other than at the points of contact, and thus is not detrimental to the effect of the alignment control film Sb (alignment is not impaired). In this way, by using fine particles with a two-layer structure, a liquid crystal display element can be provided which has an adhesive property, but without adverse effects on alignment.

Claims (17)

CLAIMS:

1. A liquid crystal display element comprising a pair of substrates, at least one of which is transparent, spacers, which maintain a uniform gap between said substrates, and liquid crystal filling said gap between said substrates; wherein: at least one of said substrates is provided with an alignment control film made of a material which includes an organic resin.

2. A liquid crystal display element comprising a pair of substrates, at least one of which is transparent, spacers, which maintain a uniform gap between said substrates, and liquid crystal filling said gap between said substrates; wherein: at least one of said substrates is provided with an alignment control film, on a surface of which an organic resin is dispersed.

3. The liquid crystal display element set forth in either claim 1 or claim 2, wherein: said organic resin is in the form of fine particles.

4. The liquid crystal display element set forth in any one of claims 1 through 3, wherein: said spacers are provided in the shape of pillars or walls on at least one of said substrates; and said substrates are attached together by adhesion of (i) upper surfaces of said spacers, or an alignment control film provided so as to cover said upper surfaces, with (ii) an alignment control film provided on the opposite substrate.

5. The liquid crystal display element set forth in any one of claims 1 through 3, wherein: said spacers are spherical.

6. The liquid crystal display element set forth in any one of claims 1 through 5, wherein: said liquid crystal is a ferroelectric liquid crystal.

7. The liquid crystal display element set forth in any one of claims 1 through 6, wherein: said organic resin is a thermosetting resin.

8. The liquid crystal display element set forth in any one of claims 1 through 6, wherein: said organic resin is an ultraviolet curable resin.

9. The liquid crystal display element set forth in any one of claims 1 through 6, wherein: said organic resin is a thermoplastic resin having a softening point higher than or equal to a phase transition temperature of said liquid crystal to the isotropic phase, and lower than or equal to a softening point of a material making up said spacers.

10. The liquid crystal display element set forth in any one of claims 1 through 6, wherein: said organic resin is a mixture of two or more types of resin having different characteristics.

11. The liquid crystal display element set forth in claim 3, wherein: said fine particles include a first resin forming a core and a second resin forming a shell covering said first resin, and said first resin has a softening point which is lower than a softening point of said second resin.

12. A method of manufacturing the liquid crystal display element set forth in claim 4, comprising: a first step, in which said spacers are formed in the shape of pillars or walls on one of said substrates; and a second step, in which said alignment control film is formed so as to cover said spacers and said substrate upon which said spacers are formed.

13. A method of manufacturing the liquid crystal display element set forth in claim 4, comprising: a first step, in which said alignment control film is formed on one of said substrates; and a second step, in which said spacers are formed in the shape of pillars or walls on said alignment control film.

14. A method of manufacturing the liquid crystal display element set forth in either claim 1 or claim 2, comprising: a first step in which, when forming said alignment control film on at least one of said substrates, said alignment control film is baked; and a second step in which, when assembling said substrates, said alignment control film is baked.

15. The manufacturing method set forth in claim 14, wherein: a baking temperature of said second step is equivalent to or higher than a baking temperature of said first step.

16. A liquid crystal display element substantially as hereinbefore described with reference to the accompanying drawings.

17. A method of manufacturing a liquid crystal display element substantially as hereinbefore described with reference to the accompanying drawings.