GB2327768A

GB2327768A - Manufacturing a liquid crystal display element

Info

Publication number: GB2327768A
Application number: GB9814965A
Authority: GB
Inventors: Masami Kido
Original assignee: UK Secretary of State for Defence; Sharp Corp
Current assignee: UK Secretary of State for Defence; Sharp Corp
Priority date: 1997-07-23
Filing date: 1998-07-10
Publication date: 1999-02-03
Anticipated expiration: 2018-07-10
Also published as: GB9814965D0; GB2327768B; JPH1138422A

Abstract

In manufacturing steps of a liquid crystal display element, after forming electrodes 2, an insulating layer 3, and an alignment control layer 4 on a substrate 1, an inorganic coating 5 made of an inorganic material is formed on the alignment control layer 4, and a region between the electrodes 2 on the inorganic coating 5 is exposed by UV light. Thereafter, a layer of adhesive including spacer beads is formed on the inorganic coating 5, and the adhesive is removed by a solvent such as water together with an unexposed portion of the inorganic coating 5 so as to form space keepers 6 made of the adhesive. Then, electrode substrates 10 and 20 are strongly bonded with each other by the space keepers 6, and as a result a constant spacing is maintained between the electrode substrates 10 and 20 by the spacer beads. This prevents the alignment control layer from being contaminated and damaged in the manufacturing steps, and improves the bond strength of the substrates, thus providing a liquid crystal display element having superior displaying quality and shock resistance.

Description

LIQUID CRYSTAL DISPLAY ELEMENT AND MANUFACTURING METHOD THE SAME The present invention relates to a liquid crystal display element for use in a flat-panel display, etc., and a manufacturing method the same.

Generaily, a liquid crystal display element is provided with a pair of substrates having transparent electrodes, a liquid crystal layer of liquid crystal enclosed between the pair of substrates, and means, for example, polaraizers for optically detecting the alignment control layer, a resin as the spacer material, and a developer used in the process of photolithography. As a result, the alignment anchoring force for the liquid crystal, given to the alignment control layer by a rubbing process is lowered. This problem can be prevented by carrying out the rubbing process after forming the spacers; however, in this case, the following problem is presented.

(ii) Because the resin spacers are also subjected to the rubbing process, the alignment anchoring force is given to the surface of the spacers. This induces (A) an abnormal alignment which cause alignment nonuniformity in the liquid crystal in a vicinity of the spacers and (B) defective switching of the liquid crystal molecules.

In order to solve the above problems, for example, the following measures can be taken.

For the problem of (i), the method as disclosed in Japanese Unexamined Patent Publication No.

59228/1994 (Tokukaihei 6-59228) (reference A) is effective. In this method, first, a protective film for protecting the alignment control layer from the which adhesive particles are dispersed with spacer beads so as to precisely control and maintain the cell gap has been developed (see Japanese Unexamined Patent Publication No. 174726/1987 (Tokukaisho 62-174726)).

However, this method has a problem that, in order to obtain a bond strength suitable for practical applications, it is required to disperse the spacers in high density, and the display quality is lowered by the spacers dispersed over the pixels.

As a countermeasure against this problem, a method in which a spacer material made of photosensitive resin is shaped into an arbitrary shape by a technique such as photolithography (see Japanese Unexamined Patent Publication No. 257824/1989 (Tokukaihei 1-257824)). With this method, the substrates are strongly bonded with each other with a constant gap by the spacers provided between pixels.

However, when resin spacers are formed on an alignment control layer of. a liquid crystal display element as above, the following problem is presented.

(i) The alignment control layer is contaminated by a solvent used when applying the spacers on the protective film formed on the alignment control layer is removed by an etching solution including hydrogen peroxide water and ammonia, etc., the alignment control layer is exposed to the etching solution and is deteriorated.

On the other hand, the method as disclosed in reference B has a problem that the shape and the position of the spacer and the rubbing direction of the alignment control layer are greatly limited. Thus, when the method of reference B is adopted, the degree of freedom of designing the liquid crystal display element is significantly limited. For example, in the case of adopting, instead of the pillar spacers which fix the substrates by pinpoint, wall spacers capable of fixing the substrates more strongly, alignment abnormal regions are generated at the both ends of each spacer. And, large numbers of effective pixels are disabled for disguising these alignment abnormal regions, and as a result the aperture ratio of pixels is significantly lowered.

It is an object of the present invention to provide a liquid crystal display element capable of high quality displaying without alignment developer is formed on the alignment control layer, and thereafter spacers in the form of pillars, made of an organic material, are formed on the protective film. For the problem of (ii), the method as disclosed in Japanese Unexamined Patent Publication No.

175133/1994 (Tokukaihei 6-175133) (reference B) is effective in which unique measures are taken in positioning of the spacers and in the alignment process of the alignment control layer so that abnormal alignment is not generated in the effective pixels.

However, the method as disclosed in reference A has a problem that the manufacturing steps are complicated. Specifically, the following complicated steps are required: The protective film is formed after forming the alignment control layer on the substrate, and unnecessary protective film is removed after applying the spacer material and forming the spacers by exposure and development.

The method as disclosed in reference A also has a problem that the deterioration of the alignment control layer cannot be prevented completely. Namely, in this method, because the unnecessary portion of the constant gap is maintained between the two substrates by the spacers of the space keeper, and the two substrates are strongly combined with each other with respect to the entire surface by the space keeper having adhesion. Also, in the arrangement wherein the space keeper is formed via the photosensitive inorganic coating, the inorganic coating is freely patterned by irradiation of light prior to forming the space keeper, thus allowing the space keeper to be formed in a desired pattern in accordance with the patterning of the inorganic coating.

In the case of forming the space keeper by directly applying an adhesive onto the alignment control layer without using the inorganic coating, it is required to accurately apply the adhesive on a region between the electrodes, and it is difficult to apply the adhesive with sufficient accuracy even by the conventional screen printing. Also, in the case of subjecting the alignment control layer to the rubbing process after forming the space keeper, unlike the case of using the resin spacers as mentioned above, the alignment anchoring force is not given to the space keeper by the rubbing process, and the alignment of the liquid crystal molecules in a vicinity of the nonuniformity and switching defect, in which a cell gap is precisely controlled and maintained, and a method for manufacturing such a liquid crystal display element with simple steps.

According to the present invention, there is provided a liquid crystal display element having a liquid crystal layer made of a liquid crystal material, a pair of substrates, each of the pair of substrates provided with, on a surface facing an other of the pair of substrates, electrodes for applying a voltage to the liquid crystal layer and an alignment control layer for controlling an alignment of the liquid crystal layer, and spacers for maintaining a spacing between the pair of substrates, the liquid crystal display element including: an inorganic coating, made of a photosensitive inorganic material, provided on the alignment control layer on a region between the electrodes adjacent to each other on one of the pair of substrates, and a space keeper having adhesion for combining the pair of substrates, the space keeper including the spacers, and provided on the inorganic coating.

In this liquid crystal display element, a forming the inorganic coating on the alignment control layer, (2) exposing the inorganic coating on a region between the electrodes, (3) forming an adhesive layer including the spacers on the inorganic coating, (4) forming the space keeper by removing unexposed portion of the inorganic coating together with the adhesive layer formed thereon, and (5) combining the pair of substrates by the space keeper.

With this method, the inorganic coating formed in step (1) is exposed in step (2), and as a result the unnecessary portion of the adhesive layer formed on the inorganic coating in step (3) is removed in step (4) together with the unexposed portion of the inorganic coating. This makes it possible to precisely form the space keeper on a region generally having a narrow width between the electrodes. Also, since the adhesive layer is removed together with the inorganic coating, the number of processing steps can be reduced. Further, by exposing the photosensitive inorganic coating beforehand, it is possible to remove the inorganic coating by a solvent whose effect in deteriorating the alignment control layer is small. As a result, it is possible to manufacture with ease a liquid crystal display element capable of high quality space keeper is not disturbed. Further, the inorganic coating also serves as a protective film for protecting the alignment control layer from the formation of the adhesive layer (application of adhesive). Moreover, since the photosensitive inorganic material can remove the unnecessary portion with ease without using a solvent which exposes the alignment control layer, the lowering of the aligning effect of the alignment control layer is minimized.

Also, with the described arrangement of the liquid crystal display element wherein a constant gap is maintained between the substrates, and the substrates are strongly combined with each other, even when the liquid crystal material is the ferroelectric liquid crystal material, the characteristics of the ferroelectric liquid crystal material are not lost.

Thus, a large display element can be realized with ease in practical applications, for which the ferroelectric liquid crystal having superior characteristics than the nematic liquid crystal is particularly suitable.

The above liquid crystal display element is manufactured by a method including the steps of (1) keeper is baked before the rubbing process, and the adhesive layer is formed using a thermoplastic adhesive material in step (3).

With this method, since the alignment control layer is subjected to a rubbing process between step (4) and step (5), the alignment anchoring force of the alignment control layer is not lost at all by the process of step (3). Here, because the space keeper formed on the alignment control layer is also subjected to the rubbing process, the inorganic coating and the adhesive layer are stripped by the rubbing process unless they have sufficient hardness.

When the inorganic coating and the adhesive layer are stripped, the space keeper cannot be formed, and the substrates are contaminated by the stripped inorganic coating and the adhesive layer.

In order to prevent this drawback, in the present manufacturing method, the hardness of the inorganic coating is increased by baking. When a thermosetting adhesive is used to form the adhesive layer, the adhesion of the thermosetting adhesive is lost after being cured when the inorganic coating is baked, and it is required to re-apply the adhesive to bond the displaying without alignment nonuniformity and switching defect, in which the cell gap is precisely controlled and maintained.

In the above manufacturing method, it is preferable that the alignment control layer is subjected to a rubbing process before step (1), and the adhesive layer is formed using a thermosetting or thermoplastic adhesive material in step (3).

With this method, the thermosetting or thermoplastic adhesive material exhibits adhesion by a heating process generally required in the following step, for example, in the step of combining the substrates by a sealant. This allows the process of step (5) to be carried out with the step of combining the substrates by a sealant. As a result, by carrying out a process required for bonding with another process, it is possible to simplify the manufacturing steps.

Also, in the above manufacturing method, it is preferable that the alignment control layer is subjected to a rubbing process between step (4) and step (5), and the inorganic coating under the space more simplified steps, and to ensure the space keeping effect between the substrates by the space keeper.

In the described manufacturing methods, it is preferable that the unexposed portion of the inorganic coating is removed by a solvent selected from the group consisting of water, weak acid, weak alkali, lower alcohol, and a mixture of lower alcohol and water. This minimizes the deterioration of the alignment control layer. As a result, it is possible to prevent the alignment anchoring force given to the alignment control layer from being lowered by the rubbing process performed before or after removal of the inorganic coating.

The present invention will now be described, by way of example, with reference to the accompanying drawings in which: Fig. 1 is shows a schematic cross sectional structure of a liquid crystal cell in accordance with one embodiment of the present invention, Fig. 2(a) through Fig. 2(c) respectively show a cross sectional structure of each step in substrates in step (5). In the present manufacturing method, thermoplastic adhesive is used instead of the thermosetting adhesive. This provides an adhesive layer which exhibits adhesion by being (i) cured by cooling after baking of the inorganic coating, and (ii) softened by a heating process in the combining process which can be carried out together with the step (5) as described above. As a result, the alignment anchoring force of the alignment control layer is substantially completely maintained.

Also, in the above manufacturing method, it is preferable that in step (3), the adhesive layer is formed by applying an adhesive material including the spacers. With this method, since the adhesive material is applied with the spacers dispersed therein, compared with a method in which the dispersion of spacers and application of adhesive are carried out separately, the number of processing steps can be reduced. Also, spacers can be dispersed on predetermined positions of the adhesive material applied. Thus, it is possible to properly distribute the spacers in the adhesive layer constituting the space keeper. As a result, it is possible to manufacture the liquid crystal display element with alignment control layer 14.

The substrates 1 and 11 are made of a transparent insulating material such as glass or plastic. On a surface of the substrate 1, the electrodes 2, which are transparent and conductive, are formed in stripes parallel to one another. On a surface of the substrate 11, the electrodes 12 similar to the electrodes 2 are provided in stripes. The electrodes 2 and the electrodes 12 are arranged so as to be orthogonal to each other, and each region where the electrodes 2 and 12 intersect makes up a pixel which is the smallest unit of display. As a material of the electrodes 2 and 12, indium oxide, tin oxide, or indium tin oxide (ITO) is commonly adopted.

On the electrodes 2, the transparent insulating layer 3 and the alignment control layer 4 for controlling the alignment of the liquid crystal layer 30 are deposited in this order. With this arrangement, the surface of the substrate 1 between adjacent electrodes 2 and the electrodes 2 are covered with the insulating layer 3 and the alignment control layer 4.

Similarly, on the electrodes 12, the transparent insulating layer 13 and the alignment control layer 14 manufacturing of one of electrode substrates constituting the liquid crystal cell, and Fig. 3 (a) and Fig. 3 (b) respectively show a cross sectional structure illustrating how an adhesive is applied on an inorganic coating of the liquid crystal cell.

Embodiment 1 The following will describe one embodiment of the present invention referring to Fig. 1 through Fig. 3.

A liquid crystal cell (liquid crystal display element) in accordance with the present embodiment is provided with, as shown in Fig. 1, a pair of electrode substrates 10 and 20, and a ferroelectric liquid crystal material is enclosed therebetween, forming a liquid crystal layer 30.

The electrode substrate 10 is provided with a substrate 1, electrodes 2, an insulating layer 3, and an alignment control layer 4, and the electrode substrate 20 is provided with a substrate 11, electrodes 12, an insulating layer 13, and an available. Also, the alignment control layers 4 and 14 are obtained by rubbing (uniaxial alignment process) the surface of the coating made of the above material, for example, with cloth.

On the alignment control layer 4, between adjacent electrodes 2 on the substrate 1 of the electrode substrate 10, via inorganic coatings 5, there are provided space keepers 6 in the form of, for example, walls. The inorganic coatings 5 are made of inorganic material, and are formed in an arbitrary shape, for example in stripes corresponding to the shape of the space keepers 6. Also, each of the space keepers 6 is composed of a spacer for regulating the gap between the substrates 10 and 20 and a thermoplastic or thermosetting adhesive. With this arrangement, the gap (cell gap) between the substrates 10 and 20 is maintained constant, and the substrates 10 and 20 are strongly bonded with each other.

As the spacer, for example, a fiber or bead made of silica glass or a bead made of resin is suitably adopted.

The substrates 10 and 20 are positioned such that for controlling the alignment of the liquid crystal layer 30 are deposited in this order. With this arrangement, the surface of the substrate 11 between adjacent electrodes 12 and the electrodes 12 are covered with the insulating layer 13 and the alignment control layer 14.

Note that, the electrode substrates 10 and 20 are not required to include the respective insulating films 3 and 13. Nonetheless, in a liquid crystal display element such as a surface stabilized ferroelectric liquid crystal element, in which the liquid crystal layer 30 is formed thin (substantially 0.1 ym to 3 yam), in order to ensure insulation between the electrode substrates 10 and 20, it is preferable that the electrode substrates 10 and 20 are provided with the insulating layers 3 and 13, respectively.

As a material of the insulating layers 3 and 13, resin such as polyamide, polyimide, polyamideimide, polycarbonate, and acrylic resin, and an inorganic material such as Si3N4, SiO2, Awl203, and Ta203 are available. As a material of the alignment control layers 4 and 14, resin such as nylon, polyamide, polyimide, polyamideimide, and polyvinyl alcohol are switched. This switching is recognized by the polarizers, and the light and dark displaying states are obtained.

The following will describe a manufacturing method of the present liquid crystal cell referring to Fig. 2(a) through Fig. 2(c) and Fig. 3(a) and Fig.

3 (b) First, as shown in Fig. 2(a), after depositing an electrode material (for example, ITO) on the substrate 1, the electrode material is patterned in stripes so as to form the electrodes 2, and thereafter the insulating layer 3 and the alignment control layer 4 are formed in this order. The insulating layer 3 is formed by vapor deposition or application onto the substrate 1 on which the electrodes 2 are formed.

Here, the alignment control layer 4 has already been subjected to a rubbing process. Then, as shown in Fig.

2(b), an inorganic coating 5 is formed by application of an inorganic material, and then by using a photomask 40, the inorganic coating 5 between adjacent electrodes 2 is exposed in stripes by ultraviolet light.

the alignment control layers 4 and 14 are on the inner sides, and the electrodes 2 and 12 are orthogonal to each other, and a uniform gap is maintained by the space keepers 6. Also, the substrates 10 and 20 are bonded and fixed each other on the peripheries of the gap by a sealant (not shown). The gap between the substrates 10 and 20 is filled with a ferroelectric liquid crystal material, forming the liquid crystal layer 30. The ferroelectric liquid crystal has desirable characteristics such as high response and memory effect, and therefore is suitable for large capacity and fine displaying.

The present liquid crystal cell is further provided with polarizers (not shown), on the outer sides of the electrode substrates 10 and 20, respectively, for optically recognizing a change in the optical axis of the liquid crystal molecules in the liquid crystal layer 30.

In the present liquid crystal cell having the described arrangement, when a voltage is selectively applied to the electrodes 2 and 12 by a driving circuit (not shown), the alignment state of the liquid crystal molecules in the liquid crystal layer 30 is patterning process of the inorganic coating 5, (c) is cured at a temperature in a vicinity of the baking temperature (1800C in Examples explained later) of the inorganic coatings 5, and (d) has heat resistance at this temperature. As such a thermosetting adhesive, specifically, a heat resistant epoxy adhesive made of multi-function resin is preferable. On the other hand, as the thermoplastic adhesive, an adhesive which (a) is not cured by the process temperature of the inorganic coating 5, (b) withstands the patterning process of the inorganic coating 5, and (c) has adhesion and heat resistance at a temperature in a vicinity of the baking temperature of the inorganic coatings 5.

Note that, in the described process of forming the inorganic coatings 5, the adhesive 22 containing the spacer beads 21 is used; however, as shown in Fig.

3 (b), it is possible instead to disperse the spacer beads 21 on the inorganic coating 5 applied with an adhesive 23 (thermoplastic adhesive) containing no spacer beads 21. With this arrangement, the thermoplastic adhesive 23 is softened by the heat applied when combining the electrode substrates 10 and 20 via sealant, and as a result the spacer beads 21 Then, after applying an adhesive 22 (thermosetting adhesive or thermoplastic adhesive) containing spacer beads 21 (spacers) as shown in Fig.

3 (a) on the inorganic coating 5, unexposed portion of the inorganic coating 5 is removed together with the adhesive 22 by water, weak acid, weak alkali, lower alcohol, or a mixed solvent of lower alcohol and water. As a result, as shown in Fig. 2(c), the inorganic coatings 5 and the space keepers 6 are formed. Then, because the polymerization of the inorganic material is insufficient by exposure of the W light alone, in order to increase the hardness of the inorganic coatings 5, the inorganic coatings 5 remaining in stripes are baked.

Note that, as the weak acid, phosphoric acid, chloric acid, or acetic acid, etc., is preferable, and as the weak alkali, sodium hydroxide is preferable.

Also, as the lower alcohol, ethanol, methanol, or isopropyl alcohol, etc., is preferable.

As the thermosetting adhesive, it is preferable to adopt an adhesive which (a) is not cured by the process temperature (800C in Examples explained later) of the inorganic coating 5, (b) withstands the ferroelectric liquid crystal material is injected into the spacing between the electrode substrates 10 and 20, and the injection opening is sealed by a sealant, thus manufacturing the liquid crystal cell.

Note that, the step of baking the inorganic coatings 5 may be carried out simultaneously with the step of combining the electrode substrates 10 and 20.

This reduces the number of manufacturing steps of the liquid crystal cell. Also, in the described manufacturing method, although the alignment control layer 4 is subjected to a rubbing process before forming the inorganic coating 5, it is possible to carry out the rubbing process after forming the inorganic coating 5. This will be described in detail later in Specific Example 2.

As described, the liquid crystal cell in accordance with the present embodiment has an arrangement including the liquid crystal layer 30 made of a liquid crystal material, the pair of substrates 1 and 10 respectively provided with, on the surface facing the other substrate, (i) the electrodes 2 and the alignment control layer 4 and (ii) the electrodes 12 and the alignment control layer 14, the alignment are included in the adhesive 23. Hence, the adhesive 23 which has incorporated the spacer beads 21 is in the same state as the state wherein the adhesive 22 already containing the spacer beads 21 are applied (see Fig. 3(a)).

The electrode substrate 20 is made by forming the electrodes 2 by patterning ITO on the substrate 11 in the same shape as the electrodes 2, and thereafter by forming the insulating layer 13 and the alignment control layer 14. Then, the electrode substrates 10 and 20 are faced and combined with each other by a sealant under applied heat that the electrodes 2 and 12 are orthogonal to each other and the rubbing directions of the alignment control layer 4 and 14 are parallel to each other.

Here, the electrode substrates 10 and 20 are bonded with each other by the adhesion exhibited under applied heat by the adhesive 22 or 23 forming the space keepers 6. After the adhesive 22 or 23 is cured, the gap between the electrode substrates 10 and 20 is regulated by the spacer beads 21, and the electrode substrates 10 and 20 are strongly combined with each other by the adhesive 22 or 23. Finally, a molecules in a vicinity of the space keepers 6 is not disturbed. Also, the inorganic coatings 5 also serve as a protective film for protecting the alignment control layer 4 from the adhesive. Further, since the photosensitive inorganic material can remove the unnecessary portion with ease without using a solvent which exposes the alignment control layer 4, it is possible to minimize the lowering of the aligning effect of the alignment control layer 4. As a result, it is possible to precisely control and maintain the cell gap, and realize high quality displaying without alignment nonuniformity and switching defect.

The following will describe in more detail the manufacturing method of the liquid crystal cell in accordance with the present embodiment using specific examples and comparative examples.

Note that, the manufacturing conditions such as the film thickness, heating time, and heating temperature of the material. in the following steps are just examples, and the present invention is not limited to these.

Specific Example 1 control layers 4 and 14, respectively provided on the electrodes 2 and 12, for controlling the alignment of the liquid crystal layer 30, the inorganic coatings 5, made of a photosensitive inorganic material, provided on the alignment control layer 4 on a region between the adjacent electrodes 2 on the substrate 1, and the space keepers 6 having adhesion for combining the substrates 1 and 11, the space keepers 6 including the spacer beads 21, and provided on the inorganic coatings 5.

With this arrangement, the gap between the substrates 1 and 11 is uniformly maintained by the spacer beads 21 included in the space keepers 6, and the substrates 1 and 11 are strongly combined with each other with respect to the entire surface by the space keepers 6 having adhesion. Also, since the inorganic coatings 5 can be freely patterned by irradiation of light prior to forming the space keepers 6, it is possible to form the space keepers 6 in a desired pattern together with the inorganic coatings 5. Further, because the alignment anchoring force is not given to the space keepers 6 by rubbing of the alignment control layer 4 after forming the spacer keepers 6, the alignment of the liquid crystal agent includes, as a main component, a precursor of a plurality of inorganic oxides, and is water soluble.

The inorganic coating agent becomes water insoluble upon irradiation of UV light and baking, as a result of oxidation and polymerization of the precursor.

Thereafter, the UV light is projected onto the inorganic coating 5 in stripes via a photomask 40 so as to expose the inorganic coating 5 between adjacent electrodes 2.

Then, the thermoplastic adhesive STAYSTIK 383 (product No.) provided by Techno Alpha Co., Ltd.

having desirable adhesion to be applied to the inorganic coating 5, which has been added, as the spacer beads 21, beforehand with silica beads (diameter of 1.5 ym) provided by Ube-Nitto Kasei Co., Ltd., is applied to the inorganic coating 5 and dried at 800C for 10 minutes. As a result, the silica beads are fixed on the inorganic coating 5, being surrounded by the thermoplastic adhesive.

Thereafter, a ultrasonic wave is applied to the substrate 1 while being soaked in pure water so as to remove the unexposed portion of the inorganic coating In a manufacturing method of a liquid crystal cell of the present specific example, first, after depositing ITO in a thickness of 0.1 ym on a substrate 1 made of glass by spattering, the ITO thus formed is patterned in stripes so as to form electrodes 2.

Thereafter, the insulating film material NHC A-2014 (product No.) provided by Nissan Chemical Industries, Ltd. is formed in a thickness of 0.1 ym on the substrate 1 and the electrodes 2 so as to form an insulating layer 3 covering the substrate 1 and the electrodes 2.

Then, the alignment film material AL-5417 (product No.) provided by Japan Synthetic Rubber is formed in a thickness of 70 nm on the insulating layer 3 so as to form an alignment control layer 4 covering the insulating layer 3, and the alignment control layer 4 is subjected to a rubbing process.

Then, the inorganic coating agent HM-5001 (product No.) provided by Nissan Chemical Industries, Ltd. is applied in a thickness of 0.1 ym onto the alignment control layer 4, and by drying at 800C for 5 minutes, an described steps, a cell gap of 1.5 Fm was obtained, which is substantially the same as the diameter of the spacer beads 21, and stripping of the spacer keepers 6 was not generated. Also, even when a pressure up to 5 kg/cm2 was applied to the liquid crystal cell, a change in alignment of the liquid crystal material (SCE-8) and stripping of the space keepers 6 was not observed. Therefore, the bond strength of the electrode substrates 10 and 20 of the liquid crystal cell of the present invention is sufficient enough for practical applications.

Specific Example 2 A manufacturing method of a liquid crystal cell of the present specific example is the same as that of Specific Example 1 except for the step that the alignment control layer 4 is subjected to a rubbing process after baking the inorganic coatings 5, not before application of the inorganic coating agent (HM5001).

In the liquid crystal cell as manufactured in this manner, the alignment of the liquid crystal material (SCE-8) is not disturbed by the space keepers 5 together with the silica beads and the thermoplastic adhesive formed thereon. Here, although the application of ultrasonic wave is not necessarily required, because polymerization of the inorganic coating 5 before baking is incomplete, it is desirable to remove the inorganic coating 5 in a short period of time using the ultrasonic wave. In this manner, the inorganic coatings 5 and the space keepers 6 are formed. Thereafter, by heating at 1800C for 1 hour, the inorganic coatings 5 are baked completely.

Then, while facing (a) the electrode substrate 10 including the inorganic coatings 5 and the space keepers 6 and (b) the electrode substrate 20 with each other, a thermoplastic bond (sealant) is applied onto the peripheries of the electrode substrates 10 and 20 so as to combine the two substrates by pressing against each other with a pressure of 2kg/cm2 and by baking at 1800C. Then, the ferroelectric liquid crystal material SCE-8 provided by Merck Ltd. is injected into the spacing between the electrode substrates 10 and 20, and the injection opening is sealed, thereby completing the liquid crystal cell.

In the liquid crystal cell as manufactured by the In a manufacturing method of the present comparative example, an electrode substrate having the same structure as that of the electrode substrate 10 as manufactured in Specific Examples 1 and 2 was manufactured except that the inorganic coatings 5 and the space keepers 6 were not provided. An alignment control layer of the electrode substrate was subjected to the rubbing process, and silica beads (diameter of 1.5 ssm) provided by Ube-Nitto Kasei Co., Ltd. were dispersed on the alignment control layer. Then, the electrode substrate thus prepared and an electrode substrate having the same structure as the electrode substrate 20 were combined with each other using the two-component mixed-type bond provided by Konishi Co.

Ltd. as a sealant, and between the two electrode substrates was filled with the SCE-8.

In the liquid crystal cell as manufactured in this manner, although the alignment of the liquid crystal material (SCE-8) was excellent, the alignment of the liquid crystal material was destroyed when a pressure of 0.5 kg/cm2 was applied to the liquid crystal cell.

Comparative Example 2 6 and is desirably maintained. Also, in the same pressure test as that for the liquid crystal cell of Specific Example 1, it was observed that the bond strength of the electrode substrates 10 and 20 is sufficient enough for practical applications.

Note that, in the above manufacturing method, since there is a case that the inorganic coatings 5 and the space keepers 6 are removed by the rubbing process when their hardness is not sufficient, the rubbing process is carried out after baking the inorganic coatings 5. For this reason, when the thermosetting adhesive is used instead of the thermoplastic adhesive for forming the space keepers 6 in the above manufacturing steps, the adhesion of the thermosetting resin is lost by the applied heat after baking the inorganic coatings 5. This necessitates re-application of adhesive for combining of the electrode substrates 10 and 20. Because it is difficult to apply this process in practical applications, it is not suitable to use the thermosetting resin in the above manufacturing method.

Comparative Example 1 alignment control layer, which is caused by application of the photosensitive resin on the alignment control layer which has been subjected to the rubbing process, and by partial removal of the coating of the photosensitive resin for forming the spacers.

Comparative Example 3 In the manufacturing method of the present comparative example, the same processes as in Comparative Example 2 were carried out except that the rubbing process was carried out after patterning the photosensitive resin in stripes, not before application of the photosensitive resin. In the liquid crystal cell as manufactured in this manner, in the liquid crystal layer surrounding the spacers (photosensitive resin), a region which does not respond to the electric field was generated, and severe impairment of the display characteristics was observed. This is a likely. result of rubbing of the resin spacer, adversely affecting the liquid crystal layer.

In a manufacturing method of the present comparative example, an electrode substrate having the same structure as that of the electrode substrate 10 as manufactured in Specific Example 1 was used except that the inorganic coatings 5 and the space keepers 6 were not provided. The alignment control layer was subjected to the rubbing process, and the photosensitive resin V-259PA (Product No.) provided by Shin-Nittetsu Chemical was applied in a thickness of 1.5 jim on the alignment control layer, and was dried.

Then, patterning by mask exposure and development and baking were carried out with respect to the coating of the photosensitive resin so as to form spacers in stripes. Then, the electrode substrate provided with the spacers and an electrode substrate having the same structure as that of the electrode substrate 20 were combined with each other, and between the two electrode substrates was filled with the SCE-8.

In the liquid crystal cell as manufactured in this manner, impairment of alignment of the liquid crystal material (SCE-8) was observed compared with the liquid crystal cells of Specific Examples 1 and 2 and Comparative Example 1. This is likely to be due to lowering of the alignment anchoring force of the 3. The liquid crystal display element as set forth in claim 1 or 2, wherein the electrodes and said space keeper are both formed in stripes.

4. The liquid crystal display element as set forth in any one of claims 1 through 3, wherein said space keeper is formed in a wall shape.

5. The liquid crystal display element as set forth in any one of claims 1 through 4, wherein the spacers are beads.

6. A method for manufacturing the liquid crystal display element of claim 1, comprising the steps of: (1) forming said inorganic coating on the alignment control layer; (2) exposing said inorganic coating on a region between the electrodes; (3) forming an adhesive layer including the spacers on said inorganic coating; (4) forming said space keeper by removing unexposed portion of said inorganic coating together with the adhesive layer formed thereon; and (5) combining the pair of substrates by said space keeper.

Claims

1. A liquid crystal display element including a liquid crystal layer made of a liquid crystal material, a pair of substrates, each of the pair of substrates provided with, on a surface facing an other of the pair of substrates, electrodes for applying a voltage to the liquid crystal layer and an alignment control layer for controlling an alignment of the liquid crystal layer, and spacers for maintaining a spacing between the pair of substrates, said liquid crystal display element comprising: an inorganic coating, made of a photosensitive inorganic material, provided on the alignment control layer on a region between the electrodes adjacent to each other on one of the pair of substrates; and a space keeper having adhesion for combining the pair of substrates, said space keeper including the spacers, and provided on said inorganic coating.

2. The liquid crystal display element as set forth in claim 1, wherein the liquid crystal material is a ferroelectric liquid crystal material.

baked before the rubbing process, and the adhesive layer is formed using a thermoplastic adhesive material in said step (3).

11. The method as set forth in claim 7 or 10, wherein an adhesive material used as the thermoplastic adhesive material (a) is not cured by a temperature of forming said inorganic coating in said step (1), (b) withstands patterning of said inorganic coating in said step (4), and (c) has adhesion and heat resistance at a temperature in a vicinity of a baking temperature of said inorganic coating.

12. The method as set forth in claim 6, wherein in said step (3), the adhesive layer is formed by applying an adhesive material including the spacers.

13. The method as set forth in claim 6, wherein in said step (3), the adhesive layer is formed by dispersing the spacers over an adhesive material applied.

14. The method as set forth in any one of claims 6 through 13, wherein the unexposed portion of said inorganic coating is removed by a solvent selected 7. The method as set forth in claim 6, wherein the alignment control layer is subjected to a rubbing process before said step (1), and the adhesive layer is formed using a thermosetting or thermoplastic adhesive material in said step (3).

8. The method as set forth in claim 7, wherein an adhesive material used as the thermosetting adhesive material (a) is not cured by a temperature of forming said inorganic coating in said step (1), (b) withstands patterning of said inorganic coating in said step (4), (c) is cured at a temperature in a vicinity of a baking temperature of said inorganic coating, and (d) has heat resistance at the temperature in a vicinity of a baking temperature of said inorganic coating.

9. The method as set forth in claim 8, wherein the thermosetting adhesive material is a heat resistant epoxy adhesive made of multi-function resin.

10. The method as set forth in claim 6, wherein the alignment control layer is subjected to a rubbing process between said step (4) and said step (5), and said inorganic coating under said space keeper is from the group consisting of water, weak acid, weak alkali, lower alcohol, and a mixture of lower alcohol and water.

15. The method as set forth in claim 14, wherein as the weak acid, an acid selected from the group consisting of phosphoric acid, chloric acid, and acetic acid is used.

16. The method as set forth in claim 14, wherein as the weak alkali, sodium hydroxide is used.

17. The method as set forth in claim 14, wherein as the lower alcohol, an alcohol selected from the group consisting of ethanol, methanol, and isopropyl alcohol is used.