GB2332953A

GB2332953A - Liquid crystal display element with spacers

Info

Publication number: GB2332953A
Application number: GB9828429A
Authority: GB
Inventors: Kazuhiko Tamai; Hideka Uchida; Mitsuhiro Shigeta
Original assignee: UK Secretary of State for Defence; Sharp Corp
Current assignee: UK Secretary of State for Defence; Sharp Corp
Priority date: 1998-01-06
Filing date: 1998-12-24
Publication date: 1999-07-07
Anticipated expiration: 2018-12-24
Also published as: GB9828429D0; GB2332953B; GB2332953A8; JP3895447B2; JPH11194350A

Abstract

A liquid crystal display element, in which liquid crystal 7 is sealed into a gap between a pair of substrates, 10,20, at least one of the substrates having light transmitting property, is provided with: pillar-shaped or wall-shaped spacers 6 having even heights on at least one of the pair of substrates, and an alignment control layer 5a for covering the substrate except for the top portions of the spacers, wherein the pair of substrates are joined to each other in a state in which the top portions of the spacers are bonded to the alignment control layer 5b formed on the other substrate.

Description

LIQUID CRYSTAL DISPLAY ELEMENT AND MANUFACTURING METHOD THEREOF FIELD OF THE INVENTION This invention relates to a liquid crystal display element which has superior shock-resistance and a favorable display quality, and further concerns a manufacturing method thereof.

BACKGROUND OF THE INVENTION Conventionally, liquid crystal display elements, which are made by bonding a pair of substrates to each other with their electrode-bearing surfaces facing inside and by sealing liquid crystal into the gap between them, have been well known. When external pressure deforms the substrate so as to change the distance between opposing substrates, this liquid crystal display element cannot provide a favorable display due to a change in the threshold voltage, short circuiting in the electrodes between substrates opposing each other, and an uneven alignment of liquid crystal molecules, etc. Therefore, some methods, in which spacers are deposited between substrates so as to keep the distance between the paired substrates, have been known.

Conventionally, one of the following methods has been adopted in general: (1) a method for spraying spherical particles or (2) a method for forming pillars made of organic or inorganic materials.

Specific examples of (1) are: a dry method in which spherical fine particles made of, for example, an organic resin such as a polymer of divinylbenzenes, are dispersed into a nitrogen gas so as to be sprayed on the substrates; and a method in which the spherical fine particles are mixed with solutions such as a solution of alcohol, and are sprayed on the substrates in a mist state.

However, method (1) has the following problems: a first problem is that since fine particles tend to coagulate with one another, it is difficult to spray the fine particles evenly on the substrates and consequently to achieve an even cell thickness. Further, a second problem is that since it is difficult to control the positions of the fine particles, the fine particles sprayed on a pixel portion may cause defects in alignment, thereby deteriorating the display quality. Moreover, a third problem is that since the substrates are supported merely on the contact portions with spherical fine particles acting as spacers, it is difficult to obtain sufficient strength against external pressure.

Furthermore, method (2) is, specifically, a method in which an organic or inorganic film is formed with a predetermined thickness, a resist film is formed thereon, and then exposure is applied thereto in a masked state so as to form pillars acting as spacers. Instead of the resist film, for example, photosensitive organic resins such as photosensitive polyimide or photosensitive acrylic resins can be used.

As described above, the method (2) makes it possible to selectively form pillars on the outside of the pixel.

Further, this method has an advantage in which the contact surface between substrates and pillars can be formed into a desired pattern; thus, this method is superior in the evenness of cell thickness, the strength against external pressure, and the display quality, as compared with method (1) In recent years, ferroelectric liquid crystal has drawn considerable attention as a liquid crystal material. The ferroelectric liquid crystal is superior in high-speed response which is provided by having spontaneous polarization; however, since the regularity of the molecule alignment is close to a crystal, when the regularity of the molecule alignment is disturbed by external pressure, it is hard to return the regularity to the initial state, that is, the ferroelectric liquid crystal is inferior in its shock resistant property. Therefore, in order to solve the abovementioned problem of the ferroelectric liquid crystal, it is necessary to provide substrate structures which are superior in shock resistance. As a method for producing such a liquid crystal display element, it has been understood that method (2) is more effective as compared with method (1).

The constructions of the conventional liquid crystal display element are: (A) a construction in which after an alignment control layer has been formed on an insulating substrate, spacers are formed thereon, and top portions of the spacers on one substrate are joined to the alignment control layer on the other substrate so as to bond the pair of substrates to each other; and (B) a construction in which after the spacers have been formed on the insulating substrate, the alignment control layer is formed thereon so as to cover the spacers, and the alignment control layer on the top portions of the spacers formed on one substrate is bonded to the alignment control layer on the other substrate so as to join the pair of substrates to each other.

However, the conventional constructions have the following problems: First of all, construction (A) forms the spacers on the alignment control layer; therefore, the production process of spacers may contaminate, deform, or destroy the alignment control layer. Spacers are formed on the substrate by photolithography using photosensitive polyimide or photoresist after an aligning operation has been performed.

Solvents used in the photolithography process may cause adverse effects on the alignment control layer. In this case, the decreasing control ability of the alignment control layer causes an uneven alignment of liquid crystal molecules; inevitably, the display quality is deteriorated.

Further, materials of the spacers or the alignment control layer are limited in order to avoid causing effects on the alignment control layer.

Furthermore, construction (B) may cause adverse effects on the control ability of the alignment control layer since the alignment control layer is softened by applying pressure and heat for bonding one alignment control layer to the other. In this case, the control ability of the alignment control layer varies so that the alignment of the liquid crystal molecules becomes uneven; inevitably, the display quality deteriorates. Moreover, in the case when an organic-solvent soluble polyimide is used to form the alignment control layer, heating does not proceed imidization as compared with the case of polyamic acids; therefore, it is not possible to obtain sufficient adhesive strength; consequently, materials for the alignment control layer are limited. Additionally, construction (A) bonds the spacers on one substrate to the alignment control layer on the other substrate so as to join the pair of substrates to each other. Thus, instead of the alignment control layer, the spacers are softened; therefore, the construction (A) does not result in softening the alignment control layer.

The softening operation tends to deteriorate he display image of construction (B).

SUMMARY OF THE INVENTION The object of the present invention is to provide a liquid crystal display element and a manufacturing method thereof which can achieve sufficient shock resistance and desirable even display quality.

In order to achieve the above-mentioned objective, the liquid crystal display element of the present invention, in which liquid crystal is sealed into a gap between a pair of substrates, at least one of the substrates having light transmitting property, is provided with pillar-shaped or wall-shaped spacers having even heights on at least one of the pair of substrates, and an alignment control layer for covering the substrate except for the top portions of the spacers, wherein the pair of substrates are bonded to each other in a state in which the top portions of the spacers are bonded to an alignment control layer formed on the other substrate.

With the aforementioned arrangement, the pillar-shaped or wall-shaped spacers, which have even heights, maintain the distance between the pair of substrates which are bonded to each other. Further, the alignment control layer can be formed on the one substrate after the spacers have been formed; therefore, it becomes possible to prevent the degradation of the display quality due to contamination, deformation, destruction, etc. of the alignment control layer during the process of forming the spacers, and to remove restrictions on materials of the spacers or the alignment control layer.

Moreover, with the aforementioned arrangement, the alignment control layer is provided so as to cover the surface of the substrate except for the top portions of the spacers, and the pair of substrates are joined to each other in a state in which the top portions of the spacers on one substrate are bonded to the alignment control layer on the other substrate. Since the spacers can be softened without softening the alignment control layer, it is possible to prevent the degradation of the display quality and adhesive strength that tends to occur in the case when the alignment control layers are softened so as to be bonded to each other. It is also possible to remove restrictions on materials of the alignment control layer.

As described above, with the aforementioned arrangement, it is possible to provide a liquid crystal display element which realizes a uniform cell thickness with higher accuracy than the conventional arrangement, favorable display quality without unevenness, and superior shock resistance.

It is desirable that the alignment control layer be repelled by the spacers when being formed so as to be selectively formed on the surface except for the regions in which the spacers are formed. Namely, in order to provide the alignment control layer so as to cover the substrate except for the regions in which the spacers are formed, the spacers preferably repel the alignment control layer.

With this arrangement, when providing the alignment control layer, even in the case when the alignment control layer is applied so as to cover the entire upper layer of the insulating substrate on which the spacers are formed, by using the spin coating method, roll coating method, or other methods, the spacers repel the alignment control layer so that the alignment control layer is applied on the upper layer of the insulating substrate except for the regions in which the spacers are formed. In other words, it is possible to selectively form the alignment control layer on the upper layer of the insulating substrate except for the top portions of the spacers. Therefore, it is not necessary to remove the alignment control layer on the top portions of the spacers; consequently, it is possible to provide a liquid crystal display element which does not cause contamination and damage to the alignment control layer, and realizes favorable display quality with a simple manufacturing method.

Further, in order to allow the spacers to repel the alignment control layer, the affinity of the alignment control layer with regard to the spacer surface is preferably set to be lower than that of the alignment control layer with regard to the region on the insulating substrate except for regions in which the spacers are formed, by using the following methods: (1) Select materials for the spacer or the alignment control layer so as to lower the affinity of the alignment control layer with regard to the spacers.

(2) Add a detergent(surface-active agent) to materials for the spacer or the alignment control layer.

(3) Perform a surface treatment using a detergent (surface-active agent) on the spacers after the spacers have been formed.

In the present invention, the pair of substrates are joined to each other in a state in which the spacers on one substrate are bonded to the alignment control layer on the other substrate; thus, the alignment control layer needs to be formed at least on the upper surface of the insulating substrate except for the top portions of the spacers, and the side surface of the spacer is allowed to be provided with the alignment control layer; however, the side surface without the alignment control layer is also adopted.

In order to achieve the aforementioned objective, the manufacturing method of the liquid crystal display element of the present invention, in which liquid crystal is sealed into a gap between the pair of substrates, at least one of the substrates having light transmitting property, includes the steps of: the first step for forming a plurality of pillar-shaped or wall-shaped spacers having even heights on at least one of the pair of substrates, the second step for forming the alignment control layer for covering the substrate except for the top portions of the spacers, and the third step for bonding the top portions of the spacers to an alignment control layer formed on the other substrate.

With the above-mentioned method, firstly, in the first step, the spacers are formed on the upper surface of the insulating substrate. Here, before or after the first step, electrodes, a light-shielding layer, and an insulating film, etc. are formed on each substrate if necessary. And then, in the second step, the alignment control layer is formed so as to cover the upper layer of the insulating substrate except for the top portions of the spacers. The spacers are formed before the alignment control layer has been formed so that it is possible to prevent solvents and others which are used in the forming process of the spacers from causing contamination or damage to the alignment control layer.

With this method, it becomes possible to provide a liquid crystal display element which realizes favorable even display quality. Further, the alignment control layer is selectively formed so as to cover the upper layer of the insulating substrate except for the top portions of the spacers, that is, the alignment control layer is not formed on the top portions of the spacers; thus, the pair of the substrates are joined to each other in a state in which the top portions of the spacers on one substrate are bonded to the alignment control layer on the other substrate. As described above, the alignment control layer is selectively formed so as to cover the upper layer of the insulating substrate except for the top portions of the spacers so that it becomes possible to prevent the degradation of the display quality and adhesive strength, that tends to occur in the case when the alignment control layers are softened so as to be bonded to each other.

For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional view which shows a schematic construction of one embodiment of a liquid crystal display element in accordance with the present invention.

Figs. 2(a) through 2(e) are sectional views which show each step of a manufacturing process of the liquid crystal display element.

Fig. 3 is a sectional view which shows a schematic construction of the liquid crystal display element which is produced in a conventional manufacturing process.

Fig. 4 is a sectional view which shows a schematic construction of another liquid crystal display element which is produced in a conventional manufacturing process.

DESCRIPTION OF THE EMBODIMENTS Referring to Figs. 1 and 2, the following explanation will discuss one embodiment of the present invention.

Fig. 1 is a sectional view illustrating a schematic construction of one embodiment of a liquid crystal display element in accordance with the present invention. The liquid crystal display element of the present embodiment has a construction in which a pair of substrates 10 and 20 are bonded to each other with their surfaces facing inside and liquid crystal 7 is sealed into a gap between them.

The substrate 10 is constituted by an insulating substrate la, a plurality of electrodes 2a which are provided in parallel with one another, a light-shielding layer 3a, an insulating film 4a which is formed so as to cover the insulating substrate la, the electrode 2a, and the light-shielding layer 3a, spacers 6 which are formed on the surface of the insulating film 4a, and an alignment control layer 5a which is formed so as to cover the entire surface of the insulating film 4a except for top portions of the spacers 6.

Further, the substrate 20 is constituted by an insulating substrate ib, a plurality of electrodes 2b which are provided in parallel with one another, an insulating film 4b, and an alignment control layer 5b which is stacked on the surface of the insulating film 4b. Moreover, the substrate 10 and 20 are bonded to each other in a state in which the top portions of the spacers 6 formed on the insulating substrate la are joined to the alignment control layer 5b formed on the insulating substrate ib. The insulating substrates la and 1b are made of transparent materials such as glass or plastic. Further, transparent electrodes made of ITO(Indium Tin Oxide) are generally used to form the electrodes 2a and 2b; however, other kinds of metals can be adopted. Moreover, the light-shielding layer 3a is made of metals such as Cr, Mo, Al, etc. or an opaque organic resin.

Furthermore, the liquid crystal 7 is made of ferroelectric liquid crystal composition. The ferroelectric liQ 1 crystal composition is superior in high-speed response with an excellent memory, thereby achieving a highdefinition image display with large capacity. ne liquid crystal disk~ .y element of the present embodiment, which is provided with the aforementioned arrangement, is produced as follows: firstly, a 100nm thickness film which is made of a metal such as molybdenum or an opaque organic resin is formed on the insulating substrate la. The film is patterned by using the photolithography so that the light-shielding layer 3a is formed into a predetermined pattern as shown in Fig. 2(a).

And then, ITO with a thickness of 100nm is formed thereon by using the sputtering method, and is patterned by using the photolithography so that the electrodes 2a are formed. Consequently, as shown in Fig. 2(b), the lightshielding layers 3a are provided along both sides of the electrode 2a.

Further, SiO2 is applied thereto by using a spin coating method, as shown in Fig. 2(c), so as to form the insulating film 4a having an even surface. Here, the insulating film 4a may be omitted in some cases.

On the insulating film 4a, for example, a negativeworking photosensitive acrylic resin V-259(manufactured by Nippon Steel Chemical Corporation) is applied with a film thickness of 1.5 Hm(after baking) by using the spin coating method. And then, the resin is subjected to ultraviolet radiation with a photomask so as to expose portions in which no electrode 2a is provided between the light-shielding layers 3a(i.e., spacer forming portions). After unexposed portions have been removed, the resin is baked at approximately 180-C for one hour so as to form the spacers 6 thereon as shown in Fig. 2 (d) . Additionally, it is possible to form the spacer 6 into a desired shape such as a pillar-shape, a wall-shape to be provided in parallel with one another, etc. by varying patterns and positions of the photomasks.

Successively, an alignment film PSI-A-2101(manufactured by Chisso Corporation)which is provided with a thickness of 50nm by using the spin coating method, is baked at approximately 200 C for one hour, and then the surface is subjected to a rubbing operation so as to form the alignment control layer 5a thereon as shown in Fig. 2(e).

As described above, upon forming the alignment control layer 5a, the spacers 6 repel materials of the alignment control layer; therefore, as shown in Fig. 2(e), it is possible to provide the alignment control layer 5a for covering the substrate 10 except for the top portions of the spacers 6. The detailed explanation will be described later.

With the above-mentioned process, it is possible to form the substrate 10. Further, the substrate 20 is produced by using the same process as mentioned above in which the electrodes 2b, the light-shielding layer (not shown), and the insulating film 4b are successively formed on the insulating substrate lb, and then, the alignment control layer Sb is formed thereon.

Next, the substrates 10 and 20 are arranged so as to oppose each other in a state in which the rubbing directions of the alignment control layers 5a and 5b are the same.

Pressure of 0.9 kg/cm2 is applied to the substrates for one hour at approximately 180-C so as to bond the spacers 6 to the alignment control layer 5b. Further, the liquid crystal 7 is sealed into the gap between the substrates 10 and 20; thus, the liquid crystal element is achieved.

The above-mentioned production process of the liquid crystal display element realizes a uniform cell thickness with a precision of +0.03 Hm. Furthermore, the lightshielding layer 3a and the light-shielding layer on the substrate 20 can shield portions in the vicinity of the spacers 6 so that it is possible to achieve a uniform alignment and switching property, and a high aperture rate in a display section of the pixels.

Additionally, as materials for the spacers 6, it is possible to adopt non-photosensitive polyimide, organic resins such as acrylic resin, and metals such as Cr, Mo, Al, etc. besides the negative-working photosensitive organic resin. However, in the case of the photosensitive organic resin, the photoresist is not necessary; thus, it is possible to produce the spacers more easily at lower cost.

Moreover, the spacers 6 can be positioned at any portion on the insulating substrate la; however, it is desirable to form the spacers on the outside of the pixel display region in order to prevent the display quality from declining.

Further, the above-mentioned construction described a case in which the spacers 6 are provided merely on the substrate 10; however, the following construction is also adopted: the required number of spacers 6 are divided so as to be formed both on the substrates 10 and 20, and the top portions of the spacers formed on one substrate are bonded to the other substrate at portions of the alignment control layer that have no spacer formed thereon so as to join the substrate 10 to the substrate 20.

Moreover, the insulating films 4a and 4b, which are not always necessary, can be omitted in the case when leakage current does not occur between substrates 10 and 20.

Further, besides the aforementioned films, it is possible to form films such as an overcoat film if necessary.

As described above, the alignment control layer Sa is provided so as to cover the regions c+ the surface of the insulating film 4a that have no spacer 6 formed thereon.

PSI-A-2101 used as the alignment control layer 5a has lower affinity to V-259 used as the spacer 6; however, PSI-A-2101 has higher affinity to SiO2 used as the insulating film 4a.

Therefore, when the alignment control layer 5a is subjected to a spin coating process, the alignment control layer 5a is repelled by the top surfaces of the spacers 6 and is not formed thereon, while the alignment control layer Sa is evenly formed on the regions of the insulating film 4a that have no spacer 6 formed thereon. Moreover, it is also possible to selectively provide the alignment control layer 5a on the regions of the insulating film 4a that have no spacer 6 formed thereon by using a screen printing method.

As described above, the liquid crystal display element of the present embodiment is provided with the pair of substrates 10 and 20. The substrate 10 has a construction in which the electrodes 2a, the light-shielding layer 3a, and the insulating film 4a, if necessary, are formed on the insulating substrate la as upper layers, the spacers 6 are formed thereon, and then the alignment control layer Sa is provided so as to cover the regions of the surface of the insulating film 4a that have no spacer 6 formed thereon.

The other substrate 20 has a construction in which the electrodes 2b are formed on the insulating substrate lb, and the insulating film 4b is formed thereon if necessary as upper layers, and then the alignment control layer 5b is stacked thereon so as to cover the entire upper layers.

Since the alignment control layer 5a is formed after the spacers 6 have been provided, it is possible to prevent contamination, deformation, destruction, etc. caused by the forming process of spacers; consequently, favorable display quality can be obtained.

Further, the alignment control layer 5a is formed so as to cover the regions of the insulating film 4a that have no spacer 6 formed thereon. As a result, the substrates 10 and 20 are joined to each other by bonding the top portions of the spacers 6 formed on the insulating substrate la to the alignment control layer 5b formed on the insulating substrate lb. Namely, the substrates can be bonded to each other merely by softening the spacers 6 without softening the alignment control layer. During the bonding process, the alignment control layer is not softened at the heating temperature of 180'C. Only spacers 6 are softened.

Furthermore, the heating temperature is lower than the baking temperature of the alignment control layer, 200 C.

Therefore, during the bonding process, the heating does not have an effect on the alignment control ability of the alignment control layer. Thus, it becomes possible to prevent degradation in alignment ability caused by the softened alignment control layer and to remove restrictions on the materials of the alignment control layer. These drawbacks are often found during a conventional operation for bonding the alignment control layers to each other.

Therefore, this arrangement makes it possible to strengthen the adhesive strength between the substrates, and consequently to provide a liquid crystal display element which is superior in shock resistance.

Moreover, the spacers 6 are made of materials that have optical isotropy, that is, the materials that have no anistropy in refractive index. Further, the spacers 6 are completely bonded to the alignment control layer 5b on the opposing substrate 20 without a gap so that the spacers 6 quench under a cross nicol condition. Namely, under the above-mentioned condition, the spacer 6 also functions as a black matrix, thereby improving the contrast by shielding light on the regions except for the pixel regions.

Further, in some cases, in the vicinity of the spacers 6, the liquid crystal alignment and the switching property become uneven, resulting in an uneven display. However, the present embodiment has a construction in which the portions around the spacers 6 are shielded by the light-shielding layer 3a. Thus, even in the case when some unevenness occurs on the display, the practical display state is not affected; consequently, it is possible to achieve high display quality.

[COMPARATIVE EXAMPLE 1] Here, a liquid crystal display element which is produced in a conventional process is taken as a comparative example for a comparison with the aforementioned liquid crystal display element of the present embodiment. Here, those members that have the same functions and that are described in the aforementioned embodiment are indicated by the same reference numerals and the detailed description thereof is omitted.

As shown in Fig. 3, the conventional liquid crystal display element has a construction in which after spacers 6 have been formed, an alignment control layer 5a is formed so as to cover the entire surface of the spacers 6 and an insulating film 4a, and substrates 11 and 20 are joined to each other in a state in which an alignment control layer Sa formed on an insulating substrate lla and an alignment control layer 5b formed on an insulating substrate 1b are bonded to each other.

The following explanation describes the production process of the aforementioned conventional liquid crystal display element.

In the same production process which is described referring to Figs. 2(a) through 2(d), electrodes 2a, lightshielding layers 3a, the insulating film 4a, and the spacers 6 are formed on the insulating substrate lla.

Next, the insulating substrate lla is dipped into an isopropyl solution of silane coupling agent SH6020(manufactured by Toray Dow Corning Industries, Inc.) and is washed by water. Successively, the alignment film PSI-A-2101(manufactured by Chisso Corporation) is applied thereon with a film thickness of 50nm by using the spin coating method, is baked for one hour at approximately 200 C, and then is subjected to a rubbing operation so that the alignment control layer 5a is formed. The substrate 11 is produced in the above process.

And then, the substrates 10 and 20 are arranged so as to oppose each other in a state in which the rubbing directions of the alignment control layers 5a and

As described above, the liquid crystal display element of the comparative example 1 is different from the embodiment of the present invention in that: an operation using silane coupling agent improves the affinity of the surface of the spacers 6, and the alignment control layer 5a is formed so as to cover the entire surface of the spacers 6 and the insulating film 4a; consequently, the substrates 11 and 20 are bonded to each other by bonding the alignment control layers 5a and 5b to each other.

The alignment control layer 5a is formed after the spacers 6 have been formed; thus, as in the present embodiment, the conventional arrangement prevents contamination, deformation, destruction, etc. of the alignment control layer 5a which are caused by the forming process of the spacers.

However, the alignment control layer 5a of the comparative example is formed so as to cover the upper surfaces of the spacers 6 and the insulating film 4a. As a result, it is necessary to soften the alignment control layer 5a on the insulating substrate lla and the alignment control layer 5b on the insulating substrate lb in order to join the substrates 11 and 20 to each other. For this operation, the heating temperature needs to be set at 250'C, which is higher than the baking temperature , 200 C, of the alignment control layer. Therefore, the heating for the bonding process gives adverse effects on the alignment control ability of the alignment control layer so that it is not possible to obtain a favorable alignment as compared with the arrangement of the present embodiment.

Additionally, in the case when the heating temperature of the bonding process is set at not more than 200 C, which is the same as that of the present embodiment, it is not possible to obtain favorable adhesive strength.

As described above, comparing the aforementioned liquid crystal display element which is produced in the conventional process with the liquid crystal display element of the present embodiment, it is understood that the latter is superior in the adhesive strength of the substrates and the display quality.

[COMPARATIVE EXAMPLE 2] As shown in Fig. 4, another conventional liquid crystal display element has a construction in which the spacers 6 are formed on the upper layer of an alignment control layer 5a, and substrates 40 and 20 are joined to each other in which the spacers 6 formed on an insulating substrate 21a are bonded to an alignment control layer 5b formed on an insulating substrate lb.

In the same production process which is described referring to Figs. 2(a) through 2(c), electrodes 2a, lightshielding layers 3a, and an insulating layer 4a are formed on the insulating substrate 21a.

Next, an alignment film PSI-A-2101(manufactured by Chisso Corporation) is applied on the insulating film 4a with a film thickness of 50nm by using the spin coating method, and is baked for one hour at approximately 200 C so as to form the alignment control layer 5a.

Successively, on the alignment control layer 5a, a negative-working photosensitive acrylic resin V259(manufactured by Nippon Steel Chemical Corporation) is applied by using the spin coating method so as to have a film thickness of 1.5 ym after the baking process. And then, the resin is subjected to ultraviolet radiation with photomasks so as to expose portions in which no electrode 2a is provided between light-shielding layers 3a and the spacers are to be formed. After portions which are not exposed have been removed, the resin is baked at approximately 180*C for one hour so as to form the spacers 6.

As described above, after the spacers 6 have been formed, the alignment control layer 5a is subjected to a rubbing operation; thus, a substrate 40 is achieved. Next, the substrates 40 and 20 are joined to each other by bonding the spacers 6 and the alignment control layer Sb to each other. Further, liquid crystal 7 is sealed into the gap between the substrates so that the liquid crystal element is achieved as illustrated in Fig. 4.

As described above, the liquid crystal display element of the comparative example 2 forms the spacers 6 on the alignment control layer 5a; therefore, the forming process of the spacers 6 gives adverse effects on the alignment control layer 5a.

Comparing the aforementioned liquid crystal display element which is produced in the conventional process with the liquid crystal display element of the present embodiment, it is understood that the latter is superior in the display quality.

As described above, the liquid crystal display element of the present invention has a construction in which at least one of a pair of substrates is provided with pillarshaped or wall-shaped spacers which have even heights, an alignment control layer is provided so as to cover the substrate except for top portions of the spacers, and the top portions of the spacers are bonded to the alignment control layer on the other substrate so that the pair of substrates are joined to each other.

It is desirable that the alignment control layer be repelled by the spacers when being formed so as to be selectively provided on the surface except for the regions in which the spacers are formed.

Further, it is also desirable that the spacer be made of a photosensitive organic resin. In the case when the materials for the spacer are non-organic or nonphotosensitive organic resins, the spacers are formed by using photolithography in which photoresist is adopted; however, in the case of the photosensitive organic resin, the photoresist is not necessary. Therefore, it is possible to provide a liquid crystal display element which is superior in the display quality and the shock resistance by using an easier production process at lower cost.

Moreover, it is desirable that the spacers be provided directly, or indirectly via another film on areas between a plurality of electrodes on one of the pair of the substrates, and have optical isotropy. With the aforementioned arrangement, the spacers are formed on the surface except for pixel regions. Therefore, it is possible to prevent a reduction in the aperture rate and degradation in the display quality that tend to occur in the case when the spacers are formed in the pixel. Further, the spacer has the optical isotropy so as to function as a black matrix.

Furthermore, it is desirable that the liquid crystal be made of ferroelectric liquid crystal. The ferroelectric liquid crystal has a spontaneous polarization and is superior in high-speed response with an excellent memory, etc., thereby achieving, for example, a liquid crystal display element which is capable of providing a highdefinition image display with a large capacity.

Here, since the regularity of the molecule alignment of the ferroelectric liquid crystal is close to a crystal as compared with nematic liquid crystal, when the regularity of the molecule alignment is disturbed by external pressure, it is hard to return the regularity to the initial state, that is, the ferroelectric liquid crystal is inferior in shock resistance. However, with the aforementioned arrangement, the substrate is sufficiently strengthened so as to be superior in shock resistance; thus, it is possible to solve the aforementioned drawback. Consequently, it becomes possible to provide a liquid crystal display element which has a favorable property peculiar to the ferroelectric liquid crystal.

In addition, the manufacturing method of the liquid crystal display element of the present invention includes the steps of: the first step for forming a plurality of pillar-shaped or wall-shaped spacers which have even heights on at least one of the pair of substrates, the second step for forming the alignment control layer for covering the substrate except for top portions of the spacers, and the third step for bonding the top portions of the spacers to the alignment control layer formed on the other substrate.

It is desirable that, in the second step, the alignment control layer be repelled by the spacers so as to be selectively provided on the surface except for the regions in which the spacers are formed. Namely, in order to allow the alignment control layer to be selectively formed on the surface except for the regions in which the spacers are formed, this manufacturing method makes use of the spacer which has property of repelling the alignment control layer.

As one possible method for forming the alignment control layer which covers the upper layer of the insulating substrate except for the regions in which the spacers are formed, firstly, the alignment control layer is formed so as to cover the entire upper layer of the insulating substrate including the spacers, and then, the alignment control layer on the spacers is removed by using photolithography, etc.

However, this method causes contamination and damage to the alignment control layer due to the photolithography process; therefore, it is not possible to obtain favorable display quality.

However, in the method of the present invention, even when the alignment control layer is applied so as to cover the entire upper layer of the insulating substrate on which the spacers are formed, by using methods such as the spin coating method and the roll coating method, the spacers repel the alignment control layer(or the material for the alignment control layer repels the spacers) so that the alignment control layer is applied on the upper layer of the insulating substrate except for the regions in which the spacers are formed. In other words, it is possible to selectively form the alignment control layer on the upper layer of the insulating substrate except for the top portions of the spacers. Therefore, it is not necessary to remove the alignment control layer on the top portions of the spacers; consequently, this method does not cause contamination and damage to the alignment control layer, and it becomes possible to realize favorable display quality with a simple manufacturing method.

Claims

CLAIMS:

1. A liquid crystal display element, in which liquid crystal is sealed into a gap between a pair of substrates, at least one of said substrates having light transmitting property, characterized by comprising: pillar-shaped or wall-shaped spacers having even heights on at least one of said pair of substrates, and an alignment control layer for covering said substrate except for top portions of said spacers, said pair of substrates being joined to each other in a state in which the top portions of said spacers are bonded to an alignment control layer formed on the other substrate.

2. The liquid crystal display element as defined in claim 1, wherein upon formation, said alignment control layer is repelled by said spacers so as to be selectively formed on said substrate except for regions in which said spacers are formed.

3. The liquid crystal display element as defined in claim 1 or 2, wherein said spacer is made of a photosensitive organic resin.

4. The liquid crystal display element as defined in any one of claims 1 through 3, wherein said spacers are placed directly, or indirectly via another film on areas between a plurality of electrodes on one of said pair of the substrate, and have optical isotropy.

5. The liquid crystal display element as defined in any one of claims 1 through 4, wherein said liquid crystal is made of ferroelectric liquid crystal.

6. A manufacturing method of a liquid crystal display element, in which liquid crystal is sealed into a gap between a pair of substrates, at least one of said substrates having light transmitting property, characterized by comprising the steps of: (1) forming a plurality of pillar-shaped or wall-shaped spacers which have even heights on at least one of said pair of substrates; (2) forming an alignment control layer for covering of said substrate except for top portions of said spacers; and (3) bonding the top portions of said spacers to an alignment control layer formed on the other substrate.

7. The manufacturing method of a liquid crystal display element as defined in claim 6, wherein, in said step (2), said alignment control layer is repelled by said spacers so as to be selectively provided on said substrate except for regions in which the spacers are formed.

8. The liquid crystal display element substantially as hereinbefore described with reference to Figure 1 and Figures. 2(a) though 2(e) of the accompanying drawings.