JP3296988B2 - Liquid crystal display device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to flat displays such as portable information terminals, personal computers, word processors, amusement equipment, and televisions used by a large number of people, display boards, windows, doors, and the like utilizing a shutter effect. The present invention relates to a liquid crystal display element used for walls and the like and a method for manufacturing the same.

[0002]

2. Description of the Related Art JP-A-6-301015 and JP-A-7-12
No. 0728 discloses a liquid crystal display device having a liquid crystal region surrounded by a polymer region and having excellent mechanical strength and viewing angle characteristics, and a method for manufacturing the same.

FIG. 10 schematically shows a partial sectional view of a liquid crystal display device 100 disclosed in Japanese Patent Application Laid-Open No. Hei 6-301015. In the liquid crystal display element 100, a pair of substrates 21 and 2
3 have a polymer region 28 and a liquid crystal region 29 substantially surrounded by the polymer region 28. The liquid crystal region 29 includes the electrodes 22 and 24 facing each other.
Are formed corresponding to the picture elements defined by The liquid crystal molecules (not shown) in the liquid crystal region 29 are axially symmetrically oriented radially or concentrically with respect to the central axis of the liquid crystal region 29 (perpendicular to the substrate). As a result, the liquid crystal display element 10
0 has a wide viewing angle characteristic.

In this liquid crystal display element, a precursor mixture containing a liquid crystal material, a polymerizable resin material, and a polymerization initiator is sandwiched between a pair of substrates, and then irradiated with light whose irradiation intensity is adjusted by a photomask or the like to polymerize the polymer. It is produced by curing a conductive resin material to form a liquid crystal region substantially surrounded by a polymer region made of the obtained polymer substance. The reason why the above liquid crystal display device has excellent mechanical strength and viewing angle characteristics is that the polymer region works to keep the distance between the two substrates together with the spacer and the sealant, and the liquid crystal molecules in the liquid crystal region surrounded by the polymer region. Are axially symmetrically oriented.

[0005]

[SUMMARY OF THE INVENTION] However, the liquid crystal display device, a reduction in T _NI of liquid crystal material in the liquid crystal region, decrease in transmittance, high voltage threshold voltage, there is a long slow (response time response speed ). Further, when a reliability test is performed at a high temperature, a polymerizable resin material and / or a polymer material generated by curing the polymerizable resin material in the liquid crystal material in the liquid crystal region (hereinafter, simply referred to as a polymer material for simplicity) In some cases) and the alignment of liquid crystal molecules is disturbed. Further, depending on the shape of the substrate, there are cases where the liquid crystal molecules cannot take an axially symmetric alignment. JP-A-8-95012
Japanese Patent Application Laid-Open Publication No. H11-150572 discloses a method of controlling a position where a liquid crystal region is formed by applying a material having a low surface free energy to a region other than a pixel portion on a substrate, and a method of controlling a liquid crystal material (liquid crystal phase) and a polymer substance ( A method for clarifying the phase separation from the polymer phase is disclosed. According to this method, the position where the liquid crystal region is formed with respect to the substrate can be controlled, and the display characteristics of the obtained liquid crystal display element can be improved. However, the phase separation between the polymer phase and the liquid crystal phase is not yet sufficient, and there are problems such as a decrease in _TNI of the liquid crystal material in the liquid crystal region, a decrease in transmittance, a higher threshold voltage, and a slow response speed. . Further, when a reliability test is performed at a high temperature, there is a problem that a polymer substance is mixed into a liquid crystal material in a liquid crystal region and the alignment of the liquid crystal is disturbed.

Accordingly, the present invention is to provide a liquid crystal display device in which the characteristics of a liquid crystal material in a liquid crystal region are very close to those inherent in liquid crystals, and to provide a method of manufacturing such a liquid crystal display device. With the goal.

[0007]

As a result of diligent studies on various substrate shapes, the present inventors have found a liquid crystal display device in which the characteristics of the liquid crystal material in the liquid crystal region are very close to those inherent in the liquid crystal.

Namely, at least the liquid crystal layer, a liquid crystal display device which is formed by sandwiching, protruding in the region on the substrate where one of the substrates corresponding to the picture element region between a pair of substrates having both at least the electrode film One or more liquid crystal regions surrounded by a structure;
A polymer substance is sandwiched between the other substrate and the height x of the protruding structure is in a range of 0.15 × h ≦ x ≦ 0.8 × h, where h is a substrate interval in the pixel region. Thus, the above object is achieved.

[0009]

[0010] The present invention also provides a method of manufacturing a liquid crystal display device formed by sandwiching at least a liquid crystal layer between a pair of substrates having both at least the electrode film, one of said pair of substrates
Forming one or more of the area surrounded by the protruding structure into One in the region corresponding to the pixel regions on the substrate, the substrate and the other substrate and a certain interval having a projecting Okoshijo structure a step of maintaining by bonding the the steps of a precursor mixture containing a liquid crystal material and the polymerizable resin material distribution between the substrates, a phase fraction to produce a liquid crystal droplets by phase separation from the precursor mixture
A separating step and a step of orienting liquid crystal molecules in the liquid crystal droplets in an axially symmetrical manner. The phase separation step is performed at a temperature at which the size of the liquid crystal droplet becomes 80% or more of the size of the picture element. Curing the polymerizable resin material on the protruding structure.
You.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

(Structure of Liquid Crystal Display Element) The liquid crystal display element of the present invention has a structure in which at least a liquid crystal layer is sandwiched between a pair of substrates having at least an electrode film.

One of the pair of substrates has one or more regions surrounded by the protruding structures in a region on the substrate corresponding to the picture element region. The liquid crystal display device according to the present invention has substantially the same configuration as the liquid crystal display device 100 shown in FIG.
Further, according to the present invention, the liquid crystal material in the liquid crystal region has characteristics very close to the original characteristics of the liquid crystal material, and thus has excellent display characteristics.

Note that the liquid crystal region 29 does not necessarily need to be formed for each picture element, but may be divided by a black matrix or the like for reasons such as a manufacturing method (for example, in the case of long picture elements having different aspect ratios). More than two picture elements n
The liquid crystal area may be formed for each of the divided areas. As used herein, the term "picture element"
In a liquid crystal display device, it refers to a basic unit for forming an image. "Picture region" refers to a portion of a liquid crystal display device that constitutes a picture element of the display device, and this portion includes a liquid crystal region sandwiched between a pair of substrates. As described above, the picture element area may include a plurality of liquid crystal areas. The liquid crystal regions of the liquid crystal display device according to the present invention have a certain correspondence with the picture elements and are spatially regularly arranged.

The liquid crystal layer of the liquid crystal display device of the present invention is formed by phase-separating a precursor mixture of a liquid crystal material and a polymerizable resin material. The precursor mixture is injected between a pair of substrates constituting the liquid crystal display element, and the precursor mixture is once heated to a temperature equal to or higher than the compatibility temperature. By gradually lowering the temperature of the precursor mixture, phase separation occurs and separates into a liquid crystal phase and a compatible phase (that is, a polymer phase that becomes a polymer region after curing the polymerizable resin material). The liquid crystal phase appears as a plurality of liquid crystal droplets (independent phases) in the compatible phase (liquid crystal droplet generation process). When a nematic liquid crystal is used as a liquid crystal material, the liquid crystal appears as a nematic liquid crystal droplet.

Thereafter, as the phase separation proceeds, for example, by further lowering the temperature of the precursor mixture, liquid crystal droplets grow (liquid crystal droplet growth process). The liquid crystal droplet grows while a plurality of liquid crystal droplets fuse with each other. In the present specification, “growing of liquid crystal droplet” means that the size of the liquid crystal droplet increases. The term “size of a liquid crystal droplet” refers to an area of the liquid crystal droplet when the liquid crystal droplet is viewed from a direction perpendicular to the substrate.

The term "substrate spacing" refers to the spacing between the surfaces of the pair of substrates in contact with the liquid crystal layer in the picture element region. If this interval is not constant, it refers to the average interval. The “height of the protruding structure” refers to the distance from the electrode film (the surface in contact with the liquid crystal layer) to the top of the protruding structure, and is smaller than the above-mentioned substrate interval.

The distance between the substrates and the height of the protruding structure are shown in FIGS. 3 and 4 showing the structure of the liquid crystal display device. FIG. 3 shows a liquid crystal display device having a black matrix on one substrate, and FIG. 4 shows a liquid crystal display device having an active matrix substrate.

The liquid crystal display device shown in FIG. 3 has a pair of substrates 1, on each of which a transparent electrode 5 is formed. A black matrix 6 having a predetermined pattern is formed on one of the pair of substrates 1. On the black matrix 6, the protruding structure 2 is formed using a photoresist. In FIG. 3, the distance between the substrates in the liquid crystal display device is indicated by an arrow h, and the height of the protruding structure 2 is indicated by an arrow x.

The height (projection height) x of the projecting structure can be determined as follows, where h is the distance between the substrates in the picture element region.

In a liquid crystal cell in which a precursor mixture containing a liquid crystal material and a polymerizable resin material is sandwiched between a pair of substrates,
The state change that occurs in the precursor mixture by changing the temperature of two types of liquid crystal cells having a protruding structure having only a different height around a region corresponding to a pixel region on one substrate is represented by a polymerizable resin material. The temperature at which the liquid crystal phase starts to separate out as liquid crystal droplets, the temperature at which the size of the liquid crystal droplets becomes the same size as the picture element, and the temperature at which the liquid crystal droplets do not exist independently (the liquid crystal droplets start to fuse with each other) Temperature) and the temperature at which all of the precursor mixture became a liquid crystal phase (the temperature at which the entire precursor mixture became a liquid crystal phase (ie, a nematic phase)).

For the liquid crystal cells when the height of the protruding structure is "high" and "low", the temperature at which liquid crystal droplets begin to precipitate and the temperature at which all of the liquid crystal phase becomes a liquid crystal phase are determined with respect to the polymerizable resin material content. As shown in FIG. As is clear from FIG. 1, the temperature at which the liquid crystal droplet starts to be deposited is not so affected by the height of the protruding structure. However, when the height of the protruding structure is reduced, the temperature range up to the temperature at which all of the precursor mixture becomes a liquid crystal phase is narrowed.

FIG. 2 schematically shows the relationship among the liquid crystal region 3, the polymer region (compatible region) 4, and the protruding structure 2. As shown in FIG. Usually, the deposited liquid crystal droplets are deposited on the substrate 1 facing the protruding structure 2.
It grows between substrates rather than between. Therefore, when the liquid crystal droplet grows large, the concentration of the polymerizable resin material excluded from the liquid crystal droplet increases between the protruding structure 2 and the opposing substrate 1. Since the space between the protruding structure 2 and the opposing substrate 1 is larger when the height of the protruding structure 2 is lower, the amount of the polymerizable resin material excluded from the liquid crystal phase accommodated in this space. Will increase. In other words, the lower the protruding structure 2, the higher the purity of the liquid crystal material in the liquid crystal droplet, and the more the phase separation between the liquid crystal phase and the compatible phase proceeds. Therefore, from the viewpoint of the purity of the liquid crystal material, it is preferable that the height of the protruding structure 2 is lower. However, as described above, when the height of the protruding structure is reduced, the temperature range up to the temperature at which all of the precursor mixture becomes a liquid crystal phase is narrowed. That is, more precise temperature control is required to grow the liquid crystal droplet to a desired size.

Therefore, considering the purity of the liquid crystal material in the liquid crystal region 3 and the manufacturing conditions of the display element, the projection-like structure 2
The height x of the liquid crystal display element is, for example, 0.15 × h ≦
It is preferable that the relationship x ≦ 0.8 × h is satisfied.

In consideration of the optical characteristics, operability and reliability of the display element, it is more preferable to satisfy the relationship of 0.3 × h ≦ x ≦ 0.55 × h.

In one protruding structure 2, the height x can be the same or different everywhere in the structure. Preferably they are the same. The protruding structure 2 includes a cylinder, a cone, a truncated cone, an elliptic cylinder, an elliptical cone, a truncated elliptical cone, a prism,
It may take the shape of a truncated pyramid, a composite of these, or a continuous dashed or linear shape. The shape of the region surrounded by the protruding structure 2 is a polygon, a circle, or a combination thereof, and is in accordance with the shape of the picture element. Can be Preferably it is square.

In the liquid crystal display device of the present invention, a polymer substance can be further sandwiched between a pair of substrates facing each other, preferably between the projecting structure and the substrate facing the same. Thereby, the alignment state of the liquid crystal molecules in the liquid crystal region substantially surrounded by the polymer region made of the polymer substance is maintained, and the strength of the liquid crystal display element is improved. The polymer substance is preferably a polymer obtained by polymerizing a polymerizable resin material. As the polymerizable resin material, for example, acrylic acid or acrylate having a long-chain alkyl group or aromatic group having 3 or more carbon atoms can be used. Examples of acrylic acid or acrylic acid esters include isobutyl acrylate, stearyl acrylate, lauryl acrylate, isoamyl acrylate, n-butyl acrylate, tridecyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, benzyl acrylate, and 2-phenoxyethyl acrylate; Methacrylates; and halides of these monomers (especially chlorinated or fluorinated monomers),
For example, 2,2,3,4,4,4-hexafluorobutyl methacrylate, 2,2,3,4,4,4-hexachlorobutyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate , 2,2,3,3-tetrachloropropyl methacrylate, perfluorooctylethyl methacrylate, perchlorooctylethyl methacrylate, perfluorooctylethyl acrylate, perchlorooctylethyl acrylate. These monomers may be used alone or in combination of two or more.

The substrate may have an alignment control layer for controlling the alignment of liquid crystal molecules as required. As the orientation control method,
After coating the polymer material or an inorganic material such as polyimide substrate, a rubbing method rubbing with a cloth, a vertical alignment method of applying a compound having a low surface free energy, the oblique orientation method by oblique deposition, such as SiO _2, also rubbed A horizontal alignment method using a horizontal alignment film that is not performed is exemplified.

The liquid crystal material that can be used in the present invention is not particularly limited as long as it shows a liquid crystal state at around normal temperature. Nematic liquid crystals (including two-frequency driving liquid crystal, liquid crystal with Δε <0), cholesteric liquid crystal (Especially, liquid crystals having selective reflection characteristics for visible light), smectic liquid crystals, ferroelectric liquid crystals, discotic liquid crystals, and the like. Among these, a nematic liquid crystal, a cholesteric liquid crystal, or a nematic liquid crystal to which a chiral agent is added is preferable. In a nematic liquid crystal to which a chiral agent is added, hysteresis, uniformity, d · Δn
It is preferable to add a chiral agent so as to have a helical pitch of 10 μm or more from the problem of coloring due to (phase difference). In addition, a liquid crystal material having excellent chemical reaction resistance is preferable because a photopolymerization reaction occurs during processing. Specifically, the compound is a liquid crystal material having a functional group such as a fluorine atom,
ZLI-4801-000, ZLI-4801-00
1, ZLI-4792 (manufactured by Merck) and the like. These liquid crystal materials can be used as a mixture.

(Manufacturing Method of Liquid Crystal Display Element) As a preferred manufacturing method of the liquid crystal display element of the present invention, first, a projection-like structure is formed in a region corresponding to a picture element region on one of a pair of substrates. To form one or more regions.
As a method of forming a region surrounded by the protruding structure,
Patterning method using resist, printing method,
A method in which the resist formed on the entire surface is partially left by etching or the like, a method in which a molded product is disposed on a substrate,
An evaporation method, a method using electroplating, or the like can be used.

The height of the formed protruding structure is 0.15 to the substrate distance h of the liquid crystal display element to be finally manufactured.
It is preferable to satisfy the relationship of xh ≦ x ≦ 0.8 × h. 0.3 × considering the optical characteristics, operability and reliability of the display element
It is more preferable that the relationship h ≦ x ≦ 0.55 × h is satisfied.
If x is smaller than 0.15 × h, problems such as a decrease in the axial symmetry may occur. If x is larger than 0.8 × h, problems such as poor injection may occur.

Next, the substrate having the protruding structure and the substrate having at least the electrode film are adhered at a constant interval to form a cell. Next, a precursor mixture containing a liquid crystal material, a polymerizable resin material, and a polymerization initiator is injected between the substrates. Subsequently, the liquid crystal molecules in the liquid crystal droplets generated by the phase separation are oriented in an axially symmetric manner. At this time, it is preferable to control the size of the liquid crystal droplet. As a method of controlling, a method of controlling the size of liquid crystal droplets by only heating a precursor mixture containing a liquid crystal material, a polymerizable resin material, and a polymerization initiator, cooling the precursor mixture and then cooling the liquid crystal droplets A method of depositing and then growing, a method of controlling the size of the liquid crystal droplet by combining heating and cooling several times, and the like can be used. Then, the size of the liquid crystal droplet is 8 which is the size of the picture element.
By curing the polymerizable resin material at a temperature of 0% or more, a liquid crystal display device can be obtained.

As a method for orienting liquid crystal molecules in an axially symmetric manner, for example, before curing the polymerizable resin material, a voltage is applied between the substrates constituting the cell, and disclination is performed along the outer periphery of the liquid crystal droplet. By raising and lowering the applied voltage so that a line exists, the liquid crystal molecules can be oriented in an axially symmetric manner.

The temperature at which the polymerizable resin material is cured can be determined as follows.

By changing the temperature of the liquid crystal cell in which the precursor mixture containing the liquid crystal and the polymerizable resin material was sandwiched between a pair of substrates, the state change occurring in the precursor mixture was observed. Plotting the temperature at which liquid crystal droplets begin to precipitate, the temperature at which the size of the liquid crystal droplets becomes the same size as the picture element, the temperature at which the liquid crystal droplets do not exist independently, and the temperature at which the precursor mixture is entirely in the liquid crystal phase. The phase diagram shown in FIG. 5 is obtained.

In the phase diagram of FIG. 5, the region A is in a state where the liquid crystal material and the polymerizable resin material are completely compatible. The straight line separating the A region and the B region indicates the temperature at which liquid crystal droplets begin to precipitate at each polymerizable resin material content. The deposited liquid crystal droplet grows with the temperature drop in the region B, but its size is smaller than the size of the picture element. The straight line separating the B region and the C region indicates the temperature at which the size of the liquid crystal droplet becomes the same as that of the picture element at each content of the polymerizable resin material. The liquid crystal droplet having the same size as the picture element further grows with the temperature drop in the region C. The straight line separating the C region and the D region indicates the temperature at which the liquid crystal droplet does not exist independently at each polymerizable resin material content. In the D area,
Since the liquid crystal droplet fuses with the adjacent liquid crystal droplet, the liquid crystal droplet becomes larger and the shape of the liquid crystal droplet becomes random. D area and E
The straight line separating the regions indicates the temperature at which all the regions become liquid crystal phases at the respective polymerizable resin material contents. In the E region, all regions are liquid crystal phases.

As is apparent from FIG. 5, when the temperature of the precursor mixture having a polymerizable resin material content of a weight% is further decreased, the size of the liquid crystal droplet grows, and at the same time, the polymerization contained in the liquid crystal droplet is increased. The amount of the conductive resin material increases. That is, the smaller the liquid crystal droplet, the higher the purity of the liquid crystal droplet. However, when the liquid crystal droplets are small, the size of the liquid crystal region substantially surrounded by the polymer region made of a polymer material obtained by curing the polymerizable resin material is small, and the aperture ratio is reduced.
The performance of the display element obtained is reduced. Therefore, in consideration of the size of the liquid crystal region to be formed (aperture ratio) and the purity of the liquid crystal material in the liquid crystal region, the size of the liquid crystal droplet is equal to the size of the pixel regardless of the content of the polymerizable resin material. It is preferable that the polymerizable resin material is cured at a temperature of 80% or more, preferably 100%, and at which liquid crystal droplets are independently present in one pixel region.

The temperature at which the liquid crystal droplet satisfies the above conditions depends on the type of liquid crystal material and polymerizable resin material used, their mixing ratio,
It depends on the shape of the substrate, the surface condition of the substrate, and the like. Therefore, the temperature at which the liquid crystal droplet satisfies the above conditions can be determined by drawing a phase diagram for each combination of the liquid crystal material, the polymerizable resin material, and the substrate material used.

The amount of the polymerizable resin material used can be determined as follows.

As shown in FIG. 5, even if the types of the polymerizable resin material and the liquid crystal material are the same, the content of the polymerizable resin material (% by weight based on the total weight of the precursor mixture containing the polymerizable resin material and the liquid crystal material) ) Is a weight% and b weight%
In the case of (a <b), the temperature at which the size of the liquid crystal droplet becomes the same as the size of the picture element region is different. When the content of the polymerizable resin material is a% by weight, the amount of the polymerizable resin material contained in the liquid crystal droplets (liquid crystal phase) and the compatible phase is small. Thus, the transmittance, threshold voltage, response speed, and reliability of the liquid crystal display element are improved. But,
Since the absolute amount of the polymer substance obtained by curing the polymerizable resin material is small, the stability against pressing is reduced as compared with the case where the content of the polymerizable resin material is b% by weight. In addition, strict temperature control is required to cure the polymerizable resin material in a state suitable for narrowing the B region and the C region. Therefore, the amount of the polymerizable resin material used can be determined in consideration of the required performance of the liquid crystal display element to be manufactured and the manufacturing conditions based on the phase diagram as shown in FIG.

As the polymerizable resin material, acrylic acid or acrylate having a long-chain alkyl group or aromatic group having 3 or more carbon atoms as described above can be used.

The precursor mixture containing the polymerizable resin material and the liquid crystal which can be used in the present invention may contain a photopolymerization initiator, if desired. Examples of photopolymerization initiators include Irgacure 651,
Irgacure 184 (Ciba-Geigy) and Darocur 11
73 (manufactured by Merck). The photopolymerization initiator may be added in an amount of 0.01 to 3% by weight based on the total weight of the precursor mixture of the liquid crystal material and the polymerizable resin material.

Curing of the polymerizable resin material can be performed mainly by irradiating light. The exposure illuminance and exposure time of the irradiation light are not particularly limited because they differ depending on the ratio between the liquid crystal material and the polymerizable resin material. In order to form a liquid crystal cell having excellent mechanical strength, it is preferable to perform exposure for a long time at a low exposure illuminance than for short time exposure at a high exposure illuminance.
Exposure to high exposure illuminance for a short time generates a large amount of high molecular weight substance having a small molecular weight. If the molecular weight of the high molecular substance is small, a liquid crystal cell having sufficient mechanical strength cannot be obtained. When a photomask is used, the photomask has a continuous or independent regular pattern and may be in a matrix or stripe shape. After the liquid crystal region is formed, the entire surface of the liquid crystal layer is irradiated with light, so that the curing of the polymerizable resin material can be completed.

Example 1 As shown in FIG. 3, a transparent electrode 5 of 100 nm thick made of ITO (a mixture of indium oxide and tin oxide) is formed on a glass substrate 1 (1.1 mm thick). This substrate 1 was patterned with a sealant (Stract Bond XN-21S) by a printing method. On the other hand, on a substrate 1 on which a transparent electrode made of similar ITO is formed, FIG.
The black matrix 6 composed of a molybdenum film having 100 μm square holes (corresponding to picture element regions) 15 as shown in FIG. Further, a negative photoresist 16 (OMR83: manufactured by Tokyo Ohkasha Co., Ltd.) is formed on the black matrix 6.
Was applied, exposed, developed, rinsed, and fired to form a 2.0 μm-thick protruding structure 2 as shown in FIG. Plastic beads (micropearl; manufactured by Sekisui Fine Chemical Co., Ltd.) having a particle size of 4.5 μm were sprayed on the substrate on which the protruding structure 2 was formed, and bonded to the previously prepared substrate to prepare a cell.

Β- (perfluorooctyl) ethyl acrylate 1.5 g, stearyl acrylate 2.6 g, R684
1.0 g (manufactured by Nippon Kayaku) and p-phenylstyrene 1.
9 g was mixed to obtain a polymerizable resin material. As a liquid crystal material
Prepare ZLI-4792 (manufactured by Merck; 0.3% by weight of chiral agent S-811), add 0.15 g of polymerizable resin material, 0.9 g of liquid crystal material, and 0.005 g of Irgacure 651 photopolymerization initiator, and mix well. It was injected into the cell to obtain a liquid crystal cell.

After heating the liquid crystal cell at 95 ° C. for 10 hours,
Slowly cool to 72 ° C at 1 ° C / min, and apply voltage (3V, 60H
z) was applied, and the liquid crystal molecules were axially symmetrically aligned. The voltage was stopped, and the temperature was gradually cooled at 0.5 ° C / min.At a temperature at which the liquid crystal droplets became the size of a pixel, UV irradiation was performed at 12 mW / cm ² under a high-pressure mercury lamp for 20 minutes to polymerize the resin material. Was cured to produce a liquid crystal display device. The T of the liquid crystal area in the picture element area formed corresponding to the picture element of the manufactured liquid crystal display element
_{When NI} was measured, it was 87 ° C., which was a value close to the liquid crystal original T _NI (91 ° C.). The transmittance when no voltage was applied reached 79% of that of the TN liquid crystal display device. The response time is the sum of τ _r (rise time) and τ _d (fall time) when 5 V is applied.
It was 44 msec, which was quite close to 40 msec of the TN liquid crystal display element.

When the manufactured liquid crystal display device was observed with a polarizing microscope, as shown in FIG. 8, an extinction pattern 17 was observed in each of the picture element regions 15, and a state in which the liquid crystal molecules were axially symmetric was observed. Was. The liquid crystal display device is placed in a 70 ° C
Even after standing for a long time, there was no significant change in the shape and electro-optical characteristics of the liquid crystal region, and the stability was extremely excellent.

The substrate with the black matrix of Example 1
0.25, 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 2.75, 3.0, 3.
Protrusion-like structures of 5, 3.75, 4.0, 4.25, and 4.5 μm were produced. On the other hand, a glass substrate (1.1 mm thick) having a thickness of 100 nm made of ITO (a mixture of indium oxide and tin oxide)
A sealant (Structbond XN-21S) was patterned on the substrate on which the transparent electrode was formed by a printing method. 5.
The cells were bonded together with a substrate interval of 0 μm maintained to produce a cell.

A polymerizable resin material was prepared by mixing 1.5 g of 2- (perfluorohexyl) ethyl acrylate, 2.6 g of stearyl acrylate, 1.0 g of R684 (manufactured by Nippon Kayaku) and 1.9 g of styrene. ZLI-4792 (manufactured by Merck; containing 0.3 wt% of chiral agent S-811) was prepared as a liquid crystal material, and 0.1 g of a polymerizable resin material, 0.9 g of a liquid crystal material, and a photopolymerization initiator Irgacure 6510.00 were used.
After mixing well with 5 g, the mixture was injected into the cell prepared above to obtain a liquid crystal cell. At the time of injection, cells with a projection height of 4.25 μm or more had poor injection at some places. Once the liquid crystal cell is 95
After heating at 10 ° C for 10 hours, the temperature of the liquid crystal droplet is gradually cooled at 1 ° C / min to a temperature at which the size of the liquid crystal droplet becomes about 50% of the pixel area, and a voltage (3 V, 60 Hz) is applied to break the liquid crystal molecules. It was oriented to be axially symmetric. For a liquid crystal cell having a projection height of more than 3.0 μm, the movement of liquid crystal molecules was slow, and it was difficult to perform an operation of orienting the liquid crystal molecules in an axially symmetric manner. When the application of the voltage was stopped, the axisymmetric alignment of the liquid crystal molecules of the liquid crystal cell having a protrusion height of 0.5 μm or less was spontaneously broken. Moreover, subjected to slow cooling at 0.5 ° C. / min, at a temperature at which the size of the liquid crystal droplets became equal to the size of the picture element, performs irradiation of 20 minutes UV at a high pressure mercury lamp under 12 mW / cm ^2, the polymerizable The liquid crystal display element was obtained by curing the resin material.

With respect to the evaluation items shown in Table 1, the liquid crystal display devices having each projection height were evaluated. The evaluations in Table 1 were as follows: ×; unsuitable, Δ: not very good, ○: good,
◎: very good In the section of the comprehensive evaluation, the symbol "o" indicates that the device can be used by restricting the intended use, such as not requiring viewing angle characteristics in all directions and not exposing it to high temperatures for a long time.

[0051]

[Table 1]

As shown in Table 1, in the liquid crystal cell having a projection height of 0.5 μm or less in which the axisymmetric alignment was spontaneously broken, no axisymmetric alignment remained after curing. Examination of the proportion of picture elements in an axially symmetric orientation per 100 picture elements (hereinafter referred to as the axial symmetry rate) showed that the higher the protrusion height, the higher the axial symmetry rate, and a practical level The axial symmetry ratio of 80% was reached after the protrusion height became 1.5 μm or more.

[0053] When the liquid crystal molecules of the liquid crystal display device was measured T _NI of liquid crystal regions in the pixels that are axially symmetrically aligned, as shown in Table 1, towards the projections lower height that the temperature was high. When the reliability test was performed at 70 ° C for 100 hours, the liquid crystal display element that showed no change after 100 hours was a liquid crystal display element with a protrusion height of 2.75 μm or less, and a liquid crystal with a higher protrusion height In the display element, the alignment of liquid crystal molecules was partially lost. For the liquid crystal display devices with protrusion heights of 0.75 μm and 1.0 μm, there was no change in the liquid crystal region that showed axial symmetry, but resinous substances were precipitated in the liquid crystal region that was not axially symmetric. Was.

As described above, the height of the projections is from 0.75 μm to 4.0
When μm (x / h is in the range of 0.15 to 0.8), a liquid crystal display device having a wider viewing angle range than before can be manufactured. Furthermore, when it is in the range of 1.5 μm to 2.75 μm (x / h is 0.3 to 0.55), the axial symmetry ratio is extremely high, and the reliability test at 70 ° C.
A very good liquid crystal display element with a wide viewing angle of 100 hours without change was produced.

(Example 2) A sealing material (Stract Bond XN-21S) was patterned on a glass substrate 1 (1.1 mm thick) on which a transparent electrode 5 made of ITO having a thickness of 100 nm was formed by a printing method. A 100 μm square hole 15 as shown in FIG. 6 is formed on the substrate 1 on which the transparent electrode 5 made of similar ITO is formed.
A negative photoresist 16 (V259-PA: manufactured by Nippon Steel Chemical Co., Ltd.) is applied, exposed, developed, rinsed, and baked on a black matrix 6 made of a molybdenum film having a thickness of 0.5 and 1.0 as shown in FIG. , 1.5, 2.0, 2.5, 3.0, 3.5, 4.0
A protruding structure 2 of μm was formed. Plastic beads (Micropearl: manufactured by Sekisui Fine Chemical Co., Ltd.) having a particle size of 4.5 μm were sprayed on these substrates, and bonded to form cells.

As a polymerizable resin material, a mixture of 0.25 g of bisphenol A diglycidyl ether, 0.2 g of isobornyl acrylate, 0.1 g of β- (perfluorooctyl) ethyl acrylate and 0.05 g of t-butyl peroxide,
ZLI-4792 (manufactured by Merck: Chiral agent S-81) as a liquid crystal material
0.54 g) and a polymerization initiator Irgacure 907
0.03 g was mixed well and injected into the produced cell to obtain a liquid crystal cell. It was not injected into the cell having a projection height of 4.0 μm. After heating these liquid crystal cells once at 95 ° C for 10 hours,
The liquid crystal was slowly cooled at 1 ° C./min, and a voltage (3 V, 60 Hz) was applied at a temperature at which the size of the liquid crystal droplet became about 50% of the pixel, thereby orienting the liquid crystal molecules in an axially symmetric manner. At this time, the projection height is 3.
In a liquid crystal cell having a size of 0 μm or more, the movement of the liquid crystal molecules was poor, and it was difficult to perform the operation of axisymmetric alignment. Stop applying voltage and continue
When slowly cooled at a rate of 0.5 ° C./min, the alignment of the liquid crystal molecules was disturbed in a part of the liquid crystal cell where the operation of the axially symmetric alignment was difficult. UV irradiation was performed at 11 mW / cm ² for 20 minutes under a high-pressure mercury lamp at a temperature at which the size of the liquid crystal droplet became the same as the size of the pixel, and the polymerizable resin material was cured to obtain a liquid crystal display device. Projection height 0.5 μm where the axisymmetric orientation has naturally been broken
After curing, the liquid crystal cell had an axial symmetry ratio of 0%.
The same items as in Example 1 were evaluated for the obtained liquid crystal display device. Table 2 shows the results.

[0057]

[Table 2]

As shown in Table 2, within the range of the protrusion height where the axisymmetric operability is good, the higher the protrusion height, the higher the axial symmetry ratio. T _NI temperature was higher even more lower projection height and measuring the T _NI of liquid crystal regions in the pixels that are axially symmetrically aligned. When the reliability test was performed at 70 ° C, there was no change after 100 hours in the liquid crystal display device with a protrusion height of 2.5 μm or less, and in the liquid crystal display device with a higher protrusion height, the alignment of the liquid crystal molecules was broken. I was

As described above, the liquid crystal display element which can be used depending on the condition where x / h is in the range of 0.22 to 0.78 is further reduced to 0.33 to 0.33.
When it was in the range of 0.55, an extremely good liquid crystal display device could be produced.

Example 3 A sealant (Structbond XN-21S) was patterned by a printing method on a glass substrate 1 (1.1 mm thick) on which a transparent electrode 5 made of ITO having a thickness of 100 nm was formed. On the other hand, a molybdenum film having a thickness of 0.0 μm is formed on the substrate 1 on which a transparent electrode 5 made of similar ITO is formed in a pattern having a hole 15 of 100 μm square as shown in FIG.
4, 1.0, 2.0 and 3.0 μm were formed, and a projection structure composed of the molybdenum film 6 was produced. Substrate 1 on which protruding structure is formed
Then, plastic beads (Micropearl: manufactured by Sekisui Fine Chemical Co., Ltd.) were sprayed so that the electrode interval in the picture element portion was 4.5 μm, and the two substrates were bonded together to form a cell.
The same liquid crystal material, polymerizable resin material and precursor mixture comprising a polymerization initiator as in Example 1 were injected into this cell to obtain a liquid crystal cell. After heating these liquid crystal cells at 95 ° C for 10 hours, they were gradually cooled at 1 ° C / min to make the size of the liquid crystal droplets about 50% of the pixel.
A voltage was applied at the time when the liquid crystal molecules reached the size, and the liquid crystal molecules were axially symmetrically aligned. In the liquid crystal cell having a projection height of 0.04 μm, the liquid crystal phase spread over the entire surface of the cell, and there was no effect of fixing the liquid crystal phase (liquid crystal droplet) in the pixel region. When the protrusion height was 3.0 μm, the response of the liquid crystal molecules to the voltage application was slow, and the alignment operation was difficult. At temperatures size of the liquid crystal droplets perform slow cooling at further 0.5 ° C. / min stopped voltage application becomes the same as the picture element size, irradiation is performed for 20 minutes ultraviolet at a high pressure mercury lamp under 12 mW / cm ^2, The liquid crystal display element was obtained by curing the polymerizable resin material.

With respect to the evaluation items shown in Table 3, the liquid crystal display devices having each projection height were evaluated.

[0062]

[Table 3]

In the 70 ° C. reliability test, there was no change in any of the liquid crystal display elements up to 50 hours. However, in the liquid crystal display element with a protrusion height of 3.0 μm, the axially symmetric alignment of the liquid crystal molecules was partially changed in 100 hours. Was crumbled. Particularly preferred projection height (2.0 μm)
In the liquid crystal display element manufactured in the above, transmittance, threshold voltage,
The response speed characteristics were also good.

(Embodiment 4) A negative photoresist 16 (OMR83: manufactured by Tokyo Ohka Co., Ltd.) is used for a portion other than the pixel electrode 8 on the active matrix substrate as shown in FIG. 1.0, 1.5, 2.0, 2.5, 3.0,
A 3.5 μm protruding structure 2 is prepared, and plastic beads (micropearl: manufactured by Sekisui Fine Chemical Co., Ltd.) are sprayed so that the distance from the pixel electrode surface to the surface of the electrode 5 of the counter substrate is 4.8 μm. Then, both substrates were bonded to each other using Structbond XN-21S as a sealant to prepare a cell.

The active matrix substrate used in this embodiment has a TFT (thin film transistor) as an active element. The TFT includes a source electrode 9, a gate channel 10, a gate electrode 11, a gate insulating film 12, and a drain electrode. 13 and an insulating film 14. The drain electrode 13 is connected to the pixel electrode 8. The counter substrate has a black matrix 6 and a color filter 7, and the color filter 7 is provided corresponding to the pixel electrode 8. The active matrix substrate and the counter substrate can be manufactured by a known method.

As the polymerizable resin material, 0.1 g of trimethylolpropane triacrylate, lauryl acrylate
0.26 g, 0.1 g of a mixture of 0.15 g of 2,2,3,4,4,4-hexafluorobutyl acrylate and 0.19 g of 4-fluorostyrene, and a liquid crystal ZLI-4472 (manufactured by Merck; Chiral S-81)
0.9g with polymerization initiator Irgacure 184 0.005
g was mixed and injected into the cell to obtain a liquid crystal cell. After heating these liquid crystal cells at 95 ° C for 10 hours, the liquid crystal was gradually cooled at a rate of 0.8 ° C / min, and a 60 Hz rectangular wave was generated at a temperature at which the size of the liquid crystal droplets became about 50% of the pixel. The applied liquid crystal molecules were axially symmetrically aligned. Since the voltage for controlling the alignment of liquid crystal molecules is limited by the withstand voltage limit of the active element,
For cells having a projection height of 3.0 μm or more, it was extremely difficult to perform an axially symmetric alignment operation, which was impossible with a 3.5 μm liquid crystal cell. The voltage application was stopped and the liquid crystal droplet was gradually cooled at a rate of 0.5 ° C./min until the size of the liquid crystal droplet became the same as the size of the picture element. When the voltage application was stopped, in the liquid crystal cell having a protrusion height of 1.0 μm, the axially symmetric alignment was partially broken. The liquid crystal display element was obtained by irradiating ultraviolet rays for 20 minutes under a high pressure mercury lamp at an illuminance of 13 mW / cm ² at a temperature at which the size of the liquid crystal droplet became the same as that of the picture element. Table 4 shows the results of evaluating the same items as in Example 3.

[0067]

[Table 4]

Even when an active matrix substrate was used, a liquid crystal display device having a wide viewing angle could be manufactured, although there were some restrictions, provided that 0.15 × h ≦ x ≦ 0.8 × h was satisfied. More optimal conditions (0.3 × h ≦ x ≦ 0.55 × h)
When a protruding structure satisfying the above condition was formed, a liquid crystal display device having improved transmittance, threshold voltage, response speed, high-temperature reliability, and easy control of axially symmetric alignment could be manufactured.

[0069]

According to the present invention, by using a substrate having a predetermined protruding structure, the stability against external pressure is extremely high, the viewing angle is wide, the phase separation between the liquid crystal phase and the polymer phase is clear, Provided are a liquid crystal display device having a high response speed, a high transmittance when no voltage is applied, a low threshold voltage, a high _TNI temperature of a liquid crystal material in a liquid crystal region, and an improved high-temperature reliability, and a method for manufacturing the same. obtain.

[Brief description of the drawings]

FIG. 1 shows a case where the height of a protruding structure is “high” and “low”.
FIG. 4 is a diagram showing the relationship between the temperature at which liquid crystal droplets begin to precipitate from a precursor mixture containing a liquid crystal material and a polymerizable resin material, the temperature at which the precursor mixture is entirely in a liquid crystal phase, and the polymerizable resin material content for the liquid crystal cell of the case. It is.

FIG. 2 is a diagram schematically showing a relationship between a liquid crystal region, a polymer region (compatible region), and a protruding structure.

FIG. 3 is a diagram illustrating a substrate interval and a height of a protruding structure in a substrate having a black matrix.

FIG. 4 is a diagram showing a substrate interval and a height of a protruding structure in an active matrix substrate.

FIG. 5 is a diagram schematically showing a phase change of a precursor mixture containing a liquid crystal material and a polymerizable resin material.

FIG. 6 is a view showing a substrate with a black matrix used in Example 1. (A) is a top view and (b) is a cross-sectional view taken along line 6B-6B 'of (a).

FIG. 7 is a view showing a substrate with a protruding structure manufactured in Example 1. (A) is a top view, (b) is 7B- of (a).
It is 7B 'sectional drawing.

FIG. 8 is a diagram schematically showing the results of observation of the liquid crystal display device manufactured in Example 1 with a polarizing microscope.

FIG. 9 is a sectional view of a liquid crystal display device having an active matrix substrate used in Example 4.

FIG. 10 is a partial cross-sectional view of a liquid crystal display device having an axially symmetric liquid crystal region.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Protruding structure 3 Liquid crystal region 4 Polymer region (compatibility region) 5 ITO electrode 6 Black matrix 7 Color filter 8 Pixel electrode 9 Source electrode 10 Gate channel 11 Gate electrode 12 Gate insulating film 13 Drain electrode 14 Insulating film 15 Omission (picture element area) 16 Photoresist layer 17 Quenching pattern

──────────────────────────────────────────────────続 き Continued on the front page (72) Nobuaki Yamada 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (56) References JP-A-5-281526 (JP, A) JP-A-4- 251222 (JP, A) JP-A-7-1114007 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1333 G02F 1/1339 G02F 1/13 101

Claims (2)

(57) [Claims] 1. A liquid crystal display device comprising at least a liquid crystal layer sandwiched between a pair of substrates having at least an electrode film, wherein one of the substrates has a projection formed in a region on the substrate corresponding to a picture element region . Having one or more liquid crystal regions surrounded by a structure,
Between the protruding structure on the one substrate and the other substrate
When the distance between the substrates in the picture element region is h, the height x of the protruding structure is 0.15.
A liquid crystal display device, wherein xh ≦ x ≦ 0.8 × h. 2. A method for manufacturing a liquid crystal display element comprising at least a liquid crystal layer sandwiched between a pair of substrates having at least an electrode film, wherein the liquid crystal layer corresponds to a pixel region on one of the pair of substrates. forming one or more of the area surrounded by the protruding structure in a region, the step of bonding the substrate and the other substrate while maintaining a certain distance with a projecting Okoshijo structure, the liquid crystal and materials and processes the precursor mixture distribution between the substrates containing a polymerizable resin material, a phase of producing a liquid crystal droplets by phase separation from the precursor mixture
A separation step, and a step of orienting the liquid crystal molecules in the liquid crystal droplets axisymmetrically
The phase separation step is such that the size of the liquid crystal droplet is the size of a picture element.
At a temperature of 80% or more, the polymerizable resin material is coated with the protruding structure.
A method for producing a liquid crystal display element , comprising curing on a structure .