JPH0961793A - Liquid crystal display panel and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display panel which is low in threshold voltage, is small in hysteresis and is high in response speed by providing the liquid crystal display panel which is larger in the average diameter of a liquid crystal region than a cell gap and is smaller than the size of pixels. SOLUTION: A uniform soln. mixture composed of a chiral nematic liquid crystal material 109 having positive dielectric constant anisotropy and a UV curing high-polymer material is injected from a liquid crystal injection port into an empty cell consisting of a pair of transparent glass substrates 101, 102 provided with transparent electrodes 103, 104. The soln. is then irradiated with UV rays from which IR rays are removed through an IR cut filter 113 by using a UV lamp 112, by which the liquid crystal display panel enclosed by high-polymer walls 111 is obtd. The average diameter of the liquid crystal domains of this liquid crystal display panel is larger than the cell gap (d) (equal to the diameter 5μm of the spacers 106). The average diameter of the liquid crystal domains is larger than the size of the pixels). Electric field response is made possible with the small energy of liquid crystal molecules by development of pretilt angles, by which the threshold voltage is lowered and the response speed is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wide viewing angle liquid crystal display panel in which a liquid crystal domain divided by a polymer step or a polymer wall is sandwiched between a pair of electrode substrates and a rubbing-free wide viewing angle liquid crystal display panel and a method for manufacturing the same. Regarding

[0002]

2. Description of the Related Art In recent years, active matrix type liquid crystal display panels in which a thin film transistor is provided as a switching element in each pixel have been actively developed in order to obtain an image of high display quality. Compared to the simple matrix method, this method can obtain a high contrast ratio even if the number of scanning lines is increased, so an engineering workstation (EWS) that requires a large capacity or a video that requires a clear image. Adoption is rapidly progressing in the field.

The twisted nematic system is widely used for such an active matrix type liquid crystal display panel. In this system, a liquid crystal panel having a structure in which liquid crystal molecules are twisted by 90 ° vertically is sandwiched by two polarizing plates between two substrates facing each other.
In the twisted nematic method, the polarization axes of two polarizing plates are orthogonal to each other, and the long axis of liquid crystal molecules at the interface of one substrate is parallel or perpendicular to the polarization axis of the polarizing plate on the same side. 2 and the normally white mode that has a relationship of
There is a normally black mode in which the polarizing axes of the polarizing plates are parallel to each other and the long axes of the liquid crystal molecules at the interface of one substrate are parallel or perpendicular to the polarizing axes of the polarizing plates on the same side. .

Conventionally, in such a liquid crystal display panel, in order to align the alignment direction of liquid crystal molecules over the entire panel,
A so-called rubbing treatment has been performed in which a polymer organic thin film such as polyimide is formed on a substrate of a liquid crystal display panel and rubbed in a predetermined direction with a cloth such as nylon or polyester. As a result, a single alignment region (mono domain) was realized over the entire surface of the panel.

However, when the rubbing treatment is performed as described above, there is a fear that electrostatic breakdown of the thin film transistor, dust generation or film contamination may be caused during the rubbing. Therefore, development for omitting the rubbing treatment process is performed. There is. For example, by applying photolithography technology,
Method of forming nematic liquid crystal by forming microgrooves on the substrate (Kawata, Takagashira, Gizu, Sakamoto, Hasegawa:
Proposals for the 17th Liquid Crystal Symposium, 2F108), etc. have been proposed.

Now, as the use of liquid crystal display panels expands, and large areas and full colors are required, even in the case of active matrix liquid crystal display panels, the narrow viewing angle is a particularly recent item which deteriorates the display quality. It has been close up.

In the liquid crystal display device, when a voltage is applied between the upper and lower substrates, the liquid crystal molecules try to be aligned in the direction of the electric field while unraveling the twisted structure. However, the liquid crystal display panel depends on the spatial alignment state of the liquid crystal molecules at this time. The polarization state of the light passing through is changed, and the transmitted light is dimmed. For example, in the normally white mode, white display is realized when no voltage is applied, and black display is realized when a sufficiently high voltage is applied. By the way, even when the liquid crystal molecules are in the same spatial arrangement state (constant applied voltage), the polarization state of light changes depending on the incident direction of light entering the liquid crystal layer. The transmitted light intensity of light is different in all directions. Further, the transmitted light intensity of the liquid crystal display panel is determined by the arrangement of liquid crystal molecules located in a plane (midplane) that passes through the center of the liquid crystal layer between the two panel substrates and is parallel to the substrates. It is determined by the positional relationship between the tilt direction of the long axis of the molecule and the transmitted light observation direction of the liquid crystal display panel.

In both the rubbing method and the photolithography method, the liquid crystal molecules located on the mid-plane are tilted by the electric field in a fixed direction with respect to the panel surface. There is a problem of the viewing angle that the difference in refraction, that is, the polarization state of light passing therethrough is changed, and the contrast and the hue are largely changed depending on the viewing angle.

Therefore, in recent years, with respect to the twisted nematic type liquid crystal display panel, a technique for expanding the viewing angle has been actively developed. As an example, two pixels of a twisted nematic liquid crystal display panel are used.
A method for expanding the viewing angle by dividing into regions (domains) having different alignment states (T. Takatori, K. Su.
miyoshi, Y .; Hirai, S .; Kaneko:
JAPAN DISPLAY '92, PP. 591,
(1992)) have been proposed. In this method, a pixel is divided into two, and in each pixel, there are two types of directions in which liquid crystal molecules located on the midplane are tilted by an electric field, and the birefringence difference depending on the viewing angle is compensated for each other. It is intended to be expanded.

However, in the above method, since the alignment region of one pixel has to be divided into two, there is a problem that the exposure process and the rubbing process are increased and the manufacturing process is complicated.

As a further advanced technology, an epoch-making method for simultaneously expanding the viewing angle without rubbing has been proposed (Y. Toko, T. Sugiyama).
a, K .; Katoh, Y. Iimura, S .; Koba
yashi: SID 93 DIGEST, PP. 62
2, (1993)). This is called "random orientation twisted nematic". In this method, a liquid crystal material is injected at a temperature above the nematic-isotropic phase transition temperature without rubbing between substrates coated with a polyimide alignment film and cooled to randomly align the liquid crystal molecules, By forming a large number of regions (domains) having different alignment directions, the viewing angle is widened.

A display system of a liquid crystal display panel which is not subjected to the rubbing treatment and which has a random orientation will be described below. FIG. 5 is a perspective view showing the orientation of liquid crystal molecules when no electric field is applied to the liquid crystal display panel with random orientation without rubbing treatment. This is a nematic-isotropic chiral nematic liquid crystal having a twist angle of about 90 ° spontaneously between an upper substrate 501 and a lower substrate 502 on which a polyimide alignment film facing each other with a certain gap is formed. It was prepared by encapsulating at a phase transition temperature or higher and then cooling to room temperature. As shown in FIG. 5, the liquid crystal molecules at the interface of the substrate are separated by each liquid crystal domain 50 on the substrate.
The orientations that can be taken among the six are random with exactly equal probability, but within one liquid crystal domain 506, the liquid crystal molecules 503 of the upper substrate 501 and the liquid crystal molecules 504 of the lower substrate 502 have a structure in which they are twisted by 90 ° with respect to each other. There is.

In this liquid crystal display panel, the liquid crystal molecules 505 located on the midplane are initially oriented substantially horizontally, but when a voltage is applied, the dielectric free energy becomes small (dielectric anisotropy). > 0) Inclining,
It stands in the vertical direction when a high voltage is applied. The liquid crystal molecules 505 located on the midplane are the upper and lower substrates 501, 5
02 is a liquid crystal molecule located in the center of the thickness direction,
When the twist angle is 90 °, the twist angle is just a half (45 °) of the total twist angle, that is, the angle formed by the liquid crystal molecules 503 of the upper substrate 501 and the liquid crystal molecules 504 of the lower substrate 502. Since the tilt direction due to the voltage application of the liquid crystal molecules 505 located on the midplane determines the viewing angle direction, the viewing angle direction is constant within one liquid crystal domain 506, but these liquid crystal domains having random alignment directions are present. Since 506 is sufficiently present in one pixel, it is macroscopically averaged, the transmittance intensities in various observation directions are substantially symmetrical, and the viewing angle dependency is eliminated. However, as can be seen from the above description, if the number of liquid crystal domains 506 in one pixel is not sufficiently large, or if the orientation of each liquid crystal domain 506 is not completely random, complete compensation cannot be performed. , The viewing angle dependence remains.

There has been proposed a method of solving the above problems and simultaneously enlarging the viewing angle without performing rubbing treatment (Japanese Patent Laid-Open No. 6-301015). In this method, a mixture of a photocurable polymer material and a liquid crystal material is injected between electrode substrates, and a polymer wall reaching both substrates and a liquid crystal region surrounded by the polymer wall are formed by optical phase separation. It is a thing. In this method, since the liquid crystal molecules are concentrically or radially aligned in one liquid crystal region, the viewing angle compensation can be completely realized.

[0015]

However, in the above liquid crystal display panel in which the polymer wall is formed by the optical phase separation, the angle formed by the liquid crystal molecules and the substrate at the substrate interface, that is, the pretilt angle is 0 °, so that the threshold value is The higher the voltage,
There is a problem that the hysteresis is large and the response speed is slow.

In order to solve the above problems in the prior art, the present invention has a low threshold voltage and a small hysteresis,
An object of the present invention is to provide a liquid crystal display panel having a fast response speed and a method for manufacturing the same.

[0017]

To achieve the above object, a liquid crystal display panel according to the present invention has a structure in which a chiral nematic liquid crystal material having a positive dielectric anisotropy and a polymer are provided between a pair of electrode substrates. The liquid crystal region is sandwiched between the walls and at least in the vicinity of the substrate, and the liquid crystal region is surrounded by the polymer wall, and the average diameter of the liquid crystal region is larger than the cell gap and smaller than the pixel size, and the liquid crystal molecules of the liquid crystal region are The liquid crystal molecules have various orientations in the plane of the substrate, and the liquid crystal molecules are obliquely oriented with respect to the substrate when no electric field is applied.

Further, in the structure of the liquid crystal display panel of the present invention, the twist angle of the liquid crystal region is preferably about 90 °. Further, in the liquid crystal display panel of the present invention, the spontaneous pitch P of the liquid crystal material and the thickness d of the liquid crystal layer.
It is preferable that the ratio d / P with is 0.2 to 0.3.

In the structure of the liquid crystal display panel of the present invention, the product Δn · d of the birefringence Δn of the liquid crystal material and the thickness d of the liquid crystal layer is preferably 0.3 to 0.6 μm. . Further, the structure of the method for manufacturing a liquid crystal display panel according to the present invention is such that a chiral nematic liquid crystal material having a positive dielectric anisotropy and a polymer wall are sandwiched between a pair of electrode substrates, and a liquid crystal is at least near the substrate. The region is surrounded by the polymer wall, the average diameter of the liquid crystal region is larger than the cell gap, and smaller than the size of the pixel, the liquid crystal molecules of the liquid crystal region have various orientations in the substrate plane, A method of manufacturing a liquid crystal display panel in which the liquid crystal molecules are tilted and aligned with respect to a substrate when no electric field is applied, injecting a mixed composition of an ultraviolet curable polymer material and a liquid crystal material between a pair of electrode substrates, The polymer walls are formed by irradiating ultraviolet rays while applying a voltage between the electrode substrates.

Further, in the structure of the method for manufacturing a liquid crystal display panel of the present invention, it is preferable that the voltage applied between the electrode substrates is equal to or higher than the threshold voltage of the liquid crystal material. Further, in the configuration of the method for manufacturing a liquid crystal display panel of the present invention, it is preferable that the waveform of the voltage applied between the electrode substrates is substantially a square wave.

Further, in the structure of the liquid crystal display panel manufacturing method of the present invention, it is preferable that the active switching element is formed on one of the pair of electrode substrates and the voltage is applied by active driving.

[0022]

According to the structure of the liquid crystal display panel of the present invention, a chiral nematic liquid crystal material having a positive dielectric anisotropy and a polymer wall are sandwiched between a pair of electrode substrates, and at least The liquid crystal region is surrounded by the polymer wall near the substrate, the average diameter of the liquid crystal region is larger than the cell gap, and smaller than the size of the pixel,
The liquid crystal molecules in the liquid crystal region have various orientations in the plane of the substrate, and the liquid crystal molecules are tilted with respect to the substrate when no electric field is applied (pretilt angle is expressed), so that the liquid crystal molecules can generate an electric field with small energy. I can respond. As a result, the threshold voltage becomes lower and the response speed becomes faster. Also, although the occurrence of disclination causes hysteresis,
The expression of the pretilt angle causes a regulating force of the liquid crystal alignment at the time of voltage decrease, so that the hysteresis caused by the fact that the alignment at the time of voltage decrease at each voltage is different from the alignment at the time of voltage increase is significantly reduced.

Further, in the liquid crystal display panel of the present invention, according to a preferable example in which the twist angle of the liquid crystal region is about 90 °, a white and bright liquid crystal display panel can be obtained. As a result, beautiful monochrome display and color display are realized.

According to a preferred example of the above-mentioned constitution of the liquid crystal display panel of the present invention, the ratio d / P between the spontaneous pitch P of the liquid crystal material and the thickness d of the liquid crystal layer is 0.2 to 0.3. , D / P and the twist angle of the liquid crystal region are twist angle = d / P × 360 °, the twist angle of the liquid crystal region is 72 to 108 °, and a white and bright liquid crystal display panel is obtained. To be As a result, beautiful monochrome display and color display are realized.

In the liquid crystal display panel of the present invention, the product Δn · d of the birefringence Δn of the liquid crystal material and the thickness d of the liquid crystal layer is 0.3 to 0.6 μm. According to this, a bright liquid crystal display panel can be obtained.

According to the structure of the method for manufacturing a liquid crystal display panel of the present invention, a chiral nematic liquid crystal material having positive dielectric anisotropy and a polymer wall are sandwiched between a pair of electrode substrates, At least in the vicinity of the substrate, the liquid crystal region is surrounded by the polymer wall, the average diameter of the liquid crystal region is larger than the cell gap and smaller than the size of the pixel, and the liquid crystal molecules of the liquid crystal region are various in the plane of the substrate. A method of manufacturing a liquid crystal display panel having an azimuth and in which the liquid crystal molecules are tilted and aligned with respect to a substrate when no electric field is applied, wherein a mixed composition of an ultraviolet curable polymer material and a liquid crystal material is used as a pair of electrode substrates A liquid crystal display that has the above-described operational effects as described below, because it is characterized in that the polymer wall is formed by irradiating ultraviolet rays while injecting it between the electrode substrates and applying a voltage between the electrode substrates. Panel can be obtained. That is, after injecting a mixed composition of an ultraviolet curable polymer material and a liquid crystal material between a pair of electrode substrates, ultraviolet rays are irradiated while applying a voltage between the electrode substrates, and liquid crystal droplets (small Drops) grow. There is an interface between the liquid crystal droplets and the separated polymer, and if optical phase separation is performed without applying a voltage, the liquid crystal molecules on the substrate side of the liquid crystal droplets form an interface because the interaction between the interface and the liquid crystal molecules is strong. And grows while being oriented substantially parallel to. However, when optical phase separation is performed while applying a voltage, the liquid crystal molecules on the substrate side respond to the electric field, and the liquid crystal molecules near the interface continue to grow while maintaining a predetermined angle (pretilt angle) with the interface. . Even when the liquid crystal droplets grow and reach the upper and lower electrode substrates, the optical phase separation is further continued, and the reaction is completed immediately before the adjacent liquid crystal droplets come into contact with each other. After the photo-phase separation reaction is completed, even if the electric field is removed, the interface between the liquid crystal droplets and the polymer remains with the pretilt angle maintained due to the memory effect. When the pretilt angle is developed in this way, the liquid crystal molecules can respond to the electric field with a small energy, so that the threshold voltage becomes low and the response speed becomes fast. In addition, although the occurrence of disclination causes hysteresis, since the regulating force of the liquid crystal alignment at the time of voltage decrease is generated by the expression of the pretilt angle, the alignment at the time of voltage decrease at each voltage is different from the alignment at the time of voltage increase. The hysteresis caused by is greatly reduced.

Further, in the configuration of the method for manufacturing a liquid crystal display panel of the present invention, according to a preferred example in which the voltage applied between the electrode substrates is equal to or higher than the threshold voltage of the liquid crystal material, the pretilt angle is easily exhibited. .

Further, according to the preferable example in which the waveform of the voltage applied between the electrode substrates is substantially a square wave in the structure of the method for manufacturing a liquid crystal display panel of the present invention, the voltage applied during optical phase separation ( Exchange) can be easily obtained.

In the liquid crystal display panel manufacturing method of the present invention, according to a preferred example in which an active switching element is formed on one of the pair of electrode substrates and the voltage is applied by active driving, the active switching element is The circuit used for display in the drive panel can be used as it is for voltage application.

[0030]

EXAMPLES The present invention will be described in more detail below with reference to examples. FIG. 1 is a sectional view showing an embodiment of a liquid crystal display panel and a method of manufacturing the same according to the present invention.

First, a pair of transparent glass substrates 10 provided with transparent electrodes 103 and 104 made of an indium / tin oxide film.
After cleaning 1, 102, these transparent glass substrates 10
1, 102 was dried at 110 ° C. for 30 minutes. Then
Polyimide resin film RN-747 (Nissan Chemical Co., Ltd.) 200
Spinner is applied under the condition of 0 revolutions / minute and 60 seconds, and 200 ℃
Cured for 1 hour. Thereby, the transparent electrodes 103, 1
On 04, the organic insulating film 110 was formed. Next, the both substrates are connected to each other by a plastic spacer 106 having a diameter of 5 μm.
(Micropearl: Sekisui Fine Co., Ltd.) and a thermosetting sealant 105 (StructBond: Mitsui Toatsu Chemical Co., Ltd.) bonded together with a liquid crystal injection port provided.
The sealing material 105 was completely cured by heating at 150 ° C. for 4 hours. Thereby, an empty cell was obtained.

Next, as a liquid crystal material, a positive dielectric constant anisotropy was obtained with the chiral material S-811 (Merck) so that the spontaneous twist pitch P was d / P = 0.25 with respect to the cell gap d. 7. A chiral nematic liquid crystal material 109 having a positive dielectric constant anisotropy, which is produced by mixing with a fluorine-based nematic liquid crystal ZLI-4792 (Merck) having a refractive index anisotropy of 0.09. 20 g of the UV curable polymer material was prepared, and 1.80 g of the UV polymerizable material PN393 (Merck) was prepared (the ratio of the liquid crystal material to the polymer-liquid crystal mixed material was 82% by weight). By thoroughly stirring at 40 ° C., a uniform mixed solution of polymer and liquid crystal was prepared. Here, the threshold voltage of the liquid crystal material is 1.1V.

The relationship between d / P and the twist angle of the liquid crystal region is as follows:
Since the twist angle = d / P × 360 °, when d / P = 0.25 as described above, the twist angle of the liquid crystal region is 90 °.
Becomes Then, the twist angle of the liquid crystal region is 90
In the case of °, the whitest and brightest liquid crystal display panel is obtained, and as a result, clear black and white display and color display are realized.

The birefringence Δn of the liquid crystal material is 0.9.
6 and the birefringence Δn of this liquid crystal material and the thickness d of the liquid crystal layer
The product Δn · d with (= 0.5 μm) is 0.48 μm. Thus, when Δn · d = 0.48 μm, the brightest liquid crystal display panel can be obtained.

Next, this mixed solution was injected from the liquid crystal injection port into the empty cell previously heated on a hot plate at 40 ° C., and the liquid crystal injection port was sealed. Next, the UV lamp 1 was applied with square waves (30 Hz) of 1 V, 2 V, 5 V and 10 V applied to the transparent electrodes 103 and 104, respectively.
After applying infrared rays through the IR cut filter 113 using the No. 12 ultraviolet ray at 40 ° C. and an intensity of 30 mW / cm ² for 200 seconds, the voltage application was stopped. As a result, a liquid crystal display panel surrounded by the polymer wall 111 having a thickness of 2 μm or less was obtained. Here, the square wave was generated using a waveform generator (HP).

Observation of this liquid crystal display panel using a polarizing microscope in a crossed Nicols state revealed a diameter of 10 to 30 μm.
The liquid crystal domain (unit liquid crystal cell) having a substantially circular shape was formed. Thus, the average diameter of the liquid crystal domains is larger than the cell gap d (equal to the spacer 106 diameter of 5 μm). Moreover, the average diameter of the liquid crystal domains is smaller than the size of the pixel. In addition, it was observed that in the liquid crystal domain, one alignment defect was present in the approximate center of the liquid crystal domain, and four black bands were radially formed around the alignment defect. And
When the polarizer and the analyzer were rotated with the liquid crystal panel fixed, the four black bands rotated in the same direction as the polarizer by the same angle. Further, although each liquid crystal domain is completely partitioned by the polymer wall 111, the polymer wall 111 itself does not transmit light, so that a black frame is formed.

FIG. 3 shows the orientation of liquid crystal molecules. In FIG. 3A, liquid crystal molecules 302 near the upper and lower substrates,
Liquid crystal molecules 305 on the central plane (midplane) 304 are arranged symmetrically about a singular point.
In addition, the liquid crystal molecules 302 on the upper substrate and the liquid crystal molecules 30 on the lower substrate
3 has a twist structure depending on the amount of chiral addition (90 °), and the liquid crystal molecules 305 of the midplane 304 are present at positions twisted by ½ of the total twist angle. On the other hand, in FIG. 3B, the liquid crystal molecules 310 of the midplane 309 are arranged concentrically around the singular point. In FIG. 3A, 301 is a polymer wall.
In (b), 306 is a polymer wall, and 307 and 308 are liquid crystal molecules near the upper and lower substrates. Incidentally, in the system of the present embodiment, FIG.
The alignment of liquid crystal molecules in (b) is considered to be the mainstream.

Next, the polarizing plates 107 and 108 were attached to the outside of the liquid crystal display panel so that the polarization axes thereof were orthogonal to each other, and the panel luminance-voltage characteristics were measured. in this case,
The measurement direction was the front of the panel, and the panel brightness was measured using a brightness meter BM-8 (Topcon). A drive voltage, contrast ratio, and hysteresis were measured by first applying a 30 Hz square wave from 0 V to 8 V in 0.05 V steps, and then applying a similar waveform from 8 V to 0 V in -0.05 V steps. .

In FIG. 4A, the applied voltage during optical phase separation is 1
The panel brightness-voltage characteristic of this liquid crystal display panel in 20 degreeC in case of 0V is shown. In FIG. 4A, the solid line shows the characteristic at the time of boosting, and the broken line shows the characteristic at the time of lowering the voltage.

The drive voltage is defined as a voltage which gives a relative value of (panel brightness when no voltage is applied)-(panel brightness when 8 V is applied). The drive voltage of this liquid crystal display panel is
It depends on the applied voltage at the time of optical phase separation.
The 0% luminance was 1.5V and the 10% luminance was 3.5V.
In addition, when the applied voltage is 2V or more, the driving voltage decreases with the applied voltage.
It was 3.0 V at 0% brightness.

The contrast ratio = (panel brightness when no voltage is applied) / (panel brightness when 30 Hz, 5 V is applied) similarly depends on the applied voltage at the time of optical phase separation, and is 50 when 1 V is applied. . Moreover, the contrast ratio increased with the applied voltage when 2 V or more was applied, and the value of 80 was obtained when 10 V was applied. Furthermore, when the response speed between 90% brightness and 10% brightness was measured, it also depended on the applied voltage at the time of optical phase separation, and was 150 ms when 1 V was applied. Further, the response speed decreased with the applied voltage when 2 V or more was applied, and was 120 ms when 10 V was applied.

The hysteresis can be defined by ((voltage which gives 50% brightness when stepping up)-(voltage which gives 50% brightness when stepping down)) / (voltage which gives 50% brightness when stepping up). When the hysteresis value of the present liquid crystal display panel was calculated according to this definition, it also depends on the applied voltage at the time of optical phase separation and is 0.10 when 1 V is applied.
Met. Further, when the applied voltage was 2 V or more, the hysteresis decreased with the applied voltage, and was 0.04 when 10 V was applied.

When the transmittance of this liquid crystal display panel was measured, it was about 10% darker than that of the comparative example described later. From this, it is considered that the pretilt angle (the angle formed by the long axis of the liquid crystal molecule and the substrate at the substrate interface) is exhibited in the liquid crystal display panel of the present embodiment.
This is because when the pretilt angle is developed, the tilt angle of the liquid crystal molecules on the midplane is tilted, the birefringence is reduced, and the transmittance is reduced.

<Comparative Example> FIG. 2 is a sectional view showing a liquid crystal display panel of a comparative example and a method of manufacturing the same. An empty cell was prepared in the same manner as in the above example. In addition, a uniform mixed solution of polymer and liquid crystal was prepared in the same manner as in the above example.

Next, this mixed solution was injected from the liquid crystal injection port into the empty cell previously heated on a hot plate at 40 ° C., and the liquid crystal injection port was sealed. Then, using the UV lamp 212, the ultraviolet rays from which infrared rays have been removed through the IR cut filter 213 are irradiated with the ultraviolet rays at 40 ° C. and 30 mW / cm ^2.
For 200 seconds. As a result, the thickness is 2μ
A liquid crystal display panel surrounded by a polymer wall 211 of m or less was obtained. In FIG. 2, 201 is an upper glass substrate, 2
02 is a lower glass substrate, 203 and 204 are transparent electrodes, 20
5 is a sealing material, 206 is a spacer, 209 is a chiral nematic liquid crystal material, and 210 is an organic insulating film.

Observation of this liquid crystal display panel using a polarizing microscope in a crossed Nicols state revealed a diameter of 10 to 30 μm.
The liquid crystal domain (unit liquid crystal cell) having a substantially circular shape was formed. It was observed that in the liquid crystal domain, one alignment defect was present in the approximate center of the liquid crystal domain, and four black bands were radially formed around the alignment defect. Then, when the liquid crystal panel was fixed and the polarizer and the analyzer were rotated, the four black bands were rotated in the same direction as the polarizer by the same angle. Further, although each liquid crystal domain is completely partitioned by the polymer wall 211, since the polymer wall 211 itself does not transmit light, a black frame is formed. The above observation results are exactly the same as in the case of the above embodiment.

Next, polarizing plates 207 and 208 were attached to the outside of this liquid crystal display panel so that the polarization axes thereof were orthogonal to each other, and the panel luminance-voltage characteristics were measured. The measuring method is the same as in the above-mentioned embodiment. Further, the driving voltage, the contrast ratio, and the hysteresis were measured in the same manner as in the above-mentioned example.

FIG. 4B shows a panel luminance-voltage characteristic curve of the liquid crystal display panel of this comparative example at 20 ° C.
In FIG. 4B, the solid line shows the characteristic at the time of boosting, and the broken line shows the characteristic at the time of lowering the voltage.

The driving voltage is 1.5 V at 90% luminance and 3. at 10% luminance, as in the case of applying 1 V in the above embodiment.
It was 5V. The contrast ratio was 50 as in the case of applying 1 V in the above example. Further, in the liquid crystal display panel of this comparative example, 90% luminance and 10%
When the response speed between the voltages giving brightness was measured, it was 150 ms, as in the case of applying 1 V in the above-mentioned embodiment. Further, when the hysteresis of the liquid crystal display panel of this comparative example was calculated according to the definition in the above example,
0.10.

As described above, the reason why the liquid crystal display panel of the above-mentioned embodiment has a lower threshold voltage, a faster response speed, and the hysteresis is significantly relaxed as compared with the liquid crystal display panel of the comparative example is as follows. It is thought to be due to. That is, in the liquid crystal display panel of the present embodiment, the pretilt angle is exhibited as described above, and since the liquid crystal molecules can respond to the electric field with a small energy, the threshold voltage becomes low and the response speed becomes fast. In addition, the occurrence of disclination causes hysteresis, but the regulation force at the time of voltage drop is generated by the expression of the pretilt angle, so that the hysteresis caused by the difference in the orientation at the time of voltage drop at each voltage is significantly relaxed. .

In the above embodiment, the square wave is used as the waveform of the voltage applied during the optical phase separation.
The present invention is not limited to this, and the same effect can be obtained by using a deformed square wave or sine wave.

Further, in the above embodiment, the waveform generator (HP) is used to generate the square wave, but the invention is not necessarily limited to this, and active switching is performed on one of the pair of electrode substrates. A voltage may be applied by forming an element and actively driving it. With this configuration, the circuit used for display in the active drive panel can be used as it is for voltage application.

In the above embodiment, the electric field is used to give the pretilt angle. However, the present invention is not limited to this configuration, and the same effect can be obtained even if the pretilt angle is given by the magnetic field. can get.

Further, in the above embodiment, the polyimide resin film RN-747 is used as the organic insulating film in order to improve the voltage holding ratio, but it is not necessarily limited to this, and for example, soluble polyimide is used. Resin film A
L-5417 (Nippon Synthetic Rubber Co., Ltd.), UV curable resin PN3
Similar effects can be obtained by using 93 (Merck) or polyurethane MS5510 (Mitsubishi Heavy Industries).

Further, in this embodiment, the mixed composition of the ultraviolet curable polymer material and the liquid crystal material is injected between the pair of electrode substrates after the empty cell is assembled, but it is not always limited to this order. It is not something that will be done. It is also possible to drop the mixed composition on one of the electrode substrates in advance, then bond the two substrates and then irradiate with ultraviolet rays to perform optical phase separation.

In this embodiment, the case where the ratio d / P of the spontaneous pitch P of the liquid crystal material and the thickness d of the liquid crystal layer is 0.25 has been described as an example, but the present invention is not limited to this. However, if d / P is 0.2 to 0.3, a white and bright liquid crystal display panel can be obtained, and clear black and white display and color display can be realized.

Further, in this embodiment, the product Δn · d of the birefringence Δn of the liquid crystal material and the thickness d of the liquid crystal layer is 0.48 μm.
Although the case of m has been described as an example, the invention is not necessarily limited to this, and if Δn · d is 0.3 to 0.6 μm, a bright liquid crystal display panel can be obtained.

[0058]

As described above, according to the present invention,
It does not require rubbing treatment, and can be manufactured without heating to a high temperature above the nematic-isotropic phase transition point at the time of injection, low driving voltage, high contrast,
It is possible to obtain a liquid crystal display panel which has a high response speed and has a reduced hysteresis.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a liquid crystal display panel and a manufacturing method thereof according to the present invention.

FIG. 2 is a cross-sectional view showing a liquid crystal display panel of a comparative example and a manufacturing method thereof.

FIG. 3 is a conceptual diagram showing the alignment of liquid crystal molecules of a unit liquid crystal cell of liquid crystal display panels of one example and a comparative example of the present invention.

FIG. 4A is a panel luminance-voltage characteristic diagram of a liquid crystal display panel of an example of the present invention, and FIG. 4B is a panel luminance-voltage characteristic diagram of a liquid crystal display panel of a comparative example.

FIG. 5 is a perspective view showing the alignment of liquid crystal molecules when no electric field is applied to the liquid crystal display panel with random alignment without rubbing treatment.

[Explanation of symbols]

 101 Upper Glass Substrate 102 Lower Glass Substrate 103, 104 Transparent Electrode 105 Sealing Material 106 Spacer 107, 108 Polarizing Plate 109 Chiral Nematic Liquid Crystal 110 Organic Insulating Film 111 Polymer Wall 112 UV Lamp 113 IR Cut Filter

Claims (8)

[Claims] 1. A chiral nematic liquid crystal material having a positive dielectric anisotropy and a polymer wall are sandwiched between a pair of electrode substrates, and a liquid crystal region is surrounded by the polymer wall at least near the substrate, The average diameter of the liquid crystal region is larger than the cell gap and smaller than the size of the pixel, the liquid crystal molecules in the liquid crystal region have various orientations in the plane of the substrate, and the liquid crystal molecules with respect to the substrate when there is no electric field. A liquid crystal display panel that is tilted. 2. The liquid crystal display panel according to claim 1, wherein the twist angle of the liquid crystal region is approximately 90 °. 3. The ratio d / P between the spontaneous pitch P of the liquid crystal material and the thickness d of the liquid crystal layer is 0.2 to 0.3.
The liquid crystal display panel according to 1. 4. The birefringence Δn of the liquid crystal material and the thickness d of the liquid crystal layer.
The product Δn · d of and is 0.3 to 0.6 μm.
The liquid crystal display panel according to 2 or 3. 5. A chiral nematic liquid crystal material having a positive dielectric anisotropy and a polymer wall are sandwiched between a pair of electrode substrates, and a liquid crystal region is surrounded by the polymer wall at least near the substrate, The average diameter of the liquid crystal region is larger than the cell gap and smaller than the size of the pixel, the liquid crystal molecules in the liquid crystal region have various orientations in the plane of the substrate, and the liquid crystal molecules with respect to the substrate when there is no electric field. A method of manufacturing a liquid crystal display panel having an oblique alignment, comprising injecting a mixed composition of a UV-curable polymer material and a liquid crystal material between a pair of electrode substrates, and applying a voltage between the electrode substrates to emit UV light. And irradiating the polymer wall to form the polymer wall. 6. The method for manufacturing a liquid crystal display panel according to claim 5, wherein the voltage applied between the electrode substrates is not less than the threshold voltage of the liquid crystal material. 7. The method for manufacturing a liquid crystal display panel according to claim 5, wherein the waveform of the voltage applied between the electrode substrates is a substantially square wave. 8. The method of manufacturing a liquid crystal display panel according to claim 5, wherein an active switching element is formed on one of the pair of electrode substrates and the voltage is applied by active driving.