JP2002229036A - Liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost, multidomain liquid crystal display element with high transmittance and with stabilized response time. SOLUTION: The liquid crystal display element has a pair of substrates, placed opposite to each other and an electrode formed on at least one from among them and controls a liquid crystal layer sandwiched between a pair of the substrates, by the electrode. A first alignment dividing means to control the tilt direction of the liquid crystal molecules is provided on one substrate out of a pair of the substrates and a second alignment dividing means to control the tilt direction of the liquid crystal molecules is provided on the other substrate. The liquid crystal display element is characterized by having a boundary line of a specified domain formed with the first alignment dividing means and a boundary line of a specified domain formed with the second alignment dividing means which is not parallel to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-domain type liquid crystal display device, and more particularly to a high definition type liquid crystal display device driven by an active device such as a TFT and having improved display characteristics.

[0002]

2. Description of the Related Art A display device using a liquid crystal element has characteristics such as light weight, thinness, and low power consumption, and is therefore used in various fields such as OA equipment, information terminals, watches, and televisions. In particular, a liquid crystal display element using a TFT element is used for a monitor for displaying data including a lot of information, such as a portable television and a computer, because of its quick response.

In recent years, with the increase in the amount of information, high definition and high-speed response have been particularly demanded. Higher definition is addressed by miniaturization of the TFT array structure. On the other hand, high-speed response is achieved by using an OLED using nematic liquid crystal.
CB mode, VAN mode, HAN mode, π alignment mode, interface stable ferroelectric liquid crystal (SSF) using smectic liquid crystal
LC) mode and antiferroelectric liquid crystal mode are being studied.

[0004] In particular, the VAN type alignment mode provides a faster response speed than the conventional twisted nematic type (TN) mode, and the rubbing which has been feared to cause a defect such as electrostatic breakdown because of vertical alignment. This is a liquid crystal display mode that has recently attracted attention because there is no alignment treatment step.

Further, in the VAN mode, a multi-domain VAN mode for realizing a wide viewing angle has attracted attention because the compensation design of the viewing angle is relatively easy. Due to the occurrence of domain boundaries, disclinations, and the like induced by domain division, there are problems such as a decrease in transmittance and a delay in response time.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an inexpensive multi-domain liquid crystal display device having a high transmittance and a stable response time. I do.

[0007]

In order to solve the above problems, the present invention provides a liquid crystal device having an electrode formed on at least one of a pair of substrates disposed opposite to each other and sandwiching the electrode between the pair of substrates. A liquid crystal display element having a controllable layer, wherein one of the pair of substrates is provided with first alignment division means for controlling a tilt direction of liquid crystal molecules, and the other substrate is provided with a liquid crystal display. A second orientation dividing means for controlling a tilt direction of the molecule is provided, and a boundary between predetermined domains formed by the first orientation dividing means and the predetermined orientation formed by the second orientation dividing means are provided. Provided is a liquid crystal display device, wherein a domain boundary line is non-parallel.

[0008] In the liquid crystal display device of the present invention configured as described above, the boundary of the predetermined domain formed by the first alignment division unit and the predetermined domain formed by the second alignment division unit. It is preferable that the angle θ with the boundary line satisfies the relationship of 5 ° <θ <15 ° or 75 ° <θ <175 °. With such a range of θ, particularly excellent effects of improving both the transmittance and the response time can be obtained.

In the liquid crystal display device of the present invention, specifically, the first alignment dividing means is formed on a missing portion of the pixel electrode formed on one of the pair of substrates or on the pixel electrode. Ridge-shaped insulator. Further, the second alignment dividing means can be a missing portion of the common electrode facing the pixel electrode formed on the other substrate, or a ridge-shaped insulator formed on the common electrode.

[0010] The first orientation division means and the second orientation division means can be constituted by the following combinations of these electrode missing portions and ridge-shaped insulators.

(1) A combination in which the first alignment dividing means is a missing part of the pixel electrode and the second alignment dividing means is a missing part of the common electrode.

(2) A combination in which the first alignment division means is a ridge-shaped insulator formed on a pixel electrode, and the second alignment division means is a ridge-shaped insulator formed on a common electrode.

(3) A combination in which the first alignment division means is a missing portion of the pixel electrode and the second alignment division means is a ridge-shaped insulator formed on the common electrode.

(4) A combination in which the first alignment division means is a ridge-shaped insulator formed on the pixel electrode and the second alignment division means is a missing part of the common electrode.

According to the present invention, a vertical alignment film is provided on each of the first and second alignment division means.
It can be suitably applied to a multi-domain vertical alignment liquid crystal display device.

Hereinafter, the operation of the liquid crystal display device of the present invention will be described.

In the liquid crystal display element according to the present invention, as described above, a part of an electrode (pixel electrode or common electrode) for applying an electric field to the liquid crystal molecules is used as an alignment dividing means for controlling the tilt direction of the liquid crystal molecules. A structure (hereinafter, referred to as a slit structure) in which the periphery shows an electric loss can be used. In this case, it is known that the tilt direction corresponding to the dielectric anisotropy of the material constituting the liquid crystal molecules can be uniquely determined on or near the slit by the fluctuation of the electric field applied between the pair of substrates. I have.

Since these electric field fluctuations have a plurality of directional components, domains are formed and the viewing angle of the liquid crystal display device can be widened. That is, in the liquid crystal display element of the present invention, of the pair of substrates, a pixel electrode formed on one substrate has a slit structure, and a common electrode provided on the other substrate and opposed to the pixel electrode has a slit structure, These slits are configured to be non-parallel. Note that the direction of the slit coincides with the direction of the domain boundary line formed by the slit.

With such a configuration, the alignment division response, which has been delayed in response to an applied electric field in almost all pixel regions at the same time, and the alignment deformation has interfered with each other, has been changed to a desired region. Since the array deformation occurs sequentially from
It was confirmed that there was no interference due to mutual array deformation and the response time was improved.

It is to be noted that the slit structure of the common electrode increases the sheet resistance of the common electrode, which is not desirable in some cases. In such a case, an insulator (dielectric) is formed on or around the common electrode. ), A ridge-shaped insulator, in particular, a ridge-shaped insulator can be formed, and this can be used as an orientation division means.

A domain is formed by the initial tilt (pretilt) of the liquid crystal molecules induced by the ridge-shaped insulator and the fluctuation of the electrode formed by the insulator, so that the viewing angle of the liquid crystal display element can be widened.

It is known that these tilt control factors form a domain boundary for widening the viewing angle and, at the same time, induce a domain boundary which causes a rapid change in transmittance. In the liquid crystal mode set to normally black, the domain boundary acts as a factor for lowering the luminance. Therefore, it is preferable to make the pattern width of the ridge-shaped insulator as narrow as possible as a method of avoiding a decrease in transmittance.

As the insulator material, general organic resist materials and inorganic metal oxides can be used.
Basically, the resistance value ρ is 10 ¹¹ Ω · cm <ρ <10 ¹⁴
Any material can be used as long as it satisfies the relationship of Ω · cm and can achieve a processing accuracy of <10 μm.

That is, in the liquid crystal display device of the present invention, the ridge-shaped insulator formed on the pixel electrode formed on one of the pair of substrates and the pixel electrode formed on the other substrate are formed on the other substrate. A ridge-shaped insulator formed on the opposing common electrode,
These ridge-shaped insulators can be configured to be non-parallel.

With such a configuration, the alignment division response, which has been delayed in response to an applied electric field in almost all pixel regions at the same time, and the alignment deformation interferes with each other, causes a desired region to be changed. Since the array deformation occurs sequentially from
It was confirmed that there was no interference due to mutual array deformation and the response time was improved.

Further, in the liquid crystal display element of the present invention, the slit structure of the pixel electrode formed on one of the pair of substrates and the common electrode provided on the other substrate facing the pixel electrode are provided on the other substrate. The formed insulating structure is configured such that these slits and the insulating structure are non-parallel.

With such a configuration, the alignment division response, which has been delayed in response to the applied electric field in almost all the pixel regions at the same time, and the alignment deformation interferes with each other, changes from the desired region. It has been confirmed that the sequential deformation causes no interference due to the mutual deformation, thereby improving the response time.

[0028]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a liquid crystal display device according to one embodiment of the present invention, and FIG. 2 is a plan view showing an example of the pixel structure.

As shown in FIG. 1, a substrate 1 with a transparent electrode
And the liquid crystal driving active element substrate 2 are arranged to face each other. A pixel electrode 4 is provided on the active element substrate 2 for driving the liquid crystal.
And an active element 6 are arranged at predetermined positions, and a ridge-shaped insulator 5 for forming alignment division is formed on the pixel electrode 4. This ridge-shaped insulator 5 functions as a first orientation division unit.

A transparent electrode 3 is provided in a display area on a substrate 1 with a transparent electrode facing the liquid crystal driving active element substrate 2 so as to form a pair with each pixel electrode 4 on the active element substrate 2. An arranged ridge-shaped insulator 7 is formed. Here, the ridge-shaped insulators 5 and 7 for forming one domain provided on the substrates 1 and 2 have a predetermined angle θ within a predetermined range (0 ° <θ <180 °). That is, they are arranged non-parallel.

The liquid crystal 8 sandwiched between the substrates 1 and 2 has a multi-domain 9 and a plurality of tilt directions indicating a plurality of tilt directions due to the arrangement of the pixel electrodes 4 and the ridge-shaped insulators 5 and 7 as shown in FIG.
Form 10.

FIG. 2 shows an example of a pixel structure constituted by ridge-shaped insulators 21 and 22 formed on an active element substrate and ridge-shaped insulators 23 and 24 formed on opposing substrates with transparent electrodes. FIG. Non-parallel lines 21, 22, 23, 24 indicating the direction in which the ridge insulator extends.
Have angles θ1, θ2, and θ3, respectively. In the alignment division regions 27, 28, and 29 formed by these non-parallel lines 21, 22, 23, and 24, the liquid crystal molecule alignment deformation occurs from the region in a predetermined direction.

As described above, according to the present invention, for example,
By simply changing the arrangement direction of the ridge-shaped insulator, a multi-domain vertical alignment liquid crystal display device having a high transmittance and a stable response time can be easily obtained without changing the conventional manufacturing process.

Hereinafter, preferred embodiments of the present invention will be described. These examples are only examples of the present invention and do not limit the present invention in any way. It goes without saying that the present invention can be variously modified within the scope of the gist.

Example 1 A ridge-shaped insulator 32 (first orientation separating means) was formed of an organic resist on an active element substrate having a pixel electrode structure 31 as shown in FIG. Further, a polyimide (JALS-682 manufactured by JSR) film was formed to a thickness of 70 nm by a conventional method, and baked at 180 ° C. to form a vertical alignment film.

On the common electrode of the opposing substrate, a ridge-shaped insulator 33 is formed of an organic resist so as to form a pair with the ridge-shaped insulator 32, and tilt control means (second orientation separation means) And As an organic resist material, a photosensitive resin (HRC-125L) manufactured by JSR Co., Ltd.
Was formed to a height of 1.4 μm.

A polyimide (JALS-6 manufactured by JSR) is placed on the substrate so as to cover the ridge insulator 33 and the common electrode.
82) was formed into a film having a thickness of 70 nm by an ordinary method, and baked at 180 ° C. to form a vertical alignment film.

In order to keep the gap between the active element substrate and the opposing substrate uniform, resin balls (micropearl made by Sekisui Fine Chemical) having a diameter of 3.5 μm are arranged between the substrates, and the resin films are bonded so that the alignment films face each other. An empty cell was constructed using the layers in a conventional manner.

Finally, a negative liquid crystal (MLC manufactured by MERCK)
-2039) was injected into the cell by a conventional method to complete a multi-domain vertical alignment liquid crystal element. The liquid crystal display device obtained in this manner was observed with a polarizing microscope for the transient phenomenon of the alignment deformation of the liquid crystal molecules on the pixel electrode 31, and the alignment deformation starting points 34, 35, 36 as shown in FIG.
From this, it was confirmed that array deformation was induced uniformly in a certain direction.

FIG. 4 shows an optical response waveform in the domain. From FIG. 4, it can be seen that the transmittance is deformed at the same time as the switching, and a stable saturated state is shown.

Comparative Example 1 A pixel electrode 40 having a ridge-shaped insulator 43 as shown in FIG.
Polyimide (JS) on the active element substrate
R JALS-682) was formed into a film having a thickness of 70 nm by an ordinary method, and baked at 180 ° C. to form a vertical alignment film.

On the common electrode of the opposing substrate, a ridge insulator 42 is formed of an organic resist in parallel with the ridge insulator 43 so as to form a pair with the ridge insulator 43, and tilt control is performed. Means. As the organic resist material, a photosensitive resin (HRC-125 manufactured by JSR Co., Ltd.) is used.
L) to give a ridge-like structure having a height of 1.4 μm.

A polyimide (JALS-6 manufactured by JSR) is placed on the substrate so as to cover these insulating structures and the common electrode.
82) was formed into a film having a thickness of 70 nm by an ordinary method, and baked at 180 ° C. to form a vertical alignment film.

In order to keep the gap between the active element substrate and the opposing substrate uniform, resin balls (micropearl made by Sekisui Fine Chemical Co., Ltd.) having a diameter of 3.5 μm are arranged between the substrates so that the respective alignment films face each other, and the resin is bonded. An empty cell was constructed using the layers in a conventional manner.

Finally, a negative liquid crystal (MLC manufactured by MERCK)
-2039) was injected into the cell by a conventional method to complete a multi-domain vertical alignment liquid crystal element.

When the liquid crystal device thus obtained was observed for a transient phenomenon of the deformation of the arrangement of the liquid crystal molecules on the pixel electrode 40 by a polarizing microscope, it was found that most of the pixel end regions 4
In No. 1, deformation starts simultaneously in the arrangement deformation direction determined by the ridge-shaped insulator 43 and the insulating structure 42, and the deformations interfere with each other at the center of the domain. Was confirmed to have occurred.

FIG. 6 shows an optical response waveform in the domain. From FIG. 6, it is confirmed that the transmittance changes at the same time as the switching, but shows a peak once, shows nonlinear attenuation, and does not reach the saturated state of the transmittance by the next switching start timing.

Example 2 A 70 nm thick polyimide (JALS-682 manufactured by JSR) was formed on an active element substrate having a pixel electrode 51 (first alignment separation means) having a slit structure as shown in FIG. Then, the resultant was baked at 180 ° C. to form a vertical alignment film.

On the common electrode of the opposing substrate, a ridge-shaped insulator 52 was formed of an organic resist so as to form a pair with the pixel electrode 51, and was used as tilt control means (second orientation separation means). As the organic resist material, a photosensitive resin (HRC-125L) manufactured by JSR Co., Ltd. was used and formed to have a height of 1.4 μm.

A polyimide (JALS-JSR manufactured by JSR) is placed on the substrate so as to cover the ridge insulator 52 and the common electrode.
682) is formed into a film having a thickness of 70 nm by an ordinary method,
To form a vertical alignment film.

In order to keep the gap between the active element substrate and the counter substrate uniform, resin balls (micropearl made by Sekisui Fine Chemical Co., Ltd.) having a diameter of 3.5 μm are arranged between the substrates, and the resin films are bonded so that the respective alignment films face each other. An empty cell was constructed using the layers in a conventional manner.

Finally, a negative liquid crystal (MLC manufactured by MERCK)
-2039) was injected into the cell by a conventional method to complete a multi-domain vertical alignment liquid crystal element. The liquid crystal element thus obtained was subjected to a polarizing microscope with a pixel electrode 51.
Observing the transient phenomenon of the alignment deformation of the liquid crystal molecules above,
It was confirmed that the alignment deformation was uniformly induced in a certain direction from the alignment deformation starting points 53 and 54 as shown in FIG.

FIG. 8 shows an optical response waveform in the domain. From FIG. 8, it can be seen that the transmittance changes simultaneously with the switching, indicating a stable saturated state.

[0055]

As described in detail above, the liquid crystal display device of the present invention comprises a first alignment division means for controlling the tilt direction of liquid crystal molecules and a second alignment division means for controlling the tilt direction of liquid crystal molecules. Since the means are made non-parallel, it is possible to achieve a wide viewing angle, a high transmission and a stable response time.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a liquid crystal display device according to one embodiment of the present invention.

FIG. 2 is a plan view showing an arrangement of pixel electrodes and ridge-shaped insulators and a deformation of a liquid crystal molecule arrangement in a liquid crystal display element according to an embodiment of the present invention.

FIG. 3 is a plan view showing the arrangement of pixel electrodes and ridge-shaped insulators and a deformation of a liquid crystal molecule arrangement in the liquid crystal display element according to Example 1.

FIG. 4 is a characteristic diagram illustrating an optical response waveform of a pixel of the liquid crystal display element according to the first embodiment.

FIG. 5 shows the arrangement of pixel electrodes and ridge-shaped insulators and the arrangement of liquid crystal molecules in a liquid crystal display device of a comparative example.

FIG. 6 is a characteristic diagram showing an optical response waveform of a pixel of a conventional liquid crystal display element.

FIG. 7 is a plan view showing the arrangement of pixel electrodes and ridge-shaped insulators and the deformation of the liquid crystal molecule arrangement in the liquid crystal display element according to Example 2.

FIG. 8 is a characteristic diagram showing an optical response waveform of a pixel of the liquid crystal display element according to the second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Counter substrate 2 ... Active element substrate 3 ... Transparent electrode 4, 31, 40, 51 ... Pixel electrode 5, 21, 22, 32, 43 ...... Ridge insulator on pixel electrode 6 ... Active element 7, 23, 24 , 33, 42, 52 ... ridge-shaped insulator on the counter substrate electrode 8 ... liquid crystal layer 9, 10 ... domain 27, 28 ... moving direction of array deformation 34, 35, 36, 53, 54 ... array deformation start area 41 ... domain Generation area

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Yamaguchi 1-9-9 Hara-cho, Fukaya-shi, Saitama Inside the Toshiba Fukaya Plant Co., Ltd. (72) Inventor Atsushi Manabe 1-9-9 Harara-cho, Fukaya-shi, Saitama No. 2 Inside the Toshiba Fukaya Plant (72) Inventor Natsuko Maya 1-9-9 Harara-cho, Fukaya-shi, Saitama Prefecture No. 2 Inside the Toshiba Fukaya Plant (72) Inventor Shoichi Kurauchi Hara-cho, Fukaya-shi, Saitama 9-9-2, Toshiba Fukaya Plant Co., Ltd. (72) Inventor Akio Murayama 1-9-2, Hara-cho, Fukaya-shi, Saitama F-term in Toshiba Fukaya Plant F-term (reference) 2H090 HB08X LA01 MA01 MA10 MA15 MA16 2H092 GA13 GA27 NA01 NA25

Claims (7)

[Claims] 1. A liquid crystal display element having electrodes formed on at least one of a pair of substrates disposed opposite to each other and capable of controlling a liquid crystal layer sandwiched between the pair of substrates by the electrodes. One of the substrates is provided with first alignment division means for controlling the tilt direction of liquid crystal molecules, and the other substrate is provided with second alignment division means for controlling the tilt direction of liquid crystal molecules. Wherein the boundary of the predetermined domain formed by the first alignment division unit and the boundary of the predetermined domain formed by the second alignment division unit are non-parallel. Display element. 2. An angle θ between a boundary of the predetermined domain formed by the first alignment division unit and a boundary of the predetermined domain formed by the second alignment division unit is 5 °. 2. The liquid crystal display device according to claim 1, wherein the relationship <θ <15 ° or 75 ° <θ <175 ° is satisfied. 3. The method according to claim 1, wherein the first alignment division unit is a missing part of a pixel electrode formed on one of the pair of substrates, and the second alignment division unit is formed on the other substrate. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal display element is a missing portion of a common electrode facing the pixel electrode. 4. The first alignment division means is a ridge-shaped insulator formed on a pixel electrode formed on one of the pair of substrates, and the second alignment division means is 2. The liquid crystal display element according to claim 1, wherein the liquid crystal display element is a ridge-shaped insulator formed on a common electrode formed on the other substrate and facing the pixel electrode. 5. The apparatus according to claim 1, wherein the first alignment division means is a missing portion of a pixel electrode formed on one of the pair of substrates, and the second alignment division means is formed on the other substrate. 2. The liquid crystal display element according to claim 1, wherein the liquid crystal display element is a ridge-shaped insulator formed on a common electrode facing the pixel electrode. 6. The first alignment division unit is a ridge-shaped insulator formed on a pixel electrode formed on one of the pair of substrates, and the second alignment division unit is 2. The liquid crystal display element according to claim 1, wherein the liquid crystal display element is a missing portion of a common electrode formed on the other substrate and facing the pixel electrode. 7. A liquid crystal display device according to claim 1, wherein a vertical alignment film is provided on each of said first and second alignment division means.