JP3183633B2 - Liquid crystal display device and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device applied to a display device of a computer, a television receiver, and the like.
More particularly, the present invention relates to a liquid crystal display device having high-speed response and wide viewing angle characteristics, and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a conventional liquid crystal display device, a twisted nematic (TN) mode liquid crystal display device using a nematic liquid crystal has been put to practical use. However, this liquid crystal display device has a disadvantage that the response speed is slow. Further, it has a disadvantage that the viewing angle at which an image can be properly viewed is narrow, and when viewed from an oblique direction, the brightness and contrast are reduced, and the brightness is inverted at a halftone. Therefore, it is difficult to apply the present invention to a display device that requires high-speed moving image display or good visibility even from an oblique direction.

There is also known a liquid crystal display device of a polymer dispersion type liquid crystal display mode utilizing light scattering. This liquid crystal display device has an advantage that a high-luminance image can be displayed because a polarizing plate is not required. However, the response speed is as low as the TN mode liquid crystal display device.
Although the viewing angle is wide to some extent, in principle, TN
There is a disadvantage that the viewing angle cannot be controlled by the phase compensation layer as in the liquid crystal display device of the mode.

Further, there is a liquid crystal display device of a display mode such as a ferroelectric liquid crystal (FLC) or an antiferroelectric liquid crystal (AFLC) which has a quick response and a wide viewing angle, but these devices have shock resistance and temperature characteristics. Has the major disadvantage that it is inferior,
It has not yet been widely used.

Therefore, for example, Japanese Patent Application Laid-Open No. 7-8425.
As disclosed in No. 4, an optically compensated bend (OCB) mode liquid crystal display device having an extremely fast response speed and a relatively wide viewing angle has been proposed.

In this OCB mode liquid crystal display device, for example, as shown in FIG. 10, a liquid crystal 12 is sealed and a pair of transparent substrates 13 and 14 constituting a liquid crystal cell 11 are provided with a pixel electrode 15, a counter electrode 16 and Alignment films 17 and 18 are formed.

By applying a predetermined voltage between the pixel electrode 15 and the counter electrode 16, the alignment films 17 and 18, as shown in FIG. 12b is oriented so as to form a symmetrically inclined bend orientation. More specifically,
The pretilt angle is several degrees to 1 on the surfaces of the alignment films 17 and 18.
Rubbing is performed in parallel and in the same direction so as to be about 0 °. Note that, depending on conditions, the bend orientation may include a twist near the center of the transparent substrates 13 and 14.

The polarizing plate 1 is provided on both sides of the liquid crystal cell 11.
9.20 are provided. Transparent substrate 14 and polarizing plate 20
Between them, a phase compensation layer 21 for optically compensating the orientation of the liquid crystal 12 is provided.

When the bend alignment is formed as described above, the change of the liquid crystal molecules with respect to the change of the driving voltage applied between the pixel electrode 15 and the counter electrode 16 is fast, so that the response speed can be increased. Can be This increase in speed can be obtained especially in a change between halftones where the difference in luminance is small.
In addition, the symmetry of the bend orientation increases the viewing angle (for example, ±±) in a plane including the XZ axis in FIG.
About 50 °). On the other hand, the phase compensation layer 21
The viewing angle in a plane including the axis (vertical direction of the display screen) is enlarged (for example, about ± 40 °). The phase compensation layer 21 also contributes to a reduction in drive voltage.

[0010]

However, the above O
The CB mode liquid crystal display device has a troublesome problem that the bend alignment must be formed before starting display of an image. This is because even if the alignment treatment is performed on the surfaces of the alignment films 17 and 18 as described above, no bend alignment is formed when no voltage is applied between the pixel electrode 15 and the counter electrode 16. As shown in FIG. 11, a splay alignment P in which liquid crystal molecules spread in a fan shape is formed. Therefore, the splay orientation P must be surely transferred to the bend orientation Q by applying high electric energy when the power is turned on. This spray orientation P
The transition from the bend orientation Q to the bend orientation Q occurs relatively quickly when a high voltage of, for example, 10 to 30 V is applied between the pixel electrode 15 and the counter electrode 16, but the number is such that an excessive load is not applied to the driving IC. At a low voltage of V, it takes tens of minutes or more, and in some cases, does not transfer even if it takes more than one hour. This makes it difficult to put the OCB mode liquid crystal display device to practical use.

In order to avoid the above-mentioned problems, Japanese Patent Application Laid-Open No. 9-96790 discloses a liquid crystal molecule having a twisted alignment state and a liquid crystal molecule having an OCB similar to the TN mode.
A technique has been proposed in which a mode is combined with an alignment state similar to the mode and rising in the normal direction of the substrate. This technique avoids the above-mentioned problems by eliminating the need for the bend alignment to be formed, and forms an alignment state similar to the bend alignment to make the response speed higher than in the TN mode. It is intended. However, actually, even if an alignment state similar to the bend alignment is formed as described above, a high response speed cannot always be obtained.

The present invention has been made in view of the above points, and the transition from the splay alignment to the bend alignment is performed quickly and reliably.
Another object of the present invention is to provide a liquid crystal display device which does not require a transition from a splay alignment to a bend alignment and has a high-speed response, and a method for manufacturing the same.

[0013]

According to the present invention, there is provided a pixel electrode substrate, a counter electrode substrate, and a liquid crystal provided between the pair of substrates. In a liquid crystal display device in which a surface is subjected to an alignment treatment so as to give a predetermined pretilt angle to liquid crystal molecules near the surface and a bent orientation is formed in the liquid crystal to change light transmittance to perform display. A high pretilt angle region is formed on at least one surface of the pixel electrode substrate or the counter electrode substrate, the high pretilt angle region being formed of an alignment film that gives a liquid crystal molecule a pretilt angle larger than the surroundings by 10 degrees or more.

Since the liquid crystal molecules in such a high pretilt angle region are in a relatively standing state, when a voltage is applied between the pixel electrode and the counter electrode, the liquid crystal molecules change from the splay alignment to the bend alignment. Since this becomes a nucleus of metastasis and the metastatic region grows and grows at the motive of the nucleus, the above-mentioned metastasis is performed in all the regions in a short time and reliably. In addition, since the electric energy required for the transfer can be low, an excessive load is not applied to the drive circuit.

In order to complete the above-mentioned invention, the present inventors have tried to elucidate the mechanism of the transition in order to cause the above-mentioned orientation state transition to occur in a short time and surely. As a result, it has been found that the above transition is likely to occur immediately after the voltage application is started, in the vicinity of the spacers scattered and arranged between the transparent substrates in which liquid crystal is provided in order to maintain a constant gap between them. Was. This is thought to be because the orientation of liquid crystal molecules near the spacer tends to be irregular due to the physical properties and shape of the spacer surface, and some have a higher tilt angle than the surroundings. Was. It is considered that such a liquid crystal molecule triggers a transition from the splay alignment to the bend alignment at that portion.

However, the above-mentioned transition is accidental, and does not occur near all the spacers.
Since the spacer may move and is not always on all the pixels, it is not certain. In particular, since a liquid crystal display device has a very large number of pixels, an image cannot be displayed properly even if some of the pixels do not undergo the transition.

Therefore, the present inventors have conceived of providing a high pretilt angle region as described above in order to perform the transition in a short time and reliably.

In the high pretilt angle region as described above, for example, an alignment film material giving a large pretilt angle to liquid crystal molecules is partially provided by phase separation or printing, or a small projection is provided on an electrode. By doing so, it can be formed.

Further, the present invention has a pixel electrode substrate, a counter electrode substrate, and a liquid crystal provided between the pair of substrates, and the respective surfaces of the pixel electrode substrate and the counter electrode substrate have the respective surfaces. In a liquid crystal display device that performs an alignment process so as to give a predetermined pretilt angle to liquid crystal molecules near the surface and forms a bent alignment in the liquid crystal, thereby changing the light transmittance to perform display, the pixel electrode substrate or A high pretilt angle region is formed on at least one surface of the counter electrode substrate so as to give a liquid crystal molecule a pretilt angle larger than its surroundings, and the liquid crystal contains a chiral agent.

As described above, even when the liquid crystal contains a chiral agent, the above transition can be easily performed. Furthermore, if a high pretilt angle region and a chiral agent are used in combination,
Metastasis is more likely to occur.

[0021]

[0022]

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) An example of an OCB mode liquid crystal display device in which a transition from a splay alignment to a bend alignment is rapidly performed will be described.

The liquid crystal cell 38 constituting the liquid crystal display device is
As shown in FIG. 1, transparent substrates 3 each made of glass
3 and a transparent substrate 36, a liquid crystal 37 (a ZLI-479 manufactured by Merck & Co.) which is a nematic liquid crystal having a positive dielectric anisotropy.
2) is enclosed. The transparent substrate 33 has a transparent pixel electrode 31 and an alignment film 32 formed thereon, while the transparent substrate 36 has a counter electrode 34 and an alignment film 35 formed thereon. The distance between the transparent substrate 33 and the transparent substrate 36 is kept constant by interposing a spherical spacer 51 having a diameter of about 6 μm between the two. On both sides of the liquid crystal cell 38, polarizing plates 39 and 40 are provided. Further, a phase compensator 43 is provided between the transparent substrate 36 and the polarizing plate 40.

The transparent pixel electrode 31 has, for example, a length of 10
It is formed in a rectangular shape having a width of 0 μm and a width of 300 μm. Actually, a plurality of the pixels are arranged so that a bitmap image can be displayed, but FIG. 1 shows only three pixels.

On the alignment films 32 and 35, high pretilt angle regions 32h and 35h are formed at a density of at least one for each pixel on each of the pixels, and the alignment films 32 and 35 are subjected to an alignment process in the same direction as each other. Have been. Thus, when no voltage is applied to the liquid crystal cell 38, the liquid crystal molecules form splay alignment, while when a predetermined voltage is applied, bend alignment is formed.

The alignment films 32 and 35 are formed and aligned, for example, as follows.

(1) A polyimide alignment film material SE-7492 of Nissan Chemical Industry Co., Ltd., which gives a liquid crystal molecule a low pretilt angle of about 5 ° of a polyamic acid type, is manufactured by Nippon Synthetic Rubber Co., Ltd. Premid type polyimide alignment film material J that gives a high pretilt angle of about 15 to liquid crystal molecules
ALS-246 is mixed at 10%, applied to the transparent pixel electrode 31 and the counter electrode 34, dried, and baked to form the alignment film 3
Form 2.35. During the drying process, the two alignment film materials undergo phase separation, and high pretilt angle regions 32h and 35h are formed.

(2) The entire surface of the alignment films 32 and 35 is rubbed with, for example, a rubbing cloth of rayon to perform an alignment treatment so as to obtain the above pretilt angle.

When a voltage of 8 V is applied to the liquid crystal cell 38 having the high pretilt angle regions 32h and 35h formed as described above by the driving circuit 41 for 10 seconds, regardless of the presence or absence of the nearby spacer 51, In all the pixels, a transition from a splay alignment to a bend alignment including a bend alignment or a twist alignment (hereinafter, simply referred to as “bend alignment”) occurred. Even when the same voltage application was repeated, the above transition occurred with good reproducibility.

The reason for the smooth transition is as follows.
First, the transition nuclei were generated in the high pretilt angle regions 32h and 35h, and the transition regions expanded and grew in response to this.

(Embodiment 2) Approximately 1 of Embodiment 1
Instead of the polyimide alignment film material having a high pre-tilt angle of 5 °, a pre-mid type polyimide alignment material JA having a high pre-tilt angle of about 70 ° also manufactured by Nippon Synthetic Rubber Co., Ltd.
Using LS-204, similarly, high pretilt angle region 32h
When a liquid crystal cell 38 having 35 h was produced and a voltage of 5 V was applied for 2 seconds, the transition surely occurred.

Further, when a small amount of an alignment film material, which forms an almost vertical alignment near 90 °, was mixed, the transition easily occurred at a lower voltage.

(Embodiment 3) Another method of forming high pretilt angle regions 32h and 35h similar to the above-described Embodiment 2 will be described.

(1) First, a pre-mid type polyimide pre-tilt angle polyimide alignment film material JALS-212 manufactured by Nippon Synthetic Rubber Co., Ltd. of about 5 ° is applied to the transparent pixel electrode 31 and the counter electrode 34 and dried. , Firing, alignment film 32
35 is formed.

(2) On a portion corresponding to each of the transparent pixel electrodes 31 of the alignment films 32 and 35, a premid type polyimide alignment film material JALS of about 70 ° made by Nippon Synthetic Rubber Co., Ltd. −204 with a diameter of about 10 μ
m, a pitch of about 100 μm is printed, dried and fired to form high pretilt angle regions 32h and 35h.

(3) An alignment treatment is performed in the same manner as in (2) of the first embodiment.

When a voltage of 5 V was applied to the liquid crystal cell 38 having the high pretilt angle regions 32h and 35h formed as described above for 1 second, the transition was surely caused.

In the first to third embodiments, the mixing ratio of the material of the high pretilt angle alignment film and the diameter of the high pretilt angle regions 32h and 35h are not limited to those described above. What is necessary is just to select according to the liquid crystal material used etc. However, at least one pixel must be formed for each pixel. In addition, the higher the pre-tilt angle and the difference between the high pre-tilt angle and the low pre-tilt angle, the more easily the transition occurs. Therefore, for example, the former
15 to 90 °, more preferably 70 to 90 °, the latter being 10
Although it is preferable to set the angle to be equal to or more than 0 °, the selection is not limited to this, and may be selected according to the above conditions.

(Embodiment 4) Another example of the liquid crystal display device in which the transition from the splay alignment to the bend alignment is quickly performed will be described. In the following embodiments, the same components as those in the first embodiment and the like will be denoted by the corresponding reference numerals, and description thereof will be omitted.

As shown in FIG. 2, on each of the transparent pixel electrodes 31 is a quadrangular prism made of an acrylic photosensitive polymer and having a height (and one side of the cross section) of 4 μm. A projection 52 is formed. In the figure, the height is exaggerated. Such protrusions 52
For example, it can be easily formed by exposure using a mask corresponding thereto and development. Each transparent pixel electrode 3
An alignment film 32 is formed on the surfaces of the first and projections 52 by applying, drying, baking, and aligning a low pretilt angle alignment film material in the same manner as a normal alignment film.

When a voltage of 3 V was applied for 1 second to the liquid crystal cell 38 on which the projections 52 were formed as described above, the transition surely occurred on all the transparent pixel electrodes 31.

This is considered to be because the liquid crystal molecules in the vicinity of the protrusion 52 are relatively standing along the surface of the protrusion 52, and this becomes a nucleus and the transition region grows. Can be

The shape, size, material,
The forming method is not limited to the above, and it is sufficient that at least one of the transparent pixel electrodes 31 is formed. For example, the shape
It may be a cylinder, cone, sphere, pyramid, prism, etc.
It does not have to be higher than the spacer 51. Further, the spacer 51 can be omitted by making it equal to the diameter of the spacer 51.

(Embodiment 5) An example of a liquid crystal display device in which the transition from the splay alignment to the bend alignment is quickly performed by adding a chiral agent to the liquid crystal 37 will be described.

As shown in FIG. 3, the liquid crystal display device of the first embodiment has the same structure as that of the liquid crystal display device of the first embodiment except for the following points.
The liquid crystal display devices A1 to A11 were manufactured.

(A) The high pretilt angle regions 32h and 35h are not formed in the alignment films 32 and 35.

(B) As the alignment films 32 and 35, a polyimide alignment film material JALS-212 having a pretilt angle of about 5 ° of preymid type manufactured by Japan Synthetic Rubber Co., Ltd. is used.

(C) The spacer 51 is a transparent pixel electrode 31
It is located in a position without.

(D) Cholesteryl nanoanoate as a left-handed chiral agent is added to a nematic liquid crystal having a positive dielectric anisotropy so that the liquid crystal 37 has a chiral pitch as shown in the following (Table 1). Have been prepared.

[Table 1]

A rectangular wave voltage having a frequency of 30 Hz and a maximum voltage of 3 V was applied to each of the above-mentioned liquid crystal display devices A1 to A11, which was required for the state of alignment transition and for transition to uniform bend alignment over the entire pixel. Time was observed. The observation results are shown in the above (Table 1).

As shown in Table 1, in the liquid crystal display devices A2 to A5 of 7 μm ≦ chiral pitch ≦ 40 μm, the transmittance was instantaneously changed over the entire surface of the pixel, and no alignment defect occurred. That is, it is considered that a smooth transition from the splay alignment to the bend alignment occurred.

Further, chiral pitch = 5 μm or 6
Liquid crystal display device A with 0 μm ≦ chiral pitch ≦ 100 μm
In 1.A6 to A8, the orientation transition occurred locally and spread over the entire pixel in a considerably short time. That is, the transition occurred on the entire surface of the pixel with a relatively small value of electric energy.

However, 120 μm ≦ chiral pitch ≦ ∞
In the liquid crystal display devices A9 to A11, after the alignment transition occurred locally, application was continued for a long time of 1 to 10 minutes, and finally the transition occurred on the entire surface of the pixel. That is, a large value of electric energy was required to transfer the entire surface of the pixel.

Therefore, the chiral pitch is 5-100.
μm, preferably 7 to 40 μm, a chiral agent is added to the liquid crystal 37 to give the liquid crystal 37 a twist alignment component, thereby reducing the electric energy required for the transition from the splay alignment to the bend alignment, Transfer can be performed easily and reliably.

(Embodiment 6) An example in which a chiral agent is added to the liquid crystal 37 of the liquid crystal display device of Embodiment 2 will be described.

That is, cholesteryl nonanoate, a left-handed chiral agent, is added to the liquid crystal 37 so that the chiral pitch becomes 50 μm. The liquid crystal cell 38 having the high pretilt angle regions 32h and 35h as in the second embodiment is configured such that the liquid crystal 37 is injected between the transparent substrates 33 and 36 and sealed. However, the spacer 51 is arranged at a position where there is no transparent pixel electrode 31.

A rectangular wave voltage having a frequency of 30 Hz and a maximum voltage of 3 V is applied to the liquid crystal display device having the liquid crystal cell 38 as described above, and the transition state of the alignment and the transition to the uniform bend alignment over the entire surface of the pixel. Was observed.

Then, first, the high pretilt angle region 32h
-The orientation transition occurred in the portion of 35h, and it spread over the entire pixel in a very short time within 1 second. That is, the transition occurred uniformly over the entire surface of the pixel with a relatively small value of electric energy.

That is, the high pretilt angle region 32h · 3
At 5h, the nucleus of metastasis was generated, which triggered
The addition of the chiral agent to the liquid crystal 37 facilitates the transition from the splay alignment to the bend alignment, and it is considered that the transition was quickly performed.

The same effect can be obtained even when a chiral agent is added to the liquid crystal 37 of the liquid crystal display of the first or third embodiment.

Further, as shown in the third embodiment, various choices can be made for the high pretilt angle and the like.

In the fifth and sixth embodiments, the spacer 51 is provided with the transparent pixel electrode 31 to facilitate observation.
Although it is arranged at a position where no transparent pixel electrode is provided, it may be arranged at a position of the transparent pixel electrode 31.

(Embodiment 7) An example of a liquid crystal display device which does not require the transition of the alignment state as in the OCB mode will be described. Although this liquid crystal display device is not in the OCB mode, it has a similar orientation state and mechanism, so that the
The same high-speed response as in the CB mode can be obtained.

As shown in FIG. 4, the mechanical structure of this liquid crystal display device is similar to that of the liquid crystal display device of the fifth embodiment (FIG. 3), but as shown in FIG. 32 ・
35, that is, the twist angle ω of the liquid crystal molecules is 18
The difference is that it is 0 °.

This liquid crystal display device is manufactured as follows.

(1) A polyamic acid type polyimide alignment film paint RN-474 manufactured by Nissan Chemical Industries is applied to two transparent substrates 33 and 36 made of glass on which the transparent pixel electrode 31 or the counter electrode 34 is formed. The alignment films 32 and 35 are formed by applying by spin coating and curing for 1 hour in a thermostat at 180 ° C.

(2) Each of the alignment films 32 and 35 is rubbed in the direction shown in FIG. 5 using a rubbing cloth of rayon to perform an alignment treatment so that the twist angle ω becomes 180 °.

(3) The transparent substrates 33 and 36 are
Structural bond 352A, which is a seal resin manufactured by Mitsui Toatsu Chemicals, Inc., with spacer 51 made by Sekisui Fine Chemical Co., Ltd. interposed so that the interval becomes 6 μm.
To form a liquid crystal cell 38.

(4) Cholesteryl nonanoate as a left-handed chiral agent was mixed with a positive nematic liquid crystal ZLI-2 manufactured by Merck Ltd. so that the chiral pitch became 12 μm.
411 (NI point = 65 degrees, Δn = 0.140) to prepare liquid crystal 37.

(5) The liquid crystal 37 is injected into the gap between the transparent substrates 33 and 36 by a vacuum injection method and sealed.

(6) Polarizing plates 39 and 40 and phase compensator 43 which is a biaxial retardation film having a retardation of 50 nm.
To the liquid crystal cell 38 in the direction shown in FIG.
A liquid crystal display device is formed.

FIG. 6 shows the result of measuring a voltage-transmittance characteristic by applying a rectangular wave having a frequency of 30 Hz to the liquid crystal display device formed as described above according to a standard method. From the figure, it is confirmed that the change in the alignment of the liquid crystal molecules is continuous, and the alignment state similar to the bend alignment can be obtained reliably and smoothly.

The contrast ratio in the case where the display was performed with the applied voltage in the range of 1.8 to 6 V was 230: 1.

The following Table 2 shows the total response time when the applied voltage was changed from V1 to V2 and when the applied voltage was changed from V2 to V1. From the table, it has been confirmed that high-speed responsiveness can be obtained in driving between gray scales, that is, in a change between halftones in which a difference in luminance is small.

[Table 2]

The operation state of this liquid crystal display device is as follows.

In the state where no voltage is applied, the orientation film 32 is adjusted so that the twist angle ω of the liquid crystal molecules becomes 180 °.
Since the liquid crystal molecules 35 are aligned, the liquid crystal molecules
It has the same orientation state as the (Super Twisted Nematic) mode.

On the other hand, as shown in FIG. 6, when a voltage of 1.8 V or more at which the transmittance has a maximum value is applied, the liquid crystal molecules are in an alignment state similar to the OCB mode. Therefore, high-speed response is obtained as described above.

Moreover, even when the above-described voltage is applied, the liquid crystal molecules are kept in a twisted state.
No discontinuous phase transition such as transition from splay alignment to bend alignment occurs in the OCB mode. Therefore,
Immediately after the start of voltage application, an image can be displayed.

In this liquid crystal display device, since the liquid crystal molecules are in a twisted alignment state as described above, FIG.
As shown in (2), the polarizing plates 39 and 40 may be arranged so as to be parallel (paranicol) instead of being arranged so that their polarization axes are orthogonal (crossed Nicols). In this case, normally black, that is, display is performed in which the lower the applied voltage, the lower the luminance. However, when the polarization axes are orthogonal and parallel, the appropriate phase compensator 43 is used.
Are different from each other, it is necessary to select a phase difference suitable for each arrangement.

(Embodiment 8) An example of a liquid crystal display device having a configuration similar to that of the above-described Embodiment 7 and mainly having a different twist angle ω of liquid crystal molecules will be described.

More specifically, seven liquid crystal display devices B1 to B7 having the same configuration as the liquid crystal display device of the seventh embodiment except for the following points were manufactured.

(A) A positive nematic liquid crystal ZLI-2293 made by Merck (NI point = 85 degrees, Δn
= 0.140), and cholesteryl nonanoate as a left-handed chiral agent is added so that the chiral pitch becomes 10 μm.

(B) The thickness of the liquid crystal layer is set to 5 μm.

(C) The phase compensator 43 of the seventh embodiment is not provided.

(D) The twist angle ω is set as shown in the following (Table 3).

[Table 3]

FIG. 7 shows each of the liquid crystal display devices B1 to B at room temperature.
7 shows the voltage-transmittance characteristic of No. 7.

The following experiments were conducted on the responsiveness of each of the liquid crystal display devices B1 to B7. Specifically, as shown in the following (Table 4), the applied voltages V1 and V2 are set corresponding to each of the liquid crystal display devices B1 to B7, and when the corresponding voltages are changed from V1 to V2 respectively, Each V2
The response time when changing from V1 to V1 was measured, and these two response times were totaled. The results are shown above (Table 3)
Are shown together.

[Table 4]

As is evident from (Table 3), 160 °
By applying a voltage equal to or higher than the voltage at which the transmittance has a maximum value in the range of the twist angle ω of 200 °, high-speed response can be obtained. In this range, the movement of the liquid crystal molecules is less hindered by the backflow generated by the application of the voltage, and a high-speed response characteristic equivalent to that of the OCB mode can be obtained.

In this embodiment, the phase compensating plate 43
Is not provided, but by attaching a phase compensator 43 suitable for each liquid crystal display device, a higher-contrast image can be displayed.

The front luminance characteristic can be adjusted by optimizing the phase difference Δnd of the liquid crystal cell 38 when no voltage is applied.

Although the chiral pitch of the liquid crystal 37 is set to twice the layer thickness of the liquid crystal 37, it is preferably 1 to 3 times.
Because, when the chiral pitch is smaller than the layer thickness, the torsion angle ω becomes larger than the desired value by 180 degrees, while when the chiral pitch is larger than three times the layer thickness,
This is because the orientation state may become unstable.

(Embodiment 9) An example of an OCB mode liquid crystal display device in which the transition between the splay alignment and the bend alignment is performed continuously and reversibly by setting the twist angle ω to 10 °. explain.

This liquid crystal display device is an OCB mode liquid crystal display device as in the case of the fifth embodiment.
2.35 orientation direction, that is, twist angle ω of liquid crystal molecules
However, the difference is that the angle is 10 ° as shown in FIG.

This liquid crystal display device is manufactured by the same method as that of the seventh embodiment except for the following points.

(A) As the alignment films 32 and 35, a pre-mid type polyimide alignment film paint AL-5062 manufactured by Nippon Synthetic Rubber Co., Ltd. is used.

(B) Each of the alignment films 32 and 35 is rubbed in the direction shown in FIG.
The orientation treatment is performed so that

(C) The transparent substrates 33 and 36 are bonded so that the distance between them is 7 μm.

(D) Positive nematic liquid crystal LIXON-5 manufactured by Chisso Co., Ltd. containing no chiral agent
052 (NI point = 104 degrees, Δn = 0.102) is used.

(E) A phase compensator 43 having a front phase difference of 45 nm, in which a uniaxial film and a biaxial film are bonded, is bonded as shown in FIG.

FIG. 9 shows the result of measuring a voltage-transmittance characteristic by applying a rectangular wave having a frequency of 30 Hz to the liquid crystal display device formed as described above according to a standard method. When no voltage is applied, the liquid crystal molecules show a splay alignment, but transitioned to a bend alignment at about 2.3 V. At this time, the change in the liquid crystal alignment was continuous and reversible, and it was confirmed that the bend alignment state was surely and smoothly obtained.

The contrast ratio when the display was performed in the range of 2.3 to 10 V in applied voltage was 315: 1.

The total response time when the applied voltage was changed from 2.3 V to 2.8 V and vice versa was 22 msec. As a result, it was confirmed that high-speed responsiveness can be obtained in inter-gray-scale driving, that is, in a change between halftones in which a difference in luminance is small. In addition, when driven with a larger driving voltage amplitude, a faster response was observed.

As described above, in the liquid crystal display device, a twisting force is applied to the liquid crystal alignment in the OCB mode, whereby the transition from the splay alignment to the bend alignment can be performed reliably and with good reproducibility. , Its practical value is extremely high.

The above embodiments can be applied to either a reflection type or a transmission type liquid crystal display device. When applied to a reflective liquid crystal display device, a reflective substrate such as a silicon substrate or a metal substrate such as aluminum is used for the substrate, or a reflective metal film is used for one of the pixel electrode and the counter electrode. You may.

The liquid crystal display device according to each of the above embodiments can be applied to a passive matrix type liquid crystal display device, but a TFT (Thin Film Transistor) is provided on one substrate.
Alternatively, the present invention may be applied to an active matrix type liquid crystal display device provided with an active element such as MIM (Metal Insulated Metal). In this way, a higher quality display can be obtained.

Further, the present invention can be applied to various types of liquid crystal display devices such as a normally white or normally black mode liquid crystal display device that becomes a white pixel or a black pixel when no voltage is applied.

Further, the material of each component is not limited to the above, and various materials may be used. For example, a plastic substrate may be used for the transparent substrate, and the alignment film material may also be used.
Not limited to the above, other materials can be applied. Further, although cholesteryl nonanoate having left-turning is used as the chiral agent, various other left- or right-turning chiral agents may be used.

The pretilt angle and the distance between the transparent substrates are not limited to those described above, but may be variously set according to the material of the liquid crystal, the optical design conditions, and the like. In particular, regarding the pretilt angle, it is preferable to set the pretilt angles of the alignment films on both sides of the liquid crystal cell to be equal from the viewpoint of the symmetry of the viewing angle. You may make it easy to change.

In Embodiment 1 and the like, the phase compensator is provided only on one surface of the liquid crystal cell. However, it may be arranged on both surfaces (two in total).

[0111]

As described above, according to the present invention, in a liquid crystal display device which performs display by changing the light transmittance by forming a bend alignment in a liquid crystal, at least one of a pixel electrode and a counter electrode is used. The surface has a high pretilt angle region that is oriented so as to give a larger pretilt angle to the liquid crystal molecules than its surroundings, so that the transition from the splay alignment to the bend alignment can be performed quickly even at a low electric energy. It is performed reliably. In addition, when the liquid crystal contains a chiral agent, the above-described transition is easily performed.

Further, the twist angle of the liquid crystal molecules in the liquid crystal is 16
A drive voltage that is 0 ° or more and 200 ° or less and is higher than a voltage that gives an extreme value of transmittance in a drive voltage-transmittance characteristic of the liquid crystal display device is applied between the pixel electrode and the counter electrode, There is an effect that a liquid crystal display device having the same high-speed response as in the case where the bend alignment is formed can be obtained without forming the bend alignment.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view illustrating a configuration of a liquid crystal display device according to Embodiments 1 to 3.

FIG. 2 is a longitudinal sectional view illustrating a configuration of a liquid crystal display device according to a fourth embodiment.

FIG. 3 is a longitudinal sectional view illustrating a configuration of a liquid crystal display device according to a fifth embodiment.

FIG. 4 is a longitudinal sectional view illustrating a configuration of a liquid crystal display device according to a seventh embodiment.

FIG. 5 is an explanatory diagram showing an arrangement direction of each optical element of a liquid crystal display device according to a seventh embodiment.

FIG. 6 is a graph showing voltage-transmittance characteristics of a liquid crystal display device according to a seventh embodiment.

FIG. 7 is a graph showing a voltage-transmittance characteristic of the liquid crystal display device of the eighth embodiment.

FIG. 8 is an explanatory diagram showing an arrangement direction of each optical element of a liquid crystal display device according to a ninth embodiment.

FIG. 9 is a graph showing a voltage-transmittance characteristic of the liquid crystal display device according to the ninth embodiment.

FIG. 10 is a longitudinal sectional view showing a configuration of a conventional liquid crystal display device.

FIG. 11 is a longitudinal sectional view showing the configuration of another conventional liquid crystal display device.

[Explanation of symbols]

 31 Transparent Pixel Electrode 32/35 Alignment Film 32h / 35h High Pretilt Angle Region 33/36 Transparent Substrate 34 Counter Electrode 37 Liquid Crystal 38 Liquid Crystal Cell 39/40 Polarizer 41 Drive Circuit 43 Phase Compensator 51 Spacer 52 Projection

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-9-90433 (JP, A) JP-A-9-179123 (JP, A) JP-A-10-20284 (JP, A) JP-A-59-1984 219720 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02F 1/1337 G02F 1/141

Claims (10)

(57) [Claims] A liquid crystal provided between the pair of substrates, wherein each surface of the pixel electrode substrate and the counter electrode substrate has a liquid crystal in the vicinity of the surface. In a liquid crystal display device which performs an alignment process so as to give a predetermined pretilt angle to molecules and forms a bent alignment in the liquid crystal to change the light transmittance to perform display, the pixel electrode substrate or the counter electrode substrate A liquid crystal display device having a high pretilt angle region formed of an alignment film that gives a liquid crystal molecule a pretilt angle larger than its surroundings by at least 10 degrees on at least one surface. 2. A liquid crystal display comprising: a pixel electrode substrate; a counter electrode substrate; and a liquid crystal provided between the pair of substrates. Each of the pixel electrode substrate and the counter electrode substrate has a liquid crystal in the vicinity of the surface. In a liquid crystal display device which performs an alignment process so as to give a predetermined pretilt angle to molecules and forms a bent alignment in the liquid crystal to change the light transmittance to perform display, the pixel electrode substrate or the counter electrode substrate A liquid crystal display device, wherein a high pretilt angle region made of an alignment film is formed on at least one surface of the liquid crystal molecules so as to give a liquid crystal molecule a pretilt angle greater than or equal to 15 degrees. 3. The liquid crystal display device according to claim 2, wherein said pretilt angle is 70 degrees or more. 4. The liquid crystal display device according to claim 3, wherein said pretilt angle is approximately 90 degrees. 5. The liquid crystal display device according to claim 1, wherein said high pretilt angle region is a source of a bend transition nucleus. 6. The liquid crystal display device according to claim 1, wherein said high pretilt angle region is formed for each pixel. 7. A liquid crystal display device comprising: a pixel electrode substrate; a counter electrode substrate; and a liquid crystal provided between the pair of substrates. In a liquid crystal display device which performs alignment treatment so as to give a predetermined pretilt angle to molecules and forms a bent alignment in the liquid crystal, thereby changing the light transmittance to perform display, the pixel electrode substrate or the counter electrode substrate A liquid crystal display device, wherein a high pretilt angle region is formed on at least one surface to give a liquid crystal molecule a pretilt angle larger than its surroundings, and the liquid crystal contains a chiral agent. 8. A liquid crystal display device comprising: a pixel electrode substrate; a counter electrode substrate; and a liquid crystal provided between the pair of substrates. The liquid crystal is formed to have a bend alignment to change light transmittance. A method for manufacturing a liquid crystal display device for performing display, wherein: a first alignment film material that gives a first pretilt angle to liquid crystal molecules near a surface of the pixel electrode substrate or the counter electrode substrate;
Forming a film containing a mixture with a second alignment film material giving a second pretilt angle larger than the first pretilt angle on at least one substrate surface of the pixel electrode substrate or the counter electrode substrate; A step of phase-separating the first alignment film material and the second alignment film material in the film. 9. A liquid crystal display device comprising: a pixel electrode substrate; a counter electrode substrate; and a liquid crystal provided between the pair of substrates. The liquid crystal has a bend alignment to change light transmittance. In the method for manufacturing a liquid crystal display device for performing display, an alignment film containing a first alignment film material that gives a first pretilt angle to liquid crystal molecules near a surface of the pixel electrode substrate or the counter electrode substrate is formed by using the pixel electrode substrate Forming on the at least one substrate surface of the counter electrode substrate; and forming a second pretilt partially larger than the first pretilt angle by at least 10 degrees on the alignment film containing the first alignment film material. Forming an alignment film containing a second alignment film material that gives a corner. 10. A liquid crystal display device comprising: a pixel electrode substrate; a counter electrode substrate; and a liquid crystal provided between the pair of substrates. The liquid crystal has a bend alignment to change light transmittance. In a method of manufacturing a liquid crystal display device for performing display,
Forming an alignment film containing a first alignment film material for giving a first pretilt angle to liquid crystal molecules near the surface of the pixel electrode substrate or the counter electrode substrate on at least one substrate surface of the pixel electrode substrate or the counter electrode substrate; And the first step
Partially on the alignment film containing the alignment film material
Forming an alignment film including a second alignment film material that provides a second pretilt angle of 15 degrees or more larger than the pretilt angle of the liquid crystal display device.