JPH1096914A - Liquid crystal display device, phase plate and manufacture of phase plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a view angle characteristic by compensating view angle dependency of an optical propagation characterrstic with a phase plate having an optical medium having negative refractive index anisotropy and twist arranging its main axis in the direction opposite to a liquid crystal molecule of a liquid crystal layer. SOLUTION: The liquid crystal layer 1 and the phase plate 6 are twisted in the direction opposite to each other by a nearly equal angle, and the arrangement direction of the liquid crystal molecule in the phase plate side boundary 1a of the liquid crystal layer 1 is nearly parallel to the main axis direction of a negative uniaxial optical medium in the liquid crystal side boundary 6a of the phase plate 6. Further, the liquid crystal layer 1 and the phase plate 6 are provided with a nearly equal retardation value. In such a case, when polarizing plates 7, 8 are arranged so that mutual polarizing axes are orthogonally intersected with each other, since the optical propagation characteristics of the liquid crystal layer 1 and the phase plate 6 are compensated perfectly with each other when no display voltage is applied, a display becomes a black display, and the view angle characteristic is improved. On the contrary, when the polarizing plates 7, 8 are arranged so that mutual polarizing axes are parallel to each other, a white display with excellent view angle dependency is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a liquid crystal display for displaying video and character information, a retardation plate used in the liquid crystal display, and a method of manufacturing the phase plate.

[0002]

2. Description of the Related Art A liquid crystal display device has been widely used as a flat display of a thin television, a car navigation system, a personal computer, a word processor, etc. due to its thin and light weight features.

[0003] Many display modes have been proposed for liquid crystal displays, and currently widely used ones are a twisted nematic type (hereinafter abbreviated as a TN type) and a super twisted nematic type (hereinafter an STN type). Abbreviated). The former is mainly used for an active matrix type liquid crystal display device in which a switching element such as a thin film transistor (TFT) is formed for each pixel.
The latter is used for a simple matrix type liquid crystal display device having no switching element in a pixel.

An STN-type liquid crystal display device uses a liquid crystal layer arranged at a twist angle of two hundred and several tens of degrees and two polarizing plates. When a voltage is applied in a direction normal to the substrate, liquid crystal molecules rise and the liquid crystal layer is multiplied. Polarized light is displayed based on the phenomenon that refraction changes (see Japanese Patent Application Laid-Open No. 60-107020). STN
Since the display is colored in the liquid crystal display device of the type, a technique of obtaining a monochrome display by adding a phase plate to remove coloring (coloring) of the display is now widely used. Examples of the phase plate for removing coloring include a second liquid crystal panel having a structure twisted in the direction opposite to the liquid crystal layer and a phase plate using a polymer liquid crystal (see Japanese Patent Application Laid-Open No. 63-149624).

FIG. 21 shows a conventional S which prevents the display from being colored.
1 shows a configuration of a TN type liquid crystal display device (hereinafter, referred to as a first conventional example). In the figure, 304 is a liquid crystal layer, 30
Reference numeral 3305 denotes a glass substrate. Two glass substrates 30
Although not shown, the liquid crystal layer 30
An electrode for applying a voltage to 4 is formed, and an overlapping portion of the electrodes forms a pixel. 301, 306
Is a polarizing plate for displaying polarized light, 302 is a phase plate, 30
7 is a back light source.

The phase plate 302 compensates for the wavelength dependence of the polarization state of light passing through the liquid crystal layer 304, and
It eliminates the wavelength dependence of the polarized light passing through 1 and serves to obtain a black and white display. The retardation of the phase plate 302 and the retardation of the liquid crystal layer 304 are equal to each other, the twist directions are opposite, and the twist angles are substantially equal.
The angle between the optical axis direction of the phase plate 302 and the rubbing direction of the liquid crystal layer 304 is 90 degrees. The phase plate 302
Can be formed between the glass substrate 305 and the lower polarizing plate 306 to perform the same operation.
It is also possible to form on both sides.

In the first conventional example, the display in the front direction is made black and white, but the birefringence of the liquid crystal layer 304 and the phase plate 302 changes depending on the observation direction.
4 and the phase plate 302 do not compensate for the amount of change in the amount of birefringence, and the display characteristics of the liquid crystal panel depend on viewing angle dependence such as display inversion and hue change due to viewing angle change. Nature occurs. That is, in this conventional example, although there is an advantage that the clear viewing direction becomes the front and the viewing angle characteristics are concentric, there is no specific configuration for widening the viewing angle.

On the other hand, as disclosed in Japanese Patent Application Laid-Open No. 4-43318, an STN-type liquid crystal display device (hereinafter referred to as a second conventional example) having improved viewing angle characteristics by using a twisted phase plate has been conventionally used. There is). In a second conventional example, a phase plate twisted in the same direction as the liquid crystal layer is laminated on the liquid crystal layer to make the total twist angle 360 degrees, and a phase plate twisted 360 degrees in the opposite direction is laminated on the liquid crystal layer. The viewing angle characteristics have been improved.

In the second conventional example, the amount of birefringence of liquid crystal molecules has a viewing angle characteristic whose axis is a symmetric axis in the molecular long axis direction, apparently increases the twist angle of the liquid crystal layer, and also increases the twist angle of the phase plate. The viewing angle dependency is improved by increasing the arrangement direction of the liquid crystal molecules and the phase plate and the main axis direction in all directions.

However, in the second conventional example, the viewing angle characteristics of the liquid crystal layer and the phase plate are dispersed in each direction to reduce the viewing angle dependence of the display. The main focus is on obtaining a black and white display by performing optical compensation, and it does not have a viewing angle compensation effect, so that sufficient viewing angle characteristics could not be obtained.

On the other hand, a TN type liquid crystal display device has a configuration in which liquid crystal molecules are arranged at a twist angle of 90 degrees (Japanese Patent Laid-Open No. 55-5 / 55).
No. 2027). In such a configuration, when light having a polarization plane parallel or perpendicular to the liquid crystal molecules is vertically incident on the substrate, the light is emitted with the polarization plane rotated by 90 degrees. When a voltage in the normal direction of the substrate is applied to the liquid crystal layer, the liquid crystal molecules rise and their twisted structure is eliminated, so that the liquid crystal loses its effect on polarized light and the incident polarized light is emitted as it is.

Therefore, in the TN type liquid crystal display device, black and white display is obtained by rotating the polarization plane of the emitted light by 90 degrees by turning on / off the voltage and using two polarizing plates. The two polarizing plates are arranged so that the polarizing axes are parallel (or perpendicular) to the main axis direction of the adjacent liquid crystal molecules. When the polarizing axes of the two polarizing plates are orthogonal, the state when no display voltage is applied is obtained. This is a normally white (NW) display in which white and black are displayed when a display voltage is applied. When the polarization axes of two polarizing plates are parallel, black is displayed when no display voltage is applied and white when a display voltage is applied. Marie black (NB) is displayed.

In the case of a TN type liquid crystal display device as well, the polarization propagation characteristics of the liquid crystal layer differ depending on the viewing direction. Dependencies arise. In a TN type liquid crystal display device using an active matrix, halftone display such as an image is often performed. Therefore, it is a performance issue to improve a viewing angle characteristic in the vicinity of a black display, which is particularly affected. I have.

Therefore, conventionally, Japanese Patent Application Laid-Open No. 6-214116 discloses
As shown in the publication, a TN type liquid crystal display device for NW display is provided by using a phase plate in which a birefringent medium having a negative refractive index anisotropy is disposed so that its optical axis is inclined from the sheet normal direction. There is one with improved viewing angle characteristics (hereinafter referred to as a third conventional example). Further, as shown in JP-A-7-13021, a phase plate in which a birefringent medium having a negative refractive index anisotropy is arranged so that its optic axis is inclined from the sheet normal direction is used, There is one in which the viewing angle characteristics of a TN type liquid crystal display device for NW display are improved by lamination (hereinafter, referred to as a fourth conventional example).

In the third and fourth conventional examples, good black display characteristics are obtained and the viewing angle characteristics are improved by compensating the viewing angle dependency when a display voltage is applied by the phase plate having the above structure. It is. In addition, as a method of manufacturing a phase plate having an inclined optical axis, a method of cutting a film obliquely from a bulk polymer having a negative birefringence, a method of mixing a polymer matrix and a low-molecular liquid crystal, and aligning the low-molecular liquid crystal obliquely. The low-molecular liquid crystal preferably exhibits negative birefringence.

However, the third and fourth prior arts compensate for the characteristics of the liquid crystal layer when a display voltage is applied in which the liquid crystal molecule arrangement is greatly deformed. It is necessary to apply a voltage of a certain level or more to the liquid crystal layer to sufficiently raise the liquid crystal molecules at the center of the liquid crystal layer. Therefore, when a sufficient voltage cannot be applied to the liquid crystal layer, good viewing angle characteristics cannot be obtained, and the width of a voltage level at which good compensation is performed is narrow, and it is difficult to set driving conditions. That is, at present, in electronic devices, there is an active movement to reduce the logic voltage from 6 volts to 3.3 volts in order to reduce power consumption and improve signal processing speed. Under these circumstances, even if the third and fourth conventional configurations are adopted in the TN type liquid crystal display device for NW display, it is difficult to obtain good display characteristics by driving a 3.3 volt signal voltage. Met. That is, the third and fourth
In the conventional example, the response speed is reduced due to the use of the high-viscosity low-voltage liquid crystal, and the contrast and viewing angle characteristics are reduced due to insufficient applied voltage.

In the fourth conventional example, the phase plate is
For example, it is formed by stacking eight films in which linearly polarized light is incident and the photoisomerized substance is oriented, shifted by 10 degrees. In this configuration, the number of steps is increased, which causes an increase in cost, and optical phase scattering at the bonding surface does not provide sufficient phase plate characteristics, resulting in a disadvantage that the contrast of the liquid crystal display device is reduced. .

Further, in the fourth prior art example, the main object is to improve the viewing angle characteristics of the TN type liquid crystal display device for NW display, and therefore, it is optically negative uniaxial or nearly uniaxial. A phase plate formed by laminating biaxial thin films so as to have a twisted structure is combined with a TN type liquid crystal. As can be seen from this, the fourth conventional example is directed to a liquid crystal display device that performs NW display, but is not directed to a TN or STN type liquid crystal display device that performs NB display. It is unclear whether the operation can be performed by a liquid crystal display device.

On the other hand, when performing NB display with a TN type liquid crystal display device, black display occurs when no display voltage is applied. According to the detailed calculation, the condition that the incident linearly polarized light is emitted by rotating the plane of polarization by exactly 90 degrees is satisfied only for a specific wavelength, so that even in the front direction, the black display is slightly colored.

In order to eliminate such coloring, a panel having a reverse twisted liquid crystal layer is conventionally laminated as shown in JP-A-57-96315 to eliminate coloring in the front direction. There is one with improved black display characteristics (hereinafter referred to as a fifth conventional example). However, the fifth
In the related art, no description is given of the viewing angle improvement characteristics, and a sufficient viewing angle cannot be obtained.

[0021]

As described above, in each of the conventional examples described above, although the display characteristics of the liquid crystal display device can be improved without changing the basic structure of the liquid crystal layer,
The display characteristics when viewing the liquid crystal display device from an oblique direction are insufficient, and particularly, in a TN type liquid crystal display device,
There was a problem that sufficient viewing angle characteristics could not be obtained unless the voltage applied to the liquid crystal layer was high.

Further, the twisted phase plate is formed by laminating the linear phase plates, and the contrast characteristic of the liquid crystal display device is increased due to an increase in the number of manufacturing steps and optical scattering on the bonding surface. However, there is also a problem that is deteriorated.

[0023]

In order to achieve the above object, the present invention has the following arrangement. That is, the present invention includes a liquid crystal layer having a positive refractive index anisotropy, and at least one first phase plate laminated on the liquid crystal layer, and the first phase plate has a negative phase anisotropy. A liquid crystal display device includes a first optical medium having a refractive index anisotropy and having a main axis twisted and arranged in a direction opposite to that of liquid crystal molecules in a liquid crystal layer.

Further, according to the present invention, a phase plate is formed by twisting an optical medium having a negative refractive index anisotropy.

Also, the present invention provides a process for forming an optical layer comprising a polymer network and a nematic liquid crystal arranged in the polymer network, a process for removing the nematic liquid crystal from the optical layer, and a process for removing the nematic liquid crystal. Filling the first holes of the optical layer formed by the step (1) with the first discotic liquid crystal.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, a liquid crystal layer having a positive refractive index anisotropy and at least one first phase plate laminated on the liquid crystal layer are provided. And the first phase plate has a first optical medium having a negative refractive index anisotropy and having a main axis twisted and arranged in the opposite direction to the liquid crystal molecules of the liquid crystal layer, It has the following effects. That is, the first phase plate compensates for the viewing angle dependence of the optical propagation characteristics of the liquid crystal layer in the display voltage non-applied state or the off-voltage applied state.

According to a second aspect of the present invention, in the liquid crystal display device according to the first aspect, a liquid crystal molecule alignment direction at an interface of the liquid crystal layer on the first phase plate side and a liquid crystal layer of the first phase plate. The angle formed between the side interface and the first optical medium main axis direction is 10 degrees or less, thereby having the following operation. That is, the viewing angle compensation effect between the liquid crystal layer and the phase plate is enhanced.

According to a third aspect of the present invention, in the liquid crystal display device according to the first or second aspect, the first phase plate is disposed on both surfaces of the liquid crystal layer, thereby providing the following operation. Having. That is, the tolerance of the optical compensation increases, and the symmetry of the characteristics also increases. Further, the viewing angle compensation effect between the liquid crystal layer and the first phase plate is further enhanced.

According to a fourth aspect of the present invention, in the liquid crystal display device according to any one of the first to third aspects, the liquid crystal layer has a liquid crystal twist angle of 200 degrees or more and 300 degrees or less. It has such an effect. That is, the liquid crystal layer has a simple matrix structure, and accordingly, a liquid crystal display device having excellent viewing angle characteristics at a low price can be provided at a low price.

According to a fifth aspect of the present invention, there is provided the liquid crystal display device according to the fourth aspect, wherein one of the twisting directions of the liquid crystal twisting angle and the principal axis twisting angle of the first optical medium is positive. Is considered to be −20 degrees or more and +20 degrees or less, thereby having the following operation. That is,
The consistency of the optical propagation characteristics between the liquid crystal layer and the phase plate is improved.

According to a sixth aspect of the present invention, in the liquid crystal display device according to the fourth or fifth aspect, the main axis direction of the first optical medium is along the plane direction of the first phase plate, and If the sum of the retardations of the first phase plate is R _p and the retardation of the liquid crystal layer is R _L , 0.85
≦ R _P / R _L ≦ are 0.96 relationship is established, thereby having the following effects. That is, the optical propagation characteristics of the phase plate approach those of the STN-type liquid crystal (the liquid crystal twist angle of the liquid crystal layer is 200 degrees or more and 300 degrees or less) in the off-voltage applied state.

According to a seventh aspect of the present invention, in the liquid crystal display device according to the fourth or fifth aspect, the main axis direction of the first optical medium is tilted and the first phase plate has a tilt angle. If the total sum of the equivalent retardations from the normal direction is R _p and the retardation of the liquid crystal layer is R _L ,
0.85 ≦ R _P / R _L ≦ are 0.96 relationship is established, thereby having the following effects. That is, the arrangement of the optical axes of the first phase plate corresponds to the liquid crystal molecular arrangement of the STN type liquid crystal (the liquid crystal twist angle of the liquid crystal layer is 200 degrees or more and 300 degrees or less) in the off-voltage application state.

According to an eighth aspect of the present invention, in the liquid crystal display device according to any one of the first to third aspects, the liquid crystal layer has a liquid crystal twist angle of 70 degrees or more and 110 degrees or less;
This has the following operation. That is, the combination with the active matrix improves the contrast and improves the viewing angle characteristics.

According to a ninth aspect of the present invention, in the invention according to the eighth aspect, a sign in which one of the liquid crystal twist angle and the principal axis twist angle of the first optical medium has a positive twist direction is considered. The sum total is −10 degrees or more and +10 degrees or less, thereby having the following operation. That is, the consistency of the optical propagation characteristics between the liquid crystal layer and the phase plate is improved.

According to a tenth aspect of the present invention, in the liquid crystal display device according to the eighth or ninth aspect, the main axis direction of the first optical medium is along the plane direction of the first phase plate,
If the total retardation of the first phase plate is R _p and the retardation of the liquid crystal layer is R _L , 0.95
≦ R _P / R _L ≦ have 1.0 relationship is established, thereby, it has the following effects. That is, the liquid crystal layer in relation to the signal processing and switching characteristics slight leak voltage is applied, the occurrence of this leakage voltage, 0.95 ≦ R _P / R
Correction is made by setting _L ≦ 1.0.

According to an eleventh aspect of the present invention, in the liquid crystal display device according to the tenth aspect, the main axis direction of the first optical medium is inclined with respect to the plane direction of the first phase plate, and the sum of equivalent retardation in the normal direction of the first phase plate and R _p, the retardation of the liquid crystal layer when the R _L, of _{0.95 ≦ R P / R L ≦} 1.0 The relationship is established, and thereby has the following operation.
In other words, the arrangement of the optical axes of the first phase plate corresponds to the arrangement of liquid crystal molecules when a slight voltage is applied to the TN type liquid crystal (the liquid crystal twist angle of the liquid crystal layer is 70 degrees or more and 110 degrees or less). .

According to a twelfth aspect of the present invention, in the liquid crystal display device according to any one of the fourth, fifth, eighth and ninth aspects, the main axis direction of the first optical medium is tilted. The tilt angle of the first optical medium increases and decreases along the thickness direction of the first phase plate, and the tilt angle of the first optical medium increases or decreases when no display voltage is applied or when an off voltage is applied. The tilt angle of the liquid crystal molecules along the thickness direction of the liquid crystal layer is increased or decreased, thereby having the following effects. In other words, the distribution of the tilt angle of the first optical medium almost completely corresponds to the liquid crystal molecular arrangement of the STN or TN liquid crystal.

According to a thirteenth aspect of the present invention, in the liquid crystal display device according to any one of the first to twelfth aspects, at least one second phase plate laminated on the liquid crystal layer is further provided, and The second phase plate has a second optical medium having a positive refractive index anisotropy and a main axis twisted and arranged in the same direction as the liquid crystal molecules of the liquid crystal layer. Has an action. That is, the viewing angle dependence of the optical propagation characteristics of the liquid crystal layer in the state where no display voltage is applied is dispersed in the azimuthal direction, and the viewing angle dependence is made more uniform.

According to a fourteenth aspect of the present invention, in the liquid crystal display device according to the thirteenth aspect, the liquid crystal molecule alignment direction at the interface of the liquid crystal layer on the second phase plate side and the liquid crystal layer of the second phase plate. The angle formed between the side interface and the second optical medium main axis direction is 10 degrees or less, thereby having the following operation. That is, the viewing angle compensation effect between the liquid crystal layer and the second phase plate is enhanced.

According to a fifteenth aspect of the present invention, in the liquid crystal display device according to the thirteenth aspect or the fourteenth aspect, the first optical medium main axis direction at the second phase plate side interface of the first phase plate and the second phase plate side are aligned. The angle formed between the second phase plate and the second optical medium main axis direction at the first phase plate side interface of the second phase plate is 10 degrees or less, thereby having the following operation. That is, the viewing angle compensation effect between the first phase plate and the second phase plate is enhanced.

According to a sixteenth aspect of the present invention, in the liquid crystal display device according to any one of the thirteenth to fifteenth aspects, the second phase plate is disposed on both sides of the liquid crystal layer. It has such an effect. That is, the tolerance of the optical compensation is increased, and the symmetry of the optical propagation characteristics is increased. Further, the viewing angle compensation effect between the liquid crystal layer and the second phase plate is further enhanced.

According to a seventeenth aspect of the present invention, in the liquid crystal display device according to any one of the thirteenth to sixteenth aspects, the liquid crystal layer has a liquid crystal twist angle of 200 degrees or more and 300 degrees or less, and The sum of the twist angle of the liquid crystal and the twist angle of the main axis of the second optical medium is not less than 330 degrees and not more than 390 degrees, thereby having the following effect. That is, the liquid crystal layer has a simple matrix structure, and accordingly, a liquid crystal display device having good viewing angle characteristics at a low price can be provided at a low price. In addition, the viewing angle dependence of the optical propagation characteristics in the liquid crystal layer in the off-voltage applied state is almost uniformly dispersed at all azimuth angles, and the difference in viewing angle characteristics due to azimuth angles is reduced.

According to an eighteenth aspect of the present invention, in the liquid crystal display device according to the seventeenth aspect, the liquid crystal twist angle of the liquid crystal layer, the principal axis twist angle of the first optical medium, and the second optical medium twist angle. The sum of the main shaft torsion angle and the sign in which one of the torsion directions is positive is considered to be −20 degrees or more and +20 degrees or less, thereby having the following operation. That is, the consistency of the optical propagation characteristics of the liquid crystal layer and the first and second phase plates is improved.

According to a nineteenth aspect of the present invention, in the liquid crystal display device according to the seventeenth or eighteenth aspect, the retardation of the liquid crystal layer is set to RLC, and the retardation of the first phase plate (or equivalent retardation) is set. D)
If the retardation (or equivalent retardation) of the second phase plate is Rpeff, 0.8
The relationship of 5 ≦ (Rneff−Rpeff) /RLC≦0.96 is established, thereby having the following operation. That is, the optical propagation characteristics of the first and second phase plates approach the optical propagation characteristics of the STN-type liquid crystal with the off-voltage applied.

According to a twentieth aspect of the present invention, in the liquid crystal display device according to any one of the thirteenth to sixteenth aspects, the twist angle of the liquid crystal molecules is 70 degrees or more and 110 degrees or less, and The sum of the twist angle of the liquid crystal and the twist angle of the main axis of the second optical medium is 180 degrees or more, thereby having the following operation. That is, the combination with the active matrix improves the contrast and improves the viewing angle characteristics. Further, the viewing angle dependence of the liquid crystal layer in the state where no display voltage is applied is broadly divided, and the difference in viewing angle characteristics depending on the azimuth angle is reduced.

According to a twenty-first aspect of the present invention, in the liquid crystal display device according to the twentieth aspect, the twist angle of the liquid crystal of the liquid crystal layer, the twist angle of the main axis of the first optical medium, and the twist angle of the second optical medium. The sum of the main shaft torsion angle and the sign in which one of the torsion directions is positive is considered to be −10 degrees or more and +10 degrees or less, thereby having the following operation. That is, the matching of the optical propagation characteristics between the liquid crystal layer and the first and second phase plates is improved.

According to a twenty-second aspect of the present invention, in the liquid crystal display device according to the twentieth or twenty-first aspect, the retardation of the liquid crystal layer is RLC, and the retardation (or equivalent retardation) of the first phase plate is set. D)
If the retardation (or equivalent retardation) of the second phase plate is Rpeff, then 0.9
The relationship of 5 ≦ (Rneff−Rpeff) /RLC≦1.0 is established, thereby having the following operation. That is, the deterioration of the viewing angle characteristics caused by applying a slight voltage to the liquid crystal layer due to the relationship between signal processing and switching characteristics is prevented.

According to a twenty-third aspect of the present invention, in the liquid crystal display device according to any one of the seventeenth, eighteenth, twentieth and twenty-first aspects, the main optical axis direction of the first optical medium is tilted. The tilt angle increases and decreases along the thickness direction of the first phase plate, and the tilt angle of the first optical medium changes in the thickness direction of the liquid crystal layer when no display voltage is applied or when an off voltage is applied. , And the tilt angle of the second optical medium along the thickness direction of the second phase plate. This has the following effects. That is, the distribution of the tilt angle of the first optical medium is equal to the STN including the second phase plate.
It almost completely corresponds to the liquid crystal molecular arrangement of the liquid crystal or TN liquid crystal.

According to a twenty-fourth aspect of the present invention, in the phase plate, the optical medium having a negative refractive index anisotropy is arranged in a twisted arrangement, thereby having the following effect.
That is, by applying the present invention to a liquid crystal display device, the viewing angle characteristics of the liquid crystal display device are improved.

According to a twenty-fifth aspect of the present invention, in a phase plate, a layer in which a first optical medium having a negative refractive index anisotropy is twisted and arranged, and a second optical medium having a positive refractive index anisotropy are provided. The second optical medium is laminated with a layer in which the first optical medium is twisted and arranged in the opposite direction to the first optical medium, thereby having the following operation.
That is, by applying the present invention to an STN or TN liquid crystal display device, the viewing angle characteristics thereof are greatly improved.

The invention according to claim 26 of the present invention comprises a step of forming an optical layer composed of a polymer network and a nematic liquid crystal arranged in the polymer network, and a step of removing the nematic liquid crystal from the optical layer. Filling the first holes of the optical layer formed by removing the nematic liquid crystal with the first discotic liquid crystal, thereby forming a phase plate. It has a great effect. That is, since a nematic liquid crystal whose alignment is easily controlled is formed and then the nematic liquid crystal and the discotic liquid crystal are replaced, a discotic liquid crystal layer whose alignment is controlled can be easily obtained.

According to a twenty-seventh aspect of the present invention, in the method for manufacturing a phase plate according to the twenty-sixth aspect, the first discotic liquid crystal is cross-linked or the first discotic liquid crystal and the polymer network are combined. The method further includes a cross-linking step, which has the following effect. That is, the optical stability of the phase plate is improved, and the mechanical stability and strength are also improved.

According to a twenty-eighth aspect of the present invention, in the method for manufacturing a phase plate according to the twenty-sixth or the twenty-seventh aspect, the step of forming the optical layer comprises the steps of: And forming a mixture layer comprising a nematic liquid crystal and irradiating the mixture layer with light, thereby curing the photopolymerizable polymer in the mixture layer to form a polymer network, and Has the following effects. That is, the nematic liquid crystal is relatively easily formed.

According to a twenty-ninth aspect of the present invention, in the method for manufacturing a phase plate according to the twenty-eighth aspect, when the mixture layer is irradiated with light, an electric field or an electric field is applied to the mixture layer along a substantially normal direction thereof. A magnetic field is applied, which has the following effect. That is, the arrangement of the optical axes in the phase plate can be controlled to a predetermined distribution.

According to a thirtieth aspect of the present invention, in the method for manufacturing a phase plate according to any one of the twenty-sixth to twenty-ninth aspects, after filling the first holes with the first discotic liquid crystal, Removing the polymer network from the layer, and filling the second holes of the optical layer formed by removing the polymer network with a second discotic liquid crystal, thereby comprising: It has the following effects. That is, the entire optical layer becomes a discotic liquid crystal, the optical characteristics of the phase plate are improved, and the contrast of the liquid crystal display device is improved.

According to a thirty-first aspect of the present invention, in the method for manufacturing a phase plate according to the thirtieth aspect, the first holes are filled with the first discotic liquid crystal or the second holes. And then forming a film layer on the back surface of the optical layer on which the substrate is adhered, which has the following effect. That is, the optical stability of the phase plate is improved, and the mechanical stability and strength are also improved.

According to a thirty-second aspect of the present invention, in the method for manufacturing a phase plate according to the thirtieth or thirty-first aspect, the method further comprises a step of crosslinking the second discotic liquid crystal. It has a great effect. That is, the optical stability of the phase plate is improved, and the mechanical stability and strength are also improved.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
20 will be described with reference to FIG.

First Embodiment FIG. 1 shows the structure of a liquid crystal display device according to a first embodiment of the present invention. In the figure, reference numerals 4 and 5 denote transparent substrates such as glass substrates, which sandwich the liquid crystal layer 1. The liquid crystal layer 1 has a super twisted nematic (S
(TN) structure. Electrodes 2 and 3 for supplying a voltage to the liquid crystal layer 1 are formed on the transparent substrates 4 and 5. Reference numerals 7 and 8 denote polarizing plates for displaying polarized light, and reference numeral 9 denotes a backlight for illumination. Reference numeral 6 denotes a phase plate, which compensates for wavelength dependence and viewing angle dependence of the optical characteristics of the liquid crystal layer 1 to make the display monochrome and expand the viewing angle characteristics.

FIG. 2 is a schematic view showing the structure of the liquid crystal layer 1. FIG. 2 (a) shows a state where no display voltage is applied to the liquid crystal layer 1, and FIG. The state where the display voltage (ON voltage) is applied to the layer 1 is shown. Liquid crystal layer 1
Has liquid crystal molecules 11 having a positive refractive index anisotropy,
The liquid crystal molecules 11 are in a state where a display voltage is applied (FIG. 2).
In (a), the main axes of the liquid crystal molecules are parallel to the plane direction of the liquid crystal layer 1 and the liquid crystal molecules are twisted in the thickness direction of the liquid crystal layer 1. On the other hand, the state where the display voltage is applied (FIG. 2)
In (b)), the liquid crystal molecules 11 are in a state of rising due to the electric field to be formed, and the twist arrangement has almost disappeared.

FIG. 3 is a schematic view showing the structure of the phase plate 6, wherein the phase plate 6 (corresponding to the first phase plate in the claims) is a uniaxial optical medium having a negative refractive index anisotropy. 12 (corresponding to the first optical medium in the claims; hereinafter, this optical medium is referred to as a negative uniaxial optical medium), the principal axis of which is parallel to the plane direction of the phase plate 6 and whose principal axis is 6 has a structure arranged to be twisted in the thickness direction. In FIG. 3, for simplification of the drawing, only one row of the negative uniaxial optical medium 12 is shown as being arranged in the normal direction. Is spread over the entire surface. Further, each molecule of the negative uniaxial optical medium 12 does not need to have a strict row structure in the normal direction, but has such a twisted structure statistically within a range considered to be optically homogeneous. Good. As the negative uniaxial optical medium 12, a discotic liquid crystal or another substance having a disk-shaped molecular structure can be used. The discotic liquid crystal includes a triphenylene-based compound and a benzene derivative in which a long-chain or plate-like functional group is radially arranged as a side chain of a benzene ring. FIG.
Then, the phase plate 6 is a uniaxial optical medium 1 having a negative refractive index anisotropy.
However, if necessary for improving mechanical strength, molecular orientation, etc., the negative uniaxial optical medium 12 may be used.
An optically isotropic support layer (not shown) may be provided on both upper and lower surfaces of the layer, or on one of the surfaces.

The liquid crystal layer 1 and the phase plate 6 are twisted by substantially the same angle in opposite directions to each other, and the arrangement direction of the liquid crystal molecules 11 at the phase plate side interface 1a of the liquid crystal layer 1 (see FIG. 1) and the phase plate The liquid crystal side interface 6a of FIG. 6 (see FIG. 1) is substantially parallel to the main axis direction of the negative uniaxial optical medium 12. The liquid crystal layer 1 and the phase plate 6 have substantially the same retardation value.

FIG. 4 is a diagram for explaining the principle of improving the viewing angle characteristics by the phase plate 6. The figure shows the molecular arrangement of the liquid crystal layer 1 and the phase plate 6 in the state where no display voltage is applied, and in order to simplify the explanation, the birefringence (refractive index anisotropy) of the liquid crystal layer 1 and the phase plate 6 is shown. Δn and thickness d are equal,
The main axes of the liquid crystal molecules 11 and the negative optical medium 12 are parallel to the plane directions of the liquid crystal layer 1 and the phase plate 6. The liquid crystal layer 1 has a left-handed structure, and the phase plate 6 has a right-handed structure. The absolute values of the twist angles are equal.

The liquid crystal layer 1 is divided into thin layers (for example, 10 layers) 21a, 22a,... 30a in order from the phase plate side interface 1a. Similarly, the phase plate 6 is divided into thin layers (the same ten layers as the liquid crystal layer 1) 21b, 22b... 30b in order from the liquid crystal side interface 6a. Considering the combination of the corresponding thin layers between the liquid crystal layer 1 and the phase plate 6 such as the thin layer 21a and the thin layer 21b and the thin layer 22a and the thin layer 22b after being divided in this way, The combination is a positive / negative birefringent medium with the principal axes parallel and having the same retardation.

Considering the propagation of polarized light in the liquid crystal layer 1 and the phase plate 6 thus configured, since the thin layers 21a and 21b are adjacent to each other, they are ideal for light traveling in all directions. Will cancel each other's effects of birefringence, and when considering the propagation of polarized light, it can be handled as if there is no combination of the thin layers 21a and 21b.

Assuming that there is no combination of the thin layer 21a and the thin layer 21b, the next is the thin layer 22a and the thin layer 22b.
Can be treated as adjacent. This combination of thin layers is also a positive / negative birefringent medium whose principal axes are parallel and have the same retardation, so that light traveling in all directions ideally cancels the effects of each other's birefringence. When propagation is considered, the combination of the thin layer 22a and the thin layer 22b can be handled as if there is no combination.

In the same way, all combinations from the combination of the thin layers 23a and 23b to the combination of the thin layers 30a and 30b cancel out the viewing angle characteristics with each other, and are not ideal. Can handle.

The propagation of polarized light is mathematically based on the propagation matrices T21a, T22a,..., T30a of each thin layer composed of elements in 4 rows and 4 columns.
Using T21b, T22b,..., T30b, it is expressed by the following equation (1). Ex and Ey represent electric field components having vibrating surfaces in the x and y directions, respectively, Hx and Hy represent magnetic field components having vibrating surfaces in the x and y directions, respectively. Subscripts in and out are incident light and outgoing light, respectively. Is shown.

[0069]

(Equation 1)

Considering this equation, the above phenomenon becomes a unit matrix in the order of the product of T21a and T21b, the product of T22a and T22b,... The product of T30a and T30b from the center of matrix multiplication. Is considered that the incident polarized light and the output polarized light become equal.

In FIG. 1, if the polarizing plates 7 and 8 are arranged such that their polarization axes are orthogonal to each other, the optical propagation characteristics of the liquid crystal layer 1 and the phase plate 6 are completely reduced as described above when no display voltage is applied. The display is black because they compensate each other. This black display is determined by the characteristics of the polarizing plate, and has very good viewing angle characteristics. As a result, when a color display is performed using a mixture of three pixels forming a red (R), green (G), and blue (B) color filter, the color in a state where no display voltage is applied is seen from the visual field. Even if the angle is changed, leakage hardly occurs, the dependence of the hue on the viewing angle is small, and the viewing angle characteristics in consideration of the hue change as well as the contrast are improved. Conversely, if the polarizing plates 7 and 8 are arranged so that their polarization axes are parallel to each other, white display with good viewing angle dependence can be performed when no display voltage is applied.

When a display voltage is applied to the liquid crystal layer 1, the liquid crystal molecules 11 as a positive birefringent medium rise, and the optical propagation characteristics between the liquid crystal layer 1 and the phase plate 6 deviate from the above compensation conditions. At this time, the value of the torsion angle between the liquid crystal layer 1 and the phase plate 6 and the retardation value and the angle between the polarization axes of the polarizing plates 7 and 8 and the main axis direction of the liquid crystal layer 1 and the phase plate 6 are determined when the display voltage is applied. The display characteristics can be set as desired.

Although the above-described principle of compensation is established when the set of thin layers in FIG. 4 is completely symmetric, actually, in the thin layers 21a and 21b, the arrangement direction of the liquid crystal molecules 11 and the negative uniaxial And the difference between the twist angles of the liquid crystal layer 1 and the phase plate 6 is not more than 20 degrees (that is, a sign that one of the twist directions is positive). Taking into account the sum of the torsion angles is -20
(In the range of +20 degrees to +20 degrees), a practically sufficient viewing angle characteristic can be obtained by slightly adjusting the arrangement angle of the polarizing plates 7 and 8, that is, when viewed from the front, black colored Can be displayed without causing the following.

When the torsion angle and the arrangement angle of each optical element are defined, they are defined by the angle as viewed from the normal direction of the liquid crystal layer 1 and the phase plate 6, that is, the orthogonal projection to the interface. Shall not be considered.

Next, the reason why the liquid crystal layer 1 and the phase plate 6 cancel each other's birefringence by providing the phase plate 6 having the negative uniaxial optical medium 12 will be described with reference to FIG. Will be explained.

FIG. 5A shows a model of a liquid crystal display device in which a phase plate 52 having a positive uniaxial optical medium 62 (hereinafter, such a phase plate is referred to as a positive phase plate) 52 is laminated on the liquid crystal layer 1 ′. FIG. 5B shows a phase plate 6 ′ having a negative uniaxial optical medium 12 ′ (hereinafter, such a phase plate is referred to as a negative phase plate) 6 ′ with respect to a similar liquid crystal layer 1 ′. It is sectional drawing which shows the model structure of the liquid crystal display device of this invention laminated | stacked. In FIG. 5, the liquid crystal molecules 1 are shown for simplicity.
1 ′, the positive uniaxial optical medium 62, and the negative uniaxial optical medium 12 ′ are arranged with their main axes parallel to the plane directions of the liquid crystal layer 1 ′ and the phase plate 6 ′.

The liquid crystal molecules 11 'are arranged in parallel with their main axes left and right in the figure. In addition, the liquid crystal molecules 11 'have optical characteristics as a positive uniaxial optical medium. That is, there is a neLC between the extraordinary refractive index neLC, which is a refractive index for light vibrating in the axial direction, and the ordinary refractive index noLC, which is a refractive index for light vibrating in a direction perpendicular to the axial direction.
> NoLC.

The positive phase plate 52 is provided for the positive uniaxial optical medium 6.
2 are arranged so that the optical axis direction is orthogonal to the liquid crystal molecules 11 ′. That is, the positive uniaxial optical media 62 are arranged in parallel with the main axis thereof being perpendicular to the paper surface.
Further, the positive uniaxial optical medium 62 has optical characteristics as a positive uniaxial optical medium. That is, there is a relationship of ne1> no1 between the extraordinary refractive index ne1 and the ordinary refractive index no1.

The negative phase plate 6 ′ is used for the negative uniaxial optical medium 1.
2 ′ is arranged so as to be parallel to the liquid crystal molecules 11 ′. In other words, the negative uniaxial optical medium 12 'is arranged in parallel with its main axis in the horizontal direction in the figure. Further, the negative uniaxial optical medium 12 'has optical characteristics as a negative uniaxial optical medium. That is, the extraordinary refractive index ne
2. There is a relationship of ne2 <no2 between the ordinary refractive index no2.

Next, the case where the vertical light 56 is incident on the configuration shown in FIGS. 5A and 5B will be considered. Vertical light 5
6 when passing through the liquid crystal layer 1 ', a polarization component 56 _V with polarization in the direction perpendicular to the sheet, a phase difference in between the polarization component 56 _H with polarization in the plane inward occur. 5
In both the configuration of FIG. 5A and the configuration of FIG.
If the retardation of the liquid crystal layer 1 ′ and the retardation of the phase plates 52 and 6 ′ are made equal, the light passing through the liquid crystal layer 1 ′ has a phase difference that cancels out the phase difference generated in the liquid crystal layer 1 ′. Is provided by the phase plates 52, 6 ', thereby creating a state of zero phase difference as a whole.

As described above, in the case of the vertical light 56, whether the phase plate 52 is the positive phase plate 52 or the negative phase plate 6 ', the phase plate 5
Light emitted through 2, 6 'has zero phase difference.

Next, consider the case where the inclined light 57 propagating in the direction inclined by an angle (incident angle) α from the perpendicular direction to the liquid crystal layer 1 ′ and the phase plates 52 and 6 ′ is incident.

The tilted light 57 is applied to the liquid crystal layer 1 ′ and the phase plate 5
The distance through 2,6 'is longer than the vertical light 56.
For example, as shown in FIG. 5B, when the thickness of the negative phase plate 6 ′ is d, the distance that the vertical light 57 passes through the negative phase plate 6 ′ is d / cos α. The same applies to the liquid crystal layer 1 'and the positive phase plate 62.

Considering the optical anisotropy, the liquid crystal molecules 11 ′
And the negative uniaxial optical medium 12 ′, the light propagates in a direction closer to the optical axis as the incident angle α increases. Therefore, the refractive index anisotropy between the two polarization components 57 _V and 57 _H of the inclined light 57 decreases with the factor of COS ² α.

In general, the retardation can be regarded as the product of the refractive index anisotropy and the propagation distance. Therefore, in the negative phase plate 6 ′, the retardation of the liquid crystal layer 1 ′ and the retardation of the negative phase plate 6 ′ As the incident angle α increases, both the retardation and the retardation of the vertical light 56
It will decrease at the rate of sα.

On the other hand, in the positive phase plate 52, the vertical light 56,
In any of the inclined lights 57, the positive uniaxial optical medium 6
2 and the light propagation direction are orthogonal to each other,
6, two polarization components 56 _V , 56 _H (5
7 _V , 57 _H ) does not fluctuate with changes in the angle α. Therefore, in the calculation of the variation of the retardation, only the factor of the distance remains, and the retardation of the positive phase plate 52 increases at a rate of 1 / cos α from the retardation in the vertical direction.

Therefore, FIG. 5 having the positive phase plate 52
When the inclined light 57 is incident on the configuration shown in FIG. 7A, the retardation of the liquid crystal layer 1 ′ is reduced, while the retardation of the positive phase plate 52 is increased, and the compensation relationship between the two is lost.

On the other hand, in the configuration of FIG. 5B having the negative phase plate 6 ′, if the inclined light 57 is incident, the retardation of the liquid crystal layer 1 ′ and the negative phase plate 6 ′ Since both retardations are reduced by substantially equal amounts, the compensation relationship between the two is kept good.

The above description applies to the case where the light incident angle α is inclined from the vertical direction to the left and right in the figure. On the other hand, when the incident angle α of light is inclined in the depth direction or the front direction of the drawing, the liquid crystal layer 1 ′ and the negative phase plate 6 ′ have a refractive index anisotropy even if the incident angle α increases. Is constant, the retardation increases as the incident angle α increases. On the other hand, in the positive phase plate 52,
Since the refractive index anisotropy decreases with the factor of cos ² α as the incident angle α increases, the retardation decreases.

As described above, even when the incident angle α of the light is inclined in the depth direction or the front direction of the drawing, in the configuration of FIG. On the other hand, it can be seen that the compensation characteristic deteriorates while the compensation characteristic with respect to the inclined light 57 is kept good in the configuration of FIG. When the incident angle α is at an intermediate angle between the horizontal direction and the vertical direction, the retardation at that time is shown in FIG.
5 shows an intermediate value between the retardation in the state of FIG. 5A and the retardation in the state of FIG. For the sake of simplicity, in the above description, light refraction at each interface is omitted.

As described above, the negative phase plate 6 'is provided on the liquid crystal layer 1'.
Are stacked, the dependence of the retardation on the viewing angle is directed in the same direction, and the dependence on the viewing angle is reduced as compared with the case where the liquid crystal layer 1 ′ is used alone. Therefore, if only the negative phase plate 6 'is mounted, the liquid crystal layer 1' and the negative phase plate 6 '
Even if the retardation is not always equal, the viewing angle characteristic of the liquid crystal display device is improved as compared with the configuration of the liquid crystal layer 1 ′ alone or the configuration in which the positive phase plate 52 is laminated on the liquid crystal layer 1 ′. be able to. If the retardation of the liquid crystal layer 1 'and the retardation of the negative phase plate 6' are made equal or similar to each other, the viewing angle characteristics will be further improved.

In the above description, for the sake of simplicity, it is assumed that neither the liquid crystal layer 1 'nor the phase plates 52, 6' have a twisted structure. apply. In particular, as shown in FIG. 4 and the like, when the liquid crystal layer 1 and the phase plate 6 can be divided into several thin layers and optical compensation in each combination can be considered, each thin layer has a twist angle. Since it can be considered to be small and approximate to a parallel arrangement, the above description can be applied to each combination of thin layers as it is.

In most cases, the actual STN type liquid crystal display device is duty-driven. In this case, a slight voltage (off voltage) is applied to the liquid crystal layer 1 even in the off state, and the liquid crystal molecules 11 are in a slightly raised state. Therefore, the retardation of the liquid crystal layer 11 as viewed from the front direction is slightly smaller than the state where no display voltage is applied. Therefore, it is desirable to set the retardation of the phase plate 6 to be slightly smaller than the retardation of the liquid crystal layer 1 in order to obtain better display characteristics in the front direction.

FIG. 6 shows the retardation Rn of the phase plate 6.
Ratio Rn / RL between the liquid crystal layer 1 and the retardation RLC of the liquid crystal layer 1
9 shows experimental results on the relationship between C and display contrast. The conditions of this experiment are as follows. That is, the driving duty ratio of the liquid crystal display device is 1
/ 300, the retardation of the liquid crystal layer 1 is 840 nm,
The twist angle of the liquid crystal layer 1 is 250 degrees counterclockwise, and the twist angle of the phase plate 6 is 250 degrees clockwise. The angle between the direction of the polarization axis of the polarizing plate 8 and the alignment direction of the liquid crystal molecules on the lower surface of the liquid crystal layer 1 is 45 degrees, and the polarization axis of the polarizing plate 7 and the polarization axis of the polarizing plate 8 are arranged orthogonally.

As apparent from the experimental results, it is desirable to set Rn / RLC between 0.85 and 0.96 in order to obtain a relatively high contrast of 20 or more. Furthermore, in order to obtain a high contrast of 40 or more, Rn / RLC is set to 0.88.
It is desirable to set it between 0.95.

FIG. 7 shows that the ratio (Rn / RLC) is 0.9.
2 shows the viewing angle dependency of the contrast in the case of 2. FIG. 7 illustrates isocontrast curves for all azimuth angles up to a tilt angle of 80 degrees. FIG.
Under the same conditions, a phase plate in which a uniaxial optical medium having a positive refractive index anisotropy is twisted is arranged such that the main axis of the optical medium is orthogonal to the orientation direction of the liquid crystal molecules at the liquid crystal layer side interface. FIG. 8 shows the viewing angle dependency of the contrast in the case of disposing them at the positions shown in FIG.

In these figures, the region A indicated by oblique lines rising to the right at the periphery indicates that the contrast is 1 or less and the display is inverted, but the uniaxial optical system having negative refractive index anisotropy. In the characteristic of FIG. 7 provided with the medium, the display inversion area A is greatly reduced as compared with the characteristic of FIG. 8 provided with the uniaxial optical medium having positive refractive index anisotropy. In addition, the region b having a contrast of 20 or more, which is indicated by an oblique line rising leftward in the center, is wider in FIG. That is, it is understood that the viewing angle characteristics are greatly improved by using a uniaxial optical medium having a negative refractive index anisotropy and having a twist direction opposite to that of the liquid crystal layer 1.

In order to perform the duty drive, the luminance-
The voltage characteristics need to be steep. To obtain this steepness, the twist angle of the liquid crystal molecules in the liquid crystal layer 1 is set to 200.
Degrees or more, and if it is 240 degrees or more, better display characteristics can be obtained. On the other hand, if the twist angle is too large, an orientation failure phenomenon is likely to occur. Therefore, the twist angle is preferably set to 300 degrees or less, more preferably 270 degrees or less.

The angle formed between the polarization axis of the polarizing plate 8 and the orientation direction of the liquid crystal molecules at the polarizing plate-side interface 1a of the liquid crystal layer 1 is in the same manner as described above, in order to obtain a sharp characteristic. , 15 degrees to 75 degrees, more preferably 30 degrees to
It is desirable to set it in the range of 60 degrees. When the twist angle of the liquid crystal layer 1 and the phase plate 6 is equal, the polarization axis direction of the polarizing plate 7 may be substantially orthogonal to the polarization axis direction of the polarizing plate 8.
If there is a difference between the two torsion angles, the rotation may be performed by that amount. However, if the angle is adjusted within a range of several degrees to tens of degrees from each of the above directions, more favorable display characteristics can be obtained. When it is desired to improve the viewing angle characteristics of the white display, the polarization axes of the polarizing plates 7 and 8 are adjusted within a range of several degrees or tens of degrees from the parallel direction or the direction obtained by adding the difference in the twist angle. It is desirable.

When the retardation of the liquid crystal layer 1 is too small, the ON luminance is insufficient, and when it is too large, the ON display is colored yellowish. Therefore, black and white display and RGB
In the case of performing color display of three colors mixed by a color filter, the retardation of the liquid crystal layer 1 is 700 to 950 n.
m, and if it is between 780 and 900 nm, better display characteristics can be obtained. In particular, when the twist angle is about 250 degrees, very good display characteristics can be obtained by setting the retardation of the liquid crystal layer 1 to around 840 nm.

Second Embodiment The liquid crystal display of this embodiment has basically the same configuration as the liquid crystal display of the first embodiment. First
The main difference from the third embodiment lies in the configuration of the phase plate. In the first embodiment, the retardation of the phase plate 6 is set to be slightly smaller than the retardation of the liquid crystal layer 1 in order to improve the display characteristics from the front during duty driving. In contrast, the phase plate 1 of the present embodiment
4 is that the main axis of the negative uniaxial optical medium 15 is tilted by an angle θ from the surface direction of the phase plate 14 to the upper right in the figure as shown in FIG.
The front characteristics at the time of duty driving are improved. In FIG. 9, the principal axis tilt angle θ of the negative uniaxial optical medium 15 is assumed to be constant irrespective of the position z in the depth direction of the phase plate 14 of the negative uniaxial optical medium 15, but this is a slight distribution. You may have it.

It is assumed that the tilt angle of the principal axis at the position z in the depth direction on the phase plate 14 is θz, the intrinsic birefringence is Δn,
The thickness of the phase plate is d. In this case, the equivalent retardation Reff from the front of the phase plate 14 is expressed by the following equation (2).

[0103]

(Equation 2)

The ratio Reff / RLC between the equivalent retardation Reff from the front direction of the phase plate 14 and the retardation RLC of the liquid crystal layer 1 when no display voltage is applied is represented by the following formula.
As in the case of the first embodiment, good display characteristics can be obtained by setting the distance between 0.85 and 0.96, more desirably between 0.88 and 0.95.

When the negative uniaxial optical medium 15 does not have the tilt structure described above, the value of the retardation Reff matches the ordinary retardation. When it is difficult to determine the tilt angle θ and the value of the retardation Reff cannot be obtained from the above equation, polarized light is incident on the phase plate 14 to observe the state of the output polarized light, and this is obtained by simulation. Compared with the theoretical outgoing polarization state, the value of the equivalent retardation can be obtained relatively easily.

The direction of the tilt angle θ is such that the main axis of the negative uniaxial optical medium 15 at the liquid crystal side interface of the phase plate 14 and the main axis of liquid crystal molecules at the phase plate side interface 1a of the liquid crystal layer 1 are in the same direction. 4, that is, the thin layer 21 a and the thin layer 2 in FIG.
It is desirable to set the main axis of 1b so as to be inclined in the same direction in order to enlarge the viewing angle. The values of the twist angle and retardation of the liquid crystal layer 1 and the arrangement of the polarizing plates 7 and 8 may be set in the same manner as in the first embodiment.

In the present embodiment, the main axis of the negative uniaxial medium 15 in the phase plate 14 is tilted (tilted) in a direction slightly rising from the plane of the phase plate 14, so that the first mode is adopted. Compared with the embodiment, even in the off-display state, a slight off-voltage is applied, so that the optical matching between the liquid crystal layer 1 in which the liquid crystal molecules rise slightly and the phase plate 14 is improved, and the viewing angle is reduced. The compensation characteristics are improved.

Third Embodiment The liquid crystal display device of the present embodiment is basically composed of first, second and third liquid crystal display devices.
It has a configuration similar to that of the liquid crystal display device of the embodiment. The main difference from the first and second embodiments lies in the configuration of the phase plate. In the present embodiment, the concept of the second embodiment is further advanced, and the following phase plate 16 is provided. That is, the phase plate 16 has the negative uniaxial optical medium 17 whose tilt angle has a distribution in the depth direction corresponding to the tilt of the liquid crystal molecules 11.

In a simple matrix type liquid crystal display device, a slight voltage (hereinafter, this voltage is referred to as an off voltage) is applied to the liquid crystal layer 1 even in an off display state due to its structure. When such an off-voltage is applied to the liquid crystal layer 1, the liquid crystal molecules 11 hardly move from the initial alignment state due to a so-called anchoring phenomenon at the interface between the liquid crystal layer 1 and the transparent substrates 4 and 5. In the vicinity of the center of the layer 1 in the thickness direction, the movement of the liquid crystal molecules 11 occurs according to the voltage change.

When an off-voltage is applied, the arrangement direction of liquid crystal molecules according to the position z in the depth direction of the liquid crystal layer 1 can be obtained by simulation. FIG. 10 shows the results of calculating the tilt angle θ and the twist (twist) angle φ of the liquid crystal molecules with respect to each position z in the thickness direction of the liquid crystal when the off voltage is applied. In this calculation, the pretilt angle is 6 degrees.

In the present embodiment, the tilt inclination of the main axis of the negative uniaxial optical medium 17 of the phase plate 16 is distributed as shown in FIG. . That is, after the twist angle of the negative uniaxial optical medium 17 is set to be opposite to the twist angle of the liquid crystal molecules, the distribution of the tilt angle of the negative uniaxial optical medium 17 in the thickness direction is determined when the off voltage is applied ( The tilt angle distribution of liquid crystal molecules in the thickness direction (when no display voltage is applied) is matched.

The arrangement relationship between the liquid crystal molecules 11 and the negative uniaxial optical medium 17 of the phase plate 16 in the present embodiment is shown in FIG.
It becomes what is shown in. FIG. 12 is a diagram according to FIG.
Equivalent parts are denoted by the same reference numerals.

In FIG. 12, as in FIG.
a and thin layer 21b, thin layer 22a and thin layer 22b, ... thin layer 30
The main axis of the liquid crystal molecules 11 and the main axis of the negative uniaxial optical medium 17 in each combination of the thin film 30a and the thin layer 30b are parallel to each other. Therefore, based on the same principle as that described in the first embodiment, each combination of thin layers can more effectively cancel each other's optical propagation characteristics and obtain a wide viewing angle characteristic.

In the present embodiment, since the negative uniaxial optical medium of the phase plate 16 is arranged so as to compensate for the optical characteristics when an off voltage is applied to the liquid crystal layer 1, the liquid crystal layer 1 is turned off even in the off display state. In a structure to which a voltage is applied, better viewing angle characteristics can be obtained as compared with the first and second embodiments.

In the first, second, and third embodiments, the phase plates 6, 14, and 16 are located on the front side when viewed from the liquid crystal layer 1, and in FIG. The backlight 9 was arranged on the side. However, the polarizing plate 7
The backlight 9 may be arranged behind the display, and the display may be observed from the side of the polarizing plate 8. Also in this case, display with good viewing angle characteristics can be performed in the same manner as described above.

Fourth Embodiment FIG. 13 shows the structure of a liquid crystal display according to a fourth embodiment of the present invention. In the present embodiment, a phase plate having a negative uniaxial optical medium is divided into a first phase plate 6A and a second phase plate 6B, and these phase plates 6A and 6B are formed on both sides of the liquid crystal layer 1. The feature is that it is arranged in.

In the present embodiment, the first liquid crystal layer 1
Liquid crystal molecules (not shown) at the phase plate side interface 1b of
The angle formed by the main axis of the negative uniaxial optical medium (not shown) at the liquid crystal layer side interface 6b of the first phase plate 6A is theoretically preferably parallel. Similarly, the liquid crystal molecules (not shown) at the second phase plate-side interface 1c of the liquid crystal layer 1 and the principal axes of the negative uniaxial optical medium (not shown) at the liquid crystal layer-side interface 6c of the second phase plate 6B. The angle formed should be theoretically parallel. However, as described in the first embodiment, in practice, good viewing angle characteristics can be obtained if the angles described above are 10 degrees or less.

As described in the first embodiment, the principle of optical compensation is that the liquid crystal layer 1 and the first and second phase plates 6A and 6B
Is divided into thin layers, and the combination of the thin layers of the liquid crystal layer 1 and each of the phase plates 6A and 6B can be considered to sequentially cancel optical characteristics.

Further, in the configuration of the present embodiment, for example, when the retardations of the first and second phase plates 6A and 6B are set to be equal, the characteristics of the upper half of the liquid crystal layer 1 are positioned on the upper side. The first phase plate 6A compensates, and the lower half characteristic of the liquid crystal layer 1 is compensated by the second phase plate 6B located on the lower side. Thus, the thickness of the liquid crystal layer 1 compensated by each of the phase plates 6A and 6B is only half the thickness of the configuration of the first embodiment. Therefore, when optical compensation is considered with a combination of thin layers, if there is a mismatch in compensation characteristics, that is, between the liquid crystal layer 1 and the phase plates 6A and 6B,
Even if there is a mismatch in the matching of the optical characteristics of the corresponding thin layers, the effect is unlikely to accumulate, resulting in good viewing angle characteristics. In addition, since the first and second phase plates 6A and 6B are provided above and below the liquid crystal layer 1, there is an advantage that the symmetry of the configuration is increased and the viewing angle characteristics are more symmetric. The first and second phase plates 6
Even if the retardations of A and 6B are not always equal, the effect described here is exerted.

In the first embodiment, the retardation Rn of the phase plate 6 and the retardation RLC of the liquid crystal layer 1 are different.
It has been stated that the ratio Rn / RLC to the above is preferably set between 0.85 and 0.96, and more preferably between 0.88 and 0.95. Is as follows. That is, the retardation Rn ₂ with retardation Rn ₁ of the first phase plate 6A second phase plate 6B
(Rn ₁ + Rn ₂ ) and the retardation R of the liquid crystal layer 1
It is desirable ratio of the _{LC (Rn 1 + Rn 2)} / RLC is between 0.85 to 0.96, further preferable to set between 0.88 to 0.95.

The torsion angle is obtained by adding the torsion angles of the liquid crystal layer 1 and the first and second phase plates 6A and 6B in consideration of a sign in which one of the torsional directions is positive.
If it is within the range of 20 degrees to +20 degrees, practically sufficient viewing angle characteristics can be obtained.

Regarding the arrangement angle of the polarizing plate, the angle formed between the polarizing axis of the polarizing plate 8 and the main axis of the negative uniaxial optical medium (not shown) at the interface 6d of the second phase plate 6B on the polarizing plate 8 side. If the angle is set in a range of preferably 15 degrees to 75 degrees, more preferably 30 degrees to 60 degrees, it is possible to obtain a liquid crystal characteristic which has a sharp luminance-voltage characteristic and is suitable for multiplex driving. it can.

FIG. 14 shows that the phase plate 6 used in the first embodiment is divided into two phase plates 6A and 6B having a twist angle of 125 degrees and the same retardation, and are arranged on both sides of the liquid crystal layer 1. 11 shows the viewing angle dependence of the contrast of the liquid crystal display device according to the fourth embodiment configured as described above.

As is apparent from this figure, the viewing angle dependency of the liquid crystal display device of the present embodiment (see FIG. 7) is different from that of the liquid crystal display device of the first embodiment (see FIG. 7). 1
4), the tilt range with a contrast of 50 or more is increased, and the left-right symmetry of the viewing angle characteristic is improved. For example, in the upper part of the figure, a region having a contrast of 50 or more (indicated by the symbol C in FIGS. 7 and 14) is enlarged by about 10 degrees as the tilt angle, and in the upper right and lower right directions, a region having a contrast of 20 or more is shown. The angle is about 10 degrees wide. As a result, in the liquid crystal display device according to the present embodiment, it is possible to obtain a very symmetrical display with a wide viewing angle and a very easy-to-view display.

When the liquid crystal display device of the present embodiment is desired to have an NB display mode in which the viewing angle dependence of black display is good,
The polarizing axis of the polarizing plate 7 may be arranged in a direction deviated from the direction orthogonal to the polarizing axis of the polarizing plate 8 by the sum of the above-mentioned twist angles. At this time, if the angle is adjusted within a range of several degrees to several tens of degrees from the above direction, still better display characteristics can be obtained. When it is desired to form an NW display mode in which the viewing angle characteristic of white display is good, the polarization axis of the polarizing plate 7 may be considered in the same manner with reference to a direction parallel to the polarization axis of the polarizing plate 8.

As in the present embodiment, a liquid crystal display device in which negative phase plates (having a uniaxial optical medium having a negative refractive index anisotropy) 6A and 6B are arranged on both sides of the liquid crystal layer 1. Also, as shown in the second embodiment, each phase plate 6
The viewing angle characteristics can be further improved by inclining the main axis of the negative uniaxial optical medium of A, 6B. Similarly, as shown in the third embodiment, the viewing angle characteristics are further improved by arranging the negative uniaxial optical media of each of the phase plates 6A and 6B in accordance with the arrangement state of the liquid crystal molecules. You can also.

Fifth Embodiment FIG. 15 shows the structure of a liquid crystal display device according to a fifth embodiment of the present invention. In the figure, the same or equivalent parts as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

The feature of the liquid crystal display device of this embodiment is that the liquid crystal layer 1 and the phase plate (negative phase plate) 6 made of a uniaxial optical medium having a negative refractive index anisotropy have a positive A phase plate provided with a uniaxial optical medium 19 having a refractive index anisotropy (a positive phase plate:
18 (corresponding to the second phase plate in the claims).

FIG. 16 shows the liquid crystal layer 1 and the two phase plates 18,
6 schematically shows the arrangement of positive and negative uniaxial optical media 19 and 12 in FIG. In this drawing, components such as the transparent substrates 4 and 5 are omitted. The phase plate 10 has a positive uniaxial optical medium 19 having a positive refractive index anisotropy,
The positive uniaxial optical medium 19 is twisted in the same direction as the liquid crystal layer 1. The main axis direction of the positive uniaxial optical medium 19 at the liquid crystal layer-side interface 18a of the phase plate 18 substantially matches the main axis direction of the liquid crystal molecules 11 at the phase plate 18-side interface 1d of the liquid crystal layer 1. The twist direction of the positive uniaxial optical medium 19 is the same as the twist direction of the liquid crystal molecules 11, and the twist angle of the liquid crystal molecules 11 in the liquid crystal layer 1 and the twist angle of the positive uniaxial optical medium 19 in the phase plate 18. Are approximately 360 degrees.

The phase plate 6 is provided in the same manner as in the first embodiment.
It has a negative uniaxial optical medium 12 having a negative refractive index anisotropy and twisted and arranged in a direction opposite to the liquid crystal layer 1.

Also in the present embodiment, the phase plate 6 compensates for the viewing angle dependence caused by the liquid crystal layer 1 and the phase plate 18 according to the same principle as the first embodiment, so that the liquid crystal having a very wide viewing angle is provided. A display device can be obtained. This is the first
As described in the embodiment, the phase plates 6, 18
And the liquid crystal layer 1 are divided into several thin layers, and the combination of the thin layers having positive and negative refractive index anisotropy can be considered as compensating the optical characteristics with each other. In an ideal state, optical compensation is completely performed in all directions. However, in reality, the value of the refractive index and the directions of the principal axes of the liquid crystal molecules 11 and the uniaxial optical media 12 and 19 are not always ideal. Therefore, when the light traveling direction is near the axial direction (the normal direction of the phase plates 6, 18 and the liquid crystal layer 1) in the combination of the thin layers, the compensation characteristics are good, and as the traveling direction of the light deviates from that direction. Compensation is often incomplete.

However, in this embodiment, as compared with the first embodiment, the phase plate 18 having the positive uniaxial optical medium 19 is provided, so that the uniaxial optical in the combination of the thin layers as described above is provided. The directions of the main axes of the medium and the liquid crystal molecules are present in all directions of 360 degrees, and the dependence of the viewing angle compensation on the axial direction is dispersed in all directions, so that better viewing angle characteristics can be obtained.

The above description is as follows from another viewpoint. That is, the phase plate 18 having the positive uniaxial optical medium 19 reduces or averages the azimuth angle dependency in the viewing angle characteristics of the liquid crystal display, and the phase plate 6 having the negative uniaxial optical medium compensates for this viewing angle dependency. It is considered to have a function.

This compensation is particularly effective in the state where no display voltage is applied (off state), as in the first embodiment. Therefore, the polarization axes of the polarizing plates 7 and 8 are arranged almost orthogonally (NB display). ), A black display with a very good viewing angle can be obtained, and the polarization axes of the polarizing plates 7 and 8 are arranged almost in parallel (NW
Display), a white display with a very good viewing angle can be obtained.

In the structure of the present embodiment, it is desirable that the relationship between the twist angles of the liquid crystal molecules 11 and the positive and negative uniaxial optical media 12 and 18 be within the range of the following equation (3). It is more desirable that the value falls within the range of the expression (3).

-30 ° ≦ ΩLC + Ωp + Ωn ≦ 30 ° (3) -10 ° ≦ ΩLC + Ωp + Ωn ≦ 10 ° (4) ΩLC: twist angle of liquid crystal molecule 11 Ωp: twist angle of positive uniaxial optical medium 19 Ωn: negative The twist direction of the uniaxial optical medium 12 is denoted by a sign, and the left twist is positive and the right twist is negative.

In the present embodiment, the twist angle of the liquid crystal layer 1, the angle formed between the polarization axis of the polarizing plate 8 and the liquid crystal molecules 11, and the polarization axis of the polarizing plate 7 and the polarization of the polarizing plate 8 The angle formed between the axis and the axis is desirably set in the same range as in the first embodiment.

The liquid crystal molecules 11 and the positive / negative uniaxial optical media 19, 1 are located on the adjacent surfaces between the liquid crystal layer 1 and the phase plates 6, 18.
2, the angle between the orientation direction and the principal axis direction, that is,
The orientation direction of the liquid crystal molecules 11 at the phase plate-side interface 1d of the liquid crystal layer 1 and the liquid crystal layer-side interface 18 of the phase plate 18 in FIG.
a, the angle formed between the positive uniaxial optical medium 19 in the main axis direction and the phase plate 6 side interface 1 of the phase plate 18
8b, the direction of the main axis of the positive uniaxial optical medium 19 and the negative uniaxial optical medium 1 at the interface 6e of the phase plate 6 on the liquid crystal layer side.
The angle formed between the two main axis directions will be described.

That is, considering a state in which no voltage is applied to the liquid crystal layer 1, ideally, these angles are theoretically parallel. However, in practice, if these angles are both within 10 degrees, practically sufficiently good viewing angle characteristics in a state where no display voltage is applied can be obtained, and other characteristics such as luminance characteristics and hue in a state where a display voltage is applied. By adjusting these angles so as to be within the above-described range in the state where no display voltage is applied in consideration of the display characteristics, the overall display characteristics can be further improved.

Phase plate 1 having positive uniaxial optical medium 19
8 preferably has a structure regarded as an extension of the liquid crystal layer 1. Therefore, the retardation Rp of the phase plate 18
May be considered based on the value Rpo calculated by the following equation (5).

Rpo = RLC × Ωp / ΩLC (5) RLC: retardation of liquid crystal layer 1 Ωp: twist angle of positive uniaxial optical medium 19 ΩLC: twist angle of liquid crystal molecules 11 However, the liquid crystal display device is driven by duty. In consideration of this, if the retardation of the phase plate 18 is set to a value smaller than this by about 10%, or if the positive uniaxial optical medium 19 is arranged in an inclined manner, furthermore, the optical Good continuity. Note that, when the positive uniaxial optical medium 19 is arranged in an inclined manner, it is desirable that the direction of the inclined arrangement is made to coincide with the inclination direction of the liquid crystal molecules 11.

The equivalent retardation Rpeff of the phase plate 18 in consideration of the inclined structure is a value calculated by the following equation (6), as in the case of the first embodiment.

[0143]

(Equation 3)

.DELTA.np: intrinsic birefringence of the positive uniaxial optical medium 19 When there is no tilt arrangement, the equivalent retardation Rpeff of the phase plate 18 is equal to Rpo calculated by the above equation (5). Retardation Rp selected based on
Is equal to

In the structure of the present embodiment, a part of the retardation of the phase plate 6 having the negative uniaxial optical medium 12 has a phase plate 1 having the positive uniaxial optical medium 19.
It is considered that the optical characteristics of the liquid crystal layer 1 are compensated for and the remaining part of the retardation of the phase plate 6 compensates for the optical characteristics of the liquid crystal layer 1. Therefore, the portion of the retardation of the phase plate 6 which compensates for the optical characteristics of the liquid crystal layer 1 is Rn-Rpeff.
Becomes

As described in the first embodiment, since the liquid crystal layer 1 is duty-driven, the position between Rn-Rpeff which compensates for the optical characteristics of the liquid crystal layer 1 and the retardation of the liquid crystal layer 1 is changed. It is desirable that the relationship described in the first embodiment be satisfied. That is, in order to realize good viewing angle characteristics, it is desirable that the relationship of the following expression (7) is satisfied. Further, if the relationship of the following expression (8) is satisfied, a better viewing angle characteristic is obtained. Obtainable.

0.85 ≦ (Rn−Rpeff) /RLC≦0.96 (7) 0.88 ≦ (Rn−Rpeff) /RLC≦0.95 (8) FIG. 17 shows a liquid crystal according to the present embodiment. 9 illustrates viewing angle dependence of contrast in a display device. Compared to the viewing angle characteristics of the first embodiment shown in FIG. 7, although there is almost no difference in the display inversion area, the area B having a contrast of 20 or more and the area C having a contrast of 50 or more spread in the lower left direction in the figure. It can be seen that the viewing angle characteristics are improved.

Modification Example 1 of Fifth Embodiment In the liquid crystal display device of the fifth embodiment, as in the second embodiment, the phase plate 6 having a negative uniaxial optical medium is used as the main axis. Is a tilted negative uniaxial optical medium 1
5 may be used.
Hereinafter, such a phase plate is referred to as a phase plate 6 ₍₁₄₎ .

In this case, the front characteristics during duty driving are improved on the same principle as that described in the second embodiment. That is, the equivalent retardation Rneff of the phase plate 6 _{(14) from} the front direction is equal to the value of Reff obtained by the above-described equation (2). Further, in the above description of the fifth embodiment it has been described as setting the range indicated by litter the value of retardation Rn previously described (7) and (8) is desired, the phase plate 6 _{(14 )}
What is necessary is just to replace the retardation Rn with the retardation Rneff.

Note that the tilt direction of the negative uniaxial optical medium of the phase plate 6 ₍₁₄₎ may be set as follows. That is, the tilt structure of the liquid crystal layer 1 is virtually extended into the positive phase plate. Then, the relative virtual tilting structure, as the tilt direction of the main axis of the negative uniaxial optical medium in the phase plate 6 ₍₁₄₎ is continuous, the negative uniaxial optical medium having a phase plate 6 ₍₁₄₎ tilt It is desirable to set the direction.

When the phase plate 6 ₍₁₄₎ is provided, the phase plate 6
The main axis of the negative uniaxial optical medium of ₍₁₄₎ is set to the phase plate 6 _(14).
Since it is inclined slightly up from the surface direction of
Compared with the structure of the fifth embodiment having the ordinary phase plate 6, the optical matching between the liquid crystal layer 1 where the liquid crystal molecules 11 rise slightly due to the off-voltage and the phase plate 6 ₍₁₄₎ is better. Thus, the compensation characteristics for the viewing angle are further improved.

Modification 2 of Fifth Embodiment In the liquid crystal display device of the fifth embodiment, the phase plate 6 having the negative uniaxial optical medium 12 is shown in the third embodiment. Phase plate 1 having negative uniaxial optical medium 17
A phase plate similar to 6 may be used. Hereinafter, referred to such a phase plate and the phase plate 6 _(16), referred to as the phase plate 6 ₍₁₆₎ a negative uniaxial optical medium negative uniaxial optical medium 12 having the _(17).

The negative uniaxial optical medium 12 ₍₁₇₎ has the following configuration. That is, the negative uniaxial optical medium 1
The tilt angle 2 ₍₁₇₎ has a predetermined distribution along the depth direction of the phase plate 6 ₍₁₆₎ . This predetermined distribution corresponds to the tilt of the liquid crystal molecules 11 of the liquid crystal layer 1 and the tilt of the main axis of the positive uniaxial optical medium 19 of the positive phase plate 18.

The arrangement distribution of the liquid crystal molecules 11 when an off-voltage is applied to the liquid crystal layer 1 can be obtained by performing a simulation in the same manner as in the third embodiment.
In the present embodiment, in addition to this, the positive uniaxial optical medium 1
In consideration of these, the tilt angle of the main axis of the negative uniaxial optical medium 12 ₍₁₇₎ is distributed in the thickness direction of the phase plate 6 ₍₁₆₎ .

In the second modification, by distributing the tilt angles of the negative uniaxial optical medium 12 _{(17) in} the main axis direction as described above, as described in the third embodiment, Optical characteristics when an off-voltage is applied to the liquid crystal layer 1 are more faithfully compensated. Therefore, better viewing angle characteristics can be obtained as compared with the fifth embodiment.

Modification 3 of the Fifth Embodiment The fifth embodiment and the first and second modifications thereof are different from those of the fifth embodiment.
Either or both of the positive and negative phase plates 18 and 6 are divided into two phase plates, and they are disposed one above and below the liquid crystal layer 1, respectively, so that better display characteristics can be obtained.

The reason why good display characteristics can be obtained by employing the above-described structure is as follows. That is, when the phase plate 18 having the positive uniaxial optical medium 19 is divided, the positive phase plate 18 is arranged symmetrically with respect to the liquid crystal layer 1. Further, when the phase plate 6 having the negative uniaxial optical medium 12 is divided, not only the symmetry is increased, but also the positive / negative birefringence characteristic is canceled in the depth direction as described in the fourth embodiment. Will be short. Therefore, if the negative phase plate 6 is divided, it is possible to obtain a greater effect of improving the viewing angle characteristics.

In the fifth embodiment and its modification, the liquid crystal layer 1, the phase plates 18, 6 are arranged in this order when viewed from the light source side. However, the order of lamination of the liquid crystal layer 1 and the phase plates 18 and 6 is not limited, and these layers may be laminated in another order as long as the layers are sandwiched between the two polarizing plates 7 and 8. Alternatively, a configuration in which a backlight is arranged on the polarizing plate 7 side and the display is observed from the polarizing plate 8 side may be adopted. Also in this case, good viewing angle characteristics can be obtained based on the same principle as that described in the fifth embodiment.

It is preferable that the angle between the principal axes of the liquid crystal molecules and the optical medium on the mutually adjacent surfaces of the liquid crystal layer 1 and the phase plates 6 and 18 be within 10 degrees on all the adjacent surfaces. That is, the angle formed between the arrangement direction of the liquid crystal molecules 11 at the phase plate-side interface 1d of the liquid crystal layer 1 and the main axis direction of the positive uniaxial optical medium 19 at the liquid crystal layer-side interface 18a of the phase plate 18 in FIG. And the positive uniaxial optical medium 19 at the interface 18b of the phase plate 18 on the side of the phase plate 6
It is desirable that the angle formed between the main axis direction and the main axis direction of the negative uniaxial optical medium 12 at the liquid crystal layer side interface 6e of the phase plate 6 be all within 10 degrees.

Further, in the fifth embodiment and its modifications, when the main axes of the negative uniaxial optical media of the phase plates 18 and 6 have a tilt angle, the phase plate 18 and the liquid crystal layer 1
Between the phase plate 6 and the liquid crystal layer 1 (the interfaces 18a and 1d, and the interfaces 18b
It is desirable to set the direction of the main axis of the positive and negative uniaxial optical media and the pretilt angle at each interface between the phase plates 18 and 6 so that the tilt angle becomes nearly continuous at the interface 6e).

Further, in the fifth embodiment and its modification, the angle formed between the polarization axis of the polarizing plate 8 and the alignment direction of the liquid crystal molecules at the interface 1d of the liquid crystal layer 1 is 15 degrees. If the angle is set in the range of 75 to 75 degrees, and more desirably in the range of 30 to 60 degrees, it is possible to obtain a liquid crystal characteristic having a sharp luminance-voltage characteristic and suitable for multiplex driving.

In the fifth embodiment and its modification, when it is desired that the display voltage non-applied state (off state) is changed to black display (NB display) and the viewing angle dependence of black display is improved. The direction of the polarization axis of the polarizing plate 7
May be arranged by shifting by the sum of the torsion angles from the direction orthogonal to the polarization axis direction, but if the adjustment is made in the range of several degrees to several tens of degrees from the orthogonal direction, still good display characteristics can be obtained. . White display (N) when no display voltage is applied (off)
When it is desired to improve the viewing angle characteristics in the white state as (W display), it is only necessary to consider the polarization axes of the polarizing plates 7 and 8 in the parallel direction as a reference.

The above is an explanation of an embodiment in which the present invention is applied to an STN type liquid crystal display device. Next, an embodiment in which the present invention is applied to a TN type liquid crystal display device will be described.

Sixth Embodiment The structure of a liquid crystal display device according to the present embodiment is basically the same as that shown in FIG. 1, and therefore the structure will be described with reference to FIG. This liquid crystal display device has a TN having a twist angle of 90 degrees.
A liquid crystal 40 composed of a type liquid crystal and a phase plate 41 in which a negative uniaxial optical medium (not shown) is twisted and arranged by 90 degrees in a direction opposite to the liquid crystal layer 40. Liquid crystal layer 40 and phase plate 4
1 are almost equal, the arrangement direction of liquid crystal molecules (not shown) at the phase plate side interface 40a of the liquid crystal layer 1 and the main axis direction of the negative uniaxial optical medium at the liquid crystal layer side interface 41a of the phase plate 41. Are almost parallel. Although not shown, a TFT as a voltage switching element is formed on the transparent substrate 42. This TFT
Can be replaced by a diode element such as MIM.

In the liquid crystal display device of the present embodiment,
In order to perform the TN mode operation, the polarizing axis of the polarizing plate 8 is arranged parallel or perpendicular to the alignment direction of the liquid crystal molecules at the interface 40 b of the liquid crystal layer 40 on the polarizing plate 8 side. The polarizing axis of the polarizing plate 7 is arranged so as to be orthogonal to the polarizing axis of the polarizing plate 8, and NB display is performed by arranging the polarizing plates 8 and 7 in this manner.

In this liquid crystal display device, the liquid crystal layer 40
When the retardation of the liquid crystal layer 40 is too small, the brightness when the display voltage is applied is not sufficient. On the other hand, when the retardation of the liquid crystal layer 40 is too large, the viewing angle compensation characteristic is deteriorated or the thickness of the liquid crystal layer 40 (cell Thickness), and the response speed decreases. For this reason, the retardation of the liquid crystal layer 40 is desirably set to 300 nm or more, and more desirably around 400 to 500 nm.

Also in this embodiment, the principle of optical compensation is the same as that described in the first embodiment.
Black display with very good viewing angle characteristics can be performed in the state where no display voltage is applied.

In general, an active matrix type liquid crystal display device having a switching element provided on a transparent substrate has a high contrast and good halftone characteristics. Therefore, a display for displaying a full-color image by mixing three color pixels of RGB. Often used as
In this case, the fact that the black display does not change with the viewing angle is
This is particularly important in that the viewing angle range viewed from the display contrast is expanded and the change in display hue due to the viewing angle is eliminated. In a conventional liquid crystal display device based on NW display,
If the display voltage to be applied is insufficient, the black display characteristics deteriorate, so that the viewing angle characteristics extremely deteriorate. On the other hand, in the liquid crystal display device of the present embodiment, good black display is realized in a state where the display voltage is zero, so that a sufficient voltage is applied to the liquid crystal layer 40 due to the withstand voltage of the driving IC and the restriction of the driving signal. Is not applied, only the white brightness decreases slightly.
The viewing angle dependence of contrast and hue is kept very good. This is because when the power supply voltage cannot be sufficiently obtained with a portable device, etc., or when it is desired to reduce power consumption, or when it is desired to reduce the radiation of electromagnetic waves from a mounted device, the viewing angle characteristics need not be significantly reduced. It leads to the advantage of being good.

Table 1 compares the display characteristics of the liquid crystal display device of the present invention and two types of NW display liquid crystal display devices (conventional examples) when driven at a driving voltage of 5 volts and 3.3 volts. It is an experimental result.

[0170]

[Table 1]

That is, consider a case where the liquid crystal display device of the NB display according to the present embodiment is driven by two kinds of signal voltages of 3.3 volts and 5 volts. In this case, the transmittance of white display is 1 in the 3.3 volt drive as compared with the 5 volt drive.
Although reduced by about 0%, in the state of black display when viewed from the front, a very good contrast of 100: 1 or more can be obtained, and a result equivalent to 5 volt drive can be obtained.
On the other hand, in NW display, when driving at 3.3 volts, sufficient contrast cannot be obtained in both types.

Further, the liquid crystal display device of this embodiment is described in 3.
The viewing angle characteristics when driven by a signal voltage of 3 volts are almost the same as those when the NB display liquid crystal display device provided with a phase plate is driven by a signal voltage of 5 volts. A conventional NW type liquid crystal display device having no phase plate, which is a feature of the present invention, is driven by a signal voltage of 5 volts, or a conventional NW type liquid crystal display device with a phase plate is driven by 3.3 volts. It is much better than it is.

In the liquid crystal display device of the present embodiment,
Since a low-viscosity liquid crystal material can be used as in the case of 5 volt drive for NW display, the response speed is sufficiently good at 5 Omsec or less.

From this, the liquid crystal display device of this embodiment has a feature that it can be incorporated into a 3.3-volt logic device such as a portable computer without adding a booster circuit for the liquid crystal display device. It can contribute to downsizing and cost reduction of equipment. Further, the power consumption of the liquid crystal display device is reduced to about half, so that the battery life of the portable device can be extended and the weight of the battery portion can be reduced.

In the above description, the liquid crystal layer and the phase plate have the same retardation and the same twist angle, and
Although the arrangement direction of the liquid crystal molecules (not shown) at the phase plate-side interface 40a of the above is substantially parallel to the main axis direction of the negative uniaxial optical medium at the liquid crystal layer-side interface 41a of the phase plate 41. The embodiment is not limited to this.

That is, the phase plate side interface 40a of the liquid crystal layer 1
Alignment direction of liquid crystal molecules (not shown) and phase plate 4
The angle formed between the liquid crystal layer-side interface 41a and the main axis direction of the negative uniaxial optical medium is 10 degrees or less, more preferably 5 degrees or less, and a sign in which one twist direction is positive is taken into consideration. If the sum of the twist angles of the liquid crystal layer 40 and the phase plate 41 is between -10 degrees and +10 degrees, practically sufficient display characteristics can be obtained.

It is desirable that the twist angles of the liquid crystal layer 40 and the phase plate 41 are both in the range of 70 to 110 degrees. In these cases, the display characteristics can be further improved by slightly adjusting the directions of the polarization axes of the two polarizing plates 7 and 8 from the directions described above.

Further, in an actual liquid crystal display device, as described above, signal processing accompanying the gamma characteristic of the liquid crystal and the characteristics of the switching element on the transparent substrate are insufficient. Voltage (off voltage) slightly
Is applied. Due to such off-state voltage, the liquid crystal molecules tend to slightly rise even when no display voltage is applied.

In view of the above, in the liquid crystal display device of the present embodiment, the retardation of the phase plate 41 is
It is desirable to set the retardation equal to or slightly smaller than the retardation of the liquid crystal layer 40. According to an experiment, when the retardation of the phase plate 41 is set between 95% and 100% of the retardation of the liquid crystal layer 40, good characteristics are given to most signal processing circuits and switching elements. ing.

If the main axis of the negative uniaxial optical medium of the phase plate 41 is inclined instead of reducing the retardation of the phase plate 41, more excellent viewing angle characteristics can be obtained. Further, as in the second embodiment, if the equivalent retardation of the phase plate 41 is between 95% and 100% of the retardation of the liquid crystal layer 40, most of the signal processing circuits and switching elements are provided. Good characteristics can be obtained.

When the tilt angle of the main axis of the negative uniaxial optical medium of the phase plate 41 has a distribution in the thickness direction of the phase plate, the tilt angle of the negative uniaxial optical medium is too large as compared with the tilt angle of the liquid crystal molecules. If there is a portion, the viewing angle characteristics of that portion become too large, which is not preferable. In this case, it is desirable to set the maximum value of the tilt angle of the negative uniaxial optical medium so as not to exceed three times the pretilt angle of the liquid crystal molecules included in the liquid crystal layer 40. It is more desirable to set the tilt angle of the negative uniaxial optical medium so as not to exceed.

When the arrangement state of the liquid crystal molecules in the liquid crystal layer 40 in the state where no display voltage is applied is known by simulation or the like, the phase plate 41 is set in the same manner as described in the third embodiment. If the negative uniaxial optical medium is arranged correspondingly, more excellent viewing angle characteristics can be obtained.

Seventh Embodiment Although the liquid crystal display device of the present embodiment has a TN type liquid crystal layer 40, the configuration is basically the same as that shown in FIG. 13 (fourth embodiment). Therefore, description will be made with reference to FIG. In the present embodiment, the fourth
The same or similar parts as those of the first embodiment are denoted by the same reference numerals.

The liquid crystal display device of the present embodiment includes first and second phase plates 41A and 41B divided into two, and these phase plates 41A and 41B are arranged on the front and back as viewed from the liquid crystal layer 40. It has a configuration. Also in the present embodiment,
According to the same principle as that described in the fourth embodiment, the viewing angle characteristics are improved, and the viewing angle symmetry is also improved.

The liquid crystal layer 40 and the first and second phase plates 4
The angles formed by the main axes of the liquid crystal molecules and the optical medium on the adjacent surfaces of 1A and 41B are within 10 degrees on all the adjacent surfaces.
More preferably, it is better to be within 5 degrees. That is, the arrangement direction of the liquid crystal molecules (not shown) at the first phase plate-side interface 40b of the liquid crystal layer 40 and the negative uniaxial optical medium (not shown) at the liquid crystal layer-side interface 41b of the first phase plate 6A.
It is desirable that the angle between the main axis direction and the main axis direction is 10 degrees, more preferably, 5 degrees or less. Similarly, the arrangement direction of liquid crystal molecules (not shown) at the second phase plate-side interface 40c of the liquid crystal layer 40 and the negative uniaxial optical medium (not shown) at the liquid crystal layer-side interface 41c of the second phase plate 41B. It is desirable that the angle between the main axis direction and the main axis direction is 10 degrees, more preferably, 5 degrees or less.

When the main axis of the negative uniaxial optical medium of the first and second phase plates 41A and 41B has a tilt angle, the first
The tilt angle at the interface (interface 41b and interface 40b or interface 41c and interface 40c) close to each other between the phase plate 41A and the liquid crystal layer 40 and between the second phase plate 41B and the liquid crystal layer 40. It is desirable to set the main axis direction and the pretilt angle of the negative uniaxial optical medium at the interfaces 41b and 41c of the phase plates 41A and 41B so as to be close to continuous.

Regarding the arrangement angles of the polarizing plates 7 and 8,
You can do as follows. That is, the second phase plate 41B
The main axis direction of the negative uniaxial optical medium at the polarizing plate 8 side interface 41d and the polarization axis direction of the polarizing plate 8 are arranged parallel or orthogonal to each other, and the negative uniaxial property at the phase plate 7 side interface 41a of the first phase plate 41A. The principal axis direction of the optical medium and the polarization axis direction of the polarizing plate 7 are basically arranged orthogonally when the former is parallel arrangement, and are arranged parallel when the former is orthogonal arrangement. Then, at this reference position, 10
The arrangement angle of the polarizing plates 7 and 8 may be adjusted in a range up to about degrees.

The retardation and torsion angle of the first and second phase plates 41A and 41B may be set as follows. That is, the sum of the retardation of the first and second phase plates 41A and 41B and the sum of the torsion angles are equal to the sixth.
The condition described for one phase plate 41 in the above embodiment may be satisfied. The first and second phase plates 41A, 41A
1B can achieve the effects described herein without dividing the optical characteristics such as retardation so that the optical characteristics are not necessarily equivalent.

Eighth Embodiment Although the liquid crystal display of this embodiment has a TN type liquid crystal layer 40, the structure is basically the same as that of the fifth embodiment shown in FIG. Since it is the same as the liquid crystal display device of FIG. Note that, in the present embodiment, the same or similar parts as in the fifth embodiment are denoted by the same reference numerals.

The feature of the liquid crystal display of this embodiment is that
In addition to a phase plate (negative phase plate) 41 provided with a uniaxial optical medium (negative uniaxial optical medium) having a negative refractive index anisotropy twisted in the opposite direction to the N-type liquid crystal layer 40, Phase plate (positive phase plate) provided with a uniaxial optical medium (positive uniaxial optical medium) having a positive refractive index anisotropy twisted in the same direction as the liquid crystal layer
43. The configuration of the phase plate 43 has the same configuration as that of the positive phase plate 18 described in the fifth embodiment.

Also in the structure shown in the present embodiment, the positive phase plate 43 relaxes or averages the azimuth angle dependence of the liquid crystal display characteristics, and uses the same principle as that described in the fifth embodiment. The phase plate 41 compensates for this viewing angle dependency, so that the viewing angle characteristics are further improved as compared with the sixth embodiment.

In the fifth embodiment, the total of the twist angle of the liquid crystal layer 1 and the twist angle of the positive phase plate 18 is set to about 360 degrees. Also in the present embodiment, if the total of the twist angle of the liquid crystal layer 40 and the twist angle of the positive phase plate 43 is set to about 360 degrees, the viewing angle dependency can be dispersed in each direction. The layer 40 has a twist angle of about 90 degrees and ST
Since it is narrower than the N-type liquid crystal layer 1, if the total twist angle is 180 degrees or more, a practically sufficient viewing angle expanding effect can be obtained.

In the structure of the present embodiment, it is desirable that the relationship between the twist angles of the liquid crystal layer 40 and the phase plates 43 and 41 be within the range of the following expression (9).

−10 ° ≦ ΩLC + Ωp + Ωn ≦ 10 ° (9) ΩLC: twist angle of liquid crystal molecules forming the liquid crystal layer 40 Ωp: twist angle of the positive uniaxial optical medium forming the positive phase plate 43 Ωn: negative The twisting direction of the negative uniaxial optical medium constituting the phase plate 41 is positive for left-handed twist and negative for right-handed twist. The retardation of the phase plates 43, 41 is as follows. If the uniaxial optical medium has a tilted arrangement, the retardation is equivalent.

Next, a desirable relationship of the retardation between the liquid crystal layer 40 and the phase plates 41 and 43 will be described. In the present embodiment, it is desirable that the positive phase plate 43 has a structure that can be regarded as an extension of the liquid crystal layer 40. Therefore, its retardation Rp is considered based on the value of Rpo obtained by the following equation (10). I just need.

Rpo = RLC × Ωp / ΩLC (10) RLC: retardation of liquid crystal layer 40 Ωp: twist angle of positive uniaxial optical medium forming positive phase plate 43 ΩLC: liquid crystal forming liquid crystal layer 40 Twist Angle of Molecules As described in the sixth embodiment, in an active matrix type liquid crystal display device, liquid crystal molecules often slightly rise even when no display voltage is applied (off state). For this reason, the retardation of the positive phase plate 43 is 2-3 times smaller than the value determined by the above equation (10).
% Or a tilt arrangement of the positive uniaxial optical medium constituting the positive phase plate 43 can provide better display characteristics.

It is preferable that the direction of the tilt arrangement of the positive uniaxial optical medium constituting the positive phase plate 43 coincides with the tilt direction of the liquid crystal molecules.

In the structure of the present embodiment, a part of the retardation of the negative
It is considered that the characteristics of the liquid crystal layer 40 are compensated for by compensating for the characteristics of the liquid crystal layer 40. Therefore, the part of the retardation of the negative phase plate 41 that compensates for the characteristics of the liquid crystal layer 40 is Rneff-Rpe
ff. For the same reason as described in the sixth embodiment, it is desirable that the following relationship (11) be established between Rneff-Rpeff and RLC.

0.95 ≦ (Rn−Rpeff) / RLC ≦ 1 (11) Also in the present embodiment, between the liquid crystal layer 40 and each of the phase plates 43 and 41, the surfaces which are close to each other. The angle formed by the liquid crystal molecules and the main axes of the positive and negative uniaxial optical media in each other is preferably within 10 degrees on all adjacent surfaces, and more preferably 5 degrees or less. Further, when the main axes of the positive and negative uniaxial optical media in the phase plates 43 and 41 have a tilt angle, the liquid crystal layer 40 and the phase plate 4
It is desirable to set the tilt angles and the orientation directions of the principal axes of the 3,41 liquid crystal molecules and the positive and negative uniaxial optical media as follows. That is, between the liquid crystal layer 40 and the phase plate 43 and between the phase plate 43 and the phase plate 41, the above-described tilt angles and orientation directions are set so that the tilt angles are close to each other on the mutually adjacent surfaces. It is desirable to do.

Regarding the arrangement angles of the polarizing plates 7 and 8,
Set as follows. That is, in the polarizing axis of the polarizing plate 8 and the liquid crystal layer 1 adjacent thereto, the polarizing axis of the polarizing plate 8 and the main axis direction of the liquid crystal molecules of the liquid crystal layer 1 are parallel or orthogonal to each other on the near surface side. The principal axis direction is basically shifted from the arrangement orthogonal to the principal axis direction of the polarizing plate 8 by the sum of the twist angles shown in the expression (9). And, based on such a basic arrangement, according to other parameters,
The arrangement angle of the polarizing plates 7 and 8 may be adjusted within a range of up to about 10 degrees. It is desirable that the twist angle and the retardation of the liquid crystal layer 40 are set in the same ranges as in the sixth embodiment.

Modification of Eighth Embodiment In the liquid crystal display device of the eighth embodiment, one or both of the positive and negative phase plates 43 and 41 are divided into two phase plates, and the liquid crystal layer 40 is formed. By arranging one by one above and below, better display characteristics could be obtained.

This is considered to be due to the same reason as described in the third modification of the fifth embodiment, and if the negative phase plate 41 is divided, the viewing angle characteristic can be more greatly improved. The effect is obtained.

The angle between the liquid crystal layer 40 and the main axes of the liquid crystal molecules and the positive and negative uniaxial optical media on the adjacent surfaces of the phase plates 43 and 41 and the arrangement angle of the polarizing plates 7 and 8 are as follows. The range may be set within the range described in the embodiment.

Next, a method of manufacturing a phase plate having a negative refractive index anisotropy used in each of the above embodiments will be described.

A phase plate in which an optical medium having negative refractive anisotropy is twisted is formed by forming an optical layer in which nematic liquid crystals are arranged in a polymer network, and then replacing the nematic liquid crystals with discotic liquid crystals. Can be produced. This is achieved by replacing the discotic liquid crystal, which is difficult to control the direction and impart a twisted structure, with a nematic liquid crystal, which can control alignment relatively easily.
A desired array distribution is provided. As a more specific and preferable manufacturing method, there is a method shown in FIG.

First, as shown in FIG. 18A, the surface of an optically isotropic film substrate 101 such as cellulose triacetate is subjected to an orientation treatment by a rubbing treatment using a rubbing roll 102 or the like. At this time, an alignment film such as polyimide may be formed on the surface of the film substrate 101.

Next, as shown in FIG. 18B, a mixture 103 of a nematic liquid crystal and a photopolymerizable polymer was prepared.
It is applied on the film equipment 101 by a roll coating method. In the figure, reference numeral 104 denotes a roll of a roll coater for applying the mixture 103. The mixture 103 may be dissolved in a solvent if necessary. Further, the mixture 103 may be applied by spin coating or various printing methods.

As described above, the nematic liquid crystal applied to the film substrate 101 together with the photopolymerizable polymer has some chiral substance (for example, S-811 manufactured by Merck).
To give a twisted structure. On the other hand, an ultraviolet curable acrylic resin or the like is used as the photopolymerizable polymer. When the mixture 103 is dissolved in a solvent, the solvent is removed by drying before the step described below.

Next, as shown in FIG.
By irradiating 03 with ultraviolet light 105, the photopolymerizable polymer is polymerized to form a polymer network in the mixture 103. The arrangement of the nematic liquid crystal molecules having a twisted structure is stabilized by the polymer network thus formed. Note that the irradiation light may be visible light as long as the wavelength is such that the photopolymerizable polymer forms a network.

Thereafter, as shown in FIG. 18D, a solvent 106 for dissolving a nematic liquid crystal such as methanol or ethanol is prepared, and the film base 101 on which the polymer network is formed is immersed in the solvent 106. Thus, the nematic liquid crystal is selectively removed from the mixture 103 on the film substrate 101. Instead of immersion,
Even if the solvent 106 is poured onto the film substrate 101 in a shower shape, the nematic liquid crystal can be selectively removed.

Next, as shown in FIG. 18E, a discotic liquid crystal 108 is dropped by a syringe 109 onto the film substrate 101 pulled up from the solvent 106. As the discotic liquid crystal 108, for example, a triphenylene-based compound or a benzene derivative in which a long-chain or plate-like functional group is arranged as a side chain of a benzene ring is used.

The discotic liquid crystal 108 penetrates and disperses into the polymer network 107 in which holes are formed by removing the nematic liquid crystal. Polymer Network 1
Since the holes in the trace of the nematic liquid crystal formed at 07 have anisotropy corresponding to the twisted structure of the nematic liquid crystal, the discotic liquid crystal 1 penetrating into the holes
08 also has a twisted structure and anisotropy. The shape of the twisted structure can be controlled by adjusting the amount of the chiral substance added to the nematic liquid crystal. In such a process, the syringe 1
If the fluidity of the discotic liquid crystal 108 is increased by heating the base material 09 or the film 101, the process time can be shortened, or a substance that does not take a liquid crystal phase at room temperature can be used.

[0213] Instead of the dropping operation using the syringe 109, the film substrate 101 is immersed in the discotic liquid crystal 108, or the discotic liquid crystal 108 is coated on the film substrate 101 by a roll coating method or a printing method. May be. Furthermore, the discotic liquid crystal 10
8 instead of using a discotic liquid crystal 108
Is prepared in an appropriate solvent, and the discotic liquid crystal 108 dissolved in this solvent is
01 may be dropped or applied. In this case, it is necessary to remove the solvent after the discotic liquid crystal 108 has penetrated the film substrate 101.

Next, as shown in FIG. 18F, the extra discotic liquid crystal 108 is removed. As a result, the optical layer 11 in which the discotic liquid crystal 108 having a twisted structure is dispersed in the polymer network 107 is formed.
0 is formed, and the film substrate 101 having the optical layer 110 becomes the above-described phase plate having the negative refractive index anisotropy. The amount of the polymer network 107 to be added is desirably about 2 to 3% by weight. Then, the optical influence on the discotic liquid crystal 108 is reduced.

When the discotic liquid crystal 108 in the optical layer 110 thus formed has low fluidity and good physical stability of the phase plate, the phase plate may be used as it is. However, otherwise, if the discotic liquid crystal 108 has a high fluidity, the optical layer 11
On the surface of 0, for example, a protective film film optically isotropic with respect to the optical layer 110, such as a cellulose triacetate film, to protect the optical layer 110, the optical stability of the phase plate, Increases mechanical stability or strength.
When a polarizing plate or another phase plate is laminated on the optical layer 110, these thin plates can be used in place of the above-mentioned protective film. Discotic liquid crystal 1
When 08 has high fluidity, it is desirable to cut the optical layer 110 and the film substrate 101 into a predetermined size, and then seal the cut surface.

In the manufacturing method described with reference to FIG. 18, the optical layer 110 is formed on the film substrate 101 to form a phase plate, but instead of the film substrate 101, a phase plate, a polarizing plate, or a liquid crystal is used. A similar optical layer may be formed on the surface of the panel.

Further, this manufacturing method is particularly suitable for continuously forming a phase plate on a roll-shaped film substrate 101 'as shown in the conceptual diagram of the process in FIG. In addition,
In FIG. 19, the same or similar parts as those in FIG. 18 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The film substrate 101 'is continuously supplied from the roll 121 on the delivery side, and undergoes a process similar to that described with reference to FIG.
9 are not shown) and are wound around a roll 122 on the receiving side.

Film substrate 1 on which optical layer 110 was formed
01 ′ may be subjected to processing such as cutting immediately after this, or may be bonded to another film such as a phase plate or a polarizing plate in the form of a roll. If the continuous production is performed in this manner, the production amount is greatly increased, and a large number of phase plates having negative refractive index anisotropy can be supplied at low cost.

The phase plate having a negative refractive index anisotropy manufactured as described above has a good optical characteristic because of having a continuous twisted structure, which is described in the first to eighth embodiments. Very good display characteristics can be obtained when used in the liquid crystal display device. Further, if continuous production using a roll-shaped film is performed, it is possible to further contribute to a reduction in the price of the liquid crystal display device.

In the above-described method for manufacturing a phase plate having a negative refractive index anisotropy, the discotic liquid crystal 108 having a reactive group formed at a terminal is used as the discotic liquid crystal 108.
08 ′ may be used. That is, the discotic liquid crystal 108 'described above is made to permeate the polymer network 107 in which holes are formed by removing the nematic liquid crystal, as in FIG. Further, between the discotic liquid crystals 108 'and the polymer network 10'
7 and a discotic liquid crystal 108 'are crosslinked. The crosslinking reaction can be caused by heating or light irradiation.

Thus, the discotic liquid crystal 1
08 ′ and between the polymer network 107 and the discotic liquid crystal 108 ′, an optical layer 110 ′ having good stability and a phase plate can be obtained. In this case, it is not necessary to seal the side surface of the phase plate. In particular, when it is not necessary to protect the upper surface (or lower surface) of the phase plate from scratches or the like, the optical layer 110 'having the discotic liquid crystal 108' does not need to be covered with the protective film.

In the method for producing a phase plate whose stability has been solidified by crosslinking, the following method may be further employed. That is, after the configuration shown in FIG. 18 (f) is created, the discotic liquid crystal 108 'is selected by selecting the polymer material and the terminal group of the discotic liquid crystal 108' and setting the crosslinking reaction conditions.
A cross-linking reaction occurs only with each other.

Then, as shown in FIG. 20 (a), the polymer network 107 is removed from the optical layer 110 'by a solvent 111 such as toluene or xylene which selectively dissolves only the polymer network 107 in the optical layer 110'. 1
07 is selectively removed. Thus, the optical layer 112 composed of only the discotic liquid crystal 108 'is formed on the film substrate 101.

Next, as shown in FIG. 20B, a discotic liquid crystal 114 having a reactive group formed at a terminal is prepared, and this discotic liquid crystal 114 is supplied to the syringe 11.
The discotic liquid crystal 114 is supplied onto the optical layer 112 by a dropping operation using 3 or the like, and the discotic liquid crystal 114 penetrates into the pores of the polymer network 107 formed in the optical layer 112. Further, the discotic liquid crystal 114 is crosslinked to form an optical layer 115 shown in FIG.

The phase plate obtained in this way is shown in FIG.
The polymer network 107 of the optical layer 110 shown in FIG.
Is replaced by the discotic liquid crystal 114, and the optical layer 11
5 is formed entirely from the discotic liquid crystal. Therefore, the phase plate manufactured in this way is
There are the following advantages. That is, in order to increase the mechanical stability of the phase plate manufactured by the manufacturing method described with reference to FIG.
It is necessary to increase the amount of 07. However, when the polymer network 107 is increased,
An adverse optical effect on the discotic liquid crystal 108 (for example, a change due to light scattering due to a difference in refractive index) increases. That is, in the phase plate manufactured by the manufacturing method of FIG. 18, the optical characteristics and the mechanical stability are in an opposite relationship.

On the other hand, the optical network 107
Is replaced with a discotic liquid crystal 114,
Although the number of processes increases, the polymer network 1
14 can be eliminated, and both optical characteristics and mechanical stability can be achieved.

In each of the above-described methods for producing a phase plate, the mixture 1 of a nematic liquid crystal and a photopolymerizable polymer was used.
When irradiating light on 03 to form a polymer network,
Light irradiation may be performed while applying an electric field (or a magnetic field) in the normal direction of the film. Then, the molecules of the nematic liquid crystal rise in the normal direction of the film substrate 101, so that the principal axis direction of the finally obtained discotic liquid crystal 108 is inclined from the normal direction of the film substrate 101, The distribution of the tilt angle can be provided in the depth direction of the material 101.

Thus, it is possible to obtain the phase plate described in the second embodiment or the like, that is, the phase plate in which the main axis direction of the negative uniaxial optical medium 15 matches the molecular arrangement of the liquid crystal layer 1. .

In the phase plate manufactured by the above-described method for manufacturing a phase plate having negative refractive index anisotropy, the interface between the optical layer 110 in contact with the film substrate 101 and the exposed optical layer At the interface 110, the tilt angles may be different from each other. If a symmetrical tilt structure is required from the optical characteristics of the display device, such a configuration is not convenient.

Therefore, when a symmetrical tilt structure is required, a plurality of phase plates produced by the above-described method for manufacturing a phase plate having negative refractive index anisotropy are connected to each other at the interface with a negative negative plate. By laminating the uniaxial optical media so that the main axes are substantially continuous to form one phase plate, a symmetric tilt structure can be obtained.

In this case, it is desirable to remove the film base material 101 from the phase plates other than at both ends in order to enhance the optical characteristics of the phase plate as a whole and not increase the thickness of the phase plate. When the number of stacked layers is large, the display characteristics deteriorate due to the influence of the interface. Therefore, it is preferable that the number of stacked layers be three or less.

Further, in the above-described method of manufacturing a phase plate, the discotic liquid crystal 108 is twisted to form a negative phase plate whose main axis is twisted. However, in these manufacturing methods, if the structure of the nematic liquid crystal to be created first is controlled so as to adopt a different alignment from the twisted alignment, it is possible to manufacture a negative phase plate with another alignment It is. For example, if no chiral agent is added, the nematic liquid crystal can be vertically, horizontally, tilted, or hybrid aligned depending on the alignment conditions at the interface and the conditions for applying an electric field or magnetic field during photocuring. This makes it possible to produce a negative phase plate in which the optical axis is vertical, horizontal, inclined, or hybrid.

[0234]

As described above, according to the present invention, the viewing angle dependence of the optical propagation characteristics of the liquid crystal layer in the state where no display voltage is applied (off state) is compensated, and a liquid crystal display device having a wide viewing angle is obtained. In particular, when the present invention is applied to a TN type liquid crystal display device, a display with sufficiently good viewing angle characteristics in NB display can be performed. Is now possible.

Further, according to the present invention, it was possible to easily form a phase plate in which the optical axis of the negative optical medium was twisted.

The above is the overall effect of the present invention. Next, the effects of each claim will be described in detail.

[0237] The effect first phase plate of claim 1, is compensated viewing angle dependence of the optical propagation characteristics of the liquid crystal layer in the absence of an applied voltage, which viewing angle characteristics are improved by.

[0238] increases the viewing angle compensation effect of the claimed effect liquid crystal layer of claim 2 and the phase plate, correspondingly,
Further, the viewing angle characteristics were improved.

Effect of Claim 3 The tolerance of optical compensation is increased, and the symmetry of characteristics is also enhanced. Further, the viewing angle compensation effect between the liquid crystal layer and the first phase plate is further enhanced. Thereby, the viewing angle characteristics were further improved.

The liquid crystal layer of the fourth aspect has a simple matrix structure, so that a liquid crystal display device having excellent viewing angle characteristics can be provided at a low price, and the cost can be reduced.

[0241] is increased integrity of the optical propagation characteristic between the effect the liquid crystal layer and the phase plate according to claim 5, correspondingly, further viewing angle characteristic is improved.

The optical propagation characteristic of the effect phase plate according to claim 6 approaches the optical propagation characteristic of the STN type liquid crystal (the liquid crystal twist angle of the liquid crystal layer is not less than 200 degrees and not more than 300 degrees) in the off-voltage applied state, and the STN liquid crystal is accordingly reduced. The viewing angle characteristics of the liquid crystal are improved.

According to the seventh aspect, the arrangement of the optical axes of the first phase plate is S
TN type liquid crystal (liquid crystal twist angle of liquid crystal layer is more than 200 degrees and 30
(Less than 0 degree)
As a result, the viewing angle characteristics of the STN liquid crystal were further improved.

In combination with the active matrix of the eighth aspect , a high contrast is obtained and the viewing angle characteristics are improved.

[0245] is increased integrity of the optical propagation characteristic between the effect the liquid crystal layer and the phase plate of claim 9, correspondingly, further viewing angle characteristic is improved.

A slight leakage voltage is applied to the liquid crystal layer due to the effect signal processing and the switching characteristics according to the tenth aspect .
It was corrected by setting 95 ≦ _RP / _RL ≦ 1.0, and the deterioration of the viewing angle characteristics could be prevented accordingly.

According to the eleventh aspect, the arrangement of the optical axis of the first phase plate is a liquid crystal molecular arrangement when a slight voltage is applied to a TN type liquid crystal (the liquid crystal twist angle of the liquid crystal layer is 70 degrees or more and 110 degrees or less). Therefore, deterioration of the viewing angle characteristics can be prevented.

According to the twelfth aspect, the distribution of the tilt angle of the first optical medium is STN type or T
The liquid crystal molecules almost completely corresponded to the liquid crystal molecular arrangement of the N-type liquid crystal, and the viewing angle characteristics were further improved accordingly.

According to the thirteenth aspect, the viewing angle dependency of the optical propagation characteristics of the liquid crystal layer in the state where no display voltage is applied is dispersed in the azimuthal direction, and the viewing angle dependency is compensated. Therefore, the viewing angle characteristics are further improved.

[0250] increases the viewing angle compensation effect of the effect the liquid crystal layer and the second phase plate of claim 14, correspondingly, was improved further viewing angle characteristics.

[0251] increases the viewing angle compensation effect of the phase plate and the second phase plate effects a first of claims 15, correspondingly, was improved further viewing angle characteristics.

The effect of claim 16 The tolerance of optical compensation is increased, the symmetry of optical propagation characteristics is enhanced, and the viewing angle compensation effect between the liquid crystal layer and the second phase plate is further enhanced. Thereby, the viewing angle characteristics were further improved.

The liquid crystal layer of the seventeenth aspect has a simple matrix structure, so that a liquid crystal display device having good viewing angle characteristics can be provided at a low price, and the cost can be reduced. In addition, the viewing angle dependence of the optical propagation characteristics in the liquid crystal layer in the state where no display voltage is applied is almost uniformly dispersed at all azimuth angles, and the difference in viewing angle characteristics due to azimuth angles is reduced. Further, the viewing angle characteristics were improved.

[0254] Effects liquid crystal layer and the first claim 18, consistency increased optical propagation characteristic of the second phase plate, that amount was further improved viewing angle characteristics.

[0255] Effect first claim 19, the optical propagation characteristics of the second phase plate, closer to the optical propagation characteristics of STN-type liquid crystal off voltage applied state, correspondingly, S
The viewing angle characteristics of the TN type liquid crystal are improved.

In combination with the active matrix of claim 20 , the contrast is increased and the viewing angle characteristics are improved. Further, the viewing angle dependence of the liquid crystal layer in the state where no display voltage was applied was broadly divided, the difference in the viewing angle characteristics depending on the azimuth angle was reduced, and the viewing angle dependence was reduced.

[0257] Effects liquid crystal layer and the first claim 21, integrity of the optical propagation characteristics is increased and the second phase plate, that amount, the viewing angle characteristic is further improved.

In view of the effect signal processing and switching characteristics of the twenty-second aspect, deterioration of the viewing angle characteristics caused by applying a slight voltage to the liquid crystal layer was prevented, and the viewing angle characteristics were further improved accordingly.

According to the twenty- third aspect, the distribution of the tilt angle of the first optical medium almost completely corresponds to the liquid crystal molecular arrangement of the STN or TN type liquid crystal including the second phase plate. The viewing angle characteristics have been improved.

Effects of Claims 24 and 25 By applying this phase plate to a liquid crystal display device, the viewing angle characteristics of the liquid crystal display device can be improved.

The layer of the discotic liquid crystal whose effect alignment is controlled according to claim 26 is accurately formed,
Moreover, it has become possible to manufacture it at low cost.

According to the twenty-seventh aspect, a phase plate having high durability can be manufactured.

According to the twenty-eighth aspect, the formation of a nematic liquid crystal is relatively easy, and
The phase plate can be manufactured at low cost.

[0264] now the phase plate having a predetermined distribution sequence effects the optical axis of claim 29 can be easily manufactured.

The effect of claim 30 is that the entire optical layer is a discotic liquid crystal, whereby the optical characteristics of the phase plate can be improved, and the contrast of a liquid crystal display device using this phase plate can be improved. I could do it.

A phase plate excellent in the effect stability and strength according to claims 31 and 32 can be manufactured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a liquid crystal display device according to first to third embodiments of the present invention.

FIG. 2 is a schematic sectional view of a liquid crystal layer in the liquid crystal display device of the present invention.

FIG. 3 is a schematic sectional view of a phase plate in the liquid crystal display device of the present invention.

FIG. 4 shows liquid crystal molecules in the liquid crystal display device of the present invention;
FIG. 4 is a cross-sectional view schematically showing an arrangement relationship with a uniaxial optical medium having negative refractive index anisotropy.

FIG. 5 is a cross-sectional view for comparing the viewing angle compensation effect between a uniaxial optical medium having a negative refractive index anisotropy and a uniaxial optical medium having a positive refractive index anisotropy.

FIG. 6 is a characteristic diagram showing a relationship between contrast and retardation ratio between a phase plate and a liquid crystal layer.

FIG. 7 is a view angle characteristic diagram of the liquid crystal display device according to the first embodiment.

FIG. 8 is a view angle characteristic diagram of a conventional liquid crystal display device using a phase plate of a uniaxial optical medium having positive refractive index anisotropy.

FIG. 9 is a schematic cross-sectional view of a phase plate constituting a liquid crystal display device according to a second embodiment of the present invention.

FIG. 10 is a diagram showing a simulation result of a molecular alignment state of a liquid crystal layer.

FIG. 11 is a diagram showing design conditions of an arrangement state of optical axes of a phase plate.

FIG. 12 is a cross-sectional view schematically illustrating an arrangement relationship between liquid crystal molecules and a uniaxial optical medium having a negative refractive index anisotropy in a liquid crystal display device according to a third embodiment of the present invention.

FIG. 13 is a sectional view illustrating a configuration of a liquid crystal display device according to a fourth embodiment of the present invention.

FIG. 14 is a view angle characteristic diagram of the liquid crystal display device according to the fourth embodiment.

FIG. 15 is a sectional view illustrating a configuration of a liquid crystal display device according to a fifth embodiment of the present invention.

FIG. 16 schematically shows an arrangement relationship between liquid crystal molecules, a uniaxial optical medium having a negative refractive index anisotropy, and a uniaxial optical medium having a positive refractive index anisotropy in the fifth embodiment. FIG.

FIG. 17 is a view angle characteristic diagram of the liquid crystal display device according to the fifth embodiment.

FIG. 18 is a process chart showing one embodiment of a method for manufacturing a phase plate of the present invention.

FIG. 19 is a process chart showing a modification of the method for manufacturing a phase plate of the present invention.

FIG. 20 is a process chart showing still another modified example of the method for manufacturing a phase plate of the present invention.

FIG. 21 is a cross-sectional view illustrating a configuration of a conventional liquid crystal display device.

[Explanation of symbols]

1,40 Liquid crystal layer 6,6A, 6B, 14,16,18,41 Phase plate having negative uniaxial optical medium 11 Liquid crystal molecule 12,15,17 Negative uniaxial optical medium 18 Positive uniaxial optical medium Having phase plate 19 positive uniaxial optical medium

Claims (32)

[Claims] 1. A liquid crystal layer having a positive refractive index anisotropy, and at least one first phase plate laminated on the liquid crystal layer, wherein the first phase plate has a negative refractive index. A liquid crystal display device comprising a first optical medium having anisotropy and having a main axis twisted and arranged in a direction opposite to that of liquid crystal molecules in a liquid crystal layer. 2. The liquid crystal display device according to claim 1, wherein
The angle formed between the liquid crystal molecule alignment direction at the first phase plate side interface of the liquid crystal layer and the first optical medium main axis direction at the first phase plate side liquid crystal layer interface is 10 degrees or less. A liquid crystal display device characterized by the above-mentioned. 3. The liquid crystal display device according to claim 1, wherein the first phase plate is disposed on both sides of the liquid crystal layer. 4. The liquid crystal display device according to claim 1, wherein the liquid crystal layer has a liquid crystal twist angle of 200 degrees or more and 300 degrees or less. 5. The liquid crystal display device according to claim 4, wherein
The sum of the twist angle of the liquid crystal and the twist angle of the main optical axis of the first optical medium is −20 in consideration of a sign in which one of the twist directions is positive.
A liquid crystal display device, wherein the temperature is not less than +20 degrees. 6. The liquid crystal display device according to claim 4, wherein a main axis direction of the first optical medium is along a plane direction of the first phase plate, and the retardation of the first phase plate is performed. Let the sum of the phases be R _p and the retardation of the liquid crystal layer be R _L
To the liquid crystal display device characterized by the relationship _{0.85 ≦ R P / R L ≦} 0.96 is satisfied. 7. The liquid crystal display device according to claim 4, wherein a main axis direction of the first optical medium is tilted, and an equivalent direction from a normal direction of the first phase plate. litter sum of retardation of the R _p, when the retardation of the liquid crystal layer and R _L, a liquid crystal display device characterized by the relationship _{0.85 ≦ R P / R L ≦} 0.96 is satisfied. 8. The liquid crystal display device according to claim 1, wherein the liquid crystal layer has a liquid crystal twist angle of 70 degrees or more and 110 degrees or less. 9. The liquid crystal display device according to claim 8, wherein
The sum of the liquid crystal torsion angle and the principal axis torsion angle of the first optical medium is −10 in consideration of a sign where one of the twist directions is positive.
A liquid crystal display device, wherein the temperature is not less than +10 degrees. 10. The liquid crystal display device according to claim 8, wherein a main axis direction of the first optical medium is along a surface direction of the first phase plate, and the retardation of the first phase plate is performed. the sum of Deshon and R _p, when the retardation of the liquid crystal layer and R _L, a liquid crystal display device characterized by the relationship _{0.95 ≦ R P / R L ≦} 1.0 is satisfied. 11. The liquid crystal display device according to claim 10, wherein the main axis direction of the first optical medium is inclined with respect to the plane direction of the first phase plate, and the sum of equivalent retardation in the normal direction and _R p, when the retardation of the liquid crystal layer and R _L, a feature that relationship _{0.95 ≦ R P / R L ≦} 1.0 is satisfied Liquid crystal display device. 12. The liquid crystal display device according to claim 4, wherein the main axis direction of the first optical medium is tilted and the tilt angle is the first angle.
Increase and decrease along the thickness direction of the phase plate
The tilt angle of the optical medium corresponds to the tilt angle of the liquid crystal molecules in the thickness direction of the liquid crystal layer when the off voltage is applied or the display voltage is not applied. 13. The liquid crystal display device according to claim 1, further comprising at least one second phase plate laminated on the liquid crystal layer, wherein the second phase plate comprises: A liquid crystal display device comprising a second optical medium having a positive refractive index anisotropy and having a main axis twisted and aligned in the same direction as liquid crystal molecules of a liquid crystal layer. 14. The liquid crystal display device according to claim 13, wherein a liquid crystal molecule arrangement direction at a liquid crystal layer side interface of the liquid crystal layer and a second optical medium at a liquid crystal layer side interface of the second phase plate. A liquid crystal display device, wherein an angle formed between the main axis direction and the main axis direction is 10 degrees or less. 15. The liquid crystal display device according to claim 13, wherein the first optical medium main axis direction and the first phase plate at the second phase plate side interface of the first phase plate. A liquid crystal display device, wherein an angle formed between the phase plate side interface and the second optical medium main axis direction is 10 degrees or less. 16. The liquid crystal display device according to claim 13, wherein the second phase plate is disposed on both sides of the liquid crystal layer. 17. The liquid crystal display device according to claim 13, wherein the liquid crystal layer has a liquid crystal twist angle of 20.
A liquid crystal display device which is at least 0 degree and at most 300 degrees, and wherein the sum of the liquid crystal twist angle of the liquid crystal layer and the principal axis twist angle of the second optical medium is at least 330 degrees and up to 390 degrees. 18. The liquid crystal display device according to claim 17, wherein a twist direction of a liquid crystal twist angle of the liquid crystal layer, a principal axis twist angle of the first optical medium, and a principal axis twist angle of the second optical medium. A liquid crystal display device characterized in that the total sum considering a sign in which one of them is positive is −20 degrees or more and +20 degrees or less. 19. The liquid crystal display device according to claim 17, wherein the retardation of the liquid crystal layer is RLC,
Let the retardation (or equivalent retardation) of the first phase plate be Rneff and the retardation (or equivalent retardation) of the second phase plate be Rneff.
A liquid crystal display device characterized in that a relationship of 0.85 ≦ (Rneff−Rpeff) /RLC≦0.96 is satisfied, where peff. 20. The liquid crystal display device according to claim 13, wherein the twist angle of the liquid crystal molecules is 70 degrees or more and 110 degrees or less, the liquid crystal twist angle of the liquid crystal layer and the second optical axis. A liquid crystal display device, wherein the sum of the torsion angle of the main shaft and the medium is 180 degrees or more. 21. The liquid crystal display device according to claim 20, wherein a twist direction of a liquid crystal twist angle of the liquid crystal layer, a principal axis twist angle of the first optical medium, and a principal axis twist angle of the second optical medium. A liquid crystal display device characterized in that the total sum considering a sign in which one of the two is positive is not less than −10 degrees and not more than +10 degrees. 22. The liquid crystal display device according to claim 20, wherein the retardation of the liquid crystal layer is RLC,
Let the retardation (or equivalent retardation) of the first phase plate be Rneff and the retardation (or equivalent retardation) of the second phase plate be Rneff.
If peff, 0.95 ≦ (Rneff−Rpeff) /
A liquid crystal display device, wherein a relationship of RLC ≦ 1.0 is satisfied. 23. The liquid crystal display device according to claim 17, wherein the main axis direction of the first optical medium is tilted and the tilt angle is the first phase. It increases and decreases along the thickness direction of the board, and
The degree of increase / decrease of the tilt angle of the first optical medium includes the degree of increase / decrease of the tilt angle of the liquid crystal molecules along the thickness direction of the liquid crystal layer when no display voltage is applied, and the degree of increase / decrease of the second optical direction along the thickness direction of the second phase plate A liquid crystal display device, which is adapted to increase or decrease the tilt angle of a medium. 24. A phase plate, wherein optical media having negative refractive index anisotropy are twisted. 25. A layer in which a first optical medium having a negative refractive index anisotropy is twisted and arranged, and a second layer having a positive refractive index anisotropy.
A phase plate, wherein the optical medium is laminated with a layer in which the first optical medium is twisted and arranged in reverse. 26. A step of forming an optical layer composed of a polymer network and a nematic liquid crystal arranged in the polymer network, a step of removing the nematic liquid crystal from the optical layer, and a step of removing the nematic liquid crystal. Filling the first holes of the optical layer with a first discotic liquid crystal. 27. The method for manufacturing a phase plate according to claim 26, further comprising a step of cross-linking the first discotic liquid crystal or cross-linking the first discotic liquid crystal with the polymer network. Characteristic method for manufacturing a phase plate. 28. The method for manufacturing a phase plate according to claim 26, wherein the step of forming the optical layer comprises: forming a mixture layer comprising a photopolymerizable polymer and a nematic liquid crystal on an alignment-treated substrate. And a step of irradiating the mixture layer with light, thereby curing the photopolymerizable polymer in the mixture layer to form a polymer network. 29. The method for manufacturing a phase plate according to claim 28, wherein when irradiating the mixture layer with light, an electric field or a magnetic field is applied to the mixture layer along a substantially normal direction thereof. Method for manufacturing a phase plate. 30. The method for manufacturing a phase plate according to claim 26, wherein the first holes are filled with the first discotic liquid crystal, and then the polymer network is removed from the optical layer. And a step of filling a second hole of the optical layer formed by removing the polymer network with a second discotic liquid crystal. 31. The method of manufacturing a phase plate according to claim 30, wherein the first holes are filled with a first discotic liquid crystal, or the second holes are filled with a second discotic liquid crystal. A method for manufacturing a phase plate, further comprising a step of forming a film layer on the back surface of the optical layer after the filling, after filling. 32. The method for manufacturing a phase plate according to claim 30, further comprising a step of cross-linking the second discotic liquid crystal.