JP3335119B2 - Reflective liquid crystal electro-optical device and projection display system using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal electro-optical device utilizing the electro-optical characteristics of a liquid crystal used in, for example, a display device or an information processing device. The present invention relates to a projection display system.

[0002]

2. Description of the Related Art Conventionally, an ECB mode liquid crystal electro-optical device using an electrically controlled birefringence effect has been known. Such a liquid crystal electro-optical device is, for example, as shown in FIG. The substrate 51 on which the electrode 52 and the orientation control layer 53 are formed, and the substrate 57 on which the electrode 56 and the orientation control layer 55 are formed are bonded via a spacer 59 and a sealing material 58. A liquid crystal 54 having a negative dielectric anisotropy is filled therebetween so as to be vertically aligned, and polarizers 60 and 61 are disposed on both outer sides of the liquid crystal electro-optical element thus formed. Has become.

In the ECB mode liquid crystal electro-optical device having such a structure, when no electric field is applied to the electrodes 52 and 56, light is not transmitted because there is no birefringence effect.
Further, when an electric field is applied to the electrodes 52 and 53, the liquid crystal molecules 54 are inclined in the horizontal direction, and light is transmitted by the birefringence effect.

Then, as shown in FIG. 7, for example, by disposing polarizing plates 10 and 11 whose polarizing axes are orthogonal to each other on both sides of the liquid crystal electro-optical element configured as described above,
The above-described light transmission and non-transmission can be recognized as a dark state and a bright state, respectively, and thus, it can be used as a display element.

Usually, in the case of a liquid crystal electro-optical device having such a structure, the direction in which the liquid crystal molecules 54 are tilted by an electric field is as follows.
It has been found that it is more preferable to incline in a fixed direction than to be random in view of screen uniformity and contrast.

Furthermore, the direction in which the liquid crystal molecules 54 are tilted is
In the case of a liquid crystal electro-optical device having a configuration as shown in FIG.
When the polarization axis of one polarizing plate 10 is set at 45 degrees from the polarization axis of the other polarizing plate 11, the display in the bright state becomes the brightest, and in such a case, good display with high contrast is performed. It has become possible.

A reflection type liquid crystal electro-optical device can be realized by the same concept as the ECB mode liquid crystal electro-optical device using the electrically controlled birefringence effect as described above.

This is, for example, as shown in FIG.
2 and the substrate 57 on which the electrode 56 and the orientation control layer 55 are formed,
Affixed via a spacer 59 and a sealing material 58,
A liquid crystal electro-optical element filled so that liquid crystal 53 having a negative dielectric anisotropy is vertically aligned between the substrates 51 and 57 is sandwiched between a polarizing device 62 and a reflecting device 63. By configuring the polarizing device 62 so that the polarization axis of the incident light is orthogonal to the polarization axis of the outgoing light, it is possible to display a dark state when no electric field is applied and a bright state when an electric field is applied. Thus, it can be used as a display element.

The same applies to the case of such a reflection type liquid crystal electro-optical device. The direction in which the liquid crystal molecules 54 incline in a fixed direction rather than in a random direction due to the electric field is better than that in the screen. The direction in which the liquid crystal molecules 54 are inclined is preferable in terms of uniformity and contrast, and the display in the bright state becomes the brightest by setting one polarization axis to a direction of 45 degrees from the other polarization axis, In such a case, it is possible to perform good display with high contrast.

[0010]

However, in such a liquid crystal electro-optical device using the ECB mode,
In a uniaxial orientation control method such as a rubbing method which is usually used,
There has been such a problem that the uniaxial orientation in the plane of the liquid crystal electro-optical element and the in-plane uniformity of the pretilt angle at which the liquid crystal molecules rise from the substrate surface are slightly varied.

This is because the interaction between the physical property value of the liquid crystal molecules in the minor axis direction and the surface of the alignment film is reduced because the pretilt angle is particularly large in the case of the vertical alignment film. This is because it is considered to be larger.

In addition, for high contrast display, as described above, both the upper and lower substrates have a uniaxial orientation direction that is 4 degrees from the polarization axis.
When the direction is set to 5 degrees, since the orientation control directions of the upper and lower substrates are parallel or anti-parallel to each other, especially in the halftone state to the bright state, these in-plane variations are strengthened mutually in the upper and lower substrates. This causes a streak-like light / dark unevenness parallel to the orientation direction, which has a problem that display quality is significantly reduced.

Further, in the reflection type liquid crystal electro-optical device as shown in FIG. 8, since light passes through the liquid crystal electro-optical element twice, it is more susceptible to the above-mentioned in-plane variation. It also has the problem of getting lost.

The present invention has been made in view of such a conventional problem, and suppresses the stripe-shaped display unevenness in which the alignment control direction appears as described above, and has a high contrast and a high display quality reflection. It is an object of the present invention to provide a liquid crystal electro-optical device and a projection display system using the same.

[0015]

According to the reflection type liquid crystal electro-optical device of the present invention, a reflection device and at least two substrates on which at least electrodes and an orientation control layer are formed are opposed to each other. In a reflective liquid crystal electro-optical device including a liquid crystal electro-optical element in which a liquid crystal layer is sealed therebetween, and a polarizing device disposed on the opposite side of the liquid crystal electro-optical element from the reflective device, the liquid crystal layer includes: When no electric field is applied by the alignment control layer, the liquid crystal molecules are oriented at 70 to 90 degrees with respect to the substrate, and when an electric field is applied, the liquid crystal molecules existing near the center in the thickness direction of the liquid crystal layer are The liquid crystal molecules are oriented substantially parallel to the substrate, and the angle between the azimuth of the liquid crystal molecules on the one substrate and the azimuth of the liquid crystal molecules on the other substrate is 45 to 135 degrees, 225 to 225.
The polarization device has a polarization axis on the incident light side and a polarization axis on the emission light side of the liquid crystal electro-optical element, and the polarization axis on the incident light side and the polarization axis on the emission light side. The axes are substantially perpendicular to each other, and the azimuthal angle of the liquid crystal molecules on the one substrate and the liquid crystal molecules on the one substrate is substantially coincident with each other. You.

At this time, the reflection device may be a reflection electrode provided on a substrate of the liquid crystal electro-optical element opposite to the polarization device.

Further, the liquid crystal layer may be a nematic liquid crystal material having negative dielectric anisotropy.

Further, the liquid crystal layer may contain a chiral dopant for causing liquid crystal molecules to twist.

Further, the alignment control layer formed on the substrate comprises a vertical alignment film, and the azimuthal angle of the liquid crystal molecules on at least one of the substrates is determined by rubbing the vertical alignment film formed on the one substrate. It may be controlled by applying.

A projection type display system using the reflection type liquid crystal electro-optical device according to the present invention comprises a reflection type liquid crystal electro-optical device, a light source, and a reflection type liquid crystal electro-optical device on a side opposite to the reflection device. A projection lens disposed thereon, and a screen for projecting an image displayed by the reflection type liquid crystal electro-optical device through the projection lens, and a polarizing beam splitter or the like as a polarizing device of the liquid crystal electro-optical device. It is characterized by using a polarized light selective reflection plate that can obtain the effect of the above, so that in such a projection display system, display is performed by an image projected on a screen, so that a wide viewing angle characteristic is required. Instead, the liquid crystal electro-optical device of the present invention can exhibit the characteristics such as high brightness and high contrast to the maximum.

[0021]

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

FIG. 1A is a sectional view showing the structure of the liquid crystal electro-optical device according to the present embodiment. As shown in the figure, a substrate 1 on which an electrode 2 and an orientation control layer 3 are formed
And the substrate 7 on which the electrode 6 and the orientation control layer 5 are formed, are adhered via the spacer 9 and the sealing material 8,
N having a chiral dopant added between the substrates 1 and 7
The liquid crystal electro-optical element is constituted by filling the nematic liquid crystal layer 4.

The alignment control layers 3 and 5 formed on the substrates 1 and 7 are composed of a vertical alignment film.
The substrates 4 and 15 are bonded so as to form an angle θ between the substrates 1 and 7.

On the other side of the substrate 1 opposite to the liquid crystal layer 4, there is provided a polarizing device 12 configured such that the polarization axis 16 of the incident light and the polarization axis 17 of the output light are orthogonal to each other. , The polarization axis 16 of either incident light or outgoing light,
17 is configured to coincide with the direction of any one of the orientation azimuths 14 and 15 of the substrates 1 and 7.

On the other side of the other substrate 7 opposite to the liquid crystal layer 4, there is provided a reflecting device 13 made of a metal such as aluminum or a dielectric material. It has a configuration sandwiched by the device 13.

In the liquid crystal electro-optical device thus configured, when no electric field is applied to the above-described liquid crystal electro-optical element, as shown in FIG.
7, and when an electric field is applied to the above-mentioned liquid crystal electro-optical element (the brightest state), as shown in FIG. The liquid crystal molecules 4 existing near the center are oriented in a state (substantially parallel) where the angle with respect to the substrates 1 and 7 is reduced.

When an electric field is not applied to the above-described liquid crystal electro-optical element, the orientation angle of the liquid crystal molecules 4 with respect to the substrates 1 and 7 does not need to be strictly perpendicular, but is 70 to 9 degrees.
0 degree, more preferably about 85 to 90 degrees,
Within such a range, it is possible to obtain substantially the same effect as in the state where the liquid crystal molecules 4 are vertically aligned with respect to the substrates 1 and 7.

The liquid crystal electro-optical device according to the present embodiment can be manufactured as follows.

In the liquid crystal electro-optical device according to the present embodiment, as shown in FIG. 1A, at least one of two substrates 1 and 7 which are transparent is disposed to face each other. This 2
Glass, quartz, ceramic resin, or the like can be used for the substrates 1 and 7, and a transparent conductive film to be the electrodes 2 and 6 is formed on the substrates 1 and 7 by a sputtering method or the like. I have. When a reflection electrode is used as the reflection device 13, the electrode 6 is formed on the other substrate 7 using a metal film such as aluminum or a dielectric.

On the electrodes 2 and 6, vertical alignment films having liquid crystal molecules 4 having an orientation perpendicular to the substrates 1 and 7 were applied as alignment control layers 3 and 5. Various types of such vertical alignment films can be used. In this embodiment, polyimide having a side chain such as JALS-203 (manufactured by Nippon Synthetic Rubber Co., Ltd.) is printed by a printing method. Formed.

Thereafter, as shown in FIGS. 1B and 1C, the surfaces of the alignment control layers 3 and 5 made of a vertical alignment film were subjected to a uniaxial alignment treatment using a rubbing method. Thus, the direction in which the liquid crystal molecules 4 fall when an electric field is applied can be aligned in one direction.

The two substrates 1 thus formed,
A spacer 9 having a diameter of 3 μm is sprayed on one of the substrates 7, a sealing material 8 is applied to the outside of the other display area, and the substrates 1 and 7 are bonded to each other. The injection port was sealed by injecting a nematic liquid crystal.

At this time, as shown in FIGS. 1B and 1C, the two substrates 1 and 7 are bonded so that the uniaxial azimuthal angles 14 and 15 become the angle θ between the substrates 1 and 7. I combined. This angle θ is 45 to 135 degrees, 225 to 31 depending on the application.
It can be set to 5 degrees, but more preferably 80
-100 degrees and 260-280 degrees. In this case, the stripe-like light and dark unevenness was minimized, and the contrast was improved. In the present embodiment, θ is set to 90 degrees.

Thereafter, the liquid crystal 4 is heated to a temperature at which the liquid crystal 4 becomes isotropic or higher, and then cooled to complete the liquid crystal electro-optical element according to the present embodiment.

In the method of manufacturing such a liquid crystal electro-optical element, the liquid crystal 4 can be injected between the substrates 1 and 7 by a usual method. Since injection is not required, the manufacturing process can be greatly simplified.

Although the above-mentioned liquid crystal and chiral dopant have a very large variety and a wide range of choices, in the present embodiment, MLC2012 (manufactured by Merck) is used as the liquid crystal, and S-811 (manufactured by Merck) is used as the chiral dopant. Was used. When the operating temperature range of the liquid crystal electro-optical device is widened, a material may be used in which the temperature dependence of the helical twisting power of the chiral dopant is reversed.

A polarizing beam splitter whose polarization axes 16 and 17 are orthogonal to the incident light and the outgoing light is provided on one outside of the liquid crystal electro-optical element manufactured as described above. Are arranged so as to coincide with the uniaxial azimuthal angles 14 and 15 of one of the substrates of the liquid crystal electro-optical element, and a reflection device 13 using an aluminum mirror surface is arranged outside the other side of the liquid crystal electro-optical element. Thus, the liquid crystal electro-optical device according to the present embodiment is completed. At this time, if the degree of polarization is insufficient, a polarizing plate may be inserted.

The liquid crystal electro-optical device manufactured by the above-described manufacturing method has the following characteristics.

(Embodiment 1) In the liquid crystal electro-optical device described above, the uniaxial orientation azimuth 1
The angle θ of 4 and 15 was set to 90 degrees, and the helical pitch in nematic was adjusted as shown in FIG. 2 by changing the addition concentration of the chiral dopant, to produce three n-type nematic liquid crystal compositions, each of which was injected. Three liquid crystal electro-optical devices were manufactured.

Comparative Example 1 In order to compare the characteristics of the above-mentioned liquid crystal electro-optical device, a normal ECB type liquid crystal electro-optical device was manufactured as follows. In this liquid crystal electro-optical device, the angle θ of the orientation azimuth of the upper and lower substrates is 180 degrees.
Degree, that is, anti-parallel, and the liquid crystal electro-optical element is arranged such that the orientation azimuth is 45 degrees from each of the polarization axes of the incident light and the reflected light, which are orthogonal to each other, so that the display with the highest contrast can be performed. Placed. The liquid crystal used was an n-type nematic liquid crystal MLC2012 (manufactured by Merck) to which no chiral dopant was added. E of this comparative example
The CB type liquid crystal electro-optical device was manufactured in this manner.

FIG. 4 shows a voltage-transmittance curve when the liquid crystal electro-optical device manufactured according to the first embodiment and the comparative example 1 is observed from the front at normal temperature. Here, the voltage V (V) is plotted on the horizontal axis, and the reflectance R is plotted on the horizontal axis.
(%). In the figure, A denotes the first embodiment.
3 shows a voltage-transmittance curve of the liquid crystal electro-optical device including the composition 1 in the above-described example, and B indicates a voltage-transmittance curve of the liquid crystal electro-optical device including the composition 2 in the first embodiment. Indicates a voltage-transmittance curve of the liquid crystal electro-optical device including the composition 3 in the first embodiment, and D indicates a voltage-transmittance curve of the ECB-type liquid crystal electro-optical device manufactured in Comparative Example 1.

As is clear from FIG. 4, the longer the helical pitch of the nematic liquid crystal, the brighter the display becomes. The better the display, the better the liquid crystal including the composition 1 having the longest pitch in the first embodiment. The voltage-transmittance curve of the electro-optical device shows almost the same characteristics as the voltage-transmittance curve of the ECB-type liquid crystal electro-optical device, so that high-contrast display can be performed.

The contrast ratio of each liquid crystal electro-optical device manufactured as described above is as shown in FIG.
In each case, a high contrast is realized. In particular, in the liquid crystal electro-optical device including the composition 1 according to the first embodiment, the contrast is almost the same level as that of the normal ECB-type liquid crystal electro-optical device manufactured in Comparative Example 1. Can be realized.

Regarding the streak-like light / dark unevenness conventionally appearing parallel to the uniaxial orientation azimuth angle, although the ECB-type liquid crystal electro-optical device manufactured according to Comparative Example 1 is very much generated, However, in the liquid crystal electro-optical device manufactured according to the first embodiment, almost no confirmation was possible.

Accordingly, with respect to the in-plane uniformity of the display at the time of halftone display, the liquid crystal electro-optical device manufactured according to the first embodiment is better than the EC manufactured according to the comparative example 1 above.
It is much higher than a B-type liquid crystal electro-optical device, and can exhibit good display characteristics.

From the above results, the liquid crystal electro-optical device manufactured according to the first embodiment has high brightness and high contrast and excellent electro-optical characteristics equivalent to those of a normal ECB type liquid crystal electro-optical device. It has been found that it is possible to prevent the occurrence of streak-like uneven brightness which is a problem in the conventional ECB-type liquid crystal electro-optical device.

In the liquid crystal electro-optical device manufactured according to the first embodiment, a polyimide having a side chain is used as the vertical alignment film. The polyimide having such a side chain has excellent pretilt angle reliability, In addition, since the ionic substance does not seep into the liquid crystal and the reliability of the voltage holding ratio indicating the specific resistance value of the liquid crystal is excellent, the liquid crystal electro-optical device does not degrade the display quality even when used for a long time. Has a unique effect that it becomes possible to obtain

Further, the liquid crystal electro-optical device of the present invention is not limited to the above-described first embodiment, but can be applied to, for example, a simple matrix type liquid crystal electro-optical device. Can be applied to an active matrix type liquid crystal electro-optical device provided with a MIM element, a thin film transistor using amorphous silicon, polysilicon, crystallized silicon, or the like.
When combined with a color filter or the like, it can be used as a liquid crystal electro-optical device for color display.

(Embodiment 2) Next, a projection type display system manufactured by combining a projection lens and a light source with a liquid crystal electro-optical device manufactured in the same manner as in Embodiment 1 will be described.

FIGS. 5 and 6 are schematic diagrams showing a projection type display system according to the second embodiment.

As shown in FIG. 5, the projection type display system according to the second embodiment includes a projection lens 22, a light source 23, and a liquid crystal electro-optical element 20 on the side opposite to the reflection device 21.
A polarizing beam splitter 24 is disposed, and the light 25 projected from the light source 23 performs projection display on a screen 26.

As shown in FIG. 6, a λ / 4 plate 27, a polarizing plate 28, a projection lens 22, a light source 23, and a beam splitter 29 are disposed on the liquid crystal electro-optical element 20 on the side opposite to the reflection device 21. The configuration may be as follows.

In such a projection type display system, a wide viewing angle characteristic is not required since display is performed by an image projected on the screen 26, and characteristics such as high brightness and high contrast of the liquid crystal electro-optical device of the present invention are not required. It is possible to demonstrate to the maximum.

In the second embodiment, a simple projection type display system is shown. However, for example, a configuration in which various lenses including a micro lens, a prism, a color filter, a dichroic mirror, and the like are combined is also possible. Also, a configuration using a plurality of liquid crystal electro-optical elements may be used.

[0055]

As described above, according to the present invention,
Reflection-type liquid crystal electro-optical device with high contrast and high display quality, which can suppress the stripe-shaped display unevenness in which the alignment control direction has been a problem, and a projection display using the same. It is possible to realize the system.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view illustrating a configuration of a liquid crystal electro-optical device according to the present embodiment, and FIG.
FIG. 1C is a schematic cross-sectional view illustrating an orientation azimuth angle and a polarization axis when an electric field is not applied to the liquid crystal electro-optical element in FIG. 1A. FIG. FIG. 3 is a schematic cross-sectional view showing an orientation azimuth angle and a polarization axis when an electric field is applied.

FIG. 2 is a drawing showing a helical pitch length of an n-type nematic liquid crystal composition injected into three liquid crystal electro-optical devices according to the first embodiment.

FIG. 3 is a drawing showing the contrast of each liquid crystal electro-optical device according to the first embodiment and Comparative Example 1.

FIG. 4 is a diagram showing a voltage-transmittance curve when each of the liquid crystal electro-optical devices according to Embodiment 1 and Comparative Example 1 is observed from the front at normal temperature.

FIG. 5 is a schematic configuration diagram illustrating a projection display system according to a second embodiment.

FIG. 6 is a schematic configuration diagram illustrating a projection display system according to a second embodiment.

FIG. 7 shows a conventional EC using a birefringence effect.
FIG. 3 is a cross-sectional view illustrating a configuration of a B-mode liquid crystal electro-optical device.

FIG. 8 shows a conventional EC using a birefringence effect.
FIG. 3 is a cross-sectional view illustrating a configuration of a B-mode reflective liquid crystal electro-optical device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Electrode 3 Alignment control layer 4 Liquid crystal 5 Alignment control layer 6 Electrode 7 Substrate 8 Sealing material 9 Spacer 10 Polarizer 11 Polarizer 12 Polarizer 13 Reflector 14 Orientation azimuth 15 Orientation azimuth 16 Incident side polarization axis 17 Emission Side polarization axis 18 Electric field direction 20 Liquid crystal electro-optical element 21 Reflector 22 Projection lens 23 Light source 24 Polarizing beam splitter 25 Light 26 Screen 27 λ / 4 plate 28 Polarizing plate 29 Beam splitter 51 Substrate 52 Electrode 53 Alignment control layer 54 Liquid crystal 55 Orientation control layer 56 Electrode 57 Substrate 58 Sealing material 59 Spacer 60 Polarizer 61 Polarizer 62 Polarizer 63 Reflector

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI G02F 1/1343 G02F 1/1343 (56) References JP-A-3-95517 (JP, A) JP-A-6-337421 (JP, A) JP-A-7-230097 (JP, A) JP-A 8-201802 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/13-1/141

Claims (6)

(57) [Claims] 1. A liquid crystal electro-optical element comprising: a reflecting device; two substrates on which at least electrodes and an orientation control layer are formed; and a liquid crystal layer sealed between the substrates. In a reflection type liquid crystal electro-optical device comprising a polarizing device disposed on the side opposite to the reflection device of the liquid crystal electro-optical element, the liquid crystal layer is formed by the alignment control layer when liquid crystal molecules are applied to the substrate when no electric field is applied. The liquid crystal molecules are oriented at 70 to 90 degrees with respect to the liquid crystal molecules, and the liquid crystal molecules existing near the center in the thickness direction of the liquid crystal layer are oriented substantially parallel to the substrate when an electric field is applied. The angle formed between the azimuth of the liquid crystal molecules on one substrate and the azimuth of the liquid crystal molecules on the other substrate is set to 45 to 135 degrees and 225 to 315 degrees. Entering the element It has a polarization axis on the light side and a polarization axis on the output light side, and the polarization axis on the incident light side and the polarization axis on the output light side are substantially orthogonal, and the polarization axis on the one side and the one on the one side A reflection type liquid crystal electro-optical device, wherein the azimuth of liquid crystal molecules on a substrate substantially coincides with each other. 2. The reflection-type liquid crystal electro-optic according to claim 1, wherein the reflection device is a reflection electrode provided on a substrate of the liquid crystal electro-optical element opposite to the polarization device. apparatus. 3. The reflective liquid crystal electro-optical device according to claim 1, wherein the liquid crystal layer is made of a nematic liquid crystal material having negative dielectric anisotropy. 4. The reflection type liquid crystal electro-optical device according to claim 1, wherein the liquid crystal layer contains a chiral dopant for causing liquid crystal molecules to be twisted. 5. The alignment control layer formed on the substrate comprises a vertical alignment film, and the azimuthal angle of the liquid crystal molecules on at least one substrate is determined by rubbing the vertical alignment film formed on the one substrate. 5. The reflection type liquid crystal electro-optical device according to claim 1, wherein the reflection type liquid crystal electro-optical device is controlled by performing the application. 6. The reflection type liquid crystal electro-optical device, a light source, a projection lens disposed on a side of the reflection type liquid crystal electro-optical device opposite to the reflection device, and an image displayed by the reflection type liquid crystal electro-optical device. A screen for projecting the projected image through the projection lens, and using a polarization beam splitter or a polarization selective reflection plate having the same effect as the polarization beam splitter as the polarization device of the liquid crystal electro-optical device. 6. A projection display system using the reflective liquid crystal electro-optical device according to any one of 1 to 5.