JPH0627467A - Liquid crystal optical device - Google Patents

Abstract

PURPOSE:To improve the ratio of contrast of the case at the time of transmitting light to that of shielding light in the case of using a liquid crystal panel using a field effect birefringence mode. CONSTITUTION:The orientation processing direction of a first orientation film formed on a first electrode 2 and one face of a first base plate is defined as an arrow mark A direction, and the orientation processing direction of a second orientation film formed on a second electrode (5) and the face of a second base plate formed by the second electrode (5) is defined as an arrow B direction set at an angle of 135 deg. to the arrow A. The directions of polarizing axes of first and second polarizing plates (10) and 11 arranged in cross nicol are respectively defined as straight line C and D directions, and the bisector of the angle formed by the arrow A and B is set at an angle of 45 deg. to both the straight lines C and D. When voltage is applied to the first and second electrodes (2) and 5, the birefringence component due to liquid crystal molecule held in the orientating state without being induced by electric field near the interface of the first base plate is canceled by the birefringence component due to liquid crystal molecule held in the orientating state being induced by electric field near the interface of the second base plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal optical device utilizing a birefringence mode.

[0002]

2. Description of the Related Art Conventionally, a birefringence mode liquid crystal optical device using a nematic liquid crystal having a positive dielectric anisotropy has a liquid crystal interposed between electrodes aligned uniaxially horizontally on a panel surface by an alignment film. The two polarizing plates are arranged in a crossed nicols position, and the long axis direction of the aligned liquid crystal molecules has an angle of 45 ° with respect to the polarizing axis of the polarizing plate. Display and the like are performed by utilizing the light transmission state when no electric field is applied (see FIG. 10a) and the light blocking state when an electric field is applied (see FIG. 10b).

[0003]

In the above, FIG.
As shown in 0b, even when an electric field is applied to the electrodes, liquid crystal molecules near the interface on the inner surface of the panel are held in a horizontal state with respect to the panel surface by adsorption with the alignment film. Therefore, in the case of a liquid crystal optical device having a thin cell thickness of 2 μm or less, for example, the light leakage due to the liquid crystal molecules in the horizontally aligned state becomes relatively large in the light-shielded state, and the light blocking property is deteriorated. There is a problem that the contrast ratio between the time of transmission and the time of interruption is lowered.

An object of the present invention is to improve the contrast ratio when light is transmitted and when light is blocked when a liquid crystal panel using a field effect birefringence mode is used.

[0005]

According to the present invention, a first electrode formed on one surface of a first substrate and a first electrode formed on one surface of the first substrate and subjected to a homogeneous alignment treatment. 1
Alignment film, a second electrode formed on one surface of the second substrate facing the one surface of the first substrate, and a homogeneous alignment treatment formed on the one surface side of the second substrate. Nematic with a positive dielectric anisotropy, which is oriented in the alignment treatment direction of the first and second alignment films and is interposed in the gap between the aligned second alignment film and the first alignment film and the second alignment film. Liquid crystal optics having liquid crystal and first and second polarizing plates arranged on the other surface side of the first substrate and the other surface side of the second substrate and having their polarization axes in crossed Nicols positions. In the device,
A desired angle is formed between the alignment treatment direction of the alignment film and the alignment treatment direction of the second alignment film, and the direction which is 1/2 of the narrow angle formed by the alignment treatment directions of the respective alignment films is the first direction. 1 and 2
The above object is achieved by forming an angle of 45 degrees or its vicinity with the polarization axis of the polarizing plate.

A compensating means for canceling the birefringence component of the liquid crystal molecules held in the aligned state when an electric field is applied between the first and second electrodes is provided between the first and second polarizing plates. By providing it, the above-mentioned object is achieved.

Further, the compensating means is a retardation film for canceling the birefringence component of the liquid crystal molecules held in the alignment state when an electric field is applied between the first and second electrodes, You have achieved your purpose.

Further, the above object is achieved by forming the retardation film by laminating a plurality of retardation films having different retardations so that the stretching directions thereof are orthogonal to each other.

Further, the retardation film is divided into a plurality of retardation films having different retardations and arranged on the other surface side of the first and second substrates so that the stretching directions thereof are orthogonal to each other. By doing so,
It has achieved the above objectives.

Furthermore, when the electric field is applied between the first and second electrodes by the compensating means, the birefringence component of the liquid crystal molecules held in the aligned state on the side of the first alignment film is offset. A second retardation film and a second retardation film for canceling the birefringence component of the liquid crystal molecules held in the aligned state on the side of the second alignment film.
The above object is achieved by using the retardation film of

Further, the first and second retardation films each have a different retardation and are made up of a plurality of retardation films whose stretching directions are orthogonal to each other. Has achieved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on an embodiment shown in the drawings.

In FIG. 1, reference numeral 1 denotes a first substrate, which is made of glass or the like, on which a first electrode 2 made of ITO (tin oxide-doped indium oxide) or the like is selectively formed on one surface. There is. A first alignment film 3 is made of polyimide or the like and is formed on the first electrode 2 and one surface of the first substrate 1.

A second substrate 4 is made of glass or the like, and a second electrode 5 made of ITO or the like is selectively formed on the surface facing the first electrode 2. A second alignment film 6 is made of polyimide or the like and is formed on the second electrode 5 and on the surface of the second substrate on which the second electrode 5 is formed.

The alignment treatment direction of the first alignment film 3 is the direction of arrow A shown in FIG. 2, and the alignment treatment direction of the second alignment film 6 is an angle of 135 degrees with this arrow A direction in this example. It is in the direction of arrow B. 2 is a plan view of FIG.

Reference numeral 7 denotes a spacer, which is made of a photosensitive acrylic resin or the like and is formed by a photolithography method in the present embodiment to about 1.8.
It is formed to a film thickness of μm. 8 is a sealant.

Reference numeral 9 is a nematic liquid crystal having a positive dielectric anisotropy, which is injected between the first alignment film 3 and the second alignment film 6, and the first alignment film 3 and the second alignment film 6 are injected. 6, the long-axis direction of the molecule is twisted by 45 degrees from the first substrate 1 to the second substrate 4 so that the orientation is homogeneous.

Reference numerals 10 and 11 are polarizing plates, and the polarizing plate 10 is the first
Is disposed on the other surface side of the first substrate 1, the polarizing plate 11 constitutes a second polarizing plate, and the second electrode 5 of the second substrate 4 is formed. It is placed on the side not facing. The polarization axis of the polarizing plate 10 is the straight line C shown in FIG.
Direction, and the polarization axis of the polarizing plate 11 is in the direction of the straight line D orthogonal to the straight line C so that they are in the crossed Nicols position. In this example, the angle θ formed by the arrow A and the straight line C is 22.5.
To make an angle of degree, that is, the narrow angle of arrows A and B
The angle of / 2 is arranged so as to form an angle of 45 degrees with the straight lines C and D.

With the above-mentioned structure, when a voltage is applied to the first electrode 2 and the second electrode 5, it is attracted to the first alignment film 3 or the like, and thus near the interface of the first substrate 1. The birefringence component due to the liquid crystal molecules 9 held in the alignment state in the direction of arrow A in FIG. 2 without being induced by the electric field (the phase of light oscillated in the long axis direction of the liquid crystal molecules 9 and the direction oscillated in the direction orthogonal to the long axis direction) 2) without being induced by the electric field near the interface of the second substrate 4 due to adsorption with the second alignment film 6 or the like.
Birefringence component due to liquid crystal molecules 9 held in the alignment state in the direction of arrow B (phase difference between the phase of light oscillated in the long axis direction of liquid crystal molecules 9 and the phase of light oscillated in the direction orthogonal to the long axis direction) Offset by the first electrode 2 and the second electrode 5
The light-shielding property when a voltage is applied between them is improved.

According to the experimental results shown in FIG. 3, the liquid crystal interposed between the electrodes was uniaxially aligned horizontally on the panel surface by the alignment film, and the polarizing plates outside the panel were positioned at the crossed Nicols position and aligned. The contrast ratio of the liquid crystal panel according to the present invention is improved by about 40% as compared with the conventional one in which the major axis direction of the liquid crystal molecules is arranged at an angle of 45 ° with respect to the polarization axis of the polarizing plate. You can see that

The material and the film thickness of the spacer 7 are not limited to the above and can be changed as appropriate, but even if the spacer is thinner than the above, the same effect as above can be obtained.

In the above example, the first alignment film 3 and the second alignment film 3
Since the angle direction which is 1/2 of the angle formed by the alignment treatment direction with the alignment film 6 is formed at an angle of 45 degrees with the respective polarization axes of the first polarizing plate 10 and the second polarizing plate 11, Although good contrast is obtained, this is not limited to the above, and an angle in the vicinity of 45 degrees, for example, an angle of 40 degrees to 50 degrees may be used. The angle formed by the alignment treatment direction is not limited to the above, and may be, for example, 120 degrees to 150 degrees. In this case, by arranging the narrow angle bisectors to form the polarization axis at 45 degrees, The same effect can be obtained.

In the above-described example, in the liquid crystal optical device using the field effect birefringence mode, the liquid crystal is twisted and aligned at a predetermined angle to attract the alignment film generated on the first substrate side to the vicinity of the substrate interface. The birefringence component (phase difference) due to the liquid crystal molecules which is not induced by the electric field and is maintained by the liquid crystal molecules which is maintained by the liquid crystal molecules which is not induced by the electric field on the second substrate side. Although an example in which the birefringence component (phase difference) that occurs is used to cancel the phase difference, an example in which the retardation film eliminates the phase difference of light due to the birefringence that cannot be canceled even in the above example will be described.

In FIG. 4, reference numerals 12 and 13 denote retardation films, which are laminated between the first substrate 1 and the polarizing plate 10 in this example, and the stretching direction of the retardation film 12 is shown in FIG. The straight line E direction is set, and the stretching direction of the retardation film 13 is the straight line F direction orthogonal to the straight line E. By thus making the stretching directions of the two retardation films orthogonal to each other, a desired retardation can be obtained by the difference in retardation of the two retardation films. The light-shielding property is improved by making the phase difference of the light to be canceled out the difference in the phase difference between the phase difference film 12 and the phase difference film 13. The same reference numerals as those in FIG. 1 are the same, and the alignment treatment directions of the first alignment film 3 and the second alignment film 6 and the polarization axes of the polarizing plates 10 and 11 are shown in FIG. 5, respectively. Arrow G, arrow H,
A straight line J and a straight line K are used. Arrow G, arrow H shown in FIG.
The straight line J and the straight line K correspond to the arrow A, the arrow B, the straight line C, and the straight line D shown in FIG. 2, respectively, and the straight line E represents an angle half the narrow angle of the arrow G and the arrow H. There is.

For example, when a voltage is applied to the first electrode 2 and the second electrode 5, the first substrate 1 and the second substrate 5
When the phase difference of the light of the birefringence component due to the liquid crystal molecules 9 held in the alignment state of the arrow G direction and the arrow H direction at the interface is 10 nm, the phase difference film 12 having a phase difference of 280 nm is By using each of the retardation films 13 having a retardation of 270 nm, the retardation of 10 nm due to the birefringence component can be canceled. That is, the retardation films 12, 13
Are laminated to form a retardation of 10 nm in the stretching direction (straight line J) of the retardation film 12, and this direction is at a half angle (straight line E) of the twist direction of the liquid crystal molecules and the polarization axis G. Therefore, the birefringence component due to the average long axis direction of the liquid crystal molecules when an electric field is applied is canceled by the retardation film.

FIG. 6 shows a liquid crystal optical device using the conventional field effect birefringence mode and the liquid crystal optical device of the above embodiment.
It is a thing which shows the voltage-contrast ratio characteristic at the time of applying the drive voltage of the square wave of +/- 10v and 10kHz between electrodes. Curve a is the characteristic of the conventional liquid crystal optical device,
Curve b is the characteristic of the liquid crystal optical device of the present embodiment. From the figure, it can be seen that the present invention can improve the contrast ratio.

In the above example, the retardation film is the first
Although it is arranged by laminating it between the substrate 1 and the polarizing plate 10, it may be arranged, for example, between the second substrate 4 and the polarizing plate 11, and each retardation film is arranged on the first substrate side. You may arrange | position separately from the 2nd board | substrate side.

Next, in the liquid crystal optical device using the field effect birefringence mode in which the liquid crystal is twisted and oriented at a predetermined angle as described above, the orientation which occurs on each substrate side when a voltage is applied between the electrodes. An example will be described in which the birefringence components due to the liquid crystal molecules that are kept in the aligned state without being induced by the electric field near the interface of the substrate due to adsorption with the film or the like are canceled using the retardation films.

In FIG. 7, reference numerals 14, 15, 16 and 17 denote retardation films. The retardation films 14 and 15 constitute a first retardation film, and are provided between the first substrate 1 and the polarizing plate 10. The stretching direction of the retardation film 14 arranged in layers is set to the bar line L direction shown in FIG. 8, and the stretching direction of the retardation film 15 is set to the bar line M direction orthogonal to the bar line L.
The retardation of the retardation film 14 and the retardation film 1
The difference from the phase difference of 5 is the phase difference due to the birefringence component of the liquid crystal molecules that are still held in the aligned state due to adsorption of the liquid crystal molecules 9 with the first alignment film 3. Retardation film 1
The second retardation film is composed of 6, 17
8 is laminated between the substrate 4 and the polarizing plate 11, and the retardation film 16 is stretched in the direction of the bar N shown in FIG. 8, and the retardation film 17 is stretched in the direction orthogonal to the bar N. The direction of line P is assumed. The difference between the retardation of the retardation film 16 and the retardation of the retardation film 17 is the difference between the liquid crystal molecules that are kept in the aligned state due to the adsorption of the liquid crystal molecules 9 with the second alignment film 6. The phase difference is due to the refraction component.

The same reference numerals as in FIG. 1 are the same, and the alignment treatment directions of the first alignment film 3 and the second alignment film 6 and the polarization axes of the polarizing plates 10 and 11 are as shown in FIG. The arrow Q, the arrow R, the straight line S, and the straight line T shown in FIG. The arrow Q, the arrow R, the straight line S, and the straight line T shown in FIG. 8 are respectively the arrow A, the arrow B, the straight line C, and the straight line C shown in FIG.
It is assumed that the bar line M is parallel to the arrow R and the bar line P is parallel to the arrow Q.

For example, when a voltage is applied to the first electrode 2 and the second electrode 5, the first substrate 1 and the second substrate 5
When the retardation of the light of the birefringence component by the liquid crystal molecules 9 which is held in the aligned state in the arrow Q direction and the arrow R direction at the interface of 10 nm is 10 nm, the retardation difference of the laminated retardation film is The retardation film 14 and the retardation film 16 each have a retardation of 280 nm so that the respective thicknesses are 10 nm.
The retardation film 17 having a retardation of 270 nm is used.

In this case, a retardation film having a retardation of 10 nm is provided between the first substrate 1 and the polarizing plate 10 and the long axis of the liquid crystal molecules 9 at the interface of the first substrate 1 with respect to the polarization axis of the polarizing plate 10. It is practically the same as existing at a position symmetrical to the direction. Therefore, when a voltage is applied to the first and second electrodes 2 and 5, the birefringence component due to the liquid crystal molecules 9 which are kept in the aligned state at the interface of the first substrate 1 is 10 nm.
It is offset by the retardation film. Further, in the same manner as above, a phase difference of 10n is provided between the second substrate 4 and the polarizing plate 11.
This is the same as the fact that the retardation film of m is present at a position symmetrical to the long axis direction of the liquid crystal molecules 9 at the interface of the second substrate 4 with respect to the polarization axis of the polarizing plate 11, and the same as above. The birefringence components generated at the interface of the second substrate 4 are canceled out.

FIG. 9 shows a liquid crystal optical device using the conventional field effect birefringence mode and the liquid crystal optical device of the above embodiment.
It is a thing which shows the voltage-contrast ratio characteristic at the time of applying the drive voltage of the square wave of +/- 10v and 10kHz between electrodes. The curve c is the characteristic of the conventional liquid crystal optical device,
A curve d is the characteristic of the liquid crystal optical device of this embodiment. From the figure, it is proved that the improvement of the contrast ratio has been achieved.

In the above example, the first retardation film is arranged on the side of the first substrate and the second retardation film is arranged on the side of the second substrate. Similar effects can be obtained by stacking and arranging on the first substrate side or the second substrate side.

The same applies to the above two embodiments in which the phase difference film is used to cancel the light leakage component.

The retardation of each retardation film is not limited to the above, and the same effect as above can be obtained by using, for example, a retardation film having a retardation of 300 nm and a retardation film having a retardation of 290 nm.

Further, the retardation due to the birefringence which is canceled by the retardation film is not limited to the above 10 nm, but can be appropriately changed according to the retardation to be canceled.

Further, a desired retardation was obtained by stacking two retardation films orthogonally to each other in the stretching direction. It is technically possible to obtain a minute retardation with one retardation film. This is because it is difficult, and if the desired retardation can be obtained with only one retardation film, the stretching direction should be set to an angle half the twist direction of the liquid crystal molecules, or the polarization of the polarizing plate. The same effect as described above can be obtained by setting the major axis direction of the liquid crystal molecules at the interface of the substrate with respect to the axis and the symmetric direction. Further, a desired retardation may be obtained by stacking two or more retardation films so that the stretching directions are orthogonal to each other.

The present invention can be applied to various display devices and liquid crystal shutters of optical printers.

[0040]

EFFECTS OF THE INVENTION A desired angle is formed between the alignment treatment direction of the first alignment film and the alignment treatment direction of the second alignment film, and 1 / n of the narrow angle formed by the alignment treatment directions of the respective alignment films. Since the direction of the angle 2 forms an angle of 45 degrees with or near the polarization axes of the first and second polarizing plates, it is not induced by an electric field near the substrate interface due to adsorption with the first alignment film or the like. Birefringence component (phase difference) due to liquid crystal molecules that are retained in the aligned state
Can be canceled by the birefringence component (phase difference) generated by the liquid crystal molecules that are held in the alignment state without being induced by the electric field near the substrate interface due to adsorption with the second alignment film, etc. It is possible to improve the light shielding property and the contrast ratio.

A compensating means for canceling the birefringence component of the liquid crystal molecules held in the alignment state when an electric field is applied between the first and second electrodes is provided between the first and second polarizing plates. By providing it, the light blocking property at the time of blocking light can be further enhanced, and the contrast ratio can be further enhanced.

Further, the compensating means is a retardation film for canceling the birefringence component of the liquid crystal molecules held in the alignment state when an electric field is applied between the first and second electrodes, whereby the light It is possible to further enhance the light-shielding property at the time of shutting off, and it is possible to further enhance the contrast ratio.

Further, the above retardation film is formed by laminating a plurality of retardation films having different retardations so that the stretching directions thereof are orthogonal to each other, whereby a retardation film having a desired retardation is obtained. Therefore, the phase difference due to the birefringence of the liquid crystal molecules held in the aligned state when an electric field is applied between the first and second electrodes can be reliably canceled by this laminated retardation film, The light-shielding property at the time of blocking can be further enhanced, and the contrast ratio can be further enhanced.

Further, the retardation film is divided into a plurality of retardation films having different retardations, and the retardation films are arranged on the other surface side of the first and second substrates so that the stretching directions thereof are orthogonal to each other. By doing so,
In addition to the effect similar to the above, the restriction on the arrangement position of the retardation film can be eliminated.

Furthermore, when the electric field is applied between the first and second electrodes by the compensating means, the birefringence component of the liquid crystal molecules held in the aligned state on the side of the first alignment film is offset. A second retardation film and a second retardation film for canceling the birefringence component of the liquid crystal molecules held in the aligned state on the side of the second alignment film.
When the voltage is applied to the first and second electrodes, the birefringent component due to the liquid crystal molecules held in the alignment state at the interface of the first substrate is Can be offset by the retardation film of
Since the birefringence component due to the liquid crystal molecules held in the alignment state at the substrate interface can be canceled by the second retardation film, the light-shielding property at the time of blocking light can be enhanced and the contrast ratio can be improved similarly to the above. .

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a front view of FIG.

FIG. 3 is an explanatory diagram showing a contrast ratio between the present invention and a conventional liquid crystal optical device.

FIG. 4 is a sectional view showing another embodiment of the present invention.

5 is a front view of FIG.

FIG. 6 is an explanatory diagram showing a voltage-contrast ratio between the present invention and a conventional liquid crystal optical device.

FIG. 7 is a sectional view showing another embodiment of the present invention.

FIG. 8 is a front view of FIG.

FIG. 9 is an explanatory diagram showing a voltage-contrast ratio between the present invention and a conventional liquid crystal optical device.

FIG. 10 is an explanatory diagram showing a state of liquid crystal molecules when an electric field is not applied and when an electric field is applied.

[Explanation of symbols]

 1 1st substrate 2 1st electrode 3 1st alignment film 4 2nd substrate 5 2nd electrode 6 2nd alignment film 9 Nematic liquid crystal with positive dielectric anisotropy 10 1st polarizing plate 11th 2 polarizing plate 12 retardation film 13 retardation film 14, 15 first retardation film 16, 17 second retardation film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideki Shoji 4-1-1 Taihei, Sumida-ku, Tokyo Inside Seikosha Co., Ltd. (72) Masanori Fujita 4-1-1 Taihei, Sumida-ku, Tokyo Shares Inside the company Seikosha

Claims (7)

[Claims] 1. A first substrate formed on one surface of a first substrate.
Electrode, a first alignment film formed on one surface side of the first substrate and subjected to a homogeneous alignment treatment, and one surface of the second substrate facing the one surface of the first substrate. A second electrode formed on the above, a second alignment film formed on one surface side of the second substrate and subjected to a homogeneous alignment treatment, the first alignment film and the second alignment film. A nematic liquid crystal having a positive dielectric anisotropy, which is aligned in the alignment treatment direction of the first and second alignment films and intervenes in the gap between, and the other surface side of the first substrate and the second substrate. A liquid crystal optical device having a first polarizing plate and a second polarizing plate disposed on the other surface side and having polarization axes in a crossed Nicol position, wherein the alignment treatment direction of the first alignment film and the second alignment film are the same. A desired angle is formed with the alignment treatment direction of the alignment film, and the alignment treatment of each alignment film is performed. Direction liquid crystal optical device in which the direction of the half angle of the narrow angle of the angle is equal to or constituting the polarization axis by 45 degrees or an angle in the vicinity of said first and second polarizing plates. 2. The first and second aspects according to claim 1.
2. A liquid crystal optical device comprising a compensating means for canceling a birefringence component of liquid crystal molecules held in an alignment state when an electric field is applied between the electrodes, between the first and second polarizing plates. 3. The retardation film according to claim 2, wherein the compensating means is a retardation film that cancels a birefringence component of liquid crystal molecules held in an aligned state when an electric field is applied between the first and second electrodes. A liquid crystal optical device characterized by being present. 4. The liquid crystal optical device according to claim 3, wherein the retardation film is formed by laminating a plurality of retardation films having different retardations so that the stretching directions thereof are orthogonal to each other. 5. The retardation film according to claim 3, wherein the retardation film has a plurality of retardation films having different retardations so that the stretching directions thereof are orthogonal to each other.
2. A liquid crystal optical device, characterized in that the liquid crystal optical device is divided and arranged on the other surface side of the substrate. 6. The compensating means according to claim 2, wherein the compensating means includes a plurality of liquid crystal molecules held in an alignment state on the side of the first alignment film when an electric field is applied between the first and second electrodes. A liquid crystal comprising a first retardation film for canceling a refraction component and a second retardation film for canceling a birefringence component of liquid crystal molecules held in an alignment state on the side of the second alignment film. Optical device. 7. The first and second devices according to claim 6,
2. The liquid crystal optical device according to claim 1, wherein each of the retardation films has a different retardation and is composed of a plurality of retardation films whose stretching directions are orthogonal to each other.