JPH11218752A - Liquid crystal electrooptical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal electrooptical element, in which a good contrast is maintained even though the number of circuit element is increased, by arranging the selectively reflecting means, which reflects the light beams having first polarizing axis components and transmits light beams having second polarizing axis components that are orthogonal to the first polarizing axis components. SOLUTION: A liquid crystal cell is composed of liquid crystal molecules 7 which are held by a substrate 2 having a transparent electrode 3 and an alignment layer 4 and a substrate 2 having a reflective member 8, has a reflection function and an alignment layer 4, thorough seal sections 5. Then, a cubic type selectively reflecting member is arranged for the cell to oppose against the member 8 so that a selectively reflecting member 9 of the cubic type selectively reflecting member and a substrate surface 2 of the liquid crystal electrooptical element make a 45 degree angle. In th element, the incident direction of S polarized light beams 15 is located in a same side of the cell with respect to the member 9 and the direction makes 90 degrees with respect to the substrate surface of the cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a structure and a display method of a liquid crystal electro-optical element used for a liquid crystal display device, a liquid crystal television, a liquid crystal projector and the like.

[0002]

2. Description of the Related Art As shown in FIG. 3, a conventional liquid crystal electro-optical element comprises a liquid crystal cell in which a liquid crystal 7 is sandwiched between two transparent electrodes facing each other or a substrate 2 having a circuit element 17 by a seal portion 5. It comprises a polarizing plate 1 arranged on both sides of a liquid crystal cell. In addition, an optically anisotropic body 11 other than the above-mentioned liquid crystal electric cell may be further provided for compensating a viewing angle.

[0003]

In recent years, with the increase in the number of displayable pixels required for a display, the number of circuit elements formed on a substrate of a liquid crystal electro-optical element has increased rapidly. In the case of a transmissive liquid crystal cell, the amount of light that can be transmitted decreases accordingly, so that the resulting liquid crystal electro-optical element increases the number of displayable pixels, but has low contrast,
There was a tendency for only dark images to be obtained. In order to improve this, the adoption of a backlight and the increase in the amount of light of the backlight, or the structure and design of circuit elements have been improved, but the effect has been insufficient.

It is an object of the present invention to improve these disadvantages and to provide a liquid crystal electro-optical element having good contrast even when the number of circuit elements increases.

[0005]

The present inventors have made intensive efforts to solve the problems inherent in these conventional liquid crystal electro-optical elements, and have arrived at the present invention.

That is, the liquid crystal electro-optical element of the present invention comprises:
A liquid crystal electro-optical element including at least a first substrate having electrodes, a second substrate having electrodes, a liquid crystal cell sandwiched between them, and a selective reflection member having a flat reflecting surface. A reflection member having a reflection function is provided in the cell, and on the opposite side of the opposite member and the liquid crystal cell,
It features a selective reflection member with a flat reflecting surface on both sides, and the major axis of the liquid crystal molecules near the substrate of the liquid crystal cell is oriented almost perpendicular to the substrate when no electric field is applied, and the length of the liquid crystal molecules when an electric field is applied The projection line of the axis to the substrate is inclined at about 45 degrees with respect to the intersection line between the liquid crystal cell substrate and the selective reflection member, and the value of the anisotropy of the liquid crystal molecules is negative. I do.

FIG. 1 shows a basic sectional view (off state) of a liquid crystal electro-optical element according to the present invention.

In the liquid crystal electro-optical element according to the present invention, it is essential that a reflection type liquid crystal cell and a selective reflection member having a flat opposite surface are combined. As the reflection member 8 having a reflection function essential for a reflection type liquid crystal cell, Al, C
r, Ag, Si, Ni, Mg, Pt, Au, etc., a metal having a reflective function alone, or a plate, a foil, a vapor-deposited film on an organic polymer film, a sputtered film made of a mixture thereof,
A vapor-deposited film or a sputtered film on the glass substrate itself is preferably used. These reflecting members 8 may be formed on the surface of the substrate that is in contact with the liquid crystal, or may be formed on the opposite side of the substrate that is not in contact with the liquid crystal. Further, a part or all of the electrode or the circuit element may be formed of these metals, or a part or all of the electrode or the circuit element may be covered with these metals. These electrodes and circuit elements other than the reflecting member having the reflecting function are manufactured by a usual method.

As shown in FIG. 4, a selective reflecting member having a flat reflecting surface combined with a reflective liquid crystal cell is a selective reflecting member made of metal or metal oxide on the inclined surfaces of two prism-shaped light transmitting members 10 as shown in FIG. A so-called cubic-type selective reflection member in which both slopes are brought into contact after the formation of 9 and, if necessary, an anti-reflection film 12 is provided on the reflection surface. In this case, the case where the selective reflection plane of the planar selective reflection member is inclined by about 45 ° with respect to the substrate surface of the liquid crystal cell works most efficiently with respect to the present invention. In the cubic type selective reflection member, as shown in FIG. 5, at a 45 ° angle to the selective reflection member 9, polarized light having a vibration direction of polarized light parallel to the selective reflection member, S-polarized light 15 (polarized light has a vibration direction of (Polarized light perpendicular to the paper surface), the S-polarized light is reflected in a direction at 90 ° to the incident direction. Also, when a polarized light having a vibration direction orthogonal to the slope and a P-polarized light 16 (polarized light whose polarization direction is parallel to the paper surface) is incident on the selective reflection member at an angle of 45 °, the incident light is affected by the selective reflection member. Go straight without receiving. Therefore, by changing the polarization direction of the incident light, control as transmitted light or reflected light becomes possible.

Next, in the liquid crystal electro-optical element according to the present invention in which the selective reflection member and the liquid crystal cell are combined, the transmitted light can be controlled by changing the polarization direction of the incident light, and as a result, the on-off of the pixel is reduced. Explain what is possible. The light used to turn the pixels on-off is S-polarized. Consider the relationship between the traveling direction of S-polarized light and the pretilt angle of the liquid crystal molecules in the liquid crystal cell when S-polarized light is incident on the liquid crystal electro-optical element according to the present invention (at this time, as shown in FIG. To place it). First, consider the case where the pretilt angle 6 of the liquid crystal molecules in the liquid crystal cell is almost vertical as shown in FIG. The S-polarized light 15 reflected by the selective reflection member 9 and incident on the liquid crystal cell is reflected by the reflection member 8 in the liquid crystal cell without being affected by the birefringence of the liquid crystal molecules, and exits the liquid crystal cell in a state of S polarization. . Then, the S-polarized light is reflected again by the selective reflection member 9 and returns in the incident direction. Therefore, in this case, when the liquid crystal electro-optical element is observed from the side opposite to the liquid crystal cell with the selective reflection member interposed therebetween, the pixels are in a dark state and an off state because light does not pass through the selective reflection member.

Next, consider the case where the pretilt angle 6 of the liquid crystal molecules in the liquid crystal cell is inclined by 30 to 60 degrees as shown in FIG. 2 (the orientation direction of the long axis of the liquid crystal molecules at this time is as shown in FIG. 9). ). The S-polarized light 15 reflected by the selective reflection member 9 and incident on the liquid crystal cell becomes elliptically polarized light under the influence of birefringence of the liquid crystal molecules, and is reflected from the liquid crystal cell. The s-polarized light component 15 of the elliptically polarized light output from the liquid crystal cell is reflected by the selective reflection member 9 and returns to the incident direction. However, most of the remaining elliptically polarized P-polarized light component 16 passes through the selective reflection member in a direction at 90 degrees to the incident direction without being affected by the selective reflection member 9 (to maximize the ratio of the P-polarized light component). It is desirable to arrange the liquid crystal molecule long axis as shown in FIG. 9). In this case, when the liquid crystal electro-optical element is observed from the opposite side of the liquid crystal cell with the selective reflection member interposed therebetween, the pixels are in a bright state and an on state because light passes through the selective reflection member.

As described above, in the liquid crystal electro-optical device according to the present invention, the pixels can be turned on and off by changing the pretilt angle 6 of the liquid crystal molecules in the liquid crystal cell.

As a method of changing the pretilt angle 6, two methods of voltage application and magnetic field application are general, but voltage application is more general. Changing the pretilt angle of liquid crystal molecules by applying a voltage will be described later.

The selective reflection member is formed by depositing a vapor deposition film 9 made of metal or metal oxide to a predetermined thickness on a flat substrate 14 as shown in FIG. Alternatively, a so-called plate-shaped selective reflection member provided with an antireflection film 12 may be used. When the S-polarized light 15 is incident on the inclined surface at an angle of about 58 ° with respect to the slope as shown in FIG.
It is reflected in the direction of 8 °. Similarly, when the P-polarized light 16 is incident at an angle of about 58 ° with respect to the slope, the incident light travels straight without being affected by the selective reflection member. In this case, the light can be turned on and off according to the present invention by the same mechanism as that of the cubic-type selective reflection member described above.

As described above, the selective reflection member has a function similar to that of a polarizing film used in a conventional liquid crystal electro-optical element in the sense of selectively transmitting polarized light. In FIG. 8, 19 and 21 indicate the maximum transmissible light amounts when the selective reflection member and the conventional polarizing film are used, respectively, and 20 and 22 indicate the minimum transmission amount when the selective reflection member and the conventional polarizing film are used, respectively. Shows the possible light quantity. However, as is apparent from FIG. 8, since the absorption of transmitted light by the selective reflection member itself is extremely small, the liquid crystal electro-optical element using the selective reflection member has advantages of being bright and having high contrast. In order to further enhance the contrast, it is possible to use a plurality of the selective reflection members or to use them together with another polarizing element.

The orientation of the liquid crystal molecules in the liquid crystal cell when no voltage is applied is a tilt orientation close to homeotropic alignment on both the first substrate and the second substrate. The pretilt angle 6 is 70 to 8
9.9 ° is preferable, and from the viewpoint of stable alignment of liquid crystal molecules, it is preferably 83 to 89.5 ° with respect to the substrate surface. The purpose of this pretilt angle is to allow liquid crystal molecules to fall in a certain direction when a liquid crystal cell voltage is applied.

As a method of aligning liquid crystal molecules to realize the pretilt angle, polyimide, Si or Ti
A method of forming an alignment film 4 by applying an aligning agent having a vertical alignment ability such as a compound and a Cr complex on the substrate surface and then rubbing the same, or a method of forming a metal oxide such as SiO and MgF ₂ on the substrate in a direction normal to the substrate. A typical method is to form the alignment film 4 by oblique deposition from a direction of about 85 ° and then applying the above-described vertical alignment agent. As a polyimide, a polyimide having a long alkyl chain in a side chain is typical. As the Si coupling agent, heptadecafluorodecylmethyldichlorosilane, heptadecafluorodecylmethyldimethoxysilane, heptadecafluorodecyltrimethoxysilane, n-octadecyltrimethoxysilane, and the like are preferably used. As the Ti compound, Ti (O-
_{C 3 H 7) 4, Ti} (O-C 4 H 9) 4, Ti (O-C
₁₇ H ₃₅ ) ₄ , and a partial hydrolyzate of the Ti alkoxide compound, Ti (O—
C ₃ H ₇ ) α (OCOC ₁₇ H ₃₅ ) β, Ti (OC
₃ H ₇ ) α (OC (CH ₃ ) CHCOCH ₃ ) β (α =
Ti acylate compounds such as 1-3 β = 4-α) are preferably used. Further, as the Cr complex, aliphatic carboxylic acid Cr complexes such as butyric acid, caproic acid, berargonic acid, capric acid, undecanoic acid, stearic acid, and myristic acid, and fluorine-substituted carboxylic acid Cr complexes such as verfluorononanoic acid are preferable. Used. As the metal oxide, MgF ₂ , Al ₂ O ₃ , Sm ₂ O ₃ , Si
O, CeF ₃ , SiO _{2 and the} like are preferably used. These Si or Ti coupling agents and Cr complexes may be used alone, or the same effect can be obtained by mixing them with each other. The incident angle of the oblique deposition is preferably 70 to 89.9 degrees with respect to the direction perpendicular to the substrate, and more preferably 83 to 89.5 degrees with respect to the alignment stability of the liquid crystal molecules.

At least the liquid crystal molecules 7 sandwiched between the electrodes formed in this way or the two substrates having the circuit element and the alignment film have a dielectric anisotropy Δ △.
The value of ε (where the dielectric constants in the directions parallel and perpendicular to the major axis direction of the liquid crystal molecules are ε‖ and ε⊥, respectively, the dielectric anisotropy △ ε is expressed by △ ε = ε‖−ε⊥) is negative. It is desirable that When a voltage is applied between the two substrates due to the negative Δε, the tilt angle of the long axis of the liquid crystal molecules according to the applied voltage from the state where the liquid crystal molecules are oriented almost perpendicular to the above-mentioned substrate. To change. At this time, the arrangement direction of the liquid crystal molecules is as shown in FIG. 9 when the liquid crystal cell is viewed from the opposite side with the planar selective reflection member interposed therebetween. In FIG.
Indicates a projected image of liquid crystal molecules on the substrate when no voltage is applied, and
4 shows a projected image of the liquid crystal molecules on the substrate surface when a voltage is applied.
When no voltage is applied between the substrates, as shown in FIG. 1, since the major axis direction of the liquid crystal molecules is arranged almost perpendicular to the substrate, the S-polarized light 1 reflected by the selective reflection agent 9
5 is reflected by the S-polarized light 15 without being affected by the birefringence of the liquid crystal molecules and exits from the liquid crystal cell. Then, the light is reflected again by the selective reflection member 9 and returns to the incident direction.
Conversely, when a voltage is applied between the substrates, as shown in FIG. 2, the long axis direction of the liquid crystal molecules arranged substantially perpendicular to the substrate changes the length of the liquid crystal molecules according to the applied voltage. Change the tilt direction of the shaft. Therefore, the S-polarized light 15 reflected by the selective reflection member 9 and entering the liquid crystal cell receives the birefringent liquid crystal of the liquid crystal molecules, is reflected in the state of elliptically polarized light, and exits the liquid crystal cell. Then, of the elliptically polarized light that has reached the selective reflection member 9, the P-polarized light component 16 is transmitted straight, and the S-polarized light component 15 is reflected and returns to the incident direction. At this time, the projection line of the long axis of the liquid crystal molecules upon application of the electric field to the substrate of the station cell and the intersection line formed by the selective reflection member,
As shown in FIG. 9, when tilted by about 45 degrees, the maximum contrast (P polarization component amount is maximum) is shown.

As described above, in the liquid crystal electro-optical element according to the present invention, the polarization direction of the S-polarized light 15 once reflected by the selective reflection member 9 is changed depending on the presence or absence of a voltage applied to the liquid crystal cell. Can be switched between the on state and the off state.

Hereinafter, the present invention will be described in more detail with reference to examples.

[0021]

[Embodiment 1] FIG. 1 is a sectional view of a liquid crystal electro-optical element according to an embodiment of the present invention.
A liquid crystal cell is constituted by the substrate 2 having the transparent electrode 3 and the alignment film 4, and the liquid crystal molecules 7 in which the reflection member 8 having the reflection function and the substrate 2 having the alignment film 4 are sandwiched via the seal portion 5. Further, the liquid crystal electro-optical element of the present invention is basically constituted by the reflection member 8 having the reflection function of the liquid crystal cell and the selective reflection member 9 installed in a manner to support the liquid crystal cell.
Here, the selective reflection member 9 and the substrate surface 2 of the liquid crystal cell are arranged so as to form an angle of 45 degrees.

The alignment film 4 of the liquid crystal cell is rubbed after performing a vertical alignment process. In the vertical alignment treatment, a myristic acid Cr complex and Ti (OC ₂ H
₅ ) The mixture was prepared by spin-coating a mixture of ₄ equivalents. Next, rubbing was performed on the surface of the substrate subjected to the vertical alignment treatment. The rubbing was rubbed once under a load of 2 kg by rotating rubbing using a nylon flocking cloth. The rubbing direction is opposite to that of the upper and lower substrates, and the projection line of the long axis of the liquid crystal molecules upon application of the electric field to the substrate is about 45 ° with respect to the intersection line between the liquid crystal cell substrate and the selective reflection agent. (See FIG. 9).

The reflection film 8 having a reflection function is made of Al
Was vacuum-deposited by 1000 Å.

The substrate thus obtained was assembled, and the liquid crystal 7 was sealed. The cell gap was set to 6.0 μm. The encapsulated liquid crystal 7 is ZLI-4318 manufactured by Merck.
(△ ε = −2.0 Δn = 0.1243) was used.

The pretilt angle 6 of the obtained liquid crystal cell is 87
(Pretilt angle was measured by a crystal rotation method in a magnetic field).

In the liquid crystal cell thus prepared, the cubic-type selective reflection member is held at 45 ° by the selective reflection member 9 and the substrate surface 2 of the liquid crystal electro-optical element so as to support the reflection member 8 having a reflection function. The liquid crystal electro-optical element of the present invention was produced by arranging the liquid crystal electro-optical element at an angle of. In this liquid crystal electro-optical element, the incident direction of the S-polarized light 15 was arranged on the same side as the liquid crystal cell with respect to the selective reflection surface 9 and was arranged at an angle of 90 degrees with the substrate surface of the liquid crystal cell.

Table 1 shows the characteristics of the obtained liquid crystal electro-optical element.

Example 2 Example 1 is exactly the same as Example 1 except that a cubic-type selective reflection agent is newly provided between the incident light source and the selective reflection agent in order to further enhance the contrast. I made it. The selective reflection surfaces of both selective reflection members were set so as to form an angle of about 90 degrees. FIG. 10 is a cross-sectional view of the liquid crystal electro-optical element when a voltage is applied.

Table 1 shows the characteristics of the obtained liquid crystal electro-optical element.

[Third Embodiment] In the second embodiment, the cubic-type selective reflection member provided between the incident light source and the selective reflection member for further enhancing the contrast is changed to a so-called Gran-Tiller polarizing prism 18. Was exactly the same as in Example 1. FIG. 11 shows a schematic view of the arrangement of the liquid crystal electro-optical element. Gran Tiller Polarizing Prism 18
Converts the incident light into P-polarized light, as shown in FIG.

Table 1 shows the characteristics of the obtained liquid crystal electro-optical element.

[Embodiment 4] In Embodiment 2, a cubic-type selective reflection member provided between the incident light source and the selective reflection member for further enhancing the contrast is replaced with a so-called Glan-Thomson polarizing prism 19. Was exactly the same as in Example 1. FIG. 13 is a sectional view of the liquid crystal electro-optical element when a voltage is applied. The Gran-Tiller polarizing prism 19 converts the incident light into S-polarized light as shown in FIG.

Table 1 shows the characteristics of the obtained liquid crystal electro-optical element.

Fifth Embodiment In the second embodiment, the cubic-type selective reflection member provided between the incident light source and the selective reflection member for further enhancing the contrast is changed to a conventional polarizing film, and S-polarized light enters. The procedure was exactly the same as that of Example 1 except that the arrangement was adjusted as described above. FIG. 15 is a cross-sectional view of the liquid crystal electro-optical element when a voltage is applied.

Table 1 shows the characteristics of the obtained liquid crystal electro-optical element.

[Embodiment 6] In the embodiment 2, the alignment film is made of S
The procedure was the same as in Example 1, except that iO was obliquely vapor-deposited at 1400 angstroms at an incident angle of 85 ° and then a Si coupling agent and octadecyltrimethoxysilane were applied by spin coating.

Table 1 shows the characteristics of the obtained liquid crystal electro-optical element.

Example 7 The procedure of Example 2 was carried out exactly as in Example 1, except that the reflective film having a reflecting function was formed by depositing Cr at 1200 Å.

Table 1 shows the characteristics of the obtained liquid crystal electro-optical element.

COMPARATIVE EXAMPLE As shown in FIG. 16, the liquid crystal cell comprises a liquid crystal 7 sandwiched between substrates 2 having two transparent electrodes 3 opposed to each other, and polarizing plates 1 arranged on both sides of the liquid crystal cell. A conventional liquid crystal electro-optical element is used as a comparative example. The procedure was the same as in Example 1 except that the reflecting member having a reflecting function was replaced with a transparent electrode, and the selective reflection film was changed to a pair of polarizing films.

Table 1 shows the characteristics of the obtained liquid crystal electro-optical element.

The measurement items in Table 1 represent the following items, and all the measurements were performed at 30 °.

[0043]

[0044]

[Table 1]

[0045]

As described above, when the liquid crystal electro-optical element according to the present invention is used, a liquid crystal electro-optical element having a high contrast can be obtained even if the number of circuit elements increases.

[Brief description of the drawings]

FIG. 1 is a basic conceptual diagram of a liquid crystal electro-optical element according to the present invention when no voltage is applied.

FIG. 2 is a basic conceptual diagram when a voltage is applied to the liquid crystal electro-optical element according to the present invention.

FIG. 3 is a view schematically showing a conventional liquid crystal electro-optical element.

FIG. 4 is a diagram illustrating a so-called cubic-type selective reflection member.

FIG. 5 is a view showing selective reflection and transmission of a so-called cubic-type selective reflection member.

FIG. 6 is a view showing a so-called flat selective reflection member.

FIG. 7 is a diagram showing selective reflection and transmission of a so-called flat selective reflection member.

FIG. 8 is a diagram comparing the transmittances of a conventional polarizing plate and a selective reflection member used in the present invention.

FIG. 9 is a diagram illustrating projection of liquid crystal molecules onto a substrate when a voltage is applied and when no voltage is applied.

FIG. 10 is a cross-sectional view of a liquid crystal electro-optical element according to the present invention when a plurality of selective reflection members are used and a voltage is applied.

FIG. 11 shows a liquid crystal electro-optical element according to the present invention.
The figure which shows the outline at the time of combining a U-polarization prism.

FIG. 12 is a diagram showing a polarization state of light in a Gran-Tiller polarization prism.

FIG. 13 shows a liquid crystal electro-optical element according to the present invention,
The figure which shows the sectional view at the time of voltage application when combining a Thomson polarizing prism.

FIG. 14 is a diagram illustrating a polarization state of light in a Glan-Thompson polarizing prism.

FIG. 15 is a cross-sectional view of a liquid crystal electro-optical device according to the present invention when a voltage is applied when a polarizing film is combined.

FIG. 16 is a cross-sectional view of a conventional liquid crystal electro-optical element used as a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polarizing plate 2 Substrate 3 Transparent electrode 4 Alignment film 5 Sealing part 6 Pretilt angle 7 Liquid crystal molecule 8 Reflection member having a reflection function 9 Selective reflection film made of metal or metal oxide 10 Prism-shaped light transmitting body 11 Optical anisotropy Body 12 Antireflection film 13 Projection of liquid crystal molecules onto substrate when no voltage is applied 14 Projection of liquid crystal molecules onto substrate when voltage is applied 15 S-polarized light 16 P-polarized light 17 Circuit element 18 Glan-Taylor polarizing prism 19 Glan-Thompson polarized light Prism 20 Incident light direction

[Procedure amendment]

[Submission date] December 21, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

That is, the liquid crystal electro-optical element of the present invention comprises:
In a liquid crystal electro-optical element having a reflection type liquid crystal cell in which a liquid crystal is sandwiched between a pair of substrates, a light of a first polarization axis component is reflected on a light incident side of the liquid crystal cell, and A selective reflection unit having a reflection surface that transmits light of the second orthogonal polarization axis component is disposed, and the long axis direction of light projected from the liquid crystal molecules onto the substrate when the electric field is applied is changed to the reflection surface. And the liquid crystal cell emits the incident light from the selective reflection means as elliptically polarized light.

Claims (1)

[Claims] 1. A liquid crystal electro-optical element having a reflection type liquid crystal cell in which liquid crystal is sandwiched between a pair of substrates, wherein a light of a first polarization axis component is reflected on a light incident side of the liquid crystal cell, and A selective reflection means for transmitting light of a second polarization axis component orthogonal to the one polarization axis component is disposed, and the liquid crystal of the liquid crystal cell enters the first incident light when no electric field is applied.
The light of the polarization axis component is emitted as the light of the first polarization axis component, and when an electric field is applied, the major axis direction of the projection light of the liquid crystal molecules onto the substrate is shifted between the reflection surface of the selective reflection unit and the plane of the substrate. A liquid crystal electro-optical element, wherein the light of the first polarization axis component, which is incident at an inclination of about 45 degrees with respect to the intersection line, is emitted as elliptically polarized light.