JP2001021923A - Liquid crystal element and liquid crystal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a liquid crystal device with low consumption of electric power, high brightness and high performance by disposing a liquid crystal layer consisting of a liquid crystalline polymer matrix and a rod-like low molecular weight liquid crystal phase between a pair of substrates and disposing an electrode in specified arrangement on at least one of substrate. SOLUTION: A liquid crystal layer 5, consisting of a liquid crystal polymer matrix 5a and a rod-like low molecular weight liquid crystal phase 5b, is disposed between a pair of substrates 1a, 1b having alignment films 2a, 2b, respectively. Electrodes 3a, 3b are formed on at least one substrate 1b of the pair of substrate 1a, 1b in suitable arrangement for switching the molecular axis of the rod-like low molecular weight liquid crystal phase 5b in a plane parallel to the substrate 1b. Namely, electrodes 3a, 3b for in-plane switching are formed on one substrate 1b, and the liquid crystal layer 5 is held between substrates with a spacer 4 which regulates thickness. The thickness of the liquid crystal layer 5 is preferably controlled to be in the range of 1 to 100 μm by the spacer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal element which can be used as a light valve for a flat panel display, a paper display, a projection display, a printer and the like, and a liquid crystal device including the liquid crystal element.

[0002]

2. Description of the Related Art A CRT is known as the most widely used display. It is widely used as a moving image output for televisions and VTRs, or as a monitor for personal computers. However CRT
Due to its characteristics, flicker and scanning fringes due to lack of resolution may lower visibility of a still image, or may cause deterioration of a phosphor due to burn-in. In addition, the power consumption is considerably large, and improvement in power saving is required. Since the CRT must have a large volume behind the screen due to its structure, the CRT
The convenience of the information device having the above is limited, and it is not suitable for saving space in offices and homes.

As a solution to such a problem of the CRT, there is a liquid crystal display element. For example, M. Shut (M.
Schadt) and W. Helfrich (W. He)
Ifrich) Applied Physics Letters
Volume 18, Number 4 (issued February 15, 1971) Issue 12
One using a twisted nematic liquid crystal shown on pages 7 to 128 is known. Recently, this type or VA (ve
technical alignment mode, IPS
2. Description of the Related Art Development and commercialization of a liquid crystal element having an active element called a TFT in each pixel using a liquid crystal in an (in plane switching) mode or the like has been performed. In this type of liquid crystal element, a transistor is formed for each pixel, so there is no problem of crosstalk. In addition, due to the rapid progress of production technology in recent years, a 10-13 inch class display can be produced with good productivity. It is being done.

[0004] However, these liquid crystal elements are usually used as a display by using a backlight and modulating light transmitted through the liquid crystal element. For this reason, strong light is required as the backlight, and most of the power consumption of the liquid crystal display is consumed by the backlight, and even if a lithium ion secondary battery is used, the continuous operation time of a mobile device or the like is at most several hours. is there. In addition, if the backlight of more liquid crystal elements can be omitted, the power consumption of more information equipment and office equipment will be reduced, which will contribute to the suppression of global warming and, consequently, the conservation of the global environment. .

Under these circumstances, a low power consumption type reflection type liquid crystal element without using a backlight has been developed, but at present, its characteristics are still required to be improved. In addition, products using a liquid crystal element as a projection type, so-called projector, are marketed by various companies as large-screen displays. In this field, further improvements are required in terms of brightness and contrast. In response to such demands, a light scattering type liquid crystal element called a polymer dispersion type or a polymer network type liquid crystal element has been proposed and studied, aiming at a high brightness liquid crystal element which does not require a polarizing plate ( For example, 93
Eurodisplay 397). However, it is still desirable for these devices to have improved driving characteristics, scattering power and other characteristics.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above prior art, and it is an object of the present invention to provide a low power consumption, high luminance, high performance liquid crystal element, a light modulation element, and a display. It is intended to realize an element.

[0007]

The inventors of the present invention have made intensive studies and have found that the above-mentioned light-scattering type liquid crystal element called a polymer dispersion type or polymer network type liquid crystal element (these liquid crystal elements are mainly composed of polymer dispersion type). The former is called the polymer network type or the latter is based on whether the former has a relatively small amount of liquid crystal with respect to the polymer constituting the matrix and exists mainly as a dispersed phase,
Alternatively, as in the latter case, the amount of liquid crystal is increased and the matrix polymer is maintained in a network state, but it is merely a difference as to whether or not the matrix polymer itself coexists as a continuous phase. Liquid crystal device ")
In the above, a liquid crystalline polymer is used as a main constituent component of the polymer matrix, and can be combined with a rod-shaped low-molecular liquid crystal component that performs switching (that is, so-called in-plane switching) in a plane parallel to the substrate. It has been found to be very effective.

The liquid crystal device (polymer matrix type liquid crystal device) of the present invention has a liquid crystal layer comprising a liquid crystal polymer matrix and a rod-shaped low molecular liquid crystal phase disposed between a pair of substrates based on such knowledge. Wherein at least one of the pair of substrates is provided with an electrode having an arrangement suitable for switching the molecular axis of the rod-shaped low-molecular liquid crystal in a plane parallel to the substrate. .

One of the main features of the polymer matrix type liquid crystal device of the present invention is that it has an extremely good light scattering ability, as can be seen from the comparison between Examples and Comparative Examples described later.
According to the present invention, by combining a matrix polymer in a polymer matrix type liquid crystal element with a rod-shaped low-molecular liquid crystal instead of a liquid crystalline polymer compound according to the present invention, a remarkable improvement in light scattering ability is obtained. It is considered that the refractive index anisotropy caused by the shape anisotropy of the contained components is highly available. That is, in the conventional polymer matrix type liquid crystal device, the matrix polymer combined with the uniaxially anisotropic rod-like low-molecular liquid crystal is isotropic, and the light scattering ability obtained essentially is one of the components. In contrast, in the present invention, the matrix polymer itself has a refractive index anisotropy, whereas the matrix polymer itself has a refractive index anisotropy. It can be understood that the large value of contributes to the improvement of the light scattering ability.

Another major feature of the polymer matrix type liquid crystal device of the present invention is that the rod-shaped low-molecular liquid crystal changes the direction of the molecular axis in a plane parallel to the substrate axis (ie, in-plane switching). It is to cause. For example, in FIG. 1, when a rod-shaped liquid crystalline polymer is used as the liquid crystalline polymer, the refractive index ellipsoid of the rod-shaped liquid crystalline polymer viewed from the direction perpendicular to the substrate surface and the two states of switching (states A and B) 3) shows an example of the mutual arrangement of the refractive index ellipsoids of the rod-shaped low-molecular liquid crystal in FIG. In such an arrangement state, when the rod-shaped low-molecular liquid crystal is in state A, the molecular axes of the rod-shaped liquid crystalline polymer and the rod-shaped low-molecular liquid crystal are arranged in almost the same direction, and their refractive indices are almost the same. The degree of light scattering is minimal. On the other hand, in the state B due to the switching of the rod-shaped low-molecular liquid crystal, the molecular axis of the rod-shaped liquid crystalline polymer is substantially orthogonal to the molecular axis of the rod-shaped low-molecular liquid crystal, and the maximum light scattering degree is obtained. As described above, the liquid crystal device of the present invention in which the rod-shaped low-molecular liquid crystal is in-plane switched between the states A and B has the highest light scattering degree when observed from the front, which is a standard viewing direction of the liquid crystal device. Therefore, the greatest feature is that high contrast light scattering display is possible. In contrast, SID98 Digest
On page 758, a polymer-dispersed liquid crystal device using a rod-like liquid crystalline polymer has been proposed. The molecular orientation of the rod-like liquid crystalline polymer used in this case is homogeneous uniaxial alignment similar to that shown in FIG. Is obtained between the homeotropic alignment state of the rod-shaped low-molecular liquid crystal and when viewed from the front of the liquid crystal element, there is a difference in the refractive index in only one direction from the rod-shaped liquid crystalline polymer. Not just. It can be said that the liquid crystal element of the present invention also has characteristics superior to those of the related art in terms of scattering mechanism, that is, high luminance and high contrast characteristics.

Also, when a discotic liquid crystal polymer having a so-called ampane-shaped refractive index ellipsoid is used in place of the rod-shaped liquid crystal polymer, two directions are required as compared with the case where a simple isotropic polymer matrix is used. As described above, a refractive index difference can be generated, and higher light scattering ability can be obtained. However, in this case, when the discotic liquid crystalline polymer is completely homogeneously oriented (that is, its xy orientation plane is parallel to the substrate surface), contrast can be obtained between the in-plane switching rod-shaped low-molecular liquid crystal. However, since a certain degree of distribution generally occurs in the plane orientation of the discotic liquid crystalline polymer, a contrast change may occur between the in-plane switching and the rod-like low molecular weight liquid crystal (Example 2 described later). . In addition, if the discotic liquid crystalline polymer can be selectively homeotropically aligned by the use of a high pretilt cell or electric field treatment, it will be effective between in-plane switching rod-shaped low-molecular liquid crystals. High contrast display becomes possible.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the polymer matrix type liquid crystal device of the present invention will be described more specifically.

FIG. 2 shows an example of the cell configuration of the polymer matrix type liquid crystal device of the present invention. In this liquid crystal cell, in-plane switching electrodes 3a and 3b are provided on one of a pair of substrates 1a and 1b provided with alignment films 2a and 2b, respectively, and the thickness is determined by a spacer 4,
The liquid crystal layer 5 is sandwiched. The liquid crystal layer 5 is composed of a liquid crystalline polymer (rod-like or discotic liquid crystalline polymer) 5a and a rod-like low-molecular liquid crystal 5b constituting a network. The thickness of the liquid crystal layer 5 is preferably 1 to 1 due to the spacer 4.
It is set between 00 μm. The pair of substrates 1a and 1b are made of glass, plastic, or the like, and at least one of the front surfaces (1a) is formed of a transparent material. Orientation control layer 2
a and 2b can be omitted. In addition to the elements shown in FIG. 2, a short prevention layer, a light absorption layer, a reflection layer, and a color filter layer can be provided. The electrodes 3a and 3b for in-plane switching are generally formed on both sides of a pixel constituting a display element unit by a metal such as chromium, aluminum or the like, for example, 5 to 1000 μm, more preferably 1 to 1000 μm.
It is provided at intervals of 0 to 500 μm.

The polymer matrix type liquid crystal device of the present invention comprises:
Although the above structure can be adopted, it is not limited to them. The polymer matrix type (in the figure, network type) liquid crystal layer 5 is formed by, for example, injecting a liquid crystal mixture containing a polymerizable liquid crystal compound and a rod-like low-molecular liquid crystal into a liquid crystal cell as described below and irradiating the mixture with ultraviolet rays By doing so, a liquid crystal mixture containing the liquid crystal polymer 5a and the rod-shaped low-molecular liquid crystal 5b can be formed. The rod-shaped low-molecular liquid crystal 5b is made of a P-type or N-type in order to perform in-plane switching of the rod-shaped low-molecular liquid crystal 5b by an electric field applied between the electrodes 3a and 3b.
It is preferably a liquid crystal of a type. Further, a nematic liquid crystal is preferably used as the rod-shaped liquid crystal 5b because it can be driven at a low voltage, the cell forming process is relatively simple, and the cell configuration is relatively simple. More preferably, a fluorine-based nematic liquid crystal is used because it is preferable for use in an active matrix element.

In the liquid crystal layer 5 of the liquid crystal element of the present invention, the liquid crystal polymer used together with the rod-shaped low-molecular liquid crystal 5b as described above, and a rod-shaped or discotic liquid crystal polymer is used as the liquid crystal polymer constituting the matrix 5a. Can be As described above, a mixture of a low-molecular rod-shaped liquid crystal and a polymerizable rod-shaped liquid crystal compound or a polymerizable discotic liquid crystal compound is placed in a cell, and the polymerizable liquid crystal compound in the mixture is actuated by an external action such as ultraviolet rays. It can be obtained by polymerizing. In this process, a rod-shaped low-molecular liquid crystal layer is phase-separated and formed. In order to obtain more preferable scattering, controlling the phase before or during the polymerization to control the droplet diameter can be performed in the same manner as in a normal polymer dispersion type or polymer network type liquid crystal.

Examples of the structure of the polymerizable rod-like liquid crystalline compound used include the following.

[0017]

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[0018]

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As the polymerizable discotic liquid crystal compound, a compound having a discotic liquid crystal structural unit and having a polymerizable group at any position is used. Here, the polymerizable group is not limited to a group containing a double bond suitable for normal addition polymerization, but may be a reactive group capable of causing condensation polymerization or a group capable of causing radiation polymerization, It is not particularly intended to limit the mechanism of polymerization. Examples of the compound having a discotic liquid crystal structural unit include those described in JP-A-8-27824 and JP-A-9-21444. Specifically, a skeleton as shown in the following formula,
Examples thereof include structures in which linear or branched alkyl groups, alkoxy groups, substituted benzoyloxy groups, and the like are radially substituted. The polymerizable discotic liquid crystal compound is one of compounds having these discotic liquid crystal structural units. It is obtained by giving a polymerizable group to the part.

[0020]

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[0021]

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[0022]

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[0023]

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[0024]

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The liquid crystal mixture containing the rod-like liquid crystalline polymer or the discotic liquid crystalline polymer of the present invention and the rod-like low-molecular liquid crystal composition is prepared by preparing the rod-like liquid crystalline polymer or the discotic liquid crystalline polymer in advance. Then, a desired mixed liquid crystal material can be obtained by mixing with a separately obtained rod-shaped low-molecular liquid crystal. Examples of the rod-like liquid crystalline polymer liquid crystal include compounds as described in JP-A-7-82183, and specific examples are given below.

[0026]

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[0027]

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[0028]

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(In the following formulas (14) to (17), q = 1 to
18, q ₁ = 1 to 18, and q ₂ = 1 to 18. )

[0030]

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(In the following formulas (18) to (62), * represents an asymmetric carbon center.)

[0032]

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[0033]

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[0034]

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[0035]

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[0036]

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[0037]

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[0038]

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[0039]

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[0040]

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[0041]

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[0042]

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[0043]

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As the discotic liquid crystalline polymer compound, for example, Macromol. Rapid
Commun. 18 pages 93-98 1997,
Alternatively, compounds such as those described in EKISHO 1:45, 1997 may be mentioned.

It is preferable that the liquid crystalline polymer of the present invention and the rod-shaped low-molecular liquid crystal are in a phase-separated state in a minute region in order to obtain a scattering suitable for a scattering type liquid crystal element in the liquid crystal element of the present invention. However, in some cases, the phase is not partially separated. The liquid crystalline polymer that constitutes this material is
In forming a more preferable scattering state as described later,
It is necessary to have a liquid crystal order. .

However, when a polymer is obtained, it is a fact that it is not clear whether the order state is a liquid crystal order, a crystalline order, or an amorphous state including a region. In any case, it is important to have a rod-like liquid crystal property or a discotic liquid crystal property at a molecular level for strong scattering.

Regarding the mixing ratio of the liquid crystalline polymer 5a and the rod-like low molecular weight liquid crystal 5b in the liquid crystal layer 5, from the viewpoint of the scattering ability and the necessity of showing each physical property,
The content of the polymer is 1% by weight to 99% by weight, preferably 5% by weight to 95% by weight, and more preferably 10% by weight to 90% by weight. On the other hand, the component ratio of the low-molecular rod-shaped liquid crystal is also 1% by weight to 99% by weight, preferably 5% by weight to 95% by weight, more preferably 10% by weight to 90% by weight. In the mixture of the present invention, if necessary, an antioxidant,
It may contain additives such as a radical scavenger, a photoreaction inhibitor, a polymerization inhibitor, and a dye.

Further, in the present invention, in order to create a more preferable orientation state, it is possible to perform a heat treatment after the device is formed. By applying the heat treatment, the liquid crystalline polymer and / or the rod-like low-molecular liquid crystal may be self-organized to create a more preferable alignment state.

As one method of orientation control, for example, an orientation control layer (2a and / or 2b) is formed as a uniaxial orientation control layer, and for example, solution coating or vapor deposition or sputtering is performed on a substrate (1a or / and 1b). By such as inorganic substances such as silicon monoxide, silicon dioxide, aluminum oxide, zirconia, magnesium fluoride, cerium oxide, cerium fluoride, silicon nitride, silicon carbide, boron nitride, polyvinyl alcohol, polyimide,
Polyimide amide, polyester, polyamide, polyester imide, polyparaxylene, polycarbonate,
After forming a film using an organic material such as polyvinyl acetal, polyvinyl chloride, polystyrene, polysiloxane, cellulose resin, melamine resin, urea resin, and acrylic resin, the surface is rubbed with a fibrous material such as velvet, cloth or paper ( Rubbing). Also, an oblique deposition method of depositing an oxide or a nitride of SiO or the like from the oblique direction of the substrate may be used.

In particular, a polyimide rubbing film is preferably used as the uniaxially oriented layer in order to obtain better uniaxial orientation. Usually, polyimide is obtained by applying a film in the form of a polyamic acid, which is a precursor of a condensation crosslinking agent, and baking it. Polyamic acid is excellent in productivity because it is easily soluble in a solvent. Recently, polyimides soluble in solvents have also been produced, and from the viewpoint of such technological advances, polyimide is preferably used because it can obtain better uniaxial orientation and has high productivity. Examples of specific repeating unit structures of polyimide that can be used include the following.

[0051]

Embedded image In the formula, [A; a tetravalent group having an aromatic ring, an aromatic polycyclic ring, a heterocyclic ring, an aliphatic ring or a condensed polycyclic structure; B; an aliphatic group containing an alicyclic group, or-(Ph) _{a- (O) c - (CH 2} ) x - (D) e
_{- (CH 2) y - (} O) d - (Ph) b - (Ph is phenyl group)

[0052]

Embedded image a = b: 0 or 1 c = d: 0 when a = b = 0, 0 or 1: 0 or 1 when a = b = 1 x, y: each independently an integer of 1 or more, where x + y + e is 2 It is 10 or less. ]

When a rod-like liquid crystalline polymer having a refractive index ellipsoid as shown in FIG. 1 is used as the liquid crystalline polymer 5a, its molecular axis is aligned with the uniaxial alignment processing axis, and
The molecular axes of the rod-shaped low-molecular liquid crystals 5b are generally arranged in the same direction (state A) under no electric field. Therefore, in order to cause high-contrast switching, by applying an electric field between the electrodes 3a and 3b, the electrodes 3a and 3b are switched to a state B orthogonal to the electrodes 3a and 3b. It is preferable to arrange the liquid crystal molecules in a direction perpendicular to the uniaxial alignment processing axis and in the direction parallel to the uniaxial alignment processing axis for the N-type rod-shaped low molecular liquid crystal (so that an electric field is generated).

FIG. 2 shows an example in which a pair of electrodes 3a and 3b are used as in-plane switching electrodes on both sides of a pixel on one substrate 1b in combination with a nematic liquid crystal 5b as a preferred example. However, for example, if a ferroelectric or antiferroelectric smectic liquid crystal is used as the rod-like low-molecular liquid crystal 5b, a plane parallel to the substrates 1a and 1b is formed by providing a pair of substrates 1a and 1b with opposing electrodes. In-plane switching within the device becomes possible.

The substrates 1a and 1b face each other with the spacer 4 interposed therebetween. The spacer 4 determines a distance (cell gap) between substrates, and silica beads, partition spacers, resin spacer beads, or the like is used. Regarding the cell gap determined here, the optimum range and the upper limit differ depending on the difference in the liquid crystal material,
It is preferable to set it in the range of 1.0 to 100 μm.

In the liquid crystal device formed as shown in FIG. 2, the electric field applied between the electrodes 3a and 3b is controlled so that the rod-shaped low-molecular liquid crystal 5b is in-plane switched, so that the transmission of the liquid crystal layer 5 is prevented. Light or reflected light can be modulated, and when the modulated light is treated as a display signal, it becomes a display element. In addition, analog gray scale expression can be easily performed by using the intermediate voltage signal.

In the liquid crystal display cell illustrated in FIG. 2, a light absorbing plate, and in some cases, a reflecting plate or a scattering plate (for example, IDRC'94 183) for obtaining more brightness, between the substrate and the lower electrode and the substrate. Page)), a reflective liquid crystal display device can be obtained. FIG. 3 shows an example of a structure including the light absorbing plate 6. For example, by using an active matrix element described later, a liquid crystal element with a large area, high definition, high speed, and excellent driving characteristics can be realized. According to the polymer matrix type liquid crystal element of the present invention, since strong scattering is obtained, a high-brightness reflective liquid crystal element having high light reflectance can be realized.
This reflection type liquid crystal element can also be used as a direct-view type liquid crystal display element using external light or an auxiliary light source. Further, the present invention can also be used as a so-called projection type liquid crystal element in which strong light enters from the front surface, and light modulated and reflected by the liquid crystal element is controlled on the optical path and then projected on a screen.

On the other hand, a projection type liquid crystal element, that is, a projection type liquid crystal element, can be used as a transmission type liquid crystal element instead of a reflection type liquid crystal element. FIG. 4 shows an example of a typical transmission type projection liquid crystal element. Liquid crystal elements 303, 303 ', 303 corresponding to each of the three primary colors
By using a liquid crystal element having a matrix pattern such as an active matrix element described later, a color image can be projected on a projection screen. In this case, the liquid crystal element of the present invention displays black in a scattering state. In other words, in the liquid crystal element of the present invention that can obtain stronger scattering, higher contrast can be realized.

Further, the liquid crystal element of the present invention can be a high-definition and high-performance liquid crystal element by using a matrix type element in which an active element is provided for each pixel. This will be described below. For example, in the element configuration described above with reference to FIG. 1, for example, by using a chiral smectic liquid crystal as the rod-like low-molecular liquid crystal 5 b in the liquid crystal layer 5, the liquid crystal layer 5 is opposed to an in-plane switching electrode provided on a pair of substrates. The active matrix element shown in FIGS. 5 and 6 having a pixel provided with an electrode on a substrate as one pixel is exemplified. Of the pair of transparent substrates (eg, glass substrates) 41 and 42 that sandwich the liquid crystal layer 5 via the spacer 4, the lower substrate 41 has a transparent pixel electrode 43 and an active element 44 connected to the pixel electrode 43. They are formed in a matrix. The active element 44 is, for example, a TFT (thin film transistor)
Consists of The transistor is made of a semiconductor such as an amorphous silicon base, a polysilicon type, a μ crystal base, and single crystal silicon.
In this example, the active element 44 represents a TFT.
The TFT 44 includes a gate electrode formed on the substrate 41, a gate insulating film covering the gate electrode, a semiconductor layer formed on the gate insulating film, and a source electrode and a drain electrode formed on the semiconductor layer. You. Further, the lower substrate 41
A gate line (scanning line) 45 is wired between rows of the pixel electrodes 43 as shown in FIG.
The information signal lines 46 are wired between the columns. Each T
The gate electrode of the FT 44 is connected to the corresponding gate line 45, and the source electrode is connected to the corresponding information signal line 46. The gate line 45 is connected to the row driver 31 via an end 45a, and the information signal line 46 is connected to the column driver 32 via an end 46a. The row driver 31 scans the gate line 45 by applying a gate signal. The column driver 32 applies a signal corresponding to the display data. The gate line 45 is covered with the gate insulating film of the TFT 44 except for the end 45a, and the information signal line 46 is formed on the gate insulating film. The pixel electrode 43 is formed on the gate insulating film, and is connected at one end to a drain electrode of the TFT 44. Further, a transparent electrode 47 facing each pixel electrode 43 of the lower substrate 41 is provided on the upper substrate 42 of FIG.
Are formed. The counter electrode 47 is composed of one electrode having an area covering the entire display area, and a reference voltage is applied thereto. The transmittance changes according to the information signal voltage, and gradation expression can be performed. In addition, a capacitor serving as an auxiliary capacitance is often arranged for each pixel.

In the active matrix type liquid crystal element described above, charge is injected into the liquid crystal cell which is a pixel when the gate is on, the gate is turned off in a short time, and information is transferred to the pixel on the next scanning line. Written.

The liquid crystal element of the present invention can be used as a light valve of a printer or the like.

A liquid crystal device having the liquid crystal element of the present invention and having various functions can be constructed. For example, mobile, PDA, desktop PC, laptop PC,
Examples include a video camera, a digital camera, a document viewer, a printer, and a copying machine.

In the liquid crystal device of the present invention, since the liquid crystal element as a medium has good switching characteristics as described above, excellent driving characteristics and reliability are exhibited, and high definition, high speed,
A large area display image can be realized.

[0064]

Next, the present invention will be described more specifically with reference to examples and comparative examples.

Example 1 <Polymerizable rod-like liquid crystalline compound A used>

[0066]

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<Low Molecular Weight Liquid Crystal B Used> As the low molecular weight liquid crystal B, a P-type fluorine-based nematic liquid crystal KN-5030 manufactured by Chisso was used.

The phase transition temperature of the rod-like low-molecular liquid crystal B (KN-5030) was as follows: Cryst-(− 30 ° C. or less) -Nematic- (8
0 ° C.)-Iso. Δε was plus 10. Using these, A and B were mixed at a weight mixing ratio of A / B = 50/50 to prepare a mixture of a polymerizable discotic liquid crystalline compound and a rod-like liquid crystal. This mixture was dissolved in the isotropic state. This mixture exhibited nematic liquid crystallinity at 50 ° C.

<Creation of Cell> A cell having a structure equivalent to FIG. 1 was prepared. That is, a pair of aluminum electrodes was formed on one glass substrate having a thickness of 1.1 mm at intervals of 50 μm. Separately, a 1.1 mm thick glass substrate without electrodes was prepared.

A 2.1% by weight solution of a polyimide precursor having a repeating unit shown below in polyamic acid was applied to both substrates at first at 500 rpm for 5 seconds, and secondly at 150 rpm.
Spin coating was performed at 0 rpm for 30 seconds.

[0071]

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After that, pre-drying was carried out at 80 ° C. for 5 minutes, followed by baking at 220 ° C. for 1 hour. Rubbing treatment with a nylon cloth was performed on the alignment films on both substrates as a uniaxial alignment treatment.

An IPA solution in which resin beads having an average particle size of 6 μm are dispersed at 0.01% by weight on the surface of one of the substrates,
Spin coating was performed at 1500 rpm for 10 seconds, and bead spacers having a dispersion density of about 100 / mm ² were sprayed. A thermosetting liquid adhesive was applied to the substrate by a printing method. The obtained two substrates were bonded to each other with their rubbing axes aligned and heated and cured in an oven at 150 ° C. for 90 minutes to obtain cells.

(Preparation of Liquid Crystal Cell) To the mixture obtained above was added 200 ppm of 2,6-ditert-butyl-4-methylphenol, and 2 parts of a photopolymerization initiator ("Irgacure 184" manufactured by Ciba Geigy). After the addition by weight, the resulting mixture was injected into the empty cell obtained above at 50 ° C. under normal pressure. It was observed under a polarizing microscope that the composition was uniaxially oriented in the rubbing direction. In this state, about 12 mW / cm ² , center wavelength 365 n
Exposure was performed for 10 minutes with ultraviolet light of m to form a liquid crystal cell.
The low-molecular rod-shaped liquid crystal undergoes phase separation well, and the phase transition of the low-molecular rod-shaped liquid crystal from the nematic to the isotropic phase is almost the same as the phase transition temperature before mixing, according to observation under a polarizing microscope in a Mettler hot stage. Observed at From this, it was confirmed that almost all of the polymerizable rod-like liquid crystal compound was polymerized to be a polymer compound. It was observed under a polarizing microscope that the low-molecular rod-shaped liquid crystal was well uniaxially oriented.
Further, when the low-molecular rod-shaped liquid crystal was heated to an isotropic phase temperature, it was found that the rod-shaped liquid crystalline polymer portion had uniaxial orientation in the same direction as the low-molecular rod-shaped liquid crystal.

[Comparative Example 1] The upper and lower substrates were changed to glass substrates with ITO transparent electrodes, and the left and right aluminum electrodes were not attached.
Using the same material as in the example, a cell was prepared in the same manner, and a polymer dispersed liquid crystal cell was prepared.

A black light absorbing plate was placed on the back of the cell prepared above, and scattered light and reflected light were visually observed under room light. There was no difference in scattering between the cell prepared in Comparative Example 1 and the cell prepared in Example 1. Next, a voltage was applied to both.
When an AC voltage of 50 V and 60 Hz was applied, it was found that the cell prepared in Example 1 visually had a strong scattering as compared to Comparative Example 1 as a clear difference. In addition, observation with a polarizing microscope in a state where an electric field was applied revealed that the optical axis of the polymer of Example 1 was shifted from that of the low-molecular rod-shaped liquid crystal.

For each of the cells of Example 1 and Comparative Example 1 obtained above, the reflected light intensity was measured by an automatic change photometer (“GP-200” manufactured by Murakami Color Research Laboratory Co., Ltd.). When the light intensity in the direction of the emission angle of 37 degrees was compared at the incident angle of 30 degrees with the electric field applied, the cell of Example 1 had a 45% higher reflected light intensity than the cell of Comparative Example 1. In the cell of Example 1, the contrast ratio between the state where no electric field was applied and the state where an electric field was applied was 1: 4.5.

Example 2 <Polymerized Discotic Liquid Crystalline Compound C Used> The following compound C was used as the polymerizable discotic liquid crystal compound.

[0079]

Embedded image The phase transition of Compound C was Cryst- (44 ° C.)-Iso (temperature increasing process) and Cryst- (15 ° C.)-Iso (temperature decreasing process).

The polymerizable discotic liquid crystal compound C and the low-molecular rod-shaped liquid crystal B used in Example 1 were mixed with 50/50
The mixture was mixed at a weight ratio of 50. To this mixture was added 200 ppm of 2,6-di-tert-butyl-4-methylphenol in the same manner as in Example 1, and further, 2% by weight of a photopolymerization initiator ("Irgacure 184" manufactured by Ciba-Geigy) was added. Inject into the cell created in 1
cm ^2, and exposed for 3 minutes at the center wavelength 365nm UV to prepare a liquid crystal cell. The rod-like liquid crystal was well phase-separated, and according to observation under a polarizing microscope in a hot stage manufactured by Mettler, a phase transition from a nematic to an isotropic phase of the rod-like liquid crystal was observed at almost the same temperature as the phase transition temperature before mixing. From this, it was confirmed that almost all of the polymerizable discotic liquid crystal compound was polymerized to be a polymer compound. Further, it was observed under a polarizing microscope that the low-molecular rod-shaped liquid crystal was well uniaxially oriented.

Comparative Example 2 The polymerizable discotic liquid crystalline compound C was changed to hexylene diacrylate,
The mixture was obtained by mixing with the rod-shaped liquid crystal B at a weight ratio of 50/50. This mixture was injected into the cell of Example 1 in the same manner as described above, and subjected to UV exposure in the same manner as described above, thereby producing a polymer-dispersed liquid crystal device.

A black light absorbing plate was placed on the back of the cell prepared above, and scattered light and reflected light were visually observed under room light. Compared to the cell prepared in Comparative Example 2, it was found that the cell prepared in Example 2 had such a strong scattering as to be seen as a clear difference visually. Example 2
It was found that in the cell prepared in the above, the scattered light was modulated in a state where an electric field of 50 V and 60 Hz was applied, and the low-molecular rod-shaped liquid crystal was in-plane switched.

For each of the cells obtained in Example 2 and Comparative Example 2 obtained above, the reflected light intensity was measured by an automatic change photometer (“GP-200” manufactured by Murakami Color Research Laboratory Co., Ltd.). When the light intensity in the direction of the emission angle of 30 degrees was compared at the incident angle of 30 degrees with the electric field applied, the cell of Example 2 had a 3.4 times higher reflected light intensity than the cell of Comparative Example 2.

In the cell of Example 2, when the state was changed from the state where no electric field was applied to the state where an electric field was applied, the reflected light intensity was 21%.
Increased.

[Embodiment 3] Both cells produced in Embodiments 1 and 2 were separately used as liquid crystal elements 303 on the liquid crystal element portion of the projection optical system shown in FIG. In each case, a change in luminance on the screen was confirmed with and without the application of an electric field of 50 V and 60 Hz.

[Embodiment 4] As shown in FIG. 7, a single crystal silicon transistor (ON resistance: 50Ω), a liquid crystal test cell (area: 0.9 cm ² ) used in the previous embodiment, and a ² nF ceramic capacitor were used. Thus, an active element was created. A gate signal having a selection period of 30 μS is applied thereto, and a voltage of 30 V, -3 is applied from the information signal line.
Waveforms were given in the order of 0V, 30V, -30V, 0V, 0V, 0V, 0V. When a voltage signal was applied to the liquid crystal cell so as to have a frame frequency of 10 Hz, light modulated under a microscope was observed.

[0087]

As described above, according to the present invention, a polymer matrix which does not require a polarizing plate and which can be driven with higher brightness and lower power consumption than a conventional polymer matrix type liquid crystal device. A liquid crystal element of the type is provided.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a rod-like liquid crystalline polymer constituting a liquid crystal element of the present invention and a refractive index ellipsoid of a rod-like low-molecular liquid crystal in two states before and after in-plane switching.

FIG. 2 is a schematic sectional view in the thickness direction of one embodiment of the liquid crystal element of the present invention.

FIG. 3 is a schematic sectional view in the thickness direction of another embodiment of the liquid crystal element of the present invention.

FIG. 4 is an explanatory diagram of a projection optical system including the liquid crystal element of the present invention.

FIG. 5 is a schematic sectional view of a liquid crystal element of the present invention including an active element.

FIG. 6 is a circuit diagram of an active matrix liquid crystal device including the liquid crystal element.

FIG. 7 is an equivalent circuit diagram of an active element driving liquid crystal element operated experimentally.

[Explanation of symbols]

npo, npe: refractive index of ordinary light and extraordinary light of rod-shaped liquid crystalline polymer no, ne: refractive index of ordinary light and extraordinary light of rod-shaped low molecular liquid crystal 1a, 1b, 41, 42: (transparent) substrates 2a, 2b, 18, 19 : Alignment layer 3a, 3b, 43, 47: In-plane switching electrode 4: Spacer 5: Liquid crystal layer 5a: Liquid crystalline polymer 5b: Bar-shaped low molecular liquid crystal 20: Seal material 43: Pixel electrode 47: Counter electrode 44: TFT 90: Liquid crystal cell

Claims (11)

[Claims] 1. A liquid crystal layer comprising a liquid crystalline polymer matrix and a rod-shaped low-molecular liquid crystal phase is disposed between a pair of substrates. At least one of the pair of substrates has molecules of the rod-shaped low-molecular liquid crystal. A liquid crystal element provided with electrodes having an arrangement suitable for switching an axis in a plane parallel to the substrate. 2. The liquid crystal device according to claim 1, wherein a surface of at least one of the pair of substrates in contact with the liquid crystal is subjected to a uniaxial alignment treatment. 3. The liquid crystal device according to claim 1, which is used without a polarizing plate. 4. The light modulation is performed by switching the molecular axis of the rod-shaped low-molecular liquid crystal to change the relative angle between the molecular axis and the molecular axis of the liquid crystalline polymer.
Any of the liquid crystal elements. 5. The liquid crystal device according to claim 1, wherein said rod-shaped low-molecular liquid crystal is a nematic liquid crystal, and a switching electrode is provided on one of a pair of substrates. 6. The liquid crystal device according to claim 1, wherein said rod-shaped low-molecular liquid crystal is a P-type or N-type liquid crystal. 7. The liquid crystal device according to claim 1, wherein a scattering state of light passing through the liquid crystal layer is modulated by switching a molecular axis of the rod-shaped low molecular liquid crystal. 8. The liquid crystal device according to claim 1, wherein reflected light from the liquid crystal device is viewed as a display signal. 9. The liquid crystal device according to claim 8, further comprising a light absorbing plate provided on the back surface. 10. The liquid crystal element according to claim 1, wherein an active element is arranged on at least one of the pair of substrates. 11. A liquid crystal device comprising the liquid crystal element according to claim 1 and an optical system for projecting the liquid crystal element.