JP2001051299A - Liquid crystal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a cell gap from fluctuating due to the free deformation of a thin film. SOLUTION: One substrate 11A of a pair of substrates 11A, 13 holding a liquid crystal 16 is composed of a semiconductor substrate 11 and a thin film 12, having pixel electrodes formed to drive the liquid crystal 16 on the substrate 11. Furthermore, the thin film 12 is supported by a solid material 15 contained in the liquid crystal 16. The semiconductor substrate 11 is preferably a single- crystal silicon substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal device,
In particular, the present invention relates to a device in which a thin film including a pixel electrode for driving a liquid crystal is provided on one substrate holding the liquid crystal.

[0002]

2. Description of the Related Art Conventionally, in a liquid crystal element in which liquid crystal is sandwiched between a pair of substrates, a thin film (hereinafter, referred to as a membrane) on which a pixel electrode for driving the liquid crystal is formed is provided on one of the pair of substrates. There is something like that. In addition,
As a liquid crystal device (hereinafter, referred to as an LCD) having a liquid crystal panel as a liquid crystal element using such a membrane, for example, Japanese Patent No. 2824828,
67205 and the like.

Incidentally, the mechanical strength of this membrane is high. For example, even if a liquid crystal element is dropped, a single crystal silicon substrate or a glass substrate provided with the membrane is destroyed first. In addition, this destruction can be escaped by covering the ends of both substrates with a soft frame material such as plastic as is well known. Further, the membrane is weak against particles, debris, etc., which collide at high speed in the vertical direction, but this can be avoided by providing a protective glass on the membrane.

[0004]

However, in such a conventional liquid crystal device, the membrane has mechanical strength as described above. However, when the liquid crystal device is upright and held, for example, the gravity in the liquid crystal device is increased by gravity. The liquid crystal starts moving downward, and the membrane may be deformed accordingly. Then, when the membrane is deformed in this way, especially when only the periphery of the membrane is connected to the single crystal silicon substrate, a serious problem occurs.

For example, when the membrane has a diagonal size of 0.6 inch (about 15 mm), when the liquid crystal element is erected and held, the liquid crystal which starts moving downward by gravity causes the membrane 202 to move downward as shown in FIG. Is "Liquid crystal dripping"
This causes a change in a gap (hereinafter referred to as a cell gap) t between the substrate 203 and the membrane 202.

[0006] In this case, the extent of this change in the cell gap t by the liquid crystal dripping width Δt (m) is a _{Δt = ρ · g · X 0} 3 / 4π 3 T · b.

Note that ρ (kg / m ³ ) is the density of the liquid crystal 205 sandwiched between the substrate 203 and the membrane 202, g (m / sec ² ) is the gravitational acceleration, and X ₀ (m) is the length of the membrane opening. , T (N / m ² ) is the membrane 202
Is the internal stress (tension), and b (m) is the membrane thickness.

For example, a TN having a normal cell gap of 4 μm
In a liquid crystal panel, the variation width Δt of the cell gap t is about 0.5 μm (total width), which is barely usable. However, if the cell gap t is further reduced, an appropriate display can be performed. become unable.

[0009] Even if a liquid crystal 205 is injected by spraying a spherical spacer (not shown) in order to suppress such deformation of the membrane 202, the membrane 202 is deformed so as to wrap around the spherical spacer. . further,
When the membrane 202 is provided on the single crystal silicon substrate 201 capable of miniaturizing the pixel and the pixel size is reduced (≦ 2
(0 μm), a spacer having a particle size of about the gap amount greatly reduces the aperture ratio of a pixel, so that it cannot be practically used.

On the other hand, since the liquid crystal dripping occurs even with a small force such as the force of gravity, there is a possibility that the liquid crystal droops due to another force larger than that. For example, when the liquid crystal element is maintained at a high temperature, the membrane 202 is deformed due to thermal deformation of the liquid crystal element and thermal expansion of the liquid crystal 205, and the cell gap t becomes non-uniform. Further, depending on the method of driving the liquid crystal element even when the liquid crystal element is placed flat, a well-known electrodynamic convection may occur and a similar nonuniform gap may occur.

One of the methods for preventing the deformation of the membrane 202 is a solid (film) described in JP-A-6-67205.
The membrane 202 is reinforced by
02 requires a large internal stress (tension) to prevent gap fluctuation, and such reinforcement is practically difficult. That is, most of the internal stress of the solid (film) that can be attached at room temperature is compressive, and it is not possible to generate the tension necessary to support the membrane 202. further,
The liquid crystal cell is pressed by the thermal expansion of this solid (film),
The cell gap fluctuates.

Accordingly, the present invention has been made in view of such circumstances, and an object of the present invention is to provide a liquid crystal element capable of preventing a cell gap from being changed due to free deformation of a membrane (thin film). It is.

[0013]

According to the present invention, there is provided a liquid crystal device in which liquid crystal is sandwiched between a pair of substrates. One of the pair of substrates has a pixel electrode for driving the liquid crystal on a semiconductor substrate. The thin film is provided with a formed thin film, and the sandwiched liquid crystal has a solid material supporting the thin film.

Further, the present invention is characterized in that the liquid crystal contains a polymer substance and the solid is formed by filling the liquid crystal between the substrates and then curing the liquid crystal.

Further, the present invention is characterized in that the liquid crystal is a one-dimensional liquid crystal.

Further, the present invention is characterized in that the solid material also supports the other of the pair of substrates.

Further, the present invention is characterized in that the semiconductor substrate is a single crystal silicon substrate.

Further, the invention is characterized in that the semiconductor substrate has an opening for exposing the thin film.

Further, the present invention is characterized in that the opening of the semiconductor substrate is formed by chemically anisotropically etching the semiconductor substrate.

Further, the present invention is characterized in that a thin film transistor for driving the driving electrode is formed on the thin film.

Further, as in the present invention, one of the pair of substrates holding the liquid crystal is provided with a thin film in which a pixel electrode for driving the liquid crystal is formed on a semiconductor substrate. The thin film is supported by a solid substance contained in the liquid crystal.

[0022]

Embodiments of the present invention will be described below.

FIG. 1 is a view showing a structure of a liquid crystal element according to a first embodiment of the present invention. In FIG. 1, 1 is a liquid crystal panel which is a liquid crystal element, 11A is an active matrix substrate, and 11 is an active matrix substrate. This is a 625 μm-thick CZN (100) single-crystal silicon substrate (hereinafter, referred to as a silicon substrate) that constitutes the matrix substrate 11A and has an opening 11a.

Reference numeral 13 denotes a counter substrate on which a color filter (not shown) is formed, and 14 denotes an active matrix substrate 1.
This is a seal 14 for attaching the counter substrate 1A to the counter substrate 13. The liquid crystal 15 is sandwiched between the pair of substrates 11A and 13. The pair of substrates 11
The size of the liquid crystal cell formed by A and 13 is 2 cm square, and the gap amount is 10 μm.

Reference numeral 12 denotes a membrane having a thickness of about 4 μm provided on the silicon substrate 11. The membrane 12 is made of SiN · SiO, and has a pixel electrode (not shown) for driving the liquid crystal 15 and a pixel electrode (not shown). TFTs and the like for driving pixel electrodes are formed. In addition, this membrane 1
The stress of No. 2 is slightly tensil-like so that wrinkles do not occur in the membrane 12 when the opaque opening forming portion of the silicon substrate 11 is removed to form the opening 11a of the silicon substrate 11 as described later. That is, it is set to be slightly pulled.

On the other hand, reference numeral 16 denotes a columnar solid material formed by curing a part of the liquid crystal 15. By forming the solid material 16 in the liquid crystal cell in this manner, the freely deformable membrane 12 is mechanically formed. And the deformation of the membrane 12 can be prevented.

When a part of the liquid crystal 15 is hardened to form the solid 16 in this manner, the liquid crystal portion to be displayed is divided by the solid 16. here,
When the liquid crystal portion is divided in this way, the liquid crystal having a higher order of two or more dimensions is disturbed in its alignment, and therefore the one-dimensional liquid crystal 15 is preferable as the liquid crystal 15 to be used. By using the one-dimensional liquid crystal as described above, at least the order in the cell gap direction can be maintained, and the columnar solid 16 supporting the membrane 12 can be arranged between the liquid crystal regions in which the order is maintained.

As the one-dimensional liquid crystal, a polymer material such as a well-known polymer dispersed liquid crystal (hereinafter, referred to as PDLC) or a polymer network liquid crystal (hereinafter, referred to as PNLC) can be used. Uses polymer network liquid crystal.

Next, the liquid crystal panel 1 thus constructed
A method of manufacturing the device will be described.

First, PNLC, which is a mixture of an acrylate polymer and TNLC, is placed in a liquid crystal cell for 0.5 t.
The solution is dropped and injected at a vacuum of orr. Next, ultraviolet light having an illuminance of 100 mW / cm ² was irradiated for 1 minute using an ultra-high pressure mercury lamp and a UV filter for cutting 350 nm or less.
The NLC is cured to form a polymer network structure as a solid 16 in the liquid crystal.

As described above, by injecting PNLC, making it liquefied before filling, and curing it after injection, PNL is cured.
The injection of C can be performed promptly, and the solids mixed in the liquid crystal can be prevented from being biased.
Also, there is no problem of wrapping of the membrane 12.

Thereafter, from the back surface of the silicon substrate 11, silicon in a portion corresponding to the opening 11a (display portion) of the liquid crystal panel 1 is removed by using a TMAH chemical anisotropic etching solution.
It is selectively removed by an aqueous solution of (tetramethylammonium bidlokind) to expose the membrane 12. Note that this TMAH aqueous solution has a high selectivity (up to 1 / 10,000) with respect to SiN / SiO as described above, and the etching is practically stopped when the membrane 12 is exposed.

At this time, the membrane 12 is PN
Free deformation does not occur due to being supported by the polymer network structure formed in the LC. Further, since this network structure also supports the opposing substrate 13, the gap amount of the liquid crystal element 1 is kept substantially the same as that at the time of injection.

The liquid crystal panel 1 constructed as described above
, The membrane 12 is driven by an LC drive circuit (not shown).
When a voltage is applied between the two substrates 12 and 13 via the pixel electrodes by driving the TFTs, the liquid crystal 15 having a structure other than the network structure responds, causing a difference in transmittance and enabling display.

As described above, since the membrane 12 provided on the active matrix substrate 11A is supported by the solid material (network structure) 16 contained in the liquid crystal 15, a uniform gap amount that does not cause dripping of the liquid crystal can be obtained. A high-quality liquid crystal element can be provided.

Next, a second embodiment of the present invention will be described.

FIG. 2 is a diagram showing a configuration of an OCB type liquid crystal element which is a liquid crystal element according to the present embodiment. The polymer stabilized (stabilized) LC used in this liquid crystal element is, for example, “S23-2 OCB-Cell”.
Using PolymerStabilized
Bend Alignment ”ASIA DISP
LAY'95 pp581 and "P-59: Polym
er-Stabilized Pi-Cells as
Switchable Phase Retard
rs "SID97DIGEST pp731.

In the liquid crystal device 1, a nematic phase liquid crystal mixture 25 composed of a UV cure monomer and a one-dimensional liquid crystal is injected into a liquid crystal cell that has been subjected to an alignment treatment to form a π cell. To form a solid polymer network 26 mainly in the gap direction between the substrate 23 and the membrane 21.

In this embodiment, the liquid crystal cell 1
Is 7 μm, and display can be performed with an applied voltage of about 7V. In addition, the OCB type liquid crystal display is capable of high-speed response in principle, and the response time is about 5 msec.

According to the present embodiment, the voltage for driving the liquid crystal panel 1 can be reduced, and an intelligent and high-performance display device such as field sequential, color sequential, etc. can be realized. .

FIG. 3 is a diagram showing a configuration of a display device in which a liquid crystal element and a schlieren optical system according to a third embodiment of the present invention are combined.

In the figure, reference numeral 1A denotes a liquid crystal element. In this liquid crystal element 1A, a liquid crystal cell includes PDLC, Darocuure 1116 manufactured by Merck and liquid crystal E manufactured by BDH.
By injecting and curing the mixture of No. 8, liquid crystal particles 35 and a polymer matrix 36 which are solids are formed.

When parallel light is incident on such a liquid crystal element 1A, the incident parallel light is condensed by a condenser lens 37, and only light passing through a pinhole plate 38 forms an image on a screen 39. Since the PDLC is scattered by application of a voltage and assumes a non-scattering state, the illumination light (parallel light)
Switching can be performed.

The voltage at this time is the cell gap amount 1
In the case of 0 μm, it may be about 10V. Further, the contrast of the display device can easily be about 200 by reducing the size of the hole 38a of the pinhole plate 38 and sacrificing the brightness.

As described above, according to the present embodiment, a display device with high contrast can be realized. further,
As in the present embodiment, a high-quality display device utilizing the characteristics of a semiconductor substrate capable of high integration and miniaturization by combining the liquid crystal element according to the other embodiments described above with an appropriate optical system is provided. Can be provided.

[0046]

As described above, the thin film provided on one of the substrates holding the liquid crystal is supported by the solid matter contained in the liquid crystal as in the present invention, whereby the cell gap due to the free deformation of the thin film is reduced. Fluctuations can be prevented.
Thereby, the gap amount of the liquid crystal element can be kept uniform, and the display quality is also improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a liquid crystal panel which is a liquid crystal element according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a liquid crystal element according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a display device using a liquid crystal element according to a third embodiment of the present invention.

FIG. 4 is a diagram illustrating a defect of a conventional liquid crystal element.

[Explanation of symbols]

 1,1A Liquid crystal panel 11A Active matrix substrate 11 Silicon substrate 12,21 Membrane 13,23 Counter substrate 15 Liquid crystal 16 Solid 25 Liquid crystal mixture 26 Polymer network 35 Liquid crystal particle 36 Polymer matrix

Continued on the front page F-term (reference) 2H089 HA04 KA08 QA14 RA05 TA01 TA09 2H090 JB04 JC01 KA11 LA04 2H092 GA59 JA24 KA03 MA17 NA01 NA25 PA01 PA06 PA08 QA07 QA15 5C094 AA03 AA36 AA43 AA47 AA54 BA03 FA02

Claims (8)

[Claims] 1. A liquid crystal element having a liquid crystal interposed between a pair of substrates, wherein one of the pair of substrates has a thin film on which a pixel electrode for driving the liquid crystal is formed on a semiconductor substrate. A liquid crystal element having a constitution, wherein the sandwiched liquid crystal has a solid material supporting the thin film. 2. The liquid crystal device according to claim 1, wherein the liquid crystal contains a polymer substance, and the solid is formed by filling the liquid crystal between the substrates and then curing the liquid crystal. 3. The liquid crystal device according to claim 1, wherein the liquid crystal is a one-dimensional liquid crystal. 4. The substrate according to claim 1, wherein the solid also supports the other of the pair of substrates.
The liquid crystal element according to the above. 5. The liquid crystal device according to claim 1, wherein said semiconductor substrate is a single crystal silicon substrate. 6. The liquid crystal device according to claim 1, wherein the semiconductor substrate has an opening for exposing the thin film. 7. The liquid crystal device according to claim 6, wherein the opening of the semiconductor substrate is formed by chemically anisotropically etching the semiconductor substrate. 8. The liquid crystal device according to claim 1, wherein a thin film transistor for driving the driving electrode is formed on the thin film.