JPH06337422A - Liquid crystal electro-optical device - Google Patents

Abstract

PURPOSE:To stabilize optical characteristics, display multiple gradation at high speed, and realize a large area and the like by arranging ferroelectric liquid crystal and PCS between a substrate where crystalline silicon TFT is connected to a picture element electrode and a substrate having a counter electrode. CONSTITUTION:A substrate 102 where crystalline silicon TFT(thin film transistor) 101 is connected to a picture element electrode 100 and a counter electrode 103 are arranged, and a substrate 104 forming an oriented film 105 to orient uniaxially a liquid crystal material is opposed to these, and both substrates 102 and 104 are fixed to each other by a sealing material through a spacer. Unhardened resin is mixed in a ferroelectric liquid crystal material 107, and it is injected between the substrates 102 and 104, and column shape resin PCS(polymerization column spacer) 106 is deposited and hardened. An action of undesirable electric charge unstabilizing a condition of liquid crystal existing in a liquid crystal layer 107 is removed by this deposition and hardening. Thereby, since the movement and the accumulation of the electric charge are eliminated, when voltage is impressed between the electrodes, it is reversed sharply and sufficiently, so that a change of a display condition with the lapse of time after being reversed can be also removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an active matrix type liquid crystal electro-optical device using a ferroelectric liquid crystal.

[0002]

2. Description of the Related Art Recently, a liquid crystal display device (LCD)
Is attracting attention. Among them, particularly, an active matrix type in which a switching element such as a thin film transistor (TFT) is provided in each pixel using a nematic liquid crystal material,
It has been actively developed as a device capable of high-speed, high-contrast, multi-gradation display.

On the other hand, an LCD using a ferroelectric liquid crystal has also been developed. In a ferroelectric liquid crystal, liquid crystal molecules have spontaneous polarization,
It can switch at high speed in tens of microseconds and has a memory property. An active matrix type LCD using this ferroelectric liquid crystal has been developed, which can display at higher speed.

In particular, since this ferroelectric liquid crystal has bistability, it is difficult to maintain an intermediate state other than ON (transmission) and OFF (non-transmission) of the display, but compared with the nematic liquid crystal. Since it can switch about 3 digits faster,
It is possible to perform so-called frame gradation display, in which N and OFF are controlled for each display frame and gradation display is performed according to the display time. By controlling this ON / OFF time with a digital value using a TFT, multi-tone digital gradation display can be performed. For details, see Japanese Patent Application No. 4-2.
No. 75413.

Amorphous silicon TFTs may be used as the TFTs, but in order to support high-speed switching of ferroelectric liquid crystal and to achieve higher digital speeds, higher gradations, and higher contrast ratios, It is necessary to inject charges into pixels more quickly. Therefore, a crystalline silicon TFT is used which operates about four orders of magnitude faster than an amorphous silicon TFT and can flow a large current sufficient to invert spontaneous polarization.

[0006]

2. Description of the Related Art An active-matrix type ferroelectric liquid crystal electro-optical device capable of high-speed and multi-gradation display as described above. It is necessary that the inversion of the liquid crystal molecules of the dielectric liquid crystal is carried out in an extremely short time, and the inversion is sufficiently completed, and that the state of the liquid crystal molecules after the inversion does not change and is constant. It is mainly the magnitude of the voltage applied to the electrodes on both substrates that determines the state of the liquid crystal molecules.

However, it is well known that impurities having a charge from the liquid crystal or the alignment film exist in the device, or that an extra charge that generates a voltage in a direction opposite to the voltage is generated when a voltage is applied. There is. These charges move freely in the liquid crystal material sandwiched between the substrates as a voltage is applied. Most of these charges move to reach the surface of the alignment film, but since the alignment film is originally insulating, the charges do not move any more and the space between the alignment film and the liquid crystal layer (layer of liquid crystal material) (alignment film) is increased. Liquid crystal interface) will be accumulated in the form.

These charges cause a problem which is not preferable for a liquid crystal electro-optical device. For example, the effect of canceling the voltage applied between the electrodes occurs, which causes attenuation of contrast. For example, when driving a TFT and applying a pulse voltage, the switching between transmission and non-transmission is not steep with respect to the pulse application, and there is a two-step response in which switching is performed once and then further switching occurs, and attenuation occurs immediately after switching. I did it. In order to solve this, it was necessary to make the applied voltage larger than the voltage required to invert the spontaneous polarization, but this was not a sufficient measure.

Further, when a voltage is applied between the electrodes, the state of the liquid crystal molecules is not stable because the charge amount in the liquid crystal layer changes with time. Further, the liquid crystal molecules that are electrically adsorbed by the charge accumulated at the alignment film-liquid crystal interface require a larger voltage to change the state than the unadsorbed liquid crystal molecules inside the liquid crystal layer, and therefore the liquid crystal molecules inside the liquid crystal layer However, there is a problem that the light transmission characteristics, which are the most important characteristics of the liquid crystal electro-optical device, are not stable because they do not change their states all at once.

In the liquid crystal electro-optical device, the display becomes unstable, the response speed of the liquid crystal material cannot be fully utilized, and the display speed is inevitably decreased, and the contrast is decreased. Especially when the frame gradation display is performed, the number of gradations is limited.

In order to solve this problem, a liquid crystal molecule is selected by selecting an alignment film material that alleviates the accumulation of charges, or by obliquely vapor-depositing SiO ₂ or the like on the electrode instead of the alignment film which is an insulating film. Although there is a method for orienting the above, it cannot be said to be a general method because it requires a lot of preliminary experiments, which takes time and is costly, and its effect changes depending on the combination of materials. There is also a method of purifying the liquid crystal to remove impurities, but this method is extremely unsuitable in view of mass productivity because the liquid crystal that can be purified and used is very small. In addition, a charge transfer complex or the like is used to adsorb or combine charges existing in the liquid crystal layer to bring positive or negative charges into plus or minus 0 (hereinafter referred to as cancellation or neutralization). Although there is a method, it is difficult to measure the charge transfer complex that completely cancels the charge into the device, and the excess charge transfer complex moves in the liquid crystal layer in the same manner as the charge described above.

As described above, it is present in the liquid crystal layer that is a factor that causes a change in the voltage applied to the liquid crystal layer, that is, a factor that causes a change in the state of liquid crystal molecules over time and destabilizes the optical characteristics of the device. Although various methods have been proposed for canceling charges, there is still no easy and complete method for canceling charges.

Further, it is desired to increase the area of the display screen. In particular, in a liquid crystal electro-optical device using a ferroelectric liquid crystal, since liquid crystal molecules have a layered structure, a large area substrate is used. Since the substrate is distorted or dull, and the layer structure is broken thereby hindering display, it is difficult to increase the area.

Further, as a method of maintaining the substrate spacing, a spherical spacer made of silicon oxide or the like held between the substrates has been used conventionally, but this only prevents the reduction of the substrate spacing, and the expansion of the substrate spacing is prevented. Was powerless. Therefore, when the area of the ferroelectric liquid crystal electro-optical device is increased, especially when the substrate is used upright, the liquid crystal material accumulates on the lower side and the distance between the substrates becomes large, and the display becomes impossible.

Further, as a method for preventing the expansion of the substrate interval,
There is a method in which particles of a spacer and an adhesive are scattered on the surface of the substrate and the particles are crushed to bring the upper and lower substrates into close contact with each other. However, when the liquid crystal material is injected into the formed liquid crystal cell and aligned, the adhesive In the vicinity of the particles, the alignment state is disturbed, so-called alignment defects are generated, and the contrast is lowered.

[0016]

SUMMARY OF THE INVENTION The present invention, in a liquid crystal electro-optical device using an active matrix type ferroelectric liquid crystal having a crystalline silicon TFT, eliminates the influence of undesired charges in the liquid crystal layer. It is intended to provide a high-performance liquid crystal electro-optical device which realizes high-speed operation of the device and stabilization of optical characteristics, enables high-speed multi-gradation display, and has a high contrast ratio. Further, the area of the device is increased.

[0017]

[Means for Solving the Problems] In order to solve the above problems,
In the present invention, a first substrate having a crystalline silicon thin film transistor connected to a pixel electrode and a second substrate having a counter electrode are provided to face each other, and at least one surface of the first and second substrates is provided. Has a uniaxial orientation means, and a ferroelectric liquid crystal material oriented according to the uniaxial orientation means and an uncured resin mixed in the liquid crystal material are deposited between the first and second substrates. And having a column-shaped resin formed by curing.

Further, the present invention is characterized in that, in the above constitution, the uncured resin is an ultraviolet curable resin.

With the above-described structure, the present invention realizes a liquid crystal electro-optical device using a high-speed, high-contrast ferroelectric liquid crystal by removing undesired charges in the liquid crystal layer, and enables high-quality digital gradation. In addition, it is possible to realize a liquid crystal electro-optical device in which the layers of the liquid crystal material are not destroyed even if the substrates are made to adhere to each other by a resin so as to prevent the distance between the substrates from increasing and the area is increased.

The conceptual structure of the liquid crystal electro-optical device of the present invention will be described with reference to FIG. A substrate 102 having a crystalline silicon TFT 101 connected to the pixel electrode 100, a substrate 104 having a counter electrode 103, and an alignment film 105 as a means for aligning liquid crystals are formed on the substrate. The alignment film may be formed on both substrates, but here, the alignment film is formed on only one substrate. In addition, a spacer (not shown) is used to maintain a constant substrate distance,
Both substrates are fixed with a sealant (not shown). A column-shaped resin 106, in which upper and lower substrates are adhered, and a liquid crystal 107 are sandwiched between the substrates to form a device. Some resins have resin bumps instead of columnar ones.

To manufacture this liquid crystal electro-optical device, a first substrate having a thin film transistor using a crystalline silicon film connected to a pixel electrode and a second substrate having a counter electrode are used.
At least one of the substrates is provided with a uniaxial orientation means such as an orientation film to face each other to form a liquid crystal cell, and a liquid crystal material and an uncured resin are mixed in the cell so that the liquid crystal is mixed well. A liquid crystal mixture prepared by heating and stirring is injected until the shows an isotropic phase. When the temperature of the device is gradually lowered from the temperature at which the liquid crystal mixture exhibits an isotropic phase, the uncured resin mixed in the liquid crystal mixture is deposited in a column shape and scattered in the device.

By irradiating this apparatus with ultraviolet rays, the resin is cured into a column shape and adheres to the upper and lower substrates or the electrodes and the alignment film on the upper surface thereof to fix the space between the substrates. Alternatively, they are present as resin bumps (resin solid matter) in the liquid crystal layer.

The columnar resin precipitated and cured from the liquid crystal material as described above is a columnar resin spacer, and is referred to as a polymerized column spacer (Polymaerized Column Spacer).
, PCS).

[0024]

The present inventors mixed an uncured resin into a liquid crystal material, injecting it between substrates, and then curing it to undesirably charge an undesired charge that makes the state of liquid crystal present in the liquid crystal layer unstable. It was discovered that the action of can be eliminated.

The effect is that the above-mentioned undesired charges are taken into the resin when the resin material is cured, or the reaction initiator generally mixed in the uncured resin diffuses into the liquid crystal material. It is conceivable that the resin is cleaved when the resin is cured to generate an electric charge, and the above-mentioned undesired electric charge is adsorbed or bonded to the electric charge.

According to the present invention, the movement of charges and the accumulation of charges at the liquid crystal interface of the alignment film, which have been problems in the past, are eliminated. Therefore, when a voltage is applied between the electrodes, the spontaneous polarization abruptly inverts and fully inverts. Further, the change with time in the display state after the reversal could be removed. Further, since there is no liquid crystal molecule adsorbed on the substrate, the entire liquid crystal layer between the electrodes changes state at the same time when a voltage is applied, and more stable optical characteristics can be obtained. Therefore, a display having a high speed and a high contrast ratio can be realized.

Further, the resin can adhere the upper and lower substrates in a column shape as shown in FIG. Since the present invention cures the resin after the liquid crystal material is aligned according to the alignment means, it is possible to maintain a good liquid crystal alignment state before curing,
The effect of the cured resin on the orientation is extremely small. Since the resin is cured with the alignment state being good, it is natural that the alignment is not damaged after the resin is cured. As a result, it is possible to prevent the occurrence of alignment defects and prevent the deterioration of contrast.

When the device display portion after the resin separation and deposition is viewed from the substrate surface, if the ratio of the area occupied by the cured resin is 0.1 to 20%, sufficient performance as a liquid crystal electro-optical device can be obtained. .

This polymerized column spacer (PCS) can prevent expansion and reduction of the substrate spacing, and can also improve the strength of the substrate to prevent distortion, resulting in collapse of the liquid crystal layer structure and uneven display. It has become possible to control the device and use the device upright. In addition, the orientation is not disturbed.
Therefore, a liquid crystal electro-optical device using a large area ferroelectric liquid crystal can be realized.

The function of removing the effect of undesired charges was obtained by mixing only the reaction initiator, which is usually added to commercially available resins, into the liquid crystal material and then cleaving it with ultraviolet rays or the like. . Even if the amount of the reaction initiator added to the resin is changed, the resin is made into a resin material (monomer or oligomer).
And the reaction initiator may be divided and mixed separately.

Examples will be shown below.

[0032]

Example In this example, a ferroelectric liquid crystal was used,
An active matrix type liquid crystal electro-optical device for performing digital gradation display in which an N-channel type crystalline silicon TFT was provided in each pixel as a switching element was manufactured. Although one pixel will be described below, a large number of pixels (generally several hundreds of thousands) are formed in the same structure.

An outline of the manufacturing process of this embodiment is shown in FIG.
In this embodiment, Corning 70 is used as the substrate 201.
59 glass substrate (thickness 1.1 mm, 300 x 400 m
m) was used. First, the base film 202 (silicon oxide) is formed by a sputtering method. After that, an amorphous silicon film (thickness 300 to 1500Å, preferably 300 to 500Å) is formed by LPCVD or plasma CVD, dehydrogenated at 400 ° C for 1 hour, and then crystallized by heating annealing. It was This annealing step
In a hydrogen reducing atmosphere (preferably, the partial pressure of hydrogen is 0.1 to
(1 atm) and 600 ° C. for 48 hours. Further, this heat annealing step may be performed in an inert atmosphere such as nitrogen.

Thus, the semiconductor film 203 made of crystalline silicon can be obtained (FIG. 2A). Next, the semiconductor film 203 was patterned to form an island-shaped semiconductor region (active layer of TFT). Further, a gate insulating film of silicon oxide (thickness 700 to 1200 Å, typically 1000 Å) 2 is formed by plasma CVD in an oxygen atmosphere using tetra-ethoxy-silane (TEOS) as a raw material.
04 was formed. The substrate temperature was 400 ° C. or lower, preferably 200 to 350 ° C., in order to prevent the glass from shrinking and warping.

Next, an aluminum film was formed to a thickness of 6000 Å by a sputtering method and patterned to form a gate electrode 205. Further, the surface of the aluminum electrode is anodized to form an oxide layer 20 on the surface.
6 was formed. This anodic oxidation was performed in an ethylene glycol solution containing 1 to 5% tartaric acid. The thickness of the obtained oxide layer 206 was 2000Å. Since the oxide layer 206 has a thickness to form the offset gate region in the next ion doping process, the length of the offset gate region can be determined by the anodizing process.

Then, using the gate electrode 205 and the surrounding oxide layer 206 as a mask, phosphorus is implanted as an N-type impurity by an ion doping method, and the source region 207, the channel formation region 208, and the drain region 20 are self-aligned.
9 was formed (FIG. 2B), and the crystallinity of the silicon film whose crystallinity was deteriorated due to ion doping was improved by irradiating the KrF laser beam. At this time, the energy density of the laser light is 250 to 30.
It was set to 0 mJ / cm ² . By this laser irradiation, the sheet resistance of the source / drain of this TFT is 30
It became 0 to 800 Ω / cm ² .

After that, the interlayer insulator 21 is made of silicon oxide.
1 was formed, and further, the pixel electrode 212 was formed of ITO. Then, a contact hole is formed and TF
Electrodes 213 and 214 were formed in the source / drain region of T by a chromium / aluminum multilayer film, and one of these electrodes 213 was also connected to the ITO 212. The chromium / aluminum multilayer film is a chromium film 200 to 20 as a lower layer.
00 Å, typically 1000 Å, an aluminum film of 1000 to 20000 Å, typically 5000 Å is deposited on the upper layer. It is desired that these are continuously formed by a sputtering method. Finally, 200-30 in hydrogen
Annealing at 0 ° C. for 2 hours completed the hydrogenation of silicon. In this way, a crystalline silicon TFT was completed (FIG. 2 (C)). And many TFTs made at the same time
Were arrayed in a matrix to provide an active matrix liquid crystal display device having 640 × 480 pixels. The TFT manufactured in this example was an N-channel type, and its mobility was 100 (cm ² / Vs).

Next, an ITO film was formed as a counter electrode also on the substrate having a silicon oxide film 200Å laminated thereon by a sputtering method on a glass substrate as a counter substrate. This ITO film is formed at room temperature to 150 ° C.
It was accomplished by annealing in oxygen or air at 0-400 ° C. Polyimide 114 was applied as an alignment film on this substrate by spin coating and baked at 280 ° C. As a polyimide, Toray LP-64 was used. Hitachi Chemical L
Q5200 and Nissan Chemical's RN-305 can also be used. The thickness was 100-300Å, here 100Å. This substrate was subjected to rubbing treatment for uniaxial orientation treatment, while the substrate on which the TFT was formed was not subjected to orientation treatment to be a unidirectional orientation cell.

On the substrate on which the counter electrode was formed, spacers made of silica particles, which were silica particles made by Catalysts and Chemicals Co., Ltd., were scattered, and a sealing material made of epoxy resin was formed on the other substrate by screen printing. The two substrates were bonded to each other with a spacer so that the distance between the electrodes was about 1.5 μm to form a cell as shown in FIG.

As the liquid crystal material, one having a phase sequence of isotropic phase-smectic A phase-smectic C ^* -crystal was used. The response speed of the liquid crystal material when the electric field strength was 6.7 V / μm was 30 μsec. A commercially available ultraviolet curable resin was used as the resin. In addition, various resins such as thermosetting type and those that can be cured by both ultraviolet rays and heat can be used.
The mixing ratio of the uncured resin in the mixture of the uncured resin and the liquid crystal material was set to 5% and 15%. The remaining 95% and 85% are liquid crystal materials. The transition point of the liquid crystal material from the isotropic phase to the liquid crystal phase was lowered by 5 to 20 ° C. by mixing the resin.

The cell and liquid crystal were heated to 100 ° C. and injected into the above cell under vacuum. After this, it was gradually cooled to room temperature at 2 to 20 ° C./hr, here 3 ° C./hr. When the alignment state at room temperature after slow cooling was observed with a polarization microscope, the alignment of the liquid crystal material was uniaxial alignment along the rubbing direction. That is,
A good extinction position could be confirmed under a polarizing microscope.

The resin was deposited so as to be scattered between the liquid crystal materials. Since the resin did not exhibit birefringence, it did not transmit light and could be observed in a black state under a polarizing microscope. In this state, the liquid crystal material and the uncured resin can be separated.

Next, this cell was irradiated with ultraviolet rays to cure the resin inside the cell. UV intensity is 3 to 30 mW / cm ²
Here, the irradiation time was 10 mW / cm ² , and the irradiation time was 0.5 to 5 minutes, and here 1 minute.

The alignment of the liquid crystal material after the irradiation with ultraviolet rays was almost the same as that during the microscopic observation before the irradiation with ultraviolet rays and was in a good alignment state. No liquid crystal was observed for the alignment state by UV irradiation.

The results of measuring the optical characteristics of this cell are shown in Table 1. The measurement method is to detect the transmitted light intensity of the liquid crystal cell with a photomultiplier under a crossed Nicols with a polarization microscope using a halogen lamp as a light source.

[0046]

[Table 1]

As shown in Table 1, the higher the ratio of the resin in the mixture is, the larger the area occupied by the PCS in the pixel electrode portion is, the lower the transmittance in bright display is, but the contrast ratio is smaller than those values. Since it was a quotient, there was not much difference, and a good contrast ratio was obtained.

When the electrode portion of the liquid crystal cell is observed with the naked eye, the presence of the resin is completely unknown. From these results, the ratio of the resin material to the display area is 0.1-2.
If it is about 0%, it can be comparable to the conventional device.

In this way, a cell having a uniform distance between electrodes could be manufactured. Even when the completed cell was made vertical, no display unevenness could be recognized. The substrate was not deformed, and the layer structure of the used ferroelectric liquid crystal was not broken.

After removing the substrate and washing and removing the liquid crystal with alcohol, the resin remaining on the substrate was observed with a scanning electron microscope. As a result, the column-shaped resin that fixed both substrates could be observed. . The cured resin depends on the type of resin or liquid crystal material and the curing conditions, but in most cases here, the shape seen from the side has a trapezoidal or rectangular shape, and the cross section of the upper surface (the surface seen from the direction perpendicular to the substrate). ) Has a rounded square or rectangle or a circle, an ellipse, and has a plateau shape as a whole. The cross-sectional size (diameter in the case of a circular shape) of the upper surface of these resins is about several μm to several tens μ,
Its height is equal to the substrate spacing. There is a dice shape whose height is about 1/10 of the thickness to almost the same size and height as the cross section of the upper surface.

The shape of this resin also changes depending on the phase transition series of the liquid crystal material, the slow cooling rate, and the like. Some have an irregular shape and others have a major axis of resin in the uniaxial orientation direction. In addition, the interval in which the cured resin was present was about 10 to 100 μm.

In this liquid crystal electro-optical device, 32 gradations were displayed by digital gradation driving. Here, a liquid crystal electro-optical device formed by mixing 5% of resin into a liquid crystal material was used. FIG. 3 shows the gate voltage V _G and the drain voltage V _G focused on one pixel in the display method used here.
Changes in _D , pixel voltage V _LC , and pixel transmittance T _LC are shown. First, as shown in FIG. 3, one frame is composed of five subframes. First of each subframe duration
Frame is 0.5 msec, second subframe is 8 ms
ec, the third subframe is 1 msec, the fourth subframe is 4 msec, and the fifth subframe is 2 msec (in FIG. 3, each subframe is shown at equal intervals),
One frame was set to 15.5 msec. That is, assuming that the duration of the first frame is the shortest duration T ₀ , the second subframe becomes 16T ₀ , and the following 2T ₀ , 8T ₀ , 4T ₀ , and 32 gradations are obtained by combining the durations of these 5 subframes. Can be displayed.

Within one sub-frame, first, a rectangular pulse signal is applied to the scanning line as the gate voltage V _G to turn on the gate electrodes of the TFTs of the pixels of one line (640 horizontal pixels). On the other hand, a pulse train showing either a positive or negative state is applied as the drain voltage V _D to the signal line connected to the drain electrode of each TFT. This pulse train contains 480 pieces of information, which is the total number of scans in the subframe interval, and each piece of information is synchronized with the scan of each line. All 480 lines are scanned to determine the ON or OFF state of all pixels, and one subframe is completed.
As described above, the intervals between the sub-frames are different, and in the meantime, the transmissivity T _LC is kept constant and ON or OFF in each pixel, even though the pixel potential V _LC gradually approaches _{0 due} to natural discharge. Stay in the state. In this example, the transmittance T _LC during this period was extremely stable and did not change with time.

When all the sub-frames are completed in this way, gradation display within one frame can be realized digitally. The pulse width of the scanning signal applied to the gate electrode of each TFT is 2 μsec, and the pulse height is −15.
V, and the data signal applied to the drain electrode was ± 10V. With this device, no display unevenness or flicker appeared, and a contrast ratio of 180 was obtained with 32 gradations.

Although 256 gradations were displayed with T _{0 set} to 65 μsec, the liquid crystal molecules in each pixel were extremely sharply inverted and fully inverted with respect to the voltage application, and there was almost no display unevenness and the contrast was small. Ratio 180
Got

In this embodiment, the N-channel type is used as the switching element connected to the pixel, but P
A channel type or a complementary type thin film transistor in which a P channel type thin film transistor and an N channel type thin film transistor are configured in a complementary type may be used.

[0057]

EFFECTS OF THE INVENTION The present invention eliminates the charge transfer and charge accumulation at the liquid crystal interface of the alignment film, which has been a problem in the past, and steeply inverts the liquid crystal molecules of the ferroelectric liquid crystal and stabilizes the molecular state after inversion. And high-speed and stable optical characteristics can be obtained. Therefore, a liquid crystal electro-optical device using a ferroelectric liquid crystal can realize a display having a high speed and a high contrast ratio.

Particularly, in an active matrix type liquid crystal electro-optical device using a crystalline silicon thin film transistor, a device having a high speed and a high contrast is to be made by fully utilizing the high speed response of the ferroelectric liquid crystal material and the crystalline silicon thin film transistor. Therefore, the number of gradations and the contrast ratio of the digital gradation display using the frame gradation can be significantly improved.

Further, the polymerized column spacer (PCS) can prevent the expansion and reduction of the substrate distance without generating the alignment disorder, and can improve the strength of the substrate to prevent the distortion of the entire liquid crystal cell. It was possible to suppress the occurrence of collapse of the liquid crystal layer structure. Therefore, a liquid crystal electro-optical device using a large-area ferroelectric liquid crystal can be realized, and this device can be used upright.

[Brief description of drawings]

FIG. 1 shows a conceptual diagram of a liquid crystal electro-optical device of the present invention.

2A to 2C show steps of manufacturing a crystalline silicon thin film transistor in an example.

FIG. 3 shows applied signals, pixel potentials, and transmissivities of transmissive pixels when performing digital gradation display in an example.

[Explanation of symbols]

 100 pixel electrode 101 crystalline silicon thin film transistor 102, 104 substrate 103 counter electrode 105 alignment film 106 columnar resin 107 liquid crystal material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Michio Shimizu 398 Hase, Atsugi City, Kanagawa Prefecture Semiconductor Energy Research Institute Co., Ltd.

Claims (5)

[Claims] 1. A first substrate having a crystalline silicon thin film transistor connected to a pixel electrode and a second substrate having a counter electrode are provided to face each other, and at least one of the first and second substrates is provided. Has a uniaxial alignment means on its surface, and between the first and second substrates, a ferroelectric liquid crystal material aligned according to the uniaxial alignment means, and an uncured resin mixed in the liquid crystal material. Has a column-shaped resin formed by precipitation and curing. 2. A liquid crystal electro-optical device according to claim 1, wherein transmission and non-transmission of each pixel are controlled by a plurality of frames to perform frame gradation display. 3. When one frame is divided into N (natural number of 2 or more) subframes having mutually different durations, and the duration of the subframe having the shortest duration is T ₀ , these subframes are The duration is T ₀ , 2T ₀ ,
The liquid crystal electro-optical device according to claim 1, which is driven by a display method that is any one of 2 ² T ₀ , ... 2 ^N T ₀ . 4. A first substrate having a crystalline silicon thin film transistor connected to a pixel electrode and a second substrate having a counter electrode are provided to face each other, and at least one of the first and second substrates is provided. Has a uniaxial orientation means on its surface, and between the first and second substrates, a ferroelectric liquid crystal material oriented according to the uniaxial orientation means and an uncured ultraviolet ray mixed in the liquid crystal material. A liquid crystal electro-optical device comprising a column-shaped resin formed by curing and curing a curable resin. 5. A first substrate having a crystalline silicon thin film transistor connected to a pixel electrode and a second substrate having a counter electrode are provided to face each other, and at least one of the first and second substrates is provided. Has a uniaxial alignment means on its surface, and between the first and second substrates, a ferroelectric liquid crystal material aligned according to the uniaxial alignment means, and an uncured resin mixed in the liquid crystal material. A liquid crystal electro-optical device characterized in that it has a deposited and cured product.