JP2503830B2 - Liquid crystal display element - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device in which a nematic liquid crystal is dispersed and held in a solidified matrix, and in particular,
The present invention relates to a liquid crystal display element in which an active element is arranged for each pixel electrode.

[0002]

2. Description of the Related Art Liquid crystal displays have recently taken advantage of their features such as low power consumption and low voltage drive, and are used in personal word processors, handheld computers and pocket T's.
Widely used for V etc. Among them, a liquid crystal display element in which an active element is arranged for each pixel electrode is attracting attention and is being actively developed.

Initially, such a liquid crystal display device was manufactured by DSM.
A liquid crystal display element using a (dynamic scattering) type liquid crystal has also been proposed, but the DSM type has a drawback that it consumes a large amount of current because the current value flowing in the liquid crystal is high.
The liquid crystal using (twisted nematic) type liquid crystal has become the mainstream, and has appeared in the market as a pocket TV. T
The N-type liquid crystal has an extremely small leakage current and consumes less power, and is therefore suitable for a battery-powered application.

[0004]

When a liquid crystal display element in which an active element is arranged is used in the DS mode, the leakage current of the liquid crystal itself is large. For this reason, there is a problem that a large storage capacitance must be provided in parallel with each pixel and the power consumption of the liquid crystal display element itself increases.

In the TN mode, since the leakage current of the liquid crystal itself is extremely small, it is not necessary to add a large storage capacity, and the power consumption of the liquid crystal display element itself can be reduced. However, the TN mode requires two polarizing plates and thus has a problem that the light transmittance is small. In particular, when performing color display using a color filter, only a few percent of the incident light can be used, and a strong light source is required, resulting in an increase in power consumption.

Further, when an image is projected, an extremely strong light source is required, and it is difficult to obtain a high contrast on the projection screen, and there is a problem that heat generation of the light source affects the liquid crystal display element. There is.

Therefore, in order to solve the problem of the TN mode,
A liquid crystal resin composite in which a nematic liquid crystal is dispersed and held in a resin matrix is used, and its scattering-transmission characteristics are utilized.
A mode that can be driven at a low voltage of 10 V or less has been proposed.

However, in the conventional liquid crystal resin composite, there is hysteresis in the voltage-transmittance characteristic,
That is, there is a problem that the transmittance is different between the step-up operation and the step-down operation, and therefore, there is a problem that the image sticking phenomenon may occur in which the information on the previous screen remains for several seconds or more when the display screen changes. Was.

[0009]

The present invention provides a liquid crystal display device having a high brightness and a high contrast ratio, capable of displaying halftones neatly, and reducing the burn-in phenomenon due to the hysteresis of the liquid crystal resin composite. It is a thing.

That is, a nematic liquid crystal is dispersed and held in a solidified matrix between a pair of substrates with electrodes, and the refractive index of the liquid crystal changes depending on the voltage application state. Light is transmitted almost in agreement,
In the other state, in a liquid crystal display element that sandwiches a liquid crystal and solidified substance composite that does not match the refractive index of the solidified substance matrix and scatters light, the refractive index anisotropy Δn of the liquid crystal used is 0.18 or more. And the dielectric anisotropy Δε _LC is 5 <Δ
The present invention provides a liquid crystal display device characterized by satisfying the relationship of ε _LC <13.

According to the present invention, by adopting the above structure, it is possible to obtain a liquid crystal display element which has a reduced image sticking phenomenon due to hysteresis, has a high contrast ratio, and can be driven at a low voltage.

In the present invention, a liquid crystal solidified substance composite in which a nematic liquid crystal is dispersed and held in a solidified substance matrix is used.
In particular, a nematic liquid crystal having a positive dielectric anisotropy is dispersed and held in a solidified matrix, and the refractive index of the solidified matrix is made to substantially match the ordinary refractive index (n ₀ ) of the liquid crystal used. It is preferable to use a solidified resin composite. Then, the liquid crystal solidified composite is sandwiched between a pair of substrates with electrodes, particularly between an active matrix substrate provided with an active element for each pixel electrode and a counter electrode substrate provided with a counter electrode.

As the substrate with an electrode, a substrate made of glass, plastic, ceramic or the like on which an electrode is provided is used. The active matrix substrate is a substrate in which electrodes and active elements such as a thin film transistor (TFT), a thin film diode, and a metal insulator metal nonlinear resistance element (MIM) are formed on a substrate such as glass, plastic, or ceramic. . One or a plurality of active elements are connected to each pixel electrode.

With this counter electrode substrate, electrodes are formed on a substrate made of glass, plastic, ceramic, or the like, and display is possible by combining with an active matrix substrate substrate.

The liquid crystal solidified composite is sandwiched between the pair of substrates with electrodes. In this liquid crystal solidified substance composite, the refractive index of the liquid crystal in the liquid crystal solidified substance complex changes depending on the voltage application state. Light is transmitted when the refractive index of the solidified matrix substantially matches the refractive index of the liquid crystal, and light is scattered when they do not match. Since a polarizing plate is not used for this, bright display can be easily obtained.

The liquid crystal display element of the present invention can be used as both a direct-view display element and a projection display element. When used as a direct-view display device, a display device may be configured by combining a backlight, a lens, a prism, a mirror, a diffusion plate, a light absorber, a color filter, etc., depending on the desired display characteristics. In addition, it can be used as a shutter for laser light and a reflective display element.

The liquid crystal display element of the present invention is particularly suitable for a projection type display device, and can be combined with a light source for projection, a projection optical system and the like to form a projection type liquid crystal display device.
The projection light source and the projection optical system are conventionally known projection light sources,
A projection optical system such as a lens can be used, and normally, the liquid crystal display device may be used by being arranged between the projection light source and the projection lens.

In the liquid crystal display device of the present invention, a transmission-scattering type liquid crystal solidified composite is sandwiched between a pair of substrates with electrodes, particularly between an active matrix substrate and a counter electrode substrate.

Specifically, in the present invention, as a liquid crystal display element, a liquid crystal solidified substance composite comprising a solidified substance matrix having a large number of fine pores formed therein and a nematic liquid crystal filled in the pores is used. The liquid crystal solidified composite is sandwiched between the active matrix substrate and the counter electrode substrate. The refractive index of the liquid crystal changes depending on the applied state of the voltage between the electrodes, and the relationship between the refractive index of the solidified matrix and the refractive index of the liquid crystal changes. It is possible to use a liquid crystal display element in which the liquid crystal display element is in a transmissive state when the refractive indexes of these two are the same, and is in a scattering state when the refractive indexes are different.

A liquid crystal solidified substance composite composed of a solidified substance matrix having a large number of fine pores formed therein and a liquid crystal filled in the pores is such that the liquid crystal is contained in a liquid bubble such as a microcapsule. It is a structure. However, individual microcapsules do not have to be completely independent, and liquid bubbles of individual liquid crystals may communicate with each other through a slit like a porous body.

The liquid crystal solidified composite used in the liquid crystal display device of the present invention is manufactured as follows. The nematic liquid crystal and the curable compound forming the solidified matrix are mixed to form a solution or latex. Then, this may be subjected to photo-curing, heat-curing, curing by removing a solvent, reaction curing or the like to separate the solidified matrix so that the nematic liquid crystal is dispersed in the solidified matrix.

The curable compound used is preferably a photocurable or thermosetting type because it can be cured in a closed system. In particular, it is preferable to use a photo-curing type curable compound because it can be cured in a short time without being affected by heat.

As a concrete manufacturing method, a cell is formed by using a sealing material as in the conventional ordinary nematic liquid crystal, and an uncured mixture of a nematic liquid crystal and a curable compound is injected from an injection port, and the injection port is injected. After sealing, the composition can be cured by irradiation with light or heating.

In the case of the liquid crystal display element of the present invention,
For example, an active matrix in which an uncured mixture of a nematic liquid crystal and a curable compound is supplied onto a substrate provided with a transparent electrode as a counter electrode without using a sealing material, and then an active element is provided for each pixel electrode. It is also possible to stack the substrates and cure by light irradiation or the like.

Of course, thereafter, a sealing material may be applied to the periphery to seal the periphery. According to this production method, the uncured mixture of the nematic liquid crystal and the curable compound may be simply supplied by roll coating, spin coating, printing, coating with a dispenser, etc., so that the injection step is simple and the productivity is high. Very good.

The uncured mixture of the nematic liquid crystal and the curable compound contains ceramic particles for controlling the substrate gap, plastic particles, spacers such as glass fibers, pigments, dyes, viscosity modifiers and the like. You may add the additive which does not adversely affect the performance of.

By curing an element that is in a transmissive state when a voltage is applied in such a state that a sufficiently high voltage is applied only to a specific portion during this curing step, that portion can be kept in a light transmissive state at all times. If there is something that is desired to be fixedly displayed, such a normal transmission part may be formed.
On the contrary, when an element that is in a scattering state when a voltage is applied is used, the ordinary scattering portion can be formed in the same manner.

The higher the transmissivity of the liquid crystal display device using this liquid crystal solidified composite in the transmissive state, the better, and the haze value in the scattering state is preferably 80% or more.

In the present invention, in the state where voltage is applied,
The refractive index of the solidified matrix (after curing) is preferably made to match the ordinary refractive index (n _o ) of the liquid crystal used. As a result, light is transmitted when the refractive index of the solidified material matrix and the refractive index of the liquid crystal match, and light is scattered (cloudy) when they do not match. The scattering property of this element is
It is possible to obtain a display having a higher contrast ratio than that of the conventional DS mode liquid crystal display element.

The greatest object of the present invention is to provide a liquid crystal display device which can reduce the image sticking phenomenon due to the hysteresis of the liquid crystal solidified composite and can be driven at a low voltage. By combining this liquid crystal display element with an active element, a higher function of high density display can be exhibited. Of course, in addition to this, the function can be effectively exhibited in other applications requiring a halftone (shutter, display, spatial modulator, etc.).

In the conventional liquid crystal solidified composite, there is a hysteresis in the voltage-transmittance characteristic, which has been a problem in gradation display. Hysteresis is a phenomenon in which the transmittance is different in the process of increasing the voltage and the process of decreasing the voltage. The presence of the hysteresis causes a phenomenon that the information on the previous screen remains in the gradation display, that is, the image is burned in, which deteriorates the image quality.

One of the causes of the existence of hysteresis in the liquid crystal solidified substance composite is due to the structure in which the liquid crystal is held dispersed in the solidified liquid crystal. That is,
It is considered that there is hysteresis due to the interaction between the liquid crystals separated and existing in the solidified substance. The magnitude of this hysteresis is determined by the elastic energy stored in the liquid crystal retained in the solidified substance, the electrical energy due to the electric field applied from the outside, and the interaction energy between the liquid crystals separated and present in the solidified substance. It is what is done. Therefore, by optimizing this energy balance, the hysteresis can be reduced, and an excellent display without burn-in can be obtained even in gradation display.

An object of the present invention is to obtain a liquid crystal display device having a high contrast ratio, high brightness, excellent responsiveness and reduced hysteresis. Furthermore, conventional TN
It is to obtain a liquid crystal display element that can be driven by an active element or a driving circuit for use.

In order to reduce the hysteresis caused by the dispersion of liquid crystal particles in the solidified matrix, among these, the dielectric constant of the liquid crystal, its anisotropy Δε _{LC and} the dielectric constant ε _P of the solidified matrix are set. Balancing is important. This is because they are a major factor in determining the interactions between the dispersed particles. In order to reduce the hysteresis, it is a preferable range that the dielectric anisotropy Δε _{LC of the} liquid crystal used satisfies the relationship of 5 <Δε _LC <13 (1).

This Δε _LC is a quantity related to both hysteresis and drive voltage, and the upper limit is determined by the size of hysteresis and the lower limit is determined by the drive voltage. This condition seems to be disadvantageous from the common sense of the conventional TN type liquid crystal display element that the driving voltage becomes lower as Δε _LC becomes larger.

However, in such a system in which liquid crystal particles are dispersed, the concept of the conventional TN type liquid crystal display element that the driving voltage is inversely proportional to the square root of Δε _LC is not established. This is because the voltage distribution to the liquid crystal portion and the matrix portion differs depending on the arrangement of the liquid crystals. The liquid crystal and solidified matrix composite such as in the present invention, [Delta] [epsilon] _LC showed no very great effect on the driving voltage, is any [Delta] [epsilon] _LC is a large range than 5, that the driving voltage by decreasing the [Delta] [epsilon] _LC is very high There is no such thing.

Further, if the [Delta] [epsilon] _LC is used too large liquid crystal, since the temperature dependence of the elastic constant is also directly voltage-transmittance problems thereby causing the temperature dependence of the properties, [Delta] [epsilon] _LC is above It will be in the range. This will be explained in a little more detail in the explanation of elastic constants.

To reduce the hysteresis, the dielectric constant ε _M for a sufficiently low voltage below the threshold voltage of the liquid crystal solidified composite and the dielectric constant anisotropy Δε _{LC of} the liquid crystal to be used are: Δε _LC < It is preferable to have a relationship of 1.45ε _M (2).

When Δε _LC is larger than this range, the movement of the liquid crystal within one liquid crystal particle causes a large change in the dielectric constant within the particle. As a result, a large electric field change is generated around the particles, and the electrical interaction between the liquid crystal particles, which is a factor that causes hysteresis, becomes large.
The epsilon _M is the solidified matrix with a dielectric constant epsilon _P is a quantity related, the solidified matrix the dielectric constant epsilon _P increases the dielectric constant epsilon _M of the entire liquid crystal and solidified matrix composite increases, the can take [Delta] [epsilon] _LC The range also expands.

The refractive index anisotropy Δn of the liquid crystal needs to be 0.18 ≦ Δn, particularly preferably 0.20 ≦ Δn, in order to enhance the scattering property in the absence of an electric field and obtain a high contrast ratio.
n. It is preferable that the ordinary refractive index n _o of the liquid crystal substantially matches the refractive index n _p of the solidified matrix, and at this time, high transparency is obtained when an electric field is applied. More specifically, n _o -0.03 <n _p
It is preferable to satisfy the relationship of <n _o +0.05.

The hysteresis in the liquid crystal solidified composite is mainly caused by the above factors, but the electro-optical hysteresis as an optical element or a display element causes the above elastic energy, electrical energy, interaction. It is not determined solely by energy. That is, the optical hysteresis also depends on how the hysteresis related to the alignment of the liquid crystal is optically reflected. For example, even if there is a region where hysteresis is present in the liquid crystal array, if this is not reflected optically, electro-optical hysteresis does not occur.

The largest factor that links the liquid crystal alignment with the optical properties is the refractive index anisotropy Δn of the liquid crystal. This is because the size of Δn determines how much the liquid crystal alignment change causes an optical change. If Δn is large, the change in the refractive index of the field when the alignment of the liquid crystal is changed by an external field such as an electric field is large, and the change in the liquid crystal alignment is reflected optically. If Δn is small, a large optical change does not occur unless the liquid crystal alignment changes significantly.

Therefore, the larger Δn, the larger the liquid crystal alignment hysteresis appears as electro-optical hysteresis. In other words, it can be said that the amplification factor from the voltage characteristic of the liquid crystal array to the optical characteristic increases as Δn increases.

From this viewpoint, it is desirable that Δn be smaller than a certain level in order to reduce the electro-optical hysteresis.
Specifically, it is desirable to satisfy the relationship of Δn ≦ 0.25. More preferably, Δn ≦ 0.24.

The main control of the drive voltage is
The diameter of liquid crystal particles and their distribution. For the former, the average liquid crystal particle diameter (average particle diameter) of the liquid crystal solidified composite.
It is desirable that R (μm) be 0.2 <Δn · R <0.7 (3). This is a necessary condition in the case of an element in which the refractive index of the liquid crystal matches the refractive index of the solidified matrix when an electric field is applied, the scattering intensity increases when no electric field is applied, and the liquid crystal can be driven in a low electric field.

Δn is also closely related to the temperature dependence of the electro-optical properties of the liquid crystal solidified composite. In the range where Δn is larger than 0.18, there is an optimum liquid crystal particle size defined by Eq. (3), and it is possible to obtain a device with high scattering or transmissivity when off. Dependencies are very different. The scattering power per liquid crystal particle at the time of off is a function of X = Δn · R / λ (λ is the wavelength). The scattering power initially increases with the increase of X, but becomes a constant value gradually. After that, the scattering power decreases.

Therefore, if the element is constructed under the condition that the scattering ability or the transmittance has a constant value, it is possible to obtain the element in which the scattering ability or the transmittance when off is hardly changed by the change of Δn. Further, in this case, the scattering ability does not easily change with respect to the change of the wavelength, and there is also an advantage that an element having a scattering ability or transmittance in the off state with little wavelength dependency can be obtained. Therefore, it is possible to easily balance each color when displaying in color.

A specific range of Δn satisfying such a condition is 0.18 ≦ Δn ≦ 0.24, and the element having R determined by the equation (3) has a scattering power or a transmittance at the time of OFF. Can be significantly reduced. For example, Δ
An element with n = 0.21 and R = 2.4 μm has almost no change in scattering power or transmittance in the off state in a temperature range around room temperature (for example, 0 to 60 ° C.).

Further, since the liquid crystal solidified composite is driven in a binary display, it is driven in an off state and a sufficiently high on state (above the saturation voltage), so that it has a response of several tens msec or less. It is generally suitable for high-speed display. However, at the time of gradation display, a voltage lower than the saturation voltage is also used to display a halftone. Therefore, there is a state where the response is slower than that in the binary display drive. The response in gradation display tends to be slower as the display on the lower voltage side (dark display). In particular, the change from the off state to the low transmittance state is the slowest, and the response at the time of driving the binary display may be several tens of times slower.

In order to reduce the afterimage also in this gradation display, the refractive index anisotropy Δn and the viscosity η (cSt) of the liquid crystal dispersed and held in the solidified matrix are Δn ² / η> 0.001 ( 4) is preferred. In particular, it is preferable to satisfy the relationship of Δn ² / η> 0.0014 (4A) in order to improve the response when the voltage is off.

Further, it is preferable that the following relationship be satisfied. 5 (K33 / η) ^0.5 >R> (K33 / Δε _LC ) ^0.5 (5) In particular, it is preferable to satisfy the following relationship. 4 (K33 / η) ^0.5 ＞ R ＞ (K33 / Δε _LC ) ^0.5 (5A) Within this range, the torque that acts on the liquid crystal at each voltage during gradation display can be balanced, and beautiful halftone display with less afterimage can be obtained. In addition, the electric field required for driving the liquid crystal can be suppressed low. The physical properties of the liquid crystal used here are values at room temperature.

The above relationship is the case where the shape of the liquid crystal particles is almost spherical. In the present invention, this shape can be made non-spherical to further improve the effect of hysteresis reduction. In this case, a shape with too complicated irregularities is not preferable because it requires a very high driving electric field although it has good response, and a spheroidal shape is desirable. Further, in this case, if the major axes are arranged in a fixed direction, the above effect does not occur. Therefore, at least the long axis of the liquid crystal is perpendicular to the perpendicular to the electrode surface, that is,
It is made two-dimensionally random. If possible, it is preferably three-dimensionally random.

Here, the average particle diameter R.sub.3 of the liquid crystal is closely related to scattering characteristics, responsiveness, operating electric field and the like. When R becomes larger, the electric field required for driving becomes smaller, but the response becomes slower. Further, when R becomes small, elastic energy accumulated per unit liquid crystal amount becomes large and the response speed becomes fast, but a high electric field is required for driving.

The viscosity η of the liquid crystal and the dielectric anisotropy Δε _LC are also factors closely related to the responsiveness, and the smaller the viscosity and the larger the dielectric anisotropy, the faster the response speed. Also, Δε
_LC is also related to the electric field required for driving, and the larger Δε _LC , the smaller the electric field required.

The elastic constant of the liquid crystal determines the elastic energy stored in the liquid crystal, but in the liquid crystal solidified composite,
In particular, the bend energy due to K33 plays a large role and is deeply involved in the response characteristics and drive characteristics, that is, the elastic torque that acts on the liquid crystal. To reduce the hysteresis, it is advantageous that the elastic constant K33 is large, but if K33 is too large, the driving electric field is increased. Therefore, it can be selected depending on the balance with other liquid crystal physical properties (eg, Δn, Δε _LC , η, etc.).

From the point of the temperature dependence of the voltage-transmittance characteristic, in addition to the relationship between Δn and R described above, the dielectric constant anisotropy Δε _{LC of the} liquid crystal used and the elastic constant K11 which are physical quantities that change with temperature. , K33 needs to be optimized.

In the liquid crystal solidified substance complex, since the liquid crystal is dispersed and held in the solidified substance matrix, not all the applied voltage is applied to the liquid crystal but is distributed to the liquid crystal portion and the matrix portion. Δε _{LC of} commonly used liquid crystals
Is larger, the larger the dielectric constant ε _// of the liquid crystal is, the more the voltage distributed to the matrix when a voltage is applied, and the smaller the voltage distributed to the liquid crystal part.

Therefore, in the region where Δε _LC is large, Δε
_{Even if LC} is increased, the effect of lowering the drive voltage is almost lost. If Δε _LC is large, the elastic constant mainly controls the voltage transmittance characteristic for this reason. Therefore, when a liquid crystal having a large Δε _LC is used, the temperature dependence of the elastic constant causes the temperature dependence of the voltage transmittance characteristic as it is. On the other hand, as Δε _LC is reduced, the voltage distributed to the liquid crystal increases, and the voltage transmittance characteristic is determined by the ratio of Δε _LC and elastic constant.

Since both the Δε _LC and the elastic constant are physical quantities that decrease with increasing temperature, by appropriately selecting each physical quantity, each temperature change is canceled, and there is little or no dependence on temperature. Thus, it becomes possible to obtain a liquid crystal solidified substance composite having a voltage transmittance characteristic of less.

From the above viewpoint, the dielectric anisotropy of liquid crystal Δε _LC
Is Δε _LC <13 as described above, and the elastic constant K (K = (K11 +
K33) / 2) (10 ⁻¹² N) preferably satisfies the condition of 1 <K / Δε _LC . Further, if K / Δε _LC becomes too large, it leads to an increase in drive voltage. Therefore, it is preferable that K / Δε _LC <3.

It should be noted that the clearing point of the liquid crystal (transition temperature from the liquid crystal to the isotropic liquid) Tc depends on these temperature dependences.
Is also important, and the above effects cannot be expected unless the temperature is higher than the normal temperature range to some extent. This is because the change in physical quantity is too rapid at the temperature near the transition point. Therefore, it is preferable that the Tc of the liquid crystal used does not fall below the higher temperature of the center temperature of the operating temperature range + 30 ° C or the upper operating temperature + 10 ° C, whichever is higher. In the above example, 0 ℃ to 60 ℃
In the temperature range of, Tc is preferably not lower than 70 ° C.

The liquid crystal dispersed and held in the solidified matrix is preferably independent particles or particles in which some of them are connected. This is effective in achieving both high scattering power and high transparency when driven at a low voltage. Scattering is caused by the presence of an interface between the liquid crystal and the solidified matrix. Therefore, the larger the area of this interface, the higher the scattering property.

In order to increase the area of this interface with a certain optimum average particle size, it is important to increase the amount of the liquid crystal separated from the solidified matrix independently, that is, increase the liquid crystal particle density. . However, when the amount of liquid crystal separated from the solidified matrix is increased, the respective liquid crystal particles eventually come into communication with each other, and further, the liquid crystal comes to have a structure in which they all come into communication. This leads to the loss of the liquid crystal interface separated from the solidified matrix, leading to a decrease in the scattering ability.

Further, in order to reduce the driving voltage, it is important that the respective liquid crystals held in the solidified matrix have substantially the same driving electric field. For this purpose, it is advantageous for the liquid crystal to have a clear interface with the solidified matrix, and the loss of the interface leads to dispersion of the driving electric field, which tends to cause a decrease in contrast ratio and an increase in driving voltage. .
For this reason, it is preferable that the liquid crystal dispersed and held in the solidified material matrix is independent particles that are present at a high density or particles that partially communicate with each other.

The particle size of this liquid crystal is preferably uniform. When the particle diameters are distributed, large liquid crystal particles lead to a decrease in scattering ability, and small liquid crystal particles lead to an increase in driving electric field, resulting in an increase in driving voltage and a decrease in contrast. The particle size dispersion σ is preferably within 0.25 times the average particle diameter, and more preferably within 0.15 times. The average particle diameter and the dispersion are the weighted average and dispersion.

The liquid crystal to be used is selected in consideration of the dielectric anisotropy Δε _LC shown in the equations (1) and (2) and the relationship between the refractive index anisotropy shown in the equation (3) and the average particle size. You can do it. Specifically, Δn is set to 0.18 or more.

Regarding the electrode substrate gap d, in the case of an element which is in a transmissive state when an electric field is applied, if d is increased, the scattering property in the absence of an electric field is improved. However, if d is too large, a high voltage is required to achieve sufficient transparency when an electric field is applied, which results in increased power consumption and the inability to use conventional active elements for TN and driving ICs. Will occur. Also, if d is made small, high transparency can be obtained at a low voltage, but the scattering property in the absence of an electric field decreases.

Therefore, in order to achieve both the scattering property when no electric field is applied and the high transparency when an electric field is applied, d (μm) satisfies 3R <d <9R (6), and further, the liquid crystal is solidified. It is preferable that the maximum effective applied voltage V (V) applied to the object complex satisfies the relationship of 0.6R · V <d <1.6R · V (7). Within this range, it is possible to perform display with a high contrast ratio using the conventional active element for TN and the driving IC.

When the above-mentioned element is used as a reflection type, since the light passes through the liquid crystal solidified substance composite twice, the scattering property at the time of scattering increases. Therefore, d can be reduced within the range of the expression (6), and the maximum drive voltage determined by the expression (7) can be reduced.

In the above description, the case of a single liquid crystal display element has been described. When using, for example, three liquid crystal display elements as in a projection type liquid crystal display device and transmitting light of three colors of RGB separately to each liquid crystal display element, the above equations should be satisfied for each color. To Further, it is preferable that the characteristics be made uniform for each color.

Specifically, the relationship between Δn, R, and d of the liquid crystal display element with respect to the central wavelength λ of the light used either satisfies the following equations (8) and (9) at the same time, or the equation (10) is satisfied. Is preferably adjusted to be substantially constant for each color. This makes it possible to obtain substantially uniform light transmission-scattering performance for each color light.

Δn _i · R _i / λ _i ≈Δn _j · R _j / λ _j (8) d _i / R _i ≈d _j / R _j (9) Δn _i · d _i ² / λ _i ≈Δn _j d _j ² / λ _j (10) In addition, i and j represent each color.

Further, in order to improve the scattering property under no electric field, it is effective to increase the volume fraction Φ of the operable liquid crystal of the liquid crystal solidified composite. Specifically, Φ> 20% is preferable, Φ> 35% is more preferable to have higher scattering property, and Φ> 45% is further preferable. On the other hand, if Φ is too large, the structural stability of the liquid crystal solidified composite is deteriorated, so Φ <70% is preferable.

In the liquid crystal display element of the present invention, the ordinary refractive index (n _o ) of the liquid crystal is made to match the refractive index of the solidified matrix so that when the electric field is not applied, the liquid crystal display device is aligned in the direction perpendicular to the substrate. Indicates a scattering state (that is, a white turbid state) due to the difference in refractive index between the unaligned liquid crystal and the solidified matrix. For this reason, in the present invention, light is scattered at the portion without electrodes.

When this liquid crystal display device is used as a projection type display device, since light is scattered in portions other than the pixel portion, light does not reach the projection screen even if a light shielding film is not provided, so that it looks black. . Thus, in order to prevent light from leaking from the portion other than the pixel electrode, it is not necessary to shield the portion other than the pixel electrode with a light shielding film or the like. Therefore, there is also an advantage that the step of forming the light shielding film is unnecessary.

An electric field is applied to desired pixels. In the pixel portion to which this electric field is applied, the liquid crystal is aligned in the electric field direction, and the ordinary refractive index (n _o ) of the liquid crystal and the refractive index of the solidified matrix are
matches (n _p ). As a result, a transparent state is shown, and light is transmitted through the desired pixel, which is brightly displayed on the projection screen.

By curing this device in such a state that a sufficiently high voltage is applied only to a specific portion during this curing step, that portion can be kept in a light transmitting state at all times. When there is something to be fixedly displayed, such a normal transmission part may be formed.

Further, the liquid crystal display device of the present invention can perform color display by providing a color filter. This color filter may be provided in three colors in one liquid crystal display element, one color in one liquid crystal display element, or a combination of three colors. This color filter may be provided on the electrode surface side of the substrate or may be provided on the outside.

Further, color display may be performed by mixing a dye, a pigment and the like in the liquid crystal solidified composite.

FIG. 1 is a sectional view of a liquid crystal display element of the present invention. In FIG. 1, 1 is a liquid crystal display element, 2 is a glass or plastic substrate for an active matrix substrate,
3 is a pixel electrode such as ITO (In ₂ O ₃ -SnO ₂ ), SnO ₂ or the like, 4 is an active element such as a transistor, a diode or a non-linear resistance element,
5 is a glass or plastic substrate for the counter electrode substrate,
Reference numeral 6 indicates a counter electrode made of ITO, SnO ₂ or the like, and reference numeral 7 indicates a liquid crystal solidified composite material sandwiched between both substrates.

FIG. 2 is a schematic view of a projection type liquid crystal display device using the liquid crystal display element of FIG. In FIG. 2, 11 is a light source for projection, 21 is a liquid crystal display element, 13 is a projection optical system including a lens and an aperture, and 14 is a projection screen for projection. Incidentally, the projection optical system is, in this example, an aperture or a spot 15 which is a plate with holes, a condenser lens 16,
It includes a projection lens 17.

FIG. 3 is a schematic view of an example using a dichroic prism of a full-color projection type liquid crystal display device using the liquid crystal display element of the present invention. In FIG. 3, 21 is a light source, 22 is a concave mirror, 23 is a condenser lens, 24 is a dichroic prism for spectroscopy, and 25A, 25B, 25C and 25D are mirrors, and 21 to 25D constitute a color light source. 26A, 26B, 26C are liquid crystal display elements sandwiching a liquid crystal solidified composite corresponding to each color,
27 is a dichroic prism for synthesis, 28 is a projection lens,
Reference numeral 29 is an aperture for removing light other than the straight light, and 30 is a projection screen for projection. The projection optical system is composed of 27 to 29.

In this example, only one aperture is required to remove diffused light other than straight-ahead light, and since there is one optical axis, adjustment is easy and the distance to the projection screen is variable.

FIG. 4 is a schematic view of an example of a full-color projection type liquid crystal display device using the liquid crystal display element of the present invention without using a dichroic prism. In FIG. 4, 31 is a light source, 32 is a concave mirror, 33 is a condenser lens, 35A, 35B, 35
C is a dichroic mirror and constitutes a color light source with 31 to 35C. 36A, 36B, and 36C are liquid crystal display elements sandwiching a liquid crystal solidified composite corresponding to each color, 38A, 38B, and 38C are projection lenses provided for each color, and 39A, 39B, and 39C are rectilinearly provided for each color. Aperture for removing other than light, 40 is a projection screen. The projection optical system is composed of 38A to 39C.

In the present invention, when a three-terminal element such as a TFT is used as an active element, the counter electrode substrate may be provided with a solid electrode common to all pixels. When using a two-terminal element such as an MIM element or a PIN diode, the counter electrode substrate is patterned in a stripe shape.

When a TFT is used as the active element, silicon is suitable as the semiconductor material.
In particular, since polycrystalline silicon has no photosensitivity like amorphous silicon, it does not easily malfunction even if the light from the light source is not blocked by the light blocking film or is not a strict light blocking film. When this polycrystalline silicon is used as a projection type liquid crystal display device as in the present invention, a strong light source for projection can be used and a bright display can be obtained.

Further, in the case of the conventional TN type liquid crystal display element, a light-shielding film is often formed between pixels in order to suppress light leakage from between pixels. At this time, the simultaneous light-shielding film can be subsequently formed on the active element portion. Therefore, forming the light-shielding film on the active element portion does not significantly affect the entire process. That is, even if polycrystalline silicon is used as the active element and the light shielding film is not formed in the active element portion, the number of steps cannot be reduced if the light shielding film needs to be formed between the pixels.

On the other hand, in the present invention, as described above,
Ordinary refractive index of liquid crystal used by refractive index of solidified matrix
Liquid crystal solidified composites that are made to closely match (n _o ) can be used. For this reason, light is scattered in the portion to which the electric field is not applied and becomes black on the projection screen, and thus it is not necessary to form the light shielding film between the pixels. on the other hand,
When polycrystalline silicon is used as the active element, the light shielding film need not be formed in the active element portion. Therefore, the step of forming the light-shielding film can be eliminated, and the productivity is improved.

Even if amorphous silicon is used, it can be used if a light shielding film is formed on the semiconductor portion thereof. The electrodes are usually transparent electrodes, but when used as a reflective liquid crystal display device, they may be reflective electrodes of chromium, aluminum, or the like.

In addition to the above, the liquid crystal display device of the present invention and the liquid crystal display device using the same may be laminated with an infrared cut filter, an ultraviolet cut filter, etc., or may be printed with characters, figures, etc., A plurality of liquid crystal display elements may be used. Further, in the present invention, a protective plate such as a glass plate or a plastic plate may be laminated on the outside of the liquid crystal display element. As a result, even if the surface is pressed, the risk of damage is reduced, and safety is improved.

In the present invention, when a photocurable compound resin is used as the curable compound forming the above-mentioned liquid crystal solidified composite, it is preferable to use a photocurable vinyl compound. Specifically, a photocurable acrylic compound is exemplified, and a compound containing an acrylic oligomer that is polymerized and cured by light irradiation is particularly preferable.

The liquid crystal used in the present invention is a nematic liquid crystal. In particular, it is preferable to use a nematic liquid crystal having a positive dielectric anisotropy, and a liquid crystal in which the refractive index of the solidified matrix matches the ordinary refractive index (n _o ) of the liquid crystal. This may be used alone or as a composition,
It can be said that it is advantageous to use the composition in order to satisfy various performance requirements such as operating temperature range and operating voltage.

When a photocurable compound is used, this liquid crystal preferably dissolves the photocurable compound uniformly. The cured product after light exposure is not dissolved or is difficult to dissolve. When a liquid crystal composition is used, it is desirable that the solubilities of the individual liquid crystals be as close as possible.

This liquid crystal composition contains a plurality of Np compounds (nematic liquid crystals having a positive dielectric anisotropy) having a large Δε _LC having a polar group at either or both of the terminal of the liquid crystal molecule and the o-position thereof. You can mix and match types,
A compound having a small dielectric anisotropy represented by | Δε _LC | ≦ 2.0 may be used in combination with them.

In general, it is preferable that it is uniformly dissolved with the curable compound when uncured and well phase-separated from the matrix after curing. For this purpose, it is preferable to use a combination of a plurality of liquid crystal compounds having appropriately different cohesive energies or compounds having a similar structure.
Therefore, [Delta] [epsilon] _LC larger compound and [Delta] [epsilon] _LC is small (| Δε _LC | ≦ 2.0) is preferably used in combination with the compound. In particular, this ratio (compound with a large Δε _LC / Δε
Compounds with small _LC (| Δε _LC | ≦ 2.0) by weight ratio
It is preferably 20/80 to 75/25.

Liquid crystal compounds include compounds having the following general formula. R _1- (A ₁ ) -Y _1- (A ₂ ) -R ₂ R _1- (A ₁ ) -Y _1- (A ₂ ) -Y _2- (A ₃ ) -R ₂ R _1- (A ₁ ) -Y _1- (A ₂ ) -Y _2- (A ₃ ) -Y _3- (A ₄ ) -R ₂

In the above formula, R ₁ is an alkyl group having 1 to 10 carbon atoms, an alkoxy group, an alkenyl group, or the like, and R ₂ is an alkyl group having 1 to 10 carbon atoms, an alkoxy group, an alkenyl group, or a hydrogen atom thereof. And a halogen atom, a cyano group, a thiocyanato group and the like. A ₁ ,
A ₂ , A ₃ , and A ₄ are 1,4-disubstituted phenylene groups, trans-1,4-
It is a ring such as a di-substituted cyclohexylene group, a 2,5-di-substituted pyridinylene group or a 2,5-di-substituted pyrimidinylene group, and a part thereof may be substituted with an alkyl group, -F, -Cl or the like.
Y ₁ , Y ₂ and Y ₃ are single bonds or -COO-,-OCO-,-C≡C-,-CH = C
It is a group such as H-,-CH ₂ CH _2- , -CH ₂ O-, -OCH _2- .

In the case of a compound having a large Δε _LC , R _{2 in} the above formula is an alkyl group, an alkoxy group, or a halogen atom, a cyano group, the hydrogen atom of which is replaced by a halogen atom,
Examples thereof include compounds having a thiocyanato group and the like. Also, Δ
In the case of a compound having a small ε _LC , a compound in which R _{2 in} the above formula is a simple alkyl group, alkoxy group, alkenyl group or the like is exemplified.

Note that this is merely an example, and there are other compounds satisfying the magnitude of Δε _LC ,
On the contrary, there may be compounds that do not satisfy the Δε _LC value even among the compounds exemplified above. Therefore, Δ of each compound
It may be appropriately selected in consideration of ε _LC , Δn, phase stability, clearing point (Tc), viscosity, elastic modulus and the like.

In the case of producing a liquid crystal solidified composite, there are the following production methods. One is to arrange a pair of substrates so that their electrode surfaces face each other like a conventional ordinary liquid crystal display element, and seal the periphery with a sealing material, and use the uncured liquid crystal solidification compound composite material through the injection port. This is a manufacturing method in which the mixed solution is injected and the injection port is sealed. The other is a manufacturing method in which a mixture of a curable compound and a liquid crystal is supplied onto a substrate and the opposing substrates are stacked.

In the liquid crystal display device of the present invention, a dichroic dye, a simple dye or a pigment may be added to the liquid crystal, or a colored curable compound may be used.

In the present invention, liquid crystal is used as a solvent in the liquid crystal solidified substance complex, and the photocurable compound is cured by light exposure, so that it is not necessary to evaporate a simple solvent or water which is unnecessary at the time of curing. Therefore, since it can be cured in a closed system, the conventional manufacturing method of injecting into a cell can be adopted as it is, and the reliability is increased. Further, since it has the effect of adhering two substrates with a photocurable compound, the reliability becomes higher.

In the present invention, the risk of short circuit between the upper and lower transparent electrodes is reduced by using the liquid crystal solidified composite in this manner. Furthermore, unlike a normal TN type display element, it is not necessary to strictly control the orientation and the substrate gap, and a liquid crystal display element capable of controlling the transmission state and the scattering state can be manufactured with extremely high productivity.

When used as a liquid crystal display device, the projection light source, the projection optical system, the projection screen, and the like may be conventional projection light sources, projection optical systems, and projection screens. The liquid crystal display element of the present invention may be arranged between them. Of course, images of a plurality of liquid crystal display elements may be combined and displayed using an optical system. As a light source used for these projection light sources, there are halogen lamps, metal halide lamps, xenon lamps, and the like, and it is possible to improve the light utilization efficiency by combining a concave mirror, a condenser lens, and the like. Further, a cooling system may be added to this, or a channel display such as an LED may be added.

In particular, in the case of this projection type display, it is possible to increase the display contrast by installing a device for reducing diffused light on the optical path, for example, an aperture or spot as shown by 15 in FIG. You can

That is, the device for reducing the diffused light is the light that goes straight to the incident light (the light that passes through the portion where the pixel portion is in the transmission state) out of the light that has passed through the liquid crystal display element, and does not go straight. Any light can be used as long as it reduces the light (light scattered by the liquid crystal solidified complex in the scattering state). In particular, it is preferable to reduce light that does not go straight (diffused light) without reducing light that goes straight.

As a concrete device, as shown in FIG. 2, the liquid crystal display element 1 is composed of a liquid crystal display element and a projection optical system.
2, some have a condenser lens 16, an aperture or a spot 15 which is a plate with holes, and a projection lens 17.

According to this example, of the light that has passed through the liquid crystal display element 12 from the projection light source, the light that goes straight with respect to the incident light is condensed by the condensing lens 16 and is opened to the aperture or spot 15. The light passes through the hole and is projected through the projection lens 17. On the other hand, the non-straight light scattered by the liquid crystal display element 12 does not pass through the aperture or the hole formed in the spot 15 even if it is condensed by the condenser lens 16. Therefore, scattered light is not projected and the contrast ratio is improved.

As another example, instead of the aperture or the spot 15, a mirror having a small area is obliquely arranged at the same position, reflected and projected through a projection lens arranged on the optical axis. You can also Further, a spot, a mirror or the like may be installed at a position where the light beam is focused by the projection lens without using such a condenser lens.
Further, the focal length and aperture of the projection lens may be selected so as to remove scattered light without using a special aperture or the like.

A microlens system or the like can also be used. Specifically, by disposing a microlens array and a spot array in which fine holes are arrayed on the projection optical system side of the liquid crystal display element, unnecessary scattered light can be removed. In this case, since the optical path length required for removing scattered light can be made extremely short, there is an advantage that the entire projection display device can be made compact. In order to shorten the optical path length, it is also effective to incorporate a scattering elimination system in the projection optical system. In this case, the size of the optical system can be reduced and the size of the optical system can be simplified as compared with the case where the projection optical system and the scattering elimination system are independently installed.

These optical systems can be combined with a mirror, a dichroic mirror, a prism, a dichroic prism, a lens, etc. to synthesize images and colorize them. Further, it is possible to colorize an image by combining it with a color filter.

The ratio of the straight-ahead component and the scattered component reaching the projection screen can be controlled by the diameter of the spot, the mirror, etc. and the focal length of the lens, and can be set so that a desired display contrast and display brightness can be obtained. good.

When a device for reducing diffused light as shown in FIG. 2 is used, it is preferable that the light incident on the liquid crystal display element from the projection light source is more parallel in order to increase the display brightness. For that purpose, it is preferable to configure a projection light source by combining a light source having high brightness and as close as possible to a point light source, a concave mirror, a condenser lens, and the like.

Further, in the above description, the transmission type liquid crystal display device was mainly explained, but a reflection type projection type liquid crystal display device may be used. For example, a small mirror may be placed instead of the spot so that only necessary light is extracted.

The device of the present invention has excellent characteristics as an active matrix liquid crystal display device for displaying a halftone, but is also effective for other inactive drive systems (static drive, multiplex drive). In particular, regarding the multiplex drive, it is significantly advantageous as compared with the conventional device. In multiplex driving, driving is performed by the difference between the off voltage and the on voltage, but in the liquid crystal resin composite, the sharpness of the voltage transmittance characteristics and the presence or absence of hysteresis have a large effect on the optical characteristics during multiplexing. Play a role.

If the voltage transmittance characteristic has a sharp threshold characteristic, it is suitable for multiplex driving, and the sharper the characteristic, the larger the number of lines to be driven simultaneously, so that higher density display can be achieved. However, if there is a large hysteresis, the transmittance varies depending on whether the voltage is stepped up or stepped down, which leads to a decrease in contrast during multiplex driving and display unevenness.

In the present invention, a sharp threshold characteristic and
Since low hysteresis can be achieved at the same time, it is possible to achieve a display with excellent contrast and uniformity that has never been obtained in multiplex driving.

There are other methods for reducing the hysteresis, such as adding distortion to the shape of dispersed liquid crystal particles or modulating the driving waveform, but in the device of the present invention,
This is advantageous over other methods in that the hysteresis can be reduced without energy loss, that is, without increasing the drive voltage. Of course, in addition to the method of the present invention, it is effective to use a combination of other methods as described above as a synergistic effect. Therefore, after considering the liquid crystal to be used, the matrix material, the driving voltage, the response characteristics, etc., It can be used in combination.

[0119]

According to the present invention, a display with a high contrast ratio can be obtained, and when used in a projection type display, light is transmitted in a transmissive-scattering type liquid crystal display element in a transmissive state, and a projection screen is obtained. Is displayed brightly, the light is scattered in the scattered state, and the projection screen is displayed darkly, so that a display with desired high brightness and high contrast ratio can be obtained.

In particular, in the present invention, since it has the above-mentioned structure, the hysteresis is reduced and the image sticking is reduced. Therefore, beautiful halftone display is possible, and by using the active element and the driving IC as used in the conventional active matrix liquid crystal display element for TN,
You can easily display moving images with fine gradation.

[0121]

EXAMPLES Example 1 Dielectric anisotropy Δε _LC is 10.5, refractive index anisotropy Δn is 0.24, elastic constant K11 is 12 × 10 ⁻¹² N, K33 is 15 × 10 ⁻¹² N, and viscosity η is about 35 cSt. An uncured mixture was prepared by uniformly dissolving the nematic liquid crystal having a positive dielectric anisotropy, acrylate monomer, urethane acrylate oligomer, and photoinitiator.

On the other hand, the active matrix substrate in which the polycrystalline silicon TFT is formed for each pixel and the counter electrode substrate in which the solid electrode is formed on the entire surface are sealed by the sealing material arranged in the peripheral portion, and the gap between the electrode substrates is 13 μm. Cells were formed. After injecting the uncured mixture into this cell,
It was cured by exposure to ultraviolet light to obtain a liquid crystal resin composite. The driving voltage of this liquid crystal display device was about 7V.

Dielectric constant ε _M below threshold voltage (0.3 V)
Was measured and found to be about 8.7 at 1 kHz. When this device was driven by a video signal, a moving image display excellent in halftone display was obtained. Further, no image burn-in (image remaining for several seconds or more) was observed when switching the images.

Then, this liquid crystal display element, a light source system and a projection optical system were combined to form a projection type display device. When an image was projected on the screen, a very bright moving image was obtained, and the display was excellent in halftone. When the contrast ratio was measured on the screen, it was about 150: 1. The converging angle of the projection optical system (2tan ^-1 (Φ / 2f), where Φ is the diameter of the aperture (spot) and f is the focal length of the lens) is about 5 degrees in full angle. It was

Examples 2 to 5 and Comparative Examples 1 to 4 Using liquid crystals whose dielectric anisotropy and refractive index anisotropy were changed,
A liquid crystal display device was prepared in the same manner as in Example 1. The electrode substrate gap was adjusted according to each liquid crystal in order to make the driving voltage almost uniform.

Here, the driving voltage is all 7V. Dielectric anisotropy Δε _LC of each liquid crystal, refractive index anisotropy Δn, electrode substrate gap d (μm), dielectric constant ε of liquid crystal resin composite at 0.3 V
_M (1kHz), liquid crystal elastic constants K11 (× 10 ^-12 N), K33 (× 10
^-12 N), viscosity η (cSt), contrast ratio CR on screen and hysteresis H in the case of projection type using the same optical system as in Example 1 are shown in Table 1.

[0127]

[Table 1]

The hysteresis in the table is a relative value when the magnitude of hysteresis in the voltage-transmittance characteristic of Comparative Example 4 is 1. The average diameter of the liquid crystal in these liquid crystal resin composites was about 2.0 μm. The liquid crystal used in Example 5 had a clearing point T _c of 80 ° C., an average particle diameter R of about 2.5 μm, and a driving voltage of this liquid crystal display device was about 7V. When the contrast ratio was measured on the screen while changing the temperature of this liquid crystal display element, there was almost no change in the contrast ratio at an element temperature of 10 to 60 ° C (ambient temperature 0 to 50 ° C), and a value of about 120 or more was obtained. Was given.

Further, the voltage V ₅₀ showing the transmittance of 50% of the saturated transmittance does not change much with temperature, and is 4.8 V at 10 ° C.
It was 4.0V at 60 ° C. Also, when the light incident on the liquid crystal display element was changed to red, green, and blue, this element had an element temperature of 30 ° C (ambient temperature 20 ° C),
It showed a high contrast ratio of over 120.

The liquid crystal used in Comparative Example 3 has a clearing point T _c
The temperature was 70 ° C., and the driving voltage of this liquid crystal display device was about 8V. When the contrast ratio was measured on the screen while changing the temperature of this liquid crystal display element, the element temperature was 10 to 60 ° C.
At (ambient temperature 0 to 50 ° C), the contrast ratio changed significantly. That is, when the element temperature is 10 ° C, it is about 170, and the element temperature is 60
It was about 7 ° C and the contrast ratio was about 100 or more in the range of 10 to 35 ° C. In addition, the saturated transmittance of 50
The voltage V ₅₀ showing% transmittance varied greatly with temperature and was 6.3 V at 10 ° C. and 2.6 V at 60 ° C.

Further, the light incident on the liquid crystal display element is changed to red,
When changed to green and blue, this element has an element temperature of 30 ° C.
At an ambient temperature of 20 ° C, it showed a high contrast ratio of about 120 or more for green and blue, but a contrast ratio of about 60 for red.

Example 6 In the liquid crystal display element of Example 1, the same liquid crystal was used as the liquid crystal, but the electrode substrate gaps d _R , d _G and d _{B for} each RGB and the average particle diameters R _R and R _{G of the} liquid crystal were used. , R _B was changed. For red, d _R = 14.5 μm, R _R = 2.1 μm, for green, d _G
= 12.0μm, R _G = 1.9μm, as is the blue, d _B = 10.5μ
m and R _B = 1.7 μm.

These three liquid crystal display elements were arranged in the path where the light was split by the dichroic mirror, and the light was condensed again and projected. The same light source and projection optical system as in Example 1 were used. With this color projection type liquid crystal display device, it was possible to obtain a clear projected image with a high contrast ratio and halftone without any image sticking. Furthermore, a projected image with good color balance was obtained without complicated color adjustment on the drive circuit side.

Example 7 A liquid crystal display device of Example 1 was manufactured by using the same liquid crystal as the liquid crystal but changing only the electrode substrate gaps d _R , d _G and d _{B for} each RGB. For red, d _R = 12.5 μm, for green, d _G = 11.0 μm, and for blue, d _B = 10.5 μm. The average particle size of the liquid crystal was R = 1.8 μm.

The three liquid crystal display elements were arranged in the same manner as in Example 6 to obtain a projection type liquid crystal display device. The contrast ratio of this color projection type liquid crystal display device was slightly lower than that of Example 6, but a high-contrast ratio and a clear projected image of halftone without a burn-in was obtained. Furthermore, a projected image with good color balance was obtained without complicated color adjustment on the drive circuit side.

Example 8 Three liquid crystal display elements were prepared in substantially the same manner as in Example 3,
It was a projection type display device. However, all electrode board gaps 11
μm, an element corresponding to three colors of RGB, an aluminum electrode as a pixel electrode, and a reflection type projection optical system using one dichroic prism for both color separation and color synthesis. And

When the device was driven at a maximum applied voltage of 8 V, a very bright display excellent in halftone display was obtained.
The contrast ratio on the screen was about 100. The converging angle of the projection optical system was about 10 °. Since there was a slight difference in the voltage dependence of the transmittance of the device for each color, the driving voltage was changed for each color to achieve color balance and obtain a color moving image display.

[0138]

In the liquid crystal display element of the present invention, the scattering state and the transmission state can be electrically controlled as a liquid crystal material sandwiched between a pair of substrates such as an active matrix substrate and a counter electrode substrate. Since the liquid crystal display element sandwiching the liquid crystal solidified composite is used, no polarizing plate is required, and the transmittance of light during transmission can be significantly improved.

The liquid crystal display device of the present invention uses a nematic liquid crystal having a positive dielectric anisotropy, and the refractive index of the resin matrix of the liquid crystal display device should be substantially the same as the ordinary refractive index (n _O ) of the liquid crystal used. As a result, it has a high scattering property when no electric field is applied, and a high transmissivity when an electric field is applied. Then, a driving IC for a conventional TN type liquid crystal display device
Also in the driving using, it is possible to display with high contrast ratio and high brightness.

Further, according to the present invention, even when the gradation driving is performed, it is possible to perform gradation display with a clear halftone, and it is possible to reduce the burn-in phenomenon due to hysteresis.
Therefore, the liquid crystal display element of the present invention is effective for projection type display, and a projection type display device which is free from image burn-in and has good contrast can be obtained. Also, the light source can be downsized. Further, since the liquid crystal display element of the present invention has little change in scattering ability with temperature and little change in voltage-transmittance characteristic with temperature, stable gradation driving can be easily performed in a wide temperature range.

Further, since it is not necessary to use a polarizing plate, there is an advantage that the wavelength dependence of the optical characteristics is small and color correction of the light source is almost unnecessary. Further, since the problems such as rubbing and other alignment treatments necessary for the TN type liquid crystal display element and the destruction of the active element due to the generation of static electricity can be avoided, the manufacturing yield of the liquid crystal display element can be greatly improved.

Furthermore, since this liquid crystal solidified composite is in the form of a film after curing, problems such as short circuit between substrates due to pressure of the substrates and breakage of active elements due to movement of spacers are unlikely to occur.

Further, this liquid crystal solidified composite has a specific resistance equivalent to that of the conventional TN mode, and it is not necessary to provide a large storage capacitance for each pixel electrode as in the conventional DS mode. Therefore, the active element can be easily designed, the ratio of the effective pixel electrode area can be easily increased, and the power consumption of the liquid crystal display element can be kept low. Further, the manufacturing process is easy because the manufacturing process of the conventional TN mode liquid crystal display device can be performed only by removing the alignment film forming process.

Further, the liquid crystal display element using this liquid crystal solidified composite has a feature that the response time is short,
It is easy to display moving images. Further, since the electro-optical characteristic (voltage-transmittance) of this liquid crystal display element is a comparatively gentle characteristic as compared with the liquid crystal display element of the TN mode, it can be easily applied to gradation display.

Further, in the liquid crystal display element of the present invention, light is scattered in a portion to which an electric field is not applied, so that light is not leaked at the time of projection even if the portion other than the pixel is not shielded by the light shielding film. It is not necessary to shield the gap between adjacent pixels from light. Therefore, in particular, by using an active element made of polycrystalline silicon as the active element, a high-luminance projection light source can be used without a light-shielding film in the active element portion,
A high-brightness projection type liquid crystal display device can be easily obtained. Further, in this case, it is not necessary to provide the light shielding film at all, and the production process can be further simplified.

In addition to the above, the present invention can be applied in various ways within the range of not impairing the effects of the present invention.

[Brief description of drawings]

FIG. 1 is a sectional view showing a basic configuration of a liquid crystal display element of the present invention.

FIG. 2 is a schematic diagram showing a basic configuration of a projection type active matrix liquid crystal display device using the liquid crystal display element of the present invention.

FIG. 3 is a schematic view of an example using a dichroic prism of a full-color projection type liquid crystal display device using the liquid crystal display element of the present invention.

FIG. 4 is a schematic view of an example of a full-color projection type liquid crystal display device using the liquid crystal display element of the present invention without using a dichroic prism.

[Explanation of symbols]

 1, 12: Liquid crystal display element 2, 5: Substrate 3: Pixel electrode 4: Active element 6: Counter electrode 7: Liquid crystal solidified composite 11: Projection light source 13: Projection optical system 14: Projection screen 15: Spot 16: Condensing lens 17: Projection lens

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-278230 (JP, A) JP-A-3-58021 (JP, A) JP-A-3-58022 (JP, A) JP-A-3- 282425 (JP, A) JP 3-126915 (JP, A) JP 4-188105 (JP, A) JP 4-263217 (JP, A) JP 5-93905 (JP, A) JP-A-5-34662 (JP, A) JP-A-4-318514 (JP, A) JP-A-4-296719 (JP, A) Technical Report of Television Society, 14 [10] (1990) P. 1-8 Proceedings of 15th Liquid Crystal Symposium Lecture Meeting (1989) P. 206-207

Claims (4)

(57) [Claims] 1. A nematic liquid crystal is dispersed and held in a solidified matrix between a pair of substrates with electrodes, and the refractive index of the liquid crystal changes depending on a voltage application state. In a liquid crystal display element sandwiching a liquid crystal solidified substance composite, which is configured to allow light to pass therethrough substantially in the same state and to scatter light in the other state so as not to match the refractive index of the solidified substance matrix, Refractive index anisotropy Δn
Is 0.18 or more, and the dielectric anisotropy Δε _LC is 5 <Δε _LC <
A liquid crystal display device characterized by satisfying the relationship of 13. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal solidified composite has a nematic liquid crystal having a positive dielectric anisotropy dispersed and held in a resin matrix, and the refractive index of the resin matrix is used. A liquid crystal display device characterized in that the liquid crystal display device has a refractive index (n 2 _O ) of liquid crystal that is substantially the same. 3. The liquid crystal display device according to claim 1, wherein the relative dielectric constant ε _M with respect to a sufficiently low voltage equal to or lower than the threshold voltage of the liquid crystal solidified composite, and the dielectric anisotropy Δε of the liquid crystal used. _LC is a liquid crystal display element characterized by satisfying the relation of Δε _LC <1.45ε _M. 4. The liquid crystal display element according to claim 1, 2 or 3, wherein the average particle diameter R (μ
m) is a liquid crystal display device characterized by satisfying the relationship of 0.2 <Δn · R <0.7.