JP2500566B2 - Liquid crystal optical element and 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 optical element and a liquid crystal display element in which liquid crystal is dispersed and held in a resin matrix between a pair of substrates with electrodes.

[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 transmissivity is different between step-up and step-down, and therefore, when the display screen is changed, the image sticking phenomenon may occur in which the information on the previous screen remains for several seconds or more. was there.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a liquid crystal optical element and a liquid crystal display which have high brightness and a high contrast ratio, can display halftones neatly, and reduce the burn-in phenomenon due to the hysteresis of the liquid crystal resin composite. It provides an element.

That is, the liquid crystal is dispersed and held in the resin matrix between the pair of electrodes-attached substrates, and the refractive index of the resin matrix is approximately equal to the refractive index of the liquid crystal used when the voltage is applied or not applied. In a liquid crystal optical element that sandwiches a liquid crystal resin composite that has the same refractive index and the other refractive index does not match, the elastic modulus of the resin material that constitutes the resin matrix is 20
Liquid crystal optical element characterized by 3 × 10 ⁷ N / m ² or less at 40 ° C. and 1 × 10 ³ N / m ² or more at 40 ° C., and loss loss modulus of the resin material constituting the resin matrix A liquid crystal optical element having a maximum temperature of 0 ° C. or less, and a resin material forming a resin matrix thereof is a photocurable vinyl compound photocured. A liquid crystal optical element to be used, and an active matrix substrate having an active element for each pixel electrode and a counter electrode substrate having a counter electrode are used as a pair of electrodes-attached substrates of the liquid crystal optical element, and between them. As a sandwiched liquid crystal resin composite, a nematic liquid crystal having a positive dielectric anisotropy is dispersed and held in a resin matrix, and the refractive index of the resin matrix substantially matches the ordinary refractive index (n ₀ ) of the liquid crystal used. Liquid crystal tree Using complex, there is provided a liquid crystal display device which is characterized in that a display including halftone.

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

In the present invention, the liquid crystal is dispersed and held in the resin matrix between the pair of electrode-attached substrates, and the refractive index of the resin matrix is used when the voltage is applied or not applied. The liquid crystal resin composite is sandwiched and used.

In particular, a nematic liquid crystal having a positive dielectric anisotropy is dispersed and held in a resin matrix, and the refractive index of the resin matrix is made to substantially match the ordinary refractive index (n ₀ ) of the liquid crystal used. A liquid crystal resin composite is used. Then, the liquid crystal resin composite is sandwiched between an active matrix substrate provided with an active element for each pixel electrode and a counter electrode substrate provided with a counter electrode.

The electrode-attached substrate refers to a substrate having electrodes formed on a substrate such as glass, plastic, or ceramic. Usually, this electrode is a transparent electrode such as ITO (In ₂ O ₃ —SnO ₂ ) or SnO ₂ . Further, if necessary, a metal electrode such as chromium or aluminum may be used together. When used in a reflective type, it may be used as a reflective electrode. Further, as the pair of substrates, there is a combination of an active matrix substrate and a counter electrode substrate.

The active matrix substrate is a substrate on which electrodes and active elements such as thin film transistors (TFTs), thin film diodes, and metal insulator metal nonlinear resistance elements (MIM) are formed. One or a plurality of active elements are connected to each pixel electrode. Further, this counter electrode substrate has electrodes formed on the substrate and is combined with an active matrix substrate substrate to enable display.

A liquid crystal resin composite is sandwiched between the pair of electrode substrates. In this liquid crystal resin composite, the refractive index of the liquid crystal in the liquid crystal resin composite changes depending on the voltage application state. Light is transmitted when the refractive index of the resin 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, a bright display can be easily obtained.

At this time, the refractive index of the resin matrix is made to substantially match the ordinary refractive index (n ₀ ) of the liquid crystal used, so that light is transmitted when a voltage is applied and is transmitted when a voltage is not applied. Light will be scattered. When a voltage is applied, the liquid crystal molecules are aligned in parallel to the direction of the electric field, so that the refractive index is easy to control, and this type of element can obtain a high transmittance when transmitting.

The liquid crystal optical element of the present invention is mainly used as a liquid crystal display element. However, it can also be used as a light control window or an optical shutter. As the liquid crystal display element, both a direct-view display element and a projection display element can be used. 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.

The liquid crystal display device 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 optical element of the present invention, a transmission-scattering type liquid crystal resin composite is sandwiched between a pair of substrates with electrodes.

Specifically, in the present invention, a liquid crystal resin composite comprising a resin matrix having a large number of fine holes and a liquid crystal filled in the holes is used as a liquid crystal optical element. The liquid crystal resin composite is sandwiched between a pair of substrates with electrodes. The refractive index of the liquid crystal changes depending on the state of voltage applied between the electrodes, and the relationship between the refractive index of the resin 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 resin composite comprising a resin matrix having a large number of fine pores and liquid crystals filled in the pores has a structure in which liquid crystals are contained in liquid bubbles such as microcapsules. is there. 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 resin composite used in the liquid crystal display device of the present invention is manufactured as follows. The liquid crystal and the curable compound forming the resin matrix are mixed to form a solution or latex. Next, the resin matrix may be separated by subjecting it to light curing, heat curing, curing by removing a solvent, reaction curing, or the like so that the liquid crystal is dispersed in the resin matrix.

In the present invention, a resin material having an elastic modulus of 3 × 10 ⁷ N / m ² or less at 20 ° C. and 1 × 10 ³ N / m ² or more at 40 ° C. is used as the resin material. In particular, it is preferable that the temperature be within the above range in many parts of the operating temperature range. Thereby, the image sticking phenomenon due to hysteresis can be reduced. Further, the curable compound used is preferably a photocurable type or a thermosetting type because it can be cured in a closed system. In particular, the use of a photocurable curable compound is preferable because it can be cured in a short time without being affected by heat.

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

In the case of the liquid crystal optical element of the present invention,
Without using a sealing material, for example, on a substrate provided with a transparent electrode, supply an uncured mixture of liquid crystal and a curable compound,
After that, the other electrode-attached substrate may be overlaid and cured 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 manufacturing method, the uncured mixture of the 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 extremely high. Good.

The uncured mixture of the liquid crystal and the curable compound contains ceramic particles for controlling the substrate gap,
Spacers such as plastic particles, glass fibers, pigments,
Dyes, viscosity modifiers, and other additives that do not adversely affect the performance of the present invention may be added.

By curing an element which 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 in 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 transmittance in the transparent state of the liquid crystal optical element using this liquid crystal resin composite, the better, and the haze value in the scattered state is preferably 80% or more.

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

The greatest object of the present invention is to provide a liquid crystal optical element capable of reducing the image sticking phenomenon due to the hysteresis of the liquid crystal resin composite and driving at a low voltage.
By combining this liquid crystal optical 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 exerted even in other applications requiring a halftone (window, shutter, display, spatial modulator, etc.).

In the conventional liquid crystal resin composite, the voltage-
Hysteresis is present in the transmittance characteristics, 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, which deteriorates the image quality.

One of the causes of the existence of hysteresis in the liquid crystal resin composite is due to the structure in which the liquid crystal is dispersed and held in the resin. That is, it is considered that there is hysteresis due to the interaction between the liquid crystals separated and present in the resin. The magnitude of this hysteresis is determined by the elastic energy stored in the liquid crystal retained in the resin, the electrical energy due to the electric field applied from the outside, and the interaction energy between the liquid crystals separated in the resin. It is something. 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 optical element having a high contrast ratio, high brightness, excellent responsiveness and reduced hysteresis. Furthermore, conventional TN
Is to obtain a liquid crystal optical element that can be driven by an active element or a driving circuit.

The important factors that determine the above energy balance are the average particle diameter R of the liquid crystal dispersed and held in the resin, the shape of the liquid crystal particles, the dielectric constant of the liquid crystal and its anisotropy Δ.
ε, elastic constant of liquid crystal, elastic modulus of resin matrix, dielectric constant and the like. When performing optimization for the above purpose, it is necessary to consider that this energy balance is closely related to the voltage-transmittance characteristic of the device and the dynamic characteristic (responsiveness) of the liquid crystal. is important.

In the above energy balance, the elastic property of the resin matrix plays an important role in the stability of the liquid crystal alignment. When the matrix has a sufficiently large elastic modulus compared to the elastic constant of the liquid crystal used (when the matrix is sufficiently harder than the liquid crystal), the matrix is almost always deformed when the liquid crystal is rearranged by applying an electric field. Absent. Therefore, the liquid crystal alignment is determined by the electric and elastic energies of the liquid crystal itself while maintaining the shape of the liquid crystal particles when there is no electric field.

On the other hand, when rearranging the liquid crystal by applying an electric field,
When the matrix itself is deformed, the liquid crystal alignment is determined by the electrical and elastic energy of the liquid crystal itself and the elastic energy of the matrix. Generally, the elastic constant of liquid crystal is about 10 ⁻¹¹ N, and the average diameter of liquid crystal particles is about 1 to 3 μm. Therefore, when the elastic modulus of the matrix is about 10 ⁷ N / m ² or smaller, the deformation of the matrix contributes energetically.
In such a soft matrix, liquid crystal rearrangement occurs with the deformation of the matrix according to the applied electric field.

One of the causes of hysteresis is that a change in the alignment of liquid crystals in each liquid crystal particle causes a large change in the dielectric constant at that location. This change in the dielectric constant causes a change in the electric field with respect to the location of other liquid crystal particles. Therefore, a phenomenon occurs in which the liquid crystal alignment in the liquid crystal particles dispersed in the system is not uniquely determined for a certain applied voltage from the outside.

From this point of view, it is desirable that the shape of the matrix can be deformed when the alignment of the liquid crystal is changed, that is, it is soft. In a sufficiently hard matrix, the boundary surface between the liquid crystal and the matrix is fixed. As a result, an abrupt array change (Freedericksz transition) occurs in a certain electric field as the applied electric field rises. Therefore, this causes a large change in the dielectric constant, which is a factor that causes hysteresis.

On the other hand, in a sufficiently soft matrix, abrupt changes in the liquid crystal alignment are unlikely to occur, and the matrix deformation stabilizes the liquid crystal alignment against the applied electric field and reduces the hysteresis. Further, in a sufficiently soft matrix, a change in alignment of the liquid crystal and a deformation of the matrix may occur by applying a small electric energy from the outside. Therefore, it also has an advantage that it is easy to simultaneously achieve reduction of hysteresis and driving at low voltage.

As described above, the elastic modulus of the resin material forming the matrix is 3 × 10 ⁷ N / m ² or less at 20 ° C. Particularly, 1.5 × 10 ⁷ N / m ² or less is preferable.

If the elastic modulus of the matrix is too low,
This may cause a problem in the structural stability of the matrix, or a problem that a sufficient force for restoring the liquid crystal alignment does not work when the electric field is turned on and off. For this reason, the elastic modulus of the matrix has a lower limit, and is 1 × 10 ³ N / m ² or more at 40 ° C. 20 when used at normal room temperature
In the temperature range of -40 ℃, it is set to 3 × 10 ⁷ N / m ² 〜 1 × 10 ³ N / m ² . Particularly, 5 × 10 ³ N / m ² or more is more preferable.

In order to reduce the hysteresis in a practical temperature range, the glass transition temperature of the matrix is preferably sufficiently lower than the operating temperature range. Specifically, the temperature at which the loss elastic modulus is maximized due to the glass transition of the main chain of the resin material forming the resin matrix of the liquid crystal resin composite is preferably lower than the operating temperature range. Generally, it is preferable that the temperature at which the loss elastic modulus becomes maximum is 0 ° C. or less.

The resin material here means the resin material itself which does not contain liquid crystal. The elastic modulus is 11H
z, adding a sine wave amplitude with a dynamic strain of 1% or less, heating rate 3
It is defined as the dynamic storage elastic modulus obtained by measuring the viscoelasticity at the time of pulling in ° C / min.

The resin portion of the resin matrix may be composed of only resin or resin swollen with liquid crystal. When the liquid crystal is swollen, the glass transition temperature of the liquid crystal resin composite generally shifts to a lower temperature range than that of the resin alone, and the absolute elastic modulus also decreases. Therefore, it is possible to control the matrix elastic modulus more finely by using the desirable resin material in the above range as the matrix constituent material and further utilizing the swelling by the liquid crystal. The amount of liquid crystal that swells in the matrix differs depending on the liquid crystal material and resin material used, and
It can take up to several tens of wt% of swelling amount.

Therefore, the elastic modulus of the matrix swollen with liquid crystal is generally defined in a range lower than the elastic modulus of the above resin alone, and is preferably 8 × 10 ⁶ N / m ² or less at 20 ° C. Particularly, 4 × 10 ⁶ N / m ² or less is more preferable. The lower limit is 10 ³ N / m ² or higher at 40 ° C, which is 2 × 10
³ N / m ² or more is more preferable. The temperature at which the loss elastic modulus of the matrix swollen with the liquid crystal of the liquid crystal resin composite becomes maximum is preferably -5 ° C or lower.

[0048] On the other hand, the resin - and (polysiloxane _{structure), -C 6 H 12 - -} (Si (CH 3) 2 -O-) n ( hexamethylene structure) or the like by including, its glass transition temperature It is possible to lower the temperature, and a part of the resin used here may be provided with such a structure.

Further, as the number of curing sites in one molecule,
1 to 10 are selected, but in terms of structural stability
2 to 6 functional ones, 5 wt% of resin that constitutes the matrix
% Or more is preferably used. Furthermore, in order to control the liquid crystal particle diameter, particle diameter distribution, particle density, etc. of the liquid crystal resin composite, it is preferable to use a mixture of two or more curable compounds having different molecular weights, and the maximum molecular weight It is preferable that the ratio of the minimum value to the minimum value is 1.5 times or more.

As a concrete manufacturing method, there is a method in which a curable compound satisfying the above physical properties is uniformly dissolved with a liquid crystal material after curing, and a phase separation structure of a liquid crystal and a resin matrix is formed by curing the curable compound. Can be mentioned. At this time, it is possible to control the balance of the compatibility of the system before and after curing and the characteristics of the matrix by appropriately mixing other curable compounds, reaction initiators and the like. In particular, it is desirable to use a photocurable vinyl compound to form a phase-separated structure by light irradiation, from the viewpoint of both structure control and productivity. In this case, an acrylic resin, particularly one having an acrylic group as a functional group is desirable.

In order to reduce the hysteresis caused by the liquid crystal particles dispersed in the resin matrix, it is important to balance the dielectric constant of the liquid crystal, its anisotropy Δε and the dielectric constant of the resin matrix. The shape of liquid crystal particles is also an important factor. The effect of the present invention can be enhanced by balancing these factors. The dielectric anisotropy Δε of the liquid crystal used is preferably in the range of satisfying the relationship of 5 <Δε <13.

Δε 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 increases. However, in such a system in which liquid crystal particles are dispersed, the driving voltage is Δ
The concept of the conventional TN type liquid crystal display device that is inversely proportional to the square root of ε does not hold.

This is because the voltage distribution to the liquid crystal portion and the matrix portion differs depending on the arrangement of the liquid crystals. Generally, in such a system, Δε does not show a great influence on the driving voltage, and in the range where Δε is larger than 5, the driving voltage does not become extremely high by reducing Δε.

In order to reduce the hysteresis, the dielectric constant ε _m of the liquid crystal resin composite at a sufficiently low voltage equal to or lower than the threshold voltage and the dielectric anisotropy Δε of the liquid crystal used are Δε <1.45 · ε. It is preferable to have a relationship of _m .

When Δε 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 occurs around the particles. Therefore, the electrical interaction between the liquid crystal particles, which is a factor that causes hysteresis, becomes large. ε _m is a quantity that is also related to the dielectric constant of the resin matrix, and when the dielectric constant of the resin matrix increases, the dielectric constant ε _{m of the} entire liquid crystal resin composite increases and the range of possible Δε also widens.

The liquid crystal used in the present invention may be a nematic liquid crystal or a smectic liquid crystal, but a nematic liquid crystal is preferably used. Further, a cholesteric liquid crystal may be added to a part thereof, or a dichroic dye or a simple dye may be added. Further, a viscosity modifier, spacers such as alumina particles and glass fibers, and other additives may be added thereto.

The refractive index anisotropy Δn of the liquid crystal is also an important factor that determines the electro-optical characteristics. In order to obtain a large scattering property without applying an electric field, the liquid crystal to be used preferably has a refractive index anisotropy of 0.18 or more, and more preferably 0.20 or more.

In the present invention, it is preferable that the liquid crystal and the resin matrix have the same refractive index when a voltage is applied, because the transmittance at the time of transmission becomes high. Therefore, a nematic liquid crystal with positive dielectric anisotropy is used, and the ordinary refractive index of the liquid crystal is used.
It is preferable that (n _o ) substantially matches the refractive index n _{p of the} resin matrix. At this time, high transparency is obtained when a voltage is applied. Specifically, it is preferable to satisfy the relationship of _{n o -0.03 <n p <n} o +0.05.

The liquid crystal dispersed and held in the resin matrix is preferably independent particles or particles partially communicating with each other. 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 the liquid crystal / resin interface. 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 diameter, it is important to increase the amount of liquid crystal separated from the resin independently, that is, increase the liquid crystal particle density. However, when the amount of liquid crystal separated from the resin 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 communicate with each other. This leads to the loss of the liquid crystal interface separated from the resin, leading to a decrease in the scattering ability.

Further, in order to lower the driving voltage, it is important that the respective liquid crystals held in the resin have substantially the same driving electric field. For this purpose, it is advantageous for the liquid crystal to have a clear interface with the resin, 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 resin is independent particles that are present at a high density or particles that partially communicate with each other.

In the above description, the case of a single liquid crystal optical element has been described. For example, when three liquid crystal display elements are used and light of RGB three colors is divided and transmitted to each liquid crystal display element as in a projection type liquid crystal display device, the liquid crystal particle size, substrate gap, Adjust the refractive index of the liquid crystal,
It is preferable to have the same characteristics for 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 resin 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 resin composite deteriorates, so Φ <70% is preferable.

In the liquid crystal optical element of the present invention, it is preferable that the refractive index of the resin matrix of the liquid crystal optical element substantially matches the ordinary refractive index (n ₀ ) of the liquid crystal used. In this case, when a voltage is not applied, a scattering state (that is, a white turbid state) is exhibited due to the difference in refractive index between the liquid crystal that is not forcibly aligned in the direction perpendicular to the substrate and the resin matrix. For this reason, light is scattered at the portion where there is no electrode.

When this liquid crystal optical element is used as a projection type display device, since light is scattered at 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, and the ordinary refractive index (n _o ) of the liquid crystal and the refractive index (n _p ) of the resin matrix match. 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 that is desired to be fixedly displayed, such a normal transmission part may be formed.

Further, the liquid crystal display element 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.

Color display may be performed by mixing a dye, a pigment or the like in the liquid crystal resin composite.

FIG. 1 is a sectional view of an example of the present invention and is a sectional view of an example of a liquid crystal display device using an active matrix substrate. 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, and 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, 6 is a counter electrode such as ITO or SnO ₂ and 7 is a liquid crystal resin composite sandwiched between both substrates Showing the body.

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.

When a three-terminal element such as a TFT (thin film transistor) is used as an active element, the counter electrode substrate may be provided with a solid electrode common to all pixels. MIM element, PI
When using a two-terminal element such as an N diode, the counter electrode substrate is patterned in a stripe shape.

When a TFT is used as the active element, silicon may be suitable as the semiconductor material. In particular, since polycrystalline silicon has no photosensitivity like amorphous silicon, malfunction does not easily occur even if the light from the light source is not blocked by the light blocking film or is not a strict light blocking film.
preferable. 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 optical element, a light-shielding film is often formed between the pixels in order to suppress light leakage between the 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,
The refractive index of the liquid crystal used is the ordinary refractive index (n
It is preferable to use a liquid crystal resin composite which is made to substantially match _o ). As a result, light is scattered in the portion to which the electric field is not applied and becomes black on the projection screen on which the light is projected. Therefore, 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 optical element of the present invention may be laminated with an infrared cut filter, an ultraviolet cut filter or the like, or may be printed with characters or figures, or a plurality of liquid crystal optical elements may be used. You may do it.

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 optical 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 is used as the curable compound constituting the above-mentioned liquid crystal resin composite, it is preferable to use a photocurable vinyl compound. Specifically, a photocurable acrylic compound is preferable.

When a photocurable compound is used in the liquid crystal of the present invention, it is preferable that the photocurable compound is uniformly dissolved. 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.

In the present invention, liquid crystal is used as a solvent in the liquid crystal resin composite, and the photocurable compound is cured by photoexposure, so that there is no need 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. Furthermore, with a photocurable compound
Since it also has the effect of adhering two substrates, the reliability becomes higher.

In the present invention, the use of the liquid crystal resin composite as described above reduces the risk of short circuit between the upper and lower transparent electrodes. Further, unlike a normal TN type display element, it is not necessary to strictly control the orientation and the substrate gap, and a liquid crystal optical element capable of controlling the transmission state and the scattering state can be manufactured with extremely high productivity.

As the projection light source, the projection optical system, the projection screen, etc., the conventional projection light source, projection optical system and projection screen can be used, and the liquid crystal display device of the present invention is provided between the projection light source and the projection optical system. Just place it. Of course, images of a plurality of liquid crystal display elements may be combined and displayed using an optical system. Also, a cooling system can be added to this, or LE
A TV channel display such as D may be added.

Particularly, in the case of this projection type display, by installing a device for reducing diffused light on the optical path, for example, an aperture or spot as shown by 15 in FIG.
The display contrast can be increased.

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 optical element and does not go straight. Any light source capable of reducing (light scattered by the liquid crystal resin composite in the scattering state) may be used. In particular, it is preferable to reduce light that does not travel straight, that is, diffused light, without reducing light that travels 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 on with respect to the incident light is condensed by the condensing lens 16 and 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.

Further, 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 removal system, which is a device for reducing diffused light, 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 an image and colorize it. Also,
Images can be colored by combining 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 desired display contrast and display brightness can be obtained. Good.

When a device for reducing diffused light as shown in FIG. 2 is used, in order to increase the display brightness, it is preferable that the light incident on the liquid crystal display element from the projection light source is more parallel. 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 can be placed instead of the spot so that only the necessary light is extracted.

[0094]

EXAMPLES Example 1 A nematic liquid crystal having a positive dielectric anisotropy (Δn = 0.24, Δε =
11.8, K33 ＝ 15 × 10 ^-12 N, η ＝ 40cSt) and 2 kinds of acrylate monomers (2-ethylhexyl acrylate, 2-hydroxyethyl acrylate), bifunctional urethane acrylate oligomer (“UX4101” manufactured by Nippon Kayaku Co., Ltd.), light The reaction initiator was uniformly dissolved to prepare an uncured mixture. The liquid crystal fraction in the mixture was 66 wt%.

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 entire surface solid electrode is formed are sealed with the sealing material arranged in the peripheral portion, and the gap between the electrode substrates is 13 μm. Cells were formed.

The above-mentioned uncured mixture was injected into this cell and then cured by exposure to ultraviolet rays to obtain a liquid crystal resin composite. The driving voltage of this liquid crystal display device was about 8V.
Below the threshold voltage of this liquid crystal resin composite (measured voltage =
The dielectric constant of 0.3 V) was about 8.2 at 1 KHz.

When this liquid crystal display device was driven by a video signal, a moving image with almost no image sticking was obtained even when the images were switched. When this element, a projection light source and a projection optical system were combined to form a projection type display device and an image was projected on the screen, the contrast ratio on the screen was about 110. The converging angle of the projection optical system (converging angle δ = 2tan ^-1 (Φ / 2f), Φ is the aperture, the diameter of the spot, and f is the focal length of the lens) is 6 degrees in all angles.

A liquid crystal was removed from the above mixture to prepare a mixture, and the mixture was UV-cured to a thickness of about 500 μm.
A film having a length of m and a length of about 15 mm was produced. The elastic modulus (dynamic elastic modulus) of this film was measured using a viscoelasticity measuring device (Rheovibron DDV type manufactured by Orientec Co., Ltd.) and found to be 5 × 10 ⁶ N / m ² at 20 ° C and 3 × at 40 ° C. 10 ⁵ N / m ² ,
It decreased monotonically with increasing temperature.

The temperature at which the loss elastic modulus becomes maximum is −
10 ° C. The measurement conditions were a frequency of 11 Hz, a sine wave amplitude with a dynamic strain of 1% or less, and a tensile rate of 3 ° C / min.

Comparative Examples 1 and 2 and Example 2 An active matrix liquid crystal display device was prepared in substantially the same manner as in Example 1 except that only the resin material was changed.

As Comparative Example 1, the bifunctional urethane acrylate oligomer of Example 1 was used as "M1200" manufactured by Toagosei Co., Ltd.
Was replaced with The driving voltage of this element was 9V.

In Comparative Example 2, a part of the monomer is different from that in Example 1, and 2-ethylhexyl acrylate is used as a bifunctional acrylate monomer (“SR640” manufactured by Sartomer).
Replaced with. The drive voltage of this element was 12V.

In Example 2, a part of the oligomer was different from that in Comparative Example 1, and the oligomer "M120" used in Comparative Example 1 was used.
One third of "0" was replaced with a curable resin having acryloyl groups at both ends of dimethylsiloxane having a molecular weight of about 3000 to obtain a liquid crystal resin composite. The drive voltage of this element was 10V.

These liquid crystal display elements were driven by a video signal, and the burn-in phenomenon when switching images was investigated. Also,
This device, a projection light source, and a projection optical system were combined to form a projection display device, an image was projected on the screen, and the contrast ratio on the screen was measured. The total angle of the projection optical system was 6 degrees.

A mixture was prepared by removing the liquid crystal from the above-mentioned three kinds of mixture, and the mixture was cured by ultraviolet rays to a thickness of about
A film having a thickness of 500 μm and a length of about 15 mm was produced. The elastic moduli of the film at 20 ° C. and 40 ° C. were measured with a viscoelasticity measuring device.

Further, the temperature at which the loss elastic modulus due to the glass transition of the main chain was maximized was measured. The measurement conditions are
Same as Example 1. Further, the magnitude of hysteresis in the voltage-transmittance characteristic of this device (area of hysteresis loop) was also measured.

The results are shown in Table 1. The presence or absence of the image sticking phenomenon at the time of image switching, the elastic modulus is N / m ² , the temperature at which the loss elastic modulus is maximum is ° C, and the magnitude of the hysteresis is the magnitude of the hysteresis of Example 1 (hysteresis loop Area). The elastic modulus decreased from 20 ℃ to 40 ℃ monotonically with increasing temperature.

[0108]

[Table 1]

[0109]

In the liquid crystal optical element of the present invention, as a liquid crystal material sandwiched between a pair of substrates with electrodes, a liquid crystal optical element sandwiching a liquid crystal resin composite capable of electrically controlling the scattering state and the transmitting state. Since a polarizing plate is used,
The light transmittance at the time of transmission can be significantly improved.

The liquid crystal optical element of the present invention has a high contrast ratio and enables high-luminance display even when it is driven using a conventional driving IC for a TN type liquid crystal optical element.

Further, according to the present invention, even when gradation driving is performed, gradation display with clear halftone can be performed, and the burn-in phenomenon due to hysteresis can be reduced.
Therefore, the liquid crystal optical element of the present invention is also effective for projection type display, and it is possible to obtain a projection type display which is bright and has a good contrast ratio without image burn-in. Also, the light source can be downsized.

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 problems such as rubbing and other alignment treatments essential to the TN type liquid crystal optical element and destruction of the active element due to static electricity accompanying it can be avoided, the manufacturing yield of the liquid crystal optical element can be greatly improved.

Further, since this liquid crystal resin composite is in the form of a film after being cured, problems such as short circuit between substrates due to pressurization of substrates and breakage of active elements due to movement of spacers are unlikely to occur.

Further, this liquid crystal resin 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 designed easily, the ratio of the effective pixel electrode area can be easily increased, and the power consumption of the liquid crystal optical element can be kept low.

Further, the manufacturing process is easy because the manufacturing process of the conventional liquid crystal optical element of TN mode can be carried out only by removing the alignment film forming process.

Further, the liquid crystal optical element using this liquid crystal resin composite has a feature that the response time is short, and a moving image can be easily displayed. Further, the electro-optical characteristic (voltage-transmittance) of this liquid crystal optical element is a comparatively gentle characteristic as compared with the liquid crystal optical element of the TN mode.
It is also easy to apply to gradation display.

Further, in the liquid crystal optical element of the present invention, it is preferable that the refractive index of the resin matrix and the ordinary refractive index of the liquid crystal are substantially the same. As a result, light is scattered in a portion to which an electric field is not applied, so that light does not leak at the time of projection even if the portion other than the pixel is not shielded by the light shielding film, and it is not necessary to shield the gap between adjacent pixels.

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, and a high-luminance 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 a range that does not impair the effects of the present invention.

[Brief description of drawings]

FIG. 1 is a sectional view showing a basic configuration of a liquid crystal optical 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.

[Explanation of symbols]

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

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yutaka Kumai, 1160 Matsubara, Hazawa-machi, Kanagawa-ku, Yokohama, Kanagawa Prefecture A-G Technology Co., Ltd. (72) Inventor, Yuki Korishima 1150, Hazawa-machi, Kanagawa-ku, Yokohama Address Asahi Glass Co., Ltd. Central Research Laboratory

Claims (4)

(57) [Claims] 1. A liquid crystal is dispersed and held in a resin matrix between a pair of substrates with electrodes, and the refractive index of the resin matrix is substantially the same as the refractive index of the liquid crystal used when a voltage is applied or not applied. In a liquid crystal optical element that is sandwiched between liquid crystal resin composites that match each other and that do not match in both refractive indices,
The elastic modulus of the resin material that constitutes the resin matrix is 3 at 20 ° C.
A liquid crystal optical element characterized by having a density of × 10 ⁷ N / m ² or less and 1 × 10 ³ N / m ² or more at 40 ° C. 2. The liquid crystal optical element according to claim 1, wherein the temperature at which the loss elastic modulus of the resin material forming the resin matrix becomes maximum is 0 ° C. or less. 3. The liquid crystal optical element according to claim 1, wherein the resin material forming the resin matrix is a photocurable vinyl compound photocured. 4. An active matrix substrate having an active element provided for each pixel electrode and a counter electrode substrate having a counter electrode are used as a pair of electrodes-provided substrates of the liquid crystal optical element of claim 1, 2 or 3. And, as a liquid crystal resin composite sandwiched between them, a nematic liquid crystal having a positive dielectric anisotropy is dispersed and held in a resin matrix, and the refractive index of the resin matrix is the ordinary refractive index (n ₀ ) of the liquid crystal used. A liquid crystal display device, which uses a liquid crystal resin composite that is made to substantially match with, and performs display including a halftone.