JP2001249363A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device of high response speed, which is suitable for moving image display and capable of being driven at low voltage. SOLUTION: In the display device 20, a glass substrate 21, having a polyimide film 22 formed on the surface thereof and a glass substrate 28 having a pixel electrode 26 and a counter electrode 27, which form a teeth-shaped electrode and a polyimide film 25 formed on the surface thereof are stuck to each other via glass fiber spacers 24 to form a gas specified to have 50 μm gap length and a medium containing polar molecules 23a made into an isotropic phase state by a heater 34, which is a phase-changing means, is shield from between the glass substrates 21 to 28.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device for displaying a television image, a personal computer, and a multimedia image with a high-speed response and a wide visual field display performance.

[0002]

2. Description of the Related Art In recent years, the market for various types of high-definition panel displays has been rapidly expanding. Among them, liquid crystal display elements are effective in reducing the size, weight, thickness, and power consumption. Such as image display devices, monitors,
Widely used in OA equipment such as word processors and personal computers.

Conventionally, as a liquid crystal display element, for example, a twisted nematic (TN) mode liquid crystal display element using a nematic liquid crystal having a positive dielectric anisotropy has been put to practical use. The display element has disadvantages such as a low response speed and a narrow viewing angle.

There are also display modes such as a ferroelectric liquid crystal (FLC) and an antiferroelectric liquid crystal (AFLC) which have a quick response and a wide viewing angle, but have major drawbacks in shock resistance and temperature characteristics. Yes, it has not yet been widely used.

Further, the polymer dispersion type liquid crystal display mode utilizing light scattering does not require a polarizing plate and is capable of high-luminance display. However, the viewing angle cannot be controlled essentially by a phase plate, and the response characteristics are not improved. And has little advantage over the TN mode.

[0006]

Problems to be Solved by the Invention Moving image display will be increasingly used in the future, but there is still no display device having sufficient response characteristics. An object of the present invention is to provide a display device having a high response speed and suitable for displaying a moving image.

[0007]

According to an aspect of the present invention, there is provided a display device, wherein at least one of the display devices is sandwiched between a pair of transparent substrates and the pair of substrates. A medium including polar molecules in an isotropic phase state; a polarizing plate disposed outside at least one of the pair of substrates; and an electric field applying unit for applying an electric field to the medium. Features.

In the display device having the above-mentioned structure, an electric field is applied to the medium by an electric field applying means, and electrons in the polar molecules in an isotropic phase are deflected in the direction of the electric field, whereby the medium has a refractive index anisotropy. Is provided. Such a display device utilizes the so-called Kerr effect, which is proportional to the second order of the electric field, exhibits a response characteristic of several μs to several ms, enables high-speed response, and can be applied to moving image display. It is possible. As described above, the display device of the present invention does not perform display by changing the arrangement of liquid crystal molecules as in the conventional liquid crystal display device, but performs display by changing the bias of electrons, and enables high-speed response. That's it.

According to a second aspect of the present invention, there is provided a display device, wherein at least one of the substrates includes a pair of transparent substrates, a medium containing polar molecules sandwiched between the pair of substrates, and the pair of substrates. A polarizing plate disposed outside at least one of the substrates, phase transition means for bringing the medium into an isotropic phase state, and electric field applying means for applying an electric field to the medium. Features.

[0010] The display device having the above-mentioned structure includes phase transition means for bringing polar molecules into an isotropic phase state, and the medium can be brought into an isotropic phase state by the phase transition means. Therefore, similarly to the display device according to the first aspect, the display device according to the second aspect utilizes the Kerr effect and can be a display device applied to a moving image display that requires a high-speed response. It is.

[0011] The invention according to claim 3 is based on claim 1.
Alternatively, in the display device according to claim 2, the electric field applying unit is a pair of comb-shaped electrodes formed on an inner surface of the one substrate, and a direction of the electric field application is parallel to the substrate surface. Features.

The invention described in claim 4 is the first invention.
3. The display device according to claim 2, wherein the electric field applying means is an electrode formed on each of inner surfaces of the pair of substrates, and a direction of the electric field application is perpendicular to the substrate surface. And

As in the above configuration, a display device capable of high-speed response is realized by the configuration of claim 3 or the configuration of claim 4.

The invention described in claim 5 is the third invention.
3. The display device according to claim 1, wherein the comb-shaped electrode has a "-" shape in plan view.

As described above, the viewing angle characteristics of the display device can be improved by forming the comb-shaped electrode in the shape of a "<" in plan view.

The invention described in claim 6 is the first invention.
6. The display device according to claim 5, wherein the polar molecules in the medium form clusters.

The term "cluster" means a group of molecules formed by polar molecules in the medium. The polar molecules are macroscopically in an isotropic state, but microscopically. It forms a molecular population arranged in a certain direction. By forming the cluster, the Kerr constant of the medium can be increased, and the applied voltage applied to the medium can be reduced by increasing the Kerr constant.

The invention according to claim 7 is the first invention.
7. The display device according to claim 6, wherein a dielectric thin film is formed on an inner surface of the substrate, and the dielectric thin film has been subjected to a predetermined alignment treatment.

As described above, by forming a dielectric thin film on the inner surface of the substrate constituting the display device and by subjecting the dielectric thin film to an alignment treatment, the degree of alignment order can be increased. Car constant is expected. Further, in the case of the invention described in claim 6, it is possible to increase the diameter of a cluster which is a molecular population, and if the diameter of the cluster increases, it is possible to increase the Kerr constant. Therefore, a further reduction in applied voltage (for example, 100 V
The following low voltage driving becomes possible, and practical use becomes possible.

The invention described in claim 8 is the same as the invention described in claim 7.
3. The display device according to claim 1, wherein the dielectric thin film is an organic thin film.

The invention according to claim 9 is the invention according to claim 8
3. The display device according to claim 1, wherein the organic thin film is polyimide.

As described above, when the dielectric thin film is made of an organic thin film, in particular, polyimide, the polyimide exhibits an extremely excellent orientation effect, so that the Kerr constant can be easily increased. Becomes The polyimide is a highly stable material and has high reliability.
Therefore, a display device exhibiting good display performance can be provided by using the polyimide.

According to a tenth aspect of the present invention, in the display device according to the second to ninth aspects, the polar molecules include a liquid crystal material.

According to an eleventh aspect of the present invention, in the display device according to any one of the second to ninth aspects, the polar molecule comprises a liquid crystal material and an isotropic phase transition temperature of the liquid crystal material. And a material for lowering.

With the above structure, when a liquid crystal material is used as polar molecules, the liquid crystal material is applied to a display device in an isotropic phase state by heating with a heater or the like as a phase transition means. In that case, the higher the heating temperature of the heater, the more the liquid crystal material becomes in the isotropic phase state, but the Kerr constant decreases. The decrease in the Kerr constant increases the applied voltage, which is not convenient for practical use.

However, by adding a material for lowering the isotropic phase transition temperature of the liquid crystal material to the liquid crystal material, it is possible to lower the isotropic phase transition temperature of the liquid crystal material without lowering the Kerr constant. Can be. Therefore, since the Kerr constant does not decrease, the display device can be driven at a low voltage without increasing the applied voltage. Further, the heating temperature of the heater or the like can be reduced, and the operating temperature range of the display device can be widened.

According to a twelfth aspect of the present invention, in the display device according to the eleventh aspect, the material for lowering the isotropic phase transition temperature of the liquid crystal material includes a cyano group, a hydroxyl group, or It is a material having a nitro group.

The liquid crystal material may be provided with a material for lowering the isotropic phase transition temperature of the liquid crystal material, for example, a cyano group at a molecular terminal,
By adding a non-liquid crystal molecule having a hydroxyl group or a nitro group, the phase transition temperature of a liquid crystal material to an isotropic state can be reduced, and thus the operating temperature range of a display device can be widened.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a display device according to an embodiment of the present invention will be described with reference to the drawings. However, parts unnecessary for description are omitted, and some parts are shown enlarged or reduced for ease of description.

Before describing the display device of the present invention in detail, the principle of the electro-optic effect applied to the present invention will be described with reference to FIG. FIG. 10 is a schematic diagram illustrating a measurement system of the electro-optic effect according to the embodiment of the present invention.

The electro-optic effect is a phenomenon in which the refractive index of a substance is changed by an external electric field, and there are an effect proportional to the first order of the electric field and an effect proportional to the second order, and the Pockels effect and the Kerr effect, respectively. being called.

Among the electro-optical effects, the Kerr effect has been applied to a high-speed optical shutter from an early stage, and in particular, has been put to practical use in special measuring instruments. Also,
Since the Kerr effect is proportional to the second order of the electric field, it is possible to expect a relatively low voltage driving, and in addition, it is essentially several μs.
Since it exhibits a response characteristic of up to several ms, it can be expected to be applied to a display device capable of high-speed response.

The magnitude of the second-order electro-optic effect is called Kerr constant.

The liquid crystal material in the isotropic phase state (the liquid crystal material is brought into the isotropic phase state by heating).
When an electric field (E) is applied to the surface, birefringence occurs. When the refractive index in the direction of the electric field is n // and the refractive index in the direction perpendicular to the electric field is n⊥, the magnitude of the birefringence (Δn = n // −n⊥) and the external electric field are represented by Δn = BλE ² (1).

Here, B is the Kerr constant, and λ is the wavelength of the incident light in vacuum.

As shown in FIG. 10, when linearly polarized light whose polarization plane is inclined by 45 degrees in the direction of the electric field is incident on the cell, at the end of the cell, the following equation is established between the polarization components in the direction of the electric field and the direction perpendicular thereto. Such a phase difference (Γ) occurs. Γ = 2πLΔn / λ (2)

Therefore, the light transmitted through the cell is the above (2)
Since the light becomes elliptically polarized light according to the equation, a part of the light can pass through the analyzer (polarizing plate) 9 and is again emitted as linearly polarized light. Then, the intensity I is represented by the following equation. I = I ₀ sin ² (Γ / 2) (3)

Here, I ₀ represents the intensity of incident light. If no electric field is applied to the cell, I = 0 from Γ = 0, but if an electric field is applied and Γ = π, then I = I _{0 and} 100% light intensity modulation can be performed. The voltage at this time is called a half-wave voltage (Vπ). On the other hand, if the relationship of E = V / d is used, Γ = 2πBV ² (L / d ² )... (4) can be calculated from the formulas (1) and (2). Can be obtained as in the following equation. Vπ = d / (2LB) ^0.5 (5)

That is, the Kerr constant B is obtained by modifying equation (5) as follows. B = d ² / 2LVπ ² (6)

In the following embodiment, the voltage Vπ at which I = I ₀
Was measured, and a Kerr constant B was obtained by calculation from equation (6).

In FIG. 10, a cell 6 is supplied with power from a modulation power supply 7. 8 and 9 are polarizing plates (however,
Is referred to as an analyzer. ), And their polarization axes are orthogonal to each other.

The polarizing plate 8 and the analyzer 9 are arranged at an angle of 45 degrees with respect to the direction in which the electric field is applied to the cell 6. When no electric field is applied to the cell 6, since the electro-optic material 1 is in an isotropic phase, the light beam 10 passes through the cell 6 without changing the polarization direction, and is detected in consideration of the arrangement of the polarizing plate 8 and the analyzer 9. The light beam 10 does not reach the vessel 11.

When an electric field is applied to the cell 6, the electro-optic material 1 exhibits birefringence, and a difference occurs in the refractive index between the direction in which the electric field is applied and the direction perpendicular thereto, so that the phase of light propagating in each direction is different. , A phase difference occurs. Therefore, cell 6
Is generally elliptically polarized light. Therefore, some components can pass through the analyzer 9, and the light beam reaches the detector 11.

The phase difference is π radian (corresponding to a half wavelength)
, The light passing through the cell 6 changes to linearly polarized light having the same polarization direction as the analyzer 9 and the light beam 10
It reaches the 0% detector 11. Cell 6 at this time
Is referred to as a half-wave voltage (Vπ).

For example, in cell 6, [1] (Table 1)
The liquid crystal material 4-cyano-4′-n-pentylbiphenyl shown in FIG. 1 is sealed and set at 33.3 ° C. (nematic-isotropic phase transition temperature).
When the Ne laser light (633 nm) was used, the output of the detector 11 reached the maximum at 517 V as the voltage was applied to the cell 6. This value indicates that the optical phase difference has reached π radians, and corresponds to a half-wave voltage (Vπ).

When the electrode interval d in the cell 6 is 1 mm and the electrode length L in the light beam passing direction is 10 mm,
Since the Kerr constant B is calculated as the equation (6), the Kerr constant B of the present material is 1.87 × 10 ⁻⁸ cm / V ² .
This means that the inter-electrode distance d = 50 μm in the horizontal electric field method.
When m and the cell gap L are 1 mm, it means that 100% luminance modulation can be performed with a voltage of 82V. (Distance between comb electrodes d = 10 μm, cell gap L = 5
In the case of 0 μm, 100% luminance modulation can be performed with a voltage of 73V. )

Table 1 shows the results of measuring the Kerr constant B of various liquid crystal materials at the nematic-isotropic phase transition temperature.

[0048]

[Table 1]

The chemical formulas of the liquid crystal materials shown in [1] to [5] in Table 1 are shown below in order.

Embedded image

Embedded image

Embedded image

Embedded image

Embedded image

As described above, the liquid crystal material of Chemical Formula 1 is 5CB (4
-Cyano-4'-n-pentylbiphenyl), the liquid crystal material of formula 2 is 5OCB (4-cyano-4'-n-pentyloxybiphenyl), and the liquid crystal material of formula 3 is 3OCB (4
-Cyano-4'-n-propyloxybiphenyl) and 5
An equivalent mixture of OCB and 7OCB (4-cyano-4′-n-heptyloxybiphenyl), a liquid crystal material of Chemical Formula 4,
The liquid crystal material of PCH5 (trans-4-heptyl- (4-cyanophenyl) -cyclohexane), Chemical formula 5 is 3HP
A mixture of FF, 5HPFF and 7HPFF (1,2-difluoro-4- [trans-4- (trans-4-n-
Propylcyclohexyl) cyclohexyl] benzene, 1,2-difluoro-4- [trans-4- (trans-4-n-pentylcyclohexyl) cyclohexyl] benzene, and 1,2-difluoro-4- [trans-4- ( Trans-4-n-heptylcyclohexyl)
Cyclohexyl] benzene). As is clear from Table 1, when the electrode interval is set to 50 μm, light modulation can be performed at a relatively low voltage (100 V or less) regardless of which of the materials shown in Chemical Formulas 1 to 5 is used. In addition, as will be described in detail later, it inherently has a high-speed response characteristic, and has excellent performance as a display device.

(Embodiment 1) The technical idea of the present invention is as follows.
A pair of substrates at least one of which is transparent, a medium including polar molecules sandwiched between the pair of substrates, and a polarizing plate disposed outside at least one of the pair of substrates,
By providing a display device including a phase transition unit for bringing the medium into an isotropic phase state and an electric field applying unit for applying an electric field to the medium, a display device with excellent high-speed response characteristics is provided. Things. Specifically, it is as follows.

FIG. 1 is a simplified partial cross-sectional view of a display device for applying an electric field parallel to the substrate surface according to the first embodiment of the present invention, and FIG. FIG. 3 is a plan view showing an electrode configuration and a rubbing direction, FIG.
FIG. 3 is a partial cross-sectional view showing a state of the display device according to the first embodiment when no electric field is applied.

This display device 20, as shown in FIG.
A glass substrate 21 on which a polyimide film 22 (alignment film SE-7792 manufactured by Nissan Chemical Industry Co., Ltd.) as a dielectric thin film is formed, and a comb-shaped electrode including a pixel electrode 26 and a counter electrode 27, and has a surface. A glass substrate 28 on which a polyimide film 25 is formed is bonded via a glass fiber spacer 24 to form a gap of 50 μm, and a liquid crystal which is a medium containing polar molecules is provided between the glass substrates 21 and 28. This is a horizontal electric field type display device in which a material 23 is sealed.

The liquid crystal material 23 is made of the liquid crystal material [3] described in Table 1 described above. Further, the display device 20 of the present invention is provided with a heater 34 which is a phase transition unit for causing the liquid crystal material [3] to undergo a phase transition to an isotropic phase state. Is 6
(5.5 ° C.), whereby the liquid crystal material [3] is in an isotropic phase state.

As will be described in detail later, the liquid crystal material
[3] is macroscopically brought into the isotropic phase state by setting the temperature to about 65.5 ° C., but microscopically, the polar molecules 23a in the liquid crystal material [3] A molecular population can be formed. Note that this molecular group is called a “cluster”, and the polar molecules 23
a ... are oriented in a certain direction.

Further, on the inner surface of the glass substrate 28,
A comb-shaped electrode composed of a pixel electrode 26 and a counter electrode 27 serving as an electric field applying means, metal wiring (image signal line, scanning signal line),
Thin film transistor (TF) as a pixel switching element
T) and the like are formed. In FIG. 1, metal wiring, TFTs, and the like are omitted. In addition, the pixel electrode 2
6 and the counter electrode 27 have a line width of 10 μm, and the electrode interval between the pixel electrode and the counter electrode is 10 μm.

On the outer surfaces of the substrates 21 and 28,
The polarizing plates 29 are arranged such that their absorption axis directions are orthogonal to each other and form an angle of 45 degrees with the rubbing directions 31 and 32.
・ 30 are arranged. Incidentally, it is also possible to arrange the polarizing plates 29 and 30 so that their absorption axis directions are parallel to each other.

As shown in FIG. 2, the polyimide films 22 and 25 are provided on the substrate 28 in the rightward direction on the paper.
In addition, the substrate 21 is subjected to the orientation processing toward the left direction 31 on the paper surface.

As described above, by subjecting the polyimide films 22 and 25 to the alignment treatment, the clusters 23c located on the surfaces of the polyimide films 22 and 25 can be oriented in a certain direction, and the diameter of the clusters 23c is further increased. It is possible to increase. As a result, the Kerr constant can be increased, and the voltage applied to the display device can be reduced.

Further, as shown in FIG. 2, the pixel electrode 26 and the counter electrode 27 constituting the comb-shaped electrode are arranged in a plan view.
It is formed in the shape of a triangle, and the viewing angle characteristics of the display device are improved.

A backlight 33 is arranged on the back side (the lower side in FIG. 1) of the display device 20. Although not shown, a display device 20 capable of color display by forming a color filter on the substrate 21.
Can also be constructed.

In the display device 20 manufactured as described above, as described above, the liquid crystal material [3] is
The temperature is maintained at 65.5 ° C., but the significance of the temperature will be described below with reference to FIG. FIG.
Is a graph showing the relationship between temperature and Kerr constant.

The liquid crystal material [3] is made of a polar molecule whose state changes like a nematic phase or an isotropic phase depending on the temperature, and the liquid crystal material [3] has a temperature (nematic liquid crystal) around 65.5 ° C. (T _{M in} FIG. 5). (Isotropic phase transition temperature),
A population of molecules called "clusters" is generated. The cluster is macroscopically presenting an isotropic phase state, but microscopically, molecules are oriented in a certain direction within the cluster.

Then, the heating temperature of the liquid crystal material [3] is
When the temperature is raised from the nematic-isotropic phase transition temperature of 65.5 ° C., the clusters are separated (decreased in order), and as a result, the Kerr constant decreases. As described above, if the Kerr constant decreases, the applied voltage must be increased, which is not practically convenient.

However, what should be noted here is that FIG.
As shown in the figure, a dielectric thin film (polyimide films 22 and 25)
Can be increased by increasing the Kerr constant.

This is because, when the polyimide films 22 and 25 are oriented in a predetermined direction, polar molecules are oriented in the orientation direction of the polyimide films 22 and 25 in the vicinity of the substrate interface to increase the degree of order. It is considered that the diameter of the cluster can be increased, and the Kerr constant increases as the diameter of the cluster increases. In addition, by increasing the Kerr constant, the applied voltage applied to the display device can be reduced, and the display device can be put to practical use.

Next, the display device 20 constructed as described above will be described.
Will be described. FIG. 4 is a conceptual diagram showing the bias of electrons in a polar molecule when no electric field is applied and when a voltage is applied in FIG.

The liquid crystal material was previously heated by the heater 34.
[3] is heated at 65.5 ° C. As shown in FIG. 4A, when no voltage is applied between the pixel electrode 26 and the counter electrode 27, the polar molecules 23a in the liquid crystal material [3]
Is a cluster 23c near the surfaces of the polyimide films 22 and 25.
Are formed, but are in an isotropic phase as a whole.

In this state, as shown in FIG.
When a voltage is applied between the pixel electrode 26 and the counter electrode 27 by a drive switch such as FT, an electric field is generated in a direction parallel to the substrate surface, and electrons 23d in the polar molecules 23a are moved in the electric field direction (rightward on the paper surface). ).

The light from the backlight 33 shown in FIG. 1 becomes linearly polarized light by passing through the polarizing plate 30, and the linearly polarized light becomes elliptically polarized light by passing through the liquid crystal layer 23, and becomes linearly polarized light. , And is again emitted as linearly polarized light out of the display device 20. In this case, the half-wave voltage Vπ was 40.0 V.

The optical response time of the display device 20 was such that the electric field off → on (rise time) was 10 μs and the electric field on → off (fall time) was 1 μs or less. The response time of a conventional TN-type liquid crystal display device is 15 m, even for a response between black and white binary values.
s, the fall time is 20 ms, and
The response time between gray levels at the time of halftone display is 100 ms or more in total.
The response time is 200 ms, and even if a high voltage is applied to the liquid crystal display device, the response speed cannot be increased as in the display device 20 of the present invention. Therefore, the display device 20 of the present invention has an excellent characteristic capable of dramatically improving the response speed as compared with the conventional TN type liquid crystal display device.

Next, a method of manufacturing the display device 20 will be described.

First, a thin film transistor (not shown), a pixel electrode 26 as a comb-shaped electrode, and a counter electrode 27 were formed on a glass substrate 28.

Next, a polyimide film 22 (alignment film SE-7792 manufactured by Nissan Chemical Industries, Ltd.) was formed on the surface of the glass substrate 28 using a spinner. A polyimide film 22 (alignment film SE-7792, manufactured by Nissan Chemical Industries, Ltd.) was also formed on the surface of the glass substrate 21 using a spinner.

Next, the glass substrates 21 and 28 were subjected to a rubbing treatment in the direction shown in FIG. 2 and then bonded together via a glass fiber spacer 24 to produce a display device having a gap of 50 μm.

Next, according to a conventional method, the liquid crystal material shown in Table 1 was used.
[3] was enclosed.

Next, polarizing plates 29 and 30 are arranged on the outer surfaces of the substrates 21 and 28 so that their absorption axes are orthogonal to each other.
The display device 20 was manufactured by bonding the rubbing directions 31 and 32 so as to form an angle of 45 degrees.

(Embodiment 2) FIG. 6 is a simplified partial cross-sectional view of a display device for applying an electric field perpendicular to the substrate surface according to Embodiment 2, and FIG. FIG. 4 is a plan view showing an electrode configuration and a rubbing direction in the display device.

This display device 40 is, as shown in FIG.
A polyimide film 44 having a transparent electrode 43 and serving as a dielectric thin film (a polyimide alignment film paint JALS-68 manufactured by JSR)
2) is coated and baked at 180 ° C. for 1 hour, and has a transparent electrode 48 and a polyimide film 4 on the surface.
And a glass substrate 49, also baked at 180 ° C. for 1 hour, is bonded via a glass fiber spacer 45 to form a gap of 50 μm, and a liquid crystal material 46 is sealed between the glass substrates 42 and 49. It is configured to be stopped.

A transparent electrode 48 is formed on the inner surface of the glass substrate 49. As in the case of the first embodiment, a metal wiring (image signal line, scanning signal line) and a pixel switching element are used. Are formed.

As shown in FIG. 7, the orientation direction of the orientation films 44 and 47 is oriented rightward on the paper of the glass substrate 49 and leftward 51 on the paper of the glass substrate. Is being processed.

On the inner surface of the glass substrate 42, a transparent electrode 43 as a counter electrode is formed, and on the transparent electrode 43, an alignment film 44 made of polyimide is formed. A polarizing plate 41 is arranged on the outer surface of the glass substrate 42, and a polarizing plate 50 is arranged on the outer surface of the glass substrate 49. The absorption axes of the polarizing plates 41 and 50 are orthogonal to each other. Rubbing direction 51
52 is bonded to form an angle of 45 degrees. Note that a color filter may be formed on the glass substrate 42 as in the case of the first embodiment.

Next, the liquid crystal material 46 will be described.

The liquid crystal material 46 is a mixture of 100 parts by weight of a mixture of the liquid crystal material [5] shown in Table 1 and 0.1 part by weight of ethyl alcohol as a non-liquid crystal substance. is there. As shown in Table 1, the liquid crystal material [5] has a nematic phase-isotropic phase transition temperature of 11
Although the temperature is 3.0 ° C., the phase transition temperature can be greatly reduced by adding ethyl alcohol to the temperature.

That is, as in Embodiment 2, the liquid crystal material
[5] By mixing 0.1 parts by weight of ethyl alcohol with respect to 100 parts by weight, the phase transition temperature can be lowered to 35.2 ° C., and when the amount of ethyl alcohol added is increased, the liquid crystal material can be further reduced. The phase transition temperature can be lowered. In this way, ethyl alcohol has a function as a phase transition unit for bringing the liquid crystal material into an isotropic phase state.

The liquid crystal material [5] is an n-type liquid crystal material. In the second embodiment, since the electric field application direction is perpendicular to the substrate, the liquid crystal material [5] is perpendicular to the electric field application direction. The electrons in the liquid crystal material (polar molecules) are biased in a certain direction.

Then, the display device 40 was maintained at 35.2 ° C. by the heater 53 as a phase transition means, and the half-wave voltage Vπ was measured. As a result, a value of 35.0 V was obtained. The optical response time is the rise time (electric field off → o
n) is 6 μs, and the fall time (electric field on → of
f) was 1 μs or less. Therefore, the display device 40 according to the second embodiment of the present invention is different from the display device 2 according to the first embodiment.
Like 0, the response speed is dramatically improved.

Further, as described above, a liquid crystal material having a nematic phase-isotropic phase transition temperature of 113.0 ° C. [5]
Even with a material having a high phase transition temperature as described above, it is possible to significantly lower the phase transition temperature by adding ethyl alcohol or the like.

When ethyl alcohol was added to the liquid crystal material, the Kerr constant of the liquid crystal material was slightly reduced. Although ethyl alcohol is used as the additive in the second embodiment, the phase transition temperature can be reduced by using a compound that is a non-liquid crystal material having a cyano group, a nitro group, and a hydroxy group. is there.

As described above, the display device according to the second embodiment has excellent responsiveness similarly to the display device according to the first embodiment, and further uses a liquid crystal material as a material composed of polar molecules. By adding a material capable of lowering the phase transition temperature to the liquid crystal material, the phase transition temperature of the liquid crystal material to an isotropic phase can be significantly reduced.

(Third Embodiment) FIG. 8 is a simplified partial sectional view of a display device according to a third embodiment. In the first and second embodiments, examples in which a transmissive display device is configured have been described. However, the present invention is not limited to these examples. You can also.

That is, as shown in FIG. 8, the reflection type display device 60 has a glass film which has an electrode 68 made of a reflection film, is coated with a polyimide film 67 as a dielectric thin film, and is baked at 180 ° C. for 1 hour. A substrate 69 and a glass substrate 62 having a transparent electrode 63 and having a polyimide film 64 formed on the surface thereof are bonded together via a glass fiber spacer 65 to form a gap of 50 μm. A liquid crystal material 66 is sealed therebetween.

Further, on the outer side of the glass substrate 69, for example, a reflection film mainly composed of metal aluminum is formed, or a reflection plate made of metal aluminum or the like is used instead of the glass substrate 69. It is also possible.

(Embodiment 4) FIG. 9 is a simplified partial cross-sectional view of a display device according to Embodiment 4 of the present invention.

First, the configuration of the display device according to the fourth embodiment will be described with reference to FIG. The display device 20 according to the fourth embodiment can perform display by changing the orientation of liquid crystal molecules and uses control of electron distribution by an electric field (that is, liquid crystal molecules (polar molecules) in an isotropic phase state). The display can also be performed by the change in the bias of the electrons inside.

That is, the display device 20 is provided with a first drive circuit 70 for performing display by changing the alignment of liquid crystal molecules.
A second drive circuit 71 for performing display by biasing electrons in polar molecules in an isotropic state, and a switch circuit 72.
A switch control circuit 73 for controlling switching of the switching mode of the switch circuit 72; and a temperature sensor 74 connected to the switch control circuit 73. Further, the heater 34 described in the first embodiment is connected to the switch control circuit 73.

The first drive circuit 70 and the second drive circuit 70
The driving circuit 71 is connected to the pixel electrode 26 and the counter electrode 27 that constitute the display device 20 via the switch circuit 72.

Next, a method of driving the display device 20 will be described.

When the display device 20 performs display by changing the orientation of liquid crystal molecules, the switch control circuit 73 switches the switch circuit 72 to the first drive circuit 70 side, and the first drive circuit 70, a voltage is applied between the pixel electrode 26 and the counter electrode 27 to perform display.

When the display device 20 performs display by bias of electrons in polar molecules, the switch control circuit 73 switches the switch circuit 72 to the second drive circuit 71 side, and The second driving circuit 71 applies a voltage between the pixel electrode 26 and the counter electrode 27 to perform display.

The temperature of the liquid crystal layer 23 is detected by the temperature sensor 74, and the detected value is input to the switch control circuit 73.
If the temperature of the liquid crystal layer 3 is equal to or higher than the temperature at which the liquid crystal layer becomes isotropic, a voltage is applied to the liquid crystal layer 23 by the second drive circuit 71 to perform display. If the temperature is lower than the phase temperature, the liquid crystal layer 23 is heated by the heater 34 connected to the switch control circuit 73 to bring the liquid crystal layer 23 into an isotropic phase state, and a voltage is applied by the second drive circuit 71. Display can also be performed.

As described above, when the display device 20 of the fourth embodiment is used as, for example, a liquid crystal television having good image quality, display is performed by changing the orientation of liquid crystal molecules, and simulation and the like are performed. When high-speed response is required for moving image display in high-speed image analysis, the display can be performed by changing the bias of electrons in liquid crystal molecules (polar molecules) in the isotropic phase state, which is excellent in convenience. It is.

(Other Matters) (1) In the display devices according to Embodiment Modes 1 to 4, a plastic film substrate can be used instead of a glass substrate.

(2) A pair of substrates, at least one of which is transparent, a medium containing polar molecules in an isotropic state sandwiched between the pair of substrates, and a medium disposed outside at least one of the pair of substrates. By providing a polarizing plate provided and electric field applying means for applying an electric field to the medium, a display device capable of high-speed response can be configured. That is, in the first to fourth embodiments, the medium containing polar molecules is brought into the isotropic phase state by the phase transition means for bringing the medium into the isotropic phase state. It is also possible to use a medium composed of polar molecules in an isotropic phase. In this case, it is not necessary to use a phase transition means.

(3) Embodiments 1 to 4
In, the polyimide film was used as the dielectric thin film, but is not limited thereto, for example, an organic thin film,
It is also possible to use polyvinyl alcohol or the like.

(4) Embodiments 1 to 4
In the above, an active matrix type display device has been described, but a simple matrix type display device may be used.

[0107]

As described above, the display device of the present invention is a display device utilizing the Kerr effect, and does not switch between transmission and blocking of light by the movement of molecules as compared with a conventional liquid crystal display device. A thin display device which switches between transmission and cutoff of light depending on the bias of electrons, can perform 100% luminance modulation at a low voltage of several tens V or less, has a high response speed, and is suitable for displaying moving images. , Its practical value is extremely high.

[Brief description of the drawings]

FIG. 1 is a simplified partial cross-sectional view of a display device for applying an electric field parallel to a substrate surface according to a first embodiment of the present invention.

FIG. 2 is a plan view showing an electrode configuration and a rubbing direction in the display device according to the first embodiment.

FIG. 3 is a partial cross-sectional view showing a state of the display device according to the first embodiment when no electric field is applied.

FIG. 4 is a conceptual diagram showing the bias of electrons in polar molecules when no electric field is applied and when a voltage is applied in FIG.

FIG. 5 is a graph showing the relationship between temperature and Kerr constant.

FIG. 6 is a simplified partial cross-sectional view of a display device for applying an electric field perpendicular to a substrate surface according to a second embodiment of the present invention.

FIG. 7 is a plan view showing an electrode configuration and a rubbing direction in the display device according to the second embodiment.

FIG. 8 is a schematic sectional view showing a configuration of a reflective display device according to a third embodiment of the present invention.

FIG. 9 is a schematic sectional view illustrating a configuration of a display device according to a fourth embodiment of the present invention.

FIG. 10 is a schematic diagram illustrating a measurement system of an electro-optic effect according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electro-optic material 4.5 electrode 6 Cell 7 Modulation power supply 8 Polarizing plate 9 Analyzer 10 Light beam 11 Detector 20 Display device 21-28 Glass substrate 22-25 Polyimide film 23 Liquid crystal material 23a Polar molecule 23c Cluster 24 Spacer 26 Pixel Electrode 27 Counter electrode 29/30 Polarizer 31/32 Rubbing direction 33 Backlight 34 Heater 40 Display 41/50 Polarizer 42/49 Glass substrate 43/48 Transparent electrode 44/47 Polyimide film 45 Spacer 46 Liquid crystal material 51/52 Rubbing direction 53 Heater

Claims (12)

[Claims] 1. A pair of substrates, at least one of which is transparent, a medium containing polar molecules in an isotropic state sandwiched between the pair of substrates, and a medium disposed outside at least one of the pair of substrates. A polarizing plate, and an electric field applying unit for applying an electric field to the medium. 2. A pair of substrates, at least one of which is transparent, a medium containing polar molecules sandwiched between the pair of substrates, and a polarizing plate disposed outside at least one of the pair of substrates. A display device, comprising: a phase transition unit for causing the medium to be in an isotropic phase state; and an electric field applying unit for applying an electric field to the medium. 3. The electric field applying means is a pair of comb-shaped electrodes formed on the inner surface of the one substrate, and the direction of electric field application is parallel to the substrate surface. Item 3. The display device according to Item 2. 4. The electric field applying means is an electrode formed on the inner surface of each of the pair of substrates, and the direction of the electric field application is perpendicular to the substrate surface. 3. The display device according to 2. 5. The display device according to claim 3, wherein the comb-shaped electrode has a “-” shape in plan view. 6. The display device according to claim 1, wherein the polar molecules in the medium form clusters. 7. The display according to claim 1, wherein a dielectric thin film is formed on an inner surface of the substrate, and the dielectric thin film has been subjected to a predetermined orientation treatment. apparatus. 8. The display device according to claim 7, wherein the dielectric thin film is an organic thin film. 9. The display device according to claim 8, wherein the organic thin film is made of polyimide. 10. The display device according to claim 2, wherein the polar molecules include a liquid crystal material. 11. The display device according to claim 2, wherein the polar molecules include a liquid crystal material and a material that lowers an isotropic phase transition temperature of the liquid crystal material. 12. The material for lowering the isotropic phase transition temperature of the liquid crystal material is a material having a cyano group, a hydroxyl group, or a nitro group at a molecular terminal.
The display device according to claim 1.