JP2000298265A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-responsive liquid crystal display device composed of a polymer dispersion liquid crystal layer which has a superior response rate and display property, uniform distribution of thickness, large film thickness, high contrast and superior durability with respect to heat cycling. SOLUTION: A polymer dispersion liquid crystal layer 302 consisting of a compsn. of a polymer and a liquid crystal is disposed on a heat generating material. The polymer used is a thermoplastic polymer, and a glass transition temp. (Tg) of the polymer and a phase transition temp. (TNI) of the liquid crystal layer satisfy the relation -20 deg.C<=(Tg-TNI)<=20 deg.C. The polymer dispersion liquid crystal layer 302 is formed by laminating a plurality of polymer dispersion liquid crystal films.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a liquid crystal display device. More specifically, the present invention relates to a liquid crystal display device including a polymer-dispersed liquid crystal layer using a liquid crystal material having a thermo-optical effect or a thermal response, and a heating element for driving the liquid crystal layer.

[0002]

2. Description of the Related Art Conventionally, image display has been performed using a liquid crystal material whose optical properties change with a change in temperature. Liquid crystal materials used for such display include smectic liquid crystals, nematic liquid crystals, cholesteric liquid crystals, and the like. These liquid crystal materials change the orientation of the liquid crystal depending on the temperature, change in transparency and opacity (white turbidity), change in color, and the like. It is known to cause

A liquid crystal display device using a liquid crystal whose optical properties change due to a change in temperature generally includes a heating element,
It is composed of a liquid crystal material, a heating element driving electrode and the like.
Such a liquid crystal display device is known. For example, Japanese Patent Publication No. 50-132940 discloses a method of selectively heating a liquid crystal material layer in which a nematic liquid crystal is microencapsulated, a transparent heating element layer, and a background layer. Discloses that a large-screen display device is manufactured at low cost.

In Japanese Patent Application Laid-Open No. 58-145985,
It consists of a thermoelectric element and a matrix electrode in which parallel strip electrodes are orthogonal to the heat absorbing part of the thermoelectric element, a heating element by an electric signal in an orthogonal part of the matrix electrode, and a temperature-effect cholesteric liquid crystal which is colored by the heat of the heating element. An indicator is disclosed.

Further, in Japanese Patent Application Laid-Open No. 62-143026,
A method is disclosed in which a liquid material layer whose optical characteristics change due to heat is provided, and the temperature of the liquid crystal layer is easily controlled by using a semiconductor element as a heating element, and the pixel portion is clearly displayed with low power consumption.

In Japanese Patent Application Laid-Open No. 01-288895,
It is disclosed that by applying a material that reversibly develops or changes color by heat change on a transparent conductive sheet heating element, it is possible to increase the area and to manufacture it inexpensively without using a polarizing plate. I have.

On the other hand, conventionally, a liquid crystal display device using a polymer dispersed liquid crystal has been developed. Polymer-dispersed liquid crystals have higher brightness and brightness than liquid crystal displays using polarized light.
It has excellent characteristics such as contrast and viewing angle.
In addition, since the liquid crystal is dispersed in the polymer, the liquid crystal does not need to be sealed, and features such that the area can be easily increased.

Further, there is a report as a thermal writing device using both electric field and heat in liquid crystal display technology (edited by the Industrial Research Council, published on September 20, 1994, pp. 53-57).

Japanese Patent Application Laid-Open No. 06-18831 discloses that a heating element that generates heat by electric current is formed on a first substrate, a conductor is formed on a second substrate, and a polymer dispersed liquid crystal is formed on the first and second substrates. It is disclosed that the manufacturing cost is reduced and the size is reduced by sandwiching the substrates.

A display material investigation report II (edited by the Japan Electronics Industry Development Association, published in March 1991, pp. 85-97) discloses a liquid crystal display device using a thermoresponsive polymer dispersed liquid crystal. Has been described. In this liquid crystal display device, a polymer dispersed liquid crystal in which a nematic liquid crystal is dispersed in a polymer is used. FIG. 1A shows a non-heated state (nematic state) of the polymer-dispersed liquid crystal.
(B) shows a mode change in a heated state (isotropic state) of the polymer-dispersed liquid crystal. FIG. 2 shows the relationship between the temperature and the refractive index of the polymer dispersed liquid crystal.

As shown in FIGS. 1 (a) and 2, the polymer-dispersed liquid crystal is cloudy when not heated. That is, it is in an opaque state. This is because, in the liquid crystal droplet 102 in the polymer dispersed type liquid crystal, the liquid crystal molecules are aligned along the interface.
The refractive index of the first屈析index n _p of the liquid crystal Dorobburetsuto 102 n _e
During,屈析index difference _{△ n (△ n = n e} -n p) exists, because the light is refracted by the polymer resin and liquid crystal interface.

On the other hand, as shown in FIG. 1 (b) and FIG. 2, the polymer dispersed liquid crystal is heated, and when the temperature exceeds a certain temperature (nematic / isotropic transition point: T _NI ), the polymer dispersed liquid crystal is heated. Changes from cloudy to transparent. This polymer dispersion type liquid crystal, the liquid crystal molecules to屈析ratio n _i of the refractive index n _e is iso tropicity poke state of being heated to the nematic / isolation tropicity arrive above the transition point in the nematic state to lose liquid crystallinity reduced, the difference △ n of屈析ratio n _e of droplets 103 in the polymeric resin屈析index n _i nematic / isolation tropicity poke transition point or more '(△
n ′ = n _i −n _p ) becomes smaller.

However, there are various problems in using the polymer dispersed liquid crystal as a thermoresponsive display element. For example, the heat conduction of the polymer is poor, the response speed is longer than that of a liquid crystal-only display element that does not use a polymer, the color erasing time is longer, the temperature distribution of each segment of the display unit is uneven, and the display is uneven. In the case of driving, it has been pointed out that the boundary between each segment is unclear, so that the visibility of display is poor. These are considered to be due to poor thermal responsiveness because the polymer-dispersed liquid crystal is a mixture of the polymer and the liquid crystal. Further, as another problem, it has been pointed out that the thermal deformation of the polymer gradually becomes apparent during the repetition of the heat cycle of heating and cooling, which deteriorates the life of the polymer dispersed liquid crystal display device. .

In order to improve the contrast in opacity-transmission change of a display element using the polymer dispersed liquid crystal, the opacity of the polymer dispersed liquid crystal layer during non-heating or the opacity during non-heating can be improved. The transparency of the polymer-dispersed liquid crystal layer may be increased. In order to improve the turbidity of the polymer when not heated, a method of thickening the polymer-dispersed liquid crystal layer, a method of homogenizing the dispersion of the liquid crystal in the polymer in the polymer-dispersed liquid crystal, and a method of mixing the polymer and the liquid crystal in the polymer-dispersed liquid crystal There is a method of making the refractive index mismatch. It is most effective to make the liquid crystal layer thicker, and it can be performed relatively easily by increasing the spacing between the blades during fabrication.

In this method, the thickness of the liquid crystal layer formed on the substrate is increased by increasing the amount of the liquid crystal composition applied on the substrate by a coating device such as a coater or an applicator. However, when a large amount of the liquid crystal composition is applied to the substrate by spreading the blade or slit of a coating device such as a coater or an applicator, the coating liquid crystal layer film is formed at each point such as the application start point, the central portion and the application end point of the substrate. The thickness varies, and it is difficult to form a liquid crystal layer having a uniform thickness.

Further, as another method, a liquid crystal layer having a conventional thickness is formed on a substrate, and after the liquid crystal layer is dried, a liquid crystal composition is applied again on the upper surface of the liquid crystal layer to thereby form a thick film. A method of forming a liquid crystal layer having the following formula is tried. However, when the second coating is performed due to the influence of the solvent, the first coating is dissolved, and thus the thickness of the liquid crystal layer is as designed (for example, 2). In the case of single coating, the thickness is not twice as large as the thickness of the single coating), and it is difficult to form a liquid crystal layer having a desired thickness.

[0017]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a thermally responsive polymer-dispersed liquid crystal display device having an excellent response speed and an excellent display property. Another object of the present invention is to provide a polymer-dispersed liquid crystal display device having excellent thermal responsiveness and thermal stability.
Another object of the present invention is to provide a polymer-dispersed liquid crystal display device having a uniform thickness distribution, a high film thickness, and a high-contrast polymer-dispersed liquid crystal layer.

[0018]

The first object is to provide a polymer-dispersed liquid crystal layer comprising a polymer and liquid crystal composition on a heating element sandwiched between a pair of electrodes. Will be resolved. In this case, the connection of the pair of electrodes to the heating element may be performed by connecting the pair of electrodes to both left and right surfaces of the heating element,
Alternatively, it is performed by connecting a pair of electrodes to both upper and lower surfaces of the heating element. In the former connection, the polymer-dispersed liquid crystal layer is in direct contact with the heating element, but in the latter case, one of the pair of electrodes is interposed between the polymer-dispersed liquid crystal layer and the heating element. . The second problem is that a polymer dispersed liquid crystal layer composed of a polymer and a liquid crystal uses a thermoplastic polymer as the polymer, and has a glass transition temperature (T _g ) of the polymer and a phase of the liquid crystal. When the transition temperature (T _NI ) is −20 ° C. ≦ (T _g −T _NI )
It is solved by satisfying the relationship of ≦ 20 ° C. Also,
The third problem is solved by forming a single layered liquid crystal layer having a large thickness by sequentially bonding a plurality of liquid crystal films formed separately.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The liquid crystal display of the present invention will be described in more detail with reference to the drawings. FIG. 3 is a schematic perspective sectional view of an example of the liquid crystal display device 300 according to the present invention.
As shown, the liquid crystal display device 300 of the present invention basically includes a protective sheet 301, a polymer dispersed liquid crystal layer 3.
02, an electrode a303, a heating element 304, and an electrode b305.

The protective sheet 301 is generally used to protect the lower polymer dispersed liquid crystal layer 302.
The protective sheet 301 is desirably transparent from the viewpoint of visibility, and a typical example is transparent plastic or glass. Transparent plastic is less expensive than glass, and because of its flexibility it can be curved.
In the present invention, plastic is particularly desirable. Examples of the plastic protective sheet that can be used in the liquid crystal display device of the present invention include polyethylene terephthalate and polyethylene naphthalate. Since such a sheet is heated by the heating element 304, it is preferable that the sheet has excellent resistance to temperature. Generally, since the polymer-dispersed liquid crystal layer 302 is heated to about 70 ° C. by the heating element 304, the plastic protective sheet is about 100 to 1 mm.
Preferably, it has a heat-resistant temperature of about 20 ° C. The thickness of the protective sheet is not particularly limited, but is generally preferably in the range of 20 μm to 400 μm. If it is less than 20 μm, the mechanical strength is too low and a sufficient protective effect cannot be expected. On the other hand, if it exceeds 400 μm, the protective effect is saturated and not only becomes uneconomical, but also may impair visibility.

The electrode a303 and the electrode b305 can be formed of a good conductive metal plate such as aluminum, copper, silver, and gold. Since these highly conductive metals generally have excellent thermal conductivity, heat generated from the heating element 304 can be directly applied to the polymer dispersed liquid crystal layer 302 from the electrode. The electrode a303 and the electrode b305 can be made of the same kind of metal, respectively, or can be made of different metals. The electrode a303 and the electrode b305 are preferably made of the same metal. The thicknesses of the electrode a303 and the electrode b305 are not particularly limited. What is necessary is just to have sufficient thickness necessary for energization.

The heating element 304 sandwiched between the electrode a 303 and the electrode b 305 has a resistive element that generates heat when a current flows from the electrode, and usually has a higher resistance than the electrode. Is used. For example, the heating element 304
Examples include, but are not limited to, carbon and nickel. The thickness of the heating element 304 is not particularly limited. It is sufficient that the polymer-dispersed liquid crystal layer 302 has an ability to generate a necessary and sufficient amount of heat to be driven at a desired response speed. Such a heating capacity can be easily determined by those skilled in the art by referring to the specification of the heating element or by repeating experiments.

FIG. 4 shows the liquid crystal display device 30 shown in FIG.
FIG. 4A is a schematic perspective sectional view showing a state in which a power supply is connected to a power supply 0 and ON / OFF driving is performed. FIG. 4A shows a power supply OFF state (that is, a state before voltage application), and FIG. Indicates a power ON state (that is, a voltage application state). Polyvinyl butyral was used for the polymer of the polymer-dispersed liquid crystal layer 302, and a nematic liquid crystal material which was opaque when not heated and became transparent when heated was used for the liquid crystal material. In the production of the polymer-dispersed liquid crystal layer 302, a solvent-evaporation phase separation method is used, and the weight ratio of the polymer and the liquid crystal is set to 1:
It was set to 1. The thickness of the polymer dispersed liquid crystal layer 302 is 60 μm.
m, carbon is used for the heating element 304, and the electrode a3
03, a copper foil is used for the electrode b305. Power supply 406
Is a DC power source such as a primary battery or a secondary battery, or a power source obtained by converting AC to DC.

From the power source 406, the electrodes a303 and b30
5 before applying a voltage to the polymer dispersed liquid crystal layer 30.
Since 2 is opaque, it is cloudy when viewed from above.
For example, when a DC voltage of 9 V is applied from the power supply 406 between the electrode a303 and the electrode b305, the carbon heating element 30
Electric current flows through 4 to generate heat. When the temperature reached about 60 ° C., the polymer-dispersed liquid crystal layer 302 changed from cloudy to transparent, and a copper color, which was the color of the electrode a303, appeared. Electrode a3
When 03 is aluminum, a silver color appears.

As another method, as shown in FIG. 5A, a reflective plate 501 having a high reflectance is provided between the polymer dispersed liquid crystal layer 302 and the electrode a 303, thereby forming the polymer dispersed liquid crystal layer 302. Can improve the reflectance when becomes transparent. Reflectors suitable for such purpose are, for example, silver, aluminum, tin, nickel, chromium, gold, platinum and the like. The thickness of the reflector is not particularly limited, but is generally preferably in the range of 5 μm to 100 μm. If the thickness is less than 5 μm, disadvantages such as breakage and kinking of the reflection plate occur in the manufacturing process, which is not preferable. On the other hand, if the thickness is larger than 100 μm, the heating element 30
This is not preferable because it causes disadvantages such as adversely affecting the heat conduction between the liquid crystal layer 4 and the polymer dispersed liquid crystal layer 302.

Alternatively, as shown in FIG. 5B, a colored background plate 502 can be inserted between the polymer dispersed liquid crystal layer 302 and the electrode a303. By using the colored background plate 502, it becomes possible not only to display various colors when the polymer-dispersed liquid crystal layer 302 becomes transparent, but also to visually confirm changes in the liquid crystal layer. Can be. Colored background plate 502
Examples of the material include plastics (for example, color films such as heat-resistant plastic films made of colored cellophane, polyester, polypropylene, polyethersulfone, polyethylene, polyvinyl chloride, and polyvinylidene chloride), paper, glass, and metal. Foil. A colored background plate made of a material other than these can be used as long as it has excellent heat resistance and heat conductivity. Colored background board 5
In general, the thickness of 02 is preferably in the range of 5 μm to 100 μm. If the thickness is less than 5 μm, disadvantages such as breakage and kinking of the colored background plate occur in the manufacturing process, which is not preferable. On the other hand, if it is thicker than 100 μm,
It is not preferable because inconveniences such as a reduction in response speed due to difficulty in conducting heat occur. When the colored background plate 502 is white, which is the same color as when the polymer dispersed liquid crystal layer 302 is not heated, the polymer dispersed liquid crystal layer 30 is not heated.
Since the color is white, which is the second color, and is also white when heated, it is difficult to visually determine the change in the liquid crystal layer. But,
In one embodiment, letters, graphics, symbols, and / or patterns may be printed in black on the surface of the white colored background plate 502. In this case, when not heated, the color of the polymer-dispersed liquid crystal layer 302 remains white, and characters on the colored background plate 502 cannot be seen.
By making the liquid crystal layer transparent, a colored background plate 50 on a white background is obtained.
2 can be clearly seen. On the other hand, when the colored background plate 502 is black, it is white, which is the color of the polymer-dispersed liquid crystal layer 302 when not heated, and changes to black when heated, so that the state of change of the liquid crystal layer is clearly identified visually. can do. In this case, the black is preferably matte black. As the colored background plate 502, a color such as blue, red, or green can be used, but one having low brightness, low saturation, and close to black is desirable. When the colored background plate 502 is silver, it is white, which is the color of the polymer dispersed liquid crystal layer 302, when not heated. At this time, since the silver color of the colored background plate 502 reflects the light transmitted and scattered through the polymer dispersed liquid crystal layer 302 from behind (backscattering), the whiteness is generally higher than that of the colored background plate 502 of another color. To rise. However, when heated, the silver color of the colored background plate 502 appears, and the difference in brightness between the white color before heating and the silver color that appears after heating is small, so that it is difficult to distinguish the color change.

Electrode a303 and polymer dispersed liquid crystal layer 30
The colored background plate 502 is inserted between the electrodes a 303
This hinders heat conduction between the liquid crystal layer 302 and the polymer-dispersed liquid crystal layer 302, so that the response speed of the liquid crystal layer may be reduced. Therefore, as an alternative, instead of the colored background plate 502, a colored paint can be applied to the surface of the electrode a303. The paint is preferably, for example, a synthetic resin paint such as an acrylic paint. The color of the paint is the same as the above-described colored background plate 502,
Matt black is preferred. The electrode a30 is formed by this black paint.
Characters, graphics, symbols, and / or patterns can be printed on the surface of the printer 3.

In the structure shown in FIG. 3, there is no problem in a liquid crystal display device having a display segment size of about 1 cm square or less, but in a large liquid crystal display device of several tens cm or more, heat is not transmitted uniformly, and the polymer dispersion type is not used. Display unevenness occurs in the liquid crystal layer. In addition, both the heating element and the electrode become large and complicated in manufacturing.

Therefore, as shown in FIG. 6A, a heat conductive plate 6 is provided between the polymer dispersed liquid crystal layer 302 and the electrode a303.
01 is inserted and brought into close contact with the polymer dispersed liquid crystal 302,
The heat conduction from the heating element 304 can be made uniform. The heat conduction plate 601 makes heat conduction uniform and eliminates display unevenness. In addition, since the heat conduction plate 601 functions as a heat dissipation plate at the time of erasing, the erasing time is shortened. Furthermore,
Another advantage of using the heat conducting plate 601 is that the heating element and the electrode can be miniaturized as compared with the polymer dispersed liquid crystal layer.

As shown in FIG. 6B, if necessary, a reflector 501 as shown in FIG. 5A is inserted between the polymer dispersed liquid crystal layer 302 and the heat conductive plate 601. Can be used. The reflection plate 501 is connected to the heat conduction plate 6
01 can also be integrated. Further, the electrode a303
And the reflection plate 501 and the heat conduction plate 601 can be all integrated. Although not shown, a color film 502 as shown in FIG. 5B can be used instead of the reflection plate 501.

FIG. 7 shows the effect of using the heat conductive plate 601.
FIG. 7A is a top view showing a display state when the heat conductive plate 601 is not used. Since heat from the heating element 304 is transmitted unevenly to the polymer-dispersed liquid crystal layer 302, display irregularities 702a and 703a occur in the process from the opaque state 701a to the transparent state 704a. On the other hand, FIG. 7B is a top view showing a display state when the heat conductive plate 601 is used. As shown in the drawing, no display unevenness occurs even in the steps 702b and 703b in the process of changing from the opaque state 701b to the transparent state, and the display uniformly changes to the transparent state 704b.

FIG. 8 shows an example in which the heat conduction plate 601 is applied.
A cross-sectional view of a liquid crystal display device 300 in which a plurality of heat conductive plates having different heat conductivities are inserted between a polymer dispersed liquid crystal layer 302 and an electrode is shown in FIG. In FIG. 8, a heat conductive plate a 801 having a heat conductivity a is inserted between the polymer monodispersed liquid crystal layer 302 and the heat conductive plate 601 at the center of the segment, and a heat conductive plate b 802 having a heat conductivity b is provided around the segment. insert. Further, a heat conductive plate c 803 having a heat conductivity c is inserted into the outer periphery. Let the thermal conductivity be a <b <c.

FIG. 9 shows an example of a display change when the liquid crystal display device 300 having the structure shown in FIG. 8 is driven. When a voltage is applied to the heating element 304, the heat conductive plate c803
Since heat transfer is faster in the center than in the center where the heat conducting plate b 802 and the heat conducting plate a 801 are located, the heat begins to change from the surroundings (see 901 to 904 in FIG. 9). Further, since the heat conduction plate b 802 transmits heat more easily than the heat conduction plate a 801, the center portion changes last (905 to 905 in FIG. 9).
906). By utilizing the difference in the heat transfer speed in this manner, the display mode in which the polymer dispersed liquid crystal layer 302 has a stepwise difference can be changed, and for example, display such as fade-out or fade-in can be performed. .

As an alternative to inserting a plurality of heat conductive plates having different thermal conductivities between the polymer dispersed liquid crystal layer 302 and the electrodes, as shown in FIG.
By providing at least one or more through-openings or voids 1001 at a predetermined position (for example, the center) of the heat conductive plate 601, a difference in heat transfer speed occurs. A display change with a difference is possible.

The liquid crystal display device of the present invention can be configured as a matrix type display device. A plan view of an example of such a matrix type liquid crystal display device 1100 is shown in FIG.
Shown in FIG. 12 is a sectional view taken along the line AA in FIG. As shown, the vertical line electrode 110
1 and the horizontal line electrode 1102 are disposed so as to be orthogonal to each other. As an example, three horizontal and three vertical electrodes are provided, and the respective segments are connected as shown in FIG. In the structures shown in FIGS. 11 and 12, the electrodes are horizontal,
Although three vertical electrodes are provided, more than three, for example, four or more vertical / horizontal electrodes can be used.
The horizontal line electrode 1102 is sequentially connected to the GND of the power supply, the vertical line electrode 1101 is selected as a segment to be changed to the horizontal line sequential drive, and time-division driving for connecting to the power supply VCC is performed. It is preferable to use a flat-plate striped electrode as the electrode. Although it is not impossible to use a wire type electrode, it is generally not so recommended because it is difficult to reduce the size of the electrode.

FIG. 13 shows pulses for driving the switches (sw) A1 to A3 and the switches B1 to B3 for performing the display shown in FIG. In FIG. 10, the shaded portion of the polymer-dispersed liquid crystal layer 302 becomes transparent by heating, and the color of the lower heat conductive plate 601 is displayed.

This pulse interval is, as shown in FIG.
After heating, the cycle until the next heating is performed can be easily determined by calculating in advance from the time during which the change of the polymer dispersed liquid crystal 302 can be maintained.

FIGS. 11 and 12 show the protective film 301 and the polymer-dispersed liquid crystal layer 302 of each segment.
However, it is troublesome to manufacture them, but it is preferable to manufacture them in one continuous form without separating them. FIG. 15 is a cross-sectional view of an example of a matrix-type liquid crystal display device 1500 in which a protective film 301 and a polymer-dispersed liquid crystal layer 302 are formed in one continuous sheet, and FIG. 16 is a top view thereof. . Protective film 3
When the 01- and polymer-dispersed liquid crystal layers 302 are formed in a continuous sheet, heat is transferred between the segments, and clear display cannot be performed. So, in matrix drive, to separate each segment,
A striped heat radiating plate 1501 having a predetermined width is arranged vertically and horizontally. Heatsink 1501 striped vertically and horizontally
Are provided, the portions surrounded by the heat sinks are divided into independent segments. As a result, even if one segment is heated by energization, a clear display is possible without transferring the heat to another adjacent segment. Striped heat sink 1501
It is preferable to select and use a material having a higher thermal conductivity than the material used for the heat conductive plate 601. The larger the difference between the thermal conductivity of the strip-shaped heat sink 1501 and the thermal conductivity of the heat conductive plate 601, the better the result. Although the thickness of the striped heat sink 1501 is not particularly limited,
Generally, it is preferable to be within the range of 1 mm to 20 mm. If it is less than 1 mm, a sufficient heat radiation effect cannot be expected.
On the other hand, if it exceeds 20 mm, since the segment interval is widened, disadvantages such as deterioration of display quality occur, which is not preferable.

FIG. 17 shows the effect of using the striped heat sink 1401. FIG. 17A shows a striped heat sink 15.
FIG. 11 is a top view showing a display state when 01 is not used.
Since heat is transferred between the adjacent segments, the boundary between the transparent portion and the opaque portion becomes an unclear display such as gradation. On the other hand, FIG. 17B is a top view showing a display state when the striped heat sink 1501 is used. Since the transfer of heat between adjacent segments is prevented by the heat sink, the boundary between the transparent portion and the opaque portion is clearly displayed.

FIG. 18 is a characteristic diagram showing the relationship between the applied voltage and the temperature of the polymer dispersed liquid crystal layer 302. FIG.
In the continuous applied voltage waveform as shown in FIG. 7A, after the temperature rise reaches the liquid crystal change temperature, the temperature rise further continues, so that the liquid crystal of the polymer dispersed liquid crystal layer 302 is decomposed and deteriorates as a display element. There is fear. Therefore, FIG.
As shown in (b), a continuous voltage pulse is applied up to the liquid crystal change temperature, and when the temperature exceeds the liquid crystal change temperature, the driving is changed to an intermittent voltage pulse drive, whereby the temperature of the polymer dispersed liquid crystal layer 302 is changed. Is preferably kept constant at a value near the liquid crystal change temperature.

FIG. 19 shows a method of determining such a voltage pulse width pattern. The outside temperature, the surface temperature of the display element, and the like are taken into the controller 1902 from the temperature sensor 1901, the optimal voltage pulse pattern is calculated, and the heating element 304 is energized through the LCD driver 1903. The calculation method by the controller 1902 is as follows.
There is a method of storing the information in the ROM in the memory 902, but the method is not particularly limited.

In the configuration shown in FIG. 3, a pair of electrodes 303 and 305 are provided on the upper and lower surfaces of the heating element 304. Therefore, one electrode 303 is interposed between the polymer-dispersed liquid crystal layer 302 and the heating element 304, and the polymer-dispersed liquid crystal layer 302 and the heating element 304 do not come into direct contact with each other.
However, as shown in FIG. 20, a pair of electrodes a, b 2001 and 2003 can be connected to both left and right ends of the heating element 304, and the polymer dispersed liquid crystal layer 302 and the heating element 304 can be brought into direct contact. In this case, when the polymer dispersed liquid crystal layer 302 is heated and becomes transparent,
4 itself becomes visible through the liquid crystal layer. Heating element 30
In the case where 4 is a black color such as carbon, the polymer-dispersed liquid crystal layer 302 has a high contrast display due to a difference from white when not heated. On the other hand, when the heating element 304 has a color close to white, the contrast between the transparent state and the opaque state of the polymer dispersed liquid crystal layer 302 may be low. Therefore, between the polymer-dispersed liquid crystal layer 302 and the heating element 304, a colored background plate (not shown) such as a visually preferable color film (for example, matte black film) as shown in FIG. Can be interpolated. Alternatively, a colored paint (for example, matte black paint) can be applied to the surface of the heating element 304. When applying the colored paint, information such as characters, figures, patterns, and / or symbols is printed on the surface of the heating element 304 by the paint, and these are changed according to the change in transparency and opacity of the polymer dispersed liquid crystal layer 302. It is also possible to display or hide information.

Further, as shown in FIG.
04 is gradually increased or decreased in one direction, thereby changing the resistance value of the heating element 304 and causing the pair of electrodes 20
The display mode can be changed by a voltage and a current applied between 01 and 2002. To change the display mode, for example, a variable resistor 2101 is inserted between the power supply 406 and the heating element 304. When the resistance value of the variable resistor 2101 is changed, the voltage applied between the pair of electrodes a, b 2001 and 2002 changes, and the heating element 304 is accordingly changed.
The display mode changes due to the change in the amount of heat generated.
That is, a transparent portion and an opaque portion are formed in the polymer dispersed liquid crystal layer 302. In addition to changing the thickness of the heating element 304, the resistance can be changed by changing the width and length of the heating element, and the same effect can be obtained.

Further, as shown in FIG. 22, a plurality of heating elements a 2201 and b 220 having different resistance values are provided.
3, a heating element 2205 is formed, and the amount of heat generated by each heating element is changed, whereby the polymer dispersed liquid crystal layer 302 is formed.
For example, full lighting, half lighting, full lighting, etc.
It is also possible to have a stage display mode. By increasing the types of the heating elements, the display stage can be further increased. By optimizing the resistance values of these heating elements, the liquid crystal display device of the present invention can be used as an indicator (for example, a battery fuel gauge) for detecting voltage or current.

FIG. 23 is a top view of a heating element sheet 2305 in which a metal 2303 such as stainless steel is etched into a plastic sheet 2301 so as to have a certain resistance. By forming a polymer-dispersed liquid crystal layer on such a heating element sheet, the entire liquid crystal display device can be made thinner.

As described in the above paragraph 0027, when characters (for example, “A”) are written on the surface of the electrode a 303 with black paint and the polymer dispersed liquid crystal layer 302 is superimposed, the polymer dispersed liquid crystal layer 302 is overlaid. Is thin, characters written on the surface of the electrode a303 may be seen through the polymer-dispersed liquid crystal layer 302 even when not heated. 24 and FIG.
As shown in FIG. 2, for example, 2
Projections 250 having a height of, for example, about 1 mm at intervals of about 3 mm
1, and a character 2503 can be written. When the polymer-dispersed liquid crystal layer 302 is superposed on the surface on which the protrusions are provided, the concealing property is improved due to the unevenness of the surface of the electrode a303,
The phenomenon in which the character 2503 written on the surface of the electrode a303 is seen through the polymer-dispersed liquid crystal layer 302 is completely resolved. The polymer dispersed liquid crystal layer 302 by the heating element
Is heated and the liquid crystal layer becomes transparent, a character 2503 written on the surface of the electrode a303 appears and becomes visible.

As another method for improving the concealing property without disposing the protrusion on the surface of the electrode a303,
There is a method using a heat conductive plate (see FIG. 6) inserted between the liquid crystal layer 302 and the polymer dispersed liquid crystal layer 302. For example, as shown in FIG. 26, on the surface of the heat conductive plate 2601, for example,
The through holes 2603 are provided at equal intervals of 3 mm. Alternatively, as shown in FIG.
Use 01. These heat conducting plates are made of, for example, aluminum. The heat conductive plate 2601 or the lattice-shaped heat conductive plate 2701 provided with the through holes is connected to the electrode a3.
03 and the polymer dispersed liquid crystal layer 302.
The lattice-shaped heat conductive plate 2701 is inserted so as to be orthogonal to the surface of the electrode a303. The polymer-dispersed liquid crystal layer 3 during non-heating is reduced while the effect of the heat conducting plate on the display is reduced.
02 can be improved.

The liquid crystal used in the polymer dispersed liquid crystal layer 302 in the liquid crystal display device 300 of the present invention may be discolored by heat, change from an opaque state to a transparent state, or vice versa. It is not particularly limited as long as it has a possible thermal response. For example, a nematic liquid crystal, a smectic liquid crystal, a cholesteric liquid crystal, or the like can be suitably used. Phase transition temperature (T _NI ) of 60 ° C to 7
Liquid crystals of about 0 ° C. are preferred.

In the display in the heat mode, the polymer in the polymer-dispersed liquid crystal layer is required to have high thermal stability and high transparency. When a conventional polymer having a low glass transition temperature (T _g ) is used for the binder resin, the phase transition temperature (T
_NI) before repeating the heating-cooling the thermal deformation of the low T _g polymer becomes significant, and consequently, not only degrade the visibility of the polymer dispersion type liquid crystal display device, its life itself degrade.

In the present invention, -20 ° C. ≦ (T _g −T _NI ) ≦
It is preferable to use a polymer that can satisfy the requirement of 20 ° C. as the binder resin. Therefore, if the phase transition temperature (T _NI ) of the liquid crystal used in the polymer dispersed liquid crystal layer is determined, the glass transition temperature (T _g ) of the polymer to be used as a binder resin for the liquid crystal is within the above range. You just have to select what is inside.

In the thermoresponsive polymer-dispersed liquid crystal display element, in the non-heated state (nematic phase state), the liquid crystal is oriented along the polymer interface, and scatters light at the polymer / liquid crystal interface, resulting in cloudiness. And become opaque. On the other hand, in the heated state (isotropic phase state), the polymer / liquid crystal interface moves at the temperature of T _g T _NI , and the orientation of the liquid crystal near the interface is randomized, and the liquid crystal is easily compatible with the polymer. Therefore, a relatively fast thermal response speed can be obtained.

In the present invention, -20 ° C. ≦ (T _g −T _NI ) ≦
A polymer that can meet the requirement of 20 ° C. is used as a binder resin. That is, the present inventors have found that good thermal responsiveness is obtained when the glass transition temperature of the polymer is equal to or close to the phase transition temperature of the liquid crystal. This is presumed that the liquid crystal molecules oriented at the polymer / liquid crystal interface are compatible in the polymer matrix during heating. Experimental results, especially -2
This tendency was remarkable in a combination of a polymer and a liquid crystal having a relationship of 0 ° C. ≦ (T _g −T _NI ) ≦ 20 ° C., and it was revealed that a rapid thermal response was obtained.

For example, when a liquid crystal having a phase transition temperature (T _NI ) of 82 ° C. is used, a binder resin for the liquid crystal is polymethyl methacrylate (PMMA) having a glass transition temperature (T _g ) of about 90 ° C. For example, an acrylic resin such as an acrylic resin can be used. Since the temperature difference between T _g and T _NI is about 8 ° C,
Even if the polymer is exposed to a thermal cycle in which the temperature is repeatedly raised and lowered to the phase transition temperature (T _NI ) of the liquid crystal, the possibility that the polymer itself undergoes thermal denaturation is reduced, and the durability of the polymer dispersed liquid crystal display element is improved. In addition, acrylic resin has high transparency,
In addition, since it has weather resistance (or UV resistance), it is possible to improve the transparency and weather resistance of the liquid crystal layer when heated even when formed in a polymer dispersed liquid crystal layer. Furthermore, -20
PMMA that satisfies the relationship of ℃ ≤ (T _g -T _NI ) ≤ 20 ℃
The use of acrylic resin such as promotes the compatibility of liquid crystal and polymer at the polymer / liquid crystal interface at the time of temperature rise,
Thermal response is also improved.

The acrylic resins other than PMMA that can be used in the present invention include, for example, high T _g methacrylates such as polyethyl methacrylate, poly (tert-butyl methacrylate) and polyethylene glycol dimethacrylate, and alkyd-modified acrylics. Modified acrylic resins such as polyester-modified acryl and silicon-modified acryl, and acrylic copolymers using hard monomers such as styrene, methyl methacrylate, acrylonitrile, and acrylamide can be used. However, the T _g of these acrylic resins, the selection of the functional groups of various monomers, the polymerization degree of the polymer, and by selection of the copolymerization ratio can be preferably set the T _g of the polymer.

Needless to say, -20 ° C. ≦ (T _g −
As long as the polymer can satisfy the relationship of T _NI ) ≦ 20 ° C., a polymer other than the acrylic resin can also be used in the present invention. For example, the thermoresponsive polymer dispersion type liquid crystal display device, when using a liquid crystal having a phase transition temperature in the vicinity of about 70 ℃ (T _NI), as a polymer for the binder resin, for example, T _g is 50 to 90 ° C. , Polyvinyl butyral, polyester, polyurethane, vinyl chloride,
Various polymer resins such as vinyl acetate copolymer, silicone, polyvinyl alcohol, polyvinylpyrrolidone, various cyanoethyl compounds such as cyanoethylated pullulan, and mixtures thereof can be used. In addition,
In the acrylic resin may be used an acrylic resin set a T _g in the 50 to 90 ° C..

What is important in the composition of the polymer and the liquid crystal for forming the polymer dispersed liquid crystal layer 302 in the liquid crystal display device 300 of the present invention is the weight ratio of the polymer and the liquid crystal. When the compounding capacity of the liquid crystal is higher than the compounding capacity of the polymer, the thermal responsiveness of the polymer-dispersed liquid crystal layer 302 formed from this composition is improved. Is too high, the workability of coating on the electrode tends to decrease. On the other hand, if the compounding capacity of the polymer is higher than the compounding capacity of the liquid crystal, the whole composition becomes viscous, and it becomes easy to apply the composition on the electrode, and the suitability for production is improved. The nature also decreases. Therefore, the weight ratio of polymer to liquid crystal in the polymer dispersed liquid crystal layer 302 of the present invention is preferably in the range of 1:10 to 10: 1. The weight ratio of polymer to liquid crystal is 1: 2 to 3:
More preferably, it is within the range of 1. The most preferred weight ratio of polymer to liquid crystal is 1: 1.

The thickness of the polymer-dispersed liquid crystal layer 302 is not particularly limited, but generally ranges from 20 μm to 200 μm.
It is preferably within the range of m. If the film thickness is less than 20 μm, a sufficient display effect cannot be expected. On the other hand, when the film thickness is 20
If it exceeds 0 μm, the thermal response speed becomes slow, and it becomes difficult to display quickly and it is difficult to obtain a uniform film thickness.

The polymer dispersed liquid crystal layer 302 of the present invention is generally known to those skilled in the art, and can be formed by a liquid crystal layer forming method commonly or commonly used by those skilled in the art. For example, a method such as an encapsulation method, a polymerization phase separation method, a thermal phase separation method, and a solvent evaporation phase separation method can be appropriately selected and used.

Alternatively, a polymer-dispersed liquid crystal layer having a uniform thickness distribution, a high film thickness and a high contrast can be manufactured by the manufacturing method shown in FIG. First, in a step (A), a substrate 2801 is prepared. The substrate 2801 is not particularly limited. Both transparent and opaque substrates can be used. Such substrates are, for example, glass,
It is made of metal or plastic. In the present invention, it is preferable to use a transparent or opaque plastic substrate. A plastic substrate is not only lower in cost than a glass substrate, but also can be formed into a curved surface due to its flexibility, and has improved wettability as compared with a glass substrate. Examples of the plastic substrate that can be used in the present invention include polyethylene terephthalate, polyethylene naphthalate, and polyether sulfone. The thickness of the substrate 1 is not particularly limited. Any thickness may be used as long as it has a necessary and sufficient mechanical strength as a substrate. The surface of the substrate 2801 on which the liquid crystal composition is applied may be subjected to an appropriate surface cleaning treatment such as solvent wiping or ultraviolet irradiation before the application of the liquid crystal composition.

Next, in step (B), an appropriate coating device 2803 such as a coater or an applicator is filled with a liquid crystal composition composed of a mixture of a liquid crystal, a polymer, and a solvent. Near the end of the.

Thereafter, in step (C), the coating device 28
03 is gently moved on the substrate surface at a constant speed toward the other end of the substrate. A polymer-dispersed liquid crystal film 2805 having a predetermined thickness is applied to the substrate according to the gap between the blades (not shown) below the application device 2803.

Thereafter, in a step (D), when the polymer dispersed liquid crystal film 2805 is dried by an ordinary method, the substrate 28
A film-shaped polymer-dispersed liquid crystal film 2805 is formed on the substrate 01. The thickness of the polymer-dispersed liquid crystal film 2805 after drying is not particularly limited, but is generally 20 μm to 20 μm.
It is preferably within a range of 0 μm. The film thickness is 20 μm
If it is less than 1, there is a risk that a pinhole is generated in the film.
On the other hand, if the film thickness exceeds 200 μm, it becomes difficult to obtain a uniform film thickness.

Steps (A) to (D) are almost the same as the steps of manufacturing a conventional polymer-dispersed liquid crystal display device.

In the composition of the polymer and the liquid crystal of the present invention,
It is preferable that the polymer and the liquid crystal are dispersed as uniformly as possible. Therefore, it is preferable to use a solvent that is soluble in all of these components. It is generally preferred that such solvents be lipophilic. The solvent used for dissolving the liquid crystal and the solvent used for dissolving the polymer may be the same or different from each other. However, when the respective solutions are mixed, it is preferable that they are mutually compatible or miscible. The use of solvents that do not mix well and cause phase separation when mixing the solutions should be avoided. The solvent that can be used in the present invention may be any of aliphatic, aromatic, alicyclic and heterocyclic compounds. Specifically, cellosolve, toluene, xylene, cyclohexanone, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, carbon tetrachloride, acetonitrile, pyridine, N, N-dimethylformamide ketone, and the like can be suitably used. The solvents can be used alone or as a mixture of two or more. The solvent used in the present invention is preferably a volatile solvent.

The amount of the solvent used is not particularly limited. It is possible to use a solvent in an amount necessary and sufficient for dissolving the liquid crystal and the polymer used in the present invention. If an unnecessarily large amount of solvent is used, although it is convenient for dissolving the liquid crystal and the polymer, it takes a long time for the drying process after application to the substrate, or abnormal discharge or display unevenness due to the residual solvent. Undesirably occurs. In fact, the amount of solvent used depends on various factors such as the solubility of the selected liquid crystal and polymer, the workability of applying the resulting mixed solution, and the drying time. Therefore, the use amount of the solvent can be appropriately determined by those skilled in the art in consideration of each factor.

The above steps (A) to (D) are repeated to form a plurality of, for example, two or more structures in which the polymer dispersed liquid crystal film 2805 is supported on one surface of the substrate 2801. Then, in step (E), one polymer dispersed liquid crystal film 2805 is
05 and 80 ° C. from both substrates 2801 side
While heating at a temperature of about 100 ° C., an appropriate pressure is applied to press the two liquid crystal films together. In this pressure bonding, a laminating machine (for example, TOLAMI-DX-350 commercially available from Tokyo Laminex Corporation) can be used to perform pressure bonding at an optimum pressure. In addition, even in the case of holding down by hand, this pressure can be easily determined by repeating the experiment. By this pressing, the polymer dispersed liquid crystal film 280 is formed.
The fine irregularities existing on the surface of No. 5 are flattened at the pressure bonding interface, and a uniform bonding surface is formed. The pressing time of both liquid crystal films is not particularly limited. It suffices if the time is sufficient and necessary to completely press-bond both liquid crystal films. Such pressurization time can be easily determined by those skilled in the art by repeating experiments.

After the pressing operation is completed, in step (F), one substrate 2801 is peeled off from the polymer dispersed liquid crystal film 2805. This peeling can be easily performed by a known and commonly used means such as an air knife. Other stripping means can of course be used.

Thus, in the step (G), a laminated polymer dispersed liquid crystal layer 2807 having a thickness approximately twice as large as that of the single polymer dispersed liquid crystal film 2805 is formed on the substrate 2801.

When two polymer dispersed liquid crystal films 2805 are superposed in the above step (E), these polymer dispersed liquid crystal films 2805 can be the same kind of polymer dispersed liquid crystal film, but they are different. It can also be a polymer dispersed liquid crystal film of any kind. In FIG. 28,
Although an example in which two polymer-dispersed liquid crystal films 5 are overlapped has been described, the present invention is not limited to the illustrated example, and three or more polymer-dispersed liquid crystal films 2805 can be overlapped.

For example, as shown in FIG.
First, polymethyl methacrylate (P
By forming a polymer dispersed liquid crystal film 2901 composed of (MMA) / liquid crystal, and then laminating a polymer dispersed liquid crystal film 2903 composed of a polymer / liquid crystal to which an ultraviolet absorber (UVA) is added on the upper surface of the liquid crystal film 2901. UV resistant
(UV) Degradable laminated polymer dispersed liquid crystal layer 2807 can be obtained. The polymer-dispersed liquid crystal film 2901 composed of PMMA / liquid crystal has high thermal responsiveness and high transparency, but is susceptible to deterioration by ultraviolet rays. On the other hand, the polymer-dispersed liquid crystal film 2903 composed of a polymer / liquid crystal containing an ultraviolet absorber (UVA) can significantly improve resistance to UV deterioration without lowering the transparency. Examples of the ultraviolet absorber (UVA) include a benzophenone type, a benzotriazole type, a salicylate type, and a cyanoacrylate type. These ultraviolet absorbers (UVA) are known, for example, “Practical Plastics Encyclopedia” edited by the Industrial Research Council.
(Issued September 20, 1993). When a benzophenone compound is used as the ultraviolet absorber (UVA), the polymer is preferably a polyolefin. When using a benzotriazole-based compound as an ultraviolet absorber (UVA), the polymer is acrylonitrile-butadiene-styrene copolymer (ABS), polystyrene, polyurethane, polyvinyl chloride, polyolefin, polycarbonate, polyethylene terephthalate, polyoxymethylenacetal And polymethyl methacrylate (PMMA) is preferred.

Further, as shown in FIG.
First, a polymer-dispersed liquid crystal film 2905 composed of polyester or urethane / liquid crystal is formed on the upper surface of the liquid crystal film 801, and a polymer dispersed liquid crystal film 2901 composed of PMMA / liquid crystal is laminated on the upper surface of the liquid crystal film 2905. By laminating a polymer-dispersed liquid crystal film 2903 made of an elastomer or an acrylic epoxy / liquid crystal on the upper surface of the film 2901, it is possible to obtain a laminated polymer-dispersed liquid crystal layer 2807 having a resistance to ultraviolet (UV) deterioration and a thermal shock resistance. Can be. If only thermal shock resistance is required, the liquid crystal film 2903 can be omitted. Examples of the polymer constituting the polymer-dispersed liquid crystal film for improving thermal shock resistance include amorphous polyolefin, polyetherimide, polyamide, polycarbonate, polysulfone, polyethersulfone, and polyetherketone.

Further, as shown in FIG.
First, a polymer-dispersed liquid crystal film 2907 composed of a highly ductile resin (for example, butyral or polyester) / liquid crystal is formed on the upper surface of the liquid crystal film 801, and then a polymer-dispersed liquid crystal film 2901 composed of PMMA / liquid crystal is formed on the upper surface of the liquid crystal film 2907. And a liquid crystal film 29
07 are laminated to form a polymer dispersed liquid crystal layer 2 having a three-layer structure.
807 can be obtained. Since the viscosity of the liquid crystal films 2907 on both sides is higher than that of the intermediate liquid crystal film 2901, the entire liquid crystal layer 2807 can flexibly cope with deformation stress such as bending or bending, and the mechanical strength is improved. . As a polymer that can improve flexibility, vinyl chloride, polyethylene, polypropylene, polyester, or styrene-butadiene rubber, butadiene rubber,
Elastomers such as silicone rubber are exemplified.

[0073]

The present invention will now be specifically illustrated by way of examples.

Example 1 In the liquid crystal display element 300 having the structure shown in FIG. 3, polyethyl methacrylate (T _g = 90 ° C., molecular weight = 1.05 × 10 ⁵ ) was used as a polymer, and a nematic liquid crystal (T _NI ) was used as a liquid crystal. = 82 ° C, Δn = 0.253). A mixed solution having a weight ratio of the polymer and the liquid crystal of 1: 1 was added to PE
After coating on a T substrate 301 to form a polymer-dispersed liquid crystal layer 302 having a thickness of 60 μm, a liquid crystal cell A was fabricated by combining electrodes and a heating element.

Embodiment 2 In the liquid crystal display element 300 having the structure shown in FIG. 3, the polymer is polyethyl methacrylate having a high T _g (T _g = 100).
C., molecular weight = 1.15 × 10 ⁵ ), and a nematic liquid crystal (T _NI = 82 ° C., Δn = 0.253) was used as the liquid crystal. Otherwise, a liquid crystal cell B was produced in the same manner as in Example 1.

Comparative Example 1 In the liquid crystal display device 300 having the structure shown in FIG. 3, polyvinyl butyral (T _g = 50 ° C.) was used as the polymer.
Nematic liquid crystal (T _NI = 72 ° C., Δn = 0.
246) was used. The weight ratio of the polymer to the liquid crystal is 1:
The liquid crystal cell C was manufactured in the same manner as in Example 1 above.

Comparative Example 2 In the liquid crystal display element 300 having the structure shown in FIG. 3, the polymer was polytertiary butyl methacrylate (T _g =
107 ° C.) and nematic liquid crystal (T _NI =
82 ° C., Δn = 0.253). Otherwise, a liquid crystal cell D was produced in the same manner as in Example 1.

Comparative Example 3 In the liquid crystal display element 300 having the structure shown in FIG. 3, the polymer was polyethylene glycol methacrylate (T _g =
130 ° C), and the nematic liquid crystal (T _NI =
82 ° C., Δn = 0.253). Otherwise, a liquid crystal cell E was produced in the same manner as in Example 1.

The cells A obtained in the above Examples and Comparative Examples,
When heat cycle tests were performed on B, C, D and E before and after the cloudiness-transparency change temperature, cells A, B,
For D and E, even after 10,000 thermal cycles, PD
The cloudy-transparent change was made without causing thermal deformation of the LC film. However, in the cell C, thermal deformation of the PDLC film occurred in 1000 thermal cycles, and a defective display portion occurred. Therefore, −20 ° C. ≦ (T _g −
T _NI ) When a polymer satisfying the relationship of ≦ 20 ° C. is used,
It was confirmed that the heat cycle durability was improved.

The cells A obtained in the above Examples and Comparative Examples,
For B, C, D and E, the measurement results of the thermal response time during heating are shown in Table 1 below. The “thermal response time” is the time required for the transmittance (λ = 555 nm) to change from the minimum value to the maximum value when each PDLC film is sandwiched between transparent electrode heating elements and heated at a constant speed. And

[0081]

[Table 1]

As is clear from the results shown in Table 1, the thermal response speeds of the cells A and B satisfying −20 ° C. ≦ (T _g −T _NI ) ≦ 20 ° C. are expressed as (T _g −T _NI )> 20 ℃
Thermal response relatively faster than cell D and cell E,
This tendency becomes prominent in the T _g -T _NI = 20 ℃. Therefore,
Experimentally, it was confirmed that the polymer having a temperature of −20 ° C. ≦ (T _g −T _NI ) ≦ 20 ° C. had improved thermal responsiveness. The cell C at T _g −T _NI <−20 ° C. is the cell A and the cell B
Although there is no inferiority in terms of heat response speed, it is inferior in heat cycle durability as described above.

Next, the production of a liquid crystal display device having a polymer liquid crystal layer having a laminated structure according to the present invention will be specifically described.

Example 3 A raw material having the following composition was prepared, and mixed at room temperature with a homogenizer.
The mixture was stirred for 1 minute to prepare a polymer-dispersed liquid crystal composition mixed solution. Polymer: 5 parts by weight of polymethyl methacrylate, Liquid crystal: 5 parts by weight of cyanobiphenyl-based E-8 manufactured by BDH, 90 parts by weight of acetone: This mixed solution was applied on a PET film with an applicator, and the thickness was 15 μm. A polymer dispersed liquid crystal film was formed. The layering method of the present invention was used for superposing liquid crystal films to increase the thickness of the liquid crystal layer. The lamination of the liquid crystal film was performed by pressing at 80 ° C. for 1 minute using TOLAMI-DX-350 commercially available from Tokyo Laminex. Various samples were prepared by changing the number of stacked liquid crystal films, and the transmittances of these samples when heated and not heated were measured. FIG. 30 shows the results.
And Table 2 below.

Table 2 Sample Number of Liquid Crystal Films Film Thickness (μm) Transmittance When Heated (%) Transmittance When Not Heated (%) A 115 85.5 3.5 B 230 89.2 1.2 C 4 60 87.7 0.5 D 6 90 90.3 0.5 E 8 120 88.0 0.4

From the results shown in FIG. 30 and Table 2, by laminating up to four liquid crystal films, the transmittance during non-heating is reduced and the opacity is improved, while the transmittance during heating is increased. It can be understood that has not changed significantly. When the contrast ratio is obtained from this numerical value, the ratio is 24: 1 for a single film (15 μm thickness) without lamination, 74: 1 for a two-layer lamination (30 μm thickness), and 175: 1 for a four-layer lamination (60 μm thickness) It has improved remarkably. When the number of layers is more than four, for example, the contrast ratio is 1 in the case of six layers (90 μm thickness).
The contrast ratio in an 80: 1, eight-layer stack (120 μm film thickness) is 220: 1, which is almost the same or slightly improved as compared with the four-layer stack. Therefore, it can be determined that a polymer-dispersed liquid crystal layer having a film thickness of 60 μm, in which four liquid crystal films are laminated, having the highest lamination effect, is optimal.

[0087]

As described above, according to the present invention,
In a thermally responsive liquid crystal display device using polymer dispersed liquid crystal, the use of thermally controllable electrodes and a heat conductive plate reduces display unevenness and slow response speed due to the low thermal conductivity of the polymer. Can be improved. Also, in a matrix type liquid crystal display device, a clear display is possible in a state where deterioration of the display element is prevented by inserting a heat sink between segments and adopting a driving method adapted to polymer dispersed type liquid crystal. Become.

Further, according to the present invention, a polymer capable of satisfying the requirement of −20 ° C. ≦ (T _g −T _NI ) ≦ 20 ° C. is used as the binder resin in the polymer-dispersed liquid crystal layer. The polymer itself is less likely to undergo thermal denaturation even if it is exposed to a thermal cycle in which the temperature rises and falls to the phase transition temperature (T _NI ) of the polymer, thereby improving the durability of the polymer dispersed liquid crystal display device. Not only can it improve the weather resistance and thermal responsiveness of the polymer dispersed liquid crystal layer.

Further, according to the present invention, a plurality of polymer dispersion type liquid crystal films formed separately are sequentially bonded to form a single polymer having a uniform high film thickness and improved contrast. A dispersion type liquid crystal layer can be obtained. In addition, by changing the type of the polymer dispersed liquid crystal film to be laminated, it is possible to obtain a laminated polymer dispersed liquid crystal layer having various functions such as UV degradation resistance, flexibility, and thermal shock resistance in addition to high contrast. .

[Brief description of the drawings]

FIGS. 1A and 1B are schematic diagrams showing a state change of a polymer-dispersed liquid crystal when not heated and when heated, where FIG. 1A shows a non-heated state and FIG. 1B shows a heated state.

FIG. 2 is a characteristic diagram showing a change in refractive index of a polymer-dispersed liquid crystal with respect to temperature.

FIG. 3 is a schematic perspective sectional view showing a configuration of an example of a liquid crystal display element of the present invention.

4 is a schematic perspective sectional view showing a state before and after voltage application of the liquid crystal display element according to the present invention shown in FIG. 3; FIG. 4 (a) shows a state before voltage application; b) shows the state after voltage application.

5 is a schematic perspective sectional view showing a modification of the liquid crystal display element shown in FIG. 3, wherein FIG. 5 (a) shows a configuration in which a reflector is inserted, and FIG. 5 (b) shows a configuration in which a color film is inserted. The following shows the configuration.

FIGS. 6A and 6B are schematic sectional views showing still another modification of the liquid crystal display element shown in FIG. 3, wherein FIG. 6A shows a configuration in which a heat conducting plate is inserted, and FIG. This shows a configuration in which a conductive plate and a reflector are inserted.

FIGS. 7A and 7B are top views showing the effect of using the heat conductive plate, FIG. 7A shows a case where the heat conductive plate is not used, and FIG.
Indicates the case where a heat conductive plate is used.

FIG. 8 is a modified example of the configuration in which the heat conductive plate shown in FIG. 6A is inserted, and is a schematic cross-sectional view of a liquid crystal display device in which the heat conductive plate is divided into a plurality. .

FIG. 9 is a schematic diagram showing an example of a display change of a polymer dispersed liquid crystal layer when a liquid crystal display device 300 having the structure shown in FIG. 8 is driven.

FIG. 10 is a further modified example of the configuration in which the heat conductive plate shown in FIG.
1 is a cross-sectional view of a liquid crystal display device having a configuration in which a through opening 1001 is provided on the surface of a liquid crystal display.

FIG. 11 is a schematic top view showing a configuration of an example of a matrix type liquid crystal display device.

FIG. 12 is a sectional view taken along line AA in FIG. 11;

FIG. 13 is a characteristic diagram showing pulses for driving switches (sw) A1 to A3 and switches B1 to B3 for performing the display shown in FIG. 11;

FIG. 14 is a characteristic diagram showing a mode change of a polymer dispersed liquid crystal layer in a liquid crystal display device having a matrix structure according to the present invention.

FIG. 15 is a cross-sectional view of an example of a matrix type liquid crystal display device 1500 in which a protective film 301 and a polymer dispersed liquid crystal layer 302 are formed in one continuous sheet.

FIG. 16 is a top view of the matrix type liquid crystal display device 1500 shown in FIG.

17A and 17B are top views showing the effect of using a heat sink, FIG. 17A shows a case where a heat sink is not used, and FIG.
Indicates the case where a heat sink is used.

FIG. 15 shows a liquid crystal display device of the present invention.
FIG. 4 is a characteristic diagram showing a relationship between a method of applying a voltage to a heating element and a temperature of a polymer-dispersed liquid crystal layer, wherein (a) shows a temperature change when a voltage is applied to the heating element without temperature control. Show,
(B) shows a temperature change when temperature control is performed by a voltage pulse width applied to the heating element.

FIG. 19 is a block diagram showing a method of setting a voltage pulse width applied to a heating element in a liquid crystal display device having a matrix structure according to the present invention.

FIG. 20 is a cross-sectional view showing the configuration of another embodiment of the liquid crystal display device of the present invention.

FIG. 21 is a cross-sectional view showing a configuration of another embodiment of the liquid crystal display element of the present invention.

FIG. 22 is a cross-sectional view showing a configuration of still another embodiment of the liquid crystal display device of the present invention.

FIG. 23 is a plan view of an example of a heating element used in the liquid crystal display device of the present invention.

FIG. 24 is a plan view of an example of an electrode a.

FIG. 25 is a partially enlarged perspective view of a portion A in FIG. 24;

FIG. 26 is a plan view of an example of a heat conductive plate.

FIG. 27 is a plan view of an example of a grid-like heat conductive plate.

FIG. 28 is a schematic view showing an example of a production process of the polymer liquid crystal layer having a laminated structure of the present invention.

FIG. 29 is a schematic cross-sectional view of a laminated polymer dispersed liquid crystal layer of the present invention, in which (a) shows a laminated polymer dispersed liquid crystal film composed of a polymer dispersed liquid crystal film and a UV-degradable polymer dispersed liquid crystal film. FIG. 2 is a schematic cross-sectional view of a liquid crystal layer, and FIG.
Is a schematic cross-sectional view of a laminated polymer dispersed liquid crystal layer comprising a thermal shock resistant polymer dispersed liquid crystal film, a polymer dispersed liquid crystal film, and a UV-resistant polymer dispersed liquid crystal film,
(C) is a schematic cross-sectional view of a laminated polymer dispersed liquid crystal layer in which a polymer dispersed liquid crystal film is interposed between highly ductile polymer dispersed liquid crystal films.

FIG. 30 is a characteristic diagram showing the relationship between the thickness of the polymer-dispersed liquid crystal layer of the laminated polymer-dispersed liquid crystal layer of the present invention and the transmittance when heated and not heated.

[Explanation of symbols]

 Reference Signs List 101 polymer resin 102 opaque liquid crystal droplet 103 transparent liquid crystal droplet 300 liquid crystal display device 301 of the present invention 301 protective sheet 302 polymer dispersed liquid crystal layer 303 electrode a 304 heating element 305 electrode b 406 power supply 501 reflecting plate 502 color film 601 Heat conductive plate 801 Heat conductive plate a 802 Heat conductive plate b 803 Heat conductive plate c 1001 Through opening 1100 Matrix type liquid crystal display device of the present invention 1101 Vertical line electrode 1102 Horizontal line electrode 1501 Striped heat sink 1901 Temperature sensor 1902 Controller 1903 LCD driver 2001 Electrode a 2003 Electrode b 2101 Variable resistor 2201 Heating element a 2203 Heating element b 2205 Heating element 2301 Plastic sheet 2303 Metal 230 5 Heating Element Sheet 2501 Projection 2503 Character 2601 Heat Conduction Plate 2603 Through Hole 2701 Lattice Heat Conduction Plate 2801 Substrate 2803 Coating Device 2805 Polymer Dispersion Type Liquid Crystal Film 2807 Laminated Structure Polymer Dispersion Type Liquid Crystal Layer 2903 UV Degradation Resistant Polymer Dispersion Type Liquid Crystal Film 2905 Thermal shock resistant polymer dispersed liquid crystal film 2907 High ductility polymer dispersed liquid crystal film

Claims (28)

[Claims] 1. A liquid crystal display device comprising a heating element and a polymer-dispersed liquid crystal layer comprising a composition of a polymer and liquid crystal disposed on the heating element. 2. A heating element is sandwiched between a pair of electrodes, and the polymer dispersed liquid crystal layer is disposed on one of the pair of electrodes. The liquid crystal display device according to claim 1. 3. The liquid crystal according to claim 1, wherein a heating element is sandwiched between the pair of electrodes, and the polymer-dispersed liquid crystal layer is directly disposed on the heating element. Display device. 4. Use of a thermoplastic polymer as the polymer, and a glass transition temperature (T _g ) of the polymer.
And the phase transition temperature (T _NI ) of the liquid crystal is −20 ° C. ≦ (T
_2. The liquid crystal display device according to claim 1, wherein a liquid crystal and a polymer satisfying a relationship of ( _g- T _NI ) ≦ 20 ° C. are used. 5. The liquid crystal display device according to claim 4, wherein the polymer is an acrylic resin. 6. The liquid crystal display device according to claim 5, wherein the acrylic resin is polymethyl methacrylate. 7. The liquid crystal display device according to claim 1, wherein a weight ratio of the polymer to the liquid crystal in the composition is in a range of 1:10 to 10: 1. 8. The liquid crystal display device according to claim 7, wherein the weight ratio of the polymer to the liquid crystal in the composition is in the range of 1: 2 to 3: 1. 9. The liquid crystal display device according to claim 8, wherein the weight ratio of the polymer to the liquid crystal in the composition is 1: 1. 10. The liquid crystal display device according to claim 1, further comprising a heat conducting member provided below the polymer dispersed liquid crystal layer. 11. The liquid crystal display device according to claim 10, wherein the heat conductive member includes a plurality of members having different heat conductivity. 12. The liquid crystal display device according to claim 10, wherein at least one or more through openings exist on the surface of the heat conducting member. 13. The liquid crystal display according to claim 10, wherein the heat conducting member has a lattice shape. 14. The liquid crystal display device according to claim 1, wherein the liquid crystal display device has a matrix structure. 15. The liquid crystal display device according to claim 14, wherein a heat radiation member is disposed between the segments in the matrix structure. 16. The liquid crystal display device according to claim 1, further comprising means for changing a pulse width of a DC voltage applied to said heating element. 17. A temperature measuring means for measuring a temperature of the polymer dispersed liquid crystal layer, wherein temperature data obtained by the temperature measuring means changes a pulse width of a DC voltage applied to the heating element. 17. The liquid crystal display device according to claim 16, wherein the liquid crystal display device is supplied to a means for performing the operation. 18. Under the polymer-dispersed liquid crystal layer,
2. The liquid crystal display device according to claim 1, further comprising a colored background plate having a color different from the color of the polymer dispersed liquid crystal layer. 19. The method according to claim 2, wherein a color paint having a color different from the color of the polymer dispersed liquid crystal layer is applied to the surface of the electrode below the polymer dispersed liquid crystal layer. Liquid crystal display. 20. The liquid crystal display device according to claim 2, wherein a plurality of protrusions are provided on the surface of the electrode below the polymer dispersed liquid crystal layer. 21. The liquid crystal display device according to claim 3, wherein the polymer-dispersed liquid crystal layer is directly disposed on a heating element having a uniform thickness. 22. The polymer-dispersed liquid crystal layer is directly disposed on a heating element whose thickness gradually decreases or increases from one end to the other end, and is connected to both ends of the heating element. 4. The liquid crystal display device according to claim 3, wherein the power supply circuit coupled to the pair of electrodes includes a variable resistor. 23. The heating element comprises a plurality of heating elements having different resistance values, and a power supply circuit coupled to a pair of electrodes connected to both ends of the heating element has a variable resistor. The liquid crystal display device according to claim 2, wherein 24. The liquid crystal display device according to claim 1, wherein the heating element is a sheet formed by etching a conductive metal on a plastic sheet in a continuous wave shape. 25. The liquid crystal display device according to claim 1, wherein the polymer dispersed liquid crystal layer is formed by stacking a plurality of polymer dispersed liquid crystal films. 26. The liquid crystal display device according to claim 25, wherein the polymer dispersed liquid crystal layer is formed by stacking two or more polymer dispersed liquid crystal films of the same type. 27. The liquid crystal display device according to claim 25, wherein the polymer dispersed liquid crystal layer is formed by laminating two or more different types of polymer dispersed liquid crystal films. 28. (a) preparing a substrate; (b) arranging a coating device filled with a liquid crystal composition comprising a liquid crystal, a polymer, and a solvent near one end of the substrate; c) forming a coating film of a liquid crystal composition on the substrate surface by moving the coating device on the substrate surface toward the other end of the substrate; (d) the liquid crystal composition Forming a polymer-dispersed liquid crystal film on the substrate surface by drying the coating film; and (e) repeating the steps (a) to (d) to form a polymer-dispersed liquid crystal film on another substrate surface. Forming a film, (f) superimposing the polymer dispersed liquid crystal film obtained in the step (d) on the upper surface of the polymer dispersed liquid crystal film obtained in the above (e), and heating the substrates on both sides. Pressure while pressing the two liquid crystal films to each other. And (g) forming a laminated polymer dispersed liquid crystal layer on the other substrate by peeling off one substrate;
A method for producing a polymer liquid crystal layer having a laminated structure, comprising: