JP2000066177A - Method for evaluating light absorption of polymer dispersed liquid crystal, liquid crystal display device and liquid crystal projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a liquid crystal display device with excellent light resistance and color purity. SOLUTION: A liquid crystal display device is produced by holding polymer dispersed liquid crystal with >= 400 nm and <= 430 nm light absorption edge between a pair of upper and lower liquid crystal supporting substrates 11, 12 having transparent electrode layers 13 via a spacer 15 which is at the same time sealant resin. Also the liquid crystal display device is provided with a light cut filter 18 which can shield a light included in a light absorption region of the polymer dispersed liquid crystal and whose cut wavelength range is <=430 nm at the longest.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device using a polymer dispersed liquid crystal in which a liquid crystal is dispersed and held in a polymer matrix, a liquid crystal projector using the same, and an optical absorption evaluation of the polymer dispersed liquid crystal. And a liquid crystal display device and a liquid crystal projector.

[0002]

2. Description of the Related Art In recent years, a polymer dispersion type liquid crystal in which a nematic liquid crystal is dispersed and held in a polymer having the same refractive index as that of liquid crystal molecules is sandwiched between a pair of upper and lower substrates having electrodes. A liquid crystal display device that changes the refractive index of the liquid crystal to switch between a scattering state and a transmission state has attracted much research and developers' attention (Japanese Patent Application Laid-Open No. 60-252).
687).

FIG. 2 is a schematic view showing the display principle of the liquid crystal display device. When no voltage is applied ((a) in the figure), the refractive index of the liquid crystal region is different from the refractive index of the surrounding polymer phase 25 because the molecular axis of the liquid crystal 24 is oriented in a random direction.
The incident light 22 entering the liquid crystal optical element becomes scattered light 23,
As a result, a scattering state is obtained. On the other hand, the transparent electrode layer 21
When an electric field is applied to the liquid crystal (FIG. 1B), the molecular axes of the liquid crystal 24 are arranged in the direction of the electric field, and the refractive index of the liquid crystal region for the light perpendicularly incident on the substrate is changed to the surrounding polymer phase Since the refractive index substantially coincides with the refractive index of 25, the light is not scattered and becomes the transmitted light 26. As a result, a transmission state is obtained.

The liquid crystal display device using the polymer-dispersed liquid crystal utilizes light scattering, so that it is not necessary to use a polarizing plate. Unlike a conventional twisted nematic (TN) liquid crystal display device, In order to obtain linearly polarized light, it is brighter than a liquid crystal optical element that must use a polarizing plate,
Display with a wide viewing angle becomes possible. Further, the conventional TN type liquid crystal optical element has a problem that it is necessary to accurately control the alignment treatment and the distance between the upper and lower substrates, and display of a large area tends to cause display unevenness.

On the other hand, a liquid crystal display device using a polymer-dispersed liquid crystal has the advantage that alignment treatment is not required, the distance between substrates is not strictly controlled, and a large-area liquid crystal display device can be easily manufactured. .

[0006] Emulsifying methods, casting methods, phase separation methods, and the like have been proposed as methods for producing polymer-dispersed liquid crystals. Among them, the phase separation method using light is particularly effective in terms of mass productivity and productivity. It is considered to be excellent and has become mainstream. This includes a step of polymerizing the polymerizable material by irradiating light to a composition of a polymerizable material including a monomer, an oligomer, and a polymerization initiator and a liquid crystal material.

[0007]

However, a liquid crystal display device using a polymer-dispersed liquid crystal has a problem in light resistance reliability. It is considered that the polymerization initiator remaining in the polymer-dispersed liquid crystal after the completion of a series of polymerization steps is a main factor affecting light fastness reliability. In other words, the remaining polymerization initiator absorbs light incident on the liquid crystal display element, thereby generating an active radical species, which triggers the decomposition of the liquid crystal material and causes the liquid crystal / polymer to be decomposed. This causes a change in the interfacial regulating force acting on the liquid crystal display, which degrades the performance of the liquid crystal display element. Specifically, phenomena such as a decrease in voltage holding ratio, a decrease in scattering performance, and a change in driving voltage occur.

From the above, it can be considered that in order to improve the light resistance of a liquid crystal display device using a polymer-dispersed liquid crystal, it is important to suppress the light absorption of a residual polymerization initiator that triggers light degradation. However, it is not easy to obtain information on the light absorption of the polymer-dispersed liquid crystal and the liquid crystal material therein, and there has never been a precedent specifically mentioning the light absorption of those materials.

An object of the present invention has been made in view of the above problems, and firstly, to provide a means for accurately measuring light absorption of a material which affects light fastness, and secondly, to provide a means for accurately measuring light absorption of a material which affects light fastness. An object of the present invention is to realize a polymer-dispersed liquid crystal display device and a liquid crystal projector having high contrast, excellent light resistance and excellent color purity.

[0010]

The method for evaluating the light absorption of a polymer-dispersed liquid crystal according to the present invention comprises measuring an absorption spectrum while applying a constant voltage to a liquid crystal display device using the polymer-dispersed liquid crystal. The light absorption evaluation method is characterized by the following.

Further, the method for evaluating the light absorption of a liquid crystal material in a polymer-dispersed liquid crystal according to the present invention is characterized in that the liquid crystal in the polymer-dispersed liquid crystal is extracted with a solvent and the absorption spectrum of the extracted solvent is measured. This is a light absorption evaluation method.

The liquid crystal display device and the liquid crystal projector of the present invention use a polymer dispersed liquid crystal or a polymer dispersed liquid crystal in which the absorption edge of light absorption of the liquid crystal material in the liquid crystal material is 400 nm or more and 430 nm or less. A liquid crystal display device and a liquid crystal projector having a light cut filter that simultaneously shields light in a light absorption region of the above-mentioned material and has a cut wavelength range not exceeding 430 nm.

[0013]

Embodiments of the present invention will be described below.

The polymer-dispersed liquid crystal display device of this embodiment has a structure in which liquid crystals are dispersed in a polymer compound in a droplet form.
Any structure in which liquid crystals are continuously connected and dispersed in the polymer compound may be used.

FIG. 1 is a sectional view schematically showing the structure of a specific example of a liquid crystal display device manufactured using the polymer dispersed liquid crystal of the present invention.

In FIG. 1, a pair of substrates 11 and 12 each having a transparent electrode layer 13 made of indium / tin oxide formed on each surface face each other at a predetermined interval. And the opposing transparent electrode layer 1
Between them, a polymer dispersed liquid crystal in which a liquid crystal 17 is dispersed and held in a polymer matrix 16 is arranged. The opposing transparent electrode layers 13 are bonded together by the spacer / seal resin 15, and the polymer dispersed liquid crystal is sealed. A light cut filter 18 is mounted on both substrates. FIG. 2 is a schematic diagram showing the display principle of a liquid crystal optical element using a polymer dispersed liquid crystal.

FIG. 6 is a graph showing the results of measuring the absorption spectrum of a polymer-dispersed liquid crystal while applying a voltage to the liquid crystal display device according to one embodiment of the present invention.

FIG. 6 shows that the absorbance of the polymer-dispersed liquid crystal becomes clear since the absorbance approaches 0 when the voltage exceeds a certain value. Some experiments were conducted on the voltage V applied to the liquid crystal display element when measuring the absorption spectrum, and as a result, the dielectric anisotropy Δε of the liquid crystal material used for the polymer dispersed liquid crystal was positive (Δε> 0). When the material satisfies the above condition, the voltage V applied to the liquid crystal display element is such that the light transmittance when no voltage is applied to the liquid crystal display element is T0, the maximum light transmittance is Tmax, and the light transmittance of the liquid crystal display element is T0. And Tma
When the light transmittance when satisfying the relationship of x and (Equation 1) is Tx, and the voltage at which the light transmittance of the liquid crystal display element is Tx is Vx,
It has been found that the voltage needs to satisfy the relationship between Vx and (Equation 2). At a voltage lower than that, the scattering of the polymer-dispersed liquid crystal is reflected in the spectrum, so that accurate absorption information cannot be obtained.

When the dielectric anisotropy Δε of the liquid crystal material is negative (Δε <0), the voltage V ′ applied to the liquid crystal display element when measuring the absorption spectrum measures the absorption spectrum. In this case, the voltage applied to the liquid crystal display element is such that the light transmittance of the liquid crystal display element when no voltage is applied is T0, the minimum light transmittance is Tmin, and the light transmittance of the liquid crystal display element is T0 and Tmi.
The light transmittance when satisfying the relationship of n and (Equation 6) is defined as Tx ′,
Assuming that the voltage at which the light transmittance of the liquid crystal display element becomes Tx 'is Vx', it was found that a voltage satisfying the relationship of Vx 'and (Equation 4) was necessary. At a higher voltage, the scattering of the polymer-dispersed liquid crystal is reflected in the spectrum, so that accurate absorption information cannot be obtained.

From the above, according to the present embodiment, the liquid crystal display device can measure the absorption spectrum while applying a voltage to the liquid crystal display device without scattering light.
Since the transmissive state is obtained, the light absorption of the polymer-dispersed liquid crystal can be accurately measured.

On the other hand, the light absorption of the liquid crystal material in the polymer dispersed liquid crystal can be evaluated by immersing the polymer dispersed liquid crystal in a solvent and measuring the absorption spectrum of the extracted solution.

FIG. 7 is a graph showing the results of measuring the absorption spectrum of a liquid crystal material in a polymer dispersed liquid crystal extracted with a solvent from a liquid crystal display device according to one embodiment of the present invention.

According to FIG. 7, since the absorbance is close to 0, the light absorption of the liquid crystal material can be determined. The solvent is not particularly limited, but is preferably an organic material having light absorption only in a short wavelength region.

Further, according to the present embodiment, a liquid crystal display element and a liquid crystal projector having high contrast, excellent light resistance reliability and excellent color purity can be realized. In other words, the contrast of the liquid crystal display device using the polymer dispersed liquid crystal depends on the scattering performance of the polymer dispersed liquid crystal according to the display principle described above. It depends on the refractive index anisotropy (Δn) of the material. The larger the value of Δn, the greater the scattering property, so that the contrast of the liquid crystal display element is improved. This Δn shows a good correlation with the light absorption of the liquid crystal material. In general, as Δn increases, the absorption edge tends to shift to the longer wavelength side. When the absorption edge is 400 nm or more, a sufficient contrast can be obtained. On the other hand, as described above, the absorption of the liquid crystal material is limited due to the light resistance, but the deterioration of the material is reduced by providing an optical cut filter capable of reducing the absorption to 430 nm or less and blocking the light absorption of the material. As a result, deterioration of element performance such as reduction in voltage holding ratio and drive voltage fluctuation does not occur, and light resistance of the liquid crystal display element is greatly improved. As a light cut filter used to suppress the absorption of the material, a type that transmits light of 430 nm or more can be used, so that the color purity including blue does not decrease. The relationship between the cut wavelength and the blue color purity is clear from the chromaticity diagram shown in FIG. FIG. 3 is a diagram showing a calculation result of a change in blue chromaticity when a mercury lamp is used as a light source and the transmittance of the cut filter is assumed as shown in FIG.

FIG. 3 shows that cutting off light of 430 nm or more lowers the blue color purity. From the above, a material having an absorption edge of 400 nm or more and 430 nm or less is used for the polymer-dispersed liquid crystal or the liquid crystal material therein,
In addition, a liquid crystal display element and a liquid crystal projector with high contrast, light fastness, and excellent color purity are realized by providing a light cut filter that does not cause a decrease in color purity, that is, has a cut wavelength range not exceeding 430 nm at the longest. Will be possible.

The light fastness of the liquid crystal display element was evaluated using the voltage holding ratio as an index in the present embodiment.

FIG. 9 is a schematic diagram showing an example of the voltage holding ratio of the liquid crystal display element. The voltage holding ratio is evaluated using the degree of voltage holding when an AC electric field having a pulse width of 60 μs, an amplitude of ± 5 volts, and a frequency of 60 Hz is applied to the liquid crystal optical element as an index. In FIG. 9, (a) is an applied waveform,
(B) is a waveform showing the state of the voltage drop of the element. Further, a value calculated from the ratio of the area A to the area B is defined as a voltage holding ratio as shown in (Formula 7), and is used as an index of charge holding. The better the charge retention, the smaller the voltage drop,
Therefore, the area B becomes large and a high voltage holding ratio is exhibited.

[0028]

(Equation 7)

Incidentally, the evaluation of the color purity of blue was evaluated by making a prototype of a liquid crystal projector having a projection optical system (Schlieren optical system) shown in FIG.

In FIG. 8, reference numeral 81 denotes a light source composed of a metal halide lamp, 82 denotes a liquid crystal display element of the present invention, 83 denotes a condenser lens, 84 denotes an aperture, 85 denotes a projection lens, 86 denotes a screen, and 87 denotes a blue filter.

[0031]

The present invention will be described below in more detail with reference to examples.

(Example 1) Two sheets of glass on which a transparent electrode made of indium / tin oxide was formed were prepared, and as shown in FIG. 4, one of the support plates (for example, the lower substrate 42) was used as a spacer. An acid anhydride-curable epoxy resin in which glass fiber having a diameter of 9 μm is dispersed is used as the sealing resin 43. Only one side of the four sides is left with 3 mm as the opening 44. The substrate 42 was pressed in a state where the substrate 42 was opposed to the substrate 42 and heated at 140 ° C. for 4 hours to cure and bond, thereby completing an empty cell.

Next, TL205 (Merck) was used as a liquid crystal material.
8.200 grams, 1.409 grams of 2-ethylhexyl acrylate (manufactured by Nacalai Tesque, Inc.) as a polymer-forming monomer, and HX as an oligomer
620 (manufactured by Nippon Kayaku Co., Ltd.) and 0.38 g of Irgacure 651 (manufactured by Cibagaiki Co., Ltd.) as a photopolymerization initiator were prepared, and the respective materials were added to form a polymerizable composition 45. did.

Next, after the polymerizable composition 45 is sufficiently stirred at 23 ° C., the opening 44 is placed in the empty cell at 23 ° C.
After sealing the opening, polymerization was performed at 23 ° C. using a high-pressure mercury lamp as a light source to complete a liquid crystal display device composed of a polymer-dispersed liquid crystal. At this time, a light cut filter (manufactured by Toshiba Color Glass Co., Ltd .: UV35) was placed on the light irradiation surface for polymerization. The intensity of ultraviolet light was about 40 mW / cm ² , and the irradiation time was 60 seconds.

The results of measuring the voltage-transmittance characteristics of the liquid crystal display device thus completed are shown in Table 1.

[0036]

[Table 1]

Calculating from Table 1, the voltage V in (Equation 2) is about 4.1 volts. This liquid crystal display element
The absorption spectrum of the polymer-dispersed liquid crystal was measured by applying a voltage of 0 volt, and it was found that the liquid crystal had absorption having an absorption edge of 400 nm. The voltage-transmittance characteristics were measured using an evaluation device LCD500 manufactured by Otsuka Electronics Co., Ltd.

Subsequently, in order to suppress the absorption of the material, FIG.
A light cut filter having a transmittance characteristic shown in FIG. 0 (Toshiba Color Glass Co., Ltd .: Y43, cuts a wavelength of 400 nm or less) is attached to both surfaces of the liquid crystal display element, and a light resistance test is performed using a metal halide lamp as a light source. Was.

The results showing the change in the voltage holding ratio of the liquid crystal display element are shown in Table 2, but there was no decrease in the voltage holding ratio, and the light resistance was extremely good.

[0040]

[Table 2]

Further, a blue filter was added to the above-mentioned liquid crystal display element, and it was incorporated into a projection optical system having the structure shown in FIG. 8 to evaluate color misregistration. The display showed a bright blue color.

(Example 2) A liquid crystal material was made into a ZLI having a negative Δε.
A liquid crystal display device was manufactured in the same manner as described in Example 1 except that 4788 (manufactured by Merck Ltd.) was used.

The liquid crystal display device thus completed (Equation 4)
Was 5.8 volts. When a voltage of 2 volts was applied to the liquid crystal display element and the absorption spectrum of the polymer-dispersed liquid crystal was measured, it was found that the liquid crystal display element had an absorption edge of 400 nm.

Subsequently, a light cut filter (Y43, manufactured by Toshiba Color Glass Co., Ltd., which cuts a wavelength of 400 nm or less) was attached to both surfaces of the liquid crystal display device, and a light resistance test was performed using a metal halide lamp as a light source. The results showing the change in the voltage holding ratio of the liquid crystal display element are shown in (Table 2), but there was no decrease in the voltage holding ratio, and the light resistance was good.

Further, a blue filter was added to the above-mentioned liquid crystal display element, and it was incorporated in a projection optical system having the structure shown in FIG. 8 to evaluate color misregistration. The display showed a bright blue color.

Example 3 Two sets of empty cells prepared by the same method as described in Example 1 were prepared (one set was used for light resistance test and color shift evaluation, and one set was used for absorption spectrum evaluation). ), PNM201 (produced by Roddick Co., Ltd.) was injected through the opening as a material for a polymer-dispersed liquid crystal, and the opening was sealed. Then, polymerization was performed at 20 ° C. using a high-pressure mercury lamp as a light source. At this time, a light cut filter (UV39, manufactured by Toshiba Color Glass Co., Ltd.) was arranged on the light irradiation surface. The intensity of the ultraviolet light was about 20 mW / cm ² , and the irradiation time was 60 seconds.

After the sample for evaluating the absorption spectrum was immersed in ethanol overnight, the absorption spectrum of this ethanol solution was measured to determine the absorption of the liquid crystal material. As a result, it was found that the liquid crystal material had an absorption edge of 400 nm. Was.

Subsequently, a light cut filter (Y43, manufactured by Toshiba Color Glass Co., Ltd., which cuts a wavelength of 400 nm or less) was attached to both surfaces of the liquid crystal display device, and a light resistance test was performed using a metal halide lamp as a light source. The results showing the change in the voltage holding ratio of the liquid crystal display element are shown in (Table 2), and there was no decrease in the voltage holding ratio and the light resistance was excellent.

Further, a blue filter was added to the above-mentioned liquid crystal display element, and it was incorporated into a projection optical system having the structure shown in FIG. 8 to evaluate the color misregistration.

(Comparative Example 1) Light cut filters (Y46, manufactured by Toshiba Color Glass Co., Ltd .: cut at a wavelength of not more than 435 nm) were attached to both sides of a liquid crystal display device produced under the polymerization conditions with the materials described in Example 1. Was evaluated for light resistance and color shift. It was found that there was no decrease in the voltage holding ratio and the light fastness was improved, but the blue color tone was greenish.

Comparative Example 2 Only the liquid crystal material was MT5536
(Manufactured by Chisso Corporation), and a liquid crystal display element was prepared by the same method as described in Example 1. Evaluation of light absorption and light resistance test of the polymer-dispersed liquid crystal were performed under the same conditions as described in Example 1. And evaluation of color shift. It was found that the absorption edge of this polymer-dispersed liquid crystal had its absorption edge extended to 430 nm. The change in the voltage holding ratio of the liquid crystal display device is shown in (Table 2). It was found that the voltage holding ratio of this liquid crystal display device was remarkably reduced and light resistance was poor. However, the color tone was bright blue.

(Comparative Example 3) A liquid crystal material was MT5536 (manufactured by Chisso Corporation), and a light cut filter provided on a liquid crystal display element was manufactured (Y46,435n manufactured by Toshiba Color Glass Co., Ltd.).
m), a liquid crystal display device was prepared in the same manner as described in Example 1, except that the wavelength was changed to less than m, and the light absorption of the polymer-dispersed liquid crystal was evaluated under the same conditions as described in Example 1. The light resistance test and the evaluation of color shift were performed. It was found that the absorption edge of this polymer-dispersed liquid crystal had its absorption edge extended to 430 nm. The change in the voltage holding ratio of the liquid crystal display device is shown in (Table 2). The voltage holding ratio of the liquid crystal display device was stable without lowering, and the light resistance was good.
The blue hue was slightly greenish.

Comparative Example 4 A liquid crystal display device was prepared in the same manner as described in Example 3 except that only the cut filter used in the polymerization was changed to UV35 (manufactured by Toshiba Color Glass Co., Ltd.).
Evaluation of light absorption, light resistance test, and color shift of the liquid crystal material in the polymer-dispersed liquid crystal were performed under the same conditions as described in (1).
It was found that the absorption edge of this polymer-dispersed liquid crystal extended to 450 nm at the absorption edge. The change in the voltage holding ratio of the liquid crystal display device is shown in (Table 2). It was found that the voltage holding ratio of this liquid crystal display device was significantly reduced and the light resistance was extremely poor. However, the color tone was bright blue.

(Comparative Example 5) A liquid crystal display device was produced in the same manner as described in Example 3, except that only the cut filter used in the polymerization was changed to UV35 (manufactured by Toshiba Color Glass Co., Ltd.). When the light absorption of the liquid crystal material in the polymer dispersed liquid crystal was evaluated by the same method as described in Example 3, the absorption edge was 450 nm.
It turned out to be extended. Subsequently, light cut filters (Y4 made by Toshiba Color Glass Co., Ltd.) are provided on both sides of the liquid crystal display element.
(Cutting a wavelength of 8,455 nm or less), and the same light resistance test and evaluation of color shift were performed. The change in the voltage holding ratio of the liquid crystal display element is shown in (Table 2). Although the voltage holding ratio did not decrease and the light resistance was good, the blue color tone was greenish.

Tables 3 and 4 show the relationship between the absorption of the materials described in the examples and comparative examples, the cut wavelength of the light cut filter, the light fastness of the liquid crystal display element, and the blue color tone. The results are summarized in a table.

[0056]

[Table 3]

[0057]

[Table 4]

The liquid crystal material, monomer, oligomer, and polymerization initiator used for the polymer-dispersed liquid crystal are not limited to those described in the above Examples, and widely commercially available materials can be applied. .

The polymer-dispersed liquid crystal is a type of a structure in which liquid crystal droplets are dispersed and held in a polymer matrix;
The present invention can be applied to any type of 2) a type of structure in which liquid crystal is held in a three-dimensional network polymer compound, and 3) a type of structure in which liquid crystal is surrounded by a polymer wall and both substrates.

Further, in this embodiment, the light cut filter is provided on both sides of the substrate.

[0061]

As described above, according to the present invention, an absorption spectrum is measured while applying a constant voltage to a liquid crystal display device using a polymer-dispersed liquid crystal.
By immersing the polymer-dispersed liquid crystal in a solvent and measuring the absorption spectrum of the extract, the light absorption of the polymer-dispersed liquid crystal and the liquid crystal material therein can be accurately evaluated.

The polymer-dispersed liquid crystal has an absorption edge of 400 nm or more and 430 nm in itself or a liquid crystal material contained therein.
A liquid crystal display element having excellent light resistance reliability and color purity by using the following, and having a light cut filter that blocks light in the light absorption region of the above-mentioned material and has a cut wavelength range not exceeding 430 nm. And a liquid crystal projector becomes feasible.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a liquid crystal display device manufactured using a polymer-dispersed liquid crystal of the present invention.

FIG. 2 is a schematic diagram showing a display principle of a liquid crystal display element manufactured using a polymer dispersed liquid crystal.

FIG. 3 is a diagram showing a relationship between a cut filter and blue color purity;

FIG. 4 is a perspective view showing a state of a manufacturing process of a liquid crystal display device using the polymer dispersed liquid crystal of the present invention.

FIG. 5 is a characteristic diagram showing transmittance of a light cut filter.

FIG. 6 is a characteristic diagram showing a light absorption spectrum of a polymer-dispersed liquid crystal measured using the evaluation method of this example.

FIG. 7 is a characteristic diagram showing a light absorption spectrum of a liquid crystal material in a polymer dispersed liquid crystal measured using the evaluation method of this example.

FIG. 8 is a conceptual diagram showing a configuration of a liquid crystal projector.

FIG. 9 is a schematic diagram showing a method for evaluating a voltage holding ratio of a liquid crystal display element.

FIG. 10 is a characteristic diagram showing light transmittance of a light cut filter.

[Explanation of symbols]

 11, 41 Upper substrate 12, 42 Lower substrate 13, 21 Transparent electrode layer 15, 43 Spacer / seal resin 16 Polymer matrix 17, 24 Liquid crystal 18 Optical cut filter 22 Incident light 23 Scattered light 25 Polymer phase 26 Transmitted light 44 Opening 45 Polymerizable composition 81 Light source 82 Liquid crystal display element 83 Condensing lens 84 Aperture 85 Projection lens 86 Screen 87 Blue filter

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G059 AA02 AA05 BB15 BB20 CC20 DD03 DD05 EE01 HH02 JJ03 JJ18 2H088 EA12 FA11 GA10 HA11 JA04 KA04 KA26 KA27 MA20 2H089 HA04 LA08 LA15 MA04Y NA24 NA45 QA05 QA16 SA05 SA05

Claims (12)

[Claims] An absorption spectrum of a polymer-dispersed liquid crystal is measured while a constant voltage is applied to a liquid crystal display device in which the polymer-dispersed liquid crystal is sandwiched between a pair of substrates having electrodes. Of light absorption of polymer dispersed liquid crystal. 2. A material in which the dielectric anisotropy Δε of a liquid crystal material used for a polymer dispersed liquid crystal satisfies the condition of (Equation 3),
The light transmittance of the liquid crystal display element when no voltage is applied is T0, the maximum light transmittance is Tmax, and the light transmittance of the liquid crystal display element when the light transmittance satisfies the relationship of (Equation 1) with T0 and Tmax is Tx. When the voltage at which the light transmittance of the liquid crystal display element becomes Tx is Vx, the voltage V applied to the liquid crystal display element when measuring the absorption spectrum is a voltage satisfying the relationship of Vx and (Equation 2). The method for evaluating light absorption of a polymer-dispersed liquid crystal according to claim 1, wherein: (Equation 1) (Equation 2) (Equation 3) 3. A material in which the dielectric anisotropy Δε of a liquid crystal material used for a polymer dispersed liquid crystal satisfies the condition of (Equation 5),
The light transmittance of the liquid crystal display element when no voltage is applied is T0, the minimum light transmittance is Tmin, and the light transmittance of the liquid crystal display element when the light transmittance satisfies the relationship of (Equation 6) with T0 and Tmin is Tx. And the voltage at which the light transmittance of the liquid crystal display element becomes Tx 'is Vx'
2. The polymer dispersion type according to claim 1, wherein the voltage V 'applied to the liquid crystal display element when measuring the absorption spectrum is a voltage satisfying the relationship of Vx' and (Equation 4). Liquid crystal light absorption evaluation method. (Equation 4) (Equation 5) (Equation 6) 4. The method according to claim 1, wherein the electrode is made of a transparent material. 5. The method according to claim 1, wherein the liquid crystal material in the polymer-dispersed liquid crystal is extracted into the solvent by immersing the polymer-dispersed liquid crystal in an organic solvent, and the absorption spectrum of the extract is measured. Method for evaluating light absorption of liquid crystal material in polymer dispersed liquid crystal. 6. A liquid crystal display device in which a polymer-dispersed liquid crystal is sandwiched between substrates having electrodes, wherein the absorption end of light absorption of the polymer-dispersed liquid crystal is 400 nm or more and 430 nm or less. Liquid crystal display element. 7. The liquid crystal display device according to claim 6, wherein an absorption edge of light absorption of the liquid crystal material in the polymer dispersed liquid crystal is 400 nm or more and 430 nm or less. 8. A light-blocking means for blocking light in a light-absorbing region of a polymer-dispersed liquid crystal or a liquid crystal material in the polymer-dispersed liquid crystal and having a wavelength range of 430 nm or less for blocking light. The liquid crystal display device according to claim 6 or 7, wherein 9. The liquid crystal display device according to claim 8, wherein the light shielding means is a light cut filter. 10. A polymer-dispersed liquid crystal has the following structure: 1) a structure in which liquid crystal droplets are dispersed and held in a polymer matrix; 2) a structure in which liquid crystal is held in a three-dimensional network polymer compound; The method for evaluating light absorption of a polymer-dispersed liquid crystal according to claim 1, wherein the method is one of a structure surrounded by a molecular wall and both substrates. 11. A polymer-dispersed liquid crystal has the following structure: 1) a structure in which liquid crystal droplets are dispersed and held in a polymer matrix; 2) a structure in which liquid crystal is held in a three-dimensional network polymer compound; 8. The liquid crystal display device according to claim 6, wherein the liquid crystal display device has one of a structure surrounded by a molecular wall and both substrates. 12. A liquid crystal projector using the liquid crystal display device according to claim 6.