JPH07199233A - Liquid crystal element and display using the element - Google Patents

Abstract

PURPOSE:To obtain a liq. crystal display element capable of forming a bright picture without need for a polarizing plate and with the white blurring of the White-Taylor type liq. crystal device improved. CONSTITUTION:A liq. crystal mixture contg. a chiral nematic liq. crystal material 1 and a dichroic pigment 2 is held between the two substrates 3 having a transparent electrode layer 4 to constitute a guest-host liq. crystal display element. The two substrates 3 are not provided with a means capable of orienting the chiral nematic liq. crystal material and dichroic pigment in a definite direction when a voltage is not impressed. The chiral nematic liq. crystal contains a compd. having a functional group shown by the formula (where R<1> is 1-10C straight-chain alkyls, and (n) is an integer of 1 to 5), and the intrinsic pitch is 2-6mum.

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 capable of achieving bright and high contrast, which can block or open a visual field and limit or block transmission of light or illumination light by electrical operation. Yes, liquid crystal display elements used as dimming glass for windows, thinning windows, show windows, screens, stages for observing optical equipment, or to display characters and figures, decorative display boards such as notice boards, and bright screens are required. The present invention relates to a liquid crystal display device used for projection or the like in combination with a clock, a calculator, a computer terminal, or an active matrix system, and more particularly to an improvement of a liquid crystal display device using a white-tailor type guest-host effect.

[0002]

2. Description of the Related Art Liquid crystal display devices that are currently in widespread use are mainly TN (twisted nematic) type devices using nematic liquid crystals and STN (super twisted nematic) type devices. Although some of these liquid crystal display devices have different driving methods depending on their use,
The structure is such that a polarizing plate is arranged on one surface of a transparent substrate, and two substrates each having an electrode layer and an alignment layer formed on the other surface are arranged so that the alignment layers face each other, and a liquid crystal is placed between the substrates. They are the same in that a liquid crystal mixture containing a chiral agent, a dichroic dye, and the like is sandwiched between the materials and, if necessary.

Since these liquid crystal display devices require a polarizing plate and have a low light utilization rate, there is a limit in obtaining a bright display. To improve this, a means for installing a backlight or the like on the back surface is used, but there is a problem that the characteristic of the liquid crystal display element that can be driven at a low voltage is impaired and the driving voltage rises. Moreover, a liquid crystal material having excellent heat resistance and light resistance must be used.

A white Taylor type guest-host liquid crystal display device (USP 3,833,287) is known as a typical technique for eliminating the need for a polarizing plate in a liquid crystal display device. Further, JP-B-62-13511, JP-B-63-32162, and JP-A-57-84437.
JP-A-57-141478, JP-A-59
Similarly, Japanese Patent Publication No. 69734 describes a technique that does not require a polarizing plate.

[0005]

The above-mentioned white-tailor type guest-host liquid crystal display device is an excellent display system having the features of no polarizing plate (bright, low cost), wide viewing angle and high contrast. .

However, in the white-tailor type guest-host liquid crystal display element, there is a phenomenon that when the voltage is turned off from the voltage applied state, the liquid crystal material transits to a cloudy state and then returns to a normal colored stable state. Occur. This cloudiness state storage time depends on the alignment treatment on the substrate.When the horizontal alignment treatment by rubbing is performed, the cloudiness state storage time is about several minutes to several tens of minutes, but the vertical alignment treatment by silane or the like is performed. If applied, it will be reduced to about a few seconds,
This cloudy state cannot be completely removed.

Conventionally, the pretilt angle formed by the alignment treatment has been approximately 0 ° (horizontal alignment) or 90 ° (vertical alignment). Furthermore, by applying this, the above-mentioned Japanese Patent Publication Sho 6
No. 3,32,162 discloses a pretilt angle of 0 ° to 90 °.
A technique for improving the above-mentioned white turbidity phenomenon by controlling the angle between 0 ° is described.

As described above, the conventional white-tailor type guest-host liquid crystal display device has a problem that the white turbidity phenomenon appears, and the pretilt angle of liquid crystal molecules is changed by the alignment film to solve this problem. Various attempts have been made, but there was a limit to the improvement.

Generally, the alignment film is formed by depositing an organic alignment agent in the case of parallel alignment or vertical alignment, but in the case of tilted alignment, it is formed by obliquely depositing and then depositing the organic alignment agent. I often do it. For vertically aligned structures,
There are methods such as vapor deposition of SiO and the like, application of a surfactant such as a silane coupling agent, and the like. S as a parallel alignment structure
The rubbing method is standard, such as oblique vapor deposition of iO or the like, or coating of a polymer film of polyimide or the like and rubbing it in one direction with fibers such as nylon or polyester. In these cases, in order to generate and control the pretilt, the evaporation angle is changed by the oblique evaporation method, and the polymer having a hydrocarbon side chain is applied by the rubbing method, and the rubbing strength is increased. Measures such as selecting the appropriateness are taken.

However, there has been a problem that no matter how the alignment treatment is performed, it cannot be improved. That is, in order to form the alignment film on the substrate, liquid crystal molecules are arranged by rubbing the surface of the alignment film on the substrate in a certain direction under a load using a cloth as described above, so that a clean surface is obtained. During the manufacturing of a liquid crystal display device, which has many steps, a dusting step of rubbing with a fiber causes a reduction in charge retention rate due to dust, fluff, and dirt, and a phenomenon of burn-in, which causes a serious deterioration in quality. In order to avoid this problem, the alignment surface must be cleaned by adding a substrate cleaning process after rubbing. In addition, there are problems such as defects and unevenness due to the alignment layer, and increase in current value.

Further, in the guest-host type liquid crystal display element, when the alignment layer for tilted alignment is formed, the dichroic dye used also becomes tilted due to the effect of the alignment film, so that the voltage which light originally should pass through. Even when the voltage is applied, the display is slightly colored with a dichroic dye, and therefore, when the background color of the liquid crystal display element is provided, there is a problem that the color loss of the background color becomes worse.

Accordingly, there has been a demand for a guest-host type liquid crystal display device capable of obtaining a high-contrast and vivid display without forming such an inconvenient alignment process and forming an alignment film which causes a reduction in yield.

The problem to be solved by the present invention is a guest-host type liquid crystal display device in which a polarizing plate and an alignment film are not present, and in particular, the white turbid state is improved and a display having a vivid hue is possible and a contrast is improved. An object of the present invention is to provide a guest-host type liquid crystal display device having excellent characteristics.

[0014]

In order to solve the above-mentioned problems, the present invention provides a method for providing a transparent electrode layer between two substrates,
In a guest-host type liquid crystal display device in which a liquid crystal mixture containing a chiral nematic liquid crystal material and a dichroic dye is sandwiched, the two substrates both contain the chiral nematic liquid crystal material and the dichroic dye when no voltage is applied. The substrate has no alignment means capable of aligning in a fixed direction, and the chiral nematic liquid crystal material is represented by the general formula (I).

[0015]

[Chemical 5]

(In the formula, R ¹ represents a linear alkyl group having 1 to 10 carbon atoms, and n represents an integer of 1 to 5.)
A liquid crystal display device is provided which is a chiral nematic liquid crystal material containing a compound having a functional group represented by and having an intrinsic pitch in the range of 2 to 6 μm.

Examples of the compound having a functional group represented by the general formula (I) according to the present invention include, for example, the general formula (I
I)-(V)

[0018]

[Chemical 6]

(In the formula, R ^2's each independently represent a linear alkyl group, alkenyl group or alkoxyl group having 1 to 10 carbon atoms, l represents 0 or 1 and m is 1
Represents an integer of 5 and R ¹ represents a linear alkyl group having 1 to 10 carbon atoms. ).

Here, typical examples of the compounds having a functional group represented by the general formula (I) used in the present invention and their phase transition temperatures are shown in Tables 1 to.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

[Table 4]

[0025]

[Table 5]

[0026]

[Table 6]

The first feature of the liquid crystal display device of the present invention is that the chiral nematic liquid crystal material used contains a compound having a functional group represented by the above general formula (I). By using the compound having a functional group represented by the general formula (I), the present inventors can achieve high contrast display in a white Taylor guest-host liquid crystal display and provide a color display with better visibility. I found what I could get.

That is, the chiral nematic liquid crystal material containing the compound having the functional group represented by the general formula (I) forms a high pretilt angle, and when the director of the liquid crystal molecule is observed by using a conoscopic image, It is oriented in the vertical direction on the interface of the substrate having no alignment means. As a result, in the liquid crystal display device of the present invention using a substrate having no alignment means, it is possible to reduce the occurrence of focal conic or disclination having a memory property and sufficiently reduce unnecessary scattering of incident light. To be

If the compound having a functional group represented by the general formula (I) is used, a compound having a functional group having a similar structure of the general formula (I), for example, a compound having an alkoxyl group as the functional group is used. In this case, the above effect becomes small and the pitch and the like need to be adjusted as described later.

In the chiral nematic liquid crystal material used in the present invention, the content of each compound having a functional group represented by the general formula (I) is preferably in the range of 3 to 20% by weight, and the total amount is 3%. It is preferably in the range of -60%.

The liquid crystal display device of the present invention comprises, in addition to the compound having a functional group represented by the above general formula (I),
Furthermore, general formulas (VI) to (XI)

[0032]

[Chemical 7]

(In the formula, R ^3's each independently represent a linear alkyl group, alkenyl group or alkoxyalkyl group having 1 to 10 carbon atoms, and R ^4's each independently have 1 to 10 carbon atoms. 10 represents a linear alkyl group or an alkoxyl group, R ⁵ represents a linear alkyl group having 1 to 10 carbon atoms, an alkoxyl group or an alkoxyalkyl group, and X ^1's each independently represent a hydrogen atom or fluorine. It is also possible to use a chiral nematic liquid crystal material containing a compound selected from the group consisting of compounds each representing an atom.

Table 2 and Table 2 show typical examples of the compounds represented by the general formulas (VI) to (XI) and their phase transition temperatures.

[0035]

[Table 7]

[0036]

[Table 8]

The liquid crystal display device of the present invention comprises, in addition to the compound having a functional group represented by the above general formula (I),
Furthermore, the general formula (XII)

[0038]

[Chemical 8]

(In the formula, R ⁶ represents a linear alkyl group having 1 to 10 carbon atoms, an alkenyl group or an alkoxyalkyl group, p represents 0 or 1, and Y ¹ and Z ¹ are each independently. , A single bond, —CH ₂ CH ₂ — or —COO—, and each of X ² and X ³ independently represents a hydrogen atom or a fluorine atom.) Is used as a chiral nematic liquid crystal material. You can also

Table 3 and Table 3 show typical examples of the compounds represented by the general formula (XII) and their phase transition temperatures.

[0041]

[Table 9]

[0042]

[Table 10]

Further, the liquid crystal display device of the present invention comprises, in addition to the compound having a functional group represented by the above general formula (I),
A chiral nematic liquid crystal material containing both a compound selected from the group consisting of the compounds represented by the general formulas (VI) to (XI) and a compound represented by the general formula (XII) can also be used.

The general formulas (VI) to (XI used here
Each compound represented by I) tends to maintain or maintain a high pretilt angle, and further tends to improve and adjust the temperature range of the chiral nematic liquid crystal phase, the driving voltage of the liquid crystal display device, and the like. In particular, the compound of the general formula (XII) is useful for improving the voltage holding ratio of the liquid crystal display element, and by using this compound, a liquid crystal material suitable for the active matrix driving system can be obtained.

In the chiral nematic liquid crystal material used in the present invention, the total content of the compounds represented by the general formulas (VI) to (XI) is preferably in the range of 0 to 60% by weight, and the general formula (XII) is used. It is preferable that the total content of the compounds represented by () is in the range of 0 to 60% by weight.

The superiority of the liquid crystal display device of the present invention is apparent from the following examples. A liquid crystal composition (No. 27) containing a compound having a functional group represented by formula (I),
For comparison, in the liquid crystal composition (No. 27), instead of the compound having the functional group represented by the general formula (I), a mixed liquid crystal using a compound having a similar structure and being widely used at present. (A) was prepared, and these were each enclosed between two substrates having no alignment means to prepare a liquid crystal display cell, and the director of liquid crystal molecules at the substrate interface was observed by a conoscopic image.

Observed by the mixing ratio of the liquid crystal composition (No. 27), the nematic phase-isotropic liquid phase transition temperature (T _NI ), the refractive index anisotropy (Δn) and the conoscopic image in Table 4 below. The results are shown in Table 5, and the mixing ratio of the comparative liquid crystal (a) and various similar properties are shown in Table 5.

[0048]

[Table 11]

[0049]

[Table 12]

From Tables 4 and 5, the liquid crystal composition (No. 27) according to the present invention shows that the director of liquid crystal molecules or dichroic dye on the substrate interface is oriented in the direction perpendicular to the substrate. Therefore, it is clear that a high pretilt angle is formed as compared with the mixed liquid crystal (a) containing a compound having a similar structure.

The liquid crystal composition (No. 2) is shown in Table 6 below.
7) and the chiral nematic liquid crystal composition (No. 28) comprising the chiral compound, the mixing ratio and the characteristic pitch are shown. Further, for comparison, Table 7 shows the mixing ratio and the specific pitch of the liquid crystal composition (a) and the chiral nematic mixed liquid crystal (b) composed of the same chiral compound.

[0052]

[Table 13]

[0053]

[Table 14]

Liquid crystal composition according to the present invention (No. 28)
In the same manner as described above, a liquid crystal display device was manufactured by encapsulating between two substrates having no alignment means, and as a result, liquid crystal molecules on the substrate interface were aligned vertically with respect to the substrate, which resulted in a memory effect. It was possible to reduce the occurrence of certain focal conic and disclination, and to sufficiently reduce unnecessary scattering of incident light. Similarly, as a result of producing a liquid crystal display element using the mixed liquid crystal (b), liquid crystal molecules at the substrate interface are aligned horizontally with respect to the substrate, which causes the occurrence of focal conic or disclination having a memory property. It was observed, and it became a white blur state due to the scattering of incident light.
From this, the superiority of the present invention is clear.

The second characteristic of the liquid crystal display device of the present invention is that it does not require a polarizing plate and that it does not require an alignment film and an alignment treatment which have been conventionally required. The substrate used in the present invention is, for example, a rubbed polyimide alignment film, a surfactant such as lecithin capable of obtaining vertical alignment, or an oblique vapor deposition of SiO having a predetermined pretilt, which has been used so far. It does not undergo any treatment or the like and has no alignment means for uniformly aligning liquid crystal molecules.

Since the conventional liquid crystal display element has an alignment layer, there are problems such as defects and unevenness caused by the alignment layer, and an increase in current value. Further, the azimuth difference of liquid crystal molecules in the vicinity of both substrates is unique to the liquid crystal material. It was necessary to match the pitch and cell thickness, but the liquid crystal display element of the present invention does not have such troublesomeness.

As described above, when the chiral nematic liquid crystal material is used in combination with the substrate having no alignment means, the liquid crystal molecules on the substrate interface are aligned in the direction of the director perpendicular to the substrate, so that the response time The white blur condition can be reduced or improved.

Such a substrate may be, for example, glass as a solid material. The flexible material may be, for example, a plastic film. In addition, an appropriate transparent or opaque electrode may be disposed on the entire surface or a part of the substrate depending on the purpose. It should be noted that a spacer for holding a gap can be usually interposed between the two substrates, similarly to a known liquid crystal display element. When the liquid crystal display device of the present invention is used in a display device of a computer terminal, a display device of a projection or the like, it is preferable to provide a non-linear element or an active element in the transparent electrode layer.

The third characteristic of the liquid crystal display element of the present invention is that the characteristic pitch of the liquid crystal material interposed between the substrates is 2 to 6.
It is in the range of μm. Conventionally, it was necessary to adjust the relationship (d / P) between the cell thickness d and the characteristic pitch P of the liquid crystal material, but in the liquid crystal display element of the present invention,
It is not necessary to adjust d / P, and the response time and the white blur state can be reduced or improved by limiting and using only the unique pitch.

The natural pitch of the liquid crystal material is, of course, sufficiently larger than the wavelength of light, or is it necessary to further reduce the occurrence of focal conic or disclination?
Since it is important to sufficiently reduce the scattering of incident light even if it is generated, it is necessary to make it 2 μm or more in the case of the liquid crystal display device of the present invention. Further, when the thickness is made larger than the cell thickness, the light absorption efficiency of the dichroic dye arranged in the liquid crystal tends to deteriorate, so that it is preferably 6 μm or less. Therefore, the liquid crystal display element of the present invention has a natural pitch of 2 to 6
It is preferred to use chiral nematic liquid crystal materials in the μm range.

The liquid crystal material used in the present invention has a helical structure between the substrates when no voltage is applied. However, as described above, these substrates are not subjected to any treatment for aligning the liquid crystal material at all, but the liquid crystal molecules near the substrate interface are considered to be oriented in the direction of the vertical director. That is, the helical structure of the liquid crystal material used in the present invention is
Macroscopically and microscopically, it is considered that the liquid crystal material intervenes at pitches of various sizes that are modulated by the characteristic pitch. Furthermore, in the liquid crystal material interposed in such a state, the action of the strong alignment regulating force that appears when the aligning means is provided is small, and the liquid crystal material is in a state in which the original interaction of the liquid crystal material itself is reflected to some extent. It appears to be.

The characteristic pitch can be adjusted by a method known in the art, that is, by appropriately changing the mixing ratio of the chiral nematic liquid crystal compound or the chiral compound capable of inducing a helical structure. The compound capable of inducing the helical structure may be a single compound, or may be a mixture of a plurality of compounds.

The chiral nematic liquid crystal material used in the present invention includes a transition temperature between an isotropic liquid phase and a liquid crystal phase, a melting point,
Nematic liquid crystal, smectic liquid crystal, cholesteric liquid crystal, which is generally recognized as a liquid crystal material in this field, for the purpose of improving viscosity, refractive index anisotropy, elastic constant, dielectric constant anisotropy, and solubility with dichroic dye. A compound such as a liquid crystal may be appropriately mixed and used. The chiral nematic liquid crystal may be any liquid crystal material having a positive dielectric anisotropy as a whole, and each compound does not necessarily have to have a positive dielectric anisotropy.

Examples of liquid crystal compounds which can be used in the chiral nematic liquid crystal material of the present invention by mixing with the compounds represented by the above-mentioned general formulas (I) to (XII) are shown below.

[0065]

[Chemical 9]

(In the formula, R ⁷ and R ⁸ are each independently
Represents a linear alkyl group or alkenyl group having 1 to 10 carbon atoms, q represents 0 or 1, X ⁴ represents a hydrogen atom or a methyl group, and Y ² and Z ² are each independently,
Single bond, -CH ₂ CH ₂ - or represent -COO-. )

Furthermore, it is necessary to add a dichroic dye to the liquid crystal material, and as the dichroic dye, those which have been used for guest-host type liquid crystal display elements so far can be used.
It can be used without particular limitation. The hue of the dichroic dye can also be used without particular limitation, but if a colored layer other than black is provided in the background part of the liquid crystal display element and a black dichroic dye is used, the most excellent visibility can be obtained. can get.

The dichroic dye used in the present invention is an azo dye,
An azoxy-based, anthraquinone-based, or perylene-based dichroic dye may be appropriately used alone or in combination. The hue of the dichroic dye thus obtained can be variously adapted and used in consideration of the combination with the background color when the colored layer is arranged in the background portion.

The hue of the dichroic dye used in the present invention is not limited to that of black, and it is possible to
The dichroic dye used in the host liquid crystal display device can be used without limitation. For example, "LSY-11
6 "(yellow)," LSR-401 "(magenta)," LS "
R-406 "(red)," LSR-426 "(purple)," L "
SB-278 "(blue)," LSB-350 "(blue),
"LSB-335" (cyan) [above, manufactured by Mitsubishi Kasei Co., Ltd.], "SI-209" (yellow), "M-710"
(Orange), "M-361" (yellow), "M-86"
(Red), "M-618" (magenta), "SI-252"
(Purple), "M-777" (Purple), "M-370"
(Red), "M-137" (Blue), "M-141"
(Blue), "M-438" (Blue), "M-412"
(Blue), "M-34" (blue), "M-430" (blue),
"M-406" (blue), "S-301" (black), "S-"
304 "(black) or" M-676 "(black) [above,
Manufactured by Mitsui Toatsu Chemicals, Inc., etc. can be used.

These dichroic dyes are 400 to 680n
Those having an absorption region in the light wavelength range of m and exhibiting a large value of the dichroic ratio are preferable, and reddish or bluish black may be used, depending on the hue of the coloring layer. Can be used.

When a fluorescent coloring layer is arranged,
It is desirable that the dichroic dye is difficult to absorb light in a wavelength region other than visible light, and particularly, a dye having a dichroic ratio as large as possible with respect to light having a wavelength of 400 nm or less, or light having a wavelength of 680 nm or more It is preferable to have a property of transmitting light as much as possible.

By selecting and using the dichroic dye having such characteristics, in the liquid crystal display device of the present invention, the on-state transmittance is 10% or more at the light wavelength of 380 to 400 nm, and 720 to 800 nm. The light wavelength can be set to 30% or more, whereby the light utilization efficiency of the fluorescent coloring layer can be sufficiently exerted, and a brighter, high-contrast liquid crystal display device can be manufactured.

As described above, the liquid crystal display element of the present invention may be provided with a colored layer as a background color on the substrate on the side opposite to the display surface, or may be used by transmitting light without providing a colored layer. . When the colored layer is provided, the hue can be variously adapted and used in consideration of the combination with the hue of the dichroic dye in the liquid crystal material. The shape is not particularly limited and may be a film, a plate, a paper, or a sticker. Further, these colored layers may be provided on the entire surface of the substrate, or may be partially provided for each pixel or corresponding to a portion including an arbitrary pixel group. Further, the hue is not limited to a single color, and a plurality of different hues may be arranged.

Among these, in the liquid crystal display element of the present invention, it is particularly preferable to use a fluorescent layer as the coloring layer. The hue of this fluorescent color is not particularly limited, and various colors can be used. Further, by arranging layers of various fluorescent colors having different hues as described above, it is possible to display a bright fluorescent color only in the portion corresponding to the pixel electrode.

These colored layers may be arranged outside the substrate, or may be formed between the substrate and the transparent electrode layer. When the colored layer is arranged between the substrate and the transparent electrode, it can be manufactured by applying the RGB micro color filter manufacturing technique which is generally used for the TN or STN type liquid crystal display device at present.

Here, the structure of the liquid crystal display element of the present invention will be described in more detail. FIG. 1 is a schematic view showing a cross section of a liquid crystal display device of the present invention in a state in which no voltage is applied. 1 is a liquid crystal molecule, 2 is a dichroic dye, 3 is a substrate, and 4 is a transparent electrode layer. Reference numeral 5 represents a fluorescent colored layer. The solid line represents the helical structure of liquid crystal molecules, and the broken line represents the helical axis.

In FIG. 1, between the substrates having no alignment means, the directors of liquid crystal molecules on the substrate interface are oriented in the vertical direction. The liquid crystal molecules between the two substrates are macroscopically disordered and microscopically form an irregular helical structure. The dichroic dye is interposed between such liquid crystal molecules, and its light absorption axis is also oriented in all directions between the substrates. Therefore, light having an arbitrary angle incident on the liquid crystal display element is absorbed by any of the dichroic dyes, and the display surface of the liquid crystal display element can see the hue of the dichroic dye. The degree of coloring shows a higher light utilization rate and a better light-shielding property than, for example, a liquid crystal display element having an alignment means for horizontally aligning a liquid crystal material with respect to a substrate.

FIG. 2 is a schematic view showing a cross section of the liquid crystal display device of the present invention in a voltage applied state, wherein 1 is a liquid crystal molecule, 2 is a dichroic dye, 3 is a substrate, and 4 is transparency. The electrode layer and 5 are fluorescent colored layers.

In FIG. 2, the liquid crystal molecules are rearranged in the direction of the electric field to be in a so-called homeotropic state. Therefore, the absorption by the dichroic dye is reduced, and the hue of the background colored layer can be seen on the display surface.

When a fluorescent colored layer is arranged in the background,
Since the colored layer absorbs light other than the visible light that has been transmitted and emits light in the visible region, this light is added to the incident visible light to obtain a brighter and high-contrast display.

When the voltage is removed from this voltage application state,
In the liquid crystal display device of the present invention, the liquid crystal molecules quickly return from the state shown in FIG. 2 to the state shown in FIG. 1, and the hue of the dichroic dye appears. In the conventional guest-host type liquid crystal display element, when the voltage is turned off from the voltage applied state, as shown in FIG. 3, a focal conic state having a memory property occurs and the state where the display surface becomes cloudy is transient. This is a problem because it appears and the response characteristics deteriorate. However, in the liquid crystal display device of the present invention, as is apparent from the examples described later, the focal conic state was almost improved by the substrate having no alignment layer and the chiral nematic liquid crystal material in which the specific pitch was carefully selected.

The liquid crystal display element of the present invention can be manufactured, for example, as follows. First, a liquid crystal material is appropriately mixed with a dichroic dye to prepare a liquid crystal mixture. This liquid crystal mixture is sandwiched between two substrates having electrode layers. As a method of sandwiching, an empty panel can be produced by using two substrates, a spacer and a sealing material, and the liquid crystal mixture can be produced by vacuum injection. Depending on the substrate used, when the liquid crystal mixture exhibits a so-called initial orientation that is remembered during injection, the empty panel or mixture is kept warm at a temperature higher than the phase transition temperature of the liquid crystal phase and the isotropic liquid phase of the mixture used. Can be injected.

The layer thickness of the liquid crystal layer thus produced can be appropriately designed according to the purpose of use, but is preferably in the range of 2 to 30 μm in order to obtain sufficient contrast.
The range of up to 16 μm is particularly preferred.

Further, the liquid crystal display device of the present invention can obtain high contrast only by the above constitution, but a backlight or a diffusion plate may be arranged in order to obtain further excellent contrast. In this case, when the light source is arranged on the back surface side of the outer peripheral portion of the substrate and at a position outside the viewing angle of the liquid crystal display element, the light source may be a point light source, a line light source, or a combination thereof, and these are installed at the liquid crystal display. It suffices that at least one point is on the back surface side of the outer peripheral portion of the display element.
Further, the light of the light source installed in these places may be guided from the peripheral portion of the substrate by using a light guide path such as an optical fiber.

[0085]

EXAMPLES The present invention will be described in more detail below by showing Examples of the present invention. However, the invention is not limited to these examples.

In the following Examples and Comparative Examples, "%" means "% by weight". Further, each of the evaluation characteristics in each example and comparative example means the following symbols and contents. The liquid crystal display device was evaluated using a light-scattering liquid crystal evaluation device "LCD-7000PN" (manufactured by Otsuka Electronics Co., Ltd.).

(1) R ₀ , R ₁₀₀ , V ₉₀ , contrast:
Diffuse light source is used as the light source, and the reflected light intensity of standard white plate is 1
When standardized to 00%, the liquid crystal display element is placed on a standard white plate, the reflectance when no voltage is applied is R _0, and the light when the light reflectance does not change with an increase in applied voltage The reflectance is R ₁₀₀ . The light reflectance (R ₀ ) of the liquid crystal display element when no voltage is applied is set to 0%, and the reflectance (R ₁₀₀ ) when the light reflectance does not change with an increase in applied voltage is 10%.
The applied voltage (volts) that gives a light reflectance of 90% when it is 0% is V ₉₀ . The light reflectance obtained at this time is R ₉₀ . The contrast is expressed by the following equation.

Contrast = R ₉₀ / R ₀

(2) T ₁₀₀ : A parallel light source is used as the light source. With the liquid crystal display element removed from the light metering state, the light transmittance when the light source is turned on is 100%, and the light transmittance when the light source is off is 0%. A liquid crystal display element is placed on the photometry, and the transmittance when the light transmittance does not change with the increase of the applied voltage is T ₁₀₀ .

(Example 1)

[0091]

[Chemical 10]

A mixed liquid crystal (A) consisting of was prepared. The mixed liquid crystal (A) was enclosed in a liquid crystal display cell made of a substrate having no alignment means, and the director of the liquid crystal molecules was observed with a conoscopic image. As a result, the liquid crystal molecules were aligned vertically to the substrate. I was able to confirm that Nematic phase-isotropic liquid phase transition temperature (T _NI ) of this mixed liquid crystal (A), TN-LC prepared using this mixed liquid crystal (A)
The threshold voltage (V _th ) and refractive index anisotropy (Δn) at D were as follows.

T _NI : 92.8 ° C. V _th : 1.81 V Δn: 0.117

A chiral nematic liquid crystal composition comprising 95.2% of this mixed liquid crystal (A) and 4.8% of cholesteric nonanoate was prepared. The characteristic pitch of this liquid crystal material was 4.0 μm. This liquid crystal material 98.3% and black dichroic dye “S-344” (Mitsui Toatsu Dyestuff Co., Ltd., 42
A liquid crystal material of 1.7% (absorbing light in a region of 5 to 710 nm) was prepared to obtain a guest-host liquid crystal. Then, on two glass substrates measuring 11 cm x 27 cm,
An ITO electrode was formed as a pixel so that a clock could be displayed, the two substrates were arranged with the electrode phases facing each other, and a 10 μm spacer was interposed between the substrates to produce an empty cell. This substrate has no alignment layer. The guest-host liquid crystal was vacuum-injected into this empty cell to obtain a liquid crystal display device of the present invention. The characteristics of this liquid crystal display element were as follows. In this liquid crystal display element, the occurrence of focal conic and disclination was reduced, and the scattering of incident light was sufficiently small.

V ₉₀ : 7.4V Contrast: 1:11

The on-state transmittance T ₁₀₀ of this liquid crystal display device is 34 at an optical wavelength in the range of 380 to 400 nm.
% Or more, and 50% or more at a light wavelength in the range of 720 to 800 nm. A special label "08046" of fluorescent color (manufactured by A-One Co., Ltd., fluorescent green) was placed as a colored layer on the outer side of the substrate on the back surface of this liquid crystal display element to manufacture the liquid crystal display element of the present invention. In this liquid crystal display device, bright fluorescent green was visible in the display area, and no dark hue was observed.

Further, instead of the fluorescent colored layer, similarly, special labels of fluorescent color "08047" (fluorescent orange), "08048" (fluorescent pink), "08095" (fluorescent yellow) Even if each of the above [made by A-One Co., Ltd.] was arranged, a bright fluorescent color could be seen in the display portion in the same manner, and no dark hue was observed. Even if lumino paper was placed as the colored layer, a bright display was similarly obtained.

Example 2 The mixed liquid crystal (A) 90.
A chiral nematic liquid crystal composition consisting of 4% and 9.6% cholesteric nonanoate was prepared. The characteristic pitch of this liquid crystal composition was 2.0 μm. This liquid crystal composition 98.3% and black dichroic dye "S-344" 1.7
% Guest-host liquid crystal material was prepared. This liquid crystal material was vacuum-injected into an empty cell in the same manner as in Example 1 to manufacture a liquid crystal display element of the present invention. The characteristics of this liquid crystal display element were as follows. In this liquid crystal display element, the occurrence of focal conic and disclination was reduced, and the scattering of incident light was sufficiently small.

V ₉₀ : 13.2V Contrast: 1:23

The on-state transmittance T ₁₀₀ of this liquid crystal display device is 34 at an optical wavelength in the range of 380 to 400 nm.
% Or more, and 50% or more at a light wavelength in the range of 720 to 800 nm. On the outside of the substrate on the back of this liquid crystal display element,
When the colored layers of the respective colors were arranged in the same manner as in Example 1, vivid display was obtained and no dark hue was observed.

(Example 3) The above-mentioned mixed liquid crystal (A) 96.
A chiral nematic liquid crystal composition consisting of 8% and cholesteric nonanoate 3.2% was prepared. The characteristic pitch of this liquid crystal composition was 6.0 μm. This liquid crystal material 98.3% and the black dichroic dye "S-344" 1.7%
Was prepared as a guest-host liquid crystal material. Pixel of ITO electrode is formed for clock display, 11 cm
Two glass substrates having a size of 27 cm were arranged with the electrode layers facing each other, and a 15 μm spacer was interposed between the substrates to prepare an empty cell. This substrate has no alignment layer.

The above-mentioned guest / host liquid crystal material was vacuum-injected into this empty cell to prepare a liquid crystal display device of the present invention. The characteristics of this liquid crystal display device were as follows. In this liquid crystal display element, the occurrence of focal conic and disclination was reduced, and the scattering of incident light was sufficiently small.

V ₉₀ : 6.4V Contrast: 1:10

The on-state transmittance T ₁₀₀ of this liquid crystal display device is 34 at light wavelengths in the range of 380 to 400 nm.
% Or more, and 50% or more at a light wavelength in the range of 720 to 800 nm. On the outside of the substrate on the back of this liquid crystal display element,
When the colored layers of the respective colors were arranged in the same manner as in Example 1, vivid display was obtained and no dark hue was observed.

(Example 4)

[0106]

[Chemical 11]

A mixed liquid crystal (B) consisting of was prepared. This mixed liquid crystal (B) was enclosed in a liquid crystal display cell consisting of two substrates without alignment means, and the director of the liquid crystal molecules was observed with a conoscopic image. As a result, the liquid crystal molecules were aligned vertically to the substrate. I was able to confirm that it is doing. Nematic phase-isotropic liquid phase transition temperature (T _NI ) of this mixed liquid crystal (B), TN-LC prepared using this mixed liquid crystal (B)
Threshold voltage (V _th ) at D and refractive index anisotropy (Δ
n) was as follows.

T _NI : 79.7 ° C. V _th : 2.02 V Δn: 0.109

A chiral nematic liquid crystal composition consisting of 89.2% of this mixed liquid crystal (B) and 10.8% of cholesteric nonanoate was prepared. The characteristic pitch of this liquid crystal composition was 2.0 μm. A guest-host liquid crystal material composed of 98.3% of the liquid crystal material and 1.7% of the black dichroic dye "S-344" was prepared. This liquid crystal material was injected into the empty cell in the same manner as in Example 1 to manufacture the liquid crystal display element of the present invention. The characteristics of this liquid crystal display element were as follows. In this liquid crystal display element, the occurrence of focal conic and disclination was reduced, and the scattering of incident light was sufficiently small.

V ₉₀ : 13.8V Contrast: 1:22

(Example 5)

[0112]

[Chemical 12]

A mixed liquid crystal (C) consisting of was prepared. This mixed liquid crystal (C) was enclosed in a liquid crystal display cell composed of two substrates without alignment means, and the director of the liquid crystal molecules was observed with a conoscopic image. As a result, the liquid crystal molecules were aligned vertically to the substrate. I was able to confirm that it is doing. Nematic phase-isotropic liquid phase transition temperature (T _NI ) of this mixed liquid crystal (C), TN-LC prepared using this mixed liquid crystal (C)
Threshold voltage (V _th ) at D and refractive index anisotropy (Δ
n) was as follows.

T _NI : 73.7 ° C. V _th : 1.71 V Δn: 0.112

A chiral nematic liquid crystal composition consisting of 95.8% of this mixed liquid crystal (C) and 4.2% of cholesteric nonanoate was prepared. The characteristic pitch of this liquid crystal composition was 4.0 μm. A guest-host liquid crystal material consisting of 98.3% of this liquid crystal composition and 1.7% of a black dichroic dye "S-344" was prepared. This liquid crystal material was vacuum-injected into an empty cell in the same manner as in Example 1 to manufacture a liquid crystal display element of the present invention. The characteristics of this liquid crystal display element were as follows. In this liquid crystal display element, the occurrence of focal conic and disclination was reduced, and the scattering of incident light was sufficiently small.

V ₉₀ : 7.8V Contrast: 1:12

(Example 6)

[0118]

[Chemical 13]

A mixed liquid crystal (D) consisting of was prepared. This mixed liquid crystal (D) was enclosed in a liquid crystal display cell consisting of two substrates without alignment means, and the director of the liquid crystal molecules was observed with a conoscopic image. As a result, the liquid crystal molecules were aligned vertically to the substrate. I was able to confirm that it is doing. Nematic phase-isotropic liquid phase transition temperature (T _NI ) of this mixed liquid crystal (D), TN-LC prepared using this mixed liquid crystal (D)
Threshold voltage (V _th ) at D and refractive index anisotropy (Δ
n) was as follows.

T _NI : 81.0 ° C. V _th : 2.32 V Δn: 0.176

A chiral nematic liquid crystal composition consisting of 95.4% of this mixed liquid crystal (D) and 4.6% of cholesteric nonanoate was prepared. The characteristic pitch of this liquid crystal composition was 4.0 μm. A guest-host liquid crystal material consisting of 98.3% of this liquid crystal composition and 1.7% of a black dichroic dye "S-344" was obtained. This liquid crystal material was injected into the empty cell in the same manner as in Example 1 to manufacture the liquid crystal display element of the present invention. The characteristics of this liquid crystal display element were as follows. In this liquid crystal display element, the occurrence of focal conic and disclination was reduced, and the scattering of incident light was sufficiently small.

V ₉₀ : 7.87V Contrast: 1:12

(Embodiment 7)

[0124]

[Chemical 14]

A mixed liquid crystal (E) was prepared. This mixed liquid crystal (E) was enclosed in a liquid crystal display cell consisting of two substrates without alignment means, and the director of the liquid crystal molecules was observed with a conoscopic image. As a result, the liquid crystal molecules were aligned vertically to the substrate. I was able to confirm that it is doing. Nematic phase-isotropic liquid phase transition temperature (T _NI ) of this mixed liquid crystal (E), TN-LC produced using this mixed liquid crystal (E)
Threshold voltage (V _th ) at D and refractive index anisotropy (Δ
n) was as follows.

T _NI : 67.0 ° C. V _th : 1.18 V Δn: 0.158

A chiral nematic liquid crystal composition containing 95.5% of this mixed liquid crystal (E) and 4.5% of cholesteric nonanoate was prepared. The characteristic pitch of this liquid crystal composition was 4.0 μm. A guest-host liquid crystal material consisting of 98.3% of this liquid crystal composition and 1.7% of a black dichroic dye "S-344" was prepared. This liquid crystal material was vacuum-injected into an empty cell in the same manner as in Example 1 to manufacture a liquid crystal display element of the present invention. The characteristics of this liquid crystal display element were as follows. In this liquid crystal display element, the occurrence of focal conic and disclination was reduced, and the scattering of incident light was sufficiently small.

V ₉₀ : 7.7V Contrast: 1:13

(Comparative Example 1)

[0130]

[Chemical 15]

A mixed liquid crystal (F) consisting of was prepared. This mixed liquid crystal (F) was enclosed in a liquid crystal display cell consisting of two substrates without alignment means, and the director of the liquid crystal molecules was observed with a conoscopic image. As a result, the liquid crystal molecules were aligned horizontally with respect to the substrate. I was able to confirm that it is doing. Nematic phase-isotropic liquid phase transition temperature (T _NI ) of this mixed liquid crystal (F), TN-LC prepared using this mixed liquid crystal (F)
Threshold voltage (V _th ) at D and refractive index anisotropy (Δ
n) was as follows.

T _NI : 85.6 ° C. V _th : 2.15 V Δn: 0.110

A chiral nematic liquid crystal composition containing 88.8% of this mixed liquid crystal (F) and 11.2% of cholesteric nonanoate was prepared. The characteristic pitch of this liquid crystal composition was 2.0 μm. This liquid crystal composition 98.3
% And a black dichroic dye "S-344" 1.7% were obtained. This liquid crystal material was vacuum-injected into an empty cell in the same manner as in Example 1 to obtain a liquid crystal display element other than the present invention. The characteristics of this liquid crystal display element were as follows. This liquid crystal display element had a lower display quality than those of the liquid crystal display elements of Examples 1 to 6, in which focal conic and disclination were significantly generated.

V ₉₀ : 15.2V Contrast: 1: 6

[0135]

The liquid crystal display device of the present invention does not require a polarizing plate and an alignment means capable of aligning a liquid crystal material in a certain direction when no voltage is applied, and enables bright display. There are no display defects due to the film and the display quality is high.

Further, as the liquid crystal material, by containing the compound having the functional group represented by the general formula (I),
It was revealed that a high pretilt angle can be formed even if a substrate that has not been subjected to an alignment treatment is used. With such a configuration, the liquid crystal display device of the present invention can improve the white blur state of the white Taylor type liquid crystal display device, and can obtain high contrast and bright display. Further, by disposing a colored layer, especially a fluorescent colored layer on the back side, it can be used as a direct-view color display device, and a clearer display can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view showing a cross section of a guest-host type liquid crystal display device of the present invention when no voltage is applied.

FIG. 2 is a schematic view showing a cross section of a guest-host type liquid crystal display device of the present invention when a voltage is applied.

FIG. 3 is a schematic diagram showing a cross section of a guest-host type liquid crystal display element other than the present invention, showing a focal conic state that transiently occurs after the voltage is cut off from a voltage applied state.

[Explanation of symbols]

 1 Liquid crystal molecule 2 Dichroic dye 3 Substrate 4 Transparent electrode layer 5 Coloring layer 6 Alignment layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C09K 19/30 9279-4H 19/34 9279-4H 19/42 9279-4H 19/44 9279-4H G02F 1/13 500 1/137 500

Claims (8)

[Claims] 1. Between two substrates having a transparent electrode layer,
In a guest-host type liquid crystal display device in which a liquid crystal mixture containing a chiral nematic liquid crystal material and a dichroic dye is sandwiched, the two substrates both contain the chiral nematic liquid crystal material and the dichroic dye when no voltage is applied. The substrate has no alignment means capable of aligning in a fixed direction, and the chiral nematic liquid crystal material is represented by the general formula (I): (Wherein R ¹ represents a straight-chain alkyl group having 1 to 10 carbon atoms, and n represents an integer of 1 to 5), and the compound having a functional group represented by the formula shown in FIG. 6μ
A liquid crystal display element, which is a chiral nematic liquid crystal material in the range of m. 2. A compound having a functional group represented by the general formula (I) is represented by the general formulas (II) to (V): (In the formula, each R ² independently has 1 to 10 carbon atoms.
Represents a straight chain alkyl group, an alkenyl group or an alkoxyl group, 1 represents 0 or 1, m represents an integer of 1 to 5, and R ¹ represents a straight chain alkyl group having 1 to 10 carbon atoms. . 3. A liquid crystal display device according to claim 1, which is a compound selected from the group consisting of compounds represented by 3. A chiral nematic liquid crystal material having a general formula (VI) to (XI): (In the formula, each R ³ independently has 1 to 10 carbon atoms.
Represents a linear alkyl group, an alkenyl group or an alkoxyalkyl group, R ⁴ each independently represents a linear alkyl group or an alkoxyl group having 1 to 10 carbon atoms, and R ⁵ represents 1 to 1 carbon atoms. 10 represents a linear alkyl group, an alkoxyl group or an alkoxyalkyl group represented by X ¹
Each independently represent a hydrogen atom or a fluorine atom. 3. A liquid crystal display device according to claim 1 or 2, which is a chiral nematic liquid crystal material containing a compound selected from the group consisting of compounds represented by 4. The chiral nematic liquid crystal material has the general formula (XII): (In the formula, R ⁶ represents a linear alkyl group having 1 to 10 carbon atoms, an alkenyl group or an alkoxyalkyl group,
p represents 0 or 1, Y ¹ and Z ¹ each independently represent a single bond, —CH ₂ CH ₂ — or —COO—,
X ² and X ³ each independently represent a hydrogen atom or a fluorine atom. ) A chiral nematic liquid crystal material containing a compound represented by the formula (1),
2. The liquid crystal display element according to 2 or 3. 5. A liquid crystal display device having a colored layer on a substrate opposite to the display surface of the liquid crystal display element according to claim 1. 6. The liquid crystal display device according to claim 5, wherein the colored layer has a fluorescent color and is arranged outside the substrate. 7. The liquid crystal display device according to claim 6, wherein the dichroic dye is a black dichroic dye having a light absorption region in a light wavelength range of 400 to 680 nm. 8. The liquid crystal display device according to claim 7, wherein a plurality of colored layers having different hues are provided at positions corresponding to the pixel electrodes.