JPH0713155A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To make a bright display, to continuously adjust a display color, and to improve the yield at the time of manufacture by composing the liquid crystal display device of a ferroelectric liquid crystal display element and a light guide plate lighting device and providing a white fluorescent light discharge tube and a colored fluorescent light discharge tube at end parts of a light guide plate. CONSTITUTION:Liquid crystal used for the liquid crystal display element 10 has ferroelectricity and the illumination light source of the light guide plate lighting device 20 is composed of the white fluorescent light discharge tube 3 and the colored fluorescent light discharge tube 4 which emits colored light in complementary color relation with the display color of the liquid crystal display element. Namely, the two kind of fluorescent light discharge tubes 3 and 4 which has different light emission colors are used as fluorescent discharge tubes separately at both the end parts of the light guide plate 1 and, for example, the white fluorescent light discharge tube 3 and blue discharge tube 4 are provided separately. Further, light source reflecting plates 5 and 6 are installed so as to make light incident on the light guide plate 1 with efficiency. In this constitution, the inverter input voltage on the side of, for example, the colored fluorescent light discharge tube 4 is varied to easily adjust the color.

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 having a liquid crystal display element and a light guide plate type illumination device. More specifically, the present invention relates to a liquid crystal display device suitable for a liquid crystal display having a color display unit.

[0002]

2. Description of the Related Art A liquid crystal display device using a ferroelectric liquid crystal is
Although it has been actively researched from the viewpoint of its high-speed response and memory property, the improvement of yield has been an issue because the cell thickness needs to be extremely thin. In order to approach a good black and white display, it is necessary to adjust the cell thickness to about 1.5 μm or to adjust the display color to a display color equivalent to that of a cell of 1.5 μm apparently by combining with a retardation plate. The transmission spectrum obtained with the ferroelectric liquid crystal element is T ∝ sin ² (π
Δn · d / λ) (Δn · d: product of birefringence of liquid crystal and cell thickness, λ: wavelength), and when d = 1.5 μm, Δn generally does not depend much on the liquid crystal material and is therefore dim when visually observed. It will be displayed in black and white. That is, since the utilization efficiency of light of the entire visible light is unavoidably low, it is difficult to maintain the brightness even when an illumination device (backlight) is used. In order to address such a problem, a ferroelectric liquid crystal electro-optical device which realizes black and white display by interposing a polymer film having a refractive index anisotropy as a retardation plate between a substrate and a polarizing means is disclosed. (Japanese Patent Laid-Open No. 2-10
8019). However, in this device, the use of the retardation plate makes it apparently the same as the display color of the element having a thin cell thickness, but the amount of transmitted light is also reduced, and the birefringence control of the retardation plate is controlled. There is a problem that it is difficult to adjust the color tone after the device is made. Further, in a liquid crystal display device having a liquid crystal panel (display element) in which the transmittance of incident light with respect to incident light differs depending on the wavelength, in the liquid crystal display device, the transmission characteristic of a polarizing plate or A liquid crystal display device has been disclosed in which the reflection characteristic of a reflection plate has a wavelength transmission characteristic opposite to that of a liquid crystal panel to perform monochrome display (Japanese Patent Laid-Open No. 60-247621).
issue). However, in this device as well, the transmission characteristics of the entire device are flat, but the display is dark, and it is difficult to maintain the brightness even when an illumination device (backlight) is used, and it is not possible to adjust the color tone after the device is used. There was a problem that it was possible.

[0003]

Further, as a liquid crystal electro-optical device having a light guide plate type illuminator, a color filter is arranged between the light guide plate of the light guide plate type illuminator and the fluorescent discharge tube, and the color of the light source is changed. There is disclosed a transmissive liquid crystal electro-optical device capable of changing the display color of a transmissive liquid crystal display element in a black and white display mode (Japanese Patent Laid-Open No. 2-238439).
issue). However, in this device, the light intensity of the backlight is greatly reduced because all the colors of the light source are changed, and the color filter itself must be mechanically moved (rotated) to change the color tone. , The display observer has not been able to do this easily. Further, since the color filter is close to the fluorescent discharge tube, there is a problem that it is easily deformed or deteriorated by heat generation and lacks long-term stability. The present invention has been made in view of the above problems, and a liquid crystal display device capable of bright display, capable of continuously adjusting display colors, and capable of improving the yield at the time of manufacturing. The purpose is to provide.

[0004]

In order to achieve the above object, according to the present invention, a liquid crystal display device having a liquid crystal sandwiched between two substrates with electrodes, and at least a light guide plate and an end portion thereof. In a liquid crystal display device having a light guide plate type illumination device composed of an arranged illumination light source, the liquid crystal used for the liquid crystal display element has ferroelectricity, and the illumination light source of the light guide plate type illumination device is Provided is a liquid crystal display device comprising a white fluorescent discharge tube for emitting white light and a colored fluorescent discharge tube for emitting colored light having a complementary color relationship with a display color of a liquid crystal display element. .

Further, the ferroelectric liquid crystal display device has
There is provided a liquid crystal display device having a thickness of 4 μm, and the colored fluorescent discharge tube emits blue light.

Further, there is provided a liquid crystal display device characterized in that the colored fluorescent discharge tube changes in luminance according to an input voltage of an inverter.

The liquid crystal display device of the present invention will be specifically described below. 1. Ferroelectric Liquid Crystal Display Device Ferroelectric Liquid Crystal The ferroelectric liquid crystal used in the present invention is not particularly limited, and examples thereof include low-molecular liquid crystal, polymer liquid crystal, and mixed liquid crystal. Above all, it is preferable to use the ferroelectric polymer liquid crystal or the composition thereof. By including the ferroelectric polymer liquid crystal, strength and durability against external force such as impact or bending can be improved. Further, the memory property of the ferroelectric liquid crystal can be utilized, and the power consumption can be reduced. In addition, when a series of continuous manufacturing methods of coating film formation of liquid crystal on one substrate, laminating with the other substrate, and bending alignment treatment are adopted, it contains a polymer liquid crystal excellent in film forming property and alignment property. Is particularly preferred. Examples of the ferroelectric polymer liquid crystal material include one or more kinds of ferroelectric polymer liquid crystals, one or more kinds of ferroelectric low-molecular liquid crystals and one or more kinds of ferroelectric polymer liquid crystals. A ferroelectric polymer liquid crystal composition composed of, a ferroelectric polymer liquid crystal composition composed of one or more kinds of ferroelectric low-molecular liquid crystal and one or more kinds of other polymer liquid crystal, etc. You can That is, as a ferroelectric polymer liquid crystal or a ferroelectric polymer liquid crystal composition, a ferroelectric polymer liquid crystal (homopolymer or copolymer or a mixture thereof) in which polymer molecules themselves exhibit ferroelectric liquid crystal characteristics, Mixture of dielectric polymer liquid crystal with other polymer liquid crystal and / or ordinary polymer, mixture of ferroelectric polymer liquid crystal and ferroelectric low molecular weight liquid crystal, ferroelectric polymer liquid crystal and ferroelectric low molecular weight liquid crystal It is possible to use all polymer liquid crystals exhibiting ferroelectricity, such as a mixture of liquid crystal and a polymer liquid crystal and / or a usual polymer, or a mixture of these and a usual low molecular liquid crystal. In this case, the mixing ratio of the ferroelectric high-molecular liquid crystal and the (ferroelectric) low-molecular liquid crystal is preferably 95: 5 to 20:80, and 80:20 to 40:60. Is more preferable.

Among the above ferroelectric polymer liquid crystals, for example, a side chain type ferroelectric polymer liquid crystal having a chiral smectic C phase can be preferably used. Further, the ferroelectric liquid crystal composition may contain an adhesive, a viscosity reducing agent, a non-liquid crystal chiral compound, a dye, etc., if necessary. For example,
In order to improve the mechanical strength of the device, a non-liquid crystalline polymer substance may be mixed. The thickness of the liquid crystal layer is not particularly limited, but it is preferably 1 to 10 μm after coating and drying, and more preferably 1.5 to 3 μm. As the ferroelectric liquid crystal polymer, for example, an acrylate main chain liquid crystal polymer represented by the following formula, a methacrylate main chain liquid crystal polymer, a chloroacrylate main chain liquid crystal polymer, an oxirane main chain liquid crystal polymer, a siloxane main chain liquid crystal polymer, Included are siloxane-olefin main chain liquid crystal polymers and ester main chain liquid crystal polymers.

[0009]

[Chemical 1]

[0010]

[Chemical 2]

[0011]

[Chemical 3]

[0012]

[Chemical 4]

In the repeating unit of the above-mentioned ferroelectric liquid crystal polymer, the side chain skeleton may be replaced with a biphenyl skeleton, a phenylbenzoate skeleton, a biphenylbenzoate skeleton, or a phenyl 4-phenylbenzoate skeleton. The benzene ring in the skeleton of may be replaced with a pyrimidine ring, a pyridine ring, a pyridazine ring, a pyrazine ring, a tetrazine ring, a cyclohexane ring, a dioxane ring, a dioxaborinane ring, or a halogen group such as fluorine or chlorine or a cyano group. May be, 1-methylalkyl group, 2-fluoroalkyl group, 2-chloroalkyl group,
2-chloro-3-methylalkyl group, 2-trifluoromethylalkyl group, 1-alkoxycarbonylethyl group, 2-alkoxy-1-methylethyl group, 2-alkoxypropyl group, 2-chloro-1-methylalkyl group ,
It may be replaced with an optically active group such as a 2-alkoxycarbonyl-1-trifluoromethylpropyl group. Further, the length of the spacer may be changed within the range of 2 to 30 in methylene chain length. The number average molecular weight of the ferroelectric liquid crystal polymer is preferably 1,000 to 200,000.
Examples of the ferroelectric low-molecular liquid crystal compound include Schiff base type ferroelectric low-molecular liquid crystal compounds represented by the following formula, azo and azoxy type ferroelectric low-molecular liquid crystal compounds, biphenyl and aromatics ester type ferroelectric low-molecular liquid crystal compounds. Examples thereof include a molecular liquid crystal compound, a ferroelectric low molecular liquid crystal compound having a ring substituent such as a halogen or cyano group introduced therein, and a ferroelectric low molecular liquid crystal compound having a heterocycle.

[0014]

[Chemical 5]

[0015]

[Chemical 6]

[0016]

[Chemical 7]

[0017]

[Chemical 8]

Incidentally, these compounds are typical of the ferroelectric low molecular weight liquid crystal compounds, and the ferroelectric low molecular weight liquid crystal compounds used in the present invention are not limited to these structural formulas.

Substrates The two substrates used in the present invention are transmissive and therefore optically transparent. As the material, a glass plate or a plastic plate can be used, but it is preferable to use a plastic plate in order to improve impact resistance and reduce the weight of the element. Specific examples of the glass plate include low expansion glass (7059 manufactured by Corning Incorporated), non-alkali glass (NA45 manufactured by HOYA), quartz glass, soda lime glass and the like. Examples of plastic plates include uniaxial PET and biaxial PET for crystalline polymers, and PE, PP, PES, PAr, etc. for amorphous polymers. A plastic plate is preferable because of high productivity of the liquid crystal element. The thickness of the substrate is not particularly limited, but a thickness of 20 to 1000 μm is preferable.

Electrode The electrode used in the present invention is not particularly limited as long as it has transparency, and examples thereof include indium and tin oxides (ITO). Transmittance is 80% or more (thin film only), film thickness is 200-2000
Å The sheet resistance is preferably 500Ω / □ or less. The forming method is not particularly limited, and a sputtering method, a vapor deposition method, a CVD method, a coating method, a pyrosol method or the like can be used.

The method of sandwiching the liquid crystal between the two substrates is not particularly limited, and any of an injection method, a coating method, a laminating method, a pressing method and the like can be used.

A polarizing plate can be used if necessary, but in the present invention, it is preferable to use a crossed Nicol arrangement that provides high contrast.

Cell Thickness The ideal cell thickness of the liquid crystal display element used in the present invention is about 1.5 μm, but the yield decreases as the cell thickness decreases, and the light in the entire visible light range is reduced. It is preferable that the thickness is 2 μm or more and 4 μm or less because the transmittance decreases and the image becomes dark. If it exceeds 4 μm, the memory performance deteriorates,
The viewing angle characteristics may deteriorate. In the range of 2 μm to 4 μm, the display color under normal crossed Nicols is centered around yellow, but the light transmittance is high in the entire visible light range, so bright display can be achieved.

2. Light guide plate type illumination device The light guide plate used in the present invention is not particularly limited,
A light guide plate using a normal transparent acrylic plate or the like can be used. Further, as the illumination light source, one or more fluorescent discharge tubes each emitting two or more colors are used. At least one type uses a normal white fluorescent discharge tube. This is to ensure the minimum required brightness as a display device. As another type of fluorescent discharge tube, a colored fluorescent discharge tube that emits colored light having a complementary color relationship with the display color of the liquid crystal display element is used. For example, in the case of a liquid crystal display element having a cell thickness of 2 to 4 μm and a display color of yellow, a blue fluorescent discharge tube is used. If necessary,
Further, fluorescent discharge tubes of other colors may be combined. As a colored fluorescent discharge tube, calcium tungstate (blue:
Fluorescence maximum 440nm), zinc silicate (green color, 525n)
m), calcium phosphate (red, 650 nm) and the like fluorescent discharge tubes can be used. Moreover, the tube surface of the white fluorescent discharge tube may be colored. These fluorescent discharge tubes may be either cold cathode tubes or hot cathode tubes.

3. Arrangement of Fluorescent Discharge Tubes An example of arrangement of the fluorescent discharge tubes used in the present invention will be described with reference to the accompanying drawings. As shown in FIG. 1A, in this arrangement example, as the light guide plate 1, a usual plastic plate such as a transparent acrylic plate can be used. On the lower surface of the light guide plate 1, a coating film (for example, titanium white) for efficiently scattering light may be provided entirely or partially, or may be provided with irregularities. A reflection plate 2 may be provided on the lower surface of the light guide plate 1 for efficiently guiding scattered light to the light exit surface. Usually, an aluminum plate or a white reflector can be used. In this example, as fluorescent discharge tubes, two types of fluorescent discharge tubes 3 and 4 having different emission colors are separately used at both ends of the light guide plate 1. For example, the white fluorescent discharge tube 3 and the blue discharge tube 4 are separately provided. Further, in this example, the light source reflectors 5 and 6 are provided in order to allow the light to efficiently enter the light guide plate. For this reflector,
For example, it is preferable to form a curved surface so as to cover the fluorescent discharge tube. As the material, a metal plate or a plastic film having a metal film such as silver formed thereon can be used. The arrangement of the fluorescent discharge tubes having different emission colors may be the arrangement shown in FIG. 1B in addition to the above arrangement. In this case, the white fluorescent discharge tube 3 and the colored fluorescent discharge tube 4 are provided close to one end of the light guide plate 1.

Further, as shown in FIG. 1C, two types of fluorescent discharge tubes 3 and 4 may be provided at both ends of the light guide plate 1, respectively, and as shown in FIG. 1D. In addition, two types of fluorescent discharge tubes 3 and 4 may be provided at opposite ends of the light guide plate 1 such that the same type faces each other. Note that FIG.
The light source reflectors 5 and 6 are not shown in FIG. Further, the above-described examples may be combined appropriately.

4. Adjustment of Brightness of Fluorescent Discharge Tube The brightness of the fluorescent discharge tube used in the present invention can usually be easily adjusted by adjusting the input DC voltage of the inverter. The input voltage of the commonly used inverter circuit is often DC 5V or 12V, but color adjustment can be easily performed by changing the inverter input voltage on the colored fluorescent discharge tube side, for example. As a configuration, as shown in FIG. 3, it is economical to provide a circuit that changes the input voltage of only the colored side inverter. As the voltage adjusting circuit, a transistor, a FET (field effect transistor), a dedicated regulator IC, an operational amplifier, or the like can be used.

[0028]

EXAMPLES The present invention will be described in more detail below with reference to examples. A ferroelectric polymer liquid crystal having the following repeating unit was used as the ferroelectric liquid crystal.

[0029]

[Chemical 9]

A PES substrate with ITO in which stripe electrodes having a pitch of 1.27 mm were previously formed by etching (Sumilite FST, Sumitomo Bakelite Co., thickness 100 μm)
m, width 150 mm, length 50 m), one side of the electrode was coated with a 30 wt% toluene solution of the above liquid crystal with a gravure coater to form a liquid crystal layer. Immediately after evaporation of the solvent, the substrate on which nothing was applied was laminated with the electrode surface facing inside. A length of 400 mm was cut out from the thus-prepared unoriented roll-shaped element, and a unidirectional flexural deformation was applied several times while applying a direct current of 60 V between the upper and lower electrodes at room temperature for orientation treatment. It should be noted that this display device includes two polarizing plates (LLC2-92- manufactured by Panak Kogyo Co., Ltd.).
18) was placed in a crossed Nicol state. When a voltage of ± 5 V was applied between the upper and lower electrodes at room temperature and the response was observed, the display colors were yellow and black switching. When this yellow spectrum was measured and calculated from the magnitude of birefringence, the film thickness of the liquid crystal was 3.1 μm. Since it was relatively thick, there were no conduction defects. Next, as shown in FIG. 2, the liquid crystal display element 10 and the light guide plate type illumination device 20 were laminated. The configuration of the light guide plate type lighting device 20 is such that an acrylic plate having a thickness of 4 mm and 150 mm × 420 mm is used as the light guide plate 1, an aluminum reflector plate (Alpet made by Panac Industrial Co., Ltd.) is used as the reflector plate 2, and the light guide plate is also used. A white cold cathode tube (normal tube manufactured by Harrison Co., Ltd.) as a white fluorescent discharge tube 3 and a blue cold cathode tube (blue tube manufactured by Harrison Co., Ltd.) as a colored fluorescent discharge tube 4 are arranged so as to be close to both ends of 1 respectively. Set up in. The light guide plate 1 covers the fluorescent discharge tubes 3 and 4.
At both ends of the, light-reflecting plates 5 and 6 made of Ni-plated iron reflecting frames were provided.

A circuit for adjusting the brightness of the fluorescent discharge tubes 3 and 4 used in this embodiment is shown in FIG. In this circuit, the forward voltage (K about 2.2V) of the LED (light emitting diode) is used for constant voltage output, and the volume (VR) is used.
The output voltage V can be changed by adjusting. When VR was adjusted and V was 6 volts or less, the display color was yellowish, but at V = 6 to 8 volts, it was close to black and white display, and at V> 8 volts, bluish white display. It was possible up to.

[0032]

As described above, the liquid crystal display device of the present invention does not impair the brightness of the display as compared with the case where a complementary color filter, a retardation plate or the like is used for black and white display, and a bright display. Is possible. Further, the display color can be adjusted continuously. Furthermore, since the cell thickness with the highest light transmittance can be set, the cell thickness can be made thicker than the conventional ideal cell thickness, and the yield in manufacturing can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing an arrangement example of fluorescent discharge tubes used in a liquid crystal display device of the present invention.

FIG. 2 is an explanatory view schematically showing an embodiment of the liquid crystal display device of the present invention.

FIG. 3 is an electric circuit diagram used for adjusting the brightness of the fluorescent discharge tube used in the liquid crystal display device of the present invention.

FIG. 4 is an electric circuit diagram used for adjusting the brightness of the fluorescent discharge tube in the embodiment shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light guide plate 2 ... Reflector plate 3 ... White fluorescent discharge tube 4 ... Colored fluorescent discharge tube 5, 6 ... Reflector plate for light source 10 ... Liquid crystal display element 20 ... Light guide plate type lighting device

Claims (3)

[Claims] 1. A liquid crystal display having a liquid crystal display element having a liquid crystal sandwiched between two substrates with electrodes, and a light guide plate type illuminating device comprising at least a light guide plate and an illumination light source arranged at an end thereof. In the device, the liquid crystal used for the liquid crystal display element has ferroelectricity, and the illumination light source of the light guide plate type illumination device has one or more white fluorescent discharge tubes each emitting white light, and a liquid crystal display element. A liquid crystal display device comprising a colored fluorescent discharge tube that emits colored light having a complementary color relationship with the display color of. 2. The ferroelectric liquid crystal display device is 2 to 4 μm.
2. The liquid crystal display device according to claim 1, wherein the liquid crystal display device has a thickness of m and the colored fluorescent discharge tube emits blue light. 3. The liquid crystal display device according to claim 1, wherein the colored fluorescent discharge tube changes brightness according to an input voltage of an inverter.