JP4054132B2 - Liquid crystal display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device that displays red on a black background.
[0002]
[Prior art]
From the viewpoint of cosmetics, visibility, etc., there is a use in which a combination of a black background and a red display is preferred, and it has been used for display parts such as calculators, advertising dials, and in-vehicle audio for a long time.
[0003]
Conventionally, in these applications, self-luminous display elements such as light-emitting diodes, electroluminescent elements, and plasma displays have been used. However, there is a problem that a so-called washout phenomenon occurs in which display is not visible under external light. It was.
[0004]
On the other hand, this problem can be avoided by using a transflective or reflective liquid crystal display element. For example, a negative mode twisted nematic (TN) transflective liquid crystal display panel and a main light emission of a light source A combination with a backlight unit having a wavelength of 620 nm or more, or a combination of a reflective liquid crystal panel of the same type and a red filter layer enables display that is not affected by external light.
[0005]
However, this system has a limit in display density, and is composed of 5 × 7 dots, which are so-called character displays, or 16 × 16 dots, with time-division driving of about 1/16 duty or more. However, when trying to display kana / kanji characters, there was a problem that they could only be seen at a specific angle.
[0006]
On the other hand, if the super twist nematic (STN) method is used, a decrease in visibility due to an increase in display density can be avoided, but a method using a phase difference plate as an optical compensator for black-and-white conversion is used as in-vehicle applications. When applied to an environment where the operating temperature range is wide, there arises a problem that the background color of the non-display portion changes at a high temperature and the contrast is lowered.
[0007]
In addition, according to the method using a liquid crystal cell (interference cell) in which the twist direction is the same as that of the liquid crystal cell for display as the optical compensator, and the direction of twist is reversed in the cell gap, this problem can be avoided. There is a problem that productivity is lowered because it is necessary to control and create a gap between both cells with high accuracy including a relative relationship.
[0008]
As a method that does not use the optical compensator for black and white as described above, specializing in the purpose of displaying two colors in red on a black background, the transmitted light is transmitted when a white backlight light source is used. A method of combining a so-called blue mode liquid crystal display panel, which is blue-green below the excitation voltage and light gray above the excitation voltage, and a red backlight is conceivable.
[0009]
According to this method, the transmitted light is red at the display unit and is blocked at the background unit to be black, but when viewed under external light, the blue mode background color is visible in the reflected light, and the display quality is impaired. In particular, when a transflective diffuser disposed outside the polarizing plate on the back side is used as the diffuser of the backlight, there is a problem that this tendency becomes remarkable.
[0010]
This problem can be avoided by using a separate diffusion plate colored with a colorant that compensates for the color of the blue mode as the diffusion plate, but the structure of the liquid crystal display device becomes complicated and the assembly is complicated. In addition, new problems such as difficulty in thinning occur.
[0011]
[Problems to be solved by the invention]
The present invention has been made to solve the above-described conventional problems, and is a liquid crystal display device that displays red on a black background, and the washout phenomenon and background color change even under external light. An object of the present invention is to provide a liquid crystal display device that is simple in structure, easy to assemble, and capable of time-division driving up to about 1/33 duty.
[0012]
[Means for Solving the Problems]
The liquid crystal display device of the present invention according to claim 1 is characterized in that a twist angle is 180 to a space surrounded by a pair of transparent substrates each having a transparent electrode and an alignment film and arranged in parallel and a peripheral sealing material. A super twist nematic liquid crystal display panel in which a liquid crystal layer made of nematic liquid crystal set at 270 ° is sandwiched and a pair of polarizing plates are arranged on both outer sides of the pair of transparent substrates, and the main emission wavelength of the light source is In a liquid crystal display device that performs two-color display of red on a black background having a backlight unit of 620 nm or more, the back-side polarizing plate is formed by integrally laminating a transflective layer on the outside, and A light-transmitting film made of a photosensitive resin material on the inner surface of one of the transparent substrates and having a light transmittance of wavelengths of 640 nm and 450 nm of 70% or more and 20% or less, respectively, and The translucent film has been extended to the bottom of the peripheral sealing material such that the gap of the gap between the display portion of the seal portion becomes the same by the peripheral sealing material, the main emission wavelength of the liquid crystal layer is backlight source And the angle between the polarization axis direction of the polarizing plate on the front side and the alignment direction of the alignment film on the front substrate is 0 from the alignment direction to the twist direction of the liquid crystal. The polarization axis directions of both polarizing plates are substantially coincident with each other, and when using a white backlight source, the transmitted light is blue when the excitation voltage is lower than the excitation voltage, and is light when the excitation voltage is higher than the excitation voltage . With this configuration, the washout phenomenon and background color change do not occur even under external light, the structure is simple, the assembly is easy, and time-division driving up to about 1/33 duty is possible. A liquid crystal display device is realized. Further, by extending the translucent film below the peripheral sealing material and making the gap of the seal part and the gap of the display part the same, it becomes easy to control the gap in cell creation. In addition, excellent display quality is maintained even at higher temperatures.
[0013]
The liquid crystal display device of the present invention according to claim 2 is characterized in that the translucent film is made of a photosensitive resin material and has an insulation resistance of 10 ¹² Ω / □ or more. By adopting such a configuration, the smoothness of the translucent film is improved, and it is possible to form a transparent electrode directly on the translucent film without using a planarizing layer. Leakage between them is prevented, and clear display without bleeding becomes possible.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0015]
As shown in FIG. 1, the liquid crystal display device of the present invention includes a pair of transparent substrates 1, 1 and a peripheral sealing material 4, each having transparent electrodes 3, 3 and an alignment film (not shown). A liquid crystal layer 7 made of nematic liquid crystal whose twist angle is set to 180 to 270 ° is sandwiched in a space consisting of the above, and a pair of polarizing plates 5, 5 are arranged on both outer sides of the pair of transparent substrates 1, 1. And a backlight unit 8 having a main light emission wavelength of 620 nm or more, and a driving means (not shown) or the like is added to the backlight unit 8.
[0016]
In the present invention, the back side (lower side in the figure) polarizing plate 5 is integrally laminated with the transflective layer 6 on the outer side (lower side in the figure), and either one of the transparent substrates 1. It is important that the light-transmitting film 2 having a light transmittance of wavelengths of 640 nm and 450 nm of 70% or more and 20% or less is provided on the inner surface.
[0017]
The transflective layer 6 also functions as a diffuser plate for backlight light. However, if the semi-transmissive reflective layer 6 is laminated and integrated with the back-side polarizing plate, the assembly process can be simplified and the apparatus can be made thinner. As a polarizing plate having a semi-transmissive reflective layer laminated and integrated, various types having different transmittance / reflectance balance and the like are on the market, but it is preferable to select appropriately according to the application of the display device.
[0018]
In the present invention, it is preferable that the light-transmitting film 2 is made of a photosensitive resin material in addition to the light absorption characteristics, and has an insulation resistance of 10 ¹² Ω / □ or more. By using the photosensitive resin material, it becomes easy to form a light-transmitting film smoothly, and it becomes possible to form a transparent electrode directly on the transparent film without using a planarizing layer. In that case, if the insulation resistance of the light-transmitting film is 10 ¹² Ω / □ or more, leakage between adjacent electrodes is prevented, clear display without bleeding is possible, and a protective layer for insulation becomes unnecessary. As a material for the light-transmitting film, a material having heat resistance that can withstand the process temperature, resistance to chemicals during patterning of the transparent electrode, and a predetermined hardness is preferable.
[0019]
A roll coater, bar coater, slit coater, etc. can be used for coating the translucent film material. However, since film thickness variations cause color variations and cell gap variations, spins with excellent film thickness uniformity can be used. Adopting a coating method is desirable. In this case, in order to reduce the amount of material used, it may be used in combination with a bar coater or a slit coater. In addition to this example, any method may be adopted as long as the method has excellent film thickness uniformity.
[0020]
A transparent conductive film is formed on the substrate on which the light-transmitting film is thus formed by a sputtering method or the like. The surface resistance value of the transparent conductive film is set to a value determined by the pattern design of the element, but a range of about 30 to 100Ω / □ is usually adopted. Thereafter, the transparent electrode is formed by patterning by a conventional method.
[0021]
An alkali prevention film and ITO are sequentially formed on the other substrate, and a transparent electrode is formed in the same manner. An alignment film having a thickness of about 60 nm is formed on the substrate on which the light-transmitting film is formed. On the other substrate, an insulating film such as an inorganic film in which titania and silica are mixed is preferably printed by, for example, a sol-gel method, and then an alignment film is formed to be rubbed. The inorganic film is effective for preventing a short circuit between the opposing substrates.
[0022]
It is preferable in terms of process that the spacers for controlling the gap between the substrates and the peripheral sealing material are printed on different substrates. In order to establish conduction between the upper and lower sides of the substrate, a part of the sealant mixed with conductive beads can be used.
[0023]
Note that by extending the light-transmitting film below the peripheral sealing material, the gap between the seal portion and the display portion becomes substantially the same, so that there is an advantage that it is easy to control the gap in cell creation.
[0024]
The substrate provided with the light-transmitting film is opposed to the other substrate, the sealing material is cured through the thermocompression bonding process, the injection port, the terminal portion, etc. are cut out, the cell and the liquid crystal injection boat are heated, and the liquid crystal is evacuated. After injecting by the injection method, a liquid crystal cell is produced by a method such as sealing the injection port with a UV curable resin.
[0025]
The twist angle of the liquid crystal layer is in the range of 180 to 270 °, but is preferably set to 180 to 240 ° from the viewpoint that domain generation at high temperatures hardly occurs. In addition, as Δnd, about 0.8 to 1.2 μm can be used. However, in a small region, the transmittance when no voltage is applied is low, and in a large region, there is a tendency that the viewing angle dependency of the transmittance is large. Therefore, about 0.9 to 1.0 μm is preferable. Polarizers are installed on both sides of the cell so that a so-called negative liquid crystal display mode is obtained in which the transmittance is low when no voltage is applied and the transmittance is high when a voltage is applied.
[0026]
As for the installation angle of the polarizing plate, the polarizing plate is generally called blue mode so that the transmittance is low when no voltage is applied, blue to blue-green, and the transmittance is high when the voltage is applied and the color is almost achromatic. It is also a preferable aspect to install.
[0027]
It is preferable that the liquid crystal layer contains a dichroic dye having the main emission wavelength of the red backlight and the maximum absorption wavelength substantially matching, since the degree of light shielding is further increased. At this time, the angle formed by the polarization axis direction of the polarizing plate on the front side and the alignment direction of the alignment film on the front substrate is 0 to 30 ° from the alignment direction to the twist direction of the liquid crystal, It is also a preferred embodiment that when a white backlight light source is used, a guest-host type liquid crystal display element that exhibits a blue absorption color below the excitation voltage and a light color above the excitation voltage.
[0028]
Examples of the light source having a main emission wavelength of the backlight unit used in the present invention of 620 nm or more include a red LED and a red CCT.
[0029]
【Example】
[Example 1]
Using a mother substrate in which a silica substrate is formed on a glass substrate with a thickness of about 20 nm by sputtering, a red photosensitive resin material (V-259R-H manufactured by Nippon Steel Chemical Co., Ltd.) is applied by spin coating. The film was applied to a thickness of about 1 μm and exposed to 300 mJ using a photomask that shielded light from the seal portion and the outer portion provided around the liquid crystal cell, followed by development, drying, and baking. . The thus formed light-transmitting film had light transmittances of wavelengths of 640 nm and 450 nm of 88% and 4%, respectively, and an insulation resistance value of 3 × 10 ¹⁴ Ω / □.
[0030]
A transparent conductive film having a thickness of about 100 nm was formed by sputtering at a temperature of 230 ° C. on the substrate on which the light-transmitting film was thus formed. The sheet resistance value was about 30Ω / □. After applying photoresist to this substrate, use a photomask that shields the wiring so that voltage is applied to the segment display area, and after exposure and development, remove unnecessary ITO with an etchant. Further, the resist was stripped off with an aqueous NaOH solution to form a transparent electrode having a pattern displaying 2 rows of 5 × 7 dot characters. An alkali prevention film and ITO were sequentially formed on the opposing substrate, and a transparent electrode was similarly formed.
[0031]
A polyimide alignment film material having a pretilt angle of about 5 degrees was used for the substrate on which the light shielding film was formed, and the film was formed to a thickness of about 60 nm by a transfer printing method. In order to form an inorganic insulating film in which titania and silica were mixed on the opposing substrate, a printed film was formed by a sol-gel method. After that, an alignment film was similarly formed and baked, and both the substrates were rubbed so that the twist angle was 240 °.
[0032]
One side of the substrate is sprayed with micropearl made by Sekisui Fine Chemical Co., Ltd., which has a diameter of 6.75 μm, and the opposite substrate is screen printed with Mitsui Chemicals' struct bond as a peripheral sealing material around the liquid crystal cell. Printed at A seal material mixed with conductive beads was printed on a portion provided with an electrode for establishing conduction between opposing substrates.
[0033]
These substrates are made to face each other, cured through a thermocompression bonding process, and after cutting out the injection port, terminal portion, etc., the nematic-isotropic phase transition temperature is 110 ° C., Δn is 0.14, and a predetermined pitch is obtained. A nematic liquid crystal with a chiral material added thereto was injected by a vacuum injection method, and a UV curable epoxy resin was applied to the injection port and sealed.
[0034]
When the gap of each segment portion was measured, the average was 6.7 μm, and the variation was within a deviation of about 0.05 μm at the maximum, and cells with good uniformity were formed. Δnd of the liquid crystal layer of this cell is 0.94 μm. Thereafter, a transmissive type polarizing plate was attached to the front side and a polarizing plate integrally laminated with a semi-transmissive reflective layer on the back side was attached at a predetermined angle to complete the liquid crystal display panel.
[0035]
The panel produced in this way is driven at 1/16 duty, and a backlight using a red LED having a main emission wavelength of 640 μm as the light source is installed on the back, and observed in a bright environment and a dark environment. A high quality red display was obtained on a black background.
[0036]
[Example 2]
Example 1 except that the liquid crystal to be injected was the same liquid crystal as in Example 1 in which 1% of an anthraquinone dichroic dye having a maximum absorption wavelength of about 640 nm was added, and that the cell gap was 6.0 μm. A liquid crystal cell was prepared in the same manner as described above.
[0037]
After that, a transmissive type polarizing plate is attached on the front side with the rubbing direction and transmission axis of the front side alignment film aligned, and a polarizing plate with a semi-transparent reflective layer laminated on the back side on the front side. A liquid crystal display panel was completed by pasting it so as to coincide with the polarization axis of the polarizing plate.
[0038]
The panel thus produced was driven at 1/16 duty, and a backlight using a red LED having a main emission wavelength of 628 μm as a light source was installed on the back, and observed in a bright environment and a dark environment. Under either condition, a high-quality red display was obtained on a black background.
[0039]
【The invention's effect】
According to the present invention, a liquid crystal display device that displays red on a black background, which maintains a high-quality display without any washout phenomenon or background color change even under external light, has a simple structure, and is assembled Therefore, a time-division drive up to about 1/33 duty is possible, and a liquid crystal display device suitable for in-vehicle use is realized.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a basic configuration of a liquid crystal display device of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Translucent film 3 Transparent electrode 4 Peripheral sealing material 5 Polarizing plate 6 Transflective layer 7 Liquid crystal layer 8 Backlight unit 9 Light source

Claims (2)

A liquid crystal layer made of nematic liquid crystal having a twist angle of 180 to 270 ° is sandwiched between a space surrounded by a pair of transparent substrates and transparent sealing materials each having a transparent electrode and an alignment film, and a peripheral sealing material. A super twist nematic liquid crystal display panel in which a pair of polarizing plates are arranged on both outer sides of the pair of transparent substrates, and a backlight unit having a main light emission wavelength of 620 nm or more and a red background with a black background In a liquid crystal display device that performs two-color display,
The back side polarizing plate is integrally laminated with a transflective layer on the outside, and is made of a photosensitive resin material on the inner surface of one of the transparent substrates, and has a light transmittance of 640 nm and 450 nm, respectively. A translucent film of 70% or more and 20% or less is provided, and the translucent film is provided under the peripheral sealing material so that the gap of the sealing portion by the peripheral sealing material and the gap of the display portion are the same. The liquid crystal layer contains a dichroic dye whose main emission wavelength and the maximum absorption wavelength of the backlight light source substantially coincide with each other, and the polarization axis direction of the polarizing plate on the front side and the orientation of the front substrate The angle formed with the alignment direction of the film is 0 to 30 ° from the alignment direction to the twist direction of the liquid crystal, the polarization axis directions of the two polarizing plates are substantially coincided, and transmitted light is transmitted when a white backlight light source is used. Excitation electricity The liquid crystal display device, characterized in that the following exhibiting light-colored in blue, the excitation voltage or more. It said transparent film is made of photosensitive resin material, and a liquid crystal display device according to claim 1 insulation resistance of 10 ¹² Ω / □ or more.

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