JP2810313B2 - Large color liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color liquid crystal display device. For more details, display or decoration of personal computers, word processors, wall-mounted televisions, pocket LCD televisions, liquid crystal displays such as liquid crystal projections, audio, instrument panels for vehicles, clocks, calculators, VCRs, fax machines, communicators, games, measuring instruments, etc. Display,
Also, the present invention relates to a color liquid crystal display element which can be suitably used for an advertising display or the like.

[0002]

2. Description of the Related Art A conventional color liquid crystal display device has a high cost because a color filter is provided inside a liquid crystal display cell, that is, on an electrode surface side, so that a coating layer for flattening is required. Did not get. In recent years, a high-resolution STN system and a ferroelectric liquid crystal system have been developed, and particularly high precision is required for the thickness of a liquid crystal display cell, so that a complicated manufacturing process and an increase in cost cannot be avoided. On the other hand, a method of simply providing a color filter outside the liquid crystal display cell is also being developed, but parallax occurs due to the thickness of the substrate and the like.
In particular, it has been difficult to obtain a device having a wide viewing angle with a large liquid crystal display device.

[0003] From such a viewpoint, there is disclosed a color display device in which a substrate of a liquid crystal display cell is made of a plastic film, and a color filter is provided on a side of the film not in contact with the liquid crystal (Japanese Patent Application Laid-Open No. 61-1491984). ). Also disclosed is an element provided on the observation (display) surface side of a liquid crystal display cell, with the surface opposite to the microlens forming surface of the microlens array sheet having microlens units formed only on one surface facing the observation surface ( JP-A-5-219453).

[0004]

However, in the former device, it is necessary to protect the opposite electrode surface when providing the color filter, and depending on the size of the screen, it is not sufficient to simply use the substrate as a film. In some cases, color mixing could not be prevented. In addition, the latter element requires alignment between the microlens sheet and the liquid crystal display cell, and when the pixel becomes large, the thickness of the lens sheet becomes considerably large and is suitable for use in a large area liquid crystal element cell. It was difficult to obtain a suitable lens sheet, and it had to be expensive.
The present invention has been made in view of the above-described problems, and has a wide viewing angle even when the display area is large, and does not cause color mixing between adjacent pixels even when viewed from an oblique direction. It is another object of the present invention to provide a color liquid crystal display device in which a decrease in display luminance is small.

[0005]

According to the present invention, in order to attain the above object, the stripe electrodes are arranged on the inner surface thereof so as to intersect each other and the intersection forms one pixel. A liquid crystal display cell having liquid crystal sandwiched between the two substrates, a color filter layer disposed outside the liquid crystal display cell corresponding to the pixels of the liquid crystal display cell, and one or more polarizing layers. Has a display area of 500
In a large dot matrix type color liquid crystal display element of cm ² or more, the pitch of the stripe-shaped electrodes is 40
A color liquid crystal display device having a thickness of 0 μm or more and a positional relationship between the stripe-shaped electrode and the color filter satisfy the following formulas (I) and (II). a + b ≦ p / 2 (I) 4d ≦ p (II) (where a is 1/2 of the gap between the striped electrodes,
b is 1/2 of the gap between adjacent color filters, d
Represents the distance from the color filter to the electrode closer to the color filter, and p represents the pitch of the striped electrodes. )

Further, the color filter layer is provided on one of a glass plate, a plastic film, and the polarizing plate provided separately from a substrate constituting the liquid crystal display cell. Is provided.

Further, there is provided a color liquid crystal display device, wherein the substrate is made of a plastic film or a plastic sheet.

Further, there is provided a color liquid crystal display device wherein the liquid crystal is a ferroelectric liquid crystal.

Further, there is provided a color liquid crystal display device wherein a backlight is further provided outside the color filter or the polarizing plate.

Hereinafter, the color liquid crystal display device of the present invention will be specifically described for each component. 1. Liquid crystal display cell As shown in FIG. 1, a liquid crystal display cell 10 used in the present invention
Is formed by sandwiching a liquid crystal 2 between two substrates 1 and 3 having striped electrodes 8 and 9 formed on the inner surface thereof. The viewing characteristics of a liquid crystal display element are more susceptible to color mixing and the like as the display area of the element (liquid crystal display panel) is larger. Therefore, since the present invention is effectively applied, the present invention is directed to a liquid crystal display panel having a display area of 500 cm ² or more.

Substrate It is preferable that, of the two substrates used in the present invention, at least the substrate on the display surface side (display substrate) is made optically transparent. As a material, a glass plate or a plastic plate can be used, but a plastic plate is used at least for the display substrate in order to improve impact resistance and reduce the weight of the element. Specifically, low expansion glass (Corning 7059), non-alkali glass (H
OYA NA45), quartz glass, soda lime glass, and the like. Examples of the plastic plate include uniaxial PET and biaxial PET for a crystalline polymer, and PE, PP, PES, PAr, and PC for an amorphous polymer. A plastic plate is preferable because of high productivity of the liquid crystal element. The thickness of the substrate is not particularly limited, but is preferably 20 to 1000 μm.

Electrodes The stripe-shaped electrodes used in the present invention are not particularly limited, but those used at least on the inner surface of a display substrate having transparency include, for example, indium and tin oxide (ITO). It is preferable to have Note that the stripe shape means a stripe shape, and may be linear or curved. The stripe-shaped electrodes are formed on the substrate so as to cross each other, and the crossing portions form one pixel (dot matrix type).

In the present invention, the size of one pixel is set to 400 μm or more in order to secure a viewing angle of 45 ° or more.
If it is too small, color mixture with adjacent pixels may occur even if the viewing angle is less than 45 °, or display luminance may be significantly reduced. Further, since the pixels are large, alignment can be easily performed even when the color filter layer is provided separately from the liquid crystal display cell.

Preferably, the transmittance is 80% or more (only the thin film), the thickness is 200 to 2000 °, and the sheet resistance is 500 Ω / □ or less. The formation method is not particularly limited, and a sputtering method, an evaporation method, a CVD method, a coating method,
A biosol 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.

Liquid Crystal The liquid crystal used in the present invention is not particularly limited, and examples thereof include a nematic liquid crystal, various smectic liquid crystals, and a polymer dispersed liquid crystal. Among them, it is preferable to use a ferroelectric polymer liquid crystal or a composition thereof. When a ferroelectric polymer liquid crystal is contained, strength and durability against external force such as impact and bending can be improved. In addition, the memory property of the ferroelectric liquid crystal can be used, and power consumption can be reduced. In addition, when a series of continuous manufacturing methods of coating and forming a liquid crystal on one substrate, laminating with the other substrate, and bending alignment treatment are employed,
It is particularly preferable to contain a polymer liquid crystal having excellent orientation properties. Examples of the ferroelectric polymer liquid crystal material include one or more ferroelectric polymer liquid crystals, one or more ferroelectric low-molecular liquid crystals and one or more ferroelectric polymer liquid crystals. And a ferroelectric polymer liquid crystal composition comprising one or more ferroelectric low-molecular liquid crystals and one or more other polymer liquid crystals. Can be. That is, as the ferroelectric polymer liquid crystal or the ferroelectric polymer liquid crystal composition, a ferroelectric polymer liquid crystal (a homopolymer or a copolymer or a mixture thereof) in which the 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 with ferroelectric low molecular weight liquid crystal, ferroelectric polymer liquid crystal with ferroelectric low molecular weight All polymer liquid crystals exhibiting ferroelectricity, such as a mixture of a liquid crystal and a high-molecular liquid crystal and / or a normal polymer, or a mixture of these with a normal low-molecular liquid crystal can be used. 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 in molar ratio, and 80:20 to 40:60. Is more preferable.

Among the ferroelectric polymer liquid crystals, for example, a side chain type ferroelectric polymer liquid crystal having a chiral smectic C phase can be suitably used. Further, the ferroelectric liquid crystal composition may contain an adhesive, a viscosity reducing agent, a non-liquid crystal chiral compound, a dye, and the like, as necessary. For example,
In order to improve the mechanical strength of the device, a non-liquid crystalline polymer may be mixed. The thickness of the liquid crystal layer is not particularly limited, but 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, 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 represented by the following formula: A siloxane-olefin main chain type liquid crystal polymer, an ester main chain type liquid crystal polymer and the like are included.

[0017]

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[0018]

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[0019]

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[0020]

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The repeating unit of the ferroelectric liquid crystal polymer may have a side chain skeleton replaced with a biphenyl skeleton, a phenylbenzoate skeleton, a biphenylbenzoate skeleton, or a phenyl 4-phenylbenzoate skeleton. The benzene ring in the skeleton 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, and may be replaced with a halogen group such as fluorine or chlorine or a cyano group. A 1-methylalkyl group, a 2-fluoroalkyl group, a 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 by an optically active group such as a 2-alkoxycarbonyl-1-trifluoromethylpropyl group. In addition, the length of the spacer may vary within a range of 2 to 30 methylene chains. The number average molecular weight of the ferroelectric liquid crystal polymer is preferably from 1,000 to 200,000.
Examples of the ferroelectric low-molecular liquid crystal compound include Schiff base ferroelectric low-molecular liquid crystal compounds represented by the following formulas, azo and azoxy ferroelectric low-molecular liquid crystal compounds, biphenyl and aromatics ester ferroelectric low-molecular compounds. Examples thereof include a molecular liquid crystal compound, a ferroelectric low-molecular liquid crystal compound into which a ring substituent such as a halogen or a cyano group is introduced, and a ferroelectric low-molecular liquid crystal compound having a heterocyclic ring.

[0022]

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[0023]

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[0024]

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[0025]

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These compounds are typical of ferroelectric low-molecular liquid crystal compounds, and the ferroelectric low-molecular liquid crystal compound of the present invention is not limited to these structural formulas.

2. Color filter layer The color filter layer used in the present invention is not particularly limited, and any known color filter layer can be used. However, it is necessary to arrange the color filter layer outside the liquid crystal display cell to prevent a voltage drop due to the thickness of the color filter layer. is there. There is no particular limitation on the production method. It may be provided directly on the surface of the substrate opposite to the electrode, or may be provided on a polarizing plate or a color filter supporting member (glass plate or plastic film) provided separately from the substrate. Good. Further, it is preferable to provide a black matrix between the respective dye layers of the adjacent color filters so as not to lower the contrast.

3. Polarizing Layer The polarizing layer used in the present invention is not particularly limited, and a known polarizing layer, for example, a polarizing plate can be used. In the case of a guest-host system in which a dichroic dye is mixed in a liquid crystal layer, one sheet may be used, but in the case of a birefringent panel, two sheets are arranged on both the outside of the panel. .

4. Backlight In the present invention, a backlight may be used for improving visibility. The backlight is not particularly limited, and a known backlight can be used.

5. Positional Relationship between Striped Electrode and Color Filter In the present invention, the positional relationship between the striped electrode and the color filter as shown in FIG. 2 needs to satisfy the above formulas (I) and (II). The principle will be described below. Here, an example of a structure in which a color filter is provided immediately outside a film substrate with one ITO electrode on one side will be described. Since the maximum viewing angle し な い not mixing with the color filter of the adjacent dot is tan ψ = (a + b) / d (III), it is necessary to increase (a + b) / d. It is also necessary to consider that the apparent aperture ratio is affected by the viewing angle. That is, the maximum area of the display portion is Smax = p ² (IV) when the gap between the electrodes is zero. As shown in FIG. 3, when observed from a direction inclined by 縦 in both the vertical and horizontal directions, the area S of the portion where the ITO electrode and the color filter appear to overlap is S = x ² = {p−2 (a + b)}. ² (V) Therefore, the apparent aperture ratio κ (%) is κ = S / Smax × 100 = [{p−2 (a + b)} ² / p ² ] × 100 = {1-2 (a + b) / p ｝ ² × 100 (VI) By substituting b = dtan ψ−a into equation (VI) from equation (III), κ = ｛(1-2 / p) × dtanψ｝ ² × 100 (VII) . In actual observation, even if the transmitted light intensity was reduced to about 1/4, the display could be viewed without any particular problem.
When the condition of 25 (%) is included, the formula (VII) becomes as follows: tanｐ ≦ p / 4d (VIII). From the formula (III), a + b ≦ p / 4 (I). In the present invention, since the viewing angle is ensured up to 45 °, the formula (VIII) is as follows: 4d ≦ p (II)

Therefore, by satisfying the positional relationships of the formulas (I) and (II), the color liquid crystal display device of the present invention can
Even when viewed from a direction inclined at a maximum of 45 ° from the display surface, no color mixing occurs between adjacent pixels, and the display luminance is 25 when the inclination is 0 ° (when observed from directly in front). % Can be maintained.

[0032]

EXAMPLES Hereinafter, the color liquid crystal display device of the present invention will be described more specifically with reference to examples. Example 1 A commercially available PES substrate with an ITO electrode (polyether sulfone: Sumitomo Bakelite Sumilite FST, thickness 10)
0μm, width 150mm, length 50m) is 150mm × 4
It was cut into 00 mm, and a stripe pattern was formed by etching so as to be orthogonal to each other. The electrode pitch was 1.27 mm, and the gap was 100 μm. An element shown in FIG. 1 was produced as an element configuration. In this case, d = 100 (μm), a = 50 (μm), p = 12
70 (μm), the expression (II) is satisfied, but the expression (I)
In order to satisfy the condition, b ≦ 267.5 (μm) needs to be satisfied. Therefore, the color filter has a pitch of 1.27 mm,
An RGB stripe pattern was printed so that the gap was 150 μm. As the liquid crystal, a mixture of the following ferroelectric polymer liquid crystal and a polystyrene resin having a number average molecular weight of 33000 at 5% by weight was used as an acetone solution, and applied to the ITO surface of one of the substrates by a gravure coater. After the solvent was dried, the substrate was laminated with a counter substrate on which nothing was applied, and was subjected to bending deformation in the position direction while applying a rectangular wave voltage of 20 Hz and ± 50 V between the upper and lower electrodes at room temperature, and oriented.
Next, this panel was arranged as shown in FIG. 1 to form a color liquid crystal display element of 80 dots × 240 dots. When the display luminance was measured in front of the display with a simple luminance meter, 220 cd
/ M ² . Next, the same measurement was performed by tilting the panel 45 ° horizontally, and 70 cd / m ² , and 8 ° when tilted vertically.
It was 5 cd / m ² and had practically sufficient viewing angle characteristics. Further, up to about 50 °, the apparent color change was extremely small, and no color mixing with adjacent pixels was observed.

[0033]

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[0034]

As described above, the color liquid crystal display device of the present invention has a wide viewing angle and does not cause color mixture between adjacent pixels even when viewed from a direction inclined at a maximum of 45 ° from the display surface. And the display luminance is 2 when the inclination is 0 °.
5% can be maintained. In addition, since the color filter layer can be provided on the surface of the substrate opposite to the surface on which the electrodes are provided, the manufacturing process can be simplified and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a specific example of a color liquid crystal display device of the present invention.

FIG. 2 is an explanatory diagram schematically showing a positional relationship between a stripe electrode and a color filter in a color liquid crystal display device of the present invention.

FIG. 3 is a plan view schematically showing, in the color liquid crystal display device of the present invention, a portion where an electrode and a color filter appear to overlap when viewed from a direction inclined by Δ in the vertical and horizontal directions.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Lower substrate 2 ... Liquid crystal 3 ... Upper substrate 4 ... Color filter layer 5 ... Polarizer 6 ... Polarizer 7 ... Backlight 8 ... ITO electrode 9 ... Counter electrode 10 ... Liquid crystal display panel 20 ... Color liquid crystal display element

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02F 1/1335 505

Claims (5)

(57) [Claims] 1. A liquid crystal display having a liquid crystal sandwiched between two substrates provided on its inner surface such that stripe-shaped electrodes intersect each other and the intersections form one pixel. A cell, a color filter layer disposed outside the liquid crystal display cell corresponding to the pixel of the liquid crystal display cell, and one or more polarizing layers.
In a large dot matrix type color liquid crystal display element of cm ² or more, the pitch of the stripe electrodes is 400 μm or more, and the positional relationship between the stripe electrodes and the color filters is expressed by the following formulas (I) and (II). A color liquid crystal display device characterized by satisfying. a + b ≦ p / 2 (I) 4d ≦ p (II) (where a is 1/2 of the gap between the striped electrodes,
b is 1/2 of the gap between adjacent color filters, d
Represents the distance from the color filter to the electrode closer to the color filter, and p represents the pitch of the striped electrodes. ) 2. The liquid crystal display device according to claim 2, wherein the color filter layer is provided on one of a glass plate, a plastic film, and the polarizing plate provided separately from a substrate constituting the liquid crystal display cell. The color liquid crystal display device according to claim 1, wherein 3. The color liquid crystal display device according to claim 1, wherein the substrate is made of a plastic film or a plastic sheet. 4. The color liquid crystal display device according to claim 1, wherein the liquid crystal is a ferroelectric liquid crystal. 5. The color liquid crystal display device according to claim 1, wherein a backlight is further provided outside the color filter or the polarizing plate.