JP3741966B2 - Horizontal electric field type color liquid crystal display element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a color liquid crystal display element, and more particularly to a color filter substrate in a color liquid crystal display element of a lateral electric field (abbreviation of In-Plane-Switching, hereinafter referred to as IPS) system.
[0002]
[Prior art]
On the color filter (CF) substrate of the color liquid crystal display element, red (R), green (G), and blue (B) color layers are formed. A technique for forming these color layers by appropriately adding additives such as pigments and dispersants to a transparent resin such as an acrylic resin in order to obtain a desired chromaticity has been established. Further, the substrate surface on which the color layers are formed is required to be as flat as possible in order to realize a uniform cell gap, so that the color layers have the same thickness.
[0003]
As described above, when the chromaticity and film thickness of each color layer are preferentially satisfied, the specific resistance of each color layer is greatly different, and a variation of about 10 ⁷ to 10 ¹⁴ (Ω · cm) occurs. In particular, it is known that the red layer has a much higher specific resistance than the green layer and the blue layer. It is also known that this large difference in specific resistance is a difference in charge amount, and when the spacer particles are sprayed by the dry spray method, the spacer distribution varies and the display performance deteriorates.
[0004]
In Japanese Patent Laid-Open No. 11-38420, as a means for solving such a problem, the light shielding portion and the spacer particles are arranged so that the dispersed spacer particles are selectively dispersed only on the light shielding portion such as a black matrix. A means for charging to the opposite polarity is used.
[0005]
On the other hand, in Japanese Patent No. 3044788, the IPS system is not targeted, but the effect of voltage drop in the color layer is reduced by reducing the specific resistance of each color layer in the color filter for the liquid crystal display device. is suggesting. For example, it is disclosed that the specific resistance of the R, G, and B layers is 10 ⁸ (Ω · cm) or less by dispersing ITO particles in each color layer.
[0006]
[Problems to be solved by the invention]
However, if the specific resistance of each color layer is made extremely low as in this patent publication, a lateral electric field is not applied, IPS mode driving cannot be performed, and it cannot be applied to a lateral electric field type color liquid crystal display element.
[0007]
Accordingly, an object of the present invention is to provide a color layer that can satisfy a desired chromaticity within a range in which the specific resistance of each color layer is not excessively lowered and that the spacer distribution is uniform even when the spacers are sprayed dry. It is in providing a color filter provided with.
[0008]
In the present invention, if the combination of each color layer is selected so that the specific resistance of each color layer is 10 ¹⁰ (Ω · cm) or more and the specific resistance ratio between each color layer is 600 or less, the chromaticity of each color layer is satisfied. At the same time, it is based on the fact that the spacer distribution can be prevented from affecting the display characteristics by experiments.
[0009]
An object of the present invention is to provide a color layer configuration that reduces uneven dispersion of spacer particles due to uneven charging of a color layer in an IPS color liquid crystal display element.
[0010]
[Means for Solving the Problems]
The IPS color liquid crystal display element of the present invention is provided on a substrate, and is provided on a color layer constituting three primary colors of red (Red), green (Green), and blue (Blue), and the substrate. A horizontal electric field type color liquid crystal display device having a color filter substrate comprising at least a black matrix filling between the color layers and an insulating film covering a surface of the substrate including the color layers and the black matrix, The fact that the relationship between the maximum value and the minimum value of the specific resistance of the color layer is set to 6 × 10 ² times or less of the minimum value of the specific value hardly causes display unevenness due to spacer scattering unevenness. This is based on the finding.
[0011]
According to the present invention, the color filter substrate disposed so that the color layers of the red layer, the green layer, and the blue layer are separated by the black matrix layer, and the color filter substrate through the dry-dispersed particulate spacers, A lateral electric field type color liquid crystal display device comprising: an electrode substrate having pixel electrodes arranged opposite to each other; and a liquid crystal layer sandwiched between the color filter substrate and the electrode substrate, wherein the specific resistance of each color layer Is 10 ¹⁰ Ω · cm or more, and the ratio between the maximum value and the minimum value of the specific resistance of each color layer is 6 × 10 ² or less. .
[0012]
The color layer and the black matrix layer of the color filter substrate are also commonly covered with an overcoat layer. Furthermore, an alignment film is formed on the overcoat layer. Each of the color layers has a composition in which a transparent resin contains a pigment and a dispersant.
[0013]
In addition, according to the present invention, the color filter substrate disposed so that the color layers of the red layer, the green layer, and the blue layer are separated by the black matrix layer, and the color filter substrate facing the color filter substrate via the particulate spacer. And an active matrix substrate having a plurality of pixel electrodes and a common electrode respectively connected to a plurality of switching elements, and a horizontal electric field comprising a liquid crystal layer sandwiched between the color filter substrate and the active matrix substrate A lateral electric field type color liquid crystal display element, wherein the ratio between the maximum value and the minimum value of the specific resistance of each color layer is 6 × 10 ² or less, is also obtained.
[0014]
In the present invention, the specific resistance of each color layer is 10 ¹⁰ (Ω · cm) or more, preferably 1 × 10 ¹¹ to 1 × 10 ¹⁶ (Ω · cm). More preferably, the red layer has a specific resistance of 1 × 10 ¹³ to 1 × 10 ¹⁴ (Ω · cm), and the green layer and the blue layer have specific resistances of 1 × 10 ¹² to 1 × 10 ¹³ (Ω · cm). cm).
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described with reference to FIG. 1 and FIG.
[0016]
The color filter substrate shown in FIG. 1A is composed of three primary colors: an R layer (red layer) 3, a G layer (green layer) 4, and a B layer (blue layer) 5 patterned on the glass substrate 1. A black matrix 2 is formed in the overlapping portion of each color layer, and is configured to shield transmitted light.
[0017]
An overcoat layer 6 is formed on each color layer to cover them in common. The overcoat layer 6 relieves unevenness of the color layer and prevents elution of impurities from the color layer. Further, an alignment film 7 is formed on the overcoat layer 6.
[0018]
Although not shown, the basic configuration of the lateral electric field type color liquid crystal display element is interposed between the color filter substrate, the spacer, and the liquid crystal layer as disclosed in the above-mentioned JP-A-11-38420. And an active matrix substrate disposed opposite to each other. Needless to say, an active matrix substrate for a horizontal electric field type has a plurality of switching elements such as TFTs arranged in a matrix on a glass substrate and the like, and a pixel electrode is connected to each switching element, and the pixel electrode is also provided. The pixel region is formed with the common electrode.
[0019]
Prior to the description of the embodiments of the present invention, the conventional problems will be described in detail with reference to FIG. 1 in order to better understand the present invention.
[0020]
The color filter substrate for IPS shown in FIG. 1A cannot be provided with a conductive film on the inner surface side of the substrate due to the IPS structure, so that the inner surface of the substrate is charged in the manufacturing process of the liquid crystal display element. For example, it is assumed that a negative charge is charged as shown in FIG. In this case, the specific resistance of the black matrix is generally about 10 ⁵ (Ω · cm), which is the lowest in comparison with the color layer. A charge is induced.
[0021]
At this time, if the difference in specific resistance of each of the R, G, and B color layers is large, the charge injection is biased, and the positive charge formed on the surface of each of the R layer 3, G layer 4, and B layer 5 is charged. Variation occurs in the distribution (FIG. 1C).
[0022]
On the other hand, the spacer spraying for forming the cell gap is generally dry spraying. This method is a method in which individual spacer particles are charged and dispersed uniformly to be dispersed, and as shown in FIG. 1C, if each pixel has uneven charging, it appears as uneven scattering of spacer particles. .
[0023]
Since the liquid crystal display element of the IPS mode is normally black, and the spacer in the pixel has a property of transmitting light, the density of the spacer density remarkably deteriorates the display quality.
As described above, the IPS color layer cannot be provided with a conductive film on the inner surface of the substrate. Therefore, an ITO film 8 which is a transparent conductive film is provided on the outer surface on the back side as an antistatic. The ITO film 8 is effective for preventing charging from the back surface in a manufacturing process such as transporting the substrate, but is not sufficiently effective for charging the inner surface of the substrate. For this reason, when charge is injected into each color layer due to charging on the inner surface of the substrate, and the specific resistance inherent in each color layer varies widely, the charged charge is biased, resulting in display defects. In addition, the charge injected into each color layer does not become uniform for 1 hour or more at room temperature even if charge removal such as an ionizer is performed.
[0024]
Based on this conventional problem recognition, in the present invention, the above-described display defects are reduced by combining the color layers so that the specific resistance difference between the R, G, and B color layers is within a certain range. By selecting the specific resistance of each of the R, G, and B color layers to satisfy the following formula (Equation 1), it is possible to prevent uneven charge injection into each color layer and to enable uniform spacer distribution. Was found in the experiment.
[0025]
Maximum specific resistance value / minimum specific resistance value ≦ 6 × 10 ² (Formula 1)
FIG. 2 shows the display unevenness occurrence rate with respect to the maximum value / minimum value of the specific resistance of each color layer. FIG. 2 shows the case where the color filter substrate of the present invention is employed in an IPS mode color liquid crystal display element based on experimentally confirmed data. The maximum specific resistance value / minimum specific resistance value is 6 ×. rapidly display failure has been confirmed to increase more than 10 ^2.
[0026]
In JP-A-11-38420 cited as a conventional example, the resistivity (Ω · cm) of red, green, and blue colored resins is 8.7 × 10 ¹⁵ and 1.1 × 10 ¹³ , respectively. An example of 1.8 × 10 ¹³ is disclosed. In this example, since the specific resistance of the red colored resin is the maximum and the specific resistance of the green colored resin is the minimum, the ratio is 7.9 × 10 ² . However, as shown in FIG. 2, since it exceeds the value defined in the present invention, it is difficult to make the display unevenness occurrence rate zero.
[0027]
As described above, the IPS color liquid crystal display device is characterized by a sharp change when the display unevenness occurrence ratio with respect to the specific resistance ratio exceeds a certain value, and the conventional vertical electric field type liquid crystal display device has a characteristic. It is not possible.
[0028]
In Japanese Patent No. 3044788 cited in the conventional example, the specific resistances of the R, G, and B layers are 10 ⁸ (Ω · cm), 10 ⁷ (Ω · cm), and 10 ⁷ (Ω · cm), respectively. Although the specific resistance maximum / minimum ratio is small, as already described in the description of the conventional example, the specific resistance of each color layer is small, so that it can be applied to an IPS type color liquid crystal display element. It is unsuitable to do.
[0029]
The present invention not only satisfies the above formula (1) for the ratio between the maximum value and the minimum value of the specific resistance of each color layer, but the specific resistance of each color layer is 10 ¹⁰ (Ω · cm) or more, preferably 1 ×. By determining the combination of each color so that it falls within the range of 10 ¹¹ to 1 × 10 ¹⁶ (Ω · cm), it can be applied to an IPS color liquid crystal display element.
[0030]
Each color layer employed in the present invention is formed by dispersing a pigment in a conventionally known transparent resin such as acrylic, and the specific resistance of each color layer is a desired value depending on the pigment concentration and additives such as a dispersant. Since the technology to decide on has already been established, the details are omitted here.
[0031]
In order to control the specific resistance, for example, there is a method of adjusting a pigment component or a dispersant component. As another method, a method of adjusting the pigment concentration is also possible, but in order to obtain a necessary chromaticity, the thickness of the color layer is adjusted at the same time. Another method is to adjust the thickness of the color layer. This adjustment inevitably causes unevenness in the film thickness of each color layer, but the overcoat layer can relieve the unevenness and causes no problem. It is also possible to selectively control the resistance by pigment concentration, dispersant concentration, or the like.
[0032]
Furthermore, as a method for controlling the specific resistance, a method in which two or more of the above methods are arbitrarily selected and combined may be used. Further, the adjustment for obtaining the chromaticity required for the color layer is generally performed by the pigment other than the film thickness and the pigment concentration.
[0033]
In a preferred embodiment of the present invention, the specific resistance of each color layer is devised so as to be close to each other within a range in which the specific resistance does not change greatly from the standard specific resistance of each color layer that achieves preferable chromaticity. That is, the red layer reduces the specific resistance in a range that satisfies the desired chromaticity, and the specific resistance of the green layer and the blue layer increases the specific resistance in the range that satisfies each chromaticity, If the specific resistance is determined so as to satisfy Expression (1), the above-described effect can be achieved without greatly deviating from a predetermined chromaticity.
[0034]
As described above, the influence of charging in the manufacturing process of the IPS mode liquid crystal display element is achieved by setting the specific resistance difference between the color layers on the color filter substrate side for the IPS mode liquid crystal display element to 6 × 10 ² or less. Can be prevented. Thereby, the density nonuniformity in spacer dispersion | distribution can be eliminated. The non-uniform spacer distribution causes a display failure such as luminance unevenness and color unevenness of the liquid crystal display element, and particularly in the case of an IPS mode liquid crystal display element, such a display failure becomes remarkable. Display defects can be reduced by the combination of layers.
[0035]
As a method for forming the spacer, in addition to the spraying method described in the above embodiment, as shown in Japanese Patent Laid-Open No. 11-38420 described above as a conventional example, a spacer is selectively formed on the light shielding portion to improve display quality. There is a technique to arrange. In this method, it is possible to concentrate the spacer on the light-shielding portion by applying an electric charge having a polarity different from that of the spacer to the light-shielding portion. However, the present invention is also applied to a method for manufacturing a liquid crystal display element using this technique. By applying the combination of color layers according to the embodiment, it is possible to prevent spacer scattering unevenness due to charging.
[0036]
【The invention's effect】
As described above, if the color layer combination structure of the present invention is used, the effect of charging in the manufacturing process can be reduced by reducing the specific resistance value difference of each color layer in the color filter substrate for the IPS mode color liquid crystal display element. It is possible to prevent the density unevenness in spacer dispersion. Therefore, display defects such as luminance unevenness and color unevenness of the IPS mode color liquid crystal display element can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a state of charging on a color filter substrate side of a liquid crystal display element.
FIG. 2 is a graph showing the dependence of the display unevenness occurrence rate, which is the basis for obtaining the color layer on the color filter substrate of the embodiment of the present invention, on the ratio of the maximum specific resistance value / minimum specific resistance value of the color layer. is there.
[Explanation of symbols]
1 Glass substrate 2 Black matrix 3 R layer 4 G layer 5 B layer 6 Overcoat layer 7 Alignment film 8 ITO film

Claims (5)

A color filter substrate disposed so that each color layer of the red layer, the green layer, and the blue layer is separated by a black matrix layer, and a pixel electrode disposed so as to face the color filter substrate through dry-dispersed particulate spacers And a liquid crystal layer sandwiched between the color filter substrate and the electrode substrate, wherein each color layer has a specific resistance of 10 ¹⁰ Ω · cm. A horizontal electric field type color liquid crystal display element as described above , wherein the ratio between the maximum value and the minimum value of the specific resistance of each color layer is 6 × 10 ² or less.   2. The lateral electric field type color liquid crystal display element according to claim 1, wherein each of the color layers and the black matrix layer of the color filter substrate are covered in common by an overcoat layer. The lateral electric field type color liquid crystal display element according to claim 2, wherein an alignment film is formed on the overcoat layer.   2. The lateral electric field type color liquid crystal display element according to claim 1, wherein each of the color layers has a composition in which a transparent resin contains a pigment and a dispersant. A color filter substrate disposed so that each color layer of the red layer, the green layer, and the blue layer is separated by a black matrix layer; and a plurality of the plurality of color filter substrates disposed opposite to the color filter substrate via dry-dispersed particulate spacers. A lateral electric field type color liquid crystal display comprising: an active matrix substrate having a plurality of pixel electrodes and a common electrode connected to each switching element; and a liquid crystal layer sandwiched between the color filter substrate and the active matrix substrate A specific resistance of each color layer is 10 ¹⁰ Ω · cm or more, and a ratio between a maximum value and a minimum value of specific resistance of each color layer is 6 × 10 ² or less. Horizontal electric field type color liquid crystal display element.

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