JP3658904B2 - Liquid crystal display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device.
[0002]
[Prior art]
FIG. 2 is a partial sectional view of an example of a conventional color liquid crystal display device. The color liquid crystal display device includes a lower glass substrate 1 and an upper glass substrate 11. A pixel electrode 2 made of ITO and a thin film transistor 3 as a switching element are provided in a matrix form in the display area on the upper surface of the lower glass substrate 1, and an overcoat film 4 is provided on the entire upper surface. Is provided with an alignment film 5.
[0003]
A light shielding film 12 made of chromium is provided in a lattice pattern in the display area on the lower surface of the upper glass substrate 11, and red, green, and blue color filter elements 13 are provided on the lower surface, and an overcoat film is provided on the lower surface. 14, a common electrode 15 made of ITO is provided on the lower surface, and an alignment film 16 is provided on the lower surface. And the lower glass substrate 1 and the upper glass substrate 11 are bonded together via the sealing material 21 formed by printing in the non-display area | region of the predetermined surface of any one glass substrate. A liquid crystal 22 is sealed between the alignment films 5 and 16 of the glass substrates 1 and 11 inside the sealing material 21.
[0004]
By the way, when the glass substrates 1 and 11 are bonded to each other through the sealing material 21, for example, a positional shift of about several μm may occur in the left-right direction in FIG. Then, the positional relationship between the pixel electrode 2 and the opening 12a of the light shielding film 12 is shifted in the left-right direction in accordance with the positional shift amount. However, even in such a case, it is necessary to prevent the left and right edges of the opening 12 a of the light shielding film 12 from protruding from the left and right edges of the pixel electrode 2. For this reason, the left and right edges of the opening 12a of the light shielding film 12 are arranged inside the left and right edges of the pixel electrode 2 at a position that is far apart to some extent in view of the above-described positional deviation. As a result, there is a problem that the aperture ratio is lowered.
[Problems to be solved by the invention]
[0005]
Conventionally, as described above, the light shielding film 12 is formed of chromium, but recently, in order to reduce the cost and reduce the reflectance of the light shielding film, carbon is included in the acrylic resin. Alternatively, it has been attempted to form the resin black by dispersing a black pigment. However, even if the light shielding film 12 is formed of resin black, the above-described problem of a decrease in aperture ratio cannot be solved.
An object of the present invention is to form a light shielding film from resin black and to increase the aperture ratio.
[0006]
[Means for Solving the Problems]
The present invention relates to a liquid crystal display device in which one substrate provided with a pixel electrode and a switching element and the other substrate provided with a common electrode are bonded together via a sealing material.
A first overcoat film is provided on the plurality of pixel electrodes and the plurality of switching elements provided in a matrix, and a plurality of color filter elements provided on the first overcoat film are in contact with each other. A light shielding film made of resin black is provided on a portion where the color filter elements are in contact with each other, and a second overcoat film having a flat upper surface is provided on the light shielding film and the color filter element. To do.
[0007]
According to the present invention, since the light shielding film made of resin black is provided on the pixel electrode and the switching element of one substrate, the pixel electrode and the switching element are not affected by the positional deviation when the two substrates are bonded together via the sealing material. The positional relationship with the opening of the light shielding film can be set. As a result, the opening of the light shielding film can be made as large as possible, and the aperture ratio can be increased.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a cross-sectional view of a main part of a color liquid crystal display device according to an embodiment of the present invention. This color liquid crystal display device also includes a lower glass substrate 31 and an upper glass substrate 41 as in the conventional case. In the display area on the upper surface of the lower glass substrate 1, pixel electrodes 32 made of ITO and thin film transistors 33 as switching elements are provided in a matrix, and an overcoat film 34 is provided on the entire upper surface. In this case, the overcoat film 34 is formed of a silicon nitride film or a silicon oxide film having a thickness of about 3000 to 4000 mm formed by plasma CVD.
[0009]
Red, green, and blue color filter elements 35 are provided in contact with each other in the display region on the upper surface of the overcoat film 34. In this case, the color filter element 35 is formed with a film thickness of about 1 to 3 μm by a dispersion method using a color resist containing a pigment, but may be formed by a single layer dyeing method or the like. On the upper surface of the color filter element 35, a light shielding film 36 is provided in a predetermined pattern, for example, in a lattice pattern. In this case, the light shielding film 36 is formed with a film thickness of about 1 μm by resin black obtained by dispersing carbon in a resin such as an acrylic resin. An alignment film 37 is provided on the top surfaces of the light shielding film 36 and the color filter element 35.
[0010]
On the other hand, a common electrode 42 made of ITO is provided in the display area on the lower surface of the upper glass substrate 41, and an alignment film 43 is provided on the lower surface thereof. And the lower glass substrate 31 and the upper glass substrate 41 are bonded together via the sealing material 51 formed by printing in the non-display area | region of the predetermined surface of any one glass substrate. A liquid crystal 52 is sealed between the alignment films 37 and 43 of the glass substrates 31 and 41 inside the sealing material 51.
[0011]
Thus, in this color liquid crystal display device, since the color filter element 35 is provided on the overcoat film 34 of the lower glass substrate 31 and the light shielding film 36 made of resin black is provided thereon, both the glass substrates 31, The positional relationship between the pixel electrode 32 and the opening 36a of the light shielding film 36 can be set regardless of the positional deviation when the 41 is bonded through the sealant 51. As a result, the opening 36a of the light shielding film 36 can be made as large as possible, and the opening ratio can be increased.
[0012]
Further, in this color liquid crystal display device, a light shielding film 36 is provided on the overcoat film 34 covering the pixel electrode 32 and the thin film transistor 33 via the color filter element 35. Moreover, the color filter elements 35 are provided in contact with each other. As a result, even if the electrical resistivity of carbon in the light shielding film 36 is small and the relative dielectric constant is large, the relatively thick color filter element 35 having a film thickness of about 1 to 3 μm functions as an insulating film in addition to the overcoat film 34. As a result, leakage current and coupling (capacity increase) between the pixel electrode 32 and the wiring (not shown, a scanning line, a signal line, etc. connected to the thin film transistor 33) can be reduced. Further, by reducing the leakage current and coupling, the distance between the pixel electrode 32 and the wiring can be reduced to some extent, and the aperture ratio can be further increased. Further, since the color filter element 35 functions as an insulating film, the influence of the lateral electric field is reduced, and the disclination can be reduced.
[0013]
In the above embodiment, the light shielding film 36 is formed of resin black obtained by dispersing carbon in a resin such as an acrylic resin. However, a resin obtained by dispersing a black pigment in a resin such as an acrylic resin. You may form with black. However, in the case of a black pigment-dispersed resin black, the optical density is lower than that of a carbon-dispersed resin black. Therefore, in order to obtain a predetermined optical density, the film thickness must be relatively thick, such as about 3 μm or more. Don't be. However, as shown in FIG. 1, the upper surface of the alignment film 37 provided on the light shielding film 36 and the color filter element 35 is uneven depending on the film thickness, arrangement position, etc. of the light shielding film 36. For this reason, when the thickness of the light shielding film 36 is increased to about 3 μm or more, the flatness of the upper surface of the alignment film 37 is deteriorated, which may cause alignment failure of the liquid crystal 52. For this reason, it is desirable to use a carbon-dispersed resin black that can obtain a sufficient light-shielding effect even if the film thickness is relatively thin as the material of the light-shielding film 36. An overcoat film having a flat upper surface may be provided on the light shielding film 36 and the color filter element 35 made of carbon black or black pigment-dispersed resin black, and an alignment film 37 may be provided thereon.
[0014]
Moreover, although the said embodiment demonstrated the case where the color filter element 35 was provided, it is applicable also to the thing which is not provided with the color filter element 35. FIG. In this case, an insulating film made of a transparent resist or the like containing no pigment is formed on the display area on the upper surface of the overcoat film 34 so as to be relatively thick with a film thickness of about 1 to 3 μm, and the upper surface is made of carbon black of resin dispersed. When the light shielding film is formed, the above-described effects can be obtained.
[0015]
【The invention's effect】
As described above, according to the present invention, since the light-shielding film made of resin black is provided on the pixel electrode and the switching element of one substrate, the positional deviation when the two substrates are bonded together via the sealing material. Regardless, the positional relationship between the pixel electrode and the opening of the light shielding film can be set. As a result, the opening of the light shielding film can be made as large as possible, and the aperture ratio can be increased.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a main part of a color liquid crystal display device according to an embodiment of the invention.
FIG. 2 is a partial cross-sectional view of an example of a conventional color liquid crystal display device.
[Explanation of symbols]
31 Lower glass substrate 32 Pixel electrode 33 Thin film transistor 35 Color filter element 36 Light shielding film 41 Upper glass substrate 42 Common electrode 51 Sealing material 52 Liquid crystal

Claims (2)

In a liquid crystal display device in which one substrate provided with a pixel electrode and a switching element and the other substrate provided with a common electrode are bonded together via a sealing material,
A first overcoat film is provided on the plurality of pixel electrodes and the plurality of switching elements provided in a matrix, and a plurality of color filter elements provided on the first overcoat film are in contact with each other. A light shielding film made of resin black is provided on a portion where the color filter elements are in contact with each other, and a second overcoat film having a flat upper surface is provided on the light shielding film and the color filter element. Liquid crystal display device.   2. The liquid crystal display device according to claim 1, wherein the light shielding film is made of resin black in which carbon is dispersed in a resin.

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