JP2000193959A - Liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the luminance unevenness in a transverse direction and to enhance a display grade by setting the outer edges near the display region of the electrical insulating parts formed by linearly removing part of a conductive film layer under a non-display region nearer the display region side than the center of a seal. SOLUTION: The conductive film layer 5 is at least partly removed linearly under the non-display region on at least one peripheral side, by which the electrical insulating parts 8 are formed at the conductive film layer 5. The outer edges near the display region of the electrical insulating parts 8 exist nearer the display region side than the center of the seal 1. The occurrence of probability of shorting itself is, therefore, lowered and even if the shorting occurs, the capacitive component loaded on display electrodes 4a is eventually restricted to the small value corresponding to the narrow area under the non-display region and the occurrence of the luminance unevenness is suppressed. As regards the liquid crystal display element of the structure in which the inter-substrate conduction connection is executed within the seal, the positions of the electrical insulating parts 8 overlap on the positions where at least part of the seal 1 is formed. The overlap width W thereof is preferably >=75% of the sealing width ws.

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 in which a substrate having a conductive layer below a display electrode and electrically insulated from the display electrode is one of the substrates.

[0002]

2. Description of the Related Art Various types of liquid crystal display devices capable of color display are known, but a liquid crystal display device using a color filter is the most common. Various methods of forming this color filter are also known, such as a pigment dispersion method, an electrodeposition method, a printing method, and a dyeing method.
Advantages such as high-precision film thickness control with a simple process, excellent color reproducibility, and film formation with a high degree of freedom in the process of manufacturing a liquid crystal display element can be enjoyed.

However, in this method, a color filter layer is formed by forming a conductive film layer on a substrate, fixing a color material using the conductive film layer as an electrode, and forming a flattening film and a display electrode thereon. Therefore, in the completed liquid crystal display element, the display electrode has a structure in which the display electrode faces the conductive film layer by inserting the insulating color filter layer and the flattening layer. Depending on the display method, display defects due to this structure may be caused. There was a problem that became noticeable.

For example, in a liquid crystal display device having such a structure, a plurality of row electrodes (selection electrodes) are simultaneously selected, and
By independently controlling the display pattern in the column direction, the frame period is shortened while the selection width is kept constant, the frame response is suppressed, and the display is driven by the so-called MLA method that enables high contrast display. Lateral luminance unevenness along the line and special crosstalk called ghost become noticeable.

[0005] The ghost referred to here is a phenomenon in which a certain image is displayed faintly in the vicinity thereof.
This is a display defect that appears as a double image like a ghost due to a radio wave interference of a television. In particular, this phenomenon strongly occurs when a window is displayed on a personal computer or the like, and display unevenness appears in a background portion above an outer frame of the window display.

[0006] The dielectric constant of the liquid crystal, the thickness from the lower surface of the color filter to the coating layer provided thereon, and the area of one of the row electrodes or column electrodes which is close to the conductive film layer and the area where the conductive film layer overlaps. A method of suppressing the ghost by setting a cell parameter such as a ratio to a pixel area in a specific range has been proposed (JP-A-10-13316).
5). However, this method was not effective in suppressing the luminance unevenness in the horizontal direction.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a liquid crystal display device having a substrate having a conductive film layer below a display electrode and electrically insulated from the display electrode. Eliminates horizontal brightness unevenness among display defects,
It is an object to provide a liquid crystal display element having excellent display quality.

[0008]

According to one aspect of the present invention, a substrate having a conductive film layer below a display electrode and electrically insulated from the display electrode is provided as one of the substrates. In the liquid crystal display element configured, a part of the conductive film layer is linearly removed under the non-display region on at least one side to form an electrical insulating portion in the conductive film layer. The outer edge of the portion near the display area is closer to the display area than the center of the seal.

The invention according to claim 2 is characterized in that the conductive film layer is a conductive film layer for forming a color filter by an electrodeposition method. The invention according to claim 3 is characterized in that electrical insulation of the conductive film layer is achieved by removing a part of the conductive film layer by laser trimming. According to a fourth aspect of the present invention, the position of the electrical insulation of the conductive film layer overlaps the position where at least a part of the seal is formed, and the conductive connection between the substrates in the seal is performed at the overlapping portion. And the width of the overlapping portion is 75% of the seal width
It is characterized by the above.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a conductive film layer is provided below a display electrode of one of the substrates constituting a liquid crystal display element so as to be electrically insulated from the display electrode. Then, a part of the conductive film layer is linearly removed under the non-display region on at least one side to form an electrical insulating portion in the conductive film layer. It is important that the outer edge is closer to the display area than the center of the seal. Among the display defects caused by the presence of the conductive film layer below the display electrode, a typical example in which the lateral luminance unevenness is remarkable is as follows.

For the purpose of enlarging the effective display area and simplifying the terminal connection, a structure in which a conductive connection portion is provided between substrates and connection terminals for external circuits are concentrated on one substrate is often used. As one example, there is known a liquid crystal display element having a structure in which conductive beads 2 are compounded in a seal 1 as shown in FIG.

In a liquid crystal display device having such a structure,
When the conductive film layer 5 is provided below the display electrode 4a of the one substrate 3a and is electrically insulated from the display electrode, the tip of the conductive bead 2 does not stop at the surface of the display electrode 4a and the insulating layer 7 does not stop. To reach the conductive film layer 5 thereunder,
There is a case where the display electrode 4a and the conductive film layer 5 are short-circuited. Even when a direct short circuit does not occur due to such conductive beads, electrostatic breakdown may occur during energization, and the insulating layer at that portion may be carbonized to cause a short circuit.

If the electrical insulation of the conductive layer is not formed as described above, the display electrode 4a short-circuited to the conductive layer 5 is loaded with a large capacitance component corresponding to the entire area of the conductive layer. As a result, the effective voltage applied to this electrode is extremely lower than that of the other display electrodes in which no short circuit occurs, and is observed as luminance unevenness in the horizontal direction.

On the other hand, by providing the above-mentioned electrical insulating portion 8 in the conductive film layer as shown in FIG. 1, the probability of occurrence of a short-circuit itself is reduced, and even if a short-circuit occurs, the display can be performed. The capacitance component applied to the electrode 4a is limited to a small value corresponding to a small area below the non-display area, and the occurrence of the luminance unevenness is suppressed.

In the present invention, the conductive film layer is most typically a transparent conductive film layer as a base of a color filter formed by the above-described electrodeposition method. However, the present invention is not limited to this, and a chromium-based inner light-shielding film, a conductive film layer as an electrode for an internal heater, and the like are also applicable.

As a method of forming an electrically insulating portion by removing a part of the conductive film layer, precise control can be performed, there is no generation of foreign matter due to dust, and there is no problem of adverse effects on other members. A preferred example is a laser trimming method excellent in productivity. When the electrically insulating portion is formed, when the conductive film layer is a transparent conductive film layer underlying a color filter formed by an electrodeposition method, the process after forming the color filter and before forming the flattening film is a process. preferable.

The electrical insulating portion is formed in a non-display area on at least one side. In a liquid crystal display element having a structure in which conductive connection between substrates is performed in a seal, as shown in FIG. 1, the position of the electrically insulating portion 8 overlaps with the position where at least a part of the seal 1 is formed. it is preferable that the width w _c of the overlapping portion is at least 75% of the seal width w _s.

If the overlapping width w _c is too small,
This is inconvenient because the short-circuit prevention effect is reduced, and a step is formed under the seal, which causes a nonuniform cell gap. On the other hand, if it is too large, there are few restrictions except for an increase in process load, and the electrical insulation forming region may protrude from the seal forming region. Regarding the protrusion, the outermost edge of the inner light-shielding film or the color filter is the inner limit, and the position corresponding to the outer edge of the substrate when the liquid crystal display element is completed is the outer limit.

When a glass substrate is used, an alkali barrier layer made of silicon dioxide or the like is generally formed below the conductive film layer in order to suppress the elution of alkali metal ions from the substrate. Partially remove the conductive film layer,
When forming the electrical insulation, the alkali barrier layer may be partially damaged.For applications that particularly dislike elution of alkali metal ions, the protrusion to the inside may be, for example, 0.3 mm or less. However, it is preferable to make it as small as possible.

In the liquid crystal display device having the structure as shown in FIG. 1, the spacer diameter to be compounded in the seal 1 corresponds to the thickness of the color filter 6 more than the diameter of the in-plane spacer 9 in order to make the cell gap uniform. It is preferable that the diameter of the spacer in the seal on the side overlapping with the electrical insulating portion 8 be larger than that of the other sides by an amount corresponding to the thickness of the conductive film layer 5.

[0021]

Next, examples of the present invention and comparative examples will be described. A transparent conductive film layer made of indium tin oxide and having a thickness of 180 nm and a sheet resistance of 15 Ω / □ is formed on a glass substrate, and a light-shielding film and color filters of three colors of RGB are formed on the transparent conductive film layer by 640 × 3 × 480. A dot was formed in a stripe pattern on the pixel.

Prior to the formation of the flattening film, a part of the transparent conductive film layer on the substrate was removed by laser trimming, and the conductive film layer was divided into two electrically insulated blocks. The position is a portion of a straight line extending directly below one side of the seal in which the conductive connection between the substrates in the seal is performed, extending to a position corresponding to the outer edge of the substrate when the liquid crystal display element is completed, and the width thereof extends beyond the bottom of the seal. And the width was set to be 80% of the seal width.

The substrate in which electrical insulation is formed on the lower conductive film layer in this manner is used as one substrate, and the diagonal of 1 is obtained by a conventional method.
A 0.4 inch STN color liquid crystal display device was prepared.
The cell gap has a diameter of 6.15 μ as an in-plane spacer.
pressure-resistant plastic beads having a thickness of 0.15 μm and a plastic bead having a diameter of 8.0 μm and plastic beads of the same diameter subjected to gold plating, each of which is 2% by weight. As a result, the thickness was controlled to 6.0 μm. The twist angle of the liquid crystal was set to 240 degrees.

When the thus obtained liquid crystal display device was driven by a multiple line simultaneous selection (MLA) method with a frame frequency of 120 Hz and the number of simultaneously selected lines of 4, no display failure occurred in any one of 50 cells.

On the other hand, in a liquid crystal display device formed without forming electrical insulation in the above-mentioned conductive film layer, 50
Brightness unevenness in the horizontal direction was observed in 6 of the cells. Also,
When the width of the electrical insulating portion 8 was set to 40% of the seal width, the occurrence of luminance unevenness in the horizontal direction was 2 out of 50 cells.

[0026]

According to the first aspect of the invention, the luminance unevenness in the horizontal direction peculiar to the liquid crystal display element in which one substrate is a substrate having a conductive film layer below the display electrode and electrically insulated therefrom. And a liquid crystal display element having excellent display quality can be obtained at a high yield. According to the second aspect of the present invention, a transparent conductive layer underlying a color filter, which is most typical as a conductive layer electrically insulated from that below the display electrode, is targeted, and a large industrial effect is exhibited. Is done.

According to the third aspect of the present invention, the formation of electrical insulation in the conductive film layer is achieved with high accuracy and high productivity, and in this step, generation of foreign matter due to dust in this step and prevention of other members from occurring. Since there is no adverse effect, a high-quality liquid crystal display device can be obtained with high productivity. According to the invention of claim 4, a short circuit between the display electrode and the lower conductive film layer at the conductive connection portion in the seal is suppressed, and the prevention of luminance unevenness in the horizontal direction becomes more complete.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a main part of an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part for describing a short circuit between a display electrode and a conductive film layer.

[Explanation of symbols]

 1: Seal 2: Conductive beads 3a, 3b: Substrate 4a, 4b: Display electrode 5: Conductive layer 6: Color filter, light shielding film 7: Flattening film (insulating layer) 8: Electrical insulating portion 9: In-plane spacer

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hiroshi Araki 5-7-18 Higashi-Nippori, Arakawa-ku, Tokyo Optrex Corporation F-term (reference) 2H048 BA62 BB02 BB43 2H089 LA07 LA15 LA19 NA09 NA24 PA04 QA16 RA10 SA07 TA03 TA06 2H091 FA02Y FC06 FD04 FD14 FD24 GA03 GA17 HA10 KA03 KA04 LA11 LA12 LA13 LA15 LA18 2H092 GA05 GA38 GA39 GA42 HA04 HA15 HA17 MA31 MA35 MA37 NA04 NA16 NA25 PA03 PA06 QA10

Claims (4)

[Claims] In a liquid crystal display element in which a substrate having a conductive film layer electrically insulated from a display electrode below a display electrode is used as one of the substrates, at least one of the conductive film layers has at least one conductive film layer. The electrically insulating portion is formed in the conductive film layer by being removed linearly under the non-display region on the side, and the outer edge of the electrically insulating portion near the display region is closer to the display region than the center of the seal. A liquid crystal display device characterized by the above-mentioned. 2. The liquid crystal display device according to claim 1, wherein the conductive film layer is a conductive film layer for forming a color filter by an electrodeposition method. 3. The liquid crystal display device according to claim 1, wherein electrical insulation of the conductive film layer is achieved by removing a part of the conductive film layer by laser trimming. 4. The electrically insulating position of the conductive film layer overlaps a position where at least a part of the seal is formed, and a conductive connection between the substrates in the seal is made at a portion where the both overlap. 4. The liquid crystal display device according to claim 1, wherein the width of the portion where the overlaps are 75% or more of the seal width.