JP2005062723A - Liquid crystal display and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To substantially reduce light escaping generated in an aperture region by superposition of colored layers, in a liquid crystal display. <P>SOLUTION: The liquid crystal display is provided with an array substrate AR, a counter substrate CT, and a liquid crystal layer LQ interposed between the array substrate AR and the counter substrate CT, and the array substrate AR includes a plurality of signal lines X located at fixed intervals as light-shielding wiring layers, a plurality of colored layers R, G, and B formed by red, green, and blue colors, respectively, having specific visibility characteristics in aperture regions partitioned by the signal lines X and a plurality of pixel electrodes PE formed on the colored layers R, G, and B, respectively. Especially, low visibility-side colored layers of the plurality of colored layers R, G, and B are superposed on the respective signal lines X so as to be mainly upheaved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention generally relates to a liquid crystal display device having a structure in which a liquid crystal layer is sandwiched between a pair of electrode substrates and a method for manufacturing the same, and in particular, a plurality of colored layers are disposed on one electrode substrate together with a plurality of pixel electrodes. The present invention relates to a liquid crystal display device and a manufacturing method thereof.

  Liquid crystal display devices are applied in various fields such as office automation equipment, information terminals, watches, and televisions because of their characteristics of light weight, thinness, and low power consumption. In a typical liquid crystal display device, a liquid crystal layer is sandwiched between a pair of electrode substrates. One electrode substrate is composed of an array substrate having a plurality of pixel electrodes arranged in a substantially matrix shape, and the other electrode substrate is composed of a counter substrate having counter electrodes facing the plurality of pixel electrodes. The array substrate and the counter substrate are bonded together by an outer edge sealing member disposed so as to surround the liquid crystal layer as a liquid crystal display panel.

  When this liquid crystal display panel is for color display, the counter substrate generally includes a color filter composed of a plurality of colored layers colored red, green, and blue, and these colored layers are opposed to a plurality of pixel electrodes. Are attached to the array substrate. However, this configuration requires high-precision alignment in which each colored layer is aligned with the corresponding pixel electrode in the bonding process between the array substrate and the counter substrate. In recent years, a COA process for forming a color filter on an array substrate has also been put into practical use as a technique that makes this alignment unnecessary (see, for example, Patent Document 1).

In the COA process, a color filter is used as a base for a plurality of pixel electrodes. These pixel electrodes are formed by patterning a light-transmitting conductive layer that covers a plurality of colored layers to be color filters. The patterning accuracy greatly depends on the misalignment of the colored layers, and the pixel openings Cause the rate to drop.
Japanese Patent Laid-Open No. 2001-281697 (FIG. 4)

  For the reasons described above, at present, a decrease in patterning accuracy is prevented by forming an adjacent colored layer on the light-shielding wiring layer that blocks light transmitted through the gap between the pixel electrodes, that is, the pixel electrodes. However, there is a problem that the contrast at the time of black display is lowered due to light leakage occurring in the opening region near the light-shielding wiring layer when the colored layers are overlapped in this way.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a liquid crystal display device and a method for manufacturing the same that can substantially reduce light leakage generated in an opening region due to overlapping of colored layers.

  According to the present invention, the first and second electrode substrates and a liquid crystal layer sandwiched between the first and second electrode substrates, wherein the first electrode substrate has a plurality of light-shielding wiring layers arranged at regular intervals, Including a plurality of colored layers formed in colors each having a unique visibility characteristic with respect to an opening region partitioned by a plurality of light-shielding wiring layers, and a plurality of pixel electrodes formed on the plurality of colored layers, respectively. There is provided a liquid crystal display device in which a plurality of colored layers are superposed on each light-shielding wiring layer so that the colored layer on the low visibility side is mainly raised.

  Further, according to the present invention, the liquid crystal layer is sandwiched between the first and second substrates, and a plurality of light-shielding wiring layers arranged at regular intervals are formed on the first substrate, and the plurality of light-shielding wiring layers are partitioned. A plurality of colored layers are formed with colors having unique visibility characteristics with respect to the aperture region to be formed, and a plurality of pixel electrodes are respectively formed on the plurality of colored layers, and the plurality of colored layers have high visibility. The manufacturing method of the liquid crystal display device formed in order is provided.

  In this liquid crystal display device and its manufacturing method, a plurality of colored layers are overlaid on each light-shielding wiring layer so as to mainly raise the colored layer on the low visibility side. The inventors of the present application have confirmed that these colored layers rise into the opening region that is not shielded by the light-shielding wiring layer due to the overlap on each light-shielding wiring layer. In this raised portion, the retardation value (= Δnd, where Δn: refractive index, d: layer thickness) is different from that in the vicinity of the central portion, and as a result, light leakage occurs. Since the colored layer is formed with a color having a unique visibility characteristic, when this light omission occurs in the colored layer on the high visibility side, this occurs at the time of black display than when it occurs in the colored layer on the low visibility side. Reduce contrast. Therefore, this liquid crystal display device mainly has a raised color layer on the low visibility side. Specifically, the colored layer on the low visibility side is overlaid on the colored layer on the high visibility side, or the width of the colored layer on the high visibility side is increased to narrow the width of the colored layer on the low visibility side, What is necessary is just to combine these, and the light omission which arises in the protruding part in an opening area | region is reduced substantially by this, and the contrast fall at the time of black display can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the liquid crystal display device which can reduce substantially the light leakage produced in an opening area | region by the overlap of a colored layer, and its manufacturing method can be provided.

  Hereinafter, a liquid crystal display device according to an embodiment of the present invention will be described with reference to the accompanying drawings. This liquid crystal display device is a transmissive XGA liquid crystal display panel that performs display in a VAN mode having a multi-domain structure.

  1 schematically shows a cross-sectional structure of the liquid crystal display panel TMD, FIG. 2 shows an appearance of the liquid crystal display panel TMD shown in FIG. 1, and FIG. 3 schematically shows a circuit structure of the liquid crystal display panel TMD shown in FIG. Shown in

  As shown in FIG. 1, the liquid crystal display panel TMD has an array substrate AR serving as a first electrode substrate, a counter substrate CT serving as a second electrode substrate facing the first electrode substrate, and negative dielectric anisotropy. A liquid crystal layer LQ that includes the liquid crystal composition and is sandwiched between the array substrate AR and the counter substrate CT. As shown in FIG. 2, the array substrate AR and the counter substrate CT are bonded together by an outer edge seal member 11 disposed so as to surround the liquid crystal layer LQ. In the liquid crystal display panel TMD, a display area DA for displaying an image is arranged inside the outer edge seal member 11, and a peripheral area EA for arranging a drive circuit is arranged around the display area DA. The liquid crystal composition is injected from the liquid crystal injection port 12 after the array substrate AR and the counter substrate CT are bonded, and is sealed by the sealing member 13 after the injection.

  As shown in FIG. 3, the array substrate AR includes m × n pixel electrodes PE arranged in a matrix and m scanning lines Y arranged along the rows of the pixel electrodes PE in the display area DA. (Y1 to Ym), n signal lines X (X1 to Xn) arranged along the column direction of the pixel electrodes PE, scanning lines Y1 to Ym and signals corresponding to m × n pixel electrodes PE. It has m × n pixel switches 15 arranged in the vicinity of the intersecting positions of the lines X1 to Xn, and further has m auxiliary capacitance lines 16 arranged along the row of the pixel electrodes PE. The scanning lines Y <b> 1 to Ym are substantially orthogonal to the signal lines X <b> 1 to Xn and are disposed substantially parallel to the auxiliary capacitance line 16. Each auxiliary capacitance line 16 is set to a predetermined potential obtained as a counter potential VCOM from a counter electrode drive circuit or the like, and capacitively couples with the pixel electrode PE in the corresponding row to form an auxiliary capacitance Cs.

  In addition, the array substrate AR has a scanning line driving circuit YD for driving the scanning lines Y1 to Ym and a signal line driving circuit XD for driving the signal lines X1 to Xn in the peripheral area EA. Each pixel switch 15 is made of, for example, a polysilicon thin film transistor, is connected to the corresponding scanning line Y and the corresponding signal line X, is made conductive by the driving voltage from the scanning line Y, and the signal voltage from the signal line X is applied to the corresponding pixel electrode PE. Apply.

  The pixel electrode PE is disposed in an opening region defined by the signal line X and the scanning line Y, which is a light-shielding wiring layer made of a conductive member such as metal. The pixel electrode PE is made of a transparent conductive member such as ITO formed above the light-transmissive insulating substrate GL2 such as a glass substrate, and applies an electric field to the pixel region of the liquid crystal layer LQ due to its planar spread. The pixel electrode PE is configured, for example, to divide the pixel region of the liquid crystal layer LQ into a plurality of domains by undulations.

  Although not shown in FIG. 1 in the array substrate AR, each pixel switch 15 is formed on a light-transmissive insulating substrate GL1 such as a glass substrate and covered with a color filter CF. The color filter CF is configured by a red colored layer R, a green colored layer G, and a blue colored layer B that are repeatedly arranged in the row direction of the plurality of pixel electrodes PE and face the corresponding pixel electrodes PE. The pixel electrode PE and the color filter CF are entirely covered with the alignment film 18. The alignment film 18 aligns the liquid crystal molecules 20 of the liquid crystal layer LQ in a direction substantially perpendicular to the array substrate AR when no voltage is applied. On the array substrate AR side, a polarizing plate PL1 is further attached to the surface of the insulating substrate GL1 on the side opposite to the liquid crystal layer LQ.

  On the other hand, in the counter substrate CT, the counter electrode CE is made of a transparent conductive member such as ITO formed on the light-transmissive insulating substrate GL2 such as a glass substrate, and the alignment film 19 is formed to cover the counter electrode CE. The counter electrode CE is disposed so as to face the entire plurality of pixel electrodes PE disposed on the array substrate AR side. The alignment film 19 aligns the liquid crystal molecules 20 of the liquid crystal layer LQ in a direction substantially perpendicular to the counter substrate CT when no voltage is applied. On the counter substrate CT side, the polarizing plate PL2 is attached to the surface of the insulating substrate GL2 on the side opposite to the liquid crystal layer LQ.

  Incidentally, the liquid crystal display panel TMD has a COA (Color filter On Array) structure in which the color filter CF is formed on the array substrate AR together with the array of the pixel switches 15 and the pixel electrodes PE. This COA structure eliminates the need for high-precision positioning required for bonding the substrates without displacement when the color filter CF is disposed on the counter substrate CT. As a result, the manufacturing process is facilitated. Costs can be reduced. When the liquid crystal display panel TMD is a transmission type as described above, the material of the color filter CF is preferably a transparent resin such as an acrylic resin, an epoxy resin, or a novolac resin from the viewpoints of transmittance and color. .

  In the manufacturing process of the array substrate AR, first, the pixel switch 15 is formed on the insulating substrate GL1, and the scanning line Y is also formed integrally with the gate electrode of the pixel switch 15. The pixel switch 15 is covered with, for example, an interlayer insulating film and the signal line X is formed on the interlayer insulating film.

Subsequently, an ultraviolet curable acrylic resin resist in which a green pigment is dispersed is applied over the entire surface with a spinner and dried at a temperature of 90 ° C. for 10 minutes. Thereafter, ultraviolet light having a wavelength of 365 nm is irradiated to expose a region for the green colored layer G. Here, exposure is performed using a photomask that forms the green colored layer G in a stripe shape and further forms a contact hole for the pixel switch 15. The exposure amount of ultraviolet rays is set to 100 mJ / cm ² . Next, this resin resist is developed for 20 seconds using an aqueous solution containing 1% by weight of potassium hydroxide, and further baked at a temperature of 200 ° C. for 60 minutes. Thereby, a green colored layer G having a thickness of 3.2 μm having a contact hole is formed.

  The red colored layer R and the blue colored layer B are also formed in the same process as the green colored layer G using an ultraviolet curable acrylic resin resist in which pigments of corresponding colors are dispersed. The red colored layer R is formed after the green colored layer G is formed, and the blue colored layer B is formed after the red colored layer R is formed. Similarly to the green colored layer G, the red colored layer R and the blue colored layer G have a film thickness of 3.2 μm. The color filter CF is obtained by the green colored layer G, the red colored layer R, and the blue colored layer B.

  Thereafter, the pixel electrode PE is formed by sputtering ITO with a thickness of about 1500 mm and patterning it by photolithography. The undulation of the pixel electrode PE can be obtained by forming a transparent resin resist pattern or the like on the color filter CF as a base of the pixel electrode PE, for example.

Thereafter, a photosensitive black resin is applied with a spinner, dried at a temperature of 90 ° C. for 10 minutes, and an ultraviolet ray is a region for a columnar spacer that defines the cell gap of the liquid crystal layer LQ and the outer edge seal shown in FIG. Irradiation is performed through a photomask that exposes a light shielding region (width 3 mm) for the frame-shaped light shielding layer surrounding the display region DA inside the member 11. The exposure amount of ultraviolet rays is set to 300 mJ / cm ² . Thereafter, the black resin is selectively removed by a development process using an alkaline aqueous solution having a pH = 11.5, and is baked at a temperature of 200 ° C. for 60 minutes, whereby a columnar spacer and a light shielding layer are formed together. .

  Thereafter, the alignment film 18 is formed by coating the alignment film material with a thickness of 600 mm covering all the pixel electrodes PE.

  Regarding the counter substrate CT, the counter electrode CE is formed on the insulating substrate GL2, and the alignment film 19 is formed by coating the counter electrode CE and similarly applying an alignment film material with a thickness of 600 mm. In addition, an epoxy thermosetting resin adhesive is formed by printing along the outer edge of the alignment film 19, and an electrode transfer material is formed on the outside of the adhesive between the auxiliary capacitance line 16 of the array substrate AR and the counter electrode CE. Formed for contact.

  The array substrate AR and the counter substrate CT thus obtained are bonded to each other using the jig of the epoxy-based thermosetting resin on the counter substrate CT as the outer edge seal member 11. . Subsequently, a nematic liquid crystal material having negative dielectric anisotropy is injected as a liquid crystal composition of the liquid crystal layer LQ from the liquid crystal injection port 12 into the space surrounded by the outer edge seal member 11 between the array substrate AR and the counter substrate CT. The liquid crystal injection port 12 is sealed with a sealing member 13 made of an ultraviolet curable resin after the injection.

  Here, the relationship between the above-described colored layers R, G, B, the signal line X, and the pixel electrode PE will be further described. The n signal lines X (X1 to Xn) are arranged as a light-shielding wiring layer at a constant interval, and the colored layers R, G, and B have a unique view with respect to the opening regions defined by these signal lines X, respectively. It is formed of red, green, and blue with sensitivity characteristics. The visibility characteristics of the colored layers R, G, and B are the sensitivities that the observer's vision shows with respect to the transmitted light of the respective colors. For example, the colored layer R = 40% based on the green colored layer G, The relative transmittance of the layer G = 100% and the colored layer B = 19% can be expressed. Each pixel electrode PE is formed on a corresponding colored layer among such colored layers R, G, and B. When the widths of the opening regions with respect to the colored layers R, G, and B are expressed as Wa (R), Wa (G), and Wa (B), respectively, the relationship is Wa (R) = Wa (G) = Wa (B). And equal to the interval between the signal lines X. The width of all the pixel electrodes PE is preferably slightly larger than the value of Wa (R) = Wa (G) = Wa (B) so as to overlap the signal line X at both ends. On the other hand, when the widths of the colored layers R, G, and B are expressed as Wc (R), Wc (G), and Wc (B), they are Wc (G)> Wc (R)> Wc (B). The values are larger than the constant interval between the signal lines X.

  Further, the colored layers R, G, and B are formed in the order of the colored layer G, the colored layer R, and the colored layer B. Referring to FIG. 1, the colored layer G is formed at both ends with only the signal line X as a base. The colored layer R is formed using only the signal line X as a base at one end, and is formed using the signal line X and the colored layer G using the signal line X as a base at the other end. The colored layer B is formed at one end with the signal line X and the colored layer G with the signal line X as a base, and at the other end with the signal line X and the colored layer R with the signal line X as a base. It is formed.

  When the colored layers R, G, and B are overlapped on each signal line X in this manner, the colored layer on the low visibility side mainly rises. The overlapping of the colored layers R and G mainly raises the colored layer R having a lower visibility than the colored layer G. The overlapping of the colored layers B and G mainly raises the colored layer B having a lower visibility than the colored layer G. The overlapping of the colored layers B and R mainly raises the colored layer B having a lower visibility than the colored layer R.

  In the liquid crystal display device of this embodiment, the colored layers R, G, and B are overlaid on each light-shielding wiring layer so that the colored layer on the low visibility side is mainly raised. These ridges enter the respective opening regions and cause light leakage indicated by broken-line arrows in FIG. 1, but these light leakages are always set in the colored layer on the low visibility side. For example, if attention is paid to the colored layer G having the highest visibility among the colored layers R, G, and B, even if it overlaps with the colored layer G or the colored layer R, the raised area corresponding to the colored layer G corresponds to the opening region. Therefore, the retardation value at the end (= Δnd, where Δn: refractive index, d: layer thickness) can be made substantially equal to the vicinity of the central portion, and as a result, light leakage occurs in the colored layer G. It does not occur in the corresponding open area. As described above, by concentrating the occurrence of light leakage on the side of the colored layers R, G, and B that has lower visibility, it is possible to improve contrast reduction during black display as a whole.

  Next, the result of actually manufacturing the liquid crystal display device of the present embodiment and measuring the contrast during black display will be shown. As described above, the colored layers R, G, and B are set to have different widths in the relationship of Wc (G)> Wc (R)> Wc (B), and these are the order of the colored layer G, the colored layer R, and the colored layer B. As a result, it was possible to obtain a good black display contrast of 550: 1. Therefore, this formation order is maintained, and the colored layers R, G, and B are not in the relationship of Wc (G)> Wc (R)> Wc (B) but Wc (R) = Wc (G) = Wc (B) Although the widths were set equal, a good black display contrast of 510: 1 could be obtained even in this case.

  As a comparative example, the colored layers R, G, and B are set to have equal widths such that Wc (R) = Wc (G) = Wc (B), and the colored layers B, R, and G A liquid crystal display device was actually manufactured by the same manufacturing process as in this embodiment except that the layers were formed in order. In this case, the contrast at the time of black display was a value of 380: 1 which is significantly lower than the above-mentioned 550: 1 or 510: 1.

  In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the summary, it can change variously further.

  In the above-described embodiment, the colored layers R, G, and B are set to different widths in the relationship of Wc (G)> Wc (R)> Wc (B), and these are colored layer G, colored layer R, and colored layer B. For example, the colored layers R, G, and B are set to have equal widths such that Wc (G) = Wc (R) = Wc (B), and these are colored layer G, colored layer R, colored You may form in order of layer B.

  In the above-described embodiment, since each of the coloring layers R, G, and B has a stripe shape assigned to one column of pixel electrodes PE, the signal lines X among the scanning lines Y and the signal lines X are colored. Although the relationship with the layers R, G, and B has been described, the colored layers R, G, and B are sequentially assigned to the pixel electrodes PE for one column and overlap even on the scanning line Y that is a light-shielding wiring layer. In the column direction of the pixel electrodes PE, the relationship between the widths of the colored layers R, G, and B and the order of formation is set in the same manner as in the case of the signal line X.

It is a figure which shows schematically the cross-section of the liquid crystal display panel which concerns on one Embodiment of this invention. It is a figure which shows the external appearance of the liquid crystal display panel shown in FIG. FIG. 3 is a diagram schematically showing a circuit structure of the liquid crystal display panel shown in FIG. 2.

Explanation of symbols

  15 ... pixel switch, TMD ... liquid crystal display panel, AR ... array substrate, CT ... counter substrate, LQ ... liquid crystal layer, PE ... pixel electrode, CE ... counter electrode, CF ... color filter, R, G, B ... colored layer, X: Signal line.

Claims (8)

  A first and second electrode substrate; and a liquid crystal layer sandwiched between the first and second electrode substrates, wherein the first electrode substrate has a plurality of light-shielding wiring layers arranged at regular intervals, and the plurality of light-shielding properties. A plurality of colored layers each formed with a color having a unique visibility characteristic with respect to the opening region partitioned by the wiring layer, and a plurality of pixel electrodes respectively formed on the plurality of colored layers, The colored layer is overlaid on each light-shielding wiring layer so that the colored layer on the low visibility side is mainly raised.   The plurality of colored layers are any one of a red colored layer, a green colored layer, and a blue colored layer, the green colored layer is a base for each of the red colored layer and the blue colored layer, and the red colored layer is the above The liquid crystal display device according to claim 1, wherein the liquid crystal display device is overlaid so as to be a base of a blue colored layer.   The width of the blue colored layer is larger than the predetermined interval, the width of the red colored layer is larger than the width of the blue colored layer, and the width of the green colored layer is larger than the width of the red colored layer, The liquid crystal display device according to claim 2.   The plurality of colored layers are any one of a red colored layer, a green colored layer, and a blue colored layer, the width of the blue colored layer is larger than the predetermined interval, and the width of the red colored layer is the width of the blue colored layer The liquid crystal display device according to claim 1, wherein a width of the green colored layer is larger than a width of the red colored layer.   A liquid crystal layer is sandwiched between a first substrate and a second substrate. A plurality of light-shielding wiring layers arranged at regular intervals are formed on the first substrate, and an opening region defined by the plurality of light-shielding wiring layers is formed. On the other hand, a plurality of colored layers are formed with colors having unique visibility characteristics, a plurality of pixel electrodes are formed on the plurality of colored layers, and the plurality of colored layers are formed in descending order of visibility. A method for manufacturing a liquid crystal display device.   The plurality of colored layers are any of a red colored layer, a green colored layer, and a blue colored layer, the green colored layer is formed prior to the red colored layer and the blue colored layer, and the red colored layer is 6. The method of manufacturing a liquid crystal display device according to claim 5, wherein the liquid crystal display device is formed prior to the blue colored layer.   The width of the blue colored layer is larger than the predetermined interval, the width of the red colored layer is larger than the width of the blue colored layer, and the width of the green colored layer is larger than the width of the red colored layer, A method for manufacturing a liquid crystal display device according to claim 6.   The plurality of colored layers are any one of a red colored layer, a green colored layer, and a blue colored layer, the width of the blue colored layer is larger than the predetermined interval, and the width of the red colored layer is the width of the blue colored layer 6. The method of manufacturing a liquid crystal display device according to claim 5, wherein the width of the green colored layer is larger than the width of the red colored layer.

Images