JP5037554B2 - LCD panel - Google Patents

Description

  The present invention relates to a liquid crystal display panel having a structure capable of reducing a printing rate and a method for developing the same.

  31 and 32 are schematic cross-sectional views showing the structure of one pixel of the liquid crystal display panel. FIG. 31 shows a state when no voltage is applied, and FIG. 32 shows a state when a voltage is applied.

  The liquid crystal display panel includes substrates 10 and 20 facing each other, and a nematic liquid crystal 30 having a positive dielectric anisotropy enclosed between them. In the substrate 10, a surface electrode 12, a dielectric 13 and a vertical alignment layer 14 are laminated on one surface of a transparent insulating substrate 11, for example, a glass substrate, and a polarizer 15 is attached to the other surface of the transparent insulating substrate 11. In the substrate 20, a common electrode 23 is formed on one surface of a transparent insulating substrate 21, for example, a glass substrate, and a pixel electrode 25 is formed thereon via an insulating layer 24. An insulating layer 26 and a vertical alignment layer 27 are stacked on the insulating layer 24 and the pixel electrode 25. A polarizer 28 is attached to the other surface of the transparent insulating substrate 21. The transmission axes of the polarizers 15 and 28 are spaced apart and orthogonal to each other.

  When backlight light in the direction indicated by the arrow enters the liquid crystal display panel, the light passes through the polarizer 28 and becomes linearly polarized light. When the plane electrode 12, the common electrode 23, and the pixel electrode 25 are at the same potential, the plane of polarization of this linearly polarized light does not change in the liquid crystal 30, and therefore cannot pass through the polarizer 15, resulting in a dark state.

  As shown in FIG. 32, when the surface electrode 12 and the common electrode 23 are set to the same potential and the pixel electrode 25 is set to a potential different from the above potential, an electric field is generated. The dotted line in FIG. 32 has shown the electric force line. Due to this electric field, the liquid crystal molecules are tilted with respect to the direction of incident light, so that birefringence occurs, and a part of this light is transmitted through the polarizer 15 to be in a bright state.

  The common electrode 23 and the pixel electrode 25 are light-shielding metals, and the behavior of liquid crystal molecules above them does not cause a problem in display.

  If the surface electrode 12 does not exist, there is a region where the transmittance of the liquid crystal molecules is lowered due to the small inclination of the liquid crystal molecules between the pixel electrode 25 and the common electrode 23. The surface electrode 12 contributes to preventing a drop in transmittance by making the lateral electric field of this portion obliquely asymmetric. The dielectric 13 is for strengthening the lateral electric field in the liquid crystal 30 so that the liquid crystal can be driven with a lower applied voltage. The common electrode 23 and the pixel electrode 25 are stripe electrodes that extend in the direction perpendicular to the paper surface and are alternately formed. The insulating layer 24 is for preventing the common electrode 23 and the pixel electrode 25 from being short-circuited at a portion where they vertically overlap as will be described later. The insulating layer 26 is for reducing the printing rate.

  FIG. 33 shows one pixel portion of the electrode pattern formed on the substrate 20. 34 and 35 are pattern diagrams of the pixel electrode 25 and the common electrode 23 in FIG. 33, respectively.

  The data line DL1 and the scanning line SL1 are orthogonal to each other through an insulating film. Each of the pixel electrode 25 and the common electrode 23 has a stripe portion and a peripheral portion connecting the end portions of the stripe portion. The stripe portion is inclined by 45 ° with respect to each of the scanning line SL1 and the data line DL1.

  When the scanning line SL1 becomes high level, the TFT 29 is turned on, the voltage on the data line DL1 is applied to the pixel electrode 25, and an electric field is generated between the stripe electrode of the pixel electrode 25 and the common electrode 23. The longitudinal direction of the stripe electrode differs by 90 ° between the upper half and the lower half of FIG. As a result, the viewing angle of the liquid crystal display panel becomes wider than when the upper half and the lower half are parallel to each other.

  The peripheral protrusion of the common electrode 23 is connected to the common electrode 23 of an adjacent pixel (not shown).

  FIG. 36A is a partially enlarged view of the vicinity of the line electrode intersection in FIG. FIG. 36B shows a line of electric force when a voltage is applied between the pixel electrode 25 and the common electrode 23 by a dotted line.

  Since the pixel is rectangular, the pixel electrode 25 and the common electrode 23 have stripe portions parallel to each other, and the pixel electrode 25 and the common electrode 23 are connected together, The portion and the peripheral portion of the common electrode 23 have portions that overlap each other via an insulating portion. For this reason, the end portions of the adjacent line electrodes of the pixel electrode 25 and the common electrode 23 intersect with each other via the insulating portion. For example, the side 251 of the pixel electrode 25 is connected to the peripheral side 252, and the side 231 of the common electrode 23 is parallel to the side 251 but intersects the side 252 at an acute angle.

  FIG. 37 is a schematic cross-sectional view showing the inclination of the liquid crystal molecules in the vicinity of the electrode when a voltage is applied between the pixel electrode of one pixel of the liquid crystal display panel and the common electrode.

  In FIG. 32, the configuration between the pixel electrode 25 and the liquid crystal 30 is different from the configuration between the common electrode 23 and the liquid crystal 30, which causes image sticking.

  In addition, as shown in FIG. 36B, since the side 252 and the side 231 intersect at an acute angle, the electric field between the electrodes in the vicinity becomes stronger than that in the parallel part. Furthermore, the direction of the electric field near the intersection is different from that of the parallel portion. For this reason, the transmission characteristics with respect to the applied voltage between the electrodes in the vicinity of the intersection are different from those in the parallel portion, which causes the image quality to deteriorate and cause burn-in.

  Further, in FIG. 37, since the insulating layer 26 exists above the pixel electrode 25, it is useless even if an electric field is applied to these portions, and the electric field cannot be efficiently applied to the liquid crystal 30. Since the insulating property of the vertical alignment layer 27 is low, if the insulating layer 26 is omitted in order to solve this problem, seizure occurs. When the pixel electrode 25 is exposed from the liquid crystal 30, image sticking is further increased and liquid crystal molecules are decomposed. Further, since the surface of the pixel electrode 25 is flat, it is impossible to effectively apply an electric field to the liquid crystal 30 in relation to the transmittance, thereby preventing a high contrast display.

  In the development of a liquid crystal display panel, if the printing ratio is measured every time the structure or material of the liquid crystal display panel is changed in order to keep the printing ratio below a predetermined value, one measurement takes, for example, 48 hours, so the development period is long. Become.

  An object of the present invention is to provide a liquid crystal display panel having a structure capable of reducing the printing rate and a liquid crystal display panel development method capable of shortening the development period.

  Another object of the present invention is to provide a liquid crystal display panel capable of improving display contrast.

  In the liquid crystal display panel of the present invention, liquid crystal is sealed between a first substrate and a second substrate, and the first substrate has an insulating substrate and a pixel electrode and a common electrode formed above the insulating substrate. In the liquid crystal display panel, each of the first substrate and the second substrate has a vertical alignment film, a surface electrode is formed on a main surface of the second substrate on the liquid crystal side, and the liquid crystal side of the insulating substrate. The pixel electrode is positioned higher than the common electrode, and the pixel electrode and the common electrode overlap with each other through the first insulating film. The pixel electrode and the common electrode The surface of the pixel electrode has a convex shape due to a portion overlapping with the first insulating film.

  The first insulating film preferably has substantially the same thickness on the pixel electrode and the common electrode. Preferably, the pixel electrode is covered with a second insulating film, and the second insulating film is not substantially formed in a display region between the common electrode and the pixel electrode.

  The pixel electrode and the common electrode have a portion that intersects with each other via the first insulating film, and each of the pixel electrode and the common electrode has a line electrode portion that is continuous with the intersecting portion and is parallel to each other. The adjacent sides of the pixel electrode and the common electrode at the intersecting portion preferably intersect at an obtuse angle.

  In another liquid crystal display panel of the present invention, liquid crystal is sealed between a first substrate and a second substrate, and the first substrate includes an insulating substrate, a pixel electrode and a common electrode formed above the insulating substrate. And a first insulating film covering the pixel electrode and the common electrode, the position of the pixel electrode relative to the position of the common electrode with respect to the liquid crystal side surface of the insulating substrate The pixel electrode and the common electrode have a portion overlapping with the second insulating film interposed therebetween, and the first insulating film has substantially the same thickness on the pixel electrode and the common electrode. .

  The common electrode is formed on the insulating substrate, the pixel electrode is formed through a second insulating film after the common electrode is formed, and the first insulating film is a portion below the pixel electrode. Preferably, the second insulating film is formed after the second insulating film is removed.

  In still another liquid crystal display panel according to the present invention, liquid crystal is sealed between a first substrate and a second substrate, and the first substrate is formed above the transparent insulating substrate and the transparent insulating substrate. A pixel electrode and a common electrode having portions intersecting each other, and each of the pixel electrode and the common electrode has a line electrode portion that is parallel to the intersection portion and is parallel to the pixel portion. And adjacent sides of the common electrode cross each other at an obtuse angle.

  It is preferable that the adjacent sides of the intersecting portion are substantially symmetric with respect to a straight line passing between the parallel line segments on a plane ignoring the height direction.

  It is preferable that the side of the pixel electrode does not overlap the side of the common electrode with respect to the vertical direction of the insulating substrate for any of the adjacent sides of the intersection.

  In the method for developing a liquid crystal display panel of the present invention, liquid crystal is sealed between a first substrate and a second substrate, a pixel electrode is formed on the first substrate, and a common electrode is formed on the first substrate or the second substrate. A signal voltage that is a sum of an alternating voltage component and a direct voltage component Vdc is applied between the pixel electrode and the common electrode, and the alternating voltage component is applied. Of the liquid crystal display panel so that the optimum DC component fluctuation width ΔVdc is substantially measured by changing the amplitude Vac and the DC voltage component Vdc, and the optimum DC component fluctuation width ΔVdc is not more than a predetermined value. Where the optimum DC component fluctuation width ΔVdc is expressed as ΔVdc = | Vdcb−Vdcw |, where Vdcb changes the DC voltage component Vdc while fixing the amplitude Vac to the black display AC voltage amplitude. If you let The value of the DC voltage component Vdc that minimizes the transmittance amplitude of the pixel, and Vdcw is the pixel when the amplitude Vac is fixed to the white display AC voltage amplitude and the DC voltage component Vdc is changed. Is the value of the DC voltage component Vdc that minimizes the transmittance amplitude. The predetermined value is preferably a value of 0.5 V or less.

  According to the liquid crystal display panel of the present invention, when the same voltage is applied between the first and common electrodes, the liquid crystal molecules can be tilted more than when the surface of the pixel electrode is flat, and the display contrast is improved. improves.

  According to another liquid crystal display panel of the present invention, when a rectangular AC voltage is applied between the pixel electrode and the common electrode, the electrical state is substantially the same above the pixel electrode and above the common electrode. For example, the image sticking is reduced as compared with the case where the thickness is different between the pixel electrode and the common electrode as shown in FIG.

  According to still another liquid crystal display panel of the present invention, the concentration of the electric field lines is reduced and the electric field strength is suppressed from being increased compared to the case of intersecting at an acute angle. Reduced.

  When the adjacent side of the intersecting portion is substantially symmetrical with respect to a straight line passing between the parallel line segments on a plane ignoring the height direction, the direction of the electric field vector is the electric field vector of the intersecting portion. Since the direction is parallel to that of the parallel portion, the display image quality is further improved and the image sticking is further reduced.

  According to the liquid crystal display panel development method of the present invention, since the optimum DC component fluctuation width ΔVdc having a high correlation with the printing ratio can be easily measured in a short time, by using the optimum DC component fluctuation width ΔVdc, It is possible to shorten a period for developing a liquid crystal display panel having a printing ratio of a desired value or less.

  In order to prevent people from recognizing image sticking, the image sticking rate must be 6% or less when the room is under normal illumination and 3% or less when the room is in a dark room.

  The predetermined value is, for example, a value of 0.5 V or less, and it was confirmed that the seizure rate was 6% when the predetermined value was 0.5V, and the seizure rate was 3% when the predetermined value was 0.2V. .

  Other objects, configurations and effects of the present invention will become apparent from the following description.

It is a schematic circuit diagram of the liquid crystal display device used for the method of this invention. It is a printing rate explanatory drawing. It is a figure which shows a pixel applied voltage waveform. It is a liquid crystal pixel transmittance | permeability measurement waveform figure in case AC amplitude Vac is 2V and DC component Vdc is -3V. It is a liquid crystal pixel transmittance | permeability measurement waveform figure in case AC amplitude Vac is 2V and DC component Vdc is -2V. It is a liquid crystal pixel transmittance | permeability measurement waveform figure in case AC amplitude Vac is 2V and DC component Vdc is -1V. It is a liquid crystal pixel transmittance | permeability measurement waveform figure in case AC amplitude Vac is 2V and DC component Vdc is -0.5V. It is a liquid crystal pixel transmittance | permeability measurement waveform figure in case AC amplitude Vac is 2V and DC component Vdc is 0V. It is a liquid crystal pixel transmittance | permeability measurement waveform figure in case AC amplitude Vac is 2V and DC component Vdc is 0.5V. It is a liquid crystal pixel transmittance | permeability measurement waveform figure in case AC amplitude Vac is 2V and DC component Vdc is 1V. It is a liquid crystal pixel transmittance | permeability measurement waveform figure in case AC amplitude Vac is 2V and DC component Vdc is 2V. It is a liquid crystal pixel transmittance | permeability measurement waveform figure in case AC amplitude Vac is 2V and DC component Vdc is 3V. It is a graph which shows the measurement result of the relationship between the direct current | flow component Vdc and liquid crystal pixel transmittance | permeability fluctuation | variation width | variety (DELTA) T when alternating current amplitude Vac is 2V. It is a graph which shows the measurement result of the relationship between alternating current amplitude Vac and the direct current | flow component Vdc from which liquid crystal pixel transmittance | permeability fluctuation | variation width (DELTA) T becomes the minimum. It is a graph which shows the measurement result of the relationship between a printing rate and the optimal direct current component fluctuation range ΔVdc. It is a schematic sectional drawing which shows the voltage non-application state of the structure of the liquid crystal pixel which can reduce the printing rate of 2nd Embodiment of this invention. It is a schematic sectional drawing which shows the voltage application state of the liquid crystal pixel of FIG. FIG. 17 is a manufacturing process diagram for the substrate 20A in FIG. 16; It is an electrode pattern figure of the liquid crystal pixel which can reduce the printing rate of 3rd Embodiment of this invention. FIG. 20 is a pattern diagram of the pixel electrode in FIG. 19. FIG. 20 is a pattern diagram of the common electrode in FIG. 19. (A) is an enlarged view of the vicinity of the electrode crossing in FIG. 19, and (B) is a diagram showing electric lines of force when a voltage is applied between the electrodes of (A) by dotted lines. It is an electrode pattern figure of the liquid crystal pixel which can reduce the printing rate of 4th Embodiment of this invention. It is a pattern figure of the common electrode in FIG. It is an electrode pattern figure of the liquid crystal pixel which can reduce the printing rate of 5th Embodiment of this invention. FIG. 26 is a pattern diagram of a common electrode in FIG. 25. It is an electrode pattern figure of two adjacent liquid crystal pixels of a 6th embodiment of the present invention. It is the cross-sectional enlarged view along the AA line in FIG. It is a figure which shows the manufacturing process of a backlight incident side board | substrate. FIG. 30 is a manufacturing process diagram following FIG. 29; It is a schematic sectional drawing which shows the voltage no application state of the structure of 1 pixel of a liquid crystal display panel contrasted with this invention. It is a schematic sectional drawing which shows the voltage application state of the pixel of FIG. It is a figure which shows 1 pixel worth of the electrode pattern formed in the board | substrate 20 in FIG. FIG. 34 is a pattern diagram of pixel electrodes in FIG. 33. It is a pattern diagram of the common electrode in FIG. (A) is an enlarged view of the vicinity of the electrode crossing in FIG. 33, and (B) is a diagram showing electric lines of force when a voltage is applied between the electrodes of (A) by dotted lines. It is a schematic sectional drawing which shows the inclination of the liquid crystal molecule | numerator of the vicinity between electrodes at the time of applying a voltage between the pixel electrode of 1 pixel of a conventional liquid crystal display panel, and a common electrode.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  [First Embodiment] First, a liquid crystal display panel development method capable of shortening the development period of a liquid crystal display panel using a structure or material capable of reducing the printing rate will be described.

  FIG. 1 is a schematic circuit diagram of a liquid crystal display device used in the method of the present invention. For the sake of simplicity, FIG. 1 shows a case where the pixel array has 3 rows and 6 columns.

  This circuit itself is the same as the conventional one. The data line DL1, the scanning line SL1, the TFT 29, the pixel electrode 25, and the common electrode 23 are formed, for example, as shown in FIG. The electrodes facing the pixel electrode 25 are both the common electrode 23 and the surface electrode 12 shown in FIG. The scan line and the data line are connected to the output terminals of the scan driver 31 and the data driver 32, respectively. The control circuit 33 controls the data driver 32 based on the pixel clock CLK and the horizontal synchronization signal HSYNC, supplies the video signal VS to the data driver 32, and scan driver 31 based on the horizontal synchronization signal HSYNC and the vertical synchronization signal VSYNC. To control. The scan driver 31 sequentially selects the rows of the pixel array, and display data (gradation voltage) is supplied from the data driver 32 to the selected rows.

  FIG. 2 is an explanatory diagram of the printing ratio.

  For example, consider the case where the display data is 64 gradations, “white” is the 64th gradation, and “black” is the first gradation. The seizure rate is measured as follows.

  (A) White (64th gradation) is displayed and the luminance Bm is measured.

  (B) Next, a fixed pattern of black and white is displayed for 48 hours, for example.

  (C) Immediately after this, halftone (32nd gradation) is displayed, and the luminances Bmw and Bmb between the area displaying white and the area displaying black in (B) are measured. The seizure rate is calculated by the following equation.

Baking rate = 100 (Bmw−Bmb) / Bm
In (C) above, in order to prevent people from recognizing seizure, the seizure rate must be 6% or less when the room is under normal illumination and 3% or less when the room is in a dark room. .

  The image sticking rate varies depending on the structure and material of the liquid crystal display panel. In the development of a liquid crystal display panel, if the printing ratio is measured every time the structure or material of the liquid crystal display panel is changed in order to keep the printing ratio below a predetermined value, one measurement takes, for example, 48 hours, so the development period is long. Become. Therefore, it is considered to search for a physical quantity that has a high correlation with the printing rate and can be measured in a short time.

  A rectangular AC voltage is applied to the liquid crystal pixels in order to prevent the deterioration. FIG. 3 shows voltage waveforms applied between the pixel electrode 25 and the common electrode 23 and between the pixel electrode 25 and the surface electrode 12 in FIG. 32. The frequency is 30 Hz.

  In order to prevent the occurrence of flicker due to the application of the AC voltage, that is, to prevent the transmittance from changing periodically, a DC voltage component is added to the liquid crystal pixel application voltage. The amplitude and DC voltage component of the rectangular AC voltage are represented by Vac and Vdc, respectively.

  The transmittance of the liquid crystal display panel was measured when the AC amplitude Vac was fixed and the DC component Vdc was changed stepwise. 4 to 12, the AC amplitude Vac is fixed to 2V which is a black display voltage, and the DC component Vdc is set to -3V, -2V, -1V, -0.5V, 0V, 0.5V, 1V, 2V and Each transmittance variation when 3V is set is shown. As shown in FIG. 4, the transmittance fluctuation range is represented by ΔT.

  FIG. 13 is a graph showing the relationship between the DC component Vdc and the transmittance fluctuation width ΔT when Vac = 2V. From this graph, it is estimated that the value of the DC component Vdc at which the transmittance fluctuation range ΔT is minimum is −0.38V.

  Further, when the AC amplitude Vac is 7 V, which is the white display voltage, and the halftone display voltage (2 + 7) /2=4.5 V, the DC component Vdc where the transmittance variation width ΔT becomes the minimum value ΔTmin is set in the same manner as described above. Asked. These results are shown in FIG. The difference between the DC components Vdc when the AC amplitude Vac is the white display voltage and the black display voltage is represented by ΔVdc. In an actual liquid crystal display device, the direct current component Vdc has a fixed value, so that the flicker becomes weaker as the optimum direct current component fluctuation width ΔVdc is narrower.

  FIG. 15 is a graph showing the relationship between the printing ratio and the optimum DC component fluctuation width ΔVdc measured by changing the structure and materials of the liquid crystal display panel. From this graph, it can be seen that the degree of correlation between the seizure rate and the optimum DC component fluctuation range ΔVdc is high. Further, in order for the seizure rate to be 6% or less, the optimum DC component fluctuation range ΔVdc must be 0.5 V or less, and in order for the seizure rate to be 3% or less, the optimum DC component variation range. It can be seen that ΔVdc must be 0.2V or less.

  Since the optimum DC component fluctuation range ΔVdc can be easily measured in a short time, using ΔVdc can significantly shorten the period for developing a liquid crystal display panel with a printing rate less than the desired value. It becomes.

  In FIG. 31, the configuration using the pixel electrode 25 and the common electrode 23 without using the surface electrode 12 and the configuration using the pixel electrode 25 and the surface electrode 12 without using the common electrode 23 are shown. However, the degree of correlation between the optimum DC component fluctuation range ΔVdc and the burn-in rate is high, and it is considered that the liquid crystal display panels having other configurations have the same correlation.

  [Second Embodiment] FIGS. 16 and 17 are schematic sectional views showing the structure of a liquid crystal pixel according to a second embodiment of the present invention capable of reducing the printing rate. FIG. 16 shows a state when no voltage is applied, and FIG. 17 shows a state when a voltage is applied.

  In the liquid crystal panel having this pixel, the configuration of the substrate 20A is different from that of the substrate 20 in FIG. The other configuration is the same as that of FIG.

  FIG. 18 is a manufacturing process diagram of the substrate 20A. In FIG. 18, the right end portion relates to a portion where the common electrode 23A and the pixel electrode 25A overlap with each other via the insulating layer 24A.

  (A) A metal common electrode 23A is formed on the transparent insulating substrate 21 by photolithography.

  (B) An insulating layer 24 is deposited on the transparent insulating substrate 21.

  (C) A pixel electrode 25A is formed on the insulating layer 24 by photolithography.

  (D) The insulating layer 24 is etched using the pixel electrode 25A as a mask, and the insulating layer 24A is left only in a portion immediately below the pixel electrode 25A.

  (E) An insulating layer 26 </ b> A is deposited on the transparent insulating substrate 21.

  (F) The vertical alignment layer 27 is stacked on the insulating layer 26A.

  By forming the substrate 20A in this way, the thickness of the insulating layer 26A on the pixel electrode 25A and the thickness of the insulating layer 26A on the common electrode 23A become substantially the same, so that the pixel electrode as shown in FIG. When a rectangular AC voltage is applied between 25A and the common electrode 23A, the electrical state is almost the same above the common electrode 23A and above the pixel electrode 25A, and the liquid crystal display panel having the configuration of FIG. Also seizure is reduced. In other words, the optimum DC component fluctuation range ΔVdc in FIG. 15 becomes smaller and the seizure rate becomes lower.

Insulating layers 24A and 26A, for example, SiNx, is either SiO _2, resist or acrylic resin. In the prototype, SiNx is used as the insulating layers 24A and 26A, JALS204 (JSR) is used as the vertical alignment layer 27, ZLI4535 (Merck Japan) is used as the liquid crystal 30, and the effect of reducing the printing rate of the prototype is confirmed. It was.

  [Third Embodiment] FIG. 19 is an electrode pattern diagram of a liquid crystal pixel according to a third embodiment of the present invention capable of reducing the printing ratio, and is similar to FIG.

  This electrode pattern is formed on, for example, the substrate 20A of FIG. 16 or the substrate 20 of FIG.

  20 and 21 are pattern diagrams of the pixel electrode 25A and the common electrode 23A in FIG. 19, respectively, which are similar to FIGS. 34 and 35, respectively.

  Since the pixel is rectangular, the pixel electrode 25A and the common electrode 23A have stripe portions parallel to each other, and the pixel electrode 25A and the common electrode 23A are all connected, the periphery of the pixel electrode 25A The portion and the peripheral portion of the common electrode 23A have portions that overlap each other with an insulating film interposed therebetween. For this reason, the end portions of the line electrodes adjacent to the pixel electrode 25A and the common electrode 23A intersect via the insulating portion. For example, the side 251 of the pixel electrode 25A and the side 231 of the common electrode 23A are parallel to each other, and the side 252 and the side 232 that are continuous with the side 251 and the side 231 intersect each other.

  FIG. 22A is an enlarged view of the vicinity of this electrode intersection. FIG. 22B shows dotted lines of electric lines when a voltage is applied between the pixel electrode 25A and the common electrode 23A.

  Since the side 252 and the side 232 intersect each other at an obtuse angle, as shown in FIG. 36A, the concentration of electric lines of force is reduced and the electric field lines are less concentrated than when the side 252 and the side 231 intersect at an acute angle. An increase in strength is suppressed.

  Further, the sides 251 and 252 and the sides 231 and 232 are symmetric with respect to a line SA passing between the sides 251 and 231. Thereby, the direction of the electric field vector between the side 252 and the side 232 is parallel to that between the side 251 and the side 231.

  For this reason, the sudden change distribution of the transmission characteristics in the vicinity of the electrode intersection is relaxed, the display image quality is improved, and the burn-in is reduced. The same applies to the vicinity of other electrode intersections.

  A liquid crystal panel using the electrode pattern of FIG. 19 and a liquid crystal panel using the electrode pattern of FIG. 33 were made in the same manner as the above prototype except for the electrode pattern, and the liquid crystal panel using the electrode pattern of FIG. Confirmed that the seizure rate was low.

  [Fourth Embodiment] FIG. 23 is an electrode pattern diagram of a liquid crystal pixel according to a fourth embodiment of the present invention capable of reducing the printing rate, and is similar to FIG. FIG. 24 is a pattern diagram of the common electrode 23B in FIG. The pixel electrode 25A is the same as that in FIG.

  Cutout portions 23B1 to 23B8 are formed around the common electrode 23B while ensuring the integrity of the common electrode 23B. The positions of the cut portions 23B1 to 23B8 are near the intersection between the common electrode 23B and the pixel electrode 25D via an insulator.

  If there is no cut-out portion, an electric field is generated in the non-display region between this portion and the pixel electrode 25A when a voltage is applied, affecting the arrangement of liquid crystal molecules in the display region in the vicinity thereof. Since this effect is eliminated by the cut portion, the display image quality is improved and the burn-in is reduced as compared with the case of the third embodiment.

  [Fifth Embodiment] FIG. 25 is an electrode pattern diagram of a liquid crystal pixel according to a fifth embodiment of the present invention capable of reducing the printing ratio, and is similar to FIG. FIG. 26 is a pattern diagram of the common electrode 23C in FIG. The pixel electrode 25 is the same as that in FIG.

  As in the case of FIG. 24, the common electrode 23C has cut portions 23B1 to 23B8 formed while ensuring the integrity of the common electrode 23C. Thereby, compared with the structure of FIG. 23, a display image quality improves for the same reason as the said 5th Embodiment, and image sticking is reduced.

  [Sixth Embodiment] FIG. 27 is an electrode pattern diagram of two adjacent liquid crystal pixels according to a sixth embodiment of the present invention. Both pixels have the same pattern.

  The frame portions of the common electrode 23D and the pixel electrode 25D overlap each other with an insulating film interposed therebetween. A stripe electrode portion of the common electrode 23D is formed below the stripe electrode of the pixel electrode 25D and between the line electrodes, and the line density thereof is twice that of the pixel electrode 25D.

  FIG. 28 is an enlarged sectional view taken along line AA in FIG.

  32 is different from the liquid crystal pixel of FIG. 32 in that the line electrode portion of the pixel electrode 25D is convex, the insulating layer 26D is formed only on the pixel electrode 25D, and the common electrode 23D and the pixel electrode 25D are displayed between the line electrodes. The insulating layer is not formed in the region. Since the vertical alignment layer 27 is thinner than the insulating layer 26D, this is indicated by a bold line in FIG.

  Since the line electrode portion of the pixel electrode 25D has a convex shape, its surface is inclined from the center line to both sides. In order to form the convex shape, unlike FIG. 32, the line portion of the common electrode 23D, which is narrower than the line electrode portion of the pixel electrode 25D, is formed below the line electrode portion of the pixel electrode 25D. In order to emphasize this convex shape, the channel protective film 31 formed when the TFT 29 of FIG. 27 is formed is left above the line portion of the common electrode 23D. The width of the channel protective film 31 is narrower than that of the line portion of the common electrode 23D.

  As a result, the line electrode portion of the pixel electrode 25D has a bank shape. Therefore, when a voltage is applied between the pixel electrode 25D and the common electrode 23D, the lines of electric force are indicated by dotted lines in FIG. That is, since the lines of electric force in the vicinity of the inclined surface of the pixel electrode 25D are perpendicular to this surface, the inclination of the liquid crystal molecules is larger than the normal to the surface of the transparent insulating substrate 21, which is whiter than in the case of FIG. Display transmittance increases. Therefore, the display contrast is improved.

  In addition, since the pixel electrode 25D and the insulating layer 26D have the same pattern and the insulating layer 26D does not exist in the display region between the pixel electrode 25D and the common electrode 23D, the electric field is used more effectively for the liquid crystal molecules than in the case of FIG. In the case of the same applied voltage, the contrast is improved as compared with the case of FIG.

  Further, since the liquid crystal is not in direct contact with the pixel electrode 25D, the liquid crystal is prevented from being decomposed and burn-in is reduced.

  29 and 30 show the manufacturing process of the substrate 20D. Each figure corresponds to a cross section taken along line BB in FIG. Next, this will be described.

  (A) A metal common electrode 23D and a scanning (gate) line SL1 are formed on the transparent insulating substrate 21 by photolithography.

  (B) The insulating layer 24, the intrinsic semiconductor film 32, and the channel protective film 31 are stacked on the transparent insulating substrate 21. The channel protective film 31 is left only above the scanning line SL1 and the common electrode 23D by photolithography.

  (D) An n + semiconductor film 33, a conductive film 25D, and an insulating layer 26D are stacked on the semiconductor film 32, and these are etched in the same pattern. The source S and the drain D of the TFT 29 are located above the scanning line SL1. Simultaneously with the formation, the line electrode portion of the pixel electrode 25D and the insulating layer 26D are formed above the line portion of the common electrode 23D. The pixel electrode 25D and the electrode of the TFT 29 are formed of three layers of conductive films 25a, 25b and 25c. The conductive films 25a to 25c are, for example, Ti / Al / Ti. If only the Al film is used as the electrode 25D, it diffuses into the n + semiconductor film 33. Therefore, a Ti film is used to avoid this, and if only the Ti film is used, the resistivity is increased, and therefore an Al film is also used. . The insulating layer 26D is a silicon nitride film or a silicon oxide film formed by DVD.

  Note that if two layers of Ti / Al are used for the pixel electrode 25D and aluminum nitride is used for the insulating layer 26D, these can be continuously formed by a sputtering apparatus, so that the number of steps can be reduced. The insulating layer 26D may be one in which a photoresist used for patterning remains.

  (E) A vertical alignment layer 27 indicated by a thick line is deposited on the insulating layers 24 and 26.

  According to the sixth embodiment, since the bank line electrode portion of the pixel electrode 25D and the insulating layer 26D thereon are formed simultaneously with the TFT 29, the number of processes is increased to form the pixel electrode 25D and the insulating layer 26D. There is no need to do.

10, 20, 20A Substrate 11, 21 Transparent insulating substrate 12 Planar electrode 13 Dielectric 14, 27 Vertical alignment layer 15, 28 Polarizer 23, 23A-23D Common electrode 231, 232, 251, 252 Side 23B1-23B8 Cutout 24 , 24A, 26, 26A, 26D Insulating layer 25, 25A, 25D Pixel electrode 25a to 25c Conductive film 29 TFT
30 Liquid crystal 31 Channel protective film 32 Semiconductor film 33 n + semiconductor film DL1 Data line SL1 Scan line

Claims (4)

In a liquid crystal display panel having a liquid crystal sealed between a first substrate and a second substrate, the first substrate having an insulating substrate, a pixel electrode and a common electrode formed above the insulating substrate,
Each of the first substrate and the second substrate has a vertical alignment film,
A surface electrode is formed on the main surface of the second substrate on the liquid crystal side,
The position of the pixel electrode is higher than the position of the common electrode with respect to the liquid crystal side surface of the insulating substrate, and the pixel electrode and the common electrode have a portion overlapping with each other through the first insulating film,
A liquid crystal display panel, wherein the pixel electrode has a convex surface due to a portion where the pixel electrode and the common electrode overlap with each other through the first insulating film.   2. The liquid crystal display panel according to claim 1, wherein the first insulating film has substantially the same thickness on the pixel electrode and on the common electrode.   3. The pixel electrode is covered with a second insulating film, and the second insulating film is not substantially formed in a display region between the common electrode and the pixel electrode. The liquid crystal display panel as described. The pixel electrode and the common electrode have portions that cross each other via the first insulating film,
Both the pixel electrode and the common electrode have line electrode portions that are parallel to each other and that are continuous with the intersecting portion.
The liquid crystal display panel according to claim 1, wherein adjacent sides of the pixel electrode and the common electrode at the intersection intersect each other at an obtuse angle.

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