JP2005157104A - Transflective liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transflective liquid crystal display device of which the viewing angle dependence or the directivity of reflected light on the periphery of an opening part edge of a transmissive part is improved. <P>SOLUTION: In the transflective liquid crystal display device equipped with the rectangular transmissive part 24 and a reflective part 28 arranged on the periphery of the transmissive part 24 and having a plurality of projecting parts 43 on an interlayer film for each pixel, the outsides of at least a pair of opposing edges of the transmissive part 24 form a pair of strip shaped reflective parts 44, 45. Arrangement patterns of the plurality of projecting parts 43 formed on the pair of strip shaped reflective parts 44, 45 on the respective sides are made to be different from each other so as to make the directivity of the reflected light on the respective sides different from each other. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a transflective liquid crystal display device, and more particularly to a transflective liquid crystal display device in which the viewing angle dependency or the directivity of reflected light around an opening edge of a transmissive portion is improved.

In recent years, the application of liquid crystal display devices has rapidly spread not only in information communication equipment but also in general electric equipment. In particular, for portable devices, a reflective liquid crystal display device that does not require a backlight is used in order to reduce power consumption. However, this reflective liquid crystal display device uses external light as a light source. Moreover, it becomes difficult to see in a dark room. Thus, in recent years, development of a transflective liquid crystal display device having both transmissive and reflective properties has been underway. (See Patent Documents 1 and 2)
This transflective liquid crystal display device has a transmissive portion having a transparent electrode and a reflective portion having a reflective electrode in one pixel, and in a dark place, the backlight is turned on to transmit the transmissive portion of the pixel region. Since the image is displayed using the external light in the reflection part without turning on the backlight in a bright place, it is not necessary to always turn on the backlight. Can be greatly reduced.

  In this transflective liquid crystal display device, in order to perform bright display using ambient light, it is necessary to increase the intensity of light scattered in a direction perpendicular to the display screen with respect to incident light from all angles. For this reason, there is a need for a reflection means with high light utilization efficiency having optimum reflection characteristics that scatter incident light from all angles in the direction of the observer.

  In addition, this reflecting means requires that the reflective layer has an appropriate diffuse reflection characteristic (light distribution) in order to realize a display having a good paper white characteristic in the reflection mode. When the reflecting surface is close to a mirror surface, specular reflection (specular reflection) becomes strong and a surrounding image is reflected, and conversely, if the diffuse reflection property is too strong, the luminance is lowered.

  An example of such a transflective liquid crystal display device will be described with reference to FIGS. 1 to 3. FIG. 1 is a plan view of one pixel of the transflective liquid crystal display device, and FIG. FIG. 3 is a cross-sectional view taken along line A ′, and FIG. 3 is a cross-sectional view taken along line BB ′ of FIG.

  In the transflective liquid crystal display device 10, a plurality of scanning lines 32 made of a metal such as aluminum or chrome are formed in parallel at substantially equal intervals on a glass substrate 12 having a transparent insulating property. The auxiliary capacitance line Cs is formed in parallel with the scanning line 32 at the approximate center between the matching scanning lines 32. A gate electrode G extends from the scanning line 32.

  A gate insulating film 14 made of silicon nitride, silicon oxide, or the like is laminated on the glass substrate 12 so as to cover the scanning lines 32, the auxiliary capacitance lines Cs, and the gate electrode G. A semiconductor layer 15 made of amorphous silicon, polycrystalline silicon, or the like is formed through the insulating film 14, and a plurality of video lines 34 are formed on the gate insulating film 14 so as to be orthogonal to the scanning lines 32. Yes. Although not shown, the video line 34 has a two-layer structure in which the lower part is made of Al and the upper part is made of Cr. A source electrode S extends from the video line 34, and the source electrode S is connected to the semiconductor layer 15.

  Further, a drain electrode D, which is the same material as the video line 34 and the source electrode S and is formed simultaneously, is provided on the gate insulating film 14 and is connected to the semiconductor layer 15.

  Here, a rectangular area surrounded by the scanning lines 32 and the video lines 34 corresponds to one pixel. The gate electrode G, the gate insulating film 14, the semiconductor layer 15, the source electrode S, and the drain electrode D constitute a TFT element 16 serving as a switching element, and the TFT element 16 is formed in each pixel. In this case, the storage capacitor of each pixel is formed by the drain electrode D and the storage capacitor line Cs.

  An interlayer insulating film (insulating protective film 18) made of, for example, an inorganic insulating film is laminated so as to cover the video line 34, the TFT element 16, and the gate insulating film 14, and an organic insulating film is formed on the insulating protective film 18. The interlayer film 20 having a convex portion formed on the surface is laminated. In the insulating protective film 18 and the interlayer film 20, a contact hole 22 is formed in a rectangular shape at a position corresponding to the drain electrode D of the TFT element 16 and a position away from the TFT element 16.

  In each pixel, a transparent electrode 17 made of, for example, ITO (Indium Tin Oxide) is formed on the interlayer film 20, the contact hole 22, and the surface of the opening 24, and of these, on the interlayer film 20 and the contact hole 22. A reflective electrode 26 made of aluminum is provided on the transparent electrode 17 positioned. Aluminum is generally used as a material for the reflective electrode 26 because of its high reflectivity and low resistance. In addition, the reflective electrode 26 can be made of an alloy containing aluminum, silver, or the like.

  When viewed from the bottom surface direction of the glass substrate 12, the reflective electrode 26 is formed so as not to contact the adjacent reflective electrode 26 and slightly overlap the scanning line 32 and the video line 34, and around the opening 24. Is formed so as to surround.

  A backlight device having a well-known light source, a light guide plate, a diffusion sheet, and the like (not shown) is disposed below the glass substrate 12, and all the pixels are above the opening 24 and the reflective electrode 26. A color filter substrate (not shown) on which an alignment film is laminated so as to cover the surface and provided with R, G, B3 color filters, counter electrodes and the like formed corresponding to the respective pixels. The transflective liquid crystal display device 10 is formed by facing the glass substrate 12, bonding the substrates together, and injecting liquid crystal between the substrates.

  In this transflective liquid crystal display device 10, the range where the transparent electrode 17 is viewed from the opening 24 is a transmissive portion, in which light emitted from the backlight device passes, and the reflective electrode 26 is laminated. The reflected area is the reflecting portion 28, and external light is reflected by the reflecting portion 28.

In this case, the shape of the convex portion of the reflective portion 28 is such that the diameter d of the skirt of the convex portion is about 10 μm, as shown in FIG. 4, so that the reflective layer has an appropriate diffuse reflection characteristic. The height h of the portion is about 0.5 μm, and the inclination angle θ of the convex portion is 10 ° or less, preferably about 7 °. The ratio of the transmissive part and the reflective part 28 in one pixel can be adjusted. However, if the ratio of the transmissive part increases too much, the ratio of the reflective part 28 decreases, so the amount of reflection of external light decreases. End up. On the other hand, if the proportion of the transmissive part is too small, it becomes insufficient to compensate for the lack of external light with the light of the backlight. Usually, the proportion occupied by the transmission part is about 20%.
JP 2001-350158 A (2-3 pages, FIG. 4) JP 2000-25882 (pages 3 to 4, FIG. 1 and FIG. 2)

  The conventional transflective liquid crystal display device as described above lights a backlight in a dark place and displays an image using a transmission part of a pixel area, and reflects without turning on a backlight in a bright place. Since the external light is used to display images in the screen, it is not necessary to turn on the backlight at all times, so power consumption can be greatly reduced. However, if you look closely at the liquid crystal display screen, Was found to change slightly.

  As a result of repeated studies on this cause, the present inventor has found that the change in brightness depending on the viewing angle is based on the fact that the amount of reflected light near the opening of each pixel varies with the viewing angle.

  That is, the reflected light is shifted in the vertical direction, for example, by the convex pattern formed in the pair of elongated reflecting portions formed around the opening of each pixel. Accordingly, the amount of reflected light recognized by the observer depending on the viewing angle differs in the vertical direction and the horizontal direction.

  Therefore, as a result of various studies to further improve the viewing angle dependency of the brightness around the edge of the opening, the inventors have controlled the viewing angle by controlling the arrangement of the convex pattern on the interlayer film around the edge. It is found that it is possible to control the change in brightness due to light, and in a transflective liquid crystal display device, a transflective liquid crystal display device that suppresses the change in brightness due to the viewing angle caused by the presence of the periphery of the opening edge of each pixel is provided The purpose is to do.

  The above object of the present invention can be achieved by the following configurations. That is, in the invention of the transflective liquid crystal display device according to claim 1 of the present application, each rectangular pixel has a rectangular transmissive portion and a reflective portion having a plurality of convex portions provided around the transmissive portion. And at least a pair of opposing sides of the transmissive portion form a pair of elongated reflecting portions, and the reflected light from the elongated reflecting portion on one side. The projecting portions of the pair of elongated reflecting portions are formed so that the directivity of the reflected light and the directivity of the reflected light in the elongated reflecting portion on the other side complement each other.

  According to a second aspect of the present invention, in the transflective liquid crystal display device according to the first aspect, in the pair of elongated reflecting portions, the peak positions of a plurality of convex portions on the one side are the elongated shape. A plurality of convex portions on the other side are arranged in alignment at substantially the center of the reflecting portion, and are arranged in alignment with positions shifted from the center of the elongated reflecting portion. .

  According to a third aspect of the present invention, in the transflective liquid crystal display device according to the first aspect, in the pair of elongated reflecting portions, the peak positions of the plurality of convex portions on the one side have the elongated shape. A plurality of convex portions on the other side are arranged in alignment at both side end portions of the reflecting portion, and are arranged in alignment with positions shifted from the center of the elongated reflecting portion. To do.

  According to a fourth aspect of the present invention, there is provided a semiconductor device comprising a rectangular transmissive portion and a reflective portion provided around the transmissive portion and having a plurality of convex portions on an interlayer film for each rectangular pixel. In the transmissive liquid crystal display device, at least a pair of opposing sides of the transmissive portion form a pair of elongated reflective portions, and the directivity of reflected light in the elongated reflective portion on one side is left and right. It is characterized in that it is stronger in the vertical direction than in the direction, and the directivity of the reflected light in the elongated reflecting portion on the other side is stronger in the horizontal direction than in the vertical direction.

  The transflective liquid crystal display device of the present invention adopts the above-described configuration so that the change in brightness due to the viewing angle of the observer caused by the presence of the peripheral portion of the opening edge of each pixel can be suppressed. Become.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to Examples and Comparative Examples.

  First, the relationship between the position of the convex portion of the interlayer film around the opening and the directivity of the reflected light will be described with reference to FIG. In FIG. 5A to FIG. 5E, two straight lines Y and Y ′ extending vertically correspond to the edge portion of the opening or the scanning line and / or the video line in each pixel of the transflective liquid crystal display device. 2 represents a steeply inclined portion of the boundary portion, and between the two straight lines Y and Y ′ is an elongated reflecting portion existing around the opening of each pixel, and a circle is a skirt portion of the convex portion 41 of the reflecting electrode Indicates. In this case, the left side of the straight line Y or the right side of Y ′ representing the steeply inclined portion in FIGS. In addition, this convex part 41 is produced by forming an interlayer film with a photoresist and forming a large number of convex patterns on the surface, and then heat-treating the corners of the surface. Further, the shape of the convex portion 41 has an appropriate diffuse reflection characteristic so that the skirt diameter d of the convex portion 41 is about 10 μm, the height h of the convex portion 41 is about 0.5 μm, The inclination angle θ of the convex portion 41 is 10 ° or less, specifically about 7 °.

  FIG. 5A shows a state in which the peak position of the convex portion 41 is arranged in alignment with the central portion of the two straight lines Y and Y ′. In this case, the region of the reflective electrode where the convex portion 41 is formed is wider in the vertical direction than in the horizontal direction. Further, in the left-right direction, both sides of the reflecting portion are steeply inclined surfaces, and thus do not contribute to display. Therefore, the light reflected in the vertical direction is stronger than that in the horizontal direction, and has directivity in the vertical direction.

  Even if the peak position of the convex portion 41 is slightly shifted from the center of the two straight lines Y and Y ′ in the right direction (see FIG. 5B) or the left direction (see FIG. 5C), The reflected light remains the main. This is because the reflected light at the steeply inclined portion does not contribute to the display, and the reflection toward the side where the steeply inclined portion exists decreases. That is, in the case of FIG. 5B, the reflected light to the right side in the drawing is reduced, and in the case of FIG. 5C, the reflected light to the left side in the drawing is reduced. The amount of reflected light in the vertical direction increases.

  When the peak position of the convex portion 41 is further shifted to the right or left, the left and right ridges of the convex portion 42 gradually appear, so the reflected light in the left and right directions gradually increases. However, finally, the peak of at least one of the convex portions 41 and 42 comes to be positioned in alignment with the positions of the two straight lines Y and Y ′, that is, both side ends of the elongated reflecting portion (FIG. 5 ( d)). In this state, in the drawing, when the peak of the convex portion 41 is located at the left end, the reflected light is mainly reflected in the right direction, and when the peak of the convex portion 42 is located at the right end, the leftward direction is assumed. Reflected light is mainly used. As a result, in the state of FIG. 5D, the reflected light in the left-right direction is the largest in the drawing. In FIG. 5D, the projections 41 and 42 are arranged in a staggered arrangement. However, as shown in FIG. 5E, the projections 41 and 42 are arranged vertically and horizontally. The same effect can be obtained even if they are arranged in an aligned state. Further, this effect is best when the convex portions 41 and 42 are simultaneously aligned with both side end portions.

  Further, as the shape of the convex portion, the same effect can be obtained even when a polygonal shape as shown in FIG. 6 is adopted in addition to a shape having a circular skirt as shown in FIG. 6 (a) to 6 (e) correspond to FIGS. 5 (a) to 5 (e), respectively, and are shown in FIGS. 5 (a) to 5 (e), respectively. Shows the same reflection directivity.

  Therefore, it is possible to control the directivity of the reflected light by controlling the positions of the convex portions 41 and 42 of at least one pair of elongated reflecting portions around the transmissive portion of each pixel. By selecting an arrangement that gives different directivity of reflected light, it is possible to substantially eliminate the change in brightness due to the viewing angle.

  7 corresponds to the first embodiment of the present invention, FIG. 8 corresponds to the second embodiment of the present invention, and FIG. 9 corresponds to one pixel of the transflective liquid crystal display device corresponding to the comparative example. It is a top view showing an opening part and a reflection part.

  7 to 9, each pixel formed in a rectangular shape of the transflective liquid crystal display device includes an opening 24 and a reflective portion 28 including a reflective electrode 26, and the boundary between the opening 24 and the reflective portion 28. A steeply inclined portion is formed in the portion. Further, a scanning line and a video line are arranged around the reflecting portion 28 (see FIG. 1), and a steeply inclined portion is formed at a boundary portion between the reflecting portion 28 and the scanning line or the video line. A circle (including a semicircular shape and an arc shape) indicates a skirt portion of the convex portion 43 of the reflective electrode.

  The pixel of the transflective liquid crystal display device shown in FIG. 9 corresponding to the comparative example has thin reflective portions 44 and 45 formed along the video lines on the left and right sides of the rectangular opening 24. The arrangement of the protrusions 43 formed in 45 is random. Since the arrangement of the convex portions 43 is random, the directivity generated by the reflecting portions 44 and 45 causes a change in brightness depending on the viewing angle of the observer. In FIG. 9, since the directivity is higher in the vertical direction than in the horizontal direction, the observer looks brighter when observing from the vertical direction than when observing from the horizontal direction.

  On the other hand, each pixel shown in FIG. 7 corresponding to the first embodiment of the present invention is thin on the left and right sides along the long side of the rectangular opening 24 as in the comparative example. Reflecting portions 44 and 45 are formed. Among them, in the right reflection part 45, the peaks of all the convex parts 43 are configured to be located at substantially the center of the reflection part 45, similar to that shown in FIG. The directivity is stronger in the vertical direction than in the horizontal direction. And the peak of the convex part 43 of the reflection part 44 on the left side is arranged at both end portions of the elongated reflection part, similar to that shown in FIG. 5 (e). The directivity is stronger in the left-right direction. Therefore, the reflection portions 44 and 45 having different directivities in the vertical direction and the horizontal direction can suppress a change in brightness due to the viewing angle of the observer caused by the presence of the periphery of the pixel opening. Moreover, since the shape of the reflection parts 44 and 45 is a regular shape, preparation is also easy and it can utilize external light efficiently, utilizing effectively the small space in the reflection parts 44 and 45. FIG.

  In addition, since the area of the reflective part on the opposite side is large for the thin reflective part 46 at the upper part, the directivity of the reflected light of this part has little influence on the overall directivity, so it is necessary to control the directivity in particular. However, if the reflecting part on the opposite side is also thin, it is necessary to control the directivity of the reflected light as in the case of the reflecting parts 44 and 45.

  Further, in each pixel shown in FIG. 8 corresponding to the second embodiment of the present invention, thin reflective portions 44 and 45 are formed on the left and right sides of the rectangular opening 24, and the reflective portion 44 on the left side of these is formed. Similar to the peak shown in FIG. 5 (b), the peaks of the convex portions are aligned at a position slightly shifted from the center of the elongated reflecting portion 44 to the right side. Occurs. Further, the peak of the convex portion 43 of the right reflecting portion 45 is arranged in alignment with both side end portions of the elongated reflecting portion 45 in the same manner as shown in FIG. The directivity is generated. Therefore, also in this second embodiment, either reflected light can reach the viewer side even if the viewer's viewing angle changes, so the area around the aperture of each pixel of the transflective liquid crystal display device can be reduced. The change in brightness due to the viewing angle of the observer caused by the presence can be greatly suppressed.

  In the first embodiment and the second embodiment described above, the convex portion has a circular shape at the skirt, but a polygonal shape as shown in FIG. 6 may be adopted. It will be apparent to those skilled in the art that similar effects are produced.

It is a top view for one pixel of a transflective liquid crystal display device. It is sectional drawing along the A-A 'line of FIG. It is sectional drawing along the B-B 'line of FIG. It is a figure explaining the shape of the convex part of a reflection part. It is a figure for demonstrating the relationship between the position of a convex part in the case where the skirt part of a convex part is circular, and the directivity of reflected light. It is a figure for demonstrating the relationship between the position of a convex part and the directivity of reflected light in case the skirt part of a convex part is a hexagon. It is a top view for one pixel of the 1st example of this application. It is a top view for one pixel of the 2nd example of this application. It is a top view for one pixel of the comparative example of this application.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Semi-transmissive liquid crystal display device 12 Glass substrate 14 Gate insulating film 15 Semiconductor layer 16 TFT element 17 Transparent electrode 24 Opening part (transmission part)
26 reflective electrode 28 reflective part 32 scanning line 34 video lines 41-43 convex part 44-46 thin reflective part

Claims (4)

  In a transflective liquid crystal display device comprising a rectangular transmissive portion and a reflective portion having a plurality of convex portions provided around the transmissive portion in each rectangular pixel, at least a pair of the transmissive portions The outer sides of the opposing sides form a pair of elongated reflectors, the directivity of reflected light in the elongated reflector on one side, and the reflected light directivity in the elongated reflector on the other side A transflective liquid crystal display device, wherein convex portions of the pair of elongated reflecting portions are formed so as to complement each other.   The pair of elongated reflecting portions are arranged such that the peak positions of the plurality of convex portions on the one side are aligned with the approximate center of the elongated shape reflecting portion, and the peaks of the plurality of convex portions on the other side are arranged. 2. The transflective liquid crystal display device according to claim 1, wherein the transflective liquid crystal display device is arranged in alignment with a position shifted from a center of the elongated reflecting portion.   The pair of elongated reflecting portions are arranged such that peak positions of the plurality of convex portions on the one side are aligned with both side ends of the elongated reflecting portion, and the plurality of convex portions on the other side are arranged. 2. The transflective liquid crystal display device according to claim 1, wherein a peak position is arranged in alignment with a position shifted from a center of the elongated reflecting portion.   In the transflective liquid crystal display device including a rectangular transmissive portion and a reflective portion provided around the transmissive portion and having a plurality of convex portions on an interlayer film, for each rectangular pixel. The outside of at least a pair of opposing sides of the part forms a pair of elongated reflecting parts, and the directivity of reflected light in the elongated reflecting part on one side is stronger in the vertical direction than in the horizontal direction. A transflective liquid crystal display device characterized in that the directivity of reflected light in the elongated reflecting portion on the other side is stronger in the left-right direction than in the up-down direction.

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