JP3910771B2 - Liquid crystal display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device, and more particularly to a reflective liquid crystal display device employing a front light system.
[0002]
[Prior art]
As is well known, as a conventional liquid crystal display device, a transflective liquid crystal display device having a backlight has been mainstream, but in this type of liquid crystal display device, light from the backlight is transmitted through a transflective plate. Then, it is configured to enter the liquid crystal panel. For this reason, when light is transmitted through the transflective reflector, a part of the light is reflected by the transflective reflector, resulting in light loss. In addition, this type of liquid crystal display device, when performing liquid crystal screen display using external light without turning on the backlight, the external light transmitted from the front side to the back side of the liquid crystal panel is transflective. It is returned to the direction of the liquid crystal panel by being reflected by the plate. For this reason, when light is reflected by the transflective plate, a part of the light is transmitted through the transflective plate, and in this case, light loss occurs. As described above, since the transflective liquid crystal display device causes a lot of light loss due to the use of the transflective reflector, it is difficult to brighten the screen display and increase the contrast. ing.
[0003]
Therefore, in recent years, a reflection type liquid crystal display device adopting a front light system has been proposed as a means for solving such problems as described later. This reflective liquid crystal display device has little loss of light incident on the liquid crystal panel, can provide an image display with high contrast, and can save power. Therefore, this reflective liquid crystal display device is expected to become the mainstream in the future.
[0004]
A specific example of the reflective liquid crystal display device is disclosed in Japanese Patent Application Laid-Open No. 11-109344. As disclosed in this publication, as shown in FIG. 9 of the present application, behind the liquid crystal panel 9 in which the liquid crystal 91 is sealed between a pair of transparent substrates 90a and 90b, a polarizing plate 80b and a reflecting plate 81 are provided. Are provided in layers. On the front surface of the liquid crystal panel 9, a light guide plate 82 and a polarizing plate 80a are provided so as to overlap each other. The light guide plate 82 is transparent, and a plurality of convex portions 83 are continuously formed on one surface thereof. Each convex part 83 has the form extended in the width direction of the light-guide plate 82, as shown, for example in FIG. A light source 84 is provided on the side of the light guide plate 82.
[0005]
In the liquid crystal display device having such a configuration, when the light source 84 is driven to turn on, the light emitted from the light source 84 enters the light guide plate 82 and is totally reflected by the outer surface of the light guide plate 82. It travels inside the light plate 82. During this progression, light is emitted downward from the surface of each convex portion 83 and enters the liquid crystal panel 9. Each convex portion 83 plays a role of facilitating emission of light traveling in the light guide plate 82 in the direction of the liquid crystal panel 9. The light transmitted through the liquid crystal panel 9 is then transmitted through the polarizing plate 80b and then reflected upward by the reflecting plate 81. The light passes through the polarizing plate 80b and the liquid crystal panel 9 again, and then passes through the light guide plate 82 and the polarizing plate 80a. . On the other hand, in the case where the light source 84 is not driven to turn on, external light sequentially passes through the polarizing plate 80a, the light guide plate 82, the liquid crystal panel 9, and the polarizing plate 80b and then is reflected upward by the reflecting plate 81, and thereafter After passing through the above members in the reverse order, the light is emitted above the polarizing plate 80a. As described above, in the liquid crystal display device having the above configuration, the light transmitted through the liquid crystal panel 9 downward is efficiently reflected by the reflecting plate 81 regardless of whether the light source 84 is used or not. Therefore, there is less light loss than that using a transflective plate, and the display on the liquid crystal screen can be brightened.
[0006]
[Problems to be solved by the invention]
However, the conventional liquid crystal display device is configured to see through the display of the liquid crystal screen through the light guide plate 82, while the light guide plate 82 has a plurality of convex portions 83. Therefore, conventionally, when viewing the liquid crystal screen, the outlines of the plurality of convex portions 83 of the light guide plate 82, that is, the linear distal end line 83a and proximal end line 83b of each convex portion 83 shown in FIG. In some cases, it appears as a large number of streaks. Conventionally, the light guide plate 2 and the liquid crystal panel 9 are combined without considering the positional relationship between the convex portions 83 of the light guide plate 82 and the pixels of the liquid crystal panel 9. In some cases, the leading end line 83a and the base end line 83b are positioned in front of the pixels of the liquid crystal panel 9 and block the pixels. As a result, when the liquid crystal screen is viewed, the lines 83a and 83b are obstructive, and the quality of the image displayed on the liquid crystal may be impaired.
[0007]
The invention of the present application has been conceived under such circumstances, and a front light that allows a display image to be seen more clearly than before by making the contour line of the unevenness of the light guide plate inconspicuous. It is an object of the present invention to provide a reflection type liquid crystal display device adopting the method.
[0008]
DISCLOSURE OF THE INVENTION
In order to solve the above problems, the present invention takes the following technical means.
[0009]
The liquid crystal display device provided by the invention of the present application emits light from a light source incident on the inside of a liquid crystal panel and one side surface disposed in front of the liquid crystal panel and extending in the width direction , toward the liquid crystal panel. In addition, a transparent light guide plate in which only one surface near the liquid crystal panel of the front and back surfaces is formed in a concavo-convex shape, and light transmitted through the liquid crystal panel from the light guide plate provided behind the liquid crystal panel. A liquid crystal display device comprising the liquid crystal panel and a reflecting plate that reflects toward the light guide plate, wherein the irregularities are arranged in a width direction having two types of inclined surfaces having different inclination directions and inclination angles. A plurality of convex portions having a uniform triangular cross section are continuously formed in a certain direction, and when viewed from the front of the light guide plate, from the front end line and the base end line of each convex portion of the light guide plate Become Outline of serial irregularities, is characterized in that positioned between the each other a plurality of pixels of the liquid crystal panel.
[0010]
In the liquid crystal display device according to the present invention, when the light guide plate and the liquid crystal panel are viewed from the front, the contour line of the unevenness of the light guide plate is located between the plurality of pixels of the liquid crystal panel. It is possible to hide the lines so as to block the pixels. Therefore, when the liquid crystal screen is viewed, the contour line of the unevenness of the light guide plate can be made inconspicuous, and the image displayed on the liquid crystal can be made clearer than before. In addition, the appearance of the liquid crystal screen can be improved.
[0011]
In a preferred embodiment of the present invention, the liquid crystal panel is a color liquid crystal panel in which a plurality of color filters are arranged in a matrix, and the contour line of the unevenness of the light guide plate is an area between the plurality of color filters. Located in front of. In the case of a color liquid crystal panel using color filters, a region where each color filter is provided is a pixel region of the liquid crystal panel. Therefore, when the contour line of the unevenness of the light guide plate is arranged in front of the region between the color filters, the contour line is located between the plurality of pixels of the liquid crystal panel in the front view of the light guide plate. Become.
[0012]
In another preferred embodiment of the present invention, the liquid crystal panel is a color liquid crystal panel having a black matrix, and an uneven outline of the light guide plate is located in front of the black matrix. In the case of a color liquid crystal panel having a black matrix, a portion where the black matrix is provided corresponds to a region between a plurality of pixels of the liquid crystal panel. Therefore, if the contour line of the unevenness of the light guide plate is arranged in front of the black matrix, the contour line is located between a plurality of pixels of the liquid crystal panel in the front view of the light guide plate.
[0013]
In another preferred embodiment of the present invention, the liquid crystal panel performs monochrome display, and the contour line of the unevenness of the light guide plate is a pair of transparent substrates of the liquid crystal panel among the liquid crystal panels. The transparent electrodes provided in each of the first and second electrodes are positioned in front of a region different from the region facing each other. In the case of a liquid crystal panel that performs monochrome display, a region where the transparent electrodes face each other is a pixel region of the liquid crystal panel. Therefore, when the concave / convex outline of the light guide plate is arranged in front of an area different from those areas, the outline is located between a plurality of pixels of the liquid crystal panel in the front view of the light guide plate. It will be.
[0015]
Other features and advantages of the present invention will become more apparent from the following description of embodiments of the invention.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be specifically described with reference to the drawings.
[0017]
1 to 3 show a first embodiment of the present invention. As clearly shown in FIG. 1, the liquid crystal display device A of the present embodiment has a liquid crystal panel 1, a light guide plate 2 provided on the front surface (upper side) of the liquid crystal panel 1, and light incident on the light guide plate 2. The light source 3 includes a pair of polarizing plates 4 a and 4 b and a reflection plate 5 provided on the front and back portions of the liquid crystal panel 1.
[0018]
The liquid crystal panel 1 is configured to be capable of color display, and includes a liquid crystal 12 enclosed in a region surrounded by a pair of glass transparent substrates 10a and 10b and a seal member 11. The transparent substrate 10a is provided with color filters 6 (6R, 6G, 6B) of R, G, and B colors in a matrix, and a black matrix 60 is provided between the color filters 6. ing. The transparent substrates 10a and 10b are also provided with alignment films 13a and 13b and transparent electrodes 14a and 14b for twisting the liquid crystal molecules. The liquid crystal panel 1 employs an active matrix driving method, and a thin film transistor (TFT) 15 for holding a voltage applied to the liquid crystal cell is disposed in one liquid crystal cell. Yes. More specifically, as clearly shown in FIG. 2, a plurality of transparent electrodes 14b (cross-hatched portions) having a constant area are provided in a matrix on one side of the transparent substrate 10b. In the gap region between the transparent electrodes 14b, a plurality of wiring portions 15a, 15b called lines or data lines are provided extending vertically and horizontally, and these wiring portions 15a, 15b and the transparent electrodes 14b are It is configured to conduct through the thin film transistor 15. The transparent electrode 14a of the transparent substrate 10a is a common electrode, and is provided over a wide area on one side of the transparent substrate 10a.
[0019]
In FIG. 1, the light guide plate 2 has a transparent substantially flat plate shape, and as its specific material, polycarbonate having excellent transparency or PMMA (polymethyl methacrylate (methacrylic resin)) is preferably used. In the present embodiment, the thickness of each part of the light guide plate 2 is made substantially uniform. However, the thickness may be reduced as the distance from the light source 3 increases, for example. The light guide plate 2 has a smooth flat surface (upper surface), while its back surface is uneven. More specifically, as clearly shown in FIG. 3, the rear surface of the light guide plate 2 has a plurality of triangular shapes in a side view having two types of inclined surfaces 20a and 20b having different inclination directions and inclination angles. The convex part 20 is made into the uneven | corrugated shape continuously formed in the fixed direction. Each convex portion 20 extends uniformly in the width direction (arrow Na direction) of the light guide plate 2. Therefore, when the light guide plate 2 is viewed from the surface side, the front end line 21 a and the base end line 21 b of each convex portion 20 are seen through as straight lines extending in the width direction of the light guide plate 2. The pitch of the plurality of convex portions 20 is, for example, about one hundred tens of μm. However, as will be described later, each convex portion 20 is positioned in a predetermined state in relation to the liquid crystal panel 1.
[0020]
As clearly shown in FIG. 1, the light guide plate 2 is provided so that the back surface thereof faces the transparent substrate 10a of the liquid crystal panel 1 through the polarizing plate 4a. The front end line 21 a and the base end line 21 b of the part 20 are arranged so as to be positioned in front of the gap region between the plurality of pixels of the liquid crystal panel 1. Here, in this liquid crystal panel 1, each color filter 6 is provided in front of each transparent electrode 14b, and when the image display by this liquid crystal panel 1 is viewed, it passes through each color filter 6 upward. In order to recognize light, a portion where each color filter 6 is provided basically becomes a pixel region. However, in the present embodiment, since a part of each color filter 6 is covered with the black matrix 60, strictly speaking, the black matrix 60 is provided in the portion where each color filter 6 is provided. The region S excluding the region that is present becomes the pixel region. Therefore, in the present embodiment, the area where the black matrix 60 is provided corresponds to a gap area between a plurality of pixels, and the front end line of each convex portion 20 of the light guide plate 2 is in front of the black matrix 60. 21a and proximal end line 21b are arranged.
[0021]
The light source 3 is provided adjacent to one side surface 22 a extending in the width direction of the light guide plate 2, and preferably includes a reflector 30. As the light source 3, a cold cathode tube extending in the same direction as the one side surface 22 a of the light guide plate 2 can be used. However, instead of this, a so-called point light source such as an LED light source may be used, and the specific type of the light source is not limited in the present invention. In the illuminating device that combines the light source 3 and the light guide plate 2, when the light source 3 is driven to turn on, the light emitted from the light source 3 enters the one side surface 22 a of the light guide plate 2 and then the surface of the light guide plate 2. The interior of the light guide plate 2 is sequentially advanced toward the other side surface 22b while repeating total reflection by the back surface. When the light traveling in the light guide plate 2 reaches the inclined surface 20a on the back surface of the light guide plate 2, the incident angle of light with respect to the inclined surface 20a is reduced by the amount that the inclined surface 20a is inclined in a predetermined direction. There is a high possibility that the incident angle is smaller than a predetermined total reflection critical angle determined by the refractive index of the light guide plate 2. For this reason, the ratio of the light totally reflected by the inclined surface 20a is reduced, and the light is promoted to be emitted toward the liquid crystal panel 1 from various places on the back surface of the light guide plate 2.
[0022]
In the liquid crystal display device A having the above-described configuration, the basic operation when performing image display is the same as that of the liquid crystal display device shown in FIG. That is, when the light source 3 is driven, light is emitted from the back surface of the light guide plate 2 to the liquid crystal panel 1 and transmitted through the polarizing plate 4a, the liquid crystal panel 1 and the polarizing plate 4b downward. By being reflected upward by the reflecting plate 5, the light again passes through the polarizing plate 4 b, the liquid crystal panel 1, and the polarizing plate 4 a, then passes through the light guide plate 2, and is emitted to the front of the liquid crystal display device A. Further, when image display using external light is performed without driving the light source 3, the external light is sequentially transmitted downward through the light guide plate 2, the polarizing plate 4a, the liquid crystal panel 1, and the polarizing plate 4b. By being reflected upward by the reflecting plate 5, the light is transmitted through each of the above portions in the opposite direction and emitted to the front of the liquid crystal display device A.
[0023]
In either case of using the light source 3 or using external light, the image by the liquid crystal panel 1 is seen through the light guide plate 2. On the other hand, in the liquid crystal display device A, the leading end line 21 a and the base end line 21 b of each convex portion 20 of the light guide plate 2 are located in front of the black matrix 60 that does not correspond to the pixel region S of the liquid crystal panel 1. Therefore, when the display image of the liquid crystal panel 1 is viewed from the front, each pixel of the image can be prevented from being blocked by the front end line 21a and the base end line 21b. Accordingly, the lines 21a and 21b are not obstructed, and the liquid crystal screen can be seen clearly.
[0024]
In the above embodiment, the front end line 21a and the base end line 21b are arranged in front of the black matrix 60. However, some color liquid crystal panels do not have a black matrix. In this case, the above-described lines 21a and 21b may be arranged in front of a plurality of color filter regions.
[0025]
4 and 5 show a second embodiment of the present invention. In FIG. 4 and subsequent figures, the same or similar elements as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment.
[0026]
As clearly shown in FIG. 4, the liquid crystal display device Aa of the present embodiment is configured for monochrome display in which the liquid crystal panel 1A does not have a color filter. In this respect, the liquid crystal display device Aa is different from the previous first embodiment. The configuration is different. Further, a simple matrix method is adopted as a driving method of the liquid crystal panel 1A. That is, as clearly shown in FIG. 5, the transparent substrate 10b is formed with a plurality of transparent electrodes 14b (cross-hatched portions) extending in a certain direction at a constant pitch, while the transparent substrate 10a has each transparent electrode A plurality of transparent electrodes 14a extending in a direction orthogonal to the electrodes 14b are formed at a constant pitch. For this reason, in this liquid crystal panel 1A, as shown in FIG. 4, the transparent electrodes 14a and 14b face each other, and the region S1 where the liquid crystal 12 is applied with a voltage by the transparent electrodes 14a and 14b has a matrix shape. This is the pixel area. The front end line 21a and the base end line 21b of each convex portion 20 formed on the back surface of the light guide plate 2 are arranged in front of the gap region between the pixel regions S1 so as to avoid the front of the pixel region S1. ing.
[0027]
Also in the liquid crystal display device Aa having such a configuration, when the image displayed on the liquid crystal panel 1A is viewed from the front through the light guide plate 2 as in the case of the first embodiment, the light guide plate 2 It is possible to prevent the front end line 21 a and the base end line 21 b from blocking each pixel of the display image of the liquid crystal panel 1. Therefore, it is possible to prevent the lines 21a and 21b from being obstructive.
[0028]
6 to 7 schematically show a reference example of the present invention.
[0029]
In the example shown in FIG. 6, a plurality of triangular convex portions 29 are formed on the back surface of the light guide plate 2 at intervals, so that the back surface is uneven. Each convex portion 29 extends uniformly in cross section in the width direction of the light guide plate 2 (direction perpendicular to the paper surface). In the present invention, it is possible to irradiate the liquid crystal panel 1 with the light emitted from the light source 3 by using the light guide plate 2 having such a configuration. The front end line 29a and the base end line 29b of each convex portion 29 are arranged in front of the region Sb between the portions Sa so as to avoid the front of the portions Sa to be a plurality of pixels of the liquid crystal panel 1. . Therefore, in this case as well, it is possible to prevent the distal end line 29a and the proximal end line 29b of each convex portion 29 from blocking each pixel of the display image.
[0030]
FIG. 7 (a), in the example shown in (b), by plurality of cylindrical projections 28 are formed on the rear surface of the light guide plate 2, the rear surface is formed in an uneven shape. Also by using the light guide plate 2 having such a configuration, it is possible to irradiate the liquid crystal panel 1 with the light emitted from the light source 3 due to the presence of the protrusions 28. Each protrusion 28 is disposed in front of a region Sb between the plurality of pixel portions Sa of the liquid crystal panel 1. For this reason, when the liquid crystal panel 1 is viewed from the front through the light guide plate 2, it is possible to prevent the lines of the outer peripheral surface 28 a that are the outlines of the protrusions 28 from blocking the pixels of the display image.
[0031]
FIG. 8 shows another embodiment of the present invention. In this embodiment, for example, the plurality of projections 28 formed in a columnar shape of the light guide plate 2 are formed larger than one pixel portion Sa, so that the outer peripheral surface 28a of each projection 28 is a plurality of pixel portions Sa. It arrange | positions in front of the area | region Sb between them .
[0033]
Note that irradiating the light emitted from the light source to the liquid crystal panel using the light guide plate is not limited to the case where the back surface of the light guide plate is formed in an uneven shape, but only the surface of the light guide plate facing the front of the liquid crystal display device. This is also possible when the is formed in a concavo-convex shape, or when both the front and back surfaces of the light guide plate are formed in a concavo-convex shape. Therefore, it does not matter whether any of the front and back surfaces of the light guide plate is formed in an uneven shape. However, since the back surface of the light guide plate is formed in a concavo-convex shape as in the above-described embodiment, the concavo-convex shape can be made closer to the pixel region of the liquid crystal panel than in the case where the surface is formed in a concavo-convex shape. When the screen is viewed from an oblique direction, it is possible to obtain an advantage that the concave and convex outlines overlap the pixel region and are difficult to see.
[0034]
In addition, the specific configuration of each part of the liquid crystal display device according to the present invention is not limited to the above-described embodiment, and various design changes can be made. The type of liquid crystal and its driving method are not limited at all.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a liquid crystal display device according to the present invention.
2 is a perspective view of a principal part showing a transparent substrate and a transparent electrode of the liquid crystal display device shown in FIG. 1;
3 is a perspective view of a main part showing a light guide plate of the liquid crystal display device shown in FIG. 1. FIG.
FIG. 4 is a cross-sectional view showing another example of a liquid crystal display device according to the present invention.
5 is a perspective view of a main part showing a transparent substrate and a transparent electrode of the liquid crystal display device shown in FIG. 4;
FIG. 6 is an explanatory view schematically showing a reference example of the present invention.
7A is a perspective view illustrating a reference example of a light guide plate, and FIG. 7B is an explanatory diagram schematically illustrating a relationship between the light guide plate and a liquid crystal panel.
FIG. 8 is an explanatory view schematically showing another example of the present invention.
FIG. 9 is a cross-sectional view showing an example of a conventional liquid crystal display device.
FIG. 10 is a perspective view showing an example of a light guide plate used in a conventional liquid crystal display device.
[Explanation of symbols]
A, Aa Liquid crystal display device 1, 1A Liquid crystal panel 2 Light guide plate 3 Light source 5 Reflector 21a Tip line (uneven outline)
21b Base line (uneven outline)

Claims (6)

A liquid crystal panel and a light source disposed on the front surface of the liquid crystal panel and incident from the side surface extending in the width direction is emitted toward the liquid crystal panel so as to emit light toward the liquid crystal panel. A transparent light guide plate that is formed in an uneven shape only on one side , and light that is provided behind the liquid crystal panel and that has passed through the liquid crystal panel from the light guide plate is reflected toward the liquid crystal panel and the light guide plate. A liquid crystal display device comprising:
The irregularities are formed by continuously forming a plurality of convex portions having a uniform triangular cross section in the width direction having two types of inclined surfaces having different inclination directions and inclination angles in a certain direction,
In the front view of the light guide plate, the contour line of the unevenness composed of the leading end line and the base end line of the convex portions of the light guide plate is located between the plurality of pixels of the liquid crystal panel. A liquid crystal display device. A liquid crystal panel, a transparent light guide plate which is arranged in front of the liquid crystal panel and has at least one surface formed in a concavo-convex shape so that light incident inside from a light source is emitted toward the liquid crystal panel, and the liquid crystal A liquid crystal display device provided with a reflector provided behind the panel and reflecting light transmitted from the light guide plate through the liquid crystal panel toward the liquid crystal panel and the light guide plate,
The unevenness is formed by a plurality of protrusions formed in a cylindrical shape,
Since each of the protrusions is formed larger than one pixel of the liquid crystal panel, the outline of the concavo-convex formed by the outer peripheral surface of each of the protrusions is formed between the pixels of the liquid crystal panel in a front view of the light guide plate. A liquid crystal display device, wherein the liquid crystal display device is located in between.   The liquid crystal panel is a color liquid crystal panel in which a plurality of color filters are arranged in a matrix, and the contour line of the unevenness of the light guide plate is located in front of the region between the plurality of color filters. 3. The liquid crystal display device according to 1 or 2.   3. The liquid crystal display device according to claim 1, wherein the liquid crystal panel is a color liquid crystal panel having a black matrix, and an uneven outline of the light guide plate is located in front of the black matrix.   The liquid crystal panel performs monochrome display, and the contour line of the concave and convex portions of the light guide plate is such that the transparent electrodes provided on the pair of transparent substrates of the liquid crystal panel are opposed to each other. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is located in front of a region different from the region to be operated. 3. The liquid crystal display device according to claim 2, wherein , of the front and back surfaces of the light guide plate, only the back surface close to the liquid crystal panel has an uneven shape.

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