JP2006323221A - Liquid crystal display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display apparatus that can effectively use light exiting from a light source and achieve a bright display or a display with low consumed power. <P>SOLUTION: A backlight unit 20 is composed of three light sources 21a to 21c (having R, G, B emission colors, respectively) and a light guide plate 22. The light guide plate 22 has a projection 23 on the bottom which reflects the irradiation light from the light sources 21a to 21c on different inclined faces of the projection 23 and guides the light to enter the corresponding pixels in a liquid crystal panel 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device capable of color display.

  In recent years, liquid crystal display devices are widely used as televisions, monitors, mobile phones, and the like as flat panel displays having features such as thinness and light weight. Various display methods for liquid crystal display devices have been proposed, but the most widely used method is a method using two or one polarizing plate.

  FIG. 27 shows a schematic diagram (cross-sectional view) of a general liquid crystal display device. The liquid crystal display device includes a liquid crystal panel 100 and a backlight unit 110. The liquid crystal panel 100 is formed by sandwiching a liquid crystal layer 103 and a color filter 104 between two transparent substrates 101 and 102 and disposing polarizing plates 105 and 106 outside the transparent substrates 101 and 102. The backlight unit 110 includes a light source 111 and a light guide plate 112. Another optical member 120 may be provided between the liquid crystal panel 100 and the backlight unit 110.

  Here, as the optical member 120, for example, an I prism-shaped film, an II scattering film, an III polarized reflection film, or the like can be used. The prism-shaped film can increase the front luminance by fulfilling the role of raising the scattered surface light to the panel side. The II scattering film has a role of making the light rising from the light guide plate uniform by the scattering film in the case where the light has unevenness in the surface or has an unfavorable light directivity. The III polarizing reflection film has a role of improving the light transmittance of the polarizing plate located above by transmitting only one polarized light and reflecting the other polarized light. With these optical members, it is possible to improve front luminance and light transmission efficiency.

  In the liquid crystal display device, the light emitted from the light source 111 travels in the direction parallel to the light emitting surface while repeating total reflection inside the light guide plate 112, and a protrusion formed inside the bottom surface of the light guide plate 112. 112A changes the traveling direction of light and stands up toward the viewer. The light rising to the observer side becomes one-polarized light by passing through the polarizing plate 105, and further passes through the liquid crystal layer 103 that functions as an optical shutter, the color filter 104 that realizes colorization, and the polarizing plate 106 for observation. Reach the person.

  In the liquid crystal layer 103, a twisted nematic mode (TN mode) in which display is performed by controlling the optical rotation of the liquid crystal by an electric field, a birefringence mode (ECB mode) in which display is performed by controlling the birefringence of the liquid crystal by an electric field, or TN A mixed mode combining the mode and the ECB mode is mainly used.

  However, liquid crystal display devices using these modes generally have a very low light use efficiency of 10% or less. The main causes of greatly reducing the light utilization efficiency in the liquid crystal display device include a polarizing plate and an absorption color filter. When a polarizing plate is used, only about 40% of the light emitted from the light source can be used. Furthermore, when an absorptive color filter is used, although it depends on the density of the color filter, usually only about 30% of the light incident on the color filter can be used.

  Therefore, various display methods that do not use polarizing plates or color filters have been proposed for the purpose of improving the light utilization efficiency.

  In particular, methods that do not use a color filter include (1) a guest-host method and a method using cholesteric liquid crystal, (2) a field-sequential method and a method using a phosphor that converts color, and (3) a diffraction grating and a hologram. And a liquid crystal display device using a spectroscopic element.

  However, the (1) guest-host method and the method using a cholesteric liquid crystal have problems such as low contrast in the displayed image or high drive voltage.

  In addition, the field sequential method (2) and the method using a phosphor that converts color are advantageous in this respect because a conventional liquid crystal layer is used for the driving part. However, the field sequential method is disadvantageous in that respect because a problem of color braking occurs in principle.

Regarding the method of using spectral elements such as diffraction gratings and holograms in (3), in Patent Document 1, the light emitted from the backlight is diffracted and dispersed by the hologram, and the RGB wavelength components are applied to the pixels displaying the corresponding colors. An incident liquid crystal display device is disclosed.
Japanese Patent No. 3400000 (publication date August 12, 1994)

  However, in the method (3) using a spectroscopic element such as a diffraction grating or a hologram, the optical characteristics of the spectroscopic element greatly change depending on the incident angle of incident light. Therefore, as in Patent Document 1, in order to make each wavelength component of RGB separated into a pixel displaying a corresponding color efficiently, the incident light to the spectroscopic element needs to be parallel light. There is. However, currently used backlights for liquid crystal displays have high light diffusivity and are far from parallel light. Therefore, in the above-mentioned Patent Document 1, there is a problem that the characteristics of the spectroscopic element cannot be effectively used, and the RGB wavelength components cannot be efficiently incident on the pixel displaying the corresponding color.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to realize a liquid crystal display device that enables effective display using light emitted from a light source and enables bright display or low power consumption display. There is.

  In order to solve the above problems, a liquid crystal display device according to the present invention is a liquid crystal display device including a liquid crystal panel having a polygonal shape and a backlight unit having a light source and a light guide plate. Installed at positions corresponding to at least three sides of the liquid crystal panel, and at least three sides are provided with light sources that irradiate different color lights on each side, and the light guide plate receives the color lights emitted from the light sources, respectively. It is characterized by being guided to a predetermined pixel of the liquid crystal panel.

  According to the above configuration, when displaying an image, all of the plurality of light sources are turned on simultaneously, and the light emitted from each light source is incident on the corresponding pixel, whereby each color can be expressed without using a color filter. Here, each color of the plurality of light sources is a combination of primary colors (for example, three primary colors of R, G, and B) that can express all colors by a combination thereof. In the liquid crystal display device, a high-quality color display capable of displaying with high color purity can be realized without greatly changing the manufacturing process of the liquid crystal display device.

  In the liquid crystal display device, the light guide plate has a protrusion on the side facing the liquid crystal panel, and the protrusion guides light emitted from the light source to a predetermined pixel of the liquid crystal panel. It is preferable to have a configuration comprising at least three inclined surfaces.

  According to said structure, each of the light launched toward the said liquid crystal panel by the said light-guide plate can be guide | induced to the pixel corresponding to those colors.

  In addition, the liquid crystal display device includes a microlens array between the light guide plate and the liquid crystal layer of the liquid crystal panel. The microlens array collects each of the light raised by the light guide plate on the corresponding pixels. It can be.

  According to the above configuration, even if the directivity of the light launched by the light guide plate is low and spreads and rises, the light is collected by the microlens array and incident on the corresponding pixel. Therefore, the incident efficiency of light to the corresponding pixel can be improved.

  In addition, the liquid crystal display device may be configured to include a viewing angle improving member that aligns the emission angles of the emitted light from the pixels on the viewer side of the liquid crystal layer in the liquid crystal panel.

  According to the above configuration, even if the incident angle of light with respect to each pixel is different, the emission angle is uniformed by the viewing angle improving member in the emitted light, so that the visibility can be improved. it can.

  As described above, the liquid crystal display device of the present invention is a liquid crystal display device comprising a polygonal liquid crystal panel and a backlight unit having a light source and a light guide plate, wherein the light source is at least the liquid crystal panel. The light source is installed at a position corresponding to the three sides, and at least three sides are provided with light sources that irradiate different color lights on each side, and the light guide plate emits the color light emitted from the light source respectively to the predetermined liquid crystal panel. This is a configuration that leads to the pixels.

  Therefore, when displaying an image, all of the plurality of light sources are turned on simultaneously, and light emitted from each light source is incident on the corresponding pixel, so that each color can be expressed without using a color filter. There is an effect that a high-quality color display capable of displaying with high color purity can be realized without greatly changing the manufacturing process.

[Embodiment 1]
An embodiment of the present invention will be described below with reference to FIGS. 1A and 1B are cross-sectional views showing a schematic configuration of a liquid crystal display device according to Embodiment 1 (hereinafter referred to as the present liquid crystal display device). 2 and 3 are a perspective view and a plan view of a backlight unit used in the present liquid crystal display device. In the following description, two orthogonal directions in the liquid crystal panel display surface are defined as an X direction and a Y direction, and a normal direction of the liquid crystal panel display surface is defined as a Z direction.

  As shown in FIGS. 1A and 1B, the present liquid crystal display device includes a liquid crystal panel 10 and a backlight unit 20. 1A shows a cross-sectional view of the present liquid crystal display device in the ZX plane, and FIG. 1B shows a cross-sectional view in the ZY plane.

  The liquid crystal panel 10 includes a liquid crystal layer 13 sandwiched between two transparent substrates 11 and 12 and polarizing plates 14 and 15 disposed outside the transparent substrates 11 and 12. The backlight unit 20 includes light sources 21 a to 21 c and a light guide plate 22.

  In the backlight unit 20, the light sources 21a to 21c are light sources having different emission colors necessary for performing full color display. In the following description, for example, it is assumed that the light source 21a has a light emission color of R (red), the light source 21b has a light emission color of G (green), and the light source 21c has a light emission color of B (blue).

  The light guide plate 22 is formed in a rectangular parallelepiped shape with a thickness of several millimeters made of a translucent member. Since the light emission angle from the light emission surface of the light guide plate 22 (that is, the surface facing the liquid crystal panel 10) is determined by the refractive index difference between the light guide plate 22 and air, the material of the light guide plate 1 is made of a refractive index. High and excellent in moldability is preferable. An example of such a material is an acrylic resin.

  In the present liquid crystal display device, as shown in FIGS. 2 and 3, the light sources 21 a and 21 b are arranged to face two sides of the light guide plate 22 parallel to the Y direction. In addition, the light source 21c is disposed to face one side of the light guide plate 22 parallel to the X direction. In addition, a plurality of protrusions 23 having inclined surfaces 23a to 23c are formed at equal intervals on the bottom surface of the light guide plate 22 (surface opposite to the light emitting surface).

  In such a structure, for example, an optical path when the light source 21a is turned on is shown in FIG. Light from the light source 21a enters the light guide plate 22 from the light incident surface 22a of the light guide plate 22, and travels in the direction parallel to the light guide plate exit surface 22e while repeating total reflection inside. A part of the light hits the inclined surface 23a of the plurality of protrusions 23 provided. The light incident on the inclined surface 23a is totally reflected, exits upward from the light exit surface 22e of the light guide plate 22, passes through the polarizing plate 14 and the lower substrate 11, and then enters the corresponding pixel 16a.

  Similarly, FIG. 4 shows an optical path when the light source 21b is turned on, and FIG. 5 shows an optical path when the light source 21c is turned on. Light from the light sources 21b and 21c enters the light guide plate 22 from the light incident surfaces 22b and 22c of the light guide plate 22, respectively, and is totally reflected by the inclined surfaces 23b and 23c of the protrusion 23. The light totally reflected by the inclined surfaces 23b and 23c exits upward from the light exit surface 22e of the light guide plate 22, passes through the polarizing plate 14 and the lower substrate 11, and then enters the corresponding pixels 16b and 16c.

  The plurality of protrusions 23 formed on the bottom surface of the light guide plate 22 are arranged in the same number as the picture elements, and all of them are formed directly below each picture element. The picture element here is a minimum unit of display, and it is assumed that each picture element includes a pixel expressing each color. The pixel is composed of a liquid crystal, a TFT element, an alignment film, a transparent electrode, and the like.

  Each protrusion 23 has a quadrangular pyramid shape as shown in FIG. 6, for example. The inclination angles of the inclined surfaces 23a to 23c in the protrusion 23 are such that incident light from the light sources 21a to 21c is on the surface. It is designed to have an angle at which the light is totally reflected, passes through the polarizing plate 14 and the lower substrate 11, and enters each of the pixels displaying the corresponding color. The inclination angles of the inclined surfaces 23a to 23c are calculated from the thickness of the polarizing plate 14 and the lower substrate 11, the size of the pixels, and the average incident angle of the light source light incident on the inclined surface. 6 has a quadrangular pyramid shape, it has a fourth inclined surface in addition to the inclined surfaces 23a to 23c, and the inclined surface reflects light from the light source. Since it is not used as a surface, angle adjustment like the inclined surfaces 23a to 23c is not performed.

  In the present liquid crystal display device, the shape of the picture element in the liquid crystal panel 10 also requires a unique shape. Some examples of pixel shapes applicable to the present invention are shown in FIGS. 7A to 7D, but the pixel shape in the present invention is not limited to this. Each picture element in the liquid crystal panel 10 is divided into three pixel areas of pixels 16a to 16c. The pixel 16a is a pixel to which light from the light source 21a is incident, and is designed to display a color corresponding to the light source 21a. That is, in the pixel 16a, the transmittance of the liquid crystal layer is controlled according to the image data of the R (red) component. Similarly, the light from the light source 21b is incident on the pixel 16b, and the transmittance of the liquid crystal layer is controlled according to the image data of the G (green) component. The pixel 16c receives light from the light source 21c, and the transmittance of the liquid crystal layer is controlled according to the image data of the B (blue) component.

  The positional relationship between the pixels 16a to 16c may be the relationship shown in FIGS. 7A and 7B according to the inclination angles of the inclined surfaces 23a to 23c, or the positional relationship between the X direction and the Y direction. The positional relationship as shown in FIGS. 7C and 7D may be used.

  In the present liquid crystal display device, when an image is displayed, all the three light sources 21a to 21c are turned on simultaneously, and light emitted from each light source can enter each corresponding pixel to express each color. If all the light emitted from the light sources 21a to 21c is incident on the corresponding pixels 16a to 16c without any loss, it is not necessary to dispose a color filter, and even if the manufacturing process of the liquid crystal display device is not significantly changed, the color A high-quality color display capable of high purity display can be realized.

  However, in the configuration of the present liquid crystal display device, when the irradiation light from the light sources 21a to 21c is not efficiently incident on the corresponding pixels 16a to 16c, light mixed in the pixels is incident. For this reason, the displayable chromaticity range may be narrower than the color purity of the original light source. In such a case, a color filter suitable for the pixel shape can be introduced immediately below or directly above the liquid crystal layer 13 to improve color purity.

  That is, by introducing a color filter, even if light emitted from a light source is incident on a pixel that does not correspond to the light, such light is absorbed by the color filter, so that the reduced color purity is improved. Even when the color filter is introduced, only part of the light that should not be incident is absorbed by the color filter, and most of the light emitted from the light source is incident on the corresponding pixel. However, there is no change in the high light utilization efficiency.

  In the present liquid crystal display device, by not using a color filter (or even if a color filter is used to improve color purity), the light use efficiency of light emitted from the light source is increased, and the color filter is used. Brighter display and lower power consumption than conventional liquid crystal display devices are possible.

  In the present liquid crystal display device, monochromatic light having different wavelength components is incident on each pixel, and a plurality of light sources are used to obtain these monochromatic lights. Thus, in the configuration of the present liquid crystal display device, in order to obtain monochromatic light having different wavelength components to be incident on each pixel, the light source is separated from the configuration of Patent Document 1 in which the light source light is dispersed using a spectroscopic element. There is an advantage that a very high degree of parallelism is not required for the irradiated light, and a general type of light source can be used. In addition, since the light source used in this liquid crystal display device irradiates the monochromatic light from which a wavelength component differs, LED (Light Emitting Diode) can be utilized suitably.

  As described above, this liquid crystal display device is not required to have a higher degree of parallelism than the light source used in the liquid crystal display device of Patent Document 1, but in order to make the light emitted from the light source enter the corresponding pixel more efficiently. It is desirable to increase the traveling directivity (parallelism) of the three light sources 21a to 21c.

  As shown in FIGS. 8 and 9, the traveling directivity includes directivity in the vertical direction (Z direction) and directivity in the horizontal direction (XY in-plane direction). When the directivity in the vertical direction is low, the incident angle of light incident on the protrusion 23 varies, and the upward emission direction after reflection is also low in directivity, so that it may not enter the corresponding pixel. Can happen. In addition, when the directivity in the horizontal direction is low, the light incident on the projecting portion 23 does not rise vertically upward but rises at an inclined angle, and may not enter the corresponding pixel.

  For this reason, in this liquid crystal display device, it is desirable to use a light source with high traveling directivity in the direction perpendicular to the light incident surface of the light guide plate 22 in the light sources 21a to 21c. For example, by optimizing the shape of the linear light guide (the prism shape inside the linear light guide and the external shape of the linear light guide), light source light (such as an LED) can be made incident efficiently and the surface can be converted into parallel light. It is possible to enter the light guide.

  Or as shown in FIG. 10, the structure which combines the parabolic mirrors 24a-24c with each of the light sources 21a-21c and obtains parallel light is also considered. That is, for each of the light sources 21a to 21c made of LEDs, parabolic mirrors 24a to 24c are arranged on the back side (opposite side to the light guide plate 22), and the light sources 21a to 21c are arranged at the focal positions. When the light from the light sources 21a to 21c is emitted in the mirror direction, the light incident on the light guide plate 22 can be converted into parallel light by reflection at the parabolic mirrors 24a to 24c.

  Moreover, in this liquid crystal display device, when the distance from the protrusion 23 to the picture element is very large compared to the distance between the adjacent protrusions 23 and 23, the directivity of the emitted light from the light sources 21a to 21c is high. However, since the light gradually spreads before entering the picture element, it becomes difficult to efficiently enter the emitted light from the light sources 21a to 21c into the corresponding pixel. Therefore, it is preferable to design the light guide plate 22 and the glass substrate 11 to be thin so that the distance between the protrusion 23 and the picture element is shortened.

  With respect to the shape of the protrusion 23, a configuration that improves the in-plane uniformity of light emitted to the liquid crystal panel leads to better display. That is, in the light guide plate 22, the same amount of light should be emitted at the same angle with respect to the protrusion 23 located near the light source and the protrusion 23 located far from the light source. It is also effective to change the shape and its size within the arrangement plane of the protrusions 23. For example, examples of the shape of the projection 23 include a keyboard type and a roof type as shown in FIGS. 11B and 11C, in addition to the square cone type shown in FIG. By changing the shape, the area of the inclined surface can be made different, and the inclination angle can be made different. In the light guide plate 22, the in-plane uniformity of the light emitted to the liquid crystal panel can be enhanced by appropriately combining the protrusions 23 having various shapes according to the arrangement positions thereof.

  In the present liquid crystal display device, the three primary colors used for display are irradiated from different light sources and are incident on the liquid crystal panel 10 through different optical paths. For this reason, from the observer side, the emission directions of the three primary color lights are slightly different (see FIGS. 4 and 5). For this reason, depending on the viewing direction of the observer, one color of the three primary color lights may be observed more strongly than the other two colors.

  In the present liquid crystal display device, it is conceivable to include a viewing angle improving member such as a light scattering film in order to prevent such a problem. As such a viewing angle improving member, use of an anisotropic scattering film such as a holographic scattering film can be considered. The anisotropic scattering film exhibits scattering characteristics as shown in FIGS.

  That is, the scattering films 1 to 3 shown in FIGS. 12A to 12B have scattering characteristics in the same direction in the emitted light with respect to incident light having different incident angles (FIG. 13). reference). Therefore, by patterning the three types of anisotropic scattering films according to the arrangement pattern of the pixels 16a to 16c, even if the incident angle of light to each pixel is different, The emission angles can be made uniform. The viewing angle improving member is disposed on the viewer side of the liquid crystal layer 13 (that is, between the liquid crystal layer 13 and the upper substrate 12, between the upper substrate 12 and the upper polarizing plate 15, or upper polarized light). The upper part of the plate 15) is preferred.

[Embodiment 2]
A second embodiment of the present invention will be described with reference to FIGS. 14 to 21 as follows. 14A and 14B are cross-sectional views showing a schematic configuration of a liquid crystal display device according to the second embodiment (hereinafter referred to as the present liquid crystal display device). 15 and 16 are a perspective view and a plan view of a backlight unit used in the present liquid crystal display device.

  As shown in FIGS. 14A and 14B, the present liquid crystal display device includes a liquid crystal panel 30 and a backlight unit 40. 14A shows a cross-sectional view of the present liquid crystal display device in the Z-X plane, and FIG. 14B shows a cross-sectional view in the Z-Y plane.

  The liquid crystal panel 30 has the same laminated structure as the liquid crystal panel 10 in the first embodiment. That is, the liquid crystal panel 30 is formed by sandwiching the liquid crystal layer 13 between the two transparent substrates 11 and 12 and disposing the polarizing plates 14 and 15 outside the transparent substrates 11 and 12. The liquid crystal panel 30 differs from the liquid crystal panel 10 only in the pixel formation pattern, but the pixel pattern of the liquid crystal panel 30 will be described later.

  The backlight unit 40 differs from the liquid crystal panel 20 in the first embodiment in that it further includes a fourth light source 21d. In addition, another inclined surface 23d whose inclination angle is adjusted is added to the protrusion 23 disposed inside the light guide plate 22 in order to reflect the light from the light source 21d toward the liquid crystal panel 30 side. . For this reason, the protrusion 25 in the backlight unit 40 can be formed in, for example, a quadrangular pyramid shape (see FIG. 17). In the backlight unit 20 according to the first embodiment, the protrusion 25 can also be a quadrangular pyramid, but one of the inclined surfaces does not need to be angle-adjusted. On the other hand, the backlight unit 40 is different from the first embodiment in that the angles of all four inclined surfaces are adjusted.

  18 and 19 show the optical paths when the light sources 21a to 21d are turned on in the structure of the present liquid crystal display device. That is, each of the light emitted from the light sources 21 a to 21 d enters the light guide plate 22 from the light incident surfaces 22 a to 22 d of the light guide plate 22, and is totally reflected by the inclined surfaces 23 a to 23 d of the protrusion 23. The light totally reflected by the inclined surfaces 23a to 23d exits upward from the light exit surface 22e of the light guide plate 22, passes through the polarizing plate 14 and the lower substrate 11, and then enters the corresponding pixels 16a to 16d.

  Since the liquid crystal panel 30 has four light sources in the backlight unit 40, the liquid crystal panel 30 has a pixel pattern different from that of the liquid crystal panel 10 in the first embodiment. Specifically, each picture element in the liquid crystal panel 30 is divided into four pixel regions of the pixels 16a to 16d. Some examples of pixel shapes applicable to the present invention are shown in FIGS. 20A to 20D, but the pixel shape in the present invention is not limited to this.

  In the present liquid crystal display device, when displaying an image, all the four light sources 21a to 21d are turned on simultaneously, and light emitted from each light source is incident on the corresponding pixel, whereby each color can be expressed. That is, each of the irradiation lights from the light sources 21a to 21d is incident on the corresponding pixels 16a to 16d. In the present liquid crystal display device, the colors in each of the four light sources 21a to 21d may be, for example, red, green, blue, and cyan. However, basically, any combination of red, green, blue, magenta, yellow, and cyan may be used, and a combination that can ensure a large reproduction range in the chromaticity diagram and maintain lightness is preferable.

  Thus, a feature of the liquid crystal display device according to the second embodiment is that the primary colors constituting the display are changed from three colors to four colors. In the present liquid crystal display device, the primary color constituting the display is increased from three colors to four colors, so that the color reproduction range can be increased (see FIG. 21). When the display signal is expressed in three primary colors (RGB) as in the NTSC format, a driver that converts the display signal into a four primary color display signal is used.

  Also in the liquid crystal display device according to the second embodiment, as in the case of the liquid crystal display device according to the first embodiment, the irradiation light from the light sources 21a to 21d is not efficiently incident on the corresponding pixels 16a to 16d. In addition, a color filter suitable for the pixel shape can be introduced immediately below or directly above the liquid crystal layer 13 to improve color purity. Further, in the light sources 21a to 21d, a light source having a high traveling directivity in a direction perpendicular to the light incident surface of the light guide plate 22 is used, and the efficiency of light incident on the corresponding pixel irradiated from the light source is improved. It is also effective to make it.

  Furthermore, in order to make the output angle of the light emitted from the liquid crystal panel 30 uniform, a configuration including a viewing angle improving member, or by appropriately combining the projections 23 of various shapes in the light guide plate 22 according to the arrangement position thereof. A configuration in which in-plane uniformity of light emitted to the liquid crystal panel is improved may be employed.

[Embodiment 3]
A third embodiment of the present invention will be described below with reference to FIGS. 22A and 22B are cross-sectional views showing a schematic configuration of a liquid crystal display device according to the second embodiment (hereinafter referred to as the present liquid crystal display device).

  As shown in FIGS. 22A and 22B, the present liquid crystal display device includes a liquid crystal panel 50 and a backlight unit 20. FIG. 22A shows a cross-sectional view of the present liquid crystal display device in the ZX plane, and FIG. 22B shows a cross-sectional view in the ZY plane.

  The liquid crystal panel 50 has substantially the same structure as that of the liquid crystal panel 10 in the first embodiment, but the microlens array 17 configured by a plurality of microlenses between the lower substrate 11 and the polarizing plate 14. Is different from the liquid crystal panel 10 in that In addition, the microlens array 17 may be disposed between the light guide plate 22 and the liquid crystal layer 13, and may be disposed between the polarizing plate 14 and the light guide plate 22. The backlight unit 20 can have the same configuration as that of the first embodiment.

  In the present liquid crystal display device, the microlens array 17 is provided for the purpose of improving the light collection efficiency of light incident on each pixel. For this reason, in the liquid crystal panel 50, it is desirable that the apex of each microlens comes directly under each picture element. In addition, it is desirable that the optical distance between the microlens and the pixel (liquid crystal layer) and the optical distance between the microlens and the protrusion are substantially equal.

  According to the configuration of the third embodiment, the distance between the protrusion 23 in the backlight unit 20 and the pixel in the liquid crystal panel 50 is not shortened, and the directivity of the light source is not increased. Condensing efficiency of light incident on each pixel can be increased.

  That is, when the light guided in the light guide plate 22 is incident on the projections 23 at various angles, the light reflected by the inclined surfaces of the projections 23 does not rise with high directivity. Since it rises and spreads, the incident efficiency entering the corresponding pixel is deteriorated. Each microlens in the microlens array 17 has a role of converging light that spreads and rises using the light condensing effect and efficiently entering the corresponding pixel.

  In the microlens array 17, the radius of curvature of each microlens is determined by the thickness and refractive index of the lower substrate 11 and the polarizing plate 14, and is designed to focus when light reaches the pixel (liquid crystal layer 13) ( (See FIG. 23).

  As shown in FIG. 24 or FIG. 25, each microlens in the microlens array 17 preferably has a shape arranged in the vertical and horizontal directions with the same diameter as the picture element pitch or the same diameter as the half pitch of the picture element. It is ensured that the apex of each microlens is arranged directly below the center of each picture element. When the microlens array 17 has such a shape, almost all of the light that rises and spreads can be incident on the corresponding pixels. This is shown in FIGS. 23 and 26. FIG. From FIG. 23 and FIG. 26, it can be seen that the light hitting the lens other than just above the protrusion 23 also enters the corresponding color pixel. Thus, color mixing can be prevented and the color reproduction range in the liquid crystal display device can be increased.

  Regarding the production of the microlens array 17, it is desirable to use a material having a high refractive index with a high transmittance over the entire visible light region as much as possible, as the lens material has the same performance as that required for the light guide plate material. In addition, as a method for producing the microlens array 17, a lens film produced by a 2P method using an acrylic UV curable resin, a thermal transfer method using a thermosetting resin, or the like is aligned with a polarizing plate or below. It is conceivable to perform bonding to the side substrate. Alternatively, it is conceivable to form a lens directly on the polarizing plate or on the lower substrate by using a photolithography method with a gray scale mask and a resist.

  In the third embodiment, in the above description, the number of light sources is three as in the first embodiment, but a configuration using four light sources as in the second embodiment may be used.

  As described above, the liquid crystal display device according to the present embodiment includes a liquid crystal panel and a backlight unit. In the liquid crystal display device, the backlight unit includes at least three light emitting colors that are different from each other. A light source and a light guide plate that rises toward the liquid crystal panel so as to guide each of the light emitted from the plurality of light sources to pixels corresponding to the colors can be provided.

  According to the above configuration, when displaying an image, all of the plurality of light sources are turned on simultaneously, and the light emitted from each light source is incident on the corresponding pixel, whereby each color can be expressed without using a color filter. Here, each color of the plurality of light sources is a combination of primary colors (for example, three primary colors of R, G, and B) that can express all colors by a combination thereof. In the liquid crystal display device, a high-quality color display capable of displaying with high color purity can be realized without greatly changing the manufacturing process of the liquid crystal display device.

  In the liquid crystal display device, the light guide plate has, on its bottom surface, a protrusion that rises with an inclined surface that is adjusted to a different inclination angle for each of the light emitted from the plurality of light sources. The liquid crystal panel preferably has a pixel pattern corresponding to the inclined surface forming pattern of the protrusion.

  According to said structure, each of the light launched toward the said liquid crystal panel by the said light-guide plate can be guide | induced to the pixel corresponding to those colors.

  Further, in the liquid crystal display device, the backlight unit guides each of four light sources having different emission colors and light emitted from the four light sources to pixels corresponding to the colors. It can be set as the structure provided with the light-guide plate raised toward the said liquid crystal panel.

  According to said structure, the color reproduction range of a liquid crystal display device can be improved by making the primary color which comprises a display into four colors.

1A and 1B show an embodiment of the present invention and are cross-sectional views showing a schematic configuration of a liquid crystal display device according to Embodiment 1. FIG. It is a perspective view of the backlight unit used in the said liquid crystal display device. It is a top view of the backlight unit used in the said liquid crystal display device. It is sectional drawing which shows the optical path of the light irradiated from a light source in the said liquid crystal display device. It is sectional drawing which shows the optical path of the light irradiated from a light source in the said liquid crystal display device. It is a perspective view which shows the example of a shape of the protrusion formed in the light-guide plate of the backlight unit used in the said liquid crystal display device. 7A to 7D are plan views illustrating pixel pattern examples in the liquid crystal display device. It is a figure which shows the directivity of the perpendicular direction (Z direction) of the light irradiated from a light source. It is a figure which shows the directivity of the horizontal direction (XY in-plane direction) of the light irradiated from a light source. It is a top view which shows the structural example of the backlight unit which can improve the directivity of light. FIGS. 7A to 7D are perspective views showing an example of the shape of the protrusions formed on the light guide plate of the backlight unit. 12A to 12C are diagrams showing the scattering characteristics of an anisotropic scattering film used as a viewing angle improving member in the liquid crystal display device. It is a graph which shows incident light angle distribution and outgoing light angle distribution at the time of using an anisotropic scattering film as a viewing angle improvement member in the said liquid crystal display device. FIGS. 14A and 14B show another embodiment of the present invention, and are cross-sectional views showing a schematic configuration of a liquid crystal display device according to the second embodiment. It is a perspective view of the backlight unit used in the said liquid crystal display device. It is a top view of the backlight unit used in the said liquid crystal display device. It is a perspective view which shows the example of a shape of the protrusion formed in the light-guide plate of the backlight unit used in the said liquid crystal display device. It is sectional drawing which shows the optical path of the light irradiated from a light source in the said liquid crystal display device. It is sectional drawing which shows the optical path of the light irradiated from a light source in the said liquid crystal display device. 20A to 20D are plan views showing pixel pattern examples in the liquid crystal display device. It is a graph which shows the color reproduction range in the said liquid crystal display device. FIGS. 22A and 22B show still another embodiment of the present invention, and are sectional views showing a schematic configuration of a liquid crystal display device according to Embodiment 3. FIG. It is sectional drawing which shows the optical path of the light irradiated from a light source in the said liquid crystal display device. It is a top view which shows an example of the arrangement | positioning relationship between a pixel and a microlens in the said liquid crystal display device. It is a top view which shows the other example of the arrangement | positioning relationship between a pixel and a microlens in the said liquid crystal display device. It is sectional drawing which shows the optical path of the light irradiated from a light source in the said liquid crystal display device. It is sectional drawing which shows a prior art and shows schematic structure of a liquid crystal display device.

Explanation of symbols

10, 30, 50 Liquid crystal panels 16a to 16d Pixel 17 Micro lens array 20, 40 Backlight units 21a to 21d Light source 22 Light guide plate 23 Projections 23a to 23d Inclined surface

Claims (4)

In a liquid crystal display device comprising a polygonal liquid crystal panel and a backlight unit having a light source and a light guide plate,
The light source is installed at a position corresponding to at least three sides of the liquid crystal panel, and at least three sides are provided with light sources that irradiate different color lights on each side,
The liquid crystal display device, wherein the light guide plate guides color light emitted from the light source to predetermined pixels of the liquid crystal panel. The light guide plate has a protrusion on the side facing the liquid crystal panel,
The liquid crystal display device according to claim 1, wherein the protrusion includes at least three inclined surfaces that guide light emitted from the light source to predetermined pixels of the liquid crystal panel.   The microlens array which condenses each of the light guide | induced by the said light-guide plate to the corresponding pixel is provided between the said light-guide plate and the liquid crystal layer of the said liquid crystal panel. A liquid crystal display device according to 1.   3. The liquid crystal display device according to claim 1, further comprising: a viewing angle improving member that aligns an emission angle of emitted light from each pixel on an observer side of the liquid crystal layer in the liquid crystal panel.

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