JP2012083558A - Display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce luminance unevenness of display screen in a backlit display.SOLUTION: A display comprises: a light guide panel 130 serving as a light guide body that internally transmits light entering from an entrance surface 132 and outputs the light from an outgoing surface 120; and a display panel 170 that uses the light from the outgoing surface 120 to display an image in a display area 170d. At a place that is included in the back surface 121 and is isolated from the entrance surface 132, a light-extraction pattern area 4 where multiple dot-shaped light diffusion parts 125 are arranged is formed. The light-extraction pattern area 4 includes: a first area 41 including a first positive slope section when it is represented graphically with locating a distance from the entrance surface 132 on the abscissa and locating a coverage on the ordinate; and a second area 42 including a second positive slope section whose slope is more gradual than the first slope in a manner connecting to the graph representing the first area 41. A line after projecting a visible outline of the display area 170d on the back surface 121 is located within the first area 41.

Description

  The present invention relates to a display device.

  Japanese Patent Laid-Open No. 2001-154193 (Patent Document 1) is a prior art document that discloses a liquid crystal display device in which the size of the light emitting region of the backlight is slightly larger than the display dot region in order to prevent light leakage. In the liquid crystal display device described in Patent Document 1, the position of the starting point of the light diffusion portion provided in the light guide is determined so that the light emission area of the backlight is slightly larger than the display dot area of the liquid crystal display panel. ing.

  An example in which a diffusion structure is provided on the back surface of the light guide member of the light source module is described in JP 2010-67442 A (Patent Document 2). In Patent Document 2, the diffusing structure is constituted by a diffusing portion which is a linear pattern, and the density of the diffusing portion is changed depending on the part in order to make the illuminance distribution in the longitudinal direction of the light guide member uniform.

JP 2001-154193 A JP 2010-67442 A

  In the liquid crystal display device described in Patent Document 1, in consideration of the parallax from within the display dot region of the liquid crystal display device, the display region of the liquid crystal display panel is opposed to the light source and the incident surface of the light guide. The light diffusion portion is formed from a position closer to the light source than the end portion on the light source side. In this case, the light incident from the incident surface of the light guide is diffused by the light diffusing portion formed at a position close to the light source and emitted from the output surface of the light guide in a high luminance state. Since the light with high brightness is incident on the edge of the display area of the liquid crystal panel, it causes uneven brightness on the display screen.

  SUMMARY An advantage of some aspects of the invention is that it provides a display device that can reduce luminance unevenness of a display screen.

  In order to achieve the above object, a display device according to the present invention includes a light source, an incident surface which is an end surface on which light from the light source is incident so as to face the light source, an output surface which is a main surface, and the above A light guide that has a rear back surface facing the light exit surface, propagates light incident from the light entrance surface, and emits the light from the light exit surface; and a display region, and the light exit surface of the light guide And a display panel that receives light emitted from the exit surface and displays an image in the display area, and each of the rear and rear surfaces is separated from the entrance surface by an individual lens. A light extraction pattern region in which a plurality of convex dots that play a role is arranged is formed, and the light extraction pattern region has a horizontal axis indicating the distance from the incident surface and a vertical axis indicating the coverage by the dots. For the graph, A first region that has a positive first slope section in contact with the horizontal axis, and is located farther from the incident surface than the first region, and is connected to the graph of the first region. And a second area having a positive second inclination section that is gentler than the first inclination, and a line obtained by projecting the outline on the incident surface side of the display area on the rear back surface is the first area. Located in the area.

  According to the present invention, the change in luminance is natural in the vicinity of the edge of the display region inside the display region, and the luminance unevenness of the display screen can be reduced.

It is an exploded view of the display apparatus in Embodiment 1 based on this invention. It is a top view in the state which extracted only the light source group and the light-guide plate from the display apparatus in Embodiment 1 based on this invention. It is explanatory drawing of the course of light when light injects into the light-guide plate with which the display apparatus in Embodiment 1 based on this invention is provided. It is explanatory drawing about the positional relationship of a light extraction pattern area | region and a display area. It is the photograph of the external appearance in the all-white state of the liquid crystal display panel with which the display apparatus as a 1st comparative example is provided. It is the photograph of the external appearance in the all-white state of the liquid crystal display panel with which the display apparatus as a 2nd comparative example is provided. It is a graph of the distribution of the brightness | luminance of the liquid crystal display panel with which the display apparatus as a 1st and 2nd comparative example is provided. It is a graph of distribution of pattern density in the 2nd comparative example. It is a graph of distribution of pattern density in the composition based on the present invention. It is the photograph of the external appearance in the all white state of the liquid crystal display panel with which the display apparatus based on this invention is provided. It is a graph of the luminance distribution of the liquid crystal display panel with which the display apparatus based on this invention is provided.

  Hereinafter, an image display device according to an embodiment of the present invention will be described with reference to the drawings. In the following description of embodiments, the same or corresponding parts in the drawings will be denoted by the same reference numerals, and description thereof will not be repeated. In the description of the embodiment, expressions of upper, lower, left, and right may be used, but these expressions represent relative sides in the drawings shown for convenience of explanation. It does not represent absolute top, bottom, left, right.

  In the following embodiments, a liquid crystal display device will be described as an example of a display device. However, the display device is not limited to a liquid crystal display device, and any other type may be used as long as the display device uses a light from a backlight device. The display device may be used.

(Embodiment 1)
(Constitution)
With reference to FIGS. 1-4, the display apparatus in Embodiment 1 based on this invention is demonstrated. This display device is a liquid crystal display device 1.

  FIG. 1 shows an exploded view of the entire liquid crystal display device 1. The liquid crystal display device 1 includes a bezel 100, a chassis 101, a reflection sheet 110, a light guide plate 130 as a light guide, a laminated sheet group 150, a liquid crystal display panel 170, light source groups 103 and 104, and a control unit 160. Between the bezel 100 and the chassis 101, a reflective sheet 110, a light guide plate 130, a laminated sheet group 150, and a liquid crystal display panel 170 are arranged in this order from the bottom. At both ends of the light guide plate 130, the light source group 104 is disposed so as to face the end faces. The light source group 104 and the liquid crystal display panel 170 are connected to the control unit 160. The liquid crystal display panel 170 has a display area 170d. The backlight device includes a reflection sheet 110, a light guide plate 130, and a light source group 104. FIG. 2 shows a plan view in a state where only the light source group 104 and the light guide plate 130 are extracted.

  In the present embodiment, the light guide plate 130 is composed of a single flat plate member. However, the light guide plate 130 is not limited to a flat plate shape, and a plurality of members may be arranged. .

  On one side of the light guide plate 130 in the longitudinal direction, a light source group 104 in which a plurality of LEDs (Light Emitting Diodes) 107 serving as light sources are mounted on the circuit board 108 at intervals is disposed. In the present embodiment, the light source group 104 is arranged on both sides of the light guide plate 130, but it may be arranged on only one of them. Hereinafter, the description will be given focusing on the vicinity of one end of the light guide plate 130.

  As shown in FIG. 3, the light guide plate 130 has an incident surface 132 on which the light from the LED 107 is incident so as to face the LED 107. In addition, the light guide plate 130 has an exit surface 120 as a main surface adjacent to the entrance surface 132. The light guide plate 130 has a rear back surface 121 that faces the emission surface 120. The rear back surface 121 has a light extraction pattern region 4. Details of the light extraction pattern region 4 will be described later. As shown in FIG. 3, the light 81 that has entered the light guide plate 130 from the incident surface 132 propagates inside the light guide plate 130 by being totally totally reflected between the output surface 120 and the rear back surface 121. The light exits from the light exit surface 120 to the outside of the light guide plate 130. The light path shown in FIG. 3 is merely an example.

Hereinafter, each component of the liquid crystal display device 1 will be described in detail.
In the present embodiment, a plurality of LEDs 107 are used as the light source, but the light source is not limited to the LED, and a fluorescent tube or other light emitters may be employed.

  The bezel 100 has a window 100a as an opening for making the display area 170d of the liquid crystal display panel 170 visible.

  The reflection sheet 110 may be made of polyester, for example. In the present embodiment, the reflection sheet 110 is made of, for example, foamed PET (Polyethylene Terephthalate) and has light reflection characteristics. The reflection sheet 110 has a function of reflecting light leaking from the rear back surface 121 of the light guide plate 130 and returning the light into the light guide 131.

  The laminated sheet group 150 includes a diffusion sheet and a plurality of prism sheets. The laminated sheet group 150 has a function of suppressing luminance unevenness of light emitted from the light guide plate 130 and condensing light emitted from the light guide plate 130 toward the liquid crystal display panel 170.

  The liquid crystal display panel 170 includes an active matrix substrate, a counter substrate, and a liquid crystal sealed between the active matrix substrate and the counter substrate. A color filter is formed on the counter substrate. A plurality of TFT (Thin Film Transistor) elements are formed on the active matrix substrate. The liquid crystal display panel 170 displays an image in the display area 170d using light that passes through the laminated sheet group 150 and enters the liquid crystal display panel 170.

  The controller 160 switches ON / OFF of each TFT element of the liquid crystal display panel 170 based on image data to be displayed. The control unit 160 applies a video signal to the liquid crystal display panel 170, and sequentially turns off each of the plurality of LEDs 107 in synchronization with the application timing. Thereby, in the liquid crystal display panel 170, a light emission period and a non-light emission period can be provided in one frame. As a result, the liquid crystal display panel 170 can alternately perform image display and black display. Thereby, a moving image display characteristic can be improved.

  The length of the light guide plate 130 may be 1358.5 mm, for example. The thickness of the light guide plate 130 may be 4 mm, for example. As shown in FIG. 3, a light extraction pattern region 4 is provided on the rear back surface 121 of the light guide plate 130. In the light extraction pattern region 4, a plurality of light diffusion portions 125 are formed apart from each other. The light diffusing portion 125 is a minute convex portion formed in a dot shape.

  In the present embodiment, as an example, the dot diameter of the light diffusing portion 125 provided in the light extraction pattern region 4 is the center of the light guide plate 130 in the longitudinal direction from the incident surfaces 132 located at both ends in the light diffusing portion forming region. It is formed so as to become larger as it goes to the part. Therefore, the dot diameter of the light diffusing portion 125 is the maximum at the central portion in the longitudinal direction, and the dot diameter of the light diffusing portion 125 is the minimum at a portion close to the end face. In addition, the dot diameter of one light-diffusion part 125 is 0.3 mm or more and 1.5 mm or less, for example.

  The light diffusion part 125 can be formed, for example, by dispersing light scattering fine particles in a polymer and then printing the polymer on the rear back surface 121 of the light guide plate 130. A phosphor may be used as the light scattering particles.

  In the present embodiment, each light diffusion portion 125 has been described as a minute convex portion, but the light diffusion portion 125 is not limited to a convex portion. The light diffusion portion 125 may be a concave portion, for example. For example, the light diffusing unit 125 may be configured by forming a minute uneven shape such as a prism on the rear back surface 121. Or you may comprise the light-diffusion part 125 by performing the blast process to the back back surface 121. FIG.

  The light diffusion portion 125 may be printed by an inkjet method or may be printed by screen printing (also referred to as “silk printing”). Or you may print by another method.

  By forming the light diffusion portion 125 on the rear back surface 121, the optical path of light propagating through the light guide plate 130 can be changed. Specifically, the light propagating through the light guide plate 130 enters the light diffusing portion 125 of the rear back surface 121, so that the light is diffused and the direction of traveling through the light guide plate 130 is changed. As a result, at least part of the light diffused by the light diffusing unit 125 is emitted from the emission surface 120 to the outside without being totally reflected by the emission surface 120.

  Light incident on the inside of the light guide plate 130 from the respective incident surfaces 132 provided at both ends of the light guide plate 130 is diffused and the luminance is attenuated as the distance from the respective incident surfaces 132 increases. As a measure considering this attenuation, as described above, the dot diameter of the light diffusing portion 125 gradually increases as the distance from the incident surface 132 approaches the central portion. By gradually increasing the dot diameter of the light diffusion portion 125, the arrangement density of the light diffusion portions 125 is gradually increased. If the arrangement density of the light diffusion portions 125 is increased, the amount of light emitted from the emission surface 120 can be increased, so that it is possible to suppress variation in the luminance of the light emitted from the emission surface 120 due to the part. .

  The structure of the light guide plate 130 and its periphery is shown in FIG. The light guide plate 130 is fixed to the chassis 101 by a connecting member (not shown). A P-chassis 109 is arranged so as to cover the ends of the light source group 104 and the light guide plate 130 from above. The bezel 100 is disposed so as to cover the P-chassis 109 from above. An end portion of the liquid crystal display panel 170 is sandwiched between the P-chassis 109 and the bezel 100 via buffer portions 211a and 211b. The bezel 100 and the chassis 101 are fixed to each other by a fixing member (not shown), so that the components located between the bezel 100 and the chassis 101 are sandwiched.

  The positional relationship between the light extraction pattern area 4 and the display area 170d will be described. The light extraction pattern region 4 includes a first region 41 and a second region 42 that are adjacent to each other. The first region 41 is located on the side close to the end surface, and the second region 42 is located on the side far from the end surface. A blank area 40 is provided outside the first area 41. The light diffusion portion 125 is not formed in the blank area 40, and the blank area 40 is not included in the light extraction pattern area 4. In FIG. 4, when a line is extended directly below the outline of the display area 170 d, it reaches the inside of the first area 41. When the light diffusion portion 125 of the light extraction pattern region 4 is formed by a printing process, the outer position of the first region 41 is also referred to as “print start position”. In FIG. 4, the position of the boundary line between the first area 41 and the margin area 40 corresponds to the print start position. Depending on how far the print start position is set from the end face of the light guide plate 130, the way the image is viewed from the user differs.

  Although the light diffusion portions 125 in the light extraction pattern region 4 appear to be arranged at equal intervals in FIG. 4, they are not actually at equal intervals. In the first region 41, the pattern density is arranged so as to change as described later, and in the second region 42, the pattern density is arranged so as to gradually increase toward the central portion of the light guide plate 130. ing.

(Comparative example)
In order to clarify the relationship between the print start position and the image appearance, two comparative examples that are not based on the present invention will be described. As a first comparative example, a printing start position was prepared with 10 mm from the end face of the light guide plate. As a second comparative example, a printing start position having a distance of 20 mm from the end face of the light guide plate was prepared. In any case, the distance from the end face of the light guide plate to the end of the display area was combined with the liquid crystal display panel so that the distance was about 15 mm. In the first and second comparative examples, the state of the liquid crystal display panel visible to the user when an all-white screen is displayed in order to check the luminance distribution is shown in FIGS. 5 and 6, respectively. 5 and 6, the configuration is reversed left and right compared to FIG. 4. That is, in FIGS. 5 and 6, the incident surface 132 that is an end surface of the light guide plate 130 is on the right side, and the display area 170 d extends on the left side. 5 and 6 indicate the position of the outline of the display area 170d. In the example of FIG. 5, since the print start position is 10 mm from the end face, the print start position is located outside the display area. In the example of FIG. 6, since the print start position is 20 mm from the end face, the print start position is located inside the display area.

  In FIG. 5, a bright portion is generated at a position slightly inside from the end of the display area 170 d. This bright part is mainly due to light leakage. In FIG. 6, a dark portion is generated at a position slightly inside from the end of the display area 170 d. A slightly bright part is generated between the dark part and the end of the display area 170d. This slightly bright part seems to be due to light leakage. For each of FIGS. 5 and 6, FIG. 7 shows a graph of the distribution of luminance in the liquid crystal display panel 170 with the distance from the end face of the light guide plate 130 on the horizontal axis and the relative luminance on the vertical axis. In the portion brightened in FIG. 5, the luminance is projected and increased as indicated by the Z1 portion in FIG. The dark portion generated in FIG. 6 has a low brightness as shown by a portion Z2 in FIG. 7, and the curve is shaped like a shoulder.

  In the first and second comparative examples, the print start position is located at a certain distance from the end face, and in the area beyond the print start position, the pattern density gradually increases as the distance from the end face increases. The light diffusing unit 125 is arranged to do so. The pattern density distribution in the second comparative example is shown in the graph of FIG. The horizontal axis in FIG. 8 indicates the position in the longitudinal direction by the distance from the end face, and the vertical axis indicates the pattern density. “Pattern density” means the ratio of the area occupied by the light diffusing unit 125 in the unit area region. Even if the number of light diffusion portions arranged per unit area is the same, the pattern density increases as the dot diameter of each light diffusion portion increases. Since what is shown in FIG. 8 is based on the second comparative example, the print start position is 20 mm from the end face. As shown in FIG. 8, the pattern density rapidly changes from 0 to 5% at the printing start position.

(Example of the present invention)
As a configuration based on the present invention in consideration of the results of FIGS. 5 to 8, the light extraction pattern region 4 is provided with the first region 41 and the second region 42 as described above. An example of the pattern density distribution in these regions is as shown in FIG. That is, FIG. 9 shows a pattern density distribution in the embodiment of the present invention. In this embodiment, the printing start position is 10 mm from the end face of the light guide plate. In this configuration, the pattern density does not increase rapidly at the printing start position. From the position of 10 mm to the position of 30 mm from the end face, the arrangement of the light diffusing unit 125 is in a so-called gradation state. That is, the pattern density gradually increases in this region. After passing 30 mm from the end face, the pattern density gradually increases as in the comparative example shown in FIG. In this example, the edge of the display area is located in the middle of the gradation area.

  In the liquid crystal display device including the light extraction pattern region 4 shown in FIG. 9, the state of the liquid crystal display panel that can be seen by the user when an all white screen is displayed is as shown in FIG. FIG. 11 shows a graph of the luminance distribution in this state. In FIG. 11, the two curves shown in FIG. 7 are also displayed for comparison. In FIG. 11, the curve obtained from the application of the present invention decreases in a natural curve without suddenly increasing brightness or causing unnatural fluctuations near the edge of the display area. ing. This is a favorable result.

(Configuration as a display device)
To summarize the above, the liquid crystal display device 1 as the display device in the present embodiment includes all the following components.
LED 107 as light source
An incident surface 132 that is positioned to face the light source and is an end surface on which light from the light source is incident; an exit surface 120 that is a main surface; and a rear back surface 121 that faces the exit surface 120; A light guide plate 130 as a light guide that propagates light incident from 132 and emits the light from the output surface 120.
A liquid crystal display panel 170 as a display panel that has a display area 170d and is located on the light emission surface 120 side of the light guide 130 and receives light emitted from the light emission surface 120 and displays an image on the display area 170d;
Furthermore, the liquid crystal display device 1 satisfies all the following requirements at the same time.
The light extraction pattern region 4 is formed by a plurality of light diffusion portions at a position away from the incident surface 132 in the rear back surface 121.
The light extraction pattern region 4 is a positive first slope section in contact with the horizontal axis when expressed in a graph with the distance from the incident surface on the horizontal axis and the coverage with the dots on the vertical axis A first region 41 having a first region 41 that is farther from the incident surface 132 than the first region 41 and is connected to the graph of the first region 41 so as to have a positive second value that is gentler than the first inclination. 2nd area | region 42 which has the area of the inclination of this.
The line obtained by projecting the outline on the incident surface 132 side of the display area 170 d on the rear back surface 121 is located in the first area 41.

(Action / Effect)
In the display device according to the present embodiment, the light extraction pattern region is divided into at least two regions, the first region in which the pattern density of the light diffusion portion forms a so-called gradation, and the second region in which the light changes as usual. Since the edge of the display area is located in the first area, the change in luminance is natural in the vicinity of the edge of the display area inside the display area, and the luminance unevenness of the display screen is reduced. be able to.

  The graph of the first region is preferably connected to the graph of the second region by drawing a convex curve downward, rising from the horizontal axis, and drawing a convex curve upward. That is, the connection method as shown in FIG. 9 is preferable. This is because if the graph is smoothly connected in a curved line, the luminance in the vicinity of the edge of the display area can be continuously changed, and the uncomfortable feeling given to the user can be minimized. .

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and includes all modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Liquid crystal display device, 4 Light extraction pattern area | region, 40 Blank area | region, 41 1st area | region, 42 2nd area | region, 81 light, 100 bezel, 100a Window part, 101 Chassis, 104 Light source group, 107 LED, 108 Circuit board, 109 P-chassis, 110 reflection sheet, 120 exit surface, 121 rear back surface, 125 light diffusion unit, 130 light guide plate, 132 entrance surface, 150 laminated sheet group, 160 control unit, 170 liquid crystal display panel, 170d display region, 211a, 211b Buffer part.

Claims (2)

A light source;
An incident surface that is positioned to face the light source and is an end surface on which light from the light source is incident, an exit surface that is a main surface, and a rear back surface that faces the exit surface, and is incident from the incident surface A light guide that propagates light internally and emits it from the exit surface;
A display panel having a display area, located on the light exit surface side of the light guide, and receiving light emitted from the light exit surface and displaying an image on the display area;
A light extraction pattern region is formed by a plurality of light diffusion portions at a position separated from the incident surface in the rear back surface,
When the light extraction pattern region is expressed in a graph with the distance from the incident surface as the horizontal axis and the coverage with the dots as the vertical axis, the positive first inclination section is in contact with the horizontal axis. A first region having a positive second slope that is located farther from the incident surface than the first region and is gentler than the first slope so as to be connected to the graph of the first region. A second region having a section of
A display device, wherein a line obtained by projecting an outline of the display area on the incident surface side on the rear back surface is located in the first area.   The graph of the first region draws a convex curve downward, rises from the horizontal axis, draws a convex curve upward, and is continuously connected to the graph of the second region. Display device.