JP2013210565A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device which includes a light guide plate having a plurality of striped uneven shape bodies formed on an emission face and can prevent generation of brightness unevenness.SOLUTION: A liquid crystal display device includes a light guide plate 20, a lower diffusion sheet 17 and an upper diffusion sheet 18 that diffuse light emitted from the light guide plate 20, and a liquid crystal panel 3 that performs display using the light diffused by the lower diffusion sheet 17 and the upper diffusion sheet 18. A plurality of striped uneven shape bodies T are formed on an emission face of the light guide plate 20, and the liquid crystal panel 3 is disposed to be separated from the upper diffusion sheet 18.

Description

  The present invention relates to a liquid crystal display device including a side edge (also referred to as a sidelight) type light guide plate that emits light from a light source in a planar shape by a light guide plate.

  In recent years, in order to reduce the thickness of a liquid crystal display device, a backlight including a side edge type light guide plate that emits light from a light source in a planar shape by the light guide plate is frequently used.

  As such a side-edge type light guide plate, a light guide plate in which a plurality of streaky irregularities are formed on the light exit surface in consideration of the condensing property and diffusibility of the emitted light is known (Patent Literature). 1 and 2).

JP 2009-277388 A (published on November 26, 2009) JP 2005-317435 A (published on November 10, 2005)

  When laminating an optical sheet and a liquid crystal panel so as to be in contact with each other in this order on a light guide plate having a plurality of streaky irregularities formed on the exit surface, the luminance is high according to the irregularities of the light guide plate There is a problem that a phenomenon (luminance unevenness) in which lines and low luminance lines appear alternately occurs. As a method for solving the problem, it is conceivable to increase the number of optical sheets having diffusibility. However, in this case, the number of parts of the optical sheet increases, resulting in an increase in cost.

  The present invention has been made in order to solve the above-described problems, and realizes a liquid crystal display device that includes a light guide plate having a plurality of streaky irregularities formed on the exit surface and that can prevent occurrence of luminance unevenness. The purpose is to do.

  In order to solve the above problems, a liquid crystal display device of the present invention is diffused by a light guide plate, at least one optical sheet that diffuses light emitted from an emission surface of the light guide plate, and the optical sheet. A liquid crystal display device including a liquid crystal panel that displays using light, wherein a plurality of streaky irregularities are formed on an emission surface of the light guide plate, and the liquid crystal panel is separated from the optical sheet. It is arranged.

  According to the above configuration, a plurality of streak-like uneven shapes are formed on the exit surface of the light guide plate, so that the light is condensed by the uneven shapes. Thereby, the brightness | luminance of the whole screen of a liquid crystal panel can be improved. And since a liquid crystal panel is arrange | positioned away from the optical sheet, the spreading | diffusion of light will be accelerated | stimulated by the space between a liquid crystal panel and an optical sheet. As a result, it is possible to prevent the occurrence of uneven brightness due to the effect of condensing the concavo-convex shape without increasing the number of optical sheets having diffusibility. For example, the number of optical sheets may be two or less.

  Furthermore, in the liquid crystal display device of the present invention, it is preferable that the light guide plate and the optical sheet are in contact with each other.

  As described above, since light diffusion is promoted by the space between the liquid crystal panel and the optical sheet, the light guide plate and the optical sheet can be brought into contact with each other. As a result, the relative positional relationship between the light guide plate and the optical sheet can be made constant over the entire screen, and uneven brightness can be prevented.

  Furthermore, the liquid crystal display device of the present invention includes an outer frame that surrounds the outer periphery of the light guide plate and the optical sheet, and a part of the outer frame is positioned between the optical sheet and the liquid crystal panel, whereby the liquid crystal It is preferable that the panel is disposed away from the optical sheet.

  Thereby, the liquid crystal panel can be easily separated from the optical sheet. Further, the distance can be easily adjusted according to the thickness of the outer frame.

  Furthermore, in the liquid crystal display device of the present invention, it is preferable that no prism sheet exists between the light guide plate and the liquid crystal panel.

  Since a plurality of streaky uneven shapes are formed on the exit surface of the light guide plate, a prism having a prism shape in a direction parallel to the streaky uneven shape formed on the exit surface of the light guide plate in addition to the light guide plate There is no need to provide a sheet. Thereby, the cost which an optical sheet requires can be suppressed further.

  According to the liquid crystal display device of the present invention, it is possible to provide a light guide plate having a plurality of streak-like irregularities formed on the emission surface and prevent occurrence of luminance unevenness.

It is a disassembled perspective view which shows the structure of the liquid crystal display device which concerns on one Embodiment of this invention. It is principal part sectional drawing which shows the structure of the outer edge part of the said liquid crystal display device. It is a principal part perspective view which fractures | ruptures and shows the structure of the light source module with which the said liquid crystal display device is equipped. It is sectional drawing which shows the emitted light from the uneven | corrugated shaped body formed in the output surface of the light-guide plate in the said light source module. (A)-(d) is sectional drawing which shows the various shapes of the uneven | corrugated shaped body formed in the output surface of the light-guide plate in the said light source module. It is a figure which shows the state of the light in the reference form with which the light-guide plate, the optical sheet, and the liquid crystal panel were laminated | stacked without gap. It is a figure which shows the luminance distribution in the reference form shown in FIG. It is a figure which shows the state of the light in the said liquid crystal display device. It is a figure which shows the luminance distribution in the said liquid crystal display device.

  One embodiment of the present invention is described below with reference to FIGS.

(Configuration of liquid crystal display device)
First, the overall configuration of the liquid crystal display device according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is an exploded perspective view showing the configuration of the liquid crystal display device of the present embodiment. FIG. 2 is a cross-sectional view of the main part showing the configuration of the outer edge portion of the liquid crystal display device.

  As shown in FIG. 1, the liquid crystal display device 1 according to the present embodiment includes a chassis 2, a light source module 10, a rectangular liquid crystal panel 3, and a bezel 4 in order from the rear. A reflection sheet 11 as a reflection plate, a light guide plate 20, a lower diffusion sheet (optical sheet) 17, and an upper diffusion sheet (optical sheet) 18 are provided.

  The chassis 2 is formed of a material such as iron, and increases the strength of the liquid crystal display device 1. The chassis 2 is substantially the same size as the liquid crystal panel 3. As shown in FIG. 2, the chassis 2 is bent vertically to the liquid crystal panel 3 side with respect to the flat plate portion 2 a at the outer edge of the flat plate portion 2 a and the flat plate portion 2 a for supporting the light source module 10. And the formed standing portion 2b. The light source module 10 is held on the surface of the flat plate portion 2a on the light guide plate 20 side. The standing portion 2 b is formed so as to face the end surface 20 a of the light guide plate 20.

  The reflection sheet 11 is for reflecting the light leaking from the light guide plate 20 and returning it to the light guide plate 20, and is disposed on the back side of the light guide plate 20.

  The light guide plate 20 is for guiding the light emitted from the light source to the liquid crystal panel 3 side, and a plurality of streaky uneven shapes are formed on the emission surface 20b. As shown in FIG. 2, a light source unit 15 including an LED 12 as a light source and an LED substrate 13 is provided on at least one side of a pair of end surfaces 20 a facing each other in the light guide plate 20. The light source unit 15 is installed on the standing portion 2 b of the chassis 2. A positioning member 21 is disposed between the light guide plate 20 and the chassis 2. The positioning member 21 is a member for setting the end face 20a of the light guide plate to an appropriate position with respect to the LED 12.

  Further, light guided inside the light guide plate 20 is scattered on the lower surface 20c as a surface opposite to the light output surface 20b of the light guide plate 20, and a part of the light is emitted to the output surface 20b. A plurality of optical path conversion units 16 are provided for taking out from the light source. The optical path conversion unit 16 is made of, for example, a scatterer formed by printing ink containing a microprism, a microlens, or a diffusing material.

  Thus, the light from the LED 12 is incident on one end face 20a of the light guide plate 20, and the light is guided while being totally reflected inside the light guide plate 20, and a plurality of optical paths provided on the lower surface 20c of the light guide plate 20 A part of the light scattered by the conversion unit 16 reaches the emission surface 20b of the light guide plate 20 in a state where the total reflection condition is broken. For this reason, the liquid crystal panel 3 is irradiated with light from the exit surface 20 b of the light guide plate 20 through the lower diffusion sheet 17 and the upper diffusion sheet 18.

  As described above, the light source module 10 of the present embodiment employs a side edge (also referred to as a side light) method. Light is emitted from the light guide plate 20 from other surfaces than the emission surface 20b. However, the reflection sheet 11 is arranged on a surface other than the emission surface 20b of the light guide plate 20 and the surface on which the LEDs 12 are arranged. Most of the light is emitted from the emission surface 20b. The light source unit 15 is provided on only one of the pair of end surfaces 20a parallel to each other in the light guide plate 20. However, the present invention is not necessarily limited to this, and the light source unit 15 may be provided on both of the pair of end faces 20 a parallel to each other in the light guide plate 20. The light source unit 15 may be provided on at least one of the pair of end surfaces 20a along the longitudinal direction of the light guide plate 20, and is provided on at least one of the pair of end surfaces 20a along the short side direction of the light guide plate 20. May be.

  The lower diffusion sheet 17 and the upper diffusion sheet 18 diffuse light emitted from the light guide plate 20. The lower diffusion sheet 17 is laminated on the emission surface 20 b of the light guide plate 20, and the upper diffusion sheet 18 is laminated on the lower diffusion sheet 17. That is, the lower diffusion sheet 17 is disposed in contact with the light emitting surface 20 b of the light guide plate 20, and the upper diffusion sheet 18 is disposed in contact with the lower diffusion sheet 17.

  In the present embodiment, the liquid crystal display device 1 includes the two diffusion sheets of the lower diffusion sheet 17 and the upper diffusion sheet 18 as optical sheets. However, the number of diffusion sheets is not particularly limited. However, in order to suppress the cost required for the diffusion sheet, the number of diffusion sheets is preferably 2 or less.

  As shown in FIG. 2, the liquid crystal panel 3 is connected to the drive circuit board 6, and displays a desired image when the light transmittance is partially changed by the drive circuit board 6. .

  As shown in FIG. 2, the liquid crystal display device 1 includes an outer frame 5 that surrounds the outer periphery of the light source module 10. The outer frame 5 is perpendicular to the frame main body portion 5a and the frame main body portion 5a in contact with the outer surface of the upright portion 2b of the chassis, and the upper diffusion sheet 18 or the light guide plate 20 of the light source module 10 and the liquid crystal panel 3 It has a flat spacer portion 5b located between them. The frame body 5a and the spacer 5b are integrally formed.

  The frame main body 5a has a bent portion into which a drive circuit board 6 for driving the liquid crystal panel 3 is inserted at the end opposite to the side connected to the spacer 5b. Further, the chassis 2 is fitted into the inner surface of the frame main body 5a.

  The spacer portion 5 b presses the non-display area of the light source module 10 to the chassis 2 side via the pressing member 22. The pressing member 22 is a member that is sandwiched between the back surface of the spacer portion 5b and the light guide plate 20, and is preferably black and elastic. Thereby, the space surrounding the light source unit 15 and the end surface 20a of the light guide plate 20 can be closed without a gap, and light leakage can be prevented. Further, the spacer portion 5 b supports a non-display area on the back surface of the liquid crystal panel 3 via the buffer member 23 on the front surface.

  Thus, the spacer portion 5 b is located between the liquid crystal panel 3 and the upper diffusion sheet 18 in the outer edge portion that is a non-display area of the liquid crystal panel 3. Therefore, the liquid crystal panel 3 is disposed at a position away from the upper diffusion sheet 18 due to the presence of the spacer portion 5b. In other words, a space corresponding to the thickness of the spacer portion 5 b exists between the liquid crystal panel 3 and the upper diffusion sheet 18.

(Configuration of light source module)
As shown in FIG. 3, the emission surface 20 b of the light guide plate 20 in the light source module 10 of the present embodiment has a plurality of streaky uneven shapes along a direction perpendicular to the end surface 20 a on which light from the light source unit 15 is incident. It has a body T. Specifically, the plurality of streak-like concavo-convex shapes T are formed by arranging a plurality of curved structures each having a curved surface having an arcuate cross section. This uneven | corrugated shaped body T ... is formed as a streak pattern along the direction perpendicular | vertical to the end surface 20a of the light-guide plate 20 in which the light source unit 15 is installed, for example. In other words, the light guide plate 20 has a plurality of concavo-convex shaped bodies T each having a curved surface having a ridge line parallel to a direction perpendicular to the end surface 20a of the light guide plate 20 on which the light source unit 15 is installed on the light emission surface 20b. doing. The concavo-convex shaped body T is a structure formed on the emission surface 20 b of the light guide plate 20, and is not provided on the light guide plate 20 as a separate member from the light guide plate 20.

  In the light guide plate 20 provided with the emission surface 20b having the plurality of streak-like uneven shapes T ..., the light scattered by the optical path changing unit 16 is caused by the uneven shape T as shown in FIG. The emitted light is refracted toward the center side of the uneven body T. For this reason, the uneven shape body T can suppress the spread of light to the side, and the straightness of the emitted light can be improved. That is, the light beam emitted from the light guide plate 20 is collected. As a result, the average luminance of the entire screen in the liquid crystal panel 3 can be improved. Here, in the case of a light guide plate having an exit surface made of a conventional flat surface, a prism sheet is provided between the lower diffusion sheet 17 and the upper diffusion sheet 18 to ensure the function of increasing the straightness of the emitted light. Was. However, in the light source module 10 according to the present embodiment, by providing the light guide plate 20 with a plurality of concavo-convex shaped bodies T, the average luminance of the entire screen in the liquid crystal panel 3 can be improved as compared with the case where a prism sheet is provided. It is possible. For this reason, in the light source module 10 of the present embodiment, no prism sheet is provided between the light guide plate 20 and the liquid crystal panel 3. However, the present invention is not necessarily limited to this, and a prism sheet can be provided.

Here, in order to improve the straightness of such emitted light, as shown in FIG. 4, the height of the light guide plate 20 in the vertical direction is set to H, and the pitch between the concavo-convex shaped bodies T is set to P. The aspect ratio H / P is
0.1 ≦ H / P ≦ 0.5
It is preferable to have a relationship satisfying This is because by setting the aspect ratio H / P in the range of 0.1 to 0.5, fluctuation due to light interference can be reduced, and characteristic fluctuations of the light source module 10 can be suppressed.

  The specific shape of the concavo-convex shaped body T for giving such an effect is preferably a semicircular cross section (H / P = 0.5) as shown in FIG. In this case, the light can be efficiently extracted at various incident angles from the vertical light A rising vertically to the light C guided at a shallow angle, and the light can be emitted from the emission surface. Further, when the thickness of the light guide plate 20 is the same, the shape shown in FIG. 5A is easy to ensure a larger cross-sectional area than the prism shape described later. As a result, in the configuration in which the uneven surface T having a semicircular cross section is formed on the light exit surface 20b of the light guide plate 20, the light coupling efficiency on the light incident surface from the LED 12 is high, and light leakage hardly occurs. Such a shape can be formed by extruding the light guide plate 20.

  Here, the structure of the concavo-convex shaped body T is not necessarily the semicircular cross-section shown in FIG. 5A, but may be the shape shown in FIGS. 5B, 5C, and 5D.

  The concave-convex shaped body T shown in FIG. 5B is formed by forming a prism having an apex angle of 90 ° on the light exit surface 20 b of the light guide plate 20. In this case, the vertical light A becomes return light without breaking the total reflection condition. Further, the light C guided at a shallow angle is once emitted from the emission surface because the total reflection condition is broken. However, the light again enters the adjacent prism and returns to the light guide plate 20.

  The concave-convex shaped body T shown in FIG. 5C is formed by forming a prism with an apex angle of 5 ° on the exit surface of the light guide plate 20. In this case, the vertical light A and the light C guided at a shallow angle are both emitted from the emission surface because the total reflection conditions are broken. However, the probability that these lights will re-enter the adjacent prism increases.

  Therefore, as shown in FIGS. 5B and 5C, when a prism is formed on the light emission surface 20b of the light guide plate 20, the efficiency of emitting light from the light guide plate 20 to confine light in the light guide plate 20 is reduced. May end up.

  In addition, the concavo-convex shape body T shown in FIG. 5D has a structure having a concave cylinder surface that is recessed with respect to the emission surface 20 b of the light guide plate 20. In this case, the vertical light A does not become return light due to total reflection. Therefore, the concavo-convex shape body T shown in FIG. 5D can emit light from the light guide plate 20 more efficiently than the configuration shown in FIGS. 5B and 5C. .

<Description of brightness unevenness prevention>
Next, a mechanism capable of preventing luminance unevenness in which a high luminance portion and a low luminance portion alternately appear according to the present embodiment will be described.

  As described above, in the present embodiment, since the spacer portion 5 b of the outer frame 5 is located between the liquid crystal panel 3 and the upper diffusion sheet 18, the liquid crystal panel 3 is disposed away from the upper diffusion sheet 18. The

  Conventionally, for the purpose of reducing the thickness, the liquid crystal panel 3 is usually disposed so as to be in contact with the upper surface of the upper diffusion sheet 18. FIG. 6 is a diagram illustrating a light state in a reference form in which a light guide plate having a plurality of streaky irregularities formed on a light exit surface, two diffusion sheets, and a liquid crystal panel are stacked without a gap. FIG. 7 shows the luminance distribution in the liquid crystal panel when the liquid crystal panel, the two diffusion sheets, and the light guide plate are laminated without gaps as shown in FIG. FIG. In FIG. 7, the horizontal axis indicates position coordinates in a direction perpendicular to the streaks of the concavo-convex shape body T, and the vertical axis indicates luminance. Moreover, in FIG. 7, the broken line shows the luminance distribution corresponding to each uneven | corrugated shaped body T, and the continuous line has shown the whole luminance distribution.

  As described above, the light emitted from the light guide plate is condensed in the direction toward the liquid crystal panel by the concavo-convex shape body T formed on the emission surface of the light guide plate. Therefore, when the light guide plate, the two diffusion sheets, and the liquid crystal panel are laminated without gaps as shown in FIG. 6, the light emitted from the light guide plate enters the liquid crystal panel immediately after passing through the two diffusion sheets. To do. At this time, as shown in FIG. 6 and FIG. 7, the diffusion is insufficient with only two diffusion sheets, and the light incident on the liquid crystal panel is a portion corresponding to the top of the concavo-convex shape body T (indicated by an arrow in FIG. 7). The brightness is increased at a portion), and the brightness is decreased at a portion corresponding to the valley of the uneven shape body T. For this reason, luminance unevenness occurs in which high luminance portions and low luminance portions appear alternately.

  On the other hand, FIG. 8 is a diagram showing the state of light in this embodiment, and FIG. 9 is a diagram showing the luminance distribution of this embodiment. In FIG. 9, the horizontal axis indicates the position coordinates in the direction perpendicular to the streaks of the concavo-convex shape body T, and the vertical axis indicates the luminance. Moreover, the broken line shows the luminance distribution corresponding to each uneven | corrugated shaped body T, and the continuous line has shown the whole luminance distribution.

  As shown in FIGS. 8 and 9, in the present embodiment, since the liquid crystal panel 3 is arranged away from the upper diffusion sheet 18, the light is diffused by the space between the liquid crystal panel 3 and the upper diffusion sheet 18. It can be seen that when the light is incident on the liquid crystal panel 3, the brightness is uniform and uniform. That is, the luminance value is almost the same whether it is a portion corresponding to the top of the concavo-convex shape body T (a portion indicated by an arrow in FIG. 9) or a portion corresponding to the valley of the concavo-convex shape body T.

  The distance between the liquid crystal panel 3 and the upper diffusion sheet 18 is set to a distance that does not cause uneven brightness. Specifically, the liquid crystal panel 3 is preferably separated from the upper diffusion sheet 18 by a distance equal to or greater than the pitch P between the concavo-convex shaped bodies T. Thereby, generation | occurrence | production of brightness nonuniformity can be suppressed further. For example, the distance between the liquid crystal panel 3 and the upper diffusion sheet 18 is set to about 6 mm with respect to the pitch P between the concavo-convex shaped bodies T: 0.3 mm.

  As described above, the liquid crystal display device 1 of the present embodiment includes the light guide plate 20, the lower diffusion sheet 17 and the upper diffusion sheet 18 that diffuse light emitted from the emission surface 20 b of the light guide plate 20, and the lower diffusion sheet 17. And the liquid crystal panel 3 that displays using the light diffused by the upper diffusion sheet 18. A plurality of streak-shaped uneven bodies T are formed on the emission surface 20 b of the light guide plate 20, and the liquid crystal panel 3 is disposed away from the upper diffusion sheet 18.

  Thereby, the diffusion of light is promoted by the space between the liquid crystal panel 3 and the upper diffusion sheet 18, and when entering the liquid crystal panel 3, the brightness is uniform and uniform. That is, the occurrence of uneven brightness can be suppressed. And since light diffusion is promoted by the space between the liquid crystal panel 3 and the upper diffusion sheet 18, the number of diffusion sheets can be reduced to two or less, and the cost required for the diffusion sheet can be suppressed. Moreover, since the diffusion of light is promoted by the space between the liquid crystal panel 3 and the upper diffusion sheet 18, there is no problem even if the lower diffusion sheet 17 and the light guide plate 20 are arranged so as to contact each other.

  In addition, since a plurality of streaky uneven bodies T are formed on the light exit surface 20 b of the light guide plate 20, it is not necessary to provide a prism sheet separately from the light guide plate 20.

  In the above-described embodiment, the light source unit 15 is configured by the LED 12. However, the present invention is not limited to this, and any light source that can couple light to the light guide plate 20 such as an organic EL can be realized.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and the embodiments can be obtained by appropriately combining the technical means disclosed in the embodiments. The form is also included in the technical scope of the present invention.

  The present invention can be applied to a liquid crystal display device such as a television, a monitor, and a tablet that includes a side edge (also referred to as a side light) type light guide plate that emits light from a light source in a planar shape by the light guide plate. is there.

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 Chassis 3 Liquid crystal panel 4 Bezel 5 Outer frame 5a Frame main-body part 5b Spacer part 10 Light source module 11 Reflective sheet 15 Light source unit 17 Lower diffusion sheet (optical sheet)
18 Upper diffusion sheet (optical sheet)
20 Light guide plate 20a End surface 20b Outgoing surface T Uneven shape body

Claims (5)

A light guide plate;
At least one optical sheet that diffuses light emitted from the exit surface of the light guide plate;
A liquid crystal display device comprising a liquid crystal panel that displays using light diffused by the optical sheet,
A plurality of streaky irregularities are formed on the light exit surface of the light guide plate,
A liquid crystal display device, wherein the liquid crystal panel is disposed apart from the optical sheet.   The liquid crystal display device according to claim 1, wherein the light guide plate and the optical sheet are in contact with each other. An outer frame surrounding the outer periphery of the light guide plate and the optical sheet,
3. The liquid crystal according to claim 1, wherein a part of the outer frame is positioned between the optical sheet and the liquid crystal panel so that the liquid crystal panel is disposed apart from the optical sheet. Display device.   4. The liquid crystal display device according to claim 1, wherein no prism sheet is present between the light guide plate and the liquid crystal panel. 5.   The liquid crystal display device according to claim 1, wherein the number of the optical sheets is two or less.

Images