JP2009168962A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device comprising a light-weight and low-cost backlight that secures uniform irradiation of light. <P>SOLUTION: The liquid crystal display device includes: a liquid crystal display panel; and a backlight disposed on the back of the liquid crystal display panel to face the liquid crystal display panel. The backlight include: a box-shaped casing with its inner face opposite to the liquid crystal display panel subjected to a light reflection treatment; a light source which is arranged in the casing on the outside of a region facing a liquid display region of the liquid crystal display panel with a gap and disposed in the thickness direction of the backlight spaced from the liquid crystal display panel. The light source is provided with a linear light source and a light reflection plate covering the linear light source, and the light reflection plate has an opening directed to a plane perpendicular to the liquid crystal display panel. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device including a backlight.

  The liquid crystal display panel is configured by using a pair of substrates made of glass, for example, that face each other with a liquid crystal interposed therebetween as an envelope.

  Pixels arranged in a matrix are formed on the liquid crystal side surface of each of the substrates using the liquid crystal as one component.

  Each pixel is configured to independently generate an electric field in the liquid crystal of the pixel, and the liquid crystal of the pixel changes light transmittance according to the strength of the electric field.

  For this reason, the liquid crystal display device is usually provided with a backlight on the back surface of the liquid crystal display panel.

  Each pixel of the liquid crystal display panel PNL is irradiated with light from the backlight, and an observer recognizes an image through light transmitted through each pixel.

  As the backlight, for example, a light guide plate having substantially the same size as the liquid crystal display panel is disposed so as to face the liquid crystal display panel, and a cold cathode ray extending along the side on the side wall surface of at least one side of the light guide plate A tube is known.

  In the backlight having such a configuration, light from the cold cathode ray tube is input from the side wall surface of the light guide plate and emitted from the surface facing the liquid crystal display panel toward the liquid crystal display panel.

A liquid crystal display device having such a backlight is disclosed in, for example, Patent Document 1 below.
JP-A-9-5737

  However, since the liquid crystal display device having such a configuration uses a light guide plate made of, for example, a resin material that is almost the same size as the liquid crystal display panel as a backlight, the liquid crystal display device has a relatively large weight and costs. I could not escape the rise.

  Therefore, there is a demand for the appearance of a backlight that can ensure the uniformity of light irradiation, is light in weight, and can be reduced in cost. Such a demand becomes remarkable in, for example, an amusement liquid crystal display device. Yes.

  An object of the present invention is to provide a liquid crystal display device including a backlight that can ensure uniformity of light irradiation, is lightweight, and can reduce costs.

   Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.

(1) A liquid crystal display device according to the present invention is, for example, a liquid crystal display device having a liquid crystal display panel and a backlight disposed on the back surface of the liquid crystal display panel so as to face the liquid crystal display panel.
The backlight includes a hollow casing having an inner wall surface that reflects visible light, and a light source body positioned in the casing at a distance outward from the display area of the liquid crystal display panel. ,
The light source body includes a linear light source and a light reflecting plate formed by breaking the linear light source, and the light reflecting plate has an opening on a surface orthogonal to the liquid crystal display panel. .

(2) A liquid crystal display device according to the present invention is premised on, for example, the configuration of (1), and the light source body is arranged with a gap from the liquid crystal display panel.

(3) The liquid crystal display device according to the present invention is premised on, for example, the configuration of (1), and the light reflecting plate includes a lens in its opening.

(4) The liquid crystal display device according to the present invention is premised on, for example, the configuration of (1), and the light reflecting plate includes an optical filter in its opening.

(5) The liquid crystal display device according to the present invention is characterized in that, for example, on the premise of the configuration of (1), an optical film is disposed between the liquid crystal display panel and the backlight.

(6) In the liquid crystal display device according to the present invention, for example, on the premise of the configuration of (1), the effective functional area of the optical film is positioned with a distance outside the display area of the liquid crystal display panel. It is characterized by that.

(7) The liquid crystal display device according to the present invention is premised on the configuration of (1), for example, and the optical film is formed including a liquid crystal cell whose light scattering characteristics can be controlled by controlling an applied voltage. It is characterized by.

(8) The liquid crystal display device according to the present invention is, for example, a liquid crystal display device having a liquid crystal display panel and a backlight arranged on the back side of the liquid crystal panel,
The backlight has a light source and a hollow casing,
The housing has a front side opening that emits light on the front side and a back side opening that emits light on the back side,
The light source is housed outside the front opening of the housing.

(9) The liquid crystal display device according to the present invention is premised on the configuration of (8), for example, and has a light diffusion layer between the liquid crystal panel and the backlight.

(10) The liquid crystal display device according to the present invention, for example, is based on the configuration of (8), and the optical film is formed including a liquid crystal cell whose light scattering characteristics can be controlled by controlling an applied voltage. It is characterized by.

  In addition, this invention is not limited to the above structure, A various change is possible in the range which does not deviate from the technical idea of this invention.

  The liquid crystal display device configured as described above can be configured to include a backlight that can ensure uniformity of light irradiation, is lightweight, and can reduce costs.

  Hereinafter, embodiments of a liquid crystal display device according to the present invention will be described with reference to the drawings.

<Overall schematic configuration>
FIG. 1 is a sectional view showing an embodiment of a liquid crystal display device according to the present invention. FIG. 1 corresponds to a cross section taken along line II in FIG.

  In FIG. 1, in the liquid crystal display device, a liquid crystal display panel PNL, an optical sheet OS, and a backlight BL are sequentially arranged from the observer side.

  The liquid crystal display panel PNL includes a pair of parallel substrates SUB1 and SUB2 made of glass, for example, as an envelope, and liquid crystal (not shown) is interposed between the substrates SUB1 and SUB2.

  Pixels (not shown) arranged in a matrix are formed on the surface of the substrates SUB1 and SUB2 on the liquid crystal side as a component of the liquid crystal so that the light transmittance of the liquid crystal can be controlled in each pixel. It has become.

  For example, the semiconductor device SC (V) for driving the pixels of the liquid crystal display panel PNl is mounted on the surface of the substrate SUB1 where the substrate SUB2 is not disposed. A printed circuit board PB made of a control circuit disposed outside (indicated by UFR, MFR, DFR) is connected via a flexible circuit board FB.

  Each pixel of the liquid crystal display panel PNL is irradiated with light from a backlight BL, which will be described later, and allows an observer to recognize an image through light transmitted through each pixel. The configuration of the liquid crystal display panel PNL will be described in detail later.

On the back surface of the liquid crystal display panel PNL, for example, a backlight BL is disposed via an optical sheet OS made of a diffusion sheet, a prism sheet, or a laminate thereof. The optical sheet OS guides the light from the backlight BL to the liquid crystal display panel PNL side by diffusing or condensing it.

  The backlight BL has a lower frame DFR, which will be described later, as a housing, and a light source LB is arranged inside the lower frame DFR, and is a surface light source having uniform brightness in a plane parallel to the liquid crystal display panel PNL. It is supposed to function as. The configuration of the backlight BL will be described in detail later.

  The liquid crystal display device is configured by modularizing the liquid crystal display panel PNL, the optical sheet OS, and the backlight BL by an upper frame UFR, a middle frame MFR, and a lower frame DFR.

  That is, for example, the liquid crystal display panel PNL is placed on the middle frame, and the optical sheet OS is sandwiched between the middle frame MFR and the lower frame DFR fixed to the middle frame MFR, and the liquid crystal display panel PNL The upper frame UFR in which the window WD for exposing the liquid crystal display area AR is formed is fixed to the middle frame MFR.

<LCD panel>
2 is a plan view of the liquid crystal display device shown in FIG. 1, showing the liquid crystal display panel PNL and the backlight BL, and omitting the upper frame UFR, the middle frame MFR, the optical sheet OS, and the printed circuit board PB. As shown.

  The liquid crystal display panel PNL shown in FIG. 2 shows a liquid crystal display area AR (area surrounded by a one-dot chain line in the figure) composed of a collection of pixels arranged in a matrix.

  This liquid crystal display area AR is an area formed inside an annular seal material (not shown) for sealing liquid crystal between the substrates SUB1 and SUB2 and also for fixing the substrate SUB2 to the substrate SUB1. .

  At least the liquid crystal display area AR of the liquid crystal display panel PNL is irradiated with light from a backlight BL, which will be described later, so that an observer can recognize an image through light transmitted through each pixel.

  In the liquid crystal display panel PNL, the substrate SUB1 disposed rearward with respect to the viewer side has, for example, portions exposed from the substrate SIUB2 on the left side and the upper side in the figure, and the semiconductor device SC (V) is in these portions. , SC (He) is mounted.

  A plurality of semiconductor devices SC (V) are arranged in parallel on the left side of the substrate SUB1 in the drawing to form a scanning signal driving circuit, and a plurality of semiconductor devices SC (He) are arranged in parallel on the upper side of the substrate SUB1 in the drawing to display video signals. A drive circuit is configured.

A signal is input to the semiconductor device SC (V) and the semiconductor device SC (He) from the printed circuit board PB side including the control circuit shown in FIG.

  In each pixel arranged in a matrix, one pixel group consisting of each pixel arranged in the column direction (x direction in the figure) is selected by the scanning signal driving circuit, and the pixel is matched with the timing of this selection. A video signal is supplied from the video signal driving circuit to each pixel of the group.

  In order to perform such driving, in addition to a pair of electrodes including a pixel electrode, each pixel is formed with a thin film transistor for pixel selection.

<Backlight>
The backlight BL has a housing in which the light source body LB is disposed, and the housing also serves as the lower frame DFR.

The lower frame DFR has a hollow shape and has an opening on the liquid crystal display panel PNL side.

  The area of the opening of the lower frame DFR is substantially the same as the area of the liquid crystal display panel PNL, and a light reflecting sheet is provided on the entire inner surface (bottom surface, inner wall surface) facing the liquid crystal display panel PNL. RS is mounted (see FIG. 1). This is because light from the light source LB, which will be described later, is reflected by the light reflecting sheet RS and the reflected light is guided to the liquid crystal display panel PNL side. For this reason, on the inner surface of the lower frame DFR, it is not necessarily limited to placing the reflection sheet RS, and it is only necessary to have a light reflection function of another method.

  As shown in FIG. 2, the light source body LB is formed on the inner wall surface of the lower frame DFR on the side of the liquid crystal display panel PNL on which the semiconductor device SC (V) composed of, for example, a scanning signal driving circuit is mounted. The liquid crystal display panel PNL is formed to extend in the side direction (y direction in the figure).

  Then, as shown in FIG. 1, the light source body LB is fixed at a position separated by a distance a ′ from the opening of the lower frame DFR in the thickness direction of the lower frame DFR (toward the bottom surface of the lower frame). Are arranged.

  Further, as shown in FIG. 2, the light source body LB does not enter the liquid crystal display area AR of the liquid crystal display panel PNL and is arranged outside the liquid crystal display area AR when viewed in a plan view. And a distance b from the region. As will be described later, this is for securing a certain distance for the light from the light source LB to reach the liquid crystal display area AR and lowering the luminance.

  The light source body LB includes a linear light source LL made of, for example, a cold cathode ray tube or the like extending in the extending direction of the light source body LB, and a reflection plate RB formed by covering the linear light source LL. .

The reflection plate RB has an opening OP directed to a surface orthogonal to the liquid crystal display panel PNL, for example, having a U-shaped cross section in a plane orthogonal to the longitudinal direction of the linear light source LL. It is configured.

The reason why the opening OP of the reflector RB is directed to a plane orthogonal to the liquid crystal display panel PNL is to prevent the direct light from the linear light source LL from being applied to the liquid crystal display panel PNL, and the luminance is reduced. This is to prevent it from becoming larger than necessary.

  Thereby, the light from the linear light source LL of the light source LB is irradiated from the opening OP of the reflection plate RB by mixing the light directly irradiated into the lower frame DFR and the light reflected by the reflection plate RB. In addition, the light reflecting sheet RS placed on the inner surface of the lower frame DFR includes various kinds of reflected light having different numbers of reflections and is irradiated to the liquid crystal display panel PNL side.

  For this reason, the light applied to the liquid crystal display panel PNL is irregularly reflected light, and the luminance is substantially uniform throughout the liquid crystal display area AR.

  In the configuration of the backlight BL described above, as shown in FIG. 3, the light source body LB is separated from the gap a ′ from the opening of the lower frame DFR (in this case, the gap a ′ is separated from the liquid crystal display panel PNL). In the output light from the light source LB that directly reaches the end e on the light source LB side of the liquid crystal display area AR of the liquid crystal display panel PNL, by taking a large (which can be regarded as being substantially equal to the gap a) The angle θ becomes steep and the distance L becomes longer.

  Since the distribution of the output light from the opening OP of the reflector RB becomes weaker as the angle θ is larger and the distance L is longer, the luminance of the end e can be lowered.

  Therefore, in this manner, in the liquid crystal display area AR of the liquid crystal display panel PNL, when the luminance of the near end portion (the portion of the end portion e) of the light source body LB is lowered, the light source body LB that can reach the far end portion. Since the output light can be relatively strengthened, it is possible to improve the uniformity of the light distribution applied to the liquid crystal display area AR.

  The backlight BL configured as described above has a gap SP as shown in FIG. 1 at least in a portion facing the liquid crystal display area AR of the liquid crystal display panel PNL. For example, the light source LB is arranged on the inner wall surface of the frame DFR.

  For this reason, since a light guide plate is not required as compared with, for example, a conventional backlight, the configuration can be reduced and the cost can be reduced.

<Other Examples>
In the embodiment described above, the light source body LB is composed of the linear light source LL and the reflector RB. However, as shown in FIG. 4, the lens LS may be arranged in the opening OP of the reflector RB. Alternatively, the spectral transmission characteristic of the refracting body forming the lens LS may be adjusted to give the lens LS a function as an optical filter. By disposing the lens LS, it is possible to adjust the color tone and luminance distribution of light irradiated to the liquid crystal display area AR of the liquid crystal display panel PNL, and to perform light irradiation with uniform luminance to the liquid crystal display panel PNL. Because you can.

  In the embodiment described above, the light source body LB is disposed only on one side of the lower frame as viewed in plan. However, the light source body LB may be configured such that a light source body different from the light source body LB is also arranged on another side facing the one side or another side not facing the one side. Good.

This is because a plurality of light source bodies may be required due to the increase in size of the liquid crystal display panel PNL. In this case, as described above, each light source body is disposed outside the area facing the liquid crystal display area AR of the liquid crystal display panel PNL.

  FIG. 5 is a cross-sectional view of a liquid crystal display device according to another embodiment of the present invention, and FIG. 6 is a plan view.

  The liquid crystal display device of FIG. 5 has a liquid crystal panel PNL and a backlight assembly BL arranged on the back side of the liquid crystal panel PNL.

  The liquid crystal panel PNL includes a first substrate SUB1 on which thin film transistors are formed, a second substrate SUB2 on which color filters are formed, and a liquid crystal material sandwiched between the first substrate and the second substrate. The second substrate SUB2 is disposed on the front side, and the first substrate is disposed on the backlight side.

  The backlight assembly BL includes a light source and a housing that houses the light source.

  The housing has a front-side opening that emits light on the front side and a back-side opening that emits light on the back side (the side opposite to the liquid crystal panel). By providing the back side opening, the structure or the background can be arranged on the back side of the backlight. That is, the observer on the front side of the panel can observe the structure or the background arranged behind the backlight. Moreover, by having an opening on the back side, it is possible to irradiate both the liquid crystal panel and the structure (or background) behind the backlight with one backlight assembly BL.

  The light source LL is accommodated outside the front opening of the housing so that the observer cannot see the light source LL.

  A light diffusion layer LDL is disposed between the liquid crystal panel and the backlight. Light diffusion layer LDL suppresses unevenness in luminance and supplies light that uniformly illuminates the liquid crystal panel.

  The diffusion layer is preferably switchable between a light transmission state and a light diffusion state. A polymer network liquid crystal is one that can switch between a light transmission state and a light diffusion state. A polymer network liquid crystal is described in, for example, Japanese Patent Application Laid-Open No. 2004-125962. The polymer network liquid crystal can control light scattering characteristics by controlling the applied voltage.

  By including a layer that can be switched between the light transmission state and the light diffusion state, the display on the liquid crystal panel can be brightened, and the display of the structure behind the backlight can be brightened. That is, by diffusing the backlight light when displaying an image on the liquid crystal panel, a good surface light source can be obtained when displaying an image on the liquid crystal panel. Further, when the light transmission state is set, the observer can observe the structure (or background) because there is a back side opening.

  In order to prevent the light source LL from being seen by the observer, the light source LL needs to be disposed sufficiently outside the effective area of the liquid crystal panel. The backlight has a light emitting part for irradiating light to the display area of the liquid crystal panel and a light source arranged outside the light emitting part, and the backlight assembly is more than the display area of the liquid crystal panel. A large light exit is provided.

  The diameter AR1 of the effective area (image display area) of the liquid crystal panel is smaller than the diameter AR2 of the effective area of the light diffusion layer. The diameter AR1 of the effective area (image display area) of the liquid crystal panel is smaller than the front-side opening diameter AR3 of the housing DFR. That is, the diameters have a relationship of AR1 <AR2 and AR1 <AR3. In the present embodiment, the horizontal diameter has been described, but the vertical diameter has the same relationship. With this configuration, the observer cannot observe the backlight BL.

  In this embodiment, the effective area of the shutter liquid crystal is approximately 1 mm larger than the effective area of the liquid crystal panel. Further, the diameter of the front side opening and the diameter of the back side opening are set to the same size. With this configuration, it is possible to suppress luminance unevenness caused by the backlight when an image is displayed on the liquid crystal panel.

  Further, the backlight of FIG. 6 has openings for transmitting light on the front side and the back side, and a light source is arranged around the openings. The light source may be arranged along the short side or the long side of the liquid crystal display device without being limited to the structure of FIG. The light source may be a cold cathode tube, and the LEDs may be arranged along the long side or the short side.

  Each of the embodiments described above may be used alone or in combination. This is because the effects of the respective embodiments can be achieved independently or synergistically.

It is sectional drawing which shows one Example of the liquid crystal display device by this invention. 1 is a plan view showing an embodiment of a liquid crystal display device according to the present invention, and is a view showing only a liquid crystal display panel and a backlight. FIG. It is explanatory drawing explaining the reason why the light with a uniform brightness | luminance is obtained in the backlight of the liquid crystal display device by this invention. It is a principal part block diagram which shows the other Example of the liquid crystal display device by this invention. It is sectional drawing which shows the other Example of the liquid crystal display device by this invention. It is a top view which shows the other Example of the liquid crystal display device by this invention.

Explanation of symbols

  PNL: Liquid crystal display panel, OS: Optical sheet, BL: Backlight, SUB1, SUB2 ... Substrate, SC (V) ... Semiconductor device (scanning signal drive circuit), SC (He) ... Semiconductor device ( Video signal drive circuit), AR ... liquid crystal display area, PB ... printed circuit board, FB ... flexible substrate, UFR ... upper frame, MFR ... middle frame, DFR ... lower frame (backlight housing), LB: Light source, LL: Linear light source, RB: Reflector, OP: Opening.

Claims (10)

A liquid crystal display device having a liquid crystal display panel and a backlight disposed on the back surface of the liquid crystal display panel so as to face the liquid crystal display panel,
The backlight includes a hollow casing having an inner wall surface that reflects visible light, and a light source body positioned in the casing at a distance outward from the display area of the liquid crystal display panel. ,
The light source body includes a linear light source and a light reflecting plate formed by breaking the linear light source, and the light reflecting plate has an opening on a surface orthogonal to the liquid crystal display panel. Liquid crystal display device.   The liquid crystal display device according to claim 1, wherein the light source body is disposed with a gap from the liquid crystal display panel.   The liquid crystal display device according to claim 1, wherein the light reflection plate includes a lens at an opening thereof.   The liquid crystal display device according to claim 1, wherein the light reflection plate includes an optical filter at an opening thereof.   The liquid crystal display device according to claim 1, wherein an optical film is disposed between the liquid crystal display panel and the backlight.   2. The liquid crystal display device according to claim 1, wherein the effective functional area of the optical film is positioned with a distance outside the display area of the liquid crystal display panel.   The liquid crystal display device according to claim 1, wherein the optical film includes a liquid crystal cell that can control light scattering characteristics by controlling an applied voltage. A liquid crystal display device having a liquid crystal display panel and a backlight disposed on the back side of the liquid crystal panel,
The backlight has a light source and a hollow casing,
The housing has a front side opening that emits light on the front side and a back side opening that emits light on the back side,
The liquid crystal display device, wherein the light source is accommodated outside the front opening of the housing.   The liquid crystal display device according to claim 8, further comprising a light diffusion layer between the liquid crystal panel and the backlight.   The liquid crystal display device according to claim 8, wherein the optical film includes a liquid crystal cell capable of controlling light scattering characteristics by controlling an applied voltage.

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