JP4655441B2 - Backlight unit of transmissive display device - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a backlight unit (back light source) and a display device including a transmissive display panel such as a liquid crystal display panel that performs display by controlling transmission of light from the backlight unit. The present invention has been developed as a display device for a mobile phone terminal, but can also be widely used.
[0002]
[Prior art]
A conventional transmissive display device will be described with reference to FIGS. FIG. 3 is a diagram showing a configuration of a conventional backlight unit. FIG. 4 is a configuration diagram of a transmissive display device. FIG. 5 is a diagram for explaining an active area and a black matrix area of a transmissive display device.
[0003]
As shown in FIG. 3, the conventional backlight unit has a light guide plate 32, an LED 33 provided along the side of the light guide plate 32, and one surface of the LED 33 and the light guide plate 32. The reflection sheet 35 is provided, a diffusion sheet 31 provided at a position facing the reflection sheet 35 with the LED 33 and the light guide plate 32 interposed therebetween, and a holder 34 that holds the LED 33 and the light guide plate 32.
[0004]
As shown in FIG. 4, the transmissive display device is configured such that the LCD panel 1 is installed on the backlight unit 3 with the rim sheet 2 interposed therebetween, and the screen 4 is installed on the LCD panel 1. The rim sheet is a double-sided adhesive sheet for bonding the backlight unit 3 and the LCD panel 1 together. The screen 4 is installed so as to cover the black matrix area (shown as BM) other than the active area shown in FIG.
[0005]
As described above, in a mobile phone terminal using a transmissive display device such as a liquid crystal display device, the screen 4 is pasted on the housing, and the active area of the display device is arranged in the window frame of the screen 4. ing.
[0006]
At this time, when looking into the display from the outside of the housing, light leakage from places other than the display area of the main unit will greatly impair the merchantability. It is one of the important elements.
[0007]
[Problems to be solved by the invention]
Conventional problems will be described with reference to FIGS. FIG. 6 is a diagram for explaining the configuration of the backlight unit from above. FIG. 7 is a diagram for explaining a high luminance region and a low luminance region of the backlight unit. FIG. 8 is a diagram showing a state in which the screen is correctly installed. 9 and 10 are views showing a state where the screen is installed at an incorrect position.
[0008]
For the purpose of preventing light leakage from places other than the display area, it is normal not only to use a jig when attaching the screen 4 to the housing, but also to check rigorously on the production line. We manage the outflow of goods. Furthermore, there are many disadvantages such as design restrictions becoming large when determining the window frame of the screen 4.
[0009]
That is, as shown in FIG. 6, the LED 33 and the light guide plate 32 are disposed adjacent to each other when the backlight unit 3 is viewed from above. When the LED 33 is caused to emit light in this state, as shown in FIG. 7, the LED 33 becomes a high luminance region, and the light guide plate 32 becomes a low luminance region. In order to use the backlight unit 3 having such a configuration in a transmissive display device of a mobile phone terminal, as shown in FIG. 8, only the portion of the light guide plate 32 can be seen from the user of the mobile phone terminal. It is necessary to install the screen 4 accurately.
[0010]
At this time, as shown in FIGS. 9 and 10, if the installation position of the screen 4 is slightly shifted, the LED 33 is directly visible to the user. In the example of FIG. 9, the distance d2 is longer than the distance d1, the light leakage of the high luminance region occurs inside the window frame, and a single line of high luminance light is present at the left end of the window frame. You will see. In this case, the low luminance region also protrudes from the right end of the screen 4. In the low brightness area, the brightness is low, so it is not often a problem. However, depending on the material of the housing, the light in the low brightness area may also be leaked from the right edge of the screen 4, which impairs the merchantability. Become. In the example of FIG. 10, the distance d 1 is longer than the distance d 2, and light leaks in the high luminance area from the left end of the screen 4. You will see the line. 9 and 10 are examples in which the installation position of the screen 4 is shifted in the horizontal direction. In addition to this, when the screen 4 is shifted in the vertical direction, or in both the horizontal and vertical directions. In some cases, light leakage occurs.
[0011]
The occurrence of such light leakage hinders normal display and results in a significant loss of merchantability. Therefore, high accuracy is required for the installation of the screen 4. As described above, the screen installation work becomes an obstacle when the production efficiency is improved or an obstacle when the defect rate is lowered.
[0012]
The present invention has been made in such a background, and can allow a slight error in the screen installation position, can relax design constraints, improve the production efficiency and increase the defect rate. It is an object of the present invention to provide a backlight unit of a transmissive display device that can realize a reduction.
[0013]
[Means for Solving the Problems]
The present invention includes a light guide plate, a light source provided along a side of the light guide plate, a reflection sheet provided adjacent to one surface of the light source and the light guide plate, the reflection sheet, the light source, and It is a backlight unit of a transmissive display device provided with a diffusion sheet provided at a position facing the light guide plate.
[0014]
Here, the feature of the present invention is that a light shielding means is provided in at least a region of the diffusion sheet facing the light source. The light shielding means preferably includes means for reflecting the light emitted from the light source. That is, the backlight unit of the transmissive display device of the present invention is characterized in that a part of the diffusion sheet is provided with a role as a light blocking member that blocks unnecessary light. Further, the light-shielding member also has a function of returning irradiation light of the light source to the reflection sheet.
[0015]
In the present invention, light outside the necessary area is shielded beforehand by the lower surface of a transmissive display panel such as a liquid crystal display panel (LCD panel) by the light shielding means applied to the diffusion sheet. Only the light of a certain area reaches. Moreover, since the light from the light source is reflected by the reflecting means applied to the diffusion sheet, it is possible to simultaneously increase the amount of light of the backlight unit.
[0016]
Therefore, a slight error can be allowed in the screen installation position, design constraints can be relaxed, and the production efficiency can be improved and the defective rate can be reduced.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
(First Example)
The backlight unit of the transmissive display device according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a configuration of a backlight unit according to the first embodiment of the present invention.
[0018]
As shown in FIG. 1, the present invention is provided adjacent to one surface of the quadrilateral light guide plate 32, the LED 33 provided along one side of the light guide plate 32, and the LED 33 and the light guide plate 32. The backlight unit 3 of the transmissive display device includes the reflective sheet 35 and the diffusion sheet 31 provided at a position facing the reflective sheet 35 with the LED 33 and the light guide plate 32 interposed therebetween.
[0019]
Here, the feature of the present invention is that a light shielding means is provided in a region of the diffusion sheet 31 facing the LED 33. This light shielding means is a back mirror print 36 that reflects the irradiation light of the LED 33.
[0020]
Using the backlight unit 3 of the transmissive display device of the present invention, as shown in FIG. 4, the LCD panel 1 and the screen 4 are installed to constitute a transmissive display device. As a result, it is possible to shield unnecessary portions of light from the backlight unit 3 and to increase the amount of light from the backlight unit 3 toward the LCD panel 1.
[0021]
Examples of the present invention will be described in detail below. As shown in FIG. 4, the LCD module unit includes an LCD panel (liquid crystal display panel) 1, a backlight unit 3 as a back light source, and a rim sheet (adhesive sheet) 2 such as a double-sided tape for fixing them. It is configured. When this LCD module unit is used in a cellular phone terminal, a screen 4 with a window frame printed thereon is attached to the casing of the cellular phone terminal with a double-sided tape or the like, and the active area of the LCD module unit is placed in this window frame. Set to be placed.
[0022]
As shown in FIG. 1, the backlight unit 3 includes an LED 33 as a light source, a light guide plate 32 for emitting light from the LED 33 in a planar shape, a diffusion sheet 31 for diffusing the light from the light guide plate 32, A reflection sheet 35 that reflects light from the light guide plate 32 toward the LCD panel 1 and a holder 34 that holds these members are included. The backlight unit 3 is used for a mobile phone terminal.
[0023]
Usually, the LCD panel 1 receives light from the back side, and performs screen display while blocking or transmitting the light by liquid crystal. An area used for normal display is generally called an active area (effective display area), and an area that does not transmit light around the active area is generally called a black matrix area (light-shielding area).
[0024]
Therefore, when such an LCD panel 1 is used, as shown in FIG. 4, the screen 4 is installed on the upper part of the LCD panel 1 so that the window frame of the screen 4 is positioned on the black matrix area. It is arranged so that the light outside the black matrix area cannot be seen from the outside.
[0025]
On the other hand, the screen 4 is generally made of clear resin or the like with a double-sided tape attached to the back surface, and there is a large variation in the attachment, and in some cases it cannot fit within the width of the black matrix area. There is. As a result, a light emitting area that should not be seen outside the black matrix area can be seen from the surface.
[0026]
Therefore, in the present invention, as shown in FIG. 1, the opening of the rim sheet 2 for fixing the LCD panel 1 is formed on the surface of the diffusion sheet 31 in the backlight unit 3 facing the LED 33 surface side. The mirror layer is printed on one side to the size that fits inside, making it possible to block the outside light from the active area.
[0027]
Due to the presence of the back mirror print 36 of the diffusion sheet 31 according to the present invention, the light from the backlight outside the black matrix area is cut by the diffusion sheet 31 and does not reach the LCD panel 1. Further, the cut light is returned to the reflection sheet 35, and an increase in the amount of light toward the LCD panel 1 can be achieved.
[0028]
As a result, the light transmitted from the backlight unit 3 to the surface of the LCD panel 1 is transmitted only to the inside of the active area. Due to the variation, the light outside the black matrix area does not leak as described with reference to FIGS. As a result, workability is greatly improved.
[0029]
9 and 10 are examples in which the installation position of the screen 4 is shifted in the horizontal direction. In addition to this, when the screen 4 is shifted in the vertical direction, or in both the horizontal and vertical directions. Even in the case of misalignment, leakage of light in the high luminance region can be eliminated.
[0030]
In this embodiment, the present invention is applied to a mobile phone terminal, but can also be applied to other products using an LCD such as an LCD monitor and a liquid crystal television. Moreover, although the backlight unit 3 is rectangular, it can have various other shapes.
[0031]
(Second embodiment)
A second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a block diagram of a backlight unit according to the second embodiment of the present invention. In the second embodiment, the printing range of the rear surface mirror printing 36 is applied so as to cover not only the area facing the LED 33 but also the entire black matrix area. According to this, leakage of light in both the high luminance region and the low luminance region can be eliminated. Further, since the cut light can be returned to the reflection sheet 35 side in a wider range than the first embodiment, the light amount on the LCD panel 1 side can be increased.
[0032]
For example, as described with reference to FIG. 9, light leakage can be eliminated even when the low luminance area protrudes from the right end of the screen 4. 9 and 10 are examples in which the installation position of the screen 4 is shifted in the horizontal direction. In addition to this, when the screen 4 is shifted in the vertical direction, or in both the horizontal and vertical directions. Even in the case of deviation, light leakage can be eliminated in both the high luminance region and the low luminance region.
[0033]
【The invention's effect】
As described above, according to the present invention, a slight error can be allowed in the screen installation position, design constraints can be relaxed, and production efficiency can be improved and defective rate can be reduced. Can do.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a backlight unit according to a first embodiment of the present invention.
FIG. 2 is a configuration diagram of a backlight unit according to a second embodiment of the present invention.
FIG. 3 is a configuration diagram of a conventional backlight unit.
FIG. 4 is a configuration diagram of a transmissive display device.
FIG. 5 is a diagram for explaining an active area and a black matrix area of a transmissive display device.
FIG. 6 is a diagram for explaining the configuration of a backlight unit from the top.
FIG. 7 is a diagram for explaining a high luminance region and a low luminance region of the backlight unit.
FIG. 8 is a diagram showing a state in which the screen is correctly installed.
FIG. 9 is a diagram showing a state where a screen is installed by mistake.
FIG. 10 is a diagram showing a state where a screen is installed by mistake.
[Explanation of symbols]
1 LCD panel 2 Rim sheet (adhesive sheet)
3 Backlight unit 4 Screen 31 Diffusion sheet 32 Light guide plate 33 LED
34 Holder 35 Reflective sheet 36 Back side mirror printing

Claims (2)

A light guide plate, a light source provided along a side of the light guide plate, a reflection sheet provided adjacent to one surface of the light source and the light guide plate, the reflection sheet, the light source, and the light guide plate. In a backlight unit of a transmissive display device, which includes a diffusion sheet provided at a position facing the sandwiched sheet, and the diffusion sheet is fixed to a liquid crystal display panel via a rim sheet .
A backlight unit of a transmissive display device, wherein a light shielding unit is provided in a peripheral region of the diffusion sheet that is opposite to a region that does not transmit light around an effective display region of the liquid crystal display panel .  The backlight unit of a transmissive display device according to claim 1, wherein the light shielding means includes means for reflecting light emitted from the light source.

Images