JP2008166175A - Display unit and illuminating device for same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an illuminating device for a display unit which reduces leakage of a light incoming onto an optical waveguide plate and exhibits superior optical utilization efficiency. <P>SOLUTION: An illuminating device for a display unit has many light sources 12 mounted in parallel with an optical waveguide plate 9 and a circuit board 13, wherein the optical waveguide plate 9 and the circuit board 13 are integrated via a double-stick tape 14, and the light sources 12 are arranged at a position in opposition to the end face 9a of the optical waveguide plate 9, on which a concave portion 9b is provided for housing the double-stick tape 14. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a display device illumination device and a display device, and more specifically to a technique for improving a decrease in luminance due to light leakage from a light source in the display device illumination device.

  In recent years, so-called flat panel displays have become the mainstream in place of cathode ray tubes that have been conventionally used as display devices, and the market is expanding. Among these, a liquid crystal display (Liquid Crystal Display) is characterized by thinness, light weight, low power consumption, and high definition, and is used in a wide range of fields such as televisions, personal computers, digital cameras, and mobile phones.

  FIG. 6 is a perspective view showing a configuration of a general edge light type liquid crystal display device. The liquid crystal display device generally includes a liquid crystal panel in which liquid crystal is sealed between a pair of opposed electrode substrates and a polarizing plate. A module, an illumination device (backlight) that illuminates the liquid crystal module from the back surface, and various circuit boards used for driving the liquid crystal module.

  The liquid crystal panel 3 includes a TFT substrate, a liquid crystal, and a color filter substrate (not shown). Reference numeral 5 denotes a control circuit. A control signal for controlling the liquid crystal panel 3 is transmitted to the driver IC 4 via the control circuit 5.

  In addition, a reflection sheet 8, a light guide plate 9, a diffusion sheet 10, and two condensing sheets (prism sheets) 11a and 11b are laminated in this order on the surface facing the liquid crystal panel 3. Reference numeral 12 denotes a backlight light source composed of a light emitting diode, and a plurality of them are arranged in parallel adjacent to one end of the light guide plate 9. Reference numeral 1 denotes a front frame, which is combined with the back case 2 to form a housing of the liquid crystal display device, and a double-sided adhesive liquid crystal panel fixing tape 7 is provided between the liquid crystal panel 3 and the resin frame 6. The liquid crystal panel 3 and the resin frame 6 are fixed integrally.

  Here, the light emitted from the light emitting diode 12 enters the light guide plate 9 from the end face 9 a of the light guide plate 9, spreads to every corner while repeating irregular reflection in the light guide plate 9, and is reflected on the lower surface of the light guide plate 9. The light is reflected upward by the sheet 8 and emitted from the upper surface of the light guide plate 9. The emitted light further sequentially passes through the diffusion sheet 10 and the light collecting sheets 11a and 11b, and uniformly irradiates the liquid crystal panel 3 from behind.

  At this time, the circuit board on which the light guide plate 9 and the light emitting diode are mounted is integrated via a double-sided tape. FIG. 7A shows a state before the circuit board 13 on which the light guide plate 9 and the light emitting diode 12 are mounted. FIG. 7B is a perspective view showing a state after the light guide plate 9 and the circuit board 13 are bonded, and FIG. 7C is a cross-sectional view taken along line AA ′ in FIG. 7B. . When the circuit board 13 on which the light emitting diode 12 is mounted is bonded to the light guide plate 9 with the double-sided tape 14, the light emitting diode 12 is disposed at a position facing the end surface 9 a of the light guide plate 9.

  However, since a gap is generated between the circuit board 13 and the light guide plate 9 by the thickness of the double-sided tape 14, a part of the light emitted from the light source 12 leaks from this gap, and the amount of light entering the light guide plate from the end face is reduced. However, there is a problem that the light use efficiency is reduced (see FIG. 7C).

2. Description of the Related Art Conventionally, in an illumination device using a plurality of light emitting diodes as a light source, the reflectance of the upper reflection sheet is changed due to the position of the light source (see Patent Document 1), a light guide plate, and a liquid crystal panel As for the double-sided tape to which is attached, there is also one in which a concave portion for storing the double-sided tape is provided in the light guide plate (see Patent Document 2).
JP 2004-296372 A Japanese Patent Laid-Open No. 7-218913

  However, in the invention described in Patent Document 1, there is no specific description about the method of bonding the substrate mounted with the light source and the light guide plate, and considering the configuration of the circuit board and the light guide plate from the drawings, a gap corresponding to the thickness of the tape is generated. It is thought that there is. Further, the invention described in Patent Document 2 is intended to reduce the thickness of the entire liquid crystal display device, and does not solve the positional relationship between the light source and the light guide plate and the accompanying luminance reduction and quality deterioration.

  Accordingly, in view of the above problems, the present invention eliminates a positional shift between the light source and the light guide plate, reduces leakage of light incident on the light guide plate, and provides an illumination device for a display device with excellent light utilization efficiency. An object is to provide a display device used.

  In order to achieve the above object, the configuration of the present invention includes a light guide plate, a circuit board integrated with the light guide plate, a plurality of light sources mounted in parallel on the circuit board, and a lower surface of the light guide plate. And a reflection sheet that reflects light upward, the light guide plate and the circuit board are bonded via a double-sided tape, and the light source is disposed at a position facing one end surface of the light guide plate In the illumination device, the double-sided tape is adhesively housed in a recess formed on at least one of the light guide plate surface and the circuit board surface.

  According to the present invention, in the illumination device for a display device having the above-described configuration, the double-sided tape is not disposed at a position facing the light exit surface of the light source in the circuit board.

  The present invention also provides a light guide plate, a circuit board integrated with the light guide plate, a plurality of light sources mounted in parallel to the circuit board, and provided on the lower surface of the light guide plate and reflects light upward. In the illumination device for a display device, wherein the light source is arranged at a position facing the one end surface of the light guide plate, and a projection protruding between the light sources is projected on the one end surface of the light guide plate facing the light source And the upper surface of the protruding portion is lower than the upper surface of the light guide plate by the thickness of the double-sided tape, and the protruding portion is bonded to the circuit board via the double-sided tape. It is an illumination device for a display device.

  In the illumination device for display device having the above-described configuration, the adhesive force of the double-sided tape is different between the front surface and the back surface.

  According to the present invention, in the illumination device for a display device having the above structure, the light source is a light emitting diode.

  According to the present invention, in the illumination device for a display device having the above structure, the circuit board is a flexible circuit board.

  Moreover, this invention is a display apparatus characterized by including the illuminating device for display apparatuses of the said structure, and the light control member which controls the light radiate | emitted from the said light source.

  According to another aspect of the invention, the light control member having the above structure is a liquid crystal panel.

  According to the first configuration of the present invention, in the illumination device for a display device in which the light source mounted circuit board and the light guide plate are bonded via the double-sided tape, the recess for storing the double-sided tape is formed on the surface of the light guide plate and the circuit board. By providing it on at least one side, the gap between the circuit board and the light guide plate, which has occurred for the thickness of the double-sided tape at the time of bonding, can be eliminated. Thereby, the light from the light source does not leak from the gap, and the light utilization efficiency is increased.

  In addition, since the gap due to the thickness of the double-sided tape is eliminated, the entire lighting device can be thinned.

  Further, according to the second configuration of the present invention, since the double-sided tape on the circuit board is not disposed at the position facing the light source, the concave portion provided on the light guide plate is not formed at the position facing the light source. The loss caused by the light emitted from the light source being blocked by the recess or being diffused by the double-sided tape accommodated in the recess can be reduced.

  Further, according to the third configuration of the present invention, a projecting portion is provided on one end face of the light guide plate facing the light source so as to project between adjacent light sources, and the projecting portion and the circuit board are bonded via a double-sided tape. Thus, the light emitted from the light source is not blocked by the double-sided tape or the like after entering the light guide plate. For this reason, the loss of light can be further reduced. Moreover, since the upper surface of the protrusion is formed at a position lower than the upper surface of the light guide plate by the thickness of the double-sided tape, there is no gap due to the thickness of the double-sided tape between the light guide plate and the circuit board. Therefore, light from the light source does not leak from the gap due to the thickness of the tape, and the light utilization efficiency is further increased.

  Further, according to the fourth configuration of the present invention, when the adhesive property of the double-sided tape is different between the front surface and the back surface, after the circuit board and the light guide plate are once bonded, and then once peeled off and reattached, the double-sided tape is guided. It can be designed to remain on either the optical plate side or the circuit board side. For this reason, the incorporation property and rework property of the light guide plate and the circuit board can be improved, and for example, when the light source is displaced from the mounting position, it can be easily corrected.

  Moreover, according to the fifth configuration of the present invention, the power consumption can be reduced by using the light emitting diode as the light source.

  In addition, according to the sixth configuration of the present invention, it is possible to further reduce the thickness of the entire lighting device by using a flexible circuit board as the circuit board.

  In addition, according to the seventh configuration of the present invention, it is possible to provide a display device with high light utilization efficiency by including a display device illumination device and a light control member that controls light emitted from the light source.

  Further, according to the eighth configuration of the present invention, it is possible to provide a liquid crystal display device with high light utilization efficiency by using a liquid crystal panel as the light control member.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the part which is common in FIG. 6, FIG. 7 of a prior art example, and description is abbreviate | omitted.

[First embodiment]
The liquid crystal display device according to this embodiment includes the liquid crystal panel 3, the diffusion sheet 10, the light collecting sheets 11 a and 11 b, the light guide plate 9, the light source 12, and the reflection sheet 8 as in the conventional example shown in FIG. 6. Here, the plurality of light emitting diodes 12 (hereinafter abbreviated as LEDs) are arranged at positions facing the end face 9 a of the light guide plate 9.

  With this configuration, the light emitted from the LED 12 enters the light guide plate 9 from the end face 9 a of the light guide plate 9, spreads to every corner while repeating irregular reflection in the light guide plate 9, and is laminated on the lower surface of the light guide plate 9. The light is reflected upward by 8 and emitted from the upper surface of the light guide plate 9, and sequentially passes through the diffusion sheet 10 and the light collecting sheets 11 a and 11 b to uniformly irradiate the liquid crystal panel 3 from behind.

  FIG. 1A is a perspective view illustrating a state before the light guide plate 9 and the circuit board 13 according to the present embodiment are bonded, and FIG. 1B is a diagram illustrating the light guide plate 9 and the circuit board according to the present embodiment. FIG. 1C is a cross-sectional view taken along the line AA ′ in FIG. 1B.

  A recess 9b is formed in the light guide plate 9 according to the present embodiment, and the double-sided tape 14 that bonds the circuit board 13 and the light guide plate 9 is accommodated in the recess 9b. As a result, the gap between the circuit board 13 and the light guide plate 9 that has conventionally occurred can be eliminated, light leaking from the gap is reduced, and the amount of light incident from the end surface 9a of the light guide plate 9 is increased. Can do.

  Further, since the light guide plate 9 converts the optical distribution in the form of a point light source generated in the LED 12 into an optical distribution in the form of a surface light source inside the light guide plate 9, if the positional relationship between the LED 12 and the light guide plate 9 is shifted, a liquid crystal panel The uniformity of the optical distribution in the form of a surface light source that emits to the 3 side may be lost. However, by eliminating the positional shift due to the thickness of the double-sided tape 14, the uniformity of the optical distribution of the surface light source form can be ensured.

  Here, the depth of the recess 9b needs to be about the thickness of the double-sided tape 14 in order to eliminate the gap. The same effect can be obtained by injecting an adhesive resin as an adhesive into the recess 9b instead of the double-sided tape 14. It should be noted that the volume of the concave portion 9b provided in the light guide plate 9 is preferably as small as possible because the optical path of light is not blocked by the concave portion 9b inside the light guide. The recess may be provided on the circuit board 13 in addition to the light guide plate 9. When the circuit board 13 is provided with a recess, it is possible to suppress the recess 9b from blocking the optical path of the light incident on the inside of the light guide plate. Further, the double-sided tape 14 may be accommodated by providing recesses in both the circuit board 13 and the light guide plate 9.

  Here, the light guide plate 9 is provided on the upper surface of the reflection sheet 8 to change the optical path of light having an optical distribution in the form of a point light source generated by the LED 12 and to convert the light into an optical distribution having a surface light source form. Yes, it is a wedge-shaped or parallel plate-type plate molded with polycarbonate, acrylic resin, or the like, and the recess 9b is formed by a mold and can be created with excellent reproducibility in the mass production process.

  The LED used for the light source 12 is a white chip-type LED, and is a pseudo white one in which a blue semiconductor element (compound such as InGaAlAs) and a yellow phosphor (YAG or the like) are combined. The LED has a feature that power consumption can be reduced as compared with the case where a cold cathode tube is used. Moreover, LED is mounted on the circuit board 13, is wired in series, and light-emits by applying a voltage to a terminal. In addition, the wiring of LED may be in series or in parallel in terms of electric circuit.

  Further, the circuit board 13 is a flexible circuit board: FPC (Flexible Printed Circuit), so that the entire apparatus is thinned. The flexible circuit board is obtained by forming a circuit on a film of polyester (PET) or the like by printing or etching.

  The reflective sheet 8 is formed by laminating a flexible white resin sheet alone or a reflective layer having a high reflectivity on which silver, aluminum, or the like is deposited, and transmits light from the light guide plate 9 in the direction of the liquid crystal panel 3. Reflects efficiently.

  Further, the diffusing sheet 10 has fine irregularities formed on one side thereof, and randomizes the light emitted from the light guide plate 9. The upper surfaces of the condensing sheets 11a and 11b are prism surfaces, and the luminance in the direction of the liquid crystal panel 3 is improved.

  In addition, once the circuit board 13 and the light guide plate 9 are bonded with the double-sided tape 14, when the positional relationship between the light guide plate 9 and the light source 12 is finely adjusted or when reassembling due to a defective member, the circuit board 13 and the light guide plate 9 are guided. The light plate 9 may be peeled off and attached again. At this time, it is possible to design the double-sided tape 14 so that the double-sided tape 14 remains on the light guide plate 9 side or the circuit board 13 side when peeled off by using the double-sided tape 14 having different adhesive strengths on the front and back surfaces. As a result, even if a slight deviation occurs in the mounting position of the light source 12 on the circuit board 13, it can be easily corrected. In addition, you may distribute | arrange the position of the recessed part 9b to the light-guide plate 9 periphery as shown in FIG.

[Second Embodiment]
In this embodiment, the same code | symbol is attached | subjected to the part which is common in a prior art example and 1st Embodiment, and description is abbreviate | omitted. Similarly to the conventional example shown in FIG. 6, the liquid crystal display device according to the present embodiment includes the liquid crystal panel 3, the diffusion sheet 10, the light collecting sheets 11 a and 11 b, the light guide plate 9, the light source 12, and the reflection sheet 8. Yes. Here, the plurality of LEDs 12 are arranged at positions facing the end surface 9 a of the light guide plate 9.

  With this configuration, the light emitted from the LED 12 enters the light guide plate 9 from the end face 9 a of the light guide plate 9, spreads to every corner while repeating irregular reflection in the light guide plate 9, and is laminated on the lower surface of the light guide plate 9. The light is reflected upward by 8 and emitted from the upper surface of the light guide plate 9, and sequentially passes through the diffusion sheet 10 and the light collecting sheets 11 a and 11 b to uniformly irradiate the liquid crystal panel 3 from behind.

  FIG. 3A is a perspective view illustrating a state before the light guide plate 9 and the circuit board 13 according to the present embodiment are bonded, and FIG. 3B is a diagram illustrating the end surface 9a of the light guide plate 9 according to the present embodiment. It is a perspective view which shows the state by which LED12 was distribute | arranged to the position which opposes. In FIG. 3B, the arrow indicates the optical path of the light emitted from the light source 12, and the circuit board 13 is indicated by a broken line.

  As in the first embodiment, the gap between the circuit board 13 and the light guide plate 9 can be eliminated by housing and bonding the double-sided tape 14 in the recess 9b. As a result, the gap between the circuit board 13 and the light guide plate 9 that has conventionally occurred can be eliminated, light leaking from the gap is reduced, and the amount of light incident from the end surface 9a of the light guide plate 9 is increased. Can do.

  In addition, the light guide plate 9 according to the present embodiment is provided with a plurality of recesses 9b, and the double-sided tape 14 is divided into a plurality of parts so as to correspond thereto. Further, when the circuit board 13 and the light guide plate 9 are bonded, the recess 9b is formed so that the recess 9b is not disposed at a position facing the LED 12.

  Thereby, the loss which arises when the light radiate | emitted from the light source 12 is interrupted | blocked by the recessed part 9b, or is spread | diffused with the double-sided tape accommodated in the recessed part 9b can be reduced. The shape of the concave portion 9b is not necessarily a rectangular parallelepiped shape, and may be an elliptical shape or a slit shape as long as the circuit board 13 and the light guide plate 9 are stably bonded and do not block the progress of light. At this time, it is necessary to match the shape of the double-sided tape 14 with the shape of the recess 9b. Further, the recess may be provided on the circuit board 13 in addition to the light guide plate 9. When the circuit board 13 is provided with a recess, the recess 9b does not block the optical path of the light incident on the inside of the light guide plate, and the light loss can be further reduced. Further, the double-sided tape 14 may be accommodated by providing recesses in both the circuit board 13 and the light guide plate 9.

  Further, the light source 12, the circuit board 13, the light collecting sheets 11a and 11b, the reflection sheet 8, the diffusion sheet 10, and the double-sided tape 14 have the same configuration as that shown in Example 1, and the position of the recess 9b is shown in FIG. In this manner, the light guide plate 9 may be arranged on the periphery.

[Third embodiment]
In the present embodiment, the same reference numerals are given to portions common to the conventional example and the first and second embodiments, and the description thereof is omitted. Similarly to the conventional example shown in FIG. 6, the liquid crystal display device according to the present embodiment includes the liquid crystal panel 3, the diffusion sheet 10, the light collecting sheets 11 a and 11 b, the light guide plate 9, the light source 12, and the reflection sheet 8. Yes. Here, the plurality of LEDs 12 are arranged at positions facing the end surface 9 a of the light guide plate 9.

  With this configuration, the light emitted from the LED 12 enters the light guide plate 9 from the end face 9 a of the light guide plate 9, spreads to every corner while repeating irregular reflection in the light guide plate 9, and is laminated on the lower surface of the light guide plate 9. The light is reflected upward by 8 and emitted from the upper surface of the light guide plate 9, and sequentially passes through the diffusion sheet 10 and the light collecting sheets 11 a and 11 b to uniformly irradiate the liquid crystal panel 3 from behind.

  FIG. 5A is a perspective view showing a state before the light guide plate 9 and the circuit board 13 according to the present embodiment are bonded, and FIG. 5B is a diagram illustrating the end surface 9a of the light guide plate 9 according to the present embodiment. This shows a state in which the LEDs 12 are arranged at opposing positions. In FIG. 5B, the arrow indicates the optical path of the light emitted from the light source 12, and the circuit board 13 is indicated by a broken line.

  The light guide plate 9 according to the present embodiment has a protruding portion 9c on the end surface 9a, and has a structure in which the circuit board 13 and the light guide plate 9 are integrated by bonding a double-sided tape 14 to the upper surface of the protruding portion 9c. Further, the upper surface of the protruding portion 9 is disposed at a position lower than the upper surface of the light guide plate 9 by the thickness of the double-sided tape, and these can be integrated without generating a gap between the circuit board 13 and the light guide plate 9.

  Further, when the circuit board 13 and the light guide plate 9 are integrated, the protruding portion 9c protrudes between the adjacent LEDs 12, so that the light emitted from the LED 12 enters the light guide plate 9 without being blocked by the protruding portion 9c. To do. Thereby, the loss of light can be suppressed and the light utilization efficiency can be further increased. In addition, the shape of the protrusion part 9c does not need to be a rectangular parallelepiped shape, and will not be specifically limited if the circuit board 13 and the light-guide plate 9 can be adhere | attached stably. Moreover, although the upper surface of the protrusion 9c is arranged at a position lower than the upper surface of the light guide plate 9, the same effect can be obtained even if a recess is provided in the circuit board 13.

  The present invention is not limited to the above-described embodiments, and various modifications are possible. Embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the present invention. Included in the technical scope. For example, the incident surface of the light source of the light guide plate 9 is not limited to one surface of the end surface 9a, and the light source may be provided on all side surfaces and the corresponding concave portion 9b may be provided on the light guide plate 9. Further, the light guide plate 9 can be provided with both the protruding portion 9c and the concave portion 9b so that the light guide plate 9 and the circuit board 13 can be integrated stably.

  The present invention can be used for an edge light type liquid crystal display device, and can be used for a portable device such as a video camera, a digital camera, and a mobile phone having a small liquid crystal display.

(A) is a perspective view which shows the state before the circuit board with which the light-guide plate and light emitting diode which concern on this invention were mounted is adhere | attached, (b) is the light-guide plate and circuit board which adhere | attached this invention. It is the perspective view which showed the state after, (c) is sectional drawing in AA 'of (b). It is a perspective view which shows the state before the circuit board with which the light-guide plate and light emitting diode which concern on this invention were mounted is adhere | attached. (A) is a perspective view which shows the state before the circuit board with which the light-guide plate and light emitting diode which concern on this invention were mounted is adhere | attached, (b) is the light-guide plate and circuit board which adhere | attached this invention. It is the perspective view which showed the state after. It is a perspective view which shows the state before the circuit board with which the light-guide plate and light emitting diode which concern on this invention were mounted is adhere | attached. FIG. 3A is a perspective view showing a state before the light guide plate according to the present invention and the circuit board on which the light emitting diode is mounted are bonded, and FIG. 3B is a view showing the bond between the light guide plate according to the present invention and the circuit board. It is the perspective view which showed the state after being done. It is an oblique view which decomposes | disassembles and shows the conventional liquid crystal display device. (A) is a perspective view showing a state before bonding of a circuit board on which a light guide plate and a light emitting diode are mounted; (b) is a perspective view showing a state after bonding of a circuit board on which a light guide plate and a light emitting diode are mounted; (C) is sectional drawing in AA 'of (b).

Explanation of symbols

1 Front frame 2 Back case 3 LCD panel 4 Driver IC
DESCRIPTION OF SYMBOLS 5 Control board 6 Resin frame 7 Fixing tape 8 Reflective sheet 9 Light guide plate 9a End surface 9b Recessed part 9c Projection part 10 Diffusion sheet 11 Condensing sheet 12 Light source (light emitting diode)
13 Circuit board 14 Double-sided tape

Claims (8)

A light guide plate, a circuit board integrated with the light guide plate, a plurality of light sources mounted in parallel on the circuit board, and a reflection sheet provided on the lower surface of the light guide plate and reflecting light upward In the illumination device for a display device, the light guide plate and the circuit board are bonded via a double-sided tape, and the light source is disposed at a position facing one end surface of the light guide plate.
The illumination device for a display device, wherein the double-sided tape is accommodated in a recess formed on at least one of the light guide plate surface and the circuit board surface.   2. The illumination device for a display device according to claim 1, wherein, in the circuit board, the double-sided tape is not disposed at a position facing a light exit surface of the light source. A light guide plate, a circuit board integrated with the light guide plate, a plurality of light sources mounted in parallel on the circuit board, and a reflection sheet provided on the lower surface of the light guide plate and reflecting light upward In the illumination device for a display device in which the light source is disposed at a position facing one end surface of the light guide plate,
One end surface of the light guide plate facing the light source is provided with a protrusion protruding between the light sources, and the upper surface of the protrusion is lower than the upper surface of the light guide plate by the thickness of the double-sided tape, An illumination device for a display device, wherein the protruding portion is bonded to the circuit board via a double-sided tape.   The lighting device for a display device according to any one of claims 1 to 3, wherein the adhesive strength of the double-sided tape differs between the front surface and the back surface.   The illumination device for a display device according to any one of claims 1 to 4, wherein the light source is a light emitting diode.   The illumination device for a display device according to claim 1, wherein the circuit board is a flexible circuit board.   A display device comprising: the display device illumination device according to claim 1; and a light control member that controls light emitted from the light source.   The display device according to claim 7, wherein the light control member is a liquid crystal panel.

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