JP2006030910A - Back light device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a display panel high in luminance and uniformity ratio by equipping a back light device with many light emitting diodes, and simplifying the structure for lower costs. <P>SOLUTION: A diffusion plate 15 which transmits and reflects illumination light emitted by many LEDs 12 is arranged between the liquid crystal panel 2 and a light source unit 7 where the LEDs 12 are arrayed. The diffusion plate 15 has, in a pattern formation area 20 having an external diameter a little larger than the external diameter of the LEDs 12, a dimming pattern 18 composed of a group of 1st large-diameter dimming dots 19a formed in a 1st area 20a having an internal diameter nearly as large as the LEDs 12 and a group of 2nd small-diameter dimming dots 19b formed in a 2nd area 20b at the outer peripheral part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a backlight device that supplies illumination light emitted from a large number of light emitting diodes to a transmissive display panel such as a transmissive liquid crystal display (LCD), and in particular, from a group of light emitting diodes. The present invention relates to a backlight device that uniformizes incident light and supplies the same to a transmissive display panel.

  The liquid crystal display device has a larger display screen, lighter weight, thinner thickness, lower power consumption, etc., compared with a cathode ray tube (CRT), for example, a self-luminous PDP (Plasma Display). Panel) and the like are used for television receivers and various displays. A liquid crystal display device encapsulates liquid crystal between two transparent substrates of various sizes, and changes the light transmittance by changing the direction of liquid crystal molecules by applying a voltage to optically display a predetermined image or the like. To do.

  In the liquid crystal display device, since the liquid crystal itself is not a self-luminous body, for example, a backlight unit that functions as a light source is provided on the back surface of the liquid crystal panel. The backlight unit includes, for example, a light source body, a light guide plate, a reflection film, a lens sheet, or a diffusion plate, and supplies illumination light with uniform luminance over the entire surface to the liquid crystal panel. Cold light source fluorescent lamps (CCLF: Cold Cathode Fluorescent Lamps) in which mercury or xenon is enclosed in a fluorescent tube are used for the backlight unit as a conventional light source. Alternatively, there is a problem of solving problems such as uniformity due to the presence of a low luminance region on the cathode side.

  By the way, in a large-sized liquid crystal display device, an area light backlight (area light backlight) device that generally arranges a plurality of long cold cathode fluorescent lamps on the back surface of a diffusion plate and supplies illumination light to a liquid crystal panel. Is provided. Such an area light type backlight device is also required to solve the same problem as the cold cathode fluorescent lamp described above. In particular, in a large-sized television receiver exceeding 40 inches, high brightness and high uniformity are obtained. The problem has become more prominent.

  In various backlight devices, a diffusion plate that controls transmission and diffusion of illumination light emitted from the light source body is disposed between the light source body and the liquid crystal panel. The diffusion plate is generally formed of a transparent acrylic resin or the like, and a dimming pattern having a function of transmitting a part of illumination light incident on a portion facing the light source body and reflecting a part thereof is formed.

  In Patent Document 1, a plurality of strip-shaped dimming patterns formed in a region facing a fluorescent tube includes a diffusion plate that is configured by a large number of reflective dots. The diffuser plate is formed so that the area of the reflection dot decreases as it moves away from the axis of the fluorescent tube, so that the light transmittance increases as the distance from the fluorescent tube increases, and illumination light with uniform brightness as a whole is emitted. Acts to be.

Japanese Patent Laid-Open No. 6-301034

  By the way, in the area light type backlight device, in place of the cold cathode fluorescent lamp described above, a large number of red, green and blue light emitting diodes (hereinafter referred to as LEDs: LED: Light Emitting Diode) 2 are provided on the back side of the diffusion plate. An LED area light type backlight that obtains white light by dimensionally arranging has attracted attention. Such an LED backlight device is designed to reduce the cost as the cost of the LED is reduced and to display a high luminance on a large liquid crystal panel with low power consumption.

  Also in the LED backlight device, a diffusion plate is arranged between a liquid crystal panel and an LED unit in which a large number of LEDs are arranged in an array. For example, a large number of light control patterns are arranged so as to face each LED on the diffusion plate. The correspondence to form is also considered. Each dimming pattern increases the brightness of the illumination light emitted from the opposing LEDs so that the illumination light is supplied to the liquid crystal panel with a uniform amount of light from the entire surface by controlling the transmission and diffusion in the diffusion plate. High uniformity can be achieved.

  However, in an LED backlight device, a large amount of heat generated from a large number of LEDs acts on a diffusion plate made of transparent acrylic resin, causing a large dimensional change in the diffusion plate and adjusting with the opposing LED. In some cases, the optical pattern may be misaligned. Further, in the LED backlight device, a positional deviation between the LED and the dimming pattern is generated due to variations in the dimensional accuracy and assembly accuracy of the liquid crystal panel, the LED unit, or the diffusion plate, and the dimming pattern printing accuracy. There was a case.

  In the LED backlight device, it is extremely difficult to accurately position the LED and the dimming pattern because of the various factors described above. In the LED backlight device, the constituent members must be manufactured with high accuracy and precise assembly must be performed, which makes it difficult to reduce the cost. In the LED backlight device, as the liquid crystal display device is increased in size and brightness, the positional deviation between the LED and the dimming pattern becomes larger, and problems such as color unevenness and the generation of a lamp image become remarkable.

  In the LED backlight device, when the dimming pattern is formed on the diffusion plate with a large area, the light transmittance is greatly reduced, so that the luminance of the display panel is lowered. In an LED backlight device, for example, when trying to cope with higher brightness by using more LEDs, it is extremely difficult to cope with not only increase in cost and power consumption but also increase in heat generation. It becomes.

  Accordingly, an object of the present invention is to provide a backlight device with a simple structure and a low cost, which is provided with a large number of light emitting diodes to achieve high luminance and high uniformity.

  A backlight device according to the present invention that achieves the above-described object is disposed between a transmissive display panel and a light source unit in which a large number of light emitting diodes are arranged, and transmits and reflects illumination light emitted from the light source unit. Thus, a diffusion plate is provided that diffuses over the entire surface and supplies the diffused light to the display panel. The backlight device has a dimming pattern in which a diffusion plate suppresses the light transmittance of illumination light emitted from each light emitting diode in each region facing each light emitting diode on a transparent synthetic resin substrate and diffuses to the surroundings Formed. The backlight device has a large number of dimming dots printed by light-reflective ink in the area where each dimming pattern is larger in diameter than each light-emitting diode. It is arranged so as to gradually increase toward the region.

  Further, in the backlight device, a large number of light control dots constituting each light control pattern are formed with a light control dot in the peripheral region having a small diameter with respect to the light control dots in the central region. Further, in the backlight device, a large number of dimming dots constituting each dimming pattern are formed with the density of the peripheral region being sparse relative to the central region. The backlight device includes a light source unit in which a large number of red light emitting diodes, green light emitting diodes, and blue light emitting diodes are arranged in a predetermined order so that color display is performed on a transmissive display panel.

  In the backlight device, a large number of light emitting diode groups provided in the light source unit are turned on to supply high-capacity illumination light to the display panel, so that the display panel performs display with high luminance. In the backlight device, each dimming pattern formed on the diffusion plate so as to face each light emitting diode reflects a part of the illumination light emitted from the opposing light emitting diode, thereby generating a partial high brightness region. The illumination light is made uniform from the entire surface of the diffusion plate and supplied to the display panel. In the backlight device, each dimming pattern composed of a large number of dimming dots reduces the loss by transmitting the illumination light at a predetermined light transmittance so that the display panel can display high brightness. To do. In the backlight device, even if there is a slight misalignment between the opposing light emitting diode and the light control pattern, the transmission and reflection functions are achieved by the light control pattern formed in a larger diameter area than the light emitting diode. To do.

  According to the backlight device of the present invention, a high luminance display is performed by using a large number of light emitting diodes as light sources. According to the backlight device, the LED and dimming which are opposed to variations in the dimensional change of the diffusion plate due to heat generated from a large number of LEDs, the dimensional accuracy or assembly accuracy of each component, and the printing accuracy of the dimming pattern, etc. Since the pattern maintains the light transmittance and the positional deviation correction is performed, the brightness and uniformity of the display panel can be increased, and the manufacturing cost and assembly cost of each component can be reduced. Figured.

  Hereinafter, a transmissive liquid crystal color display device (hereinafter abbreviated as a display device) 1 shown in the drawings as an embodiment of the present invention will be described in detail. The display device 1 is used for a display panel such as a television receiver or a display monitor having a large display screen of 40 inches or more, for example. As shown in FIGS. 1 and 2, the display device 1 includes a liquid crystal panel unit 2 and a backlight unit 3 that is combined with the back side of the liquid crystal panel unit 2 to supply illumination light. The liquid crystal panel unit 2 includes a frame-shaped front frame member 4, a liquid crystal panel 5, and an outer peripheral edge portion of the liquid crystal panel 5 sandwiched between the front frame member 4 via spacers 2 </ b> A, 2 </ b> B, guide members 2 </ b> C, and the like. And a frame-like back frame member 6 held by

  Although not described in detail, the liquid crystal panel 5 encloses a liquid crystal between a first glass substrate and a second glass substrate, which are held at an opposing interval by spacer beads or the like, and applies a voltage to the liquid crystal to apply liquid crystal. Change the light transmittance by changing the direction of the molecule. In the liquid crystal panel 5, a striped transparent electrode, an insulating film, and an alignment film are formed on the inner surface of the first glass substrate. In the liquid crystal panel 5, a color filter of three primary colors, an overcoat layer, a striped transparent electrode, and an alignment film are formed on the inner surface of the second glass substrate. In the liquid crystal panel 5, a deflection film and a retardation film are bonded to the surfaces of the first glass substrate and the second glass substrate.

  The liquid crystal panel 5 has a polyimide alignment film in which liquid crystal molecules are horizontally aligned at the interface, and the deflection film and the retardation film achromatic and white the wavelength characteristics to achieve full color using a color filter. Etc. are displayed in color. In addition, about the liquid crystal panel 5, it is not limited to this structure, Of course, it may be a liquid crystal panel provided with the various structure provided conventionally.

  The backlight unit 3 is arranged on the back side of the liquid crystal panel unit 2 described above and supplies a light source unit 7 for supplying illumination light, a heat radiating unit 8 for radiating heat generated in the light source unit 7, and these light source units 7. And a heat sink unit 8 and a back panel 9 which is combined with the front frame member 4 and the rear frame member 6 and constitutes a mounting member for a housing (not shown). The backlight unit 3 has an outer dimension that is opposed to the entire rear surface of the liquid crystal panel unit 2 and is combined in a state where the opposed space portions facing each other are optically sealed.

  In the backlight unit 3, the light source unit 7 includes an optical sheet block 10 and a light source block 11 having a large number of light emitting diodes (hereinafter referred to as LEDs) 12. The optical sheet block 10 is installed opposite to the back side of the liquid crystal panel 5, and details thereof are omitted. However, the optical sheet block 10 is an optical film formed by laminating various optical function sheets such as a polarizing film, a retardation film, a prism sheet, or a diffusion film. The sheet laminated body 13, the diffusion light guide plate 14, the diffusion plate 15, the reflection plate 16, and the like are included.

  The back panel 9 is formed of, for example, a horizontally-long rectangular plate having a size substantially equal to the outer shape of the liquid crystal panel 5 by using an aluminum material that is relatively light and has mechanical rigidity. The back panel 9 itself has thermal conductivity, and thus has a function of dissipating heat generated from the LEDs 12 and circuit components. The back panel 9 is formed with an outer peripheral wall portion 9a combined with the back frame member 6 at the outer peripheral portion, and fixes a plurality of mounting portions 9b for mounting the optical stud member 17 and a heat radiating plate 24 as will be described later. A pull-out opening or the like for drawing out the mounting hole or the lead wire 21 is formed. The back panel 9 is assembled such that the heat radiation unit 8, the light source unit 7, and the liquid crystal panel 5 are superimposed on the front surface, and further assembled to the mounting portion of the housing.

  Although not described in detail, the optical sheet laminate 13 is a functional sheet that decomposes the illumination light supplied from the light source block 11 and incident on the liquid crystal panel 5 into orthogonal polarization components, and compensates for the phase difference of the light wave and wide-angle viewing angle. A plurality of optical function sheets having various optical functions, such as a functional sheet for preventing the coloration and coloring or a functional sheet for diffusing illumination light, are laminated. The optical sheet laminate 13 is not limited to the optical function sheet described above, and may include, for example, a brightness enhancement film for improving brightness, a retardation film, or two upper and lower diffusion sheets sandwiching a prism sheet. Good.

  In the optical sheet block 10, the diffusion light guide plate 14 is disposed on the main surface side facing the liquid crystal panel 5 of the optical sheet laminate 13, and the illumination light supplied from the light source block 11 is incident from the back side. The diffusion light guide plate 14 is made of a slightly thick plate body formed of a transparent synthetic resin material having a light guide property, such as an acrylic resin or a polycarbonate resin. The diffusion light guide plate 14 guides the illumination light incident from one main surface side while diffusing and refracting the illumination light inside, and makes the light incident on the optical sheet laminate 13 from the other main surface side. The diffusion light guide plate 14 is laminated on the optical sheet laminate 13 as shown in FIG. 2, and is attached to the outer peripheral wall portion 9a of the back panel 9 via the bracket member 14A.

  In the optical sheet block 10, as shown in FIG. 2, the diffusion plate 15 and the reflection plate 16 are held by a large number of optical stud members 17 such that the opposing distance between them and the opposing distance between the diffusion light guide plate 14 described above. And attached to the back panel 9. The diffusion plate 15 is a plate material formed of a transparent synthetic resin material, for example, an acrylic resin, and the illumination light supplied from the light source block 11 is incident thereon. As shown in FIGS. 2 and 3, the diffusion plate 15 is formed by arranging a large number of light control patterns 18. Each dimming pattern 18 is formed to face a large number of LEDs 12 of the light source block 11 arranged in an array as will be described in detail later.

  The diffusion plate 15 is formed with a fitting hole 15a into which the optical stud member 17 is fitted at an appropriate position. On the diffusion plate 15, when the LEDs 12 are arranged in the horizontal direction in four rows on the light source block 11 and auxiliary LEDs 12 are also arranged on both sides, although not shown, the dimming is performed to face these LEDs 12. A pattern 18 is formed.

  As shown in FIG. 4, the diffusion plate 15 is formed by printing each dimming pattern 18 with light-reflective ink in a pattern forming region 20 having a diameter D slightly larger than the outer diameter d of the LED 12 indicated by a broken line in the figure. Further, it is constituted by a large number of light control dots 19. Each dimming pattern 18 forms a first dimming dot group 19a having a large diameter in the first area 20a having an inner diameter substantially equal to that of the LED 12, and in the second area 20b on the outer periphery surrounding the first area 20a. Each of them forms a second light control dot group 19b having a small diameter.

  Each light control pattern 18 is formed by using, for example, a screen printing method or the like, using a light reflective ink in which various ink raw materials including a light shielding agent and a diffusing agent are mixed at a predetermined ratio. The light-reflective ink is used as a light-shielding agent, for example, titanium oxide, barium sulfide, calcium carbonate, silicon oxide, alumina oxide, zinc oxide, nickel oxide, calcium hydroxide, lithium sulfide, iron trioxide, methacrylic resin powder, mica ( Sericite), porcelain clay powder, kaolin, bentonite, gold powder or pulp fiber. The light-reflective ink uses, for example, silicon oxide, glass beads, glass fine powder, glass fiber, liquid silicon, crystal powder, gold-plated resin beads, cholesteric liquid crystal liquid or recrystallized acrylic resin powder as a diffusing agent. .

  The diffusing plate 15 shields the illumination light, in which each dimming pattern 18 is emitted from the corresponding LED 12 and travels straight, by reflecting the dimming dots 19 at the site where the dimming dots 19 are formed. Permeate at the site of formation. The diffusion plate 15 adjusts the amount of illumination light directly incident from each LED 12 by forming a dimming pattern 18 to reduce the occurrence of a partial high-brightness region, and uniformize the illumination light from the entire surface. It acts to be supplied to the optical sheet laminate 13.

  As described above, the diffusion plate 15 has the first dimming dot 19a group in the first region 20a having a large diameter and the second dimming dot 19b group in the second region 20b having a small diameter. The light transmittance of the illumination light is larger in the second region 20b than in the first region 20a. Therefore, in the diffusing plate 15, the adjustment of the transmission amount of the illumination light from the first region 20a where the incident light amount of the illumination light is large and the transmission amount of the illumination light from the second region 20b where the incident light amount is small is achieved. It acts as a so-called gradation pattern that blurs the shape of the light control pattern 18.

  In the light control pattern 18, for example, the diameter of the first region 20a is about 6 mm, the diameter of the second region 20b is about 8 mm, the dot diameter of the first light control dot 19a is about 0.5 mm, and the second region 20b. The dot diameter of the light control dot 19b is formed to be about 0.1 mm. The dimming pattern 18 is formed with a mutual interval of about 14 mm. Of course, the dimming pattern 18 is formed according to appropriate specifications according to the light emission amount of the LED 12 group, the interval between the LEDs 12, the size of the liquid crystal panel 5, the composition of the reflective ink, and the like.

  As described above, in the diffusion plate 15, each dimming pattern 18 is configured by a circular pattern having a diameter larger than the outer diameter of the LED 12 opposed as a whole. Therefore, the diffusion plate 15 has various dimensional accuracy, printing accuracy of each dimming pattern 18, expansion / contraction dimensional change due to heat generated from a large number of LEDs 12, dimensional accuracy of each component, assembly accuracy, and the like. Even if a slight misalignment occurs between the light control pattern 18 and the LED 12, the above-described illumination light transmission control is reliably performed. The diffusion plate 15 reduces the dimensional accuracy and assembly accuracy of the constituent members so that the cost can be reduced. The diffusion plate 15 also has a function of reflecting on the surface when part of the illumination light emitted from each LED 12 is incident beyond the critical angle.

  The reflection plate 16 reflects the dimming pattern 18 of the diffusion plate 15, the illumination light reflected on the surface, and the illumination light emitted to the periphery from the LED 12 and makes it incident on the diffusion plate 15. The reflection plate 16 is formed, for example, by bonding an expandable PET (polyethylene terephthalate) material containing a fluorescent agent to an aluminum base material. The reflective plate 16 is characterized in that the foaming PET material has a high reflectance characteristic of about 95% and has a feature that the reflective surface is not noticeable with a color tone different from the metallic luster color. Reflects efficiently. The reflection plate 16 also has a function of improving the reflectivity based on the principle of increased reflection by repeatedly reflecting the illumination light with the diffusion plate 15. Note that the reflection plate 16 may be formed of, for example, silver or stainless steel having a mirror surface.

  Although not described in detail, the reflecting plate 16 is formed with a large number of guide holes corresponding to the respective LEDs 12, and as shown in FIG. The reflection plate 16 prevents light leakage to the back side by such a structure.

  The optical sheet block 10 includes a large number of optical stud members 17, and these optical stud members 17 accurately maintain the parallelism between the main surfaces facing the diffusion plate 15 and the reflection plate 16 over the entire surface. In addition, the parallelism between the opposing main surfaces of the diffusion plate 15 and the diffusion light guide plate 14 is configured to be accurately maintained over the entire surface. The optical stud member 17 is a substantially columnar member integrally formed of milky white synthetic resin material having light guiding properties, mechanical rigidity, and a certain degree of elasticity, such as a polycarbonate resin, for example, as shown in FIG. 9 are attached to the attachment portions 9b of the substantially trapezoidal convex portion integrally formed on the inner surface of 9.

  In the back panel 9, the upper surface of the attachment portion 9 b constitutes the placement surface of the reflection plate 16, and the attachment hole 9 c is provided through each of the back panel 9. In the optical sheet block 10, the diffusion plate 15 and the reflection plate 16 are positioned and combined on the bottom surface 9 d with respect to the back panel 9 via the optical stud members 17. A large number of attachment holes 15a and 16a are formed in the diffusion plate 15 and the reflection plate 16 corresponding to the attachment holes 9c provided in the attachment portions 9b on the back panel 9 side.

  Each optical stud member 17 includes a shaft-shaped base portion 17a, a mounting portion 17b formed at the base end portion of the shaft-shaped base portion 17a, and a circumference of the shaft-shaped base portion 17a with a predetermined distance from the mounting portion 17b. A flange-shaped first receiving plate portion 17c integrally formed around the periphery, and a flange-shaped first receiving plate portion 17c integrally formed around the circumference of the shaft-shaped base portion 17a with a predetermined interval from the first receiving plate portion 17c. 2 receiving plate portion 17d. Each optical stud member 17 is formed with an axial length in which the shaft-like base portion 17a defines the facing distance between the attachment portion 9b of the back panel 9 and the diffusion light guide plate 14, and a predetermined length from the second receiving plate portion 17d. A step portion 17e is formed at the height position.

  Each optical stud member 17 is formed such that the shaft-like base portion 17a has a long conical shape in which the stepped portion 17e has a larger diameter than the mounting hole 15a of the diffusion plate 15 and gradually becomes smaller in diameter toward the tip portion. Has been. Each optical stud member 17 is formed with an axial stealing hole 17f in the axial base portion 17a located slightly above the stepped portion 17e. The meat stealing hole 17f is formed in the shaft base 17a in a range of a portion whose outer diameter is larger than that of the mounting hole 15a of the diffusion plate 15, and imparts convergence to this portion.

  In each optical stud member 17, the first receiving plate portion 17 c and the second receiving plate portion 17 d are formed with an interval that defines the facing interval between the diffusion plate 15 and the reflection plate 16. Each optical stud member 17 has a shaft-like base portion 17a formed with a portion having a first receiving plate portion 17c and a second receiving plate portion 17d having substantially the same diameter as the mounting hole 15a of the diffusion plate 15. Each optical stud member 17 has a mounting portion 17b whose outer diameter is substantially equal to the outer diameter of the mounting hole 9c on the back panel 9 side and is gradually larger than the mounting hole 9c in the axial direction. It has an arrowhead shape. Each optical stud member 17 is given converging habits when the mounting portion 17b forms a slit 17g from the large diameter portion toward the distal end side.

  Each optical stud member 17 has an attachment portion 17a formed so that the distance between the large diameter portion and the first receiving plate portion 17c is substantially equal to the thickness of the back panel 9 and the thickness of the reflection plate 16. In each optical stud member 17, the first receiving plate portion 17 c has a larger diameter than the mounting hole 16 a of the reflecting plate 16, and the second receiving plate portion 17 d has a larger diameter than the mounting hole 15 a of the diffusion plate 15. Has been formed.

  In the optical sheet block 10, the mounting hole 9 c and the mounting hole 16 a facing the reflection plate 16 are combined on the mounting portion 9 b of the back panel 9 so as to face each other. In the optical sheet block 10, each optical stud member 17 is pushed into the attachment portion 17 b from the bottom surface 9 d side of the back panel 9 from the attachment hole 16 a side of the reflection plate 16. In the optical sheet block 10, the mounting portion 17 b converges by the action of the slit 17 g and returns to the natural state after passing through the mounting hole 9 c on the back panel 9 side, whereby each optical stud member 17 is prevented from coming off. It is assembled in a standing state on the mounting portion 9b.

  In the optical sheet block 10, each optical stud member 17 sandwiches the mounting portion 9 b and the reflection plate 16 in the thickness direction between the mounting portion 17 b and the first receiving plate portion 17 c, so that The reflection plate 16 is held in a positioned state. In the optical sheet block 10, in this state, each optical stud member 17 protrudes from the first receiving plate portion 17c of the shaft-like base portion 17a from the reflecting plate 16 on the mounting portion 9b of the back panel 9. Established.

  In the optical sheet block 10, the diffusion plate 15 is combined with each optical stud member 17 by fitting each mounting hole 15 a into the opposite tip portion 17 h. In the optical sheet block 10, each optical stud member 17 converges the large diameter portion by the action of the meat stealing hole 17 f so that the diffusion plate 15 is pushed in the axial direction. In the optical sheet block 10, the diffusion plate 15 gets over the step 17e against each optical stud member 17, hits the second receiving plate portion 17d, and between these step portions 17e and the second receiving plate portion 17d. It is pinched.

  In the optical sheet block 10, each optical stud member 17 projects an upper portion from the diffusion plate 15 from the second receiving plate portion 17 d of the axial base portion 17 a. In the optical sheet block 10, the diffusion light guide plate 14 in which the optical sheet laminate 13 is overlapped is assembled to the tip end portion 17 h of each optical stud member 17 so that the bottom surface side thereof is abutted.

  In the optical sheet block 10 configured as described above, a large number of optical stud members 17 that are respectively assembled on the bottom surface 9d of the back panel 9 by a simple method of pushing the mounting portion 17b into the mounting hole 9c. And the reflection plate 16 are positioned, and the function of accurately maintaining the facing distance between the diffusion plate 15, the reflection plate 16, the diffusion light guide plate 14, and the optical sheet laminate 13 is achieved. The optical sheet block 10 includes the plurality of optical stud members 17 described above, thereby eliminating the need for complicated positioning structures and spacing structures, and simplifying the assembly process. Each optical stud member 17 can be used interchangeably with liquid crystal panels 5 of various sizes, and parts can be shared.

  In addition, about the optical stud member 17, it is not limited to the structure mentioned above, The specific structure of each part is formed with the structure of the optical sheet block 10. FIG. The optical stud member 17 is attached by being pushed into the attachment hole 9c of the back panel 9 by, for example, forming the slit 17g of the attachment portion 17b and imparting convergence habitability. The convex portion may be formed integrally and fitted into the mounting hole 9c having a key groove on the inner peripheral portion, and then rotated to be prevented from coming off.

  In the optical sheet block 10, the illumination light emitted from the light source block 11 in the light guide space H configured between the diffusion light guide plate 14 and the reflection plate 16 is obtained by precisely positioning each member. Since the operations such as light guide, diffusion, and reflection are performed in a stable state, the occurrence of color unevenness in the liquid crystal panel 5 is suppressed. In the optical sheet block 10, each optical stud member 17 provided in the light guide space portion H is formed of milky white light guide synthetic resin material and diffuses illumination light incident on the inside thereof from its outer peripheral surface, so that a tip portion 17h is formed. The illumination light is uniformly incident on the diffusing light guide plate 14 from the light guide space portion H by preventing the light from being partially illuminated.

  In the backlight unit 3, the light source unit 7 includes the optical sheet block 10 described above, so that illumination light emitted from each LED 12 of the light source block 11 is efficiently incident on the liquid crystal panel unit 2 in a stable state. So that As shown in FIG. 5, the light source block 11 includes four rows of light emitting arrays 11 </ b> A to 11 </ b> D arranged in the lateral direction on the bottom surface 9 d of the back panel 9. The light source unit 11 includes a plurality of light source block bodies 21 in which the light emitting arrays 11A to 11D are arranged in the length direction.

  As shown in FIGS. 2 and 6, each light source block body 21 includes a plurality of red LEDs, green LEDs, and blue LEDs (collectively referred to as LEDs 12), and these LEDs 12 are predetermined on the main surface 22a in the length direction. And a horizontally-long rectangular wiring board 22 which is mounted in this order. In the light source block 11, the number of the light source block bodies 21 and the number of LEDs 12 to be mounted on the respective light source block bodies 21 are appropriately determined according to the size of the liquid crystal panel 5, the light emission capability of each LED 12, and the like.

  Although not shown, the light source block 21 is formed with a wiring pattern for connecting the LEDs 12 in series, lands for connecting the terminals of the LEDs 12, and the like on the main surface 22 a of the wiring board 22. Each of the wiring boards 22 is formed with the same specifications, and is located in the vicinity of one side of the main surface 22a in the width direction and on both sides in the longitudinal direction, and the first connector 23A on the signal output side and the signal input side A second connector 23B is mounted.

  As shown in FIG. 5, the light source block 11 includes a first light emitting array 11A, a second light emitting array 11B, a third light emitting array 11C, and a fourth light emitting array 11D. The wiring boards 22 are arranged side by side in the length direction with the side where the connectors are mounted facing each other. In the light source block 11, the adjacent wiring boards 22 in each row are arranged so that the first connector 23A and the second connector 23B are adjacent to each other, so that these are connected by a lead wire with a connector (not shown) and the shortest wiring is provided. To be done.

  The light source block 11 includes a light emitting array 11A in the first column, a light emitting array 11B in the second column, a light emitting array 11C in the third column, and a light emitting array 11D in the fourth column for signal output. The lead wire is pulled out, bundled with a clamper, and pulled out to the back side of the back panel 9 through the pull-out opening. In the light source block 11, the efficiency of the space and the simplification of the wiring process are achieved by providing a signal input / output lead wire holding space and a guide structure using the space between the light emitting arrays 11A to 11D. In the light source block 11, each light emitting array 11 </ b> A to 11 </ b> D is prevented from being mistaken in the assembly of the wiring boards 22 depending on the positions of the first connector 20 </ b> A and the second connector 20 </ b> B. Simplification of process or common use of lead wires is achieved.

  The light source block 21 is mounted on the main surface 22a of the wiring board 22 by arranging red LEDs, green LEDs, and blue LEDs, which are combined in an appropriate number as described above, in this order on the same axis. . Although not described in detail, each LED 12 has a light emitting element held by the resin holder and a terminal drawn from the resin holder. Each LED 12 emits illumination light from the light emitting element, and heat is also generated at that time.

  Since the display device 1 forms the light guide space portion H whose periphery is sealed by combining the light source block 11 on the back side of the optical sheet block 10 as described above, the heat generated from the multiple LEDs 12 is large. It becomes a quantity of heat and is in a state of being trapped in the light guide space H. The display device 1 efficiently dissipates the heat trapped in the light guide space H by the heat radiating unit 8, changes the characteristics of the optical sheet bodies described above of the optical sheet block 10, and destabilizes the lighting state of the LEDs 12. The color unevenness of the liquid crystal panel 5 and the instability of the operation of the electronic parts constituting the circuit unit are suppressed.

  The heat radiating unit 8 is provided for each of the light emitting arrays 11A to 11D described above and serves as a mounting member for the light source block body 21, and a plurality of heat pipes 25 respectively attached to the heat radiating plates 24. The heat pipe 25 is configured by a heat sink 26 to which both ends thereof are connected, a cooling fan that promotes a cooling function of the heat sink, and the like. The heat radiating unit 8 forms an efficient heat conduction path for the heat sink by assembling a heat pipe 25 integrally with each heat radiating plate 24 as will be described in detail later.

  Each of the heat radiating plates 24 is made of an aluminum material having excellent thermal conductivity, good workability, light weight and low cost, and has a long length substantially equal to the length and width of each of the light emitting arrays 11A to 11D described above by extrusion. It is formed in a rectangular plate shape. Each heat dissipating plate 24 also serves as an attachment member for the light source block body 21, and thus is formed with a predetermined thickness having mechanical rigidity. Note that each heat radiating plate 24 is not limited to an aluminum material, and may be formed of, for example, an aluminum alloy material, a magnesium alloy material, a silver alloy material, or a copper material having good thermal conductivity. When each heat radiating plate 24 is relatively small, it is formed, for example, by pressing or cutting, and the wiring board 22 is fixed on the main surface 24a with mounting screws.

  Each heat radiation plate 24 is formed with a heat pipe fitting recess 24b having a substantially arch-shaped cross section in which the heat pipe 25 is fitted on the back side. The heat pipe fitting recess 24b has an opening width substantially equal to the outer diameter of the heat pipe 25 and is formed with a slightly small height (depth) so that the heat pipe 25 is not interposed via a holding member or the like. It is formed with an opening shape that can be temporarily held. Each heat radiating plate 24 arranges the heat pipe 25 at a position closer to the LED mounting region where the temperature of the wiring board 22 is highest by the heat pipe fitting recess 24b.

  The heat pipe 25 is a member generally used for conducting heat from a high-temperature power supply unit or the like to various heat dissipating means in various electronic devices, and is made of a metal pipe such as copper having excellent heat conductivity. It is configured by enclosing a conductive medium such as water that is vaporized at a predetermined temperature in a state where the inside of the material is exhausted, and has a highly efficient heat conduction capability. As described above, the heat pipe 25 is integrally assembled with each heat radiating plate 24, and both ends thereof are connected to the heat sink 26 together with each heat radiating plate 24. In the heat pipe 25, the conduction medium enclosed inside receives heat conduction from the high-temperature side heat radiating plate 24 and vaporizes from liquid to gas. In the heat pipe 25, the vaporized conductive medium flows through the pipe to the connection portion with the low-temperature heat sink 26 and is cooled, thereby releasing condensation heat and liquefying. In the heat pipe 25, the liquefied conductive medium moves to the heat radiating plate 24 side by a capillary phenomenon in a plurality of longitudinal grooves or porous layers formed on the inner wall of the metal pipe and circulates in the pipe. As a result, it has a highly efficient heat conduction effect.

  In the heat radiating unit 8, the heat pipe 25 having a high efficiency of heat conduction is integrated and attached to the heat radiating plate 24 having the above-described configuration, so that the heat pipe 25 is close to the area immediately below the arrangement region of the LEDs 12 of the heat source. Thus, the configuration is extended. In the heat dissipation unit 8, the wiring board 22 on which each LED 12 is mounted, the heat dissipation plate 24 that holds the wiring board 22, and the heat pipe 25 are overlapped with each other to form a heat conductor to the heat sink 26. . In the heat dissipating unit 8, space efficiency is achieved by such a configuration, and heat generated from each LED 12 is conducted to the heat sink 26 very efficiently to dissipate heat, thereby reducing the high temperature of the light guide space H and the backlight. The unit 3 supplies illumination light to the liquid crystal panel 5 with a stable operation.

  In the backlight unit 3, as described above, each of the diffusion plates 15 has a large area located in the first region 20 a having an inner diameter substantially equal to the LED 12 in the pattern formation region 20 having a diameter D slightly larger than the outer diameter d of the LED 12. The dimming pattern 18 is configured by the first dimming dot group 19a having a diameter and the second dimming dot group 19b having a small diameter located in the second region 20b on the outer periphery. In the backlight unit 3, when the high-precision second light control dots 19b are formed by the screen printing method, the printing conditions such as the accuracy of the printing holes formed in the metal mask or the composition and viscosity of the light-reflective ink are set. It is necessary to consider carefully.

  The dimming pattern 30 shown as the second embodiment in FIG. 7 includes a large number of dimming dots 31 in the pattern formation region 20 having a diameter D slightly larger than the outer diameter d of the LED 12. The configuration formed by the screen printing method is the same as that of the light control pattern 18 described above, but is characterized in that each light control dot 31 is formed with the same diameter. Each dimming pattern 30 has the other configuration substantially the same as that of the dimming pattern 18 described above, and thus the description thereof is omitted.

  Each dimming pattern 30 is also configured by printing a large number of dimming dots 31 with a light-reflective ink in the pattern formation region 20 having a diameter D slightly larger than the outer diameter d of the LED 12. Each dimming pattern 30 has a large number of dimming dots 31 in the first area 20a having an inner diameter substantially equal to that of the LED 12 and the second area 20b on the outer periphery surrounding the first area 20a with different printing densities. It is formed. Each of the light control patterns 30 is formed by forming the light control dots 31a in the first region 20a with a high print density, and forming the light control dots 31b through the print density in the second region 20b with a low density.

  Each dimming pattern 30 also reflects the illumination light emitted from the opposing LEDs 12 and going straight as described above by the dimming dots 31 and transmitted through the non-formation sites of the dimming dots 31. . The diffusion plate 15 suppresses the amount of transmitted illumination light in the first region 20a in which the printing density of the light control dots 31 is dense and increases in the second region 20b in which the printing density is sparse. The diffusion plate 15 adjusts the amount of illumination light that is directly incident from each LED 12 by the light control dots 31 to reduce the occurrence of a partial high-brightness region, and uniformizes the illumination light from the entire surface to laminate the optical sheet. It acts to supply to the body 13.

It is a principal part disassembled perspective view of the display apparatus shown as embodiment. It is a principal part longitudinal cross-sectional view of a display apparatus. It is a top view of a diffusion plate. It is a principal part top view which shows the structure of a light control pattern. It is a top view of a light source unit. It is a perspective view of a light source block. It is a principal part top view which shows the structure of another light control pattern.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Display apparatus, 2 Liquid crystal panel unit, 3 Backlight unit, 5 Liquid crystal panel, 7 Light source unit, 8 Heat radiation unit, 9 Back panel, 10 Optical sheet block, 11 Light source block, 12 Light emitting diode (LED), 13 Optical sheet lamination | stacking Body, 14 diffusion light guide plate, 15 diffusion plate, 16 reflection plate, 17 optical stud member, 18 dimming pattern, 19 dimming dot, 20 pattern formation area, 21 light source block body, 22 wiring board, 24 heat radiation plate, 25 Heat pipe, 26 heat sink

Claims (4)

Arranged between the transmissive display panel and the light source unit in which a large number of light emitting diodes are arranged, the illumination light emitted from the light source unit is transmitted and reflected to be uniformed from the entire surface and supplied to the display panel. In a backlight device including a diffusion plate,
The diffusion plate is formed on a transparent synthetic resin substrate with a dimming pattern that diffuses to the surroundings while suppressing the light transmittance of the illumination light in each region facing each light emitting diode,
Each of the dimming patterns is composed of a large number of dimming dots that are printed and formed with light-reflective ink in a region having a diameter larger than that of the light emitting diodes, and reflect the illumination light. A backlight device characterized in that a gradation pattern is formed by gradually increasing the light transmittance of illumination light from a central region toward a peripheral region.   2. The light control dots of the plurality of light control patterns that form the light control patterns are formed with a light control dot in a peripheral region having a smaller diameter than a light control dot in a central region. Backlight device.   2. The backlight device according to claim 1, wherein the plurality of light control dots constituting each light control pattern are formed with a density of a peripheral region sparse relative to a central region. 2. The light source unit according to claim 1, wherein a plurality of red light emitting diodes, green light emitting diodes, and blue light emitting diodes are arranged in a predetermined order, and color display is performed on the transmissive display panel. The backlight device described.

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