JP5391847B2 - Backlight device and image display device - Google Patents

Description

  The present invention relates to a backlight device using a light emitting diode (LED) as a light source and an image display device using the backlight device.

  2. Description of the Related Art Conventionally, an image display device that displays an image by illuminating a liquid crystal display panel from the back side with a backlight device is known.

  As a light source of a backlight device used in such an image display device or the like, a fluorescent tube such as a cold cathode fluorescent lamp (CCFL) is often used. A fluorescent tube requires a high voltage to be lit, and its life is shortened if lighting and extinguishing are frequently repeated. Furthermore, since the fluorescent tube is generally formed of a glass material, the degree of freedom in shape as a backlight light source is limited.

  Therefore, the use of LEDs is spreading as a light source that replaces fluorescent tubes. In general, white light is used for the backlight device, and white LEDs are arranged to emit white illumination light, and LEDs of three colors R (red), G (green), and B (blue) are arranged. Some of these three colors are mixed into white light. For white LEDs, a method of obtaining white by combining RGB phosphors with a short wavelength LED chip, a method of obtaining white by combining yellow phosphors with a blue LED chip, or a mixture of RGB three-color LED chips There are a method for obtaining white, a method for obtaining white as mixed light of two complementary color LED chips, and the like.

  The LED can be driven at a lower voltage than the fluorescent tube, has superior performance such as low power consumption and long life. In addition, the backlight device using three color LEDs has a feature that the degree of freedom of color is increased as compared with the case where a fluorescent tube is used in order to obtain white light from wavelengths close to the three primary colors of light. In particular, the color reproducibility can be greatly expanded so that the color reproducibility exceeding 100% compared to the NTSC standard can be realized and the white point (white color) can be freely adjusted. Become.

  In backlight devices using LEDs, an edge-light type backlight device that illuminates a liquid crystal display panel with light emitted from the surface of the light guide plate is incident on a transparent light guide plate, and liquid crystal There is a direct-type backlight device or the like in which an LED is arranged directly below the back side of the display panel.

  An LED, which is a semiconductor element, has temperature dependency in its optical characteristics, electrical characteristics, lifetime, etc., and exhibits the characteristics that as the temperature rises, the emission luminance decreases, the emission wavelength increases, and the lifetime decreases.

  The rate of change in characteristics due to the temperature of the LED varies depending on the emission color of the LED. For example, when three colors of RGB LEDs are arranged and white light is obtained by mixing these three colors of light, the composition of R LEDs is different from that of AlGaInP, and the LEDs of G and B are different from InGaN. The temperature characteristics of the brightness obtained are different. The brightness decreases by about 20% in the AlGaInP system and about 10% in the InGaN system at a temperature increase value of 80 ° C. from room temperature. Moreover, in white LED by the combination with the yellow fluorescent substance by blue LED excitation, about 25% of luminous efficiency falls per 60 degreeC temperature rise value from room temperature.

  The LED generates heat by driving, but the heat generated from the LED in the backlight device is first diffused to the mounting substrate, further transmitted to the casing of the backlight device, etc., and finally dissipated to the surrounding air by convection and radiation. .

  An image display device including a backlight device is erected on a horizontal plane so that the display surface of the liquid crystal display panel is along the vertical direction. For this reason, during convection heat radiation from the backlight device surface to the surrounding air, a temperature boundary layer develops from the lower portion of the device toward the upper portion, and the temperature of the device surface increases as it goes upward. Therefore, the surface temperature is non-uniform between the upper part and the lower part of the apparatus.

  In the backlight device, in order to uniformly illuminate the liquid crystal display panel, it is required that the luminance, emission wavelength (emission color), and lifetime of the plurality of LEDs used as the light source are uniform. However, the non-uniformity of the surface temperature of the backlight device as described above causes non-uniform luminance, non-uniform emission color, and variation in lifetime among a plurality of LEDs. This is because the LED characteristics have temperature dependency as described above.

  In Patent Document 1, in a direct-type and edge-light type backlight device, a conductive member having a high reflectance is formed on the surface of a substrate on which the LED is mounted, so that the LED can be formed without providing a separate reflector. A technique for effectively diffusing heat generated from an LED while effectively utilizing light is disclosed. And in patent document 1, in order to cope with the nonuniformity of the apparatus surface temperature by the heat_generation | fever of LED as mentioned above, at least one of the area and thickness of the pattern of the electroconductive member of the LED mounting substrate surface is gradually made up and down. And adjusting the degree of thermal diffusion.

JP 2007-142256 A

  As described above, in Patent Document 1, in order to adjust the degree of thermal diffusion, at least one of the area and thickness of the pattern of the conductive member on the surface of the LED mounting substrate is gradually changed in the vertical direction. However, the thickness of the conductive member used for pattern formation on the surface of the LED mounting substrate is actually about 17.5 μm, 35 μm, and 70 μm, which is not sufficient as a heat diffusion path for an LED having a large heat generation density. The width of is also limited. If the thermal diffusion is further increased, the conductive member becomes thicker, which leads to an increase in cost.

  When attempting thermal diffusion by enlarging the area of the pattern, if it is a direct-type backlight device, there is an area margin in the LED mounting interval, and an adjustment range according to the degree of thermal diffusion in the vertical direction of the device is secured. it can.

  However, an image display device using an edge light type backlight device is thin because of its dimensional features, and an area margin cannot be secured on an LED mounting substrate unlike a direct type. Therefore, it is difficult to adjust the degree of thermal diffusion by expanding the area of the conductive member.

  Further, an edge light type backlight device uses a light source in which a plurality of LEDs are arranged in a straight line at a relatively narrow interval, but such a light source has a large heat generation density. For this reason, as described above, in order to adjust the degree of thermal diffusion by increasing the thickness of the conductive member, any practical range of 17.5 μm, 35 μm, and 70 μm is not sufficient for adjustment.

  As described above, in the edge light type backlight device, it is difficult to suppress the nonuniformity of the surface temperature generated in the backlight device. For this reason, non-uniform brightness, non-uniform light emission color, and variation in lifetime occur among a plurality of LEDs, and as a result, non-uniformity in the luminance distribution of the exit surface, which is the surface from which light is emitted from the light guide plate, is caused. Could not be illuminated uniformly.

  The present invention has been made in view of the above, and an object of the present invention is to provide an edge-light type backlight device having good uniformity of luminance distribution on an exit surface from which light is emitted, and an image display device using the same. To do.

  In order to achieve the above object, a backlight device according to claim 1 includes a light source in which a plurality of LED packages each having an LED chip are arranged in a straight line, two flat supporting surface portions facing each other, and the flat surface portion. One of the flat surface portions is a reflecting surface having a plurality of reflecting portions formed in the surface, and the other flat surface portion is a light emitting plate that emits light, and the reflection of the light guiding plate When the light guide plate is disposed such that the surface and the exit surface are along the vertical direction, the light source is disposed along at least one of the side surfaces along the vertical direction of the light guide plate, and the plurality of the light sources The arrangement interval of the LED package is wider toward the upper side in the vertical direction, and the arrangement interval of the plurality of reflection portions on the reflection surface is narrower toward the upper side in the vertical direction.

  The backlight device according to claim 2 includes a light source in which a plurality of LED packages having LED chips are arranged in a straight line, two flat supporting surface portions facing each other, and one flat surface portion of the flat surface portions. Is a reflection surface in which a plurality of reflection portions are formed in the surface, and the other flat surface portion is an emission surface that emits light, and the reflection surface of the light guide plate and the emission surface are When the light guide plate is disposed along the vertical direction, the light source is disposed along at least one of the side surfaces along the vertical direction of the light guide plate, and an interval between the LED packages of the light source is The cross-sectional area of the boundary surface with the light guide plate in the plurality of reflection portions of the reflection surface is wider toward the upper side in the vertical direction, and is larger toward the upper side in the vertical direction.

The backlight device according to claim 3 includes a light source in which a plurality of LED packages having LED chips are arranged in a straight line, two flat supporting surface portions facing each other, and one flat surface portion of the flat surface portions. Is a reflection surface in which a plurality of reflection portions are formed in the surface, and the other flat surface portion is an emission surface that emits light, and the reflection surface of the light guide plate and the emission surface are When the light guide plate is disposed along the vertical direction, the light sources are respectively disposed along the upper side surface and the lower side surface, which are side surfaces of the light guide plate in a direction orthogonal to the vertical direction, and along the upper side surface. The arrangement interval of the plurality of LED packages in the arranged light source is wider than the arrangement interval of the plurality of LED packages in the light source arranged along the lower side surface, and the arrangement of the plurality of reflection portions on the reflection surface Interval is characterized that it is narrowest at a predetermined position above the center position in the vertical direction in the light guide plate.

The backlight device according to claim 4 has a light source in which a plurality of LED packages each having an LED chip are arranged in a straight line, two flat supporting surface portions facing each other, and one flat surface portion of the flat surface portions. Is a reflection surface in which a plurality of reflection portions are formed in the surface, and the other flat surface portion is an emission surface that emits light, and the reflection surface of the light guide plate and the emission surface are When the light guide plate is disposed along the vertical direction, the light sources are respectively disposed along the upper side surface and the lower side surface, which are side surfaces of the light guide plate in a direction orthogonal to the vertical direction, and along the upper side surface. The arrangement interval of the plurality of LED packages in the arranged light source is wider than the arrangement interval of the plurality of LED packages in the light source arranged along the lower side surface, and the plurality of LED packages are arranged in the plurality of reflecting portions of the reflecting surface. Cross-sectional area of the boundary surface between the light guide plate is characterized in that is the largest at a predetermined position above the center position in the vertical direction in the light guide plate.

  The backlight device according to claim 5 is the backlight device according to claim 3 or claim 4, wherein the light source is further arranged along at least one of the side surfaces along the vertical direction of the light guide plate, The arrangement interval of the plurality of LED packages of the light source becomes wider toward the upper side in the vertical direction.

  The backlight device according to a sixth aspect is the backlight device according to any one of the first to fifth aspects, wherein the reflecting portion is made of a white paint.

  An image display device according to a seventh aspect is provided on the light emission plate side of the backlight device according to any one of the first to sixth aspects and the light guide plate of the backlight device, and is emitted from the light guide plate. And a liquid crystal display panel illuminated by the light.

  ADVANTAGE OF THE INVENTION According to this invention, the backlight apparatus of an edge light system with favorable uniformity of the luminance distribution of the emission surface which inject | emits light, and an image display apparatus using the same can be provided.

1 is an external view of an image display device including a backlight device according to an embodiment of the present invention. It is a fragmentary sectional view along the AA line in FIG. It is a top view which shows the principal part of the backlight apparatus which concerns on embodiment of this invention. It is a figure which shows the relationship between the arrangement | positioning space | interval of an LED package, and a temperature rise. It is the elements on larger scale around a reflective part. (A) is a figure which shows the temperature distribution of the LED package and frame surface in the backlight apparatus which concerns on embodiment of this invention, (b) shows the luminance distribution of the light source in the backlight apparatus which concerns on embodiment of this invention. FIG. It is a figure which shows an example of the principal part of the backlight apparatus of a comparative example. (A) is a figure which shows the temperature distribution of the LED package and flame | frame surface in the backlight apparatus of a comparative example, (b) is a figure which shows the luminance distribution of the light source in the backlight apparatus of a comparative example. FIG. 11 is a plan view showing a main part of a backlight device according to Modification 1. FIG. 11 is a plan view showing a main part of a backlight device according to Modification 2. FIG. 11 is a plan view showing a main part of a backlight device according to Modification 3. It is sectional drawing of the light-guide plate in which the microlens protruded as a reflection part. It is sectional drawing of the light-guide plate in which the recessed part was formed as a reflection part.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or equivalent parts are denoted by the same or equivalent reference numerals. However, it should be noted that the drawings are schematic and different from the actual ones. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  Further, the embodiment described below exemplifies an apparatus and a method for embodying the technical idea of the present invention. The technical idea of the present invention is the arrangement of each component as described below. It is not something specific. The technical idea of the present invention can be variously modified within the scope of the claims.

  1 is an external view of an image display device including a backlight device according to an embodiment of the present invention, FIG. 2 is a partial cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is the present embodiment. It is a top view which shows the principal part of the backlight apparatus which concerns on.

  As shown in FIG. 1, the image display device 1 includes a liquid crystal display panel 2 that displays an image according to an input image signal, and a backlight device 3 that illuminates the liquid crystal display panel 2 from the back side. The image display device 1 is erected on a horizontal plane such that the display surface of the liquid crystal display panel 2 is along the vertical direction. Here, the vertical direction is the Y direction, the direction parallel to the display surface of the liquid crystal display panel 2 and orthogonal to the Y direction is the X direction, and the direction orthogonal to both the X direction and the Y direction is the Z direction.

  As shown in FIGS. 2 and 3, the backlight device 3 according to the present embodiment includes a light guide plate 4, light sources 5 </ b> A and 5 </ b> B, an optical sheet unit 6, a reflection sheet 7, a frame 8, and a rear cover 9. With.

  The light guide plate 4 is made of a transparent plate made of a transparent material and having a thickness of about 1.5 mm to 4 mm. As the material of the light guide plate 4, a material having high light transmittance such as PMMA resin (polymethyl methacrylate resin) is used.

  A large number of dot-like reflecting portions 10 are formed on the back surface 4 b that is the reflecting surface of the light guide plate 4. The reflecting portion 10 is formed by printing a white paint containing titanium oxide or the like on the back surface 4b of the light guide plate 4 by a screen printing method, an ink jet printing method, or the like. The reflection unit 10 irregularly reflects light incident on the reflection unit 10 among the light traveling in the light guide plate 4. The reflection part 10 is formed, for example, with the light guide plate 4 as a flat surface and a planar view shape that is a shape of an interface with the light guide plate 4 and a diameter of about 300 μm. In addition, the planar view shape of the reflection part 10 is not restricted circular.

  As shown in FIG. 3, the reflection portion 10 is formed so that the arrangement interval becomes smaller toward the upper side (+ Y side) in the Y direction and becomes smaller toward the center side from the left and right sides in the X direction. The 3 is a plan view seen from the back surface 4b side of the light guide plate 4. FIG. The arrangement interval of the reflection units 10 is, for example, about 800 μm on average, and is set in a range of, for example, about 400 μm to 1200 μm.

  The reason why the arrangement interval in the Y direction of the reflecting portion 10 is reduced toward the upper side is that the arrangement interval P of the LED packages 51 of the light sources 5A and 5B increases toward the upper side as will be described later, and the light incident on the light guide plate 4 is reduced. This is because the luminance is lowered, and by arranging the reflecting portions 10 densely, the luminance in the Y direction of the exit surface 4a of the light guide plate 4 is made uniform.

  Further, the reason why the arrangement interval in the X direction of the reflecting portions 10 decreases toward the center of the light guide plate 4 is that the reflecting portions 10 are densely arranged in the vicinity of the center far from the light sources 5A and 5B and the amount of light that arrives decreases. This is because the luminance in the X direction of the exit surface 4a of the light guide plate 4 is made uniform.

  The light guide plate 4 guides light from the light sources 5A and 5B incident from the side surfaces 4c and 4d along the Y direction, and opposes at least a part of the light irregularly reflected by the reflecting portion 10 to the back surface 4b substantially in parallel. It injects from the injection surface 4a which is the surface.

  The light source 5A includes a plurality of LED packages 51 having LED chips (not shown) and a substrate 52 on which the LED packages 51 are mounted. The light source 5B has the same configuration. The light sources 5A and 5B are arranged to face the side surfaces 4c and 4d along the two sides in the Y direction of the light guide plate 4, respectively, and make the light from the LED package 51 enter the side surfaces 4c and 4d.

  The LED package 51 emits white light by, for example, covering a blue LED chip with a yellow phosphor or a phosphor obtained by mixing a red phosphor and a green phosphor and exciting the phosphor with blue light. is there. The LED packages 51 are arranged in a line or a plurality of lines on the substrate 52, and the arrangement interval P in the Y direction (the distance between the centers of the LED packages 51 in the Y direction) increases toward the upper side. Has been placed.

  The substrate 52 is made of a highly heat-dissipating substrate that efficiently conducts and diffuses the heat generated by the LED package 51, such as a polyimide-based flexible substrate or an aluminum thin plate-based metal base substrate.

  The board | substrate 52 is closely_contact | adhered to the flame | frame 8 with the heat conductive thermal radiation sheet | seat which is not shown in figure. Thereby, the contact thermal resistance between the contact surfaces of the substrate 52 and the frame 8 can be reduced, and the heat from the substrate 52 can be efficiently conducted to the frame 8. A heat sink (not shown) formed of a rod-like metal such as aluminum may be provided between the substrate 52 and the heat conductive heat radiating sheet so that heat from the substrate 52 is uniformly diffused in the heat sink. . Further, the heat sink and the frame 8 may be thermally connected to efficiently dissipate heat.

  The optical sheet unit 6 is disposed between the liquid crystal display panel 2 and the exit surface 4a of the light guide plate 4, and imparts light distribution characteristics and luminance uniformity characteristics to the light emitted from the exit surface 4a. The optical sheet unit 6 includes a diffusion sheet that diffuses incident light. In addition, a prism sheet that controls the traveling direction of incident light in a predetermined direction, and transmits only linearly polarized light in a predetermined direction among incident light. A polarizing sheet or the like is appropriately combined.

  The reflection sheet 7 is provided on the back surface 4b side of the light guide plate 4 and reflects the light leaked to the outside from the back surface 4b of the light guide plate 4 to the light guide plate 4 side, thereby improving the utilization efficiency of the light emitted from the LED package 51. Increase.

  The frame 8 and the rear cover 9 are both made of aluminum or the like, and constitute a housing for housing the light guide plate 4 and the light sources 5A and 5B. The frame 8 constitutes an outer frame that surrounds the periphery of the light guide plate 4 and the like, and holds the liquid crystal display panel 2 with the optical sheet portion 6 sandwiched on the exit surface 4 a side of the light guide plate 4. The rear cover 9 covers the back side of the backlight device 3.

  The frame 8 made of aluminum has good heat dissipation, and also has a function of efficiently diffusing the heat of the light sources 5A and 5B to convection and radiate heat to the surrounding air.

  Here, the arrangement interval P in the Y direction of the LED package 51 in the light sources 5A and 5B will be described.

  In general, in the case of convection heat radiation by natural convection, the lowermost part of the heating element arranged in the vertical direction is convectively radiated (cooled) at the temperature of the ambient air, and the temperature is raised below it except for the lowermost part. It becomes convection heat radiation (cooling) by the temperature of air. For this reason, in the upper part of a heat generating body, since it becomes the convection heat radiation by high temperature, the amount of heat radiation becomes small and temperature goes up, so that it goes up.

  The rate of heat transfer to the ambient air (heat transfer rate) is expressed as a function of the temperature difference from the ambient air, as in (Equation 1) below.

H = K (ΔTa / L) ^0.25 (W / m ² · ° C.) (Equation 1)
Here, ΔTa is the temperature difference between the ambient air temperature and the heating element, L is the length of the heating element, H is the heat transfer coefficient, and K is the product of the coefficient of air properties and the form of the heating element.

  As described above, the temperature of the ambient air gradually increases as it goes upward due to the temperature of the air raised at the lower portion of the heating element, but from (Equation 1), the heat transfer coefficient H decreases as the temperature of the ambient air increases. . Therefore, the amount of heat released from the heating element decreases as it goes upward, and the temperature rises.

  Here, when there is a temperature difference between the heating element and the ambient air, a light source 5A that is a heating element arranged in the vertical direction is defined as a temperature boundary layer that is a region where the temperature changes greatly in the contact region between the two. , 5B, when the LED packages 51 are arranged at equal intervals, a temperature boundary layer develops (thickens) as it goes from the lower part to the upper part in the convection heat radiation by the natural convection from the backlight device 3 to the surrounding air. The temperature of the LED package 51 and the surface of the device becomes higher at the upper part, and the surface temperature becomes uneven between the upper and lower parts of the device.

  On the other hand, the LED package 51 receives heat from the surrounding LED package 51 in addition to its own heat generation. The mutual heat effect between the LED packages 51 is greatly influenced by the size of the arrangement interval P of the LED packages 51.

When a plurality of LED packages 51 are arranged in a straight line on the substrate 52, the temperature effect from the adjacent LED packages 51 is that when all the LED packages 51 are turned on simultaneously and when the LED packages 51 are turned on alone. It can be easily grasped by the difference in temperature. FIG. 4 shows the relationship between the arrangement interval P of the LED packages 51 and the temperature rise ΔTb received from the adjacent LED packages 51.
As shown in FIG. 4, when the arrangement interval P is the minimum, the temperature increase ΔTb is the maximum. The arrangement interval P is minimized when the gap between adjacent LED packages 51 is zero, that is, when the arrangement interval P is the package width B, which is the length in the arrangement direction (Y direction) of the LED packages 51. It is. As the arrangement interval P increases, the temperature rise ΔTb decreases.

  Specifically, when adjacent LED packages (B = 2.5 mm) are driven with a power of 0.5 W per LED package, 5 mm intervals (P = 2B) and 20 mm intervals (P = 8B) In some cases, an experimental result was obtained in which the temperature difference between adjacent LED packages was approximately 30 ° C. Note that the temperature rise ΔTb varies depending on the input power to the LED package 51.

  As described above, when the LED packages 51 are arranged at equal intervals in the light sources 5A and 5B, the LED package 51 arranged on the upper side by the temperature boundary layer that develops from the bottom to the top during convective heat radiation by natural convection. The higher the temperature. On the other hand, as shown in FIG. 4, when the distance between the adjacent LED packages 51 is increased, the temperature increase ΔTb is decreased.

  Therefore, in the backlight device 3, the LED package 51 is disposed at a distance P larger toward the upper side in the light sources 5A and 5B to reduce the temperature increase ΔTb, thereby generating a temperature rise as it is disposed on the upper side. The nonuniformity of the temperature of the LED package 51 that becomes higher is eliminated. Thereby, the brightness | luminance of the LED package 51, luminescent color, and lifetime are equalized.

  By the way, if the arrangement interval P of the LED package 51 is increased toward the upper side of the light sources 5A, 5B, the luminance of light incident on the light guide plate 4 from the light sources 5A, 5B decreases. Therefore, as described above, in the backlight device 3, the arrangement interval in the Y direction of the reflecting portions 10 formed on the light guide plate 4 is reduced toward the upper side, so that the emission surface 4 a of the light guide plate 4 in the Y direction is reduced. Uniform brightness.

  However, when the arrangement interval P of the LED packages 51 becomes too large, it becomes difficult to make the luminance of the emission surface 4 a uniform by reducing the arrangement interval in the Y direction of the reflection portion 10 in the light guide plate 4. As a result of the experimental study, the arrangement interval P of the LED package 51 is limited to about 10 times the package width B of the LED package 51.

  Therefore, the arrangement interval P of the LED packages 51 in the light sources 5A and 5B is set such that the arrangement interval P1 in the lowermost portion is B or more and the arrangement interval P2 in the uppermost portion is 10B or less. Therefore, the range in which the temperature difference between the LED packages 51 in the light sources 5A and 5B caused by the convection heat radiation can be corrected by the temperature increase ΔTb is the temperature increase ΔTb corresponding to the range in which the LED package 51 is disposed at intervals P of B to 10B. .

  The arrangement interval P in the Y direction of the LED package 51 in the light sources 5A and 5B depends on conditions such as the relationship between the arrangement interval P of the LED package 51 and the temperature rise ΔTb, the length of the light guide plate 4 in the Y direction, and the like. The LED packages 51 in the light sources 5A and 5B are appropriately designed in the range of B to 10B so that the temperatures of the LED packages 51 are substantially uniform.

  Moreover, the arrangement | positioning space | interval of the reflection part 10 in the light-guide plate 4 is the brightness | luminance in the surface of the output surface 4a of the light-guide plate 4 according to conditions, such as the arrangement | positioning space | interval of the LED package 51 in the light sources 5A and 5B, and the brightness | luminance of the LED package 51. Is appropriately designed to be substantially uniform.

  Note that the actual surface temperature of the image display device 1 is generally designed so that the upper limit is practically around 50 ° C. Therefore, the temperature range in which the temperature difference of the LED package 51 in the light sources 5A and 5B caused by convection heat radiation should be corrected by the temperature increase ΔTb is within 50 ° C. Actually, the temperature difference from the room temperature of the housing surface is about 25 ° C., and the temperature difference to be corrected is about 10 to 15 ° C. in a practical range.

  Next, the operation of the backlight device 3 will be described.

  When power is supplied and the LED package 51 in the light sources 5A and 5B is driven, the light emitted from the light sources 5A and 5B is incident from the side surfaces 4c and 4d of the light guide plate 4, respectively. The light guide plate 4 travels while being reflected by the back surface 4b and the like. The light leaked to the outside from the back surface 4b of the light guide plate 4 is reflected by the reflection sheet 7 and returns to the light guide plate 4 side.

  As shown in FIG. 5, the light that travels through the light guide plate 4 and reaches the reflecting portion 10 is irregularly reflected by the reflecting portion 10, and the light reflected toward the emitting surface 4 a is emitted from the emitting surface 4 a. The

  The light emitted from the exit surface 4 a of the light guide plate 4 is given light distribution characteristics and luminance uniformity characteristics by the optical sheet portion 6 and then enters the liquid crystal display panel 2.

  In the liquid crystal display panel 2, the liquid crystal of each pixel is controlled in accordance with an image signal input from the outside. Thereby, the light emitted from the exit surface 4 a of the light guide plate 4 and incident on the liquid crystal display panel 2 is modulated, and part of the light is transmitted, and an image is displayed on the liquid crystal display panel 2.

  When the LED package 51 of the light sources 5A and 5B is driven to generate heat, a temperature boundary layer develops from the lower part of the apparatus toward the upper part during convection heat radiation from the backlight device 3 to the surrounding air via the frame 8. . On the other hand, in the backlight device 3, the arrangement interval in the Y direction of the LED package 51 is increased toward the upper side of the light sources 5A and 5B so that the temperature of the LED package 51 in the light sources 5A and 5B becomes uniform. Yes. For this reason, as shown in FIG. 6A, the temperature Tj at the junction of the LED package 51 with the substrate 52 and the surface temperature Tc of the frame 8 are substantially uniform in the Y direction.

  As shown in FIG. 6B, the luminance of light incident on the light guide plate 4 from the light sources 5A and 5B decreases as it goes upward as the arrangement interval of the LED packages 51 increases. The arrangement interval in the Y direction of 10 is reduced toward the upper side, so that the luminance in the Y direction of the exit surface 4a of the light guide plate 4 is made uniform. Moreover, about the X direction, the arrangement | positioning space | interval of the reflection part 10 is made small toward the center side of the light-guide plate 4 in which the light which arrives from light source 5A, 5B reduces, and the brightness | luminance in the X direction of the output surface 4a of the light-guide plate 4 is reduced. Is made uniform. For this reason, the luminance distribution in the surface of the exit surface 4a of the light guide plate 4 becomes substantially uniform.

  Here, as a comparative example, an example of a main part of a conventional backlight device is shown in FIG. The backlight device 3A shown in FIG. 7 has a configuration in which the light sources 5A and 5B are replaced with the light sources 5C and 5D with respect to the backlight device 3 shown in FIGS.

  The light sources 5C and 5D are different from the light sources 5A and 5B shown in FIG. 3 in that the arrangement intervals of the plurality of LED packages 51 in the Y direction are equal intervals. Further, the arrangement intervals in the Y direction of the reflection portions 10 in the light guide plate 4 are equal intervals.

  As described above, in the backlight device 3A, the LED packages 51 are arranged at equal intervals in the Y direction in the light sources 5C and 5D, and are designed to obtain uniform luminance in the Y direction if there is no temperature influence. ing.

  In the backlight device 3A, when the light sources 5C and 5D are driven to generate heat, a temperature boundary layer develops from the lower portion of the device toward the upper portion during convection heat radiation from the backlight device 3A to the surrounding air. For this reason, as shown in FIG. 8A, the temperature Tj of the LED package 51 and the surface temperature Tc of the frame 8 are not uniform in the Y direction.

  Since the LED package 51 has a characteristic that the brightness decreases as the temperature increases, the brightness of the light incident on the light guide plate 4 from the light sources 5C and 5D is on the upper side as shown in FIG. It goes down as you go. And since the arrangement | positioning space | interval in the Y direction of the reflection part 10 in the light-guide plate 4 is equal intervals, the brightness | luminance of the output surface 4a of the light-guide plate 4 becomes non-uniform | heterogenous in a Y direction.

  In addition, the lifetime of the LED package 51 is also non-uniform due to the non-uniformity of the temperature of the LED package 51, so that the brightness of the upper LED package 51 decreases earlier as a long time elapses, and the Y of the exit surface 4 a of the light guide plate 4 is reduced. The uneven luminance in the direction becomes more prominent.

  On the other hand, the backlight device 3 according to the present embodiment is thin by increasing the arrangement interval in the Y direction of the LED package 51 toward the upper side of the light sources 5A and 5B as described above. Thus, the temperature Tj of the LED package 51 can be made uniform without impairing the features of the edge light type backlight device, thereby making it possible to make the brightness, emission color, and life of the LED package 51 uniform.

  By increasing the arrangement interval of the LED packages 51 toward the upper side of the light sources 5A and 5B, the luminance of the light incident on the light guide plate 4 decreases as it goes upward, but the Y direction of the reflecting portion 10 on the light guide plate 4 By reducing the arrangement interval in the direction upward, the luminance of the exit surface 4a of the light guide plate 4 can be made uniform.

  Thus, according to the backlight device 3 according to the present embodiment, the luminance, emission color, and life of the LED packages 51 of the light sources 5A and 5B are made uniform, and the arrangement interval of the reflecting portions 10 in the light guide plate 4 is set. By adjusting, it is possible to realize good luminance distribution uniformity on the exit surface 4 a of the light guide plate 4.

  In the backlight device 3, either one of the light sources 5A and 5B may be omitted. In this case, the arrangement | positioning space | interval in the X direction of the reflection part 10 in the light-guide plate 4 is made so small that it distances from a light source. For example, when the light source 5B is omitted in FIG. 3, the arrangement interval in the X direction of the reflecting portion 10 is gradually reduced from the side surface 4c side where the light source 5A is arranged to the side surface 4d side.

(Modification 1)
FIG. 9: is a top view which shows the principal part of the backlight apparatus which concerns on the modification 1 of embodiment of this invention. As shown in FIG. 9, the backlight device 3B according to the modification 1 has a configuration in which the light sources 5A and 5B are replaced with light sources 5E and 5F in the backlight device 3 shown in FIGS.

  The light sources 5E and 5F include a plurality of LED packages 51 and a substrate 52 on which the LED packages 51 are mounted, and face the side surfaces 4e and 4f along two sides in the X direction (horizontal direction) of the light guide plate 4, respectively. The light from the LED package 51 is incident on the side surfaces 4e and 4f.

  In each of the light sources 5E and 5F, the LED packages 51 are arranged at equal intervals in the X direction. However, the arrangement interval P3 of the LED packages 51 in the light source 5E arranged along the upper side surface 4e of the light guide plate 4 is the same. The distance between the LED packages 51 in the light source 5F arranged along the lower side surface 4f is larger than the arrangement interval P4.

  Moreover, the reflection parts 10 in the light guide plate 4 are arranged at equal intervals in the X direction, and in the Y direction, the arrangement intervals are arranged so as to decrease from the upper and lower sides toward a predetermined position above the center.

The reason why the arrangement interval in the Y direction of the reflectors 10 is reduced toward the center side of the light guide plate 4 is that the reflectors 10 are arranged densely on the center side where the light that arrives far from the light sources 5E and 5F decreases. This is because the luminance in the Y direction of the exit surface 4a of the light guide plate 4 is made uniform. As described above, the LED package 51 is arranged more densely in the light source 5F than in the light source 5E, and the light incident from the side surface 4f is more than the light incident from the side surface 4e. The reflective portion 10 is arranged so that the arrangement interval becomes the smallest at a predetermined position slightly above.

  Assuming that the arrangement intervals of the LED packages 51 in the light sources 5E and 5F are the same, the temperature of the light source 5E is higher than that of the light source 5F in the light source 5E due to a temperature boundary layer that develops from the bottom to the top during convection heat dissipation. Becomes higher. For this reason, the luminance, light emission color, and life of the LED package 51 become non-uniform due to the temperature difference between the light sources 5E and 5F, resulting in non-uniform luminance of the exit surface 4a of the light guide plate 4.

  Therefore, in the backlight device 3B, the temperature of the LED package 51 between the light sources 5E and 5F is made uniform by increasing the arrangement interval of the LED packages 51 in the light source 5E and reducing the temperature increase ΔTb than the light source 5F. Yes.

  For the same reason that the arrangement interval of the LED packages 51 in the light sources 5A and 5B of the backlight device 3 is set to B to 10B or less, the arrangement interval P3 of the LED packages 51 in the light source 5E is 10 B or less, and the LED package 51 in the light source 5F. Is set to be B or more.

  The arrangement intervals P3 and P4 in the X direction of the LED packages 51 in the light sources 5E and 5F depend on conditions such as the relationship between the arrangement interval P of the LED packages 51 and the temperature increase ΔTb, the distance between the light sources 5E and 5F, and the like. The temperature of the LED package 51 in the light sources 5E and 5F is appropriately designed so as to be substantially uniform.

  Moreover, the arrangement | positioning space | interval of the reflection part 10 in the light-guide plate 4 is the brightness | luminance in the surface of the output surface 4a of the light-guide plate 4 according to conditions, such as the arrangement | positioning space | interval of the LED package 51 in the light sources 5E and 5F, and the brightness | luminance of the LED package 51. Is appropriately designed to be substantially uniform.

  Also with the backlight device 3B according to the first modification, the temperatures of the LED packages 51 of the light sources 5E and 5F are made uniform, and the luminance, emission color, and life of the LED package 51 are made uniform, and further the reflection on the light guide plate 4 By adjusting the arrangement interval of the portions 10, it is possible to achieve good luminance distribution uniformity on the exit surface 4 a of the light guide plate 4.

(Modification 2)
FIG. 10: is a top view which shows the principal part of the backlight apparatus which concerns on the modification 2 of embodiment of this invention. As shown in FIG. 10, the backlight device 3 </ b> C according to the modified example 2 has a light source 5 </ b> F arranged along the lower side surface 4 f of the light guide plate 4 with respect to the backlight device 3 shown in FIGS. 2 and 3. It is the structure which added.

  The arrangement interval of the LED packages 51 in the light sources 5A, 5B, and 5F depends on conditions such as the relationship between the arrangement interval P of the LED package 51 and the temperature increase ΔTb, the length of the light guide plate 4 in the Y direction, and the like. The temperature is appropriately designed so that the temperatures of the LED packages 51 in 5A, 5B, and 5F are substantially uniform.

  Since the LED package 51 of the light source 5F and the lowermost LED package 51 of the light sources 5A and 5B have the same position in the Y direction, the arrangement interval P4 of the LED packages 51 arranged at equal intervals in the X direction in the light source 5F. Is approximately the same as the arrangement interval P1 at the bottom of the light sources 5A and 5B.

  In addition, the arrangement interval of the reflecting portions 10 in the light guide plate 4 is within the plane of the exit surface 4a of the light guide plate 4 according to conditions such as the arrangement interval of the LED packages 51 in the light sources 5A, 5B, and 5F, the luminance of the LED package 51, and the like. The brightness is appropriately designed so as to be substantially uniform. The reflection portion 10 is formed such that the arrangement interval decreases toward the upper side in the Y direction, and the arrangement interval decreases from the left and right sides toward the center side in the X direction.

  Also with the backlight device 3C according to the second modified example, the temperature of the LED package 51 of the light sources 5A, 5B, and 5F is made uniform, the luminance, the emission color, and the life of the LED package 51 are made uniform, and the light guide plate 4 By adjusting the arrangement interval of the reflection portions 10 in the above, it is possible to achieve good luminance distribution uniformity on the exit surface 4 a of the light guide plate 4. Further, since the light source 5F is provided in addition to the light sources 5A and 5B, the luminance of the exit surface 4a can be increased.

(Modification 3)
FIG. 11: is a top view which shows the principal part of the backlight apparatus which concerns on the modification 3 of embodiment of this invention. As shown in FIG. 11, the backlight device 3 </ b> D according to Modification 3 includes a light source 5 </ b> E disposed along the upper side surface 4 e of the light guide plate 4 with respect to the backlight device 3 illustrated in FIGS. 2 and 3. In this configuration, a light source 5F arranged along the lower side surface 4f is added.

  The arrangement interval of the LED packages 51 in the light sources 5A, 5B, 5E, and 5F depends on conditions such as the relationship between the arrangement interval P of the LED packages 51 and the temperature increase ΔTb, the length of the light guide plate 4 in the Y direction, and the like. The LED packages 51 in the light sources 5A, 5B, 5E, and 5F are appropriately designed so as to have a substantially uniform temperature.

  Since the LED package 51 of the light source 5E and the uppermost LED package 51 of the light sources 5A and 5B have the same position in the Y direction, the arrangement interval P3 of the LED packages 51 arranged at equal intervals in the X direction in the light source 5E. Is approximately the same as the arrangement interval P2 at the top of the light sources 5A and 5B. Further, since the LED package 51 of the light source 5F and the lowermost LED package 51 of the light sources 5A and 5B have the same position in the Y direction, the arrangement of the LED packages 51 arranged at equal intervals in the X direction in the light source 5F. The interval P4 is approximately the same as the arrangement interval P1 at the bottom of the light sources 5A and 5B.

  In addition, the arrangement interval of the reflecting portions 10 in the light guide plate 4 is set on the exit surface 4a of the light guide plate 4 in accordance with conditions such as the arrangement interval of the LED packages 51 in the light sources 5A, 5B, 5E, and 5F, the luminance of the LED package 51, and the like. It is appropriately designed so that the in-plane luminance is substantially uniform. The reflection portion 10 is formed such that the arrangement interval decreases from the upper and lower sides in the Y direction toward a predetermined position above the center, and the arrangement interval decreases in the X direction from the left and right sides toward the center.

  Even with the backlight device 3C according to the third modified example, the temperatures of the LED packages 51 of the light sources 5A, 5B, 5E, and 5F are made uniform so that the brightness, light emitting color, and life of the LED package 51 are made uniform, and further, By adjusting the arrangement interval of the reflecting portions 10 in the optical plate 4, it is possible to achieve a good luminance distribution uniformity on the exit surface 4 a of the light guide plate 4. Moreover, since light injects from all the side surfaces 4c-4f of the light-guide plate 4, the brightness | luminance of the output surface 4a can be made still larger.

  In the backlight device 3D, one of the light sources 5A and 5B may be omitted. In this case, the arrangement | positioning space | interval in the X direction of the reflection part 10 in the light-guide plate 4 is made so small that it distances from a light source. For example, when the light source 5B is omitted in FIG. 11, the arrangement interval in the X direction of the reflection portion 10 is gradually reduced from the side surface 4c side where the light source 5A is arranged to the side surface 4d side.

  In the above-described embodiment and each modification, the arrangement interval of the reflection units 10 is changed in order to make the luminance distribution on the exit surface 4a of the light guide plate 4 uniform. Even when the directions are equally spaced, the luminance distribution on the exit surface 4a can be made uniform by changing the planar view area (boundary surface cross-sectional area) which is the shape of the interface between the light guide plate 4 and the reflecting portion 10. Good.

  In this case, in the light guide plate 4 of the backlight devices 3, 3 </ b> B to 3 </ b> D, the planar view area of the reflection unit 10 may be gradually increased instead of gradually reducing the arrangement interval of the reflection units 10.

  For example, in the backlight device 3 shown in FIG. 3, the reflective unit 10 is arranged on the upper side of the light guide plate 4 in the Y direction, and the planar view area increases, and in the X direction, the center side What is necessary is just to form so that a planar view area may become large so that it may arrange | position.

  Further, in the backlight device 3B shown in FIG. 9, the reflection unit 10 has the same planar view area in the X direction, and in the Y direction, from the upper and lower sides toward the predetermined position above the center. What is necessary is just to form so that a planar view area may become large.

  Further, the adjustment of the arrangement interval of the reflecting portions 10 and the adjustment of the area in plan view may be combined to make the luminance distribution on the exit surface 4a uniform. For example, in the light guide plate 4 of the backlight devices 3, 3 </ b> B to 3 </ b> D, in addition to gradually reducing the arrangement interval of the reflection units 10, the planar view area of the reflection unit 10 may be gradually increased.

  Further, the reflecting portion 10 may be configured by a microlens 11 which is a transparent lens-like member protruding from the back surface 4b of the light guide plate 4 as shown in FIG. . The light traveling in the light guide plate 4 is diffusely reflected by the curved surface 11a of the microlens 11, and at least a part of the light reflected toward the emission surface 4a is emitted from the emission surface 4a.

  The microlens 11 is made of acrylic resin, epoxy resin, or the like, and can be formed on the back surface 4b of the light guide plate 4 by a micro ink jet method or the like.

  Moreover, you may comprise the reflection part 10 by the recessed part 12 recessedly provided in the back surface 4b of the light-guide plate 4 as shown in FIG. The curved surface 12a of the recess 12 diffuses the light traveling in the light guide plate 4, and at least a part of the light reflected toward the exit surface 4a is emitted from the exit surface 4a. The recess 12 can be formed by laser processing or the like.

DESCRIPTION OF SYMBOLS 1 Image display apparatus 2 Liquid crystal display panel 3, 3A, 3B, 3C, 3D Backlight apparatus 4 Light guide plate 5A, 5B, 5C, 5D, 5E, 5F Light source 6 Optical sheet part 7 Reflective sheet 8 Frame 9 Rear cover 10 Reflective part 11 Microlens 12 Recess 51 LED package 52 Substrate

Claims (7)

A light source in which a plurality of LED packages having LED chips are linearly arranged;
An emission surface that has two flat surface portions facing each other, one of the flat surface portions is a reflection surface in which a plurality of reflection portions are formed, and the other flat surface portion emits light. A light guide plate,
With
When the light guide plate is disposed such that the reflection surface and the exit surface of the light guide plate are along the vertical direction, the light source is disposed along at least one of the side surfaces along the vertical direction of the light guide plate. The arrangement interval of the plurality of LED packages of the light source is wider toward the upper side in the vertical direction, and the arrangement interval of the plurality of reflection portions on the reflection surface is narrower toward the upper side in the vertical direction. Backlight device to do. A light source in which a plurality of LED packages having LED chips are linearly arranged;
An emission surface that has two flat surface portions facing each other, one of the flat surface portions is a reflection surface in which a plurality of reflection portions are formed, and the other flat surface portion emits light. A light guide plate,
With
When the light guide plate is disposed such that the reflection surface and the exit surface of the light guide plate are along the vertical direction, the light source is disposed along at least one of the side surfaces along the vertical direction of the light guide plate. The interval between the plurality of LED packages of the light source is wider toward the upper side in the vertical direction, and the cross-sectional area of the boundary surface with the light guide plate in the plurality of reflection portions of the reflection surface is higher toward the upper side in the vertical direction. A backlight device characterized by an increase in size. A light source having a plurality of LED packages are arranged in a straight line having an LED chip,
An emission surface that has two flat surface portions facing each other, one of the flat surface portions is a reflection surface in which a plurality of reflection portions are formed, and the other flat surface portion emits light. A light guide plate,
With
When the light guide plate is arranged so that the reflecting surface and the exit surface of the light guide plate are along the vertical direction, the light source is an upper side surface and a lower side surface that are side surfaces of the light guide plate in a direction orthogonal to the vertical direction. Each of the plurality of LED packages in the light source arranged along the upper side surface is wider than the arrangement interval of the plurality of LED packages in the light source arranged along the lower side surface, The backlight device is characterized in that the arrangement interval of the plurality of reflection portions on the reflection surface is the narrowest at a predetermined position above the center position in the vertical direction of the light guide plate. A light source having a plurality of LED packages are arranged in a straight line having an LED chip,
An emission surface that has two flat surface portions facing each other, one of the flat surface portions is a reflection surface in which a plurality of reflection portions are formed, and the other flat surface portion emits light. A light guide plate,
With
When the light guide plate is arranged so that the reflecting surface and the exit surface of the light guide plate are along the vertical direction, the light source is an upper side surface and a lower side surface that are side surfaces of the light guide plate in a direction orthogonal to the vertical direction. Each of the plurality of LED packages in the light source arranged along the upper side surface is wider than the arrangement interval of the plurality of LED packages in the light source arranged along the lower side surface, The backlight device, wherein a cross-sectional area of a boundary surface with the light guide plate in the plurality of reflection portions of the reflection surface is largest at a predetermined position above a center position in a vertical direction of the light guide plate.   The light source is further disposed along at least one of the side surfaces along the vertical direction of the light guide plate, and the interval between the plurality of LED packages of the light source becomes wider toward the upper side in the vertical direction. The backlight device according to claim 3 or 4, wherein the backlight device is characterized.   The backlight device according to claim 1, wherein the reflection portion is made of a white paint. The backlight device according to any one of claims 1 to 6,
A liquid crystal display panel installed on the exit surface side of the light guide plate of the backlight device and illuminated by light emitted from the light guide plate;
An image display device comprising:

Images