The present invention relates to a light-emitting device such as a backlight including a cap configuration at, for example, a light source portion, also relates to a display device having a backlight, and the like.
Recently, display devices such as liquid crystal display devices, typified by, for example, a liquid crystal display television and a liquid crystal display monitor, have adopted a backlight as a light-emitting device for emitting light from the back, side or the like of a display panel. As the backlight, what is called a direct-lighting type exists in which a light source is disposed on a plane surface beneath the liquid crystal panel (a rear surface), for example. In addition, what is called an edge-lighting type also exist in which a light source is disposed on two or one side of a light guide plate made of a transparent resin so that light incident on the light guide plate is reflected by a reflector disposed on the back surface of the light guide plate, thus illuminating, for example, the surface of a liquid crystal display panel. Here, the direct-lighting type has an advantage of securing high brightness, but has a disadvantage of difficulty in achieving a thinner backlight. On the other hand, the edge-lighting type has an advantage of achieving a thinner backlight than the direct-lighting type, but has a disadvantage of difficulty in obtaining evenness of the brightness for a large display.
A fluorescent tube such as a hot-cathode fluorescent tube or a cold-cathode fluorescent tube is generally used as the above-mentioned backlight device. On the other hand, technologies of backlight device using light-emitting diodes (LEDs), which are one type of light-emitting elements, as a light source, have been recently developed as a substitute for the backlight devices using the fluorescent tubes.
Here, the backlight device is provided with a reflection plate (a reflector) that reflects light emitted from, for example, an LED toward an observer, and the reflector reflects, for example, light emitted in a side direction so that the light exits from a top surface. Also, a cap having a lens function as necessary is often used for the purpose of sealing the LED or of focusing light emitted from an LED light source and thereby performing any given control on, for example, luminous intensity distribution.
Related arts disclosed in Official Gazette include one adopting a sawtooth-shaped lens that refracts light emitted from an LED light source. Here, light is efficiently coupled to a reflector of shallow depth and a thin light guide, thereby providing a relatively large range of irradiation to a secondary optical element (for example, refer to Patent Document 1).
Patent Document 1: Japanese Patent Application Laid Open Publication No. 2003-8068
As mentioned above, the reflector and the cap are often combined to be used with the LED light source. However, if the reflector and the cap are formed separately and are used in combination, the formation of each member requires advanced technology, and moreover, it is required that these members be combined with high positioning accuracy. Further, the formation and combination of these members require many working processes, thus leading to a rise in manufacturing costs, and in turn to a rise in product costs.
The present invention has been made in order to address the foregoing technological problems. An object of the present invention is to achieve a light reflection function and a light transmission function possessed by a cap with a simple structure in alight-emitting device using a solid-state light-emitting element such as an LED.
In order to address the above object, according to the present invention, there is provided a display device including a display panel that displays an image, and a backlight disposed on a back side of the display panel and irradiating the display panel with light from the back side of the display panel. The backlight is provided with: a solid-state light-emitting element; and a cap that covers the solid-state light-emitting element, and the cap has a light reflection portion that reflects light from the solid-state light-emitting element, and a light transmission portion that transmits light from the solid-state light-emitting element toward the display panel. The light reflection portion and the light transmission portion are integral with each other.
Here, the cap forms a dome shape having an end and a ceiling, the light reflection portion is provided to have a width from the end of the dome shape, and the cap is mounted on a mounting substrate with the end of the dome shape fixedly bonded to the mounting substrate on which the solid-state light-emitting element is mounted, in order to easily fix the cap to the mounting substrate with a bonding layer provided at, for example, a lower part of the light reflecting portion.
On the other hand, the cap to which the present invention is applied having an opening end and a ceiling, and forming a hollow shape. The cap includes: a light reflection portion that is provided to have a width from the end toward the ceiling; and a light transmission portion that is provided toward the ceiling, and that is continuous with the light reflection portion.
Here, other than a hemispherical shape, the external shape of the cap may be any of various cubes, a shape of sawtooth as shown in
Also, the reflectance of a light reflector and the transmittance of a light transmitter may be defined as total transmittance and total reflectance based on a testing method for optical properties based on JISK7105. In other words, it is preferable that the light reflector is made of a white resin so that its total reflectance may be equal to or more than 60% (based on the JISK7105 testing method). Also, it is preferable that the light transmitter is made of a transparent resin so that its transmittance may be equal to or more than 70% (based on the JISK7105 testing method), or more preferably is equal to or more than 80% (based on the JISK7105 testing method). Then, the cap to which the present invention is applied may be configured of the white resin integral with the transparent resin.
According to another aspect of the present invention, there is provided a light-emitting device to which the present invention is applied including: a mounting substrate; a solid-state light-emitting element that is mounted on the mounting substrate; and a cap that is attached to the mounting substrate and that covers the solid-state light-emitting element. The cap has a light reflection portion of a width from a side of the cap, the side being attached to the mounting substrate, and has a light transmission portion continuous with the light reflection portion. The light reflection portion and the light transmission portion are formed integrally with each other.
Here, the light reflection portion of the cap is provided with a reflection film.
Further, a plurality of the solid-state light-emitting elements are mounted on the mounting substrate, and the cap is attached to each of the plurality of the solid-state light-emitting elements.
Furthermore, a plurality of the solid-state light-emitting elements are mounted on the mounting substrate. Each solid-state light-emitting element has, as a unit, at least three LEDs (light-emitting diodes) included in a plurality of LEDs each emitting red, green, or blue light, and the cap is attached to each unit of the solid-state light-emitting elements having at least the three LEDs as the unit.
According to further aspect of a present invention from a standpoint of a category of a manufacturing method, there is provided a method of manufacturing a backlight device to which the present invention is applied, including: placing a cap on a mounting substrate having a solid-state light-emitting element mounted thereon, with its end in contact with the mounting substrate, the cap having, as an external shape, a dome shape with a hollow portion, and having a light reflection portion that reflects light from the solid-state light-emitting element and a light transmission portion that transmits light from the solid-state light-emitting element, the light reflection portion and the light transmission portion being integral with each other, the light reflection portion having high reflectance with a width from an end of the external shape; and injecting a curing liquid resin into a void formed by the hollow portion of the cap and the mounting substrate, and then curing the liquid resin.
Here, the injection of the liquid resin is performed through a resin injection port penetrating a surface of the mounting substrate opposite to a mounting surface on which the solid-state light-emitting element is mounted and a region of the mounting surface where the void is formed, and the liquid resin, including the resin within the resin injection port, is cured.
According to a furthermore aspect of the present invention, there is provided a method of manufacturing a cap for covering a solid-state light-emitting element, including: forming a light transmission portion that forms a hollow and that has a ceiling and an end by injecting a first liquid resin into a mold; and forming a light reflection portion continuous with the end of the light transmission portion by injecting, into a mold, a second liquid resin having higher light reflectance than the first liquid resin after forming the light transmission portion, thereby forming the cap having the light reflection portion that reflects light from the solid-state light-emitting element and the light transmission portion that transmits light from the solid-state light-emitting element. The light reflection portion and the light transmission portion are integral with each other.
According to the present invention having the above-mentioned configuration, it is possible to considerably reduce a manufacturing process of the backlight device, for example.
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.
On the other hand, a liquid crystal display module 30 includes a liquid crystal panel 31 that is configured by two glass plates sandwiching liquid crystal in between, and polarization plates (polarization filters) 32 and 33 for restricting the oscillation of optical wave to a given direction, which are each laminated on each glass plate of the liquid crystal panel 31. The liquid crystal display device includes peripheral members (not shown in the figure) such as an LSI (Large Scale Integration) for driving.
The liquid crystal panel 31 includes various components not shown in the figure. For example, the two glass plates have display electrodes, active elements such as a thin film transistor (TFT), liquid crystal, a spacer, sealant, an orientation film, a common electrode, a protective film, a color filter, and others, none of which is shown in the figure.
Incidentally, the structural unit of the backlight device 10 is selected in an arbitrary way. For example, the unit including only the backlight frame 11 with the LED substrate 12 may be called as the “backlight device (backlight)” and distributed so as not to include the laminated body of the optical films such as the diffusion plate 13 and the prism sheets 14 and 15.
The backlight frame 11 has a chassis structure made of, for example, aluminum, magnesium, iron, or a metallic alloy including these materials. To the inside of the chassis structure, a polyester film or the like having a high performance of reflecting white light is adhered, for example. The polyester film also functions as a reflector. The chassis structure is composed of a rear portion corresponding to the size of the liquid crystal display module 30 and side portions enclosing the four sides of the rear portion. On the rear portion or the side portions, a heat sink configuration including a cooling fin for exhaust heat may be provided as necessary.
In the instance shown in
Also, each individual light-emitting diode (LED) 21 disposed on the LED substrate 12 is provided with a cap 50. The cap 50 is a hemispherical member including a lens unit that transmits light and a reflector unit that reflects light, and is fixed on the LED substrate 12 so as to cover each individual light-emitting diode (LED) 21. As will be described later, the cap 50 functions as a reflector that reflects light in a predetermined range on the side on which the LED substrate 12 is fixed, and has the cap function of transmitting light from this portion to its vertex.
A description will be given with regard to hitherto adopted technology to facilitate an understanding of the present exemplary embodiment.
With reference to
On the other hand, in
The method shown in
The inventors have devised the cap 50 shown in FIGS. 3A and 3B as the result of their efforts to address the above problems.
More specifically, as shown in
Preferably, when the height of the light-emitting diode (LED) 21 being a light-emitting element is set equal to 0.1 mm, for example, and the value of the width w is set to 10 to 20 times the height of the light-emitting diode (LED) 21 (between 1 and 2 mm inclusive), light emitted from the light-emitting diode (LED) 21 is efficiently used as a backlight. As mentioned above, the width w may be defined according to the height of the light-emitting diode (LED) 21. On the other hand, as other references, the value of the width w may be designed to be less than ½ of the diameter of the cap 50, thereby allowing the application of direct light of an angle wider than about 45 degrees, of light from the light-emitting diode (LED) 21, to the lens portion 51.
Also, resin materials for the lens portion (or the light transmission portion) 51 and the reflector portion (or the light reflection portion) 52 include a thermosetting resin such as a silicone resin or an epoxy resin, and a thermoplastic resin such as a polycarbonate resin or a cyclic olefine polymer. The thermoplastic resin is preferable because it is capable of facilitating two-color molding by injection molding. The thermoplastic resin includes, for example, a methacrylate resin or a polycarbonate resin that is lightweight and excellent in transparency and heat resistance, a cyclic olefine polymer typified by Zeonex (registered trademark), and a polymer composition having other polymers combined therewith. Other polymers include the above resins, a known styrene-based resin, an acrylic resin, and a polycarbonate resin.
As a molding resin, the above resins may be used singly, or two or more types of the above resins may be blended for use. Also, mica, talc, a glass filler, or the like may be added for the purpose of controlling mechanical strength or molding shrinkage factor for the injection molding, or of preventing the occurrence of a burr or a warp.
The resin for the reflector portion (or the light reflection portion) 52 may be obtained by mixing one or more kinds of filler such as titanium oxide, zinc oxide or barium sulfate into the above transparent resin. Although the form of the filler is not specifically limited, the filler in bead, fiber or other forms may be used. The amount of filling is appropriately selected according to molding conditions such as a resin molding method or resin flow ability, or according to characteristics such as reflectance or mechanical strength, and 2 wt % to 60 wt % is generally preferable.
Incidentally, the preferable values of the transmittance and reflectance of the lens portion (or the light transmission portion) 51 that is a first resin layer and the reflector portion (or the light reflection portion) 52 that is a second resin layer may be defined, using total transmittance and total reflectance based on the testing method for optical properties according to JISK7105. For example, preferably, light transmittance of the lens portion (or the light transmission portion) 51 is equal to or more than 80%, or more preferably equal to or more than 70%. Also, preferably, the total reflectance of the reflector portion (or the light reflection portion) 52 is equal to or more than 60%. Adoption of such transmittance and reflectance allows achieving good focusing and output of light for use in the backlight device 10.
Incidentally, the hemispherical shape shown in
Here, in the reflector portion (or the light reflection portion) 52, a reflecting film may be used on a resin surface to further increase the reflectance.
Metal or an inorganic compound may be used as the reflecting film by using a known process such as a dry process or a wet process. For example, metal such as gold, silver, platinum, nickel, titanium or aluminum, or an oxide or nitride of these metals may be formed as the reflecting film on the resin surface of the reflector portion (or the light reflection portion) 52 by using CVD, vacuum evaporation, sputtering or other methods.
Incidentally, the film thickness of the reflecting film may be set such that sufficient reflection occurs, and the reflecting film may be formed of a single layer or a multilayer construction having a combination of several layers and preferably has a thickness of 10 nm to several hundreds nm.
Also, a second transparent resin 25 for protecting the light-emitting diode (LED) 21 and also for transmitting light is formed in a void formed by adhesively bonding the dome-shaped cap 50 to the LED substrate 12 through the adhesive layer 24. A predetermined thermosetting resin is used for the second transparent resin 25, and the resin is injected in liquid form into the void through a resin injection port 26 and is then cured. By this curing, the resin is filled into the void between the cap 50 and the LED substrate 12 and into the resin injection port 26. Any given resin may be used for the second transparent resin 25; however, it is required that the resin be resistant to deterioration due to heat or light from the light-emitting diode (LED) 21 and be excellent in weather resistance. For example, silicone or the like having heat resistance and light resistance is used. Incidentally, the resin injection port 26 penetrates through a surface of the LED substrate 12 opposite to a mounting surface of the light-emitting diode (LED) 21 and a region of the mounting surface in which the void is formed.
Here, when the light-emitting diode (LED) 21 emits light in the LED light source configured as shown in
A description will be given with regard to a method of manufacturing the LED light source shown in, for example,
Then, as shown in
Then, as shown in
A description will be given of a method of manufacturing the cap 50.
A known injection molding method or injection molding machine may be used for cap (or lens) molding. An injection apparatus or a mold clamping apparatus that constitutes the injection molding machine may be appropriately selected according to the shape or productivity of the cap 50, and the arrangement of the injection apparatus and the mold clamping apparatus is not specifically limited. Also, molding conditions for a molding process may be selected according to the type of molding machine for use, the shape of the cap, or the like.
When the injection molding machine is used for the molding process, it is preferable that the temperature of the resin is higher than the glass transition temperature of the resin, and it is preferable that the temperature of the mold is in the vicinity of the glass transition temperature or lower. In particular, when an optical lens requires surface accuracy, it is effective that the temperature of the mold is set higher than a typical temperature of the mold in order to improve surface transfer characteristics.
Further, a known steel material may be used for an injection mold, and the surface of the mold may be coated with a material such as titanium, chromium or carbon according to the purpose such as wear resistance or lens surface accuracy. Also, if it is required to form a pattern or the like on the surface of the lens, a pattern of a desired shape may be formed on the inner surface of the mold by sandblasting, etching, electrocasting method, or the like.
Also, the gate shape of the mold is not limited, and a known method such as a direct gate or a pin gate may be used according to the shape of the cap.
Further, a known method such as an ejection method using a pin or the like or a method using air or the like to float the cap off may be used as a method for removing the cap from the mold.
The moving mold is moved relative to the fixed molds (or the primary and secondary molds) by a driving mechanism (not shown in the figure) to form, in its clamped position, a cavity according to the shape of a lens part. A fluid resin or liquid resin obtained by melting a solid resin typically in pellet form is injected and filled into the cavity through a nozzle (not shown in the figure). Then, the molding resin is cooled, and is removed from the mold, for example, by pushing out a pin provided on the moving mold. A two-color cap is manufactured by injecting a reflecting resin into the cavity formed by the primary mold and the common mold shown in
This molding procedure will be described in further detail with reference to
As described in detail above, the present exemplary embodiment allows simplification of the manufacturing process for the backlight device 10, and also facilitates bonding of the LED substrate 12 and the cap 50. Also, the injection of the silicone resin generally having weak adhesion to the LED substrate 12 into the void of the cap 50, for example, allows achieving a long lifetime and also providing the LED light source having a high degree of light output efficiency.
Further, this allows increasing the positioning accuracy of the cap 50 and the light-emitting diode (LED) 21, thus providing the backlight device 10 with high quality.
Number | Date | Country | Kind |
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2007-151187 | Jun 2007 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2008/060347 | 6/5/2008 | WO | 00 | 12/3/2008 |