JP2008263083A - Planar light source, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin planar light source which can be used as a backlight of a liquid crystal display device. <P>SOLUTION: A segment U1 comprises: a circuit wiring board 10 composed of a substrate part 10a into which phosphors of three primary colors are dispersed and a circuit interconnection part 10c; a group III nitride compound semiconductor light-emitting element 201 for emitting ultraviolet rays; a bump 3b; sealing resin 4 into which the phosphors of the three primary colors are dispersed; and a reflection film 5 composed of a highly reflective metal. In the segment U1, ultraviolet light emitted from a light-emitting area (thick line) of the group III nitride compound semiconductor light-emitting element 201 is converted into red, green and blue lights by the phosphors of the three primary colors which are dispersed into the substrate part 10a of the circuit board substrate 10 and the sealing resin 4. Since red, green and blue lights are respectively radiated from the phosphors of the three primary colors as if they were secondary light-emitting sources, lights of the three primary colors are emitted from the whole segment U1 upwards in the shown figure. The segment U1 is an extremely thin white planar light source which can be used as a backlight of a color liquid crystal display device. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surface light source and a liquid crystal display device. The present invention relates to a thin surface light source using several to very many light emitting diodes, and also relates to a liquid crystal display device using it as a backlight.

  When a liquid crystal is used as a display device, a light source that emits light that is transmitted or blocked by the liquid crystal, that is, a so-called backlight is necessary. In recent years, color liquid crystals have been used not only for computer monitors but also for mobile phone operation screens and television screens, and the amount of backlight light required has become large.

When a liquid crystal display device is used for a monitor screen of a notebook computer or an operation screen of a mobile phone, it is required to reduce the thickness in the direction perpendicular to the display surface including the light source. Under such circumstances, as in Patent Document 1, for example, a light source is arranged outside the liquid crystal display region, and light is first guided to the back of the liquid crystal by a light guide plate, and light is guided from the back of the liquid crystal to the front by a reflective film and a diffusion plate Is popular.
JP 2002-72242 A

  In the prior art, since the light from the light source is once guided to the back of the liquid crystal in parallel with the liquid crystal display surface, the use efficiency of the light emitted from the light source is never high. Further, simply disposing the light source on the back surface of the liquid crystal requires, for example, increasing the distance between the light source and the back surface of the liquid crystal in order to uniformly irradiate the entire liquid crystal. In particular, for the purpose of miniaturization, when individual red, green, and blue light emitting diodes (LEDs) are arranged in a matrix, the three primary colors are used even when the three primary color LED matrix and the light diffusion plate are arranged on the back of the liquid crystal. The distance between the LED matrix and the liquid crystal back surface has to be extremely large.

  The present invention has been made to solve the above problems, and an object thereof is to provide a thin surface light source that can be used as a backlight of a liquid crystal display device.

The invention according to claim 1 is arranged on a circuit wiring board in which a phosphor or a light diffusing material is dispersed and a second surface different from the first surface on the light extraction side of the circuit wiring board. A light-emitting diode connected to the light-emitting diode, a sealing resin in which a phosphor or a light diffusion material is dispersed, which seals the light-emitting diode, and a reflection that covers the sealing resin and reflects light from the light-emitting diode to the circuit wiring board side A surface light source characterized by having a film.
According to a second aspect of the present invention, there is provided a liquid crystal display device comprising the surface light source according to the first aspect and having a display surface parallel to the first surface of the circuit wiring board.

  In the invention according to each claim of the present application, the circuit wiring board needs not to be light-shielding, but when the phosphor or the light diffusing material is dispersed, it is not necessarily required to be highly transmissive to light. No. Furthermore, in any of the claimed inventions, the film has an arbitrary translucency (transmittance with respect to the wavelength of light) such as a so-called smoked or colored one for visual effect. Good as a thing. For example, a transparent material may be used as the circuit wiring formed on the circuit wiring board, but a metal film made of an opaque material may be used. A method of connecting the configuration of the light emitting diode and the circuit wiring of the circuit wiring board is arbitrary. The sealing resin is not necessarily required to be highly permeable to light. For example, a phosphor is a substance that converts the light emission wavelength of a light emitting diode. It is assumed that the light of the light emission wavelength of the light emitting diode itself and the light of the light emission wavelength converted by the phosphor are combined and can be visually recognized in other colors. To do. The light diffusing material does not extract light from the light emitting diode only in the linear direction, but allows the entire light transmission region to be visually recognized as emitting light from any direction.

  According to the present invention, the light emitted from the light emitting diode provided on the first surface side of the circuit wiring board is transmitted by the phosphor or the light diffusing material dispersed in the sealing resin and the circuit wiring board. The direction changes irregularly. Further, light in a direction away from the circuit wiring board is reflected to the circuit wiring board by the reflection film. Thereby, from the 2nd surface side of a circuit wiring board, the very wide area | region centering on a light emitting diode is visually recognized as if it emitted light. That is, a surface light source can be configured using a light emitting diode that is substantially a point light source. If a large number of light emitting diodes are used, a surface light source having a desired area can be obtained. Thereby, an extremely thin surface light source that can be employed as a backlight of a liquid crystal display device can be configured. That is, the occupied volume of the entire unit of the liquid crystal display device having the backlight can be reduced. In addition, a reflective film is used, and the light use efficiency is high.

  Further, when three chips of the three primary colors are provided as a color tone of the light emitting diode, they are radiated to the second surface side of the circuit wiring board. Alternatively, for example, if a light emitting diode in the ultraviolet region, a sealing resin in which phosphors of three primary colors are dispersed, and a circuit wiring board are used, white light is emitted to the second surface side of the circuit wiring board by one type of light emitting diode. it can. In this case, the near-ultraviolet light-emitting diode that is the excitation light source is disposed in the light guide of the surface light source, so that the light use efficiency is increased. Thereby, an extremely thin white surface light source that can be employed as a backlight of a color liquid crystal display device can be configured. That is, the occupied volume of the entire unit of the color liquid crystal display device having the backlight can be reduced. In addition, a reflective film is used, and the light use efficiency is high.

The light-emitting diode used in the present invention is monochromatic, full-color, or other arbitrary. Further, the number of light emitting diodes used is also arbitrary. As the light emitting diode, a light emitting diode which emits light having a necessary color tone can be arbitrarily selected. For example, a purple or green light emitting diode using a group III nitride compound semiconductor (Al _x Ga _y In _1-xy N) may be selected. When combined with a phosphor, a light emitting diode having an emission wavelength in the near ultraviolet to blue region and a yellow phosphor may be combined to form a white diode, or a phosphor of a desired color and an ultraviolet light emitting diode may be combined.

The electrode structure of the light emitting diode is also arbitrary, and the connection method with the circuit wiring of the circuit wiring board can be arbitrarily selected. For example, when using a group III nitride compound semiconductor (Al _x Ga _y In _1-xy N) light emitting element, a reflective film is formed on the back surface of the chip substrate with a so-called face-up type structure (light extraction on the p-type semiconductor layer side). You may do it. In this case, the connection to the circuit wiring board may be a solder bump. Alternatively, a so-called flip chip type structure (light extraction on the insulating substrate side) having a reflective film on the p-type semiconductor layer side may be wire-bonded. When performing wire bonding, wedge bonding using ultrasonic waves eliminates the need for heat treatment and reduces the adverse effects on other components. Details of these will be described later.

  The material of the circuit wiring board is completely arbitrary except that a light-shielding base material is inappropriate. The base material is preferably a light-transmitting resin or inorganic material. When the wiring material corresponding to the light transmission region is made of indium tin oxide (ITO), the shadow of the wiring does not occur during display. As the light diffusing material, spherical or other fine particles are available, and in addition to being dispersed in the base material of the circuit wiring board, a thin film coated and fixed with the light diffusing material may be used. The same applies to the case of using a phosphor or an organic dye.

  The sealing resin is completely arbitrary with respect to the base material resin and other additives, and can be arbitrarily selected when a light diffusing material, a phosphor, an organic dye or the like is contained. In the present invention, replacing the sealing resin with an inorganic material is not excluded.

  An arbitrary metal or the like can be used for the reflective film formed so as to cover the light emitting diode. However, when using metal, in order to maintain insulation from the circuit wiring of the circuit wiring board, it is necessary to devise measures such as coating the circuit wiring with an insulating material or arranging a spacer.

  FIG. 1 is a cross-sectional view showing a configuration of a vicinity segment U1 of one light emitting diode 201 of a surface light source according to a specific first embodiment of the present invention. An overall image of the surface light source is obtained by arranging arbitrary number of segments U1 in FIG. 1 vertically and horizontally.

  A segment U1 in FIG. 1 is a circuit wiring board 10 composed of a substrate portion 10a in which phosphors of three primary colors are dispersed and a circuit wiring 10c, and a group III nitride compound semiconductor light emitting device emitting ultraviolet light having a peak at a wavelength of about 370 nm. 201, a bump 3b, a sealing resin 4 in which phosphors of primary colors are dispersed, and a reflective film 5 made of aluminum which is a highly reflective metal. The group III nitride compound semiconductor light emitting device 201 includes an insulating substrate 20, an n-type group III nitride compound semiconductor region 21n, and a p-type group III nitride compound semiconductor region 22p in this order. In FIG. 1, the light emitting region is indicated by a thick line A sandwiched between an n-type group III nitride compound semiconductor region 21n and a p-type group III nitride compound semiconductor region 22p. The region A can be a light emitting layer having a single layer, a single quantum well structure, or a multiple quantum well structure in addition to the pn interface, and is simply illustrated. A segment U1 in FIG. 1 connects the group III nitride compound semiconductor light emitting device 201 to the circuit wiring 10c like a flip chip. The p-type group III nitride compound semiconductor region 22p is connected to the circuit wiring 10c via a p electrode (not shown), and the n-type group III nitride compound semiconductor region 21n is a circuit via an n electrode (not shown) and bumps 3b. It is connected to the wiring 10c. Note that a p-electrode (not shown) is a translucent thin film electrode. In FIG. 1, the circuit wiring 10 c is described as if it covers most of the area where the group III nitride compound semiconductor light emitting element 201 is not disposed on the lower side of the substrate portion 10 a in FIG. 1. 10c may be formed so as to be able to energize the group III nitride compound semiconductor light emitting device 201, and does not need to cover the lower side of the substrate portion 10a. The circuit wiring 10c is assumed to be ITO or other transparent electrode.

  In the segment U1 of FIG. 1, when the ultraviolet light emitted from the light emitting region (thick line) A of the group III nitride compound semiconductor light emitting device 201 directly reaches the substrate portion 10a of the circuit wiring substrate 10, the substrate portion The three primary color phosphors dispersed in 10a are converted into red, green, and blue wavelengths, and each of the three primary color phosphors is a secondary light source. Of light is emitted. Similarly, when ultraviolet light emitted from the light emitting region (thick line) A of the group III nitride compound semiconductor light emitting device 201 is reflected by the reflective film 5 or directly reaches the sealing resin 4, the sealing resin 4. Are converted into red, green, and blue wavelengths by the three primary color phosphors dispersed in the red, green, and blue colors as if each of the three primary color phosphors was a secondary light source. Light is emitted. In this way, red, green, and blue light are emitted from the three primary color phosphors dispersed in the circuit board 10a and the sealing resin 4 as if they were secondary light sources. Thus, light of the three primary colors is emitted from the entire segment U1 in FIG. 1 in the upward direction in FIG. This is indicated by a thick arrow in FIG. That is, the segment U1 in FIG. 1 is a surface light source that uses the semiconductor light emitting element 201 that is substantially a point light source, and the surface light source in which the segments U1 in FIG. It becomes a white surface light source with primary colors. This is an extremely thin white surface light source that can be used as a backlight of a color liquid crystal display device.

[Modification 1]
The group III nitride compound semiconductor light emitting device 201 of the segment U1 in FIG. 1 is replaced with a light emitting device in another wavelength region instead of ultraviolet light emission, and dispersed in the substrate portion 10a of the circuit wiring board 10 and the sealing resin 4. When the phosphors of the three primary colors are replaced with a light diffusing material, a surface light source in the wavelength region can be configured. In this case, heat generation associated with wavelength conversion by the phosphor can be suppressed, and light utilization efficiency can be improved.

  FIG. 2 is a cross-sectional view showing the configuration of the vicinity segment U2 of one light-emitting diode 202 of a surface light source according to a specific second embodiment of the present invention. The entire image of the surface light source is obtained by arranging arbitrary number of segments U2 in FIG. 2 vertically and horizontally.

  The segment U2 in FIG. 2 shows that the segment U1 in FIG. 1 connected the light emitting element 201 to the circuit wiring 10c in a flip-chip manner, and the light emitting element 202 connected to the circuit wiring 10c by wire bonding 3n and 3p. Other than that, the configuration is the same. That is, the group III nitride compound semiconductor light emitting device 202 used for the segment U2 in FIG. 2 is basically the same as the group III nitride compound semiconductor light emitting device 201 in FIG. It has a group III nitride compound semiconductor region 21n and a p-type group III nitride compound semiconductor region 22p in this order, and includes an n-type group III nitride compound semiconductor region 21n and a p-type group III nitride compound. A light emitting region (thick line) A is sandwiched between the semiconductor regions 22p. Ultraviolet rays are emitted from the light emitting region (thick line) A. An n-electrode is formed between the n-type group III nitride compound semiconductor region 21n and the wire bonding 3n, and a p-electrode is formed between the p-type group III nitride compound semiconductor region 22p and the wire bonding 3p. It shall be. In addition, at least a p-electrode (not shown) is a light-transmitting thin film electrode.

  Similarly to the segment U1 in FIG. 1, the segment U2 in FIG. 2 is a surface light source that uses the semiconductor light emitting element 202 that is substantially a point light source, and is a surface light source in which the segments U2 in FIG. Becomes a white surface light source with three primary colors having an extremely large area. This is an extremely thin white surface light source that can be used as a backlight of a color liquid crystal display device.

[Modification 2]
The group III nitride compound semiconductor light emitting element 202 in the segment U2 in FIG. 2 is replaced with a light emitting element in another wavelength region instead of ultraviolet light emission, and dispersed in the substrate portion 10a of the circuit wiring board 10 and the sealing resin 4. When the phosphors of the three primary colors are replaced with a light diffusing material, a surface light source in the wavelength region can be configured. In this case, heat generation associated with wavelength conversion by the phosphor can be suppressed, and light utilization efficiency can be improved.

  In the segment U1 in FIG. 1, a highly reflective metal film may be formed on the back surface (lower side in the figure) of the substrate 20. In the segment U2 in FIG. 2, the p electrode (not shown) is a light-transmitting thin film electrode, but may be a highly reflective metal electrode.

  FIG. 3 is a cross-sectional view showing the configuration of a full-color liquid crystal display device 100 according to a specific third embodiment of the present invention. The full-color liquid crystal display device 100 of FIG. 3 includes a full-color liquid crystal device main body 60 and a white surface light source U that is a mixture of three primary colors.

  The white surface light source U is obtained by forming a large number of segments U1 shown in Example 1 or segments U2 shown in Example 2 vertically and horizontally. In the figure, a white surface light source U is a circuit wiring board 10 in which three primary color phosphors are dispersed, a group III nitride compound semiconductor light emitting element 201 or 202, a sealing resin 4 in which three primary color phosphors are dispersed, and a reflection. Only the film 5 is shown in a simplified manner.

  The full-color liquid crystal device main body 60 has the following known laminated structure. That is, from the side closer to the white surface light source U, the first polarizing plate 61a, the first glass substrate 62a, the drive electrode layer 63a, the first polarizing plate 64a, the liquid crystal (LC) 65, the second polarizing plate 64b, The common electrode 63b, the planarizing layer 66, the three-color filter layer 67, the second glass substrate 62b, and the second polarizing plate 61b. The surface 60S of the second polarizing plate 61b is the display surface of the full-color liquid crystal display device 100.

  In the full-color liquid crystal display device 100 of FIG. 3, uniform planar light is supplied to the first polarizing plate 61a by the white surface light source U of the three primary colors. Since the three primary color mixed white surface light source U is a very thin surface light source, the entire full color liquid crystal display device 100 of FIG.

[Modification 3]
In FIG. 3, the full-color liquid crystal main body 60 having the three-color color filter layer 67 and the three-primary color mixed white surface light source U are combined. However, if it is not a full-color liquid crystal display device, other colors are used as surface light sources. Also good. For example, when the white surface light source of the present invention, which is a mixture of blue light and yellow light by a yellow phosphor, is used, it is easy to construct a monochrome liquid crystal display device. Or you may comprise a monochrome liquid crystal display device using the surface light source of another color.

  The present invention is not limited to the above embodiments. On the basis of the configuration described in the embodiment, it can be appropriately changed using any available member. For example, the light-emitting element is not limited to a group III nitride compound semiconductor light-emitting element, and red to yellow-green GaAs-based or InP-based light-emitting elements may be used. When an element using a conductive chip substrate is connected to circuit wiring, the substrate may be directly connected to circuit wiring. In the present invention, light-transmitting elements are not necessarily used for circuit wiring, light-emitting elements, wires, solders, bumps and the like for conducting them. Naturally, the combined use of the light diffusing material and the phosphor is included in the present invention.

  In addition, the fixing method to the circuit wiring board of a light emitting element is arbitrary. The description of the substrate having an insulating substrate is omitted in the figure, but an adhesive may be used.

Sectional drawing which shows the principal part of the segment U1 of the surface light source which concerns on the specific 1st Example of this invention. Sectional drawing which shows the principal part of the segment U2 of the surface light source which concerns on the specific 2nd Example of this invention. Sectional drawing which shows the structure of the liquid crystal display device 100 which concerns on the specific 3rd Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10: Circuit wiring board 10a: The board | substrate part in which 3 primary color fluorescent substance was disperse | distributed 10c: Circuit wiring 201, 202: III group nitride compound semiconductor light emitting element 4: Sealing resin in which 3 primary color fluorescent substance was disperse | distributed 5: High Reflective film made of reflective metal A: Light emitting region of group III nitride compound semiconductor light emitting device 201, 202

Claims (2)

A circuit wiring board in which phosphors or light diffusion materials are dispersed;
A light emitting diode disposed on a second surface different from the first surface on the light extraction side of the circuit wiring board and connected to the circuit wiring;
A resin in which a phosphor or a light diffusing material is dispersed to seal the light emitting diode;
A surface light source comprising: a reflective film that covers the resin and reflects light from the light emitting diode toward the circuit wiring board. The surface light source according to claim 1,
A liquid crystal display device having a display surface parallel to the first surface of the circuit wiring board.

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