JP4575248B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a structure of a backlight using a light emitting diode element.

  In a liquid crystal panel display device typified by a thin display, a cold-cathode tube is conventionally used as a backlight light source. Recently, a large-sized liquid crystal television using a semiconductor light-emitting diode element as a backlight light source has been developed and announced. In the contents shown in Non-Patent Document 1, the mounted light-emitting diode elements are configured such that each of the R red, G green, and B blue elements is mounted on the package, and the packages are arranged in a line. It has a configuration. The light-emitting diode elements used in these devices have a configuration in which they are mounted with Au wires. Conventionally, as shown in Non-Patent Document 2 as a well-known example, the light-emitting diode element has bipolar electrodes set on one side, in order to set the divergence angle large and bring out the light output high, There is a surface emitting type configuration that enables flip chip mounting. It has been shown that a light emitting diode element mounted on a flip chip can extract light from the entire element with a surface emitting type structure from a transparent substrate side.

  Further, a configuration in which a surface light emitting diode element is mounted is described, and it is described in Patent Documents 1 and 2 to provide a liquid crystal lighting device on which a resin-sealed element is mounted after mounting.

Tanaka Akira et al., JP 2002-365634 A Yoshiyuki Masuda et al., Japanese Patent Laid-Open No. 2003-7114 Koichiro Kakinuma, FPD International 2005 Pre-Seminar, 1st, 2005.2.4 S. Nakamura et al, Jpn Journal of Appl. Phys., 34, L1332 (1995).

  The light-emitting diode element used in the above-mentioned document has elements for each RGB light source mounted in each package, and the optical design becomes difficult and the distance to diffuse light is so large that the liquid crystal display device cannot be thinned. Therefore, there is a problem that it becomes a high-cost package or packaging form. In light-emitting diode devices that are flip-chip mounted, there are still problems with respect to direct mounting for realizing high efficiency and reliability and for realizing low cost.

  An object of the present invention is to propose a configuration that is suitable for optical design and that can reduce the thickness of a liquid crystal display device, that can be reduced in cost, and that can be mounted. Another object of the light-emitting diode element is to enable flip chip mounting which is advantageous for high luminance and high efficiency, and to reduce the influence of thermal strain and thermal stress due to thermal expansion of the wiring to be mounted.

  Below, the structure of this invention for solving the said subject is demonstrated.

  In this invention, it has a board | substrate and several wiring provided on this board | substrate, each of these wirings has two or more bending parts in the said board | substrate surface, Each of them has a light source configuration in which one or a plurality of light emitting diode elements are directly mounted. That is, by providing a plurality of bent portions in the wiring, a wiring pattern is obtained in which one or a plurality of light emitting diode elements can be mounted on one wiring. It should be noted that the bending angle is more preferably in the vicinity of 90 degrees as shown in FIG.

  Each of the plurality of wirings has a configuration in which a plurality of light emitting diode elements having different sizes are directly mounted. Each of the plurality of wirings has a configuration in which wirings having different widths are joined. In addition, the wiring having a different width has a configuration including a main wiring and a branch wiring having a narrower width than the main wiring. The main direction in which the branch wiring thermally expands is substantially the same as the main direction in which the main wiring thermally expands, and the light emitting diode element is mounted over the main wiring and the branch wiring. In addition, the electrode of the light emitting diode element has a flip chip-compatible electrode configuration in which electrodes having both polarities are formed on one surface of the element. Further, the electrode of the light emitting diode element is configured to be flip-chip mounted on the wiring. The light emitting diode element is composed of a red element, a green element, and a blue element, and elements of each color are connected in series by the wiring. In addition, the elements of each color connected in series are controlled in operation by lines, and a line scan is performed by arranging the lines formed in series in the vertical direction.

  Moreover, in this invention, it has a board | substrate and several wiring provided on this board | substrate, and each of these wirings has two or more bending parts in the said board | substrate surface, and the said bending part The structure of the light source is characterized in that the light emitting diode element is directly mounted. Further, the substrate includes a substrate, a plurality of wirings provided on the substrate, and a light-emitting diode element mounted on the wiring, and the light-emitting diode element is flip-chip mounted. The configuration of the light source is characterized in that is bent. In this way, one wiring and the other wiring connected to one light emitting diode are arranged so as not to be linear with each other.

  Further, the present invention discloses a liquid crystal display device using the light source. That is, the liquid crystal display device includes a pair of substrates and a liquid crystal layer disposed between the pair of substrates and uses the light source as a backlight.

  In the present invention, a high-brightness and high-efficiency light-emitting diode element can be flip-chip mounted on a light-emitting diode element serving as a backlight source of a liquid crystal display device.

  The best mode will be described below.

  An embodiment of the present invention will be described below with reference to FIGS.

  As shown in FIG. 1, a panel including a diffusion plate 2, a regular prism sheet 3, a regular reflection laminated sheet 4, a mat 5, a polarizing plate 6, a thin film transistor, and a liquid crystal layer on a circuit using the backlight source 1 of the present invention. 7. A liquid crystal display device constituting the polarizing plate 6 is formed. This is formed as follows. As shown in FIG. 2, the backlight light source of this embodiment has a light emitting diode element 10 mounted on a wiring 9 provided on a metal substrate with an insulating film, a ceramic substrate, or an insulating resin substrate 8, and then reflects light. Sealing is performed by the plate 11 and the sealing resin 12 with a diffusing material. At this time, the light emitting diode element 10 is formed by integrally molding the light reflecting plate 11 on a metal substrate with an insulating film, a ceramic substrate, or an insulating resin substrate 8 and then mounting the light reflecting plate 11 on the wiring 9. The sealing resin 12 may be used for sealing. Thereafter, the mounting substrate is mounted on the housing 13 to constitute a backlight light source. The metal substrate with an insulating film or the ceramic substrate or the insulating resin substrate 8 may be a single mounting substrate as shown in FIG. 3, or may be a continuous mounting substrate as shown in FIG. If the mounting substrate shown in FIGS. 3 and 4 is repeatedly mounted on the housing 13, the backlight light source shown in FIG. 2 is obtained. As an example of the wiring in the present invention, there is a method in which the light emitting diode elements are arranged in a straight line and connected in series to the opposing wiring as shown in FIG. 5 showing a wiring pattern in the inner diameter hole of the reflector. . Alternatively, as shown in FIG. 6 showing another wiring pattern in the inner diameter hole of the reflecting plate, there is a method in which light emitting diode elements are arranged oppositely in the center and connected. Here, in order to efficiently mix the colors of the light from each of the RGB light emitting diode elements, it is more effective to arrange the elements in a centralized manner in the arrangement as shown in FIG.

Here, there are roughly the following two methods for mounting the light-emitting diode element on the wiring. One is mounting of the light emitting diode element by wire bonding using the metal wire 18 shown in FIG. The other is flip-chip mounting using the bumps 20 shown in FIG. Among these mountings, the transparent substrate of the light emitting diode element can be placed on top, there is no light shielding material, the light emitting angle distribution and the light emitting brightness can be increased, and flip chip mounting is effective for the high brightness and high efficiency of the element. is there. A means for performing the flip chip mounting and mounting a plurality of light emitting diode elements will be described below. It is important to configure the wiring pattern according to the electrode of the light emitting diode element. FIG. 9 shows a top view of an electrode pattern having the p-side electrode 22 and the n-side electrode 23 of the light-emitting diode element. Further, when the size of the element is increased, the light emitting diode element has an electrode pattern showing the upper surface of FIG. 10 by changing the electrode pattern according to the large element configuration and introducing an n-side comb electrode into the n-side electrode 23. Element.

  In order to mount a plurality of light emitting diode elements having these electrode patterns, the following wiring configuration was adopted. First, a plurality of elements are flip-chip mounted on a light-emitting diode element having an electrode top view of FIG. 9 and having an element size of about 0.3 mm square, so that opposing wirings are not linear, as shown in FIG. The wiring pattern was provided with several complicated rectangular shapes. The wiring pattern shape shown in FIG. 11 is combined with the electrode configuration of the element shown in FIG. 9 to set a shape that can be mounted. By adopting such a shape, flip chip mounting 27 can be performed on a plurality of elements, not just one light emitting diode element, on the same wiring. If this shape is set, after one element is mounted, if it is determined by inspection that the element is defective or has poor characteristics, another element having the same electrode pattern can be mounted. In this way, the device mounting yield can be improved. Also, when a high-brightness backlight is required depending on the application, the output can be increased by increasing the number of elements by mounting two light-emitting diode elements on the same wiring.

Further, by adopting the wiring structure as shown in FIG. 12, the element of about 0.3 mm square shown in FIG. 9 and the element of the size of 0.3 mm square or more shown in FIG. 10 can be mounted on the same wiring. . That is, a region for mounting an element having a size of about 0.3 mm square and a region for mounting an element having a size of 0.3 mm square or more are distinguished in advance, and each region can be determined and mounted.
For elements with a size of 0.3 mm square or larger, even if the type of element size increases, such as about 0.6 mm square elements and 1 mm square elements, the wiring structure must be considered in advance. Can be implemented. By making it possible to mount a plurality of light emitting diode elements having different element sizes, for example, two elements of about 0.3 mm square are used, or elements of about 0.6 mm square or elements of about 1 mm square are used. It is possible to select and set whether to construct a high-luminance backlight light source with an increased target light output while utilizing optical design.

  As described above, in this embodiment, a plurality of light emitting diode elements can be flip-chip mounted, and a plurality of elements of the same size or different sizes can be mounted on the same wiring. . For this reason, since the mounting element can be redundantly designed, defective mounting elements and defective elements can be exchanged with good elements to improve the mounting yield. It becomes possible to use a light source. Further, it is possible to provide a backlight light source that achieves a desired high luminance by using light emitting diode elements having different element sizes depending on the application. As described above, flip-chip mounted light emitting diode elements can be mounted with a high yield, and a high-brightness and high-efficiency backlight light source can be provided.

  Another embodiment of the present invention will be described below with reference to FIGS.

  Similarly to Example 1, a light-emitting diode element is flip-chip mounted to constitute a backlight light source. Here, it is necessary to consider thermal strain and thermal stress due to thermal expansion in the facing wiring. When the light-emitting element is flip-chip mounted on the opposing wiring, the vector direction causes thermal expansion in opposite directions, resulting in thermal distortion and thermal stress in the mounting bump connection, which is disadvantageous in terms of reliability. In order to reduce thermal strain and thermal stress due to the thermal expansion of the wiring, a narrow branch wiring different from the wide main wiring for conducting the light emitting diode element is formed. Furthermore, as shown in FIG. 13 and FIG. 14, a pattern of branch wiring that thermally expands mainly in the same vector direction with respect to the direction of thermal expansion of the main wiring is configured.

  For example, a wiring pattern having an intricate shape as shown in FIG. 13 is used to flip-chip mount a plurality of elements on a light emitting diode element having an electrode top view of FIG. It was. The wiring pattern shape shown in FIG. 13 and the electrode configuration of the element shown in FIG. By adopting such a shape, as in the first embodiment, a plurality of elements can be flip-chip mounted on the same wiring, so that the mounting yield of the elements can be improved and the number of elements can be increased. In addition to being able to be mounted for the purpose of high brightness that increases output, it is possible to mount with reduced thermal strain and thermal stress of the wiring. This is made possible by mounting the element so that the configuration of the narrow branch wiring and the vector direction of thermal expansion are the same as those of the main wiring.

Further, by adopting the wiring structure as shown in FIG. 14, the element of about 0.3 mm square shown in FIG. 9 and the element of the size of 0.3 mm square or more shown in FIG. 10 can be mounted on the same wiring. . That is, a region for mounting an element having a size of about 0.3 mm square and a region for mounting an element having a size of 0.3 mm square or more are distinguished in advance, and each region can be determined and mounted.
For elements with a size of 0.3 mm square or larger, even if the type of element size increases, such as an element of about 0.6 mm square or an element of about 1 mm square, the wiring structure should be taken into consideration in advance. Can be implemented. By making it possible to mount a plurality of light emitting diode elements 30 having different element sizes, for example, two elements of about 0.3 mm square are used, or elements of about 0.6 mm square or about 1 mm square are used. It is possible to select and set using an optical design as to whether or not to constitute a high-brightness backlight light source that is mounted by using one element and has an increased target light output. Furthermore, when the element is mounted, the main wiring can be mounted with reduced thermal strain and thermal stress. This is made possible by mounting the element so that the configuration of the narrow branch wiring and the vector direction of thermal expansion are the same as those of the main wiring.

  In this embodiment, a plurality of light emitting diode elements can be flip-chip mounted, and a plurality of elements having the same size or different sizes can be mounted on the same wiring. For this reason, the redundant design of the mounting elements can be performed, so that defective mounting elements and defective elements are replaced with good elements to improve the mounting yield, and the high luminance backlight light source can be added by adding the good elements. It becomes possible to do. Further, it is possible to provide a backlight light source that achieves a desired high luminance by using light emitting diode elements having different element sizes depending on the application. Further, by forming a narrow branch wiring having the same vector direction of thermal expansion as that of the main wiring, it is possible to mount the main wiring with reduced thermal strain and thermal stress. As a result, the characteristics of the light-emitting diode element mounted on the flip chip are stable and reliable, and a high-brightness and high-efficiency backlight light source can be provided.

  In the present embodiment, a liquid crystal display device is formed to which a light emitting diode element flip-chip mounted on the wiring pattern of the first embodiment or the second embodiment and a backlight light source using the light emitting diode element are used.

  In the liquid crystal display device configured in this embodiment, the light emitting diode element is directly mounted on the substrate serving as the base of the backlight light source, compared with the case where each RGB element is mounted in the conventional package, and a high luminance and high efficiency element is obtained. By being mounted close to each other, the three primary colors of high luminance can be mixed at a short distance, so that the distance between the backlight light source and the diffusion plate of this content can be reduced to make a thin liquid crystal display device. When the light-emitting diode element of the present content is used as a light source, a large-screen television liquid crystal panel display device having a backlight light source whose distance from the diffuser plate is set to 20 mm or less can be configured.

  The present invention can be applied to a backlight light source using a light emitting diode LED element as a light source, a computer monitor using the light source, and a liquid crystal display display device for a large TV.

FIG. 3 is a schematic cross-sectional view of a liquid crystal display device. The upper surface schematic which shows the backlight light source in this invention. The upper surface schematic of the unit element of the backlight light source in this invention. The upper surface schematic of the unit element of the backlight light source in this invention. The top view which shows the wiring with respect to the light emitting diode element in the backlight light source unit element of this invention. The top view which shows the wiring with respect to the light emitting diode element in the backlight light source unit element of this invention. Sectional drawing which shows the wire bonding mounting of a light emitting diode element. Sectional drawing which shows the flip-chip mounting of a light emitting diode element. The top view which shows the electrode pattern in the light emitting diode element of flip chip mounting. The top view which shows the electrode pattern in the light emitting diode element of flip chip mounting. The top view which shows the wiring pattern of this invention which carries out the flip chip mounting of the light emitting diode element of the same size. The top view which shows the wiring pattern which carries out the flip chip mounting of the light emitting diode element from which size differs. The top view which shows the wiring pattern of this invention which carries out the flip chip mounting of the light emitting diode element of the same size. The top view which shows the wiring pattern which carries out the flip chip mounting of the light emitting diode element from which size differs.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Backlight light source of this invention, 2 ... Diffusing plate, 3 ... Regular prism sheet, 4 ... Regular reflection laminated sheet, 5 ... Matt, 6 ... Polarizing plate, 7 ... Panel containing thin-film transistor and liquid crystal layer on a circuit, 8 ... Metal substrate with insulating film or ceramic substrate or insulating resin substrate, 9 ... Wiring, 10 ... Light emitting diode element, 11 ... Light reflecting plate, 12 ... Sealing resin, 13 ... Housing, 14 ... Single mounting substrate, 15 ... Continuation Mounting board, 16... Upper surface showing an example of wiring structure, 17... Upper surface showing another example of wiring structure, 18... Wire, 19... Cross section of light emitting diode element by wire bonding mounting, 20. Cross-section of light-emitting diode element, 22... P-side electrode, 23... N-side electrode, 24.

Claims (6)

A substrate,
A plurality of wirings provided on the substrate;
Each of the plurality of wirings has two or more bent portions on the substrate surface,
And one or a plurality of light emitting diode elements are directly mounted on each of the plurality of wirings,
Each of the plurality of wirings is formed by joining wirings having different widths,
The wiring having a different width includes a main wiring and a branch wiring having a narrow width compared to the main wiring.
By the two or more bent portions are present in said branch wiring, the main direction in which the branch wiring is thermally expanded is the main direction same to the main wiring is thermally expanded,
The light emitting diode element is mounted over the main wiring and the branch wiring,
The light emitting diode element has a flip chip-compatible electrode configuration in which an electrode having both polarities is formed on one surface of the element.   The light source according to claim 1, wherein the plurality of light emitting diode elements having different sizes are directly mounted on each of the plurality of wirings. The light emitting diode element comprises a red element, a green element and a blue element,
The light source according to claim 1, wherein a red element, a green element, and a blue element are connected in series by the wiring. The operation of each color element connected in series is controlled by a line,
The light source according to claim 3, wherein line scanning is performed by arranging the lines formed in series in a vertical direction.   The light source according to any one of claims 1 to 4, wherein a light emitting diode element is directly mounted at the bent portion. A pair of substrates;
A liquid crystal layer disposed between the pair of substrates,
6. A liquid crystal display device using the light source according to claim 1 as a backlight.

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