JP2007220369A - Lighting system and display device equipped with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that optical characteristics of a backlight are degraded by displacement of light-emitting elements and a light guide body. <P>SOLUTION: An engagement sliding groove is provided for each light-emitting element and a light guide body. With that, positional accuracy of the light-emitting elements is greatly improved to have variations of individual differences in optical characteristics reduced. Moreover, as the light-emitting elements are so structured to be pressed onto incident faces of the light guide body, gaps are eliminated between the light-emitting elements and the light guide body to maximize an emission efficiency. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a display device including an illumination device for illuminating a display element. Specifically, the present invention relates to a structure that holds a point light source and a light guide in an optimal positional relationship in an illumination device including the point light source and the light guide.

Many backlights used in display elements, particularly small color LCDs, are so-called side-emitting illumination devices that use white LEDs as a light source. In a side light-emitting type lighting device, a structure in which an FPC board on which an LED chip is mounted is fixed to a light incident portion of a light guide with a double-sided tape or the like is widely used. As described above, there is known an illumination device that introduces LED light from the side surface of the light guide and performs surface light emission (see, for example, Patent Document 1).
JP 2002-075038 A

  In the conventional lighting device, the positional relationship between the light source and the light guide is determined by attaching and fixing the FPC board on which the white LED light source is mounted to the light guide with a double-sided tape or the like. In order to efficiently guide the light from the light source into the light guide and to make the optical characteristics of the lighting device favorable, it is important to maintain the positional relationship between the light source and the light guide in an optimal state. That is, the optical characteristics deteriorate due to the misalignment of the point light sources, and the light emitted from the LED elements cannot be efficiently guided to the light guide. One of the causes that the positions of the LED element as the light source and the light guide are displaced are mounting accuracy when the LED element is mounted on the FPC board. Although LED elements have a certain degree of mounting accuracy due to the self-alignment effect at the time of surface mounting, there is a problem that it is very difficult to accurately control the position and inclination of the LED element in the mounting pattern, the thickness of the solder, etc. is there.

  Another cause of the misalignment between the LED element and the light guide is the pasting accuracy between the FPC board and the light guide. There has been a problem that it is difficult to attach the FPC board so that there is no gap between the light incident surfaces of the LED element and the light guide, and the attachment variation is large. The thickness of the double-sided tape used for attaching the FPC board to the light guide is the same as the above-described solder thickness, and the lower surface of the LED element and the lower surface of the light guide are the same height. Since the thickness of the solder is about several tens of μm, it is necessary to select a thin double-sided tape, and since the adhesive force is not sufficient, the double-sided tape is easily peeled off and the LED element is liable to be displaced. There was also.

  As described above, the conventional method for fixing the LED element is based on the overlapping of the two positional accuracy variations, that is, the mounting accuracy between the LED element and the FPC board and the attaching accuracy between the FPC board and the light guide. The positional variation between the light guides is large, which causes the optical characteristics of the backlight to deteriorate.

  Therefore, in the present invention, the positional accuracy can be greatly improved by adopting a structure in which the LED and the light guide are directly fitted. Further, by using the LED fixing member to press the LED against the light guide entrance surface, the light entrance efficiency is maximized by eliminating the gap between the LED and the light guide.

  An illuminating device of the present invention is an illuminating device including a light emitting element in which a point light source is packaged, and a light guide that guides light from the light emitting element and emits the light from an irradiation surface. A fitting groove is provided, and the light emitting element is fitted to the light guide by the fitting groove.

  Further, a fixing member for fixing the light emitting element to the light guide is provided. Furthermore, the fixing member has a spring structure that generates a force that presses the light emitting element against the light incident surface of the light guide. Further, the fixing member is made of a conductive material so that a driving voltage can be applied to the light emitting element via the fixing member.

  The display device of the present invention is a display device that irradiates a non-self-luminous display element by guiding light from a light emitting element packaged with a point light source using a light guide plate. A fitting groove is provided in each of the elements, and the light emitting element is fitted to the light guide using the fitting groove.

  Since the LED is always fixed at an optimum position with respect to the light guide, variations in the optical characteristics of the backlight can be suppressed.

  The liquid crystal display device mainly includes a liquid crystal element portion and a backlight portion. The backlight unit includes an LED as a light source, a light guide that converts a point light source into a surface light source, a brightness enhancement film, a reflection sheet, and a frame. The focus of the present invention is to optimize the backlight optical characteristics by always fixing the LED at the optimal position with respect to the light incident surface of the light guide, and minimize individual characteristic variations. It is what.

  In the LED used for the backlight of the present invention, one surface is a light emitting surface and the other five surfaces are surrounded by a reflecting wall. Grooves for sliding fitting with the light guide are formed on the two side surfaces of the LED. At the position where the LED of the light guide is arranged, a rectangular recess is made so as to be fitted with the groove of the LED. The LED regulates the amount of deviation in the thickness direction by setting the LED and the light guide so as to engage with each other.

  Further, an LED fixing member is used to fix the LED to the light guide. The LED fixing member is fixed to the light guide, and the electrode portion on the light emitting face of the LED is pressed by a spring structure. Thereby, the clearance gap between LED and a light guide is eliminated. Further, by making the LED fixing member with a conductive material, it is possible to serve as a current supply to the LED. This eliminates the need for a soldering step for the LED element, and does not apply thermal stress to the LED element, which is advantageous in terms of reliability. Hereinafter, a method for fixing the LED to the light guide will be described in detail based on the drawings.

  The configuration of the liquid crystal display device according to this embodiment is shown in FIG. The backlight of this liquid crystal display device is a three-chip LED-mounted backlight in which three LEDs 10 are linearly arranged at the end of the light guide 1 and LED light is received from one side of the light guide 1. is there. The light guide 1 is made by molding a transparent resin such as acrylic or polycarbonate, and fine irregularities are formed on the front or back surface of the light guide 1 so that light is uniformly emitted from the surface of the light guide. Let The light emitted from the light guide 1 is condensed upward by passing through the diffusion film 3 and the two brightness enhancement films 4 to illuminate the liquid crystal display element 2 from the back. A reflective film 6 is disposed below the light guide 1 so that light emitted downward from the light guide 1 is reflected upward. The frame 6 is made of a white resin and holds the entire liquid crystal display device, and also serves to reflect leaked light from the side surface of the light guide and return it to the light guide.

  FIG. 2 is a detailed view of the LED 10 used in the present invention. One surface is a light emitting surface. The light emitting surface is surrounded by five white reflecting walls, and the light from the light emitting element is concentrated on the light emitting surface 22. Grooves 21 for fitting with the light guide are formed on the two side surfaces of the LED. Further, an anode electrode 23 and a cathode electrode 24 are arranged on the end opposite to the light emitting surface 22 at the longitudinal end. The anode electrode 23 and the cathode electrode 24 are subjected to a gold plating process for reducing the contact resistance with the LED fixing member.

  FIG. 3 is an enlarged view of the LED mounting portion of the light guide 1. The LED mounting portion is formed with a rectangular recess that is just large enough to accommodate the LED 10, and a groove 31 that is paired with the groove 21 of the LED 10 is formed on the side of the recess. A triangular prism is formed on the light incident surface 32 in order to spread light from the LED.

  FIG. 4 is an enlarged view of the LED fixing member a. It consists of a conductive metal and also serves to supply current to the LED. The LED pushing portion 41 has a thin beam shape so as to have a spring property, and serves to push the LED 10 against the light incident surface. In addition, the LED pressing portion is plated with gold to ensure electrical contact.

  FIG. 5 is an enlarged view of the LED fixing member b. It plays the role which fixes LED10 similarly to the LED fixing member a, and fixes LED of an edge.

  FIG. 6 is a diagram showing a procedure for fixing the LED. The LED 10 is inserted from the vertical direction into the light guide entrance surface so that the groove 21 and the groove 31 are fitted. After the LED 10 is arranged, the LED fixing member a and the LED fixing member b are inserted so as to sandwich the light guide, and the hole 42 opened in the LED fixing member and the protrusion 33 formed on the light guide are fitted. Fixed.

  The LED 10, the LED fixing member a, and the LED fixing member b are in an electrically serial connection state, and the LED drive current is supplied through the LED fixing member a and the LED fixing member b. The current supply to the LED fixing member b is electrically connected through the control board 7 and the spring contact 8.

  According to the present invention, the LED can be fixed to the optimal position of the light guide without variation, and the best optical characteristics as a backlight can be obtained. That is, variations in optical characteristics due to LED position deviation can be suppressed. Moreover, cost reduction can be achieved by standardizing the LED fixing member. In addition, since the LED is not subjected to thermal stress in a process such as solder reflow, not only is it advantageous in terms of reliability, but there are also advantages such as an increase in choices of LED package materials.

  In addition, the Example mentioned above only shows an example of this invention, and various deformation | transformation, such as the number and arrangement | positioning of LED, the shape and fixing method of an LED fixing member, a film structure, are possible.

  The present invention can be applied to an illumination device using an LED element as a light source and a liquid crystal display device using the same.

The perspective view which shows schematic structure of a liquid crystal display device Explanatory drawing showing details of LED Enlarged view showing the light incident part of the light guide in detail External view showing LED fixing member a External view showing LED fixing member b Schematic diagram explaining the LED fixing procedure

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light guide 2 Liquid crystal display element 3 Diffusion film 4 Brightness enhancement film 5 Reflective film 6 Frame 7 Liquid crystal display device control board 8 Spring connection terminal 10 LED
11 LED fixing member a
12 LED fixing member b
21 Groove 22 Light emitting surface 31 Groove 32 Light incident surface 33 Projection 41 LED pressing portion 42 Fixing hole 51 LED pressing portion 52 Fixing hole

Claims (5)

In a display device comprising a light emitting element in which a point light source is packaged, a non-self-luminous display element, and a light guide that guides and emits light from the light emitting element to the display element.
A display device, wherein a fitting groove is provided in each of the light guide and the light emitting element, and the light emitting element is fitted into the light guide by the fitting groove. In a lighting device including a light emitting element in which a point light source is packaged and a light guide that guides light from the light emitting element and emits the light from an irradiation surface.
An illumination device, wherein a fitting groove is provided in each of the light guide and the light emitting element, and the light emitting element is fitted into the light guide by the fitting groove.   The lighting device according to claim 2, further comprising a fixing member that fixes the light emitting element to the light guide.   The lighting device according to claim 3, wherein the fixing member has a spring structure that generates a force that presses the light emitting element against a light incident surface of the light guide.   5. The lighting device according to claim 3, wherein a material of the fixing member is conductive, and a driving voltage is applied to the light emitting element through the fixing member.

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