JP2005285389A - Lighting device and display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the thickness of a sidelight type lighting device. <P>SOLUTION: The lighting device is composed of a light guide body having a light irradiation part irradiating light from a light source as illumination light, and a light-incident body guiding the light of the light source to the light guide body, further, the light-incident body has a light conducting part conducting the light to the light guide body and a light incident face on which the light of the light source is incident. The light-incident body is formed so as to reduce its thickness as it is headed from a light-incident face side to a light guiding part side. Further, a reflection layer is formed on the surface excluding the light-incident face and the light conducting part, and a fine reflection structure is formed at least on one surface of the light irradiation part of the light guide body. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a display device used in a watch, a mobile phone, an audio, an electronic device, and the like, and a lighting device used in the display device.

  In recent years, liquid crystal display devices having a thin and light feature have been widely used for portable devices and the like. In particular, since a display element used in a mobile phone is required to be small and light, a liquid crystal display device is used in most mobile phones. However, since the liquid crystal display device is a light receiving type, there is a problem in visibility in a dark place required for a mobile phone. Therefore, an illuminating device is often installed on the front or back of the liquid crystal display device.

In order to realize this thin and light weight, a sidelight type lighting device in which an LED (Light-Emitting-Diode) is arranged as a light source on the side surface of the light guide plate is often used (for example, see Patent Document 1).
Patent No. 3301752 (pages 1 to 3 and FIG. 1)

  However, in the conventional sidelight type illumination device, if the thickness of the light guide plate is made thinner than the size of the LED light source, the light from the LED light source cannot be efficiently guided to the inside of the light guide plate. Had the problem of not being able to.

  An illumination device according to the present invention includes a light source, a light guide having a light irradiation unit that emits light from the light source as illumination light, a reflection structure provided on at least one surface of the light illumination unit, and a light source The light incident body includes a light incident body that guides light to the light guide, and the light incident body includes a light incident surface that receives light from the light source and a light transmission section that transmits the light to the light guide. The light incident body is configured such that the thickness of the light incident body gradually decreases from the light incident surface side toward the light transmitting portion side.

  With such a configuration, even if the light illumination part of the light guide plate is thinned to about 1 mm, the light from the light source can be efficiently introduced into the light guide plate.

  ADVANTAGE OF THE INVENTION According to this invention, the thin and lightweight illuminating device which has favorable brightness | luminance and brightness distribution can be provided. Therefore, not only the display quality of the liquid crystal display device using the same is improved, but also the liquid crystal display device can be reduced in thickness and weight.

  The illumination device of the present invention includes a light source, a light guide, and a light incident body that guides light from the light source to the light guide. The light incident body has a light incident surface on which light from the light source enters and a light transmission portion that transmits light to the light guide, and the thickness is gradually reduced from the light incident surface side toward the light transmission portion side. It is configured. In addition, the light guide has a light irradiating unit that emits illumination light, and a reflective structure is provided on at least one surface of the light illuminating unit. Alternatively, the light incident body is formed to be thin stepwise sequentially from the light incident surface side. Further, the stepped step portion formed in the light incident body is formed substantially vertically. Furthermore, the light entrance and the light guide are integrally formed of the same material. Alternatively, the light guide is formed of a transparent film material.

  The display device of the present invention includes the illumination device having the above-described configuration and a non-self-luminous display element provided on the light irradiation surface side of the illumination device.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a cross-sectional view of the illumination device of this embodiment. In the illuminating device of this embodiment, the light guide plate is formed integrally with the light incident body, and the wedge-shaped light incident section 2 is provided with the function of the light incident body. And the light illumination part 3 of a light-guide plate is formed with the thickness of about 1 mm or less.

  The light emitted from the LED light source 1 is narrowed down by the wedge-shaped light incident unit 2, guided in the light illumination unit 3 of the light guide plate, and the upper surface of the light illumination unit 3 of the light guide plate which is the light irradiation surface of the illumination device. The object to be illuminated, which is not shown in the figure, is uniformly irradiated from the side. By illuminating a non-self-luminous display element, for example, a liquid crystal display element, with a lighting device having such a configuration, a thin display device with uniform brightness and brightness can be realized.

  Although only one LED light source 1 is drawn in FIG. 1, a plurality of, for example, 3 to 5, LED light sources are usually used. Although not shown, the light incident surface that is the light source side end surface of the wedge-shaped light incident portion 2 facing the LED light source 1 has an in-plane direction inside the wedge-shaped light incident portion 2 of the light emitted from the LED light source 1. A small prism is formed to control the spread angle. This microprism has a vertical ridgeline in the plane of FIG. 1, and the spread angle of light inside the wedge-shaped light incident portion 2 can be controlled by the apex angle and height of the microprism.

  The wedge-shaped light incident part 2 is stepped and has a plurality of steps, and is gradually thinner toward the light emitting end face. These step portions are formed with a substantially vertical angle. Although the figure shows a case where the number of stages is three, actually, about 20 to 100 stages are formed.

  Further, the light reflection layer 5 is formed except for the end surface on the light source side of the wedge-shaped light incident portion 2. This light reflecting layer is formed by laminating Al, Ag, or a compound of Ag and Pd with a film thickness of 100 nm or more, preferably about 1 μm. The light reflecting layer can be easily formed by a vapor phase growth method such as vacuum deposition or a method in which electroless plating and electrolytic plating are combined.

  The light guide plate having the wedge-shaped light incident portion 2 is made of a transparent polymer such as acrylic resin, polycarbonate resin, polyethylene resin, or cycloolefin resin.

  A light reflecting layer 4 is formed on three side surfaces of the light illuminating unit 3 of the light guide plate excluding the light source side. This light reflecting layer is formed by laminating Al, Ag, or a compound of Ag and Pd with a film thickness of 100 nm or more, preferably about 1 μm. The light reflecting layer can be easily formed by a vapor phase growth method such as vacuum deposition or a method in which electroless plating and electrolytic plating are combined.

  A minute reflection structure is formed on the back surface of the light illumination unit 3 of the light guide plate. As the fine reflection structure, a fine prism group having a ridge line in a direction perpendicular to the paper surface of FIG. 1, a minute triangular prism group convex or concave toward the inside of the light guide plate 3, or a texture structure is used. be able to. As a method for forming these fine reflective structures, a normal injection molding method can be used.

  Since the light guide plate 3 is thinly formed with a thickness of about 1 mm, the number of times the light guided inside is reflected by the inner surface of the light guide plate is smaller than that of a normal light guide plate having a thickness of about 5 to 10 mm. Therefore, the formation density of the fine reflecting structures may be about 1/10 to 1/5 that of the normal light guide plate. This also significantly improves the luminance distribution of the illumination light as compared to an illumination device having a normal light guide plate thickness.

  FIG. 2 schematically shows another cross-sectional configuration relating to the thin illumination device of the present embodiment. As shown in the drawing, a light reflection plate 6 is disposed outside the light illumination section 3 of the light guide plate on the side where the fine reflection structure is formed. Thus, by forming the light reflecting plate 6 on the back surface of the light illuminating unit 3 of the light guide plate, the light that has passed through the back surface of the light guide plate 3 is efficiently irradiated with light, that is, the surface of the light illuminating unit 3 of the light guide plate. It can be returned to the side, that is, the light irradiation surface.

  FIG. 3 schematically shows a cross-sectional configuration of an illumination device having a wedge-shaped light incident portion of another shape. As shown in the figure, the wedge-shaped light incident portion 2 has a step formed only on the upper surface, and has a wedge shape that becomes narrower as the distance from the light incident end increases. There is no restriction on the height of each step, but it is desirable to make the step height as low as possible. Specifically, the height of each step can be arbitrarily set in the range of 50 to 1000 μm. In such a structure, the length of the wedge-shaped light incident portion 2 is longer than that shown in FIGS. 1 and 2, but the bottom surface of the light guide plate including the wedge-shaped light incident portion 2 can be made flat. It has the advantage that the lighting arrangement is easy.

  FIG. 5 shows the behavior of light inside the wedge-shaped light incident portion 2 shown in FIG. Light emitted from the light source 1 enters the wedge-shaped light incident portion 2 from the light incident end face of the wedge-shaped light incident portion 2. First, the light indicated by the optical path 20 is reflected by the light reflecting layer 4 formed on the upper surface of the light incident portion and directly enters the light illumination portion 3 of the light guide plate from the wedge-shaped light incident portion 2. On the other hand, the light indicated by the optical path 21 is reflected by the light reflecting layer 4 formed in the step part and once returns to the light incident end face side, but is reflected again by the light incident end face and enters the light illumination part 3 of the light guide plate. . As shown here, the wedge-shaped light incident part 2 used in the present invention is formed of a vertical stepped part, so that the side surface of the wedge-shaped light incident part 2 can be The angle of incidence on the top and bottom surfaces does not change. That is, it is possible to guide to the light illumination unit 3 of the light guide plate without substantially changing the emission angle from the light source 1.

  If a wedge-shaped light incident portion having a normal smooth taper or a wedge-shaped light incident portion having a stepped portion having a taper is used, the light reflected by the taper is consequently larger than the emission angle from the light source. Since it is equivalent to light having a large emission angle and enters the light illumination part 3 of the light guide plate and immediately leaks to the outside, the formation of the fine reflection structure should have a higher order change. Therefore, it is important that the illumination luminance distribution is not biased toward the light source.

  Next, the behavior of light inside the light illumination unit 3 of the light guide plate will be described. Since most of the light incident on the light illumination unit 3 of the light guide plate from the wedge-shaped light incident unit 2 is incident at a large incident angle greater than the critical angle, it is repeatedly reflected inside. A fine reflecting structure is formed on the back surface of the light illuminating unit 3 of the light guide plate, and the guided light incident on the fine reflecting structure is deflected in the optical path and is incident on the light of the light guide plate at an incident angle smaller than the critical angle. The light is incident on the surface of the illuminating unit 3, and as a result, is emitted from the surface of the light illuminating unit 3 of the light guide plate to irradiate the object to be illuminated.

  The fine reflecting structure formed on the back surface of the light illuminating unit 3 of the light guide plate is formed densely with increasing distance from the light source side so that the luminance of light emitted from the surface of the light guide plate is uniform.

  Moreover, although the above description demonstrated the example which formed the fine reflective structure in the back surface of the light illumination part 3 of a light-guide plate, it cannot be overemphasized that you may form in the upper surface of the light illumination part 3 of a light-guide plate.

  FIG. 4 schematically shows a cross-sectional configuration of a liquid crystal display device using the illumination device of the present invention. The lighting device used in FIG. 4 has the same configuration as that shown in FIG. 3, but a light reflection plate 6 is disposed on the back surface of the light guide plate 3. As the liquid crystal panel 8, either an active matrix type liquid crystal display panel using TFT elements, a passive matrix type liquid crystal panel, or any type of liquid crystal panel can be used. A prism sheet 7 is disposed in the gap between the liquid crystal panel 8 and the light guide plate 3. This prism sheet is a transparent sheet in which minute prisms having irregularities facing the light illumination unit 3 side of the light guide plate and having ridge lines in a direction perpendicular to the paper surface of FIG. 4 are regularly formed. By arranging the prism sheet 7 between the illumination device of the present invention and the liquid crystal panel 8, the illumination light can be efficiently incident on the surface of the liquid crystal panel 8. Can increase the brightness. As can be seen from FIG. 4, in the illumination device of the present invention, the light illumination part of the light guide plate can be made thin, and as a result, the liquid crystal display device itself can be made thin.

  Hereinafter, more specific examples will be described.

  A lighting device having the structure shown in FIG. 1 was produced. A wedge-shaped light incident portion 2 having a thickness of 7 mm on the light source side and a width of 35 mm was molded from an acrylic resin. The light illumination part 3 of the light guide plate had a thickness of 1 mm and a length of 40 mm. Aluminum was deposited on the surface of the wedge-shaped light incident portion 2 to a thickness of about 1 μm. The height of each step portion of the wedge-shaped light incident portion was 80 μm, and the number of steps was 37 on each side. On the three side surfaces of the light guide plate except for the upper and lower surfaces of the light illuminating unit 3, an aluminum light reflection layer was formed by vapor deposition of about 1 μm. On the back surface of the light guide plate 3, convex fine triangular prisms having a height of 5 μm, a base angle on the light source side of 30 degrees, and a base angle on the side opposite to the light source of 80 degrees are scattered in the light guide plate. The formation density was such that the bottom area of the fine triangular prism was proportional to the square of the distance from the light source. Three white LED light sources were used as light sources.

  When the luminance of the thin lighting device thus manufactured was measured, a value of 2000 to 2400 cd / m 2 was obtained, and performance equivalent to that of a normal sidelight type lighting device was obtained. Moreover, the thickness of the illumination part of the illuminating device can be reduced to 1 mm, which is 1/7 of the conventional thickness.

  A film type illumination device shown in FIG. 3 was produced. The number of stages of the light incident part 2 was 74 with a height of 80 μm. As the light illumination part 3 of a light-guide plate, the thing similar to Example 1 was used. However, a fine prism having a ridge line parallel to the light incident end was formed on the back surface of the light illumination unit 3 of the light guide plate. The prism had a height of 5 to 50 μm and an apex angle of 90 degrees. Also, the prism pitch and height were increased so that the prism surface area was proportional to the square of the distance from the light source.

  Moreover, the aluminum plate which made the reflective surface the mirror surface as the light reflection plate 6 was used for the back surface of the light-guide plate. Further, three white LED light sources were used as the light source.

  When the luminance of this thin illuminating device was measured, a luminance of 1900 to 2200 Cd / m 2 was obtained.

It is sectional drawing which shows typically the Example of the thin illuminating device of this invention. It is sectional drawing which shows typically the Example of the thin illuminating device of this invention. It is sectional drawing which shows typically the Example of the thin illuminating device of this invention. It is sectional drawing which shows the liquid crystal display device of this invention typically. It is sectional drawing which shows typically an example of the optical path in a wedge-shaped light incident part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 LED light source 2 Wedge-shaped light entrance part 3 Light illumination part of a light-guide plate 4, 5 Light reflection layer 6 Light reflection plate

Claims (7)

  A light source having a light source, a light guide that emits light from the light source as illumination light, a reflection structure provided on at least one surface of the light illumination unit, and light from the light source. The light incident body includes a light incident body that leads to a light body, and the light incident body includes a light incident surface into which light from the light source enters and a light transmission section that transmits light to the light guide body. An illuminating device, wherein the lighting device is configured to be thinner from the writing light surface side toward the light transmission unit side.   The lighting device according to claim 1, wherein the light incident body is configured to be thin stepwise sequentially from the light incident surface side.   The lighting device according to claim 2, wherein the stepped step portion formed in the light incident body is formed substantially vertically.   The lighting device according to claim 1, wherein the light incident body and the light guide body are integrally formed of the same material.   The lighting device according to claim 1, wherein the light guide is made of a transparent film material.   The lighting device according to claim 1, wherein a light reflection layer is provided on a surface of the light incident body except for the light incident surface and the light guide portion.   A display device comprising: the illumination device according to any one of claims 1 to 6; and a non-self-luminous display element provided on a light irradiation surface side of the illumination device.

Images