JP2009301912A - Back light unit and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent leakage of light from an adhesion portion when a reflection sheet is pasted on a shading frame in a backlight unit and a liquid crystal display. <P>SOLUTION: The backlight unit is provided with a light guide plate 3 which guides light incident from an LED light source, and by changing an optical path, emits planar illumination light to a liquid crystal display panel 2 from the upper face, a frame-shape shading frame 4 which supports the outer circumference of the light guide plate 3, a reflection sheet 8 arranged at the lower side of the light guide plate 3, and a double-sided adhesive material 9 which is interposed between the reflection sheet 8 and the lower face of the shading frame 4 and pastes these mutually. The double-sided adhesive material 9 is formed of an opaque shading material. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a backlight unit and a liquid crystal display device that illuminate a liquid crystal display panel and the like.

  2. Description of the Related Art Liquid crystal display devices for displaying images are widely used as displays for mobile phones, PDAs, mobile type PCs (personal computers), ATMs (automated teller machines), and the like. This liquid crystal display device uses a backlight unit that emits light from the back side of the liquid crystal display panel to increase the brightness of the display screen.

  In this backlight unit, a light guide plate that guides light from a light source such as a fluorescent tube or an LED and emits the light from the entire main surface toward the liquid crystal display panel is used. In the conventional backlight unit, a reflection sheet is provided on the lower surface (back surface) of the light guide plate, and the light emitted from the light guide plate is reflected and returned into the light guide plate, thereby improving the brightness of the light guide plate. For example, in Patent Document 1, a light guide plate is disposed inside a light shielding frame that is a frame-shaped housing, and a reflective sheet disposed on the lower surface side of the light guide plate is bonded to the bottom surface of the light shielding frame with a double-sided tape (double-sided adhesive sheet). A fixed backlight has been proposed.

Japanese Patent Laying-Open No. 2007-206546 (FIG. 1)

However, the following problems remain in the conventional technology.
In recent years, as the entire backlight unit including the light guide plate and each optical sheet has been reduced in thickness in order to reduce the weight and thickness of the final product, the shading frame has also been reduced in thickness. Therefore, as in Patent Document 1, a light-shielding frame in which the bottom surface is replaced with a reflective sheet has been studied. However, since the thickness of the double-sided tape to which the reflective sheet is attached is constant and transparent, There is a possibility that light leaks to the outside of the light shielding frame, and the light shielding effect of the light shielding frame is reduced. When such light leakage occurs, light leaks to components such as operation keys provided in the vicinity of the backlight unit, and there is a possibility that the lighting effect and visual quality of the device may be reduced.

  The present invention has been made in view of the above-described problems, and provides a backlight unit and a liquid crystal display device that can prevent light leakage from an adhesive portion when a reflective sheet is attached to a light shielding frame. Objective.

  The present invention employs the following configuration in order to solve the above problems. That is, the backlight unit of the present invention includes a light guide plate that guides light incident from a light source and changes the optical path to emit planar illumination light from the upper surface to an illumination target, and an outer periphery of the light guide plate. A frame-shaped light shielding frame that supports the portion, a reflection sheet disposed on the lower surface of the light guide plate, and a double-sided adhesive that is interposed between the reflection sheet and the lower surface of the light shielding frame and bonds them together And the double-sided adhesive material is formed of an opaque light-shielding material.

  In this backlight unit, the double-sided adhesive that is interposed between the reflective sheet and the lower surface of the light-shielding frame and is attached to each other is formed of an opaque light-shielding material. Therefore, it is possible to prevent light in the light shielding frame from being blocked and leaking outside.

  The backlight unit of the present invention is characterized in that the double-sided adhesive material is formed of a black or white light-shielding material. That is, in this backlight unit, the double-sided adhesive is formed of a black or white light-shielding material, so that if the double-sided adhesive is a black light-shielding material, the light in the light shielding frame is effectively shielded. In addition, if the double-sided adhesive is a white light-shielding material, the light in the light-shielding frame can be shielded and reflected inward to improve the luminance.

  In the backlight unit of the present invention, the double-sided adhesive material is a base material layer formed of an opaque light-shielding film, and an adhesive material layer formed of an opaque light-shielding pressure-sensitive adhesive material on both sides of the base material layer. And a double-sided tape composed of That is, in this backlight unit, the double-sided adhesive material is a double-sided tape composed of an opaque base material layer and an adhesive material layer, respectively. Compared with a tape in which only the layer or only the adhesive material layer is made opaque, the entire structure becomes opaque so that a high light shielding property can be obtained.

  The liquid crystal display device of the present invention comprises a liquid crystal display panel and the backlight unit of the present invention disposed on the back side of the liquid crystal display panel. That is, in this liquid crystal display device, since the backlight unit of the present invention is provided on the back side of the liquid crystal display panel, light is prevented from leaking to parts such as operation keys arranged around the backlight unit. As a result, the lighting effect and visual quality can be improved.

The present invention has the following effects.
That is, according to the backlight unit according to the present invention, the double-sided adhesive that is interposed between the reflective sheet and the lower surface of the light shielding frame and is attached to each other is formed of an opaque light shielding material. It is possible to prevent the light in the light shielding frame from being blocked by the double-sided adhesive material to which the light is added and leaking to the outside. Therefore, according to the liquid crystal display device of the present invention provided with the backlight unit, light is prevented from leaking to parts such as operation keys arranged around the backlight unit, and the lighting effect and visual quality as a device are improved. Can be made.

  Hereinafter, an embodiment of a backlight unit and a liquid crystal display device according to the present invention will be described with reference to FIGS. In each drawing used in the following description, the scale is appropriately changed to make each member a recognizable size.

  As shown in FIGS. 1 to 3, the backlight unit 1 in the present embodiment illuminates the liquid crystal display panel 2, and includes an LED light source (light source) L and light incident from the LED light source L. A light guide plate 3 that emits planar illumination light from the upper surface to the liquid crystal display panel 2 that is an illumination target by guiding the light and changing the optical path, and a rectangular frame-shaped light shield that supports the outer periphery of the light guide plate 3 The outer periphery of the frame 4, the diffusion sheet 5, the first prism sheet 6A and the second prism sheet 6B, which are laminated on the light guide plate 3 and disposed in the light shielding frame 4, and the light shielding frame 4 are attached to the second peripheral portion. A rim sheet 7 laminated on the prism sheet 6B, a reflection sheet 8 disposed on the lower surface of the light guide plate 3, and a double-sided adhesive that is interposed between the reflection sheet 8 and the lower surface of the light shielding frame 4 and bonds them together 9 and It is equipped with a.

The liquid crystal display device 10 of the present embodiment is a liquid crystal display device applied to a liquid crystal display such as a mobile phone, and includes the liquid crystal display panel 2 and the backlight unit arranged on the back side of the liquid crystal display panel 2. 1 is provided.
In the present embodiment, the screen side of the liquid crystal display panel 2 and the light emission surface side of the backlight unit 1 are described as the surface side or the upper surface side.

The LED light source L is a white LED mounted on a light source mounting substrate (not shown) so as to be able to emit light toward a side end surface that is an incident surface of the light guide plate 3, for example. Note that reference numeral 11 in FIG. 1 denotes an FPC connected to the LED light source L.
This white LED is, for example, a semiconductor light emitting element on a substrate sealed with a resin material. As the semiconductor light emitting element, for example, a blue (wavelength λ: 470 to 490 nm) LED element or ultraviolet light (wavelength λ: less than 470 nm). An LED element is formed by laminating a plurality of semiconductor layers of a gallium nitride compound semiconductor (for example, an InGaN compound semiconductor) on an insulating substrate such as a sapphire substrate.

  Further, the resin material for sealing the semiconductor light emitting element is mainly composed of a silicone resin and, for example, a YAG phosphor is added. This YAG phosphor converts white light or ultraviolet light from a semiconductor light emitting element into yellow light and generates white light by a color mixing effect. Various white LEDs other than those described above can be used.

The light guide plate 3 is made of, for example, a translucent resin material, guides light from the LED light source L incident from the side end face thereof, changes the optical path, and liquid crystal from the main surface (upper surface in the present embodiment). It is a thin plate-shaped or sheet-shaped thin light guide plate that emits planar illumination light to the display panel 2.
Note that a plurality of fine optical shapes for performing optical path conversion such as convex dots and prisms may be formed on the surface of the light guide plate 3.

The shading frame 4 is formed in a rectangular frame shape by injection molding using a synthetic resin material or the like. A step portion 4a is formed inside the light shielding frame 4, and the rim sheet 7 is attached on the step portion 4a, and the liquid crystal display panel 2 is installed thereon.
The rim sheet 7 is a double-sided tape used for joining the liquid crystal display panel 2 and the backlight unit 1 and has a light shielding and reflection function.
The diffusion sheet 5 is, for example, a sheet in which silica particles or the like are dispersed in a transparent resin such as an acrylic resin or a polycarbonate resin.

  The first prism sheet 6A is disposed on the diffusion sheet 5, and the second prism sheet 6B is disposed on the first prism sheet 6A. The first prism sheet 6A and the second prism sheet 6B are transparent sheet-like members for condensing the light from the diffusion sheet 5 on the upper surface side, and have a prism portion having a plurality of parallel ridge lines on the upper surface side. is doing. Further, the first prism sheet 6A has the ridge line of the prism portion set at a twisted position with respect to the optical axis of the LED light source L, and in particular, the light of the LED light source L as a direction in which high upward directivity is obtained. It is set parallel to the direction orthogonal to the axis. In the second prism sheet 6B, the ridge line of the prism portion is set parallel to the optical axis of the LED light source L. That is, the first prism sheet 6A and the second prism sheet 6B are arranged such that the ridge lines of the prism portions are twisted and the ridge lines are orthogonal to each other in plan view.

  The reflection sheet 8 is a metal plate, film, foil or the like having a light reflection function, and in this embodiment, a film provided with a silver vapor deposition film is employed. Note that an aluminum metal vapor deposition film or the like may be employed instead of the silver vapor deposition film.

  The liquid crystal display panel 2 is a transmissive or transflective liquid crystal display panel. For example, in the case of the transflective liquid crystal display panel 2, a panel body in which a liquid crystal such as TN liquid crystal or STN liquid crystal is sealed with a sealing material in a gap between an upper substrate and a lower substrate each having a transparent electrode, an alignment film, and a polarizing plate. And a transflective plate having both light-transmitting and light-reflecting functions on its lower surface side.

The double-sided adhesive material 9 is formed of a black or white opaque light-shielding material, and is provided in a strip shape along the outer edge portion of the reflection sheet 8 corresponding to the shape of the lower surface of the light-shielding frame 4. As shown in FIG. 4, the double-sided adhesive 9 includes a base material layer 9a formed of an opaque light-shielding film and an adhesive material layer formed of an opaque light-shielding adhesive material on both sides of the base material layer 9a. 9b.
The base material layer 9a is formed of, for example, a PET or polyester film containing a black or white pigment. The adhesive material layer 9b is formed of a light-shielding adhesive material such as an acrylic resin containing a black or white pigment, for example.

Thus, in the backlight unit 1 of the present embodiment, the double-sided adhesive 9 that is interposed between the reflective sheet 8 and the lower surface of the light shielding frame 4 and affixes them to each other is formed of an opaque light shielding material. It is possible to prevent the light in the light shielding frame 4 from being blocked by the double-sided adhesive material 9 to which the light shielding function is added and leaking to the outside.
In particular, since the double-sided adhesive 9 is formed of a black or white light-shielding material, if the double-sided adhesive 9 is a black light-shielding material, the light in the light-shielding frame 4 can be effectively shielded. If the double-sided adhesive material 9 is a white light-shielding material, the light in the light-shielding frame 4 can be shielded and reflected inward to improve luminance.

Furthermore, since the double-sided adhesive material 9 is a double-sided tape composed of an opaque base material layer 9a and an adhesive material layer 9b, respectively, a tape whose surface is made opaque with a light-shielding material, or only a base material layer or Compared with a tape in which only the adhesive layer is made opaque, a high light shielding property can be obtained by making the whole opaque.
Therefore, in the liquid crystal display device 10 provided with the backlight unit 1, light is prevented from leaking to parts such as operation keys arranged around the backlight unit 1, and the lighting effect and visual quality as a device are improved. Can do.

  In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.

For example, the base material layer and the pressure-sensitive adhesive layer in the above embodiment are preferably formed of an opaque light-shielding material containing a black or white pigment, but may be colored with other opaque colors. Further, Ag particles may be included as the reflective particles to add a high reflection effect.
Moreover, in the said embodiment, although the diffusion sheet is used, it is good also as a backlight unit which abbreviate | omitted the diffusion sheet. In addition, although two prism sheets are used, a backlight unit employing one prism sheet may be used.

Moreover, in the said embodiment, although the LED light source is employ | adopted as a light source, you may use other light sources, such as a fluorescent tube.
In the above-described embodiment, the present invention is applied to a mobile phone, but may be employed in other electronic devices. For example, the present invention can be applied to various electronic devices such as PDAs and mobile type PCs (personal computers).

FIG. 3 is an exploded perspective view showing a reflection sheet, a light shielding frame, and a double-sided adhesive material of the backlight unit in one embodiment of the backlight unit and the liquid crystal display device according to the present invention. In this embodiment, it is an expanded sectional view of the principal part which shows a liquid crystal display device. In this embodiment, it is an expanded sectional view of LED light source periphery which shows a liquid crystal display device. In this embodiment, it is an expanded sectional view which shows the double-sided adhesive material on a reflective sheet.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Backlight unit, 2 ... Liquid crystal display panel, 3 ... Light guide plate, 4 ... Light shielding frame, 5 ... Diffusion sheet, 6A ... 1st prism sheet, 6B ... 2nd prism sheet, 8 ... Reflective sheet, 9 ... Double-sided adhesion Material 9a ... Base material layer 9b ... Adhesive material layer 10 ... Liquid crystal display device L ... LED light source (light source)

Claims (4)

A light guide plate that guides the light incident from the light source and changes the optical path to emit planar illumination light from the upper surface to the illumination object;
A frame-shaped shading frame that supports the outer periphery of the light guide plate;
A reflective sheet disposed on the lower surface of the light guide plate;
A double-sided adhesive that is interposed between the reflective sheet and the lower surface of the light shielding frame and affixes them together,
A backlight unit, wherein the double-sided adhesive is made of an opaque light-shielding material. The backlight unit according to claim 1,
The backlight unit, wherein the double-sided adhesive is formed of a black or white light-shielding material. In the backlight unit according to claim 1 or 2,
The double-sided adhesive is a base material layer formed of an opaque light-shielding film;
A backlight unit comprising a double-sided tape comprising an adhesive layer formed of an opaque light-shielding adhesive material on both sides of the base material layer. A liquid crystal display panel;
A backlight unit according to any one of claims 1 to 3, which is disposed on the back side of the liquid crystal display panel.

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