JP5312919B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device, and more particularly to a technique effective when applied to a liquid crystal display device having an edge light type backlight unit.

  2. Description of the Related Art Conventionally, some liquid crystal display devices have a backlight unit (illumination device) disposed behind a liquid crystal display panel as viewed from an observer. This backlight unit is roughly divided into a so-called direct type and an edge light type.

  In the direct type backlight unit, a light source such as a fluorescent lamp or a light emitting diode is disposed behind the display area of the liquid crystal display panel. On the other hand, in the edge light type backlight unit, a light guide plate is disposed behind the liquid crystal display panel, and a light source is disposed in the vicinity of an end surface of the light guide plate.

  The edge-light type backlight unit has conventionally had a display area of several inches to several tens of inches, such as a liquid crystal display of a portable electronic device such as a mobile phone terminal, a portable game machine, and a notebook computer. It was used in relatively small liquid crystal display devices. However, liquid crystal display devices, for example, are becoming thinner, lighter, and lower in power consumption. In recent years, large-size liquid crystal display devices such as liquid crystal televisions and liquid crystal displays for stationary computers are also edge-lit. The one using the backlight unit can be seen.

  In addition to the light source and the light guide plate, the edge light type backlight unit includes, for example, one or more optical sheets disposed on the first surface of the light guide plate (the surface facing the liquid crystal display panel), And a reflection sheet disposed on the second surface side opposite to the first surface of the light guide plate. At this time, the reflection sheet is usually attached to the light guide plate with an adhesive or an adhesive. At this time, the positional relationship between the light source, the light guide plate to which the reflection sheet is attached, and the optical sheet, and the positional relationship between these members and the liquid crystal display panel are held by, for example, a substantially box-shaped holding member. .

  By the way, in the liquid crystal display device, for example, the temperature in the device rises due to heat generated by circuit components for driving the light source and the liquid crystal display panel during use. Thus, when the temperature in the liquid crystal display device rises, the light guide plate and the optical sheet are thermally expanded. Therefore, in the conventional edge light type backlight unit, as the temperature rises, for example, the optical sheet may be distorted or the positional relationship between the light guide plate and the optical sheet may be shifted. Thus, when the optical sheet is distorted or the positional relationship between the light guide plate and the optical sheet is shifted, the edge light type backlight unit, for example, emits light (planar light beam) to the liquid crystal display panel. ) Surface luminance uniformity decreases.

In recent years, for example, a method for holding the light guide plate and the optical sheet to prevent the distortion of the optical sheet and the positional relationship between the light guide plate and the optical sheet with increasing temperature has been studied, and various methods have been proposed. (For example, refer to Patent Document 1).
JP 2002-31430 A

  As described above, the reflection sheet of the conventional edge light type backlight unit is usually attached to the light guide plate with an adhesive or an adhesive.

A common material for the light guide plate is polycarbonate, and its coefficient of thermal expansion (linear expansion coefficient) is about 6.2 × 10 ⁻⁵ / ° C. Moreover, in many cases, the reflective sheet is generally provided with a reflective layer on the surface of a base material made of polyethylene terephthalate (PET), and the thermal expansion coefficient (linear expansion coefficient) of polyethylene terephthalate is 2.0 × 10 ⁻⁵ / It is about ℃.

  Therefore, when the reflective sheet is attached to the light guide plate, for example, the light guide plate may bend as the temperature rises.

  Further, the temperature in the liquid crystal display device repeatedly rises and falls every time it is used. Therefore, when the reflective sheet is attached to the light guide plate, for example, the reflective sheet may be partially peeled and distorted.

  In the conventional edge light type backlight unit, even when the light guide plate is bent or the reflection sheet is distorted, the surface luminance uniformity of light (planar light beam) applied to the liquid crystal display panel is lowered. In particular, the light guide plate and the reflection sheet of the edge light type backlight unit used in the relatively large liquid crystal display devices in recent years have a large area, and the displacement amount of the outer peripheral portion when the temperature changes is the center portion. It becomes very large compared to the amount of displacement. Therefore, an edge light type backlight unit used in a large-sized (large screen) liquid crystal display device has a high degree of reduction in surface luminance uniformity.

  As a method for solving the above problem, for example, a method of holding the positional relationship between the light guide plate and the reflection sheet by a holding member without attaching the reflection sheet to the light guide plate is conceivable. At this time, for example, like the optical sheet, the reflection sheet may be provided with a protruding portion on the outer periphery, and the protruding portion may be fitted and held in a notch or an opening provided in the holding member.

  By the way, a liquid crystal display device using an edge light type backlight unit is often used conventionally as a liquid crystal display of a portable electronic device, and its use environment is various. Therefore, many liquid crystal display devices using an edge light type backlight unit are used in a high temperature and high humidity environment, for example.

  At this time, if there is a gap between the reflection sheet and the light guide plate, for example, moisture enters between the reflection sheet and the light guide plate during use in a high humidity environment, and the moisture reflects There is a case where the sheet and the light guide plate are in close contact with each other. In this way, when the ambient temperature changes in a state where the reflection sheet and the light guide plate are partially in close contact, the reflection sheet is, for example, the amount of displacement of the portion in close contact with the light guide plate and the surrounding light guide plate. The difference from the amount of displacement of the part that is not in close contact is increased. Therefore, when the positional relationship between the reflection sheet and the light guide plate is maintained by fitting a part of the reflection sheet to the holding member without attaching the reflection sheet to the light guide plate, for example, the liquid crystal display device is When used in a humid environment, there is a concern that deformation such as distortion occurs in the reflection sheet, and the uniformity of the surface brightness of the backlight is reduced.

  In addition, when the positional relationship between the reflection sheet and the light guide plate is maintained by fitting a part of the reflection sheet to the holding member without attaching the reflection sheet to the light guide plate, the use environment of the liquid crystal display device In accordance with the change, for example, the uniformity of the surface brightness of the backlight may decrease, and then the uniformity may increase again.

  As described above, the edge light type backlight unit has a problem that the uniformity of the surface luminance is easily changed due to a change in the environment, and it is difficult to maintain the uniformity of the surface luminance in a high state.

  An object of the present invention is to provide a technique capable of preventing a change in uniformity of surface luminance of a backlight unit due to a change in environment in a liquid crystal display device having an edge light type backlight unit.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  The outline of typical inventions among the inventions disclosed in the present application will be described as follows.

  (1) It has a liquid crystal display panel and a backlight unit, and the backlight unit is one or a plurality of light sources, a light guide plate, and one sheet disposed on the first surface side of the light guide plate. Or a plurality of optical sheets, a reflection sheet disposed on the second surface side opposite to the first surface of the light guide plate, the light source, the light guide plate, the optical sheet, and the reflection sheet A holding member that holds a positional relationship, wherein the holding member has a bottom surface facing the second surface of the light guide plate, and the reflection sheet includes the reflection sheet and the holding A liquid crystal display device fixed to the bottom surface of the holding member by a fixing member disposed between the bottom surface of the member.

  (2) The liquid crystal display device according to (1), wherein the fixing member is a double-sided pressure-sensitive adhesive tape in which an adhesive layer is provided on both surfaces of a thin film substrate.

  (3) The liquid crystal display device according to (1), wherein the fixing member is a thin-film adhesive material.

  (4) The liquid crystal display device according to (1), wherein the fixing member is an adhesive.

  (5) In the liquid crystal display device of (1), the fixing member is disposed only between one or a plurality of regions located near the end of the reflective sheet and the bottom surface of the holding member. Liquid crystal display device.

  (6) The liquid crystal display device according to (1), wherein the fixing member has a strip shape, and the reflection sheet is fixed to the bottom surface of the holding member by a plurality of fixing members.

  (7) The liquid crystal display device according to (1), wherein the fixing member is annular.

  (8) In the liquid crystal display device according to (1), the reflection sheet has a surface facing the bottom surface of the holding member wider than a display area of the liquid crystal display panel, and the fixing member is formed of the reflection sheet. A liquid crystal display device disposed only between a region outside a region overlapping with a display region of the liquid crystal display panel and the bottom surface of the holding member.

(9) In the liquid crystal display device of (1), the reflection sheet includes a base material made of a sheet-like resin, and a light reflection layer provided on a surface of the base material, and the holding member is The bottom surface is made of resin, and the difference between the thermal expansion coefficient of the base material of the reflective sheet and the thermal expansion coefficient of the bottom surface of the holding member is 1.0 × 10 ⁻⁵ / ° C. or less. Display device.

  According to the liquid crystal display device of the present invention, it is possible to prevent a change in uniformity of the surface brightness of the edge light type backlight unit due to a change in the environment, and in particular, the surface brightness when used in a high temperature and high humidity environment. It is possible to prevent a decrease in uniformity.

Hereinafter, the present invention will be described in detail together with embodiments (examples) with reference to the drawings.
In all the drawings for explaining the embodiments, parts having the same function are given the same reference numerals and their repeated explanation is omitted.

FIG. 1A to FIG. 1C are schematic views showing a schematic configuration of a liquid crystal display device according to an embodiment of the present invention.
FIG. 1A is a schematic exploded perspective view showing a schematic configuration of a main part in a liquid crystal display device of one embodiment according to the present invention. FIG. 1B is a schematic plan view showing the planar configuration of the backlight of the liquid crystal display device of this embodiment. FIG.1 (c) is a schematic cross section which shows the cross-sectional structure in the AA 'line of FIG.1 (b).

  The liquid crystal display device according to the present embodiment includes, for example, a liquid crystal display panel 1 and a backlight unit 2 as shown in FIG.

  As the liquid crystal display panel 1 in the liquid crystal display device of this embodiment, a conventional liquid crystal display panel in a liquid crystal display device called a transmissive type or a semi-transmissive type can be used as it is. For this reason, in this embodiment, a detailed description of the specific configuration of the liquid crystal display panel 1 is omitted.

  In addition, the backlight unit 2 in the liquid crystal display device of the present embodiment is of an edge light type. For example, as shown in FIGS. 1A to 1C, a light source 2A, a light guide plate 2B, and 4 Each of the optical sheets 2C, 2D, 2E, and 2F, the reflection sheet 2G, and the first holding member 2H and the second holding member 2J that hold the positional relationship thereof are included. At this time, the light guide plate 2B, the four optical sheets 2C, 2D, 2E, 2F, and the reflection sheet 2G are arranged such that the area DA ′ indicated by the two-dot chain line overlaps the display area DA of the liquid crystal display panel 1. Be placed.

  The light source 2A is a component for obtaining light to be applied to the liquid crystal display panel 1, and for example, a light emitting element such as a cold cathode fluorescent lamp (CCFL) or a light emitting diode (LED) is used. At this time, the light source 2A may be only one light emitting element, or a plurality of light emitting elements may be connected in series or in parallel. At this time, the light source 2A is arranged in the vicinity of the end face of the light guide plate 2B.

  The light guide plate 2B is a component for converting light emitted from the light source 2A into a planar light beam, and is formed of a transparent resin such as an acrylic resin or a polycarbonate resin. At this time, the light emitted from the light source 2A enters the light guide plate 2B from the end face (not shown) of the light guide plate 2B and propagates through the light guide plate 2B, and the first surface S1 (liquid crystal display panel) of the light guide plate 2B. 1 is gradually emitted from the surface facing 1 and converted into a planar light beam.

  The four optical sheets 2C, 2D, 2E, and 2F are components for equalizing the surface luminance of the planar light beam emitted from the first surface S1 of the light guide plate 2B, and are the first surface of the light guide plate 2B. On S1, for example, a first light diffusion sheet 2C, a first prism sheet 2D, a second prism sheet 2E, and a second light diffusion sheet 2F are stacked in this order.

  The reflection sheet 2G is a component for returning light emitted from the second surface S2 opposite to the first surface S1 of the light guide plate 2B to the light guide plate 2B. For example, a resin such as polyethylene terephthalate (PET) What provided the light reflection layer in the surface of the base material which consists of is used.

  The first holding member 2H and the second holding member 2J hold the positional relationship among the light source 2A, the light guide plate 2B, the four optical sheets 2C, 2D, 2E, 2F, and the reflection sheet 2G, and their components. This is a component that holds the positional relationship between the LCD panel 1 and the liquid crystal display panel 1. The first holding member 2H is a component generally called a lower frame or the like. For example, the first holding member 2H is formed by molding a metal plate into a substantially box shape, and a bottom surface S3 facing the second surface S2 of the light guide plate 2B. Have The second holding member 2J is a component generally called a mold frame or an intermediate frame, and is formed, for example, by molding a resin into a generally U shape.

  The second holding member 2J is used for holding the positional relationship between the light guide plate 2B and the four optical sheets 2C, 2D, 2E, 2F, for example. The first holding member 2H is used, for example, to hold the positional relationship between the second holding member 2J, the light source 2A, and the reflection sheet 2G. Although not shown in FIGS. 1A and 1C, the liquid crystal display device of this embodiment has a generally frame-like shape generally called an upper frame above the liquid crystal display panel 1. For example, the positional relationship between the liquid crystal display panel 1 and the backlight unit 2 is held by fixing the upper frame and the first holding member 2H.

  The edge light type backlight unit of this embodiment is different from the conventional edge light type backlight unit only in the method of holding the reflection sheet 2G. That is, the light source 2A, the light guide plate 2B, the four optical sheets 2C, 2D, 2E, 2F, the reflection sheet 2G, the first holding member 2H, and the second holding member 2J in the backlight unit 2 of the present embodiment are as follows. Those parts in the conventional edge light type backlight unit can be used as they are. Therefore, in this embodiment, specific shapes of the light source 2A, the light guide plate 2B, the four optical sheets 2C, 2D, 2E, and 2F, the reflection sheet 2G, the first holding member 2H, and the second holding member 2J. A detailed description of the above will be omitted.

  In addition, the backlight unit 2 of the present embodiment is, for example, a conventional edge light type backlight method in which the light guide plate 2B and the four optical sheets 2C, 2D, 2E, and 2F are held by the second holding member 2J. The holding method used in the light unit can be used as it is. Therefore, in this embodiment, a detailed description of a method for holding the light guide plate 2B and the four optical sheets 2C, 2D, 2E, and 2F by the second holding member 2J is omitted.

  In addition to the liquid crystal display panel 1 and the backlight unit 2, the liquid crystal display device of the present embodiment controls, for example, circuit components for driving the liquid crystal display panel 1 and the luminance of the light source 2A of the backlight unit 2. However, these components can also be used as they are in the conventional liquid crystal display device. Furthermore, the liquid crystal display device of this embodiment can be operated by the same driving method as that of the conventional liquid crystal display device. For this reason, in this embodiment, the description of the detailed configuration and driving method of the liquid crystal display device is omitted.

  The edge light type backlight unit 2 of the present embodiment is different from the conventional edge light type backlight unit only in the method of holding the reflection sheet 2G as described above. In the conventional edge light type backlight unit, the reflective sheet 2G is usually attached to the second surface S2 of the light guide plate 2B to maintain the positional relationship between the light guide plate 2B and the reflective sheet 2G.

  On the other hand, the reflection sheet 2G of the backlight unit 2 of the present embodiment is disposed between the reflection sheet 2G and the bottom surface S3 of the first holding member 2H, for example, as shown in FIG. The fixed fixing member 2K is fixed to the bottom surface S3 of the first holding member 2H. The positional relationship between the light guide plate 2B and the reflection sheet 2G is maintained by fixing the second holding member 2J to the first holding member 2H.

  At this time, the fixing member 2K is, for example, a double-sided pressure-sensitive adhesive sheet in which pressure-sensitive adhesive layers are provided on both surfaces of a sheet-like base material such as a polyester film, and faces the bottom surface S3 of the first holding member 2H of the reflective sheet 2G. It touches almost the entire surface.

  Unlike the conventional general edge light type backlight unit, the backlight unit 2 used in the liquid crystal display device of the present embodiment has a reflective sheet 2G attached to the first holding member 2H. Therefore, the liquid crystal display device according to the present embodiment has, for example, the thermal expansion of the light guide plate 2B and the thermal expansion of the reflection sheet 2G when the temperature in the device rises due to heat generated by the light source 2A, circuit components, and the like during use. Are independent. For this reason, the liquid crystal display device of the present embodiment has a large difference between the thermal expansion coefficient of the light guide plate 2B and the thermal expansion coefficient of the reflection sheet 2G, the deflection of the light guide plate 2B as the temperature rises, and the reflection sheet 2G. The occurrence of distortion can be prevented.

  Various methods have already been proposed for preventing distortion of the optical sheets 2C, 2D, 2E, and 2F as the temperature rises and the positional relationship between the light guide plate 2B and the optical sheets 2C, 2D, 2E, and 2F. Has been. In the backlight unit 2 of the present embodiment, for example, as shown in FIGS. 1A and 1B, rectangular projections provided on the four optical sheets 2C, 2D, 2E, and 2F, respectively. By fitting the portion into the second holding member 2J in a groove (concave portion) corresponding to the protruding portion, the positional relationship between the light guide plate 2B and the four optical sheets 2C, 2D, 2E, 2F is maintained. ing. That is, the four optical sheets 2C, 2D, 2E, and 2F each thermally expand independently when the temperature rises. Therefore, in the liquid crystal display device of the present embodiment, by applying these methods, the distortion of the optical sheets 2C, 2D, 2E, 2F as the temperature rises, the light guide plate 2B, and the optical sheets 2C, 2D, 2E, Occurrence of the positional relationship with 2F can also be prevented.

  Therefore, the liquid crystal display device according to the present embodiment prevents, for example, a decrease in the surface luminance uniformity of the planar light beam irradiated from the backlight unit 2 to the liquid crystal display panel 1 when used in a high temperature environment. it can.

  Further, in the backlight unit 2 of the present embodiment, since the reflective sheet 2G is not attached to the light guide plate 2B, for example, when the liquid crystal display device of the present embodiment is used in a high humidity environment, In some cases, moisture enters the gap between the light guide plate 2B and the reflective sheet 2G and the light guide plate 2B are partially in close contact with each other. However, since the reflection sheet 2G is affixed to the first holding member 2H, when it thermally expands or contracts due to a change in temperature, it is affected by the thermal expansion or contraction of the first holding member 2H. Furthermore, the reflection sheet 2G is in contact with the fixing member 2K over almost the entire area of the surface facing the bottom surface S3 of the first holding member 2H. Therefore, the liquid crystal display device of the present embodiment prevents the reflection sheet 2G from being distorted due to an increase in humidity even if the difference between the thermal expansion coefficient of the light guide plate 2B and the thermal expansion coefficient of the reflection sheet 2G is large. it can.

  Therefore, the liquid crystal display device of the present embodiment prevents, for example, a reduction in the uniformity of the surface brightness of the planar light beam irradiated from the backlight unit 2 to the liquid crystal display panel 1 when used in a high humidity environment. Can do.

  That is, the liquid crystal display device of the present embodiment prevents a reduction in the uniformity of the surface brightness of the planar light beam irradiated from the backlight unit 2 to the liquid crystal display panel 1 when used in a high temperature and high humidity environment. Can do. In addition, the liquid crystal display device according to the present embodiment can also prevent a change in uniformity of surface luminance due to a change in the degree of deformation such as distortion of the reflection sheet 2G when repeatedly used in a high temperature and high humidity environment.

  As described above, according to the liquid crystal display device of the present embodiment, it is possible to prevent a change in uniformity of surface luminance of the edge light type backlight unit 2 due to a change in environment.

FIG. 2A to FIG. 2C are schematic views showing a modification of the reflection sheet fixing method in the liquid crystal display device of this embodiment.
FIG. 2A is a schematic plan view showing a method for fixing the reflection sheet in the backlight unit shown in FIG. FIG. 2B is a schematic plan view showing a first modification of the reflection sheet fixing method. FIG.2 (c) is a schematic plan view which shows the 2nd modification of the adhering method of a reflective sheet.

  In the liquid crystal display device of this embodiment, the reflective sheet 2G is fixed (attached) to the first holding member 2H, not the light guide plate 2B, so that the surface luminance uniformity of the backlight unit 2 due to environmental changes can be improved. Preventing change. At this time, if the fixing member 2K is formed into a sheet shape as shown in FIG. 2A, for example, the entire reflection sheet 2G, particularly the entire area DA ′ overlapping the display area DA of the liquid crystal display panel 1 is fixed to the fixing member 2K. It will be in close contact with. Therefore, by sticking the reflection sheet 2G to the first holding member 2H using the sheet-like fixing member 2K, the distortion of the area DA ′ overlapping the display area DA of the reflection sheet 2G due to changes in temperature and humidity is prevented. The effect is considered high.

  However, when the sheet-like fixing member 2K is used, if the area becomes large, for example, when the fixing member 2K is attached to the reflection sheet 2G or the first holding member 2H, wrinkles or bubbles may occur. There are things to do. For this reason, the reflection sheet 2G attached to the first holding member 2H by the fixing member 2K may be distorted by wrinkles or bubbles, and the uniformity of the surface luminance of the backlight unit 2 may be reduced.

  For this reason, when the reflecting sheet 2G is attached to the first holding member 2H by the fixing member 2K, for example, as shown in FIG. 2B, it may be attached using four strip-shaped fixing members 2K.

  The reflection sheet 2G is usually larger in area than the display area DA of the liquid crystal display panel 1, and has an annular surplus area outside the area DA 'that overlaps the display area DA. Therefore, it is desirable that the four fixing members 2K be arranged outside the area DA 'that overlaps the display area DA of the reflection sheet 2G so as to surround the area DA', for example. In this case, since the area DA ′ overlapping the display area DA of the reflection sheet 2G does not come into contact with the fixing member 2K, for example, when the reflection sheet 2G is attached to the first holding member 2H by the fixing member 2K, the reflection is performed. It is possible to prevent wrinkles and bubbles from occurring in the area DA ′ overlapping the display area DA of the sheet 2G.

  Further, at this time, for example, if the fixing member 2K is disposed outside the area DA ′ overlapping the display area DA of the reflection sheet 2G, for example, when the reflection sheet 2G thermally expands and contracts, the heat of the first holding member 2H Even under the influence of expansion and contraction, deformation of the area DA ′ overlapping the display area DA is unlikely to occur. Therefore, even with the fixing method as shown in FIG. 2 (b), the effect of preventing a reduction in uniformity of surface luminance due to environmental changes is maintained.

  2A shows an example in which four strip-shaped fixing members 2K are arranged on each of the four sides of the reflection sheet 2G. However, when a plurality of fixing members 2K are used, Of course, for example, a larger number of small-area fixing members 2K may be annularly arranged along the edge of the reflection sheet 2G.

  Further, when only the outside of the area DA ′ of the reflective sheet 2G that overlaps the display area DA is attached to the first holding member 2H, the fixing member 2K is, for example, a reflective member as shown in FIG. It may be annular so as to surround an area DA ′ overlapping the display area DA of the sheet 2G. In this case, since the area DA ′ overlapping the display area DA of the reflection sheet 2G does not come into contact with the fixing member 2K, for example, when the reflection sheet 2G is attached to the first holding member 2H by the fixing member 2K, the reflection is performed. It is possible to prevent wrinkles and bubbles from occurring in the area DA ′ overlapping the display area DA of the sheet 2G.

  Further, at this time, for example, if the fixing member 2K is disposed outside the area DA ′ overlapping the display area DA of the reflection sheet 2G, for example, when the reflection sheet 2G thermally expands and contracts, the heat of the first holding member 2H Even under the influence of expansion and contraction, deformation of the area DA ′ overlapping the display area DA is unlikely to occur. Therefore, even with the fixing method as shown in FIG. 2C, the effect of preventing a reduction in uniformity of surface luminance due to environmental changes is maintained.

  Furthermore, when the annular fixing member 2K is used, for example, moisture can be prevented from entering between the reflection sheet 2G and the first holding member 2H. For this reason, in the case of the fixing method as shown in FIG. 2C, for example, it is considered that the effect of preventing a reduction in uniformity of surface luminance due to a change in humidity is enhanced.

  The present invention has been specifically described above based on the above-described embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. is there.

  For example, the fixing member 2K is not limited to a double-sided pressure-sensitive adhesive sheet or a double-sided pressure-sensitive adhesive tape in which an adhesive layer is provided on both surfaces of the base material, and of course, for example, may be only a thin-film adhesive material. Of course, the fixing member 2K is not limited to the adhesive material, and may be, for example, an adhesive material. Furthermore, instead of providing the fixing member 2K different from the reflection sheet 2G, for example, the base material of the reflection sheet 2G may be provided with adhesiveness or adsorptivity.

Further, the first holding member 2H is not limited to a metal material. For example, the difference between the first holding member 2H and the thermal expansion coefficient comparable to that of the base material of the reflection sheet 2G, for example, 1. You may form with the resin material which is about ^0x10 < ^-5 > / ^degreeC . Furthermore, a third holding member made of a resin material having the same thermal expansion coefficient as that of the base material of the reflection sheet 2G is fixed to the bottom surface S3 of the first holding member 2H made of a metal material, and the third holding member is fixed. The reflection sheet 2G may be fixed to the member.

  The first holding member 2H may have a shape having one or a plurality of openings on the bottom surface S3, for example.

  Moreover, in the said Example, although the light source 2A is provided only in the position facing one end surface among the four end surfaces of the light-guide plate 2B, the light source 2A is not restricted to this, For example, it overlaps with the display area DA. Of course, it may be arranged at two places across the area DA ′, or along two orthogonal end faces.

  Moreover, in the said Example, although the 2nd holding member 2J is a substantially U shape, the 2nd holding member 2J is not restricted to this, For example, it is the cyclic | annular form which surrounds the light source 2A and the light-guide plate 2B. Of course there may be.

  In the embodiment, the positional relationship between the light guide plate 2B and the four optical sheets 2C, 2D, 2E, and 2F is held by the second holding member 2J. Of course, the positional relationship with the sheets 2C, 2D, 2E, and 2F is not limited to this, and may be held by another method.

  In the embodiment, four optical sheets 2C, 2D, 2E, and 2F are provided on the first surface S1 of the light guide plate 2B. However, the optical sheet is not limited to this, and one to three optical sheets are provided. Of course, the number may be five or more.

  Furthermore, in the said Example, although the reflection sheet 2G is provided only in 2nd surface S2 of the light-guide plate 2B, in the backlight unit 2 by this invention, it is not restricted to this, For example, the end surface of the light-guide plate 2B Of course, another reflective sheet (reflective member) may be disposed on an end face other than the end face on which light from the light source 2A is incident.

  The backlight unit 2 having the configuration described in the above embodiment can prevent a reduction in surface luminance uniformity due to environmental changes. Therefore, it is considered that the backlight unit 2 of the present invention can be used for an illumination device for indoor lighting or outdoor lighting, for example.

1 is a schematic exploded perspective view showing a schematic configuration of a main part in a liquid crystal display device of one embodiment according to the present invention. It is a schematic plan view which shows the plane structure of the backlight of the liquid crystal display device of a present Example. It is a schematic cross section which shows the cross-sectional structure in the A-A 'line | wire of FIG.1 (b). It is a schematic plan view which shows the adhering method of the reflective sheet in the backlight unit shown in FIG.1 (b). It is a schematic plan view which shows the 1st modification of the adhering method of a reflective sheet. It is a schematic plan view which shows the 2nd modification of the adhering method of a reflective sheet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display panel 2 ... Backlight unit 2A ... Light source 2B ... Light guide plate 2C ... Optical sheet (1st light-diffusion sheet)
2D ... Optical sheet (first prism sheet)
2E ... Optical sheet (second prism sheet)
2F: Optical sheet (second light diffusion sheet)
2G ... reflection sheet 2H ... first holding member 2J ... second holding member 2K ... fixing member

Claims (9)

A liquid crystal display panel and an edge light type backlight unit;
The edge light type backlight unit includes one or a plurality of light sources, a light guide plate, one or a plurality of optical sheets disposed on a first surface side of the light guide plate, and the light guide plate. A reflection sheet disposed on the second surface opposite to the first surface; a first holding member that holds a positional relationship between the light source, the light guide plate, the optical sheet, and the reflection sheet; A liquid crystal display device having a second holding member that holds a positional relationship between the light guide plate and the optical sheet,
The first holding member is a lower frame, has a bottom surface that is shaped like a box and faces the second surface of the light guide plate,
The second holding member is an intermediate frame, fixed to the first holding member,
The liquid crystal display device, wherein the reflection sheet is fixed to the bottom surface of the first holding member by a fixing member disposed between the reflection sheet and the bottom surface of the first holding member. .   The liquid crystal display device according to claim 1, wherein the fixing member is a double-sided pressure-sensitive adhesive sheet or a double-sided pressure-sensitive adhesive tape in which an adhesive layer is provided on both surfaces of a thin film-like substrate.   The liquid crystal display device according to claim 1, wherein the fixing member is a thin film adhesive.   The liquid crystal display device according to claim 1, wherein the fixing member is an adhesive. The said fixing member is arrange | positioned only between the one or some area | region located in the edge part vicinity of the said reflection sheet, and the said bottom face of a said 1st holding member, The 1st aspect is characterized by the above-mentioned. The liquid crystal display device described. The fixing member has a strip shape,
The liquid crystal display device according to claim 1, wherein the reflection sheet is fixed to the bottom surface of the first holding member by a plurality of the fixing members.   The liquid crystal display device according to claim 1, wherein the fixing member is annular. The reflective sheet has a surface that faces the bottom surface of the first holding member wider than a display area of the liquid crystal display panel.
The fixing member is disposed only between a region outside the region overlapping the display region of the liquid crystal display panel in the reflective sheet and the bottom surface of the first holding member. The liquid crystal display device according to claim 1. The reflection sheet has a base body 2 composed of a sheet-like resin, and a light reflecting layer provided on the surface of the substrate,
In the first holding member, the bottom portion is made of resin, and the difference between the thermal expansion coefficient of the base material of the reflective sheet and the thermal expansion coefficient of the bottom surface of the first holding member is 1 The liquid crystal display device according to claim 1, wherein the liquid crystal display device is 0.0 × 10 ⁻⁵ / ° C. or lower.

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