JP4661765B2 - Backlight unit - Google Patents

Description

  The present invention relates to a backlight structure used for a liquid crystal display module and the like, and more particularly to a backlight unit structure in which a backlight and optical sheets are integrated in a backlight chassis.

  FIG. 8 is a plan view of the backlight unit 10 shown as the background art of the present invention viewed from the light emission observation surface side. The backlight unit 10 includes a backlight chassis 1 that is a housing that houses a light source and a light guide plate that guides light from the light source, and a frame 11 that is attached to the upper surface of the backlight chassis 1. The frame body 11 is rectangular in appearance and has an opening 14 corresponding to the emission observation surface.

  FIG. 9 is an enlarged view of a cross section of the periphery of the backlight chassis 1, that is, a cross section taken along the line AA of FIG. In the backlight chassis 1, a reflective sheet 6, a light guide plate 5 including a light source (not shown), and an optical sheet unit 4 for optically controlling light emitted from the light guide plate are stacked in order from the bottom. Are stored. The optical sheet unit 4 has a structure in which two prism lens sheets 42 and 43 are laminated on a diffusion sheet 41.

  On the lower surface of the frame 11 on the optical sheet portion 4 side, a plurality of cone-shaped projections 2 are arranged in a plurality of rows along each side of the frame forming the opening 14. ing. In FIG. 8, the projection group is drawn with a solid line only on the short side of the frame, and the projection group on the other side is omitted by being shown with a dotted line. The projection group 2 can be easily formed by drawing the frame body 11.

  As shown in FIG. 9, the present backlight unit closes a gap 13 generated between the frame body 11 and the upper surface of the optical sheet portion 4 with the projection group 2 of the frame body 11, thereby providing a gap 13 from the outside. It is intended to prevent foreign objects from entering. Preferably, in order to completely close the gap, the projection group 2 is contacted so as to press the optical sheet. In addition, by providing the projection group in this way, the optical sheet portion 4 is firmly pressed toward the light guide plate 5, and vibration noise due to the optical sheet shifting can be eliminated.

JP 2001-210128 A.

  However, in the conventional backlight unit, since the optical sheet is pressed with sufficient strength on the surface of the light guide plate in the four-side directions, wrinkles occur on the surface of the optical sheet due to thermal expansion of the optical sheet. . In other words, there is a difference in the thermal expansion coefficient between the optical sheet and the frame, so if the ambient temperature of the backlight unit increases, the expanded optical sheet near the opening that is not pressed by the protrusions will emit light. It will be deformed toward the surface. Thus, when wrinkles occur on the surface of the optical sheet, the optical characteristics of the backlight unit are adversely affected. On the other hand, if the number of protrusions formed per unit surface of the frame is excessively reduced, it is impossible to suppress vibration noise due to the optical sheet moving in the housing.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a backlight unit that eliminates the vibration noise caused by the displacement of the optical sheet and does not cause wrinkling of the optical sheet.

  In order to achieve the above object, a backlight unit according to the present invention includes a light source, a light guide that guides light from the light source, an optical sheet unit laminated on the light guide, In a backlight unit including a housing to be accommodated and a frame body disposed in an opening of the housing, the frame body has a protrusion at a corner on the shortest side among the sides forming the outer shape. The backlight unit is characterized in that the projection is in contact with the upper surface of the optical sheet portion.

  The surface of the protrusion is preferably a curved surface that is convex in the direction of the optical sheet portion. The shape of the protrusion is preferably an ellipse or a circle when viewed from the front. It is preferable that the longitudinal direction of the protrusions is matched with the shortest side direction of the frame. The amount by which the protrusions press down the upper surface of the optical sheet portion is preferably 0.05 mm or more and 0.30 mm or less.

The backlight unit further includes a frame having an opening for accommodating the light guide, and the frame is disposed between the light guide and the housing.
It is preferable that the peripheral edge portion of the optical sheet portion is extended on the upper surface of the side wall forming the opening of the frame and is sandwiched between the upper surface and the protrusion.

  The casing has a bent portion in which a part of the side wall is bent inward, and a peripheral edge portion of the optical sheet portion extends to an upper surface of the bent portion. It is preferable that it is pinched by.

  The housing has a protruding portion in which a part of the side wall protrudes inward, and a peripheral edge portion of the optical sheet portion extends to an upper surface of the protruding portion. It is preferable that it is pinched by.

  It is preferable that the side wall of the frame, the bent portion or the protruding portion of the housing, or the upper surface of the light guide has a concave portion directly below the protrusion. The shape of the opening of the recess is preferably substantially similar to the outer shape of the protrusion.

  The present invention can eliminate the wrinkles of the optical sheet and provide a backlight unit with little deterioration of optical characteristics by providing the minimum necessary protrusions that prevent the optical sheet from rattling.

  The best mode for carrying out the present invention will be described below with reference to the drawings. However, the form shown below illustrates the backlight unit for embodying the technical idea of the present invention, and the present invention does not limit the backlight unit to the following.

  Further, the present specification by no means specifies the members shown in the claims to the members of the embodiments. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the embodiments are not intended to limit the scope of the present invention only to the description unless otherwise specified. It is just an example. Note that the size, positional relationship, and the like of the members shown in each drawing may be exaggerated for clarity of explanation. Further, in the following description, the same name and reference sign indicate the same or the same members, and detailed description will be omitted as appropriate. Furthermore, each element constituting the present invention may be configured such that a plurality of elements are constituted by the same member and the plurality of elements are shared by one member, and conversely, the function of one member is constituted by a plurality of members. It can also be realized by sharing.

  A light source, a light guide that guides the light of the light source, an optical sheet portion laminated on the light guide, a housing that accommodates them, and a rectangle disposed in an opening of the housing In order to eliminate wrinkles of the optical sheet while suppressing the backlash of the optical sheet portion, the present inventor conducted various studies. And the corner | angular part by the side of the shortest side (one side when there are multiple shortest sides) among the sides which constitute the outline of a frame, for example, the short side rather than the long side of a rectangular frame Protrusions were provided at the corners, and the protrusions were brought into contact with the upper surface of the optical sheet portion, thereby solving the problem.

  That is, the present invention has a particularly important configuration in which the protrusions that are in contact with the upper surface of the optical sheet portion are provided at the corners on one short side rather than the long side of the rectangular frame. To do. That is, the protrusion provided on the frame body is only one short side of the two short sides of the rectangle of the frame, and is not substantially provided on the long side and the other short side. By providing protrusions only at the corners on one short side in this way, the optical sheet is sufficiently deformed by thermal expansion while being sufficiently pressed on the short side so that the optical sheet does not rattle. Since relaxation is performed on the side, wrinkles of the optical sheet can be eliminated.

  FIG. 1 is a bottom view of the frame according to this embodiment as seen from the bottom surface on which the protrusions are formed. FIG. 2 is a partially enlarged view of a corner portion of the frame shown in FIG. FIG. 3 is a plan view of the backlight unit 200 according to the present embodiment as viewed from the light emission observation surface side. The backlight unit 200 includes a light source (not shown), a housing 201 that houses a light guide 202 that guides light from the light source, and a frame 100 that is attached to the top of the housing 201. Prepare. The frame 100 has an opening 102 corresponding to a light emission observation surface, and the upper surface of the optical sheet is exposed at the opening 102.

  4 is an enlarged view of a cross section of the periphery of the backlight unit 200, that is, a cross section taken along line II-II shown in FIG. Inside the housing 201, a light source (not shown), a light guide 202 for guiding light from the light source in order from the bottom, and an optical for optically controlling the light emitted from the light guide 202 Sheet portions are stacked and stored. In the optical sheet portion of this embodiment, a diffusion sheet 203, a first prism lens sheet 204, and a second prism lens sheet 205 are laminated in order from the light guide 202 side. The shapes of the diffusion sheet 203, the first prism lens sheet 204, and the second prism lens sheet 205 are rectangular shapes corresponding to the size and shape of the rectangle that forms the light exit surface of the light guide 202. ing.

  As shown in FIG. 1 and FIG. 3, the outline shape and the opening 102 of the frame 100 of this embodiment are a short side a, a short side b facing the short side a, and a long side that connects the sides and faces each other. It is a rectangle consisting of c and a long side d.

  The protrusions of this embodiment are provided at intervals in two corners formed by two different long sides and a common short side. The protrusions can be provided on the long side of the corners out of the long side or the short side of the corners, but are preferably provided on the short side. This is because deformation due to thermal expansion of the optical sheet can be relaxed in the long side direction of the frame 100.

  For example, as shown in FIG. 1, protrusions 101 are formed on corners A and B on one short side a of the corners of the frame 100 on the lower surface of the frame 100 on the optical sheet portion side. One by one. As shown in FIG. 4, there is a gap 13 between the frame body 100 and the uppermost part of the optical sheet portion 4, and the frame body 100 exerts a pressing force on the optical sheet portion by arranging the protrusion 101 in the gap. Can be added. Note that, on the long side b, the long side d side, and the other short side c side of the frame body 100, no projection is formed, or even if a projection is formed, between the projection and the optical sheet portion. May be in contact with each other as long as the optical sheet portion can move in the long side direction. The protrusion 101 may be formed by bonding another member to the corner of the frame 100 or may be formed integrally with the frame 100. For example, the frame body 100 can be easily formed by drawing.

  The surface of the protrusion is preferably a curved surface that is convex in the direction of the optical sheet portion. Thereby, the damage to the optical sheet part by a protrusion can be eliminated. It is preferable that the outer edge shape of the protrusion is a track shape or an ellipse shape composed of a pair of semicircles and a pair of straight lines facing each other when viewed from the front. It is preferable that the longitudinal direction of the protrusions is matched with the short side direction of the frame. Accordingly, the optical sheet can be sufficiently pressed so as not to move in the long side direction of the frame. The protrusions in the present embodiment have a track shape composed of a pair of semicircles and a pair of straight lines facing each other when viewed from the front direction, and the longitudinal direction of the protrusions matches the short side direction of the frame. is there. Moreover, the external shape of the vertical cross section of the protrusion in the longitudinal direction and the short direction is a dome shape.

  In this embodiment, the number and shape of the protrusions arranged at the corners on the short side of the frame body may be any form as long as it is the minimum necessary to prevent rattling of the optical sheet part, When a plurality of protrusions are formed at each corner on the short side of the frame, a sufficient distance is provided between the first protrusion group at one corner and the second protrusion group at the other corner. It is preferable. Thereby, generation | occurrence | production of the wrinkle of an optical sheet part can be eliminated. Similarly to the form of the individual protrusions described above, the surface including the entire protrusion group is preferably a curved surface that is convex in the direction of the optical sheet portion. Thereby, the damage to the optical sheet part by a protrusion can be eliminated. Moreover, it is preferable that the longitudinal direction of the shape when the projection group is viewed is matched with the short side direction of the frame. Accordingly, the optical sheet can be sufficiently pressed so as not to move in the long side direction of the frame. Moreover, it is preferable that the general shape including the entire protrusion group is a circle or an ellipse when viewed from the front.

  The shape of the protrusion or the protrusion group is preferably such that the cross-sectional area parallel to the main surface of the frame gradually decreases from the main surface of the frame toward the optical sheet portion. This is because wrinkles that are likely to occur when the protrusions press down the sheet by reducing the area of the uppermost portion of the protrusions in contact with the surface of the optical sheet portion are prevented. Further, if the cross-sectional area on the main surface side of the frame is reduced, the pressure applied to the optical sheet portion of the frame is insufficient. For example, the shape of the protrusion or the protrusion group can be a cone shape such as a mountain shape, a cone, a triangular pyramid, or a quadrangular pyramid.

  The amount by which the protrusions press the upper surface of the optical sheet is preferably 0.05 mm or more and 0.30 mm or less. Thereby, it can fully hold down so that an optical sheet may not move. The amount by which the protrusion presses the upper surface of the optical sheet is measured by measuring the depth of the deepest portion of the optical sheet deformed by the contact of the protrusion, with the upper surface of the optical sheet portion when the protrusion is not in contact as a reference surface. Shall be. The height of the protrusion is appropriately adjusted according to the size of the backlight unit. This is because if the height of the protrusion is too low, the optical sheet portion cannot be sufficiently pressurized, and if the height of the protrusion is too high, the backlight unit cannot be thinned.

  The backlight unit of this embodiment can further include a frame having an opening that accommodates the light guide. By disposing the frame between the light guide and the housing, the light source and the light guide can be held at predetermined positions of the housing. In the backlight unit having such a frame, the upper surface of the side wall forming the opening of the frame can be used for fixing the optical sheet portion. That is, the peripheral portion of the optical sheet portion is extended and disposed on the upper surface of the side wall of the frame, and the peripheral portion of the optical sheet portion is sandwiched between the upper surface and the protrusions provided on the lower surface of the frame. Thereby, an optical sheet part can be fixed. The optical sheet to be sandwiched is not limited to the form of all optical sheets constituting the optical sheet portion, but may be a part of the optical sheets constituting the optical sheet portion. In addition, the “peripheral portion” of the optical sheet portion in the present embodiment refers to a portion outside the effective light emitting region of the optical sheet portion, and refers to a region having a sufficient width that can be used for fixing the optical sheet portion. .

  Thus, by fixing the optical sheet portion through the frame, the selection of the material of the frame can be performed without considering the optical characteristics as compared with the embodiment in which the optical sheet portion is fixed through the light guide. The material can be selected by focusing only on the mechanical strength. Therefore, the optical sheet portion can be firmly fixed to the frame made of a material having excellent mechanical strength.

  As still another form, the protruding portion is formed by protruding a part of the side wall of the housing inward. Alternatively, the bent portion is formed by bending a part of the side wall of the housing inward. Further, the peripheral edge portion of the optical sheet portion is extended and arranged on the upper surface of the protruding portion or the bent portion, and the peripheral edge portion of the optical sheet portion is sandwiched between the upper surface and the projection of the frame body. Thereby, since the optical sheet part is fixed by the housing and the protrusion selected from the material having excellent mechanical strength, the optical sheet part can be fixed more firmly.

  It is preferable that an upper surface of at least one member selected from the side wall of the frame, the bent portion or the protruding portion of the casing, or the light guide has a recess directly below the protrusion. A part of the optical sheet portion sandwiched between these members and the protrusion is deformed in the thickness direction of the optical sheet and fits into the recess, and the optical sheet moves in a direction parallel to the main surface. Deterred. Therefore, the optical sheet portion is firmly fixed to other members constituting the backlight unit, and the optical sheet is prevented from shifting. Furthermore, it is preferable that the planar shape of the opening of the recess is larger than the outer shape of the protrusion and is substantially similar to the outer shape of the protrusion. Thereby, a part of the optical sheet portion deformed along the surface shape of the protrusion is easily fitted into the recess, so that the optical sheet portion can be more firmly fixed.

  The frame 100 and the casing may be fixed using an adhesive sheet or an adhesive, or may be fixed by providing a shape that can be fitted to each other. For example, by providing a concavo-convex shape on the wall surface of the side wall portion 103 of the frame body 100 and an uneven shape on the wall surface of the side wall portion 206 of the housing 201 and fitting the two together when forming the backlight unit, Both cases may be fixed by fitting the housing 201 into the frame 100.

  Although not shown, the liquid crystal display panel is mounted on the upper surface of the frame 100, and a liquid crystal display module in which the backlight unit 200 and the liquid crystal display panel are combined is configured. At this time, on the upper surface of the frame opposite to the side on which the projections 101 are provided, the L-shaped projections 207 extending on the two sides are fitted to the shape of the liquid crystal display panel, and both are positioned accurately. To be combined. Hereinafter, each structure of this form is explained in full detail.

(light source)
The light source in this embodiment is a light emitting member that emits light that can be incident on a light guide, such as a semiconductor light emitting element such as a light emitting diode or a semiconductor laser, a cold cathode ray tube, or a composite light source that is selected and combined variously. Say. Regarding the arrangement of the light source on the light guide, an edge light system in which a light source is arranged on the side end face of the light guide may be used, or a direct type system in which a light source is arranged on the lower surface of the light guide.

  Hereinafter, although a light emitting diode is demonstrated, it is not limited to this. The light emitting diode can be variously selected depending on the dominant wavelength of light emitted from the semiconductor layer. In particular, light-emitting diodes that emit white mixed light are widely used. Such light-emitting diodes include various combinations of LED chips that emit RGB colors, light-emitting diodes including LED chips, and phosphors that emit light excited by light emitted from the LED chips. Things. An LED chip capable of emitting blue light can emit light with high brightness by using, for example, a gallium nitride compound semiconductor.

  In addition, the light emitting diode in this embodiment includes a package serving as a support for the LED chip. The electrode disposed on the support and the electrode of the LED chip are electrically connected by a conductive wire such as a gold wire or a conductive paste such as an Ag-containing epoxy resin. The semiconductor element and the conductive wire are covered with a light-transmitting resin such as an epoxy resin or a silicone resin, and are protected from the external environment.

  The package used in this embodiment is preferably one in which an LED chip can be disposed at the bottom of the recess, and various resins such as epoxy resin, silicone resin, acrylic resin, PBT (polybutylene terephthalate), liquid crystal polymer, and aromatic nylon are used. And is preferably formed.

  The package can be a ceramic package obtained by laminating and firing ceramic green sheets. Since the ceramic package is superior in heat resistance and light resistance as compared to a package made of a resin material, a high-output and highly reliable semiconductor light-emitting device can be obtained.

  The package is preferably filled with an LED chip and a translucent resin electrically connected to the lead electrode. Here, the translucent resin that covers the LED chip may contain a fluorescent material as necessary.

The fluorescent material used in the present embodiment converts the wavelength of the LED chip light. That is, the fluorescent material absorbs at least a part of the light of the LED chip and emits light having a different wavelength. Here, the phosphor is preferably a phosphor that converts light from the LED chip to a longer wavelength side. When light from the LED chip is high-energy short-wavelength visible light, organic phosphors such as perylene derivatives, ZnCdS: Cu, and YAG: Ce (a kind of aluminum oxide phosphor) (for example, YAlO ₃ : Ce). , Y ₃ Al ₅ O ₁₂ : Ce), and inorganic phosphors such as nitrogen-containing CaO—Al ₂ O ₃ —SiO ₂ activated by Eu and / or Cr. In particular, the YAG: Ce phosphor absorbs part of the blue light from the LED chip depending on its content and emits yellow light that is a complementary color. Can be formed relatively easily.

(Mounting board)
The mounting board is for mounting and fixing and arranging a light source, and is provided with a conductor wiring for supplying power to the light source. For example, it can be suitably formed by a glass epoxy substrate on which a conductive pattern made of copper foil or the like is formed, or a metal body bonded with an insulating resin. Or it can be set as the board | substrate with high heat dissipation by which conductor wiring was given to the metal material which consists of aluminum and copper via the insulating material. Moreover, it is preferable that a mounting board | substrate is closely_contact | adhered and arrange | positioned through a heat conductive member like a heat dissipation sheet.

(Light guide)
The light guide in this embodiment refers to a light which can guide light from a light source incident from a part of an end face by utilizing internal reflection and emit light in a desired shape from a predetermined light exit surface. It is an optical member. Therefore, depending on the desired shape of the light emitting surface, various shapes such as a needle shape of a meter needle and a plate shape usable as a liquid crystal backlight light source can be taken. The light guide has translucency in order to efficiently emit light from the light emitting diode or light obtained by wavelength conversion of the light from the light emitting surface. As a material for such a light guide, various materials such as acrylic resin, epoxy resin, and glass are preferably exemplified.

(Casing)
The housing in this embodiment has a recess that accommodates a mounting substrate on which a light source is disposed, a light guide, and an optical sheet portion, and a frame is disposed in the opening of the recess, and these members It is a member holding.

  As the material for the housing, various materials such as resins and metals containing various light diffusing agents are preferably exemplified. In particular, in consideration of heat dissipation and light reflection of a light emitting diode that generates heat, metals such as nickel, iron, copper, and aluminum, and various alloys such as stainless steel are more preferably used. The size and shape of the housing can be variously selected according to the size and shape of the member to be accommodated.

(Frame)
The frame body in this embodiment is a member that is provided on the opening side of the housing and presses the optical sheet portion disposed on the light guide housed in the housing. In particular, the overall shape of the frame in the present embodiment is rectangular, and when the backlight unit is configured, the upper surface of the optical sheet portion is exposed from the opening of the frame to form a light emission observation surface.

  The frame material is made of metal such as nickel, iron, copper, aluminum, stainless steel, etc. considering the elastic force required to hold down the optical sheet, heat dissipation from the light source that generates heat, and light reflection. Various alloys are more preferably used. The size and shape of the frame can be variously selected according to the size and shape of the member to be accommodated. In particular, the ratio between the long side and the short side of the rectangle of the frame body in this embodiment is preferably 1.6 to 1.7. By adopting such a rectangle, by providing protrusions at the corners on the short side rather than the long side of the rectangle, the optical sheet is sufficiently pressed so that the optical sheet does not rattle on the short side, and the long side direction Thus, deformation due to thermal expansion of the optical sheet can be alleviated, and wrinkles of the optical sheet can be eliminated.

(flame)
The frame in this embodiment has an opening that accommodates the light guide, and is disposed between the light guide and the housing to hold the light source and the light guide at predetermined positions of the housing. It is a member. The shape of the frame may be various shapes according to the shape of the housing or the light guide. The frame in this embodiment has at least a recess or a through hole having an opening that can accommodate the light guide. The size and shape of the recess or the through hole are appropriately adjusted according to the size, shape, and number of light guides to be accommodated. The thickness of the side wall forming the opening of the frame is smaller than the size of the gap formed by the side surface of the light guide and the inner wall surface of the recess of the housing. Accordingly, the light guide and the frame can be accommodated in the recess of the casing by fitting the frame into the gap formed by the side surface of the light guide and the inner wall surface of the recess of the casing.

  The frame preferably has a light diffusing agent such as calcium carbonate, aluminum oxide or titanium oxide or a white pigment at least on the inner wall surface of the side wall forming the opening. The side wall portion of such a frame reflects light from the light source in the direction of the incident surface of the light guide or reflects light emitted from the side surface of the light guide toward the light guide to guide the light. Or re-enter the body.

  As the material of the frame, a material having a lower thermal conductivity than the material of the mounting substrate is selected. For example, an insulating material such as polycarbonate, polyether ether ketone, or fluorine-based resin having excellent mechanical strength can be used. Furthermore, the frame can also be formed by injection molding with a resin material containing a light diffusing agent such as calcium carbonate, aluminum oxide or titanium oxide.

  Examples according to the present invention will be described in detail below. Needless to say, the present invention is not limited to the following examples.

  FIG. 1 is a bottom view of the frame according to the present embodiment as viewed from the bottom surface on which the protrusions are formed. FIG. 2 is a partially enlarged view of a corner portion of the frame shown in FIG. FIG. 3 is a plan view of the backlight unit 200 of this embodiment as viewed from the light emission observation surface side. 4 is a partial cross-sectional view taken along line II-II in FIG.

  As shown in FIGS. 3 and 4, the backlight unit 200 of this embodiment includes a light source (not shown) and a housing 201 that houses a light guide plate 202 that guides light from the light source. A frame 100 attached to the upper part of the body 201. The frame 100 has an opening 102 that forms a light emission observation surface, and the upper surface of the optical sheet is exposed in the opening 102.

  More specifically, the housing 201 includes a light source, a light guide 202 that guides light from the light source in order from the bottom, and optical control for light emitted from the light guide 202. Optical sheet portions are stacked and stored. The optical sheet portion of this embodiment is formed by laminating a diffusion sheet 203, a first prism lens sheet 204, and a second prism lens sheet 205 in order from the light guide 202 side.

  The frame body 100 of this embodiment is formed by punching a metal flat plate (thickness 0.3 mm) made of stainless steel. The peripheral edge of the frame 100 is bent in the direction of the lower surface on which the protrusions 101 are formed to form side walls 103. As shown in FIG. 1, the protrusion 101 of the present embodiment has four corners in a frame body having an opening 102 having a pair of short sides a, a short side c, a pair of long sides b, and a long side d. Of these, one is provided on each of the short sides of the two corners.

  The opening 102 of the frame 100 includes a short side a (92.4 mm), a short side b (92.4 mm) facing the long side c, a long side c (153 mm) and a long side that connect the sides and face each other. d (153 mm). Further, the short side a and the long side d are the corner A, the short side a and the long side b are the corner B, the long side b and the short side c are the corner C, the short side c and the long side d. A corner portion D is formed. The protrusions 101 of this embodiment are formed one by one on the short side a side in the corners A and B formed by the common short side a. The center distance between the two protrusions is 90.6 mm, and the center of the protrusion at the corner A is disposed 7.9 mm from the outer edge on the long side d side of the frame 100.

  The protrusion 101 of the present embodiment is formed by drawing, and the outer edge shape thereof is composed of a pair of semicircular arcs and a pair of straight lines facing each other as seen from the front direction as shown in FIG. The longitudinal direction of the protrusion 101 coincides with the short side direction of the frame 100. Moreover, the external shape of the cross section perpendicular | vertical to the flame | frame main surface of the protrusion 101 is a dome shape in a longitudinal direction and a transversal direction, respectively.

  The protrusion 101 is in contact with the upper surface of the optical sheet portion and presses the optical sheet on the short side a side. Further, the deformation due to thermal expansion of the optical sheet is relaxed in the long side b and d directions, and the generation of wrinkles of the optical sheet can be eliminated.

  FIG. 5 is a partial cross-sectional view of the backlight unit of the present embodiment. The backlight unit of this embodiment includes a frame 301 for holding the light guide plate 202 at a predetermined position of the housing 201. The light guide plate 202 is housed in a through hole provided in the frame 301, and the side wall forming the through hole of the frame 301 is between the outer side surface of the light guide plate 202 and the side wall portion 206 of the housing 201. Is intervened.

  The optical sheet portion is disposed on the upper surface of which the peripheral edge portion extends to the upper surface of the side wall of the frame 301. Further, the peripheral edge portion of the optical sheet is pressed and sandwiched in the thickness direction by the upper surface of the side wall of the frame 301 and the lower surface of the protrusion 101 of the frame body 100.

  FIG. 6 is a partial cross-sectional view of the backlight unit of the present embodiment. In the backlight unit of this embodiment, the housing 201 has a protrusion 302 whose inner wall surface protrudes toward the light guide plate 202.

  The optical sheet portion is arranged on the upper surface with the peripheral edge portion extended to the upper surface of the protruding portion 302. Further, the peripheral edge of the optical sheet is pressed and sandwiched in the thickness direction by the upper surface of the protrusion 302 and the lower surface of the protrusion 101 of the frame body 100. In addition, the optical sheet portion is accurately positioned by the inner wall surface of the side wall portion 206 of the housing 201 and the upper surface of the protruding portion 302.

  FIG. 7 is a partial cross-sectional view of the backlight unit of the present embodiment. The backlight unit of the present embodiment has a recess 303 provided on the upper surface of the side wall of the frame 301 in the second embodiment. As shown in FIG. 7, the width of the cross-sectional shape of the recess 303 is larger than the width of the cross-sectional shape of the protrusion 101. Although not illustrated, the planar shape of the opening of the recess is such that the outer shape in plan view is larger than the shape of the oval-shaped protrusion 101 and the rough shape is an oval or rectangular shape. In the optical sheet portion, the entire optical sheet constituting the optical sheet portion is deformed by the protrusions 101, and a part of the optical sheet laminated on the lowermost layer is fitted in the recess 301.

  INDUSTRIAL APPLICABILITY The present invention is applicable to an in-vehicle liquid crystal display device or the like as a backlight that is resistant to vibration and is thinned, miniaturized, and reduced in power consumption.

FIG. 1 is a bottom view of a frame according to an embodiment of the present invention. FIG. 2 is an enlarged view of a corner portion of the frame according to the embodiment of the present invention. FIG. 3 is a top view of the backlight unit according to the embodiment of the present invention. 4 is a partial cross-sectional view taken along line II-II in FIG. FIG. 5 is a partial cross-sectional view of a backlight unit according to an embodiment of the present invention. FIG. 6 is a partial cross-sectional view of a backlight unit according to an embodiment of the present invention. FIG. 7 is a partial cross-sectional view of a backlight unit according to an embodiment of the present invention. FIG. 8 is a top view of a conventional backlight unit. FIG. 9 is an enlarged view of a cross section taken along the line AA of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Frame body 200 ... Backlight unit 101 ... Protrusion 102 ... Opening part 103, 206 ... Side wall part 201 ... Case 202 ... Light guide 203 ... Diffusion Sheet 204... First prism sheet 205... Second prism sheet 207... Projection 301... Frame 302.

Claims (7)

A light source, a light guide that guides the light of the light source, an optical sheet portion laminated on the light guide, a housing that accommodates them, and a rectangle disposed in an opening of the housing In a backlight unit having a frame body,
The frame body has a protrusion that is in contact with the upper surface of the optical sheet portion ,
The backlight unit according to claim 1, wherein the protrusions are provided only at two corners formed by two long sides and one short side of the frame .
The backlight unit according to claim 1 , wherein the protrusion is provided on a short side of each corner of the two corners .
The shape of the protrusion is an ellipse or a track shape when viewed from the front direction,
The backlight unit according to claim 1 , wherein a longitudinal direction of the protrusion is made to coincide with a short side direction of the frame.
The backlight further includes a frame having an opening for accommodating the light guide ,
The optical sheet portion is arranged extending to the upper surface of the frame,
The backlight unit according to claim 1, wherein the optical sheet portion is held between the upper surface of the frame and the protrusion.
The housing has a bent portion in which a part of the side wall is bent inward,
4. The backlight unit according to claim 1 , wherein a peripheral edge portion of the optical sheet portion extends on an upper surface of the bent portion and is sandwiched between the upper surface and the protrusion.
The housing has a protruding portion in which a part of the side wall protrudes inward,
4. The backlight unit according to claim 1 , wherein a peripheral edge portion of the optical sheet portion extends on an upper surface of the protruding portion and is sandwiched between the upper surface and the protrusion.
Said frame, said bent portion, an upper surface of at least one member selected from the protruding portion or the lightguide according to any one of claims 1 to 6, characterized in that a recess directly below the projection Backlight unit.

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