JP2005250269A - Backlight structure for liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a backlight structure for a liquid crystal display device, which is miniaturized so as not to make the liquid crystal display device be moved. <P>SOLUTION: The backlight structure for the liquid crystal display device is constructed by forming a stage part composed of a recessing part on a frame body 22, containing a light guide plate 28 formed to be larger than the size of the display region of the liquid crystal display device in the recessing part, arranging the frame body 22 so as to mount the contained light guide plate 28 on a position directly below the display region of the liquid crystal display device 12, disposing a diffusion sheet 20 with a size larger than the size D of the display region of the liquid crystal display device 12 and smaller than the outer size of the liquid crystal display device 12 between the light guide plate 28 and the liquid crystal display device 12, arranging adhesives 26a, 26b, 26c, 26d on at least a part of a region out of a regional part of upper and lower surfaces of the diffusion sheet 20 lying outside the display region of the liquid crystal display device 12, joining the lower face of the liquid crystal display device 12 and the diffusion sheet 20 via the adhesives, and further joining the upper face 22p of the stage part of the frame body 22 to the diffusion sheet 20. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a backlight mounting structure for a liquid crystal display device.

  Conventionally, regarding the backlight structure of a liquid crystal display device, various structures are used depending on the liquid crystal display device. One of them is the structure shown in Patent Document 1 below.

JP 2003-195265 A

  The backlight structure disclosed in Patent Document 1 will be described with reference to FIGS. FIG. 6 is an exploded perspective view showing the backlight structure of the liquid crystal display device shown in Patent Document 1, and FIG. 7 is a cross-sectional view of the main part showing the assembled state of the components shown in FIG. . This backlight structure has a structure in which a liquid crystal display device 12, a diffusion sheet 10, a circuit board 4 provided with a light emitting element 6 and a light guide plate 8 are assembled in a frame 2 in an assembling manner. And the structure of these components has taken the structure shown below.

  The frame body 2 has an opening 2a at the upper side, and a concave first housing portion 2c for housing the circuit board 4 provided with the light emitting element 6 on the bottom portion 2b, the light guide plate 8, and the diffusion sheet 10. The 2nd accommodating part 2d which accommodates is connected. In addition, a third storage portion 2h that stores the liquid crystal display device 12 is provided on the first storage portion 2c and the second storage portion 2d that are provided in series. A pair of grooves 2g communicating with the first storage portion 2c and the second storage portion 2d are provided at the lower ends of the opposing side walls 2e and 2f of the frame body 2, respectively. The side wall 2j has an opening 2i for taking out a flexible printed board (hereinafter referred to as FPC) attached to the liquid crystal display device 12, and a circuit board 4 with the light emitting element 6 in the first storage part 2c. An opening for storage is also provided.

  The light guide plate 8 is provided with a pair of projecting portions 8a on both side end surfaces, and the projecting portions 8a are formed by projecting portions having a substantially triangular cross section, have a guide slope 8b on the lower side, and have a horizontal surface on the upper side. The engaging surface 8c is formed. Also, a recess 8d that fits the LED is provided at one end thereof. The diffusion sheet 10 is provided with a pair of rectangular projecting portions 10 a at opposite ends at positions corresponding to the projecting portions 8 a of the light guide plate 8. The liquid crystal display device 12 includes an upper glass 12a and a lower glass 12b in which liquid crystal is sealed, an upper polarizing plate 12c provided on the upper surface of the upper glass 12a, and is provided on the lower surface of the lower glass 12b. The lower polarizing plate 12d has an FPC 14 attached to one end of the upper glass 12a. The circuit board 4 has a light emitting element 6 made of LED mounted on the upper surface thereof.

  And the assembly method of the liquid crystal display device 12, the diffusion sheet 10, the light guide plate 8, the circuit board 4, and the frame 2 having such a configuration is as follows. First, an adhesive is applied with a double-sided adhesive tape 16 along a pair of opposing sides of the diffusion sheet 10. The pair of opposite sides is a side corresponding to the FPC attachment side, and a double-sided adhesive tape is attached to the outer portion of the display area of the liquid crystal display device 12. Next, the circuit board 4 with the light emitting element 6 is accommodated in the first accommodating portion 2c from the opening portion on the side wall 2j side of the frame body 2, and then the light guide plate 8 is secondly inserted from the upper surface side opening portion 2a of the frame body 2. In the storage portion 2d. As a method of storing, a pair of protruding portions 8a provided on both end faces of the light guide plate 8 are fitted and fixed to a pair of grooves 2g provided on the lower ends of the side walls 2e and 2f. The light guide plate 8 is tilted and inserted and fitted using the guide slope 8b of the overhang portion 8a. At this time, the light emitting element 6 mounted on the circuit board 4 is accommodated in the recessed portion 8 d of the light guide plate 8. Next, the diffusion sheet 10 with an adhesive is stored in the second storage portion 2 d from the upper surface side opening 2 a of the frame 2. The storage method is a method in which the diffusion sheet 10 is curved and inserted from the opening 2 a of the frame 2, and the protruding portion 10 a is fitted into the groove 2 g of the frame 2. Next, the liquid crystal display device 12 is projected from the upper surface side opening 2a of the frame body 2 and the FPC 14 is projected from the opening 2i provided on the side wall 2j, and is accommodated in the third storage portion 2h. The diffusion sheet 10 and the liquid crystal display device 12 are bonded and fixed via the agent 16. As a result, the liquid crystal display device 12, the diffusion sheet 10, the light guide plate 8, and the circuit board 4 are accommodated in the frame 2.

  The backlight structure of the liquid crystal display device having such a configuration has the following problems. As a first problem, the size of the frame 2 itself becomes considerably large. In order to store the thick light guide plate 8 in the second storage portion 2d, the second storage portion 2d cannot be accommodated unless the storage portion is of a size having a considerable backlash amount. Further, since the method of hooking the protruding portion 8a of the light guide plate 8 into the pair of grooves 2g provided on the side walls 2a and 2f of the frame body 2 is used, the light guide plate 8 must be provided with a considerable thickness on the side walls 2e and 2f. It will come off. On the other hand, since the diffusion sheet 10 is curved and inserted, it can be inserted into the second storage portion 2d without any backlash, but if the side walls 2e and 2f are not thickened, for the same reason as the light guide plate 8, The diffusion sheet 10 comes off. For this reason, the frame 2 must be designed to be considerably larger than the liquid crystal display device 12.

  As a second problem, when the FPC 14 moves and a large force is applied to the liquid crystal display device 12, the liquid crystal display device 12 is lifted. Although the liquid crystal display device 12 is fixed to the diffusion sheet 10 with an adhesive, the diffusion sheet 10 is only fixed by inserting the protruding portion 10a into the groove 2g of the frame 2 so that the surface contact is achieved. It is in a fixed state of line contact, not fixed. Accordingly, the fixing force is weak, and when the pulling force from above is applied, the protruding portion 10a is easily bent and the diffusion sheet 10 is lifted upward.

  As a third problem, since the light guide plate 8 is easy to move, the brightness of the illumination varies. The light guide plate 8 is stored in the second storage portion 2d of the frame body 2 with a considerable amount of backlash (margin). Further, a method is adopted in which the overhanging portion 8a is fitted and fixed to the groove portion 2g of the frame body 2. However, a slight amount of play is required to insert the overhanging portion 8a into the groove portion 2g, and the amount of play is a gap in the gap. Occurs as. Moreover, although the upper surface side of the light guide plate 8 is in contact with the diffusion sheet 10, no large pressure is applied thereto, and when a single force is applied to the light guide plate 8, the light guide plate may move by the gap described above. Get up. Therefore, the light guide plate 8 moves due to a single vibration. When this happens, the brightness of the illumination changes every time the light guide plate 8 moves.

  The present invention has been made in view of the above-described problems. The object of the present invention is to reduce the frame as much as possible, to firmly fix the liquid crystal display device, and to ensure that the brightness of the illumination does not fluctuate. Is to get the light structure.

  As a means for solving the above-mentioned problems, the backlight structure according to claim 1 of the present invention has a light diffusion sheet disposed between the liquid crystal display device to which the FPC is attached and the frame body in which the light guide plate is accommodated. In the backlight structure of the liquid crystal display device, the frame body has a stepped portion formed of a concave portion, and the light guide plate formed larger than the size of the display area of the liquid crystal display device is accommodated in the concave portion, A frame is arranged so that the stored light guide plate is arranged at a position directly below the display area of the liquid crystal display device, and a light diffusion sheet is provided between the light guide plate and the liquid crystal display device. An adhesive or an adhesive is provided on at least a partial area of the upper and lower surfaces of the diffusion sheet that is out of the display area of the liquid crystal display device, and the adhesive or adhesive is provided on the light diffusion sheet. Under the liquid crystal display device through And bonding the light diffusing sheet, further, it is characterized in that it has joined the top and a light diffusing sheet of the stepped portion of the frame body.

  In the backlight structure according to claim 2 of the present invention, the frame has an upright wall that reaches the upper surface of the liquid crystal display device on the outer peripheral side surface in three directions excluding the FPC mounting side of the liquid crystal display device. It is characterized by having.

  The backlight structure according to claim 3 of the present invention is characterized in that the thickness of the light guide plate is smaller than the depth of the recesses in the frame.

  In the backlight structure according to claim 4 of the present invention, the adhesive or adhesive provided on the upper surface of the light diffusing sheet is disposed near the display area line of the liquid crystal display device. It is provided outside.

  Further, in the backlight structure according to claim 5 of the present invention, the pressure-sensitive adhesive or adhesive provided on the light diffusing sheet is formed in two opposing regions on the FPC mounting side of the liquid crystal display device. It is characterized by providing.

  In the backlight structure according to claim 6 of the present invention, the bonding area between the light diffusion sheet and the liquid crystal display device is substantially the same as the bonding area between the light diffusion sheet and the frame. It is characterized by an area.

In the backlight structure according to claim 7 of the present invention, the area width of the adhesive or adhesive provided on two sides of the light diffusion sheet on the side facing the FPC mounting side of the liquid crystal display device is FPC. The region width provided closer to the attachment portion is wider than the region provided on the side opposite to the FPC attachment side.
The backlight structure according to claim 8 of the present invention is characterized in that the light guide plate is fixed in a recess of the frame.

  As an effect of the invention, under the invention described in claim 1, the liquid crystal display device, the diffusion sheet, and the frame are completely bonded and fixed via an adhesive or an adhesive. Therefore, the problem of moving even when force is applied to the liquid crystal display device does not occur. Further, the light diffusion sheet is at most the size of a liquid crystal display device. Therefore, it can be made smaller than the diffusion sheet used in the above cited reference 1 of the background art.

  According to the second aspect of the present invention, the liquid crystal display device is prevented from being completely exposed. External impact is applied to prevent damage to the liquid crystal display device. Also, it can be easily attached to a display device.

  Moreover, under the invention described in claim 3, the diffusion sheet is sufficiently bonded to the frame body via the pressure-sensitive adhesive or the adhesive. If the light guide plate is larger than the depth of the recess, the adhesive or the adhesive mainly adheres to the light guide plate, and the adhesion to the frame is insufficient. Then, the bonding strength with the frame body may be weakened or peeled off.

  Further, as in the invention described in claim 4, when the formation area of the pressure-sensitive adhesive or the adhesive is provided close to the boundary line of the display area, the size of the diffusion sheet can be reduced.

  Further, under the invention according to claim 5, by providing a pressure-sensitive adhesive or an adhesive in the region of the two opposite sides on the FPC attachment side, the liquid crystal display device and the frame body via the diffusion sheet, It becomes possible to bond together in a well-balanced manner, and since the strength is increased, it becomes difficult to peel off.

  According to the sixth aspect of the present invention, the liquid crystal display device and the frame body have substantially the same bonding strength and can be balanced. There is no problem that either the liquid crystal display device or the frame is easily peeled off.

Further, under the invention according to claim 7, the area width on the FPC attachment side is wider than the adhesion area on the opposite side, out of the adhesion areas on the opposite sides of the FPC attachment side. Therefore, even when a force pulling the FPC toward the liquid crystal display works, the liquid crystal display device can be prevented from floating from the frame.
According to the eighth aspect of the invention, there is no problem that the light guide plate moves, so that a constant brightness is always obtained without changing the brightness of the illumination.

  Hereinafter, the best embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view of a backlight-equipped liquid crystal display device showing a backlight structure of the liquid crystal display device according to the first embodiment of the present invention, and FIG. 2 is an exploded view of the backlight-equipped liquid crystal display device shown in FIG. 3 shows a cross-sectional view of the main part of the liquid crystal display device with backlight in FIG. 4 is a cross-sectional view of a main part of a liquid crystal display device with a backlight according to a second embodiment of the present invention, and FIG. 5 is a cross-sectional view of a main part of a liquid crystal display device with a backlight according to a third embodiment of the present invention. Show. Parts having the same configurations as those of the conventional example described in the background art will be described with the same reference numerals.

  As shown in FIG. 1, the backlight structure according to the first embodiment of the present invention has a structure in which a liquid crystal display device 12 attached with a light guide plate, a diffusion sheet, and an FPC 14 is housed in a frame 22. The frame 22 has upright walls 22e, 22f, and 22k on three sides, and the upright walls protect the liquid crystal display device 12 from external impacts and the like. In addition, a circuit board with a light emitting element is inserted from the opening 22c provided in the side wall 22j of the frame 22 in the foreground in the figure, and is arranged inside the frame 22 and on the side of the light guide plate. Yes. As shown in FIG. 2, the components of the backlight-equipped liquid crystal display device having the backlight structure are the liquid crystal display device 12 with the FPC 14 attached, the light diffusion sheet 20 provided with the adhesive 26, the light guide plate 28, the LED The circuit board 24 provided with the light emitting element 25 composed of the frame 22 and the frame body 22 are configured.

  The liquid crystal display device 12 has the same configuration as the liquid crystal display device used in the conventional example, and includes an upper glass 12a and a lower glass 12b in which liquid crystal is sealed, an upper polarizing plate 12c provided on the upper surface of the upper glass 12a, Although it is hidden and visible in 2, it is composed of a lower polarizing plate 12 d provided on the lower surface of the lower glass 12 b, and the FPC 14 is attached to one end of the upper glass 12 a. A portion indicated by diagonal lines indicates a display area, and B indicated by a dotted line indicates a boundary line of the display area, that is, a boundary line of the display area.

  The light diffusion sheet 20 is provided for diffusing the light emitted from the light guide plate 28 toward the liquid crystal display device 12, and is provided in order to eliminate unevenness in the amount of light emission and achieve uniform brightness. Is. The diffusion sheet 20 is formed to be larger than the display area A of the liquid crystal display device 12 and smaller than the outer size of the liquid crystal display device 12. The diffusion sheet 20 is formed of adhesives 26a and 26b in strips on the two opposite sides 20a and 20b of the diffusion sheet 20 on the upper surface side and the lower surface side of the liquid crystal display device 12 on the side where the FPC 14 is attached. An adhesive 26 is provided. In this embodiment, a double-sided adhesive tape is used, and the tape is peeled off and pasted. In this case, the adhesive may be provided by a technique such as printing, and is not particularly limited to the pressure-sensitive adhesive. Although the adhesive 26 on the lower surface side is hidden and cannot be seen, the adhesive 26 including the adhesives 26c and 26d is also provided on the lower surface side in the same manner (see FIG. 3). The area where the adhesives 26a and 26b on the upper surface side are provided is an area corresponding to the outside of the display area A of the liquid crystal display device 12, and is preferably provided as close to the boundary line of the display area as possible. The diffusion sheet 20 is formed of a resin film, and includes a sheet in which countless minute irregularities are formed on the surface and a film in which light diffusion particles are dispersed in the film.

  The light guide plate 28 is provided to guide the light incident from the light emitting element 25 disposed on the side surface thereof and radiate it to the liquid crystal display device 12 side. The light guide plate 28 is provided with a pair of hooks 28g on a side surface 28a and a side surface 28b, which contact the FPC attachment side. This hook 28g is provided for the purpose of fixing the light guide plate 28 to the frame 22 by engaging with a groove 22g of the frame 22 described later. The light guide plate 28 needs to be larger than the display area A of the liquid crystal display device 12. However, it is not necessary to make it extremely large, and a slightly large degree is good. The function can be satisfactorily achieved when the vertical and horizontal dimensions are about 0.5 mm larger than the display area A of the liquid crystal display device 12. The light guide plate 28 is made of a transparent acrylic resin or the like.

  The circuit board 24 is made of a bake board or an FPC board, and a conductive pattern is formed on the surface side thereof so as to conduct to the light emitting element 25. The light emitting element 25 uses an LED in this embodiment.

  The frame 22 is used to house the liquid crystal display device 12, the diffusion sheet 20, the light guide plate 28, the circuit board 24, etc., and to form a unit of a liquid crystal display device with a backlight, and is formed by injection molding of a plastic resin. . The frame body 22 has an opening 22a on the upper side, the inside is divided into two stages, and has a storage part composed of an upper stage part 22h and a lower stage part 22d. The upper step portion 22h and the lower step portion 22d are separated by a step portion 22m at the boundary, and a recess having a bottom surface 22b below the step portion 22m is a lower step portion 22d. On the other hand, the upper step 22h has an upper step above the step 22m. The lower step portion 22d is a continuous storage portion for storing the circuit board 24 on which the light emitting element 25 is mounted and the light guide plate 28, and the upper step portion 22h on the lower step portion 22d is the diffusion sheet 20 and the liquid crystal display device 12. It is a storage part that stores The frame body 22 has an opening 22i on the side wall 22j on the front side in the drawing in order to take out the FPC 14 attached to the liquid crystal display device 12, and the circuit board 24 is accommodated on the same side wall 22j side. Has an opening 22c to be inserted into the. Further, the outer peripheral side surfaces in three directions other than the side wall 22j have upright walls 22e, 22k, and 22f that reach the upper surface of the liquid crystal display device 12, and the upright walls serve to protect the liquid crystal display device 12 from external shocks. ing. In order to make the frame 22 as small as possible, the width of the upper surface 22n of the upright wall can be formed as narrow as possible. If the width of the upper surface 22n is 0.5 to 1.0 mm, the purpose is sufficiently achieved. Also, a pair of grooves 22g are provided on the inner wall on the near side and the far side in the drawing of the lower step portion 22d. Further, a slit 22q connected to the pair of grooves 22g is provided on the back surface side (see FIG. 3). The slot 22q is provided so that the inner wall of the lower step portion 22d bends and spreads outward when the hook 28g of the light guide plate 28 is inserted into the groove 22g to be engaged. By spreading both inner walls, the light guide plate 28 is accommodated and fixed in the lower step portion 22d.

  Next, a method for making these components into units will be described with reference to FIGS. First, the circuit board 24 on which the light emitting element 25 is mounted is inserted through the opening 22c and is housed and fixed in the lower step 22d. The fixing method is fixed using a known method such as an adhesive method or a method of fitting a hole and a boss. Next, the light guide plate 28 is inserted into and fixed to the lower step portion 22 d formed of the concave portion of the frame body 22. As described above, the method of inserting and fixing is to insert the light guide plate 28 by inserting the hook 28g of the light guide plate 28 into the groove 22g on the inner wall of the lower step portion 22d, bending the inner wall outward, and expanding the inside. A pair of hooks 28 g on both side surfaces of the light guide plate 28 engage with a pair of grooves on both inner walls of the lower step portion 22 d of the frame body 22, so that the light guide plate 28 is fixed to the lower step portion of the frame body 22. Is done. The light guide plate 28 may be fixed first, and then the circuit board 24 may be fixed. Next, the diffusion sheet 20 provided with the adhesive 26 on the upper and lower surfaces is placed on the upper surface 22 p of the stepped portion 22 m of the frame body 22. At this time, the upright walls 22e, 22k, and 22f in the three directions also serve as positioning guides. Next, the liquid crystal display device 12 is placed on the diffusion sheet 20. Also at this time, the upright walls 22e, 22k, and 22f in the three directions also serve as positioning guides. After the diffusion sheet 20 and the liquid crystal display device 12 are stacked on the frame body 22 in this way, the liquid crystal display device 12, the diffusion sheet 20, and the frame body 22 are pressed onto the liquid crystal display device 12 to apply the pressure on the diffusion sheet 20. It joins via the adhesive 26 provided in the lower surface.

  In FIG. 3, D indicates the area width of the display area A of the liquid crystal display device 12, and is drawn up to the arrangement position of the diffusion sheet 20 and the light guide plate 28 with a one-dot chain line so that the area can be clearly seen. As described above, the adhesives 26a and 26b provided on the upper surface side of the diffusion sheet 20 are provided outside the display area A and close to the boundary line between the display area A and the outer area. The pressure-sensitive adhesives 26c and 26d provided on the lower surface side of the diffusion sheet 20 are provided on the opposite side of the pressure-sensitive adhesives 26a and 26b provided on the upper surface side. It is provided at a position where it adheres to the upper surface 22p. The total width of the width E1 of the adhesive 26a on the upper surface side that joins the liquid crystal display device 12 and the diffusion sheet 20 and the width E2 of the adhesive 26b is the lower surface side that joins the frame 22 and the diffusion sheet 20. The width F1 of the adhesive 26c and the width F2 of the adhesive 26d are set to be approximately equal to the total width. That is, the width of the adhesive is set to be E1 + E2 = F1 + F2. In this way, the bonding force between the liquid crystal display device 12 and the diffusion sheet 20 and the bonding force between the diffusion sheet 20 and the frame body 22 become substantially the same bonding force, and the balance between the liquid crystal display device 12 and the frame body 22 is balanced. The unit is completed with a strong fixing force. The adhesives 26 a and 26 b provided on the diffusion sheet 20 are adhered to the lower polarizing plate 12 d of the liquid crystal display device 12.

  In this embodiment, in FIG. 4, the adhesive region F1 on the opposite surface of the FPC 14 is set slightly larger than the adhesive region F2 on the opposite side. That is, there is a relationship of F1> F2. In many cases, the FPC 14 is often mounted on the liquid crystal display device side, that is, upward in FIG. 4, and the liquid crystal display device 12 is likely to be lifted from the frame 22. The purpose is to prevent this. Due to restrictions on the display area of the liquid crystal display device 12, the difference between F1 and F2 cannot be made extremely large. A range in which the mutual bonding force of the liquid crystal display device, the diffusion sheet, and the frame can be secured in a balanced manner, that is, E1 + E2 = F1 + F2 is satisfied, and F1> F2 is set.

  Since the display area A of the liquid crystal display device 12 is illuminated with the light radiated from the light guide plate 28, the adhesive 26 provided on the diffusion sheet 20 may be provided close to the boundary line of the display area A. Absent. Further, sufficient illumination can be obtained if the light guide plate 28 is arranged to be slightly larger than the display area A and arranged just below the display area of the liquid crystal display device. The light guide plate 28 shown in FIG. 3 is arranged so as to be located immediately below the display area A of the liquid crystal display device 12.

  By taking such a structure, the diffusion sheet 20 can be made small. It can be at least smaller than the liquid crystal display device 12. Similarly, the frame 22 can be made smaller. Although the frame 22 is provided with an upright wall, the frame 22 itself can be further reduced by designing the wall width to be narrow within an allowable range. Further, at least the amount of the diffusion sheet 20 and the frame 22 on the FPC attachment side does not jump out from the liquid crystal display device 12. Compared to the hook locking structure or the like that provides a gap between the frame and the light guide plate described in the background art and locks the groove and the overhanging portion. In this embodiment, an upright wall is provided. However, the upright wall can be used as a mounting part when the upright wall is attached to a front cover of a display device. Further, when the usage is such that an upright wall is not required, there is no need to provide it. Further, since the liquid crystal display device 12, the diffusion sheet 20, and the frame 22 are completely adhered and fixed, the liquid crystal display device does not move. Further, since the light guide plate 28 is also fixed to the frame body 22, it does not move, and constant and bright illumination can be obtained constantly.

  In the present embodiment, the thickness of the light guide plate 28 is designed to be smaller than the depth of the lower step portion 22d, that is, the recess depth. In this way, the adhesive does not adhere to the light guide plate 22. In this embodiment, the outer peripheral end surfaces of the adhesives 26a and 26b provided on the upper surface side of the diffusion sheet 20 are provided so as to be located inside the outer peripheral end surface of the diffusion sheet 20, but are aligned with the outer peripheral end surface of the diffusion sheet 20. It may be a different position.

    Next, the backlight structure of the liquid crystal display device according to the second embodiment of the present invention will be described with reference to FIG. The difference between the backlight structure of the second embodiment and the backlight structure of the first embodiment is that the thickness of the light guide plate 28 is the depth of the lower step portion 22d of the frame body 22, that is, the concave portion. The difference is that the adhesives 26c and 26d provided on the lower surface of the diffusion sheet 20 are provided close to the boundary line of the area width D of the display area. The rest of the configuration is the same as that of the first embodiment.

  Under such a configuration, the adhesives 26c and 26d provided on the lower surface of the diffusion sheet 20 form the light guide plate 28 slightly larger than the region width D of the display region. It adheres to the upper surface 22p of the step portion of the frame body 22. However, even in such a case, the sum of the width F1 in which the adhesive 26c is adhered to the stepped portion upper surface 22p of the frame body 22 and the width F2 in which the adhesive 26d is adhered to the stepped portion upper surface 22p of the frame body 22, That is, F1 + F2 is set to be the same as the width E1 + E2 adhered to the lower polarizing plate 12d of the liquid crystal display device 12 by the upper surface side adhesives 26a, 26b of the diffusion sheet 20. The adhesives 26c and 26d are adhered to both ends of the light guide plate 28 with a small amount of G1 and G2, but the size of the light guide plate 28 is in a range about 0.5 mm larger than the region width D of the display region. The balance between the bonding force between the liquid crystal display device 12 and the diffusion sheet 20 and the bonding force between the frame 22 and the diffusion sheet 20 is not greatly lost, and a substantially similar bonding force can be obtained. It is considered that there is almost no influence on the bonding force between the diffusion sheet 20 and the frame 22 in the portions G1 and G2. In FIG. 4, the position of the outer peripheral end surface of the diffusion sheet 20 is introduced as a shape protruding from the outer peripheral end surfaces of the adhesives 26 c and 26 d, but a configuration in which part or all of the outer peripheral ends are aligned may be used. Also in the present embodiment, the liquid crystal display device can be prevented from floating above the frame by setting F1> F2.

    Next, the backlight structure of the liquid crystal display device according to the third embodiment of the present invention will be described with reference to FIG. The difference between the backlight structure of the third embodiment and the first backlight structure is that the thickness of the light guide plate 28 is larger than the depth of the lower step portion 22d of the frame body 22, that is, the depth of the recess. In addition, the width of the light guide plate 28 is considerably larger than the area width D of the display area, and the adhesives 26c and 26d provided on the lower surface of the diffusion sheet 20 are connected to the boundary line of the area width D of the display area. The place where it is provided to the vicinity is different. The rest of the configuration is the same as that of the first embodiment.

  When the thickness of the light guide plate 28 is considerably larger than the depth of the lower step portion 22d of the frame body 22 and considerably protrudes from the upper surface 22p of the step portion of the frame body 22, the adhesives 26c and 26d are placed on the upper surface 22p in the vicinity of the step. A missing part, that is, a bridge part comes out. Assuming that the width of the bridge portion is H1 and H2, H1 and H2 increase when the pop-out amount is large, and H1 and H2 decrease when the pop-out amount is small.

  Even when such a bridge is generated, the widths F1 and F2 where the adhesives 26c and 26d are actually adhered to the upper surface 22p of the stepped portion are set so that F1 + F2 = E1 + E2. However, it is not preferable that the bridge is greatly generated, and there is a risk that the bonding strength is also lowered. If the amount of protrusion from the upper surface 22p of the light guide plate 28 is in the range of 20 μm or less, bridges hardly occur and a strong bonding strength can be obtained. If F1> F2 is set, the same effect as in the above-described two embodiments can be obtained.

  By using the backlight structure as described above, the diffusion sheet 20, the light guide plate, and the frame can be reduced, and the backlight-equipped liquid crystal display device unit can be reduced in size. Further, a strong bonding strength is obtained, and there is no problem that the liquid crystal display device moves or peels off. In addition, illumination with constant brightness can be obtained constantly.

1 is a perspective view of a backlight-equipped liquid crystal display device showing a backlight structure of a liquid crystal display device according to a first embodiment of the present invention. It is an exploded view of the liquid crystal display device with a backlight shown in FIG. It is principal part sectional drawing of the liquid crystal display device with a backlight in FIG. It is principal part sectional drawing which shows the backlight structure of the liquid crystal display device which concerns on 2nd Embodiment of this invention. It is principal part sectional drawing which shows the backlight structure of the liquid crystal display device which concerns on 3rd Embodiment of this invention. It is a disassembled perspective view which shows the backlight structure of the liquid crystal display device as shown by patent document 1. FIG. It is principal part sectional drawing which showed the state which assembled each component shown in FIG.

Explanation of symbols

12 Liquid crystal display device
12a Upper glass 12d Lower glass 12c Upper polarizing plate 12d Lower polarizing plate 14 FPC
20 diffusion sheet 20a, 20b side 22 frame 22a, 22c, 22i opening 22b bottom 22d lower step 22h upper step 22e, 22f, 22k upright wall 22j side wall 22g groove 22n upper surface 22m step 22p upper surface 22q slit 24 circuit board 25 Light emitting element 26, 26a, 26b, 26c, 26d Adhesive 28 Light guide plate 28a, 28b, 28c, 28d Side face 28g Hook A Display area B Boundary line

Claims (8)

In a backlight structure of a liquid crystal display device in which a light diffusion sheet is disposed between a liquid crystal display device to which an FPC is attached and a frame body in which a light guide plate is housed,
The frame has a stepped portion formed of a recess, and the light guide plate formed larger than the display area of the liquid crystal display device is stored in the recess, and the stored light guide plate displays the display of the liquid crystal display device. Arrange the frame so that it is placed on the lower surface side of the area,
A diffusion sheet is disposed between the light guide plate and the liquid crystal display device, and an adhesive or an adhesive is bonded to at least a part of the region of the upper and lower surfaces of the diffusion sheet that is out of the display region of the liquid crystal display device. Agent,
A back of the liquid crystal display device, wherein the lower surface of the liquid crystal display device and the light diffusion sheet are bonded via the pressure-sensitive adhesive or adhesive, and further, the upper surface of the stepped portion of the frame body and the light diffusion sheet are bonded. Light structure. 2. The liquid crystal according to claim 1, wherein the frame has an upright wall that reaches an upper surface of the liquid crystal display device on an outer peripheral side surface in three directions excluding an FPC mounting side of the liquid crystal display device. Backlight structure of display device. 3. The backlight structure of a liquid crystal display device according to claim 1, wherein a thickness of the light guide plate is smaller than a depth of a concave portion of the frame body. The liquid crystal display according to claim 1, wherein the adhesive or adhesive provided on the upper surface of the light diffusion sheet is provided outside the display area in the vicinity of a boundary line of the display area of the liquid crystal display device. The backlight structure of the device. 5. The liquid crystal according to claim 1, wherein the pressure-sensitive adhesive or adhesive provided on the light diffusion sheet is provided in two opposing regions on the FPC attachment side of the liquid crystal display device. Backlight structure of display device. 6. The bonding area between the light diffusion sheet and the liquid crystal display device and the bonding area between the light diffusion sheet and the frame body are substantially the same area. The backlight structure of the liquid crystal display device as described in one. The area width of the adhesive or adhesive provided on the two sides of the light diffusion sheet facing the FPC attachment side of the liquid crystal display device is the same as the area width provided on the side closer to the FPC attachment portion. 7. The backlight structure of a liquid crystal display device according to claim 1, wherein the backlight structure is wider than a width of a region provided on the opposite side. The backlight structure of the liquid crystal display device according to claim 1, wherein the light guide plate is fixed in a concave portion of the frame body.

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