JP2003156739A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device with a thin backlight in which the size the device is not restricted by the size of an LED. SOLUTION: A light transmission plate 22 disposed on the lower surface side of a liquid crystal cell 10 has a terminal part 22c formed in such a way that it protrudes from an end face 10a of the liquid crystal cell 10. A notched part 22d is arranged in a central part of the terminal part 22c. An LED 21 installed in a branch flexible board 41 is mounted in the notched part 22d and, at the same time, the branch flexible board 41 is stretched around an upper surface of the terminal part 22c and is fixed via an adhesive. A reflection sheet 23 is integrated with a lower face and a side face of the light transmission plate 22, and at the same time, the light transmission plate 22 is made to fixedly adhere to a lower glass substrate 12 of the liquid crystal cell 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device having a backlight.

[0002]

2. Description of the Related Art In recent years, display devices using liquid crystal cells have been installed in all kinds of electronic equipment such as watches, telephones and personal computers. Among such electronic devices, in particular, clocks, mobile phones and the like are used at night or in a dark place, and therefore, many of them have a backlight for illuminating a liquid crystal cell.

9 to 13 show one structure of a conventional liquid crystal display device with a backlight. 9 is a front view of the liquid crystal display device, FIG. 10 is a sectional view taken along line XX in FIG. 9, FIG. 11 is a sectional view taken along line YY in FIG. 9, FIG. 12 is an exploded perspective view of the liquid crystal display device, and FIG. 7 shows a state in which the branching flexible substrate and the frame body are positioned and fixed in FIG.

As shown in FIGS. 9 to 12, a conventional liquid crystal display device 100 with a backlight includes a liquid crystal cell 110 and a liquid crystal cell 110.
A backlight unit 120 provided on the lower surface side thereof, and a frame body 130 for holding the liquid crystal cell 110 and the backlight unit 120.
Etc. The liquid crystal cell 110 encloses a liquid crystal substance between two upper and lower glass substrates 111 and 112 on which transparent electrode films are formed.
Polarizing plates 115 and 116 are attached to the outside of the frame, respectively, and are held by the frame body 130.
A flexible substrate 140 is mounted on the upper glass substrate 111 of the liquid crystal cell 110. An IC 140a for controlling and driving the liquid crystal cell 110, electronic parts 140b such as resistors and capacitors, etc. are mounted on the flexible substrate 140. The flexible board 140 is formed with a branching flexible board 141 that is branched on the right side of the drawing, and the end side thereof is the frame body 130.
It is built into the inside of.

In addition, the backlight unit 120 has an LED 121 as a light source, a light guide plate 122 for guiding the light emitted from the LED 121 to the lower surface side of the liquid crystal cell 110, and a light leaked from the lower surface of the light guide plate 122 and the like again. The light guide plate 122 includes a reflection plate 123 for reflecting the light toward the light guide plate 122 side, and both are housed and disposed inside the frame body 130.
The light guide plate 122 is formed of a transparent acrylic material or the like and takes in the light of the LED 121 from one side surface 122a thereof and guides it to the inside, and also has a function of radiating the light from the upper surface 122b side by utilizing the action of the reflection plate 123 and the like. Eggplant At this time, a light diffusing plate 124 is also provided between the light guide plate 122 and the liquid crystal cell 110 in order to make the brightness of the emitted light uniform. As described above, the liquid crystal display device 100 includes the backlight unit 120 on the lower surface side of the liquid crystal cell 110,
It has a structure in which it is firmly held by the frame body 130.

Here, the LED 121 is a branched flexible substrate 14 branched from the flexible substrate 140.
The light emitting surface 121a of the LED 121 faces the light receiving wall surface 122a of the light guide plate 122 inside the frame body 130, which is attached to the front end of the light guide member 1 by a known method such as a conductive adhesive or soldering. It is arranged in such a form. This LED
121 is a single light emitting element such as white or red,
A device provided with light emitting elements of three primary colors of blue and green is appropriately selected and used according to the application.

The branch flexible board 141 on which the LED 121 is mounted has two pins 130a formed in the frame 130 in the frame 130 as shown in FIG.
And two holes 141a formed in the branching flexible substrate 141 are fitted and positioned and fixed.

The liquid crystal display device 100 includes a light guide plate 122.
The liquid crystal cell 110 is fitted into the upper part of the frame 130 accommodating the liquid crystal cell 110. However, as shown in FIG. 12, the lower glass substrate of the liquid crystal cell 110 is located at two positions, namely, the front part 130b and the inner part 130c of the frame 130. A structure in which 112 and the double-sided adhesive tape 131 adhere and fix the adhesive tape is used.

The above-described liquid crystal display device 100 has a structure in which the liquid crystal cell 110 and the frame body 130 are bonded and fixed. However, as a structure without bonding, the frame body 1 is used.
The liquid crystal cell 1 is formed by forming hooks at several places on the outer periphery of 30.
There is also seen a structure in which the glass substrate 10 is hooked and fixed.

Further, the liquid crystal display device 100 includes an LED
In order to prevent the light emitted by 121 from leaking to the outside, the light shielding plate 132 covers the upper portion of the LED 121.

A liquid crystal display device 100 having such a structure
In this case, the light emitted from the LED 121 is guided by the light guide plate 122.
The light emitting surface 12 of the LED 121 in order to be effectively taken in
The center of 1a is designed to be substantially in the center of the thickness of the light guide plate 122. Therefore, for this reason, the thickness of the frame 130 below the light guide plate 122 is increased, or alternatively, the light guide plate 12 is increased.
The light emitting surface 121 of the LED 121 is formed by forming 2 thickly.
The height of a is adjusted to the center of the light guide plate 122.

[0012]

In the conventional liquid crystal display device 100, the thickness of the entire liquid crystal display device 100 is greatly affected by the chip size of the mounted LED 121. FIG. 14 is an explanatory diagram for explaining the influence of the thickness depending on the chip size of the LED 121. From this figure, L
The chip size of the ED 121 is greatly affected by the height dimension (H) to the light emitting surface 121a. This light emitting surface 121
When the height H to a is larger than half the thickness of the light guide plate 122, in order to bring the position (H) of the LED light emitting surface 121a to the position (t / 2) of the center thickness of the light guide plate,
It is necessary to provide the step n on the frame 130 and lower the mounting position of the flexible board 141 at the branch where the LED 121 is mounted. Therefore, the thickness of the frame body 130 must be set thicker by the amount corresponding to the step difference n, and the liquid crystal display device 10
There was a problem that the overall thickness of 0 became thicker by that amount, and it was difficult to reduce the thickness.

Further, since the branch flexible board 141 is fixed by a fitting and fixing method in which the pin and the hole are slightly loose, the LED 121 mounted on the branch flexible board 141 is misaligned. And light guide plate 1
There is also a problem in that there is a large variation in luminance due to a change in the position interval with 22.

Therefore, an object of the present invention is to reduce the thickness of the entire liquid crystal display device in a liquid crystal display device having a side surface type backlight structure in which a backlight light source such as an LED is arranged on the side surface of a light guide plate. The present invention is intended to provide a liquid crystal display device capable of efficiently guiding light from a backlight light source into a light guide plate.

[0015]

In order to achieve the above object, the invention according to claim 1 of the present invention provides a liquid crystal display device comprising a light guide plate and a backlight source on the lower surface side of a liquid crystal cell. The light guide plate has an end portion protruding from the end face of the liquid crystal cell, and has a cutout portion or a hole portion at a substantially central portion of the end portion, and the backlight light source is mounted on a flexible substrate to form the light guide plate. Of the flexible substrate on which the backlight light source is mounted is disposed on the upper surface of the end portion of the light guide plate.
The light guide plate is characterized in that the lower surface and the side surface thereof are integrally provided with a reflection sheet via an adhesive.

In the invention according to claim 2 of the present invention, a recess is provided in the upper surface of the end portion of the light guide plate, and the backlight light source is mounted via an adhesive disposed in the recess. The flexible substrate is fixed to the light guide plate.

The invention according to claim 3 of the present invention is characterized in that a light-shielding sheet is provided on the flexible substrate disposed on the upper surface of the end portion of the light guide plate.

The invention according to claim 4 of the present invention is characterized in that the light shielding sheet is fixed to the upper surfaces of the end portions of the flexible substrate and the light guide plate with an adhesive.

Further, the invention according to claim 5 of the present invention is characterized in that the backlight light source arranged in the notch or hole of the light guide plate is fixed to the reflection sheet with an adhesive. It is what

The invention according to claim 6 of the present invention is characterized in that the light guide plate is fixed to a glass substrate of the liquid crystal cell via an adhesive.

The invention according to claim 7 of the present invention is characterized in that the thickness of the end portion of the light guide plate is adjusted according to the height dimension of the backlight light source.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 to 6 show the first embodiment of the present invention.
9 is a view showing a liquid crystal display device including the backlight according to the embodiment. 1 is a front view of the liquid crystal display device, FIG. 2 is a sectional view taken along line XX in FIG. 1, and FIG. 3 is YY in FIG.
FIG. 4 is a sectional view, FIG. 4 is an exploded perspective view of the liquid crystal display device, and FIG.
2 is a cross-sectional view of an essential part of the mounting portion of the LED 21 and the flexible substrate 41 of the branch in FIG. 6, and FIG. 6 is an explanatory view for explaining the bonding state of the flexible substrate 41 of the branch in FIG.

As shown in FIGS. 1 to 4, the liquid crystal display device 1 of this embodiment comprises a liquid crystal cell 10 and a backlight section 20 provided on the lower surface thereof. Since the liquid crystal cell 10 here has the same structure as the liquid crystal cell described in the related art, the description thereof is omitted here. A flexible substrate 40 is mounted on the upper glass substrate 11 that constitutes the liquid crystal cell 10, as described in the conventional technique. The liquid crystal cell 1 is mounted on the flexible substrate 40.
An IC 40a for controlling and driving 0 and other electronic components 40b are mounted, and a flexible substrate 41 having branched branches is formed.

The backlight unit 20 is mounted on the light guide plate 22 and the branched flexible substrate 41, and the LED 21 is disposed in the cutout 22d of the light guide plate 22.
A reflection sheet 23 integrally formed on the lower surface and side surfaces of the light guide plate 22, a light shielding sheet 32 provided on the LED 21 and the like. The backlight unit 20 is integrally provided on the lower surface of the liquid crystal cell 10 by being adhesively fixed to the lower glass substrate 12 with an adhesive 31c provided on the upper end portion of the light guide plate 22. A light diffusion plate 24 is provided between the backlight unit 20 and the liquid crystal cell 10.
Are installed narrowly so that the illumination brightness is uniform.

As shown in FIGS. 2 and 4, the light guide plate 22 has an end portion 22c protruding from the end face 10a of the liquid crystal cell 10 (which also corresponds to the end faces of the upper and lower glass substrates 11 and 12). is doing. Then, a cutout portion 22d is formed substantially in the center of the end portion 22c. Further, as described above, the light guide plate 22 has the reflection sheet 23 integrally formed on its lower surface and four side surfaces with an adhesive.

An LED 21 which is a light source is disposed and housed in the cutout portion 22d of the light guide plate 22. The cutout portion 22d is provided to accommodate and store the LED 21, but the cutout portion 22d is not limited to the cutout portion and may be a hole portion capable of storing the LED 21. The LED 21 is mounted on the tip lower surface 41a side of the branched flexible board 41, and by mounting the branched flexible board 41 on the upper surface 22e of the end 22c of the light guide plate 22, the LED 21 is cut out 22d. It can be installed and stored in the.

The LED 21 disposed and housed in the notch 22d
Has its light emitting surface 21a facing the light incident side surface 22a of the light guide plate 22 at the cutout portion 22d, and the light emitted from the LED 21 is guided deeply through the light incident side surface 22a of the light guide plate 22. It has become so.

Further, referring to FIGS. 5 and 6, the flexible substrate 41 of the branch attached to the upper surface 22e of the end portion 22c of the light guide plate 22 is attached to the light shielding sheet 32 provided on the upper portion thereof via the adhesive 31a. Adhesively fixed. As can be seen from FIG. 6, the light shielding sheet 32 is also directly adhered to the upper surface 22e of the end portion 22c of the light guide plate 22 at both side portions and the tip portion which are separated from the branch flexible substrate 41 area. With this adhesive structure, the flexible substrate 41 of the branch is completely fixed, and the LED 21 is also fixed. A double-sided adhesive tape or the like is used as the adhesive 31a here.

The light shielding sheet 32 is used to prevent the light of the LED 21 from leaking out from the side of the liquid crystal cell 10. The upper surface side is black-printed and the lower surface side is Ag. A sheet material formed of a reflective film such as a vapor deposition film is preferably used.

Furthermore, as shown in FIG. 5, the notch 22
The LED 21 housed in the d portion can be adhesively fixed to the reflection sheet 23 integrally provided on the lower surface of the light guide plate 22 with the adhesive 31b. Under such a bonded structure, the LEDs 21 are completely fixed on the upper and lower surfaces.

The reflection sheet 23 is provided to reflect the light leaked from the lower surface and side surfaces of the light guide plate 22 back into the light guide plate 22, and is preferably made of a material having a high reflectance and as thin as possible. For example, an aluminum foil sheet, a film sheet in which a white pigment is dispersed, a film sheet coated with white paint, an aluminum metal film formed on the film sheet, or the like. Alternatively, the white paint may be directly applied to the light guide plate 22.

With the above structure, the LED 2
The emitted light of 1 is guided deep into the light guide plate 22, and is radiated from the upper surface 22b of the light guide plate 22 by the action of the reflection sheet 23 to illuminate the display of the liquid crystal cell 10 brightly.
Since the frame used in the past is not used at all, the frame can be made thinner accordingly.

Next, what is shown in FIGS. 7 and 8 is the second embodiment of the present invention.
2 shows a liquid crystal display device according to the embodiment. FIG. 7 is a cross-sectional view of a main part of the liquid crystal display device 5, and FIG. 8 is a cross-sectional view showing a fixed state of the flexible substrate 41 of the branch in FIG.

The second embodiment differs from the first embodiment described above in that, as shown in FIG. 7, a step portion 52g is formed at the end portion 52c of the light guide plate 52 to increase the thickness. It has become. Further, as shown in FIG. 8, the positioning and fixing structure of the branch flexible board 41 are provided on the branch flexible board 41 and two projecting pins 52j provided on the upper surface 52e of the end 52c of the light guide plate 52. Two
LED51 by engaging the hole 41b of the location
And the concave portion 5 formed in the light guide plate 52.
In the portion 2i, the flexible substrate 41 and the light guide plate 52 for branching are bonded and fixed via an adhesive 31d such as a double-sided adhesive tape. The light-shielding seal 32
Since the fixing method is the same as that of the first embodiment, detailed description thereof will be omitted here.

Now, in the light guide plate 52 in this embodiment, the step portion 52g is formed toward the liquid crystal cell 10, and the step portion 52g is formed by that amount.
The end portion 52c is formed thick. When the height H of the light emitting surface 51a of the LED 51 is large, the thickness of the end portion 52c is increased, and the branch flexible substrate 41 on which the LED 51 is mounted is mounted.
By increasing the mounting position of the light emitting surface 51a, the position of the light emitting surface 51a is brought to the center of the thickness of the light guide plate 52.

In the above structure, the thickness of the end portion of the light guide plate is adjusted according to the LED chip size, that is, the height (H) of the light emitting surface of the LED, and the adjustment is made on the liquid crystal cell side. Since it is moving toward the end, there is no need to change the thickness of the liquid crystal display device itself. Therefore, the light of the LED can be guided to the light guide plate very efficiently without changing the thickness of the entire liquid crystal display device, and bright illumination can be obtained.

Further, in this embodiment, since the protruding pin formed on the light guide plate and the hole formed on the branch flexible substrate are engaged and positioned, the LED is accurately positioned at a predetermined position of the notch of the light guide plate. Can be installed and stored.
Then, it can be fixed at that position.

[0038]

As described above in detail, according to the liquid crystal display device of the present invention, a notch or a hole is formed in the end portion of the light guide plate projecting from the end surface of the liquid crystal cell to form the LED of the light source. Pull the mounted flexible board to the upper surface of the end,
Since the LED is arranged and housed in the cutouts and holes, even if the LED chip size, that is, the height of the light emitting surface of the LED is changed, the thickness of only the end portion of the light guide plate is set to the liquid crystal. Since the adjustment can be performed by changing it toward the cell side, the thickness of the liquid crystal display device can be kept constant without being affected by the LED chip size.

Further, according to the liquid crystal display device of the present invention, since the conventional frame is not used, the reflection sheet or the light shielding plate used conventionally is replaced with a thin reflection sheet or light shielding. Since the sheet is used, the thinning effect can be obtained.

Further, since the branch flexible substrate on which the LED is mounted is firmly adhered and fixed to the light guide plate or the light shielding plate via an adhesive, or LE
Since D has a structure in which it is adhered and fixed to the reflection sheet, there is no concern that the LED will move, and it is possible to constantly obtain light emitted in a fixed direction.

[Brief description of drawings]

FIG. 1 is a front view of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX in FIG.

FIG. 3 is a sectional view taken along line YY in FIG.

FIG. 4 is an exploded perspective view of the liquid crystal display device according to the first embodiment of the present invention.

5 is a cross-sectional view of an essential part of a mounting portion of a flexible substrate of the LED and the branch in FIG.

FIG. 6 is an explanatory diagram illustrating a bonded state of the branch flexible substrate in FIG.

FIG. 7 is a cross-sectional view of essential parts of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 8 is a cross-sectional view showing a fixed state of the flexible substrate of the branch in FIG.

FIG. 9 is a front view of a conventional liquid crystal display device.

10 is a cross-sectional view taken along line XX in FIG.

11 is a sectional view taken along line YY in FIG.

FIG. 12 is an exploded perspective view of a conventional liquid crystal display device.

13 is a diagram showing a positioning and fixing state of the flexible substrate and the frame body of the branch in FIG.

FIG. 14 is an explanatory diagram illustrating the influence of the thickness of the LED chip size.

[Explanation of symbols]

1, 5 liquid crystal display device 10 Liquid crystal cell 10a End face of liquid crystal cell 11 Upper glass substrate 12 Lower glass substrate 15 Upper polarizing plate 16 Lower polarizing plate 20, 50 Backlight part 21, 51 LED 21a, 51a light emitting surface 22, 52 Light guide plate 22a Light incident side surface 22b, upper surface 22c, 52c end 22d notch 22e, 52e upper surface 23 Reflective sheet 24 Light diffuser 31a adhesive 31b adhesive 31c adhesive 31d adhesive 32 Light-shielding sheet 40 flexible board 40a IC 40b electronic parts 41 branch flexible board

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Claims (7)

[Claims] 1. A liquid crystal display device comprising a light guide plate and a backlight source on the lower surface side of a liquid crystal cell, wherein the light guide plate has an end portion protruding from an end surface of the liquid crystal cell, and the end portion is substantially centered. Has a notch or hole in the part,
The backlight light source is mounted on a flexible substrate and arranged in a cutout portion or a hole portion of the light guide plate, and the flexible substrate on which the backlight light source is mounted is arranged on an upper surface of an end portion of the light guide plate. The liquid crystal display device, wherein the light guide plate is integrally provided with a reflection sheet on a lower surface and a side surface of the light guide plate via an adhesive. 2. A concave portion is provided on an upper surface of an end portion of the light guide plate, and a flexible substrate on which the backlight light source is mounted is fixed to the light guide plate through an adhesive provided in the concave portion. The liquid crystal display device according to claim 1. 3. The liquid crystal display device according to claim 1, wherein a light shielding sheet is provided on the flexible substrate disposed on the upper surface of the end portion of the light guide plate. 4. The liquid crystal display device according to claim 3, wherein the light shielding sheet is fixed to the upper surfaces of the end portions of the flexible substrate and the light guide plate with an adhesive. 5. The backlight source arranged in the cutout portion or the hole portion of the light guide plate is fixed to the reflection sheet with an adhesive agent, according to any one of claims 1 to 4. The described liquid crystal display device. 6. The liquid crystal display device according to claim 1, wherein the light guide plate is fixed to a glass substrate of the liquid crystal cell via an adhesive. 7. The liquid crystal display device according to claim 1, wherein an end portion of the light guide plate has a thickness adjusted according to a height dimension of the backlight light source.