JP2003195302A - Backlight for liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight for a liquid crystal display device with which light with a plurality of colors emitted from a light source is certainly and easily converted to white light. <P>SOLUTION: A forced light whitening means 6 to convert the light with a plurality of colors emitted from the light source 5 to the white light by color mixing is provided. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight of a liquid crystal display device, and more particularly to a multicolor LED chip which emits light of plural colors by LED elements of plural colors and emits light from the light source. The present invention relates to a backlight of a sidelight type liquid crystal display device in which light of a plurality of colors enters a light guide.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal display device using a liquid crystal display panel in which liquid crystal is sealed between two transparent substrates is known as a kind of display device for displaying various images such as characters and figures. Has been. In such a liquid crystal display device,
There is known a configuration in which a display unit of a liquid crystal display panel is brightly displayed by using external illumination light from a backlight called back illumination. There are various types of backlights for liquid crystal display devices, such as direct type and sidelight type (edge light type). A sidelight type backlight is widely used because it is advantageous in reducing the thickness and taking measures against heat, and can provide uniform brightness. Further, in a backlight used in a small color display liquid crystal display device such as a folded mobile phone, a multicolor LED in which light of a plurality of colors is emitted by a plurality of LED elements is used for further miniaturization. The chip is used as a light source.

According to the backlight of the liquid crystal display device having such a structure, the light of a plurality of colors emitted from the light source is incident on the incident surface provided on the side surface of the light guide body, and inside the light guide body. The light is multiply reflected to form a surface light source having the upper surface of the light guide as a light emitting surface, and the light from the light emitting surface can be emitted as flat light toward the back surface of the liquid crystal display panel.

[0004]

However, in the above-mentioned conventional backlight, when it is used in a small liquid crystal display device, the multicolor LED chip is arranged in the immediate vicinity of the incident surface of the light guide. There is. As a result, multicolor LE
There is a problem in that the distance between the D chip and the light guide becomes short, and the lights of a plurality of colors emitted from the light source cannot be sufficiently mixed to enter the light guide as white light.

The present invention has been made in view of this point. Even when the distance between the multicolor LED chip and the light guide body is short, the light of a plurality of colors emitted from the light source can be reliably and easily emitted. Another object of the present invention is to provide a backlight of a liquid crystal display device capable of producing white light.

[0006]

In order to achieve the above-mentioned object, the backlight of the liquid crystal display device of the present invention according to claim 1 is characterized in that a plurality of LED elements emit light of a plurality of colors. A backlight of a liquid crystal display device in which a multicolor LED chip is used as a light source, and light of a plurality of colors emitted from the light source is incident on an incident surface provided on a side surface of a light guide. In the above, there is provided a forced light whitening means for mixing light of a plurality of colors emitted from the light source into white light. Further, by adopting such a configuration, it is possible to forcibly whiten the light of a plurality of colors from the light source by the forced light whitening unit and make it enter the light guide. Therefore, even when the distance between the multicolor LED chip and the light guide is short, the light of a plurality of colors emitted from the light source can be reliably and easily turned into white light.

Further, the backlight of the liquid crystal display device of the present invention according to claim 2 is characterized in that, in claim 1, the forced light whitening means is at least a multicolor LED chip on the incident surface of the light guide. The point is that the light diffusing section is formed of fine irregularities provided in the facing portion. Further, by adopting such a configuration, the light diffusing unit acts to diffusely reflect the light of a plurality of colors emitted from the light source and mix the light of a plurality of colors, so that the light is incident on the light guide. The light can be whitened more easily and reliably.

Further, the backlight of the liquid crystal display device according to the third aspect of the present invention is characterized in that, in the first aspect, the forced light whitening means is a light having fine irregularities provided on one surface of the transparent sheet. This is a diffusing section, and this light diffusing section is disposed at a portion of the incident surface of the light guide body facing at least the multicolor LED chip so as to face the light source. Further, by adopting such a configuration, the light diffusing unit acts to diffusely reflect the light of a plurality of colors emitted from the light source and mix the light of a plurality of colors, so that the light is incident on the light guide. The light can be whitened more easily and reliably.

Further, the backlight of the liquid crystal display device of the present invention according to claim 4 is characterized in that, in any one of claims 1 to 3, the multicolor LED chip of the light source emits red light. It is formed by a red LED element, a green LED element that emits green light, and a blue LED element that emits blue light, and each LED element is arranged so as to form a triangle. By adopting such a configuration, the three LED elements that emit light of the three primary colors of red, green, and blue are arranged so that the distances between them are the shortest, so that the multicolor It is possible to easily optimize the formation of white light by the LED chip.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the embodiments shown in the drawings.

1 to 3 show a first embodiment of a backlight of a liquid crystal display device according to the present invention.

This embodiment exemplifies a case where the backlight of the liquid crystal display device according to the present invention is used for a small-sized color display liquid crystal display device such as a folded mobile phone, and the size of the backlight is 10 mm in length. , Width 20mm, thickness 1
mm, size of multicolor LED chip is 1mm in length, 3 in width
mm, and the thickness (including the electrode portion) is about 1.4 mm.

As shown in FIGS. 1 to 3, the backlight 1 of the liquid crystal display device of this embodiment has a flat light guide 2. The light guide 2 is fixed to the bottom of a case body (not shown) whose upper portion is formed in a substantially rectangular plane shape with an opening, and an optical film 3 is laminated on the upper surface of the light guide 2. This optical film 3 is, as shown in FIG.
The diffusion sheet 3a and the two prism sheets 3b are laminated in this order, and the diffusion sheet 3a is arranged so as to face the upper surface of the light guide 2. Further, on the inner surface of the case body, a reflection sheet 4 for reusing light leaked from the light guide body 2 is arranged. A portion inside the upper surface of the optical film 3 shown by an imaginary line in FIG. 1 is a portion facing a display area of a liquid crystal display panel (not shown).

The right side surface of the light guide 2 in FIG. 1 is an incident surface 2a, and a rectangular parallelepiped multicolor LED is formed on the right side of the central portion of the incident surface 2a.
The chips 5 are arranged close to each other. In addition, the incident surface 2a
A light diffusing portion 6 (exaggeratedly shown in the drawing) formed of fine irregularities as a forced light whitening means is formed on the entire surface facing the multicolor LED chip 5. That is, the light diffusion portion 6 is directly provided on the incident surface 2 a of the light guide 2. The light diffusing section 6 is provided on the light incident surface 2 a of the light guide 2.
On the other hand, various types of processing such as satin processing, grain processing, laser processing, patterning processing using photolithography, and the like can be performed easily and reliably. It is important for the light diffusing section 6 to ensure the transparency of the surface of the light diffusing section 6 in order to allow light to enter the light guide 2. Further, it is preferable that the light diffusing section 6 is provided at a portion of the incident surface 2a of the light guide 2 facing at least the multicolor LED chip 5 so as to face the multicolor chip 5 serving as a light source.

As shown in FIG. 3, the multicolor LED chip 5 has three LED elements 7. Of these three LED elements 7, one shown on the upper side of FIG. 3 is a red LED element 7R that emits red light. One shown in the lower left of FIG. 3 is a green LED element 7G that emits green light. Further, one shown on the lower right side of FIG. 3 is a blue LED element 7B that emits blue light. Each of these LED elements 7 is arranged so as to form a triangle.

That is, the multicolor LED chip 5 as a light source has a red LED element 7R for emitting red light and a green LED element 7G for emitting green light in the sense that white light can be easily formed. It is preferably formed by a blue LED element 7B that emits blue light.

The multicolor LED chip 5 is shown in FIG.
As shown in FIG.
May be arranged in a line in the longitudinal direction of the incident surface 2a). According to the multicolor LED chip 5A having such a configuration, the two LED elements 7 can be arranged such that the distance between them is the shortest. In this case, 2
As a color of light of one LED element 7, a combination of blue and yellow can be exemplified.

The multicolor LED chip 5 is shown in FIG.
As shown in FIG.
May be aligned in the horizontal direction along the longitudinal direction of the incident surface 2a. According to the multicolor LED chip 5B having such a configuration, it is possible to arrange the three LED elements 7 so that the distance between them is the shortest without increasing the size in the vertical direction.

Further, as the multicolor LED chip 5, as shown in FIG. 6, three LED elements 7 are arranged in the vertical direction (vertical direction orthogonal to the longitudinal direction of the incident surface 2a of the light guide 2).
It may be arranged to be aligned. According to the multicolor LED chip 5C having such a configuration, the three LED elements 7 can be arranged such that the distance between them is the shortest without increasing the size in the lateral direction.

Furthermore, as shown in FIG. 7, the multicolor LED chip 5 may have a configuration in which five LED elements 7 are arranged in a polygon (pentagon). According to the multicolor LED chip 5D having such a configuration, five LEDs are provided.
The elements 7 can be arranged such that the distance between them is the shortest. In this case, as the light colors of the five LED elements 7, a combination of red, green, blue, yellow and orange can be exemplified.

That is, when the multicolor LED chip 5 including a plurality of LED elements 7 is used, the distance between the respective LED elements 7 is minimized in consideration of the shape of the multicolor LED chip 5. It is essential to place it in. For example, when using the multicolor LED chip 5 composed of two LED elements 7, the two LED elements 7 are aligned so as to be closest to each other in the vertical or horizontal direction, and four or more LEs are arranged.
When the multicolor LED chip 5 including the D element 7 is used, each LED element 7 may be arranged in a polygonal shape.

The other structure is similar to that of the conventionally known backlight, and its detailed description is omitted.

Next, the operation of this embodiment having the above-mentioned structure will be described.

According to the backlight 1 of the liquid crystal display device of the present embodiment, the forced light whitening means for mixing the lights of a plurality of colors emitted from the multicolor LED chip 5 serving as a light source into white light. Since the light diffusing unit 6 is provided, the light diffusing unit 6 can forcibly whiten the lights of a plurality of colors from the multicolor LED chip 5 and allow the lights to enter the light guide 2. Therefore, even when the distance between the multicolor LED chip 5 as a light source (point light source) and the light guide 2 is short, the multicolor L
The light of a plurality of colors emitted from the ED chip 5 can be reliably and easily turned into white light. As a result, the distance between the incident surface 2a of the light guide 2 and the multicolor LED chip 5 can be shortened, and the miniaturization can be easily achieved.

Further, according to the backlight 1 of the liquid crystal display device of the present embodiment, the forced light whitening means is provided in at least a portion of the incident surface 2a of the light guide 2 facing the multicolor LED chip 5. Since the light diffusing section 6 is composed of fine irregularities, the light diffusing section 6 diffuses and reflects light of a plurality of colors emitted from the light source, and mixes the light of a plurality of colors. The light incident on the body 2 can be whitened more easily and reliably.

According to the backlight 1 of the liquid crystal display device of the present embodiment, the multicolor LED chip 5 serving as a light source includes the red LED element 7R for emitting red light and the green LED element 7G for emitting green light. , Blue LED emitting blue light
The LED elements 7R, 7G, and 7B are formed so as to form a triangle, and the three LED elements 7 that emit light of the three primary colors of red, green, and blue are respectively formed. Are arranged such that the distance between them is the shortest, and the optimization of the formation of white light by the multicolor LED chip 5 can be easily achieved.

FIG. 8 shows a second embodiment of the backlight of the liquid crystal display device according to the present invention. In the backlight 1A of this embodiment, the incident surface 2a of the light guide 2 is
The portion facing the multicolor LED chip 5 is curved concavely to form the curved portion 2b, and the light diffusion portion 6 is formed only on the curved portion 2b. Other configurations are the same as those of the backlight 1 of the first embodiment described above.

According to the backlight 1A having such a structure, the same effects as those of the backlight 1 of the first embodiment described above can be obtained, and the incident surface 2 of the light guide 2 is obtained.
Since the light incident on a can be received by the concave surface of the curved portion 2b, the light utilization efficiency is improved.

9 and 10 show a third embodiment of the backlight of the liquid crystal display device according to the present invention.
In the backlight 1B of this embodiment, the multicolor LE is used.
A lens 8 is attached to the light emitting surface of the D chip 5. Other configurations are the same as those of the backlight 1 of the first embodiment described above.

According to the backlight 1B having such a configuration, the same effects as those of the backlight 1 of the above-described first embodiment can be obtained, and the light emitted from the multicolor LED chip 5 by the lens 8 is emitted. Since the light can be spread and applied to the light diffusing portion 2b formed on the incident surface 2a of the light guide 2, the light utilization efficiency is further improved.

FIG. 11 shows a fourth embodiment of the backlight of the liquid crystal display device according to the present invention. In the backlight 1C of this embodiment, the multicolor LED chip 5 is used.
The lens 8 is attached to the light emitting surface facing the light guide 2, and the portion of the incident surface 2a of the light guide 2 facing the multicolor LED chip 5 is concavely curved to form the curved portion 2b.
The light diffusing portion 6 is formed only on the curved portion 2b. Other configurations are the same as those of the backlight 1 of the first embodiment described above.

According to the backlight 1C having such a structure, the same effects as those of the backlight 1 of the first embodiment described above can be obtained, and the light emitted from the multicolor LED chip 5 by the lens 8 is emitted. Since the light can be spread out and applied to the light guide 2 and the light incident on the light guide 2 entrance surface 2a can be received by the concave surface of the curved portion 2b, the light utilization efficiency is further improved.

FIG. 12 shows a fifth embodiment of the backlight of the liquid crystal display device according to the present invention. In the backlight 1D of this embodiment, the incident surface 2 of the light guide 2 is
A transparent sheet 9 (the transparent sheet 9 is exaggerated in FIG. 12) having a light diffusing portion 6 having fine irregularities is fixed to a. The light diffusion portion 6 is provided on the entire surface of the transparent sheet 9 that faces the multicolor LED chip 5. That is, the light diffusion portion 6 is indirectly provided on the incident surface 2 a of the light guide 2.

The light diffusing portion 6 can be easily and surely formed by pressing a transfer roller having a fine uneven pattern on its one surface when the transparent sheet 9 is formed.

It is important for the light diffusing section 6 to ensure the transparency of the surface of the light diffusing section 6 in order to allow light to enter the inside of the light guide 2.

Further, the light diffusing section 6 is provided on the incident surface 2 of the light guide 2.
It is preferable to provide the light diffusing portion 6 in the multicolor L of the transparent sheet 9 so as to face the multicolor chip 5 serving as a light source at least in a part of the a facing the multicolor LED chip 5.
A structure provided only in a portion facing the ED chip 5, a transparent sheet 9 having the same length as a portion facing the multicolor LED chip 5, and a multicolor LED chip 5 on the incident surface 2a of the light guide 2. The transparent sheet 9 is formed by curving the portion facing
One type or a plurality of types may be combined, such as a configuration for fixing the above, a configuration for mounting the lens 8 on the light emitting surface of the multicolor LED chip 5, and the like.

The other structure is the same as that of the backlight 1 of the first embodiment described above.

According to the backlight 1D having such a structure, the same effects as those of the backlight 1 of the first embodiment described above can be obtained, and the transparent sheet 9 is provided when the light diffusing portion 6 is damaged. Can be easily replaced.

The present invention is not limited to the above-mentioned embodiments, but various modifications can be made as necessary.

[0040]

As described above, according to the backlight of the liquid crystal display device of the present invention, it is extremely excellent in that light of a plurality of colors from the light source can be forcibly whitened and made incident on the light guide. Produce the effect.

[Brief description of drawings]

FIG. 1 is an enlarged front view showing a main part of a first embodiment of a backlight of a liquid crystal display device according to the present invention.

FIG. 2 is a plan view of FIG.

FIG. 3 is an enlarged front view of the multicolor LED chip of FIG. 1 viewed from a direction facing a light source.

FIG. 4 is a view similar to FIG. 3 showing a main part of another example of the arrangement of the LED elements of the multicolor LED chip of FIG.

5 is a view similar to FIG. 3 showing a main part of still another example of the arrangement of LED elements of the multicolor LED chip of FIG. 1.

FIG. 6 is a view similar to FIG. 3, showing a main part of still another example of the arrangement of the LED elements of the multicolor LED chip of FIG. 1.

7 is a view similar to FIG. 3 showing a main part of still another example of the arrangement of LED elements of the multicolor LED chip of FIG. 1.

FIG. 8 is a view similar to FIG. 1 showing a main part of a second embodiment of a backlight of a liquid crystal display device according to the present invention.

FIG. 9 is a view similar to FIG. 1, showing a main part of a third embodiment of a backlight of a liquid crystal display device according to the present invention.

FIG. 10 is a plan view of FIG.

FIG. 11 is a view similar to FIG. 1 showing essential parts of a fourth embodiment of a backlight of a liquid crystal display device according to the present invention.

FIG. 12 is a view similar to FIG. 1 showing essential parts of a fifth embodiment of a backlight of a liquid crystal display device according to the present invention.

[Explanation of symbols]

1, 1A, 1B, 1C, 1D backlight 2 Light guide 2a Incident surface 2b curved part 3 Optical film 4 Reflective sheet 5, 5A, 5B, 5C, 5D Multicolor LED chips 6 Light diffuser (as means for forced light whitening) 7 LED element 7R Red LED element 7G green LED element 7B blue LED element 8 lenses 9 Transparent sheet

Claims (4)

[Claims] 1. A light source is a multicolor LED chip that emits light of multiple colors by a plurality of LED elements, and light of multiple colors emitted from the light source is provided on a side surface of a light guide. In a backlight of a liquid crystal display device which is formed so as to be able to enter an incident surface, a forced light whitening means for making white light the light of a plurality of colors emitted from the light source is provided. Liquid crystal display backlight. 2. The forcible light whitening means is a light diffusing portion formed of fine irregularities provided at least at a portion of the incident surface of the light guide facing the multicolor LED chip. The backlight of the liquid crystal display device according to claim 1. 3. The forced light whitening means is a light diffusing section provided on one surface of a transparent sheet and having fine irregularities, and the light diffusing section is at least the incident surface of the light guide body. The backlight of the liquid crystal display device according to claim 1, wherein the backlight is arranged at a portion facing the multicolor LED chip so as to face the light source. 4. The multicolor LED chip of the light source comprises a red LED element that emits red light and a green LED that emits green light.
4. An ED element and a blue LED element that emits blue light, and each LED element is arranged so as to form a triangle. 4. The backlight of the liquid crystal display device described in 1.