JPH1064321A - Light guide device, liquid crystal display device, and electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce uneven brightness producing on an outgoing light surface of a light guide plate and enhance alignment accuracy in the thickness direction of the light guide plate in a light guide device in which a linear light source is arranged on the side surface of the light guide plate. SOLUTION: A linear light source 42A is formed by sealing an LED chip 22 mounted in a line on a circuit board with mold resin 43 (an optical path conversion element). The mold resin 43 is formed in a triangular prism shape, and has a uniform cross section in the arranging direction of the LED chip 22. An incident light from the linear light source 42A to a light guide plate as viewed from the outgoing light surface is not converged in the arranging direction of the LED chip and uneven brightness is difficult to be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a light guide device and a liquid crystal display, and more particularly to an electronic device using the liquid crystal display.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been characterized by being lightweight and thin, and have been used for personal computers such as laptops and books, and displays for word processors, electronic notebooks, mobile phones, and liquid crystal televisions. , Other portable terminal devices, displays for video cameras and the like. Further, it is also used for a display unit of a measuring device such as a timer counter, an overhead display of virtual reality, a liquid crystal projector, and the like.

(Direct Type Surface Light Source Devices) These liquid crystal display devices include a type in which a direct type surface light source device is disposed on the back of a liquid crystal display panel (LCD panel) and a type in which an edge light type surface light source device is disposed. There is. 1 (a) and 1 (b) show a front view and a sectional view of the former direct-type surface light source device 1 among them. The direct-type surface light source device 1 has a structure in which a reflector 5 is disposed behind a linear light source 4 such as a cold cathode tube (fluorescent tube) provided on the back of the diffusion plates 2 and 3. The light emitted from the surface light source device 1 is diffused by the diffusion plates 2 and 3 so that the diffused light is uniformly emitted from the emission surface of the surface light source device 1.

A liquid crystal display device using such a direct-type surface light source device has a feature that a high emission luminance can be obtained because a plurality of linear light sources can be arranged on the back surface of a diffusion plate. . However, on the other hand, in order to obtain uniform brightness over the entire surface light source device, the distance between the light source and the diffusion plate needs to be increased to some extent, so that the surface light source device becomes thick, and as a result, the liquid crystal display device has There is a problem that the thinning is hindered.

(Edge light type surface light source device) On the other hand, in the edge light type surface light source device, since the linear light source is located on the side surface of the light guide plate, the light source can be made thinner. As the demand for thinner liquid crystal display devices has further increased, those using an edge light type surface light source device which can be made relatively thin have become mainstream.

FIG. 2 is an exploded perspective view of such an edge light type surface light source device 6 with a part cut away. The edge light type surface light source device 6 includes, as optical elements, a linear light source 7, a reflector 8, a light guide plate 9, a reflection plate 10, a diffusion plate 11, and a pair of condenser lens plates 12, 13. The linear light source 7 and the reflector 8 are arranged on the incident side of the optically transparent light guide plate 9, and the light emitted from the linear light source 7 is directly
Alternatively, after being reflected by the reflector 8, the light enters the light guide plate 9 from the incident side surface. A side reflector 14 (FIG. 5) made of a metal rough surface or a dielectric rough surface is provided on a side surface other than the incident side surface of the light guide plate 9 with a gap therebetween. Here, a cold cathode tube (fluorescent tube) is used as the linear light source 7, and a linear single tube or an L-shaped tube is used in accordance with the display luminance required for the liquid crystal display device 6. Is done.

[0007] A diffusion layer 15 is formed on the lower surface of the light guide plate 9, and a reflection plate 10 is provided below the diffusion layer 15. The diffusion layer 15 is formed, for example, by dot printing of a light-diffusing paint or the like by screen printing, and as shown in FIG. 3A or 3B, the diffusion layer 15 is located on the side away from the linear light source 7. Area is gradually increasing. Alternatively, as shown in FIGS. 4A and 4B, the diffusion layer 15
The diffusion layer 15 may be wider as the distance from the linear light source 7 increases.
The light in the light guide plate 9 is totally reflected by the upper surface of the light guide plate 9, or is reflected by the reflector 10 on the lower surface of the light guide plate 9 and the upper surface of the light guide plate 9, or is directly incident on the diffusion layer 15 and diffused by Only the light that is diffused, transmitted or reflected at 15 and reflected by the diffusion layer 15 or the reflecting plate 10 and out of the total reflection condition is emitted from the upper surface of the light guide plate 9. In addition, since the area of the diffusion layer 15 is increased on the side far from the linear light source 7, light is emitted with uniform luminance throughout the light guide plate 9.

On the upper surface of the light guide plate 9, a diffusion plate 11 and a pair of condenser lens plates 12, 13 are superposed. The diffusion plate 11 is a sheet or film made of a synthetic resin whose surface is subjected to fine unevenness processing (matting, embossing, satin finishing). Light emitted from the upper surface of the light guide plate 9 is
1 is diffused. The condenser lens plates 12 and 13 have a structure in which prism portions having a triangular cross section are arranged in parallel, and the upper condenser lens plate 13 and the lower condenser lens plate 1 are arranged.
2 are arranged in directions rotated by 90 ° with respect to each other. Thus, the light diffused by the diffusion plate 11 is converged in two directions by the condenser lens plates 12 and 13 and is emitted as a light beam substantially perpendicular to the upper surface of the light guide plate 9.

(Light Guide Efficiency by Light Guide Plate) Here, the efficiency of guiding the light of the linear light source 7 to the exit surface (upper surface) by the light guide plate 9 will be described. First, the diffusion layer 1 is formed on the lower surface of the light guide plate 9.
Assuming that 5 does not exist, light confinement inside the light guide plate 9 will be considered. A light ray F1 shown in FIG. 5 indicates a light ray incident from the incident side surface 16 of the light guide plate 9 at an incident angle of 90 ° with respect to the normal line. That is, the refraction angle θ ₁ of the ray F1
Is a critical angle of total reflection in the light guide plate 9. Therefore, assuming that the refractive index in the air is n ₁ and the refractive index of the light guide plate 9 is n ₂ , the refraction angle θ ₁ is expressed by the following equation. θ ₁ = sin ⁻¹ (n ₁ / n ₂ ) Also, the incident angle θ ₂ to the lower surface of the light guide plate 9 is θ ₂ = 90 ° −θ ₁ . Here, assuming that the material of the light guide plate 9 is polycarbonate, since n ₂ = 1.59, the above equation and the value of the equation are θ ₁ = 38.97 ゜ θ ₂ = 51.03 ゜. Since the incident angle θ ₂ is larger than θ ₁ which is a critical angle of total reflection, if the diffusion layer 15 does not exist on the lower surface of the light guide plate 9, the light ray F 1 is totally reflected on the lower surface of the light guide plate 9.
Similarly, the light is totally reflected also on the upper surface of the light guide plate 9.

For another light beam, such as the light beam F2, entering the light guide plate 9 from the linear light source 7, the refraction angle θ ₃ is smaller than the refraction angle θ ₁ , so that the refraction angle θ ₃ the incident angle θ4 is larger than the incident angle theta _2. Therefore, the light beam F <b> 2 incident from the linear light source 7 to the inside of the light guide plate 9 is totally reflected by the upper surface and the lower surface of the light guide plate 9 unless the diffusion layer 15 is provided on the lower surface of the light guide plate 9.

Further, since the side reflectors 14 are provided on the side surfaces other than the incident side surface 16 of the light guide plate 9, almost all the light reflected by the side reflectors 14 re-enters the light guide plate 9. Even with this re-incidence, the angles of incidence of light on the upper and lower surfaces of the light guide plate 9 do not change, so that they are also totally reflected. Note that the side reflector 14 made of metal or dielectric is used.
There is almost no light loss due to

Next, considering the light source side, a cold cathode tube is used as the linear light source 7. A fluorescent layer is applied to the surface of the glass tube of the cold cathode tube, and the fluorescent layer has a function of completely diffusing external light. That is, the light incident on the linear light source 7 is reflected again from the linear light source 7 without any loss.

As described above, in the light guide plate 9 in which the diffusion layer 15 is not formed on the lower surface, light incident from the linear light source 7 into the light guide plate 9 can be confined inside the light guide plate 9 with very high efficiency. I understand. However, merely confining the light does not become a light source, and it is necessary to extract this light only from the emission surface 17 on the upper surface of the light guide plate 9. For this purpose, a diffusion layer 15 is formed on the lower surface of the light guide plate 9, and the light inside the light guide plate 9 that has entered the diffusion layer 15 is diffused, and light having an angle out of the total reflection condition is extracted to the outside. . This light is further diffused by the diffusion plate 11 on the upper surface of the light guide plate 9.

Accordingly, the light from the linear light source 7 is emitted with very little efficiency toward the display surface of the liquid crystal display device 6 with little loss. Further, the incident light from the display surface direction is similarly re-emitted to the display surface direction without any loss.

(LED surface light source device) Further, as compared with a cold cathode tube used as a light source, a light emitting diode (hereinafter, referred to as an LED) has advantages such as long life, low power consumption, and low cost. As the linear light source of the mold surface light source device, an LED array in which LEDs are linearly arranged may be used. Such an LED surface light source device is particularly used as a display device for a mobile phone or the like.

FIG. 6 shows an example of such an LED surface light source device 18, which is made of polycarbonate or polymethyl methacrylate having a diffusion layer 15 formed on the lower surface by printing or the like. A diffusion plate 11 and a reflection plate 10 are disposed on upper and lower surfaces of a light guide plate 9 made of a resin material,
A plurality of LEDs 19 are mounted on a circuit board 20 and a linear light source 21 arranged at regular intervals is formed on a light incident surface 1 of the light guide plate 9.
6 and are arranged.

The linear light source 21 of the LED surface light source device 18 has a method of mounting an LED element (bulk element) in which an LED chip is mounted as an LED 19 on a circuit board 20 and a method of mounting the LED chip as it is on the LED 19. There is a method of mounting on the circuit board 20. FIG. 7 (a)
(G) are diagrams illustrating a process of manufacturing the linear light source 21 by mounting the LED chip 22 as the LED element 23 with the lead on the circuit board 20. That is,
As shown in FIG. 7A, the leads 24 of the LED element 23
After aluminum or solder plating is applied to the lead frame 25 made of iron or copper alloy on which the a and 24b are formed, the LED chip 22 is die-bonded to the end surface of the lead 24a (FIG. 7 (b)). Wire bonding between the lead 22 and the lead 24b is performed by the Au wire 26 (FIG. 7C). Then, LED chip 2
2 and the tips of the leads 24a and 24b were sealed with a molding resin 27 such as an epoxy resin (FIG. 7D).
Then, by cutting the leads 24a and 24b, L
The ED element 23 is separated from the lead frame 25 (FIG. 7).
(E)). The leads 24a, 24b of the LED element 23 thus formed are inserted into through holes of the circuit board 20, and a plurality of LED elements 23 are mounted on the circuit board 20 in a line (FIG. 7 (f)). The extra leads 24a and 24b are cut by soldering to the circuit board 20, and the linear light source 21 is manufactured (FIG. 7 (g)).

However, such an LED element 23
In the linear light source 21 using
There is a problem that the mold resin shape of the ED element 23 is not suitable for the use of the edge light type linear light source 21.

On the other hand, FIGS. 8 (a) to 8 (f) [FIG.
(E) and (f) are side views of FIG.
In the method of manufacturing the linear light source 21 by directly mounting the ED chip 22 on the circuit board 20, the number of manufacturing steps can be reduced by half. That is, two wirings 29a and 29b having electrodes 28a and 28b at the ends are provided.
In FIG. 8A, a circuit board 20 on which pads 30 are formed at predetermined pitches is prepared (FIG. 8A).
The LED chip 22 is bonded on each of the pads 30 of FIG. 8 (FIG. 8B). Next, the other wiring 29b and LE
The D chip 22 is wire-bonded with an Au wire 31 (FIG. 8C), and the LED chip 22 and the Au wire 31 are resin-molded with a mold resin 32 (FIGS. 8D and 8E). (F)).

According to the linear light source 21 having such a structure,
Although the number of manufacturing steps is reduced, the shape of the molding resin surrounding each LED chip 22 is an edge-light type linear light source 21.
The fact that it is not suitable for the use of is still unchanged.

[0021]

SUMMARY OF THE INVENTION LED surface light source device 18
In this regard, the linear light sources 21 are regarded as the linear light sources 21 by arranging the LEDs 19, which are originally point light sources, in a linear manner. Further, as described above, the molding resin 2 that seals the LEDs 19 is used.
Since the shapes of the light guides 7 and 32 are not suitable for the edge light type linear light source 21, the occurrence of uneven brightness in the light guide plate 9 is problematic.

The reason why luminance unevenness is caused by the linear light source 21 using the LED 19 will be described with reference to FIGS. 9 to 11 in the case of an LED chip type LED 19 as shown in FIG. FIG. 9 is a perspective view showing the behavior of a light beam r emitted from one LED chip 22, and FIG. 10 shows the behavior of a light beam r emitted from the LED chip 22 and entering the light guide plate 9.
11 is an enlarged view of the light guide plate 9 viewed from the light exit surface 17 side, and FIG. LED chip 22
Since the light beam r emitted from the light receiving member is subjected to a convex lens action by the mold resin 32, as shown in FIG. (Thickness direction). Further, since the refractive index of the light guide plate 9 is larger than the refractive index in air, FIG.
As shown in FIG. 0, even when this light ray r enters the inside of the light guide plate 9 from the incident side surface 16, it is refracted by the incident side surface 16 and passes through the inside of the light guide plate 9 at a small angle with respect to the normal to the incident side surface 16. move on. Therefore, when viewed from the emission surface 17 side of the light guide plate 9,
As shown in FIGS. 10 and 11, the linear light source 2 of the light guide plate 9 is
At the end on the side close to 1, luminance unevenness consisting of a dark portion (dark portion) D and a bright portion (bright portion) B occurs over a considerably wide area. Such luminance unevenness is caused by LE
Since the quality of the D surface light source device 18 will be reduced,
It is desired to eliminate luminance unevenness.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and has as its object to provide a light guide device for guiding light from a light source to a light guide plate, the light guide device being provided on the exit surface side of the light guide plate. It is to reduce the generated luminance unevenness.

[0024]

A light guide device according to claim 1 includes a light source,
In a light guide device comprising a light guide plate that guides light from a light source incident from an end face, an optical path is converted so that divergence of light emitted from the light source is reduced mainly only in the thickness direction of the end face of the light guide plate. It is characterized in that an optical path changing means for making the light incident on the light guide plate is provided.

According to this light guide device, the light emitted from the light source has its light path converted by the light path converting means in the thickness direction of the end face of the light guide plate so that the light path is converted. The alignment accuracy of the light source in the direction and the alignment accuracy of the light source in the direction perpendicular to the end surface can be reduced. Therefore, the required accuracy of alignment between the light source and the light guide plate is relaxed, and the assembling process can be simplified.

Moreover, the optical path changing means is uniaxial,
Since the optical path is not substantially changed in the width direction of the end face where the light of the light guide plate is incident, in the width direction of the end face, the light enters the light guide plate at a wide angle as it is emitted from the light source, and It is possible to reduce a dark portion that does not reach light. Therefore, luminance unevenness in the light guide plate can be reduced, and the quality of the light guide device can be improved.

According to a second aspect of the present invention, there is provided a liquid crystal display device including the light guide device according to the first aspect and a liquid crystal display panel, wherein light emitted from the surface of the light guide plate is incident on the liquid crystal display panel. It is characterized by:

In this liquid crystal display device, since the brightness unevenness of the light guide device is reduced, it is possible to prevent the deterioration of the image quality of the liquid crystal display device due to the brightness unevenness of the light guide device.

According to a third aspect of the invention, there is provided an electronic device including the liquid crystal display device according to the second aspect and a liquid crystal driving circuit.

The electronic device may be any device provided with a liquid crystal display device, and includes, for example, a mobile phone and a liquid crystal television. Since the image quality of the liquid crystal display device used in this electronic device is improved by reducing the unevenness in luminance, the visibility of the display portion constituted by the liquid crystal display device can be improved.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 12 is a side view showing a light guide device 41 according to one embodiment of the present invention. This light guide device 41
Is a light guide plate 9 having a diffusion layer 15 formed by printing on the lower surface.
The diffusion plate 11 and the reflection plate 10 are disposed on the light exit surface 17 and the opposite surface thereof, and the linear light source 42A is disposed so as to face the incident side surface 16 of the light guide plate 9.

As shown in FIG. 13, the linear light source 42A has a plurality of LED chips 22 on the surface of the circuit board 20.
(Although two LED chips 22 are shown in FIG. 13, a larger number of LED chips 22 are actually arranged.) Are mounted at regular intervals, and the LED chips 22 on the circuit board 20 are mounted. Is entirely covered with a transparent mold resin 43. Here, the mold resin 43 is formed in a triangular prism shape having a uniform cross section along the longitudinal direction of the circuit board 20 (the arrangement direction of the LED chips 22). The optical path conversion element is constituted by the mold resin 43 having a triangular prism shape.

The operation of this embodiment will be described with reference to FIG. When the light beam r emitted from the LED chip 22 travels inside the mold resin 43 and reaches the slope of the mold resin 43, the light beam r emitted from the mold resin 43 is refracted on the surface of the mold resin 43. The light is condensed toward the incident side face 16 of the light guide plate 9 as shown in FIG. Therefore, the light use efficiency in the thickness direction of the light guide plate 9 can be improved.

Further, as shown in FIG. 14A, the change in the coupling power P when the center of the linear light source 42A is shifted by y from the thickness center C of the light guide plate 9 having a thickness of 2Δy is shown in FIG.
Shown in As can be seen from FIG. 14B, the linear light source 42
As long as the center of A is within the range of the thickness of the light guide plate 9 [−Δy to Δy], the coupling power P is kept substantially constant and the light guide plate 9
In the thickness direction, the alignment accuracy between the linear light source 42A and the light guide plate 9 is relaxed.

FIG. 15B shows a change in the coupling power P when the linear light source 42A is shifted by z in the optical axis direction as shown in FIG. 15A. Here, the deviation z = 0 indicates a state where light is condensed on the incident side face 16 of the light guide plate 9 as shown in FIG. 12, and ± Δz indicates a linear light source on the incident side face 16 of the light guide plate 9. The state in which the light beam r emitted from the light guide 42A spreads to a beam diameter equal to the thickness of the light guide plate 9.
As can be seen from FIG. 15B, the linear light source 42A has ± Δ
The coupling power P is kept substantially constant within the error of z, and the alignment accuracy between the linear light source 42A and the light guide plate 9 in the optical axis direction of the linear light source 42A is relaxed.

FIG. 16 is a diagram showing the behavior of the light beam r as viewed from the light exit surface 17 side of the light guide plate 9. Since the triangular prism-shaped mold resin 43 which is an optical path conversion element is uniaxial, the L of the linear light source 42A in the width direction of the incident side surface 16 of the light guide plate 9 is set.
The light beam r emitted from the ED chip 22
Since the light is hardly refracted by the light guide plate 9, the light enters the light guide plate 9 from the incident side surface 16 of the light guide plate 9 as a light beam group that spreads widely. For this reason, the dark portion D generated on the incident side surface 16 side of the light guide plate 9 can be reduced, and the brightness unevenness of the light guide plate 9 can be reduced to make it less noticeable. Therefore, according to the light guide device 41 of the present invention, the brightness unevenness of the light guide device 41 is reduced to improve the product quality, and the alignment accuracy of the linear light source 42A and the light guide plate 9 is relaxed to simplify the assembly process. Can be

(Second Embodiment) FIG. 17 is a perspective view showing a linear light source 42B according to another embodiment of the present invention. In the linear light source 42B, the optical path conversion element formed by the mold resin 44 has a trapezoidal prism shape.

As in the case of the linear light source 42A of the embodiment shown in FIG. 13, in the case of the mold resin 43 having a triangular prism shape, the light beam r that has exited from the LED chip 22 and travels toward the center (near the vertex) of the mold resin 43 The light is totally reflected on the surface of the resin 43. On the other hand, in the linear light source 42B, the central portion of the mold resin 44 which is the optical path changing element has a flat surface 44.
a, the light beam r that has exited the LED chip 22 and traveled toward the flat surface 44a is not totally reflected,
The light exits from the mold resin 44 and enters the light guide plate 9.

Therefore, according to this embodiment, the efficiency of optical coupling between the linear light source 42B and the light guide plate 9 can be improved. As is apparent from the operation of the present embodiment, the shape of the optical path conversion element is such that a flat surface 44a is provided so as to cut the sloped region of the mold resin 44 that totally reflects the light beam r emitted from the LED chip 22. Is preferred.

(Third Embodiment) FIG. 18 is a perspective view showing a linear light source 42C according to still another embodiment of the present invention. In the linear light source 42C, an optical path conversion element including a Fresnel pattern (diffraction grating) 46 is provided on the surface of a mold resin 45 formed so as to cover the entire surface of the circuit board 20.

In the linear light source 42C, the direction in which the Fresnel pattern 46 extends while maintaining a uniform sectional shape is as follows.
The light guide plate 9 is opposed to the light incident surface 16 so as to face the width direction of the light incident surface 16 of the light guide plate 9. Then, LE
The light beam r emitted from the D chip 22 reaches the Fresnel pattern 46 through the mold resin 45, condenses the light beam r only in the thickness direction of the light guide plate 9, and enters the light guide plate 9.

The optical path conversion element composed of the Fresnel pattern 46 may be formed integrally with the molding resin 45, or may be formed of a molding resin 4 having a uniform thickness.
The surface of 5 is made of a so-called 2P (Ph)
(oto-Polymerization) method.

(Fourth Embodiment) FIG. 19 is a partially broken perspective view showing a light guide device 47 according to still another embodiment of the present invention. In the light guide device 47, the optical path conversion element is configured as a bulk element different from the linear light source 42D. In the linear light source 42D, the LED chip 22 mounted on the circuit board 20 is sealed with a mold resin 48 having a uniform thickness. The optical path conversion element is constituted by a cylindrical lens 49, and the optical axis direction of the cylindrical lens 49 is parallel to the length direction of the linear light source 42 </ b> D between the linear light source 42 </ b> D and the incident side surface 16 of the light guide plate 9. , A cylindrical lens 49 is arranged.

The light rays emitted from the linear light source 42D are condensed by the cylindrical lens 49 in the thickness direction of the light guide plate 9 as shown in FIG.
From the light incident side 16 of the light guide plate 9. On the other hand, when viewed from the exit surface 17 side of the light guide plate 9, the direction of the light beam r does not change by the cylindrical lens 49,
The light enters the light guide plate 9 from the incident side surface 16 of the light guide plate 9 in a wide spread state. As in the case of the first embodiment, the dark portion D that does not enter the light beam r is reduced, and the uneven brightness is reduced.

Although not shown, between the linear light source and the light guide plate, a triangular prism-shaped optical path converting element or a trapezoidal prism-shaped optical path converting element as shown as the mold resin in the first and second embodiments. A prism type optical path conversion element such as an element may be provided.

(Fifth Embodiment) FIG. 21 is a partially cutaway perspective view showing a light guide device (light guide plate 9 is omitted) according to still another embodiment of the present invention. In this embodiment, the optical path conversion element 50 is connected to the linear light source 42E by holders 51 provided at both ends of, for example, a cylindrical lens-shaped optical path conversion element 50 formed separately from the linear light source 42E. It is designed to be attached.

According to such an embodiment, since the optical path conversion element 50 can be attached to the linear light source 42E so as to have a fixed positional relationship with the linear light source 42E, the mounting of the optical path conversion element 50 is easy. And the positional accuracy of the optical path conversion element 50 and the linear light source 42E is improved.

(Sixth Embodiment) FIG. 22 shows a linear light source 4 used in a light guide device according to still another embodiment of the present invention.
It is a perspective view which shows 2F. In the linear light source 42F, the LE 52a, 52b made of a copper alloy or the like is placed on the LE.
The D chip 22 is bonded, and the bonding between the LED chip 22 and the adjacent leads 52b, 52c is performed by a bonding wire 53, and the leads 52a, 52b,
52c and the LED chips 22 are encapsulated and molded with a transparent mold resin 54 so as to surround them. The front surface of the mold resin 54 is formed in a semi-cylindrical lens shape having a uniform cross section along the direction in which the LED chips 22 are arranged, and the semi-cylindrical lens-shaped portion serves as an optical path conversion element 55. .

(Seventh Embodiment) FIG. 23 shows a linear light source 4 used in a light guide device according to still another embodiment of the present invention.
It is a perspective view which shows 2G. In the linear light source 42G, the circuit board 20 on which the plurality of LED chips 22 are mounted is mounted.
Is put in a can case 56, and a mold resin 54 is poured into the can case 56. The front surface of the mold resin 54 is formed in a semi-cylindrical lens shape having a uniform cross section along the arrangement direction of the LED chips 22, and the semi-cylindrical lens-shaped portion serves as an optical path conversion element 55. . Instead of using the can case 56, a box-shaped circuit board may be used.

(Eighth Embodiment) FIG. 24 is a perspective view showing a linear light source 42H according to still another embodiment of the present invention. In this linear light source 42H, red light (emission wavelength λ _R = 45) is applied on the ground wiring 57 on the circuit board 20.
An LED chip (hereinafter, referred to as a red light LED chip) 22R that emits light of 0 to 500 nm) and a green light (light emission wavelength λ _G).
= 500-560 nm) and an LED chip (hereinafter, referred to as a green LED chip) 22G that emits blue light (emission wavelength λ _B = 630-700 nm) 22B. Bonded as one set. Of the plurality of LED chips 22R, 22G, and 22B arranged on the circuit board 20, the red light control wiring 57R and the red light LED chip 2
2R is bonded by a bonding wire 58, the green light control wiring 57G and the green LED chip 22G are also bonded by the bonding wire 58, and the blue light control wiring 57B and the blue light LED chip 22B are also bonded by the bonding wire 58. Have been. Also, the surface of the circuit board 20 and the LE
The D chips 22R, 22G, 22B are covered with a mold resin 59. The applied voltage for each color is controlled by the wiring 57R, 57G, and 57B for each color, so that each LED chip
2R, 22G, 22B can be added to the upper electrode,
The applied voltage is adjusted so as to obtain a white luminescent color.
In the linear light source 42H, since the white light source is formed by the LED chips 22R, 22G, and 22B of three kinds of emission colors, the luminance can be improved.

In the linear light source 42H, the red light LED chip 22R, the green light LED chip 22G, and the blue light LED chip 22B are arranged close to each other, so that a white light source having no color separation is provided. Can be obtained.
In particular, the red, green, and blue light LED chips 22R, 22R
The color unevenness of the linear light source 42H can be reduced by reducing the interval Q between the G and 22B and increasing the arrangement interval P of each set.

In the linear light source 42H, each LED
Since the chips 22R, 22G, and 22B are mounted on the circuit board 20, the mass production effect is high, the cost can be reduced, and the size of the linear light source 42H can be reduced.

The mold resin 59 may have uniaxial light-collecting characteristics as in the first embodiment.

(Ninth, Tenth, and Eleventh Embodiments) In addition to mounting the LED on the circuit board 20 as the LED chip 22,
(See FIG. 7). That is, FIG.
The LED element 23 shown in FIG.
The red light LED chip 22R, the green light LED chip 22G, and the blue light LED chip 22B are mounted on the stem 61a in the can case 61 which is electrically connected to the red light LED chip 22R and the bonding wire 62 is connected to the red light control lead 60R. And the green LED chip 22G is connected to the green light control lead 60G by a bonding wire 62, and the blue LED chip 22B is connected to the blue light control lead 60B by a bonding wire 62. , 22G, 22B are covered with a cover 61b having a glass window 63.

In the LED element 23 shown in FIG.
Red LED chip 2 at the end of the ground lead 60
2R, the green LED chip 22G, and the blue LED chip 22B are die-bonded, and the red LED chip 22R is bonded to the lead 60R for red light control by a bonding wire 62.
The green LED chip 22G is connected to the green light control lead 60G by a bonding wire 62, and the blue LED chip 22B is connected to the blue light control lead 60B.
To the LED chips 22R, 22G, 22B and the leads 60, 60R,
The tips of 60G and 60B are sealed with a molding resin 64 such as epoxy resin. LED with such structure
According to the element 23, the cost can be reduced as compared with the can-case type LED element 23 of FIG.

The plurality of LED elements 23 are connected to the circuit board 2
The leads 60, 60R, and 60 are not arranged on a linear light source as shown in FIG.
On the surface of the base 65 in which the G and 60B are insert-molded, a ground wire 57, a red light control wire 57R, a green light control wire 57G, and a blue light control wire 57B are provided. A plurality of sets of the red LED chip 22R, the green LED chip 22B, and the blue LED chip 22B are integrally mounted thereon, and the respective LED chips 22R, 22G, 22B and the respective wirings 57R, 57G, 5 are mounted.
7B are connected by bonding wires 58, and the LED chips 22R, 22G, 22
B may be sealed and molded with a mold resin 66.

(White Balance Control) As described above,
Red light LED chip 22R, green light LED chip 22G
In general, a linear light source 42K in which a white light source is formed by integrating a blue light LED chip 22B and
Since the relationship between the light emission power and the drive current is different for each of the 2R, 22G, and 22B, as shown in FIG. 28, the wires or leads for each color control connected to each color LED chip 22 are connected to each output of the drive current controller 67. Terminals OUT1, OUT2, OUT
3 and the ground wiring is grounded via the resistor R, and the drive current of the LED chips 22R, 22G, 22B of each color is adjusted so that white light can be obtained with the same emission power.

(Surface light source) In each of the above embodiments, 1
Although the case of a two-dimensional linear light source has been described, a two-dimensional linear light source (surface light source) may be used. That is,
FIG. 29 shows a surface light source 68 in which the LED chips 22 are arranged in a two-dimensional array on the circuit board 20 and the diffusion plate 11 is arranged thereon. FIG. 30 is an enlarged view of a part of the arranged LED chips 22. Is shown. Such a surface light source 68 can also be used as a linear light source by extending it in one direction.

(Liquid Crystal Display Device) FIG. 31 is an exploded perspective view showing a liquid crystal display device 70 using a light guide device 69 according to the present invention. The light guide device 69 includes a linear light source 42F as shown in FIG. 22, for example, on the end surface of the light guide plate 9 sandwiched between the diffusion plate 11 (including the prism sheet) and the reflection plate 10.
Is arranged. A liquid crystal display panel 71 is provided on the front surface of the light guide device 69. Liquid crystal display panel 71
Is to seal a liquid crystal material between two liquid crystal substrates (glass substrate, film substrate) 72, 73 on which a transparent electrode, a TFT, a color filter, a black matrix, etc. are formed, and to cover both outer surfaces of the liquid crystal substrates 72, 73 The polarizing plate 74 is provided. The light guide device 69 and the liquid crystal display panel 71 are sequentially stacked and integrated by a housing 75, and the liquid crystal display panel 71 is connected to a liquid crystal driving circuit by a flat cable 76.

According to such a liquid crystal display device 70, since the luminance unevenness of the light guide plate 9 is reduced, the image quality of the liquid crystal display device 70 can be improved.

(Electronic Device Equipped with Liquid Crystal Display Device) The liquid crystal display device according to the present invention is used for a wireless information transmission device such as a mobile phone or a low power radio, and an information processing device such as an electronic organizer or a calculator. Preferred for FIG. 32 is a perspective view showing a mobile phone 77 provided with a liquid crystal display device 70 as shown in FIG. 31 for display according to the present invention, for example.
3 is a functional block diagram thereof. A button switch 78 such as a numeric keypad for dial input is provided on the front of the mobile phone 77, a liquid crystal display device 70 is disposed above the button switch 78, and an antenna 79 is provided on the upper surface. When a dial or the like is input from the button switch 78, the input dial information or the like is transmitted from the antenna 81 to the base station of the telephone company through the transmission circuit 80. On the other hand, the input dial information and the like are sent to the liquid crystal driving circuit 82, and the
0 is driven by the liquid crystal drive circuit 82, and dial information and the like are displayed on the liquid crystal display device 70.

FIG. 34 is a schematic diagram showing an embodiment of the present invention.
1 is a perspective view showing an electronic organizer 83 having a liquid crystal display device 70 as shown in FIG. 1 for a display, and FIG. 35 is a functional block diagram thereof. When the cover 84 is opened, the electronic organizer 83 includes a key input unit 85 and a liquid crystal display device 70,
A liquid crystal drive circuit 86, an arithmetic processing circuit 87 and the like are provided inside. Thus, for example, when a ten key, a kana key, or the like is input from the key input unit 85, the input information is sent to the liquid crystal drive circuit 86 and displayed on the liquid crystal display device 70. Then, when a control key such as a calculation key is pressed, a calculation processing circuit 87 is pressed.
A predetermined process or calculation is executed in the step, and the result is sent to the liquid crystal drive circuit 86 and displayed on the liquid crystal display device 70.

In each of the above embodiments, the case where the LED is used as the light emitting element has been described.
A surface light emitting element such as an EL other than D or a laser diode (LD) may be used.

[Brief description of the drawings]

1A and 1B are a front view and a cross-sectional view of a direct-type surface light source device.

FIG. 2 is an exploded perspective view of the edge light type surface light source device with a part cut away.

FIGS. 3A and 3B are diagrams showing patterns of a diffusion layer provided on a light guide plate.

4A is a bottom view of the light guide plate showing another diffusion layer provided on the light guide plate, and FIG. 4B is a cross-sectional view taken along line C1-C1 of FIG.

FIG. 5 is an explanatory view of an operation of the above light guide plate.

FIG. 6 is a perspective view showing an example of an LED surface light source device.

FIGS. 7A to 7G are diagrams illustrating a process of manufacturing a linear light source by mounting an LED chip as a leaded LED element on a circuit board.

FIGS. 8 (a) to 8 (f) are views for explaining a process of manufacturing a linear light source by mounting an LED chip directly on a circuit board.

FIG. 9 is a perspective view showing a behavior of a light beam emitted from one LED of the linear light source.

FIG. 10 is an enlarged view of the behavior of a light beam emitted from the LED and incident on the light guide plate as viewed from the light exit surface side of the light guide plate.

FIG. 11 is a diagram showing brightness unevenness of light and dark that occurs in the light guide device.

FIG. 12 is a side view showing a light guide device according to an embodiment of the present invention.

FIG. 13 is a perspective view showing a linear light source used in the above light guide device.

14A is a diagram illustrating a state in which a linear light source is shifted from the center of the thickness of a light guide plate, and FIG. 14B is a diagram illustrating a change in coupling power P at that time.

15A is a diagram illustrating a state where a linear light source is shifted in the optical axis direction, and FIG. 15B is a diagram illustrating a change in coupling power at that time.

FIG. 16 is a diagram showing the behavior of light rays as viewed from the light exit surface side of the light guide plate.

FIG. 17 is a perspective view showing a linear light source according to another embodiment of the present invention.

FIG. 18 is a perspective view showing a linear light source according to still another embodiment of the present invention.

FIG. 19 is a partially broken perspective view showing a light guide device according to still another embodiment of the present invention.

FIG. 20 is a diagram illustrating the operation of the above light guide device.

FIG. 21 is a partially broken perspective view showing a light guide device (light guide plate is omitted) according to still another embodiment of the present invention.

FIG. 22 is a perspective view showing a linear light source used in a light guide device according to still another embodiment of the present invention.

FIG. 23 is a perspective view showing a linear light source used in a light guide device according to still another embodiment of the present invention.

FIG. 24 is a perspective view showing still another embodiment of the present invention, showing different linear light sources on which LED chips of three colors are mounted.

FIG. 25 is a partially broken perspective view showing an LED element on which LED chips of three colors are mounted.

FIG. 26 shows another LED mounted with a three-color LED chip.
It is a perspective view which shows an element.

FIG. 27 is a perspective view showing a linear light source on which LED chips of three colors are mounted, according to still another embodiment of the present invention.

FIG. 28 is a diagram illustrating a configuration for controlling white balance of LED chips of three colors by a drive current control unit.

FIG. 29 is a perspective view showing a surface light source in which LED chips are arranged in a two-dimensional array.

FIG. 30 is an enlarged perspective view, partially broken away, showing two-dimensionally arranged LED chips in the surface light source.

FIG. 31 is an exploded perspective view showing a liquid crystal display device using the light guide device according to the present invention.

FIG. 32 is a perspective view showing a mobile phone provided with a liquid crystal display device according to the present invention for a display.

FIG. 33 is a block diagram showing a configuration for driving a liquid crystal display device in the mobile phone of the above.

FIG. 34 is a perspective view showing an electronic organizer provided with a liquid crystal display device according to the present invention for a display.

FIG. 35 is a block diagram showing a configuration for driving a liquid crystal display device in the above electronic organizer.

[Explanation of symbols]

 Reference Signs List 9 light guide plate 20 circuit board 22, 22R, 22G, 22B LED chip 42A to 42F linear light source 43, 44 mold resin (optical path conversion element) 46 Fresnel pattern (optical path conversion element) 49 cylindrical lens (optical path conversion element) 50 holder part Optical path-changing element provided with a lens 55

Claims (3)

[Claims] 1. A light guide device comprising a light source and a light guide plate for guiding light from the light source incident from an end face, wherein divergence of light emitted from the light source is reduced mainly in a thickness direction of the end face of the light guide plate. A light path conversion means for converting the light path to make the light path incident on the light guide plate. 2. A liquid crystal display device comprising: the light guide device according to claim 1; and a liquid crystal display panel, wherein light emitted from a surface of the light guide plate is incident on the liquid crystal display panel. 3. An electronic device comprising the liquid crystal display device according to claim 2 and a liquid crystal drive circuit.