JP2002040415A - Illumination unit of liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the thickness of a liquid crystal display device and to lessen the attenuation of a light quantity. SOLUTION: The illumination unit of the liquid crystal display device consisting of a light source and a light transmission plate for introducing the light from the light source and projecting the light over the entire surface of a liquid crystal unit in a direction nearly orthogonal therewith is formed with microprisms on one surface of a substrate of a polarizing plate constituting part of the liquid crystal unit, by which the substrate of the polarizing plate is used as the light transmission plate of the illumination unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting unit of a liquid crystal display device in which light from a light source illuminates a liquid crystal unit via a light guide plate.
The present invention relates to a lighting unit of a liquid crystal display device that is suitably used for a device that is required to be reduced in size and thickness, such as a DA (portable information terminal) device.

[0002]

2. Description of the Related Art A liquid crystal display device having an illumination unit is:
It is widely used in mobile phones, various PDA (Personal Digital Assistant) devices, personal computers, TVs, and the like. In addition, the liquid crystal display devices used in these devices usually have an illumination unit using a light guide plate to illuminate the entire surface of the liquid crystal unit. And a lighting unit using a light guide plate are used as a set.

However, in a conventional liquid crystal display device, a liquid crystal unit and a lighting unit are separately manufactured, and these are usually set and combined to form a liquid crystal display device. For this reason, in devices that are required to be reduced in size and thickness, such as mobile phones and PDAs (Personal Digital Assistants), the current situation is that thinning of liquid crystal display devices has almost reached its limit. It is very difficult to further reduce the thickness.

[0004] Also, mobile phones and PDAs (portable information terminals)
In small devices such as devices, battery life is always a problem, but the power consumption of the light source in the lighting unit of a liquid crystal display device accounts for a large part of the power consumption of these small devices. Extending battery life by reducing power consumption has always been a major challenge for these small devices.

FIG. 4 is a sectional view schematically showing a conventional reflection type liquid crystal display device 1. As shown in FIG. The lighting unit 2 of the liquid crystal display device 1 includes a light source 3 and a light guide plate 4. Light projected from a light emitting body 5 such as a light emitting diode provided in the light source 3 is reflected inside the light source 3. Then, a linear light flux 6 is projected from a slit (not shown) provided in the light source 3 toward the light guide plate 4. The linear light flux 6 enters the inside from the end face 4 a of the light guide plate 4, propagates inside the light guide plate 4 so as to spread over the entire surface of the liquid crystal unit 8 to be illuminated, and forms on the upper surface of the light guide plate 4. The reflected light is reflected by the micro prism 7 and projected in a direction substantially orthogonal to the entire surface of the liquid crystal unit 8 arranged below the light guide plate 4.

In the prior art liquid crystal display device 1 as shown in FIG.
And a liquid crystal cell 10 and a reflection plate 11 disposed therebelow.
As shown in FIG. 5, the polarizing plate 9 has a polarizing material 9c applied and sandwiched between two substrates 9a and 9b made of glass or plastic having high translucency such as acrylic. It has a configuration.

As shown in FIG. 4, a liquid crystal cell 10 has transparent electrodes 1 on the inner surfaces of two glass substrates 12 and 13, respectively.
4 and 15 and alignment films 16 and 17 are formed, and a liquid crystal 18 is filled between the two glass substrates 12 and 13. Therefore, by applying a voltage to the transparent electrodes 14 and 15 so that the characters or figures to be displayed are displayed, the liquid crystal 18 filled between them is oriented and the characters or figures are displayed. In order to make this visible from the outside, in the reflection type liquid crystal display device 1, a polarizing plate 9 is disposed on the upper surface of the liquid crystal cell 10, and a reflection plate 11 is disposed below the liquid crystal cell 10, and these are disposed. The liquid crystal unit 8 is integrally formed.

Since the liquid crystal unit 8 according to the prior art is configured as described above, when trying to view characters and figures displayed on the liquid crystal display device 1 in a place where the surrounding brightness is not sufficient, the lighting unit 2 is not used. The light emitter 5 serving as the light source 3 is turned on, and the light projected from the light source 3 that is turned on enters the inside from the end face 4a of the light guide plate 4 and propagates as shown by the arrow. The light is reflected and projected toward the liquid crystal unit 8, passes through the liquid crystal cell 10, is reflected by the reflection plate 11, passes through the liquid crystal cell 10 again, passes through the light guide plate 4, and is projected to the outside. Thus, characters or figures displayed on the liquid crystal cell 10 can be visually recognized.

In the reflection type liquid crystal display device 1 according to the prior art, as described above, the liquid crystal unit 8 and the illumination unit 2 are manufactured independently and individually, and these are configured as a set and combined. Therefore, as shown in FIG. 4, a slight gap is generated between the light guide plate 4 and the liquid crystal unit 8. Therefore, the thickness of the liquid crystal display device 1 is uniquely determined by the thickness of the illumination unit 2, the thickness of the liquid crystal unit 8, and the gap between them. Was the limit.

The light reflected by the microprisms 7 of the light guide plate 4 and projected toward the liquid crystal unit 8 once exits from the light guide plate 4 to the air layer in the gap, and the liquid crystal cell 10
Incident on the upper glass substrate 12, it is unavoidable that a loss of several percent occurs in the amount of light because it passes through a boundary surface having a different refractive index.

[0011]

SUMMARY OF THE INVENTION In order to solve the problems of the prior art, the present invention makes it possible to further reduce the thickness of the liquid crystal display device by reviewing the structure of the liquid crystal display device from the ground up. It is another object of the present invention to provide a lighting unit for a liquid crystal display device that reduces attenuation of light from a light source in the liquid crystal display device as much as possible.

[0012]

In order to solve the above-mentioned problems, the present invention provides a light source and a light guide plate for introducing light from the light source and projecting the light on the entire surface of the liquid crystal unit in a direction substantially orthogonal to the liquid crystal unit. In a lighting unit of a liquid crystal display device, a microprism is formed on one surface of a substrate of a polarizing plate constituting a part of the liquid crystal unit, and the substrate of the polarizing plate is used as the light guide plate of the lighting unit. And an illumination unit for a liquid crystal display device.

Here, it is preferable that the microprism formed on the substrate of the polarizing plate is a prism film adhered to the substrate of the polarizing plate, and that the illumination unit of the liquid crystal display device includes the liquid crystal. It is a front light of a liquid crystal display device that projects illumination light from the surface side of the unit and the reflected light reflected by the liquid crystal unit is projected to the outside and visually recognizes the reflected light, or the illumination device of the liquid crystal display device, It is preferable that the backlight is a backlight of a liquid crystal display device that projects illumination light from the back side of the liquid crystal unit and transmits light transmitted through the liquid crystal unit to the outside and visually recognizes the transmitted light.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings showing embodiments. FIG. 1 is a cross-sectional view schematically showing one example of a reflection type liquid crystal display device employing the illumination unit of the liquid crystal display device of the present invention. As shown in FIG. 1, the illumination unit 2 of the reflection type liquid crystal display device 1 according to the present embodiment includes a light source 3 having a light emitting body 5 such as a light emitting diode, which is arranged to face an end face 4 a of a light guide plate 4. The light projected from the light emitting body 5 is reflected inside the light source 3, and enters as a linear light flux 6 in the direction of the light guide plate 4 from a slit (not shown) provided in the light source 3. .

Here, the light guide plate 4 in the embodiment of the present invention is used.
As shown in FIG. 2, fine prism-like irregularities are formed on the upper surface of a substrate 9a above a polarizing plate 9 formed by applying and sandwiching a polarizing substance 9c between two substrates 9a and 9b. Is formed. As is well known, the microprism 7 includes one surface 7a having a small inclination angle and the other surface 7b having a large inclination angle. The light projected and incident on the light guide plate 4 (the substrate 9a on the upper side of the polarizing plate 9) is formed at an angle at which the light is totally reflected and propagates inside the light guide plate 4, and the inclination angle of the other surface 7b is Light incident on the inside of the light plate 4 is reflected downward (in the direction of the liquid crystal cell 10).
Is formed at an angle projected toward.

The microprisms 7 of the light guide plate 4 are not only formed directly on the substrate 9a above the polarizing plate 9, but also as shown by imaginary lines in FIG. Alternatively, a sheet-like prism film 19 manufactured separately may be attached. At this time, the substrate 9a above the polarizing plate 9 and the prism film 19
For the adhesive between them, a material having the same refractive index of light must be selected so that reflection at the interface, in particular, total reflection does not occur.

As described above, the substrate 9a on the upper side of the polarizing plate 9 and the prism film 19, which are selected so that the refractive indexes of light are exactly the same, eliminate unevenness of the adhesive and form a fine bubble-like air layer. By affixing them so that they do not come together, they can be handled optically as one. 1 and 2, the upper surface and the lower surface of the light guide plate 4 are drawn in parallel, but as is well known as the light guide plate 4,
A wedge-shaped shape that becomes thinner as the distance from the light source 3 increases.

Since the light guide plate 4 is configured as described above, the light projected from the light source 3 and incident on the inside of the substrate 9 a above the polarizing plate 9 constituting the light guide plate 4
a one surface 7 of the microprism 7 formed on the upper surface
a and the lower surface of the substrate 9a are repeatedly reflected and propagated inside the upper substrate 9a constituting the light guide plate 4, and the light projected on the other surface 7b of the microprism 7 is directed downward. And is projected toward the liquid crystal cell 10 so as to be substantially orthogonal.

Below the light guide plate 4, a liquid crystal cell 10 similar to the prior art is arranged. However, as described above, since the light guide plate 4 also serves as the substrate 9a on the upper side of the polarizing plate 9, it is not possible to clearly distinguish the illumination unit 2 and the liquid crystal unit 8 as in the related art.

In the liquid crystal cell 10 of the present invention, transparent electrodes 14 and 15 and alignment films 16 and 17 are formed on the inner surfaces of two glass substrates 12 and 13, respectively, as in the prior art. Liquid crystal 18 is filled between the glass substrates 12 and 13. In the liquid crystal cell 10, when a voltage from a control circuit (not shown) is applied to the transparent electrodes 14 and 15 so that predetermined characters or figures are displayed, the liquid crystal 18 filled therebetween is oriented so that a required Characters or figures are displayed. Reflector 11 below liquid crystal cell 10
Is also the same.

Since the reflection type liquid crystal display device 1 of the present invention is configured as described above, when the user tries to see characters and figures displayed on the liquid crystal display device 1 in a place where the surrounding brightness is not sufficient, The light emitter 5 serving as the light source 3 of the lighting unit 2 is turned on, and the light projected from the light emitter 5 of the light source 3 that is turned on enters the light guide plate 4 also serving as the substrate 9a on the upper side of the polarizing plate 9, Light incident on the inside of the light guide plate 4 is, as indicated by arrows, one surface 7a of the microprism 7 formed on the upper surface of the substrate 9a above the polarizing plate 9 and the lower surface of the substrate 9a above the polarizing plate 9. Is repeatedly propagated inside the polarizing plate 9.

On the other hand, the other surface 7b of the micro prism 7
The light reflected directly or on the lower surface of the substrate 9a above the polarizing plate 9 is reflected downward and projected toward the liquid crystal cell 10, and after passing through the liquid crystal cell 10,
After being reflected by the reflecting plate 11 and passing through the liquid crystal cell 10 again, the light passes through the polarizing plate 9 also serving as the light guide plate 4 and is projected to the outside, thereby illuminating the characters or figures displayed on the liquid crystal cell 10. And can be visually recognized brightly.

FIG. 3 is a sectional view schematically showing one example of a transmission type liquid crystal display device employing the illumination unit of the liquid crystal display device of the present invention. As shown in FIG. 3, the illumination unit 22 of the transmissive liquid crystal display device 21 according to the present embodiment includes a light source 23 having a light emitting body 25 such as a light emitting diode, similar to the reflective liquid crystal display device 1. End face 2 of light plate 24
The light projected from the light emitting body 25 is reflected inside the light source 23, and is linearly emitted from a slit (not shown) provided in the light source 23 in the direction of the light guide plate 24. It is incident as 26.

The light guide plate 24 has an inverted shape of the light guide plate 4 shown in FIG. 2, and as shown in FIG.
A micro prism 27 made of fine prismatic irregularities is formed on the lower surface of a substrate 29a below a polarizing plate 29 formed by sandwiching a polarizing substance 29c between two substrates 29a and 29b. . This micro prism 27
Is composed of one surface 27a having a small inclination angle and the other surface 27b having a large inclination angle. The inclination angle of the one surface 27a is projected from the luminous body 25 of the light source 23 and the light guide plate 24
The light incident on (the substrate 29a below the polarizing plate 29) is formed so as to be totally reflected and propagated inside the light guide plate 24, and the inclination angle of the other surface 27b is incident on the inside of the light guide plate 24. The reflected light is formed at an angle at which the reflected light is reflected upward (in the direction of the liquid crystal cell 30).

The micro prism 27 of the light guide plate 24
May be formed not only directly on the lower substrate 29a of the polarizing plate 29 but also by attaching a sheet-like prism film (not shown) to the lower surface of the lower substrate 29a of the polarizing plate 29. The same is true for Although the light guide plate 24 shown in FIGS. 2 and 3 has the upper surface and the lower surface drawn in parallel, it is also possible to have a wedge-shaped shape that becomes thinner as the distance from the light source 23 increases, as is well known. The same is true for

Above the light guide plate 24, a liquid crystal cell 30 similar to the prior art is arranged. The liquid crystal cell 30 includes transparent electrodes 3 on the inner surfaces of two glass substrates 32 and 33, respectively.
4 and 35 and alignment films 36 and 37 are formed, and a liquid crystal 38 is filled between the two glass substrates 32 and 33. In the liquid crystal cell 30, when a voltage from a control circuit (not shown) is applied to the transparent electrodes 34 and 35 so that predetermined characters or figures are displayed, the liquid crystal 38 filled therebetween is oriented and the required Characters or figures are displayed. A polarizing plate 40 is disposed above the liquid crystal cell 30, and the liquid crystal unit 28 as a whole is disposed.
Is composed.

Since the transmissive liquid crystal display device 21 of the present invention is configured as described above, when a character or a figure displayed on the liquid crystal unit 28 is to be viewed in a place where the surrounding brightness is not sufficient, the illumination is required. The illuminant 25 serving as the light source 23 of the unit 22 is turned on, and the illuminant 2 of the illuminated light source 23 is turned on.
The light projected from 5 is directed to a substrate 29a below the polarizing plate 29.
As shown by an arrow, one surface 27a of the microprism 27 formed on the lower surface of the substrate 29a below the polarizing plate 29 and the substrate 29a below the polarizing plate 29 as shown by an arrow. Is repeatedly propagated inside the polarizing plate 29 by repeating total reflection with the upper surface of the polarizing plate 29.

On the other hand, the other surface 2 of the micro prism 27
The light reflected directly on the substrate 7b or on the upper surface of the substrate 29a below the polarizing plate 29 is reflected upward and projected toward the liquid crystal cell 30. After passing through the liquid crystal cell 30, the light is polarized. By passing through the plate 40 and projecting outside, the characters or figures displayed on the liquid crystal cell 30 are illuminated and can be visually recognized brightly.

[0029]

The illumination unit of the liquid crystal display device according to the present invention is configured as described above, so that the thickness of the liquid crystal display device can be further reduced by configuring the light guide plate also as the substrate of the polarizing plate. In addition, the attenuation of the light from the light source can be reduced by eliminating the air layer between the liquid crystal cell and the polarizing plate through which the illumination light passes.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of a reflection type liquid crystal display device employing a lighting unit of the liquid crystal display device of the present invention.

FIG. 2 is a cross-sectional view illustrating a structure of a polarizing plate of the present invention.

FIG. 3 is a cross-sectional view schematically showing one example of a transmission type liquid crystal display device employing the illumination unit of the liquid crystal display device of the present invention.

FIG. 4 is a cross-sectional view schematically illustrating a conventional reflection-type liquid crystal display device.

FIG. 5 is a cross-sectional view showing a structure of a conventional polarizing plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reflection type liquid crystal display device 2 Illumination unit 3 Light source 4 Light guide plate 4a End face 5 Light emitting body 6 Linear luminous flux 7 Microprism 7a One surface 7b The other surface 8 Liquid crystal unit 9 Polarizing plate 9a, 9b Substrate 9c Polarizing substance 10 Liquid crystal cell 11 Reflector plate 12, 13 Glass substrate 14, 15 Transparent electrode 16, 17 Alignment film 18 Liquid crystal 19 Prism film 21 Transmissive liquid crystal display device 22 Illumination unit 23 Light source 24 Light guide plate 24a End face 25 Light emitter 26 Linear light flux 27 Microprism 27a One surface 27b The other surface 28 Liquid crystal unit 29 Polarizer 29a, 29b Substrate 29c Polarizer 30 Liquid crystal cell 31 Reflector 32, 33 Glass substrate 34, 35 Transparent electrode 36, 37 Alignment film 38 Liquid crystal 39 Prism film 40 Polarizing plate

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Junji Miyashita 1-23-1 Kagurechi, Fujiyoshida-shi, Yamanashi Prefecture F-term (reference) 2H038 AA55 BA01 2H091 FA08X FA21X FA23X FA41X FA41Z FD06 FD15 LA11 LA18 5G435 AA03 AA18 BB12 BB15 BB16 EE22 EE27 FF05 FF08 GG03 KK07

Claims (4)

[Claims] An illumination unit for a liquid crystal display device comprising a light source and a light guide plate for introducing light from the light source and projecting the light in a direction substantially orthogonal to the entire surface of the liquid crystal unit. An illumination unit for a liquid crystal display device, wherein a microprism is formed on one surface of a substrate of a polarizing plate to constitute, and the substrate of the polarizing plate is used as the light guide plate of the illumination unit. 2. The illumination unit of a liquid crystal display device according to claim 1, wherein the microprism formed on the substrate of the polarizing plate is a prism film attached to the substrate of the polarizing plate. 3. The front of the liquid crystal display device, wherein the illumination unit of the liquid crystal display device projects illumination light from the front side of the liquid crystal unit, and the reflected light reflected by the liquid crystal unit is projected to the outside and visually recognized. The lighting unit of the liquid crystal display device according to claim 1, wherein the lighting unit is a light. 4. A back light of a liquid crystal display device, wherein the illumination device of the liquid crystal display device projects illumination light from the back side of the liquid crystal unit, and the transmitted light transmitted through the liquid crystal unit is projected to the outside to visually recognize the light. The lighting unit of the liquid crystal display device according to claim 1, wherein the lighting unit is a light.