JPH10198497A - Input tablet and liquid crystal display device using the tablet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easy-to-see and bright input tablet imparted with a two-dimensional illuminating function simple in structure by guiding light flux made incident from an end face to a light emitting plane and illuminating an object to be illuminated from the light emitting plane. SOLUTION: A light transmission body 11 is formed in the shape of rectangular plate as a whole, four end faces vertical to the surface of that plate are formed in the direction of plate surface orthogonal to the direction of plate thickness and the side faces of light transmission body 11 are formed from them. At the position facing one-side end face along with a short-side direction among these four end faces, a light source 2 composed of a linear light source such as a fluorescent lamp, for example, is arranged along with that end face 16. Both the surfaces of light transmission body 11 are formed as a light emitting plane 13 and a light reflecting plane 17. The light flux radiated from the light source 2 is made incident from the end face 16 to a light transmission plate 11 as shown by a light beam 19a or 19b, repeatedly fully reflected inside that plate later and emitted only from the side face 15 of projection 12. Therefore, there are a lot of beams emitted from the back of illuminator and an object 6 to be illuminated can effectively be illuminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an input tablet having a two-dimensional illumination function and a liquid crystal display using the input tablet.

[0002]

2. Description of the Related Art Input tablets are generally classified into a resistance detection method, a capacitance method, an electromagnetic induction method, and the like when classified according to their detection methods. However, structurally, the input tablet has a transparent electrode having one or more transparent electrodes. Generally, it is composed of a substrate. Usually, a glass plate or PET (polyethylene terephthalate) is used as a transparent substrate, and ITO or tin oxide is used as a transparent electrode. The transparent electrode may be uniform over the entire surface or may be used after being patterned. The pen input surface has a structure in which a plastic film is stuck or a fine uneven surface is provided on the surface to improve writing taste and to prevent glare. The input tablet is used not only as a stand-alone input device but also as a device capable of operating information on a display screen in combination with a CRT or LCD.

Conventionally, as an illuminating device arranged in front of a liquid crystal display device, for example, Japanese Unexamined Patent Publication No.
The structure described in No. 1 is known. According to the proposed structure, illumination suitable for a reflective liquid crystal display mode frequently used in portable equipment can be achieved.

[0004]

However, since the conventional input tablet has a structure having a transparent substrate having one or more transparent electrodes, although the amount of light in the transparent substrate is hardly attenuated, the input tablet is particularly difficult to use. There was a problem that 10% or more of the light was lost due to surface reflection at the interface with air, resulting in darkness. Further, the panel is difficult to see due to surface reflection, and this is a serious problem particularly when used in combination with a display element. Furthermore, if an anti-glare film is attached for anti-glare, or a structure with fine irregularities on the surface is adopted, the amount of light of 10% to 20% of the total light transmission is further lost, and irregular reflection on the surface causes There is a problem that the image quality is deteriorated due to white blur.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and is an intuitive and bright input tablet provided with a two-dimensional illumination function by an inexpensive and simple structure, and in particular, a reflective tablet. It is an object of the present invention to provide a liquid crystal display device provided with an input tablet suitable for a liquid crystal display mode of a type.

[0006]

According to the present invention, there is provided an input tablet, comprising: a light source for emitting a light beam;
And a light guide means for guiding the light beam incident from the end surface to the light output surface to illuminate the illuminated object from the light output surface.

Preferably, the light guide means includes a light guide having a transparent flat plate shape and having a surface perpendicular to the end face as the light exit surface, and is substantially perpendicular to a surface substantially parallel to the light exit surface. A projection comprising a surface is integrally formed with the light exit surface. For example, the protrusion is formed of a plurality of rib-shaped protrusions. In this case, the ratio between the width and the height of each of the projections is approximately one to one. Further, the protrusion may be formed of a plurality of columnar protrusions. Also in this case, the ratio between the diameter and the height of each of the projections is approximately one to one.

Further, preferably, a transparent electrode body is provided on a side of the light guide opposite to the light exit surface on a side opposite to the light exit surface.

Further, the light guide means is a transparent flat plate-shaped light guide having a surface perpendicular to the end face as the light output surface, and is attached to the light output surface and substantially parallel to the light output surface. And a film body having a projection formed of a substantially perpendicular surface and a substantially perpendicular surface. For example, the protrusion is formed by a plurality of rib-shaped protrusions. In this case, the ratio between the width and the height of each of the projections is approximately one to one. Further, the protrusion may be formed of a plurality of columnar protrusions. In that case, preferably, the input tablet wherein the ratio between the diameter and the height of each of the projections is approximately 1: 1.

Further, a transparent electrode body may be provided on a side of the light guide opposite to the light exit surface on a side opposite to the light exit surface.

On the other hand, a liquid crystal display device according to the present invention comprises a liquid crystal display panel having a display surface, and an input tablet disposed on the liquid crystal display panel on the side of the display surface. A light source that emits light; and a light guide unit that has an end surface on which the light beam enters and guides the light beam incident from the end surface to a light output surface to illuminate the display surface from the light output surface.

For example, the liquid crystal display panel is a reflection type display. Preferably, the light guide means includes a light guide having a transparent flat plate shape and having a surface perpendicular to the end face as the light exit surface, and a light guide surface substantially parallel to the light exit surface and a surface substantially perpendicular to the light exit surface. The protrusions are formed on the light exit surface. As another preferred example, the light guide means is a transparent flat plate-shaped light guide having a surface perpendicular to the end surface as the light output surface, and is attached to the light output surface and substantially attached to the light output surface. A film body having a projection formed of a parallel surface and a substantially vertical surface. Further, a polarizing plate may be disposed on the front surface of the light guide plate opposite to the light exit surface of the light guide plate.

According to the present invention, an inexpensive and simple structure 2
It is possible to provide a liquid crystal display device including an input tablet that is easy to see and has a three-dimensional illumination function and is particularly suitable for a reflective liquid crystal display mode. In an application such as a portable computer terminal, the display quality is not degraded even when the light is turned off in a bright place to save power, and a liquid crystal display with high contrast is possible even when the light is turned on.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. The input tablet uses the resistance detection method as a representative, but any method may be basically used.

(First Embodiment) An input tablet according to a first embodiment of the present invention will be described with reference to FIGS.
This input tablet includes a light guide plate 11 as a light guide. The light guide plate 11 is configured as a transparent substrate on which a transparent electrode is formed. A light source 2 is provided on one end face side of the light guide plate 11.
Is arranged. The light guide plate 11 has a function of causing a light flux from the light source 2 to enter from an end face and emitting the light mainly in the direction of one surface (light emitting surface) as irradiation light, and almost dispersing a light beam intersecting in the plate surface direction of the light guide plate 11. It has the function of transmitting light without being transmitted. A reflector is arranged around the light source 2, and guides light rays from the light source 2 to the light guide plate 11 effectively. The illuminated body 6 is arranged on the light emitting surface side of the light guide plate 11, and a film with a transparent electrode is arranged adjacent to the opposite light emitting surface side via a spacer.

Hereinafter, this structure will be described in detail. The entire light guide plate 11 is formed in a rectangular and plate shape having long sides and short sides, and four end surfaces perpendicular to the plate surface are formed in a plate surface direction orthogonal to the plate thickness direction. The side surface of the light plate 11 is formed. At a position facing one of the four end faces along the short side direction, a light source 2 composed of a linear light source such as a fluorescent lamp is arranged along the end face. The light source 2 may have a structure in which point light sources are arranged in a row.

Both surfaces of the light guide plate 11 are formed as a light emitting surface 13 and a counter light emitting surface 17. On the light emitting surface 13,
As shown in FIG. 2, the rib-shaped projection 1 is substantially parallel to the light source 2.
2 are provided. All of the surfaces constituting the projections 12 are constituted only by a surface (bottom surface 14) substantially parallel to the light emitting surface 13 and a surface (side surface 15) substantially perpendicular to the light emitting surface 13.

The light guide plate 11 is formed of a transparent material having a refractive index of about 1.4 or more. The light beam emitted from the light source 2 is a light beam 1
9a and the light guide plate 11 from the end face 16 as shown by the light beam 19b.
, After which total reflection is repeatedly emitted only from the side surface 15 of the projection 12. Therefore, a large amount of light is emitted from the back surface of the lighting device, and the illuminated body 6 can be effectively illuminated.

As the transparent material forming the light guide plate 11, a transparent resin such as an acrylic resin, a polycarbonate resin, an amorphous polyolefin resin or the like, an inorganic transparent material such as a glass or a composite thereof is used. The light guide plate 11 is injection molded,
An integral type such as cast molding or extrusion molding, or a method in which projections are formed on a transparent substrate by a method such as etching of a photocurable resin can also be employed. A transparent electrode such as ITO is formed on the surface opposite to the protrusion by vapor deposition or sputtering, and photoetching is performed as necessary. On the back surface of a glass plate with transparent electrodes currently mass-produced, a method of pasting a film with projections formed in advance or applying a transparent resin thin film, and then applying a shape with a roller with irregularities, etc., The light guide plate can be easily configured.

A reflector 21 is arranged around the light source 2, and functions to effectively guide light rays from the light source 2 to the light guide plate 1. The reflector 21 is mainly made of a resin film or a resin molded product, and is colored white or provided with a deposited film of aluminum or silver. These have high light reflectance,
This is effective for improving the efficiency of the power / luminance ratio.

A transparent electrode is formed on the light guide plate 11 on the side opposite to the light exit surface 17, and a film 8 with a transparent electrode is disposed via a spacer 9. Light guide plate 11 and transparent film 8
There is no close contact, and there is an air layer. Light guide plate 11
If the surface is slightly flawed, the light that guides the interior is reflected there, and is recognized as a bright spot or a bright line from the surface.
These are not only unsightly for transmissive lighting,
This significantly reduces the visibility, such as a decrease in contrast. Since the transparent film 8 passes through the air layer with respect to the light guide plate 11, the light flux from the light source 2 does not enter, and even if it is scratched, no bright spots or bright lines appear. Also, in this case, the relative area of the wound is small,
The influence on the visibility of the illuminated body 6 is extremely small. As the transparent plate 8, a transparent resin such as an acrylic resin, a polycarbonate resin, or an amorphous polyolefin resin, or an inorganic transparent material such as glass is used. In the case of a configuration in which a transparent film having a protrusion is attached to a transparent substrate, a resin film such as polyester, polycarbonate, polypropylene, or acetate is used as the transparent film.

As shown in FIG. 3, the light beam 19 incident from the end face 16 is refracted with respect to the axis of the light guide plate 11 in the long side direction.
Since it has an optical axis of 5 degrees or less, it is necessary to have a height higher than the width of the protrusion 12 in order to irradiate the side surface of the protrusion 12. In the case below this, the light ray 19 is emitted to the upper surface of the light guide plate 11 through the path as shown in FIG. However, when the ratio greatly exceeds one-to-one, not only is it optically meaningless, but also there is a problem that manufacturing becomes difficult. In addition, when the lighting device is viewed obliquely, the visibility may be reduced. As described above, it is desirable that the ratio of the width (long side direction) to the height (plate thickness direction) of the protrusion 12 be exactly 1: 1.

Since the wavelength of visible light is about 380 nm to about 700 nm, the width, height, and the like of the projections 12 need to be about 5 μm or more in order to prevent spectral stripes from being generated by interference due to diffraction. Further, since the size of the pixel of the liquid crystal display panel is 200 μm to 300 μm, the size should be 100 μm or less in order to prevent the occurrence of a stripe pattern due to interference with the pixel. In addition to the above contents, the size of the protrusion 12 is desirably about 10 μm or more and 50 μm or less for convenience in manufacturing.

By adjusting the density of the protrusions 12 on the light guide plate 11, the uniformity of the irradiation luminance can be improved.
Actually, the protrusions 12 are arranged sparsely in the vicinity of the light source 2, and are continuously arranged densely as the distance increases. In this case, protrusion 1
2, a method of varying the density while keeping the size constant, a method of varying the size while keeping the density constant, a method of varying both, and the like are taken. In actual machining, the size of the projection 12 is kept constant. The method of changing the density is easy and advantageous.

On the upper surface of the light guide plate 11, a transparent electrode 18 is formed. As the transparent electrode, ITO or tin oxide is used, and has a refractive index of 1.7 or more, which is higher than that of the transparent substrate. Due to the presence of the transparent electrode, there is no adverse effect such that the light beam 19 is emitted to the upper surface of the light guide plate 11.
Since the film 8 with the transparent electrode 18 is arranged via the spacer 9, the position can be detected in the same manner as in a normal resistance detection method. Further, since bright illumination in close contact with the illuminated body 6 can be performed, low transmittance and fogging of the input tablet are not bothered, and good visibility can be obtained.

As described above, according to the input tablet of this embodiment, the light flux from the light source 2 disposed on the end face is mainly used as the irradiation light 3 in one direction, that is, in the direction toward the light exit surface 4 as shown in FIG. It can have a function of emitting light and a function of transmitting light rays 5 intersecting in the direction of the flat plate of the light guide plate 1 with almost no dispersion. As a result, when there is sufficient external light, the light source 2 is turned off and used, and in this case, the light guide plate 1 functions simply as a transparent plate. When the external light is not enough, the light source 2 is turned on to illuminate the illuminated body 6.

As the illuminated body 6 of the illuminating device described above, a printed matter printed on paper or the like, a liquid crystal display, or the like is suitable.

(Second Embodiment) FIG. 6 shows a second embodiment. In this embodiment, the projections 12 are formed in a prismatic shape, and in this case, the same effect as the above-described rib can be obtained.
The side surface perpendicular to the light source 2 of the projection 12 is irradiated with light rays at a critical angle or more, and is totally reflected and has no relation to the emitted light.

(Third Embodiment) FIG. 7 shows a third embodiment. In this embodiment, a prism having a square bottom surface is formed on a substantially rectangular light guide plate 11. In this case, light sources 2 are arranged on two adjacent sides of the light guide plate 11, and light rays incident from the two sides are provided. Can be emitted from each side surface of the projection 12.

(Fourth Embodiment) As a fourth embodiment, a structure in which the projections 12 are formed in a columnar shape is shown in FIG. The light beam 19 irradiated to the cylindrical surface of the protrusion 12 at a critical angle or less emits light, and the light beam irradiated at the critical angle or more repeats reflection on the cylindrical surface, then inverts on the bottom surface of the protrusion 12 and further reflects on the cylindrical surface. Is repeated to follow the path in the light guide plate again. The irradiation range of the light beam 19 emitted from the cylindrical surface can be broadened as shown in FIG. 10 as compared with the case of the prism shown in FIG.

(Fifth Embodiment) FIG. 11 shows a fifth embodiment. In this embodiment, a liquid crystal display panel is used for an object to be illuminated. Input tablet 10 with lighting function
1 is arranged on the front surface of the liquid crystal display panel 102. A reflection plate 103 is arranged on the back surface of the liquid crystal display panel 102 to constitute a reflection type liquid crystal display device.

The input tablet 101 is a liquid crystal display panel 1
It has a function of projecting a light beam on the 02 side and transmitting a light beam reflected by the reflection plate 103 with almost no dispersion. This is because when there is sufficient external light, the illumination of the input tablet 101 is turned off and used. In this case, the input tablet 101 having the illumination function acts as a mere input tablet and does not reduce the visibility, and affects the display quality. Is effective in not giving When used in a dark place where external light is not sufficient, the input tablet 101 with the illumination function illuminates the liquid crystal display panel 102, and the reflected light from the reflector 103 is emitted by the input tablet 101 with the illumination function. As in the case of the above-mentioned light-off state, it functions as a mere input tablet and is transmitted as it is, which is effective for maintaining high visibility.

In the transmission type liquid crystal display device in which the illumination device is arranged on the back of the liquid crystal display panel, the light from the illumination device transmits through the liquid crystal display panel only once to generate a contrast between a bright portion and a dark portion. In a reflection type liquid crystal display device in which a lighting device as in the present invention is disposed in front of a liquid crystal display panel, light from the lighting device passes through the liquid crystal display panel once, is reflected by the reflector, and is transmitted again. This is effective for obtaining higher visibility by increasing the contrast.

(Sixth Embodiment) FIG. 12 shows a sixth embodiment. The light guide plate 11 is superimposed directly on the liquid crystal display, and the polarizing plate 10
4 is superimposed on the transparent film 8 further above the light guide plate 11. An antiglare hard coat layer is formed on the outermost surface of the polarizing plate 10, so that pen input is not damaged. Further, even if some scratches occurred, the visibility of the liquid crystal display was hardly adversely affected.

The liquid crystal display has one upper and lower polarizing plate, and the polarizing axis of the polarizing plate 104 on the light guide plate corresponds to these. Since the polarizing plate cuts the scattered light upward from the light guide plate, the visibility of the liquid crystal display can be improved.

[0036]

As described above, according to the present invention,
It is possible to provide an easy-to-view and bright input tablet provided with a two-dimensional illumination function with a cheap and simple structure, and a liquid crystal display device including an input tablet particularly suitable for a reflective liquid crystal display mode.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a configuration of an input tablet according to a first embodiment of the present invention.

FIG. 2 is a perspective view illustrating a light guide plate.

FIG. 3 is an explanatory diagram showing a light guiding operation of the light guide plate.

FIG. 4 is an explanatory diagram showing a light guiding operation of the light guide plate.

FIG. 5 is an explanatory diagram showing a light guiding operation of the entire light guide plate.

FIG. 6 is a perspective view illustrating a protrusion of an input tablet according to a second embodiment of the present invention.

FIG. 7 is a perspective view illustrating a protrusion of an input tablet according to a third embodiment of the present invention.

FIG. 8 is a perspective view illustrating a protrusion of an input tablet according to a fourth embodiment of the present invention.

FIG. 9 is a diagram illustrating an irradiation range of a light-emitting light beam when the protrusion is a prism.

FIG. 10 is a view for explaining an irradiation range of a light-emitting ray when a projection is a cylinder.

FIG. 11 is a sectional view schematically showing a liquid crystal display device according to a fifth embodiment of the present invention.

FIG. 12 is a sectional view schematically showing a liquid crystal display device according to a sixth embodiment of the present invention.

[Explanation of symbols]

1,11 ··· Light guide plate with transparent electrode 2, ··· Light source, 3 ·
・ Irradiation light, 4 ・ ・ Light emitting surface, 5,19 ・ ・ Light beam, 6 ・ ・ Certified object, 7,17 ・ ・ Reflective light surface, 8 ・ ・ Transparent film with transparent electrode, 9 ・ ・ Spacer, 12 ・ ・Projection, 13 ...
Light-emitting side plane, 14 ... Bottom of projection, 15 ... Side of projection, 16 ... Boundary, 18 ... Transparent electrode, 21 ... Reflector, 101 ... Input tablet with certification function, 1
03 ・ ・ Reflection plate, 104 ・ ・ Deflection plate

Claims (18)

[Claims] 1. A light source for emitting a light beam, and a light guide means having an end surface for receiving the light beam and guiding the light beam incident from the end surface to a light output surface to illuminate an object to be illuminated from the light output surface. And an input tablet with. 2. The invention according to claim 1, wherein the light guide means includes a light guide having a transparent flat plate shape and having a surface perpendicular to the end face as the light output surface, and substantially parallel to the light output surface. An input tablet, wherein a projection composed of a flat surface and a surface substantially perpendicular to the light exit surface is integrally formed. 3. The input tablet according to claim 2, wherein the projection is formed by a plurality of rib-shaped projections. 4. The input tablet according to claim 3, wherein the ratio between the width and the height of each of the projections is approximately one to one. 5. The input tablet according to claim 2, wherein the projection is formed by a plurality of columnar projections. 6. The input tablet according to claim 5, wherein the ratio between the diameter and the height of each of the projections is approximately one to one. 7. The input tablet according to claim 2, wherein a transparent electrode body is provided on a side of the light guide opposite to the light exit surface on a side opposite to the light exit surface. 8. The light guide according to claim 1, wherein the light guide is a light guide having a transparent flat plate-shaped surface perpendicular to the end face as the light output surface, and is attached to the light output surface. An input tablet including a film body having a projection formed of a surface substantially parallel to the light exit surface and a surface substantially perpendicular to the light emission surface. 9. The input tablet according to claim 8, wherein the projection is formed by a plurality of rib-shaped projections. 10. The input tablet according to claim 9, wherein a ratio of a width to a height of each of the projections is approximately one to one. 11. The input tablet according to claim 8, wherein the projection is formed by a plurality of columnar projections. 12. The input tablet according to claim 11, wherein the ratio between the diameter and the height of each of the projections is approximately one to one. 13. The input tablet according to claim 8, wherein a transparent electrode body is provided on a side of the light guide opposite to the light exit surface on a side opposite to the light exit surface. 14. A liquid crystal display panel having a display surface, and an input tablet disposed on the display surface side of the liquid crystal display panel, wherein the input tablet is provided with a light source that emits a light beam, and a light source that receives the light beam. A liquid crystal display device comprising: a light guide means having an end surface for causing the light beam incident from the end surface to be directed to a light exit surface and illuminating the display surface from the light exit surface. 15. The liquid crystal display device according to claim 14, wherein the liquid crystal display panel is a reflection type display. 16. The invention according to claim 15, wherein said light guide means includes a light guide having a transparent flat plate shape and having a surface perpendicular to said end face as said light output surface, and substantially parallel to said light output surface. A liquid crystal display device, wherein a projection composed of a flat surface and a substantially vertical surface is formed on the light exit surface. 17. The light guide according to claim 15, wherein the light guide is a transparent flat plate-shaped light guide having a surface perpendicular to the end face as the light output surface, and is attached to the light output surface. A liquid crystal display device comprising a film body having a projection formed of a surface substantially parallel to the light exit surface and a surface substantially perpendicular to the light emission surface. 18. The liquid crystal display device according to claim 15, wherein a polarizing plate is disposed on a front surface of the light guide plate opposite to the light exit surface of the light guide plate.