JP2002297044A - Narrow viewing angle mobile display, method of manufacturing filter used therefor, and mobile terminal device - Google Patents

Abstract

(57) [Summary] The present invention relates to a mobile display,
It is an object of the present invention to improve the security of display information by narrowing the viewing angle by a simple means and realize a simple mobile terminal that can be used anywhere. SOLUTION: This is a narrow viewing angle mobile display device characterized in that a light emission angle limiting filter formed by integrating optical fibers aligned and aligned in the thickness direction is arranged on the surface of a display element. The light emission angle limiting filter focuses a plurality of optical fibers each having a core and a cladding layer, and orients the fibers in one direction to form a bundle. Forming a block of the optical fiber, and cutting the block of the optical fiber in a direction perpendicular to the longitudinal direction of the optical fibers constituting the block to form a sheet. Can be manufactured from

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display used for a mobile terminal, and more particularly to a display which is difficult to be visually recognized by a third party other than a display user, a method for manufacturing the same, and a portable terminal using the display.

[0002]

2. Description of the Related Art As conventional portable terminals, so-called mobile terminals, there are a PDA, a palmtop PC, an i-mode terminal, and the like. As displays for these mobile terminals, liquid crystal display elements are frequently used because of their high resolution and low cost. This mobile terminal is used indoors due to the development of communication and the lightening of the mobile terminal, so that the number of scenes used outdoors is increasing.

[0003] Regarding the use of such mobile terminals outdoors, a serious problem in terms of confidentiality has become apparent. That is, when the mobile terminal is used in a public place usually outside, a display on the mobile terminal can be seen by a third party. In other words, the current mobile terminal display has no means to hide the display screen from the people near the user, and the mobile terminal can be used in a free place when handling important information. There was a restriction that it could not be used, which was inconvenient.

[0004] Conventionally, in a liquid crystal display device,
In a surface light source device including a primary surface light source means and two prism sheets arranged along a light emitting surface of the primary surface light source means, the two prism sheets are each formed by a row of V-shaped grooves. The prism surfaces are formed, the extending directions of the groove rows of the two prism sheets are orthogonal to each other, and each prism surface of the two prism sheets is opposite to the primary surface light source means. And the prism apex angle of each of the two prism sheets is approximately 7
The surface light source device in a range of 0 ° to approximately 110 °, wherein the light emitted from the light emission surface of the primary surface light source means is narrowed two-dimensionally in the process of passing through the two prism sheets. Is known (Japanese Patent Application Laid-Open No. 8-271894).

In this liquid crystal display device, the use of the above-mentioned prism sheet makes it possible to increase the brightness and narrow the field of view of the liquid crystal display device. To achieve a device suitable for these purposes,
With such a technique, it is difficult to manufacture a device that narrows the field of view, and it is difficult to mass-produce the device as an inexpensive device.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention is to provide a conventional mobile display in which the viewing angle is narrowed by a simple means to enhance the security of display information, and the mobile display can be easily used in any location. It is intended to realize a terminal.

[0007]

According to a first aspect of the present invention, a light emission angle limiting filter formed by integrating optical waveguides aligned and aligned in a thickness direction is disposed on a display element surface. The mobile display device has a narrow viewing angle.

In the above narrow viewing angle mobile display device, the light emission angle limiting filter aligns a large number of optical fibers each composed of a core and a cladding layer, and provides a light absorber in a gap between the optical fibers to slice the optical fiber in a direction perpendicular to the optical waveguide direction. A narrow-viewing-angle mobile display device characterized by being formed in a sheet shape.

Further, in the above narrow viewing angle mobile display device, the light emission angle limiting filter forms a large number of through holes serving as core portions in a sheet made of a clad layer material mixed with light absorber fine particles. A narrow viewing angle mobile display device characterized by being formed by injecting a material.

The light emission angle limiting filter desirably has a core that gradually widens from the filter incident surface to the filter exit surface, and a liquid crystal display device is suitable as the display device.

A second aspect of the present invention is a step of converging a plurality of optical fibers each having a core and a cladding layer, orienting the optical fibers in one direction to form a converged body, and providing a light absorber in a gap between the optical fiber converged bodies. From the step of injecting and solidifying to form a block of an optical fiber, and the step of cutting the block of the optical fiber in a direction perpendicular to the longitudinal direction of the optical fibers constituting the block to form a sheet. A method for producing a light emission angle limiting filter, characterized in that:

Further, a through hole serving as a core portion is formed in a sheet made of a clad material mixed with light absorber fine particles, or a clad layer material mixed with light absorber fine particles is injected into a replica mold of the core and solidified. A step of forming a clad layer sheet with through holes; and a step of filling and solidifying a core material into the through holes of the clad layer sheet with through holes to form an optical waveguide. It is a manufacturing method.

Further, a third aspect of the present invention is characterized in that a light emitting angle limiting filter formed by integrating optical waveguides aligned and aligned in the thickness direction is used on a display element surface. Mobile terminal device.

The light emission angle limiting filter used in the present invention transmits light in the thickness direction of the sheet, that is, in the direction perpendicular to the plane of the sheet, but the light guide of the optical waveguide does not. It has the property of not allowing light with an angle greater than the angle to pass, and a display device using this sheet-like body as a filter can see the display screen when viewed from the direction perpendicular to the surface, It has a feature that the display cannot be recognized when viewed from other directions.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION (Light Emission Angle Limiting Filter) A light emission angle limiting filter used in the present invention is a block-shaped body in which a plurality of optical fibers composed of a core and a clad are bundled, oriented in one direction, and fixed to each other. Is cut perpendicularly to the orientation direction of the optical fiber to obtain a sheet-like filter. FIG. 3 shows a schematic configuration.

The filter must have a thickness of at least one wavelength in order to effectively guide light. However, the filter has a thickness of 50 μm to 1 mm for ease of handling and manufacture.
Is preferable. The optical fiber used in the present invention may be a quartz glass optical fiber used for communication or the like, a multi-component glass optical fiber, or a plastic optical fiber, but these optical communication cables are optical fibers. Although the thickness of the cladding layer is increased in order to avoid attenuation as much as possible, in the present invention, a thin cladding layer, for example, a cladding thickness of about 10 μm is promoted in order to promote the loss of the cladding mode (wide-angle radiation). Having an optical fiber is sufficient.

The optical fiber of the present invention has a core layer and a cladding layer having mutually different refractive indexes, and the diameter of the core is about 10 to 100 μm. Particularly, those having a thickness of about 50 μm are preferable. Since the diameter of the core affects the resolution of the filter of the present invention, it is desirable that the diameter be as small as possible. That is, when the filter of the present invention is applied to a liquid crystal display, and when an optical fiber having a diameter larger than the resolution of the liquid crystal display is used, the filter lowers the resolution of the element, which is not preferable. Therefore, it is required to use an optical fiber having a core whose diameter is sufficiently smaller than the resolution of the liquid crystal display.

In the present invention, since the cladding of the adjacent fiber can be used, a cladding having a thickness of about 2 to 5 μm can be used. In a general optical fiber for optical communication, a clad layer having a thickness of about 30 μm is used. However, in the present invention, in order not to reduce the resolution of an image and to suppress a clad mode having a wide radiation angle. The clad layer is preferably thin.
However, if the thickness is excessively small, the optical fiber does not function as an optical fiber, which is not preferable.

As described above, quartz glass, multi-component glass, plastic, and the like can be used as the material of the optical fiber. In particular, the multi-component glass optical fiber and the plastic optical fiber are inexpensive and are preferably used in the present invention. Used. As a material of the plastic optical fiber, a plastic material containing polymethyl methacrylate as a main component is preferable because of high transparency in a visible region.

As a means for fixing the plurality of optical fibers, the clad layers may be bonded to each other using an adhesive, or the clad layers may be melted and bonded to each other. In any case, it is necessary that the clad layer maintain the difference in the refractive index from the core and maintain the light to be guided.

When glass or quartz optical fibers are joined by an adhesive, it is preferable to mix glass powder in the adhesive. Since such a material has a similar expansion coefficient to that of the optical fiber, it is possible to avoid a defect in which the adhesive is separated from the optical fiber due to heat.
Specifically, it is preferable to use an epoxy adhesive filled with a soda glass filler.

In order to manufacture the filter of the present invention by this method, approximately 4 million optical fibers are converged and oriented in one direction, and then formed into a block by pressing with a jig. The block-shaped body is housed in a vacuum container, evacuated and deaerated, then impregnated with a light-absorbing adhesive or an adhesive mixed with a light-absorbing material, dried and cured. After sufficient curing, the block body can be sliced using a cutting tool such as a wire saw to form a filter.

It is also possible to form a block by arranging about 2,000 optical fibers on a plane and laminating sheets fixed with a light absorbing adhesive or an adhesive mixed with a light absorbing material. .

The light absorbing material has a function of absorbing and attenuating non-guided light and cladding mode of an optical fiber, that is, light of a wide angle, to limit stray light of a filter. The light absorber may be a powder of metal, carbon, or the like, a dye, or the like, and may be used by being mixed with an adhesive.

Bonding by welding of the clad layer is effective when the melting temperature of the clad layer is relatively low, such as a plastic optical fiber or a multi-component glass optical fiber.
In order to manufacture the filter of the present invention by this method, about 4 million optical fibers are converged and orientated in one direction, and then formed into a block by pressing using a jig. Next, the block is heated to melt a part of the clad layer of the optical fiber, and is heated while applying pressure so that the clad layer material between the bound optical fibers is fused. After the heating is stopped and cooled, when the filling and solidification of the light absorbing material is completed, a sheet is cut out from the block body using a cutting tool such as a wire saw in a direction orthogonal to the orientation method of the optical fibers, thereby forming a filter. In this process, the heating temperature
This can be performed if the temperature is equal to or higher than the softening temperature of the clad material.
C. is preferable, and in the case of a plastic optical fiber, the range is preferably 100C to 300C.

In the above manufacturing method, the filling of the light absorbing material was performed after the fusion of the cladding layer. However, the optical fiber was coated with the light absorbing material in advance, and the space between the optical fibers bound by fusion was filled. May be heated while applying pressure so that the material of the clad layer and the light absorbing material in which the material is melted are filled. At the time of heating in this step, it is desirable to heat the block body in a vacuum atmosphere. This is because, if the clad is melted in a vacuum atmosphere, air is desorbed from the holes existing between the optical fibers, and a uniform melt without voids can be obtained.

In the above, an example has been shown in which the optical radiation angle limiting filter is bundled with an optical fiber and processed into a sheet shape, but this can also be formed by a method in which a core is injected by forming a through hole in a sheet-like clad. FIG. 5 is a view showing a schematic configuration of the light emission angle limiting filter of the present invention, and is an embodiment in which a through hole is provided in a clad sheet and a core material is injected. In this embodiment, the light absorber is dispersed in the clad material, instead of providing the light absorber in the gap between the optical fibers. In this case, since the sheet can be continuously processed, there is an advantage that the productivity is higher than the method of binding optical fibers. When a sheet-shaped clad is used, there is a method of providing a light absorber for each core, but if the light absorber fine powder is mixed and dispersed in advance in the sheet-shaped clad, there is an effect that processing can be performed at once. . The amount of the light absorber fine powder may be such that light does not propagate through the clad over a long distance. If added in a large amount, light guided through the core is also absorbed. For example, the ratio between the cladding material and the light absorbing material may be 5 to 20% by weight, and may be determined based on the filter thickness and the optical waveguide structure parameters.

FIG. 4 is a diagram showing a schematic configuration of a light radiation angle limiting filter according to the present invention, in which the optical waveguide of the filter is tapered, and the radiation angle of the emitted light is further restricted as compared with the embodiment of FIG. It is. In this embodiment, the light incident surface (FIG. 4)
The core is gradually widened from the lower surface to the light emitting surface (the upper surface in FIG. 4), and the radiation angle from the light emitting surface is narrowed by performing light propagation angle conversion inside the core. In this embodiment, since the cross section of light incident on the filter is narrow, it is necessary to consider a trade-off with light transmission efficiency.On the contrary, it is necessary to optimize the brightness and the display angle according to the application of the display to be applied. It is desirable that the optical waveguide be tapered in applications where information confidentiality is prioritized.

(Configuration of Display Apparatus) FIG. 1 is a sectional view showing an example of a display element of the present invention using the above filter. The device shown in FIG. 1 has a filter of the present invention adhered to the surface of a surface glass substrate of a liquid crystal panel.
In the drawing, reference numeral 1 denotes a backlight panel, which is used in a liquid crystal display element to improve display brightness and contrast. When a reflection type liquid crystal display element is used, a reflection plate is used instead of the backlight panel. In the figure, 2 and 9 are polarizing plates, and 3 and 8 are glass substrates. On the inner surface of this glass substrate, a transparent electrode layer 4,
7 are formed, and pixels are formed by this pattern. The glass substrate on which the transparent electrode is formed is sealed by a sealing member 5 and a liquid crystal material is sealed therein to form a liquid crystal element. The narrow viewing angle limiting filter of the present invention is formed on a polarizing plate on the surface. With this configuration, transmission of light other than light perpendicularly entering and exiting the liquid crystal display element surface can be restricted in the image of the liquid crystal display element.

FIG. 2 shows another embodiment. The display element of FIG. 2 uses the filter of the present invention instead of the glass substrate of the liquid crystal display element. That is, FIG.
, The backlight layer 1, the polarizing plate 2, the glass substrate 3,
The transparent electrode 4, the liquid crystal material 6, and the sealing material 5 are not different from the device of FIG. 1, but the filter 10 provided with the transparent electrode 7 on the other surface of the liquid crystal material layer 6 is arranged as shown in FIG.
This is different from the element described above. Such an element is required to have a surface smoothness as the filter layer 10, but is more preferable because it can be made thinner than the element of FIG. Further, there is no difference from the element of FIG. 1 in the characteristic of narrow viewing angle restriction.

In the above description, a liquid crystal display element has been described as an example of a display element.
For example, a plasma display, electroluminescence display, such as a light emitting diode display, such as a light-emitting type or permeability variation type, of course it can also be applied to a display device using other di spray <br/> ray device.

(Example: Production method of sheet-like body) An optical fiber having a core of 50 m and a core diameter of 50 m and a cladding diameter of 55 m having a core and a cladding layer of quartz glass was prepared. These were bundled, and carbon powder having an average particle size of 0.1 μm was added to the blackened epoxy resin to obtain an average particle size of 1 μm.
Was mixed to produce an adhesive. The content of glass powder in the adhesive was 80% by mass. The adhesive was impregnated into the above-mentioned bundled optical fibers and cured by heating to produce a block in which the optical fibers were oriented in one direction. Then, using a wire saw to a thickness of 250μ
m sheet-like body was manufactured. This sheet had a light transmittance of 75% or more in the direction perpendicular to the surface plane.
On the other hand, the transmittance of light in a direction inclined by 15 degrees with respect to the surface plane was about 5%.

This filter was adhered to the surface of a TFT color liquid crystal display device with a backlight of 11.4 inches using an adhesive. A standard pattern was displayed using this liquid crystal display device. As a result, there was no distortion of the image and the decrease in luminous intensity was suppressed to 25%, as compared with the case where no filter was attached, and it was within a range that could be sufficiently used practically. Also, as a result of observing the display from the direction perpendicular to the display element plane and at an angle of 15 degrees, the screen display information could not be recognized.

[0034]

As described above, when a display is constructed using the narrow viewing angle limiting filter of the present invention,
In the case where the luminous intensity of the display hardly decreases and the viewing angle differs even at a slight angle from the display screen, a display device excellent in security that cannot recognize display information can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a display device using a viewing angle limiting filter of the present invention.

FIG. 2 is a cross-sectional view of another display element using the viewing angle limiting filter of the present invention.

FIG. 3 is a view showing a viewing angle limiting filter of the present invention.

FIG. 4 is a view showing a viewing angle limiting filter of the present invention.

FIG. 5 is a view showing a viewing angle limiting filter of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Backlight panel 2,9 ... Polarizer 3,8 ... Glass substrate 4,7 ... Transparent electrode 5 ... Seal material 6 ... Liquid crystal material 10 ... Viewing angle restriction filter

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H042 AA02 AA03 AA07 AA26 2H046 AA02 AA09 AB01 AC02 AD13 AD16 2H091 FA24X FA41Z LA30 5G435 AA00 BB12 BB15 DD11 EE25 FF05 GG11 HH01 KK07 LL07

Claims (8)

[Claims] 1. A narrow viewing angle mobile display device, wherein a light emission angle limiting filter formed by integrating optical waveguides aligned and aligned in the thickness direction is arranged on the surface of a display element. 2. The light emission angle limiting filter according to claim 1, wherein a large number of optical fibers comprising a core and a cladding layer are aligned, a light absorber is provided in a gap between the optical fibers, and the optical fiber is sliced perpendicularly to the optical waveguide direction to form a sheet. The narrow-view-angle mobile display device according to claim 1, wherein: 3. The light emission angle limiting filter according to claim 1, wherein a plurality of through holes serving as core portions are formed in a sheet made of a clad layer material mixed with light absorber fine particles, and the core material is injected into the through holes. The narrow display angle mobile display device according to claim 1, wherein: 4. The narrow viewing angle mobile display according to claim 1, wherein the core of the light emission angle limiting filter gradually widens from the filter entrance surface to the filter exit surface. apparatus. 5. The mobile display device with a narrow viewing angle according to claim 1, wherein the display element is a liquid crystal display element. 6. A step of converging a plurality of optical fibers having a core and a cladding layer and orienting them in one direction to form a converged body, and injecting and solidifying a light absorber in a gap between the optical fiber converged bodies to form an optical fiber. Forming a block-like body, and cutting the optical fiber block-like body in a direction perpendicular to the longitudinal direction of the optical fibers constituting the block-like body, and forming a sheet-like body, Of manufacturing a light emission angle limiting filter. 7. A through hole serving as a core portion is formed in a sheet made of a clad material mixed with light absorber fine particles, or a clad layer material mixed with light absorber fine particles is injected and solidified in a replica mold of the core, and solidified. A light-emitting angle limiting filter, comprising: forming a cladding layer sheet with through holes; and filling and solidifying a core material into the through holes of the cladding layer sheet with through holes to form an optical waveguide. Production method. 8. A portable terminal device comprising a display element on which a light emission angle limiting filter formed by integrating optical waveguides aligned and aligned in the thickness direction is disposed on a display element surface.