WO2006027847A1

WO2006027847A1 - Display

Info

Publication number: WO2006027847A1
Application number: PCT/JP2004/013231
Authority: WO
Inventors: Takayuki Kasahara; Kenichi Haruhara
Original assignee: Kabushiki Kaisha Iiyama
Priority date: 2004-09-10
Filing date: 2004-09-10
Publication date: 2006-03-16

Abstract

A display wherein contrast is enhanced by reducing reflection of external light. A display (1) comprising a display body (70) outputting a linearly polarized light is provided, in front of the display body (70), with an optical filter (10) having at least a linear polarizing plate (20) such that the polarization axis of a linearly polarized light outputted from the display body (70) coincides with the transmission axis of the linear polarizing plate (20). Consequently, the display has enhanced contrast.

Description

Display device

Technical field

[0001] The present invention relates to a display device provided with an optical filter.

Background art

[0002] When a display device is used in a bright place where external light is incident, the contrast is lowered and the image is seen. This is because the external light incident on the display device is reflected on the display surface or inside of the display device to become reflected light, and is visually recognized as video information together with the emitted light of the display device power.

In recent years, display devices that display video information, such as notebook computers, touch panel displays, etc., are moving from CRT (Cathode Ray Tube) type to flat type using liquid crystal or plasma. In particular, display devices that use liquid crystals have a growing demand for low power consumption in addition to space saving.

As a method of reducing or diffusing the reflection of external light on the display surface of the display device, in the CRT type display device, a reflection reducing treatment layer such as an AR (anti-reflection) coating that coats the display surface with a plurality of thin films having different refractive indexes. Generally, it is necessary to provide On the other hand, in a display device using liquid crystal, an antiglare treatment layer such as a silica coat that generates fine irregularities is often provided on the display surface.

In addition, the display device reflects outside light not only on the display surface but also on the inner side of the display surface. Therefore, as a method of reducing the reflection of these external lights, there is a technique of attaching a protective film for a display surface having a light transmittance of 30% to less than 80% in the wavelength range of 450 to 800 nm to the display surface. It is disclosed in Patent Document 1.

According to this prior art, for example, when the visible light transmittance of the protective film for display surface attached to the display surface of the display device is 70%, the amount of reflected light from the display device of the external light is By passing through the protective film twice, it becomes 0.7 X 0.7 = 0.49, 49% of the case without the protective film for the display surface. As a result, the amount of light reflected by the display device is reduced, and the contrast can be improved. Furthermore, according to this prior art, the protective film for the display surface is a laminate of a base film and a rubber film, and the impact resistance can be improved by adhering it directly to the display surface.

Patent Document 2 discloses a structure of an optical filter incorporated in an LCD module in a display device.

According to this conventional technique, it is possible to improve the contrast by forming an integrated LCD module in which a colored glass having wavelength selectivity and a polarizing plate are provided in the LCD module. The LCD module is an LCD panel having a polarizing plate, a package component that also has a knocklight and the like.

Patent Document 1: Japanese Patent Laid-Open No. 2001-083886

Patent Document 2: Japanese Patent Laid-Open No. 7-253505

Disclosure of the invention

However, according to the protective film for display surface according to the prior art, the amount of light emitted from the display device passes through the protective film for display surface once in order to reduce the light transmittance over the entire visible light region. As a result, there is a problem that the brightness of the display device itself is lowered.

Further, the protective film for display surface according to Patent Document 1 is a laminate having a thickness of several hundreds / zm—several mm, in which a base film and a rubber film are laminated, and is directly attached to the display surface. For this reason, external forces and impacts applied to the protective film for the display surface may propagate to the display surface and damage the display device.

The present invention has been made to solve such problems, and the object of the present invention is to reduce the amount of reflected light without reducing the amount of light emitted from a display device that emits linearly polarized light. An object of the present invention is to provide an optical filter capable of improving the contrast of a display device and a display device having improved contrast.

Note that the optical filter according to the present invention is not provided in the LCD module inside the display device body as in Patent Document 2, but is provided outside the LCD module.

A display device according to the present invention comprises a display device body that emits linearly polarized light. The optical filter having at least a linearly polarizing plate is provided on the front surface of the display device body so that the polarization axis of the linearly polarized light emitted from the display device body and the transmission axis of the linearly polarizing plate coincide with each other. It is characterized by that.

According to the present invention, the external light incident on the display device main body that emits linearly polarized light absorbs the polarized light component that is orthogonal to the transmission axis of the linearly polarizing plate when transmitted through the optical filter. Then, the external light that has passed through the optical filter is reflected by the display device main body and is emitted to the outside again through the optical filter. In other words, when the external light is first transmitted through the optical filter, only the polarization component parallel to the transmission axis of the linear polarizing plate is transmitted. It is about half of. On the other hand, the output light of the display device main body that emits linearly polarized light is hardly reduced by the optical filter because the transmission axis of the linearly polarizing plate is parallel to the polarization direction of the emitted light. That is, the optical filter hardly causes a decrease in luminance of the display device body itself. As described above, according to the present invention, contrast intensity can be improved by reducing the intensity of reflected light of external light and maintaining the intensity of light emitted from the display device main body as it is.

The optical filter is characterized by having a linearly polarizing plate and an optical member that does not have polarization and transmits light.

The optical member may include one or both of a resin plate and a glass plate.

By including the optical member in the configuration of the optical filter in this way, the strength of the optical filter can be increased.

Furthermore, the optical member may have a function of a touch panel. Thus, by providing the optical member on the front surface of the display device main body that emits linearly polarized light, the display device can have a function as a touch panel.

Further, the optical filter may be provided with at least one of a surface treatment layer of a reflection reduction treatment layer, an antiglare treatment layer, a hardening treatment layer, a conductive treatment layer, or an antifouling treatment layer. Thereby, the display device can improve or have low reflectivity, antiglare property, scratch resistance, conductivity, or antifouling property.

The optical filter is provided with the reflection reduction treatment layer on both sides, Experiments have shown that the contrast is improved.

Further, it has been experimentally found that the optical filter further improves the contrast by disposing the linearly polarizing plate and the optical member in the center and providing the reflection reduction processing layer on both surfaces thereof.

[0004] Effect of the Invention

As is clear from the above description, according to the present invention, the reflection of external light is reduced compared to the case where no optical filter is provided without reducing the emitted light from the display device body that emits linearly polarized light. The contrast of the display device can be improved.

In addition, according to the present invention, the contrast is increased in the direction of darkening the whole, which is easy on the eyes.

Brief Description of Drawings

FIG. 1 is a cross-sectional view showing an example of the present invention.

FIG. 2 is an explanatory diagram showing experimental conditions for verifying the effect of the AR coating and the optimum structure of the optical filter.

FIG. 3 is a table showing the results of experiments verifying the effects of AR coating.

FIG. 4 is a table showing the results of an experiment for verifying the optimum structure of an optical filter.

BEST MODE FOR CARRYING OUT THE INVENTION

[0006] Hereinafter, a display device according to the present invention will be described based on the embodiments shown in the drawings.

In the following description, the side facing the liquid crystal display device, which is the display device main body that emits the linearly polarized light of the optical filter, is the inside, and the other is the outside.

FIG. 1 shows a sectional view of a display device 1 which is an embodiment of the present invention. The display device 1 includes an optical filter 10 and a liquid crystal display device (display device body in the claims) 70. The LCD module inside the liquid crystal display device 70 is provided with a polarizing plate (not shown), and the liquid crystal display device 70 emits linearly polarized light.

The optical filter 10 includes a surface treatment layer 40, a linearly polarizing plate 20, an optical member 32, and a surface treatment layer 42 arranged in this order from the liquid crystal display device side (inner side). Installed in front of.

The relationship between external light and outgoing light in the display device 1 will be described. The polarization direction of the outgoing light 60 from the liquid crystal display device 70 is parallel to the transmission axis of the linear polarizing plate 20, and the linear polarizing plate 20 hardly reduces the transmitted light amount of the outgoing light 60. On the other hand, the external light 50 has a polarization component almost equal in both directions parallel and perpendicular to the transmission axis of the linear polarizing plate 20, and is transmitted through the linear polarizing plate 20. The polarized light component orthogonal to the axis is absorbed and becomes transmitted external light 52 that is approximately half the amount of external light 50.

The transmitted external light 52 is reflected by the liquid crystal display device 70 to become reflected light 54. The reflected light 54 is again transmitted through the linear polarizing plate 20 and is emitted from the optical filter 10 as transmitted reflected light 56. Hereinafter, each configuration of the optical filter 10 will be described.

The linearly polarizing plate 20 includes a polarizer 24 and optical films 26 and 28 provided on both the inside and outside of the polarizer 24.

The optical films 26 and 28 made of a film-like resin having a thickness of several to several hundred m are adhered to both the inner and outer surfaces of the polarizer 24 to prevent the polarizer 24 from being damaged.

The optical member 32 having a thickness of several millimeters and having a glass plate force having no polarizing property is bonded to the outside of the linear polarizing plate 20 and forms a part of the configuration of the optical filter 10, thereby forming the optical filter 10. The strength of the display device 1 provided with is improved.

The surface treatment layer 40 formed of a reflection reduction treatment layer and provided inside the linear polarizing plate 20 reduces reflection of reflected light 54 (external light reflected light) and outgoing light 60 on the inner surface of the linear polarizing plate 20. . The smaller the reflectance of the surface treatment layer 40, which is the reflection reduction treatment layer, is, the lower the reflection at the surface treatment layer 40 is, and the emission light 60 is hardly reduced upon transmission through the optical filter 10. Therefore, the lower the reflectance of the surface treatment layer 40, the more the decrease in the luminance of the liquid crystal display device 70 can be suppressed.

Further, the surface treatment layer 42 formed of a reflection reduction treatment layer and provided on the outer side of the optical member 32 reduces the reflection of the external light 50 on the outer surface of the optical member 32.

Thus, in this embodiment, the liquid crystal display device 70 of the external light 50 is compared with the case where the optical filter 10 that hardly reduces the emitted light 60 from the liquid crystal display device 70 by the linearly polarizing plate 20 is not provided. The reflected light 54 from the light source is reduced. Thereby, the transmitted / reflected light 56 is reduced, the contrast of the display device 1 is improved, and the image can be easily viewed.

Further, by providing the optical member 32, the strength of the display device 1 can be improved. Become.

Furthermore, by providing the surface treatment layer 40 made of the reflection reduction treatment layer, it is possible to suppress the decrease in the luminance of the display device 1, and similarly, by providing the surface treatment layer 42 made of the reflection reduction treatment layer, the display device 1 It becomes possible to further improve the contrast of 1. Further, when manufacturing such an optical filter 10, it is necessary to prevent air from entering between the layers. For this reason, when bonding each layer, use an adhesive glue to push out the air!

In the above-described embodiment, the reflected light 54 reflected by the transmitted external light 52 on the liquid crystal display device 70 is a combination of the display surface 72 of the liquid crystal display device 70 and the reflected light inside (not shown).

In the above-described embodiments, the optical member is a glass plate, but a resin plate may be used for the optical member. As the resin board, an acrylic resin resin that is light in weight and low in processing cost and excellent in impact resistance is preferable.

The optical member is composed of one or more resin plates and glass plates, and the stacking order and the number of the optical members are not limited.

The linear polarizing plate generally has the structure shown in the examples, and a film-like polarizer formed by stretching PVC (polybulal alcohol) is sandwiched between film-like optical films made of TAC (triacetyl cellulose). A film-like one is known. The optical film made of TAC functions as a protective layer that prevents the polarizer from being scratched. This improves the workability when handling the linearly polarizing plate, and the effect is great even when the display device according to the present invention is manufactured.

The thickness of the optical film made of TAC is generally several tens to several hundreds; about zm, and the strength of the display device can be improved only by the film-like linearly polarizing plate having the structure shown in the examples. Not enough.

Furthermore, by using an optical member having a touch panel function and combining it with a linear polarizing plate, a display device capable of improving contrast and strength can be obtained, and a touch panel function can be provided.

The touch panel comes in various types, such as a resistive film method, an ultrasonic method, a capacitance method, and an electromagnetic induction method. However, the optical filter according to the present invention can be configured without being limited to the touch panel system. The touch panel detects position information and the like by contact with a finger or a dedicated pen, and the touch panel itself has sufficient strength to withstand such contact.

Further, in the above-described embodiments, only the reflection reduction treatment layer has been described as the surface treatment layer, but as the surface treatment layer, at least one of an antiglare treatment layer, a curing treatment layer, a conductive treatment layer, and an antifouling treatment layer is used. And can be provided on any surface of the linearly polarizing plate, the optical member, and the touch panel.

Further, the surface treatment layer may be formed by stacking, and the stacking order, the number of layers, and the type thereof are not limited. For example, by providing a conductive treatment layer on the optical member and further providing a cured treatment layer thereon, it is possible to improve the conductivity of the optical member provided with the surface treatment layer and improve the surface strength. . However, the effect can be obtained or can be easily obtained depending on the kind of the surface treatment layer.

As the reflection reduction processing layer, for example, there is a layer formed by coating the surface of an optical filter with two types of thin films having different refractive indexes, which improves low reflectivity. Thereby, reflection on the surface of the optical filter is reduced, and the contrast of the display device is improved.

The antiglare layer includes, for example, a layer formed by spraying silica on the surface of an optical filter and baking it to generate fine irregularities on the surface, and has antiglare properties. Thereby, the specular reflection on the surface of the optical filter is reduced, the reflection of external light is reduced, and the contrast of the display device is improved.

As a hardening process layer, there exists a thing comprised by coating the surface of an optical filter with acrylic resin, for example, and scratch resistance is improved. As a result, the hardness of the surface of the optical filter is improved and the surface becomes scratched.

As the conductive treatment layer, for example, there is a layer formed by coating a conductive metal oxide on the surface of the optical filter, which improves the conductivity. Thereby, an electromagnetic wave shield is formed on the surface of the optical filter, and electromagnetic waves radiated from the display device are reduced. As the antifouling treatment layer, for example, there is a layer constituted by vacuum-depositing a fluorine chemical on the surface of the optical filter, which improves the antifouling property. This makes it easier to wipe off dirt such as fingerprints adhering to the surface of the optical filter.

The liquid crystal display device 70 (display device body) has a polarizing plate provided inside the LCD module to emit linearly polarized light. Therefore, the transmission axis of the linear polarizing plate of the optical filter must be arranged so as to be parallel to the polarization axis of the outgoing light of the liquid crystal display device 70. In particular, there are various types of polarization axes of emitted light, such as 0 °, 45 °, and 90 °, which need attention.

That is, before attaching the optical filter to the liquid crystal display device 70, information on the direction of the transmission axis of the polarizing plate provided in front of the LCD module and the transmission axis of the linear polarizing plate of the optical filter is required.

The optical filter is preferably configured so as to be easily attached to and detached from the liquid crystal display device 70 that emits linearly polarized light. As a result, the optical filter can be easily replaced when it is desired to change the specification of the optical filter or when the optical filter is contaminated.

When an optical filter is provided in front of the liquid crystal display device 70 that emits linearly polarized light, the distance between the optical filter and the liquid crystal display device 70 that emits linearly polarized light is not limited.

Next, an experiment was conducted on the effect of AR coating. Figure 2 outlines the experimental conditions.

In the experiment, an incandescent bulb was placed at a position where the central axial force of the liquid crystal display device 70 was off 45 ° so that the illuminance at the center of the liquid crystal display device 70 would be 500 lux. At this time, the distance from the front surface of the liquid crystal display device 70 to the incandescent bulb was 100 cm.

When a luminance measuring device is arranged on the central axis of the liquid crystal display device 70 that is 50 cm away from the front surface of the liquid crystal display device 70, and (1) nothing is provided on the front surface of the liquid crystal display device 70, (2) the liquid crystal display device The luminance of the liquid crystal display device 70 was measured with three patterns: when a simple acrylic plate was provided on the front of 70, and (3) when an AR coating was provided on both sides of the acrylic plate. Incidentally, the contrast is calculated by calculating the ratio of the brightness when the display of the liquid crystal display device 70 is all white and the brightness when it is all black (all white brightness Z all black brightness).

Figure 3 shows the results of the above experiment. From this result, the contrast is lower when a simple acrylic plate is provided on the front of the LCD 70 than when nothing is provided. When both sides of the acrylic plate are AR-coated, only a single acrylic plate is used. It was found that the contrast was improved.

Next, an environment similar to the actual office environment is set, and an experiment is performed on the change in contrast when the configuration of the optical filter is changed variously. The outline of the experimental conditions is the same as that shown in Fig. 2.

However, unlike Fig. 2, the external light is changed to fluorescent light instead of using incandescent light. The illuminance at the center of the monitor at this time was 830 lux.

When a luminance measuring device is arranged on the central axis of the liquid crystal display device 70 that is 50 cm away from the front surface of the liquid crystal display device 70, and (1) nothing is provided on the front surface of the liquid crystal display device 70, (2) the liquid crystal display device When an acrylic plate with AR coating on both sides of an acrylic plate is installed on the front side of 70, (3) From the side of the liquid crystal display device 70 on the front side of the liquid crystal display device 70, the AR coating, linear polarizing plate, glass plate, and AR coating When the optical filters arranged in order were provided, (4) the optical filter arranged in the order of AR coating, glass plate, linear polarizing plate, AR coating was provided on the front surface of the liquid crystal display device 70 from the liquid crystal display device 70 side. In this case, the brightness of the liquid crystal display device 70 was measured with the following four patterns. Incidentally, the contrast is also calculated by calculating the ratio of the brightness when the display of the liquid crystal display device 70 is all white and the brightness when it is all black (all white brightness Z all black brightness).

Figure 4 shows the experimental results.

The results show that the luminance power when the monitor is OFF.When the front surface of the liquid crystal display device 70 is not provided, and when both are provided with AR coating on both sides of the acrylic plate ((1) and (2)) In comparison, when an optical filter having a linear polarizing plate is provided ((3) and (4)), it is approximately half.

From this result, as described above, the reflected light intensity when external light is input to the linear polarizing plate and reflected by the liquid crystal display device 70 to become transmitted reflected light is not provided with the linear polarizing plate! /, I was able to verify the explanation about half of the case.

Further, from the results of FIG. 4, the optical filter having the linearly polarizing plate and the optical member (glass plate) is compared with the case where no optical filter is provided and the case where the AR coating is provided on both sides of the simple acrylic plate. As a result, it was found that the contrast was improved to about 2 times. Further, in an optical filter having a linearly polarizing plate and an optical member (glass plate), when the order of the linearly polarizing plate and the optical member (glass plate) is changed, the linearly polarizing plate becomes a liquid crystal display device.

It was also found that the contrast when the optical member (glass plate) is arranged closer to 70 is better than the case where the optical member (glass plate) is located closer to the liquid crystal display device 70 and closer to the liquid crystal display device 70.

By comparing the experimental results in Fig. 3 with the experimental results in Fig. 4, the following points were also found.

That is, comparing the results of (2) in Fig. 3 with the results of (2) in Fig. 4, the intensity of external light is larger, and the experiment in Fig. 4 has better contrast. The effect is considered to increase as the value increases. In addition, from these results, since the intensity of external light is usually increased when the screen of the display device is faced upward, it is considered that the effect increases as the screen is faced upward, for example, when used for a touch panel. It is done.

Such an improvement in contrast is also effective when viewed from an oblique direction as viewed only from the front of the display device. That is, a clear and high-contrast image can be provided in a wider angle range than before.

While the present invention has been described in detail with reference to preferred embodiments, it is needless to say that the present invention is not limited to these embodiments, and many modifications can be made without departing from the spirit of the invention.

Claims

The scope of the claims

[1] In a display device comprising a display device body that emits linearly polarized light,

An optical filter having at least a linearly polarizing plate is provided on the front surface of the display device body so that the polarization axis of the linearly polarized light emitted from the display device body and the transmission axis of the linearly polarizing plate coincide with each other! / ヽA display device.

2. The display device according to claim 1, wherein the optical filter includes a linearly polarizing plate and an optical member that does not have polarization and transmits light.

3. The display device according to claim 2, wherein the optical member includes one or both of a resin plate and a glass plate.

4. The display device according to claim 2, wherein the optical member has a touch panel function.

[5] For the optical filter! 5. At least one surface treatment layer of a reflection reduction treatment layer, an antiglare treatment layer, a hardening treatment layer, a conductive treatment layer, or an antifouling treatment layer is provided. The display device according to any one of the above.

6. The display device according to claim 5, wherein the optical filter is provided with the reflection reduction processing layer on both surfaces.

7. The display device according to claim 6, wherein the optical filter is arranged around the linearly polarizing plate and the optical member, and the reflection reduction processing layer is provided on both surfaces thereof.