JP5162805B2 - Electroluminescence display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is an electroluminescent display which is one of self-luminous type display device (hereinafter, referred to as "EL display") is intended to relate to. Specifically, the present invention relates to an EL display that is easy to see.
[0002]
[Prior art]
EL displays are attracting attention as display devices because of their low power consumption, thinness, and light weight. Since this EL display is a self-luminous type, it has a wide viewing angle, has high-speed reactivity that can handle moving images, and can be used in a wide temperature range. It has been. Conventional EL displays generally employ a configuration in which a light emitting layer made of phosphor is interposed between a transparent electrode and a metal flat electrode, but incident light from the outside is reflected by the metal flat electrode. Therefore, there is a problem that the display itself is difficult to see due to the reflected light.
[0003]
Therefore, in order to reduce these reflected lights, a configuration in which a colored filter for controlling the amount of light transmission is arranged on the front side of the EL display and a configuration in which a circularly polarizing plate for absorbing the reflected light is also arranged on the front side are proposed. Has been. By adopting these configurations, it is possible to reduce the reflected light from the metal planar electrode. The circularly polarizing plate may be directly bonded to the surface of the display body. However, when the front panel is provided on the display body, the circularly polarizing plate is often bonded to the front surface or the back surface of the front panel.
[0004]
An example in which such a circularly polarizing plate is arranged on the front plate is shown in a schematic cross-sectional view in FIG. The EL display 1 in this example includes a display body 2 and a front plate 3 provided on the front side (observer side) thereof. The display body 2 is composed of a transparent electrode 4 on the front side and a metal electrode 6 on the back side across the light emitting unit 5, and the light emitting unit 5 emits light by energization between the transparent electrode 4 and the metal electrode 6. , To display images. The front plate 3 provided on the front side of the display body 2 is obtained by attaching a circularly polarizing plate comprising a linearly polarizing plate 8 and a λ / 4 retardation plate 9 to a transparent substrate 7. Hereinafter, the λ / 4 retardation plate may be simply referred to as a λ / 4 plate.
[0005]
Here, an operation mechanism of the front plate 3 in the EL display having the configuration shown in FIG. 1 will be described with reference to FIGS. These drawings are used to schematically explain the state of transmission and reflection of external incident light and the state of transmission and reflection of electroluminescence (hereinafter referred to as “EL light”) that is light emitted from the light-emitting portion 5. The numbers without the leader line are the light amounts at each stage with respect to the initial light amount, expressed in% units, and “%” is omitted.
[0006]
First, when the light reflectance at the reflecting surface of the metal electrode 6 is 100%, as shown in FIG. 2A, about 50% of the incident light from the outside is circularly polarized by the front plate 3. The remaining light is absorbed by the linearly polarizing plate 8. The entire amount of the circularly polarized light after passing through the front plate 3 is reflected by the reflecting surface of the metal electrode 6. At that time, the circularly polarized light is converted into reversely polarized circularly polarized light and further passes through the λ / 4 plate 9. All are absorbed by the linearly polarizing plate 8. Therefore, finally, almost 100% of incident light is absorbed by the front plate 3. That is, in this case, the reflectance of external incident light is ideally 0%.
[0007]
On the other hand, as shown in FIG. 2B, about 50% of the EL light from the light emitting portion 5 is transmitted through the front plate 3 and about 4% is reflected on the surface of the front plate 3. The total amount of the light thus reflected is reflected by the reflecting surface of the metal electrode 6 and reaches the front plate 3, and about half (about 2% of the generated EL light) is transmitted through the front plate 3. Thus, about 4% of the light reaching the front plate 3 (about 0.16% with respect to the generated EL light) is reflected. The light reflected by the front plate 3 repeats a reflection cycle between the reflective surface of the metal electrode 6 and the front plate 3 in the same manner as described above.
[0008]
By the way, in general, when the light is reflected by the reflecting surface of the metal electrode 6, a light loss is caused by the light emitting unit 5. For example, as a result of the loss, the light reflectivity at the reflecting surface of the metal electrode 6 is about For example, as shown in FIG. 3A, about 50% of the incident light from the outside is transmitted as circularly polarized light by the front plate 3, and the rest is a linearly polarizing plate 8 as shown in FIG. To be absorbed. About 20% of the circularly polarized light after passing through the front plate 3 is reflected by the reflecting surface of the metal electrode 6, that is, about 10% of the initial light quantity is converted to reversely polarized circularly reflected and reflected. All of the reflected light is absorbed by the linearly polarizing plate 4 by passing through the λ / 4 plate 9. Therefore, finally, almost 100% of the external incident light is absorbed by the front plate 3. That is, also in this case, the reflectance of external incident light is ideally 0%.
[0009]
On the other hand, as shown in FIG. 3B, about 50% of the EL light from the light emitting section 5 is linearly polarized light and is transmitted through the front plate 3, and about 4% is reflected from the surface of the front plate 3. . The light reflected here is
About 20% of the light is reflected by the reflecting surface of the metal electrode 6, and about 0.8% (= 4% × 0.2) of the generated EL light reaches the front plate 3 again. About 0.4% of the generated EL light is transmitted as linearly polarized light, while about 4% (about 0.032% of the generated EL light) is reflected. Thereafter, the reflection cycle is repeated between the reflection surface of the metal electrode 6 and the front plate 3 by the same mechanism.
[0010]
[Problems to be solved by the invention]
Thus, even when the light reflectance at the reflecting surface of the metal electrode 6 is 20%, the primary EL light is transmitted about 50% and the secondary EL light is transmitted about 0.4%. Observed as a double image. That is, in the configuration in which the circularly polarizing plates 8 and 9 are provided on the front plate 3, although the reflected light generated from the back surface of the front plate 3, the surface of the display body 2, and the surface of the metal electrode 6 can be reduced, the light is emitted. There is a problem that EL light is reflected on the back surface of the circularly polarizing plate (front plate), and the returned EL light is re-reflected by the metal flat electrode, resulting in multiple display.
[0011]
[Means for Solving the Problems]
As a result of diligent research to solve the above problems, to provide an EL display that reduces reflected light and improves multiple reflection of display, a layer having an antireflection function is provided on the display body side of the front plate. As a result, it was found that multiple shots of display can be prevented and visibility can be improved, and the present invention has been achieved.
[0012]
That is, the present invention comprises a display body having a transparent electrode on the front side and a metal electrode on the back side across the light emitting portion, and a front plate having a circularly polarizing plate disposed on the front side thereof. The front plate and the front plate are disposed with a gap of 0.1 to 3 mm, and provide an EL display in which the display side surface of the front plate is subjected to anti-reflection treatment. Here, the process for the anti-reflection to be applied to the display side surface of the front plate, it can be reflection preventing film For example, also, it may be, for example, anti-glare treatment. The circularly polarizing plate constituting the front plate can be composed of a linearly polarizing plate and a λ / 4 plate, or may have a plurality of retardation plates and a combination of the linearly polarizing plate. .
[0013]
In this specification, a front plate suitable for use in the above-described EL display is also disclosed . The front plate has a circularly polarizing plate, and the surface on the display body side is subjected to anti-reflection treatment. Is. Specifically, a circularly polarizing plate is laminated on a transparent substrate, and the surface of the circularly polarizing plate opposite to the surface facing the transparent substrate is subjected to antireflection treatment. It can be configured so that the treated surface is on the display body side, and a circularly polarizing plate is laminated on the transparent substrate, and antireflection is applied to the surface of the transparent substrate opposite to the surface facing the circularly polarizing plate. It is also possible to configure such that the surface subjected to the antireflection treatment is on the display body side.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The light emitting part constituting the EL display of the present invention may be an inorganic substance or an organic substance, and the effect of the present invention is not changed. Lower portion electrode, Ru is a metal.
[0015]
The circularly polarizing plate is generally composed of a linearly polarizing plate and a λ / 4 plate. For example, a linearly polarizing plate obtained by adsorbing iodine or a dichroic dye on a stretched polyvinyl alcohol film is used. The linear polarizing plate preferably has a polarization degree of 90% or more. If the degree of polarization is less than that, the effect as a circularly polarizing plate becomes poor. The λ / 4 plate is not particularly limited, but can be obtained by uniaxially stretching a polymer film such as polyvinyl alcohol, polycarbonate, polysulfone, polyarylate, cellulose resin, norbornene resin, or olefin resin. The value of the wavelength λ is generally adjusted to 550 nm, which is high in human visibility, but the contrast can be increased even in accordance with the emission wavelength of the EL display.
[0016]
On the other hand, in order to obtain good antireflection performance not only at a specific wavelength λ but also over a wide wavelength range, a combination of a plurality of types of retardation plates and a reverse wavelength dispersion comprising a copolymer of a plurality of types of monomers It is effective to use a λ / 4 plate having characteristics and combine it with a linearly polarizing plate. For example, as disclosed in Japanese Patent Application Laid-Open No. 11-183723, a circularly polarizing plate in which a linearly polarizing plate, a λ / 2 plate and a λ / 4 plate are laminated in this order, or a feature related to the prior application of the present applicant. Examples thereof include a circularly polarizing plate obtained by combining the reverse wavelength dispersion retardation plate described in Japanese Patent Application No. 2001-32041 with a linearly polarizing plate.
[0017]
FIG. 4 is a schematic cross-sectional view showing an example of an EL display according to the present invention. In this figure, the structure of the display body 2 is the same as the example of ( A) and the example of (B), and between the transparent electrode 4 made of a conductive film such as indium tin oxide (ITO) and the metal flat electrode 6. The light emitting part 5 made of a phosphor light emitting layer is integrated and integrated. Such a configuration is known as a basic configuration of an EL display. When a predetermined voltage is applied between the transparent electrode 4 and the metal flat electrode 6, electroluminescence emission is performed from the phosphor of the light emitting unit 5, and the desired configuration is obtained. Is displayed.
[0018]
In the present invention, the front plate 3 is arranged on the front side (observer side) of such a display body 2. In the example of FIG. 4 (A), the front plate 3 is a transparent substrate 7 in which a circularly polarizing plate comprising a linearly polarizing plate 8 and a λ / 4 plate 9 is laminated on the linearly polarizing plate 8 side, and An antireflection film 10 is formed on the surface of the display body 2, that is, the surface opposite to the surface of the λ / 4 plate 9 bonded to the linearly polarizing plate 8 in this example. On the other hand, in the example shown in FIG. 4B, a circularly polarizing plate composed of a linearly polarizing plate 8 and a λ / 4 plate 9 is laminated on the transparent substrate 7 to form the front plate 3, but in this example, The transparent substrate 7 is disposed on the display body 2 side, and thus is laminated on the transparent substrate 7 on the λ / 4 plate 9 side of the circularly polarizing plate. And the antireflection film 10 is formed in the display body 2 side of this front board 3, the surface on the opposite side to the bonding surface to (lambda) / 4 board 9 of the transparent substrate 7 in this example.
[0019]
Thus, in the present invention, it is important that the surface on the side of the front plate 3 facing the display body 2 is subjected to antireflection treatment. In the two examples shown in FIG. Treatment for antireflection is achieved by the antireflection film 10.
[0020]
In the front plate 3, a transparent substrate 7, a linear polarizing plate 8, and a λ / 4 plate 9 are laminated and integrated. In order to perform such lamination and integration, for example, these may be bonded using a transparent and optically isotropic adhesive such as an acrylic adhesive. As shown in FIG. 4A, the stacking order may be the order of the λ / 4 plate 9, the linearly polarizing plate 8, and the transparent substrate 7 from the display body side, or the transparent substrate 7 is optically isotropic. If it is a simple material, the transparent substrate 7, the λ / 4 plate 9, and the linear polarizing plate 8 may be used in this order, as shown in FIG. Further, the λ / 4 plate 9, the transparent substrate 7, and the linear polarizing plate 8 may be laminated in this order . As the transparent substrate 7, a glass plate, an optically transparent resin plate, or the like can be used. In addition, the transparent substrate 7 is comprised with a touchscreen, and the display apparatus containing this can also be used as a touchscreen type display apparatus.
[0021]
Hereinafter, the operation mechanism of the front plate will be described with reference to FIG. 5, taking the EL display shown in FIG. 4A as an example. FIG. 5 is a diagram for schematically explaining the state of transmission and reflection of external incident light, and the state of transmission and reflection of EL light, which is light emitted from the light emitting unit 5. FIG. As in FIG. 3, the numbers without the leader lines indicate the light amount at each stage with respect to the initial light amount in% units, and “%” is omitted.
[0022]
Here, as described above with reference to FIG. 3, as an example, the case where the light reflectance at the reflecting surface of the metal electrode 6 is about 20% as a result of the light loss in the light emitting unit 5. explain. In the case where the antireflection film 10 is formed on the display body side surface of the front plate as shown in FIG. 4A, if the reflectance at the antireflection film 10 is about 0.5%, the incident light from the outside is as shown in FIG. As shown in FIG. 5 (A), about 50% of the front plate 3 is transmitted as circularly polarized light, and the rest is absorbed by the linearly polarizing plate 8. About 20% of the circularly polarized light after passing through the front plate 3 is reflected by the reflecting surface of the metal electrode 6, that is, about 10% of the initial light quantity is converted to reversely polarized circularly reflected and reflected. All the reflected light is absorbed by the linear polarizing plate 8 by passing through the λ / 4 plate 9. Therefore, finally, almost 100% of the external incident light is absorbed by the front plate 3. That is, the reflectance of external incident light is ideally 0%.
[0023]
On the other hand, as shown in FIG. 5B, about 50% of the EL light from the light-emitting portion 5 is linearly polarized light and is transmitted through the front plate 3. About 0.5% is reflected. About 20% of the reflected light is reflected by the reflecting surface of the metal electrode 6, and about 0.1% (= 0.5% × 0.2) of the generated EL light reaches the front plate 3 again. Here, about 50% (about 0.05% with respect to generated EL light) is transmitted as linearly polarized light, while about 0.5% (about 0.0005% with respect to generated EL light) is transmitted. reflect. Thereafter, the reflection cycle is repeated between the reflection surface of the metal electrode 6 and the front plate 3 by the same mechanism.
[0024]
Thus, when the light reflectance at the reflecting surface of the metal electrode 6 is 20%, the primary EL light is transmitted 50% and the secondary EL light is transmitted 0.05%. Little image is observed. FIG. 5 illustrates the mechanism of transmission and reflection of external incident light and transmission and reflection of generated EL light based on the example shown in FIG. 4A. The example shown in FIG. But it can be explained in exactly the same way. Further, the reflectivity and transmissivity shown here are temporarily set for ease of understanding, and the present invention is not limited to these values.
[0025]
The antireflection film 10 formed on the display body side surface of the front plate 3 is composed of one or more layers less than the optical film thickness, and is formed by a method such as sputtering, vapor deposition, ion plating, coating, etc. It is preferable that the design has a particularly low reflectance at a wavelength of. A typical example of such an antireflection film is a layer made of an inorganic metal oxide or inorganic metal fluoride. In the case of forming the antireflection film 10, it is preferable to form a hard coat layer on the base because of excellent handling properties such as scratch resistance.
[0026]
So far, an example of forming an antireflection film as an antireflection treatment has been described. However, the same effect can be expected by applying an antiglare treatment to the display body side surface of the front plate. Anti-glare treatment here refers to a process of scattering incident light by forming fine irregularities on the surface to reduce the reflectance, and such irregularities are directly applied to the surface of the phase difference plate or the surface of the transparent substrate. it may also be formed, on the surface in need, it is also possible to focus pasting a transparent film anti-glare treatment has been performed. Concavities and convexities for anti-glare are, for example, a method of applying an ultraviolet curable resin and curing it by irradiating it with ultraviolet light while pressing the embossed mold on it, or pressing an embossed mold on a thermoplastic transparent film in a heated state. It can be formed by a method or the like.
[0027]
4 and 5 show an example in which the circularly polarizing plate is composed of the linearly polarizing plate 8 and the λ / 4 plate 9, but the present invention is not limited to this example. For example, as described above A plurality of retardation plates can be used and combined with a linear polarizing plate to form a circular polarizing plate. In this case, in the example shown in FIG. 4, the circularly polarizing plate constituted by the linearly polarizing plate 8 and the λ / 4 plate 9 is replaced with one constituted by a plurality of retardation plates and linearly polarizing plates. At that time, the antireflection film 10 may be provided on the display body 2 side as shown in this figure, or antiglare treatment may be applied thereto.
[0028]
The display body 2 and the front plate 3, in view of Table示体protected, are arranged with a gap of about 0.1 to 3 mm.
[0029]
Various other additional functions can also be imparted to the observer side of the front plate. For example, it stuck a transparent protective film for preventing scratching can often a useful provided directly hard coat layer. Further, in order to improve the antiglare property, an antiglare layer for irregularly reflecting external light by forming fine irregularities on the surface or an antireflection layer can be provided. Furthermore, a transparent protective film on which an antireflection layer is formed can be bonded.
[0030]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these Examples. In the examples, the measurement wavelength of the retardation value is 550 nm.
[0031]
Example 1
A 1 mm thick glass plate was bonded with Sumitomo Chemical's linear polarizing plate “Sumikaran STW822A” with an adhesive, and on the linear polarizing plate, Sumitomo Chemical's λ / 4 plate “Sumikalite SEF340138B” ( A front plate was prepared by laminating a retardation value of 138 nm) with an adhesive. In addition, on the λ / 4 plate used here, an acrylic ultraviolet curable hard coat is formed with a thickness of 4 μm, and further, it is composed of SiO ₂ / TiO ₂ / SiO ₂ / TiO ₂ / SiO ₂ . The antireflection film to be formed was formed by vapor deposition, and was bonded to the linear polarizing plate on the surface opposite to the antireflection film. When a 1 mm gap is provided on a commercially available EL display that emits light in green and the front plate obtained above is placed so that the glass plate is on the viewer side, there is no reflection of external light and the display A display with good visibility without multiple shots was obtained. The layer structure of the display device obtained in this example is as shown in FIG.
[0032]
Example 2
A λ / 4 plate manufactured by Sumitomo Chemical Co., Ltd. on the surface opposite to the antireflection film of the acrylic resin plate on which the antireflection film composed of SiO ₂ / TiO ₂ / SiO ₂ / TiO ₂ / SiO ₂ is formed. “Sumikalite SEF340138B” (retardation value 138 nm) was bonded with an adhesive. Further, a linear polarizing plate “Sumikaran STW822A” manufactured by Sumitomo Chemical Co., Ltd. was bonded to the upper surface of the λ / 4 plate with an adhesive to prepare a front plate. When a 1 mm gap is provided on a commercially available EL display that emits light in green and the front plate obtained above is placed so that the linear polarizing plate is on the observer side, there is no reflection of external light and display A display with good visibility was obtained without multiple images. The layer structure of the display device obtained in this example is as shown in FIG.
[0033]
Comparative Example The same configuration as in Example 1, but replaced with a λ / 4 plate without an antireflection film. As a result, although the reflection of external light was reduced, there was a problem in visibility because multiple displays were shown. The layer structure of the display device obtained in this example is as shown in FIG.
[0034]
【Effect of the invention】
ADVANTAGE OF THE INVENTION According to this invention, the double image of EL light by a front board can be reduced, and visibility can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a conventional EL display .
2 is a diagram for explaining the operation mechanism of the EL display of FIG. 1, and is an explanatory diagram in the case where the reflectance on the reflecting surface of the metal electrode is 100%, and (A) is an external incident. FIG. (B) represents the state of transmission and reflection of EL light, respectively.
3 is also a diagram for explaining the operation mechanism of the EL display of FIG. 1, and is an explanatory diagram in the case where the reflectance on the reflecting surface of the metal electrode is 20%, (A) is an external view. The state of transmission and reflection of incident light, (B) represents the state of transmission and reflection of EL light, respectively.
FIG. 4 is a schematic cross-sectional view showing two different aspects of the EL display of the present invention.
FIG. 5 is a diagram for explaining the operation mechanism of the EL display of FIG. 4A, and is an explanatory diagram in the case where the reflectance on the metal reflecting surface is 20%, and FIG. The state of transmission and reflection of incident light, (B) represents the state of transmission and reflection of EL light, respectively.
[Explanation of symbols]
1 ... EL display ,
2 …… Display body,
3 …… Front plate,
4 ... Transparent electrode,
5 …… Light emitting part,
6 …… Metal electrode,
7: Transparent substrate,
8 ... Linear polarizing plate,
9 ... λ / 4 plate,
10: Antireflection film.

Claims (5)

A display body having a transparent electrode on the front side and a metal electrode on the back side across the light emitting part,
It is composed of a front plate having a circularly polarizing plate arranged on the front side,
The display body and the front plate are arranged with a gap of 0.1 to 3 mm, and
Electroluminescent display having antireflection film, wherein it has been found provided only on the display side surface of the front plate. The electroluminescent display according to claim 1, wherein the circularly polarizing plate includes a linearly polarizing plate and a λ / 4 retardation plate . The electroluminescent display according to claim 1 , wherein the circularly polarizing plate has a plurality of retardation plates . The front plate is formed by laminating a circularly polarizing plate composed of a linearly polarizing plate and a λ / 4 retardation plate on a transparent substrate on the linearly polarizing plate side, so that the λ / 4 retardation plate is on the display body side. The electroluminescence display according to claim 1, wherein an antireflection film is formed on a surface of the λ / 4 retardation plate opposite to a surface to be bonded to the linear polarizing plate . The front plate is a transparent substrate in which a circularly polarizing plate composed of a linear polarizing plate and a λ / 4 retardation plate is laminated on the λ / 4 retardation plate side, and the transparent substrate is on the display body side. The electroluminescence display according to claim 1, wherein an antireflection film is formed on a surface of the transparent substrate opposite to a surface to be bonded to the λ / 4 retardation plate .

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