WO2010010611A1 - Display device using transparent light-emitting panel - Google Patents

Abstract

A display device is composed of a first display part (1) composed of a first electrode (4) formed of an optically transparent material, a second electrode (6) formed of an optically transparent material and a light emitting layer (5) formed between the first electrode and the second electrode, and a second display part (2) provided on the rear surface side of the first display part. From the front surface side of the first display part, a display by the first display part and that by the second display part through the first display part are observed simultaneously. The light emitting luminance (A) of the front surface side (the side of an observer (P)) is set to be smaller than the light emitting luminance (B) of the rear surface side generated by the light-emitting layer (5) of the first display part (1). This makes it possible to clearly observe the display (2i) by the second display part through the first display part.

Description

Display device using transparent self-luminous panel

The present invention uses a transparent self-luminous panel that includes a transparent self-luminous panel, and can display a display by the transparent self-luminous panel and a display by a display unit disposed on the back side of the self-luminous panel. Related to the display device.

For example, with the spread of portable information devices, there is an increasing demand for display panels that have high-definition display functions, can be thin, and can achieve low power consumption. Display panels using EL (electroluminescence) elements have been put into practical use.

In the display panel using the organic EL element described above, a transparent electrode, a light emitting layer, and the other electrode are provided in this order on a transparent substrate, and a sealing member for preventing moisture from entering from above is provided. A bottom emission type display panel that emits light from the substrate side has been proposed. There has also been proposed a top emission type display panel in which an electrode, a light emitting layer, and a transparent electrode are sequentially provided on a substrate, sealed with a transparent sealing member, and light is emitted from the transparent sealing member side. .

In addition, a transparent electrode, a light emitting layer, and another transparent electrode are sequentially provided on a transparent substrate, sealed with a transparent sealing member, and light is emitted from both the transparent substrate side and the transparent sealing member side. A dual emission (double-sided light emission) type display panel has also been proposed. A dual emission type display panel that is transparent in a non-light-emitting state is sometimes called a transparent organic EL (TOLED) panel.

In the above-described TOLED panel, the light (luminance) emitted from both sides is usually not equal. This is because the TOLED panel uses different materials for both electrodes sandwiching the light emitting layer due to its light emission principle, and the structure of the light emitting element is not symmetrical when viewed from the light emitting layer.

Generally, a material having a large work function is used for the anode electrode in order to efficiently inject holes serving as carriers, and a work function is used for the cathode material in order to efficiently inject electrons serving as carriers. Use small materials. In addition, the light emitting layer is not a single layer but is generally composed of a plurality of layers such as a hole transport layer, an organic light emitting layer, and an electron transport layer made of different materials.

For this reason, even if light is evenly generated in the light emitting layer due to a difference in transmittance of each layer or a difference in reflectance between layers due to a difference in refractive index of each layer, one transparent substrate and the other transparent sealing member There is a difference in the amount of light emitted from the.

By the way, as an example of using the above-mentioned TOLED panel, for example, there can be considered a usage mode in which two game players face each other with the TOLED sandwiched by a game machine or the like and images are observed from both sides of the TOLED.

Further, for example, instead of the cover glass in a photo stand, the above-mentioned TOLED is used, and a usage form in which both the display by the TOLED and the observation object such as a photograph arranged close to the back side of the TOLED can be considered. Furthermore, similarly, a use form in which TOLED is mounted instead of the cover glass of a wristwatch and both the display by TOLED and the clock display on the back side thereof are observed is also conceivable. A configuration in which TOLED is combined with a wristwatch in this manner is disclosed in Patent Document 1 shown below.
JP 2002-258774 A

By the way, in the case of the usage method in which the TOLED is observed from both sides as described above, the luminance on both sides is increased by providing a layer for adjusting the reflectance between the transparent substrate and the electrode or between the transparent sealing member and the electrode. It would be common to employ an equal structure. In addition, as described above, TOLED is used instead of a photo frame cover glass or watch cover glass, and in the usage mode in which the display by this TOLED is observed only from one direction, the observation by the ease of recognition of the display by TOLED is observed. It is thought that it is common to install it with the surface with high brightness facing the user.

In the present invention, as in the latter case described above, the form of observing both the display by the TOLED and the observation object arranged on the back side of the TOLED from one direction is repeatedly studied. In order to provide a display device that can be observed more clearly through the above, the luminance distribution on the front and back sides of the TOLED was considered.

As a result, if the configuration in which the surface with low emission brightness of the TOLED is set toward the observer side rather than the surface with high emission luminance of the TOLED is set toward the viewer side, it is arranged on the back side of the TOLED. The inventor has experimentally found that the observed object can be observed more clearly.

Therefore, the display device according to the present invention, which has been made to solve the above-described problems, is formed of the first electrode made of a light-transmitting material and the light-transmitting material as described in claim 1. A first display unit by a transparent self-luminous panel comprising a second electrode, a light emitting layer formed between the electrode 1 and the electrode 2, and a second display unit provided on the back side of the first display unit, A display device for simultaneously observing the display by the first display unit and the display by the second display unit from the front surface side of the first display unit, wherein the back surface by the light emitting layer of the first display unit It is characterized in that the light emission luminance on the surface side is set smaller than the light emission luminance on the side.

It is the schematic diagram which showed the basic form of the display apparatus concerning this invention. It is the schematic diagram which showed the example of a structure of the 1st display part mainly in the display apparatus concerning this invention. It is the diagram which showed the relationship of the brightness | luminance of the surface side of a 1st display part with respect to the thickness of the refractive index adjustment layer in a 1st display part, and a back surface side. It is the diagram which showed the relationship of the luminance factor of the surface side with respect to the thickness of the refractive index adjustment layer in a 1st display part.

Explanation of symbols

1 First display (TOLED panel)
DESCRIPTION OF SYMBOLS 1i Display by 1st display part 2 2nd display part 2i Display by 2nd display part 3 Transparent substrate 4 Transparent anode electrode 5 Light emitting layer 6 Transparent cathode electrode 7 Refractive index adjustment layer 8 Transparent sealing member P Observer

Hereinafter, a display device according to the present invention will be described based on an embodiment shown in the drawings. FIG. 1 schematically shows a basic configuration of a display device according to the present invention. An observer P is provided on a first display unit by a transparent self-luminous panel indicated by reference numeral 1 and on the back side of the first display unit. The display by the second display unit indicated by reference numeral 2 provided is observed simultaneously. That is, the observer P sees the display 1i by the second display unit through the first display unit at the same time as viewing the display 1i by the first display unit.

FIG. 2 is a schematic diagram mainly illustrating the configuration of the first display unit using the transparent self-luminous panel described above, and shows an example of a transparent organic EL (TOLED) panel using an organic EL element as the self-luminous element. As schematically shown in FIG. 2, the laminated structure of the TOLED panel 1 has a transparent anode electrode 4 made of, for example, ITO formed in a stripe shape on one surface of a transparent substrate 3 made of, for example, glass.

A light emitting layer 5 is further laminated on the transparent anode electrode 4. Although not shown in the drawing, the light emitting layer 5 is composed of a plurality of layers such as a hole transport layer, an organic light emitting layer, an electron transport layer, and an electron injection layer. A transparent cathode electrode (counter electrode) 6 made of, for example, an Al and Ca layer is laminated on the light emitting layer 5.

The transparent cathode electrode 6 is also formed in a stripe shape, and is configured to intersect (orthogonally) the transparent anode electrode 4 formed in a stripe shape. Thereby, the light emitting layer 5 sandwiched between the transparent anode electrode 4 and the transparent cathode electrode 6 constitutes a passive matrix display panel that constitutes a pixel.

Further, a refractive index adjustment layer 7 made of, for example, Alq3 is formed on the transparent cathode electrode 6 described above, and a transparent sealing member 8 made of a glass substrate is formed on the refractive index adjustment layer 7 to form a TOLED panel. Is formed. That is, in this embodiment, the refractive index adjusting layer 7 is disposed on the surface side of the first display unit 1 relative to the light emitting layer 5. And the 2nd display part 2 is arrange | positioned at the transparent substrate 3 side (the back side of a 1st display part), and as above-mentioned, the observer P sees the display 1i by the 1st display part 1, and is the 1st display. The display 2i by the second display section is also seen through the section.

In the TOLED panel shown in FIG. 2, the symbol a schematically shows direct light emitted from the light emitting layer 5 to the transparent cathode electrode 6 side, and the symbol a2 passes through the sealing member 8 to transmit the TOLED panel. The direct light emitted to the surface side is typically shown. Reference symbol b schematically represents direct light emitted from the light emitting layer 5 to the transparent anode electrode 4 side, and reference symbol b2 represents direct light transmitted through the transparent substrate 3 and emitted to the back side of the TOLED panel. This is shown schematically.

Further, a part of the direct light emitted to the transparent cathode electrode 6 side indicated by the symbol a is reflected by the transparent cathode electrode 6 and the refractive index adjusting layer 7, and this reflection component is transmitted through the transparent substrate 3 to form the TOLED panel. Released to the back side. This reflected light is shown as a3. Similarly, a part of the direct light emitted to the transparent anode electrode 4 side indicated by the symbol b is reflected by the transparent anode electrode 4, and this reflected component is transmitted through the transparent sealing member 8 and emitted to the surface side of the TOLED panel. Is done. This reflected light is shown as b3.

The refractive index adjustment layer 7 in the TOLED panel having the above-described configuration reflects a part of the direct light a emitted to the transparent cathode electrode 6 side as reflected light a3 on the back side of the TOLED panel by changing the thickness thereof. The degree can be controlled.

Therefore, in the TOLED panel having the above-described configuration, the luminance B emitted from the transparent substrate 3 side (the back side of the first display unit) and the transparent sealing member 8 side (when the thickness of the refractive index adjustment layer 7 is changed) FIG. 3 shows the relationship between the luminance A emitted from the surface of the first display unit (the luminances A and B are the amounts of light per unit area, respectively). Further, from the relationship shown in FIG. 3, the luminance factor C [C = A / (A + B)] on the transparent sealing member 8 side when the thickness of the refractive index adjusting layer 7 is changed is shown in FIG.

When an attempt is made to create a panel having the same luminance A and luminance B, the film thickness of the refractive index adjustment layer 7 can be controlled at about ± 5 nm, so the luminance ratio C is maintained at 0.47 or more. Is possible. The inventor has found that the brightness ratio C is 0.43 or less, a difference occurs in the observation state of the display 2i of the second display unit 2, and the difference is clear when the brightness ratio C is 0.4 or less. . That is, it was confirmed that when the luminance ratio C was 0.4 or less, the display 2i of the second display unit 2 through the TOLED panel could be clearly observed.

On the other hand, when the input power to the TOLED panel constituting the first display unit 1 is made constant and the luminance ratio C is made small, the luminance A of the first display unit decreases and the observation state of the display 1i on the first display unit deteriorates. . For this reason, in order to maintain the observation state of the first display unit, it is necessary to increase the input power to the TOLED panel in order to keep the luminance A constant. As a result, the power consumption of the display device increases as the luminance ratio C decreases.

For the above reasons, considering the observation state of the display 2i of the second display unit 2 and the increase in power consumption, the luminance ratio C is considered to be within a practical range where 0.3 ≦ C ≦ 0.4. Can do.

In the above-described embodiment, the refractive index adjustment layer is provided in order to grasp the relationship between the luminance ratio and the visibility of the observation object, but this refractive index adjustment layer is not always necessary. In the embodiment, the glass substrate is used for each of the transparent substrate and the transparent sealing member. However, the present invention is not particularly limited to this, and other transparent materials can be used.

Further, in the above-described embodiment, a gap is provided between the first display unit and the second display unit, but the first display unit and the second display unit may be in contact with each other, and the second display unit A display panel such as an organic EL element or a liquid crystal display can also be used.

Claims (3)

1. A transparent self-luminous panel comprising a first electrode formed of a light-transmitting material, a second electrode formed of a light-transmitting material, and a light-emitting layer formed between the electrode 1 and the electrode 2 1 display part and the 2nd display part provided in the back surface side of the 1st display part, from the surface side of the 1st display part, the display by the 1st display part and the 2nd display part A display device for simultaneously observing the display,
   The display device is characterized in that the light emission luminance on the front surface side is set smaller than the light emission luminance on the back surface side of the light emitting layer of the first display section.
2. The relationship between the light emission luminance A on the front surface side and the light emission luminance B on the back surface side of the first display unit is set in a range of 0.30 ≦ A / (A + B) ≦ 0.4. 1. The display device described in 1.
3. The display device according to claim 1, wherein a refractive index adjustment layer is disposed on a surface side of the light emitting layer in the first display unit.

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