JP2003031355A - Display panel - Google Patents

Abstract

(57) [Problem] To provide a high image quality display panel having high light extraction efficiency from a light emitting layer and suppressing light interference. SOLUTION: In a display panel in which light from a light emitting layer provided on one surface of a transparent substrate is transmitted through the transparent substrate and emitted to the outside from the other surface, the light emitting layer is provided on the light emitting layer side. The partition is divided into pixels by a protruding partition, and the partition includes a reflection unit that causes light from each of the partitioned light emitting layers to be incident on an interface with the outside of the transparent substrate at an angle equal to or greater than a critical angle. A display panel characterized by the following.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display panel in which light from a light emitting layer provided on one surface of a transparent substrate is transmitted through the transparent substrate and is emitted to the outside from the other surface thereof, and particularly to the outside. The present invention relates to a display panel with improved emission efficiency.

[0002]

2. Description of the Related Art Conventionally, there is known an organic electroluminescence device (hereinafter referred to as an organic EL device) which emits light by passing an electric current through a phosphor formed on a glass plate or a transparent organic film. As an organic EL device, as shown in FIG. 9, an organic hole transport layer 3 made of an organic compound and an organic light emitting layer 4 made of an organic compound are provided between a cathode 6 which is a metal electrode and an anode 2 which is a transparent electrode. This is represented by a structure in which an organic electron transport layer 5 made of an organic compound and a cathode 6 are sequentially stacked. In the following description, the organic hole transport layer 3, the organic light emitting layer 4, and the organic electron transport layer 5 will be collectively referred to as the “light emitting layer”. Further, the anode 2 and the cathode 6 are connected to an external power source 7 and are energized.

The organic hole transport layer 3 has a function of transporting holes from the anode 2 and a function of blocking electrons, and the organic electron transport layer 5 has a function of transporting electrons from the cathode 6. In these organic EL elements, a glass substrate 91 is arranged outside the anode 2, and excitons are generated by recombination of electrons injected from the cathode 6 and holes injected from the anode 2 to the organic light emitting layer 4. The generated excitons emit light in the process of radiation deactivation, the light passes through the anode 2 and the glass substrate 91, and is emitted from the end surface 92 of the glass substrate 91 to the outside.

The anode 2 includes indium tin oxide (hereinafter,
A transparent conductive material having a large work function such as ITO) and tin oxide, which emits light emission to the outside, is used. The cathode 6 is made of a simple metal such as aluminum (Al), magnesium (Mg), indium (In), or silver (Ag), or an alloy of these metals such as Al-Mg and Ag-Mg, which has a small work function. Is used.

For the organic light emitting layer 4, for example, an aluminum complex of 8-hydroxyquinoline is used, and for the organic hole transport layer 3, for example, N'-diphenyl-N, N '.
-Bis (3methylphenyl) -1,1'-biphenyl-
4,4'-diamine (TPD) is preferably used. For the organic electron transport layer 5, for example, an aluminum complex of 8-hydroxyquinoline or the like is used.

In the above-mentioned organic EL device, as shown in FIG. 10, both the anode 2 and the cathode 6 are formed in a strip shape, both electrodes are arranged orthogonally with the light emitting layer 21 interposed therebetween, and pixels are formed in a matrix at intersections. And configure the display panel.

[0007]

According to Snell's law, the relationship between the refractive indices of light at the boundary surface of different kinds of media is
When light travels from a medium having a refractive index n _{1 to} a medium having a refractive index n ₂ (n ₁ > n ₂ ), the critical angle θ is “θ = sin ⁻¹ (n ₂ / n ₂ /
n ₁ ) ”is given. When this is applied to the above display panel, as shown in FIG. 11, when the light from the light emitting layer 21 is transmitted through the glass substrate 91 and emitted from the end surface 92 into the atmosphere, the refractive index of general glass is Since the refractive index of air is 1.5, the critical angle is θ = sin ⁻¹ (1 / 1.5) = 41.8 °, and θ is the critical angle (41.8 °). Light emitting layer 21 beyond
The light from is totally reflected by the end surface 92 of the glass substrate 91 and is not emitted into the atmosphere.

Usually, in the above display panel, the light from the light emitting layer 21 spreads radially with respect to the glass substrate 91, enters the glass substrate 91, propagates inside the glass substrate 91, and propagates through the end surface 92 of the glass substrate 91. Emitted into the atmosphere from. Therefore, a part of the light from the light emitting layer 21 reaches the end surface 92 of the glass substrate 91 over the critical angle and is not emitted to the outside, and the visually effective light amount is reduced.

Further, a part of the light from the light emitting layer 21 and the light reflected by the end surface 92 as described above travel to the adjacent pixel region to cause the light interference, which is one of the factors causing the deterioration of the image quality. Has become.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a display panel of high image quality in which the light extraction efficiency from the light emitting layer is high and the light interference is suppressed.

[0011]

In order to solve the above-mentioned problems, the invention according to claim 1 of the present invention is directed to the case where light from a light-emitting layer provided on one surface of a transparent substrate is transferred to the transparent substrate. In the display panel that transmits the light and emits the light from the other surface to the outside, the light emitting layer is partitioned into pixels by partition walls protruding toward the light emitting layer side, and the partition walls are separated from each of the partitioned light emitting layers. It is characterized by comprising a reflecting means for making light incident on an interface with the outside of the transparent substrate at an angle of a critical angle or more.

The invention described in claim 2 is the same as claim 1.
In the display panel according to the item 1, the partition wall has a groove that gradually narrows from an end surface protruding toward the light emitting layer toward the other surface of the transparent substrate, and a reflective film is formed on a side wall of the groove. It is characterized by

The invention described in claim 3 is the same as that of claim 2
In the display panel described above, the groove side wall is formed of a plurality of inclined surfaces having different inclination angles.

The invention according to claim 4 is the same as claim 1.
The display panel according to any one of items 1 to 3, wherein the partition wall is further blackened at the bottom of the groove.

The invention described in claim 5 is the same as claim 1.
5. The display panel according to any one of items 4 to 4, wherein the partition wall is further filled with a dry material inside the groove.

The invention according to claim 6 is the same as claim 1.
The display panel according to any one of items 1 to 5, wherein the partition wall is formed integrally with the transparent substrate.

The invention described in claim 7 is the same as claim 1.
7. The display panel according to any one of items 6 to 6, wherein the light emitting layer is made of an organic compound.

[0018]

In the display panel of the present invention having the above-described structure, the light from the light emitting layer is exposed to the interface (=) with the outside of the transparent substrate.
By providing the partition wall having the reflecting means for making the light incident on the end surface 92) at an angle equal to or greater than the critical angle, it is possible to reduce the light that is reflected by the end surface of the transparent substrate and is not emitted to the outside, and to extract the light as compared with the related art. The efficiency can be improved. Further, the amount of light traveling to adjacent pixels is reduced, and light interference can be suppressed.

Further, by blackening the bottom of the groove,
The contrast is increased and the image quality is further improved. Further, in the organic EL display, the organic compound forming the light emitting layer is deteriorated by the surrounding water, which is a factor of the life. However, by filling the groove with a dry material, the light emitting layer is formed in the vicinity of the light emitting layer. The dehumidification treatment can be performed and the life can be improved.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The organic EL according to the present invention will be described below.
A display panel will be described in detail as an example.

FIG. 1 is a partial sectional perspective view showing an embodiment thereof, and FIG. 2 is a partial sectional perspective view showing only a transparent substrate.
As shown in the drawing, partition walls 10 are projected in a grid pattern on one surface of the transparent substrate 91, and an anode 2, an organic light emitting layer 4, and a cathode 6 are provided at the bottom of each grid in order from the transparent substrate side. A light emitting layer 21 that is stacked and serves as a pixel is formed. Both the anode 2 and the cathode 6 are formed in a strip shape, and are orthogonally arranged so as to intersect in each lattice. The cathode 6 is a partition wall 10.
Is formed on the insulating layer 8 (which also serves as a reflection film (for example, an oxide such as BaO)) provided on the outer wall surface of. The organic hole transport layer and the organic electron transport layer (see FIG. A) that form the light emitting layer 21 are not shown. Further, the electrodes and the light emitting layer are the same as conventional ones.

The partition wall 10 has a substantially trapezoidal cross section,
Along the center line C of the protruding end face 10a, the transparent substrate 9
The groove 11 that is gradually narrowed toward the first end surface 92 is formed. The transparent substrate 91 having such a partition 10 is
When it is made of glass, a suitable glass plate may be processed by dry etching so as to have the illustrated cross-sectional shape. When it is made of resin, it can be obtained by molding using an appropriate mold.

On the side wall 11a of the groove 11 of the partition wall 10,
The reflective film 12 is formed. The reflective film 12 may be a conductive film made of metal or an insulating film made of a metal oxide film or the like. The film thickness of the reflective film 12 is appropriately set to a film thickness that can be reflected according to the wavelength of light from the light emitting layer.
The reflective film 12 can be formed by a normal film forming technique such as sputtering or vacuum evaporation.

Further, in the partition wall 10, it is preferable that the bottom portion 11b of the groove 11 is blackened. The blackening method is not limited, but the method of filling the black pigment 13 to a predetermined thickness is the simplest and most effective. Due to this blackening,
The contrast is increased and the image quality is improved.

Further, it is preferable that the inside of the groove 11 of the partition wall 10 is filled with the dry material 14. In the organic EL display panel, the organic compound forming the light emitting layer 21 is easily deteriorated by water, which is a factor of life. Therefore, usually, a desiccant is placed so as to cover the entire panel, or sealing is performed with a can. However, both of them are measures at a position away from the organic compound. On the other hand, the presence of the dry material inside the partition wall 10 adjacent to the light emitting layer 21 enables the dehumidification treatment in the very vicinity of the organic compound, thereby improving the life. still,
Silica gel is suitable as the dry material 14.

The cross-sectional shape of the groove 11 is not limited as long as it reflects the light from the light emitting layer 21 and makes it incident on the end surface 92 of the transparent substrate 91 at an angle equal to or less than the critical angle. The method of designing the cross-sectional shape of the groove 11 will be described below.

FIG. 3 schematically shows the sectional shape around the partition wall 10 and the groove 11. Light emitted from the light emitting layer 21 at an emission angle θ ₀ is inclined at an angle α with respect to the end surface 92 of the transparent substrate 91. When reflected by the reflection film 12 provided on the side wall 11a of the groove 11 and incident on the end surface 92 of the transparent substrate 91 at an angle θ ₁ , the relationship of “θ ₁ = θ ₀ −2α” is established. Since the critical angle is 41.8 ° as described above, θ ₀ is 4
Even if the light of less than 1.8 ° reaches the end 92 of the transparent substrate 91 as it is, it is emitted without being reflected. Therefore, the problem is that θ ₀ is larger than 41.8 ° and 90
° a light (light-emitting layer 21 parallel to the exit) below, theta ₁ of the light in this range, to be less than 41.8 ° at 0 ° or more, the inclination angle α of the side wall 11a of the groove 11 This allows almost all of the light from the light emitting layer 21 to be emitted to the outside from the end surface 92 of the transparent substrate 91.

The above relationship is expressed by an equation, "0 ° ≤θ ₀ -2
α <41.8 ° (41.8 <θ ₀ ≦ 90 °) ”, which is shown by the hatched portion in FIG. Therefore, the cross-sectional shape of the groove 11 can take various shapes as long as the inclination angle α of the side wall 11a is within this range. For example, as shown in FIG. It is also possible to use an inclined surface in which a plurality of different surfaces a, b, c are connected. Light is emitted from the light emitting layer 21 at various angles. However, by forming the side walls 11a of the groove 11 by changing the inclination angle thereof, the reflection mode becomes diverse, and more light can be emitted at the critical angle. Within this, the light can be guided to the end surface of the transparent substrate 91, and the light extraction efficiency can be further improved.

FIG. 6 is a diagram schematically showing how light from the light emitting layer 21 propagates through the transparent substrate 91 in the organic EL display panel in which the groove 11 of the partition wall 10 is defined as described above. . As shown, the light emitting layer 2
The light emitted at various angles from 1 travels straight or in a groove 1.
The light is reflected by the reflective film 12 formed on the No. 1 and enters the end surface 92 of the transparent substrate 91 at an angle less than the critical angle. Further, the light entering the inside of the partition wall 10 from the light emitting layer 21 is also reflected multiple times by the end surface of the partition wall 10 and the reflective film 12, and thus the transparent substrate 91.
Is incident on the end surface 92 of the laser light at an angle less than the critical angle. In this way, the light that goes straight to the adjacent pixel side and is reflected by the end surface 92 of the transparent substrate 91 beyond the critical angle is also reflected by the reflective film 12 and emitted to the outside, so that the light extraction efficiency is improved. Greatly improved.

In the present invention, the partition wall 10 can be variously modified as long as the side wall 11a of the groove 11 is defined as described above. For example, as shown in FIG.
Since the crossing portion 15 does not participate in light emission by the organic layer 21, the structure in which the groove 11 is not formed in the crossing portion 15 can be obtained, and thereby the strength of the entire partition wall can be increased.

The partition wall 10 is formed of the transparent substrate 9 as described above.
It is preferable to integrally mold the same with No. 1 because the number of parts can be reduced and the manufacturing process can be simplified. However, the flat plate member including the partition wall 10 and a flat plate made of another transparent material are joined to each other to form a substrate for a display panel. Can also be

(Design example of partition wall) Design example of partition wall 10 is shown in FIG.
For example. If the transparent substrate 91 is made of glass, the end face 21a of the light emitting layer 21 has a critical angle of 41 ° at the end face.
Light emitted at an angle of 49 ° or more is emitted to the outside even if it goes straight through the transparent substrate 91. Here, assuming that the width of the light emitting layer 21 is 100 μm, the distance from the end 21a of the light emitting layer 21 to the side wall 11a of the groove 11 is 50 μm, and the inclination angle of the side wall 11a of the groove 11 is 10 ° from the relationship shown in FIG. At the point k where the light emitted from the end 21a of the light emitting layer 21 at an angle of 49 ° intersects with the side wall 11a of the groove 11,
The distance x from the side wall 11a in the horizontal direction of the light emitting layer 21 is (100 μm + 50 μm + x μm) tan49 ° = xμ
From the relationship of m · tan80 °, it becomes about 38 μm. The distance (depth) h from the light emitting layer 21 at the distance x is (x μm ·
tan80 °), that is, about 216 μm. Therefore, the bottom portion 11b of the groove 11 is at least 2 times larger than the light emitting layer 21.
By forming it to a depth of 16 μm, the light emitted from the light emitting layer 21 at an angle of less than 49 ° can be reflected by the sidewall 11 a of the groove 11, and almost the entire light from the light emitting layer 21 can be emitted to the outside. Like The amount of protrusion of the partition wall 10 from the light emitting layer 21 is not limited, but may be 50 μm, for example, as illustrated.

Although the present invention has been described by exemplifying the organic EL display panel, the light emitted from the light emitting layer, such as a display panel using an inorganic EL element, can be transmitted through the transparent substrate. It goes without saying that the present invention can be applied to any display panel that emits light to the outside.

[0034]

As described above, the display panel of the present invention is provided with the partition wall having the reflection means for allowing the light from the light emitting layer to enter the interface with the outside of the transparent substrate at an angle equal to or greater than the critical angle. It is possible to reduce the amount of light that is reflected by the end surface of the transparent substrate and is not emitted to the outside, and it is possible to improve the light extraction efficiency as compared with the conventional case.
In addition, the number of pixels traveling to adjacent pixels is reduced, and light interference can be suppressed.

Further, by blackening the bottom of the groove, the contrast is enhanced and the image quality can be further improved.
By filling the groove with a dry material, deterioration of the substance forming the light emitting layer due to water can be more effectively suppressed, and the life can be improved.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional perspective view showing an embodiment (organic EL display panel) of the present invention.

2 is a partial cross-sectional perspective view showing only a transparent substrate of the organic EL display panel shown in FIG.

FIG. 3 is a diagram schematically showing the periphery of a partition wall and a light emitting layer of the organic EL display panel shown in FIG. 1, and a diagram for explaining a method of designing a groove sidewall of the partition wall.

FIG. 4 is a graph for explaining a relationship between an emission angle of light from a light emitting layer and an inclination angle of a groove side wall.

FIG. 5 is a schematic view illustrating the cross-sectional shape of a groove.

FIG. 6 is a schematic diagram showing a mode of propagation of light from a light emitting layer in a transparent substrate in the organic EL display panel of the present invention.

FIG. 7 is a partial cross-sectional perspective view showing another embodiment of the transparent substrate.

FIG. 8 is a cross-sectional view showing a design example of a partition wall.

FIG. 9 is a cross-sectional view showing a structure of a conventional organic EL display panel.

FIG. 10 is a perspective view showing a structure of a conventional organic EL display panel.

FIG. 11 is a diagram showing the principle of emitted light in a conventional organic EL display panel.

[Explanation of symbols]

2 anode 3 Organic hole transport layer 4 Organic light emitting layer 5 Organic electron transport layer 6 cathode 10 partitions 11 grooves 12 Reflective film 13 Black pigment 14 Dry material 21 Light-emitting layer 91 transparent substrate 92 End face

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05B 33/04 H05B 33/04 33/14 33/14 A 33/22 33/22 Z 33/24 33 / 24 F term (reference) 3K007 AB02 AB17 BA06 BB05 CA01 CA05 CB01 CC01 DA01 DB03 EA01 EB00 5C094 AA09 AA10 AA38 BA27 CA19 DA13 DB04 EB02 ED11 ED15 FA01 FA04 FB01 FB20

Claims (7)

[Claims] 1. A display panel, wherein light from a light emitting layer provided on one surface of a transparent substrate is transmitted through the transparent substrate and emitted to the outside from the other surface, wherein the light emitting layer is on the light emitting layer side. The partition wall is divided into pixels by a partition wall protruding inward, and the partition wall is provided with a reflection unit that causes light from each of the partitioned light-emitting layers to enter the interface with the outside of the transparent substrate at an angle of a critical angle or more. A display panel characterized by the above. 2. The partition wall has a groove that gradually narrows from an end surface protruding toward the light emitting layer toward the other surface of the transparent substrate, and a reflective film is formed on a side wall of the groove. The display panel according to claim 1, wherein the display panel is a display panel. 3. The display panel according to claim 2, wherein the groove side wall is formed by a plurality of inclined surfaces having different inclination angles. 4. The display panel according to claim 1, wherein the partition further has a blackened bottom portion of the groove. 5. The display panel according to claim 1, wherein the partition wall is further filled with a dry material inside the groove. 6. The display panel according to claim 1, wherein the partition wall is formed integrally with the transparent substrate. 7. The display panel according to claim 1, wherein the light emitting layer is made of an organic compound.