JP4816851B2 - EL element and display medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an EL element, and more particularly to an element that displays a still image such as a specific character, pattern, or photograph. In particular, the present invention relates to a display medium such as a greeting card.
[0002]
[Prior art]
Conventionally, when a pattern or a character is lit by a display element using an electroluminescence element, a method of illuminating a pattern or a character by using an EL element as a backlight and a method of forming a light emitting material into a pattern of a pattern or a character are used. It was. However, in the former method, since a picture, a photograph, a character, etc. are only watermarked through the backlight, a clear light emission image cannot be obtained. In the latter case, the light emitting layer of a desired color is simply applied separately for each large pattern to form characters, designs, etc. The design could not be expressed.
[0003]
There is also a method of expressing a clear image by forming red, green, and blue light emitting materials in a dot matrix type and controlling them with TFTs. This is mainly for expressing moving images. Although it is not impossible to express a photograph or a picture as a still image, it becomes very expensive.
[0004]
For this reason, it has been difficult to inexpensively manufacture display media such as cards and posters that can display fine still images such as photographs in display media using EL elements.
[0005]
[Problems to be solved by the invention]
The present invention provides an EL element that can express a pattern such as a photograph, a picture, or a character with high production efficiency, low cost, and fine pixels, and a display medium using the EL element.
[0006]
[Means for Solving the Problems]
The invention according to claim 1, at least a substrate, an anode layer, a light-emitting layer, the EL element including a cathode layer, wherein the light emitting layer, the red, green, the color-separated images in blue, red, green, and blue light emission An EL element formed by printing a material in the shape of a halftone dot and adjusting the size of the halftone dot to add color shading .
[0007]
According to a second aspect of the invention, at least a substrate, an anode layer, a light-emitting layer, the EL element including a cathode layer, wherein the light emitting layer, the red, green, the color-separated images in blue, red, green, and blue light emission The FM is formed by printing the material in the shape of dots , and the light emitting material randomly arranges red, green, and blue dots so that dark areas are dense and light colors are sparse. It is an EL element formed by a screening method .
[0008]
The invention according to claim 3 is the EL element according to claim 1 , wherein the red, green and blue halftone dots or dots do not overlap each other .
[0009]
The invention of claim 4 is the EL device according to any one of claims 1 to 3 , wherein an overcoat layer containing a conductive substance is laminated on the light emitting layer .
[0010]
A fifth aspect of the present invention is the EL element according to any one of the first to fourth aspects, wherein a black shielding layer is provided on a surface of the light emitting layer opposite to the display surface .
[0011]
The invention of claim 6 is the EL device according to any one of claims 1 to 5 , wherein the light emitting material is printed by an offset printing method or a gravure printing method .
[0012]
A seventh aspect of the invention is a display medium using the EL element according to any one of the first to sixth aspects .
[0016]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, in order to display a clear image such as a photograph or a picture with high accuracy in an EL element composed of at least a base material, an anode layer, a light emitting layer, and a cathode layer, an original such as a photograph or a picture is colored in two or more colors. The luminescent material which decomposes | disassembles and light-emits each color is formed by printing with a printing method, It is characterized by the above-mentioned. Hereinafter, the present invention will be described in detail.
[0017]
The EL device of the present invention is composed of at least a substrate, an anode layer, a light emitting layer, and a cathode layer. If necessary, a hole transport layer, a light emitting layer and a cathode layer are interposed between the anode layer and the light emitting layer. A black shielding layer may be provided between the charge transport layer and the side opposite to the display side. The shielding layer may be between the light emitting layer and the cathode, or may be outside the cathode. In addition, the hole transport layer and the electron transport layer may be laminated separately from the light emitting layer or may be mixed and laminated with the light emitting layer. Moreover, each structure is laminated | stacked in an order from a base material.
[0018]
First, a method for forming a light emitting layer, which is a feature of the present invention, will be described.
First, color separation is performed on a manuscript such as a photo, picture, illustration, or character to be displayed. A known method can be used as the color separation method. Specifically, a method using a color scanner is generally used. In this method, a captured original passes through a color filter, and the light passing therethrough is converted into an electrical signal to separate the colors into two or more colors. At this time, color correction may be performed simultaneously. In addition, there are methods such as a drum type and a planar scanner for this color scanner, but they can be used properly according to the application. In addition, when two or more primary colors of light are used on a computer after being separated into indigo, red, yellow, and black used for printing by this color scanner or the like, they may be converted into red, green, and blue.
You can also use a color filter that is complementary to the desired color without using a scanner, shoot a color document, create a color-separated negative or positive, and then create a plate of the desired color. good. Specifically, a blue plate using a yellow filter, a green plate using a red filter, and a red plate using an indigo filter may be created.
In the present invention, not only a printed matter and a photo original, but also CG image data created on a computer, and image data such as photographs and illustrations previously taken in a computer may be color-separated on the computer.
[0019]
Since the EL element expresses an image with a light emitter, it is preferable that the color separation is divided into three primary colors of light, red, green, and blue. In order to represent black, an insulating layer may be simply provided as a non-light emitting portion, but by providing a black shielding layer that blocks light on the side opposite to the display side of the light emitting layer, the contrast is improved. Become. Further, in order to express black or dark color, a black pigment or dye may be printed as a dark color portion of an image.
[0020]
Next, a plate is made for each color separated by the above method, and the light emitting material is printed by a printing method using each plate.
Various printing methods can be used depending on the purpose. For example, there are a flexographic printing method, an offset printing method, and a gravure printing method. With offset printing, it is possible to print finely, so a sharp display can be obtained. If it is gravure printing, the durability of the plate is high. In the gravure printing, the conventional gravure method is a method of expressing the gradation of an image by the amount of light emitting material depending on the depth of the plate, and can be preferably used.
[0021]
Further, the formation method of each color is not particularly limited, and for example, as shown in FIG. 3, the respective light emitting materials may be arranged in a straight line so that the respective colors do not overlap. This method is preferable because the light emitting materials do not overlap with each other, so that problems such as absorption of light emission do not occur and the light emission can be easily controlled. In this method, the color density is adjusted by adjusting the size of the halftone dots of the luminescent material. The size here means the size and / or thickness of the halftone dot of the luminescent material.
[0022]
There are mainly two methods for forming the red, green, and blue colors, and one is a method (AM screening method) in which dots are formed in a straight line at regular intervals for each color. . In this method, the shade of the color is adjusted by adjusting the size of the halftone dots. The other is a method in which dots of the same size are randomly arranged for each color and the color density is adjusted by the density. The red, green, and blue halftone dots may be formed by shifting their angles by 30 °.
In addition, since the light emitting materials are overlapped in these methods, the absorption wavelength of the light emitting material laminated on the display side among the light emitting materials is preferably different from the light emitting wavelengths of the other light emitting materials. Then, the light emitting material on the display side does not absorb light emitted from other light emitting materials, and the light emission color can be easily controlled.
[0023]
Any material can be used as the light emitting material as long as the required performance is satisfied, but an organic material, particularly a polymer material is preferable. Fluorescent dyes such as coumarin, perylene, pyran, anthrone, porphyrene, quinacridone, N, N'-dialkyl substituted quinacridone, naphthalimide, N, N'-diaryl substituted pyrrolopyrrole, polystyrene, Those dissolved in a polymer such as polymethyl methacrylate and polyvinyl carbazole, and polymer light emitters such as polyarylene and polyarylvinylene can be used. By using a polymer as the light emitting layer, it is possible to provide a long-life EL element having high mechanical strength and high durability.
[0024]
For the black shielding layer, dyes such as aniline black and other black pigments and inks are dissolved and dispersed in a suitable solvent, and coating and printing methods such as spin coating, flexo, gravure, microgravure, and offset are used. To form a film. Further, a conductive substance may be included.
[0025]
Further, an overcoat layer containing a conductive substance may be stacked over the light emitting material. Thereby, the flatness of a printing surface increases and the short circuit of a cathode can be prevented. Moreover, in order to make the applied voltage more uniform, a substance that exhibits the same degree of conductivity as the light emitting material is preferable. Further, for the same purpose, an electron transport layer may be used instead of the overcoat layer.
[0026]
Next, a method for laminating other layers will be described.
The substrate is not particularly limited, and any material such as glass and resin film can be used. A resin film is preferable because it is flexible and transparent and can be used for display media such as cards, posters, and telegrams. As such a resin film, polyethylene terephthalate (PET), polypropylene, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, polycarbonate, or the like can be used. Moreover, a gas barrier film such as a ceramic vapor-deposited film, polyvinylidene chloride, or polyvinyl chloride may be laminated on the surface on which the anode layer is not provided.
[0027]
As an anode layer, it is preferable that it is transparent or translucent, and a well-known thing can be used. For example, a complex oxide (ITO) of indium and tin can be used. Moreover, vapor deposition, sputtering method, etc. can be used for the lamination | stacking method. Further, the anode layer may be solid or patterned on the entire surface.
[0028]
When a hole transport layer is provided, copper phthalocyanine or a derivative thereof, 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane, N, N′-diphenyl-N, N′-bis (3-methyl) Phenyl) -1,1′-biphenyl-4,4′-diamine, N, N′-di (1-naphthyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine, etc. Although low molecular weight compounds such as aromatic amines can be used, polymer materials such as polyaniline, polythiophene, polyvinylcarbazole, a mixture of poly (3,4-ethylenedioxythiophene) and polystyrenesulfonic acid are produced by a wet method. Film formation is possible and more preferable.
[0029]
When an electron transport layer is provided, oxadiazole derivatives such as 1,3,5-tris (4-tertbutylphenyl-1,3,4-oxadiazole) benzene (TPOB) and tris (8-quinolinol) aluminum Small molecules such as 8-quinolinol derivatives or their metal complexes can also be used, but poly (pyridine-2,5-diyl), poly (quinoline-5,8-diyl), poly (quinoxaline-5,8- A polymer material such as diyl) is more preferable because it can be formed by a wet process.
[0030]
The hole transport layer, polymer light emitting layer and electron transport layer can be used in a single or mixed solvent such as toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methanol, ethanol, isopropyl alcohol, ethyl acetate, butyl acetate, water, etc. The polymer material can be dissolved, and a film can be formed using a coating method such as spin coating, spray coating, flexo, gravure, micro gravure, or intaglio offset, or a printing method. It is preferable to use the wet method as described above because the production efficiency is high and manufacturing can be performed at low cost. Moreover, you may add surfactant, antioxidant, a viscosity modifier, a ultraviolet absorber, etc. as needed. These film thicknesses are 1000 nm or less in total even when a single layer or a plurality of layers are laminated, and preferably 50 to 150 nm.
[0031]
As the cathode layer, a single metal such as Mg, Al, Yb, Ca, or Ba is used, or a compound such as Li or LiF is sandwiched by about 1 nm at the interface in contact with the light emitting medium, and Al or Cu having high stability and conductivity. Are used in a stacked manner. Alternatively, in order to achieve both electron injection efficiency and stability, an alloy system of a metal having a low work function and a stable metal, for example, an alloy such as MgAg, AlLi, or CuLi can be used. As a method for forming the cathode, a resistance heating vapor deposition method, an electron beam method, or a sputtering method can be used depending on the material. The thickness of the cathode is preferably about 10 nm to 1000 nm. The cathode layer may be formed on the entire surface or patterned.
[0032]
In addition, the EL element of the present invention uses an elongated flexible base material as the base material, so that the anode layer, the polymer EL layer and the light absorption layer, the cathode are wound continuously. A layer can be formed and finally the substrate can be wound and cut to a predetermined size. At this time, the anode layer can be formed by the above-described vapor deposition, sputtering method, coating thermal decomposition method or the like, and the light emitting layer and the black shielding layer can be formed by the above-described printing method or the like. The layer can be formed by the above-described vapor deposition method, electron beam method, sputtering method, or the like. Moreover, a hole transport layer or / and an electron transport layer can be included as needed. Thus, by continuously forming a polymer EL layer mainly by a wet method, the production efficiency is increased and an EL element can be provided at a low cost.
[0033]
【Example】
Hereinafter, the present invention will be described in detail using examples.
<Example 1>
An ITO film 2 was formed as an anode layer on a base material 1 made of PET by a sputtering method.
Next, the light emitting layer was formed by the following method. First, a photograph as a manuscript was taken with a drum scanner, converted into electrical signal data, and then separated into red, green, and blue on a computer. Based on the color-separated data, red, green and blue gravure printing plates were prepared, and the light emitting layers of each color were printed by gravure printing using the respective plates. Note that poly (3-hexylthiophene) was used as a red light-emitting material, poly (3-cyclohexylthiophene) was used as a green light-emitting material, and poly (octylfluorene) was used as a blue light-emitting material.
As shown in FIG. 5, the color-separated light-emitting layer was formed so that red, green, and blue halftone dots were arranged in a straight line so as not to overlap each other.
Next, as a black shielding layer, aniline black dissolved in a toluene solution was formed to a thickness of 20 nm by spin coating.
Next, MgAg was formed as a cathode layer with a film thickness of 200 nm by binary co-evaporation.
[0034]
When a voltage of 5 V was applied to the obtained EL element, light emission of an average of 100 cd / m ² was obtained, and the same still image as that of the original original photograph was obtained.
[0035]
<Example 2>
The original was color-separated in the same procedure as in Example 1, and each light-emitting material was formed by halftone dots, and each color light-emitting material was printed with a film thickness of 30 nm by gravure printing while shifting the angle by 30 °. . Furthermore, instead of the overcoat layer, sodium polystyrene sulfonate with a film thickness of 50 nm was formed as an electron transport layer by a spin coat method instead of the overcoat layer.
Next, as a black shielding layer, aniline black dissolved in a toluene solution was formed to a thickness of 20 nm by spin coating.
Next, MgAg was formed as a cathode layer with a film thickness of 200 nm by binary co-evaporation.
[0036]
When a voltage of 5 V was applied to the obtained EL element, light emission of an average of 50 cd / m ² was obtained, and the same still image as the photograph as the original document was obtained.
[0037]
<Example 3>
The light emitting material was produced in the same manner as in Example 2 except that the light emitting material was formed in a dot shape for each color.
When a voltage of 5 V was applied to the obtained EL element, light emission of an average of 50 cd / m ² was obtained, and the same still image as the photograph as the original document was obtained.
[0038]
【The invention's effect】
According to the present invention, the image data of the original is color-separated, a printing plate is made for each separated color, and the light-emitting material is formed by printing the light-emitting material of each color, so that a clear still image can be obtained. EL elements can be produced at low cost.
[0039]
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing the structure of an EL element of the present invention. FIG. 2 is a cross-sectional view showing another structure of the EL element of the present invention. It is explanatory drawing which shows the example of printing (for 3 colors).
FIG. 4 is an explanatory view showing one printed example (for one color) of the light emitting material of the EL element of the present invention.
FIG. 5 is an explanatory view showing another printing example (for one color) of the light emitting material of the EL element of the present invention.
[Explanation of symbols]
1 Base Material 2 Anode 3 Luminescent Material 3A Luminescent Material A
3B Luminescent material B
3C Luminescent material C
4 Overcoat layer (electron transport layer)
5 Shielding layer 6 Cathode

Claims (7)

At least a base material, an anode layer, a light-emitting layer, the EL element including a cathode layer, wherein the light emitting layer, the red, green, the color-separated images in blue, red, green, and blue light-emitting material to the shape of the halftone dots An EL element which is formed by printing , and adds color shading by adjusting the size of a halftone dot . At least a base material, an anode layer, a light-emitting layer, the EL element including a cathode layer, print the luminescent layer is, red, green, the color-separated images are blue, red, green, and blue light-emitting material in the shape of a dot And the light emitting material is formed by an FM screening method in which red, green, and blue dots are randomly arranged so that dark portions are dense and light portions are sparse. Characteristic EL element. The EL element according to claim 1, wherein the red, green, and blue halftone dots or dots do not overlap each other . The EL element according to claim 1, wherein an overcoat layer containing a conductive substance is laminated on the light emitting layer . The EL element according to claim 1, wherein a black shielding layer is provided on a surface opposite to the display surface side of the light emitting layer . The EL device according to claim 1, wherein the light emitting material is printed by an offset printing method or a gravure printing method . A display medium using the EL element according to claim 1.

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