JP4801297B2 - Light emitting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light emitting device using an element (hereinafter referred to as a light emitting element) in which a light emitting material is sandwiched between electrodes. In particular, the present invention relates to a light-emitting device using a light-emitting material (hereinafter referred to as EL material) from which EL (Electro Luminescence) can be obtained.
[0002]
[Prior art]
In recent years, development of a light emitting device (hereinafter referred to as an EL display device) using a light emitting element utilizing an EL phenomenon (hereinafter referred to as an EL element) has been advanced. The EL display device does not require a backlight like a liquid crystal display because the light emitting element itself has a light emitting capability. In addition, the wide viewing angle makes it suitable for outdoor use.
[0003]
There are two types of EL display devices, a passive type (simple matrix type) and an active type (active matrix type), both of which are actively developed. In particular, active EL display devices are currently attracting attention. In addition, EL materials serving as a light emitting layer of an EL element include an organic material and an inorganic material, and the organic material is further classified into a low molecular (monomer) organic material and a high molecular (polymer) organic material. Both are actively studied, and low molecular weight organic materials are mainly formed by vacuum deposition, and high molecular weight organic materials are mainly formed by spin coating.
[0004]
Organic materials are characterized by higher luminous efficiency than inorganic materials and can be driven at a low voltage. In addition, since it is an organic compound, it is possible to design and create various new substances. Therefore, there is a possibility that an element that emits light with higher efficiency may be discovered by future progress in material design.
[0005]
The EL element includes an anode, a light emitting layer, and a cathode, and is formed so that the light emitting layer is sandwiched between the anode and the cathode. An anode or a cathode may be formed on the substrate, but an anode is generally formed on the substrate for ease of production.
[0006]
In the EL element, when the light emitting layer or the cathode reacts with water, the element deteriorates. Due to the deterioration of the element, a region that does not emit light, commonly called a black spot (also called a dark spot), is formed. In order to prevent the deterioration of the element, the conventional EL display device is sealed as shown in FIG. An EL element 302 is formed over the substrate 301, and the substrate 301 is fixed by a sealing material 303 and an adhesive 305. The sealing material 303 has a shape having a recess whose inner dimension is larger than the outer dimension of the EL element 302, and a hygroscopic substance 304 is disposed there. The EL element 302 is in a sealed space surrounded by the substrate 301, the sealing material 303, and the adhesive 305. The sealed space is filled with an inert gas (nitrogen or a rare gas). In this specification, a sealing material refers to what is bonded to a substrate through an adhesive in order to protect an EL element that is weak against water.
[0007]
[Problems to be solved by the invention]
As shown in FIG. 3, the EL element is sealed in a sealed space surrounded by a substrate, a sealing material, and an adhesive. In the EL element, when the light emitting layer or the cathode reacts with water, the element deteriorates. Therefore, the sealed space is filled with an inert gas, and the moisture concentration is kept low. However, the resin normally used as an adhesive permeates water at a certain rate. In the conventional sealing method, a hygroscopic substance is mixed in the sealed space. However, when water that has passed through the adhesive enters the sealed space, the EL element is absorbed before the water is adsorbed by the hygroscopic substance. May react.
[0008]
In the case of manufacturing a top emission EL display device, in the conventional method, there is a problem that when a hygroscopic substance is sprayed on the sealing material, the hygroscopic substance blocks light that is about to be emitted from the sealing material side.
[0009]
[Means for Solving the Problems]
The structure of the EL display device proposed in the present invention is shown in FIGS. As shown in FIGS. 1 and 2, an adhesive A105 is formed in a closed curve around a region where the EL element 102 exists, and an adhesive B106 is formed around the adhesive A105 in a closed curve. A hygroscopic substance 106 is dispersed between the adhesive A105 and the adhesive B106. With this configuration, the water that has passed through the adhesive B passes through the space where the hygroscopic substance 104 is dispersed before entering the sealed space containing the EL element, and thus may be adsorbed there. . Therefore, the amount of water that enters the sealed space containing the EL element can be reduced.
[0010]
When a groove is formed in the substrate 101, the sealing material 103, or the region of the substrate 101 and the sealing material 103 where the hygroscopic substance is dispersed, a gap (hereinafter referred to as a cell gap) between the substrate and the sealing material is formed. It is good because it gets smaller.
[0011]
With the configuration as shown in FIGS. 1 and 2, even when an EL display device with top emission is produced, a hygroscopic substance can be dispersed at a position where light emission is not blocked.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
A method for sealing the EL display device of the present invention will be described. A cross-sectional view of the EL display device of the present invention is shown in FIG. 1, and a top view thereof is shown in FIG. In FIG. 2, the sealing material is omitted.
[0013]
An adhesive is applied to the sealing material 103. The application method is performed by a dispenser method or screen printing. 2, the adhesive A105 is formed in a closed curve around the area where the EL element 102 exists, and the adhesive B106 is formed around the adhesive A105 in a closed curve.
[0014]
As a material of the sealing material 103, an insulating material such as glass or polymer is preferable. Examples thereof include amorphous glass (borosilicate glass, quartz, etc.), crystallized glass, ceramic glass, organic resin (acrylic resin, styrene resin, polycarbonate resin or epoxy resin), and silicone resin. . Ceramics may also be used. In addition, if the adhesive 105 is an insulator, a metal material such as a stainless alloy can be used.
[0015]
As the material of the adhesive, an adhesive such as an epoxy resin or an acrylate resin can be used. A thermosetting resin or a photocurable resin can also be used as an adhesive. However, it is desirable that the adhesive is made of a material that does not transmit water as much as possible.
[0016]
A powdery hygroscopic substance 104 is dispersed between the adhesive A105 and the adhesive B106. When spraying, care should be taken that the hygroscopic substance 104 does not enter the area where the adhesive is applied. When the hygroscopic substance 104 enters the area where the adhesive is applied, the adhesive may not come into contact with the substrate or the sealing material. Note that either step of applying the adhesive or spraying the hygroscopic substance may be performed first.
[0017]
As the material of the hygroscopic substance, for example, alkali metal oxides, alkaline earth metal oxides, sulfates, metal halides or perchlorates are used.
[0018]
Examples of the method of spraying the hygroscopic substance include, for example, a method of applying by a dispenser method, a method of forming a film on a sealing material using a vacuum deposition method, a sputtering method, and placing a mask on the sealing material, A method of spraying a mixture of nitrogen and nitrogen gas from above can be employed. It is preferable to finely break the hygroscopic substance powder with a tool such as a mortar and pestle. Further, it is preferable to use only a small particle size by screening the powder through a 0.03-0.05 mm mesh sieve. Since a hygroscopic substance is sprayed between the adhesive A105 and the adhesive B106, the cell gap is several times the particle size.
[0019]
As a method of spraying a hygroscopic substance, a container having a hygroscopic substance on the inside may be attached to a sealing material. The container should be made of a material that allows water vapor to pass but not hygroscopic material.
[0020]
The sealing material 105 and the substrate 101 on which the EL element 103 is formed are attached to each other. In the bonding method, the sealing material 103 and the substrate 101 are marked, the positions are aligned by a CCD (charge coupled device) camera, and the bonding is performed. In order to fill the sealed space where the EL element is sealed with an inert gas, the bonding is performed in an inert gas (nitrogen or noble gas) atmosphere. Keep the moisture concentration in the atmosphere as low as possible. Specifically, the water concentration is desirably 1 ppm or less.
[0021]
After the substrate 101 and the sealing material 103 are bonded together, the adhesive is cured. When the adhesive is a thermosetting resin, the adhesive is cured by hot pressing in a clean oven, and when the adhesive is a photocurable resin, the adhesive is cured by ultraviolet irradiation by an ultraviolet lamp. In either case, attention should be paid because the EL element may be damaged during curing.
[0022]
When the adhesive is completely cured, the dividing line between the substrate 101 and the sealing material 103 is cut by a scriber. Then, it divides | segments by applying force from the surface opposite to the surface where the cut was made. At this time, a device for applying pressure called a breaker may be used.
[0023]
【Example】
[Example 1]
FIG. 4 shows an EL display device in which the present invention is applied to a bottom emission element. An anode 402 is formed on the substrate 401. As a material of the substrate 401, a glass substrate, a quartz substrate, or a plastic substrate is used. As a material of the anode 402, a conductive film having a large work function, typically a transparent conductive film (such as a compound of indium oxide and tin oxide), platinum, gold, nickel, palladium, iridium, or cobalt is used. The anode is formed by a method such as sputtering or vacuum vapor deposition, and is patterned by photolithography.
[0024]
A light emitting layer 403 is formed on the anode 402. The light emitting layer 403 is used in a single layer or a stacked structure, but the light emitting efficiency is better when the light emitting layer 403 is used in a stacked structure. In general, a hole injection layer / a hole transport layer / a light emitting layer / an electron transport layer are formed on the anode 402 in this order, but a hole transport layer / a light emitting layer / an electron transport layer or a hole injection layer / a positive layer is formed. A structure such as a hole transport layer / a light emitting layer / an electron transport layer / an electron injection layer may be used. In the present invention, any known structure may be used, and the light emitting layer 403 may be doped with a fluorescent dye. As the EL material used for the light emitting layer 403, either a high molecular organic material or a low molecular organic material may be used.
[0025]
A cathode 404 is formed on the light emitting layer 403. The cathode 404 is formed by a vacuum evaporation method using a metal mask. The material of the cathode 404 is a metal having a small work function, typically an element belonging to Group 1 or Group 2 of the periodic table (magnesium, lithium, potassium, barium, calcium, sodium, or beryllium) or a work function close thereto. Use the metal you have. Alternatively, aluminum may be used as a cathode material, and lithium fluoride or a lithium acetylacetonate complex may be formed under the aluminum as a cathode buffer layer.
[0026]
Thereafter, the EL element is sealed according to the present invention. An adhesive A407 is formed in the shape of a closed curve around the area where the EL element exists, and an adhesive B408 is formed in the shape of a closed curve around the adhesive A407. A hygroscopic substance 406 is sprayed between the adhesive A407 and the adhesive B408. In the EL display device of FIG. 4, the sealing material 405 is in the form of a sheet. However, as in the prior art, an EL display device in which the sealing material 405 has a recess having an inner dimension larger than the outer dimension of the EL element is also possible, and the recess is filled with a hygroscopic substance. Is effective. FIG. 5 shows such an EL display device.
[0027]
[Example 2]
An EL display device in which the present invention is applied to a top emission element is shown in FIG. A cathode 604 is formed over the substrate 601, a light emitting layer 603 is formed over the cathode 604, and an anode 602 is formed over the light emitting layer 603. Since light passes through the sealing material 605 and is emitted, the sealing material 605 must be transparent. In the case of the configuration shown in FIG. 4 as well, an EL display device with top emission is obtained by thinning the cathode to extract light. Since light is transmitted through the sealing material 405 and emitted, the sealing material 405 must be transparent. Other element configurations are the same as those in the first embodiment.
[0028]
In the conventional sealing method, the hygroscopic substance is dispersed in the central portion of the sealing material. However, the hygroscopic substance is generally not transparent, so that the emission of light is hindered. According to the method of the present invention, a hygroscopic substance can be dispersed even when light is emitted from the upper surface, and the moisture concentration in the sealed space can be kept low.
[0029]
Example 3
The present invention can also be applied to an active EL display device. An example in which the present invention is applied to an active EL display device is shown in FIG. 701 is a substrate, 702 is a switching TFT (Thin Film Transistor), 703 is a current control TFT, 704 and 705 are insulating films, 706 is an anode, 707 is a light emitting layer, 708 is a cathode, 709 is a sealing material, 710 is an adhesive A, 711 is an adhesive B, and 712 is a hygroscopic substance.
[0030]
Example 4
The present invention can also be applied to a passive EL display device. An example in which the present invention is applied to a passive EL display device is shown in FIG. Reference numeral 801 denotes a substrate, 802 an anode, 803 a light emitting layer, 804 a cathode, 805 an insulating film, 806 a sealing material, 807 an adhesive A, 808 an adhesive B, and 809 a hygroscopic substance.
[0031]
Example 5
In Example 1, Example 2, Example 3 and Example 4, a groove is formed in the substrate, the sealing material or the substrate and the sealing material, and the groove is formed in a region where the hygroscopic substance is dispersed. FIG. 9 shows the EL display device of the present invention. In Example 1, Example 2, Example 3 and Example 4, the size of the cell gap was required to be several times the particle size of the hygroscopic substance in order to ensure the volume into which the hygroscopic substance entered. With this configuration, the cell gap can be further reduced as the depth of the groove is increased. The smaller the cell gap, the smaller the area of the resin exposed to the outside air, and the smaller the amount of permeated water.
[0032]
In Example 1, Example 2, Example 3 and Example 4, the depth of the groove is made sufficiently large, and the film is covered with a film 1010 to fill the groove with a hygroscopic substance. Is shown in FIG. A film is not particularly necessary when the hygroscopic material is formed by vacuum deposition or sputtering. The film uses a material that allows water vapor to pass but does not pass hygroscopic material. Accordingly, the hygroscopic substance is filled in the groove, and the water vapor also enters the groove, so that the amount of water vapor existing between the adhesive A1007 and the adhesive B1008 can be reduced. The film material is 4-fluoroethylene or the like. In this configuration, the size of the cell gap is irrelevant to the amount of the hygroscopic substance, and is determined by the type of adhesive or the size of the filler.
[0033]
9 and 10 show the EL display device shown in FIG. 4 applied with the above contents. Even when the sealing material has a concave shape as shown in FIG. 5, the top emission as shown in FIG. In the case of an element, the above-described contents can be applied to an active EL display device as shown in FIG. 7 and a passive EL display device as shown in FIG.
[0034]
Example 6
Since the self-luminous device of the present invention is a self-luminous type, it is superior in visibility in a bright place as compared with a liquid crystal display and has a wide viewing angle. Therefore, it can be used as a display unit of various electric appliances. For example, in order to appreciate a TV broadcast or the like on a large screen, the self-luminous device of the present invention is preferably used in a display portion of an EL display having a diagonal size of 30 inches or more (typically 40 inches or more).
[0035]
The EL display includes all information display devices such as a personal computer display device, a TV broadcast reception display device, and an advertisement display device. In addition, the self-luminous device of the present invention can be used for display portions of various electric appliances.
[0036]
Such an electric appliance of the present invention includes a video camera, a digital camera, a goggle type display device (head mounted display), a navigation system, a sound reproduction device (car audio, audio component, etc.), a notebook type personal computer, a game machine, A portable information terminal (mobile computer, mobile phone, portable game machine, electronic book, or the like), an image playback device equipped with a recording medium (specifically, a playback medium such as a digital video disc (DVD)) A device having a display capable of displaying). In particular, a portable information terminal that is often viewed from an oblique direction emphasizes the wide viewing angle, and thus it is desirable to use an EL display. Specific examples of these electric appliances are shown in FIGS.
[0037]
FIG. 11A illustrates an EL display, which includes a housing 1101, a support base 1102, a display portion 1103, and the like. The self-luminous device of the present invention can be used in the display portion 1103. Note that since the self-luminous device of the present invention is self-luminous, a backlight is not required, and a display portion thinner than a liquid crystal display can be obtained.
[0038]
FIG. 11B illustrates a video camera, which includes a main body 1111, a display portion 1112, an audio input portion 1113, operation switches 1114, a battery 1115, an image receiving portion 1116, and the like. The self-luminous device of the present invention can be used in the display portion 1112.
[0039]
FIG. 11C illustrates a part (right side) of the head mounted EL display, which includes a main body 1121, a signal cable 1122, a head fixing band 1123, a display portion 1124, an optical system 1125, a display device 1126, and the like. The self-luminous device of the present invention can be used in the display device 1126.
[0040]
FIG. 11D shows an image reproducing device (specifically, a DVD reproducing device) provided with a recording medium, which includes a main body 1131, a recording medium (DVD or the like) 1132, operation switches 1133, a display unit (a) 1134, and a display unit. (B) 1135 and the like are included. The display unit (a) 1134 mainly displays image information, and the display unit (b) 1135 mainly displays text information. The self-luminous device of the present invention includes the display unit (a) 1134 and the display unit (b) 1135. Can be used. Note that an image reproducing device provided with a recording medium includes a home game machine and the like.
[0041]
FIG. 11E illustrates a goggle type display device (head mounted display), which includes a main body 1141, a display portion 1142, and an arm portion 1143. The self-luminous device of the present invention can be used in the display portion 1142.
[0042]
FIG. 11F illustrates a personal computer, which includes a main body 1151, a housing 1152, a display portion 1153, a keyboard 1154, and the like. The self-luminous device of the present invention can be used in the display portion 1153.
[0043]
If the emission brightness of the EL material is increased in the future, the light including the output image information can be enlarged and projected by a lens or the like and used for a front type or rear type projector.
[0044]
In addition, the electric appliances often display information distributed through electronic communication lines such as the Internet or CATV (cable television), and in particular, opportunities to display moving image information are increasing. Since the response speed of the EL material is very high, the self-luminous device of the present invention is preferable for displaying moving images.
[0045]
FIG. 12A illustrates a mobile phone, which includes a display panel 1201, an operation panel 1202, a connection unit 1203, a display unit 1204, a sound output unit 1205, operation keys 1206, a power switch 1207, a sound input unit 1208, and an antenna 1209. Including. The self-luminous device of the present invention can be used in the display portion 1204. Note that the display portion 1204 can suppress power consumption of the cellular phone by displaying white characters on a black background.
[0046]
FIG. 12B illustrates a sound reproducing device, specifically a car audio, which includes a main body 1211, a display portion 1212, and operation switches 1213 and 1214. The self-luminous device of the present invention can be used in the display portion 1212. Moreover, although the vehicle-mounted audio is shown in the present embodiment, it may be used for a portable or household sound reproducing device. The display unit 1214 can reduce power consumption by displaying white characters on a black background. This is particularly effective in a portable sound reproducing apparatus.
[0047]
FIG. 12C illustrates a digital camera, which includes a main body 1221, a display portion (A) 1222, an eyepiece portion 1223, operation switches 1224, a display portion (B) 1225, and a battery 1226. The self-luminous device of the present invention can be used in the display portion (A) 1222 and the display portion (B) 1225. In the case where the display portion (B) 1225 is mainly used as an operation panel, power consumption can be suppressed by displaying white characters on a black background.
[0048]
Further, in the portable electric appliance shown in this embodiment, as a method for reducing power consumption, a sensor unit for sensing external brightness is provided, and when used in a dark place, a display unit is provided. For example, there is a method of adding a function such as reducing the brightness of the image.
[0049]
As described above, the application range of the present invention is extremely wide and can be used for electric appliances in various fields. Moreover, any of the configurations shown in the first to fifth embodiments may be applied to the electric appliance of the present embodiment.
[0050]
【The invention's effect】
In the EL display device of the present invention, water that has passed through the adhesive is adsorbed by the hygroscopic substance before entering the sealed space containing the EL element. Therefore, the amount of water that enters the sealed space containing the EL element can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing a cross-sectional structure of an EL display device of the present invention. FIG. 2 is a diagram showing a top structure of an EL display device of the present invention. FIG. 3 is a diagram showing a cross-sectional structure of a conventional EL display device. FIG. 5 is a cross-sectional view of the EL display device of the present invention using the bottom emission element. FIG. 5 is a cross-sectional view of the EL display device of the present invention using the bottom emission element. FIG. 7 is a diagram showing a sectional structure of an EL display device according to the present invention. FIG. 7 is a diagram showing a sectional structure of an active EL display device according to the present invention. 9 is a diagram showing a cross-sectional structure of an EL display device of the present invention. FIG. 10 is a diagram showing a cross-sectional structure of an EL display device of the present invention. FIG. 11 is a diagram showing an electric appliance of the present invention. Illustration showing electrical appliances

Claims (2)

A substrate on which an EL element is formed;
A sealing material facing the EL element;
An adhesive A and an adhesive B provided between the substrate and the sealing material,
The EL element is surrounded by the adhesive A,
The adhesive A is surrounded by the adhesive B,
The substrate is provided with an annular first groove formed in a region overlapping between the adhesive A and the adhesive B,
The sealing material is provided with an annular second groove formed in a region overlapping between the adhesive A and the adhesive B,
First the annular groove, the second groove of said annular, and the space between the adhesive A and the adhesive B, luminescence powdered hygroscopic substance characterized in that it is filled apparatus. Oite to claim 1,
A light emitting device, wherein a space in which the EL element is disposed is filled with an inert gas.

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