JPH0384024A - Dielectric material composition and dispersion type el luminous element obtained from the same composition - Google Patents

Abstract

PURPOSE:To obtain a dielectric material composition having high dielectric constant, excellent film forming properties, providing a dispersion type EL luminous element having high luminance, comprising a specific low molecular cyanoethylated substance or a mixture of the substance and high molecular cyanoethylated substance and isocyanic acid group-containing compound. CONSTITUTION:A low-molecular cyanoethylated substance (e.g. cyanoethylsorbitol) containing a hydroxyl group and a cyanoethyl group and having >=80% substitution ratio of cyanoethyl group liquid at normal temperature or a mixture of the substance and a high molecular cyanoethylated substance (e.g. cyanoethyl cellulose) are blended with a compound (e.g. hexamethylene diisocyanate) containing two or more isocyanic acid groups to give a dielectric material composition, which is mixed with fluorescence substance powder to give a coating solution for a luminous layer. The coating solution is blended with high dielectric material powder to give a coating solution for electrical insulating layer, both the coating solutions are applied to electrodes and cured under heating to give a dispersion type EL luminous element suitable for facial fluorescent substance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a dielectric composition and a high-brightness distributed EL light-emitting element useful as a surface light-emitting material obtained from the dielectric composition.

(Prior Art) EL (electroluminescence) light emitting elements have recently been applied to various light sources and display devices by taking advantage of their characteristics as planar light emitters. In particular, distributed EL light-emitting elements can be manufactured easily at a relatively large area at low cost.
Practical use is progressing as backlights for liquid crystal display elements and flat TVs.

Such a distributed EL light-emitting element includes a back electrode made of metal foil or a metal thin plate, a reflective insulating layer formed by dispersing high dielectric powder such as titanium oxide or barium titanate into an organic dielectric to form a thin film, and a phosphor. A laminate consisting of a phosphor layer formed by dispersing powder in an organic dielectric material to form a thin film, and a transparent electrode formed by vapor-depositing indium oxide or the like on an insulating film such as polyester, is made of glass, polychlorotrifluorocarbon, etc. A structure in which the capacitor is coated and sealed with a transparent moisture-proof material such as ethylene is known.

Conventionally known organic dielectrics used here include cyanoethylated polysaccharides such as cyanoethyl cellulose, cyanoethyl starch, and cyanoethyl pullulan, and cyanoethylated polyols such as cyanoethyl polyvinyl alcohol. However, these cyanoethylated polymers have a dielectric constant of about 20 at room temperature, and their adhesion to transparent electrodes may not be sufficient. It had the disadvantage of being low.

On the other hand, conventionally known low-molecular-weight cyanoethyl compounds with a high dielectric constant include cyanoethylated sugar alcohols such as cyanoethyl sorbitol with a dielectric constant of 38 to 40, and cyanoethylated sugar alcohols such as cyanoethyl sucrose with a dielectric constant of 32 to 35. There are cyanoethylated products of low molecular weight polyhydric alcohols such as cyanoethyl glycerol having a dielectric constant of 45 to 50. However, since these are liquid at room temperature, it is extremely difficult to manufacture EL light emitting devices using them as dielectrics, and they have not yet been put into practical use.

In order to solve these problems, flexibility, adhesiveness, etc. are imparted to a film formed by mixing a high-molecular cyanoethyl compound and a low-molecular cyanoethyl compound that has a high dielectric constant and is liquid at room temperature in an arbitrary ratio. Method 1 For example, JP-A-57-
It is known from the publication No. 145295. However, if the mixing ratio of the polymer cyanoethylated compound is large in this mixture, the dielectric constant cannot be increased, and the brightness of the EL light emitting device manufactured using this mixture is not sufficient.

In addition, the dielectric constant can be increased by increasing the mixing ratio of liquid cyanoethylated in this mixture.
In this case, the formed film is soft and has poor moldability, so if this is used as a dielectric, it is difficult to manufacture an EL light emitting element with stable brightness.

(Problems to be Solved by the Invention) An object of the present invention is to eliminate the drawbacks of the prior art as described above, and to improve the dielectric constant of a low-molecular-weight cyanoethylated compound or a mixture of this and a high-molecular-weight cyanoethylated compound that is liquid at room temperature. The object of the present invention is to provide a dielectric composition useful for manufacturing a high-luminance dispersion type 81 light emitting device by imparting film forming performance without degrading it.

(Means for Solving the Problems) In order to achieve the above object, the present invention has been developed as a result of intensive research, and has been developed to produce a liquid at room temperature, which has a hydroxyl group and a cyanoethyl group in the molecule and has a substitution rate of cyanoethyl group of 80% or more. A dielectric composition prepared by blending a compound having two or more isocyanate groups in the molecule with a low-molecular-weight cyanoethyl compound or a mixture of this and a high-molecular-weight cyanoethyl compound is heat-treated to form a light-emitting layer or an insulating layer. When laminated between electrodes, a thin film with sufficient strength can be formed without reducing the dielectric constant, and when this material is used as an organic dielectric for a dispersion type 81 light emitting device, it can be used as a dispersion type light emitting device with higher brightness than conventional ones. 81
This was achieved by discovering that it can be used as a light emitting device.

The present invention will be explained in more detail below.

The cyanoethylated product having a hydroxyl group and a cyanoethyl group in the molecule as the first component constituting the dielectric composition of the present invention is a low molecular weight cyanoethylated product that is liquid at room temperature or a mixture of this and a high molecular weight cyanoethylated product. This liquid low-molecular-weight cyanoethylated product consists of:

Cyanoethyl sorbitol, cyanoethyl sucrose, cyanoethyl glycerol, cyanoethyl mannitol, cyanoethyl glucose, cyanoethylglycerol sucrose, etc., and polymeric cyanoethyl compounds include cyanoethyl cellulose, cyanoethyl starch, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethylglycerol pullulan, cyanoethyl hydroxy Examples include ethyl cellulose.

The mixing ratio of these low-molecular-weight cyanoethylated products and high-molecular-weight cyanoethylated products is such that when the mixing ratio of high-molecular-weight cyanoethylated products is increased, the dielectric constant of the mixed system decreases. The content of the cyanoethylated product is preferably 50 to 0%, preferably 30 to 0%.

Further, it is necessary to use these cyanoethyl compounds having a substitution ratio of cyanoethyl groups of 80% or more, preferably 85% or more. If this is less than 80%, the dielectric force is small and E
Since the luminance decreases when used as an L light emitting element, it is not suitable for the present invention.

Furthermore, 2 isocyanate groups as the second component are added to the molecule.
Examples of compounds having more than one isocyanate group include hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, and 4-methylene-1,3-phenylene diisocyanate. Compounds whose reactivity is controlled by protecting the structure are suitable because they reliably cause a crosslinking reaction with the residual hydroxyl group of the cyanoethyl compound at a certain temperature or higher. An example of such a compound is blocked isophorone diisocyanate sold by Daicel Co., Ltd. One example is one sold by Huls.

When the compounding ratio of the liquid low-molecular-weight cyanoethyl compound having a hydroxyl group and a cyanoethyl group and a compound having two or more isocyanate groups is 50% or more, the two components cannot be completely miscible. It may become impossible to obtain a uniform heat-treated product, or the ratio of cyanoethylated compounds may become relatively small, resulting in a decrease in dielectric constant.
% or less, the degree of crosslinking will be weak and sufficient film strength will not be obtained, and the light emitting surface will be disordered when used as an EL light emitting device. The content of the compound having an acid group is preferably 0.5 to 50%, preferably 1 to 15%.

In order to use the dielectric composition of the present invention as a light emitting layer of an EL light emitting device, the phosphor powder added as a third component may be a conventionally known phosphor powder. Examples include those calcined with copper, manganese, aluminum, bromine, chlorine, iodine, etc. added, but these are powders and granules with an average particle size of 50 um or less due to their luminescent properties when used as EL light emitting elements. It is preferable to do so.

Similarly, the high dielectric constant powder added as a third component to make the dielectric composition an insulating layer of an EL light emitting device may be a conventionally known powder, such as barium titanate, lead titanate, titanium dioxide, etc. Among these, the most common is Norium Titanate S, and its average particle size is preferably 1 to 5 um.

In order to produce an EL light emitting device from the dielectric composition according to the present invention, first 1) a cyanoethylated compound having a hydroxyl group and a cyanoethyl group and an isocyanate group in the above weight proportions are mixed together;
A homogeneous solution is obtained by mixing and stirring a compound having at least
(2) The above-mentioned phosphor powder or high dielectric powder is dispersed and blended into this mixture, (2) the resulting coating solution mainly consisting of the two types of dielectric compositions is sequentially applied to one electrode surface, and then dried.
This is carried out by heat-treating at 80 to 200° C. and laminating them as a light-emitting layer and an insulating layer, and (2) finally overlapping the other electrode.

The mixing of the first component and the second precept in Step 2 and the dispersion of the phosphor powder or high dielectric powder as the third component into this mixture in Step If the viscosity is extremely high, an organic solvent may be used as necessary. In this case, first, a cyanoethyl compound and a compound having an isocyanate group are mixed in an organic solvent consisting of only one type of acetone, ethylene glycol monomethyl ether, dimethyl formamide, cyclohexanone, etc., or a mixture of two or more thereof. This is carried out by dispersing and dissolving the material under stirring, and then adding and mixing the phosphor powder or the high dielectric powder. The amount of the phosphor powder or high dielectric powder added as the third component is determined by the amount of the phosphor powder or high dielectric powder as the third component. 20~ by volume ratio to the mixture of the second component
75% is preferred; if it is less than 75%, the concentration of the phosphor powder in the light emitting layer or the high dielectric powder in the insulating layer is too low and sufficient brightness cannot be obtained when used as an element; It becomes difficult to uniformly disperse and blend bulk powder or high dielectric constant powder.

The two types of coating liquids obtained in the above step A coating solution for an insulating layer is applied to the surface by a method such as a roll coater or screen printing, and dried to form an insulating layer with a thickness of about 10 to 30 mm.
Heat treatment and hardening at 00°C. Next, on this insulating layer, a coating liquid for a light emitting layer is applied and dried in the same manner as for the insulating layer to form a light emitting layer with a thickness of about 20 to 70 mm, and then,
It is hardened by heat treatment at 80 to 200°C. If the temperature of the heat treatment is below the above range, the crosslinking between the hydroxyl groups and isocyanate groups of the cyanoethylated product will not be sufficient, and the strength of the light-emitting layer or insulating layer will be insufficient, making it difficult to manufacture devices with a certain quality. become. In addition, if the temperature is higher than the above, the temperature approaches the thermal decomposition point of the cyanoethylated product, which may cause it to turn yellow, and when used as a device, it may cause a decrease in brightness or a change in the color of the emitted light. Undesirable.

In addition, when forming this insulating layer or luminescent layer, a catalyst such as butyltin laurate may be added to promote crosslinking between the hydroxyl group and isocyanate group of the cyanoethylated product, and various pigments may be added for the purpose of changing the luminescent color. , a dye, an organic phosphor, etc. may optionally be added to the coating liquid for the phosphor layer.

Next, a transparent conductive polyester film coated with an indium oxide/tin oxide thin film is crimped onto the light emitting layer as a transparent electrode to form a front electrode, and lead terminals are attached to the front electrode and back electrode. If the whole is sealed with a polychlorotrifluoroethylene film, the desired dispersed EL light emitting device can be obtained.

Hereinafter, specific embodiments of the present invention will be explained using examples.
The invention is not limited to this example.

(Example) Example 1 After completely dissolving 200 g of cyanoethylsucrose with a cyanoethyl group substitution rate of 85% and 20 g of hexamethylene diisocyanate in a mixed solution of acetone/methyl ethyl ketone (1/1 weight ratio), It was divided into two equal parts. On one side of this, barium titanate (
Add 468g of BT-100P (manufactured by Fuji Titanium@) and uniformly disperse it to make an insulating layer coating solution, and add to the remaining solution a mean particle size of 28. zinc sulfide phosphor for EL (type 727EL
, manufactured by Sylvania Corporation in the United States, ZnS: Cu) 315
g was added and uniformly dispersed to prepare a coating solution for a light-emitting layer.

Next, the above coating solution for an insulating layer was screen printed on a 100μ thick aluminum plate in a size of 5 x 10aa,
Vacuum drying was performed at 70° C. for 4 hours, and heat treatment was further performed at 150° C. for 1 hour to form an insulating layer with a thickness of 15 μs.

On top of this, the above coating liquid for the light emitting layer is screen printed,
After vacuum drying at 70°C for 4 hours, heat treatment was further performed at 150°C for 1 hour to form a 50μ thick luminescent layer.

Further, silver paste was printed and dried as a power supply line on a transparent conductive film (EleCrystar 300C, manufactured by Nitto Denko Koku), which had indium oxide vapor-deposited on one side of polyester, and a lead electrode made of phosphor bronze was attached.

The printed surface of the power supply line and the light emitting layer were superimposed and bonded under heat and pressure using a hot roller. The entire integrated multilayer device was sealed with a moisture-proof sheet (EL sealer, manufactured by Nitto Denko ■) made of polychlorotrifluoroethylene to obtain a dispersed EL light emitting device.

This gave uniform high-intensity light emission as shown in the following table.

Example 2 A dispersed EL light-emitting device was prepared in the same manner as in Example 1, except that the low-molecular-weight cyanoethyl compound, which is liquid at room temperature, was cyanoethyl sorbitol with a cyanoethyl group substitution rate of 86%. High brightness was obtained.

Example 3 A mixture of 20 g of cyanoethyl pullulan (87% cyanoethyl substitution rate) and 180 g of cyanoethyl sucrose (90% cyanoethyl group substitution rate) was used as a cyanoethylated product to block compounds having two or more isocyanate groups in the molecule. polyisocyanate (IPDI-8-
A dispersion type EL light-emitting device was prepared in the same manner as in Example 1, except that the compounding amount was 15 g.As shown in the following table, the light emitting surface was High brightness without any disturbance was obtained.

Comparative example 1゜cyanoethyl pullulan (cyanoethylated polysaccharide)
200g of cyanoethyl group substitution rate 87%) was mixed with acetone/
After dissolving in a mixed solution of methyl ethyl ketone (171 weight ratio), it was divided into two equal parts. Add 486 g of barium titanate with an average particle size of 1.5 um to one side and disperse it uniformly to make a coating solution for the insulating layer, and add 328 g of zinc silicide phosphor for EL with an average particle size of 28 μs to the other and disperse it evenly. Using this as a coating solution for a light-emitting layer, a dispersion type EL light-emitting device was prepared in the same manner as in Example 1, and the products shown in Table 1 were obtained.

Comparative Example 2. A mixture of 100 g of cyanoethyl pullulan (cyanoethyl group substitution rate: 87%) and 100 g of cyanoethyl sucrose (cyanoethyl group substitution rate: 90%) was used as a cyanoethyl compound to prepare a coating solution for the insulating layer and the light emitting layer. Except for the above, a dispersion type EL light emitting device was prepared in the same manner as in Example 1, and the devices shown in the first table were obtained.

Comparative example 3゜cyanoethyl sorbitol (cyanoethyl group substitution rate 86
%) and blocked polyisocyanate (supra, IPDI
-8-1530), the insulating layer and the luminescent layer were sequentially coated and dried, and then the transparent conductive film was heat-pressed without heat treatment at 150'C for 1 hour. The insulating layer leaked out from between the aluminum sheet and the transparent conductive film, making it impossible to create a dispersed EL light emitting device that gave uniform light emission.

In addition, the brightness and the uniformity of light emission in the table were determined by the following methods.

・Brightness: Initial light emission brightness when a power source of 10100 VR and 400 Hz is input under conditions of a temperature of 20°C and a relative humidity of 65%.

- Uniformity of light emission: The uniformity of the light emitting surface when turned on at 10100 VR and 400 Hz under conditions of a temperature of 80° C. and a relative humidity of 65% was observed w4 and judged according to the following criteria.

0: Uniform light emission, ×: There are variations in brightness.

(Effects of the Invention) The dielectric composition according to the present invention can form a thin film having a high dielectric constant and sufficient strength by thermal crosslinking treatment, so that a dispersed EL light emitting device manufactured using the same can have high brightness. It provides uniform light emission and can be widely applied industrially as a planar light emitter.

hand Continued Supplementary Positive book (spontaneous) 1999 Patent Application No. 2 No. 19949 2. Name of the invention a dielectric composition; Dispersed EL light emitting device obtained from this 3. Person who makes corrections Relationship with the incident Name (206)

Claims (2)

[Claims] 1. A low-molecular-weight cyanoethyl compound that is liquid at room temperature, or a mixture of this and a high-molecular-weight cyanoethyl compound, which has a hydroxyl group and a cyanoethyl group in the molecule and a substitution rate of cyanoethyl group of 80% or more, and an isocyanate group in the molecule. A dielectric composition comprising a compound having two or more of. 2. A dispersion type EL light emitting element having a light emitting layer or an insulating layer formed by adding a phosphor powder or a high dielectric powder to the dielectric composition, respectively, between electrodes.