JPH02309593A - Dielectric composition and dispersion-type electric field luminous element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a dispersion electroluminescent device that is heat resistant and has excellent performance even under high temperature conditions, and a dielectric composition used therein. be.

(Prior art) Electroluminescent elements are divided into dispersion type and thin film type depending on the structure of the light emitting layer, but unlike conventional light emitting elements, electroluminescent elements have the characteristic of providing planar light emission with low power consumption, and are suitable for various light sources. In recent years, it has rapidly attracted attention as a display panel. In particular, distributed electroluminescent devices have the advantage of being easy to manufacture, inexpensive, and can be manufactured into devices of any shape, and are used in backlights for liquid crystal displays, guide lights, and night lights. Practical implementation is progressing as such.

Such a dispersion type electroluminescent device is generally produced by first dispersing insulating powder such as barium titanate in a dielectric material solution onto a back electrode such as aluminum foil, then coating and drying it. After forming the #L layer, ZnS, Z
Electroluminescent powder such as n5e is dispersed in a dielectric material solution, which is coated and dried to form a luminescent layer, and an indium oxide/tin oxide thin film (hereinafter simply ITO
A polyester film coated with a transparent conductive film, such as ( There is.

The dielectric materials used here include cyanoethylated polysaccharides such as cyanoethyl cellulose, cyanoethyl starch, and cyanoethyl pullulan, cyanoethylated polysaccharide derivatives such as cyanoethyl hydroxyethyl cellulose and cyanoethylglycerol pullulan, and polyols such as cyanoethyl polyvinyl alcohol. Examples include polymeric substances with a high dielectric constant such as cyanoethylated substances, but these have various drawbacks and are not satisfactory.

(Problems to be Solved by the Invention) For example, cyanoethyl cellulose has a too high softening temperature, so if it is used as a dielectric material in the light emitting layer,
It becomes difficult to thermocompress polyester-based transparent electrodes, and it becomes necessary to coat with silver paste or the like when forming transparent electrodes. This means that the transparency of the transparent electrode,
This brings about the drawbacks of impairing uniformity and impairing production efficiency.

On the other hand, cyanoethyl starch, cyanoethyl pullulan, cyanethyl glycerol pullulan, cyanoethyl cellulose, cyanoethyl hydroxyethyl cellulose, etc. have a low softening temperature, so when they are used as dielectric materials for the light emitting layer, polyester transparent electrodes can be easily bonded by thermocompression bonding. On the other hand, distributed electroluminescent devices that use materials with a low softening temperature for the emissive layer and insulating layer are used in fields that require use at high temperatures, such as in automobiles, because the emissive layer and insulating layer are This leads to deformation due to softening, which leads to problems such as a decrease in life span and loss of uniformity of light emission.

In addition, the light-emitting layer in a distributed electroluminescent device is generally formed by coating and drying on an insulating layer, but in this case, the dielectric material in the insulating layer is partially dissolved depending on the solvent composition of the coating solution, resulting in a uniform layer. This hinders the formation of a clear laminated layer and causes defects such as peeling, cracking, and bubbles in the luminescent layer and insulating layer of the final product.

Accordingly, one object of the present invention is to provide a dielectric composition which has a softening temperature low enough for thermocompression bonding of polyester transparent electrodes, and which has improved heat resistance and solvent resistance after curing.

(Means for Solving the Problems) As a result of intensive research to solve the problem of dielectric material theft used in conventional distributed electric field devices, the present invention has developed A cyanoethylated compound derivative in which the hydrogen atom of the hydroxyl group of the compound is substituted with an N-methylene acrylamide group (-CH2-NH<○-CH=C:H2), a photopolymerization initiator, and an electroluminescent powder or a highly dielectric material. It has been discovered that when a dielectric composition consisting of powder and granules is used as a material for a light-emitting layer or an insulating layer of a dispersion-type electroluminescence device, a dispersion-type electroluminescence device having unprecedented advantages can be obtained. This led to the invention.

The present invention will be explained in more detail below.

In the cyanoethylated derivative as the first component constituting the dielectric composition of the present invention, the hydrogen atom of the hydroxyl group of the cyanoethylated compound having a hydroxyl group and a cyanethyl group in the molecule is an N-methylene acrylamide group (-CH2-NH-C ○
-CH=CH,) has a cyanoethyl group and an N-methylene acrylamide group in two molecules, so it basically has the same high dielectric constant as a cyanoethylated compound, but has a high dielectric constant as a photopolymerization initiator. It also has the function of an N-methylene acrylamide group in which a crosslinking reaction proceeds when irradiated with light such as ultraviolet rays or electron beams.

Such cyanoethylated product derivatives are produced by starting from a cyanoethylated product having a hydroxyl group and a cyanoethyl group in the molecule, such as cyanoethyl pullulan, cyanoethylglycerol pullulan, cyanoethyl starch, cyanoethyl cellulose, cyanoethyl hydroxyethyl cellulose, or cyanoethyl polyvinyl alcohol, and then adding N to it. -methylolacrylamide (CHyo=CH-Go-NH(
;H2) can be easily produced by reacting.

This method involves adding a cyanoethylated compound, N-
Stirring or kneading the reaction mixture in a state in which methylolacrylamide, an acid catalyst, a polymerization inhibitor, etc. are dissolved and dispersed, giving the temperature and time necessary for the reaction of the desired amount of N-methylolacrylamide. This can be done by

The total functional group (
The molar ratio of cyanoethyl group to hydroxyl group (1N-methylene acrylamide group) is 60 to 98.
%, N-methylene acrylamide groups is preferably 2 to 40%. This means that the molar ratio of cyanoethyl groups is 6.
It is less than 0%.

This is because the dielectric constant is too low to increase the brightness of the dispersion type electroluminescent device, and if it exceeds 98%, the molar ratio of N-methylene acrylamide groups decreases, making it impossible to cause a sufficient crosslinking reaction.

Note that among these derivatives, those used in the light emitting layer in particular have a softening temperature of 200° C. or lower from the viewpoint of thermocompression adhesion to the polyester transparent electrode.

The photopolymerization initiator as the second component constituting the dielectric composition includes acetophenone and benzyl.

Examples include those commonly used in the production of photocurable resins, such as biacetyl and azobisisobutyronitrile.

Further, the electroluminescent powder serving as the third component may be of conventionally known type, including CdS, ZnS, Zn5e, and Zn5e.
Fluorescent substances such as 5iO, BN, and SiC are exemplified, but from the viewpoint of luminescent properties when used as an electroluminescent device, it is preferable to use powder particles with an average particle size of 504 or less.

Similarly, the highly dielectric powder may be any conventionally known inorganic compound with a high dielectric constant, such as lead titanate, titanium dioxide, barium titanate, etc. Barium titanate is the most common, and those with an average particle size of 1 to 2p are particularly preferred.

The production of a dispersion type electroluminescent device according to the present invention involves firstly (1) forming a light-emitting layer of a dielectric composition comprising a cyanoethylated derivative, a photopolymerization initiator, and an electroluminescent powder or highly dielectric powder; @ After preparing the coating liquid for the edge, ■ apply these two types of coating liquid alternately to one electrode surface. After drying, photo-cure and laminate as a light-emitting layer or an insulating layer, and finally coat the other electrode surface. This is achieved by overlapping the electrodes.

The preparation of the coating solution of the dielectric composition in step ① is as follows.
The second component, the cyanoethylated derivative and the photopolymerization initiator, are mixed with only one organic solvent such as acetone, N,N″-dimethylformamide, nitromethane, ethylene glycol 7-methyl ether, and N-methyl-2-pyrrolidone. or after being dissolved in a mixture of two or more,
This is carried out by dispersing and blending the third component, electroluminescent powder or highly dielectric powder, to form a luminescent layer coating liquid or an insulating layer coating liquid, respectively.

In this case, the amount of the electroluminescent powder or highly dielectric powder to be added is preferably 20 to 80% by volume relative to the cyanoethylated derivative as the first component, and if it is less than 20%, The concentration of the electroluminescent powder in the luminescent layer or the highly dielectric powder in the insulating layer is too low to provide sufficient brightness when used as an element, and if it exceeds 80%, the electroluminescent powder Uniform dispersion of granules or highly dielectric powder becomes difficult.

In step 2, first, a coating solution for an insulating layer containing highly dielectric powder is applied to the back electrode surface of an aluminum foil, etc. using a roll coater.
Alternatively, after coating and drying by screen printing or the like, it is cured by light irradiation to a thickness of about 10 to 50 mm. form an insulating layer. Next, a coating liquid for a luminescent layer containing electroluminescent powder is similarly applied to the surface of this insulating layer, dried, and then cured by light irradiation to form a luminescent layer having a thickness of about 20 to 70 mm.

A transparent electrode with a polyester film surface covered with a transparent conductive film such as ITO is placed on top of this light emitting layer at 100 to 200°C.
The transparent electrode and the back electrode are bonded by thermocompression, lead wires as electrode terminals are attached to each of the transparent electrode and the back electrode, and finally, the whole is covered and sealed with a moisture-proof film, thereby producing a distributed electroluminescent device according to the present invention. is obtained.

This dispersed electroluminescent element has a softening temperature and solvent solubility suitable for thermocompression bonding in its untreated state as a dielectric material, but it can be cross-linked by being irradiated with light in the presence of a photopolymerization initiator. Because it uses a cyanoethylated derivative that reacts and improves heat resistance and solvent resistance, it not only has good productivity but also reduces the frequency of defective products, and even under high-temperature conditions, there is no reduction in service life or luminescence. This has the advantage of not causing disadvantages such as non-uniformity.

Hereinafter, specific embodiments of the present invention will be explained with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

(Example) Reference Example IQ acetone was placed in a reactor equipped with a 1° stirring blade, and while stirring, 150 g of cyanoethyl pullulan (Sialzin CR-3, part name manufactured by Shin-Etsu Chemical Co., Ltd.) was added and dissolved.

Add to this 1 g of hydroquinone methyl ether, 0.5 g of 85% phosphoric acid, and 100 g of N-methylolacrylamide.
was added and reacted at a temperature of 50°C for 4 hours.

After the reaction solution was cooled, it was poured into water with strong stirring to precipitate the product, which was then washed repeatedly with pure water, dehydrated, and dried to obtain an N-methylene acrylamide group-substituted product of cyanoethyl pullulan. The molar ratio of each substituent in this cyanoethylated derivative was as follows.

Cyanoethyl group: 91% N-methylene acrylamide group: 5/J Reference example 2゜N-methylene acrylamide of cyanoethyl polyvinyl alcohol was obtained in the same manner as in the previous example except that cyanoethyl polyvinyl alcohol was used instead of cyanoethyl pullulan in the previous example. A group-substituted product was obtained. The molar ratio of each substituent in this cyanoethylated derivative was as follows.

Cyanoethyl group: 91% N-methylene acrylamide group: 5〃Reference example 3゜Cyanoethyl starch was used instead of cyanoethyl starch in Example 1. An acrylamide group-substituted product was obtained. The molar ratio of each substituent in this cyanoethylated derivative was as follows.

Cyanoethyl group = 92% N-methylene acrylamide group: 4! I Examples 1-3
゜80 g of each of the cyanoethyl derivatives obtained in Reference Examples 1 to 3 was dissolved in 300 g of N,N'-dimethylformamide along with 3 g of benzyl, each of the resulting solutions was divided into two equal parts, and one of them was poured into two equal parts. Barium titanate with a particle size of 1 to 2 μm is added at a volume ratio of 50% and uniformly dispersed to form a coating solution for an insulating layer.
Electroluminescent zinc sulfide phosphor (ZnS: Cu
Cl ) was added at a volume ratio of 50% and uniformly dispersed to obtain a coating liquid for a light-emitting layer.

Next, each insulating layer coating solution was screen printed on a 50 μI thick aluminum foil, dried at 120°C for 8 hours, and then exposed to ultraviolet light 10 times at a running speed of 5 m/min using a high-pressure mercury lamp with a lamp power of 80 W/am. irradiation to form an insulating layer with a thickness of 15 μm. A coating solution for a light-emitting layer was further screen-printed on top of this, and similarly dried at 120°C for 8 hours to a thickness of 40. luminescent layers were laminated.

A polyester film coated with a transparent conductive film such as ITO was placed on top of this light emitting layer and heated at 170°C.
After thermocompression bonding at 0 kg/cd, ultraviolet rays were irradiated from the transparent electrode side under the same conditions as above.

Finally, the entire structure was covered with a polychlorotrifluoroethylene-based moisture-proof film and sealed, thereby producing three types of dispersion type electroluminescent devices 1-1■ according to the present invention.

The uniformity of light emission, brightness, and half-life of each of the obtained dispersion type electroluminescent devices 1 to 1 were examined, and the results shown in the attached table were obtained.

Comparative Examples 1 to 3° 80 g each of cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, and cyanoethyl starch were
, dissolved in 300 g of N'-dimethylformamide, and the resulting solution was divided into two equal parts.
50% by volume of barium titanate (μs) is added and uniformly dispersed to form a coating solution for an insulating layer.On the other hand, an electroluminescent zinc sulfide phosphor (Z
nS: CuC1) was added at a volume ratio of 50% and uniformly dispersed to obtain a coating liquid for a light-emitting layer.

Next, each coating solution for an insulating layer was screen printed on an aluminum plate having a thickness of 50 μm, and dried at 120° C. for 8 hours to form an insulating layer having a thickness of 15 μm. On top of this, a coating solution for a luminescent layer was further screen printed, and similarly dried at 120° C. for 8 hours to form a luminescent layer with a thickness of 40 μs.

A polyester film coated with a transparent conductive film such as ITO was layered on top of this light emitting layer, and heated to 1.70°C.
Thermocompression bonding was carried out at 10 kg/ad.

Finally, the entire structure was covered with a polychlorotrifluoroethylene-based moisture-proof film and then sealed to produce three types of dispersed electroluminescent devices (1) to (2).

When the uniformity of light emission, brightness, and half-life of each of the obtained dispersion type electroluminescent devices IV to IV were examined, the results shown in the attached table were obtained.

The molar ratios of cyanoethyl groups in the cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, and cyanoethyl starch used are as follows.

Cyanoethyl pullulan: 92% cyanoethyl polyvinyl alcohol: 9111 Cyanoethyl starch: 911r The luminescent properties of uniformity of luminescence, brightness, and half-life in Table 1 were measured by the following methods.

- Uniformity of light emission: The uniformity of the light emission surface was observed when the light was turned on at 51.200V under conditions of a temperature of 80° C. and a relative humidity of 65%, and was judged according to the following criteria.

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

- Brightness: Initial brightness when 50) 1z, 200v power is input under conditions of temperature 80°C and relative humidity 65%.

・Half-life: The time required for the brightness to decrease by half when the light is turned on at 507.200V under conditions of a temperature of 80°C and relative humidity of 65%.

(Effect of the invention) According to the dielectric composition of the present invention.

■The emissive layer formed using a cyanoethylated derivative together with a photopolymerization initiator and electroluminescent powder has a softening temperature low enough to thermocompress a polyester transparent electrode, and Since the derivative undergoes a crosslinking reaction and is cured by ultraviolet irradiation, the light-emitting layer does not soften even under high-temperature conditions, thus providing a dispersed electroluminescent device with a long life and uniform luminescence.

■The insulating layer formed by using the above derivative together with a photopolymerization initiator and highly dielectric powder particles has improved heat resistance as it undergoes a crosslinking reaction when irradiated with ultraviolet rays, as in the above (■). Even if the above-mentioned coating liquid for forming a luminescent layer is used, the insulating layer will not be dissolved by the solvent.
Defects such as peeling, cracking, and bubbles do not occur in the light emitting layer or insulating layer.

Furthermore, the dispersed electroluminescent device obtained from this dielectric composition has excellent heat resistance and solvent resistance, has a low rate of defective products during manufacturing, and has a short lifespan and no luminescence under high-temperature operating conditions. Since it has the advantage of not causing uniformity, it can be widely applied industrially as a planar light emitter.

Claims (2)

[Claims] 1. A cyanoethylated derivative having a hydroxyl group and a cyanoethyl group in its molecule, in which the hydrogen atom of the hydroxyl group is substituted with an N-methylene acrylamide group, a photopolymerization initiator, and an electroluminescent powder or highly dielectric powder. A dielectric composition consisting of. 2. A dispersed electroluminescent device in which a light-irradiated material of a dielectric composition containing the electroluminescent powder or highly dielectric powder according to claim 1 is interposed between electrodes as a light-emitting layer or an insulating layer, respectively. .