JP2512334B2 - Distributed EL lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a distributed EL lamp, and more particularly to a distributed EL lamp with improved luminous efficiency.

<Conventional technology> Dispersion type EL lamps generally use a metal foil such as an aluminum foil as a back electrode, and disperse an inorganic high dielectric powder such as titanium oxide or barium titanate in an organic high dielectric binder on the back electrode. A reflective insulator layer, and a phosphor layer such as zinc sulfide dispersed in an organic high-dielectric binder. A light-emitting layer is formed on the reflective insulator layer. Finally, ITO (a mixture of indium oxide and tin oxide) is used. It has a structure in which a transparent electrode is provided as a counter electrode, and the phosphor emits light when an AC voltage is applied between the two electrodes.

In addition, a dispersion type EL lamp in which only a light emitting layer is interposed between a back electrode and a transparent electrode is also used.

The binder for the phosphor layer and the insulator layer used in such an EL lamp is required to have a high dielectric constant. Conventionally, as a bander for EL lamps, cyanoethylated polymer dielectrics such as cyanoethylated cellulose, cyanoethylated poval, cyanoethylated hydroxyethylcellulose, and cyanoethylated pullulan cyanoethylated starch have been used. However, these binders have a dielectric constant
It is about 10 to 20 and sufficient luminance cannot be obtained.

Therefore, as described in Patent Application Publication No. 59-15937, cyanoethylated sorbitol, cyanoethylated diglycerin, cyanoethylated pentaerythritol,
By using as a binder a mixture of a low molecular weight cyanoethylated polyol and a cyanoethylated polymer dielectric having a high dielectric constant of 20 to 60, including cyanoethylated trimethylolpropane, cyanoethylated inositol, and cyanoethylated methylglucose, as a binder. It has been proposed to increase the dielectric constant.

The above cyanoethylated compound can be obtained by reacting a compound having a hydroxyl group with acrylonitrile in the presence of an alkali according to a synthesis method described in US Pat. Nos. 3,615,539 and 3,637,656.

For example, about 0.2 mol of sodium hydroxide per one hydroxyl group in a polyol molecule is added as a 10% aqueous solution to form an alkaline solution, and about 1.5 times the molar amount of acrylonitrile is stirred at a reaction temperature of 35 to 45 ° C for 30 to 60 minutes. Drip over.
After stirring at the same temperature for about 2 hours, the resulting cyanoethylated polyol is extracted with an appropriate amount of an organic solvent (chloroform, ethyl acetate, etc.), and extracted with water, 1N acetic acid (or 1N hydrochloric acid),
After washing with water and drying over anhydrous calcium sulfate, the organic solvent is distilled off under reduced pressure, and the volatile matter is completely removed by keeping at 100 ° C. and 0.5 mmHg for 3 to 5 hours.

The dispersion-type EL lamp using the thus obtained cyanoethylated polyol and cyanoethylated polymer dielectric as a binder can show sufficient luminance, but cannot be said to be still sufficient in terms of luminous efficiency.

<Problems to be Solved by the Invention> As described above, in addition to the luminance, the characteristics required for the EL lamp include the life and the luminous efficiency. With the miniaturization of personal computers and word processors, it is desirable that the power consumption of EL lamps used for liquid crystal backlights be low. In particular, in the case of a portable device, since it is driven by a battery, if the power consumption by the EL lamp is large, the usable time is significantly shortened. The intensity of light emission per power consumption is represented by light emission efficiency. In other words, the higher the conversion ratio into the light energy per consumed power, the higher the luminous efficiency.

When a conventional binder having a high dielectric constant is used, any of the compounds has substantially no difference in luminous efficiency, and has a high luminous efficiency.
No EL lamp has been obtained. It is considered that the luminous efficiency is related to the dielectric constant, the dielectric loss tangent, and the insulation resistance of the binder.

<Means for Solving the Problem> The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, when a cyanoethylated xylitol is used as a binder in a cyanoethylated product of a polyol having a small number of carbon atoms, the luminance is particularly high. The inventors have found that a dispersion-type EL lamp having not only excellent properties but also extremely high luminous efficiency can be obtained, and based on this finding, the present invention has been accomplished. It is quite surprising that a dispersive EL lamp having excellent luminous efficiency in the time when cyanoethylated xylitol is used is obtained.

The cyanoethylated xylitol of the present invention is xylitol Is reacted with acrylonitrile in the presence of an alkali.

The cyanoethylation substitution rate is generally 95% or more, preferably
99% or more, more preferably 99.5% or more is used.

Although cyanoethylated xylitol can be used alone as a binder, it is used as a mixture with a cyanoethylated polymer dielectric. When used in combination with a cyanoethylated polymer dielectric, cyanoethylated xylitol is used in an amount of 10% by weight or more, preferably 20% by weight or more, and a cyanoethylated polymer dielectric is used in an amount of 90% by weight or more and preferably 80% by weight or less. used. The purpose of adding the cyanoethylated polymer dielectric is to reduce the fluidity of the liquid by mixing the cyanoethylated polymer dielectric with the liquid cyanoethylated xylitol, and to reduce the high dielectric particles such as phosphor particles and barium titanate. It is to prevent aggregation and sedimentation and to stabilize dispersion.

The cyanoethylated polymer dielectric is preferably a solid at room temperature having a dielectric constant of 10 or more (1 KHz, 25 ° C.). For example, cyanoethylated poval, cyanoethylated ethylene vinyl alcoholated copolymer, cyanoethylated pullulan, cyanoethylated cellulose, Examples thereof include cyanoethylated hydroxyethyl cellulose and cyanoethylated starch, and at least one of them is used.

In general, cyanoethylated polyols are liquid or waxy, and the lower the molecular weight, the higher the dielectric constant. When used as a binder, the brightness of EL lamps tends to increase. However, it is considered that the lower the molecular weight, the higher the dielectric loss tangent, the higher the power loss due to the lower insulation resistance, and the lower the luminous efficiency. On the other hand, if the molecular weight is too high, the inductivity decreases and the luminance decreases. It is considered that cyanoethylated xylitol has 5 carbon atoms and has preferable values of dielectric constant, dielectric loss tangent, and insulation resistance, respectively. As a result, it is considered that the luminance is large and the luminous efficiency is exceptionally excellent.

10% by weight or more of cyanoethylated xylitol or cyanoethylated xylitol and cyanoethylated polymer dielectric 90
Dispersion type EL using a bander containing a composition of not more than 5% by weight
The lamp is manufactured by a known method. One example will be described.

The binder is dissolved in a solvent to prepare a binder solution of 5 to 50% by weight. Next, the binder 100 was added to this solution.
The inorganic high dielectric powder is dispersed and mixed at a ratio of 50 to 900 parts by weight with respect to parts by weight to obtain a uniform slurry. This is applied on the back electrode by a general method such as a screen printing method or a casting method, and the solvent is evaporated and dried to form a reflective insulator layer. On the other hand, the phosphor is dispersed and mixed in the binder solution at a ratio of 50 to 900 parts by weight with respect to 100 parts by weight of the binder to obtain a uniform slurry. This is applied on the reflective insulator layer in the same manner as described above, and the solvent is dried to form a light emitting layer. Then, after attaching the electrode terminal to each of the obtained coating film and the glass or transparent electrode film coated with the transparent electrode, the coating surface and the conductive surface of the transparent electrode are brought into contact with each other, and these are integrated to have a composite structure. Obtain a dispersion type EL device.

It should be noted that a dispersion type EL lamp in which only the light emitting layer is sandwiched between the back electrode and the transparent electrode is manufactured by the same method.

That is, a binder containing a composition of 10% by weight or more of cyanoethylated xylitol or cyanoethylated xylitol and 90% by weight or less of a cyanoethylated polymer dielectric is dissolved in a solvent to prepare a 5 to 50% by weight binder solution.
The phosphor is dispersed and mixed in a ratio of 50 to 900 parts by weight with respect to 100 parts by weight of the binder to obtain a uniform slurry. This slurry is applied to the back electrode, and the solvent is dried to form a light emitting layer. After attaching each electrode terminal to the glass or transparent electrode film coated with the obtained coating film and transparent electrode,
The coated film is brought into contact with the conductive surface of the transparent electrode and integrated to obtain a dispersion type EL lamp.

As the phosphor used here, any phosphor such as zinc sulphide and selenium sulphide may be used as long as it is usually used for EL devices.

In addition, the inorganic high dielectric powder may be any one such as titanium oxide or barium titanate as long as it is used in a normal dispersion type EL lamp.

Solvents used to prepare the binder solution include, for example, N, N 'dimethylformamide (DMF), N,
N'-dimethylacetamide, dimethylsulfoxide,
Acetone, methyl ethyl ketone, acetonitrile and the like are exemplified.

As the electrode, any of those usually used for EL elements can be used, but for the back electrode, for example, a thickness of about 50 to 10
On the other hand, as a transparent electrode, for example, a film in which an ITO film is disposed on one surface of a polyester film having a thickness of about 75 to 125 μm to give conductivity is given as a transparent electrode.

<Effects of the Invention> The dispersion type EL device of the present invention uses a cyanoethylated xylitol or a mixture of a cyanoethylated xylitol and a cyanoethylated polymer derivative as a binder for a light emitting layer or a light emitting layer and an insulator layer, and thus is conventionally used as a binder. Compared to the cyanoethylated polyol thus obtained, it is not only inferior in luminance but also extremely excellent in luminous efficiency. The dispersion type EL lamp of the present invention has excellent luminous efficiency and requires little power consumption, and is particularly suitable for manufacturing a portable personal computer and a backlight EL lamp for word processors.

 Hereinafter, description will be made based on embodiments.

Example 1 A mixture of 30 g of cyanoethylated xylitol and 30 g of cyanoethylated pullulan was dissolved in DMF to prepare a 30% binder solution. To 100 g of this solution, 139.2 powder of barium titanate (BT-100M manufactured by Fuji Titanium Co.) as an inorganic high dielectric substance was added.
g was kneaded and dispersed to form a uniform slurry, which was applied to an aluminum plate to form a reflective insulator layer having a dry film thickness of 30 μm.

On the other hand, 98.4 g of powder of zinc sulfide (Sylvania 723 manufactured by GTE Products) was kneaded and dispersed as a phosphor in 100 g of the binder solution to form a uniform slurry, which was coated on the reflective insulator layer to form a light-emitting layer having a dry film thickness of 55 μm. Formed.

The laminate created by the above series of steps is 10 cm
After cutting to the size of × 10cm and attaching the lead terminal,
Let dry.

On the other hand, a transparent conductive film having an ITO film formed on one side of polyethylene terephthalate is similarly cut into a size of 10 cm × 10 cm, and after attaching the lead terminals, the light emitting layer of the laminate and the ITO surface of the transparent conductive film are heated. And laminated. Thereafter, a nylon film was laminated on each of the surface of the back electrode and the surface of the front electrode, and the entire circumference was surrounded and sealed with a poly (chlorotrifluoroethylene) ethylene film.

When an AC electric field of 100 V-400 Hz was applied between both electrodes of the obtained EL element, the luminance was 125 cd / m ² and the luminous efficiency was 8.1 lm / W
(Lumens / watt).

The luminous efficiency was determined from the luminance and the power consumption per unit area of the EL lamp.

Example 2 An EL lamp was prepared in the same manner as in Example 1 except that cyanoethylated poval was used instead of cyanoethylated pullulan. The luminance at 100 V-400 Hz was 105 cd / m ² , and the luminous efficiency was 8.7 lm / W.

Example 3 An EL lamp was prepared in the same manner as in Example 1 except that cyanoethylated hydroxyethyl cellulose was used instead of cyanoethylated pullulan. The luminance at 100 V-400 Hz was 114 cd / m ² and the luminous efficiency was 8.7 lm / W.

Comparative Example 1 EL was prepared in the same manner as in Example 1 except that cyanoethylated sucrose was used instead of cyanoethylated xylitol.
Prototype of lamp. The luminance at 100V-400Hz is 91cd /
m ² , and luminous efficiency was 5.7 lm / W.

Comparative Examples 2 to 6 Instead of cyanoethylated xylitol, respectively, cyanoethylated sorbitol (Comparative Example 2), cyanoethylated diglycerin (Comparative Example 3), cyanoethylated trimethylolpropane (Comparative Example 4), and cyanoethylated glycerin (Comparative Example 5). An EL lamp was experimentally manufactured in the same manner as in Example 1 except for using. As Comparative Example 6, only cyanoethylated pullulan was used as a binder. 100V for each EL lamp
Table 1 shows the luminance and luminous efficiency at -400 Hz.

Example 4 A mixture of 30 g of cyanoethylated xylitol and 30 g of cyanoethylated pullulan was dissolved in DMF to prepare a 30% binder solution. 98.4 g of powder of zinc sulfide (Sylvania 723 manufactured by GTE Products) as a phosphor was kneaded and dispersed in 100 g of this solution to form a uniform slurry, which was applied on an aluminum plate to form a light-emitting layer having a dry film thickness of 55 μm.

The laminate created by the above series of steps is 10 cm
After cutting to the size of × 10cm and attaching the lead terminal,
Let dry.

On the other hand, a transparent conductive film having an ITO film formed on one side of polyethylene terephthalate is similarly cut into a size of 10 cm × 10 cm, and after attaching the lead terminals, the light emitting layer of the laminate and the ITO surface of the transparent conductive film are heated. And laminated. Thereafter, a nylon film was laminated on each of the surface of the back electrode and the surface of the front electrode, and the entire circumference was surrounded and sealed with a poly (chlorotrifluoroethylene) ethylene film.

When an AC electric field of 100 V-400 Hz was applied between both electrodes of the obtained EL element, the luminance was 125 cd / m ² and the luminous efficiency was 7.5 lm / W
Met.

Example 5 60 g of cyanoethylated xylitol was dissolved in DMF, and 30%
Was prepared. Using this solution, an EL element was obtained in the same manner as in Example 4.

When an AC electric field of 100 V-400 Hz was applied between both electrodes of the EL device, the luminance was 130 cd / m ² and the luminous efficiency was 7.0 lm / W.

Claims (2)

(57) [Claims] 1. A light-emitting layer in which a phosphor powder is dispersed in a binder containing 10% by weight or more of cyanoethylated xylitol or a composition of 10% by weight or more of cyanoethylated xylitol and 90% by weight or less of a cyanoethylated polymer dielectric. A distributed EL lamp sandwiched between electrodes. 2. An insulating layer in which an inorganic high dielectric powder is dispersed in a binder containing a composition of 10% by weight or more of cyanoethylated xylitol or cyanoethylated xylitol and 90% by weight or less of a cyanoethylated polymer dielectric is further provided. The dispersion type EL lamp according to claim 1.