JPH03252494A - Plane light-emitting panel - Google Patents

Abstract

PURPOSE:To obtain a plane light-emitting panel, having fluorescent substance particles subjected to hydrophobic surface treatment with an organosilazane as a light-emitting layer and capable of preventing deterioration of the fluorescent substance particles by moisture absorption and remarkably increasing life. CONSTITUTION:The objective panel having fluorescent substance particles composed of ZnS:Cu, Al, ZnS:Cu, Mn, etc., subjected to hydrophobic surface treatment with an organosilazane preferably composed of a 1,3-bis(2-perfluoroalkyl) ethyl-1,1,3,3-tetramethyl-1,3-disilazane and having preferably <=44mum particle diameter as a light-emitting layer. The aforementioned panel is especially effective in an organic dispersion type electroluminescent plane light-emitting panel.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a surface-emitting type backlight for a liquid crystal display used in a personal computer or a word processor, particularly an organic dispersion type electroluminescent surface-emitting panel (hereinafter abbreviated as EL panel). ), and particularly relates to an EL panel that prevents deterioration of phosphor particles due to moisture absorption and dramatically increases the service life of the EL panel.

[Conventional technology]

In recent years, thin (less than 1 square inch thick) and lightweight (less than 1 piece thick) and lightweight (3.5 mm thick) 0.1gf/ci) and low power consumption (less than 5I111/-), research into the practical use of EL panels is progressing, and they are being used, for example, as buff lights for transmissive LCDs, for book-type personal computers, notebook-type word processors, etc. It is now installed.

Organic dispersion type EL panels, which emit light by applying an alternating electric field, are mainly used in EL panels, but these panels have a particle size of 10
~50 μm ZnS-based phosphor particles were dispersed in a highly dielectric polymer such as cyanoethyl pullulan (relative dielectric constant εS - about 16), and a back electrode made of A1 foil and a bus electrode were formed around the outer periphery. It is sandwiched between transparent electrodes made of ITO (indium tin oxide) vapor-deposited film to form a kind of parallel plate capacitor, and by applying an alternating electric field between the two opposing electrodes, the crystal grain boundaries of the phosphor are It excites the luminescent centers formed in the rays, producing blue-green, white, etc. luminescence. That is, for example, as a phosphor that emits blue-green light, Zn5HCu and AI are used, ZnS is a fluorophore, Cu is an impurity for forming a luminescent center and is called an activator, and A1 is an activator. Cu is an impurity that makes it electrically neutral and allows it to enter ZnS.
Cu and S precipitate at the grain boundaries of S, forming a moft junction or a Schottky junction with ZnS, and when a voltage is applied, an electric field is concentrated in this part, and the luminescent center is excited, producing light emission. It is.

[Problem to be solved by the invention]

These EL panels not only exhibit effective light emitting performance, but also
Easy to replace when the service life has expired, visible light range (wavelength 3)
80~7B0nm), so it is easy on the eyes.However, compared to cold cathode fluorescent lamp backlights (hereinafter referred to as CCFL), which are commonly used as LCD backlights, they have the disadvantages of a shorter lifespan and lower brightness. Its lifespan (half-life of luminance) is an order of magnitude lower, less than 3,000 hours compared to CCFL's 20,000 hours, and its luminance is 1,000 to 5,000 cd/
It is as low as 60 to 120 cd/M.

The reason for the short lifespan of EL panels is that the ZnS-based phosphor particles are hydrolyzed by the presence of moisture in the atmosphere, resulting in a significant decrease in brightness. Package the front and back surfaces of the opposing picture electrodes with a moisture-proof film such as polychlorotrifluoroethylene (moisture permeability ≦0.02g-Tsuru/day),
In addition, the edges of the moisture-proof film are sealed using real-melt adhesive or direct heat-sealing, and a water-trapping layer such as nylon 6 (moisture absorption rate -9.5%) film is placed between the moisture-proof film and the electrode. Although this has been improved to a practical level, the moisture-proofing effect is not sufficient, and due to the absorption of moisture by the phosphor particles, the lifespan gradually decreases when the applied voltage and/or frequency is increased to increase the brightness. There are drawbacks. In other words, the currently widely used EL panel is AC100V
When applying 400Hz, the life is about 3,000 hours and the brightness is 60cd/rr+, but AC120V x 600
When Hz is applied, the brightness increases to 120 cd/m, but the lifetime decreases to 1,500 hours, and if you try to obtain the same brightness as a CCFL, the lifetime will decrease to several tens of hours, which is a problem.

Therefore, since conventional EL panels do not have sufficient moisture-proofing measures for the phosphor particles, they have problems of short lifespan and low brightness due to moisture absorption of the phosphor particles, and are thought to have inferior luminous performance compared to CCFL. The current situation is that

The present invention eliminates these conventional problems, and completely hydrophobicizes the surface of the phosphor particles to prevent moisture absorption, extend the life of the phosphor, and achieve high brightness. It provides panels at low cost.

[Means to solve the problem]

The present invention is characterized in that an EL panel is subjected to hydrophobic surface treatment with organosilazane and is provided with phosphor particles having a hydrophobic surface as a light emitting layer.

[For production]

Inorganic substances such as phosphor particles ZnS in the light-emitting layer of the EL panel of the present invention have hydrophilic -OH groups ion-adsorbed on the surface, and when moisture in the atmosphere comes into contact with this, it adsorbs it and hydrolyzes it. Wake up, Zn, 302. A decrease in brightness occurs due to the change to H2, and the present invention suppresses the decrease in brightness due to hydrolysis by actively eliminating contact with moisture by the phosphor particles themselves. As a result, the lifespan of the EL panel can be extended reliably.

〔Example〕

In the implementation of the present invention, the phosphor particles 2 were subjected to hydrophobic surface treatment with organosilazane as in the first round.
The luminescent N4 dispersed in a highly dielectric polymer binder 3 is laminated between the back electrode 5 and the fog electrode 6, and is covered with a package film 7 as necessary to form the EL panel 1. be. In this case, the organosilazane used is a silazane represented by the formula (i) in which hydrogen is replaced with an organic group (when n is 1, it is called disilazane, when n is 2, it is called trisilazane, etc.), and 1.1. 3.3-tetramethyldisilazane (formula (ii)), hexamethyldisilazane ([1
ii) formula), heptamethyldisilazane (formula (iv))
, 1.3-divinyl-1,1,3,3-tetramethyldisilazane ([V] formula), 1.3-bis(chloromethyl)4.1.3.3-tetramethyldisilazane ((vi)
2), 1.1.3.3.5.5-Hexamethylcyclotrisilazane 1Vi) Formula), 1.1.3.3.5.5.
7.7. -octamethylcyclotetrasilazane ([43
Formula), 1,3-bis(2-perfluoroalkyl)ethyl-1,1,3,3-tetramethyl-1,3-disilazane (Cix) formula), etc., but when the hydrophobic trimethyl group is Hexamethyldisilazane (hereinafter referred to as HMDS), which can be formed on an inorganic surface and is easy to produce and is the cheapest, or 1,3-, which can form a more water-repellent perfluoroalkyl group on an inorganic surface. Preference is given to using bis(2-perfluoroalkyl)ethyl-1,1,3,3-tetramethyl-1,3-disilazane.

B)1B-(Si-NH), -St-1(...
(i) II) 1 C1's CH3 H-St -NH 31H...i] 1h C) I3 CHl CI (3 CHs St NHSi CH3.
= (iii)C)13 CH3 CHs CH3 CH3-Si -N(CH3) -Si CL
-(iv) CH3 CFI.

CL CFI3 CHx =CH5i-NH-5i-CH=CH2-[
v) CI (3 ll5 CH.

CH.

CICHz 5i-N)l-5i-CHlCl
-(vi) CH3CL,. Hs)zsi / \o(.Hs)x-(vi) ■\ /NH 31(CI(3) z N)I,. l5) zsi / / ■\ \Si(.H3)2 \ /NH-(anatomyil CHl CH3 CJ*m*ICBzCHt Si NH5i-CT
l*CHxCaFzn*+-(ix)CHs C
Hs [However, in the formula, n is −・−・・−・−・・−・・−・・−
] Taking HMDS as an example,
HMDS has a structural formula of [13] with a boiling point of 126°C (
Vapor pressure 79mHgat 50℃), density 0.77g/d
, is a solvent-free solution with a viscosity of 0.7 cP, and surface treatment can be easily performed by immersing inorganic phosphor particles therein and air drying. That is, two hydrophilic 10H groups ionically adsorbed on the inorganic surface and one HMDS undergo a condensation reaction, releasing ammonia NH3, and forming a hydrophobic trimethylsiloxy group 0-5i (Cl co). (FIG. 2).

This hydrophobic surface treatment can block contact with moisture entering from the atmosphere, and can prevent hydrolysis of ZnS, that is, a decrease in brightness over time.

In addition, the fluorine-containing silazane, 1,3-bis(2-perfluoroalkyl)ethyl-1,1,3,3-tetramethyl-1,3-disilazane, has a solid content of 1 to 1% dissolved in Freon 113 solvent. Surface treatment can be performed by dipping inorganic phosphor particles in a 10% solution, air drying, and then heating at 150° C. for about 30 minutes.

At this time, since the perfluoroalkyldimethylsiloxy group formed on the surface contains fluorine, it exhibits water repellency greater than that of the trimethylsiloxy group, and is more effective for the purpose of the present invention. is a perfluoromethyl group -CF3. Perfluorobutyl group
Examples include CaFq, perfluorohexyl group -CJI3+, perfluorooctyl group -CJ+q, and the use of perfluorooctyl group is most preferred since it provides the maximum water repellency.

In addition, the phosphor particles used in this EL panel include ZnS; Cu, ^1, ZnS; Cu,
It is desirable to use a 325 mesh bath (44 μm or less) product in terms of particle size range, but if necessary, ZnS; Cu, CI, ZnS; Cu, ), Zn.
S; Cu, ZnS; Mn”, ZnS; DingbF3,
ZnS; EuF2, ZnS; SmFx,
ZnS:PrF3, CaS:EuFs, SrS:Ce, etc. are selected and used.

In addition, to make an EL panel, a light-emitting layer consisting of a highly dielectric polymer binder (cyanoethyl pullulan) that disperses and fixes the phosphor particles, a transparent electrode (ITO vapor-deposited polyester film), a back electrode (AI foil), and a water-trapping layer are also used. N (nylon 6 film), the front and back package films (PCTFE films) and the sealing method (hot melt resin bonding@), etc., are preferably conventionally used. Since the phosphor particles themselves are hydrophobic or water-repellent, they can block and protect the phosphor particles from moisture in the atmosphere, and the hydrophobic surface can actively exclude moisture, making it possible for EL panels to It is easy to achieve long service life, and it is also possible to omit the water replenishment layer and use inexpensive engineering plastic films such as polyester films and polycarbonate films as package films instead of using expensive fluororesin films. be.

Next, examples of the present invention will be shown.

〔Example〕

The particle size range is 325 menshu pass, the compound structural formula is Zn5HCu, AI, and the peak wavelength is 508 nm.
, 100 parts by weight of phosphor particles Sylvania #723 (manufactured by GTE Products, USA, trade name) for EL panels, which emit blue-green color, were added to HMDS, and 300 parts by weight of LS-7150 (manufactured by Shin-Etsu Chemical Co., Ltd., trade name). The sample was immersed in a portion by weight for 5 minutes, and then air-dried for 30 minutes or more. Hereinafter, this will be referred to as processed ZnS.

On the other hand, 1 to 10 kl (100 parts by weight of cyanoethyl pullulan with a relative dielectric constant εS at z of about 16, Sialdin "CR-5" (manufactured by Shin-Etsu Chemical, trade name)) was added to an acetone/dimethylformamide (9/1) mixed solvent. To this solution, 100 parts by weight of treated ZnS powder was added and dispersed to prepare a treated ZnS dispersed binder solution having a solid content of 25% by weight.

This treated ZnS dispersed binder solution was applied to a 90 μm thick AI foil using a comma coater to a dry thickness of 6 μm.
CEREC "K -" is a transparent conductive film with a visible light transmittance of 80%, which is made by coating a polyester film with a thickness of 0 μm and volatilizing the solvent, and then forming an ITO vapor-deposited film with a surface resistance of 300 Ω/hole on a 125 μm thick polyester film. E
A transparent electrode formed with a paste bath electrode was layered around C, and the molding pressure was 1 kgf/ci, 1 by hot pressing.
The above binder was cured under the conditions of 20°C x 10 minutes, and a treated ZnS-filled cyanoethyl cellulose layer with a thickness of 60 μm was tightly sandwiched between the back electrode (AI foil) and the transparent electrode, and the outer dimensions were 1100 wm x 100 cm. It was cut into

Next, a water-trapping layer film, Bonyl l' (manufactured by Kojin ■, 5 Product name) External dimensions 110
0m x 100, stacked on the outside of the above counter electrode with the true melt adhesive layer inside, and further on the front and back sides, a PC with a permeability of 1.0g/rd-day or less and a thickness of 200μm.
Nidoflon is a moisture-proof film with a 50 μm thick ethylene-ethyl acrylate copolymer (melting point 85°C) N formed as a true melt adhesive layer on one side of a TFE film.
Cut l1k14810 (manufactured by Nitto Electric Kogyo ■, trade name) into outer dimensions of 1 l 10 m x 110 mm, and stack the melt adhesive layer on the inside with the melt adhesive layer protruding 5 days on each side from the outer shape of the counter electrode. (100 days x 10
A molding pressure of 1 ksrf/cI was applied by hot pressing using a jig that applied equal pressure to the edge (0 m) and the edge (5 m).
11. Heat sealing and bonding was performed under the conditions of 130°C x 10 minutes. In addition, the bus electrode of the transparent electrode and a part of the back electrode were pulled out in a tail shape to the outside with external dimensions 11 (1 w x 110 m) to serve as terminals.

Next, connect the A
Apply C120VX600Hz and measure luminance meter LS in a dark room.
-100 (Minolta camera g%.

When the brightness was measured using the product name), it was 120 cd/
I got -.

[Comparative example]

Next, in addition to this treated ZnS-filled EL panel (hereinafter referred to as A panel), a ZnS;Cu without HMDS treatment was prepared.
, A1 particles, and Sylvania #723 (manufactured by GTE Products, USA, trade name) were used, and the other manufacturing methods were exactly the same to produce an untreated ZnS-filled EL panel (hereinafter referred to as B panel).
) was made in the same way and the brightness was measured and it was the same <
120 cd/rrr was obtained.

Although it is difficult to evaluate the luminance half-life over a long period of time, assuming that the luminance decays logarithmically linearly over time, the time it takes for the luminance to decay to 90% is Δt0.
．． and the time Δt until it decays to 50%, -1og0.9/Δta1. we-10go, 5/
Since there is a relationship between Δte and s, Δt0. ．． If evaluated, the luminance half-life Δt0. ．． evaluation becomes possible.

When evaluating Δto, 9 for the above A panel and B panel, it was found that while the B panel was 250 hours, the A panel had a brightness decay rate of 3 after 1000 hours.
%, and this can be expressed as the above relationship (-1og0.97/Δt
++, qt = -1og0.5/Δto, s), the luminance half-life was approximately 20,000 hours. In addition, the applied voltage and frequency conditions are AC150VX800H.
When the brightness was measured as z, it was 400 cd/rrr, and the brightness decay rate after 1000 hours under these conditions was 6%. Therefore, if the brightness half-life was evaluated in the same way as above, it would be about 11,000 hours, and the brightness 400cd/d
Since this is currently considered the target value for EL panels, it can be said that the EL panel is sufficiently durable for practical use.

〔Effect of the invention〕

The present invention provides a surface-emitting panel that includes phosphor particles whose surface has been hydrophobically treated with organosilazane as a light-emitting layer, so that each phosphor particle can have a hydrophobic surface. Since it blocks moisture from entering from the atmosphere, it is possible to prevent a decrease in brightness due to hydrolysis of ZnS-based phosphor particles, which dramatically increases the lifespan (brightness half-life). In order to block the intrusion of moisture, there is no need to use expensive fluororesin films on the front and back surfaces when creating a pancage, and it is possible to replace it with an inexpensive engineering plastic film, and the water-trapping layer film can be omitted. Therefore, not only can the manufacturing process be simplified, but also the hydrophobic surface treatment of the phosphor particles can be achieved by a simple dipping treatment, making it possible to provide a surface-emitting panel with a simple structure and low cost.

[Brief explanation of drawings]

FIG. 1 shows a longitudinal sectional view showing an embodiment of the present invention, and FIG.
The figure shows a schematic diagram of the chemical structure of the hydrophobic surface treatment of the present invention. DESCRIPTION OF SYMBOLS 1... EL panel of the present invention, 2... Fluorescent particles subjected to hydrophobic surface treatment, 3... High dielectric polymer binder, 4... Light emitting layer, 5... Back electrode, 6...Transparent electrode, 7...Buff cage film.

Claims (1)

[Claims] (1) A surface emitting panel characterized in that it includes phosphor particles whose surface has been hydrophobically treated with organosilazane as a light emitting layer.