KR100814469B1 - Dielectric paste composition for inorganic el sheet - Google Patents

Abstract

A dielectric paste composition for an inorganic electroluminescence(EL) sheet is provided to impart excellent luminance and voltage resistance to an organic EL sheet even with a small thickness, and to realize excellent flexibility, soft touch feel, printability, readhesion and dimensional stability. A dielectric paste composition for an inorganic EL sheet comprises, based on 100 parts by weight of strontium titanate(SrTiO6), 2-60 parts by weight of a fluororesin, 2-10 parts by weight of a polyester binder polymer, and 2-20 parts by weight of a polyurethane adhesive. The dielectric paste composition further comprises 0-2 parts by weight of a dispersant and 0-2 parts by weight of a stabilizer. The fluororesin has a molecular weight of 150000-300000.

Description

Dielectric paste composition for inorganic EL sheet {DIELECTRIC PASTE COMPOSITION FOR INORGANIC® EL SHEET}

1 is a view schematically showing a standard build of a general EL sheet.

2 is a view schematically showing a reverse build of a general EL sheet;

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the fabrication of a thick film type inorganic EL device, and more particularly, by using a strontium titanate (SrTiO ₃ ) inorganic filler and a polyurethane adhesive component as a dielectric paste composition, even when a dielectric layer is formed to a thinner thickness, The present invention relates to a dielectric paste composition having a high voltage resistance and capable of producing an inorganic EL sheet having excellent flexibility and soft touch.

As shown in FIG. 1, the thick film type inorganic EL sheet having a standard build includes a phosphor paste forming a phosphor layer 2 on a lowermost PET film 1, a dielectric paste forming a dielectric layer 3, and a dielectric paste. Carbon electrode paste constituting the back electrode layer (Bus bar, 4), silver terminal electrode (Termination conductor, 5), and protective layer (Encapsulant, 6) are sequentially laminated by screen printing.

In addition, as shown in FIG. 2, in the reverse build thick film type inorganic EL sheet, a circuit board (PWB substrate) 1 is positioned at the bottom, and a PUR or PET film (Clear Encapsulant, 6) at the top is disposed on the bottom. A transparent conductive ink (7) is applied, and phosphor paste forming the phosphor layer (2), dielectric paste forming the dielectric layer (3) and carbon electrode paste forming the back electrode layer (4) and silver terminals Terminal electrodes 5 are sequentially laminated by screen printing.

The thick film EL sheet of the standard structure has been used mainly as a backlight that is responsible for the light emitting function of a black and white LCD screen in advertising signs and mobile phones because of the advantages of thin thickness, impact resistance, and uniform brightness. . In addition, the light emission reaction time is short, such as a few microseconds, the viewing angle is wide, and excellent durability against vibration, the development of a portable light source as a light source for easy mobility is continuously made.

The conventional dielectric paste is a product developed exclusively for ITO film substrates and is closely related to the luminance of the entire device according to the function of the dielectric layer and the barrier film function which protects the phosphor layer of the EL sheet and prevents penetration of moisture.

Moisture-proof dielectric pastes for these applications are typically high-k dielectric polymers with various additive-dispersants, viscosity modifiers, storage stabilizers, along with CYANOETHYL series resins or Thermoplastic fluorocarbon resins, polyesters, and finely dispersed inorganic fillers. And the like in an appropriate proportion.

However, the dry type of cyanoethylated ethylene-vinyl alcohol copolymer or fluorinated olefin copolymer of the prior art is inferior in life time, flexible film matching, bending resistance, and abrasion resistance. There is a problem that the use is limited for advertising.

In addition, in order to impart desired luminance and good pressure resistance, it is necessary to print the dielectric layer to have a thickness of 20 microns or more, but on the contrary, there is a problem that the flexibility is lowered and the click feeling is damaged.

Recently, the development scope has been expanded to include not only advertising lighting and LCD backlight unit (BLU) but also slim cell phone keypad light source and automobile interior materials. Therefore, high reliability / high brightness inorganic EL materials are urgently needed not only in standard structure but also in reverse structure.

An object of the present invention devised to solve the above problems is to provide a dielectric paste composition that can produce an inorganic EL sheet having a high brightness and withstand voltage even when the dielectric layer is formed to a thinner thickness.

Another object of the present invention is to provide a dielectric paste composition capable of forming an inorganic EL sheet having a smaller thickness of the dielectric layer, which has excellent flexibility and a soft touch feeling and at the same time has an improved wear resistance and a smaller luminance reduction rate.

Another object of the present invention is to provide a dielectric paste composition for an inorganic EL sheet which is excellent in printing characteristics and can improve re-adhesiveness and dimensional stability in an inverse structure as well as a standard structure.

Dielectric paste composition for an inorganic EL sheet of the present invention for achieving the above object is 20 to 60 parts by weight of fluorocarbon resin, 2 to 10 parts by weight of polyester binder polymer, polyurethane adhesive component 2 with respect to strontium titanate (SrTiO ₃ ) To 20 parts by weight is characterized in that the mixture.

Preferably, 0 to 2 parts by weight of a dispersant and 0 to 2 parts by weight of a stabilizer are further mixed.

Hereinafter, the dielectric paste composition of the present invention will be described in more detail.

The dielectric paste composition of the present invention is characterized in that it comprises strontium titanate (SrTiO ₃ ), a fluororesin, and a polyester binder polymer.

Strontium titanate (SrTiO ₃ ) of the present invention is an inorganic filler, in the form of a powder uniformly dispersed in a nano size of 100 to 1000 nm, and when a thick film dielectric layer having a double insulating layer structure is made, the luminance is emitted with time under constant voltage driving conditions. Reduces the rate of degradation. In particular, since it has a high dielectric constant, the light emitting efficiency is increased by moving the light emitting layer by an alternating electric field, expanding the emission center excitation, and increasing the maximum amount of charge (the amount of charge held on both sides immediately before the insulating layer causes breakdown). Breakdown of insulation can be prevented.

In addition, the dielectric properties of SrTiO ₃ are highly dependent on the Sr / Ti ratio and the polarization characteristics of the powder, and the smaller the porosity is, the better.

Fluorine resin has excellent properties that cannot be found in other rubbers such as heat resistance, oil resistance, chemical resistance, and water vapor resistance, so it replaces polyester and cyanoethyl resins that have been used in the past. High brightness and long life can be given. The dielectric constant (ε) of the fluorine-based resin is about 5 to 10, and is relatively higher than that of other resins. In order to compensate for this, the phosphor layer and the dielectric layer are formed of the same resin, it is possible to increase the luminance and increase the dimensional stability. The specific gravity of the fluorine-based resin is about 1.7 to 1.9 g / cm 3.

The fluororesin of the present invention is a binary or terpolymer of polyvinylidene fluoride and tetrafluoroethylene or hexafluoropropylene, monofluoroalkoxy (MFA), perfluoroalkoxy (PFA) and polytetra It is selected from the copolymer of fluoroethylene (PTFE; Polytetrafluoroethylene), and it is preferable to have a molecular weight of 150,000-300,000. The fluororesin is mixed in an amount of 20 to 60 parts by weight based on strontium titanate (SrTiO ₃ ).

Polyester (PET) binder polymer is used as a binder, and a copolymer of polyester resin containing 1 to 50 mol% of polyalkylene glycol or polycarboxyl repeating unit in the resin is preferable. Strontium titanate (SrTiO) 2 to 10% by weight based on ₃ ) is added. In this case, when the content is 2% by weight or less, the binder may be insufficient as a binder matrix of the inorganic filler to cause cracking, and when the amount is 10% by weight or more, the dielectric constant of the dielectric layer is reduced.

Polyurethane-based components are added to improve dimension stability or matching with base films such as PET films or urethane films, and to increase flexibility and durability. Preferred polyurethane adhesives include blocked polyisocyanates (blocked type, one-component for heat curing), non-yellowing polyisoanates (aliphatic isocyanate type), and the like based on strontium titanate (SrTiO ₃ ). 2 to 20 weight percent. In particular, polyisocyanates having a glass transition temperature of 30 degrees or more and a water absorption of 0.04% or less (@ 20C immersion / 24hr) are preferred to increase flexibility. In addition, the polyurethane adhesive can withstand low Tg or slightly higher water absorption, compared to the case without crosslinking functionality. Polyisocyanate polymers, on the other hand, provide improved thermal and humidity resistance during thermal curing.

The polyurethane-based component stabilizes fluorine resin and strontium titanate (SrTiO ₃ ), which is an inorganic filler, increases Tg, and improves chemical resistance and thermal stability of the cured coating composition. And withstand voltage characteristics and flexibility to improve the EL sheet and its adhesion.

In the dielectric paste composition of the present invention, a dispersant and a stabilizer are further mixed.

Dispersants include carboxylic acid esters (EFKA 5055), carboxylic acid esters with inorganic filler affinity groups, sodium bis (tridecyl) sulfosuccinnate Di (2-ethyl hexyl) sodium sulfosuccinnate, sodium dihexylsulfosuccinnate, sodium dicyclohexyl sulfosuccinnate and their It is preferably selected from the group consisting of a mixture, and 0 to 2 parts by weight based on strontium titanate (SrTiO ₃ ) is added. At this time, if the content is more than 2 parts by weight, there is a disadvantage in that the instability of the viscosity is increased.

The stabilizer is 1,3,5-trimethyl benzene (1,3,5-Trimethyl Benzene), alkyl benzene, polyamineamide of unsaturated carbolic acid and the like, 0 to 2 parts by weight based on strontium titanate (SrTiO ₃ ) do. At this time, if more than 2 parts by weight has a disadvantage that the viscosity becomes unstable.

After preparing the dielectric paste composition according to the present invention having such a composition, a standard structure having a laminated structure of a phosphor layer, a dielectric layer, and an electrode layer on an ITO-coated PET film or an inverse structure using a transparent electrode and a urethane film or a transparent PET film. EL sheet can be manufactured by printing by screen printing with dielectric layer of (Reverse Build).

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the scope of the present invention is not limited only to the following examples.

<Example>

Sr / Ti element ratio 0.998-1.002, 44 wt% SrTiO ₃ nanopowder (manufactured by Nanostructured and Amorphous Materials, Inc.) with an average particle size of 500 nm (SEM), 20 wt% polyvinylidene fluoride (PVDF) resin, 2.5% by weight of blocked polyisocyanate (urethane-based, DESMODUR BL3574 from Bayer Chemical), 2.0% by weight of polyester resin, 30% by weight of Dibasic Esters Solvent (DBE-9) (mixture of dimethyl glutarate and dimethyl succinate), carboxylic acid ester ( 5055) 1% by weight of a dispersant and 0.5% by weight of a stabilizer of 1,3,5-Trimethyl Benzene were mixed and stirred for 2 hours or more to prepare a dielectric paste. The final product was prepared as a finished product by adjusting the viscosity to 6000 ~ 15000 cps with Cyclohexanone after measuring the viscosity.

Comparative Example

44 wt% BaTiO3 powder, 20 wt% hexafluoropropylene (HFP), 4.5 wt% polyester adhesive, 30 wt% Dibasic Esters Solvent (DBE-9) (mixture of dimethyl glutarate and dimethyl succinate), carboxylic ester (product name; Drewplus ZV-55) 1% by weight of dispersant and 0.5% by weight of stabilizer of polyamineamide of unsaturated carbolic acid (BYK-130 by BYK Chemie) were mixed and stirred for 2 hours or more to prepare a dielectric paste. Final product was prepared by adjusting the viscosity to 6000 ~ 15000 cps with Cyclohexanone after measuring the viscosity.

Experimental Example 1

Phosphor (product name GGS22 Blue-Green) produced in OSRAM was printed on the ITO-coated polyethylene terephthalate (PET) binder by screen printing and cured at about 130 ° C. for 20 minutes to form a phosphor layer. The thickness of the binder and the phosphor layer was set to 25 microns. The dielectric pastes produced in Examples and Comparative Examples on the resulting phosphor layer were printed 1 to 7 times at 3.5 micron as shown in Table 1 by screen printing method and cured at about 130 ° C. for 20 minutes to form a dielectric layer. An EL device was fabricated on the dielectric layer using Ketty's C-7 carbon black electrode as an electrode, and the thickness was changed using KT's D8-H and Dupont's Luxprint (r) 9153 Dielectric paste. Table 2 shows the luminance characteristics with increasing number of times. In this case, the luminance measurement was performed under the conditions of 100V-400Hz AC with an LS-100 luminance meter.

Sample Phosphor layer Dielectric Layer (Print Recovery) ** Back electrode One M8 binder + YG fluorescent * (25 micron)  3.5 micron X 1 C-7 Carbon (Self) 2 "  3.5 micron X 2 " 3 "  3.5 micron X 3 " 4 "  3.5 micron X 4 " 5 " 3.5 micron X 5 " 6 "  3.5 micron X 6 " 7 "  3.5 micron X 7 "

Print count Thickness (micron) Brightness Example Comparative example One 3.5 77.2 69.0 2 7 85.3 78.3 3 10.5 91.0 82.0 4 14 89.2 83.0 5 17.5 83.5 79.0 6 21 75.6 73.8 7 24.5 71.0 62.4

As described in the results of Table 2, the EL device using the dielectric paste of the present invention exhibited a luminance of 91 (Cd / m ² ) at 10.5 microns so that the EL device using the conventional dielectric paste was 14 microns. It can be seen that 8 (Cd / m ² ) is increased from 83 (Cd / m ² ), which is a luminance at the time. In addition, it can be seen that even when the dielectric layer of the present invention has a minimum thickness of 7 microns, it is higher than 83.0 (Cd / m ² ), which is the highest luminance when the conventional dielectric layer is 14 microns.

Therefore, it can be seen that the use of the dielectric paste of the present invention can significantly reduce the thickness of the dielectric layer by 50% or more when fabricating an EL element requiring a constant luminance.

Experimental Example 2

The luminance and withstand voltage characteristics of the EL device having a dielectric layer coated with a thickness of 14 microns among the manufactured EL devices of Example 1 were measured and shown in Table 3.

division Example 1 Comparative Example 1 Dry micron 14 14 Polished, 60 degree / 20 degree 95/81 100/75 Knoop 14.3 15.2 Durability (Abrasion Resistance) 3% 11% Adhesion 100/100 100/93 Luminance (Cd / m ² ) 400 Hz, 150 V Early 91 83.0 72 hours 88 81 168 hours 84 79 240 hours 81.4 73 Withstand voltage (V / 25㎛) If more than 500Volt Early OK OK 72 hours OK OK 168 hours OK OK 240 hours OK x

As shown in Table 3, the initial luminance of the Example is 8 (Cd / m ² ) or more higher than the Comparative Example, and even after 240 hours the luminance of the Example is about 8 (Cd / m ² ) higher than the Comparative Example Able to know. In addition, in terms of durability, the luminance reduction rate of 1 million tahoo was reduced by 3% in the case of the present invention, but in the comparative example, 11% was reduced, indicating that the present invention was excellent in durability (wear resistance). In addition, it can be seen that the Example is superior in adhesive strength while having a smaller hardness than the comparative example.

Further, when a voltage of 500 Volt or more is applied, the voltage is maintained even after 240 hours has elapsed in the embodiment, but in the comparative example, it can be seen that the breakdown voltage characteristic is weakened and the dielectric breakdown may occur before 240 hours have elapsed. In other words, strontium titanate (SrTiO ₃ ), which has a high dielectric constant with a uniform particle size, is a nonpolar material with a small dipole moment and an insulation material that insulates AC voltage, and has a small amount of tangent delta for suppressing dielectric loss. It is possible to more effectively prevent the breakdown caused by the increase of.

As described above, the EL sheet using the dielectric paste composition of the present invention has an advantage of maximizing luminous efficiency.

In addition, when the dielectric layer is formed using the dielectric paste composition of the present invention, the thickness of the dielectric layer may be made thinner than that of the conventional dielectric layer, thereby providing a soft touch feeling with a reduced thickness of the keypad for a mobile phone.

In particular, it is expected to reduce the number of times of printing / usage due to the improved pressure resistance, it is possible to implement a high reliability EL material with improved adhesion to prevent the generation of gas, peeling in the coating film.

In addition, the present invention can produce an EL sheet having a high brightness even when forming a dielectric having a minimum thickness, so that the passive passive printed circuit board, FED (Field Emission Display), It may also be applied to a thick-film dielectric electroluminescent technology (TDEL) display.

Claims (7)

A dielectric paste composition for an inorganic EL sheet, characterized in that 20 to 60 parts by weight of fluororesin, 2 to 10 parts by weight of polyester binder polymer, and 2 to 20 parts by weight of polyurethane adhesive component are mixed with strontium titanate (SrTiO ₃ ). The dielectric paste composition for inorganic EL sheet according to claim 1, wherein 0 to 2 parts by weight of the dispersant and 0 to 2 parts by weight of the stabilizer are further mixed. delete The method of claim 1, wherein the fluororesin is a binary or terpolymer of polyvinylidene fluoride and tetrafluoroethylene or hexafluoropropylene, monofluoroalkoxy (MFA) and perfluoroalkoxy (PFA). ), A dielectric paste composition for an inorganic EL sheet, characterized in that any one selected from copolymers of polytetrafluoroethylene (PTFE; Polytetrafluoroethylene). The dielectric paste composition for an inorganic EL sheet according to claim 1, wherein the fluororesin has a molecular weight of 150000 to 300,000. 2. The dielectric paste composition of claim 1, wherein the polyurethane is any one or more of blocked polyisocyanates and non-yellowing polyisoanates. The method of claim 2, wherein the dispersant is a carboxylic acid ester, sodium 2-tridecyl sulfonuccinnate, di (2-ethyl hexyl) sodium sulfosuccinnate ), Sodium dihexylsulfosuccinnate, sodium dicyclohexyl sulfosuccinnate, and a dielectric paste composition for an inorganic EL sheet, characterized in that any one selected from the mixture thereof.

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