JPH04255322A - Moistureproof film - Google Patents

Abstract

PURPOSE:To obtain the film being suitable for a film for coating and sealing of an EL element with extremely excellent moistureproof properties by making a trifluochloroethylene resin or a copolymer thereof into a sheet by means of melt-extrusion method and drawing and heat-setting the sheet. CONSTITUTION:A film with extremely excellent moistureproof film is obtd. by drawing uniaxially a sheet obtd. from a trifluorochloroethylene resin at a temp. which is 50-140 deg.C higher than the glass transition temp. When the drawing temp. is lower than the temp. which is 50 deg.C higher than the glass transition temp., uniform drawing is difficult and when the drawing temp. is higher than the temp. which is 140 deg.C higher than glass transition temp., drawing effect becomes small. The drawing direction is pref. longitudinal from the viewpoint of drawing suitability and the drawing effect is obtd. by drawing at a draw ratio of 1.5-4-fold. The film thickness after drawing is pref. 100-300mum. In addition, heat setting at a temp. being higher than the drawing temp. is performed after drawing.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film for covering and sealing electroluminescent devices (hereinafter referred to as EL devices) with excellent moisture resistance.

0002

[Prior Art] In recent years, EL elements have been widely used in backlights, lighting, indicator lights, etc. of liquid crystal displays.
The device has the disadvantage of being easily deteriorated by moisture absorption, resulting in a decrease in performance. Therefore, in order to prevent this, conventional unstretched trifluorochloroethylene resin (hereinafter referred to as PCTFE)
It is used covered and sealed with a film. However, since the life of an EL element is greatly affected by moisture absorption deterioration caused by insufficient moisture resistance, further improvement in moisture resistance has been desired.

0003

SUMMARY OF THE INVENTION An object of the present invention is to provide a film for covering and sealing an EL element that has extremely excellent moisture resistance.

0004

[Means for Solving the Problems] The present invention involves forming PCTFE or a copolymer thereof into a sheet by melt extrusion, and then uniaxially stretching the sheet at a temperature 50 to 140°C higher than the glass transition temperature. This is a moisture-proof film that is heat-set.

[0005] PCTFE used in the present invention is a trifluorochloroethylene homopolymer or a copolymer with other monomers copolymerizable with it, and the content of other monomers is determined depending on moisture resistance. It is preferably 20% by weight or less, more preferably 5% by weight or less. Also, PC
Regarding the degree of polymerization of TFE, Z. S. T. (Zero strength
time) is preferably 150 to 400 seconds in terms of mechanical strength and sheet formability.

In the present invention, when melt extruding into a sheet, it is preferable to suppress crystallization in the cooling process from the viewpoint of sheet transparency and stretching suitability.
It may be extruded from a die in a molten state at ~350°C and cooled on a cooling roll whose surface temperature is controlled at 10-100°C.

[0007] By uniaxially stretching the sheet thus obtained at a temperature 50 to 140°C higher than the glass transition temperature, a film with extremely excellent moisture resistance can be obtained. If the stretching temperature is less than 50°C higher than the glass transition temperature, uniform stretching will be difficult;
If the temperature is higher than that, the effect of stretching will be reduced. The stretching direction is preferably the longitudinal direction in view of stretching suitability, and effects can be obtained by stretching the stretching ratio from 1.5 times to 4 times. In this case, the film thickness after stretching is preferably 100 to 300 μm. Further, by heat setting the film at a temperature higher than the stretching temperature after stretching, it is possible to prevent thermal deformation of the film when laminating the adhesive resin.

[0008] In order to use the film obtained by the above process for sealing the EL element, it is necessary to adhere the edges, but in the case of PCTFE film, adhesion is difficult unless surface treatment is performed. Although methods such as plasma treatment, corona treatment, and sputter treatment have been used, corona treatment is preferable from a cost standpoint. By laminating ethylene-glycidyl methacrylate-vinyl acetate terpolymer (hereinafter referred to as EGV resin) on the corona-treated surface, an adhesive layer with good heat-sealing properties can be obtained. It is preferable to laminate an ethylene/ethyl acrylate/maleic anhydride ternary copolymer (hereinafter referred to as EEM resin) on the EGV resin in order to provide the resin.

[0009]

[Example] <<Example 1>> PCTFE (glass transition temperature 5
2℃ Z. S. T. 300 seconds) is extruded in molten form through a die with a set temperature of 340°C, cooled on a cooling roll set at 30°C to form a sheet with a thickness of 600 μm, and this sheet is then tripled in the longitudinal direction at a sheet temperature of 150°C. The film was stretched to 200 μm and heat set at 180°C. Furthermore, one side of this film was treated with corona to activate it to a wetting index of 48 dyn/cm, and then EG was applied to this side.
V resin (Bond First 7B, manufactured by Sumitomo Chemical Industries) was laminated by melt extrusion and cooled while being pressed with a pressure roll to obtain a film.

<<Example 2>> EEM resin (Bondine AX806) was applied on the EGV resin layer of the film obtained in Example 1.
4 (manufactured by Sumitomo Chemical Industries) were laminated by melt extrusion and cooled while being pressed with a pressure roll to obtain a film.

<Comparative Example 1> PCTFE was melt-extruded to form a film having a thickness of 200 μm, and after corona treatment in the same manner as in Example 1, an EGV resin was laminated to obtain a film.

Comparative Example 2 An EEM resin was laminated on the EGV resin layer of the film obtained in Comparative Example 1 in the same manner as in Example 2 to obtain a film.

Comparative Example 3 A film was obtained in the same manner as in Example 1 except that the corona treatment was not performed.

[0014] Regarding the above five types of films, moisture resistance,
Table 1 shows the results of heat sealing properties measured using the measurement method shown below. (Measurement method) Moisture resistance: 6
Water vapor transmission rate was measured in an atmosphere of 0° C. and 95% RH. Heat-sealability: The adhesive layer surfaces of two films were placed one on top of the other, and a 180° peel test was performed by pressing the films together under two conditions of temperature and pressure of 10 kg/cm for 23 seconds.

[0015]

[Table 1]

[0016]

[Effects of the Invention] The film of the present invention has extremely excellent moisture resistance and is suitable as a film for EL devices.

Claims (4)

[Claims] Claim 1: A trifluorochloroethylene resin or a copolymer thereof is formed into a sheet by melt extrusion, and then uniaxially stretched at a temperature of 50 to 140°C higher than the glass transition temperature, and then stretched at a temperature higher than the stretching temperature. A moisture-proof film characterized by being heat-set. 2. A moisture-proof film, characterized in that the surface of the moisture-proof film according to claim 1 has been subjected to corona treatment. 3. A moisture-proof film, characterized in that an ethylene-glycidyl methacrylate-vinyl acetate terpolymer is laminated on the corona-treated surface of the moisture-proof film according to claim 2. 4. The moisture-proof film according to claim 3, wherein an ethylene/ethyl acrylate/maleic anhydride ternary copolymer is laminated on the ethylene/glycidyl methacrylate/vinyl acetate ternary copolymer layer. Moisture-proof film.