JPH0258023A - Package film for backlighting of liquid crystal display - Google Patents

Abstract

PURPOSE:To obtain high-level moisture preventive performance at low cost by providing a plastic sealant layer on a film substrate where a transparent silicon oxide thin film layer is formed on the opposite surface from a specific plastic protection layer. CONSTITUTION:The transparent silicon oxide thin film layer 2 is formed on the transparent flexible plastic substrate film 3. The thickness of the thin film layer 2 is 100 - 5,000Angstrom and curling, cracking, or peeling are caused when the thickness exceeds 5,000Angstrom . The transparent plastic protection layer 4 of <=20gr/m<2>24H moisture permeability is provided on the thin film layer across an adhesive layer 6 and the transparent plastic sealant layer 5 for heat sealing is provided on the opposite surface across an adhesive layer 7. Consequently, excellent transparency and extremely high-level moisture prevention are obtained and the film is used suitably for the backlighting of the liquid crystal device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a backlight package film for liquid crystal displays. More specifically, the present invention relates to a transparent film that hardly transmits gas such as water vapor and is suitable for a backlight package film for a liquid crystal display.

[Prior Art] Liquid crystal display elements have become established as display elements for digital watches and electronic desktop calculators by taking advantage of their main characteristic of low power consumption, and with the advent of liquid crystal games,
Demand expanded explosively, and subsequently, automotive, musical instrument, and OA
Applications are becoming more diverse, including industrial and FA applications.

On the other hand, organic dispersion type electroluminescence (EL) elements are being used as inexpensive planar backlights (auxiliary light sources) for liquid crystal devices due to their thinness and light weight. , ZnS:Mn5Zn
Since the luminance of fluorescent substances such as S:Cu is significantly impaired by moisture absorption, they are used packaged with a film that has excellent moisture resistance and transparency.

Conventionally, fluorine films, especially polychlorinated trifluoroethylene (PCTFE), have been used in packages of organic dispersion type EL elements used as backlights for liquid crystal displays.
) is used because it has excellent moisture-proofing performance and transparency.

Organic dispersion type EL elements used in backlights for liquid crystal displays are generally made of P with a thickness of about 70 to 300 μm.
20~ for CTFE as a sealant for heat sealing
A film laminated with polyolefin about 100 μm in thickness is used, and this film hardly allows water vapor to pass through, and is said to have the best moisture-proofing performance of any existing transparent plastic film.

Recently, transparent plastic films in which the surface of a transparent plastic base film is coated with a metal oxide, particularly silicon or aluminum transparent oxide thin film, have been commercialized as packaging materials with gas barrier properties.

[Problems to be Solved by the Invention] However, fluorine films, which are conventional packaging films for organic dispersed EL devices, particularly laminated films mainly made of polychlorinated trifluoroethylene (P'CTFE), , which is extremely expensive, increases the manufacturing cost of backlights, which has been a major obstacle to reducing the cost of liquid crystal displays. In addition, a film made of PCTFE laminated with a sealant for heat sealing is cheaper than PCTFE and can be used as a package film for organic dispersion type EL elements for backlights, which aims to reduce the cost and improve the performance of extremely expensive liquid crystal displays. It is desired to develop a transparent plastic film with excellent moisture-proofing performance.

Furthermore, transparent plastic films, which are made by coating the surface of a transparent plastic base film with a transparent thin film of metal oxide, do not have sufficient moisture-proofing performance in their current state, and are suitable for use in organic dispersion EL elements for backlights of liquid crystal displays. It has not yet reached the point where it can be used as a packaging film.

This invention was made based on the above-mentioned background,
The purpose of this film is to provide packaging films for EL elements for backlights of liquid crystal displays, which have excellent transparency and moisture resistance, and are also excellent in terms of strength and economy. The purpose is to provide a material suitable for use as a material.

[Means for Solving the Problems] As a result of intensive studies to solve the above problems, the present inventors have discovered that a specific silicon oxide thin film has excellent transparency and moisture-proofing performance, and has identified this thin film. It was discovered that stable moisture-proofing performance can be maintained over a long period of time by coating with a transparent protective film, and based on this knowledge, the present invention was completed.

Therefore, the gist of the present invention of a package film for an organic dispersion type EL element for a backlight of a liquid crystal display is that a transparent thin film layer of silicon oxide is formed on at least one side of a transparent plastic base film. In a preferred embodiment of the present invention, the bonding energy of silicon in the silicon oxide of the thin film layer is different between the surface and central portions of the thin film layer and the vicinity of the base film, and the bond energy of silicon in the silicon oxide of the thin film layer is different between the surface layer and the center of the thin film layer and the vicinity of the base film. It has a silicon oxide thin film layer with greater silicon bonding energy, and the surface of the silicon oxide thin film layer has a moisture permeability of 20% as a protective layer.
gr/nf 24 H or less, preferably 15 gr/m2
A transparent plastic protective layer of 24H or less is laminated, and a heat-sealable transparent plastic sealant layer is laminated as a sealant on the opposite side of the protective layer.

The present invention will be explained in detail below.

In the package film according to the present invention, a transparent thin film layer of silicon oxide is formed on at least one side of a transparent plastic base film.

In order to obtain the particular silicon oxide thin film layer preferred in accordance with the present invention, it is desirable to select the plastic substrate film on which the thin film layer is formed.

Examples of such plastic base films include polyvinyl alcohol films made of resins such as polyvinyl alcohol and ethylene-vinyl alcohol copolymers. These films may be unstretched or -axially or biaxially stretched.

The thickness of the plastic base film on which the silicon oxide thin film layer is formed can be selected within the range of 5 to 400 microns.

Among these, it is preferable to select a thickness in the range of 10 to 200μ.

In a preferred embodiment of the present invention, it is desirable that the bonding energy of silicon in the silicon oxide of the silicon oxide thin film layer is greater in the vicinity of the plastic base film than in the surface layer or central portion.

Silicon oxides other than this preferred embodiment, such as those in which there is no change in the bonding energy of silicon oxide between the surface layer or center of the silicon oxide thin film layer and the vicinity of the plastic base film, may have poor moisture-proof performance. Does not improve well.

In a preferred embodiment of the present invention, the 5i2p binding energy of the silicon oxide thin film layer near the plastic is:
It is preferable that Q is 5 eV or more larger than the binding energy of the surface layer portion.

The bond energy of silicon in silicon oxide according to the present invention is determined by X-ray photoelectron spectroscopy (ES CA-Electro
n5pectroscopy to Chemi
It refers to the binding energy of 5i2p determined by cal analysis.

The 5i2p bond energy in the thickness direction of the silicon oxide thin film layer can be measured while etching the thin film layer with argon ions or the like. In order to form a transparent thin film layer of silicon oxide on at least one side of a transparent plastic base film, silicon oxide, silicon dioxide, or a mixture thereof is used as a vapor deposition raw material, and a vacuum evaporation method, a sputtering method, or an ion blasting method is used. This shall be done by any method of law.

It is also possible to employ a reactive vapor deposition method in which silicon, -silicon oxide, silicon dioxide, or a mixture thereof is used as a vapor deposition raw material and oxygen gas is supplied.

Furthermore, if the silicon oxide contains impurities such as calcium, magnesium, or their oxides, if it is less than 10% by weight, the moisture-proof performance of the transparent plastic base film will not be significantly reduced. I can't.

The thickness of the transparent thin film layer of silicon oxide formed on at least one side of the plastic base film is 100 to 50
It is best to choose within the range of 00 people.

If the thickness of the transparent thin film layer is less than 1,000 amps, the moisture-proof performance will be insufficient, and if it exceeds 5,000 amps, the film may curl, causing problems, or the transparent thin film layer itself may crack or peel. This is not preferable because it is easy to cause this.

In the present invention, on the surface of the transparent thin film layer of silicon oxide,
A transparent plastic protective layer with a moisture permeability of 20 gr/m224H or less is laminated as a protective layer, and a transparent heat-sealable plastic sealant layer is laminated on the other side as a sealant.

In order to provide the above-mentioned protective layer and sealant layer, a method of laminating films or forming a coating film can be adopted. The transparent plastic thin film (film or coating film) used as a protective layer is based on ASTM F372.
Moisture permeability measured at a temperature of 40°C and a relative humidity of 90% is 20g/m224H or less, preferably 15gr
It is preferable to use a material having a property of /rf24H or less, and its thickness can be selected within the range of 5 to 400μ.

Transparent plastic base films that meet the above performance and can be used as a protective layer include polypropylene and propylene copolymers, vinyl chloride resins such as polyvinyl chloride and its copolymers, and vinyl chloride-vinylidene chloride. A film made of a vinylidene chloride resin such as a copolymer can be used, and further examples include a coated film in which a film made of a polyester resin such as polyethylene terephthalate is coated with a resin equivalent to a vinylidene chloride resin. Alternatively, a transparent film having a silicon oxide thin film may be directly coated with a resin such as a vinylidene chloride resin.

Examples of the heat-sealable sealant layer include low density polyethylene, ethylene-vinyl acetate copolymer, polypropylene, and ionomer.

When laminating a protective layer and a sealant layer on a transparent film surface having a silicon oxide thin film, known methods such as a dry lamination method using a urethane adhesive, an acrylic adhesive, a polyester adhesive, etc. or an extrusion lamination method can be used. method can be adopted.

Further, the films used for the protective layer and the sealant layer may be unstretched, or may be stretched in a cross- or two-way direction. The order of stacking the sealant layer may be before or after the formation of the silicon oxide thin film.

When applying a vinylidene chloride resin to a silicon oxide thin film, an anchor coating agent is used to increase the adhesive strength of the vinylidene chloride resin. Suitable anchor coating agents include isocyanate-based, polyethyleneimine-based,
Examples include adhesion promoters such as organic titanium-based adhesives and adhesives such as polyurethane polyester-based adhesives.

The thickness of the transparent plastic film with excellent moisture resistance according to the present invention is 10 to
The range is preferably 500 μ, more preferably 10 to 20
The thickness is 0μ.

An example of the structure of the film of this invention is shown in FIG.

The package film 1 of this example includes a transparent flexible plastic base film 3 on which a transparent silicon oxide thin film layer 2 is formed on one side, a plastic protective layer 4 laminated on two sides of the silicon oxide thin film, and a plastic protective layer 4 on the other side. It consists of a laminated plastic sealant layer 5.

The silicon oxide thin film layer 2 and the plastic protective layer 4, and the plastic base film 3 and the sealant layer 5,
They are bonded by adhesive layers 6 and 7, respectively.

[For production]

The operation of the present invention having the above configuration will be explained below, but this description is for better understanding of the invention and is not intended to limit the scope of the invention.

In a preferred embodiment of the present invention, the bonding energy of silicon in the silicon oxide thin film layer has a component having a larger energy in the vicinity of the plastic base film than in the surface layer portion or the central portion. This results in extremely excellent moisture resistance.

That is, when a silicon oxide thin film layer is formed on a base film having a polar group such as a hydroxyl group by a vacuum evaporation method or the like, like the above-mentioned polyvinyl alcohol film,
At the initial stage when the thin film layer is formed, that is, near the plastic base film, the polar groups of the base film interact with the silicon oxide, resulting in a stronger bond compared to those without polar groups. A thin film of energetic silicon oxide is formed.

From this, it is thought that a thin film of silicon oxide having a large bonding energy exhibits excellent moisture-proofing performance.

[Effects of the Invention] The transparent plastic film according to the present invention has excellent transparency and excellent moisture resistance, is flexible, and has excellent strength and economical efficiency. . Moreover, even when used under harsh conditions, the moisture-proof performance is not impaired. Therefore, E
It is suitable as a package film for L elements, and its industrial value is extremely large.

The film of the preferred embodiment according to claim 2 exhibits extremely excellent moisture resistance because the silicon bond energy of the thin film layer is larger in the vicinity of the plastic base film than in other parts, and therefore, It is ideal as a packaging film for EL elements for backlights in liquid crystal displays, which require a high degree of moisture resistance.

[Examples] Hereinafter, the present invention will be described in detail based on Examples and in contrast with comparative examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

In addition, in the following example, 5i2p of the silicon oxide thin film layer
The binding energy, water vapor permeability, and transparency of the obtained transparent plastic base film were measured or determined by the following method. Further, the thickness of the transparent thin film layer of silicon oxide was measured using a quartz crystal film thickness meter.

Binding energy (eV) of silicon oxide thin film
The silicon oxide thin film was etched with + ions at 3 minute intervals, and changes in the binding energy of 5i2p in the thickness direction were measured.

Moisture permeability of package film (gr/rrl”24H)
Measurement was conducted in accordance with ASTMF-372 at a temperature of 40° C. and a relative humidity of 90%. In the measurement, the protective layer surface was positioned on the high humidity (90% RH) side and the sealant layer surface was positioned on the bone dry side, and the value after 10 days was taken as the Δ)I constant value.

Luminance of EL element (cd/go) The luminance of the EL element was fixed at Δ11 at an operating voltage of 100 V and an operating frequency of 400 Hz. Temperature 40℃, relative humidity 90%RH
The deterioration of the luminance of the EL element after being left for 15 days and 30 days under these conditions was measured and evaluated.

FIG. 2 is a schematic diagram of the structure of the organic dispersion type EL device used for evaluation.

Transparency (%) of EL element package film The light transmittance of the film in visible light was measured using a spectrophotometer newly manufactured by Hitachi, and the light transmittance at 550 nm was taken as the transparency of the film.

Example 1 On the surface of a polyvinyl alcohol film with a degree of saponification of 99.9 mol% (stretching ratio 3 x 3 times, biaxial stretching, thickness 12 μm), an electron beam heating method was applied under a vacuum of 5 x 10' Torr. Silicon monoxide (Sin) with a purity of 99.9% was heated and evaporated to form a transparent thin film of silicon oxide with a thickness of 1000 nm on one side of a polyvinyl alcohol base film to obtain a transparent plastic film.

A polypropylene film (stretching ratio 3 x 3 times, biaxial stretching, thickness 20μ, moisture permeability 9gr/rrr24H, hereinafter referred to as OPP film) is attached to the silicon oxide thin film layer side of the transparent plastic film using urethane adhesive. A transparent laminated plastic film as shown in Figure 1 was obtained by laminating a low-density polyethylene film (unstretched, thickness 60μ) on the other side using a urethane adhesive. .

The silicon bond energy, moisture permeability, and transparency of the obtained film were measured using the methods described above.

Furthermore, an organic dispersion type EL element was packaged using the obtained film, and a backlight for evaluation as shown in FIG. 2 was manufactured. The resulting backlight was measured for deterioration in luminance using the method described above.

The measurement results are shown in FIG. 3 and Table 1.

Example 2 In the example described in Example 1, the base film forming the silicon oxide thin film was replaced with a polyvinyl alcohol film, and an ethylene/vinyl alcohol copolymer film (ethylene content 32 mol%, stretching ratio 3x3 times, two-wheel stretching,
A transparent thin film layer of silicon oxide was formed on one side of the ethylene vinyl alcohol copolymer film in the same manner as in the same example except that a film having a thickness of 12 μm was used.

Regarding the obtained transparent plastic film, Example 1
An evaluation test was conducted for the same items as in . 4th result
It is shown in Figure and Table 1.

Example 3 In the example described in Example 1, except that a 12μ OPP film (moisture permeability 15gr/r+f24H) was used instead of the 20μ OPP film as a protective film for the polyvinyl alcohol film having a silicon oxide thin film. A transparent laminated film was obtained and evaluated in the same manner as in the same example.

The results are shown in Table 1.

Example 4 A transparent laminated film was obtained and evaluated in the same manner as in Example 1, except that the thickness of the silicon oxide thin film was changed to 200. The results are shown in Table 1.

Example 5 The same example as described in Example 1 except that silicon dioxide (S i02 ) with a purity of 99.9% was heated and evaporated on one side of the polyvinyl alcohol film instead of silicon monoxide (Sin). A transparent laminated film was obtained and evaluated in the same manner as in . The results are shown in Table 1.

Reference Example 1 In the example described in Example 1, the transparent film forming the silicon oxide thin film was replaced with a polyvinyl alcohol film, and a polyethylene terephthalate film (stretching ratio 3x3, two-wheel stretching, thickness 12μ) was used.
A transparent thin film layer of silicon oxide was formed on one side of a polyethylene terephthalate film as in the same example.

The obtained transparent plastic film was evaluated in the same manner as in Example 1. The results are shown in FIG. 5 and Table 1.

Reference Example 2 In the example described in Example 1, the transparent film forming the silicon oxide thin film was replaced with a polyvinyl alcohol film, and a polypropylene film (stretching ratio 3 x 3 times, biaxial stretching, thickness 12μ) was used. A transparent thin film layer of silicon oxide was formed on one side of a polypropylene film in the same manner as in the same example.

The obtained transparent plastic film was evaluated in the same manner as in the same example. The results are shown in FIG. 6 and Table 1.

Comparative Example 1 In the example described in Example 1, as a protective film for the polyvinyl alcohol film having a silicon oxide thin film, a 12μ polyethylene terephthalate film (moisture permeability 50gr/m22
4H) in the same manner as in the same example, except that
A transparent laminated film was obtained and evaluated. The results are shown in Table 1. This result shows that the moisture resistance is poor.

Reference example 3 Polychlorinated trifluoroethylene film (unstretched, thickness 75
Example 1 The EL device was packaged with a transparent film laminated with a low-density polyethylene film (unstretched, thickness 60μ) on one side of
The same evaluation was conducted.

The results are shown in Table 1.

From this result, the film of this conventional example showed relatively good moisture resistance, but was extremely expensive.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the layer structure of the packaging film according to the present invention, and Figure 2 is an EL packaged with the film.
3 is a graph obtained from Example 1 showing the change in the bond energy of silicon in the silicon oxide thin film layer in the thickness direction; FIG. 4 is a graph obtained from Example 2 showing the change in silicon bond energy in the silicon oxide thin film layer. 5 is a graph showing the change in the bond energy of silicon in the silicon oxide thin film layer in the thickness direction, and FIG. 6 is a graph showing the change in the bond energy of silicon in the silicon oxide thin film layer in the thickness direction obtained from Reference Example 1. is a graph obtained from Reference Example 2 and showing the change in the bond energy of silicon in the silicon oxide thin film layer in the thickness direction. DESCRIPTION OF SYMBOLS 1...Package film, 2...Silicon oxide thin film layer, 3...Plastic base film, 4...Plastic protective layer, 5...Plastic sealant layer, 6.7...Adhesive layer. Applicant's agent Mr. Sato Figure 1 Figure 2 Nearby central area table MIJ - Silicon oxide r! In the thickness direction of J expansion Figure 3 Nearby part Central part Surface layer - Silicon oxide rl Thickness direction near part Central part Surface layer - Kay T, +12 Compound Thickness direction Figure 5 Nearby part Central part Surface layer part -Silicon oxide ball rJ thickness direction

Claims (4)

[Claims] 1. In a packaging film for an electroluminescent (EL) dispersion type element used as a backlight for a liquid crystal element, the packaging film is a transparent flexible plastic base film on which a transparent silicon oxide thin film layer is formed on at least one side. and a moisture permeability of 20 gr/m^224 laminated on the silicon oxide thin film surface.
A package film for a backlight of a liquid crystal display, comprising a transparent plastic protective layer of H or less and a heat-sealable transparent plastic sealant layer laminated on the other side of the protective layer. 2. 2. The transparent silicon oxide thin film layer according to claim 1, wherein the silicon bonding energy of the thin film layer differs in the thickness direction of the thin film layer, and the silicon oxide having a larger silicon bonding energy is present in the vicinity of the plastic base film. Package film for backlights of liquid crystal displays. 3. 3. The package film for a backlight of a liquid crystal display according to claim 1, wherein the transparent thin film layer of silicon oxide is formed by any one of a vacuum deposition method, a sputtering method, and an ion plating method. 4. The thickness of the transparent flexible plastic base film is in the range of 5 to 400μ, the thickness of the transparent thin layer of silicon oxide is in the range of 100 to 5000Å, and the total thickness of the protective layer and sealant layer is in the range of 5 to 400μ. Claims 1 and 2, wherein the total thickness is in the range of 10 to 500μ.
Or a package film for backlight of a liquid crystal display according to 3.