DE102011106827A1 - Method for covering flexible transparent plastic film with phototropic layer to protect e.g. container in food industry from excessive sunlight/ UV irradiation, involves attaching phototropic layer on surface of film by printing process - Google Patents

Abstract

The method involves providing a phototropic layer (2) for reversible adaptation of transparency of a transparent plastic film (1) to change lighting conditions. The phototropic layer is attached on a surface (1') of the film by a printing process e.g. screen printing process, flexographic printing process, direct or indirect gravure printing process and offset printing process. A phototropic substance of the phototropic layer is merged into a physical, chemical or reactive drying binder system. The transparency of the film is controlled by variation of thickness (h) of the phototropic layer. An independent claim is also included for a transparent plastic film.

Description

The present invention relates to a process for coating a translucent substrate with a photochromic layer and to a plastic film coated with a photochromic layer by such a process.

Phototropic substances, d. H. Substances that change color when exposed to light and return to their original color in the dark have long been known.

Particularly in the field of high-quality spectacle optics, such substances are used for so-called self-darkening or self-tinting spectacle lenses, which can be colored depending on the strength of the ultraviolet solar radiation and back again and thus additionally offer a sunglass function.

The photochromic substances are either added directly to the glass material or applied in a layer on the glass front surface. In the DE 33 45 639 A1 describes a method for applying a photochromic coating on an optical element, in particular on plastic glasses, in which the photochromic layer is realized via a paint application.

However, the known Lackierverfahren (spraying or spraying, dipping or brushing) are not or only partially for a large-scale application of photochromic layers, for example on window facades or the like, so that photochromic coatings today usually only small-sized sun protection articles such. B. glasses come into application.

Furthermore, coating methods have the disadvantage that the carrier material can not or only in a very complex manner with a partial or otherwise controlled with respect to the order quantity or distribution coating can be provided.

It is accordingly the object of the present invention to further develop a method for coating a translucent support with a photochromic layer in such a way that the support can be coated with the photochromic layer in a targeted manner with regard to the layer application amount and distribution.

This object is achieved by a method in which the photochromic layer is applied by a printing process on the surface of the transparent substrate.

In contrast to the known application method for photochromic layers, which allow only a full-surface or at most gradually extending coating, the invention provided for printing process application method, the carrier specifically equipped with the photochromic effect.

Printing processes also offer the advantage of a screened layer application, so that a specific distribution of the photochromic substance over the surface of the support can be set by a simple variation of the screen ruling. Clearly separated areas with different darkening effects in the case of solar radiation can thus be provided over the support surface.

By incorporating the photochromic substances in a known binder system, similar to a printing ink or a printing varnish, the photochromic coatings can be quickly and easily applied to the substrate by means of a known printing machine while setting an optimum pattern.

The use of a printing process also ensures optimal adhesion of the photochromic layer even on a flexible carrier material, such as a plastic film.

The photochromic coating can advantageously be integrated into an existing printing production line, for example in a label printing machine, so that an individually adjustable, partial photochromic coating (also adapted to specific shapes, patterns, texts, etc.) is made possible.

Further details, features and advantages of the subject of the invention will become apparent from the dependent claims and from the following description of the accompanying drawings.

In the drawing shows:

1 a schematic cross-sectional view through a self-adhesive plastic film with a photochromic layer applied according to the invention.

In 1 is shown in a highly schematic sectional view of a product, which according to the inventive method with a photochromic layer 2 has been coated.

The carrier material is a flexible transparent plastic film 1 For example, from polyamide, polyvinyl chloride or polyethylene, used on their surface 1' with a photochromic layer 2 is provided.

The photochromic layer 2 was by means of a known printing process (screen printing, flexographic printing, gravure, offset printing, etc.) on the plastic film 1 applied. By the printing process, it is possible in a simple way, the surface 1' the plastic film 2 not completely, but only partially, ie at arbitrary discrete points, with the phototropic layer 2 to print, leaving only in areas where a photochromic layer 2 the plastic film 1 Covered a darkening effect depending on the incident UV light intensity is achieved.

Moreover, printing techniques offer the advantage that the photochromic coating 2 the plastic films 1 can be done on existing film printing equipment in cost-effective mass production by the photochromic substances are added, for example, the respective used inks or coatings.

Advantageously, the provided with reversible photochromic properties plastic film 1 additionally equipped with self-adhesive properties. This is indicated by the plastic film 1 on her photochromic layer 2 opposite surface 1'' a self-adhesive coating 3 on, in turn, of a peelable release film 4 is covered to the glue 3 to keep fresh.

For such flexible self-adhesive films 1 with photochromic coating 2 opens up an extremely wide range of applications, as they are after deduction of the non-stick film 4 can also be easily glued to large objects.

One possible area of application opens up, for example, in the food industry, where transparent plastic or glass containers with such films 1 can be covered for protection from sunlight.

Another field of application are special containers for filling in pharmaceutical companies, for example, to protect light-sensitive ingredients of the drug substances from sunlight.

Another broad field for the use of such photochromic films 1 emerges in the photovoltaic industry. For example, such films 1 To protect against excessive sunlight on corresponding photovoltaic modules are applied.

Generally, such films 1 are used wherever protection against excessive solar or UV radiation is required, such. As well as sun protection in transport, for window facades on buildings or for converting conventional glasses in sunglasses.

Also, the photochromic films can 1 serve as a security feature for bank notes, tokens or the like by their individually adjustable blackout pattern.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 3345639 A1 [0004]

Claims (15)

Process for coating a translucent support ( 1 ) with a photochromic layer ( 2 ) for reversibly adjusting the light transmission of the wearer ( 1 ) to changing light conditions, characterized in that the photochromic layer ( 2 ) by a printing process on the surface ( 1' ) of the carrier ( 1 ) is applied. A method according to claim 1, characterized in that a screen printing method is used as the printing method. A method according to claim 1, characterized in that a high-pressure method, in particular flexographic printing, is used as the printing method. A method according to claim 1, characterized in that a direct or indirect gravure printing method is used as the printing method. A method according to claim 1, characterized in that an offset printing method is used as the printing method. Method according to one of claims 1 to 5, characterized in that the photochromic layer ( 2 ) comprises a photochromic substance incorporated into a physically, chemically or reactively drying binder system. Method according to one of claims 1 to 6, characterized in that the light transmittance of the carrier ( 1 ) over the area ( 1' ) varies. Method according to one of claims 1 to 7, characterized in that the light transmittance of the carrier ( 1 ) by a variation of the thickness (h) of the applied phototropic layer ( 2 ) is controlled. Method according to one of claims 1 to 8, characterized in that the light transmittance of the carrier ( 1 ) by a variation of the print pattern of the photochromic layer ( 2 ) is controlled. Method according to one of claims 1 to 9, characterized in that the surface ( 1' ) of the carrier ( 1 ) only partially with the photochromic layer ( 2 ) is printed. A method according to claim 10, characterized in that the photochromic layer ( 2 ) on the surface ( 1' ) of the carrier ( 1 ) is printed as a pattern, text or image motif. Translucent plastic film ( 1 ) with a photochromic layer ( 2 ), characterized in that the photochromic layer ( 2 ) according to one of claims 1 to 11 on the plastic film ( 1 ) has been applied. Plastic film according to claim 12, characterized in that the plastic film ( 1 ) is coated on one or both sides self-adhesive or self-adhesive. Plastic film according to claim 12 or 13, characterized in that the self-adhesive or self-adhesive coating ( 3 ) directly on one or both sides of the plastic film ( 1 ) is applied. Plastic film according to one of claims 12 to 14, characterized in that the adhesive or adhesive side ( 1'' ) with a non-stick film ( 4 ) is occupied.

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