JPS63264350A - Laminated sheet made of plastics - Google Patents

Abstract

PURPOSE:To prevent generation of creases at the time of heating by enabling firm printing, by a method wherein printing is performed on a cast polypropylene film by making use of uncurable printing ink and fused thermally with a polypropylene sheet on the printed surface side. CONSTITUTION:Printing is performed on a cast polypropylene film by making use of uncurable printing ink and fused thermally with a polypropylene sheet on the printed surface side. The uncurable ink 2, 3 mean that they are not such curing type ink as being cured with the lapse of time and the uncurable ink does not lose softness even after drying. Among those uncurable ink, chlorinated polypropylene is most preferable. Polypropylene in a sheetlike state is called a polypropylene sheet 1, and not only a single polymer of the polypropylene but also a copolymer of the propylene may be good for the polypropylene sheet 1.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to printed plastic sheets.

(b) Prior Art Conventionally, plastic sheets have been manufactured from various plastics, and their uses are very wide. In particular, polypropylene is very cheap and is used in large quantities, and strong printing on it is a big demand in the plastics and printing industries. Printing has been carried out using various methods, but polypropylene has poor compatibility with printing inks, making it impossible to achieve strong printing.

In order to solve this problem, it may be possible to perform pretreatment on the surface of polypropylene to improve printability. This includes a method in which polypropylene is treated with an acid, a method in which the surface is physically treated, and the like.

However, these processes are complicated and expensive.

Therefore, it is common practice to cover the printed surface with a plastic film. There are two methods: printing on a polypropylene sheet and covering it with a plastic film, and printing on a plastic film and bonding it to the sheet.

tc) Problems to be Solved by the Invention However, these methods require adhesives, but none have good adhesion to polypropylene.

Furthermore, the adhesion of the printing ink portion is also poor.

It is also possible to heat-seal without using an adhesive, but since the adhesive strength of the printing ink portion is weak, this may cause peeling if the printing area is large.

Furthermore, when a printed plastic sheet is bent, the print is cut off in that area, so-called ink bleed, which deteriorates the aesthetic appearance.

In addition, the Petit Stiff Sheet itself often breaks at bent portions.

Due to the recent advancement of industrial products and the importance of product aesthetics, printing itself is required to be very precise.

In other words, it has become strongly desirable to avoid wrinkles caused by printing misalignment or a difference in heat shrinkage rate with non-printed areas.

(dl Means to Solve the Problems In view of the above-mentioned current situation, the present inventor has completed the present invention sheet as a result of intensive research, and its characteristics are that , printed using a non-curing printing ink, and thermally fused to a polypropylene sheet on the printing surface side.

Here, the cast polypropylene film is a film produced by the T-shaped die method, and is characterized in that it is not stretched. This was selected because it is easy to adhere to a polypropylene sheet and because it is not stretched, it has flexibility.

Non-curing printing ink is not a curable ink that hardens over time after printing.

Therefore, it has the advantage of not losing flexibility even after drying.

Among these non-curable printing inks, chlorinated polypropylene is most preferred. This is because it has the advantages of good adhesion to polypropylene and no ink running out. Chlorinated polypropylene is obtained by dissolving polypropylene in carbon tetrachloride and passing chlorine gas through it, and is preferably 38 to 65% chlorinated.

Other than this, a one-liquid type urethane paint can be used. This has good adhesive properties compared to polypropylene and has the same effect as the above-mentioned chlorinated polypropylene.

The polypropylene sheet refers to a sheet of polypropylene, and may be not only a medium polymer of polypropylene but also a copolymer of propylene and other monomers. The other monomers may be anything that is commonly used in copolymerization with polypropylene, such as olefins such as ethylene, aromatic olefins such as styrene, acrylics, etc.

That is, in the present invention, in order to print on a polypropylene sheet, which is normally difficult to print, an ink with good adhesiveness is used to print on both the polypropylene sheet and cast polypropylene, and the two are fused.

A simple method for this fusion is to pass the film and sheet through a heating device and between lamination rollers or the like. However, the present invention is not limited to this, and it is also conceivable to take the sheet out of the extrusion molding machine and laminate it with a printed film while it is still in a molten state.

Also, when printing ink is applied to the entire film,
There is no drawback that wrinkles form in non-printed areas when the film is heated. Therefore, in the case of partial printing, for example, printing of characters, it is advantageous to apply transparent ink to the non-printing parts.

For this method, it is preferable to apply transparent ink to the entire surface over partial printing of characters, etc., or to perform a partial coating.

Part coat is transparent printing using a printing plate that is the opposite of the printing plate. This method is more advantageous because the printing thickness is uniform throughout.

These advantages are particularly advantageous for packaging materials for products that require the inside to be seen and that have a transparent portion (conventionally, a non-printed portion), that is, a window portion.

tel Example FIG. 1 shows a cross-sectional view of an example of the sheet of the present invention. A transparent ink (2) is applied to the entire surface of a polypropylene sheet (1), a colored ink (3) is partially applied on top of the transparent ink (2), and a polypropylene film (4) is applied over the entire surface of the polypropylene sheet (1).
is glued.

(fl　Effects of the invention The present invention has the following great effects.

(1) Strong printing is possible on polypropylene sheets. The adhesion to the cover film and ink is very strong. No adhesive required.

(2) When ink is applied to the entire surface, wrinkles can be prevented from forming during heating.

(3) No cutting of the striations occurs during striation processing.

(4) Ink does not run out during stamping.

(5) No scratches or ink runs out on the sheet during sheet hinge processing.

(6) Can be used for various purposes.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the sheet of the present invention. 1...Polypropylene sheet 2...Transparent ink 3... Colored ink

Claims (1)

[Scope of Claims] 1. A plastic laminate sheet characterized by printing on a cast polypropylene film using non-curing printing ink and heat-sealing the printed surface side to a polypropylene sheet. 2. The plastic laminate sheet according to claim 2, wherein the printing ink uses chlorinated polypropylene as a vehicle. 3. The plastic laminate sheet according to claim 1 or 2, wherein the printing ink is applied to the entire surface of the sheet. 4. The plastic laminate sheet according to claim 2 or 3, wherein the polypropylene sheet is a polypropylene copolymer.