JPH10128821A - Coextrusion sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce light transmittance with little pigment, to raise a strength and to optimize for a perfecting printing by sheet molding resin containing dark color pigment and having specific light transmittance and resin containing tint pigment by coextrusion. SOLUTION: Resin containing dark color pigment and having 1% or less of light transmittance and resin containing tint pigment are sheet molded by coextrusion. The dark color pigment is generally carbon. The resin mixed with the dark color resin is normally polyolefin such as polyethylene or polypropylene. The tint pigment is generally titanium white. As the resin, the same type as the resin mixed with the dark color pigment is preferable to eliminate adhesive properties and a difference of expansion or contraction due to heat to coextrude it. And, the sheet has a thickness of about 0.1 to 3.0mm. Dark color sheet may have a thickness of about 1 to 20% of the entirety. A product of the coextruded sheet 1 is obtained, for example, by sandwiching a resin layer 2 containing the dark color pigment between resin layers 3 each containing the tint pigment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a coextruded sheet suitable for printing.

[0002]

2. Description of the Related Art Printing plastic sheets are widely used for advertisement sheets, stationery and the like. This is a white sheet usually produced by mixing a white pigment with a resin, and replaces the previous paper (cardboard). Although this may be used in a white color, printing is generally performed.

[0003]

When the amount of the white pigment mixed is small, the plastic sheet for printing has a low concealing ratio and the back surface can be seen through. When the back surface is seen through, the printing on the front surface is not clear as well as the double-side printing cannot be performed.

[0004] To prevent this, if the mixing amount of the white pigment is increased, the cost is increased and the strength is also reduced. Further, when the mixing amount of such an inorganic pigment is increased, so-called stains adhere to the mold, and cleaning and care of the mold are difficult. In addition, the smoothness of the surface is reduced, and it is difficult to perform delicate printing.

[0005] In addition, when foamed, the concealment ratio increases,
In any case, the smoothness of the surface is reduced, and precise printing cannot be performed.

[0006]

In view of the above situation, the present inventor has completed the present invention sheet as a result of diligent research and is characterized by containing a dark pigment and transmitting light. A resin having a light transmittance of 1% or less and a resin containing a light-colored pigment are formed into a sheet by co-extrusion. A resin containing a light-colored pigment is formed into a sheet by co-extrusion by sandwiching a resin layer containing a dark-colored pigment from both sides with a resin layer containing a light-colored pigment.

[0007] The dark pigment refers to a pigment having a relatively low brightness such as black, navy blue, or dark brown. However, it is generally carbon that is black. This may be a normal one. Also,
The light transmittance (the value after molding, hereinafter the same) is 1% or less because if it is less than this, the rear surface is hardly transparent.

The resin mixed with the dark pigment may be any resin as long as it can be formed into a sheet by extrusion molding, but is usually a polyolefin such as polyethylene or polypropylene. An amount of 2% or less of the pigment is sufficient. However, it differs depending on the type and color of the pigment. In short, it is an amount that can achieve a light transmittance of 1% or less.

[0009] The light-colored pigments are pigments having relatively high lightness such as white, pink, and yellow. However, titanium white, which is generally white, is used. The resin is preferably the same as the resin mixed with the above-mentioned dark pigment for co-extrusion. However, in the case of a material having good adhesiveness, different types may be used. In the case where different types of adhesive are not good, an adhesive layer (such as ethylene vinyl acetate) may be provided therebetween.

[0010] The mixing amount of the light-colored pigment is larger than that of the dark-colored pigment. However, in terms of light transmittance, about 10% is sufficient, so that 5% or less is generally sufficient. For a conventional white sheet, 20
%, It causes a problem of strength and a problem of a mold. The resin having a dark pigment and the resin having a light pigment are the same type of resin. Needless to say, the degree of polymerization and the like do not completely match, but are about the same as polyethylene and polyethylene and polypropylene and polypropylene. This is to eliminate the difference between adhesiveness by coextrusion and expansion and contraction due to heat.

Since the particles of the dark pigment and the bright pigment do not transmit light themselves, the light transmittance of the resin layer as a whole seems to be proportional to the amount of the pigment. In the resin, light is reflected on the pigment in the resin, and reflected light in various directions emerges on the opposite side of the resin layer. In this case, since the reflectances of the dark pigment and the bright pigment are completely different (a difference of several percent and about 90%), it is considered that the light transmittance as a whole is different. Therefore, when pigments having the same amount and the same particle size are used, the light transmittance of the pigment having a lower brightness is generally lower as a whole.

However, when black or the like is used as a pigment, not only cannot printing be performed, but also a very dark image as a whole.

The present invention satisfies both of these requirements.
Light transmission is prevented by the dark pigment, and the brightness of the surface is ensured by the light pigment.

Light transmission is substantially blocked by a resin layer having a dark pigment, and white (or a light color) by a light pigment.
To secure the groundwork. Of course, since the resin layer having the bright color pigment does not completely reflect light as in the related art,
The color becomes slightly dull due to the effect of the resin layer having the dark pigment on the back surface, but there is almost no difference in appearance. When printing is performed on the resin layer having such a bright color pigment, characters and patterns become clear because light does not pass through the back surface.

The two colors of resin are coextruded.
The coextrusion method may be a conventional method, and need not be special. Moreover, as a sheet, 0.1-3.0 mm
The thickness of the dark sheet on the back is 1% of the total thickness.
It may be about 20%.

In another embodiment of the present invention, there may be two resin layers having a bright color pigment. That is, the resin layer having a dark pigment is sandwiched between two resin layers having a bright pigment. In this manner, printing can be performed on both sides, and is most suitable for hanging advertisements and the like. Further, it can also be used for affixing to glass or the like. Further, an adhesive layer may be provided as described above, or another plastic film layer may be provided.

The resin of the present invention may contain additives which are usually added. For example, ultraviolet absorbers and the like.

[0018]

FIG. 1 is a sectional view of a coextruded sheet 1 of the present invention. In this example, the resin layer 2 having a dark pigment
Are sandwiched by the resin layer 3 having a bright color pigment. In this example, all resins are polypropylene. In the resin layer having a dark color pigment, 1% by weight of carbon is mixed, and in the resin layer having a light color pigment, 4.5% by weight of titanium white is mixed. This is extruded from a common co-extrusion machine to form a sheet. The thickness is 0.5mm as a whole
In, the resin layer having an intermediate dark pigment is 0.05 mm, and the resin layers having upper and lower bright pigments are each 0.225 mm.
It is.

The overall light transmittance of this coextruded sheet is:
It was 0.5% or less. When printing was performed on the top and bottom of this sheet, the printing on the back side was not visible at all, and only the design on the front side was visible.

[0020]

The coextruded sheet of the present invention described in detail above has the following significant effects. Although the total amount of the pigment is very small, the pigment is white as a whole and has low light transmittance. The cost is lower and the strength is higher than the conventional light transmittance of the same level. Since the amount of the pigment is small, the mold is easy to clean, and the frequency is small. Because of its low light transmittance, it is optimal for double-sided printing.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one example of a co-extruded sheet of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 coextruded sheet 2 resin layer having dark pigment 3 resin layer having light pigment

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29L 9:00

Claims (2)

[Claims] 1. A co-extruded sheet formed by co-extrusion of a resin containing a dark pigment and having a light transmittance of 1% or less and a resin containing a light pigment. 2. A resin containing a dark pigment and having a light transmittance of 1% or less and a resin containing a light pigment are combined with a resin layer containing a dark pigment from both sides by a resin layer containing a light pigment. A co-extruded sheet which is sandwiched and formed into a sheet by co-extrusion.