JPS608223B2 - Manufacturing method of retroreflective sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a retroreflective sheet, and more particularly, to a method for manufacturing a retroreflective sheet that is improved so as to arbitrarily obtain a glass bead filling rate.

Retroreflective sheets are called focusing resin layers because glass beads are embedded in a colored or colorless transparent surface resin layer, and the reflective layer must be placed where the parallel light incident from the surface resin layer is focused. It is formed by applying a colored or cool-colored transparent resin layer to a thickness from the surface of the embedded piece to the focal point, and then depositing, for example, aluminum to provide a reflective layer.

The incident light beam from the light source passes through the surface resin layer, glass beads, and focusing resin layer, and is focused and reflected by the reflective layer, providing a conical retroreflection function centered in the direction of the light source. When irradiated with light from a car headlight or flashlight at night, it is retroreflected in the direction of incidence, making it easy to identify this retroreflective sheet. Such retroreflective sheets are used for road signs, fire signs, safety signs, automobile sign boards, stickers, etc. related to regulations, guidance, oaths, and instructions.
Performance requirements vary depending on the application, from those that require high reflective brightness to those that can be satisfied with relatively low brightness.

Glass beads account for a high proportion of the cost of such retroreflective sheets. However, in current retroreflective sheets, the glass bead filling rate is negative and has not been adjusted. Therefore, at present, glass beads are embedded in the most tightly packed state to form a surface resin layer, and a focus adjustment resin layer is laminated on this with a thickness different from the appropriate thickness, or the surface resin layer is colored. The reflected brightness is set to a desired low brightness value. The present invention improves on the current method and provides a method for manufacturing a retroreflective sheet that allows a desired glass bead filling rate to be obtained.

That is, a colored or colorless transparent thermoplastic surface resin layer is distributed on one side of the base film, glass beads are embedded in this surface resin layer to form a bead-embedded sheet, and then this sheet is biaxially stretched to adjust the bead filling rate. The present invention provides a method for producing a retroreflective sheet in which a focus adjusting resin layer and a reflective layer are sequentially provided.
．． Since the base film used in the above method is to be stretched, an unstretched film is preferable, but depending on the degree of stretching, a film that has already been slightly stretched can also be used.

Polyethylene terephthalate, polyvinyl chloride, polyethylene, polypropylene, polyamide, polycarbonate, etc. may be used as the base film material. In addition, since the base film is to be peeled off from the surface resin layer formed thereon, it should be selected so that it can be easily peeled off. If it is difficult to peel off, a release treatment may be applied to the base film surface. . The surface resin layer coated on the base film is a thermoplastic resin, such as polyester resin, polyurethane resin, polyvinyl chloride resin, polyacrylic resin, polyamide resin, polyethylene resin, polypropylene resin, etc. The dry film thickness is preferably 10 to 80 r.Examples will be described below.

An example of compounding the surface resin layer on the base film, which is a polyester resin in this example, is shown below. '1] Vinyl chloride resin 10 anchor plastic DOP
20-5 parts 0.7 parts 2-0 parts Soku; Gohi Fusai U) Total ■ Thermoplastic polyurethane resin 10 parts Silicone for staining 0.1 parts Dimethylformamide (DMF) 5 Methyl ethyl ketone ( M Old K) 5$ Part After coating and distributing any of the surface resin layers on the base film, glass beads are scattered and embedded in the surface resin layer while drying is insufficient.

FIG. 1 shows the piece-embedded sheet 4 in this state. This sheet 4 has a surface resin layer 2 formed on a base film, and glass beads 3 are densely embedded therein. This bead-embedded sheet is then biaxially stretched. When the sheet is subjected to stretching, {1) it is not sufficiently dried and the base film can be stretched;
The surface resin layer is in a dry state and the base film is stretched only after being reheated, or [3] the surface resin layer is sufficiently dried and the base film is peeled off and then stretched. For stretching, a tenter used for stretching plastic films may be used. Figure 2 A is a diagram of a tenter with a horizontal restriction type and a mouth restricted in both vertical and horizontal directions.
The sheet 4' is shown stretched below the rollers 51 and 52 while being gripped by chuck groups 61 and 62, respectively. Stretching may be done by simultaneous biaxial stretching in the mid-length direction or sequential biaxial stretching.The stretching temperature ranges from 50 degrees to 2 degrees.
00oo is normal. Table 1 shows the relationship between stretching ratio and glass bead filling rate. Table 1 and FIG. 3 show the sheet 4' which was cooled and fixed after being stretched.

Both the base film 1' and the surface resin layer 2' are stretched to make the distribution density of the beads 3 coarse. Next, a focusing resin layer material is applied to the surface of the glass beads. The resin layer material may be the same as the surface resin layer, and thermosetting resins such as thermosetting polyester resins, acrylic resins, polyurethane resins, etc. can also be used, and polyvinyl butyral resins are often used. A compounding example of the resin layer material for focus adjustment used in this example is shown below. {1} Polyvinyl butyral resin
2 parts DBP 2 to 1 parts toluene 10 parts butyl alcohol 10 parts One-component polyurethane resin 5 Silicone resin for stamen rings 0.1 part DMF
IO Cape K
After coating the resin layer material for focus adjustment, a reflective layer 8 is formed on the surface of the layer 7 by vapor deposition of aluminum or by coating with an aluminum powder mixture paint to form a retroreflective sheet 9 in FIG.

Bead filling rate when the film thickness of the focusing resin layer 7 is appropriate and the angle of incidence -40 according to JIS Z9117 and the angle of observation 0. Table 2 shows the relationship between the brightness and the reflected brightness. Table 2 As is clear from Table 2, according to the method of the present invention, when a retroreflective sheet with a reflection brightness of 4 Fahrenheit is desired, the amount of glass beads used in the current sheet can be reduced to 40%, resulting in a low cost. Moreover, it is possible to obtain appropriate quality.

[Brief explanation of the drawing]

Figures 1 and 3 are cross-sectional views showing semi-finished products of retroreflective sheets produced by the method of the embodiment, Figure 4 is a cross-sectional view of finished products, and Figures 2A and 3 are both relative to the semi-finished products in Figure 1. FIG. 3 is a drawing track diagram showing a tenter that may be used in biaxial stretching. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1 After coating and distributing a colored or colorless transparent thermoplastic surface resin layer on one side of the base film and embedding glass beads in this surface resin layer to form a bead-embedded sheet,
A method for producing a retroreflective sheet, which comprises biaxially stretching this sheet to adjust the bead filling rate, and then sequentially providing a focusing resin layer and a reflective layer to form a retroreflective sheet.