JPH07104111A - Cellular retroreflection sheet - Google Patents

Abstract

PURPOSE:To provide the cellular retroreflection sheet which is entirely free from trouble, such as generation of small wrinkles, in practicable use at all and has excellent strain resistance by specifying the thickness and tensile strength of a releasable sheet. CONSTITUTION:The thickness of the releasable sheet of the cellular retroreflection sheet consisting of a cellular retroreflection base sheet, an adhesive layer laminated and formed on the rear surface of the base sheet and the releasable sheet laminated on the adhesive layer is specified to 25 to 200mum and the tensile strength thereof to >=500kg/cm<2>. This releasable sheet is not particularly limited, insofar as the sheet satisfies the thickness and tensile strength specified above. A polyethylene phthalate resin sheet which has excellent smoothness and is subjected to a release treatment by a silicone resin, etc., is preferably used. The cellular retroreflection sheet is not particularly restricted and sheets of known capsule lens types and capsule cube corner types, etc., are usable.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is useful for signs such as road signs and construction signs, license plates for vehicles such as automobiles and motorcycles, safety materials such as clothes and life preservers, and marking of signs. The present invention relates to a retroreflective sheet.

[0002]

2. Description of the Related Art Conventionally, a retroreflective sheet that retroreflects light toward a light source is well known, and the sheet is widely used in the above-mentioned fields of application by utilizing its retroreflectivity. Among them, the cellular retroreflective sheet in which a low-refractive-index gas such as air is enclosed in a sealed small-compartment chamber (cell) by forming a sealed small-compartment chamber (cell) is The amount used is increasing year by year.

Generally, a cellular retroreflective sheet comprises a protective film, a support film, a retroreflective element provided on the surface of the protective film or the support film, which face each other through a narrow gas layer, and, for example, the support. Cellular retroreflection consisting of continuous linear connecting walls that are formed by thermal deformation of the film or printing of adhesive on the support film and connect both films to form a large number of closed small compartments. A base sheet, an adhesive layer for adhering a retroreflective sheet laminated on the back surface of the base sheet to an adherend, and the adhesive adheres to an unspecified object or stains adhere to the adhesive. It consists of a peelable sheet based on a polypropylene film, polyethylene laminated paper or the like laminated on the adhesive layer for the purpose of preventing adhesion.

Further, the closed small compartment contains a number of retroreflective elements such as cube-corner elements provided on the surface of the protective film or retroreflective glass beads provided on the surface of the support film. Therefore, the excellent retroreflective performance can be exhibited by cooperating with the low refractive index gas in the closed small compartment vacant space.

Usually, the cellular retroreflective sheet is about 50 m in a paper tube having an inner diameter of about 75 mm and a wall thickness of about 3 to 20 mm in actual use.
It is supplied to customers in the form of a roll wound up to a length of about 100 m. And this cellular retroreflective sheet,
Generally, the customer unwinds the required amount from the roll, cuts it into the desired shape, and after processing such as printing,
The peelable sheet is peeled off and attached to the adherend, and processed into signs, license plates, safety materials, signboards, and the like.

However, in general, the thickness is about 300 μm to about
In the thick cellular retroreflective sheeting of 600 μm,
When wound in a roll shape, a difference in length occurs between the front layer side and the back layer side, a stretching force acts on the front layer side, and a compressive force acts on the back layer side, which causes strain in the sheet. Often cause problems.

That is, in the cellular retroreflective sheet unwound from the roll shape, the difference in length between the cellular retroreflective base sheet which is usually the surface layer side and the peelable sheet which is usually the back layer side due to strain. Also, the base sheet or the protective film is stressed due to the relaxation of the strain,
In a severe case, both of them often have small wrinkles, which loses smoothness, makes it impossible to perform printing, and causes troubles such as poor appearance. Also, when using a cellular retroreflective sheet that has been unwound from a roll and kiss-cutting cut characters with a cutting machine, etc., there are often problems such as small wrinkles in the cut characters in actual use. It's a big problem.

Such troubles often occur at the core of the roll-like material, which is generally considered to have a large curvature and a large amount of distortion, but the retroreflective sheet does not contain a gas layer other than the cellular retroreflective sheet. In the reflective sheet, the occurrence is small, so the special structure of the cellular retroreflective sheet as described above is considered as the main cause of the trouble, and
At least this special structure seems to have contributed to the occurrence of troubles.

[0009]

In view of these drawbacks of the prior art, the present invention intends to provide a cell-like retroreflective sheet having excellent distortion resistance and having no wrinkles or the like in actual use as described above. To do.

The inventors of the present invention have conducted various studies on improving the strain resistance of the cellular retroreflective sheet, and as a result, changed the peelable sheet from a flexible sheet used conventionally to a sheet having rigidity. It was found that excellent strain resistance can be obtained by a simple operation.

[0011]

Thus, according to the present invention, it comprises a cellular retroreflective base sheet, an adhesive layer laminated on the back surface of the base sheet, and a peelable sheet laminated on the adhesive layer. A cellular retroreflective sheet, characterized in that the peelable sheet has a thickness of 25 µm to 200 µm and a tensile strength of 500 kg / cm ² or more.

The present invention will be described in detail below. The peelable sheet in the present invention needs to be a synthetic resin sheet having a tensile strength of 500 kg / cm ² or more. Tensile strength is 50
If it is less than 0 kg / cm ^2, it is difficult to obtain excellent strain resistance. In order to obtain more preferable strain resistance, the tensile strength of the peelable sheet should be
1000 kg / cm ² , more preferably 1500 kg / cm ² or more, and particularly preferably 2000 kg / cm ² or more.

The thickness of the peelable sheet according to the present invention is
It should be 25 to 200 μm. When the thickness is less than 25 μm, it is difficult to obtain preferable strain resistance, and when the thickness is 200 μm or more, handling workability is deteriorated, which is also disadvantageous in cost. The thickness of the peelable sheet is preferably 35 to 150 μm, more preferably 40 to 100 μm from the viewpoint of the balance of strain resistance, workability, cost and the like.

The peelable sheet in the present invention is not particularly limited as long as it satisfies the above tensile strength and thickness, but a polyethylene terephthalate resin sheet having excellent smoothness is subjected to a peeling treatment with a silicone resin or the like. Those are preferably used.

The cellular retroreflective base sheet used in the present invention is not particularly limited, and known capsule lens type, capsule cube corner type and the like may be used.

For example, in order to form a capsule lens type retroreflective element, first, a refractive index of 1.7 to 2.0 and an average particle size of 40 to 40 are formed on a temporary support such as polyethylene laminated paper.
About half to about one-third of glass beads of about 90μ are embedded and supported, and metal vapor deposition of aluminum or the like is applied to the upper surface of the glass beads to form a metal vapor deposition film on the exposed hemispherical surface of glass beads, Then, a support film having a thermosoftening resin surface is placed on the temporary support, and the glass beads side of the temporary support and the support film are pressed to perform metal vapor deposition of the glass beads. A method may be mentioned in which the above-mentioned temporary support is integrally peeled after the above-mentioned portion is substantially embedded in the support film. Further, a resin solution for forming a support film may be applied and dried instead of stacking the support film on the temporary support.

In order to form a cube-corner retroreflective element, for example, a transparent synthetic resin sheet is embossed with an embossing roll having a concave cube-corner element so that one side of the sheet is entirely covered. Means such as forming a large number of convex cube-corner retroreflective elements can be preferably employed.

When the cellular retroreflective base sheet used in the present invention is of a capsule lens type, for example, a protective film is provided on the surface of the support film in which the glass beads are embedded in the capsule lens type retroreflective element. The support film is placed and heat-embossed from the back surface of the support film to thermally deform the support film to form a continuous linear connecting wall, and both films form a large number of closed small compartments. It can be manufactured by connecting as described above.

In the case of the cube-corner type, for example, the support film is placed on the embossed surface of the cube-corner retroreflective element, and the back surface of the support film is similarly used. By heat embossing, it is possible to manufacture a cube-corner retroreflective sheet base having a large number of closed small compartments by forming continuous linear connecting walls.

As the support film used for producing the cellular retroreflective base sheet, retroreflective glass beads are preferably used in order to make the shape of the connecting wall portion formed by thermal deformation or the like as uniform and constant as possible. At least a heat-softening bonding resin layer that is embedded and forms a continuous linear connecting wall by heat embossing, and a reinforcing resin layer that forms a surface opposite to the glass bead embedding surface and reinforces the bonding resin layer. A multi-layer structure including two layers is preferable.

EXAMPLES The present invention will be described in more detail below with reference to examples.

Example 1 A process in which a polyethylene resin having a thickness of about 20 μm is laminated on paper is heated to about 105 ° C., and an average particle diameter of about 65 μ is placed on the paper.
Glass beads having a m and a refractive index of about 1.91 were uniformly and densely dispersed and pressed by a nip roll to embed the glass beads in a polyethylene resin to about 1/3 of the diameter. Then, aluminum was vacuum-deposited on the surface of the process paper in which the glass beads were embedded by using a vacuum vapor deposition machine to form a vapor deposition film having a thickness of about 0.1 μm on the surface of the glass beads.

Next, based on the composition shown in Table 1, a resin composition for forming a reinforcing resin layer was dried on a silicone-treated polyethylene terephthalate process film to a thickness of about 40 μm.
To form a reinforcing resin layer by drying, and further coating the resin composition for forming the bonding resin layer on the reinforcing resin layer so that the thickness after drying is about 80 μm, and then drying. After forming the bonding resin layer, the glass beads embedding step is laminated so that the bonding resin layer side of the above laminate faces the aluminum deposition side of the paper, and the glass beads are embedded in the bonding resin layer by about 1/3 by applying pressure. I did it. Then, in this state, aging was carried out at 35 ° C. for 14 days to complete crosslinking of the reinforcing resin layer.

The polyethylene resin laminating process paper was removed from this laminate and a thickness of about 75 was placed on the exposed glass beads.
Between a metal roll with a surface temperature of about 190 ° C and a rubber roll with a surface temperature of about 60 ° C on which a non-stretched acrylic film with a total light transmittance of about 93% and a line width of 0.3mm is engraved and placed on top of each other. Was passed under pressure while the acrylic film side was in contact with the rubber roll, and was thermally deformed to form a closed small compartment vacancy. The process film was removed from the heat-deformed molded product to prepare a cellular retroreflective base sheet.

Next, a solution of an acrylic pressure-sensitive adhesive is applied onto the silicone release treated surface of polyethylene terephthalate (PET) having a thickness of about 50 μm to be a peelable sheet and dried to obtain a pressure-sensitive adhesive having a thickness of about 40 μm. Form a drug layer,
This was laminated on the reinforcing resin layer of the above base sheet to prepare a capsule lens type retroreflective sheet.

The tensile strength of the base sheet and the peelable sheet in the obtained capsule lens type retroreflective sheet was measured in an atmosphere of 23 ° C. with a gripping interval of 50 mm and a pulling speed of 20.
The tensile strength of the base sheet was 13 when the test was performed at 0 mm / min.
Was 0 kg / cm ^2, tensile strength of the peelable sheet 1900kg
It was / cm ² .

The completed capsule lens type retroreflective sheet was wound around a paper tube having an inner diameter of 3 inches and a thickness of 8 mm for about 50 m, left at 50 ° C. for 10 days, cooled to room temperature and then rewound to check the occurrence of small wrinkles. It was visually observed. Table 1 shows the resin composition used for forming the reinforcing resin layer, the adhesive resin layer and the adhesive layer.
The test results are shown in Table 2.

Example 2 A capsule lens type reflection sheet was prepared in the same manner as in Example 1 except that the thickness of the peelable sheet was changed to about 75 μm. went. The resin formulations used for forming the reinforcing resin layer, the bonding resin layer and the adhesive layer are shown in Table 1 and the test results are shown in Table 2.

Example 3 A capsule lens type reflection sheet was prepared in the same manner as in Example 1 except that the thickness of the peelable sheet was changed to about 100 μm. went. Table 1 shows the resin composition used for forming the reinforcing resin layer, the bonding resin layer, and the adhesive layer, and Table 2 shows the types, thicknesses, and test results of the peelable sheets used.

Example 4 Capsule lens mold was prepared in the same manner as in Example 1 except that the composition of the bonding resin was changed as shown in Table 1 and the thickness of the peelable sheet was changed to about 75 μm. A reflection sheet was prepared and tested in the same manner as in Example 1 below.
Table 1 shows the resin composition used for forming the reinforcing resin layer, the bonding resin layer, and the adhesive layer, and Table 2 shows the types, thicknesses, and test results of the peelable sheets used.

Comparative Example 1 A capsule lens type reflection sheet was prepared in the same manner as in Example 1 except that the thickness of the peelable sheet was changed to about 20 μm. went. Table 1 shows the resin composition used for forming the reinforcing resin layer, the bonding resin layer, and the adhesive layer, and Table 2 shows the types, thicknesses, and test results of the peelable sheets used.

Comparative Example 2 A capsule lens type reflection sheet was prepared in the same manner as in Example 1 except that the release sheet was an unstretched polypropylene (PP) film having a thickness of about 80 μm. The test was conducted in the same manner as in Example 1. Table 1 shows the resin composition used for forming the reinforcing resin layer, the bonding resin layer, and the adhesive layer, and Table 2 shows the types, thicknesses, and test results of the peelable sheets used.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

The cellular retroreflective sheet of the present invention comprises a cellular retroreflective base sheet, an adhesive layer laminated on the back surface of the base sheet, and a peelable sheet laminated on the adhesive layer. The characteristic is that a highly rigid sheet having a specific thickness and tensile strength is used as the peelable sheet.

As a result, the cellular retroreflective sheeting of the present invention has excellent strain resistance without any trouble such as wrinkles in actual use.

Claims (3)

[Claims] 1. A cellular retroreflective sheet comprising a cellular retroreflective base sheet, an adhesive layer laminated on the back surface of the base sheet, and a peelable sheet laminated on the adhesive layer. Is a thickness of 25 μm to 200 μm, and its tensile strength is 500 kg / cm ² or more, a cellular retroreflective sheet. 2. The tensile strength of the cellular retroreflective base sheet is 300 kg / cm ² or less.
The described cellular retroreflective sheet. 3. The cellular retroreflective sheet according to claim 1, wherein the releasable sheet is a release-treated polyethylene terephthalate resin-based sheet.