JPH087281B2 - Manufacturing method of retroreflective sheeting - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retroreflective sheet which employs a micro retroreflective structure for retroreflecting a light beam hitting it at night. And the nature of the color of the underlying substrate in the daytime.

[0002]

BACKGROUND OF THE INVENTION Retroreflective sheeting materials are widely used for a variety of safety and decorative purposes and are particularly useful when night visibility is highly necessary in low ambient light conditions. . In a retroreflective material, light rays are retroreflected toward the illumination source in a generally parallel path toward the front surface. If headlights or searchlights on boats and airplanes are the only sources of illumination,
It is particularly important that most of the light rays incident on it can be retroreflected.

Minnesota Mining and Manufacturing Co., Ltd. provides such retroreflective property by manufacturing a retroreflective sheet in which small glass beads are embedded in a base material of an artificial resin and used. Is marketed under the name Scotchlight. Illustrative examples of such materials are shown in U.S. Pat. No. 4,637,950 issued to Bergerson et al. On Jan. 20, 1987.

The assignee's assignee, Reflectex Co., Ltd., widely sells a reflecting sheet having a micro-prism structure exhibiting such retroreflectivity under the name of Reflectexite. Illustrative examples of such materials are 1972
Roland, US Pat.
9, 346.

As an example of application of such a retroreflective material,
There are reflective bands found on columns, barrels, and conical signs used for traffic control.

A prism in the corner of a cube surrounded by air will retroreflect rays incident on its front or basal plane and striking the prism surface at an angle greater than the Fresnel angle. However, it is common to coat the prism surface with a reflective material such as vacuum deposited aluminum or a mirror material to provide a retroreflective interface. In this method, an adhesive or other backing material may be deposited on the metallized cubic corner prisms to thin the backing sheet and other structures.

[0007]

However, when metallized aluminum is applied on the surface of the prism and used, it tends to give a gray color to the viewer under the conditions of ambient light or daylight. is there. In some applications, this gray appearance is aesthetically undesirable.

In order to prevent or minimize the failure of such metallized retroreflective sheet material due to salt or other corrosives or moisture entering the retroreflective structure. It is common to provide a protective backing over the structure and seal the backing against a retroreflective sheet in a grid pattern to create isolated cells of clusters of isolated retroreflective structures. is there. An example of such a lattice structure is January 2, 1987.
U.S. Pat. No. 4,637,9 by Bergason et al.
It is shown at 50.

Martin, US Pat. No. 4,801,193, dated Jan. 31, 1991, uses a partially metallized microprism sheet with a grid of adhesive to bond the backing. Are disclosed and claimed. In this structure, the prisms under the grid-like adhesive are metallized, exhibiting retroreflectivity in that area, and the interface with air reverses the light in the area between the grid lines. To reflect. This structure is
It looks more white in the daytime.

However, some contractors and government officials desire to place retroreflective elements on barrels that have a uniform color even during the day or on traffic control devices such as conical signs. In certain instances, retroreflective elements are actually removed during the day to prevent white (or gray) interference in the fluorescent orange that is customarily used for such conical traffic signs. are doing.

[0011]

The object of the present invention is to show, under daylight conditions, the color of the foundation on which it is mounted and, at night, to enhance the light rays that strike it. It is an object of the present invention to provide a novel method for producing a retroreflective sheet for retroreflection.

Another object of the present invention is to provide such a novel retroreflective sheeting which is easy to manufacture and which makes the element durable and resistant.

Another object of the present invention is to provide a traffic sign device or the like using such retroreflective material.

The objects set forth above, and related objects, can be readily achieved by using a retroreflective sheeting having a micro retroreflective structure formed proximate one surface of the sheet. This structure is shaped so as to retroreflect the light rays that have entered the other surface of the sheet and hit the inner surface of the structure. A clear adhesive is applied on the prismatic surface of the sheet in a pattern that leaves most of the surface uncoated. A transparent backing element is adhered to the one surface by the adhesive, the backing element extending entirely in the structural plane and spaced from most of the surface of the structure. Thus, the structures on most of the surface are exposed to the surrounding atmosphere. As a result, rays incident on the other surface of the sheet and striking the prisms on the majority of the surface are retroreflected by the interface with the surrounding atmosphere and also coated by the adhesive. Light rays striking the structure in different areas will pass through the adhesive and the backing element and will be reflected by the surface of the base body to which the sheet is attached.

Preferably, the adhesive is applied in a grid pattern and the retroreflective structure is a micro prism. Desirably, the retroreflective sheeting and the backing element are made of synthetic resin.

In use of the sheet, the sheet is mounted on a colored support, and light rays passing through the backing element create the color in the sheet. The backing element is adhesively engaged on the support.

Usually, the support is a traffic sign member and the sheet is formed as a band adhesively engaged thereon.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, a prior art conical traffic sign, generally designated by the numeral 10, is a frustoconical band 1 of retroreflective sheeting around its circumference.
2 are glued together. Traditionally, such conical traffic signs 10 are made of synthetic resin and have an orange fluorescent color, and are therefore clearly visible during the day, as they are for stability. Base 1
6 and a truncated cone-shaped hollow body 18 are molded.

As can be seen in FIGS. 2 and 3, arcuate strips or blocks 20 of retroreflective material are formed on the band 12 with their overlapping ends 22 secured together by rivets 44. This overlapping end 22
As another means for fixing the above, it is possible to adopt a method such as adhesion with an adhesive or sonic welding.

Referring now to FIG. 5, a fragmentary and extremely magnified cross-sectional view of the retroreflective material of FIG. 2 is shown, with microprisms 22 formed on the backside of a flat surfaced body portion 24. It is shown. The microprisms 22 are closely spaced and can be described as having cube-shaped corners. Further details regarding this structure and the operation of such microprisms are described in Roland US Pat. No. 3,684,348, issued Aug. 15, 1972. The shape of the corners of these micro prisms 22 or cubes is 0.025 inch (0.64 inch).
Although a side edge size up to 10 mm) may be included, the preferred construction uses an edge size of 0.010 inch (0.25 mm) or less, and most preferably 0.004-0.
The order is 008 (0.10 to 0.20 mm). The body portion 24 of the seat is generally 0.002-0.03
It has a thickness on the order of 0 inches (0.05-0.76 mm), preferably about 0.003-about depending on the manufacturing process, the resin and the desired properties for the retroreflective sheeting.
It has a thickness of 0.010 inch (0.08 to 0.25 mm).

A particularly advantageous method for making such retroreflective sheeting is described and claimed in Roland US Pat. No. 3,689,346 dated Sep. 5, 1972, but is cubic. The corners of the are molded in a correspondingly shaped mold and adhered to the sheets placed on them to provide a composite structure, and the cubic corners have a shape of one of the sheets. Protruding from one surface.

Another method for making such a microprism sheet is shown in Roland US Pat. No. 4,244,683, issued Jan. 13, 1981, where the shape of the cubic corners is: Produced by punching a long sheet in a suitable punching machine with a precisely formed mold, preventing entrainment of air.

To attach this structure to a support surface,
It is customary to provide a backing or backing sheet 26 behind the microprisms 22 to protect them and provide a smooth surface. Adhesive 28 is employed to attach such backing sheet to the retroreflective sheeting to form a lamina.

As can be seen in FIG. 4, the micro-prism surface of the retroreflective sheeting is shown schematically, with the adhesive 28 applied in a grid. As a result, the adhesive 2 can be applied to only a limited number of micro prisms 22.
8 is not applied and there is no adhesive 28 on most of the surface area. Backing sheet 26 extends above prism 22 in a plane spaced therefrom. As a result, most of the surface area of the microprisms 22 will be surrounded by air or other atmosphere.

In this embodiment, on the front surface of the main body 24, there is a protective film made of a lacquer containing an ultraviolet absorber. A pressure sensitive adhesive film 30 is present on the opposite surface of the backing sheet 26. Overlying this adhesive film 30 is a release film or film 32, which is removed to adhere the retroreflective material to the surface of the support.

Next, referring to FIG. 6, the backing sheet 2
It can be seen that 6 is shown to be attached to the conical traffic sign 10 by the adhesive 30.

When an adhesive is used, it is known that this adhesive tends to wet the surface of the microprisms, thus destroying the air interface and eliminating retroreflectivity.

In daylight, conical traffic sign 1
0 is slightly changed in the band 12 area,
An orange fluorescence color is shown. At night, a viewer located near the light source of the rays incident on the conical traffic sign 10 sees a bright white band 12 on the conical traffic sign 10 because the band retroreflects the light toward the light source. It will be.

As can be seen in FIG. 7, the retroreflective sheet 12
Light rays 5 incident from the front surface of the main body portion (not shown)
0 indicates the adhesive-coated surface of the micro prism 22, penetrates the adhesive film 28, the backing sheet 26, and the adhesive film 30 to reach the surface of the base body 10, and from there, various types are directed upward and outward of the sheet. Is reflected and scattered through the path of. As a result, these reflected and scattered rays will show the color of the substrate.

Light ray 52 enters the body of sheet 24 and strikes the left surface of prism 22. It is reflected to the right prism surface and then to the outside through parallel paths. At night, when the surface is receiving light rays from a light source near the viewer, the viewer's eyes will see these retro-reflected rays and the sheet will have a bright white color. Let's do it.

Further, during the daytime, a large amount of light rays are incident on the front surface from various directions. Ray 54
Is incident on the front surface at a steep angle of 30 degrees or more from a vertical line, and is a steep angle larger than the Fresnel angle with respect to the uncoated surface of the prism 22. As a result, the light rays pass to the outside of the prism 22, pass through the air layer, the backing sheet 26, and the adhesive film 30 to reach the surface of the base body 10, where they are reflected and scattered. Therefore, some of the light rays striking the unpainted prism will be colored when reflected.

As previously mentioned, the microprism sheet may be formed by molding a prism on a film acting as a main body or stamping a preformed sheet.
Alternatively, it can be formed by simultaneously molding both the main body and the prism. Generally, the resins employed for micro-prism sheets are cross-linked thermoplastic formulations, desirably these resins exhibit flexibility, light stability and good weather resistance properties. Have In some examples, the front surface of the retroreflective sheet is coated with a lacquer or other coating material containing a UV absorber in an amount of 0.0002 to 0.0005.
A protective film may be provided by applying a thickness of inch (0.005 mm to 0.013 mm). Suitable resins for the retroreflective sheeting include polyvinyl chloride, polycarbonate, polymethylmethacrylate, polyester, polyurethane, acrylic urethane.

The backing sheet is also a flexible, durable polymeric material. Suitable resins include polyethylene, polypropylene, polyesters, polyurethanes, acrylated polyurethanes, ethylene / vinyl acetate copolymers. Generally, a flexible material of polyethylene and its copolymer is preferable.

The particular clear adhesive utilized in the process of the present invention will depend on the process employed and whether pressure sensitive or heat sensitive adhesive is desired and the mode of application. Will be chosen. In the preferred technique, the coating material is a pressure sensitive adhesive. Preferred adhesives include solvent-containing ethylene-propylene elastomeric block copolymers and solvent-containing acrylic-based adhesives. As the other adhesive, one made of pure silicone and polyester may be used. Water-based ones can be used, but this sometimes requires a drying time before further processing. A specific example of a suitable adhesive is Kraton-G from Pierce and Stevens.
Ethylene / commercially available under the name (KRYTON-G)
Propylene block copolymer adhesives and acrylic-based adhesives marketed by Coating Sciences under the name UV405 are mentioned.

The adhesive is applied in a grid pattern by a modified intaglio printing type roller. However, to provide a limited area pattern,
A spray method through a mask or another coating method may be used.

The adhesive "flows" under pressure during thinning
Because of the tendency, applying the adhesive pattern after thinning is a bit difficult to control, but it is also possible to apply the adhesive pattern to the backing film before thinning.

The adhesive applied to the opposite surface of the backing sheet to attach the retroreflective sheet to the base must be continuous to allow the desired passage of light rays to the base, This is a spray method, a roller coating method,
It may be applied by an intaglio printing coating method and a similar method. The backing sheet may be pre-coated with the coating layer or coating for its removal.

The process for adhering the backing sheet to the retroreflective sheet is simply a step of passing the adhesive-coated retroreflective sheet together with the backing sheet between a pair of rollers to provide an adhesive effect. Included is the application of appropriate pressure.
If a heat-acting adhesive is used, the retroreflective sheet may either be preheated before it is passed between the rollers, or the rollers may be heated to obtain the required effect. Good.

Although the present invention has been described as applicable to retro-reflective conical traffic signs, the band may also be used on barrels, columns, and other structures that utilize retro-reflective bands at the perimeter. You can

Examples of the efficacy of the present invention are shown in the following examples.

EXAMPLE 1 A center height of 0.0028 inches (0.07 mm) was obtained by using the method generally described and described in Roland US Pat. No. 3,689,346.
And a spacing of 0.006 inch (0.15 mm) microprisms are molded on a polyester film having a thickness of 0.002 inch (0.05 mm). The resin used for the micro prisms is an acrylic epoxy low polymer modified with monofunctional and trifunctional acrylic monomers.

On the surface opposite the surface having the micro-prisms, an acrylic lacquer containing a UV absorber, marketed under the name Tenuvin 328 by the company Chibergaghi, is 0.0003 inches (0. It is applied to a thickness of 007 mm).

The prismatic surface of the sheet is then engraved in a grid pattern by a modified intaglio printing roller and pressure sensitive, normally tacky ethylene / commercially available under the name Kraton-G from Pierce & Stevens. Deposit the block copolymer adhesive of propylene. The grid has a 0.25 inch (6.4 mm) spacing between lines, a wire thickness of about 0.04 inch (1.02 mm), and an adhesive covering about 40 percent of the surface, The depth is greater than the height of the prism. This sheet was laminated with a 0.001 inch (0.03 mm) thick polyethylene backing sheet between a pair of pressure rollers to form a thin layer,
For the backing sheet, U from Coating Science
An acrylic, pressure-sensitive, normally tacky adhesive commercially available under the name V405 is applied, and a water-soluble release agent is applied.

The resulting sheet material has excellent weathering properties in a weathering tester, excellent retroreflective properties,
It will exhibit the desired orange color during the day when glued to the fluorescent orange cone traffic sign.

[0045]

As described above, from the detailed description so far and the accompanying drawings, the present invention shows the color of the underlying base body during the daytime and exhibits excellent retroreflectivity at night. It will be appreciated that such new retroreflective microprism sheet materials are provided. The method for making this sheet is relatively simple, economical, and produces a material that exhibits a fairly long life.

[Brief description of drawings]

FIG. 1 is a side view of a conical traffic sign fitted with retroreflective bands embodying the present invention.

FIG. 2 is a plan view of a retroreflective sheet before being formed into a truncated cone shape in FIG.

3 is a side view of a band formed from the sheet of FIG.

FIG. 4 is a fragmentary plan view of a grid pattern of adhesive applied to the surface of a microprism made of the retroreflective material used in FIGS. 1-3.

5 is an overall enlarged fragmentary plan view of the sheet material shown in FIG.

FIG. 6 is a fragmentary plan view in which the reflection band and the cone shown in FIG. 1 are greatly enlarged.

FIG. 7 is a schematic view of the band and cone of FIG. 6 showing the projected rays.

[Explanation of symbols]

 18 Basic body 22 Retro-reflective structure (micro prism) 24 Retro-reflective sheet 26 Backing element 28 Transparent adhesive

Claims (12)

[Claims] 1. A method for producing a retroreflective sheet which retroreflects light rays at night and which appears to have the color of the underlying support during the day, comprising: (a) A micro retroreflective structure near one surface, which is shaped to retroreflect light rays incident on the other surface of the sheet and striking the inner surface of the structure; Forming such a retroreflective sheet; and (b) applying a transparent adhesive on the one surface in a pattern that leaves most of the surface uncoated. And (c) adhering a transparent backing element to the one surface with the adhesive, the backing element extending entirely in the structural plane.
And spaced from most of the surface of the structure, the structure on most of the surface is exposed to the surrounding atmosphere, and thus is incident from the other surface of the sheet. , The light rays striking the prism on most of the surface are retro-reflected by the interface with the surrounding atmosphere, and the light rays striking the structure in the area coated with the adhesive are the adhesive And a method of manufacturing a retroreflective sheet, which comprises reflecting and refracting after passing through a backing element. 2. The manufacturing method according to claim 1, wherein the adhesive is applied in a lattice pattern. 3. The manufacturing method according to claim 1, wherein the retroreflective structure is a microprism. 4. The manufacturing method according to claim 1, wherein the retroreflective sheet and the backing element are made of an artificial resin. 5. The method of claim 1, including the additional step of mounting the sheet on a colored support, such that light rays passing through the backing element are in the sheet. , A method of manufacturing a retroreflective sheet that produces the above-mentioned color. 6. The method of claim 5, wherein the backing element is adhesively engaged on the support. 7. The method of claim 6, wherein the support is a traffic sign member and the sheet is formed as a band adhesively engaged thereon. 8. A retroreflective sheeting that retroreflects light rays at night and appears to have the color of the underlying support during the day, comprising: (a) one surface of the sheet; A retroreflective sheet having a plurality of micro retroreflective structures adjacent to each other; (b) a transparent adhesive pattern covering a partial area of the one surface on the one surface, wherein the pattern is an adhesive The backing element, which includes a pattern thereof, which leaves most of its uncoated surface, and (c) a transparent backing element adhered to the one surface of the retroreflective sheet by the adhesive. Extends entirely through the structural plane,
The structures on most of the surface are exposed to the surrounding atmosphere, and thus
Rays incident from one surface and hitting the structure on the non-adhesive surface are reflected by the interface with the surrounding atmosphere, and rays hitting the adhesive-coated area are A retroreflective sheeting characterized by passing through the adhesive and a backing element. 9. The retroreflective sheeting of claim 8, wherein the adhesive is arranged in a grid pattern on the one surface and the backing element adheres to the retroreflective sheet along the grid pattern. Retroreflective sheet. 10. The retroreflective sheet according to claim 9, wherein the structure between the lines of the lattice pattern is barely coated with the adhesive and has a boundary surface with the atmosphere. Sheet. 11. The retroreflective sheet according to claim 8, wherein the retroreflective structure is a micro prism. 12. The retroreflective sheet according to claim 8, wherein the retroreflective sheet and the backing element are made of an artificial resin.