KR20030041619A - Retroreflective sheet having the good weatherability as well as flexibility and the method of manufacturing the same - Google Patents

Abstract

PURPOSE: A reverse reflection sheet having excellent weather resistance and flexibility and the manufacturing method are provided to maximize night visibility of a number plate for a vehicle and secure the reverse reflection sheet not cracked at lower temperature in high-speed press forming. CONSTITUTION: A reverse reflection sheet having excellent weather resistance and flexibility comprises the uppermost film layer(10), a resin for adhering glass beads(11), fine glass beads(12), a focal resin layer(13), a metal deposition layer(14), an adhesive(15), and release base paper(16). Elongation of the sheet material is maximized, using a polyvinyl-chloride resin to the uppermost film layer. The degree of polymerization of the polyvinyl-chloride resin is 800¯1500 and the thickness after drying is 25¯60 micron.

Description

Retroreflective sheet having the good weatherability as well as flexibility and the method of manufacturing the same}

The present invention relates to a retroreflective sheet for a license plate which increases the night visibility of the license plate and a method of manufacturing the same. The built-in lens retroreflective sheet basically consists of a top film, a binder resin for fixing the lens, a fine glass bead (lens), a focus resin, a metal reflective layer, an adhesive, and a release paper. The top film is the outermost part of the finished product, which protects the sheet product from the external environment and plays a dominant role in the mechanical properties and weather resistance of the whole product.

Polyurethane-based resins, copolymers such as ethylene or propylene, and acrylates and methacrylates have been used as materials that can be used for the top film 10. The binder resin for fixing the lens plays a role of partially embedding and fixing the fine glass beads 12. In general, polyester polyol having a glass transition temperature of 0 ° C. or less and polyisocyanate are used as a crosslinking agent before crosslinking. Urethane resins have been used.

The fine glass bead layer embedded in the binder resin 11 is dispersed in a single layer, and about 30 to 70% of the total diameter of the beads is embedded in the resin layer. And the focus resin 13 layer is formed in the lower layer. This focus resin layer exhibits the best retro-reflective brightness when applied to a thickness as long as the distance of focus of the light refracted through the fine glass beads. A metal reflective layer is formed on the surface of the focus resin layer, and a vacuum deposition method is commonly used. The lens-embedded retroreflective sheet having such a structure greatly depends on the physical properties of the material used for each layer, and in particular, the physical properties of the uppermost film have the most dominant influence. In the contents disclosed in Korean Patent No. 2000-0005284, a retroreflective sheet for a license plate made of a material of a physical property suitable for high speed embossing is introduced.

As described above in the technical background, the retroreflective sheet used for the embossed license plate becomes the basic property of emboss compliance. This is because when the retroreflective sheet does not have sufficient elongation, bursting or lifting occurs around letters during molding of the press 17 of the license plate. In particular, this problem occurs a lot when working in an environment where the room temperature is 10 ℃ or less, in the present invention is excellent in elongation than the conventionally published patent, even at a relatively low temperature (0 ℃ or more) high-speed press molding does not occur at all retroreflection To prepare a sheet.

It is possible to apply the polyvinyl chloride resin having a very high elongation characteristic to the top film, and also reduce the manufacturing cost. And the weak point of weather resistance, which is a disadvantage of polyvinyl chloride, is to be solved by adding various additives such as heat stabilizer, light stabilizer.

1 is a cross-sectional view of the finished product retroreflective sheet for license plates according to the present invention,

Figure 2 is a cross-sectional view showing a process of press-molding by attaching the finished product retroreflective sheet for license plates according to the present invention to an aluminum plate.

Explanation of symbols on the main parts of the drawings

10 top film layer 11: glass beads fixing resin

12 fine glass beads (lens) 13 focus resin

14 metal deposition layer (metal reflective layer) 15: adhesive

16: release paper 17: press mold

18: Retroreflective sheet for license plate (after release paper peeling)

19: aluminum plate

Lens-embedded retroreflective sheet devised in the present invention is basically composed of a top film, a lens fixing binder resin, a fine glass beads (lens), a focus resin, a metal reflective layer, an adhesive, a release paper.

First, the top film 10 uses polyvinyl chloride resin to maximize the elongation of the product. The method is preferably a method in which a polyvinyl chloride sol is mixed and coated on a carrier film. At this time, the polymerization degree of polyvinyl chloride is suitably 800 to 1500, and the viscosity is preferably 2000 cps or less after completion of the compounding. A thickness of 25 to 60 microns is recommended after drying of the top film. Since the transparency of the film varies depending on the drying conditions, the polyvinyl chloride resin is preferably dried at a temperature as high as possible.

Addition of plasticizer is essential to reinforce the elongation of the polyvinylchloride resin. The amount of plasticizer added is about 20 to 50% by weight based on the main polyvinyl chloride, and the stabilizer is a light stabilizer, a heat stabilizer, and a diluent for viscosity adjustment, toluene, ethyl acetate, xylene, butyl glycol, etc. This can be used and, if desired, a functional viscosity control additive can also be introduced.

Colored pigments include organic pigments and inorganic pigments, and organic pigments are preferred in view of light transparency. Weather resistance should also be taken into account when selecting organic pigments. The uppermost film may be a commercially available polyester film or a release-treated paper as a carrier film for coating polyvinyl chloride resin, and basically a heat-resistant material that does not shrink or deform even at about 150 to 200 ° C. desirable.

In the second process, the binder resin 11 for fixing the fine glass beads is coated on the uppermost film. The coating method is comma coating, bar coating, roll coating, etc., and a thickness of 20 to 35 microns after drying is appropriate.

The binder resin is preferably a two-component thermosetting resin crosslinked with an acrylic polyol and a copolymer such as acrylate, methyl methacrylate, butyl acrylate, ethyl acrylate, vinyl acetate, and polyfunctional polyisocyanate.

In order to fix the fine glass beads 12, the binder resin is coated and then dried at about 60 to 100 ° C. for about 1 minute, and then the fine glass beads are dispersed in a single layer in a sticky state on the surface. After dispersing, the fine glass beads settle and adhere to the binder resin while passing through a high temperature oven at about 100 to 170 ° C. At this time, if the coating thickness of the binder resin is too thick compared to the fine glass beads, blocking may occur during the winding of the semi-finished product, so only about 30 to 70% of the fine glass beads should be manufactured to be immersed in the resin.

The semi-finished product with the glass beads dispersed and fixed is aged at 50 ° C. for about 24 hours and then enters the focus resin coating process. As the focus resin 13, two-component thermosetting resins of polyester polyols and polyisocyanates are used, or copolymers of acrylic polyols with acrylates, methyl methacrylates, butyl acrylates, ethyl acrylates, vinyl acetates and the like Two-component thermosetting resins crosslinked with isocyanates are suitable. At this time, considering the elongation of the whole product, the ratio of the main material and the crosslinking agent should be adjusted to obtain a high elongation. The thickness of the focusing resin layer should be set so that 10 to 20 microns, which is about 10 to 30% of the diameter of the fine glass beads, is appropriate and exhibits the optimum brightness. The viscosity of the focus blending resin is suitably 300 to 1500, and a viscosity control agent is added to allow the resin layer to form a curved surface on the fine glass beads.

A metal deposition layer (metal reflective layer) should be introduced below the focus resin layer so that the light that is refracted to form the focus may be reflected in the direction of the original light source. The metal silver, silver, aluminum, platinum, nickel, chromium, etc. at this time can be used, and as a vapor deposition method, the vacuum vapor deposition method, sputtering vapor deposition method, electron beam vapor deposition method, etc. are possible.

In order to enable the interfacial adhesion between the focus resin layer and the metal deposition layer, it is possible to increase the bonding strength by adjusting the reaction ratio of the main resin and the curing agent of the focus resin layer, and a separate additive that increases the adhesion force between the metal and the raw material prepared as the focus resin layer. You can also use In this case, polyvinyl chloride containing maleic anhydride or polyvinyl chloride resin containing a hydroxyl group is generally used as an additive.

The adhesive layer serves to freely attach the reflective sheet to the aluminum plate used in the license plate. The pressure-sensitive adhesive used herein may be acrylic or rubber pressure-sensitive adhesives, and a small amount of curing agent is added to adjust the pressure-sensitive adhesive properties. In particular, it is very important that the adhesive holding force of the pressure-sensitive adhesive to prevent the bending portion of the embossed characters from lifting in various external environments during press molding of the license plate. The coating thickness of the pressure-sensitive adhesive is 20 ~ 80㎛, the release paper used at this time is polyethylene coated on one side or both sides, on one side weight 50 ~ 150g / ㎡ paper with a release treatment such as silicon, or thickness 25 ~ 100㎛ Use a polyester film or polypropylene film that has been released on one side.

Example

30 phr of polyester plasticizer adipic acid polyester was added to polyvinyl chloride resin 100, 3 phr of barium zinc organic complex of thermal stabilizer of inorganic metals and 0.5 phr of TINUVIN 123, a liquid ultraviolet absorber of ester system, were added. After compounding, the mixture is diluted with xylene and butyl glycol and coated on a 100 micron polyester carrier film. At this time, drying temperature is 60-200 degreeC, and the thickness of the uppermost film after drying is 50 micron. Next, a binder resin blended with an acrylic polyol and a copolymer such as acrylate, methyl methacrylate, butyl acrylate, ethyl acrylate, and vinyl acetate and a trimer type polyisocyanate to fix the fine glass beads is top film. Coating on top. At this time, the molecular weight of the binder resin before crosslinking is about 250,000 and has a glass transition temperature of about 20 ℃. The binder resin is about 20 microns after drying and the diameter of the fine glass beads applied is 40-70 microns. After drying for about 3 minutes in an oven at 100-170 ℃ and aged at 50 ℃ 24 hours. As the focusing resin, a two-component thermosetting resin of polyester polyol and polyisocyanate is used. The glass transition temperature of the main material before crosslinking is 20 ° C., and the molecular weight is 30,000. The focal thickness after drying was made to 18 microns.

Under the focus resin layer, an aluminum thin film was formed by a vacuum deposition method as a reflective layer, and a small amount of polyvinyl chloride containing maleic anhydride was added to the focus resin to improve adhesion to the aluminum deposition layer. The pressure-sensitive adhesive layer compensated for the adhesive holding force by using an acrylic pressure-sensitive adhesive. The release paper was coated with polyethylene on both sides, and on one side, a paper having a weight of 150 g / m 2 with a release treatment such as silicone was used.

The retroreflective sheet for license plate according to the present invention configured as described above helps the night driving safety by maximizing the night visibility of the license plate, and can work without the phenomenon of popping during press molding even in the process of manufacturing a reflective license plate, especially at a relatively low temperature. Also has the advantage that the embossing can be stable. In terms of manufacturing cost, it can be said that it is advantageous to apply polyvinyl chloride resin. In addition, by introducing various additives such as heat stabilizer, light stabilizer, it is possible to ensure the practical use stability by supplementing the outdoor weather resistance.

Claims (5)

In a lens-integrated retroreflective sheet material composed of a top film layer, a resin for fixing glass beads, a fine glass bead (lens), a focus resin layer, a metal deposition layer (metal reflective layer), an adhesive, and a release paper, the top film layer is made of polyvinyl Reverse reflection sheet material that maximizes elongation of product using chloride resin. The retroreflective sheet material according to claim 1, wherein the polyvinyl chloride resin has a degree of polymerization of 800 to 1500 and a thickness of 25 to 60 microns after drying. The retroreflective sheet material according to claim 1, wherein a polyester plasticizer is added to reinforce the elongation of the polyvinyl chloride resin layer, and the weight fraction of the plasticizer is 10-50 phr. The method according to claim 1, wherein in order to maintain the durability of the polyvinyl chloride resin, 2 to 10 phr of an ester-based liquid ultraviolet absorber and 0.1 to 2 phr of a barium zinc organic complex of a heat stabilizer of an inorganic metal are added. Retro-reflective sheet material, characterized in that. The polyvinyl chloride containing maleic anhydride or polyvinyl chloride containing a hydroxyl group as an additive to the focus resin so as to enable interlayer adhesion between the focus resin layer and the metal deposition layer (metal reflecting layer). A retroreflective sheet material, characterized in that a resin is used.