KR-102964000-B1 - RETRO-REFLECTION SHEET WITH IMPROVED VISIBILITY AND DURABILITY AND AUTO NUMBER PLATE INCLUDING THE SAME SHEET

KR102964000B1KR 102964000 B1KR102964000 B1KR 102964000B1KR-102964000-B1

Abstract

The present invention relates to a retroreflective sheet with improved visibility and durability and a vehicle license plate including the same. Specifically, the invention relates to a retroreflective sheet capable of adjusting whiteness and retroreflective performance, thereby having excellent daytime and nighttime visibility and improved durability, and a vehicle license plate including the same.

Inventors

김진우
김희영
이겨레
조성대
김훈성

Assignees

미래나노텍글로벌(주)

Dates

Publication Date: 20260512
Application Date: 20201231
Priority Date: 20191231

Claims (15)

A base optical layer having a pattern of multiple retroreflective optical elements on its lower surface; A lower layer comprising a low-refractive region formed of a low-refractive material having a lower refractive index than that of the base optical layer and bonded to the lower surface of the base optical layer, and a sealing material that seals the side and lower surface of the low-refractive region; and An upper layer comprising a printed pattern that is coupled to the upper surface of the base optical layer and partially blocks light transmission; wherein The above low-refractive region is in contact with the lower surface of the base optical layer and is partitioned in a predetermined pattern, and the sealing material seals the side and lower surface of the low-refractive region and is attached to the lower surface of the base optical layer from the side of the low-refractive region. At least a portion of the above printing pattern is formed in an area corresponding to at least a portion of the above low-refractive region, and A retroreflective sheet characterized in that the printing pattern of the upper layer and the pattern of the low-refractive region of the lower layer satisfy the following relationship 1: [Relationship 1] In the above relationship 1, ... represents the average repetition period in any one direction of the low-refractive region pattern of the lower layer above, and Is It represents the average repetition cycle of the upper layer printing pattern in the same direction as above.
In paragraph 1, A retroreflective sheet characterized in that the above-mentioned low-refractive index material is air.
In paragraph 1, A retroreflective sheet characterized in that the above-mentioned retroreflective optical element is a corner-cube structure.
In paragraph 1, A retroreflective sheet characterized in that the low-refractive region occupies an area of 5% to 30% of the lower layer.
In paragraph 4, A retroreflective sheet characterized in that the area not blocked by the printing pattern among the areas corresponding to the low-refractive index region is 0.5% to 15% of the total area of the retroreflective sheet.
In paragraph 1, A retroreflective sheet characterized in that the area where the sealing material is attached to the lower surface of the base optical layer is 70% to 95% of the total retroreflective sheet area.
In paragraph 1, The sealing material has a sealing line attached linearly to the lower surface of the base optical layer along the side of the low-refractive region, and A retroreflective sheet characterized in that the sealing line width attached to the lower surface of the base optical layer of the above sealing material has a width of 100 μm to 2000 μm.
In paragraph 1, A retroreflective sheet characterized in that the above-mentioned low-refractive region is divided and sealed into a repeating pattern of triangle, square, or hexagon shape.
In paragraph 1, A retroreflective sheet characterized in that the above-described printing pattern is a linear, regular, or irregular wave-shaped pattern printed in one direction at intervals of 100㎛ to 2,000㎛.
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In Paragraph 9, A retroreflective sheet characterized in that the upper layer comprises two or more printed patterns arranged in different directions.
In paragraph 1, The above-described printing pattern is a retroreflective sheet characterized by being printed using a paint containing one or more additives selected from titanium dioxide ( TiO2 ) and silicon dioxide ( SiO2 ).
In paragraph 1, The upper layer mentioned above is, A protective layer positioned above the above-mentioned printing pattern to protect the above-mentioned printing pattern from the outside; and A retroreflective sheet characterized by comprising: an adhesive layer formed on the lower surface of the protective layer and bonding the upper surface of the protective layer and the base optical layer.
In paragraph 1, A retroreflective sheet characterized in that the area where the sealing material is attached to the lower surface of the base optical layer is formed such that the low-refractive region is larger than the area in contact with the lower surface of the base optical layer.
A vehicle number plate comprising a retroreflective sheet according to any one of paragraphs 1 through 9 and paragraphs 11 through 14.

Description

Retro-reflective sheet with improved visibility and durability and vehicle number plate including the same The present invention relates to a retroreflective sheet with improved visibility and durability and a vehicle license plate including the same. Specifically, the invention relates to a retroreflective sheet capable of adjusting whiteness and retroreflective performance, thereby having excellent daytime and nighttime visibility and improved durability, and a vehicle license plate including the same. The retroreflective function of a retroreflective sheet is characterized by causing light entering from the outside to be reflected back in the direction from which it entered by a structured surface, such as a corner cube. Methods for implementing this retroreflective include a method that utilizes total reflection with an air layer by forming a sealing layer on the structured surface, or a method that utilizes mirror reflection by forming a metal layer on the structured surface. Retroreflective sheets, which are attached to road signs, safety signs, license plates, and letter plates requiring a clear or bright background, are not suitable when a deposited metal layer is formed on a structured surface due to the dark color of the metal layer; however, cases where an air layer and a sealing layer are formed on a structured surface are primarily used because they provide a bright and clear image. However, conventional retroreflective sheets have a problem in that the line width and pitch of the sealing pattern in the sealing layer are large, making the sealing pattern visible to the naked eye when observed from close range, which is aesthetically unpleasing. For this reason, they were not suitable for applications requiring a uniform appearance, such as graphics (advertising boards, etc.) or various vehicle license plates. In addition, in the case of retroreflective sheets attached to various plates such as vehicle license plates, sufficient whiteness of the background color around the characters is required to improve visual visibility of the characters during the day; however, due to insufficient whiteness, there was a problem of low visual visibility of plates containing numbers during the day. In addition, regarding license plate cameras such as parking lot cameras or speed enforcement cameras, when light such as infrared is shone on a vehicle license plate with a retroreflective sheet attached for photography, the light retroreflected from the vehicle license plate is too intense, causing the photograph to be taken too brightly, which makes it difficult to identify the license plate. In such cases, vehicle license plates require technology to achieve appropriate retroreflective performance by effectively controlling the high retroreflective performance realized by the corner cube, air layer, and sealing layer, but there have been significant difficulties. Meanwhile, efforts have been made to improve the visual visibility of the sealing pattern among the aforementioned problems. However, as shown in FIG. 1b, when high temperature and high pressure sealing, problems such as deformation or discoloration of the resin, dye, or pigment forming the barrier layer (22) make it unsuitable for forming the sealing layer (21) at high temperature and high pressure. Furthermore, there was a problem where the corner cube layer (11) and the sealing layer (21) easily separated after the sealing layer was formed. Even if sealing is performed using a pressure-sensitive adhesive instead of high temperature and high pressure sealing, the sheet separates due to the limitations of adhesive strength in the outdoor environment over a long period, resulting in a problem with durability. Therefore, due to the physical limitations of the materials forming the barrier layer (resins, polymer materials, dyes, pigments, etc.) and the insufficient adhesion of the adhesive to the corner cube pattern, there were problems with poor durability, causing the sheet to easily separate or tear. Additionally, the manufacturing process for forming the barrier layer was also complex. Currently, there is a need to develop technologies that can overcome these problems. FIG. 1a is a schematic diagram showing the layered structure of a retroreflective sheet according to a preferred embodiment of the present invention. FIG. 1b is a schematic diagram showing the layered structure of a retroreflective sheet according to the prior art. FIG. 2a is a photograph of a vehicle license plate with a retroreflective sheet applied according to the prior art. FIGS. 2B and FIGS. 2C are photographs of a vehicle license plate with a retroreflective sheet applied according to an embodiment of the present invention. FIGS. 3a and 3b are planar photographs taken by magnifying the lower layer coupled to the base optical layer of a retroreflective sheet according to one embodiment of the present invention. FIGS. 3c to 3e are planar photographs of a retroreflective sheet acco