KR20210086559A - Retro reflective sheet and vehicle license plate using the same - Google Patents

Abstract

The present embodiments disclose a retro reflective sheet and a license plate for a vehicle using the same. A retro reflective sheet according to an embodiment of the present invention may include a reflective layer on which a retro reflective optical element is formed; a light transmission control layer laminated on one surface of the reflective layer and having a light transmission control pattern for controlling light transmitted through the retro reflective optical element; and a reflection suppressing layer laminated on the other surface of the reflective layer and having a reflection control pattern for controlling light reflected by the retro reflective optical element. The main purpose of the present invention is to easily adjust retro reflective performance suitable for an article through a light transmission control layer and a reflection suppression layer, improve whiteness to increase daytime and nighttime visibility, and realize uniform retro reflective performance.

Description

Retroreflective sheet and license plate for vehicle using same

The present invention relates to a retroreflective sheet and a license plate for a vehicle using the retroreflective sheet.

The content described in this section merely provides background information for the present embodiment and does not constitute the prior art.

The retroreflective sheet is a film whose purpose is to make the light coming from the outside return in the direction it came in by using a corner cube pattern. Retroreflective sheets have been developed with the goal of maximally reflecting incident light in various environments.

There are two types of license plates for vehicles: a painted license plate by painting on a metal plate and a film-type license plate in which a retroreflective sheet is attached to the metal plate and painted with numbers, letters, and symbols.

The automatic license plate recognition system for automatically reading and recognizing the characters of the license plate for a vehicle operates a lamp emitting infrared wavelengths, etc. at night for readability of the conventional license plate, and reads it as an image obtained by shooting with a camera. For example, a speeding and signal enforcement camera or an automatic license plate recognition camera in a parking lot uses a lamp that emits infrared wavelengths at night, and the infrared that has been reflected from the license plate after emitting infrared light is captured and recognized by the camera.

However, when light in the infrared region is incident on the retroreflective sheet, a halation phenomenon occurs in the photographed image. The halation phenomenon refers to a phenomenon in which the image is blurred and blurred due to being too bright in the photo by strong light. That is, when a strong light shines on the subject, it glows and sparkles, and a halo appears around it. The conventional retroreflective sheet has a problem in that visibility of a photographed image is not very good.

In order to compensate for this, a material that absorbs light in a specific wavelength region may be included in the retroreflective pattern, and tungsten oxide may be used as an example.

Tungsten oxide has a property of absorbing wavelengths in the infrared region, but sometimes because of the blue color of tungsten oxide, the background color of the license plate appears blue as shown in FIG. 1a, which causes a decrease in contrast with the black number characters of the license plate. There is a problem that reduces the readability of the .

In order to compensate for this problem, conventionally, as shown in FIG. 1B , a technique for improving readability has been developed by partially irradiating a retroreflective sheet with radiation in a specific area to decolorize the blue color in tungsten oxide to whiten it.

However, this requires expensive equipment that emits radiation in a specific area, and there is a problem in that the infrared absorption ability of tungsten oxide is reduced when decolorizing by this radiation. In addition, there is a problem in that the flexibility of the technology is inferior compared to the printing coating method when designing the retroreflective sheet to control the reflection performance.

Korean Patent Publication No. 10-1741863 (2017.05.24.)

The present invention relates to a retroreflective sheet and a license plate for a vehicle using the same, wherein (i) a light transmission control pattern for controlling the transmission amount of light flowing in the direction of the retroreflective optical element and light retroreflected by the retroreflective optical element Through the formed light transmission control layer and (ii) the reflection control pattern formed with the reflection control pattern for controlling the light reflected by the retroreflective optical element, the retroreflective performance suitable for the article can be easily adjusted, and the whiteness is improved, so that the daytime and daytime and The main purpose is to increase visibility at night and to implement uniform retroreflective performance.

Other objects not specified in the present invention may be additionally considered within the scope that can be easily inferred from the following detailed description and effects thereof.

According to one aspect of the present embodiment, in the retroreflective sheet, a reflective layer formed with a retroreflective optical element; a light transmission control layer laminated on one surface of the reflective layer, the light transmission control layer having a light transmission control pattern for controlling a transmission amount with respect to the light flowing in the direction of the retroreflective optical element and the light retroreflected by the retroreflective optical element; and a reflection suppression layer laminated on the other surface of the reflection layer and having a reflection control pattern for controlling light reflected by the retroreflective optical element.

The light transmission control pattern may control the light adjusted through the reflection suppression layer again.

The retroreflective optical element may be formed of a corner cube structure.

An infrared ray absorbing material may be used for the reflective layer, the light transmission control layer, the reflection suppression layer, or a plurality of layers in which they are combined.

The infrared absorbing material may be used in an amount of 0.5% to 20% based on the weight of the total resin.

A pigment, a dye, or a material in which they are combined may be used for the light transmission control layer, the reflection suppression layer, or a plurality of layers in which they are combined to improve whiteness.

The reflection suppression layer may be divided into a retroreflection active region and a retroreflection inactive region based on the reflection control pattern.

The line width of the reflection control pattern may be set in the range of 100 to 2000 micrometers.

The retroreflective active region may occupy an area ratio of 5% to 30% with respect to the total area of the reflective layer.

A region that is not blocked by the light transmission control pattern among the retroreflective active region may occupy an area ratio of 0.5% to 15% with respect to the total area of the reflective layer.

The light transmission control layer may be divided into a transmissive area and a non-transmissive area based on the light transmission control pattern.

When the light transmission control layer is viewed in a vertical direction of the retroreflective sheet, the transmission region may include a sub retroreflective active region and a sub retroreflective inactive region separated by the reflection control pattern.

The reflection control pattern and the light transmission control pattern include (i) a first average repetition period calculated in one direction with respect to a predetermined shape included in the reflection control pattern, and (ii) a predetermined shape included in the light transmission control pattern. With respect to the shape, a relationship defined by using the second average repetition period calculated in the same direction as the one direction may be satisfied.

According to another aspect of this embodiment, in the license plate for a vehicle to which a retroreflective sheet is applied, the retroreflective sheet includes: a reflective layer on which a retroreflective optical element is formed; a light transmission control layer laminated on one surface of the reflective layer and having a light transmission control pattern for controlling light transmitted through the retroreflective optical element; And it is laminated on the other surface of the reflective layer, it provides a vehicle license plate characterized in that it comprises a reflection control pattern for controlling the light reflected by the retroreflective optical element is formed.

As described above, according to the embodiments of the present invention, the retroreflective active region and the retroreflective inactive region are adjusted to an appropriate area by the fine sealing layer (reflection suppressing layer) bonded while sealing the low refractive region to the corner cube pattern layer. By partially transmitting and partially transmitting light retroreflected from the retroreflective active area by the adjustable, finely divided pattern layer (light transmission control pattern), retroreflection performance suitable for the article such as a vehicle license plate or billboard can be easily adjusted. There is an advantage that uniform retroreflection performance can be implemented.

According to the embodiments of the present invention, there is an advantage in that the whiteness is improved and the control is easy due to free pattern formation for the finely divided pattern layer (light transmission control layer) and the ease of material mixing, and when applied to a license plate, readability is increased. .

According to embodiments of the present invention, by disposing the finely divided pattern layer on the upper side of the sheet, there is an advantage in that the background color of the retroreflective sheet is uniform and the overall brightness of the sheet is improved, thereby increasing visibility.

According to the embodiments of the present invention, the design and design can be freely designed according to the purpose and required properties of the product due to the overall structure, so that the flexibility of the product process is good.

According to the embodiments of the present invention, special equipment for emitting radiation used in the process of decolorizing blue and whitening in the prior art is unnecessary, and since the finely divided pattern layer with easy color adjustment is formed by printing coating, white It is easy to make and manufacture the same, and there is an advantage that roll-to-roll mass production is possible.

According to embodiments of the present invention, there is an effect of increasing visibility and readability of a night camera by using a property of absorbing light in an infrared region using a tungsten oxide material.

1A and 1B are views illustrating a conventional license plate for a vehicle.
2A and 2B are views illustrating a cross-section of a retroreflective sheet of a retroreflective sheet according to an embodiment of the present invention, and FIG. 2C is a partially exploded state of the retroreflective sheet according to an embodiment of the present invention It is a drawing.
3 is a view showing a license plate for a vehicle using a retroreflective sheet of a retroreflective sheet according to an embodiment of the present invention.
4 is a view illustrating a fine sealing layer of a retroreflective sheet according to an embodiment of the present invention.
5 is a view for explaining a criterion for indicating an angle in the arrangement direction of a finely divided pattern of a retroreflective sheet according to an embodiment of the present invention.
6A to 6D are views illustrating a retroreflective sheet and a vehicle license plate to which the retroreflective sheet is applied according to an embodiment of the present invention.
7A to 7B are views illustrating a finely divided pattern layer of a retroreflective sheet according to another embodiment of the present invention.
8A to 8D are views illustrating a finely divided pattern layer of a retroreflective sheet according to another embodiment of the present invention.
9 is an exemplary view for explaining the daytime visibility of a vehicle license plate to which a finely divided pattern layer of a retroreflective sheet is applied according to an embodiment of the present invention.
10A and 10B are exemplary views for explaining the night visibility and attachment form of a license plate for a vehicle to which a finely divided pattern layer of a retroreflective sheet is applied according to an embodiment of the present invention.
11 is a diagram illustrating a definition of color coordinates for explaining a change in performance of a retroreflective sheet according to an embodiment of the present invention.
12A and 12B are pictures taken of a retroreflective sheet according to an embodiment of the present invention, and FIG. 12C is a picture taken of the result of performing an immersion test on the retroreflective sheet according to an embodiment of the present invention, FIG. 12d is a photograph of the result of performing an immersion test on the retroreflective sheet according to the prior art.
13 and 14 are diagrams for explaining changes in reflection performance, color coordinates, and infrared absorptivity according to whether the content of the infrared absorbing material is increased and the finely divided pattern layer is applied according to embodiments of the present invention.
15 is a view for explaining the difference in physical properties of a license plate product according to the presence or absence of a finely divided pattern layer and the presence or absence of an infrared absorbing material according to embodiments of the present invention.

Hereinafter, in the description of the present invention, if it is determined that the subject matter of the present invention may be unnecessarily obscured as it is obvious to those skilled in the art with respect to related known functions, the detailed description thereof will be omitted, and some embodiments of the present invention will be described. It will be described in detail with reference to exemplary drawings.

The present invention relates to a retroreflective sheet and a license plate for a vehicle using the same. The present invention is provided with a finely divided pattern layer and a fine sealing layer, so that retroreflection performance suitable for an article can be easily adjusted, whiteness is improved to increase daytime and nighttime visibility, and retroreflection capable of realizing uniform retroreflection performance sheets are provided. Provided is a retroreflective sheet that uses an infrared absorbing material to increase visibility and readability of a night camera. The present invention provides a retroreflective sheet having a uniform appearance and freely designing according to the purpose and required properties of an article.

2A and 2B are views illustrating a cross-section of a retroreflective sheet of a retroreflective sheet according to an embodiment of the present invention, and FIG. 2C is a partially exploded state of the retroreflective sheet according to an embodiment of the present invention It is a drawing.

The retroreflective sheet 10 includes a lower multi-layer portion 100 and an upper multi-layer portion 200 . The retroreflective sheet 10 includes a light transmission control layer, a reflection layer, and a reflection suppression layer. The upper multi-layer part 200 includes a light transmission control layer, and the lower multi-layer part 100 includes a reflective layer and a reflection suppression layer.

The reflective layer is formed with retroreflective optical elements to reflect light. The light transmission control layer is laminated on one surface of the reflective layer, and a light transmission control pattern (fine division pattern) having a predetermined structure for controlling light transmitted through the retroreflective optical element is formed. The light transmission control layer is also referred to as a finely divided pattern layer. The reflection suppression layer is laminated on the other surface of the reflection layer, and a reflection control pattern for controlling the light reflected by the retroreflective optical element is formed. The reflection suppression layer may also be referred to as a fine sealing layer, and the reflection control pattern may also be referred to as a sealing line. The light transmission control pattern may re-adjust the light controlled through the reflection suppression layer. That is, it is easy to control the reflectance through the light control twice by the reflection control pattern and the light transmission control pattern.

The reflective layer includes a base layer 110 and a corner cube pattern layer 120 that is a retroreflective element.

The lower multilayer part 100 includes a base layer 110, a corner cube pattern layer 120, a low refractive index layer 130, a fine sealing layer 140, an external adhesive layer 150, and a release film 160, The upper multi-layer part 200 includes an overlay layer 210 , a finely divided pattern layer 220 , and an inner adhesive layer 230 .

The retroreflective sheet 10 of FIGS. 2A to 2C is according to an embodiment, and not all blocks shown in FIG. 2 are essential components, and in another embodiment, some blocks included in the retroreflective sheet 10 are It may be added, changed or deleted.

The lower multi-layer part 100 and the upper multi-layer part 200 may be adhesively integrated by the inner adhesive layer 230 to be manufactured as the retroreflective sheet 10 .

The lower multi-layer part 100 of the retroreflective sheet 10 will be briefly described.

In the lower multi-layer part 100 , the base layer 110 in the form of a film and the corner cube pattern layer 120 are structured and formed on one surface of the base layer 110 . The corner cube pattern layer 120 may include an infrared absorbing material such as tungsten oxide.

A sealing line 142 of the fine sealing layer 140 is adhered to the corner cube pattern layer 120 to seal the low refractive index layer 130 (air layer) between the corner cube pattern layer 120 and the fine sealing layer 140 . do. And an external adhesive layer 150 is formed on the outer surface of the fine sealing layer. The sealing line 142 forms a reflection control pattern.

The outer adhesive layer 150 is used for adhering the retroreflective sheet 10 to an external adherend and may be formed of a pressure-sensitive adhesive.

The upper multi-layer portion 200 of the retroreflective sheet 10 will be briefly described.

On the upper multi-layer part 200 , an overlay layer 210 in the form of a film having a protection function from an external environment (ultraviolet rays, foreign substances, etc.) and a finely divided pattern layer 220 are formed on the bottom surface of the overlay layer 210 .

The finely divided pattern layer 220 is formed in a light transmission control pattern having a predetermined thickness and a predetermined interval so that a light transmitting region and a non-transmissive region exist. The non-transmissive area by the light transmission control pattern has an opaque characteristic, and it is preferable to include a material such as a white pigment to improve whiteness. The finely divided pattern layer 220 may be formed in various patterns and may be expressed as simple images, symbols, and characters.

Referring to FIG. 2A , an inner adhesive layer 230 may be formed on one surface of the overlay layer 210 and the finely divided pattern layer 220 . The overlay layer 210 and the finely divided pattern layer 220 may be adhered to the base layer 110 by the inner adhesive layer 230 .

Referring to FIG. 2B , the finely divided pattern layer 220 may be formed by printing on the base layer 110 . The overlay layer 210 may be adhered to the finely divided pattern layer 220 and the base layer by the inner adhesive layer 230 .

In FIG. 2C , the overlay 210 and the inner adhesive layer 230 are removed to make it easier to see the structure. In reality, the two are in contact.

Light is incident from the outside of the upper layer, passes through the upper layer and the base layer 110 , causes total reflection in the retroreflective optical element 120 , and is returned, and in the process returns in the 180° direction of the incident light.

The lower surface of the base layer 110 includes a low-refractive region 130 and a fine sealing layer 140 that have a predetermined shape and are partitioned. The fine sealing layer 140 is located on the side and lower surfaces of the low refractive region 130 to seal each section of the low refractive region and divide the low refractive regions so that they are not connected to each other, and the base layer from the side of the low refractive region It is attached to the lower surface of (110). What is attached to the lower surface of the base layer 110 from the side of the low refractive region is referred to as a sealing line or a reflection control pattern. Similarly, the low refractive region 130 is in contact with the lower surface of the base layer 110 .

The low refractive region 130 is made of a material having a lower refractive index than that of the corner cube pattern layer 120 material, so that the incident light incident on the corner cube pattern layer 120 from the base layer 110 is in contact with the low refractive region. It facilitates total reflection at the interface of the pattern layer 120 . On the other hand, the sealing line 142 may have a higher refractive index than that of a low refractive material. Accordingly, in the portion where the sealing line 142 is in contact with the lower surface of the corner cube pattern layer 120 , total reflection hardly occurs compared to the portion where the corner cube pattern layer 120 is in contact with the low refractive index region 130 .

An area in which the low refractive region 130 contacts the lower surface of the corner cube pattern layer 120 may mean an effective retroreflection area.

The upper layer includes a finely divided pattern (transmission control pattern) that blocks the transmission of incident light or reflected light. Therefore, when both incident and reflected light are considered, retroreflection can occur only in an area excluding the area covered by the print pattern.

Referring to FIGS. 2A to 2C , it can be seen that the low refractive region 130 is separated from other low refractive regions 130 in the lower layer by the sealing line 142 and is partitioned in a predetermined repeated pattern. An effective area in contact with the low-refractive region 130 and the corner cube pattern layer is partially covered by the finely divided pattern of the upper layer.

Hereinafter, a detailed structure of the retroreflective sheet 10 will be described.

First, the configuration of the lower multi-layer part 100 of the retroreflective sheet 10 will be described in detail.

First, the optical layer may include a base layer and a retroreflective optical element.

<Base layer 110>

The base layer 110 serves as a base material for the retroreflective sheet 10 and is used in the form of a film, and the material may be various thermosetting and thermoplastic materials. Such materials may include polycarbonate, polyethylene terephthalate, polymethyl methacrylate, polyurethane, polyvinyl chloride, and the like.

The base layer 110 may include a copolymerized resin or a co-extruded film substrate as needed, and may consist of one to two layers. The light transmittance of the film included in the base layer 110 is 85% or more, and it is generally preferable when it is 90% or more, and it is preferable to use polycarbonate, polymethyl methacrylate, or polyvinyl chloride.

The thickness of the base layer 110 may preferably have a thickness of 50 μm to 300 μm. If the thickness of the base layer 110 is less than 50 μm, there is a risk that durability between the respective layers of the retroreflective film may be lowered, and conversely, when the thickness of the base layer 110 exceeds 300 μm, the Since the thickness is too thick, the light transmittance is lowered, and there is a problem in that the appearance such as visibility and aesthetics is lowered.

The base layer 110 has a corner cube pattern formed on the cross-section of the base layer 110 for implementing retroreflective performance, and requires impact resistance, heat resistance, and flexibility to protect it, and uses a film with excellent workability. In addition, a UV blocking agent may be added to prevent discoloration of the film by UV rays, and the content of the UV blocking agent is adjusted according to the corner cube pattern forming method (UV imprinting, hot stamping, etc.). In particular, when forming a corner cube pattern by UV imprinting, it is important to control the UV transmittance so that a sufficient amount of light can be irradiated for UV curing to proceed.

<Corner cube pattern layer 120>

The corner cube pattern layer may be formed of a plurality of corner cube structures on one surface of the base layer.

For the corner cube pattern layer 120 , the selection of a material may vary according to a method of forming the corner cube pattern.

1) When the corner cube pattern layer 120 is formed by UV imprinting, the corner cube pattern layer 120 may be formed of a UV curable resin material.

As constituting the UV curing resin, polyurethane-based, polycarbonate-based, polysilicon-based oligomers, such as polyester-based oligomers, and monofunctional and polyfunctional monomers are included. As the photoinitiator, at least one compound selected from the group consisting of benzophenone-based, acetophenone-based, triazine-based, biimidazole-based compounds, oxime ester-based and thioxanthone-based compounds may be used. In addition, it is preferable to prescribe a UV stabilizer and a blocker as an additive in order to provide stability to product properties.

The present invention aims to improve the visibility of the license plate for a vehicle using the retroreflective sheet 10 (resolving the problem in which camera visibility for license plate characters, etc. is reduced due to strong retroreflectivity when operating a camera lamp that emits infrared rays) with the goal of wavelength in a specific region Absorbent materials may be used. For example, a region of a specific wavelength may refer to an infrared region, and materials exhibiting absorption properties in this region may include cesium tungsten oxide, tungsten carbide oxide, sodium tungsten oxide, and potassium tungsten oxide. It may also include antimony tin oxide, indium tin oxide, mixed valence tungsten oxide, and infrared absorbing dyes, infrared absorbing pigments, and the like.

The infrared absorbing material is preferably mixed with the material forming the corner cube pattern layer 120 . However, the present invention is not limited thereto, and the infrared absorbing material may be used as a material for other layers such as the base layer 110 , the overlay layer 210 , and the inner adhesive layer 230 .

2) When the corner cube pattern layer 120 is formed by hot stamping, the corner cube pattern layer 120 has good flowability (MI 5g/10min~30g/10min) and a pattern using polycarbonate resin with excellent refractive index. to form In this case, the polycarbonate film used can improve weather resistance by adding a UV stabilizer or absorber to block the UV region as much as possible.

In addition, it is recommended to mix the aforementioned infrared absorbing material with the polycarbonate resin material. However, it is not limited to this position and may be mixed and used for various other layers of materials.

The thickness of the corner cube pattern layer 120 is preferably 30 ~ 120 ㎛.

The retroreflective optical element 120 may be a microsphere or a corner cube structure, preferably a corner cube structure. The retroreflective optical element 120 totally reflects the incident light so that the direction of the reflected light can be returned to 180 degrees of the direction of the incident light.

The retroreflective optical element 120 is formed on the lower surface of the base layer 110 , and excellent retroreflective efficiency can be achieved by causing total reflection at the interface with the low refractive region 130 adjacent to the retroreflective optical element.

The corner cube pattern layer 120 is a layer in which a plurality of corner cube patterns are formed in order to implement retroreflective performance, and has a triangular pyramid shape having three inclined surfaces based on one vertex. The corner cube structure may be a triangular pyramid-shaped pattern in which three surfaces are at right angles to each other. In this case, as the difference in refractive index between the corner cube forming the triangular pyramid and the low refractive region 130 adjacent thereto increases, total reflection may occur more easily.

In this corner cube pattern, the incident light irradiated from the light source is totally reflected on each surface within the triangular pyramid, and serves to be retroreflected in the direction in which the light source is irradiated. In this case, as the refractive index difference between the corner cube forming the triangular pyramid and the low refractive index layer 130 (eg, air, etc.) adjacent thereto increases, the intensity of reflected light may increase.

In addition, if there is a material that acts as an impurity among the materials constituting the corner cube, the reflection performance is affected. For example, when a corner cube pattern is formed using a UV curing resin, the UV resin having an acrylate reactive group participates in the crosslinking reaction and does not affect the light path, but the material that does not participate in the crosslinking reaction (for example, Since tungsten oxide does not have an acrylate reactive group, it does not cause a crosslinking reaction in the UV curing system), which may affect the path of light.

Since the infrared absorbing material does not have an acrylate reactive group and does not participate in the UV crosslinking reaction, selection of the amount of use is important.

The content of the infrared absorbing material is preferably 0.5% to 20% based on the weight of the total resin based on 23% of the non-volatile matter, and the optimal content is 2% to 10%. If the amount of infrared absorbing material is 0.5% or less by weight, the infrared absorption power does not reach the goal of improvement of the invention, and if it is more than 20%, the proportion of nonvolatile matter (not participating in the crosslinking reaction) in the total resin increases and becomes a product There is a difficulty in expressing the required reflective performance.

<Low refractive layer 130>

The low refractive index layer 130 is in contact with the corner cube pattern layer 120 in order to induce retroreflected light to the corner cube pattern layer 120 and has a low refractive index. As an example, air may be mainly used for the low refractive property, but the present invention is not limited thereto, and other gases or materials having low refractive index, vacuum, etc. may be used so that a large difference in refractive index appears at the contacting interface. In order to adjust the intensity of the retroreflected light, the material of the low refractive index layer 130 may be selected.

The low refractive index layer 130 is disposed between the corner cube pattern layer 120 and the fine sealing layer 140 , is sealed and maintained by the fine sealing layer 140 , and a plurality of units of the low refractive index layer 130 are formed by the fine sealing layer 140 . It is divided into refractive regions.

When external light is introduced into the retroreflective sheet 10 , retroreflected light is generated from the corner cube in contact with the low refractive index layer 130 , so this low refractive index region operates as a retroreflective active region.

<Fine sealing layer 140>

The fine sealing layer 140 of the present invention is formed by a hot melt adhesive method, and the material may include ethylene vinyl acetate, polyamide, polyurethane, polyester resin, and the like. The fine sealing layer 140 may be formed by using the resin material alone or by coating the material on a substrate such as PET.

The fine sealing layer 140 requires heat resistance suitable for a high-temperature hot-melt process, and it is preferable to use a polyester-based material because it requires a property to be bonded to a corner cube formed by UV-curable imprinting.

_{In addition, the fine sealing layer 140 may use additives such as titanium oxide (TiO2) and silicon oxide (SiO 2} ) to improve whiteness due to the characteristics of the product, and pigments and dyes may be used to add color. have. The additive used at this time may be added to the milling process for smooth dispersion into nano-sized particles.

The fine sealing layer 140 is formed of a sealing line 142 bonded to the corner cube at the side of the unit low refractive area and a sealing cover 144 that covers the lower surface of the unit low refractive area. Through this, in a state in which the unit low refractive regions of the low refractive index layer 130 are in contact with the corner cube, the side and the lower surface thereof are sealed and maintained by the fine sealing layer 140 .

The type of the pattern of the fine sealing layer 140 formed by the sealing line 142 of the fine sealing layer 140 and the sealing cover 144 may include various polygons such as a square and a rhombus, and these sealing layer patterns are close to each other. It is so small that it cannot be recognized even from a distance.

The sealing lines 142 of the fine sealing layer 140 are bonded to the corner cube pattern layer 120, and the difference in refractive index is set so that the difference in refractive index is not large at the interface of this bonding surface, so that the sealing lines 142 are attached to the corner cube pattern layer 120. A retroreflective inactive region in which the retroreflective function is greatly weakened or lost is induced in the portion in contact with the , and the retroreflective function is reduced in the portion where the corner cube pattern layer 120 is in contact with the low refractive regions of the low refractive index layer 130 . An actuated retroreflective active region is induced. That is, the sealing line functions as a reflection control pattern, and the sealing layer functions as a reflection suppression layer.

As shown in FIG. 4 , the planar area of the sealing lines 142 in the fine sealing layer 140 becomes the retroreflective inactive region area 420 , and the planar area of the low refractive regions in the low refractive index layer 130 is retroreflective. reflective active area area 410 .

In the present invention, retroreflection performance can be adjusted by adjusting the area of the retroreflective inactive region by the sealing line 142 region and the retroreflective active region by the low refractive region.

In order to suppress the strong reflection performance of the retroreflective sheet 10, the retroreflective inactive area area by the sealing line 142 area of the fine sealing layer 140 is 70 to 95% of the total area of the retroreflective sheet 10. desirable.

Conversely, the retroreflective active region area by the low refractive index region of the low refractive layer 130 is preferably 5 to 30% of the total area of the retroreflective sheet 10 .

To prevent halation, widening the sealing line (reflection control pattern) adhesion area of the fine sealing layer (reflection suppressing layer) to the above 70 to 95% range so that a substantial portion of the total area of the retroreflective sheet 10 becomes a retroreflection inactive region. effective in

The thickness of the fine sealing layer 140 is preferably 30 ~ 35 ㎛. When the thickness of the lower layer is less than 30 μm, the durability of the sealing layer 140 is weak, so that the retroreflective film is easily damaged, and there is a risk that moisture or the like may penetrate. In addition, when the thickness of the sealing layer 140 exceeds 35 μm, the thickness of the retroreflective film may be excessively thick. When the thickness of the retroreflective film is excessively thick, the difference between the inner radius of curvature and the outer radius of curvature increases when bent, so that there is a problem in that durability is weakened such as delamination between layers.

The fine sealing layer 140 is generally formed to have a finer pattern size than the size of the sealing pattern for the low refractive index region used for road signs. In particular, the area of the unit low refractive index region is very small, so that it is finely sealed.

The line width of the sealing line 142, which is the retroreflective inactive region in the fine sealing layer 140, is preferably in the range of 100 to 2000 micrometers, and more preferably 200 to 1000 μm.

If the line width of the sealing line 142 is less than 100 μm, sealing of the low refractive region is not properly performed, and there is a problem in that durability may be weakened due to weakening of adhesive force. On the other hand, when the line width of the sealing line 142 exceeds 2000 μm, there is a problem in that the retroreflective performance is too deteriorated.

The sealing cover 144 that covers the low refractive area, which is the retroreflective active area, has the same or similar planar shape and planar size to the planar shape and planar size of the low refractive area, and the sealing cover 144 (or unit low refractive index). The unit width of the region) is preferably in the range of 100 μm to 1,500 μm.

For example, when the sealing cover 144 (or the unit low refractive area) has a square or triangular shape in a plane, the length of one side may be 100 μm to 1,500 μm, and in the case of a rhombic, hexagonal or octagonal shape The inner maximum diagonal length may be between 100 μm and 1,500 μm. It is more preferable that the sealing cover 144 (or the unit low refractive region) has a more preferable width of 200 μm to 1,000 μm.

The fine sealing layer 140 is a component for sealingly forming the low refractive index layer 130 such as air on the surface of the corner cube pattern layer 120 , and is patterned to be partially adhered to the corner cube pattern layer 120 . is formed to adjust the retroreflection performance through.

The fine sealing layer 140 is adhered to the corner cube pattern layer 120 at high temperature and high pressure to block foreign substances (water, adhesive, etc.) from entering the corner cube pattern layer 120 to maintain retroreflective performance and durability. can improve In particular, the retroreflective sheet 10 used outdoors must be able to prevent snow or rainwater from flowing between the corner cube pattern layer 120 and the sealing layer, and for this purpose, a water immersion test and strength against adhesion High standards are required.

In the case of a conventional license plate specific product as shown in Fig. 3 (a), there is a disadvantage that the sealing pattern is visually recognized, but in the present invention, this problem is solved through fine sealing as in the license plate of Fig. 3 (b). The sealing pattern is further finely divided by the fine sealing layer 140 and the fine division pattern layer 220 that is additionally laminated like the license plate of FIGS. 3 (c) and 3 (d), so that the apparent pattern is not visually recognized by the naked eye. Beautiful appearance is improved. Here, the license plate of Fig. 3 (c) is a vehicle license plate to which the fine sealing layer 140 and the fine division pattern layer 220 are applied, and the license plate of Fig. 3 (d) is the fine sealing layer 140 and the fine division pattern. It shows the license plate for the vehicle to which the layer 220 and the infrared absorbing material are applied.

The fine sealing layer 140 is formed by pressing a pressing roller having an uneven surface of a fine sealing pattern on the sealing film. At this time, the temperature is compressed at a high temperature of 170 to 195 degrees, preferably 180 to 185 degrees and high pressure and pressure, in order to prevent problems such as immersion and inflow of foreign substances and to improve durability, and is manufactured in a roll-to-roll method.

<External adhesive layer 150>

The outer adhesive layer 150 may be formed of an adhesive material, and a thermosetting resin may be selected as the adhesive material. Thermosetting resins include acrylic, urethane, silicone, and the like, and isocyanate, epoxy, and urea-based curing agents can be selected and used according to the resin. Preferably, 2-ethylhexyl acrylate is used as the main raw material to control the molecular weight of the main material, and the glass transition temperature is lowered to give strong adhesive properties. In addition, it is preferable to use acrylic acid as the reactor, and to use 10 to 30% of a rosin ester-based adhesion enhancer to realize strong adhesion.

The external adhesive layer 150 may include pigments, dyes, titanium oxide (TiO ₂ ), silicon oxide (SiO ₂ ), etc. to suit the performance required of the product, and the color, brightness, etc. through the material. can be regulated.

The above materials are selected and used according to the type of the adherend to which the external adhesive layer 150 is to be attached or the required level of physical properties.

The thickness of the outer adhesive layer 150 is preferably 40 ~ 80 ㎛.

The external adhesive layer 150 is an adhesive layer formed on the rear surface of the micro-sealing layer 140 and is a layer that adheres to an adherend (object to which the retroreflective sheet 10 is to be attached). In particular, when the external adhesive layer 150 is used in an outdoor structure such as the retroreflective sheet 10 for a road, it requires a holding force of at least a certain level to prevent the product from falling off and detaching.

The outer adhesive layer 150 may be used by adding 5% to 15% of _{toner (TiO 2} dispersed ink) as needed to improve whiteness of a specific product such as a license plate.

<Release film 160>

The release film 160 serves to protect the outermost adhesive layer of the product, and is releasably attached to the external adhesive layer. As the release film 160, silicone release-treated PET, paper release paper, OPP film, CPP film, etc. are used depending on the type of product. The release film 160 has excellent workability because it protects the product and at the same time, there is no release unnecessary for the operator to use (movement, cutting, etc.), and there is no tearing during release over a large area.

Hereinafter, the configuration of the upper multi-layered portion 200 of the retroreflective sheet 10 will be described in detail.

<Overlay layer 210>

The overlay layer 210 may be used in the form of a film, and various thermosetting and thermoplastic materials are suitable for this material. These materials include polycarbonate, polyethylene naphthalate, polyethylene terephthalate, polyester, polyamide, polystyrene, polymethyl methacrylate, polyurethane, polyvinyl chloride, polyethylene, polypropylene, polyvinylidene fluoride, polyvinyl fluoride. , etc., and the most suitable fabric may be selected from polyethylene terephthalate, polyvinyl chloride, and the like.

The overlay layer 210 may use a copolymerized resin if necessary, and may include a co-extruded film substrate manufactured by laminating two or more films during an extrusion process for manufacturing a film.

The thickness of the overlay layer 210 is preferably 50 to 100 μm.

The overlay layer 210 has a surface protection and UV blocking function. There should be no discoloration of the film itself due to sunlight or heat. Depending on the use of the product, a flexible or rigid film may be selectively used. A flexible film is desirable for applications that are attached to curved surfaces or are curved, such as license plates.

As an additive for improving the weather resistance of the overlay layer 210, one or a mixture of benzotriazole-based, hindered amine-based, benzophenone-based, and salicylate-based compounds is used. As it is added and extruded, it is included in the film and manufactured.

<Finely divided pattern layer 220>

A paint may be used to form the finely divided pattern layer 220 , and the paint includes a thermosetting paint or a UV curable paint.

The finely divided pattern layer 220 may be formed on the bottom surface of the overlay layer 210 . It is not limited to this position, and the finely divided pattern layer 220 may be formed on the upper surface of the base layer 110 to which light is incident.

In the finely divided pattern layer 220 , a non-transmissive region through which retroreflected light cannot pass (pattern line itself) and a transparent region through which retroreflected light can be optically transmitted (a region between pattern lines) are formed in order to adjust retroreflection performance.

Through this, it is formed in a pattern that controls light transmission, so that the finely divided pattern layer is also referred to as a light transmission control layer.

The finely divided pattern layer 220 is formed in a structured pattern having a predetermined interval and thickness to form a non-transmissive region and a non-transmissive region, and is formed in a pattern to control light transmission, and a pigment that implements white or color according to the purpose of the product. , dye, titanium oxide (TiO ₂ ), silicon oxide (SiO ₂ ), and the like are used to control the color and brightness of the paint.

In order to prevent discoloration of the finely divided pattern layer 220 due to ultraviolet rays, a paint having light resistance is used.

In order to adjust the height of the light transmission control pattern in the finely divided pattern layer 220, a solvent such as IPA, MEK, or toluene is used to adjust the viscosity of the solid content.

The finely divided pattern layer 220 may be formed of various types of finely divided light transmission control patterns such as a plurality of straight lines, curves, a lattice structure, a wave design, and a random design. When the light transmission control pattern is a straight line pattern, in order to solve a defect in appearance quality such as a moiré phenomenon that may be caused by overlapping the sealing pattern of the fine sealing layer 140 with the finely divided light transmission control pattern, when the light transmission control pattern is a straight line pattern, The width is 0.1-2.0 mm (preferably 0.1-1.0 mm, optimally 0.2-0.4 mm), and the spacing between pattern lines is 0.1-2.0 mm (preferably 0.1-1.0 mm, optimally 0.1-0.4 mm). ) is good, and the angle of the pattern arrangement direction can be used in a variety of 0 degrees to 360 degrees, but the direction that does not coincide with the possible sealing pattern direction is better. An arbitrary direction is set when calculating the average repetition period.

The thickness of the pattern line is preferably 1 to 25 μm, preferably 3 to 20 μm, and optimally 5 to 15 μm.

When the width of the pattern line is 0.1 mm or less, the pattern height is collapsed and the pattern uniformity is lowered. On the contrary, when the width of the pattern line is 2.0 mm or more, the optically active area is too narrow, so it is difficult to realize the desired retroreflective performance. .

When the distance between pattern lines is 0.1 mm or less, the pattern uniformity decreases and the optically active area is covered by the collapsed pattern line, so retroreflection performance cannot be properly implemented. When the distance between the pattern lines is 2.0 mm or more, the optically active area becomes weak. It exposes too much to the front, making it difficult to achieve low retroreflective performance.

In the retroreflective sheet according to the present embodiment, the retroreflective performance may be adjusted by adjusting the area of the retroreflective inactive region of the fine sealing layer 140 and the area of the non-transmissive region of the finely divided pattern layer 220 .

In order to suppress the strong reflection performance of the retroreflective sheet 10, the retroreflective non-transmissive area by the pattern line area of the finely divided pattern layer (light transmission control layer) is 50 to 90% of the total area of the retroreflective sheet 10 desirable.

Conversely, the retroreflective transmission area by the area between the pattern lines of the finely divided pattern layer (light transmission control layer) is preferably 10 to 50% of the total area of the retroreflective sheet 10 .

<Inner adhesive layer 230>

The inner adhesive layer 230 includes a urethane or urethane acrylic-based functional group (monofunctional, polyfunctional), and may be formed of a transparent adhesive material including an isocyanate curing agent. More preferably, a pressure-sensitive adhesive is good.

The thickness of the inner adhesive layer 230 is preferably 10 to 30 μm.

The inner adhesive layer 230 has a function of bonding the overlay layer 210 and the finely divided pattern layer 220 to the base layer 110 . Through this, the upper multi-layer part 200 and the lower multi-layer part 100 are integrated to form the retroreflective sheet 10 .

The inner adhesive layer 230 may be used as a pressure-sensitive adhesive, and is optically transparent, so that retroreflective performance is not affected. The inner adhesive layer 230 has good physical properties so that pores are not formed by the thickness of the finely divided pattern layer 220 during adhesion.

5 is a view for explaining a criterion for indicating an angle in the arrangement direction of a finely divided pattern of a retroreflective sheet according to an embodiment of the present invention. Referring to FIG. 5 , the angle of the arrangement direction of the finely divided pattern can be confirmed.

6A to 6D are views illustrating a finely divided pattern layer of a retroreflective sheet and a license plate for a vehicle to which the same is applied according to an embodiment of the present invention.

The finely divided pattern layer 220 having a linear structure will be exemplified and described. This is only an example for description, and the light transmission control pattern and the reflection control pattern are not limited to the shapes illustrated in the drawings, and various patterns including straight lines, curves, and combinations thereof may be applied.

The finely divided pattern layer 220 may form a pattern in a form in which pattern lines having a linear structure are distributed. The finely divided pattern layer 220 may be formed to have a width of 0.35 mm of pattern lines, a spacing of 0.2 mm between pattern lines, and a pattern arrangement angle of 90 degrees.

6A shows a plan photograph of the finely divided pattern layer 220 formed in a straight pattern, the width of the pattern line as the optically non-transmissive region 610 may be 0.35 mm, and the distance between the pattern lines as the optically non-transmissive region 620 is the distance between the pattern lines. 0.2 mm.

6B shows a laminated plan photograph when the fine sealing layer 140 is adhered to the corner cube pattern layer 120, and the retroreflective active region 630 and the sealing line 142 corresponding to the low refractive index region are retrospectively used. and a reflective inactive region 640 .

FIG. 6c shows an enlarged plan photograph when the structure of FIG. 6b is overlapped below the structure of FIG. 6a.

Referring to FIG. 6C , an optically non-transmissive region 610 and an optically non-transmissive region 620 exist, and a retroreflective active region 630 and a retroreflective inactive region 640 exist in the optically non-transmissive region 620 .

When the light transmission control layer is viewed in the vertical direction of the retroreflective sheet, the reflection control pattern and the light transmission control pattern overlap, and the transmission region 620 is a sub retroreflective active region 630 and a sub region separated by the reflection control pattern. It may include a retroreflective inactive region 640 .

The sub retroreflective active region is a region between pattern lines of the light transmission control pattern in the retroreflective active region, and the sub retroreflective inactive region can be viewed as a region between pattern lines of the light transmission control pattern in the retroreflective inactive region .

The light transmission control pattern and the reflection control pattern are not limited to the shapes illustrated in FIGS. 6 to 8 , and various patterns including straight lines, curves, and combinations thereof may be applied.

Referring to FIG. 6C , it can be confirmed that the retroreflective active region and the inactive region shown in FIG. 6B are alternately and repeatedly displayed between the finely divided pattern lines (the optically non-transmissive region). A portion of retroreflected light emitted from the retroreflective active region is blocked by the optically non-transmissive region of the finely divided pattern layer 220 , and the remaining light is transmitted through the optically transmissive region and retroreflected to the outside.

The shape in which the retroreflective active region and the inactive region are alternately expressed may be variously expressed according to the pattern shape of the finely divided pattern layer 220 , the pattern shape of the sealing layer, and the arrangement angle thereof. Through this, the retroreflective active region can be controlled to be limitedly expressed, and also according to the pattern shape and size of the finely divided pattern layer 220 and the pattern shape and size of the fine sealing layer 140 and the arrangement angle between these patterns. Accordingly, it is possible to control the amount of retroreflective transmission for the retroreflective active area, so that it is possible to implement retroreflective performance suitable for license plates (or billboards).

By adjusting the area of the retroreflective active region of the fine sealing layer 140 and the area of the non-transmissive region of the finely divided pattern layer 220 , the retroreflective performance may be further maximized.

Among the regions corresponding to the low refractive regions, the region not blocked by the finely divided pattern layer 220 (that is, the area in which the retroreflected light can be emitted to the outside) is 0.5% to 0.5% to the total area of the retroreflective sheet 10 preferably 15%

Conversely, it is effective to prevent halation by setting the preferred area for blocking and disappearing retroreflected light by lamination and synthesis of the fine sealing layer 140 and the finely divided pattern layer 220 to be in the range of 85 to 99.5%.

Figure 6d shows a vehicle license plate to which the finely divided pattern layer 220 and the fine sealing layer 140 of the present invention are laminated.

6d is a photograph of a license plate for a vehicle in which the finely divided pattern layer 220 and the fine sealing layer 140 are laminated to implement retroreflective performance suitable for the license plate. Such a license plate for a vehicle has a bright white background color, and a high contrast contrast so that numbers and letters are clear, so that visibility can be improved.

7A to 7B are views illustrating a finely divided pattern layer of a retroreflective sheet according to another embodiment of the present invention.

The finely divided pattern layer 220 having a wavy structure will be described. The finely divided pattern layer 220 may include a finely divided pattern layer 220 in which pattern lines having a random structure are distributed. The finely divided pattern layer 220 may be configured to randomly adjust the pattern line width of the finely divided pattern based on the pattern line thickness of 0.35 mm and the spacing between the pattern lines 0.2 mm, the arrangement angle of 115 degrees, and the like.

7A shows a plan photograph of the finely divided pattern layer 220 formed in an inclined random pattern, the width of the pattern line as the optically non-transmissive region 710 may be 0.35 mm or less, and the optically non-transmissive region 720 between the pattern lines The distance may be 0.2 mm or less.

7B shows a plan photograph when the structure of FIG. 6B is superimposed on the lower side of the structure of FIG. 7A.

Referring to FIG. 7B , an optically non-transmissive region 710 and an optically non-transmissive region 720 are present, and a retroreflective active region 730 and a retroreflective inactive region 740 are present in the optically non-transmissive region 720 .

8A to 8D are views illustrating a finely divided pattern layer of a retroreflective sheet according to another embodiment of the present invention.

8A to 8D , the finely divided pattern layer 220 may be formed in various patterns.

8A shows a finely divided pattern layer 220 having a lattice structure pattern. In FIG. 8A , a white region 810 denotes an optically transmissive region, and a black region 820 denotes an optically non-transmissive region.

8B shows the finely divided pattern layer 220 having a wavy structure pattern. In FIG. 8B , a white region 810 denotes an optically transmissive region, and a black region 820 denotes an optically non-transmissive region.

8C and 8D show the finely divided pattern layer 220 having a random structure pattern. In FIGS. 8C and 8D , a white region 810 denotes an optically transmissive region, and a black region 820 denotes an optically non-transmissive region.

The thickness of the finely divided pattern layer is preferably 5 to 100 μm, and the optimized thickness may be 5 to 20 μm.

In the finely divided pattern layer, an optically non-transmissive region is formed using a finely divided pattern to control retroreflection performance, and an optically non-transmissive region is formed between these non-transmissive regions, through which retroreflected light can be transmitted and the color of the sealing layer can be transmitted. do.

Through this, retroreflection performance can be easily controlled according to the design of the finely divided pattern and the width of the pattern line. Uniformity of retroreflective performance can be improved by uniform pattern arrangement.

The finely divided pattern layer solves the previous problem that the sealing pattern or the low-refractive region was visually recognized at a short distance, which is superimposed when superimposed with the above finely divided pattern layer after performing fine sealing to refine the pattern of the sealing layer more than before. The fine sealing layer pattern and the low-refractive region are divided and further refined by the patterned pattern, so that it is not visually recognized by the naked eye, thereby having a beautiful surface appearance.

The reflection control pattern of the reflection suppression layer and the light transmission control pattern of the light transmission control layer include (i) a first average repetition period calculated in one direction for a predetermined shape included in the reflection control pattern and (ii) the light transmission control pattern A relationship defined by using a second average repetition period calculated in the same direction as one direction for a predetermined shape included in . That is, the finely divided pattern 220 may satisfy Equation 1 in relation to the pattern of the low refractive region 130 of the lower layer.

In Equation 1, L ₁ represents the average repetition period in any one direction of the low refractive index region pattern of the lower layer, and L ₂ represents the average repetition period of the finely divided upper layer pattern 220 in the same direction as L _{1 .}

The average repetition period is the length of a repeating unit that is averaged by measuring the length when the shape is repeated N times (eg, 10 times) in an arbitrary direction when a predetermined shape is formed in a repeated pattern. indicates the length.

In other words, when a straight line is drawn in any one direction on the retroreflective film, the average of the repetition period of the pattern of the low refractive index region 130 of the lower layer in the same direction as the average of the period in which the printed pattern 210 is repeated 10 times is obtained by the equation 1 can be satisfied.

When the difference in the period of the two patterns is within the range of these conditions, the wavelength of the moire pattern caused by the mismatch of the period of the two patterns is generated as a wavelength that is difficult to recognize with the naked eye, so that the appearance of the retroreflective film is not impaired. It is not easy to have a difference smaller than the degree of these conditions due to the occurrence of technical errors.

For example, referring to the straight line illustrated in FIGS. 6A to 6C , the fine division pattern has a preset width and is spaced apart from each other with a preset interval therebetween. The fine segmentation pattern repeats with a period of summing the width and spacing.

(i) The first average repetition period calculated in one direction with respect to the predetermined shape included in the reflection control pattern is calculated in the same direction as L ₁ and (ii) the predetermined shape included in the light transmission control pattern is calculated in the same direction as L 1 Assuming that one second average repetition period is L ₂ , _{the relationship between L 1} and L ₂ may be expressed as Equation (1). Since L2 is not necessarily perpendicular or parallel to the shape, but is for an arbitrary direction, it may be a period for a tilted line such as a diagonal direction.

9 is an exemplary view for explaining the daytime visibility of a license plate for a vehicle to which a finely divided pattern layer of a retroreflective sheet is applied according to an embodiment of the present invention.

The finely divided pattern layer applied to the vehicle license plate serves to increase whiteness when white pigment is mixed with the material, and a blind effect can be expected by the pattern height and directionality. This blind effect serves to improve the license plate visibility 900 by being brightly recognized from the front during the day when manufacturing a film-type license plate for automobiles. That is, by reducing the light introduced or reflected in the lateral direction of the license plate, it is possible to increase the visibility of the characters of the license plate by blocking the spread of the license plate characters.

10A and 10B are exemplary views for explaining the night visibility and attachment form of a license plate for a vehicle to which a finely divided pattern layer of a retroreflective sheet is applied according to an embodiment of the present invention.

As shown in FIG. 10A, the finely divided pattern layer applied to the license plate for the vehicle blocks some of the bright light of the flash 1020 of the camera 1010, which is illuminated from a higher position than the car at night, from flowing into the license plate. It prevents the retroreflective sheet from developing too brightly and improves the camera recognition rate. That is, the vehicle license plate can increase the photographing properties of the license plate characters at night.

As shown in Figure 10b, a vehicle license plate to which the finely divided pattern layer 220 is applied may be attached to the vehicle. Here, the vehicle license plate may include a retroreflective film attached to the aluminum plate 1030, and the retroreflective film may include a corner cube pattern layer 120, an overlay layer 210, a finely divided pattern layer 220, and the like. have. In addition, the retroreflective film may include a micro-sealing layer.

11 is a diagram illustrating a definition of color coordinates for explaining a change in performance of a retroreflective sheet according to an embodiment of the present invention.

If the retroreflective film is applied to a vehicle license plate, for example, it can satisfy the following license plate background color conditions by adjusting the amount of light transmission or active area based on the KS A 0067 L*a*b* color system.

L*: 85 or more

ΔE: 3 or less (Meaning: ΔE is the distance from the point where a* and b* are each reference 0 to the measured point)

By satisfying the above conditions, daytime and nighttime visibility may be improved with high brightness and high whiteness. When L* is 85 or more, it has bright brightness, and when ΔE of a* and b* is 3 or less, it has a white color that is close to an achromatic color, thereby realizing bright whiteness as a whole.

L*, a*, b*, and ΔE will be described with reference to FIG. 11. L* values indicate brightness (brightness), a* and b* values indicate chromaticity, and ΔE values indicate chromaticity. L* = 0 indicates black, and L* = 100 indicates white. a* indicates which side is biased toward red or green. If a* is negative, it is a color biased toward green, and if a* is positive, it is a color biased toward red/violet. b* stands for yellow and blue. If b* is negative, it is blue; if b* is positive, it is yellow.

In addition, ΔE refers to the color difference, and a* and b* are the distance values from the coordinate point to the keymark point measured based on a certain standard. That is, an error is expressed as a three-dimensional distance between positions of two colors in a spherical color space. Three-dimensionally, if the coordinate distance of two colors is far from each other, there is a large color difference, and if there is little difference in the coordinate distance, the same color is recognized.

The retroreflective film according to the present invention may have a reflective performance of 3 cd/lx·m 2 to 12 cd/lx·m 2 , measured by a PR-3000 instrument at an incident angle of 5° and an observation angle of 0.2°. If the reflective performance is less than 3 cd/lx m2, the retroreflection ability is weak and it may not function as a retroreflective film, and if it exceeds 12 cd/lx ㎡, the retroreflection is too strong due to retroreflection. Distinguishing power of characters, such as printed on film, is weakened by light bleed, and there is a possibility that visibility of the night camera may deteriorate. That is, in Korea, there is a problem in that it is difficult to identify the license plate taken through the night camera due to the nature of the camera.

12A and 12B are pictures taken of a retroreflective sheet according to an embodiment of the present invention, and FIG. 12C is a picture taken of the result of performing an immersion test on the retroreflective sheet according to an embodiment of the present invention, FIG. 12d is a photograph of the result of performing an immersion test on the retroreflective sheet according to the prior art.

In Example 1, a corner cube structure pattern was formed with a retroreflective optical element on the lower surface through a UV imprinting process on a polyvinyl chloride base substrate having a thickness of 100 μm. The lower layer was formed by pressing a sealing film made of a polyester material in a hot melt method at a temperature of 185° C. to form a low-refractive region pattern in the shape of a rhombus lattice so that the low-refractive material could be in contact with the corner cube structure pattern.

In the low-refractive region, the long diagonal line connecting the opposite vertices in the rhombus shape has an average length of 445 μm, the short diagonal has an average length of 443 μm, the line width of the sealing material is 450 μm on average, and the thickness of the sealing material is average. It was formed to be 30 μm.

On the lower surface of the sealing layer, an external adhesive layer was formed using a pressure-sensitive adhesive composition containing 15% by weight of white toner.

An upper layer was formed on the upper surface of the base substrate by the following method.

On the lower surface of the 50 µm-thick and polyvinyl chloride overlay layer, a printed pattern in the form of parallel lines having a pattern width of 0.35 mm and a distance between the patterns of 0.2 mm was formed. At this time, the print pattern was printed using a paint containing _{titanium dioxide (TiO 2 ).}

Thereafter, a pressure-sensitive adhesive was coated on the lower surface of the overlay layer on which the print pattern was printed, and an adhesive layer was formed.

The upper layer and the lower layer bonded to the base substrate were bonded by a laminating process. It was laminated so that the adhesive layer of the upper layer and the upper surface of the base substrate were combined. A retroreflective film was obtained by bonding.

Example 2 was performed in the same manner as in Example 1, except that the pattern width was adjusted to 0.3 mm and the distance between the patterns was adjusted to 0.1 mm in the print pattern to prepare a retroreflective film.

In Example 3, a retroreflective film was prepared in the same manner as in Example 1, but the lower layer was sealed at a temperature of 185° C. at a line speed of 6.0 m/min to prepare a retroreflective film.

In Comparative Example 1, a corner cube structure pattern was formed with a retroreflective optical element on the lower surface through a UV imprinting process on a polycarbonate base material having a thickness of 125 μm. The lower layer was formed by pressing a sealing film made of a polyester material in a hot melt method at a temperature of 185° C. to form a low-refractive region pattern in a rhombus lattice shape so that the low-refractive material could contact the corner cube structure pattern.

The low-refractive region is a size visually recognized in the prior art, and the long diagonal line connecting the opposite vertices in the rhombus has an average length of 5200 μm, and the short diagonal has an average length of 4220 μm, and the line width of the sealing material is 450 on average. ㎛ and the thickness of the sealing material was formed to an average of 30㎛.

On the lower surface of the sealing material, an external adhesive layer was formed using a transparent pressure-sensitive adhesive composition.

Comparative Example 2 was manufactured in the same manner as in Comparative Example 1.

Experimental Example 1: Evaluation of whiteness and retroreflectance

The whiteness and retroreflectance of the retroreflective films according to Examples 1 and 2 and Comparative Example 1 were respectively compared and shown in Table 1 below. In addition, the retroreflectance by the effective area ratio of the optically active area to the lower layer and the ratio of the non-blocking area to the upper layer of each retroreflective film is shown in Table 2.

As an example, the whiteness for the background color of the license plate is shown based on the CIE L*a*b* color system of FIG. 9, and CIE L*a*b* is a value measured using CM2500 equipment (KONICA MINOLTA) , The retroreflectance is a value measured using PR-3000 equipment (Pymax) at an incident angle of 5.0˚ and an observation angle of 0.2˚, and has a unit of cd/lx·m2.

Each evaluation is performed once (A) with the base substrate alone, once (B) for the film in which the lower layer is bonded to the base substrate, and once (C) for the completed retroreflective film including the upper layer, respectively, and the results are indicated separately.

(Reflectance unit: cd/lx ㎡, L*: Brightness, a* b*: Chromaticity, △E: Color difference)

Referring to Table 1, in Examples 1 and 2, it can be seen that the brightness L* significantly increased from 66.6 and 66.9 to 89.01 and 89.78, respectively, after the upper and lower layers were combined. In Comparative Example 1, it was found that L* was 73.4 and the brightness was low.

In addition, in Examples 1 and 2, it was confirmed that the reflectance (retroreflective performance) was greatly limited in the upper layer and the lower layer, respectively, due to the reduction of the effective area by the sealing material and the partial blocking of the retroreflection by the printing pattern. However, in the case of Comparative Example 1, it was found that the reflectance was remarkably high because the upper layer was not combined.

Therefore, Examples 1 and 2 are remarkably excellent in whiteness, and by limiting the retroreflectance to a reference value range, both daytime visibility and nighttime camera visibility are excellent, and in the case of Comparative Example 1, both whiteness and reflection performance do not meet the required standards It can be seen that there is a problem in the visibility at night of the enforcement cameras installed on the market in Korea.

Referring to Table 2, in Example 1, after forming the corner cube pattern on the lower surface of the base substrate, the lower layer (including the sealing layer and the low refractive region) forming process proceeded under the conditions of line speed 6 m/min and 185° C., and the effective area ratio of the optically active area (effective area ratio reflecting manufacturing error) was formed as 10.1%, and reflectance was obtained as 31.4. In addition, 66.6% of the light blocking area (actual blocking area reflecting manufacturing error) was further formed using the upper layer (including a printed pattern with a width of 0.35 mm and an interval of 0.2 mm), and the reflectance was lowered to 10.5. The brightness was 89.01 and the color difference (ΔE) was 2.64, so good daytime visibility and nighttime camera visibility were secured.

In Example 2, after forming a corner cube pattern on the lower surface of the base substrate, in the process of forming the lower layer (including the sealing layer and the low-refractive region), the line speed was 5 m/min and the effective area ratio of the optical active area was 185 ° C. The effective area ratio) was 9.5%, and the reflectance was obtained as 29. In addition, 79.6% of the light blocking area (actual blocking area reflecting manufacturing error) was further formed using the upper layer (including a printed pattern with a width of 0.3mm and an interval of 0.1mm), and the reflectance was lowered to 6.7. Brightness was 89.78 and color difference (ΔE) was 2.41, so good daytime and nighttime camera visibility was secured.

In Comparative Example 1, after forming the corner cube pattern on the lower surface of the base substrate, the lower layer (including the sealing and low flexure region) forming process was carried out under the conditions of a line speed of 5 m/min and 185° C. to have an effective area ratio of an optically active area of 65%. According to the reflectance, the reflectance performance was 199.6 and the brightness 73.4 was obtained, so the visibility of the night camera and the naked eye was not good due to the too intense reflection performance and not high brightness, so the result was not suitable for license plates, etc.

Experimental Example 2: Comparison of immersion test results

After the retroreflective films according to Example 3 and Comparative Example 2 were immersed in water at a temperature of 50° C. for 24 hours, it was observed whether water penetrated into the low refractive index region, and is shown in FIGS. 12c and 12d , respectively.

12c and 12d, as the retroreflective film of the present invention, the retroreflective film according to Example 3, in which the lower refractive region of the lower layer is fine, did not cause immersion, and it was found that the durability was good.

However, in the case of the retroreflective film of Comparative Example 2 of the prior art, it can be seen that there is a problem in durability due to flooding.

Comparing and explaining the reason for this difference in durability, when comparing the area of the low refractive region of Example 3 and Comparative Example 2, the area of the low refractive region of Comparative Example 2 is much larger than the area of the low refractive region of Example 3. Because the seal is not as densely as possible, the durability is weakened.

Conversely, since the area of the low refractive region of Example 3 is much smaller and finer than the area of the low refractive region of Comparative Example 2, the micro-sealing is densely formed to the extent that durability is strengthened, and in Example 3, Since the adhesive area of Comparative Example 2 or more is formed, the overall adhesive force is much stronger, so that the retroreflective film according to the present invention has very strong durability.

13 and 14 are diagrams for explaining changes in reflection performance, color coordinates, and infrared absorptivity according to whether the content of the infrared absorbing material is increased and the finely divided pattern layer is applied according to embodiments of the present invention.

13 shows changes in reflection performance, color coordinates, and infrared (IR) absorptivity according to an increase in the content of an infrared absorbing material in Comparative Examples 3 to 3-7, and FIG. 14 is a finely divided pattern in Examples 4 to 4-7. The reflective performance, color coordinates, and infrared (IR) absorption rate change according to the increase in the content of the infrared absorbing material due to the introduction of the layer.

Referring to FIG. 13, through Comparative Examples 3 to 3-7 and Examples 4 to 4-7, changes in reflection performance, color coordinates, and infrared absorptivity according to the increase in the content of the infrared absorbing material and whether or not the finely divided pattern layer is applied are confirmed.

<FIG. 13: Comparative Examples 3 to 3-7 Preparation of retroreflective sheet without finely divided pattern layer>

① Manufacturing the lower multi-layer part of the retroreflective sheet: A corner cube pattern layer is formed on one surface of the base layer in the form of a film. At this time, the corner cube pattern layer is formed by a UV curing method, and the material is a UV-curable resin and an infrared absorbing material according to the content described in FIG. 13 . The UV curable resin uses MR810 resin from Mirae Nanotech Global. As an infrared absorbing material, tungsten oxide (N2005-15 by NST, 23% non-volatile content) was used by mixing each content relative to the total weight of UV-curable resin. Thereafter, in order to seal the air layer (low refractive layer) on the surface on which the corner cube pattern is formed, the hot melt sealing film is compressed with a pressing roller at a temperature of 185 degrees to form a fine sealing patterned fine sealing layer (retroreflective active region and retroreflection). create an inactive region). For the sealing film used at this time, a white sealing film (thickness 30 ㎛, additive 18%, inorganic material type) was used to improve the brightness of the product and to prevent the sealing pattern from being recognized, and fine sealing was performed. Thereafter, an external adhesive layer is formed on the outer surface of the sealing layer using a pressure-sensitive adhesive (white toner 15%).

② Manufacture of the upper multi-layer part of the retroreflective sheet: An internal adhesive layer 230 is formed on one surface of the film-type overlay layer using a transparent pressure-sensitive adhesive.

에서 제작된 상부 다층부의 내부 접착층이 접착되도록 라미네이팅 공정으로 하부 다층부와 상부 다층부를 접합시켜 재귀 반사 시트를 제작하였다. ③ Retroreflective sheet without finely divided pattern layer: On the base layer of the lower multi-layer part produced in η above

A retroreflective sheet was manufactured by bonding the lower multi-layer part and the upper multi-layer part by a laminating process so that the inner adhesive layer of the upper multi-layer part manufactured in .

<FIG. 14: Preparation of retroreflective sheets with finely divided pattern layers in Examples 4 to 4-7>

① Preparation of the lower multi-layered part of the retroreflective sheet: It was manufactured in the same manner as η of Comparative Examples 3 to 3-7.

② Manufacture of the upper multi-layer part of the retroreflective sheet: A finely divided pattern layer (straight line structure, pattern line width 0.35 mm, pattern line distance 0.2 mm) is formed on one surface of the film-type overlay layer. In this case, for the finely divided pattern layer, _{a paint containing titanium oxide (TiO 2} ) was used to form an optically non-transmissive region and to improve whiteness. Thereafter, an inner adhesive layer was formed with a transparent pressure-sensitive adhesive in the direction in which the finely divided pattern layer was formed on the overlay layer to prepare an upper multilayer part.

에서 제작된 상부 다층부의 내부 접착층이 접착되도록 라미네이팅 공정으로 하부 다층부와 상부 다층부를 접합시켜 재귀 반사 시트를 제작하였다.③ Retroreflective sheet with finely divided pattern layer: on the base layer of the lower multi-layer part produced in η above

A retroreflective sheet was manufactured by bonding the lower multi-layer part and the upper multi-layer part by a laminating process so that the inner adhesive layer of the upper multi-layer part manufactured in .

<Result Interpretation>

In FIG. 13 , Comparative Example 3 shows initial physical properties in a state in which there is no finely divided pattern layer and no infrared absorbing material is applied. Comparative Examples 3-1 to 3-7 show the behavior of reflection performance, color coordinates, and infrared absorption rate as the content of the infrared absorbing material increases in the absence of the finely divided pattern layer. Here, it can be seen that as the content of the infrared absorbing material increases, the reflective performance decreases and the whiteness decreases. The reason for the decrease in the reflection performance seems to be that the nonvolatile content of the infrared absorbing material increased in the corner cube causing retroreflection, which affected the light movement path. The reason for the decrease in whiteness is as the brightness L* significantly decreases and the chromaticities a* and b* increase in the negative direction. That is, referring to FIG. 13 , as the content of the infrared absorbing material increases, the brightness decreases and the chromaticity tends to stand out in the blue and green directions, and thus the whiteness decreases.

Comparative Example 3-1 and Comparative Example 3-2 did not show a significant difference from Comparative Example 3 in infrared absorption. It is confirmed that the effect is small when the infrared absorbing material is less than 1% based on the total weight. This means that the content of the infrared absorbing material is small and the infrared absorbing ability is small.

In Comparative Examples 3-6 and 3-7, it can be seen that the brightness and color change are severe, and the reflection performance is rapidly decreased. This is because the content of infrared absorbing material is 15% and 20%, so the green and blue colors are becoming more and more prominent, and there is a slight negative effect on the product properties due to the decrease in brightness. Therefore, it is difficult to apply it to license plates for vehicles.

In FIG. 14, Example 4 shows a case in which an infrared absorbing material is not applied and a finely divided pattern layer is applied, and Examples 4-1 to 4-7 show a case in which an infrared absorbing material and a finely divided pattern layer are applied. This can confirm how the finely divided pattern layer affects the entire retroreflective sheet.

First, in Example 4 compared to Comparative Example 3, it can be seen that the reflection performance significantly decreased from 66 to 7.1, a decrease of about 90% was confirmed, the infrared absorption rate was similar, and the brightness was increased by about 3. This trend is similarly shown in the series of processes of Examples 4-1 to 4-7 in which the content of the infrared absorbing material is increased as compared with Comparative Examples 3-1 to 3-7.

Accordingly, when the finely divided pattern layer is applied to the retroreflective sheet for a vehicle license plate, the retroreflective performance can be dramatically lowered, and when the color coordinate performance of a specific white color of the license plate is required, the whiteness improving material for the finely divided pattern layer By mixing and applying , the brightness is increased (L*) and the chromaticity (a*, b*) is adjusted to further increase the whiteness to match the license plate.

By controlling the pattern shape of the finely divided pattern layer and controlling the paint component mixed into the material, it becomes possible to manufacture retroreflective sheets for various uses, such as vehicle license plates as well as graphics and advertisement boards.

The application of the infrared absorbing material in FIG. 14 further increases the visibility of the night camera for the license plate for the vehicle. Based on the experimental results of Examples 4-1 to 4-7, retroreflective performance, brightness (L*), chromaticity ( a*,b*), and the infrared absorption material content range that can expect the most comprehensive and stable effect in consideration of the infrared absorption rate is selected and used in the range of 2% to 10% based on the total resin weight of the corner cube pattern layer 120 It is most preferable to be

15 is a view for explaining the difference in physical properties of the license plate product according to the presence or absence of a finely divided pattern layer and the presence or absence of an infrared absorbing material according to embodiments of the present invention.

15 is a comparison of the physical properties of the license plate products according to the presence or absence of the finely divided pattern layer and the presence or absence of an infrared absorbing material through Comparative Examples 4 and 5, 6 and shows.

The camera recognition evaluation was conducted with signal and speed cameras, and the location of the cameras was located in Yeoju, Gyeonggi-do, Republic of Korea. The camera light emitting lamp was conducted under the conditions of the IR-LED method. The conditions for obtaining the intermittent camera image were iris 47, gain value of 200, shutter speed of 605, and focus of 2000.

<Comparative Example 4: Preparation of retroreflective sheet without finely divided pattern layer and without infrared absorbing material>

① Manufacturing the lower multi-layer part of the retroreflective sheet: A corner cube pattern layer is formed on one surface of the base layer in the form of a film. Thereafter, to seal the air layer (low refractive layer) on the surface on which the corner cube pattern is formed, the hot melt sealing film is compressed with a pressing roller at a temperature of 185°C to form a fine sealing patterned fine sealing layer. For the sealing film used at this time, a white sealing film (thickness 30 ㎛, additive 18%, inorganic material type) was used to improve the brightness of the product and to prevent the sealing pattern from being recognized, and fine sealing was performed. Thereafter, an external adhesive layer is formed on the outer surface of the sealing layer using a pressure-sensitive adhesive (white toner 15%).

② Manufacture of the upper multi-layer part of the retroreflective sheet: An internal adhesive layer is formed on one surface of the film-type overlay layer using a transparent pressure-sensitive adhesive.

에서 제작된 상부 다층부의 내부 접착층이 접착되도록 라미네이팅 공정으로 하부 다층부와 상부 다층부를 접합시켜 재귀 반사 시트를 제작하였다.③ Retroreflective sheet: on the base layer of the lower multi-layer part manufactured in η above

A retroreflective sheet was manufactured by bonding the lower multi-layer part and the upper multi-layer part by a laminating process so that the inner adhesive layer of the upper multi-layer part manufactured in .

에서 제작된 재귀 반사 시트를 외부 접착층이 접착되도록 접합하여 번호판을 제작한다.④ License plate fabrication: on aluminum plate

A license plate is manufactured by bonding the retroreflective sheet manufactured in .

The retroreflective sheet may additionally include an information (number, character) layer on top.

<Example 5: Preparation of retroreflective sheet with finely divided pattern and without infrared absorbing material>

① Manufacturing the lower multi-layer part of the retroreflective sheet: A corner cube pattern layer is formed on one surface of the base layer in the form of a film. At this time, the corner cube pattern layer is formed by the UV curing method, and the material is UV-curable resin, and the UV-curable resin uses MR810 resin from Mirae Nanotech Global. Thereafter, to seal the air layer (low refractive layer) on the surface on which the corner cube pattern is formed, the hot melt sealing film is compressed with a pressing roller at a temperature of 185°C to form a fine sealing patterned fine sealing layer. For the sealing film used at this time, a white sealing film (thickness 30 ㎛, additive 18%, inorganic material type) was used to improve the brightness of the product and to prevent the sealing pattern from being recognized, and fine sealing was performed. Thereafter, an external adhesive layer is formed on the outer surface of the sealing layer using a pressure-sensitive adhesive (white toner 15%).

② Manufacture of the upper multi-layer part of the retroreflective sheet: A finely divided pattern layer (straight line structure, pattern thickness 0.35 mm, distance between patterns 0.2 mm) is formed on one surface of the film-type overlay layer. In this case, for the finely divided pattern layer, _{a paint containing titanium oxide (TiO 2} ) was used to form an optically non-transmissive region and to improve whiteness. Thereafter, an inner adhesive layer is formed with a transparent pressure-sensitive adhesive in the direction in which the finely divided pattern layer is formed on the overlay layer, thereby manufacturing the upper multi-layer part.

에서 제작된 상부 다층부의 내부 접착층이 접착되도록 라미네이팅 공정으로 하부 다층부와 상부 다층부를 접합시켜 재귀 반사 시트를 제작하였다.③ Retroreflective sheet with finely divided pattern layer: on the base layer of the lower multi-layer part produced in η above

A retroreflective sheet was manufactured by bonding the lower multi-layer part and the upper multi-layer part by a laminating process so that the inner adhesive layer of the upper multi-layer part manufactured in .

에서 제작된 재귀 반사 시트를 외부 접착층이 접착되도록 접합하여 번호판을 제작한다.④ License plate production: on aluminum plate

A license plate is manufactured by bonding the retroreflective sheet manufactured in .

The retroreflective sheet may additionally include an information (number, character) layer on top.

<Example 6 of Fig. 15: Preparation of a retroreflective sheet having a finely divided pattern and having an infrared absorbing material>

① Manufacturing the lower multi-layer part of the retroreflective sheet: A corner cube pattern layer is formed on one surface of the base layer in the form of a film. At this time, the corner cube pattern layer is formed by the UV method, and the material is a UV curable resin and an infrared absorbing material. The UV curable resin uses MR810 resin from Mirae Nanotech Global. The infrared absorbing material was used by mixing 10% of tungsten oxide (N2005-15 by NST, 23% non-volatile content) based on the total weight of the UV curable resin. Thereafter, the hot melt sealing film (fine sealing layer) is compressed with a pressing roller at a temperature of 185 degrees to seal the air layer (low refractive layer) on the surface where the corner cube pattern is formed to form a fine sealing patterned fine sealing layer (retroreflection). Create an active region and a retroreflective inactive region). For the sealing film used at this time, a white sealing film (thickness 30 ㎛, additive 18%, inorganic material type) was used to improve the brightness of the product and to prevent the sealing pattern from being recognized, and fine sealing was performed. Thereafter, an external adhesive layer is formed on the outer surface of the sealing layer using a pressure-sensitive adhesive (white toner 15%).

② Manufacture of the upper multi-layer part of the retroreflective sheet: A finely divided pattern layer (straight line structure, pattern thickness 0.35 mm, distance between patterns 0.2 mm) is formed on one surface of the film-type overlay layer. In this case, for the finely divided pattern layer, _{a paint containing titanium oxide (TiO 2} ) was used to form an optically non-transmissive region and to improve whiteness. Thereafter, the inner adhesive layer is formed with a transparent pressure-sensitive adhesive in the direction in which the finely divided pattern layer is formed on the overlay layer, thereby manufacturing the upper multi-layer part.

에서 제작된 상부 다층부(200)의 내부 접착층이 접착되도록 라미네이팅 공정으로 하부 다층부와 상부 다층부를 접합시켜 재귀 반사 시트를 제작하였다.③ Retroreflective sheet having a finely divided pattern: on the base layer of the lower multi-layer part produced in η above

A retroreflective sheet was manufactured by bonding the lower multi-layer part and the upper multi-layer part by a laminating process so that the inner adhesive layer of the upper multi-layer part 200 manufactured in .

에서 제작된 재귀 반사 시트를 외부 접착층이 접착되도록 접합하여 번호판을 제작한다. ④ License plate fabrication: on aluminum plate

A license plate is manufactured by bonding the retroreflective sheet manufactured in .

The retroreflective sheet may additionally include an information (number, character) layer on top.

<Result Interpretation>

Comparative Example 4 is evaluated by producing a film-type license plate that does not have a finely divided pattern layer and does not use an infrared absorbing material. It was confirmed that the images taken by the intermittent camera after the night flash was activated did not recognize the numbers and letters of the information layer at all. This is due to the high retroreflective performance.

On the other hand, Example 5 had a finely divided pattern layer and did not use an infrared absorbing material, and as compared to Comparative Example 4, the reflective performance range was sharply lowered. Accordingly, the intermittent camera captured image obtained in Example 4 had no problem in reading information such as numbers and characters of the information layer.

In addition, Example 6 had a finely divided pattern layer and used an infrared absorbing material, and it was confirmed that the information such as numbers and characters of the information layer became clearer when compared with Example 5.

Through Examples 5 and 6, the finely divided pattern layer significantly suppresses the reflection performance, improves the uniformity of the reflection performance over the entire sheet surface, and improves the whiteness of the license plate background color to increase the contrast with the information layer. It is confirmed that the readability of the letters and numbers of the layer has been improved.

The reflection performance range of Example 5 is 5 to 7, and the reflection performance range of Example 6 is 5 to 9, and it can be seen that the reflection performance range of Example 6 is expanded compared to the reflection performance range of Example 5.

The optimal range of reflective performance for the background color of vehicle license plates is 3 to 12. The wider the reflective performance numerical range measured in license plate products, the easier it is to match the reflective performance uniformity in production. As the numerical range is higher within the optimal range, visibility is increased.

Example 6, having the infrared absorbing material and the finely divided pattern layer, has a synergistic effect in that the value of the reflection performance is larger and the range is wide, so the product productivity is good and the average reflection performance is increased.

The above description is merely illustrative of the technical idea of the embodiment of the present invention, and those of ordinary skill in the art to which the embodiment of the present invention pertains may make various modifications and changes within the scope not departing from the essential characteristics of the embodiment of the present invention. transformation will be possible.

The present embodiments are for explaining the technical idea of the present embodiment, and the scope of the technical idea of the present embodiment is not limited by these embodiments. The protection scope of the present embodiment should be interpreted by the following claims, and all technical ideas within the equivalent range should be construed as being included in the scope of the present embodiment.

Claims (14)

In the retroreflective sheet,
a reflective layer having a retroreflective optical element formed thereon;
a light transmission control layer laminated on one surface of the reflective layer, the light transmission control layer having a light transmission control pattern for controlling a transmission amount of light flowing in a direction of the retroreflective optical element and light retroreflected by the retroreflective optical element; and
and a reflection suppression layer laminated on the other surface of the reflection layer and having a reflection control pattern for controlling light reflected by the retroreflective optical element. According to claim 1,
The retroreflective sheet, characterized in that the light transmission control pattern adjusts the light adjusted through the reflection suppressing layer again. According to claim 1,
The retroreflective sheet, characterized in that the retroreflective optical element is formed of a corner cube structure. According to claim 1,
An infrared ray absorbing material is used for the reflection layer, the light transmission control layer, the reflection suppression layer, or a plurality of layers in which they are combined. 5. The method of claim 4,
The retroreflective sheet, characterized in that the infrared absorbing material is used in the range of 0.5% to 20% based on the weight of the total resin. According to claim 1,
A retroreflective sheet, wherein a pigment, a dye, or a material in which they are combined is used for the light transmission control layer, the reflection suppression layer, or a plurality of layers in which they are combined to improve whiteness. According to claim 1,
The retroreflective sheet, characterized in that the reflection suppressing layer is divided into a retroreflective active region and a retroreflective inactive region based on the reflection control pattern. 8. The method of claim 7,
The retroreflective sheet, characterized in that the line width of the reflection control pattern is set in the range of 100 to 2000 micrometers. 8. The method of claim 7,
The retroreflective sheet, characterized in that the retroreflective active region occupies an area ratio of 5% to 30% with respect to the total area of the reflective layer. 8. The method of claim 7,
The retroreflective sheet, characterized in that among the retroreflective active regions, a region not blocked by the light transmission control pattern occupies an area ratio of 0.5% to 15% with respect to the total area of the reflective layer. 8. The method of claim 7,
The retroreflective sheet, characterized in that the light transmission control layer is divided into a transmission region and a non-transmission region based on the light transmission control pattern. 12. The method of claim 11,
When the light transmission control layer is viewed in a vertical direction of the retroreflective sheet, the transmission region includes a sub retroreflective active region and a sub retroreflective inactive region separated by the reflection control pattern. . According to claim 1,
The reflection control pattern and the light transmission control pattern include (i) a first average repetition period calculated in one direction with respect to a predetermined shape included in the reflection control pattern, and (ii) a predetermined shape included in the light transmission control pattern. A retroreflective sheet, characterized in that it satisfies a relationship defined by using a second average repetition period calculated in the same direction as the one direction with respect to the shape. In the license plate for a vehicle to which a retroreflective sheet is applied,
The retroreflective sheet,
a reflective layer having a retroreflective optical element formed thereon;
a light transmission control layer laminated on one surface of the reflective layer and having a light transmission control pattern for controlling light transmitted through the retroreflective optical element; and
and a reflection suppression layer laminated on the other surface of the reflection layer and having a reflection control pattern for controlling light reflected by the retroreflective optical element.

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