JP2008020565A - Retroreflective sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retroreflective sheet in which retroreflective light has a hue different from the hue under natural light, as regards the colored enclosure type retroreflective sheet which can be manufactured in similar processes as the conventional enclosure type retroreflective sheet. <P>SOLUTION: The enclosure type retroreflective sheet comprises: at least a surface protective layer; a retention layer of retaining glass spheres; the glass spheres; a focusing layer; and a mirror reflection layer, wherein the retention layer comprises two or more layers and the hues of the respective retention layers which are measured individually are made different from one another by 0.05 or more when expressed as δ of (x-y) measured according to the colorimetric method of XYZ system. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention includes road signs, signs such as construction signs, license plates for vehicles such as automobiles and motorcycles, safety materials such as clothing and life preservers, markings such as signs, various authentication stickers, visible light, and laser light. Or a retroreflective sheet having a novel structure useful for reflectors of infrared light reflective sensors

Conventionally, a retroreflective sheet that reflects incident light toward a light source is well known, and the sheet using the retroreflective property is widely used in the fields of use as described above.
As such a retroreflective sheet, an encapsulated lens type retroreflective sheet is well known, which uses a microscopic glass sphere and a metal, most often aluminum, which is vacuum-deposited to provide a specular reflection layer as a retroreflective element. Yes.

  Examples of the encapsulated lens type retroreflective sheet are disclosed in detail in Japanese Patent Application Laid-Open No. Sho 59-71848 (Patent Document 1, corresponding US Pat. No. 4,721,649) of Berisle. The above references are replaced with specific descriptions of these retroreflective sheets.

Further, the inventors of the present invention provide an encapsulated lens type retroreflective sheet comprising at least a surface protective layer, a holding layer for holding a glass sphere, a glass sphere, a focus forming layer, and a specular reflection layer. Thus, an application has been filed for a retroreflective sheet, wherein the light incident side holding layer is transparent and at least one other holding layer is colored. (Patent Document 2)

However, Patent Document 1 has neither a description nor a suggestion that there are two or more holding layers. Patent Document 2 describes that the holding layer is composed of two or more layers. However, the holding layer on the light incident side is colorless and transparent or the same color system as the holding layer on the focus forming layer side and a light-colored one is described. Therefore, there is no description or suggestion that the hue when measured by each of the holding layers as in the present application is 0.05 or more different in δ of xy when measured by an XYZ colorimetric method.

JP 59-71848 A Japanese Patent Application No. 2006-78470

The problem to be solved by the present invention is an encapsulated retroreflective sheet that can be manufactured in the same manner as an ordinary encapsulated retroreflective sheet, and can provide a retroreflective sheet that is different in hue from natural light and retroreflective light.

In particular, information that is difficult to visually recognize under natural light can be visually recognized under retroreflected light, which is useful for preventing counterfeiting, and at least a surface protective layer, a holding layer for holding a glass bulb, a glass bulb, a focus forming layer, and In an encapsulated lens type retroreflective sheet comprising a specular reflection layer, the holding layer is composed of two or more layers, and the hue when measured by each of the holding layers alone is δ of xy of 0.05 when measured by an XYZ colorimetry method. A retroreflective sheet characterized by the above differences can be provided.

In the encapsulated lens type retroreflective sheet consisting of at least a surface protective layer, a holding layer for holding a glass sphere, a glass sphere, a focal point forming layer, and a specular reflection layer, the holding layer is composed of two or more layers, each of the holding layers alone The problem can be solved by providing a retroreflective sheet in which the hue when measured is different by 0.05 or more in δ of xy when measured by an XYZ color measurement method.

  Hereinafter, the retroreflective sheet of the present invention will be described in more detail.

FIG. 1 is a schematic cross-sectional view illustrating an encapsulated lens type retroreflective sheet.
The encapsulated lens type retroreflective sheet shown in FIG. 1 includes a surface protective layer (1), a colored holding layer (3a) for holding glass (4), and a holding layer colored in a different hue from 3a ( 3b), comprising a specular reflection layer (6) disposed at the focal position of the glass sphere and a focus formation layer (5) for arranging the specular reflection layer at the focal position.

It is also preferable to provide a printed layer (2) for transmitting information to the observer or coloring the sheet.

In the present invention, the surface protective layer (1) is a layer forming a surface layer of a retroreflective sheet having transparency with a total light transmittance of 80% or more, and is usually an acrylic resin, an alkyd resin, a fluororesin, It is formed by using resins such as vinyl chloride resin, polyester resin, urethane resin, polycarbonate resin alone or in combination. An acrylic resin, a polyester resin, and a vinyl chloride resin are preferable from the viewpoint of weather resistance and processability, and an acrylic resin is particularly preferable in consideration of coating suitability and dispersibility of a coloring agent when coloring.

Various additives such as an ultraviolet absorber, a stabilizer, a plasticizer, and a crosslinking agent can be added to the surface protective layer as long as the transparency is not significantly impaired. Further, when a transparent protective film or a transparent plate is used on the surface, the surface protective layer (1) can be omitted.

In the retroreflective sheet of the present invention, the glass sphere shown in FIG. 1 (4) is held by the colored holding layer (3a) and the holding layer (3b) colored in a hue different from 3a. Both the colored retaining layer (3a) and the retaining layer (3b) colored in a hue different from 3a are usually made of acrylic resin, alkyd resin, fluororesin, vinyl chloride resin, polyester resin, urethane resin, polycarbonate resin, etc. It is formed by using resins alone or in combination. Acrylic resins and polyester resins are preferred from the viewpoint of weather resistance and processability, and acrylic resins are most preferred in view of coating properties and dispersibility of the colorant.

In the present invention, the colorant contained in the surface protective layer or the holding layer is preferably 1 to 30 parts by weight, more preferably 2 to 20 parts by weight, and more preferably 2 to 20 parts by weight, based on 100 parts by weight of the solid content of the base resin. Preferably it contains 5 to 15 parts by weight. If the addition amount of the colorant is not less than the lower limit value, sufficient coloring can be obtained and excellent visibility can be obtained, and if it is not more than the upper limit value, the holding layer becomes too hard and brittle. This is preferable because no inconvenience occurs and characteristics such as mechanical strength and flexibility are not impaired.

Since the excellent retroreflective performance cannot be obtained if the light transmittance of the manifestation protection layer is poor, the surface protection layer is preferably uncolored or colored with a colorant capable of obtaining transparency.

In the present invention, the glass spheres are held in two holding layers, a colored holding layer (3a) and a holding layer (3b) colored in a different hue from 3a.

In a conventionally known retroreflective sheet in which only a surface protective layer that does not hold a glass bulb is colored, the hue under natural light and the hue under retroreflective light do not change much.

In addition, when the holding layer 3a and the holding layer 3b are the holding layers having the same hue, optically, the hue under natural light and the hue under retroreflected light are the same as when the holding layer is one layer. , Not much changed.

In the present invention, the glass sphere is held across the two holding layers having different hues, whereby the hue under natural light and the hue under retroreflected light are different.

In the present invention, the coloring concentration and thickness of the colored retaining layer (3a) and the retaining layer (3b) colored in a hue different from 3a, the burying rate of the glass bulb in each layer, and the like are changed. Thus, the hue under natural light and the hue under retroreflected light can be adjusted to a desired hue.

The embedding rate of the present invention is the ratio of the thickness at which each holding layer holds the glass bulb to the diameter of the glass bulb. More specifically, when the glass sphere has a diameter of 60 μm and the holding layer 3 a and the holding layer 3 b each hold 15 μm of glass bulbs, the embedding rate in the holding layer 3 a is 25%, and the holding layer 3 b The burial rate is 25%.

In the above case, the volume of the glass sphere held in the holding layer 3b is larger than the volume of the glass sphere held in the holding layer 3a, but the embedding rate is said to be equal in the present invention.

In the present invention, when the embedment ratios in 3a and 3b are equal, the influence of hue on retroreflected light is stronger in 3a. This is because the ratio of the optical path of retroreflected light through 3a is high.

In the present invention, a retroreflective sheet having an anti-counterfeit effect can be provided by making use of this property so that information that is difficult to view under natural light can be viewed under retroreflective light.

In addition to the colorant, various additives such as an ultraviolet absorber, a stabilizer, a plasticizer, and a crosslinking agent can be added to the holding layer as long as the physical properties are not impaired.

Also, if necessary, curing agents such as alkylated amino resins, alkylated urea resins, isocyanate-based crosslinking agents; release agents such as silicon-based release agents and cellulose-based release agents; polyester-modified polydimethylsiloxane, silicon-based surfactants , May contain additives such as surface modifiers such as acrylic polymers

The molecular weight of the resin forming the holding layer is not particularly limited, but the resin has a weight average molecular weight (hereinafter sometimes abbreviated as Mw) of 50,000 or more, more preferably 50,000 to 400,000. Resin, more preferably 100,000 to 300,000 resin is used. When a resin that is within this range and reacted with an appropriate curing agent is used, beads can be appropriately submerged in the resin.

The holding layer (3a), the holding layer (3b) colored in a different hue from the colored holding layer (3a), and can be applied in several times as necessary. It may be laminated.

In the present invention, the holding layer is at least two layers of a colored holding layer (3a) and a holding layer (3b) colored in a hue different from 3a. As a production method, a colored holding layer (3a) is laminated on the surface protective layer and semi-dried, and a colored colored holding layer (3b) different from 3a is laminated thereon and semi-dried. And the glass spheres are buried in the holding layers (3a and 3b). At this time, if the holding layer (3a) is insufficiently dried, it is difficult to apply the holding layer (3b), and if the holding layer (3a) is too dry, the glass layer is colored with the holding layer ( 3a) is not reached.

In order to prevent the drying of the holding layer (3a) from progressing excessively, for example, the holding layer (3a) is semi-dried at a lower temperature than the semi-drying of the holding layer (3b), or used for the holding layer (3b). The weight average molecular weight of the resin used for the holding layer (3a) is made smaller than the resin used, or the amount of the crosslinking agent used for the holding layer (3a) is made smaller than the amount of the crosslinking agent used for the holding layer (3b). It is preferable that the holding layer (3a) can hold the glass bulb when the glass bulb is applied.

The resin solid content of the resin for the holding layer is 25 to 50%, preferably 30 to 40%, more preferably 33 to 38%, and the resin coating thickness of the holding layer is 15 μm to 50 μm. When several layers are laminated, the coating thickness of the holding layer for holding the glass sphere is determined according to conditions such as the glass sphere diameter.

The retroreflective sheet of the present invention is preferably formed using a glass sphere having a function of retroreflecting light in cooperation with the specular reflection layer located at the focal position. The refractive index of the glass sphere is 2.0 to 2.5, preferably 2.0 to 2.3.

The size of the glass sphere used as the retroreflective element is usually about 10 μm to 150 μm, but in order to increase the reflectivity to the front, it is preferable to use a larger diameter, preferably Are those having an average diameter of about 25 μm to 120 μm, more preferably about 40 μm to 90 μm.

The glass spheres of the retroreflective sheet of the present invention are held in at least two holding layers of a colored holding layer (3a) and a holding layer (3b) colored in a different hue from 3a.

In the present invention, the brightness of the retroreflective sheet is considered within a range in which the hue can be adjusted, but when the total light transmittance of the colored holding layer is 60% or more, for example, when the transparency is good, It is preferable that 1/15 or more of the diameter of the glass bulb is held by the colored holding layer (3a) in order to supply sufficient light to the glass bulb. Further, it is preferable that 1/5 or more of the diameter of the glass bulb is held by the colored holding layer (3a) in order to supply sufficient light to the glass bulb.

When the total light transmittance of the colored holding layer (3a) is inferior, for example, less than 60%, the distance from the surface protective layer to the glass bulb should be 15 μm or less, preferably 5 μm or less. Is preferred for supplying sufficient light to the glass bulb.

In the retroreflective sheet of the present invention, if the diameter of the glass sphere is large, higher reflection performance can be obtained. Therefore, even if the light incident on the glass sphere is slightly less, sufficient reflection performance can be obtained. When the diameter of the glass sphere is small, it is preferable to reduce the distance from the surface protective layer to the glass sphere in order to increase the light incident on the glass sphere.

The retroreflective sheet of the present invention further has a focus forming layer shown in FIG. The focal point forming layer is a layer for disposing the specular reflection layer at the focal position of the glass sphere. Usually, acrylic resin, alkyd resin, fluororesin, vinyl chloride resin, polyester resin, urethane resin, polycarbonate resin, butyral resin, etc. the resin alone or are formed using a combination, weather resistance, coatability, thermal stability acrylic resin in terms of, butyral resins are preferred.

Various additives such as a colorant, an ultraviolet absorber, a stabilizer, a plasticizer, and a crosslinking agent can be added to the focus forming layer as long as the transparency is not significantly impaired.
The resin forming the focal resin layer is not particularly limited, and examples thereof include acrylic resin, urethane resin, and butyral resin. Acrylic resin and butyral resin are preferable from the viewpoint of durability, and acrylic resin is most preferable in view of coating properties.

The molecular weight of the resin forming the focus forming layer is not particularly limited, but the resin has a Mw of 100,000 or more, more preferably 100,000 to 400,000, and further preferably 150,000 to 300,000. It is preferable to use a resin. When a resin within this range and reacted with an appropriate curing agent is used, a spherical focus forming layer can be formed.

The viscosity at the time of application of the resin forming the focus forming layer is 10 to 600 cP, preferably 30 to 600 cP, more preferably 50 to 200 cP, and the resin solid content of the focus forming layer resin is 10 to 40%, Preferably it is 15 to 35%, more preferably 15 to 25%. If the resin solid content is large, it is easy to entrain air bubbles and foam easily, and if it is less than 10%, the coating amount becomes considerably large, which is not preferable.

The thickness of the focus forming layer is determined in consideration of the refractive index of the resin so that the incident light beam is focused on the specular reflection layer, but is usually 10 μm to 60 μm, preferably 15 μm to 50 μm, particularly preferably 20 μm. ~ 40 μm.

Even if the focus-forming layer (5) is colored in a different hue from the colored holding layer (3a) instead of 3b, a retroreflective sheet having a different hue from the natural light and retroreflective light can be obtained. Since the required thickness of the focus forming layer differs depending on the embedding rate in the layer, it is not preferable because a desired hue cannot always be obtained with a thickness at which optimum luminance can be obtained.

The retroreflective sheet of the present invention also has a specular reflection layer shown in FIG. The specular reflection layer is a layer for reflecting light, and is usually formed by means such as vacuum deposition or sputtering using a metal such as aluminum or silver, but a metal thin film reflecting the shape of the base is used. In order to form uniformly, a vapor deposition method is particularly preferable. The thickness of the metal layer is 0.05 μm to 0.2 μm, preferably 0.05 μm to 0.15 μm, particularly preferably 0.05 to 0.1 μm.

The chromogenic retroreflective sheet of the present invention has an adhesive layer for adhering the sheet to a substrate, if necessary. The type of resin forming the adhesive layer is not particularly limited, and a resin used as a normal adhesive resin may be used. For example, acrylic resin, silicon resin, rubber resin, phenolic resin Resin or the like is used. Among them, an acrylic resin or a silicon resin having excellent weather resistance and good adhesive properties is preferably used.

The molecular weight of the resin forming the adhesive layer is not particularly limited, but a resin having a higher molecular weight tends to obtain a suitable holding force, and has a weight average molecular weight (hereinafter sometimes abbreviated as Mw) 50. It is suitable to use 10,000 or more resins, more preferably 500,000 to 1,000,000 resins, and still more preferably 600,000 to 1,000,000 resins. Among them, Mw having a functional group
The use of a resin obtained by crosslinking a resin of 500,000 or more with a crosslinking agent such as an isocyanate-based crosslinking agent is most preferable because a particularly excellent holding force can be obtained.

The retroreflective sheet of the present invention is manufactured by the method described below. First,
The resin for the process substrate surface protective layer is applied and dried. The process base material is not particularly limited as long as it has sufficient strength and expands and contracts sufficiently when heated, but a base material such as polyethylene terephthalate (PET), polyimide, or vinyl chloride is used. It is possible and PET is particularly preferred.

The coating method is not particularly limited as long as it can be uniformly applied with a predetermined thickness, but there are methods such as reverse roll coating and comma direct coating.

Next, the colored resin for the holding layer (3a) is coated on the surface protective layer and semi-dried. Next, a resin for the holding layer (3b) colored in a hue different from 3a is applied on the semi-dried colored holding layer (3a) and semi-dried.
Subsequently, a glass bulb is sprayed on the holding layer (3b) colored in a hue different from 3a.
With this semi-drying degree, the embedding rate for embedding the glass spheres in the retaining layer can be adjusted. For example, when acrylic is used as the resin, 50 ° C. to 150 ° C., preferably 70 ° C. to 130 ° C., especially Preferably, it is dried at 80 ° C. to 120 ° C. for about 5 minutes to facilitate embedding the glass bulb.

Here, the colored holding layer (3a) is dried twice when the colored holding layer (3a) is semi-dried and when the holding layer (3b) colored in a hue different from 3a is semi-dried. Since the steps are included, it is preferable that the colored holding layer (3a) is semi-dried so that the colored holding layer can be applied and the drying is sweet.

By further heat treatment after spraying the glass sphere, the glass sphere is embedded in the holding layer by the surface tension of the holding layer.

The embedding rate of the glass spheres in the holding layer is not particularly limited and varies depending on the type of the holding layer resin. For example, when acrylic is used as the resin, 20% from the point of holding the glass spheres. The above is good.

Next, the focus forming layer resin is applied to the surface of the glass bulb. The coating method is not particularly limited as long as it can be uniformly applied with a predetermined thickness, and there are methods such as reverse roll coating and comma direct coating.

Apply at room temperature and heat-treat as necessary to cure the resin. The curing temperature varies depending on the type of the resin / curing agent, but when an acrylic resin is used as the focus forming layer resin, it is preferably heated to 50 ° C. to 160 ° C., preferably 70 ° C. to 155 ° C. Moreover, you may apply | coat a focus formation layer in several times as needed.

Next, a metal thin film is formed on the focus formation layer. As a method for forming the metal thin film, a coating method, a vapor deposition method, or the like can be used. However, the vapor deposition method is particularly preferable in order to uniformly form the metal thin film reflecting the shape of the base. The thickness of the metal layer is 0.05 μm to 0.2 μm, preferably 0.05 μm to 0.15 μm, particularly preferably 0.05 to 0.1 μm.

Conditions such as the deposition rate, temperature and degree of vacuum may be selected according to the equipment, but it is preferable to select the rate, temperature and degree of vacuum so that the metal thin film has a uniform thickness. .

In the case of an embodiment having an adhesive layer, the adhesive layer is then applied onto the release film and bonded to the intermediate product after metal deposition on the adhesive layer surface. The bonding conditions vary depending on the adhesive, but when an acrylic resin is used as the adhesive, it is preferable to apply pressure while applying a certain amount of heat.

Finally, if the process substrate is peeled off, the retroreflective sheet of the present invention can be obtained. The peeling angle, peeling speed, etc. are not particularly limited, but peeling is carried out by appropriately adjusting the angle and speed so as not to break the sheet.

The reflectivity of the retroreflective sheet of the present invention is determined as desired in consideration of the balance with the color developing property, but in order to sufficiently function as a retroreflective sheet, the front reflection performance (incident angle 0.2 °) , Retroreflective performance at an observation angle of 5 °) is 20 cd / lx. m2 or more, preferably 30 cd / lx. m2 or more, more preferably 40 cd / lx. It should be m2 or more.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. In addition, the measuring method used in the Example and the comparative example is as follows.

(1) Hue The hue of the retroreflective sheet was measured according to JIS Z 9117 using a Nippon Denshoku color difference meter (Model SE-2000).
In addition, the hue of the retaining layer in the present invention is such that the retaining layer forming resin is applied on a PET film so that the thickness after drying is 30 μm, and a white standard plate for SE-2000 is applied to the film when measuring the hue. Measured by placing on top.

(2) Front retroreflective performance Using “Model 920” manufactured by Advanced Retro Technology (INC) as a retroreflective performance measuring instrument, the retroreflective light quantity of a 100 mm x 100 mm retroreflective sheet sample conforms to JISZ9117. Then, measurement was made at five appropriate points with an observation angle of 0.2 ° and an incident angle of 5 °, and the average value was used as the retroreflection performance value.

(3) Evaluation of the difference between the hue under natural light and the hue of the retroreflected light There was a difference between the daytime hue of the obtained retroreflective sheet and the hue observed at the driver's seat of the car that turned on the night headlight. 50 monitors of 18 to 60 years old judged visually whether it was felt.
Judgment criteria:
0 point: Does not have different hues under natural light and reflected light.
1 point: Slightly different hue between natural light and reflected light.
Two points: have different hues under natural light and reflected light.
3 points: Clearly different hues under natural light and reflected light.
judgment result:
×: 30 points or less (there is no difference in hue)
Δ: 30 points or more and less than 90 (there is no difference in hue depending on the person observing)
○: 90 or more and less than 120 (there is a difference in hue)
A: 120 or more (there is a clear difference)

Example 1
A 75 μm thick transparent polyethylene terephthalate film (trade name, Teijin Tetron Film S-75) manufactured by Teijin Ltd. was used as the carrier film, and an acrylic resin solution (trade name, RS-- 1200 parts by weight, methylated melamine resin solution manufactured by Sanwa Chemical Co., Ltd. (trade name, Nicalac MS-11) and 14 parts by weight cellulose derivative (trade name, CAB) by Special Colorant Co., Ltd. In part, 0.5 parts by weight of UV absorber made by Sipro Kasei Co., Ltd. (trade name, Seasoap 103), 0.04 parts by weight of leveling agent (trade name, BYK-300) made by Big Chemie Japan, Dainippon Ink and Chemicals Co., Ltd. catalyst (trade name, Beccamin P-198) in 0.12 parts by weight, and MIBK / As the addition of 16.7 parts by weight comprising the ratio of ene = 8/2 to form a colorless transparent surface protective layer having a thickness of 36μm was coated with a stirred mixture.

On the surface protective layer, 100 parts by weight of acrylic resin (trade name RS-3000) manufactured by Onkiai Co., Ltd., 120 parts by weight of color base (trade name AR-4300) manufactured by Tokiki Co., Ltd., Sumitomo Bayer Urethane Co., Ltd. An isocyanate-based crosslinking agent (trade name, Sumidur N-75) made by mixing 20 parts by weight of toluene, 26 parts by weight of toluene as a solvent, and 61 parts by weight of MIBK was applied onto the surface protective layer, and 70 ° C. And dried for 5 minutes to obtain a yellow transparent light incident side holding layer having a thickness of 10 μm.
Next, RS-3000 was added to 100 parts by weight, Tokiki Color Base Co., Ltd. (trade name AR-4300) to 30 parts by weight, Tokushi Co., Ltd. Color Base (trade name AR-5300) to 86 parts by weight, A mixture of 21 parts by weight of -75, 26 parts by weight of toluene and 61 parts by weight of MIBK mixed and stirred on the light-incident holding layer, dried at 100 ° C. for 5 minutes, and a red transparent focus with a thickness of 13 μm. A holding layer on the formation layer side was obtained.

A glass sphere (trade name, NB-45S) manufactured by Enkiai Co., Ltd. was attached to the holding layer on the focus forming layer side, and heat treatment was performed to submerge the glass sphere in the holding layer.
When the cross section was observed with a microscope, the head of the glass beads was in contact with the surface protective layer, and approximately 1/5 of the diameter of the glass sphere was held in the holding layer on the light incident side.
In addition, the thickness of each holding layer is separately applied on a Teijin Limited polyester film (trade name, Teijin Tetron Film S-75) having a thickness of 75 μm, and the thickness is 75 subtracted from the total thickness. Asked.

Next, on the retaining layer and the glass bulb, 100 parts by weight of an acrylic resin solution (trade name, RS-5000) manufactured by Unki Aika Co., Ltd., a methylated melamine resin solution (trade name, manufactured by Sanwa Chemical Co., Ltd.) Nicarak MS-11) was added to 5.5 parts by weight, 39.3 parts by weight of MIBK / toluene = 4/6 as a solvent, and stirred and mixed to form a focus having an average thickness of 23 μm. A layer was formed.

Subsequently, aluminum was vacuum-deposited on the focus forming layer to obtain a specular reflection layer.

Moreover, as a release paper, a release paper (trade name, E2P-H (P)) manufactured by Lintec Corporation is used, and an ethyl acetate of a BA / AA copolymer (weight ratio: BA / AA = 90/10) is provided thereon. / Toluene (1/1) solution (solid content 34%) 100 parts by weight, white colorant (trade name, AR-9127W) manufactured by Special Colorant Co., Ltd., 9 parts by weight, isocyanate system manufactured by Nippon Polyurethane Industry Co., Ltd. A cross-linking agent (trade name, Coronate L) is added to 0.5 parts by weight, and 16.1 parts by weight of ethyl acetate as a solvent is added, followed by stirring and mixing to form a 41 μm thick adhesive layer. did.

After laminating the specular reflection layer and the pressure-sensitive adhesive layer, the carrier film was peeled off to obtain the retroreflective sheet of the present invention.

Example 2
In Example 1, the coating solution for the holding layer on the focus-forming layer side was RS-3000 in 100 parts by weight, Tokushi Co., Ltd. color base (trade name AR-6300) in 113 parts by weight, and Sumijoule N-75. 21 parts by weight of toluene, 25 parts by weight of toluene and 59 parts by weight of MIBK were mixed and stirred on the light-incident-side holding layer and dried at 90 ° C. for 5 minutes to form a 13 μm thick blue transparent focus. A retroreflective sheet was obtained in the same manner as in Example 1 except that the holding layer on the layer side was obtained.

Example 3
In Example 1, the coating liquid for the holding layer on the focus-forming layer side was RS-3000 in 100 parts by weight, Tokushi Co., Ltd. color base (trade name AR-8300) in 270 parts by weight, and Sumijoule N-75. 34 parts by weight of toluene, 57 parts by weight of toluene and 131 parts by weight of MIBK were mixed and stirred on the light-incident-side holding layer and dried at 90 ° C. for 5 minutes to form a green transparent focus with a thickness of 13 μm. A retroreflective sheet was obtained in the same manner as in Example 1 except that the holding layer on the layer side was obtained.

Comparative Example 1
In Example 1, the surface protective layer is 100 parts by weight of RS-1200, 26 parts by weight of a color base (trade name, AR-N-4100) manufactured by Tokiki Co., Ltd., and a methylated melamine resin manufactured by Sanwa Chemical Co., Ltd. 14 parts by weight of solution (trade name, Nicarak MS-11), 4 parts by weight of cellulose derivative (trade name, CAB) manufactured by Special Colorant Co., Ltd., and UV absorber (trade name, Sea Soap 103) manufactured by Sipro Kasei Co., Ltd. To 0.5 parts by weight, a leveling agent (trade name, BYK-300) manufactured by Big Chemie Japan Co., Ltd. is added to 0.04 parts by weight, and a catalyst (trade name, Beccamin P-198) manufactured by Dainippon Ink & Chemicals, Inc. is added. Add 16.7 parts by weight to 0.12 parts by weight as a solvent so that the ratio of MIBK / toluene = 8/2, stir and mix, and apply a yellow transparent surface with a thickness of 36 μm. A protective layer is formed, RS-3000 is 100 parts by weight, Tokushi Co., Ltd. color base (trade name AR-4300) is 30 parts by weight, and Tokushi Co., Ltd. color base (trade name AR-5300) is 86 parts by weight. Then, 21 parts by weight of Sumidur N-75, 26 parts by weight of toluene, and 61 parts by weight of MIBK were mixed and stirred on the light incident side of the holding layer to form a holding layer having a thickness of 25 μm. A retroreflective sheet was obtained in the same manner as in Example 1 except that the holding layer on the focus forming layer side was not provided.

Comparative Example 2
In Comparative Example 2, the coating liquid formulation for the holding layer was 100 parts by weight of the trade name RS-3000, 113 parts by weight of the color base (trade name AR-6300) manufactured by Tokushi Co., Ltd., and 21 of Sumidur N-75. Comparative example except that 25 parts by weight of toluene and 59 parts by weight of MIBK were mixed and stirred and applied onto the light incident side holding layer to obtain a 25 μm-thick focusing layer side holding layer. A retroreflective sheet was obtained in the same manner as in Example 1.

Comparative Example 3
In Comparative Example 2, the coating liquid formulation of the holding layer is 100 parts by weight of the trade name RS-3000, 270 parts by weight of the color base (trade name AR-8300) manufactured by Tokiki Co., Ltd., and 34 of Sumidur N-75. Comparative Example 1 with the exception that 57 parts by weight of toluene and 131 parts by weight of MIBK were mixed and stirred as a mixture and stirred on the light incident side holding layer to obtain a 25 μm thick focus forming layer side holding layer. Similarly, a retroreflective sheet was obtained.

The hue of the obtained retroreflective sheet is shown in Table 1, and δ (xy) reflection performance and visibility are shown in Table 2.

It is sectional drawing of the enclosure lens type retroreflection sheet of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Surface protective layer 2 Print layer 3a, 3b Holding layer 4 Glass sphere 5 Focus formation layer
6 Specular reflection layer 7 Adhesive layer 8 Peeling base material 9 Incident direction of light

Claims (1)

In the encapsulated lens type retroreflective sheet consisting of at least a surface protective layer, a holding layer for holding a glass sphere, a glass sphere, a focal point forming layer, and a specular reflection layer, the holding layer is composed of two or more layers, each of the holding layers alone A retroreflective sheet characterized in that the hue when measured is different by 0.05 or more in δ of xy when measured by an XYZ color measurement method.