JP2007304488A - Retroreflective sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retroreflective sheet which is an encapsulated type retroreflective sheet capable of being manufactured in the same manner as the conventional encapsulated retroreflective type sheet and has improved whiteness. <P>SOLUTION: An encapsulated lens type retroreflective sheet is composed of at least a surface protective layer, glass spheres, a retaining layer which retains the glass spheres, a focus-forming layer and a mirror surface reflection layer, wherein a Y value of the retaining layer is 35 or more. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention includes road signs, signs for construction, etc., license plates for vehicles such as automobiles and motorcycles, safety materials such as clothing and lifesaving equipment, marking for signs, etc., various authentication stickers, visible light, 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. 59-71848 (Patent Document 1, corresponding US Pat. No. 4,721,694) 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, in the above-mentioned two patent documents, the Y value of the holding layer is... Or more, and there is no description or suggestion regarding improving the whiteness (Y value) of the retroreflective sheet.

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 provides a retroreflective sheet having both improved whiteness (Y value) and retroreflective properties. It is in.

  In particular, there are two or more holding layers, and the glass spheres are held in a holding layer having a high total light transmittance and a holding layer having a low degree of whiteness in order to increase the Y value, thereby improving whiteness (Y value). And providing a retroreflective sheet having both retroreflective properties.

An 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 focus forming layer, and a specular reflection layer, wherein the Y value of the holding layer is 35 or more. The problem can be solved by providing the reflection sheet.

  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 holding layer (3) for holding a glass bulb (4), and a specular reflection layer (6) arranged at the focal position of the microsphere. ) And a focal point forming layer (5) for arranging the specular reflection layer at the focal point 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 holding layer (3). The holding layer is usually formed by using resins such as acrylic resin, alkyd resin, fluororesin, vinyl chloride resin, polyester resin, urethane resin, polycarbonate resin 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 is obtained and excellent visibility is preferable, and if it is not more than the upper limit value, the retention 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.

As the colorant that can be used for the surface protective layer and the transparent holding layer of the retroreflective sheet of the present invention, general colorants such as organic pigments, inorganic pigments, organic dyes, fluorescent pigments, fluorescent dyes, and the like can be used.

As the colorant that can be used in the colored holding layer of the present invention, general colorants such as organic pigments, inorganic pigments, organic dyes, fluorescent pigments, and fluorescent dyes can be used, but the Y value of the retroreflective sheet is improved. Above, the colored holding layer is preferably white, blue white, green white, yellow white, reddish white, yellow or the like.

Of these, white, bluish white, and green white are preferable because the color of the reflective sheet does not fade.

Moreover, the colored holding layer of this invention can obtain a holding layer with a high Y value by adding a brightening agent or a fluorescent dye, and can improve the Y value of a reflective sheet.

Moreover, even if the colored holding layer of the present invention is a layer colored only with a whitening agent or a fluorescent dye, a holding layer having a high Y value can be obtained, and the Y value of the reflective sheet can be improved.

When the colored holding layer of the present invention is a layer colored in white or a color close to white, it is preferable that the concealability is higher because the effect of improving the whiteness (Y value) of the retroreflective sheet is higher, As the colorant, it is preferable to include at least a pigment capable of obtaining high hiding power.

“By making the holding layer on the focal layer side concealed white, the Y value of the sheet can be improved by about 15%.”

As the colorant used in the colored holding layer of the present invention, for example, a white inorganic pigment and other colors such as blue, green, yellow, orange, red and the like are mixed and used. This is preferable because a concealable holding layer is obtained.

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 In addition, an additive such as a surface conditioner such as an acrylic polymer may be included.

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 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.

In the retroreflective sheet of the present invention, since the holding layer is colored, the distance between the top of the glass sphere and the surface protective layer is within 15 μm, and more preferably not 5 μm, so that the glass sphere supplies sufficient light. Is preferable.

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 shorten the distance from the surface protective layer in order to increase the amount of 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 arranging the specular reflection layer at the focal position of the glass sphere, and 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 cross-linking 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, butyral resin, and the like. From the viewpoint of durability, acrylic resin and butyral resin are preferable, 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.

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.

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

FIG. 2 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 transparent holding layer (3a) for holding microspheres (4), a colored holding layer (3b), and microspheres. It consists of a specular reflection layer (6) arranged at the focal position 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.

The retroreflective sheet of the present invention holds the glass sphere shown in FIG. 2 (4) with a transparent holding layer (3a) and a colored holding layer (3b). Both transparent and colored retaining layers are usually formed using resins such as acrylic resin, alkyd resin, fluororesin, vinyl chloride resin, polyester resin, urethane resin, polycarbonate resin alone or in combination. The 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 is obtained and excellent visibility is preferable, and if it is not more than the upper limit value, the retention 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.

Even if the colored holding layer is colored with a colorant capable of obtaining transparency, or colored with a colorant that does not provide transparency, the head part of the glass sphere is light transmissive in any aspect. Since the glass is held by the holding layer, sufficient light is supplied to the glass sphere to obtain excellent retroreflection performance.

In the present invention, an opaque colorant that has not been used in a conventional encapsulated lens type retroreflective sheet can be used, and in particular, whiteness (Y value) of the retroreflective sheet can be improved by making it white or yellow. is there.

As the colorant that can be used for the surface protective layer and the transparent holding layer of the retroreflective sheet of the present invention, general colorants such as organic pigments, inorganic pigments, organic dyes, fluorescent pigments, fluorescent dyes, and the like can be used.

As the colorant that can be used in the colored holding layer of the present invention, general colorants such as organic pigments, inorganic pigments, organic dyes, fluorescent pigments, and fluorescent dyes can be used, but the Y value of the retroreflective sheet is improved. Above, the colored holding layer is preferably white, blue white, green white, yellow white, reddish white, yellow or the like.

Of these, white, bluish white, and green white are preferable because the color of the reflective sheet does not fade.

Moreover, the colored holding layer of this invention can obtain a holding layer with a high Y value by adding a brightening agent or a fluorescent dye, and can improve the Y value of a reflective sheet.

Moreover, even if the colored holding layer of the present invention is a layer colored only with a whitening agent or a fluorescent dye, a holding layer having a high Y value can be obtained, and the Y value of the reflective sheet can be improved.

When the colored holding layer of the present invention is a layer colored in white or a color close to white, it is preferable that the concealability is higher because the effect of improving the whiteness (Y value) of the retroreflective sheet is higher, As the colorant, it is preferable to include at least a pigment capable of obtaining high hiding power.

As the colorant used in the colored holding layer of the present invention, for example, a white inorganic pigment and other colors such as blue, green, yellow, orange, red and the like are mixed and used. This is preferable because a concealable holding layer is obtained.

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 can be applied in several steps as necessary, and a transparent holding layer and a colored holding layer can be applied, or different types of resins may be laminated.

In the present invention, the holding layer is at least two layers of a transparent holding layer and a colored holding layer. As a manufacturing method, a transparent holding layer is laminated on the surface protective layer and semi-dried, and a colored holding layer is laminated thereon and semi-dried, a glass bulb is applied, and the glass bulb is embedded in the holding layer. It is. At this time, if the transparent holding layer is insufficiently dried, it is difficult to apply the colored holding layer, and if the transparent holding layer is too dry, the glass bulb does not reach the transparent holding layer.

In order to prevent the drying of the transparent holding layer from progressing excessively, for example, the transparent holding layer is semi-dried at a lower temperature compared to the semi-drying of the colored holding layer, or the resin used for the colored holding layer. Glass ball coating by reducing the weight average molecular weight of the resin used for the transparent holding layer or reducing the amount of the crosslinking agent used for the transparent holding layer compared to the amount of the crosslinking agent used for the colored holding layer Sometimes it is preferred that a transparent holding layer holds the glass bulb.

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.

In the retroreflective sheet of the present invention, the top of the glass sphere is held by a transparent holding layer, and it is the glass sphere that 1/15 or more of the diameter of the glass sphere is held by the transparent holding layer. This is preferable for supplying sufficient light. Furthermore, it is preferable that 1/5 or more of the diameter of the glass bulb is held by a transparent holding layer in order to supply 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 increase the portion held by the transparent holding layer 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 arranging the specular reflection layer at the focal position of the glass sphere, and 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 cross-linking 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, butyral resin, and the like. From the viewpoint of durability, acrylic resin and butyral resin are preferable, 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.

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.

When the holding layer is one layer, the resin for the holding layer is applied on the surface protective layer and semi-dried. Next, a glass bulb is sprayed on the semi-dried holding layer.
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.

After spraying the glass spheres, the glass spheres are embedded in the holding layer by the surface tension of the holding layer by performing a heat treatment at about 150 ° C. for about three and a half minutes.

When the holding layer is a transparent holding layer and a colored holding layer, a transparent holding layer resin is applied on the surface protective layer and semi-dried. Next, the colored resin for the holding layer is coated on the semi-dried transparent holding layer and semi-dried.
Next, a glass bulb is sprayed on the colored holding layer.
With this semi-drying degree, it is possible to adjust the embedding rate of embedding the glass spheres in the holding layer. For example, when using acrylic as a resin, 40 ° C. to 150 ° C., preferably 50 ° C. to 130 ° C., especially It is preferable to dry at 60 ° C. to 120 ° C. for about 5 minutes so that the glass bulb can be easily embedded.

Here, since the transparent holding layer is subjected to a drying process twice when the transparent holding layer is semi-dried and when the colored holding layer is semi-dried, the semi-drying of the transparent holding layer is colored. It is preferable that the holding layer can be applied and the drying is sweet.

After spraying the glass spheres, the glass spheres are embedded in the holding layer by the surface tension of the holding layer by performing a heat treatment at about 150 ° C. for about three and a half minutes.

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 for uniformly forming a 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) Saturation Using a Nippon Denshoku color difference meter (Model SE-2000), the hue of the retroreflective sheet was measured according to JISZ9117, and the intensity of color development was determined from the Y value.
Further, the Y value of the holding layer in the present invention was applied to a PET film so that the thickness of the holding layer forming resin was 30 μm after drying, and the hue of the holding layer single layer was measured.

(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) Color development 50 monitors of 18 to 60 years old visually judged whether the obtained retroreflective sheet felt that the color development (Y value) was improved under natural light.
Judgment criteria:
0 point: No improvement compared to the conventional reflective sheet 1 point: Slightly improved compared to the conventional reflective sheet 2 points: Good color developability compared to the conventional reflective sheet 3 points : Judgment result with excellent color development compared to conventional reflective sheets:
×: 30 points or less (no improvement in color development)
Δ: 30 points or more and less than 90 (no improvement in color developability depending on the person observing)
○: 90 or more and less than 120 (good color developability)
A: 120 or more (excellent color development)

(4) Appearance The appearance of the obtained retroreflective sheet was visually determined.
×: Opaque colorant is not uniformly dispersed, and appearance is uneven Δ: The whole is dull and discolored ○: Appearance unevenness is partially observed when observed carefully ◎: Normal recursion Appearance that is not inferior to the reflective sheet

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) and 0.04 parts by weight of leveling agent (trade name, BYK-300) made by Big Chemie Japan Co., Ltd. In addition, 0.12 parts by weight of a catalyst (trade name, Beccamin P-198) manufactured by Dainippon Ink & Chemicals, Inc. as a solvent and MIBK / En = 8/2 by adding 16.7 parts by weight so that the ratio to form a 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. and 12 parts by weight of isocyanate-based cross-linking agent (trade name, Sumidur N-75) manufactured by Sumitomo Bayer Urethane Co., Ltd. Then, 21 parts by weight of toluene as a solvent and 9 parts by weight of MIBK were mixed and stirred on the surface protective layer, dried at 70 ° C. for 5 minutes, 10 μm thick and 95% transmittance on the light incident side. A retention layer was obtained.
Next, 100 parts by weight of RS-3000, 5 parts by weight of a white colorant (trade name DAD-101) manufactured by Shanghai DIC Ink Co., Ltd., 12 parts by weight of Sumidur N-75, 10 parts by weight of toluene, and MIBK 20 parts by weight of the mixture was applied onto the light incident side holding layer and dried at 100 ° C. for 5 minutes to obtain a focus forming layer side holding layer having a thickness of 13 μm and a transmittance of 0%.

A glass sphere (trade name, NB-45S) manufactured by Aki Ai Co., Ltd. was attached to the holding layer on the focus forming layer side, and heat-treated at 145 ° C. for 3 minutes and 30 seconds, so that the glass sphere was submerged 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 and transmittance of each holding layer were separately applied to a Teijin Limited polyester film (trade name, Teijin Tetron Film S-75) having a thickness of 75 μm and a transmittance of 93%. Was determined by subtracting 75 from the total thickness, and the transmittance was determined by measuring the transmittance in the state of being laminated on the polyester film and dividing by 0.93.

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 pressure-sensitive adhesive layer having a thickness of 41 μm. 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 surface protective layer is 100 parts by weight of an acrylic resin solution (trade name, RS-1200) manufactured by Enki Aika Corporation, and a color base (trade name, AR-) manufactured by Special Colorant Co., Ltd. N-4100) to 26 parts by weight, Miwa Chemical Co., Ltd. methylated melamine resin solution (trade name, Nicalac MS-11) to 14 parts by weight, Special Colorant Co., Ltd. cellulose derivative (trade name, CAB) ) 4 parts by weight, 0.5 parts by weight of a UV absorber manufactured by Sipro Kasei Co., Ltd. (trade name, Sea soap 103), and a leveling agent (trade name, BYK-300) manufactured by BYK Japan Japan Co., Ltd. To 04 parts by weight, 0.12 part by weight of a catalyst manufactured by Dainippon Ink and Chemicals Co., Ltd. (trade name, Becamine P-198) and 13 to have a ratio of MIBK / toluene = 8/2 as a solvent. Adding 1 part by weight, except for using a stirred mixture to obtain a retroreflective sheet in the same manner as in Example 1.

Example 3
In Example 1, the holding layer on the focus forming layer side is 100 parts by weight of RS-3000 and 8 parts by weight of a white colorant (trade name DAD-101) manufactured by Shanghai DIC Oil Co., Ltd. The color base (trade name, AR-4300) is 118 parts by weight, Sumijoule N-75 is 20 parts by weight, toluene is 26 parts by weight, and MIBK is 60 parts by weight. A retroreflective sheet was obtained in the same manner as in Example 1 except that it was dried at 100 ° C. for 5 minutes and used as a holding layer on the focus forming layer side having a thickness of 13 μm and a transmittance of 0%.

Example 4
In Example 1, a retroreflective sheet was obtained in the same manner as in Example 1 except that the thickness of the light incident side holding layer was 12 μm. The transmittance of the holding layer on the light incident side was 94%. The head of the glass sphere is not in contact with the surface protective layer, and the ratio of the glass sphere held by the holding layer on the light incident side and the ratio held by the focus forming layer are the same as in Example 1. It was.

Example 5
In Example 4, a retroreflective sheet was obtained in the same manner as in Example 4 except that the drying temperature of the holding layer on the light incident side was 60 ° C. and the drying temperature of the holding layer on the focus forming layer side was 90 ° C. The head of the glass sphere was in contact with the surface protective layer, and about 1/4 of the diameter of the glass sphere was held in the holding layer on the light incident side. The focal layer was formed so that the average thickness was 21 μm.

Example 6
The light incident side holding layer is pale yellow, the focus forming layer side holding layer is dark yellow, and the light incident side holding layer is RS-3000 so that the hue as the retroreflective sheet is the same as in Example 2. 100 parts by weight, 80 parts by weight of AR-4300, 15.5 parts by weight of Sumidur N-75, 21 parts by weight of toluene, and 50 parts by weight of MIBK were mixed and stirred at 75 ° C. for 5 minutes, A holding layer on the light incident side having a thickness of 10 μm and a transmittance of 70% was obtained. The holding layer on the focus forming layer side is 100 parts by weight of RS-3000, 8 parts by weight of DAD-101, 40 parts by weight of AR-4300, 13.4 parts by weight of Sumidur N-75, 18 A mixture obtained by mixing 42 parts by weight of MIBK with 42 parts by weight was dried at 100 ° C. for 5 minutes to obtain a holding layer on the side of the focus forming layer having a thickness of 13 μm and a transmittance of 0%. A sheet was obtained.

Comparative Example 1
In Example 1, the retaining layer was applied as a retaining layer to 100 parts by weight of RS-3000, 12 parts by weight of Sumidur N-75, 10 parts by weight of toluene, and 20 parts by weight of MIBK. A retroreflective sheet was obtained in the same manner as in Example 1 except that the film was dried at 110 ° C. for 5 minutes, prepared to have a thickness of 25 μm, and no holding layer on the focus forming layer side was provided.

Comparative Example 2
In Comparative Example 1, a retroreflective sheet was obtained in the same manner as in Comparative Example 1 except that the coating liquid formulation for the surface protective layer was the same as in Example 2.

The properties, color developability and appearance of the obtained retroreflective sheet are shown in Table 1.

Table 1

It is sectional drawing of the enclosure lens type retroreflection sheet of this invention. 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 Printing layer 3, 3a, 3b Holding layer 4 Glass sphere 5 Focus formation layer 6 Specular reflection layer 7 Adhesive layer 8 Release base material 9 Incident direction of light

Claims (4)

In 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, the Y value of the holding layer is 35 or more. Retroreflective sheet. The recursion according to claim 1, wherein the holding layer is composed of two or more layers, and the holding layer in contact with the surface protective layer is transparent, and the total light transmittance of the transparent holding layer is 60% or more. Reflective sheet. The retroreflective sheet according to claim 1 or 2, wherein the holding layer comprises two or more layers, and the total light transmittance of the holding layer not in contact with the surface protective layer is 70% or less. The retroreflective sheet according to any one of claims 2 to 3, wherein 1/15 or more of the diameter of the glass sphere is held in the transparent holding layer.