JP4818015B2 - Retroreflective sheet - Google Patents

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. Alternatively, the present invention relates to a retroreflective sheet having a novel structure that is useful for a reflector of infrared light reflection type 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 present inventors have at least a large number of micro glass spheres, a holding layer made of a light-transmitting resin that holds the glass spheres, a specular reflection layer that reflects incident light, and the glass sphere and the specular reflection layer. An encapsulated lens type retroreflective sheet comprising a focus forming layer made of at least one light-transmitting resin and a specular reflection layer disposed therebetween, and an adhesive layer is further provided below the specular reflection layer of the retroreflective sheet When the retroreflective sheet is attached to the base material via the adhesive layer and the retroreflective sheet is peeled off from the base material, the focus forming layer is the glass sphere and / or the holding layer. An application has been filed for a retroreflective sheet characterized in that it is configured to delaminate and / or destruct and / or destroy the focus forming layer, thereby damaging or losing retroreflective performance. (Patent Document 2)

  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 3)

In addition, in the 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 holding layer is composed of two or more layers, An application has been filed for a retroreflective sheet characterized in that the hue when measured alone is different by 0.05 or more in xyδ when measured by an XYZ colorimetric method. (Patent Document 4)

However, Patent Document 1 has neither a description nor a suggestion that there are two or more holding layers. There is no description or suggestion regarding destruction.

Patent Document 2 describes a retroreflective sheet for preventing forgery and tampering with the focus forming layer of the retroreflective sheet as destructive, but both the holding layer and the focus forming layer are uncolored, and the hue changes after peeling. Not what you want. Further, there is no description or suggestion regarding the number of retaining layers being two or more.

Patent Document 3 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. There is no description or suggestion regarding destruction.

Patent Document 4 describes that the holding layer is composed of two or more layers, and the hue when measured by each of the holding layers is different by 0.05 or more in x-yδ when measured by an XYZ colorimetric method. However, there is no description or suggestion regarding destruction.

JP 59-71848 JP PCT / JP2006 / 302790 Specification Japanese Patent Application No. 2006-78470 Specification Japanese Patent Application No. 2006-191002 Specification

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 when peeled from an adherend, the hue of the retroreflective sheet changes. It is possible to provide a retroreflective sheet that can be identified as having been determined.

In particular, at least the surface protective layer, one or more holding layers for holding the glass sphere, a glass ball, a focus forming layer, and a surface protective layer composed of a specular reflection layer and at least one of the one or more holding layers. In a sealed lens type retroreflective sheet provided with layers of different hues, the holding layers of the retroreflective sheet are colored in different hues in two or more layers, and any one of the two or more holding layers is destructive Or when a destructive layer is provided between the glass bulb and the holding layer and / or between the two holding layers, and when the retroreflective sheet attached to the base material is peeled off from the base material Furthermore, the retroreflective sheet is characterized in that the hue under visible light before and after peeling differs by 0.05 or more in xy δ as measured by an XYZ color measurement method.

At least the surface protective layer, one or more holding layers that hold the glass spheres, a glass sphere, a focus forming layer, and a surface protective layer composed of a specular reflection layer and one or more holding layers, a hue different from at least the other layers In the encapsulated lens type retroreflective sheet provided with the above layer, the holding layer of the retroreflective sheet is colored in two or more different colors, and any one of the two or more holding layers is destructive. Or when a destructive layer is provided between the glass bulb and the holding layer and / or between the two holding layers, and when the retroreflective sheet attached to the substrate is peeled from the substrate, A retroreflective sheet characterized in that the hue under visible light before and after peeling differs by 0.05 or more in xy δ as measured by an XYZ color measurement method.

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

FIG. 1 and FIG. 2 are schematic cross-sectional views showing 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.

In the present invention, as the first embodiment, when the holding layer (3a) and / or (3b) is a destructive layer, the compound that can be used for the destructive holding layer (3a) or (3b) is: A polymer or a prepolymer may be used, and alicyclic polyolefin resin or alicyclic acrylic resin, cellulose derivative, silicon compound, fluorine resin, polyurethane resin, acrylic resin, alkyd resin, butyral resin, polyester resin or a mixture thereof is preferable. Depending on the destruction mode, it is appropriately selected.

A preferred alicyclic polyolefin resin of the present invention has an alicyclic structure in the main chain, and as a cyclopentane resin, a cyclopentane resin (Chemical Formula 1a), a bicyclopentane resin (Chemical Formula 1b), a cyclopenta It is a norbornene resin (chemical formula 1c), and the vinylcyclopentane resin is a vinylcyclopentane resin (chemical formula 2a), a vinylcyclopentanorbornene resin (chemical formula 2b), or a cyclohexadiene resin (chemical formula). 3a), a cyclohexane resin (chemical formula 3b),
(R ₁ , R ₂ , R ₃ , R ₄ , and R ₅ are each a hydrogen atom, an alkyl group, a cyano group, a cyclohexyl group, or an alkyl carboxylate group, and n represents the number average degree of polymerization)

Usually, cyclopentane resins (Chemical Formula 1a) ring-opening polymerize cycloolefins such as norbornene, dicyclopentadiene and tetracyclododecene using a metathesis catalyst composed of transition metal compounds such as tungsten and molybdenum and alkylaluminum. Is obtained by saturating double bonds by hydrogenation. As a commercially available product, ZEONEX manufactured by Nippon Zeon Co., Ltd. can be used.

The substituent R ₁ of the above cyclopentane resin (Chemical Formula 1a) is particularly preferably a hydrogen atom or a cyclohexyl group. In a structure in which two substituents are hydrogen atoms, crystallinity increases and transparency tends to decrease. When the substituent R ₁ is a hydrogen atom or a cyclohexyl group, it is an amorphous polymer and the transparency is improved. Therefore, the substituent R ₁ is particularly preferable for use in the destructive holding layer (3a) and / or (3b) of the present invention. .

As the resin used for the destructive holding layer (3a) and / or (3b) of the present invention, a vinylcyclopentane resin (Chemical Formula 2a) and a vinylcyclopentanorbornene resin (Chemical Formula 2b) are usually norbornene and It is obtained by saturating a vinyl group by hydrogenation of an intermediate compound obtained by ring-opening polymerization of a norbornene derivative having a methacrylic group in the side chain obtained by methyl methacrylate using a catalyst combined with a tungsten-aluminum compound. Since such a compound has an ester group structure, it tends to have relatively high adhesion to other resin layers and reflection layers constituting the retroreflective sheet. As a commercially available product, ARTON manufactured by JSR Corporation can be listed.

The substituents R ₂ and R ₃ of this vinylcyclopentane resin (Chemical Formula 2a) and vinylcyclopentanorbornene resin (Chemical Formula 2b) are a hydrogen atom (—H), a methyl group (—CH ₃ ), a cyano group (—CN). ), A methoxycarbonyl group (—COOCH ₃ ), an ethoxycarbonyl group (—COOC ₂ H ₅ ), a cyclohexyloxycarbonyl group (—COO (cyclo-C ₆ H ₁₁ )), an n-butoxycarbonyl group (—COO (n— It is particularly preferable to use C ₄ H ₉ )) in order to adjust optical properties such as transparency and refractive index, heat resistance, and adhesion with adjacent layers.

Further, the cyclohexadiene resin (chemical formulas 3a and 3b) is particularly preferably a 1,3-cyclohexadiene resin or a cyclohexane resin. These cyclohexadiene-based polymers can be obtained by living anion polymerization of 1,3-cyclohexadiene using a catalyst comprising an alkyl lithium and an amine compound. In particular, 1,3-cyclohexadiene resin is particularly preferable from the viewpoint of heat resistance.

The alicyclic acrylic resin used in the destructible holding layer (3a) or (3b) of the present invention has an alicyclic structure in the acrylic ester portion, and is represented by the chemical formula (4). acrylic resin
(R ₆ represents a hydrogen atom, a methyl group, R ₇ represents a cyclohexyl group, a group represented by the following chemical formula (4-1) or chemical formula (4-2))
Is preferred.

The alicyclic acrylic resin is preferably a methacrylic acid ester polymer (Chemical Formula 4), particularly a copolymer of tricyclodecyl methacrylate and methyl methacrylate. As a commercially available product, an optlet manufactured by Hitachi Chemical Co., Ltd. can be used. Further, a copolymer of benzyl methacrylate, tricyclodecane methacrylate and methyl methacrylate having high heat resistance can also be used.

The cellulose derivative used as the resin used in the destructible retaining layer (3a) and / or (3b) of the present invention is cellulose acetate (hereinafter also referred to as CA), cellulose acetate propionate (hereinafter also referred to as CAP) or It is preferably any of cellulose acetate butyrate (hereinafter also referred to as CAB) or a mixture thereof. These cellulose derivatives have good transparency and poor adhesion to glass spheres and resins, and when peeled, they are peeled off due to delamination and / or cohesive failure with the glass spheres or holding layer, damaging retroreflective performance. Or it can be lost. As a commercial product, CAB manufactured by Eastman Chemical Co. can be used.

The compounds used in the destructible retaining layer (3a) and / or (3b) of the present invention include silicone resins such as phenylmethyl silicone resin and methyl silicone resin, or modified or non-modified silicone varnish. Any or a mixture thereof is preferable. These silicone compounds have moderate adhesion to glass spheres and resins, and when peeled, they are peeled off due to delamination and / or cohesive failure with the glass sphere or holding layer, resulting in damage or loss of retroreflective performance. Can be made. As a commercially available product, a silicone coating agent manufactured by Toray Dow Corning Silicone Co., Ltd. can be used.

The fluororesin used in the destructible holding layer (3a) and / or (3b) of the present invention is preferably a reactive organic fluorine compound having a long-chain fluorinated alkyl group and a reactive group. By coating these fluorine compounds, a thin film of fluorine can be formed, and delamination from other resin layers can damage or lose the retroreflection performance. As a commercially available product, Lumiflon manufactured by Asahi Glass Co., Ltd. can be used.

The polyurethane resin, acrylic resin, butyral resin, and polyester resin used in the destructible holding layer (3a) and / or (3b) of the present invention can be easily broken and coagulated by reducing the molecular weight. It can be used as a destructive layer.

The resin that can be used for these destructive holding layers (3a) and / or (3b) is preferably adjusted in terms of molecular weight, cross-linking density, etc. as appropriate so that peeling can easily occur.

An appropriate molecular weight range is 1,000 to 100,000, preferably 5,000 to 50,000, in terms of styrene equivalent weight molecular weight. Destructive such that delamination occurs between the glass sphere (3) and the destructive holding layer (3a) or delamination occurs between the destructive holding layer (3b) and the focus forming layer (4). The molecular weight of the compound used in the holding layer is 10,000 to 100,000, preferably 50,000 to 100,000, so that the destructive holding layer (3a) and / or (3b) may be peeled off. The molecular weight of the compound used in such a destructive holding layer is 1,000 to 5,000, preferably 1,000 to 3,000, but must be appropriately adjusted depending on the molecular structure and polymerization method.

Further, by adding other resins to the resin used for the destructive holding layer (3a) and / or (3b), the adhesive strength with the adjacent layer can be adjusted, and the destructive holding layer (3a) and It is also possible to reduce the cohesive force of (3b).

Examples of additive resins that can be used include various cellulose compounds such as cellulose acetate butyrate, and various waxes such as aliphatic hydrocarbons, fatty acid esters, saturated aliphatic acids, saturated alcohols and metal soaps. Further, examples of the aliphatic hydrocarbon type include polyethylene wax, polypropylene wax, microcrystalline wax, paraffin wax, and Fischer-Trops wax. Examples of the fatty acid ester type include sazol wax, Examples include montanic acid ester wax, carnauba wax, rice wax, beeswax and candelilla wax. Examples of saturated aliphatic acids include stearic acid and montanic acid. Te, such as can be exemplified stearic alcohol and behenyl alcohol, as the metal soap, such as calcium stearate and zinc stearate can be exemplified, and can be added these waxes in the range of amount 1 to 100 parts by weight.

In addition, silicon resin, fluororesin, etc. are mixed individually or in the resin used so that the form of destruction can be easily peeled off at the interface between the destructive holding layer (3a) and / or (3b) and the adjacent layer Can be used.

In the present invention, as a second aspect, in addition to the holding layers (3a) and (3b), between the glass bulb (4) and the holding layer (3a) and / or between (3a) and (3b) in FIG. Thus, the destructive layers (3c, 3d) can be provided.

In the second embodiment, the holding layer (3a) and the holding layer (3b) may be destructive or nondestructive, and at least one of the 3 to 4 holding layers is destructible. If it is.

When both the holding layer (3a) and the holding layer (3b) colored in a hue different from 3a are non-destructive layers, usually acrylic resin, alkyd resin, fluororesin, vinyl chloride resin, polyester resin, urethane It is formed by using resins such as resin and 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.

Examples of the compound that can be used in the destructive layer (3c, 3d) of the present invention include compounds that can be used in the destructive holding layer (3a, 3b). It can be used by mixing.

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.

If the light transmittance of the surface protective layer is poor, an excellent retroreflective performance cannot be obtained. Therefore, the surface protective layer is preferably uncolored or colored with a colorant capable of obtaining transparency.

In the second aspect of the present invention, the glass sphere is composed of 3 to 4 layers of a colored retaining layer (3a), a retaining layer (3b) colored in a hue different from 3a, and a destructive layer (3c, 3d). Although (3a, 3b) may be destructive, (3c, 3d) may be colored.

In the present invention, an adhesive layer can be provided on the specular reflection layer side of the retroreflective sheet, and the retroreflective sheet can be attached to the adherend via the adhesive layer, or the light is incident on the light incident side of the retroreflective sheet. It is also possible to provide a transparent adhesive layer and attach a retroreflective sheet to a light-transmitting adherend through the adhesive layer.

In an aspect in which an adhesive layer is provided on the specular reflection layer side and the retroreflective sheet is pasted on the adherend, after peeling, the adherend has neither a glass ball nor a holding layer (3a). In addition, since the hue changes greatly before and after peeling, it can be easily recognized that an attempt has been made to falsify.

In a mode in which a light-transmitting adhesive layer is provided on the light incident side of the retroreflective sheet and the retroreflective sheet is attached to the adherend, after peeling, the holding layer (3b) is also specularly reflected on the adherend. Since there is no layer, the retroreflectivity after peeling is remarkably inferior to that before peeling, and the hue also changes, so that it can be easily recognized that an attempt has been made to falsify.

At this time, when the holding layer 3a, the holding layer 3b, the holding layer 3c, and the holding layer 3d are holding layers having the same hue, the hue change after peeling is only light and shade. Among the retention layers, at least one retention layer has a hue different from that of other retention layers by 0.05 or more in x-yδ when measured by the XYZ color measurement method, making counterfeiting difficult and easily recognizing tampering This is preferable.

  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 non-destructive 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. It is better to use ~ 400,000 resin, more preferably 100,000 ~ 300,000 resin. 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.

Each holding layer (3a, 3b, 3c, 3d) can be coated in several times as necessary, and different types of resins may be laminated.

In the present invention, as a third aspect, either the colored surface protective layer and one or more colored holding layers are destructive, or the colored surface protective layer and one or more colored layers are colored. The destructive layer (3c) of FIG. 2 can be provided between the holding layers.

In the present invention, as a fourth aspect, only the surface protective layer or the holding layer of the retroreflective sheet is colored, and the surface protective layer and / or the holding layer is destructive, or the holding layer and the breaking layer are destroyed. The destructive layer (3c) of FIG. 2 can be provided between the layers.

In the third aspect and the fourth aspect, when the surface protective layer and the colored holding layer (3a, 3b) are both non-destructive layers, usually an acrylic resin, an alkyd resin, a fluororesin, a vinyl chloride resin, It is formed by using a resin such as a polyester resin, a urethane resin, or a 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.

When both the surface protective layer of the present invention and the colored retaining layer (3a, 3b) are destructible layers, the compounds that can be used are the above destructible retaining layers (3a, 3b). The compound which can be used can be mentioned, It can use individually or in mixture of 2 or more types.

In the present invention, an adhesive layer can be provided on the specular reflection layer side of the retroreflective sheet, and the retroreflective sheet can be attached to the adherend via the adhesive layer, or the light is incident on the light incident side of the retroreflective sheet. It is also possible to provide a transparent adhesive layer and attach a retroreflective sheet to a light-transmitting adherend through the adhesive layer.

In an embodiment in which an adhesive layer is provided on the specular reflection layer side and the retroreflective sheet is attached to the adherend, after peeling, the adherend has neither a glass ball nor a colored holding layer, so that the retroreflective property is present. In addition, since the hue changes greatly before and after peeling, it can be easily recognized that an attempt has been made to falsify.

In a mode in which a light-transmitting adhesive layer is provided on the light incident side of the retroreflective sheet and the retroreflective sheet is attached to the adherend, after peeling, the colored holding layer is also specularly reflected on the adherend. Since there is no layer, the retroreflectivity after peeling is remarkably inferior to that before peeling, and the hue also changes, so that it can be easily recognized that an attempt has been made to falsify.

At this time, in the case of a retaining layer having the same hue as the surface protective layer, the hue change after peeling is only shade, so it is preferable to greatly change the shade in order to easily recognize tampering.

In the present invention, in the first aspect or the second aspect, the holding layer is at least two layers. 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.

In the third aspect and the fourth aspect of the present invention, the holding layer is one or more layers. When two or more holding layers are used, it is preferable that the manufacturing method is the same as the manufacturing method of the holding layer of the first aspect or the second aspect.

When the holding layer is one or more layers, the holding layer is semi-dried even when the holding layer is laminated on the surface protective layer or when the holding layer is laminated on the breaking layer laminated on the back surface of the surface protective layer. In this state, a glass bulb is applied and embedded in the holding layer.

About the other requirements regarding the retention layer of a 3rd aspect, it can be made to be the same as that of the retention layer of a 1st aspect, or the retention layer of a 2nd aspect, except a retention layer being 2 layers or more. It is duplicated but described below.

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 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.

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. 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.

In the present invention, there is an aspect in which a destructive holding layer (3c, 3d) is provided between the surface protective layer and the holding layer (3a) and / or between the holding layer (3a) and the holding layer (3b). The protective layer is sequentially laminated on the protective layer, semi-dried, and the next layer is repeatedly laminated and semi-dried.

After all the holding layers are laminated and semi-dried, glass balls are sprayed on the laminated and semi-dried holding layer. With the degree of semi-drying of each holding layer, it is possible to adjust the embedding ratio of embedding the glass spheres into the holding layer. For example, when using acrylic as a resin, 50 ° C to 150 ° C, preferably 70 ° C to Drying at 130 ° C., particularly preferably from 80 ° C. to 120 ° C. for about 5 minutes, makes it easy to embed the glass bulb.

Here, since the first laminated and semi-dried holding layer is subjected to a drying process at the time of the semi-drying and the next holding layer semi-dried, the semi-drying of the previously laminated holding layer is the next holding It is preferable that the layer can be applied and the drying is sweet.

By further processing after the glass spheres are dispersed, the glass spheres are 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) Peel strength An aluminum plate having a thickness of 2 mm was used as a base material on which the retroreflective sheet was adhered. Peel off the release paper for providing the adhesive layer on the retroreflective sheet used in the test according to JIS Z-0237, and paste together using a 2 Kg roller, then 3 under conditions of a temperature of 23 ° C. and a relative humidity of 60%. Held for days. The peel strength (N / 25 mm) of this test piece was measured. The peel strength was measured by pulling one end of the attached reflection sheet at a speed of 300 mm / min in the direction perpendicular to the aluminum plate at 90 ° using a tensile tester. The measurement was performed three times, and the average value was taken as the peel strength (N / 25 mm).

4) Peeling condition The peeling part and peeling state of the test piece after the test were visually observed, and the peeling condition was observed and evaluated according to the following evaluation criteria. Evaluation criteria: Peeling state A: Peeling between the surface protective layer and the holding layer (3a) B: Peeling due to cohesive failure in the holding layer (3a-3d) C: Reflective sheet is broken or between other layers The peel location and peel state of the test piece after the peel test were visually observed, and the peel condition was observed and evaluated according to the following evaluation criteria.

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., and 20% by weight of non-volatile content of vinylcyclopentanorbornene resin (trade name, ARTON FX4727) manufactured by JSR Corporation. % Toluene solution 100 parts by weight, Tokushi Co., Ltd. color base (trade name AR-4300) to 120 parts by weight, Sumitomo Bayer Urethane Co., Ltd. isocyanate cross-linking agent (trade name, Sumidur N-75) 20 15 parts by weight of toluene as a solvent and 36 parts by weight of MIBK mixed and stirred are coated on the surface protective layer, dried at 70 ° C. for 5 minutes, and a 10 μm-thick yellow transparent light incident side holding layer Got.
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, Tokushi Co., Ltd. white colorant (trade name, AR-9127W) 9 parts by weight, Nippon Polyurethane Industry Co., Ltd. isocyanate-based crosslinking agent (Product name, Coronate L) was added to 0.5 parts by weight, and 16.1 parts by weight of ethyl acetate as a solvent was added and stirred and mixed to form a pressure-sensitive adhesive layer having a thickness of 41 μm.

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
Sumitomo Bayer Urethane Co., Ltd. has a holding layer on the light incident side with 100 parts by weight of acrylic resin (trade name RS-3000) manufactured by Onuki Ai Co., Ltd. and 120 parts by weight of color base (trade name AR-4300) manufactured by Tokushi Co. 70 parts by weight of a company-made isocyanate-based crosslinking agent (trade name, Sumidur N-75), 26 parts by weight of toluene as a solvent, and 61 parts by weight of MIBK were applied on the surface protective layer, and 70 A toluene solution having a non-volatile content of 20% by weight of a vinylcyclopentanorbornene resin (trade name, ARTON FX4727) manufactured by JSR Corporation between the holding layer on the focus forming layer side and a thickness of 10 μm after drying at 5 ° C. for 5 minutes. A retroreflective sheet was obtained in the same manner as in Example 1 except that a destructive layer having a thickness of about 0.5 μm was used.

Example 4
In Example 1, the coating solution for the surface protective layer was 100 parts by weight of an acrylic resin solution (trade name, RS-1200) manufactured by Enki Aika Chemical Co., Ltd., and a color base (trade name, AR-N- 4100) to 26 parts by weight, methylated melamine resin solution (trade name, Nicalak MS-11) manufactured by Sanwa Chemical Co., Ltd. to 14 parts by weight, cellulose derivative (trade name, CAB) 4 manufactured by Special Colorant Co., Ltd. 0.5 parts by weight of UV absorber (trade name, Seasoap 103) manufactured by Sipro Kasei Co., Ltd. is 0.04 weight of leveling agent (trade name, BYK-300) manufactured by Big Chemie Japan Co., Ltd. In a part, 0.12 part by weight of a catalyst manufactured by Dainippon Ink & Chemicals, Inc. (trade name, Beccamin P-198) and a solvent having a ratio of MIBK / toluene = 8/2 is used. Add 1 part by weight, mix with stirring, and use 100 parts by weight of acrylic resin (trade name RS-3000) manufactured by Akiai Co., Ltd. as the coating solution for the holding layer, and color base (trade name AR -4300) to 120 parts by weight, Sumitomo Bayer Urethane Co., Ltd. isocyanate-based cross-linking agent (trade name, Sumidur N-75) to 20 parts by weight, toluene as a solvent to 26 parts by weight, and MIBK to 61 parts by weight What was stirred was applied onto the surface protective layer, dried at 100 ° C. for 5 minutes, and a retroreflective sheet was obtained in the same manner as in Example 1 except that only one layer having a thickness of 23 μm was obtained and a retaining layer was obtained.

Example 5
Retention layer coating solution: 100 parts by weight of RS-3000, 113 parts by weight of Tokushi Color Base (trade name AR-6300), 21 parts by weight of Sumidur N-75, 25 parts by weight of toluene A retroreflective sheet was obtained in the same manner as in Example 4, except that 59 parts by weight of MIBK was mixed and stirred and applied onto the surface protective layer.

Comparative Example 1
A retroreflective sheet was obtained in the same manner as in Example 3 except that the breaking layer of vinylcyclopentanorbornene resin was not provided.

Comparative Example 2
The surface protective layer is the same as in Example 2, and the coating liquid composition of the holding layer is mixed with 100 parts by weight of an acrylic resin (trade name RS-3000) manufactured by Onuki Ai Co., Ltd., and an isocyanate cross-linking agent manufactured by Sumitomo Bayer Urethane Co., Ltd. A retroreflective sheet was obtained in the same manner as in Example 4, except that 12 parts by weight of Sumijoule N-75), 9 parts by weight of toluene as a solvent, and 23 parts by weight of MIBK were mixed and stirred.

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

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 Print layer 3a, 3b, 3d Holding layer or destruction layer 3c Destruction 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)

At least the surface protective layer, one or more holding layers that hold the glass spheres, a glass sphere, a focus forming layer, and a surface protective layer composed of a specular reflection layer and one or more holding layers, a hue different from at least the other layers In the encapsulated lens type retroreflective sheet provided with the above layer, the holding layer of the retroreflective sheet is colored in two or more different colors, and any one of the two or more holding layers is destructive. Or when a destructive layer is provided between the glass bulb and the holding layer and / or between the two holding layers, and when the retroreflective sheet attached to the substrate is peeled from the substrate, A retroreflective sheet characterized in that the hue under visible light before and after peeling differs by 0.05 or more in xy δ as measured by an XYZ color measurement method.