JPH0843615A - Retroreflection sheet - Google Patents

Abstract

PURPOSE:To provide an excellent retroreflection sheet which can avoid such problems as swelling of the sheet to produce appearance defects or peeling of the film even when the sheet is sticked to such a body that produces gas or the like by volatilization of a residual solvent or water content adsorbed or by chemical reaction. CONSTITUTION:This retroreflection sheet consists of a retroreflection element layer 8, adhesive layer 6 on the back of the retroreflection element, and release base 7 on the back of the adhesive layer 6. The adhesive layer 6 has <=10mm/1000min holding strength at 100 deg.C and has >=50% wettability to a polycarbonate resin plate in 30min after sticking.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retroreflective sheet useful for signs such as road signs and construction signs, license plates for automobiles and motorcycles, safety materials such as life preserver clothes, and particularly polycarbonate resin ( The present invention relates to a retroreflective sheet useful for sticking to an adherend such as a plate (hereinafter sometimes abbreviated as PC) plate or a fiber reinforced resin (hereinafter sometimes referred to as FRP) plate that easily generates gas.

[0002]

2. Description of the Related Art Conventionally, a retroreflective sheet that retroreflects light toward a light source is well known, and the sheet is used in the above-mentioned fields of application by utilizing its retroreflective property. As a result, since the excellent visibility at night based on the retroreflective performance of the retroreflective sheet has been widely recognized, the retroreflective sheet has come to be widely used in various fields other than the above.

Accordingly, in addition to the adherend made of metal such as an aluminum plate and an iron plate which has been generally used as a pasting base material for the retroreflective sheet, acrylic resin, polyester resin, polyethylene resin, polypropylene resin,
It has been desired to be able to adhere even to adherends using various resins such as vinyl chloride resin, PC, FRP and urethane resin. The adherend using these resins (hereinafter, also referred to as “resin adherend” in some cases) is different from the metal adherend that has been generally used in the past, depending on the type of resin used and its molding. It has various characteristics depending on the method. Therefore, in a retroreflective sheet to be attached to a resin adherend, it is important to select an adhesive suitable for the resin used, and various problems may occur if this adhesive is selected improperly.

Above all, there are many resin adherends that generate gas and the like from the adherend, and when a normal retroreflective sheet is attached to the resin adherend which generates these gases and the like, The retroreflecting sheet swells due to the generated gas or the like, resulting in a remarkable poor appearance. Further, in a severe case, there is a problem that the retroreflective sheet is peeled off, which is a big problem.

For example, when the adherend is formed by molding a resin containing a solvent by means such as painting, a small amount of solvent usually remains in the adherend even after the molding. It is released into the atmosphere as a gaseous substance from the surface of the adherend over time. Further, for example, even when the adherend uses a resin that generates a gas by a chemical reaction during molding, the gas remaining in the adherend or the gas generated by the unreacted resin due to a reaction over time And the like may be released into the atmosphere from the surface of the adherend. Further, for example, when the adherend is made of a resin that easily contains water or the like, the moisture is released from the surface of the adherend to the atmosphere over time as a liquid or as a vaporous gaseous substance. Sometimes.

When a retroreflective sheet is attached to an adherend which generates these gases or the like, the generated gas or the like cannot be released into the atmosphere, so that the adhesive layer of the retroreflective sheet and the adherend are adhered to each other. Will accumulate on the interface and the like, resulting in blisters on the retroreflective sheet, and in severe cases, peeling troubles will occur.

Conventionally, several attempts have been made to improve such troubles.
For example, attempts have been made to suppress the generation of gas or the like from the adherend by using an adhesive layer having a good adhesive force to the adherend. However, according to the study of the present inventors, only by improving the adhesive force of the adhesive layer to the adherend, it is possible to temporarily suppress the generation of blisters, but the generation of gas or the like over a long period of time. It has been found that it is very difficult to suppress, and consequently blistering of the retroreflective sheet cannot be prevented.

Further, for example, a special layer having a large number of voids capable of transmitting gas or the like is provided in or on the adhesive layer, and the gas or the like is trapped by this layer, or this special layer is provided. Attempts have also been made to release gases and the like into the atmosphere through the layers. However, in this attempt, by providing this special layer, the thickness of the retroreflective sheet becomes thicker and the workability etc. deteriorates.
It is very complicated to manufacture a special layer, and it is also disadvantageous in terms of cost, or if such a special layer is provided in the adhesive layer, the adhesive strength is reduced. ing.

[0009]

An object of the present invention is to provide an excellent retroreflective sheet having a simple structure and excellent anti-blurring property without using the above-mentioned special void-containing layer in the adhesive layer. To provide.

As a result of various studies on the adhesive layer of the retroreflective sheet, the present inventors have found that the retroreflective sheet has an excellent anti-blurring property by providing the retroreflective sheet with an adhesive layer having excellent cohesive force and wettability. The present invention has been completed, and the present invention has been completed.

[0011]

Thus, in accordance with the present invention, a layer of retroreflective element, an adhesive layer located on the backside of the retroreflective element, and a release group located on the backside of the adhesive layer. In a retroreflective sheet consisting of
Holding power at 100 ° C is 10mm / 1000min or less, and after 30 minutes from the wetting of the polycarbonate resin plate
Provided is a retroreflective sheet having a content of 50% or more.

The retroreflective sheeting of the present invention will be described in more detail below.

In the retroreflective sheeting of the present invention, it is necessary that the adhesive layer has a holding power at 100 ° C. of 10 mm / 1000 min or less, and the holding power is 5 mm / 1000 min or less, particularly 2 mm / 1000 min or less. Is preferred. If an adhesive layer having a holding power exceeding the upper limit is used, excellent anti-blurring property cannot be obtained. The generation of gas, etc. usually tends to increase as the temperature of the adherend becomes higher, while the adhesive layer usually becomes softer and its cohesive force decreases as the temperature of the adherend decreases, and the generation of gas, etc. The function to suppress blisters based on is tending to decline. Therefore, it is particularly important to increase the cohesive force of the adhesive layer at high temperature in order to obtain excellent anti-blurring property, and for that purpose, the holding force of the adhesive layer at 100 ° C is 10 mm / 1000 min or less. You can do it.

In the retroreflective sheeting of the present invention, the adhesive layer must have a wetness of 50% or more 30 minutes after the wetness is applied to the PC plate, and preferably the wettability value is 70%.
% Or more, and more preferably 90% or more. If the wetting value is less than the lower limit value of 50%, excellent anti-blurring property cannot be obtained in the initial stage of application. The generation of gas, etc.
Immediately after the adherend has been molded, the amount of generation is usually the largest and tends to decrease with time. Therefore, the retroreflective sheet attached to the adherend tends to cause blisters immediately after attachment, and therefore, in order to obtain a retroreflective sheet having excellent blistering resistance, the blisters immediately after attachment are It is important to prevent. For that purpose, it is important to improve the wetting property of the adhesive layer with respect to the adherend, and as a measure of the wetting property, the wetting property after 30 minutes from attaching the adhesive layer to the PC plate may be 50% or more.

The wettability is a transparent P with a surface smoothness of 850 seconds.
Attach the retroreflective sheet to the C plate using a 2 kg roller, and after 30 minutes, observe the adhesive layer of the retroreflective sheet from the side of the PC plate, where the PC plate and the adhesive layer are completely wet. It can be measured by determining the area% of.

The adhesive strength of the adhesive layer is not particularly limited, but a higher adhesive strength tends to obtain a more preferable anti-blurring effect, and after 60 minutes after the retroreflective sheet is attached to the PC board. The adhesive strength of is preferably 200 g / 25 mm or more, more preferably 300 g / 25 mm or more, 500 g /
More preferably, it is at least 25 mm.

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 power, and a weight average molecular weight (hereinafter, abbreviated as Mw). There are more than 500,000 resins, more preferably 600,000 to 1,000,000 resins, and even more preferably 800,000 to 100
It is preferable to use any resin. Among them, a resin obtained by crosslinking reaction of a resin having a Mw of 500,000 or more having a functional group with a crosslinking agent such as an isocyanate crosslinking agent is most suitable because a particularly excellent holding power is obtained.

The type of resin forming the adhesive layer is not particularly limited, and a resin used as a usual resin for adhesives may be used, for example, an acrylic resin,
Silicon-based resin, rubber-based resin, phenol-based resin or the like is used. Above all, an acrylic resin or a silicone resin having excellent weather resistance and good adhesive properties is preferably used.

The thickness of the adhesive layer is not particularly limited as long as it has a holding force as described above and is excellent in wetting characteristics, but a thickness of about 20 to 60 μm is usually used. It is preferably 30 to 50 μm.

The release base material used in the retroreflective sheeting of the present invention is not particularly limited, and ordinary release paper, release film and the like may be used, but in order to obtain more preferable wetting characteristics, the release group is as much as possible. It is preferable to use a material having a high smoothness, a release base material having a smooth surface with a smoothness of 1000 seconds or more is preferably used, and most preferably a silicone-treated polyethylene terephthalate (hereinafter
A release substrate (sometimes abbreviated as PET) is used.

The retroreflective sheeting of the present invention can be manufactured using conventionally known materials and methods, except that the adhesive layer is formed as a layer having the holding power and the wetting property described above. , The adhesive-forming resin dissolved in a solvent, the additive solution such as a cross-linking agent is added and sufficiently stirred, the mixture is coated on the release substrate by direct coating method, reverse coating method, etc. The solvent is removed to form the adhesive layer. And a layer of a retroreflective element such as a separately known conventionally known open lens type retroreflective element, encapsulated lens type retroreflective element, capsule lens type retroreflective element, or capsule cube corner type retroreflective element. Laminating sheets having,
It can be easily manufactured by using a method such as laminating.

FIG. 1 is a schematic sectional view showing the configuration of an enclosed lens type retroreflective sheet which is an embodiment of the retroreflective sheet of the present invention. In FIG. 1, reference numeral 8 is a layer of an enclosed lens type retroreflective element, a surface layer 1 made of a transparent resin layer or the like for imparting abrasion resistance to the surface, glass having a refractive index of about 2.1 to 2.3 that functions as a lens. A microsphere lens layer 2 made of spheres, a coupling layer 3 made of transparent resin or the like for coupling and fixing the microsphere lenses, and a light reflection layer 5 such as an aluminum vapor deposition film for forming an optical focus position of the lens. The space layer 4 is made of transparent resin or the like. An adhesive layer 6 having excellent holding power and excellent wetting suitability is formed on the back surface of the layer of the retroreflective element, and a release base material 7 for protecting the adhesive layer is provided on the back surface of the adhesive layer. Has been.

Since the retroreflective sheeting of the present invention has good adhesive layer holding power and excellent wetting characteristics, it can be adhered to an adherend using a resin or the like which generates gas or the like. Even without blistering, it is possible to maintain an excellent appearance for a long time.

[0024]

EXAMPLES The present invention will be specifically described with reference to Examples and Comparative Examples. The measuring methods used in Examples and Comparative Examples are as follows.

(1) Holding force All the measurements except JIS Z- except that the time from pressure bonding to measurement was 1 hour and the holding force was measured 1000 minutes after heating at 100 ° C.
It carried out according to 0237.

(2) Wetting characteristics A transparent P with a smoothness of 850 seconds was prepared by cutting the sample into 50 mm x 50 mm.
After sticking to the C plate with a 2 kg roller, the plate was left at 23 ° C. for 30 minutes, and the ratio of the area in which the adhesive of the sample was in contact with the PC plate was measured visually from the PC plate side.

(3) Three samples having an adhesive strength of 25 mm × 250 mm were prepared and bonded to a PC board using a 2 kg roller and left at 23 ° C. for 1 hour, then 300 mm / min
The sample was peeled off in the direction of 180 ° at the speed of and the adhesive strength was measured. All measurements were made in accordance with JIS Z-0237.

(4) Smoothness of peeling base material The measurement surface of the test piece is set to a standard surface, the back surface is pressed with a specified pressure, the inside of the container is decompressed by a vacuum pump, and the mercury is 10 to 20 mm from the marked line of 380 mm. When the temperature reached the upper limit, the cock was closed and the switching cock was turned to measure the passage time of 1 ml. JIS measurement
It carried out according to P-8119. Measuring equipment: Beck's smoothness tester

(5) Evaluation method for blisters A sample of 25 mm × 75 mm is attached to a PC plate or an FRP plate with a 2 kg roller, left at 23 ° C. for 30 minutes, heated at 70 ° C. for 24 hours, and visually checked for blisters. It was observed and judged. The evaluation was based on the following scores. 5: No blistering occurred. 4: 1 to 10 blisters having a maximum diameter of less than 2 mm were generated. 3: Ten or more blisters having a maximum diameter of less than 2 mm were generated. 2: Blisters having a maximum diameter of 2 to 5 mm occurred. 1: Blisters having a maximum diameter of more than 5 mm occurred.

Example 1 First, a layer of a retroreflective element was prepared by the following procedures A to C. A. Polyester resin "Q-203" [trade name; manufactured by Mitsui Toatsu Chemicals, Inc.] 80 parts by weight, also polyester resin "P-
647BC "[trade name; manufactured by Mitsui Toatsu Chemicals, Inc.] 20 parts by weight, melamine-based cross-linking agent" NICALAC MS-11 "[trade name; manufactured by Sanwa Chemical Co., Ltd.], 8 parts by weight, cellulosic release agent" CAB "
[Brand name; manufactured by Special Colorants Industry Co., Ltd.] 8 parts by weight, leveling agent liquid [acrylic leveling agent "RL-4" {Brand name: manufactured by Mitsui Toatsu Co., Ltd.} with methyl isobutyl ketone (MIBK) 3.2 parts by weight diluted with a solid content of 10% by weight, a defoaming agent liquid [silicone defoaming agent "TSF-4445" {trade name; manufactured by Toshiba Silicone Co., Ltd.} with MIBK having a solid content of 10 parts by weight %)] 0.055 parts by weight, MIBK 39.2 parts by weight, and toluene 16.8 parts by weight were stirred and mixed to prepare a uniform blended liquid. This compounded liquid was applied onto PET having a thickness of about 75 μm, and most of the solvent was removed to form a transparent resin surface layer having a thickness of about 26 μm.

B. Acrylic resin "ST-310" [trade name;
Special Colorants Industry Co., Ltd.] 100 parts by weight, cross-linking agent “Duranate D-201” [trade name; hexamethylene diisocyanate (HMDI) type; Asahi Kasei Co., Ltd.] 11 parts by weight, cross-linking agent “Sumijour N-” 75 "[Product name: HMDI system; Sumitomo Bayer Urethane Co., Ltd.] 1 part by weight, MIBK 19.1 parts by weight, toluene 8.1
Parts by weight and petroleum hydrocarbon solvent "Supersol
1500 "[trade name; manufactured by Mitsubishi Petroleum Co., Ltd.] 16 parts by weight of a mixed solution is stirred and mixed onto the surface of the transparent resin surface layer prepared in A, and most of the solvent is removed to obtain a thickness of about A 21 μm tie layer was formed.

Beads “K-43” having an average particle size of about 40 μm and a refractive index of about 2.2 on this bonding layer [trade name; Nippon Electric Glass Co., Ltd.
The glass beads were embedded in a single layer in a dense manner, and heat and pressure were applied to the glass beads so that about 1/2 of the diameter was embedded in the bonding layer.

C. Acrylic resin "ST-400" [trade name;
Special Colorants Industry Co., Ltd.] 100 parts by weight, 5.5 parts by weight of melamine-based cross-linking agent "Nikalac MS-11", 31.8 parts by weight of MIBK, and 47.7 parts by weight of toluene are mixed with stirring to prepare the above bonding layer and glass. The transparent layer having a thickness of about 14 μm was formed by coating on the beads to remove most of the solvent.

Furthermore, an acrylic resin "ST
-400 "20 parts by weight, acrylic resin" ST-540 "[Product name;
Special Colorants Industry Co., Ltd.) 80 parts by weight, melamine-based cross-linking agent "Nikalac MS-11" 5.5 parts by weight, MIBK 46.6 parts by weight, and
Apply 69.9 parts by weight of toluene with stirring and mix,
Most of the solvent was removed to form a space layer with a total thickness of about 21 μm. The space layer was formed in a shape along the spherical surface of the glass beads. After that, aluminum was vapor-deposited on the space layer to form a light-reflecting layer having a thickness of about 0.3 μm.

Next, as an adhesive resin, an acrylic resin "Nissetsu KP-1749" having an Mw of about 800,000 and a solid content of 30% by weight.
[Nippon Carbide Industry Co., Ltd .: trade name] 100 parts by weight, ethyl acetate 20 parts by weight, and crosslinking agent "Nissetsu CK-401"
[Product name: HMDI type; manufactured by Nippon Carbide Industry Co., Ltd.] 3 parts by weight are mixed by stirring, and this is a PET release substrate "RFT-100" with a smoothness of 1900 seconds [Product name: San-A Chemical Co., Ltd.] Manufactured by the above method and most of the solvent was removed to form an adhesive layer having a thickness of about 35 μm.

Next, the layers of the retroreflective element produced by the above-mentioned procedures A to C and the adhesive layer were laminated so that the light reflection layer adheres to the adhesive layer to produce the retroreflective sheet of the present invention. . The obtained retroreflective sheet sufficiently satisfied the object of the present invention as shown in Table 1.

Example 2 All of Example 1 except that the release base material was a paper release base material “E2P-L” having a smoothness of 2100 seconds [trade name; manufactured by Lintec Co., Ltd.].
A retroreflective sheet was produced in the same manner as in. The obtained retroreflective sheet satisfied the object of the present invention as shown in Table 1.

Example 3 The amount of "Nisetsu CK-401", which is a cross-linking agent for the adhesive layer, was 10.5 parts by weight, and the release base material was a PET release base material "PET 7511" having a smoothness of 3500 seconds [trade name]. Manufactured by Lintec Co., Ltd.], and a retroreflective sheet was produced in the same manner as in Example 1. The obtained retroreflective sheet sufficiently satisfied the object of the present invention as shown in Table 1.

Example 4 All the examples except that the adhesive resin was an acrylic resin "Nissetsu KP-1477" [trade name; manufactured by Nippon Carbide Industry Co., Ltd.] having a Mw of about 750,000 and a solid content of 35% by weight. A retroreflective sheet was produced in the same manner as in 1. The obtained retroreflective sheet satisfied the object of the present invention as shown in Table 1.

Example 5 The adhesive resin was an acrylic resin "Nissetsu SX-4096" [trade name; manufactured by Nippon Carbide Industry Co., Ltd.] having a Mw of about 500,000 and a solid content of 40% by weight, and the amount of ethyl acetate added. A retroreflective sheeting was produced in the same manner as in Example 1 except that the amount was 60 parts by weight. The obtained retroreflective sheet satisfied the object of the present invention as shown in Table 1.

Comparative Example 1 The adhesive resin was an acrylic resin "Nissetsu KP-802L" [trade name; manufactured by Nippon Carbide Industry Co., Ltd.] having a Mw of about 480,000 and a solid content of 39% by weight, and a crosslinking agent "Nissetsu CK". -401 "was 1 part by weight and ethyl acetate was 60 parts by weight, and a retroreflective sheet was produced in the same manner as in Example 1. As shown in Table 1, the obtained retroreflective sheet could not suppress blistering.

Comparative Example 2 "Sepak", a release base material of paper having a smoothness of 250 seconds
A retroreflective sheet was produced in the same manner as in Example 4 except that the product name was manufactured by Oji Kako Co., Ltd. As shown in Table 1, the obtained retroreflective sheet could not suppress blistering.

[0043]

[Table 1]

[0044]

INDUSTRIAL APPLICABILITY The present invention is a retroreflective sheet comprising a layer of a retroreflective element, an adhesive layer located on the back surface of the retroreflective element, and a release substrate located on the back surface of the adhesive layer. In the above, the adhesive layer is characterized by having a holding force of a specific value or less and a specific wetting behavior with respect to the polycarbonate resin plate.

As a result, gas or the like is generated by volatilization of residual solvent or adsorbed water, chemical reaction, etc. without using complicated and problematic means such as providing a large number of gas permeable voids in the adhesive layer. It is possible to provide an excellent retroreflective sheet capable of avoiding the occurrence of troubles such as the retroreflective sheet swelling, resulting in poor appearance and peeling even when it is attached to an adherend.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional configuration diagram of an encapsulated lens type retroreflective sheet that is one embodiment of the retroreflective sheet of the present invention.

[Explanation of symbols]

 1 ・ ・ Surface layer 2 ・ ・ Microsphere lens 3 ・ ・ ・ ・ ・ ・ Coupling layer 4 ・ ・ ・ ・ Space layer 5 ・ ・ ・ ・ ・ ・ Light reflecting layer 6 ・ ・.... Adhesive layer 7 ... Release base material 8 ... Encapsulated lens type retroreflective element layer

Claims (6)

[Claims] 1. A retroreflective sheet comprising a layer of a retroreflective element, an adhesive layer located on the back surface of the retroreflective element, and a release substrate located on the back surface of the adhesive layer, wherein the adhesion The holding power of the agent layer at 100 ℃ is 10mm / 1000min or less,
In addition, paste is attached to the polycarbonate resin plate.
A retroreflective sheet characterized by being 50% or more after 30 minutes. 2. The retroreflective sheet according to claim 1, wherein the adhesive force of the adhesive layer to the polycarbonate resin plate is 200 g / 25 mm or more 60 minutes after the application. 3. The retroreflective sheet according to claim 2, wherein the adhesive layer is a resin layer obtained by crosslinking a resin having a weight average molecular weight of 500,000 or more by a crosslinking reaction. 4. The retroreflective sheet according to claim 1, wherein the adhesive layer is made of an acrylic resin or a silicone resin. 5. The retroreflective sheet according to claim 1, wherein the release substrate has a smooth surface with a smoothness of 1000 seconds or more. 6. The retroreflective sheet according to claim 5, wherein the release substrate is a silicone-treated polyethylene terephthalate film.