WO2005068726A1

WO2005068726A1 - Abrasion resistant marking sheet

Info

Publication number: WO2005068726A1
Application number: PCT/US2005/001342
Authority: WO
Inventors: Hidetoshi Abe; Hiroshi Tsuji
Original assignee: 3M Innovative Properties Company
Priority date: 2004-01-13
Filing date: 2005-01-13
Publication date: 2005-07-28
Also published as: JP4524117B2; JP2005199463A

Abstract

To provide a structural material useful as a material for a flooring marking sheet excellent in abrasion resistance and stripping properties at low temperatures. A marking sheet having an elongation percentage of 20% or more under an environment of 5°C (in accordance with JIS Z 0237, 2000), said marking sheet comprising (a) an adhesive-applied film which permits images to be formed thereon, and (b) a glass fiber-containing transparent resin layer which protects the formed images.

Description

ABRASION RESISTANT MARKING SHEET Background The present invention relates to a marking sheet with improved stripping properties at low temperatures and excellent in abrasion resistance and anti-slip properties. In particular, the invention pertains to an abrasion resistant marking sheet useful as a decorative image-printed marking sheet. In the field of advertisement, a variety of graphic arts are employed for the presentation of various pieces of information and for decorative purposes. For example, JP-A-2002-505453 (corresponding to WO099/44840) discloses an outdoor advertising system for the purpose of attaching graphic arts to concrete walls or asphalt planes outdoors. This publication teaches that it is desirable for pedestrians to walk in safety on such graphic arts displayed outdoors, for example without slipping thereon, and therefore that the surfaces of such graphic arts should have predetermined resistance to slip (anti- slip properties). To improve such anti-slip properties, embossing or surface-roughing treatments are made on the surfaces of the image-protective layers of the graphic arts, or abrasive particles are embedded and bound in the exposed surfaces of the binder layers thereof. Japanese Patent Registration No. 2753697 discloses the use of resin sheets as flooring materials, i.e., the use of transparent vinyl chloride resin sheets containing glass fibers, and the production process thereof. According to this publication, scratch resistance and abrasive resistance are imparted to the resin sheets by forming the resin sheets from the dispersions of glass fibers in plasticized vinyl chloride resins. This publication does not disclose the use of glass fibers in resins other than the vinyl chloride resins, or the properties of products obtained from such vinyl chloride resins containing glass fibers. JP-A-9-52209 discloses a flooring material having a short fiber-containing surface layer. According to this publication, glass fibers are kneaded into a PNC synthesized resin matrix to thereby improve the dimensional stability and the abrasive resistance. However, this publication does not disclose any application of the flooring material to an adhesive- applied marking sheet or the stripping properties thereof at low temperatures. JP-A-9-272802 discloses a low abrasive plastic molding material comprising a polyolefm resin which contains a lubricant and glass fibers therein. This resin containing such a lubricant is not suitable as a flooring material, because the lubricant is used to lower the frictional properties. This is apparent from the description that this molding material is subjected to gears, teethed rack, bearings, driving unit, rolls, chains and sliding members. Further, this publication has no disclosure on the application of the above molding material to an adhesive-applied marking sheet.

Summary As is understood from the foregoing, there hitherto have been known marking sheets which comprise surface layers formed from thermoplastic resins kneaded with fibers to improve the anti-slip properties and abrasion resistance, and thus which are suitable for use as flooring materials. Flooring marking sheets are attached to the floors of stations, department stores, etc. on which lots of pedestrians walk, and thus are expected to have abrasive resistance. In general, such marking sheets are stripped off the floors every several months so as to exchange the designs of the graphic arts. In particular, the stripping of the marking sheets is hard at low temperatures. For example, a marking sheet formed from a vinyl chloride resin having glass fibers kneaded therein has a problem in workability, because it easily ruptures when stripped off at low temperatures after having been attached to a floor for several months. The present application is directed to a structural material which has abrasion resistance and anti-slip properties and which can maintain stripping properties at low temperatures and thus which is useful as a marking sheet for a floor or the like. For example, a marking sheet which shows excellent elongation even at low temperatures is effective to improve the stripping properties at low temperatures. Additionally, a surface protective layer formed from a polypropylene resin or an acrylic resin having glass fibers kneaded therein is excellent in light transmittance and abrasion resistance, and that the elongation percentage of a marking sheet at low temperatures is improved when such a surface protective layer is combined with an image- formed receptor film. The foregoing problems can be solved by a marking sheet which comprises

(a) an adhesive-applied film which permits images to be formed thereon, and

(b) a glass fiber-containing transparent resin layer for protecting the formed images on the film; and which show an elongation percentage of 20% or more at 5°C in accordance with JIS Z 0237: 2000. The present invention also relates to a marking sheet comprising a glass fiber- containing polypropylene resin layer or a glass fiber-containing acrylic resin layer as the above glass fiber-containing resin layer.

Brief Description of the Drawings Fig. 1 schematically shows one example of the marking sheet of the present invention. Detailed Description A marking sheet according to the present invention is found to be superior in abrasive resistance and anti-slip properties to the marking sheets containing no glass fiber, when attached to floors on which pedestrians walk. The marking sheet of the present invention shows a sufficient elongation percentage at low temperatures, as compared with the conventional marking sheets. Further, since the total light transmittance of the adhesive-applied transparent resin layer which protects the images is high, the surface of the film can be protected without impairing the quality of the images. Therefore, the marking sheet of the present invention is useful, for example, as a table top advertising image-printed marking sheet. The marking sheet of the present invention shows an improved elongation percentage at low temperatures as compared with the conventional marking sheets, and therefore hardly ruptures when stripped off a floor under an environment of low temperatures after the use on the floor (stripping properties at low temperatures). The marking sheet of the present invention comprises (a) an adhesive-applied film which permits images to be formed thereon, and (b) a glass fiber-containing transparent resin layer for protecting the formed images on the film. There is no particular limit in selection of a material for the adhesive-applied film which permits images to be formed thereon, in so far as the material can have elongating properties at low temperatures. Preferably, a polyolefin resin film is suitably used. Examples thereof include films of polyethylene, polypropylene and their blends or copolymers. A preferred example of the marking sheet of the present invention will be illustrated with reference to Fig. 1. Fig. 1 schematically shows one example of the marking sheet of the present invention. An image layer (2) is formed on the base film layer (3) of the marking sheet (100). The base film layer (3) has a surface (31) and a reverse (32). The surface (31) of the base film layer (3) receives a colorant, i.e. toner to form the image layer (2). The toner on the surface (31) of the base film layer forms the image visible from the uppermost surface (41) of the protective film (4) through the protective film (4). To clearly recognize the image layer, a white base film layer is preferably used as the base film layer (3). The white base film layer is formed from a resin mixed with a white pigment such as titanium oxide, or is prepared by coating the surface of the base film with a white pigment. The reverse (32) of the base film (3) has an adhesive layer (5) fixedly applied thereon. Although not shown herein, release paper, a release film (6) or the like is laminated on the adhesive surface (51) of the adhesive layer (5) so as to protect the adhesive surface. An adhesive for the adhesive layer (5) is generally a pressure sensitive adhesive containing an adhesive polymer, although not limited thereto. As such a pressure sensitive adhesive layer, a single-layer pressure sensitive adhesive film and a double coated sheet having two pressure sensitive adhesive layers on both sides, both of which contain adhesive polymers, are preferably used. To enhance the adhesion between the base film layer and the adhesive layer, the base film layer may be subjected to a physical pretreatment such a corona discharge treatment or a plasma discharge treatment, or a primer layer for facilitating the chemical bond may be applied to the base film layer, as required. The protective film (4) is adhered to the base film layer (1) having the image layer formed thereon, usually through an adhesive layer (40) on the protective film. The adhesive for the adhesive layer (40) on the protective film is usually a pressure sensitive adhesive containing an adhesive polymer, although not limited thereto. The pressure sensitive adhesive is advantageous, because the pressure sensitive adhesive can sufficiently fill and smoothen the unevenness formed by the toner on the surface (11) of the base film layer having the image formed thereon and can closely adhere the protective film (4) to the base film layer (1) without forming any bubble therebetween. Desirably, any bubble should not be left to remain, because the bubbles degrade the visibility of the image. A method for forming the image layer on the base film layer and a colorant for forming the image layer may be known ones. The colorant is usually toner or ink. For example, when toner is transferred to the base film layer to fonn an image, a conventional printing method is employed: the image is formed on the surface of the base film layer by transferring the toner thereto, hi case of electrostatic process toner printing, an image is temporarily printed on a tentative carrier, and then, the image is transferred to the base film layer. In this transfer method, an image is formed on a tentative carrier called a transfer medium, and the image is transferred to the reverse of a protective film by heating under a pressure. Thus, the image-printed protective film is completed. The toner for fonning the image comprises a binder resin and pigment particles dispersed therein. The binder resin may be at least one selected from the group consisting of, for example, vinyl chloride- vinyl acetate copolymers, acrylic resins and polyester resins, or may be a mixture of at least two selected therefrom. The details of the electrostatic process printing method are disclosed in, for example, JP-A-4-216562, JP-A- 11-513818, etc. The adhesive layer for attaching the marking sheet to a subjective article may be formed as follows. Firstly, a liner having a release face is prepared. A coating composition containing an adhesive polymer (i.e., an adhesive coating composition for forming an adhesive layer of an adhesive sheet) is applied to the release face of the liner and dried to form an adhesive layer. The liner is generally made of paper or a plastic film. A paper liner is made by laminating a release coating (or a release layer) such as a polyethylene coating, a silicone coating or the like on the surface of paper. When a silicone release coating is laminated on paper, an undercoating such as a clay coating, a polyethylene coating or the like is laminated on the paper, and then, the release coating is laminated thereon. For example, the adhesive layer is composed of a coating layer of an adhesive containing an adhesive polymer. One of preferred adhesives comprises an adhesive polymer and a crosslinking agent which crosslinks the adhesive polymer. The term

"adhesive polymer" herein referred to is a polymer which shows adhesive properties at a normal temperature (about 25°C). Examples of the adhesive polymer include acrylic polymers, polyurethanes, polyolefins, polyesters and the like. One of the syntheses of adhesive polymers is described, taking an acrylic polymer as an example. Firstly, an acrylic unsaturated acid (e.g., acrylic acid, methacrylic acid, itaconic acid, maleic acid or the like), or a polar (meth)acryl monomer such as acrylonitrile is prepared as a first monomer. The first monomer is mixed with an acrylic monomer as a second monomer to prepare a monomer mixture. As the second monomer, there can be used alkyl acrylate such as isooctyl acrylate, butyl acrylate, 2-methylbutyl acrylate, 2- ethylhexyl acrylate, isononyl acrylate or the like. The monomer mixture thus prepared is polymerized by a conventional polymerization method such as solution polymerization, emulsion polymerization, bulk polymerization or the like to thereby synthesize an adhesive polymer having a predetermined molecular weight. When a cross-linking agent is used to crosslink the adhesive polymer, the amount of the cross-linking agent to be added is generally 0.02 to 2 mass parts, preferably 0.03 to 1 mass parts based on 100 mass parts of the adhesive polymer, although it depends on the kind of a cross-linking agent to be used. Examples of the crosslinking agent include isocyanate compounds, melamine compounds, poly(meth)acrylate compounds, epoxy compounds, amide compounds, and bisamide compounds [bisaziridine derivatives of dibasic acids such as isophthaloylbis(2-methylaziridine) and the like]. The thickness of the adhesive layer is usually 20 to 100 μm, preferably 25 to 80 μm. In the meantime, the pressure sensitive adhesive layer may contain additives such as an adhesivity-imparting agent, fine elastic balls, fine adhesive polymer balls, crystalline polymer, inorganic powder, UN-absorbant and the like, to such an extent that the effect of the present invention is not impaired. The marking sheet of the present invention comprises (b) the glass fiber-containing transparent resin layer for protecting the formed images, in addition to the above adhesive- applied film which permits the images to be formed thereon. This transparent resin layer is not particularly limited, in so far as the object of the present invention is not impaired. A preferred resin for use in such a transparent resin layer is a resin having a Tg of 80°C or lower in view of the stripping properties at low temperatures. Above all, polypropylene resins or acrylic resins are preferably used. Preferably, this resin layer is disposed in the marking sheet of the present invention by laminating a film formed from a resin composition containing glass fibers, on the above film which permits the images to be formed thereon. Otherwise, the resin composition containing glass fibers may be coated on the above film having the images formed thereon. The protective layer (e.g., a protective film) to be used in the present invention has light transmittance as a whole. The light transmittance thereof is usually 60% or more, preferably 70% or more, most preferably 80% or more. The term "light transmittance" herein referred to means total light transmittance which is measured relative to light with a wavelength of 550 mn, using a spectrophotometer, or a color meter having a function as a photometer. The thickness of the protective layer is usually 10 to 300 μm, more preferably 20 to 200 μm. The adhesive for use in adhering the protective layer to the film having the image layer formed thereon is not particularly limited. Preferably, an acrylic adhesive is used in view of transparency and weather resistance. The thickness of the adhesive layer is usually 10 to 100 μm, particularly 20 to 50 μm. The marking sheet of the present invention produced as above shows an elongation percentage of 20% or more under an environment of 5°C (according to JIS Z 0237: 2000), and normally shows 1,000% or less. When the marking sheet has such a structure and has an image layer formed thereon is attached to a floor, the marking sheet shows excellent stripping properties at low temperatures. Preferably, the elongation percentage of the marking sheet is 20 to 500% under an environment of 5°C. To achieve this elongation percentage under the environment of 5°C, proper selection of an image-printed film, a transparent protective layer and an adhesive layer is important.

Examples: Hereinafter, the present invention will be described in more detail by way of Examples, which should not be construed as limiting the scope of the present invention in any way. The properties of the film, etc. used in Examples were evaluated as follows. Transmittance A color meter (∑90 manufactured by Nippon Denshoku K.K.) was used to measure the total light transmittance of a transparent protective layer (e.g. a film). The total light transmittance is determined by the following equation: (Total light transmittance) = (parallel transmittance) + (diffuse transmittance) Evaluation (see Table 1): Good: The image visually recognized through the transparent protective layer is clear. Poor: The image visually recognized through the transparent protective layer is vague. Abrasion resistance Abrasion tests were conducted using a taper abrasion tester in accordance with JIS A 1453. The abrasion ring of S-42 was used under a load of 750 gf. A loss in the mass of the sheet after having undergone 100 rotations was measured. The number of rotations at which the adhesive was exposed and the number of rotations at which the image layer was exposed, provided that Urethane Clear was used as the protective layer, were counted. The calculation was made in terms of the thickness of 150 μm. (See Table 2). Anti-slip properties A marking sheet with a width of 1,200 mm and a length of 1,200 mm was attached to a floor and fully wetted with water. Then, an adult wearing safety shoes with black rubber soles walked on the above sheet and felt the sensitivity from the sheet. The anti- slip properties of the sheet were evaluated based on the following criteria: A: not slid B: partially slid C: slid

Xg RSAIII (manufactured by Rheometrix Scientific Inc.) was used to make measurement in the following modes: - Dynamic Temperature Ramp Test - Temperature-elevating rate: 5.0°C/min. - Frequency: 10 Hz - Stretch mode Sheet elongation percentage The elongation percentage of the sheet was measured according to the procedure regulated in JIS Z 0237: 2000: that is, the sheet was cut into strips with widths of 25 mm, and a tensile strength tester commercially available from ORIENTEC Corporation, Japan under the trade designation Tensilon RTC-1210A was used to grasp such strips at 100 mm intervals and pull the same at a pulling rate of 300 mm/min. under environments of 20°C and 5°C, respectively, to measure the elongation percentages of the strips. The maximum elongation was determined at a point of time when a whole of the marking sheet had ruptured. (See Table 2)

Workability at low temperatures Marking sheets were attached to a flooring material, and then stripped off under an environment of 5°C. A marking sheet which was stripped off without any rupture under the environment of 5°C was evaluated "Good", and a marking sheet which ruptured when stripped off was evaluated as "Poor". (See Table 2.)

Example 1

Preparation of a film having images formed thereon Scotch Print(R) 9512 system (an electrostatic process printer manufactured by 3M) was used to form digital images on Trident (a transfer medium manufactured by 3M). Next, Orca III(R) (a heat laminating machine manufactured by 3M) was used to heat- transfer the images to an acrylic adhesive-applied white polyolefin (polypropylene/polyethylene) film (SP4235C manufactured by 3M). The Orca III(R) was operated under the following setting conditions: The upper roll temperature: 135°C The lower roll temperature: 50°C Speed: 70 crn/min. Pressure: 60 psi An acrylic adhesive was applied with a thickness of 30 μm to a silicone-treated release paper, which was then laminated on a polypropylene resin film having glass fibers kneaded therein (PC 203 with a thickness of 150 μm, manufactured by BANDO CHEMICAL INDUSTRIES LTD) to obtain a transparent protective film. The transparent protective film was laminated on the above film having the images formed thereon at an ordinary temperature. The total light transmittance of the transparent protective film of Example 1 was 89%, which showed sufficient transparency. Thus, the visibility of the images seen through the transparent protective film was evaluated as "Good". The sheet of Example 1 showed 0.04 g of a loss in the mass, and the adhesive was exposed at 630 rotations. The time spent until the images were exposed after the abrasion of the transparent protective film proved that the abrasion resistance of the transparent protective film was improved due to the glass fibers kneaded into the film, i.e., that the above time was about 50% longer than the time spent for a polypropylene resin film containing no glass fiber (Comparative Example 1). The anti-slip properties of the sheet were good. The elongation percentages at 20°C and 5°C were 100% or more, respectively, which proved that the sheet had excellent elongation properties. The sheet was easily stripped off under an environment of 5°C, and thus, the workability of the sheet at low temperatures was evaluated as "Good".

Example 2 A sample of a sheet was made in the same manner as in Example 1, except that a white vinyl chloride resin film (ER010 manufactured by 3M) was used as a film on which images were formed. The total light transmittance of the transparent protective film was 89%, which showed sufficient transparency. Thus, the visibility of the images seen through the transparent protective film was evaluated as "Good". The sheet of Example 2 showed 0.04 g of a loss in the mass, and the adhesive was exposed at 630 rotations. The anti-slip properties of the sheet were good. The elongation percentages at 20°C and 5°C were 100% or more and 38%>, respectively, which proved that the sheet had excellent elongation properties. The sheet was easily stripped off under an enviromnent of 5°C, and thus, the workability at low temperatures was evaluated as "Good".

Example 3 A sample of a sheet was made in the same manner as in Example 1, except that an acrylic resin film having glass fibers kneaded therein (PC202 with a thickness 150 μm manufactured by BANDO CHEMICAL INDUSTRIES LTD) was used as a transparent protective film. The total light transmittance of the transparent protective film of Example 3 was 88%, which showed sufficient transparency. Thus, the visibility of the images seen through the transparent protective film was evaluated as "Good". The sheet of Example 3 showed 0.12 g of a loss in the mass, and the adhesive was exposed at 380 rotations. The time spent until the images were exposed after the abrasion of the transparent protective film proved that the abrasion resistance of the transparent protective film was improved due to the glass fibers kneaded into the film, i.e., that the above time was about 50%> longer than the time spent for an acrylic resin film containing no glass fiber (Comparative Example 3). The anti-slip properties of the sheet were good. The elongation percentages at 20°C and 5°C were 40% and 100% or more, respectively, which proved that the sheet had excellent elongation properties. The sheet was easily stripped off under an environment of 5°C, and thus, the workability at low temperatures was evaluated as "Good". Comparative Example 1 A sample of a sheet was made in the same manner as in Example 1, except that a polypropylene resin film with a thickness of 100 μm containing no glass fiber was used as the transparent protective film. The total light transmittance of the transparent protective film was 88%, which showed sufficient transparency. Thus, the visibility of the images seen through the transparent protective film was evaluated as "Good". The sheet of Comparative Example 1 showed 0.03 g of a loss in the mass, and the adhesive was exposed at 430 rotations, which indicated that the abrasion resistance of this sheet was inferior to that of Example 1. The anti-slip properties of the sheet were unsatisfactory. The elongation percentages at 20°C and 5°C were 100% or more, respectively. The sheet was easily stripped off under an environment of 5°C, and thus, the workability at low temperatures was evaluated as "Good".

Comparative Example 2 An adhesive-applied transparent vinyl chloride film containing glass fibers kneaded therein (SP4856 manufactured by 3M) was used as a transparent protective film; and an adhesive-applied white vinyl chloride film (SP4287C manufactured by 3M) was used as a receptor film on which images were formed, and was laminated on the transparent protective film in the same manners as in Example 1. Thus, a sample of a sheet of Comparative Example 2 was obtained. The total light transmittance of the transparent protective film was 87%>, which showed sufficient transparency. Thus, the visibility of the images seen through the transparent protective film was evaluated as "Good". The sheet of Comparative Example 2 showed 0.04 g of a loss in the mass after the abrasion test, and the adhesive was exposed at 520 rotations, which indicated that the abrasion resistance of this sheet was inferior to that of Example 1. The film, SP4856, could be used on a floor for about 3 months. The anti-slip properties of the sheet were good. The elongation percentage at 20°C was 95%, whereas the elongation percentage at 5°C was 8%, which indicated that the sheet was hardly elongated, and had problems in the workability at low temperatures. The sheet ruptured when stripped off under an environment of 5°C, and thus, the workability at low temperatures was evaluated as "Poor".

Comparative Example 3 A sample of a sheet was made in the same manner as in Example 1, except that an acrylic resin film with a thickness of 100 μm containing no glass fiber was used as the transparent protective film. The total light transmittance of the transparent protective film was 89%, which showed sufficient transparency. Thus, the visibility of the images seen through the transparent protective film was evaluated as "Good". The sheet of Comparative Example 3 showed 0.14 g of a loss in the mass after the abrasion test, and the adliesive was exposed at 250 rotations, which indicated that the abrasion resistance of this sheet was inferior to that of Example 3. The anti-slip properties of the sheet were unsatisfactory. The elongation percentages at 20°C and 5°C were 80% and 100% or more, respectively. The sheet was easily stripped off under an environment of 5°C, and thus, the workability at low temperatures was evaluated as "Good". Comparative Example 4

Preparation of film having images formed thereon Scotch Print(R) 9512 system (an electrostatic process printer manufactured by 3M) was used to form digital images on Trident (a transfer medium manufactured by 3M). Next, Orca ILI(R) (a heat-laminating machine manufactured by 3M) was used to heat- transfer the images to an acrylic adhesive-applied white vinyl chloride resin film (ER010 manufactured by 3M). The Orca III(R) was operated under the following setting conditions: The upper roll temperature: 135°C The lower roll temperature: 50°C Speed: 70 cm/min. Pressure: 60 psi A transparent urethane resin (GA3S Clear manufactured by 3M) was applied to the above resin film with a knife coater so that the resultant coating layer could have a thickness of 20 μm after dried, to thereby form a transparent resin layer in place of the laminated transparent protective film. The sheet showed 0.51 g of a loss in the mass after the abrasion test, and the adhesive was exposed at 230 rotations. The anti-slip properties of the sheet were unsatisfactory. The elongation percentages at 20°C and 5°C were 100%> or more and 29%, respectively, which proved that the sheet had sufficient elongation properties. The sheet ruptured when stripped off under an environment of 5°C, and thus, the workability at low temperatures was evaluated as "Good". Comparative Example 5 A sample of a sheet was made in the same manner as in Comparative Example 4, except that an ER008 film manufactured by 3M was used as the acrylic adhesive-applied white vinyl chloride resin film. The sheet showed 0.51 g of a loss in the mass after the abrasion test, and the adhesive was exposed at 230 rotations. The anti-slip properties of the sheet were unsatisfactory. The elongation percentages at 20°C and 5°C were 100% or more and 4%, respectively. The sheet ruptured when stripped off under an environment of 5°C, and thus, the workability at low temperatures was evaluated as "Poor".

The results are shown in Tables 1 and 2. Table 1

Table 2

Claims

What is claimed is:

1 A marking sheet having an elongation percentage of 20% or more under an environment of 5°C (in accordance with JIS Z 0237, 2000), said marking sheet comprising (a) an adhesive-applied film which permits images to be formed thereon, and (b) a glass fiber-containing transparent resin layer which protects the formed images.

2. A marking sheet as claimed in claim 1, wherein said glass fiber-containing resin layer is a polypropylene resin layer containing glass fibers or an acrylic resin layer containing glass fibers.

3. A marking sheet as claimed in claim 1 or 2, wherein the total light transmittance of said glass fiber-containing resin layer is 60% or more.

4. A flooring marking sheet comprising a marking sheet as defined in any of claims 1 to 3.