WO2002078978A2

WO2002078978A2 - Graphics-protection sheet and graphics-displaying sheet

Info

Publication number: WO2002078978A2
Application number: PCT/US2002/009376
Authority: WO
Inventors: Takahide Okuyama
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2001-03-30
Filing date: 2002-03-25
Publication date: 2002-10-10
Anticipated expiration: 2003-09-30
Also published as: WO2002078978A3; AU2002306887A1; JP2002307621A

Abstract

A graphics-protection sheet that can easily and freely impart an appearance with improved decorativeness without damaging the graphics, and has increased abrasion resistance comprising a protective layer, that includes a layer containing a cured resin and hard beads dispersed therein at least as the outermost layer, wherein the graphics provided on the back surface of the protective layer is seen from the surface of the protective layer, wherein the protective layer has a cushioning layer.

Description

GRAPHICS-PROTECTION SHEET AND GRAPHICS-DISPLAYING SHEET

Field of the Invention

The present invention relates a graphics-protection sheet comprising a protective layer that includes a layer containing a cured resin and a plurality of hard beads dispersed therein at least as the outermost layer.

Background of the Invention

Hitherto, media that are produced by drawing or printing images or graphics on recording media having an adhesive layer with printing means such as electrostatic printing or ink jet printing, have been increasingly used as signs for advertisement or information. Such media having the drawn graphics is used with adhering it on the surface of a material such as the wall or floor of a building through the adhesive layer that is already provided to the media. A transparent protection film (or sheet) is usually laminated on the surface of such a medium having printed graphics to protect the graphics from damage or contamination. Such a protection film is adhered to the medium having printed graphics through an adhesive.

Currently, the media having the printed graphics have been adhered to the wall or floor of a building. Thus, a relatively large abrading force (a force causing abrasion) such as frictional contact with hard materials such as cleaning equipment or the soles of shoes, or impact caused by wind and rain is applied to the protection film.

A sheet-form material that uses such a protective layer comprising the cured resin and the hard beads for the protection of the graphics is disclosed in several publications including JP-A-11-10823, JP-A-11-115141, JP-A-11-129428, etc. For example, JP-A-11-10823 discloses a decorative sheet that uses a coating layer comprising (A) inorganic beads having an average particle size of 3 to 50 μm and (B) a reactive resin, in that the content of the inorganic beads (A) is from 5 to 50 wt. % of the total weight of (A) and (B), as a protective layer. Such a decorative sheet is a sheet having graphics printed in that the graphics can be seen through the protective layer. In general, the graphics is formed on the surface of a substrate, and the protective layer is then place on the graphics.

The above JP-A publications describe that the inorganic beads in the protective layer are preferably hard beads comprising alumina and having relatively large hardness.

The decorative sheet having such a coating layer has effectively improved abrasion resistance of the protective layer.

With the decorative sheet disclosed in the above JP-A publications, it is a prerequisite to form a protective layer when applying a coating composition directly on the graphics to cover it. In general, a dimly glossy appearance with a certain surface roughness like a mat texture is spontaneously imparted to the surface of the protective layer in the course of applying and drying a coating for the protective layer. Such spontaneous formation of the appearance is inevitable in the production of conventional protection films since the protective layers contain the hard beads. According to the kinds and applications of the graphics, it is required to alter the appearance of the surface of the protective layer (appearance to be observed) so that decoration effects, that cannot be achieved with such a spontaneous appearance, are achieved.

To satisfy such a requirement, the surface of the conventional protective layer is generally compression-processed when the protective layer contains neither hard beads nor a cured resin. Here, the compression-processing is usually embossing. The embossing means a processing method that forms a plurality of convex parts having the cured resin and the hard beads on the surface of the protective layer to impart solid appearance that is generated from the combination of the convex parts and concave parts around them so that the decorativeness is increased. Also the compression-processing includes calendering. The calendering is a processing method that makes the surface roughness of the protective layer as small as possible to form a smooth surface and imparts specular gloss to the surface of the protective layer to increase the decorativeness. However, with the conventional protective layer containing the hard beads and the cured resin, it is difficult to freely change the surface appearance with the compression- processing of the surface of the protective layer. This may be for the following reasons: In general, in the above compression-processing, it is necessary to physically change (deform) the surface with compressing the protective layer so as to impart the uneven shape and roughness to the surface, that are different from those spontaneously formed in the course of the formation of the film. However, it is very difficult to process the relatively hard protective layer alone that contains the hard beads and the cured resin, or the protective layer laminated on a relatively hard adherend, since the processing requires a relatively large pressure, etc. When the adherend carrying the graphics is soft, the graphics may be damaged if the protective layer is processed with a large pressure.

That is, it is impossible to easily and freely impart an appearance, that is different from the appearance spontaneously imparted by the film formation process, to the protective layer protecting the graphics by simply applying the processing method of the conventional protection film.

Accordingly, one object of the present invention is to provide a graphics-protection sheet that can easily and freely impart an appearance with improved decorativeness, that is different from the appearance formed on the surface of the protective layer spontaneously without damaging the graphics, and that can have an effect to increase abrasion resistance and decoration effect, that are not achieved at the same time with the conventional protection sheets. Summary of the Invention Brief Description of the Drawings

Fig. 1 is a cross section of one example of the graphics-protection sheet of the present invention. Description of the Preferred Embodiment(s)

The graphics-protection sheet of the present invention comprises a protective layer having a surface and a back surface, the protective layer comprises a layer containing a cured resin and a plurality of hard beads dispersed therein at least as the outermost layer (the top layer), and the sheet as a whole has light transmission properties, like the conventional graphics-protection sheets.

The characteristics of the present invention is that the graphics-protection sheet has the following constructions (1) and (2) to facilitate the compression-processing of the surface of the protective layer: (1) the protective layer has a cushioning layer that comprises a resin layer adhered to the back surface of the protective layer and has light transmission properties and thermoplasticity, and

(2) the outermost layer of the protective layer comprises a coating film that comprises the cured resin and the hard beads. Herein, the term "compression-processing" is intended to include the embossing and calendering as defined above.

The cushioning layer in (1) functions as a cushion that itself deforms in the course of the compression-processing. Thus, the protection sheet alone can be processed. That is, when the whole protection sheet is embossed to form unevenness having the roughness with shapes and sizes (e.g. Ra of at least 3), that are different from those of the unevenness spontaneously formed in the coating film-forming process on the surface of the protective layer (the outermost layer), the cushioning layer itself is compressed and deformed to facilitate the physical deformation of the surface of the protective layer. When the protective layer is processed with laminating the protection sheet on a relatively hard substrate (an adherend carrying graphics), high pressure is not required. Furthermore, when a substrate carrying the graphics is relatively soft, the cushioning layer functions as an inner protective layer that protects the graphics from damages, since it is not necessary to process the protection sheet under a high pressure.

When the protection sheet is calendered, the cushioning layer functions to effectively transfer the pressure of the calendering roll to the whole surface to be processed uniformly and effectively (that is, avoiding the application of unnecessarily high pressure) over the surface of the protective layer. The mechanism of such an effect of the cushioning layer may not be clarified, but may be assumed. Although such a theory is not relied upon.

If the pressure is applied to the surface of the protective layer unevenly, the cushioning layer containing a softer thermoplastic resin than that of the protective layer absorbs the excessive force. As a result, the force can be uniformly applied to the protective layer.

The compression-processing of the surface of the protective layer may not be effectively carried out by making use of the cushioning layer that is combined with the protective layer. That is, the protective layer itself should be a layer suitable for compression-processing. Thus, the above construction (2) is necessary.

The formation of the outermost surface of the protective layer from the coating film containing the cured resin and the hard beads may increase the processability of the protection sheet alone by the following mechanism. Different from a coating film consisting of a resin, the coating film containing the resin and the beads includes interfaces between the resinous phase and the beads. At the interfaces, the entire beads cannot be in complete contact with the resin, and thus air layers

(voids) partly remain. For example, such air layers may function like vents from that the volatile solvent is evaporated. The air layers are easily crushed in the course of the processing of the protective layer and facilitate the compressive deformation of the protective layer as a whole. That is, the protective layer can be easily and effectively compression-processed due to the synergistic effect of such air layers with the effect of the ^•cushioning layer combined with the protective layer.

The total volume of the air layers tends to increase as the filling percentage of the beads increases. When the volume of the air layers is too large, the beads tend to drop out from the protective layer. From such a viewpoint, the volume of the air layers is preferably made as small as possible. Accordingly, the content of the hard beads is preferably from 50 to 200 wt. parts, more preferably from 60 to 150 wt. parts, per 100 wt. parts of the cured resin (nonvolatile component).

With the graphics-protection sheet of the present invention, various embossing processes can be applied, since it is easy and possible to compression-process the surface of the protective layer. For example, (i) irregular unevenness with a relatively large surface roughness is formed to impart the non-glossy appearance to the surface and increase the texture of the graphics, (ii) unevenness with the specific configuration corresponding to the designs or patterns of the graphics to imitate a genuine piece or create a three-dimensional (solid) appearance, (iii) minute prismatic projections are formed to increase the reflectance or luminance, (iv) projections such as minute lenses (e.g. lenticular lenses, etc.) are formed to change the observed appearance of the graphics using the refractive effect of the lenses. As one example of (ii), on the protective layer covering the graphics having wood grain patterns, unevenness imitating the conducting vessels of wood is formed to imitate the natural wood or create the three-dimensional appearance.

Furthermore, it is very easy to provide three-dimensional patterns having stone texture, Japanese paper textures, fabric texture, hair line texture, suede texture, etc. by embossing the protective layer in accordance with or not in accordance with the designs or patterns of the graphics. The above-described effect of the cushioning layer to unify the pressure is advantageous when the embossing is precise processing with minute roughness. That is, it is possible to form the unevenness with the precise shapes and small sizes, that cannot be formed in the absence of the cushioning layer, on the protective layer. Such a precise processing is required to improve the optical design such as (iii) the formation of the projections of the minute prisms and (iv) the formation of the projections of the minute lenses. The cured resin used herein is intended to mean a cured material of a curable resin.

When a curing component such as a curing agent is essential, the cured resin is a mixture of the curable resin and the curing component, as described in detail below.

As shown in Fig. 1, one preferred example of the graphics-protection sheet (100) of the present invention comprises a cushioning layer (2) having a back surface (22) that is adhered to the surface of an adherend (3) including graphics, and protective layer (1) adhered to the surface (21) opposing to the back surface (new number?) of the cushioning layer (22). Adherend (3) may be a base layer that is explained in detail below, or an image-recording medium that has been already imaged.

In general, the cushioning layer is a layer comprising a thermoplastic resin. It may comprise a curing component, insofar as the layer is thermoplastic.

In the example shown in Fig. 1, protective layer (1) consists of a first layer (11) having a back surface (112) adhered to surface (21) of cushioning layer (2), and a second layer (12) having a back surface (122) adhered to a surface (111) of first layer (11) opposing to back surface (112). This second layer (12) forms the outermost layer (surface layer) of the protective layer.

The second layer, that is, surface layer (12) contains the cured resin and the hard beads, as described above. First layer (11) preferably contains the cured resin but no hard beads so that it has hardness between the hardness of cushioning layer (2) that is the thermoplastic resin layer, and that of surface layer (12) containing the hard beads to allow the precise control of the surface roughness of the protective layer in the compression- processing process. Surface (121) of surface layer (12) containing the hard beads and the cured resin opposing to back surface (122) is compression-processed. In the example of Fig. 1, it is embossed so that convex parts (13) containing the cured resin and the hard beads are formed. Around convex parts (13), concave parts (14) are formed. That is, embossing compresses and deforms the parts corresponding to the concave parts more greatly than the parts corresponding to the convex parts, and forms the unevenness with roughness having the specific shapes and sizes on the surface of the protective layer.

First layer (11) and cushioning layer (2) are also compressed and deformed in the parts where concave parts (14), that are shown in the example of Fig. 1, are formed. However, the deformation of cushioning layer (2) does not reach the back surface (22) that is adhered to the surface of the adherend (3). Therefore, after the compression-processing of protection sheet (100) alone, unnecessary unevenness that interferes with the adhesion of the protection sheet to the surface of the adherend is not formed. Furthermore, the graphics provided on the surface of the adherend is not damaged even when the protection sheet is compression-processed after it is adhered to the surface of the adherend (3).

When cushioning layer (2) comprises the thermoplastic resin, the protection sheet (100) can be adhered to the surface of the adherend (3) with heat lamination. Furthermore, coloring toners or inks are fixed to the back surface of the cushioning layer (2) to form the graphics consisting of such toners or inks. That is, since the cushioning layer (2) comprises the thermoplastic resin, it can function as a coloring material-receptive layer that receives the toners or inks. In this case, the thermoplastic resin is preferably selected from resins having good affinity with the toners or inks used as the coloring materials.

In another preferable embodiment, the protection sheet further comprises an adhesive layer fixed to the back surface of the cushioning layer. In addition, a transparent base layer (a base layer having no graphics) may be inserted between this adhesive layer and the cushioning layer. In this case, the cushioning layer is fixed to the surface of the base layer (for example, with heat lamination), and the adhesive layer is fixed to the back surface of the base layer (opposing to the surface). That is, in this embodiment, the protection sheet may be regarded as an adhesive-sheet type protection sheet comprising the support consisting of a laminate including the base layer, the cushioning layer fixed to the surface of the base layer and the protective layer fixed to the cushioning layer, and the adhesive layer provided on the back surface of the support, that is, the back surface of the base layer.

Since the graphics-protection sheet of the present invention has the above- described construction, it can have the scratch resistance with a sufficient level (for example, the pencil hardness of 2H or more in the pencil hardness test according to JIS K 5400), when it is intended to protect the graphics on the adherend to that the protection sheet is adhered.

The total thickness of the graphics-protection sheet is not limited, and it is usually from 100 to 750 μm.

In a further preferable embodiment of the present invention, a graphics-displaying sheet is provided, that comprises the base layer adhered to the back surface of the cushioning layer and carrying the graphics, and the adhesive layer fixed to the back surface of the base layer. In this case, the base layer is fixed to the cushioning layer with the heat lamination, etc., while the adhesive layer is fixed to the back surface of the base layer (opposing to the surface). That is, such a graphics-displaying sheet may be regarded as an adhesive-sheet type graphics-displaying sheet comprising the support consisting of a laminate including the base layer, the cushioning layer fixed to the surface of the base layer and the protective layer fixed to the cushioning layer, and the adhesive layer provided on the back surface of the support, that is, the back surface of the base layer.

In general, the base layer has the graphics formed with a drawing method such as printing. The adhesive layer usually comprises a self-adherent polymer. Thus, in such a case, the graphics-displaying sheet can be adhered to the floor or wall of a building like the conventional adhesive sheets. When the base layer has the graphics, it can be used as an adhesive graphics-displaying sheet that decorates the floor or wall of the building.

Herein, the self-adherent polymer means a polymer that exhibits tackiness at room temperature (about 25°C), and easily provides pressure-sensitive adhering properties to the adhesive layer comprising the self-adherent polymer.

The graphics-displaying sheet may be produced by providing the support comprising the three layers, that is, the base layer, the cushioning layer and the protective layer, and forming the adhesive layer on the back surface of the support layer (that is, the back surface of the base layer). The adhesive layer can be formed from a coating film comprising the self- adherent polymer and the crosslinking agent, like the conventional adhesive sheets. Minute unevenness can be formed on the adhesive surface of the adhesive layer by transferring such unevenness from a release paper (liner) having the minute unevenness on its surface, to control the adhesion force or improve degassing in the course of adhering. Such minute unevenness is designed so that it disappears through the plastic deformation of the adhesive layer after the completion of adhesion to prevent the deterioration of the observability of the graphics.

Since the graphics-displaying sheet of the present invention has the above- described construction, it can have a scratch resistance with a sufficient level (for example, the pencil hardness of 2H or more in the pencil hardness test according to JIS 5400), when it is intended to protect the graphics drawn on base layer.

The total thickness of the graphics-displaying sheet is not limited, and it is usually from 110 to 1,000 μm.

The protective layer is preferably a layer that has sufficient transparency so that the graphics of the adherend can be well seen through it. In such a case, the hard beads are preferably transparent beads such as inorganic oxide beads, ceramics beads, glass- ceramics beads, etc. From such a viewpoint, the diameter of the beads is preferably as large as possible. The diameter of the beads is usually from 5 to 100 μm, preferably from 10 to 50 μm. Here, the diameter of the beads is usually measured with an image-processing apparatus comprising an optical microscope. The surface roughness of the protective layer embossed is at least 3 μm in terms of

Ra, that is measured at a measuring length of 0.4 mm with a surface roughness meter. When Ra is too small, it may be difficult to impart the solid appearance described above, or the decorative appearance using the optical function of the convex parts. The surface roughness of the protective layer usually does not exceed 250 μm. When Ra is too large, the visibility of the graphics under the protection sheet may deteriorate. Thus, Ra is as small as possible. Accordingly, the surface roughness Ra of the protective layer embossed is preferably from 3.5 to 50 μm, preferably from 4 to 30 μm.

The surface roughness of the protective layer, that is calendered to impart the specular gloss to the appearance, is from 0.02 to 0.5 μm in terms of Ra, that is measured at a measuring length of 0.4 mm with a surface roughness meter. When Ra is too large, the specular gloss may not be increased so that the observer (user) can recognize the surface to have high decorativeness. When Ra is too small, although the appearance has no problem, the surface of the protective layer with small roughness tends to cause some problems in the production such as sticking to a calendering roll, etc. From such a viewpoint, the surface roughness Ra is preferably from 0.03 to 0.4 μm, more preferably from 0.05 to 0.3 μm.

As already described, the graphics-protection sheet of the present invention is transparent as a whole. A total light transmittance, that is measured with light being incident from the surface opposite to the surface of the protective layer (for example, the back surface of the cushioning layer or the adhesion surface of the adhesive layer), is usually at least 65%, preferably at least 70%, particularly preferably at least 80%. When the light transmittance is too low, the visibility of the graphics formed on the adherend surface of the medium may deteriorate. The "light transmittance" herein used is a light transmittance measured according to JIS K 7105 "Method for Measuring Light Transmittance".

Apart from the surface layer, the protective layer preferably has the cured resin layer between the cushioning layer and the surface layer of the protective layer as described above, and the protective layer is preferably produced in the form of a lamination type protective layer as follows:

Firstly, the first layer, that consists of the resin layer, is formed on the surface of the cushioning layer, and then the surface layer comprising the curable resin and the hard beads dispersed in the cured resin is formed on the surface of the first layer to prepare a precursor of the protection sheet comprising the cushioning layer and the lamination type protective layer (first layer/surface layer), that are laminated in this order. Next, the curable resin contained in the lamination type protective layer is cured to finish the protection sheet. As the separate resin layer (the first layer) described above, it is preferable to use the cured resin layer so that the abrasion resistance of the protective layer is increased. The thickness of the first layer is usually from 1 to 50 μm. In addition, one or more additional resin layers (the second and third layers, and so on) may be provided between the surface layer and the first layer insofar as the total thickness of the lamination type protective layer is not excessively large to make the protection sheet too bulky as a whole.

That is, the total thickness of the protective layer (the lamination type protective layer) is preferably from 50 to 150 μm, more preferably from 60 to 130 μm to control the total thickness of the graphics-protection sheet in the suitable range.

The thickness of the surface layer of the lamination type protective layer is not limited insofar as the effects of the invention are not impaired, and it is usually from 10 to

150 μm, more preferably from 20 to 120 μm. When the thickness of the surface layer is too low, the durability against rubbing contact and abrasion resistance tend to deteriorate. When the thickness of the surface layer is too large, the flexibility of the sheet as a whole tends to deteriorate and the adhering work may become difficult.

The light transmittance of the protective layer as a whole is usually at least 75%, preferably at least 80%. When the light transmittance of the protective layer is too low, the graphics on the adherend may not be observed in good conditions. Thus, the light transmittance of the protective layer is particularly preferably at least 90%.

When the adhesive sheet type sheet (the graphics-protection sheet or the graphics- displaying sheet) with the protective layer is produced, firstly the protection sheet including neither the base layer nor the adhesive layer is produced and then it is laminated on the base layer and so on, that are separately produced, by the method comprising the following steps (1) to (4):

(1) providing (a) the surface layer comprising a surface-improving agent, the curable resin and the hard beads dispersed in the curable resin, and (b) the protective layer with the cushioning layer that will be fixedly provided on the back surface of the surface layer,

(2) curing the curable resin in the protective layer to form the precusor of the protection sheet,

(3) compression-processing the precursor of the protection sheet, and

(4) fixing the base layer or the adhesive layer on the back surface of the cushioning layer to form the sheet with the protection layer.

According to the above method, the sheet with the protective layer, that is fixed to the base layer with the high fixing force, can be easily produced.

In this case, the adhesive sheet type graphics-protection or graphics-displaying sheet can be finished with using the base layer having the adhesive layer as the above base layer, or adhering the adhesive layer to the back surface of the base layer of the support

(the laminate of the protective layer and the base layer) that has been produced as described above. In general, the curable resin is cured with heat or radiation (UN ray, electron beam, etc.), that is most effective (to shorten the curing time). When the curable resin is cured with heat, sometimes the heating should be carried out at a temperature of 120 to 200°C for 1 to 20 minutes. When the radiation such as UV ray or electron beams is used, the amount of heat in the same level as or larger than the above level may be generated in the protective layer. Therefore, the curing of the protective layer prior to the lamination on the base layer can make it possible to produce the graphics-protection sheet without exposing the base layer to such a high temperature for a relatively long time (several minutes to several ten minutes). When it is not necessary to shorten the production time, it is possible to use resins that are completely cured at a relatively low temperature (lower than 100°C) such as moisture-curable resins, room temperature-curable resins, etc.

The surface layer may be formed by preparing a slurry containing the essential^' components such as the curable resin, and then applying and curing the slurry. The slurry with good application properties can be obtained with the adjustment of the concentration of the nonvolatile component in the solution of the curable resin in the range of 20 to 40 wt. % when the components of the slurry are mixed. The slurry is preferably applied with a notch bar, a round bar, etc., since it contains the beads.

Besides the above essential components such as the curable resin, the surface layer preferably contains a curing component such as a surface-modifying agent, a curing agent, a crosslinking agent, a curing accelerator, a polymerization initiator, and so on. Furthermore, the surface layer may contain other additives such as a surfactant, a filler, a flame-retardant, a UN ray absorber, an antioxidant, a tackifying resin, a colorant, an antimicrobial agent, etc. Preferably, the amount of the other additive is 20 wt. parts or less per 100 wt. parts of the curable resin. The other resin layers (such as the first layer) included in the protective layer may be formed by preparing a paint containing the essential components such as the curable resin, etc. and applying and curing it, like the surface layer.

The compression processing may be carried out by pinching the precusor of the protection sheet between a processing roll and a backup roll to transfer the surface roughness of the processing roll to the sheet. That is, the sheet is compression-processed with compressing the surface of the protective layer to the processing roll having the concave-convex shape or the roughness corresponding to the negative of the concave- convex shape or the roughness that is imparted to the surface of the protective layer. Preferably, the compression-processing is carried out while heating.

The heating temperature is usually from 120 to 270°C, preferably from 130 to 260°C. The pressure is usually from 4 to 10 kg/cm2, (about 0.4 to about 1.0 MPa).

The processing roll is a steel roll the surface of that is plated with a metal (for example, chromium), and the surface roughness is precisely controlled. The backup roll is usually a soft roll made of a metal roll the surface of that is covered with a surface-covering material of a soft material such as a rubber or cotton, although it may be made of the same material as the processing roll.

Other processing conditions may be the same as those employed in the compression processing of the surface of the conventional protective layer containing no hard beads.

The thickness of the cushioning layer is selected so that the physical deformation of the surface of the protective layer is facilitated in the course of the compression processing. The thickness of the cushioning layer is usually from 25 to 500 μm, preferably from 30 to 400 μm, particularly preferably from 35 to 350 μm. When the thickness of the cushioning layer is too low, the physical deformation of the surface of the protective layer may not be facilitated. When the cushioning layer is too thick, the thickness of the sheet as a whole becomes too large so that the flexibility or handling of the sheet may deteriorate.

The cushioning layer is usually a thermoplastic layer comprising a thermoplastic resin with high transparency. Also, it functions as a thermally adhesive layer, when the cushioning layer is heat laminated on the adherend. The softening point of the cushioning layer is usually from 60 to 220°C, preferably from 80 to 200°C.

The light transmittance of the thermoplastic resin is usually at least 70%, preferably at least 80%, particularly preferably at least 90%. Examples of the thermoplastic resin include vinyl chloride resins (including copolymers of vinyl chloride with other vinyl monomers), urethane resins, acrylic resins, polyester resins, silicone resins (including silicone-polyurea resins), ionomer resins, etc.

The cushioning layer may optionally contain additives such as a curing agent, a crosslinking agent, a polymerization initiator, a catalyst, a surfactant, a filler, a flame retardant, a UN ray absorber, an antioxidant, a tackifying resin, a colorant, etc. The cushioning layer can be formed by applying a coating liquid containing the resin for the cushioning layer with a conventional coating means.

The curable resin is not limited insofar as it can provide the cured material having good transparency and abrasion resistance. The cured resin (the cured material of the curable resin) has a light transmittance of usually at least 70%, preferably at least 80%, particularly preferably at least 90%. Examples of the curable resin include urethane resins, acrylic resins, polyester resins, silicone resins, epoxy resins, etc. Among them, the polyurethane resins are preferable, since they have good adhesion properties with the hard beads, that will be explained in detail, and relatively high toughness so that the abrasion resistance of the surface layer is effectively improved. Specific examples of such resins include urethane resins "SH-1011" (trade designation available from NIPPON POLYURETHANE INDUSTRY Co., Ltd.), etc.

Preferably, the mixture of such a resin and a curing agent (e.g. COLONATE (trade name) HX available from NIPPON POLYURETHANE INDUSTRY Co., Ltd.) is used as the curable resin.

When the curing component (e.g. the curing agent, etc.) is essential, the amount of the curing component usually does not exceed 50 wt. parts, preferably 30 wt. parts, more preferably 20 wt. parts, per 100 wt. parts of the curable resin.

The softening point of the cured resin is selected from a range in that the compression processing is easy, and is usually from 100 to 250°C, preferably from 120 to 220°C.

The hard beads may be ceramic beads, inorganic oxide beads, etc. The Nickers hardness of the hard beads is preferably at least 1,000 kg/mm2. When the hardness is less than 1,000 kg/mm2, the beads may be broken in the course of the compression processing of the protective layer, or the durability against rubbing contact and abrasion resistance of the protective layer may not be effectively increased.

Herein, the Vickers hardness is measured by binding about 10 to 20 hard beads having a particle size of about 1 mm with 10 g of an epoxy resin to form a cylindrical sample having a diameter of about 3 cm and a height of about 1 cm, abrading the sample to expose the bead surfaces, and measuring the hardness on the exposed bead surfaces with a micro-hardness meter. In the measurement, a load is 300 g, and a loading time is 15 seconds. The upper limit of the hardness is not limited, and preferably does not exceed

5,000 kg/mm2 from a viewpoint of suppressing the wear of a dispersing apparatus.

The hard beads are preferably the inorganic oxide beads, since they have a high binding function (affinity) with the resin of the protective layer, and can achieve the particularly high abrasion resistance and durability against rubbing contact. Preferable examples of such inorganic oxide beads include those comprising alumina, silica, titania, zirconia, etc. In particular, the alumina beads are preferable. The inorganic beads are preferably surface-treated with a silane coupling agent to improve the adhesion with the resin.

Specific examples of such hard beads include alumina beads "CB A40" (trade designation) available from SHOWA DENKO K.K.), etc. The refractive index of the hard beads is preferably substantially the same as that of the curable resin to increase the transparency of the surface layer. Thus, the refractive index of the hard beads is preferably from 1.3 to 1.9.

The base layer is required to constitute a part of the support and maintain the mechanical strength of the entire sheet high in the adhesive sheet type graphics-protection or graphics-displaying sheet. In addition, the base layer functions as the adherend to carry the graphics in the case of the graphics-displaying sheet.

The base layer can be formed from any layer that is used as a substrate of a conventional graphics-protection sheet. For example, a resin film can be used.

Examples of the resin of such a film include vinyl chloride resins (including copolymers of vinyl chloride with other vinyl monomers), polyolefin resins, urethane resins, acrylic resins, polyester resins, silicone resins (including silicone-polyurea resins), etc.

The thickness of the base layer is usually from 10 to 80 μm, preferably from 15 to 50 μm. The light transmittance of the base layer is usually at least 70%, preferably at least 80% , particularly preferably at least 90% .

The base layer may optionally contain a curing agent, a crosslinking agent, a polymerization initiator, a catalyst, a surfactant, a filler, a flame retardant, a UN ray absorber, an antioxidant, a tackifying resin, a colorant, etc.

The base layer may be produced by making a film with extruding a raw material containing the above resins. Alternatively, the base layer may be formed by applying a coating liquid containing the above resin on a process substrate and curing it. Preferably, the base layer, that is formed by the above method, is dry laminated on the protective layer or the surface layer, that has been produced separately, to produce the graphics-protection or graphics-displaying sheet of the present invention.

Preferably, at least the surface layer of the protective layer contains the surface- modifying agent to increase the stain-proofing properties of the protective layer. Such a surface-modifying agent is usually a silicone or fluorine-containing surface modifying agent.

A plurality of minute concave and convex parts resulted from the hard beads are formed on the surface of the surface layer. Therefore, a contact area between dusts and the surface of the surface area increases in comparison with a smooth surface. In such a case, the surface of the surface layer should be modified to decrease a surface tension so that the stains caused by the dusts, etc. are easily wiped away without unnecessarily strongly polishing the surface with a cleaning machine.

To decrease the surface tension of the surface of the surface layer, a surface- modifying agent for a paint, that is described in JP-A-6-240201, may be added to the surface layer of the protective layer. Such a surface-modifying agent is preferably a nonionic material, since it can bleed out from the inside of the surface layer to the surface and thus the surface is maintained in the fluorinated state always.

The fluorine-containing surface-modifying agent is preferably an oligomeric compound, and in the liquid state at room temperature (about 25 °C). The viscosity of the liquid agent is usually less than 50 cps, particularly preferably 1 to 30 cps. When the viscosity is too high, the bleeding of the agent from the inside of the surface layer to the surface may become difficult. When the viscosity is too high, the maintenance of the surface-modifying effect may decreases.

The amount of the surface-modifying agent contained is usually from 0.1 to 10 wt. parts, preferably from 0.5 to 5 wt. parts, particularly preferably from 1 to 3 wt. parts, per

100 wt. parts of the cured resin (the nonvolatile components including the curing components). When the amount of the surface-modifying agent is too low, the maintenance of the surface-modifying effect may deteriorate. When the amount of the surface-modifying agent exceeds the necessary amount, the effect to prevent staining may not increase proportionally. Rather, some adverse effects (for example, the generation of coating defects in the course of the formation of the surface layer, etc.) may be caused. As the above surface-modifying agent, a fluorine-containing compound having the following chemical structure may be used. That is, a surfactant has a perfluoroalkyl group, that is, an alkyl group the hydrogen atoms of that are all substituted with fluorine atoms, and a hydrophilic group (e.g. a hydroxyl group, etc.) or a lipophilic group. Such a compound modifies the surface of the surface layer using the migration property of the perfluoroalkyl group, and can migrate to the surface of the layer and modify its surface properties in a small amount. Specific examples of such a compound include fluorine- based surface modifiers DEFENSA® Series MCF-300, MCF-310, MCF-312 and MCF- 232 (available from DAINIPPON INK & CHEMICALS, INC.), and the like.

The protective layer may contain an antimicrobial agent as the other additive, insofar as the effects of the present invention are not impaired. For example, the dusts adhered to the surface of the surface layer often carry bacteria or spores of fungi, and the adhesion of the dusts may cause the contamination with the bacteria and fungi. Even when the dusts are wiped off, the bacteria and fungi may remain on the surface. Thus, the antimicrobial agent is preferably added at least to the surface layer in order to impart an anti-contamination effect against the bacteria and fungi.

The amount of the antimicrobial agent contained is usually from 0.01 to 2 wt. parts, preferably from 0.05 to 1 wt. part, per 100 wt. parts of the cured resin (nonvolatile). When the amount of the antimicrobial agent is too low, the maintenance of the effect may decrease. When the amount of the antimicrobial agent exceeds the necessary amount, the effect may not increase proportionally. Rather, some adverse effects (for example, the generation of coating defects in the course of the formation of the surface layer, etc.) may be caused. The microbial agent herein used includes a narrow "antibacterial" agent that kills bacteria or suppress their proliferation and also a narrow "antifungal" that kills fungi or suppress their proliferation.

Examples Example 1 and Comparative Example 1

A graphics-protection sheet with a lamination type protective layer was formed as follows:

1. On a paper sheet that was treated to impart releasing properties, a coating liquid containing a polyvinyl chloride resin (PNC) was applied to form a cushioning layer (50 μm), that could be heat laminated to a base layer.

2. On the cushioning layer, a composition, that was prepared by mixing the components in accordance with "First Layer Formulation" in Table 1, was applied and dried at 90°C for 2 minutes to form the first layer of the protective layer, that was a layer of a cured resin containing no hard beads. The first layer had a thickness of 15 μm. 3. Subsequently, on the first layer, a composition, that was prepared by mixing the components in accordance with "Second Layer Formulation" in. Table 1, was applied to form the second layer as the surface layer (outermost layer) of the protective layer. Thus, a laminate consisting of the thi'ee layers, that is, the cushioning layer, the first layer and the outermost layer, was produced. 4. Then, this laminate was heated at 100°C for 1 minute and then at 160°C for

4.5 minutes to dry and cure it. Thus, the precursor of the protection sheet of this Example was obtained. The total thickness of the first and surface (second) layers of the protective layer was 40 μm.

5. The precursor of the protection sheet obtained in the previous step was compression processed using a processing roll and a backup roll, that is, embossed and calendered. Thus, the graphics-protection sheet of this Example was obtained. The light transmittance of the lamination type protective layer was 93%.

Table 1

In Table 1, "SH-1011" is an aliphatic polyurethane resin coating available from

NIPPON POLYURETHANE INDUSTRY Co., Ltd. having a solid content (nonvolatile) of 30 wt. %.

"Colonate HX" is an aliphatic isocyanate curing agent available from NIPPON ., POLYURETHANE INDUSTRY Co., Ltd. Having a solid content (nonvolatile) of 100 wt.%.

"Alumina beads CB A40" are alumina beads having an average particle size of 40 μm and a Nickers hardness of 2,500 kg/mm2 available from SHOWA DEΝKO K.K..

The "fluorine-containing surface modifier" used in each Example was "DEFEΝSA® Series MCF-312" available from DATΝIPPOΝ INK & CHEMICALS, INC. The compression processing was carried out using three kinds of the compression rolls, and the processing conditions included a temperature of 180°C and a pressure of 0.6 MPa in each case. The embossing was carried out using two kinds of the processing rolls, one of that was a sand blasted type roll, while the other of that was a textured roll.

The surface roughness (Ra) of the protective layer processed with the sand blasted roll was 10 μm, while that of the protective layer processed with the textured roll was 2 μm. The surface roughness (Ra) of the protective layer planished with calendering was 0.15 μm. Here, the surface roughness Ra was measured with a stylus-type surface roughness meter (a micro-surface roughness meter "HANDISURF® E-30A" available from TOKYO SE ITSU KABUSHIKIKAISHA) at a measuring length of 0.4 mm.

Separately, a protective sheet precursor, that had been produced by repeating the above steps 1 to 4, and the base layer were laminated and then compression processed in the same manner as above and at the same time the protective sheet and the base layer were heat laminated to obtain a graphic-displaying sheet precursor of this Example. That is, the release paper was removed from the protection sheet precursor, and the protection sheet precursor was heat laminated while compress processing on the surface of a colored base layer having a thickness of 80 μm (a vinyl chloride resin film available from

BANDO CHEMICAL INDUSTRIED LTD.; light transmittance of 97%), on that graphics was printed, to obtain the precursor of the graphics-displaying sheet except an adhesive layer.

Separately, a coating liquid, that was prepared by mixing a self-adhesive acrylic polymer (ALLOSET® 8167 available from NIPPON SHOKUB Al CO., LTD.) and a crosslinking agent, was applied on a release paper so that a dry thickness was 40 μm, and dried to form an adhesive layer (with the release paper). The weight ratio (nonvolatile) of the self-adhesive acrylic polymer to the crosslinking agent was 100:0.5.

The above-prepared adhesive layer and the precursor of the graphics-displaying sheet were laminated to finish the graphics-displaying sheet.

The crosslinking agent used was isophthaloyl bis(2-methylazilidine) as a non- yellowing crosslinking agent.

Now, the performance tests performed with the graphics-displaying sheet of this Example and the results are explained. 1) Compression-processability

After the processing, the surface of the protective layer was observed with an eye to confirm whether the concave-convex shapes and the roughness corresponding to the surface shapes and the roughness of the processing roll were clearly transferred and whether the appearance with good decorativeness was imparted to the sheet. With the protection sheet of this Example, the physical deformation of the surface of the protective layer was easy, and the concave-convex shapes and the roughness of each of the processing rolls having the different roughness could be clearly transferred to the sheet.

Also, the decorativeness of the appearance was judged good.

2) Abrasion resistance

The graphics-displaying sheet was adhered to the surface of an aluminum plate, and used as a sample. Each sample was subjected to the abrasion test using a Taber abrader with a S-42 sandpaper under a load of 1 kg, and a number of revolutions was counted until the graphics completely disappeared.

In Comparative Example 1, a graphics-displaying sheet was produced in the same manner as in Example 1 except that the outermost layer contained no hard beads, and subjected to the same tests. As a result, the abrasion resistance of the sheet of Comparative Example 1 was 950 revolutions, while that of the sheet of Example 1 was 1,800 revolutions. Thus, it was found that the graphics-protection sheet of the present invention had excellent abrasion resistance.

3) Scratch resistance The samples of Example 1 and Comparative Example 1, that were produced in the same manners as described in the above test 2) were subjected to the pencil hardness test according to JIS K 5400. The pencil hardness of the sheet of Comparative Example 1 was "H", while that of the sheet of Example 1 was "4H". Thus, its was found that the graphics-protection sheet of the present invention had excellent scratch resistance. 4) Stain-proofing

A graphics-displaying sheet of this Example was adhered directly to a floor surface, and maintained in such a state for one week. Then, the surface of the graphics- displaying sheet was washed with water, and the staining condition was compared with an eye. As a result, the surface of the sheet was kept at the same clean state as that of the sheet prior to the test. Thus, it was found that the sheet of the present invention had good stain proofing properties. When no surface-modifying agent is contained in the surface layer, the sheet is stained to the extent that the difference can be recognized when compared with the sheet prior to testing, or the stain is adhered to the sheet to the extent that it cannot be removed by washing with water.

Example 2

The graphics-protection sheet of this Example was produced in the same manner as in Example 1 except that the thickness of the cushioning layer was changed to 25 μm. Since the physical deformation of the surface of the protective layer was more difficult than the protective layer of Example 1, the transfer of the concave-convex shapes and the roughness was insufficient when it was calendered with the sand blasted roll having the relatively large roughness and when it was planished. However, with the three types of compression processing, the appearance, that was different from the spontaneously formed appearance in the coating process, could be imparted to the surface, and the finished sheet had good decorativeness for the practical use.

Comparative Example 2

A graphics-protection sheet of this Comparative Example was produced in the same manner as in Example 1 except that no cushioning layer was formed. With the protection sheet of this Comparative Example, the physical deformation of the surface of the protective layer was very difficult, and it was hardly possible to impart an appearance that was different from the spontaneously formed appearance in the coating process.

Claims

We claim:

1. A graphic-protection sheet comprising a protective layer having a surface and a back surface, that comprises a layer containing a cured resin and a plurality of hard beads dispersed therein at least as the outermost layer that constitutes the surface of said protective layer, wherein said graphics-protection sheet has light transmission properties as a whole and graphics provided on the back surface side of the protective layer can be seen from the surface side of said protective layer, characterized in that said protective layer has a cushioning layer that comprises a resin layer having a surface adhered to said protective layer and a back surface opposing to said surface, and has light transmission properties and thermoplasticity, the outermost layer of said protective layer comprises a coating film that comprises said cured resin and said hard beads, and the surface of said protective layer is compression-processed to provide surface roughness with a specific size thereto.

2. The graphics-protection sheet according to claim 1, wherein the thickness of said cushioning layer is from 25 to 500 μm.

3. The graphics-protection sheet according to claim 1, wherein said protective layer further comprises a layer that is adhered to said outermost layer and comprises a cured resin but no hard beads.

4. The graphics-protection sheet according to claim 1 , wherein said compression-processing is embossing, a plurality of convex parts comprising said cured resin and at least two hard beads are formed on the surface of said protective layer, and the back surface of said cushioning layer has no unevenness due to the embossing.

5. The graphics-protection sheet according to claim 1, wherein said compression-processing is calendering, and the surface of said protective layer has specular gloss.

6. A graphics-displaying sheet comprising

(i) a graphics-protection sheet claimed in claim 1, (ii) a base layer that has a surface fixed to said cushioning layer and a back surface opposing to said surface, and includes graphics, and

(iii) an adhesive layer fixed to the back surface of said base layer.