JP7519064B2 - Resin composition for writable screen, writable screen using same, and method for producing same - Google Patents

Description

The present invention relates to a resin composition for a writeable screen, a writeable screen using the same, and a method for manufacturing the same. More specifically, the present invention relates to a resin composition for a writeable screen that improves both the projectability and the erasability after writing with a marker, a writeable screen using the same, and a method for manufacturing the same.

In recent years, screens have become known that function as projection screens that project characters, photos, figures, etc. emitted from a projector connected to an information or communication device such as a personal computer, tablet terminal, or smartphone, and that also allow writing on them with a whiteboard marker or the like and erasing that information with a whiteboard eraser. Such screens are also known as writable screens.

Conventional projection screens have a textured surface, created by embossing the surface material or incorporating fine particles, which diffuses the light projected from the projector, reducing glare known as hot spots and expanding the viewing angle of the image.

In contrast, a satisfactory writable screen that is free of hot spots and glare during use, and has a well-balanced combination of writability, erasability, and scratch resistance over long-term use has yet to be found.

For example, Patent Document 1 proposes a screen in which an ultraviolet-curable resin is applied to the surface of a polyethylene terephthalate resin film and cured, and the cured coating surface is embossed to create irregularities with an arithmetic mean roughness of 1.5 to 3.0 μm and an average peak-to-peak distance of about 50 to 280 μm. The screen in Patent Document 1 is intended to improve the erasability of characters written with whiteboard markers.

Patent Document 2 describes a writable screen in which a resin layer containing fine particles is provided on a substrate, and the arithmetic mean roughness Ra1 (arithmetic mean roughness of the surface conforming to JIS B0601 (2001) at a cutoff value of 0.8 mm and a stylus tip radius of 2.5 μm) on the writing and projection surface is 0.1 to 3.0 μm, and Ra2 (arithmetic mean roughness of the surface conforming to JIS B0601 (2001) at a cutoff value of 0.08 mm and a stylus tip radius of 2.5 μm) on the writing and projection surface is 0.05 to 0.20 μm. The screen in Patent Document 2 aims to improve writability and erasability as well as hot spots and glare.

Patent document 3 describes a projection screen made by applying and curing an ultraviolet-curing resin containing fine particles with an average particle size of 2 to 12 μm onto a substrate made of a thermoplastic resin. Patent document 3 also describes that by adding a fluorine-based or silicone-based compound to the ultraviolet-curing resin, the gloss (60-degree surface gloss) of the cured surface becomes about 3 to 38, improving hot spots and erasability.

However, while the screens described in Patent Documents 1 to 3 are all expected to achieve the desired improvement effects as intended by each of the patent documents, it is difficult to say that they provide a good balance between the writing function, which relates to the ease of writing and erasing when using a whiteboard marker or whiteboard eraser, and the projection function, which relates to the prevention or reduction of hot spots and glare. For this reason, further development of writable screens is desired.

WO 01/032440 International Publication No. 2013/137099 JP 2018-54809 A

The present invention aims to solve the above problems, and its objective is to provide a resin composition for a writeable screen, a writeable screen using the same, and a method for producing the same, which can improve in a well-balanced manner the writing function related to the ease of writing and erasing when using a whiteboard marker or whiteboard eraser, and the projection function related to the prevention or reduction of hot spots and glare.

The present invention relates to a resin composition for a writable screen, which contains an ultraviolet-curable resin and a solventless reactive silicone, and the content of the solventless reactive silicone is 0.5 to 10 parts by weight per 100 parts by weight of the ultraviolet-curable resin.
In one embodiment, the ultraviolet curable resin is an epoxy-modified acrylate-based resin, a urethane-modified acrylate-based resin, or a silicone-modified acrylate-based resin.
In a further embodiment, the UV-curable resin is a urethane-modified acrylate-based resin.

In one embodiment, the content of the solventless reactive silicone is 1 to 8 parts by weight per 100 parts by weight of the ultraviolet-curable resin.

In one embodiment, the solventless reactive silicone is a polysiloxane modified with an acrylic acid group or a methacrylic acid group.

The present invention also relates to a writable screen having a resin layer on a substrate layer, the resin layer being composed of a cured product of the resin composition for the writable screen.

In one embodiment, the arithmetic mean roughness Ra of the resin layer is 0.3 to 0.8 μm.

In one embodiment, the average spacing Sm between adjacent projections and recesses in the resin layer is 40 to 80 μm.

The present invention relates to a method for producing a writable screen, the method comprising the steps of:
A step of disposing the above-mentioned resin composition for a writing screen on a substrate layer; and a step of irradiating the resin composition disposed on the substrate layer with ultraviolet light.
The method includes:

The present invention achieves both writability and erasability with whiteboard markers and whiteboard erasers, while preventing or reducing hot spots and glare. The writable screen of the present invention also has excellent scratch resistance against the markers and erasers, since the screen surface (the surface on the resin layer side) has good strength.

1 is a schematic cross-sectional view showing an example of the writable screen of the present invention.

The present invention is described in detail below.

(Writable Screen Resin Composition)
The writable screen resin composition of the present invention contains an ultraviolet-curable resin and a solventless reactive silicone.

The UV-curable resin in the present invention is a monomer or oligomer that has the property of undergoing a polymerization reaction and solidifying when irradiated with light (particularly UV light), and examples of such resins include those that have the property of inducing radical polymerization of unsaturated double bonds when irradiated with light (acrylate-type UV-curable resins) and those that have the property of inducing cationic polymerization when irradiated with light (epoxy-type UV-curable resins). Specific examples of such UV-curable resins include epoxy-modified acrylates, urethane-modified acrylates, silicone-modified acrylates, and epoxy resins, as well as their fluorine-modified oligomers or monomers, or resins containing known photopolymerization initiators.

Examples of ultraviolet-curable resins include the "Shiko (registered trademark)" series of ultraviolet-curable resins manufactured by Nippon Synthetic Chemical Industry Co., Ltd. (e.g., UV-1700B, UV-7510B, UV-7640B, UV-7605B).

Solventless reactive silicone is a silicone oil in which reactive functional groups have been introduced into some of the silicon atoms that make up the silicone. When combined with the above-mentioned UV-curable resin, it is a material that can impart the properties of silicone oil when the resin is cured by UV light. Examples of such solventless reactive silicones include those in which a reactive functional group has been added to one end of the molecule that constitutes the polysiloxane (single-end reactive silicone), those in which a reactive functional group has been added to the side chain of the molecule that constitutes the polysiloxane (side-chain reactive silicone), and combinations thereof. Single-end reactive silicones can be graft-copolymerized with, for example, resins (UV-curable resins), and can impart water repellency and slipperiness to the resin surface. Side-chain reactive silicones can be randomly copolymerized with, for example, resins (UV-curable resins), and can impart water repellency and slipperiness to the resin surface.

Examples of reactive functional groups constituting the one-end reactive silicone and/or side-chain reactive silicone include amino groups, diamino groups, epoxy groups, alicyclic epoxy groups, carbinol groups, mercapto groups, carboxyl groups, diol groups, acrylic groups, and methacrylic groups, as well as combinations thereof. In order to provide the resulting screen with good writing functionality (e.g., writability and erasability with a whiteboard marker or whiteboard eraser), the solventless reactive silicone is preferably a polysiloxane modified with an acrylic acid group or a methacrylic acid group, and more preferably a one-end reactive polysiloxane (one-end reactive silicone) in which one end of the polysiloxane molecule is modified with an acrylic acid group or a methacrylic acid group.

Solvent-free reactive silicones are commercially available, for example, from Shin-Etsu Silicone Co., Ltd. in the "Shin-Etsu Silicone Oil X-22-174" series, with Shin-Etsu Silicone Oil X-22-174BX being particularly preferred.

The content of the solventless reactive silicone in the resin composition of the present invention is 0.5 to 10 parts by weight, preferably 1 to 8 parts by weight, based on 100 parts by weight of the ultraviolet-curable resin. If the content of the solventless reactive silicone is less than 0.5 parts by weight, the erasability and/or slipperiness of the obtained screen with a board eraser may decrease. If the content of the solventless reactive silicone exceeds 10 parts by weight, dispersibility when blended with the ultraviolet-curable resin may decrease, making it difficult to obtain a homogeneous resin composition.

The resin composition of the present invention may contain fine particles to further improve both the writing function and the projection function of the resulting screen. Examples of such fine particles include organic materials (e.g., thermoplastic resins such as polyethylene, polypropylene, and acrylic resins), inorganic materials (e.g., glass, silica, alumina, titanium compounds, and zirconium compounds), and combinations thereof. The average particle size and content of the fine particles are not particularly limited, and an appropriate average particle size and amount can be selected by those skilled in the art.

The resin composition of the present invention may contain other additives as necessary. Examples of such other additives include antioxidants (e.g., phenol-based antioxidants, sulfur-based antioxidants, and/or phosphorus-based antioxidants); antistatic agents (e.g., anionic activators, cationic activators, nonionic activators, and/or amphoteric activators); lubricants (e.g., hydrocarbon-based lubricants, fatty acid-based lubricants, higher alcohol-based lubricants, fatty acid amide-based lubricants, metal soap-based lubricants, and/or ester-based lubricants); and flame retardants (e.g., organic flame retardants and/or inorganic flame retardants); and combinations thereof. The content of the other additives that may be contained in the present invention is not particularly limited, and any amount may be selected by a person skilled in the art.

(Writable screen)
The writable screen of the present invention has a resin layer on a substrate layer.

Figure 1 is a schematic cross-sectional view showing an example of a writable screen of the present invention. In the screen 100 of Figure 1, the resin layer 120 is disposed on one side of the base layer 110. In Figure 1, the resin layer 120 is disposed so as to be in direct contact with the base layer 110, but the present invention is not limited to this embodiment. For example, an adhesive layer may be provided between the resin layer 120 and the base layer 110 using a material as described below.

Materials constituting the base layer include, for example, paper (e.g., cardboard, Western paper, Japanese paper), synthetic paper, fabric (e.g., woven fabric, knitted fabric, nonwoven fabric), and synthetic resin sheets or films, as well as laminates thereof. Since it constitutes a screen, it is preferable that at least one side of the base layer (i.e., the side constituting the base layer 110 in FIG. 1 above, on which the resin layer 120 is disposed) is white.

In the present invention, among the materials constituting the base layer, a synthetic resin sheet or film is preferred because of its excellent durability and flatness. Furthermore, the synthetic resin sheet or film is preferably a white polyester resin sheet or film, and more preferably a white biaxially stretched polyester film, because of its excellent strength, dimensional stability, heat resistance, etc. Examples of such white biaxially stretched polyester films include Diafoil W400J manufactured by Mitsubishi Chemical Corporation, Lumirror E28G manufactured by Toray Industries, Inc., Teijin (registered trademark) Tetoron (registered trademark) Film U292W manufactured by Teijin Film Solutions Co., Ltd., and Crisper K2323 manufactured by Toyobo Co., Ltd., etc., which are commercially available.

The thickness of the substrate layer in the writable screen of the present invention is not necessarily limited, but is, for example, 25 μm to 250 μm, more preferably 75 μm to 200 μm. If the thickness of the substrate layer is less than 25 μm, the resulting screen cannot be given sufficient strength and may be prone to breakage during use (for example, when erasing characters with a board eraser). If the thickness of the substrate layer exceeds 250 μm, there is no change in the desired improvement in the writing function and projection function, and instead the weight of the resulting screen itself may become heavy.

On the other hand, in the present invention, the material constituting the resin layer is composed of the cured product of the resin composition for a writable screen of the present invention. The cured product is obtained by curing the resin composition for a writable screen of the present invention by irradiating it with light (e.g., ultraviolet light). The resin layer has an appropriate water repellency and slipperiness on its surface due to the additive-free reactive silicone contained in the resin composition.

In the writable screen of the present invention, the surface of the resin layer (particularly the surface of the resin layer 120 shown in FIG. 1 opposite to the surface in contact with the base layer 110) preferably has a predetermined arithmetic mean roughness Ra. This arithmetic mean roughness Ra is measured in accordance with JIS B0601 (2001). In the writable screen of the present invention, the arithmetic mean roughness Ra of the resin layer is preferably 0.3 μm to 0.8 μm, more preferably 0.5 μm to 0.7 μm. If the arithmetic mean roughness Ra of the resin layer is below 0.3 μm, the resulting screen may have hot spots and glare, and the anti-glare properties may be deteriorated. If the arithmetic mean roughness Ra of the resin layer exceeds 0.8 μm, the erasability with a board eraser may be reduced.

In the writeable screen of the present invention, the surface of the resin layer (particularly the surface of the resin layer 120 shown in FIG. 1 opposite to the surface in contact with the base layer 110) preferably has a predetermined value of the average spacing between adjacent convex portions (also called the surface roughness or the average spacing between peaks and valleys) Sm. This average spacing between adjacent convex portions Sm is measured in accordance with JIS B0601 (2001). In the writeable screen of the present invention, the average spacing between adjacent convex portions Sm of the resin layer is preferably 40 μm to 80 μm, and more preferably 50 μm to 70 μm. If the average spacing between adjacent convex portions Sm of the resin layer is less than 40 μm, erasability with a board eraser may decrease. If the average spacing between adjacent convex portions Sm of the resin layer is more than 80 μm, anti-glare properties may deteriorate.

The thickness of the resin layer in the writable screen of the present invention is not necessarily limited, but is, for example, 2 μm to 50 μm, and more preferably 5 μm to 20 μm. If the thickness of the resin layer is less than 2 μm, it may be difficult to maintain the uniformity of the coating (i.e., to arrange the resin layer on the substrate layer with a substantially uniform thickness). If the thickness of the resin layer is more than 50 μm, the resulting screen may curl.

In the writable screen of the present invention, when an adhesive layer is disposed between the substrate layer and the resin layer, the material constituting the adhesive layer is not particularly limited, and any material known in the art may be used. The thickness of the adhesive layer is also not particularly limited, and an appropriate thickness may be selected by a person skilled in the art.

The writeable screen of the present invention may have another layer, such as a magnetic sheet, provided, for example, via an adhesive layer, on the other side of the base layer, i.e., the side opposite to the side in contact with the resin layer. When the writeable screen of the present invention is provided with such a magnetic sheet, it can be easily installed and removed in a predetermined location, such as a blackboard or metal partition. Such magnetic sheets are commercially available.

The writable screen of the present invention is manufactured, for example, as follows.

First, the resin composition for a writable screen of the present invention is placed on the substrate layer.

Specifically, the resin composition for a writable screen, which contains the ultraviolet-curable resin and the solventless reactive silicone, is applied, for example, in the form of a uniform mixture, to one surface of the material that constitutes the base layer. The resin composition for a writable screen is applied to the base layer by a method known in the art, for example, by coating or spraying.

After the resin composition for the writable screen is placed on the substrate layer, the surface on which the resin composition for the writable screen is placed may be textured to give it a specific unevenness or physical shape in order to prevent the occurrence of hot spots by diffusely reflecting the projection light emitted from the projector on the resulting screen surface. This texture processing may be performed using a method known in the art.

This places the resin composition for a writable screen of the present invention on the substrate layer.

In the present invention, the resin composition disposed on the substrate layer is then irradiated with ultraviolet light.

The ultraviolet irradiation is carried out by means known in the art, for example, by using an ultraviolet device equipped with a UV light source. Types of UV light sources that can be used in the present invention include, for example, lamps such as mercury lamps, metal halide lamps, high-efficiency metal halide lamps, and high-power metal halide lamps; and LED lights. In the present invention, the ultraviolet light irradiated preferably has an emission wavelength of 254 nm and/or 365 nm, and the irradiation time is not necessarily limited because it varies depending on the type and output of the UV light source used. By irradiation with ultraviolet light, the resin composition for the writable screen forms a resin layer as a cured product on the substrate layer.

In this manner, the writable screen of the present invention is manufactured.

The writable screen of the present invention allows free writing on the resin layer using, for example, a commercially available whiteboard marker. Furthermore, written characters and figures can be easily erased using a commercially available whiteboard eraser. In addition, the writable screen of the present invention allows light emitted from a projector to be projected onto the resin layer while preventing or reducing hot spots and glare. In this way, the writable screen of the present invention is excellent in both writing and projection functions, and both functions are improved in a well-balanced manner compared to conventional screens.

The writable screen of the present invention is useful in a variety of facilities, such as offices, schools or educational facilities, libraries, hospitals, rental conference rooms, exhibition halls, theaters, concert halls, commercial facilities, airports, and government offices.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

(Screen evaluation)
The screens produced or obtained in the following Examples and Comparative Examples were evaluated for the following evaluation items.

(1) Writability For the screens produced or obtained in the Examples and Comparative Examples, five panelists checked the ease of writing on the screen by drawing a straight line of about 10 cm long on the screen surface with a whiteboard marker. After that, the panelists discussed and judged the ease of writing on the screen according to the following criteria:
“○”: The marker was able to draw a smooth straight line without any interruptions.
"△": The marker was able to draw a straight line without any interruptions, but it felt a bit rough.
"X": The marker was not sliding well, so the straight line was broken and it had to be redrawn.

(2) Erasability Five straight lines, each about 10 cm long, were drawn on the surface (the surface on the resin layer side) of the screens produced or obtained in the Examples and Comparative Examples with a commercially available whiteboard marker, and the screens were left for 5 minutes in a room at about 25° C. The five straight lines were then rubbed with a commercially available whiteboard eraser, and the ease of erasing the ink drawn with the marker was checked by five panelists, who then discussed and judged the results according to the following criteria:
"○": The ink was completely removed by rubbing it several times without applying too much pressure.
"△": When I rubbed it a few times without applying too much pressure, some ink remained, but by rubbing it further it could be erased.
"X": The ink could not be erased even by rubbing without applying any pressure, but it was finally erased by rubbing with pressure and repeatedly.

(3) Surface Smoothness Five straight lines, each about 10 cm long, were drawn on the surface (surface on the resin layer side) of the screens produced or obtained in the Examples and Comparative Examples using a rigid PVC melamine foam (5 × 5 × 5 cm ³ ; foam). Five panelists checked the smoothness of the foam on the screen surface when five straight lines, each about 10 cm long, were drawn on the surface (surface on the resin layer side) of the screens produced or obtained in the Examples and Comparative Examples. After that, the panelists discussed and judged the smoothness of the foam on the screen surface according to the following criteria:
"◯": The foam could be moved smoothly.
"Δ": The foam felt somewhat rough when sliding.
"X": The foam felt quite rough and slippery.

(4) Stain Retention A screen sample cut to 10 cm x 10 cm was placed on a flat surface with the resin layer facing upward, and an arbitrary line was drawn on the screen surface (surface on the resin layer side) with a commercially available whiteboard marker. Immediately afterwards, a panelist rubbed the screen surface back and forth five times lightly with a whiteboard eraser to erase the line. Even if stains remained, the marker line drawing and erasing were repeated 20 times, and the remaining state of stains on the screen surface was visually evaluated. The remaining stains were judged on a scale of 1 to 5, with 1 point for dark stains and 5 points for no stains at all. This was done by five panelists, and the scores of each panelist were tallied and the average value was calculated.

(5) Surface gloss (gloss; 60 degree specular gloss)
For the screens produced or obtained in the Examples and Comparative Examples, the surface gloss (60 degree specular gloss) of the screen surface (surface on the resin layer side) was measured in accordance with JIS Z8741 (1997).

(6) Arithmetic mean roughness (Ra)
For the screens produced or obtained in the examples and comparative examples, the arithmetic mean roughness (Ra) of the screen surface (surface on the resin layer side) was measured in accordance with JIS B0601 (2001).

(7) Average spacing between adjacent irregularities (Sm)
For the screens produced or obtained in the examples and comparative examples, the average spacing (Sm) of adjacent irregularities on the screen surface (surface on the resin layer side) was measured in accordance with JIS B0601 (2001).

(8) Hot Spots For the screens produced or obtained in the Examples and Comparative Examples, the screen surface (surface on the resin layer side) was irradiated with white light using a single focus projector (VX425NXGA manufactured by Panasonic Corporation), and the presence or absence of hot spots was visually confirmed by five panelists. After that, all the panelists discussed and made a judgment based on the following criteria:
"◯": No hot spots were observed.
"△": Slight hot spots were observed, but it was judged to be practically usable.
"X": Hot spots were observed and it was determined that the material was not suitable for practical use.

(9) Glare For the screens produced or obtained in the Examples and Comparative Examples, white light was irradiated onto the screen surface (the surface on the resin layer side) using a single focus projector (VX425NXGA manufactured by Panasonic Corporation), and the presence or absence of glare was visually confirmed by five panelists. After that, all the panelists discussed and made a judgment based on the following criteria:
"◯": No glare was observed.
"△": A slight glare was observed, but it was judged to be usable.
"X": Glare was observed and it was determined that the product was not suitable for practical use.

Example 1
To 100 parts by weight of ultraviolet-curing resin (Shikoh (registered trademark) UV-7510B manufactured by Nippon Gosei Co., Ltd.), 1 part by weight of solvent-free reactive silicone (X-22-174BX manufactured by Shin-Etsu Chemical Co., Ltd.) was added to obtain a resin composition (E1). Next, as a substrate layer, this resin composition (E1) was applied to a 125 μm thick white biaxially oriented polyethylene terephthalate film (Lumirror E28G manufactured by Toray Industries, Inc.) with easy adhesion on both sides (anchor coat treatment completed), and pressed at a pressure of 0.3 MPa with a commercially available embossed sheet (A), irradiated with ultraviolet light (irradiation conditions: 1700 mJ / cm ² ), and the embossed sheet was peeled off to form a 10 μm thick coating film (resin layer) on the white biaxially oriented polyethylene terephthalate film to produce a screen (ES1). The arithmetic mean roughness Ra of this resin layer was 0.3 μm. The evaluation results of the obtained screen (ES1) are shown in Table 1.

(Examples 2 to 4)
A 125 μm thick white biaxially stretched polyethylene terephthalate film (Diafoil W400J manufactured by Mitsubishi Chemical Corporation) with easy adhesion on both sides (anchor coat treated) was used as the base layer, and the resin layer was subjected to a finishing process using any one of the commercially available embossed sheets (B) to (D) so that the arithmetic average roughness Ra of the resin layer was as shown in Table 1. The resin composition (E1) was applied onto the base layer in the same manner as in Example 1, and screens (ES2) to (ES4) were produced in the same manner as in Example 1. The evaluation results of the obtained screens (ES2) to (ES4) are shown in Table 1.

(Comparative Example 1)
Except for not using the solvent-free reactive silicone, a screen (CS1) was produced in the same manner as in Example 1. The evaluation results of the obtained screen (CS1) are shown in Table 1.

(Comparative Example 2)
A resin composition was prepared in the same manner as in Example 1, except that 1 part by weight of a solvent-free non-reactive silicone (non-reactive KF640 manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of the solvent-free reactive silicone. The silicone had poor dispersibility, and a homogeneous resin composition could not be obtained. However, a screen (CS2) was prepared in the same manner as in Example 1, except that the resin composition was used. The evaluation results of the obtained screen (CS2) are shown in Table 1.

As shown in Table 1, the screens (ES1), (ES2), (ES3) and (ES4) obtained in Examples 1 to 4 were equivalent to or superior to the screens (CS1) and (CS2) of Comparative Examples 1 and 2 in almost all of the screen evaluation items, and were found to be superior overall as writable screens.

The present invention is useful, for example, in the fields of office equipment manufacturing and resin molding.

100 Writable screen 110 Base layer 120 Resin layer

Claims (5)

A writable screen having a resin layer on a base layer, the resin layer being formed of a cured product of a resin composition for a writable screen,
the resin composition for a writable screen contains an ultraviolet-curable resin and a solventless reactive silicone, the content of the solventless reactive silicone being 0.5 to 10 parts by weight per 100 parts by weight of the ultraviolet-curable resin;
the resin layer has an arithmetic mean roughness Ra of 0.5 to 0.8 μm;
The resin layer has an average spacing Sm between adjacent projections and recesses of 40 to 80 μm. The writable screen according to claim 1, wherein the ultraviolet-curable resin is an epoxy-modified acrylate resin, a urethane-modified acrylate resin, or a silicone-modified acrylate resin. The writable screen according to claim 2, wherein the ultraviolet-curable resin is a urethane-modified acrylate resin. The writable screen according to any one of claims 1 to 3, wherein the content of the solvent-free reactive silicone is 1 to 8 parts by weight per 100 parts by weight of the ultraviolet-curable resin. The writable screen according to any one of claims 1 to 4, wherein the solvent-free reactive silicone is a polysiloxane modified with an acrylic acid group or a methacrylic acid group.

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