JP7175607B2 - writing sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a writing sheet on which an image can be recorded by changing the color density of a pressed portion, and which can be easily erased and restored, and which can be repeatedly written and erased.

Conventionally, it is composed of a base material having an adhesive surface and a transparent cover sheet provided thereon, and by applying pressure from the top of the cover sheet, the base material and the cover sheet at the pressed portion are bonded together. A writing sheet is known in which an image can be recorded on a contact portion in close contact. Also known are writing sheets composed of a non-stick substrate and a transparent cover sheet having a sticky surface disposed thereon. Such a writing sheet can be restored to its initial state by erasing the image by peeling off the base and cover sheet. Therefore, recording and erasing can be performed repeatedly.

Such writing sheets can be applied to recording sheets, store displays, educational toys, educational materials, and the like, and various products have been researched and developed. For example, Patent Literatures 1 and 2 disclose repetitively writing sheets and teaching toys.

JP 2010-042618 A Japanese Patent Application Laid-Open No. 2001-142387

However, according to the investigations of the present inventors, these writing sheets have a low contrast in the recorded image, the contrast of the recorded image deteriorates over time, and the adhesiveness is excessively high, so peeling does not occur. Further improvement was necessary because it was difficult and problems such as damage to the base material or cover sheet occurred during peeling.

The writing sheet according to the present invention is
a substrate comprising a colored support and an adhesive layer formed on the surface thereof;
A writing sheet comprising a film and a transparent cover sheet having a matte surface formed on one surface of the film, wherein the adhesive layer and the matte surface are arranged so as to be in contact with each other. hand,
The matte surface has an arithmetic mean height Sa of 0.10 to 0.50 μm.

According to the present invention, a writing sheet is provided on which a high-contrast image can be recorded, the contrast of the image hardly changes with time, and recording and erasing are easy.

1 is a conceptual cross-sectional view of a writing sheet according to the present invention; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail.

[Writing sheet]
A conceptual cross-sectional view of a writing sheet according to one embodiment of the present invention is shown in FIG. This writing sheet 100 comprises a substrate 110 and a cover sheet 120 . The base material 110 and the cover sheet 120 are arranged so that their surfaces face each other. Here, the base material and the cover sheet may be adhered or fixed at their ends so as not to be separated from each other, or may be independent without being bonded to each other. When the substrate and coversheet are not bonded together, the combination is called a writing sheet.

In this writing sheet, in the initial state before recording an image, the substrate and the cover sheet are not in close contact with each other, and an air layer exists at the interface between them.

When recording an image, a desired portion is pressed from above the cover sheet. The base material and the cover sheet are brought into close contact directly under the pressed portion. As a result, the air layer existing at the interface between the substrate and the cover sheet is substantially eliminated, and the refractive index at the interface changes.

As a result, the refractive index changes between the interface of the non-pressurized portion and the interface of the pressurized portion, contrast occurs, and an image is recorded. In general, the color of the base material can be recognized from above the cover sheet in the pressed portion. The method of applying pressure is arbitrary, and includes a method of applying pressure in the shape of letters with a pen made of a resin material, a method of pressing a relief such as a stamp to transfer a pattern, and the like.

Then, by peeling off the cover sheet from the base material, an air layer is generated again at the interface and the image is erased. The method of peeling off the cover sheet is arbitrary, and the cover sheet can be lifted from the ends or moved by inserting a bar between the substrate and the cover sheet.

Thus, the writing sheet according to the present invention can be repeatedly subjected to image recording and erasing.

[Base material]
The substrate used in the present invention comprises a colored support 111 and an adhesive layer 113 on the surface facing the cover sheet. The adhesive layer 113 is a layer that comes into close contact with the cover sheet during image recording, and the close contact allows, for example, the color of the colored support 111 to be observed from the surface of the writing sheet.

The adhesive layer 113 is formed on at least one surface of the colored support 111 . By providing an adhesive layer on both sides of the colored support and combining two cover sheets facing each side, a writing sheet capable of recording on both sides can be obtained.

Here, the colored support is not particularly limited, but it must be colored in order to maintain high contrast of the image observed from the surface of the writing sheet during image recording. In addition, the colored support is also required to have strength in order to impart sufficient physical strength to the writing sheet.

From this point of view, as shown in FIG. 1, in one embodiment, a colored support comprising a core plate 111b and a colored layer 111a can be used. By using a core plate having sufficient physical strength, it becomes possible to select various colored layers according to cost and color. At this time, the core plate preferably has sufficient physical strength, and can be selected from any conventionally known materials. For example, it can be selected from polyolefin resins and polyester resins. More specifically, the (i) polyolefin resin film includes polyethylene (PE) resin, polypropylene (PP) resin, ethylene-propylene copolymer, ethylene- The (ii) polyester resin can be selected from polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, polyethylene naphthalate resin, polybutylene naphthalate resin, and the like from butene copolymers and the like. Among these, polyester-based resins are preferred, and PET resins are particularly preferred in terms of strength and workability.

The surface of these films may be subjected to conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, application of an undercoat agent (formation of an undercoat layer), and the like.

The thickness of the core plate is not particularly limited, but the thickness is preferably 50 to 250 μm in order to achieve sufficient physical strength.
These core plates may be clear, colored, or opaque. When the core plate is colorless and transparent, it is preferably laminated with a colored layer. In either case, the colored support as a whole is preferably opaque. In the present invention, being opaque means having a transmittance of less than 80%, preferably less than 60%, over the entire wavelength range of 400 to 760 nm. On the other hand, being colorless and transparent means having a transmittance of 80% or more, preferably 90% or more, over the entire wavelength range. Furthermore, the term "colored transparent" means that part of the wavelength region has a transmittance of less than 80%.

When a colored layer is used to make the colored support opaque, the colored layer may be a colored sheet-like material or the like laminated to a transparent core plate, or the surface of the transparent core plate may be colored. Layers may be applied and formed.

Examples of colored sheet materials include colored paper, dyed resin films, films made of resin materials in which colored particles are dispersed, and colored fiber aggregates. When the colored layer is formed by coating, a composition containing a binder in which colored particles are dispersed is coated and dried or cured to form the colored layer. Examples of colored particles include inorganic pigment particles, metal powders, metal oxide powders, and the like.

It is also possible to use a metal plate as the colored support or a colored support having a metal layer as the colored layer. Special effects can be obtained when such a metal-like surface is used for a colored support. In this case, the contrast of the image obtained by writing is relatively low. However, when the recorded image is copied by a copying machine, a high-contrast image is copied. By using such an effect, a watermark effect can be obtained.

The cover sheet side surface of the colored support preferably has high smoothness. A pressure-sensitive adhesive layer is provided on the surface as described later, and since it is preferable that the surface of the pressure-sensitive adhesive layer has high smoothness, the cover sheet side surface of the colored support that serves as the base is also smooth. It is preferable that the From this point of view, the cover sheet side surface of the colored support is preferably a core plate made of resin. Therefore, when the colored support has a structure in which a core plate and a colored layer are laminated, the colored layer should be formed on the side opposite to the side facing the cover sheet, as shown in FIG. is preferred.

The substrate 110 has an adhesive layer 113 . Prior to forming this adhesive layer 113 on the surface of the substrate 110, an intermediate layer 112 can be provided to improve adhesion between the substrate and the adhesive layer. When the writing sheet is used, the adhesive layer and the cover sheet are repeatedly adhered and peeled off, so that the adhesive layer may peel off from the surface of the base material. It can also improve the storage stability of the writing sheet.

Various resins such as polyester resins, acrylic resins, polyurethane resins, acrylic-grafted polyester resins, and silicone resins can be used as materials for the intermediate layer. This intermediate layer can be formed of polyester resin, for example. Increasing the thickness of the intermediate layer can improve the adhesiveness between the substrate and the adhesive layer, while decreasing the thickness facilitates reproduction of the color of the colored support during image recording. From this point of view, the intermediate layer preferably has a thickness of 0.05 to 1.0 μm.

In the substrate used in the present invention, an adhesive layer is formed directly on the surface of the colored support or on the surface via an intermediate layer. An image is recorded on the adhesive layer by being brought into close contact with the cover sheet during image recording. Therefore, from the viewpoint of image recording stability, it is preferable that the adhesive strength is high. It can damage the adhesive layer or the cover sheet. Furthermore, even when the writing sheet is left unattended, the cover sheet and the adhesive layer may adhere to each other, and an unintended image may be recorded. Therefore, the adhesive strength of the adhesive layer is preferably 1.0 to 5.0 N/m, more preferably 1.5 to 4.0 N/m. Here, the adhesive strength can be measured according to the 180° peeling adhesive strength measurement for a test plate shown in JISZ 0237 Method 1.

Such a pressure-sensitive adhesive layer is generally formed by mixing a pressure-sensitive adhesive composition with a catalyst or the like, if necessary, and then coating the colored support or core plate with an intermediate layer if necessary, It is formed by heating or the like to cause a reaction.

As a material for the adhesive layer, any one can be selected from conventionally known adhesives.

Such adhesives include acrylic adhesives, rubber adhesives, polyester adhesives, urethane adhesives, polyether adhesives, silicone adhesives, polyamide adhesives, fluorine adhesives, and the like. Various adhesives are mentioned.

Among these, the silicone-based pressure-sensitive adhesive is mainly composed of a polymer having a siloxane bond as a main skeleton. Silicone pressure-sensitive adhesives are preferable because many of them exhibit suitable adhesiveness and are excellent in chemical resistance, water resistance, and heat resistance. Another reason why silicone-based pressure-sensitive adhesives are preferable is that the change in pressure-sensitive adhesive strength is small. A urethane-based pressure-sensitive adhesive is mainly composed of a polymer obtained by condensing an isocyanate compound and a hydroxy compound. Although it is a preferable pressure-sensitive adhesive because of its excellent releasability, it is often higher in pressure-sensitive adhesive strength than silicone-based pressure-sensitive adhesives, and it may be necessary to adjust the pressure-sensitive adhesive properties. Further, when a urethane adhesive is used, the adhesive force between the cover sheet and the adhesive layer tends to change depending on the pressure applied during image recording. Therefore, when the uniformity of the force required for peeling the cover sheet and the uniformity of the contrast of the recorded image are important, it is preferable to use a silicone-based pressure-sensitive adhesive.

Various adhesives are commercially available for use in such a method, and a suitable one can be selected and used from them. Specifically, examples of silicone adhesives include LTC755, SD4580PSA (all trade names, sold by Dow Corning Toray Co., Ltd.), KR3700, KR3701, KR3704 (all trade names, sold by Shin-Etsu Chemical Co., Ltd.). ), and the catalysts to be combined therewith include NC-25 Catalyst (trade name, sold by Dow Corning Toray Co., Ltd.) and CAT-PL-50T (trade name, sold by Shin-Etsu Chemical Co., Ltd.). . Examples of urethane-based pressure-sensitive adhesives include Siavane series SH-101M, SH-101, and SP-205 (all trade names, sold by Toyochem Co., Ltd.), and a catalyst to be combined with them is Siavane T501B (polyfunctional isocyanate system cross-linking agent) (trade name, sold by Toyochem Co., Ltd.).

The catalyst to be combined with the silicone adhesive is preferably a platinum-containing noble metal catalyst because it can adjust the crosslink density, and platinum-ruthenium alloys, platinum-palladium alloys, platinum-titanium alloys, and the like are particularly preferably used.

The method of applying the pressure-sensitive adhesive composition is not particularly limited, and for example, it can be performed using a conventionally known coater such as a gravure roll coater, a die coater, and a bar coater. Alternatively, the adhesive composition may be applied by impregnation, curtain coating, or the like.

After coating, it is preferable to heat in order to accelerate the cross-linking reaction and improve production efficiency. The heating temperature is generally selected from the range of 40-150°C, preferably 60-130°C.

The thicker the adhesive layer, the easier it is to adhere to the cover sheet, and the thinner the adhesive layer, the easier it is to reproduce the color of the colored support during image recording, and the lower the production cost. Therefore, the thickness of the adhesive layer is preferably 5 to 30 μm, more preferably 10 to 20 μm. Moreover, the surface of the adhesive layer is preferably smooth.

In addition, the adhesive layer may be colored. By making the color of the colored support and the color of the adhesive layer different, it is possible to record an image with a color that is a combination of the color of the adhesive layer and the color of the colored support. Further, by making the color of the colored support and the color of the adhesive layer the same, it is possible to record an image with a higher color density by combining the color density of the adhesive layer and the color density of the colored support. be possible. Furthermore, the adhesive layer can also have the function of a colored layer. In other words, it is possible to omit providing a separate colored layer by imparting a high-concentration color to the adhesive layer.

[Cover sheet]
When the cover sheet 120 used in the present invention is in close contact with the adhesive layer 113, it is necessary that the color of the substrate can be observed from the surface of the writing sheet. For this reason, the cover sheet should be transparent. Generally, the cover sheet is preferably colorless and transparent. The high transmittance of the coversheet over the entire wavelength range of 400-760 nm enables image recording faithful to the coloration applied to the substrate. However, it is also possible to color the cover sheet. By using a cover film that is partially transmissive in the wavelength range of 400 to 760 nm, it is possible to record an image with a color different from that applied to the substrate.

Such cover sheets generally comprise a transparent film. Since the cover sheet is required to have not only transparency but also physical strength, a film made of the material exemplified for the colored support is preferably used.

In the present invention, a matte surface is formed on the adhesive layer side surface of the cover sheet. The characteristics of the writing sheet greatly vary depending on the shape of the matte surface.

In the writing sheet according to the present invention, when the arithmetic mean height Sa of the matte surface is large, matte expression can be easily achieved. When is small, there is a tendency that an image with high contrast can be formed. From such a viewpoint, in the present invention, the arithmetic mean height Sa of the matte surface is 0.10 to 0.50 μm, preferably 0.15 to 0.30 μm.

The arithmetic mean height Sa can be measured with a three-dimensional roughness meter. Specifically, a laser microscope LEXT-OLS4100 (trade name, manufactured by Olympus Corporation) can be used for these measurements.

Furthermore, the unevenness on the matte surface prevents the adhesive layer and the cover sheet from sticking together before the image is recorded. and can be easily peeled off when erasing the image. In order to obtain such a matte surface, the haze value is preferably 70 to 95%. The haze value can be measured with a haze meter TC-HIII (trade name, manufactured by Tokyo Denshoku Co., Ltd.).

The method of forming the matte surface 121 on the surface of the cover sheet 120 is not particularly limited, but includes a method of directly etching the surface of the film, which is the main structure of the cover sheet, a method of laminating with a film having unevenness, and a method of forming fine particles. A method in which a resin composition in which is dispersed is applied to the film surface and dried or cured to form an uneven surface; A method of forming unevenness on the surface by generating air bubbles in the material layer and the like can be mentioned. A cover sheet having a matte surface formed on the surface can also be obtained by molding a resin composition in which fine particles are dispersed into a film as the cover film.

Among these, it is preferable to use a resin composition in which fine particles are dispersed, since the roughness of the matte surface can be easily controlled. In particular, a method in which a resin composition in which highly transparent fine particles such as silica are dispersed is applied to the surface of the film and heated to cure the resin is preferably employed in terms of quality stability and cover film characteristics. be. Microparticles may be organic or inorganic materials. Organic materials used for the fine particles include acrylic resins such as polymethyl methacrylate, polystyrene, styrene-acrylic resins, polycarbonate resins, urethane resins, epoxy resins, polyester resins, and polyester urethane resins. Examples of inorganic materials used for fine particles include silicon dioxide (silica), titanium dioxide, barium sulfate, calcium carbonate, talc, mica, metal flakes, and metal oxide flakes. Among these, when mica, metal flakes, or metal oxide flakes are used, a metallic color is produced during image recording, and a beautiful image is recorded. In this case, it is preferable to use a color with a high density, typically black, for the colored layer because the contrast is increased and the metallic color can be observed more beautifully.

The average particle size of these fine particles is preferably 0.05 to 5.0 μm. Here, the average particle size is measured by a laser diffraction method (principle) on a volume basis, and can be measured by, for example, MICROTRAC 9320-X100 (manufactured by Honeywell).

Examples of resins used as a binder for the composition include vinyl chloride-vinyl acetate copolymer resins, epoxy resins, acrylic resins, polyester resins, urethane resins, and melamine resins. Among these, acrylic melamine resins, polyester melamine resins, acrylic urethane resins, and the like are considered to be excellent in terms of physical strength and optical properties, and are preferably used.

Furthermore, examples of solvents for dissolving or dispersing them include toluene and methyl ethyl ketone.

FIG. 1 shows a structure in which a matte coat layer 121a having a matte surface 121 is laminated on the surface of a film 122 by any method.

Methods for directly etching the film surface include physical methods and chemical methods. Among these methods, the physical method is preferable because the process is relatively simple and finer irregularities can be formed. Examples of methods for physically etching the film surface include sandblasting and scratching.

In the present invention, the hardness of the matte surface of the cover sheet is preferably high. Specifically, the pencil hardness (JIS K 5600-5-4) is preferably F or higher, more preferably H or higher. According to studies by the present inventors, when an image is recorded on a writing sheet and then erased, traces of the image may remain on the cover sheet. As a result, the contrast of the subsequently formed recorded image is lowered. However, in the present invention, by appropriately setting the hardness of the matte surface, such a problem can be improved and such contrast reduction can be suppressed. Furthermore, the adhesiveness between the cover sheet and the adhesive layer becomes appropriate, and image recording and erasing can be facilitated.

The surface of the cover sheet opposite to the matte surface is subjected to pressure and stress during image recording. When applying pressure with a stamp or the like, a force is applied in the direction perpendicular to the surface of the writing sheet. On the other hand, when recording an image with a pen, for example, a vertical force is applied to bring the cover sheet and the adhesive surface into close contact with each other. occurs. As a result, the surface of the cover sheet may be damaged and the contrast of the recorded image may be reduced. In order to prevent such problems, the cover sheet used in the present invention preferably has a surface protection layer 123 on the surface opposite to the surface on which the matte surface is formed.

Such a surface protective layer can be formed by laminating a surface protective film on the surface of the film constituting the cover sheet, or by coating and curing a composition containing a resin material. In particular, since various types of surface protection films are commercially available, it is convenient to use one of them according to the purpose. Such protective films include those that protect the surface with high hardness, those that reduce surface friction to prevent scratches, and those that have appropriate elasticity to reduce physical impact and Examples include those that self-repair after being damaged once. The surface protection film having high hardness is, for example, a film made of hard plastic, and preferably has a specific hardness of HB or more in pencil hardness. Films with a low frictional force include, for example, films made of high-molecular-weight polyethylene having a smooth surface. Specifically, the coefficient of friction of the surface is preferably 0.15 or less. Also, the film that absorbs physical impact or self-repairs is a film that has a flexible structure and is made of polymeric material such as silicone resin. In the present invention, it is preferable to use a surface protective film having some of these characteristics as the protective film. Various types of such films are commercially available, for example, Tufftop self-repairing coated film SR-TEBF (trade name, manufactured by Toray Kako Co., Ltd.), Tokuro HC film hard-coated product HC1000 (manufactured by Toyo Cloth Co., Ltd.), and the like. ing.

The thickness of the cover sheet is preferably thin in order to achieve high transparency and transmit pressure during image recording to the interface between the cover sheet and the adhesive layer, and in order to increase physical strength. Thick is preferred. From this point of view, the thickness of the main film constituting the cover sheet is preferably 38-100 μm, more preferably 50-75 μm. Further, when a matte coat layer is provided, it is preferable to make the matte coat layer thick in order to obtain the desired surface roughness, and it is preferable to make the matte coat layer thin in order to maintain the transparency of the cover sheet. From this point of view, the thickness of the matte coat layer is preferably 2 to 20 μm, more preferably 5 to 10 μm. When a surface protective layer is provided, the thickness of the surface protective layer is preferably 0 to 100 μm, more preferably 25 to 50 μm.

The present invention will be described using various examples as follows.

[Example 1]
A polyester film (core plate) with a thickness of 50 μm is coated with 90 parts of a silicone adhesive (LTC 755 Coating (trade name), Dow Corning Toray Co., Ltd.), a silicone adhesive (SD 4580 PSA (trade name), Toray Dow Corning Co., Ltd.) 10 parts, platinum catalyst (NC-25 (trade name), Dow Corning Toray Co., Ltd.) 0.7 parts are dissolved in toluene, the solution is sufficiently stirred, and then coated with an applicator. and cured at 120° C. for 2 minutes to form a transparent adhesive layer with a thickness of 15 μm on the film surface. Further, black paper was laminated on the opposite side of the adhesive layer to obtain a substrate.

Also, the back surface of a polyester film having a thickness of 50 μm was coated with a coating liquid containing a polyester melamine resin and silica fine particles to obtain a cover sheet 1 having a matte surface on the surface. This sheet had an Sa of 0.15 μm, a haze value of 72.8, and a pencil hardness of H.
A writing sheet was produced by combining this base material and the cover sheet.

[Examples 2-7 and Comparative Examples 1-2]
Writing sheets of Examples 2 to 7 and Comparative Examples 1 and 2 were prepared by changing the material of the adhesive layer and the method of forming the matte surface of the cover sheet from Example 1. The materials for the adhesive layer were as shown in Table 1. Cover sheets 2 to 6 were produced as follows.
Cover sheet 2: The back surface of a polyester film having a thickness of 50 μm was coated with a coating liquid containing a polyacrylic melamine resin and fine silica particles to obtain a cover sheet 2 having a matte surface. This sheet had an Sa of 0.24 μm, a haze value of 80.0, and a pencil hardness of F.
Cover sheet 3: Cover sheet 3 was obtained by changing the types and blending amounts of polyester melamine resin and silica fine particles to cover sheet 1. This sheet had an Sa of 0.29 μm, a haze value of 77.0, and a pencil hardness of H.
Cover sheet 4: A cover sheet 4 was obtained by sandblasting the surface of a polyester sheet having a thickness of 50 µm to form a matte surface. This sheet had an Sa of 0.11 μm, a haze value of 76.2, and a pencil hardness of 6B.
Cover sheet 5: Cover sheet 5 was obtained by changing the types and blending amounts of the polyacrylic melamine resin and the silica fine particles from cover sheet 2 . This sheet had an Sa of 0.07 μm, a haze value of 60.0, and a pencil hardness of H.
Cover sheet 6: A light-diffusing polyethylene terephthalate sheet (Light Up LDE 50 μm (trade name), manufactured by Kimoto Co., Ltd.) was used as the cover sheet 6 . This sheet had an Sa of 0.95 μm, a haze value of 91.0, and a pencil hardness of 6B.

[evaluation]
Storage property over time After the writing sheet was assembled, it was allowed to stand still, and the state change was visually evaluated.
A: Good with no sticking between the adhesive layer and the mat layer.
B: The adhesive layer and the mat layer stick together over time.
C: The adhesive layer sticks to the mat layer.

Writing Performance A recorded image was visually evaluated when writing was performed with the writing tip of the fiber bundle.
A: A good recorded image can be obtained.
B: A recorded image is obtained, but the contrast is low.
C: No recorded image remained even after writing, or disappeared spontaneously immediately after writing.

Erasing Performance After recording, the matte layer and the adhesive layer were peeled off, and the difficulty of peeling off when the recorded image was erased was evaluated.
A: A recorded image can be easily and cleanly erased with a light force.
B: The image cannot be erased without a large peeling force. Or there is a loud peeling sound. C: The cover sheet or adhesive layer is damaged during erasing.
Recording performance The recorded image was visually evaluated one day after recording the image.
A: No change in the recorded image is observed.
B: The image became unclear compared to immediately after recording.
C: The recorded image cannot be visually recognized (the image has disappeared).

100 writing sheets
110 Base material 111 Colored support 111a Colored layer 111b Core plate 112 Intermediate layer 113 Adhesive layer 120 Cover sheet 121 Matt surface 121a Matt coat layer 122 Film base material 123 Surface protection layer

Claims (6)

a substrate comprising a colored support and an adhesive layer formed on the surface thereof;
A writing sheet comprising a film and a transparent cover sheet having a matte surface formed on one surface of the film, wherein the adhesive layer and the matte surface are arranged so as to be in contact with each other. hand,
The matte surface is the surface of the fine particle-containing layer disposed on the surface of the film, and the transparent cover sheet on which the matte surface is formed has an arithmetic mean height Sa of 0.10 to 0.50 μm. A haze value of 70 to 95% ,
A writing sheet, wherein the fine particles contained in the fine particle-containing layer are silica . 2. The writing sheet according to claim 1, wherein said matte surface has a hardness of pencil hardness F or higher. 3. The writing sheet according to claim 1 , wherein the adhesive layer comprises a silicone-based adhesive. The writing sheet according to any one of claims 1 to 3 , wherein the adhesive layer has an adhesive strength of 1.0 to 5.0 N/m. The writing sheet according to any one of claims 1 to 4 , wherein the cover sheet comprises the film and a matte coat layer formed on the surface thereof. The writing sheet according to any one of claims 1 to 5 , further comprising a surface protective layer on the surface opposite to the matte surface of the cover sheet.

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