JP7493183B2 - Writing sheet - Google Patents

Description

The present invention relates to a writing sheet that has both writability and erasability.

In various places such as the workplace and home, it is customary to write down messages and lists of actions on sticky notes as reminders and attach them to stationery such as notebooks or personal belongings in conspicuous places so as not to forget them. Such sticky notes are generally made of paper, so characters written with a ballpoint pen, which is highly clear, cannot be erased, and although they have excellent storage properties, they are disposable. In addition, in the case of clear files in which documents are stored together, in order to make it easier to keep track of the documents stored, the above-mentioned sticky notes are used or the clear file is written directly with an oil-based felt-tip pen, etc., but there is a problem in that the written characters cannot be erased and cannot be reused.

Nowadays, from the perspective of environmental conservation, the ability to be reused has become extremely important as a product's value. For example, there are clear files made of resin, such as the clear file in Patent Document 1, which allow direct writing with a pencil or ballpoint pen, and erasing with an eraser, etc. This clear file allows direct writing and erasure with a pencil or ballpoint pen, etc., by optimizing the resin material and surface roughness that makes up the clear file.

JP 2014-223783 A (page 17)

The clear file in Patent Document 1 is made only of synthetic resin, so if it is thick, it is highly rigid, and the tip of the writing implement does not sink into the surface of the clear file, meaning that friction between the tip of the writing implement and the surface of the clear file cannot be ensured when writing with the writing implement. This causes the problem that not enough ink is applied, causing smudges and making it difficult to write clearly. On the other hand, if the clear file is not thick enough, there is a risk that the clear file itself will be damaged when the tip of a ballpoint pen is pressed against it.

The present invention was made with a focus on these problems, and aims to provide a writing sheet that has both writability and erasability, allowing clear writing with a writing instrument while preventing damage when writing.

In order to solve the above problems, the writing sheet of the present invention comprises:
The writing layer is made of PP synthetic paper made mainly of polypropylene resin having a plurality of fine pores on the front and back surfaces , an adhesive layer is attached to the back surface of the writing layer, and a base layer is attached to the back surface of the adhesive layer,
the writing layer has a thickness of 60 μm to 200 μm, and has a writability that allows ink to be retained in the pores on the surface, and an erasability that is obtained by retaining ink in the pores without soaking in the ink due to high water repellency of the polypropylene resin,
the adhesive layer has a thickness of 15 μm to 35 μm, and is made of a synthetic resin, and has viscoelasticity due to elasticity resulting from its solid properties and viscosity resulting from its liquid properties, and is formed to be more easily elastically deformed than the writing layer , which has elasticity due to its solid properties and is substantially not viscous;
The substrate layer is characterized by having a higher rigidity than the writing layer.
According to this feature, the adhesive layer has a higher viscosity than the writing layer, so the relaxation time of the response relaxation is long, and when both the writing layer and the adhesive layer are distorted and deformed by the pressure load of the writing tool, they slowly return to their original shape before the pressure load is applied. Therefore, the state in which the tip of the writing tool sinks into the surface of the writing layer continues temporarily, and the contact area between the surface of the writing layer and the tip of the writing tool is increased, and sufficient friction force can be secured between the tip of the writing tool and the surface of the writing layer, allowing clear writing. In addition, the base layer has a higher rigidity than the writing layer, so that it has the effect of suppressing excessive distortion and deformation of the writing layer and the adhesive layer due to the pressure load. This allows clear writing and prevention of damage during writing to be achieved at the same time.

The writing sheet is characterized in that it has a weak adhesive layer, which has a weaker adhesive strength than the adhesive layer, on the back surface of the base layer to form a seal.
According to this feature, the base layer suppresses excessive distortion and deformation of the writing layer and the adhesive layer, so that when attached to an object with the weak adhesive layer, clear writing can be performed regardless of the hardness of the object.

The writing sheet is characterized in that it forms a folded file with the bottom edge bound.
According to this feature, it is possible to directly write the classification of the contents stored in the file on the surface of the writing layer located on the outside, without using sticky notes or the like.

The writing sheet is characterized in that it forms a clipboard having a clip on the upper surface side of the base layer.
According to this feature, additional notes and the like relating to the document held by the clip can be written directly on the surface of the writing layer located on the upper side.

1 is a perspective view showing a writing sheet according to a first embodiment of the present invention and a notebook to which the writing sheet is attached. 1A is a cross-sectional view of the writing sheet, and FIG. 1B is an enlarged cross-sectional view of the attachment portion between the writing layer and the adhesive layer. FIG. 1A is a diagram showing how characters are written on a writing sheet, and FIG. 1B is a diagram showing how the written characters are erased. FIG. 2 is a cross-sectional view showing how writing is performed on a writing sheet with a writing implement. This is a table summarizing the evaluation results from a questionnaire about the ease of writing on the writing sheet. FIG. 11 is a perspective view showing a writing sheet according to a second embodiment of the present invention. FIG. 11 is a cross-sectional view of a writing sheet in Example 2. FIG. 11 is a perspective view showing a writing sheet according to a third embodiment of the present invention. FIG. 11 is a cross-sectional view of a writing sheet in Example 3.

The following describes how to implement the writing sheet of the present invention based on the examples.

A sticker using the writing sheet according to the first embodiment will be described with reference to Figs. 1 to 5. As shown in Fig. 1, the writing sheet 1 is a sticker that is attached to stationery such as a notebook N or to everyday items, and can be used to write down matters to be communicated, lists of actions, etc. as memos on its surface. By placing it in a conspicuous place, it is possible to avoid forgetting matters to be communicated, lists of actions, etc.

As shown in FIG. 2, the writing sheet 1 is composed of a writing layer 2, an adhesive layer 3, a base layer 4, a slightly adhesive layer 5, and a release layer 6, which are polymerized from the surface side. If the writing sheet is in a roll, the release layer 6 can be omitted. The writing layer 2 is a so-called PP synthetic paper formed into a sheet shape using polypropylene as the main raw material. It is more durable and water repellent than paper, and has fine holes 2c (see FIG. 2) on the surface 2a, back surface 2b, and inside. By holding ink in these holes 2c, writing with a writing instrument such as a ballpoint pen is possible. The writing layer 2 is also 100 μm thick.

The adhesive layer 3 is made of an acrylic synthetic resin, and maintains both liquid and solid properties, with a higher viscosity than the writing layer 2. In other words, the adhesive layer 3 has elasticity due to its solid properties, viscosity due to its liquid properties, and a viscosity that the solid writing layer 2 does not substantially have, that is, it has so-called viscoelasticity. The adhesive layer 3 is also 25 μm thick, and is more susceptible to elastic deformation than the writing layer 2, which is 100 μm thick. The adhesive layer 3 is attached to the back surface 2b of the writing layer 2 by its own adhesive force.

The base layer 4 is formed in a sheet shape using polyethylene terephthalate as the main raw material. The base layer 4 is 25 μm thick, but has a lower elastic modulus as a material compared to polypropylene and has higher rigidity than the adhesive layer 3. The base layer 4 is attached to the back side 3b of the adhesive layer 3 by the adhesive force of the adhesive layer 3.

The slightly adhesive layer 5 is made of an acrylic synthetic resin, and the type of monomer, the molecular weight of the polymer, the crosslinking density, etc. are adjusted, resulting in a weaker adhesive strength than the adhesive layer 3. Therefore, it is removable and can be easily peeled off from objects such as notebooks.

In addition, since the adhesive strength of the weak adhesive layer 5 is lower than that of the adhesive layer 3, the writing layer 2 and the adhesive layer 3, and the adhesive layer 3 and the base layer 4 will not be peeled off by the external force applied when peeling the writing sheet 1 from the notebook N or the like. In other words, damage to the writing sheet 1 when peeling it from the notebook N or the like can be prevented. The weak adhesive layer 5 is attached to the back surface 4b of the base layer 4 by its own adhesive strength.

The release layer 6 is formed by coating the surface of the paper with a release agent and is approximately 150 μm thick.

As described above, the writing layer 2 has minute pores on the surface 2a and inside, and by holding ink in these pores, it is possible to write with a ballpoint pen P, as shown in FIG. 3(a). In addition, since PP synthetic paper has high water repellency, the ink of the ballpoint pen P does not soak into the paper, but is only held in the pores on the surface 2a of the writing layer 2. Therefore, as shown in FIG. 3(b), by rubbing an eraser E against the surface 2a of the writing layer 2, the ink held in the pores on the surface 2a of the writing layer 2 is caught up, and written characters, etc. can be erased.

The writing layer 2 is 100 μm thick, but has a high elastic modulus due to the material properties of polypropylene, which is the main raw material. In addition, an adhesive layer 3 is attached to the back surface 2b of the writing layer 2. Therefore, as shown in FIG. 4, when the pen tip Pt of the ballpoint pen P is pressed against the front surface 2a of the writing layer 2, the adhesive layer 3 also has elasticity, and both the writing layer 2 and the adhesive layer 3 are distorted and deformed by the pressure load.

In other words, the adhesive layer 3 does not interfere with the distortion and deformation of the writing layer 2, and sufficient friction can be secured between the ballpoint pen P and the surface 2a of the writing layer 2, allowing the ball of the tip Pt of the ballpoint pen P to rotate sufficiently and scrape out the ink, resulting in clear writing. Also, as shown in FIG. 4, the tip Pt of the ballpoint pen P sinks into the surface 2a of the writing layer 2, increasing the contact area between the surface 2a of the writing layer 2 and the tip Pt, and therefore increasing the area onto which ink is applied, resulting in clear writing.

In addition, the back side 3b of the adhesive layer 3 is attached with a base material layer 4 having a higher rigidity than the writing layer 2, which has the effect of suppressing excessive distortion and deformation of the writing layer 2 and the adhesive layer 3 due to the pressure load. This makes it possible to achieve both the clear writing described above and the prevention of damage during writing.

As described above, the adhesive layer 3 has viscoelasticity that the solid writing layer 2 does not substantially have. Therefore, the time required for stress relaxation, which is a phenomenon in which stress changes over time under a certain displacement (hereinafter referred to as the "relaxation time"), is longer than that of the writing layer 2, which has elastic properties.

In other words, after both the writing layer 2 and the adhesive layer 3 are distorted and deformed by the pressure load of the pen tip Pt of the ballpoint pen P, the adhesive layer 3 has a long relaxation time and slowly restores to its original shape before the pressure load was applied. Because the adhesive layer 3 is directly attached to the writing layer 2, it is affected by the gradual stress relaxation of the adhesive layer 3 and restores to its original shape before the pressure load was applied more slowly than the relaxation time required for restoration due to its own elastic modulus.

As a result, the tip Pt of the ballpoint pen P remains sunken into the surface 2a of the writing layer 2 until the shape of the surface 2a of the writing layer 2 slowly returns to its original shape, increasing the contact area between the surface 2a of the writing layer 2 and the tip, and ensuring sufficient friction between the tip Pt of the ballpoint pen P and the surface 2a of the writing layer 2.

In particular, when writing, the tip Pt of the ballpoint pen P is slid over the surface 2a of the writing layer 2, and the tip Pt is released from the writing layer 2 each time writing is completed, so that the tip Pt of the ballpoint pen P does not actually stay in the same position for a long time, and sufficient frictional force can be secured between the tip Pt of the ballpoint pen P and the surface 2a of the writing layer 2 while writing. In addition, the repulsive force that the user receives from the writing sheet 1 via the ballpoint pen P is momentarily reduced, which also has the effect of reducing fatigue.

In addition, since a plurality of minute voids 2c are formed on each of the front surface 2a and back surface 2b of the writing layer 2, the adhesive layer 3 can penetrate into the voids 2c on the back surface 2b, and the gradual response relaxation of the adhesive layer 3 can be surely influenced in restoring the shape of the writing layer 2.

Figure 5 is a table summarizing the individual evaluations from a questionnaire when selecting the thickness of the writing layer 2 and adhesive layer 3. Here, nine types of writing sheets with different thicknesses and combinations were prepared, and 100 randomly selected people were asked to write on them using the same type of ballpoint pen, and were asked to select clarity on a five-point scale, with the average being converted into a score.

Referring to the table, the score for the thickness of the writing layer 2 is relatively high when it is between 60 μm and 200 μm, regardless of the thickness of the adhesive layer 3. From this, it can be seen that if it is less than 60 μm, the rigidity of the writing layer 2 itself is unnecessarily low and writing is difficult, and if it is more than 200 μm, the rigidity of the writing layer 2 itself is unnecessarily high and writing is difficult, so it is preferable to select a thickness between 60 μm and 200 μm.

Also, referring to the table, the score for the thickness of the adhesive layer 3 is relatively high when the thickness of the adhesive layer 3 is between 15 μm and 35 μm. From this, it can be seen that when the thickness is less than 15 μm, the rigidity of the adhesive layer 3 is lower than necessary, making it difficult to write on, and when the thickness is greater than 35 μm, the rigidity of the writing layer 2 itself is higher than necessary, making it difficult to write on.

In addition, the scores were significantly higher for adhesive layer 3 having a thickness of 15 μm to 35 μm and writing layer 2 having a thickness of 60 μm to 200 μm. From this, it was found that when the thickness of adhesive layer 3 is 15 μm to 35 μm and the thickness of writing layer 2 is less than 60 μm, the writing layer 2 has low rigidity, so the relaxation time of stress relaxation against the pressing load of the pen tip Pt of the ballpoint pen P becomes excessively long, which may cause stress in writing. Also, when the thickness of adhesive layer 3 is 15 μm to 35 μm and the thickness of writing layer 2 is greater than 200 μm, the writing layer 2 has high rigidity, so the effect of viscoelasticity of adhesive layer 3 is limited, and the relaxation time of stress relaxation against the pressing load of the pen tip Pt of the ballpoint pen P is short, and it was found that sufficient frictional force cannot be secured between the pen tip Pt of ballpoint pen P and the surface 2a of the writing layer 2. Based on the above survey results, it was found that when the thickness of the adhesive layer 3 is between 15 μm and 35 μm and the thickness of the writing layer 2 is between 60 μm and 200 μm, the rigidity of the writing layer 2 and the viscoelasticity of the adhesive layer 3 can be optimized for writing, so that the effect of the adhesive layer 3 in slowing down the relaxation time of the stress relaxation of the writing layer 2 can be optimized for writing.

In addition, because the writing sheet 1 has a base layer 4 and a slightly adhesive layer 5 below the adhesive layer 3, the base layer 4 can suppress excessive distortion and deformation of the writing layer 2 and the adhesive layer 3 caused by the pressure load of the ballpoint pen tip. As a result, not only can clear writing be performed when the writing sheet 1 is not attached to an object such as a notebook, but clear writing can also be performed when the writing sheet 1 is attached to an object, regardless of the hardness of the object.

Next, the writing sheet according to the second embodiment will be described with reference to Figs. 6 and 7. Note that the same components as those in the first embodiment will be given the same reference numerals and the duplicated description will be omitted.

The writing sheet 11 is a file that is folded in half and stapled at the bottom, allowing documents and the like to be stored inside, and is configured with a sheet-like base layer 14 on the back side of the adhesive layer 3. The writing sheet 11 is folded in half so that the surface 2a of the writing layer 2 is located on the outside. The base layer 14 is made primarily of polypropylene resin, is 200 μm thick, and is more rigid than the writing layer 2.

With this writing sheet 11, you can directly write the classification of the contents stored in the file on the surface 2a of the writing layer 2 located on the outside, without using sticky notes or the like. This prevents the sticky notes from coming off and causing a mismatch between the association of the sticky notes and the documents held by the clip.

Next, the writing sheet according to the third embodiment will be described with reference to Figs. 8 and 9. Note that the same components as those in the first embodiment will be given the same reference numerals and duplicated descriptions will be omitted.

The writing sheet 21 is a clipboard equipped with a clip 22 at the top that can hold documents, etc., and is configured with a board-like base layer 24 on the back side of the adhesive layer 3. The writing sheet 21 has the surface 2a of the writing layer 2 located on the upper side where the clip 22 is fixed. The base layer 24 is made primarily of acrylic resin, is 30 mm thick, and is more rigid than the writing layer 2.

With this writing sheet 21, additional notes about the document held by the clip 22 can be written directly on the surface 2a of the writing layer 2 located on the upper side, without using sticky notes or the like. This makes it possible to prevent discrepancies in the association between the sticky note and the document held by the clip caused by the sticky note coming off.

Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these embodiments, and additions and modifications that do not deviate from the gist of the present invention are also included in the present invention.

For example, in the above embodiment, a ballpoint pen was used as the writing implement, but the writing implement is not limited to this and may be, for example, a water-based felt-tip pen or pencil. Furthermore, the written characters are not limited to being erased with an eraser. For example, characters written with a writing implement that uses ink that can be erased by thermal change can be erased with a corresponding friction body.

The writing sheet can be used in a variety of ways, not just as a sticky note, file, or clipboard, as described above. For example, it can be used on stationery such as document files and boards, or on the surface of desks, smartphone cases, etc.

The adhesive layer is not limited to being made of an acrylic synthetic resin, but may be made of, for example, a urethane-based material, or may be formed by polymerizing two or more types of adhesive layers.

REFERENCE SIGNS LIST 1 Writing sheet 2 Writing layer 2a Front surface 2b Back surface 3 Adhesive layer 3b Back side 4 Base layer 4b Back surface 5 Slightly adhesive layer 6 Peel layer 11 Writing sheet 14 Base layer 21 Writing sheet 22 Clip 24 Base layer E Eraser N Notebook P Ballpoint pen Pt Pen tip

Claims (4)

The writing layer is made of PP synthetic paper made mainly of polypropylene resin having a plurality of fine pores on the front and back surfaces , an adhesive layer is attached to the back surface of the writing layer, and a base layer is attached to the back surface of the adhesive layer,
the writing layer has a thickness of 60 μm to 200 μm, and has a writability that allows ink to be retained in the pores on the surface, and an erasability that is obtained by retaining ink in the pores without soaking in the ink due to high water repellency of the polypropylene resin,
the adhesive layer has a thickness of 15 μm to 35 μm, and is made of a synthetic resin, and has viscoelasticity due to elasticity resulting from its solid properties and viscosity resulting from its liquid properties, and is formed to be more easily elastically deformed than the writing layer , which has elasticity due to its solid properties and is substantially not viscous;
A writing sheet, characterized in that the base layer has a higher rigidity than the writing layer. 2. The writing sheet according to claim 1 , wherein the writing sheet has a weak adhesive layer, which is weaker in adhesive strength than the adhesive layer, on the back surface of the base layer to form a seal. 2. The writing sheet according to claim 1 , wherein the writing sheet is in the form of a folded file bound at the bottom. 2. The writing sheet according to claim 1 , wherein the writing sheet is in the form of a clipboard having a clip on the upper surface side of the base layer.

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