JP2014028506A - Board sheet and white board using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a board sheet for constituting a white board in which irregularities are formed almost uniformly, substantially on the whole area of a writing surface, a brush head is hard to slip and writing is facilitated, and also the reflection or dazzle of light is hardly caused and further the irregularities are minute and less likely to attract attention, so that the writing or a projected image is easily viewed, the erasure is easy, having superior productivity and irregularity durability, and further the printing of a substrate is easily viewed, and to provide a white board constituting a writing surface by the board sheet.SOLUTION: A board sheet 1 is configured such that the surface of a base material 2 including at least a white sheet is coated with a coating agent including at least two kinds of cross-linkable resin contents having physical properties different from each other and is dried, and furthermore is subjected to cross-linking reaction, and thereby the resin contents are phase-separated with the drying of the coating agent to form a resin layer 3 formed of irregular surfaces, and the irregular surface of the resin layer is used as a writing surface 4. The white board constitutes a writing surface by the board sheet 1.

Description

  The present invention relates to a board for forming a writing surface of a white board that can be repeatedly written and erased, and a white board in which the writing surface is constituted by the board sheet.

Whiteboards are widely used as a writing medium to replace a blackboard that can be repeatedly written and erased. In recent years, white boards (reflection type screen boards) in which the writing surface also serves as a projection surface such as a projector, an overhead projector, and a slide are becoming widespread.
In order to write on the writing surface of the whiteboard, for example, a felt pen using an ink containing a colorant but not a fixing agent, a so-called whiteboard marker pen is used. The writing surface of the white board is a non-absorbing surface that does not allow the ink to penetrate. For this reason, after writing, the ink on the writing surface can be easily erased by wiping off the ink on the writing surface using, for example, a felt eraser.

In order to facilitate wiping off the ink, it has been conventionally considered that the writing surface is preferably as flat as possible (for example, Patent Document 1).
However, on the flat surface, when writing with the whiteboard marker pen, there is a case where the pen tip slips and writing is difficult.
The flat writing surface reflects light caused by, for example, light from indoor lighting fixtures or outside light inserted through a window, making it difficult to see writing, or reflecting light from a projector or the like on the writing surface. There was also a problem that it was easy to feel and write or project the projected image. This problem occurs not only when the writing surface is viewed directly, but also in an image obtained by photographing the writing surface, for example.

Therefore, for example, by applying a curable resin to almost the entire surface of the whiteboard writing surface of a base material made of PET (polyethylene terephthalate), making it semi-curing reaction, and then embossing it, the writing surface is fine. It has been proposed to form a rough surface (for example, Patent Documents 2 and 3).
However, since the size of the uneven pattern formed by embossing is as large as about 300 μm in the surface direction of the writing surface, there is a problem that the unevenness is conspicuous and the written or projected image is difficult to see.

In addition, in consideration of the workability at the time of embossing, the unevenness is not sufficiently durable because it is formed of a semi-cured curable resin as described above, and by repeatedly writing and erasing, There is a problem that it is easily lost in a relatively short period of time.
It may be possible to further improve the durability of the unevenness by further curing reaction of the curable resin after embossing, but in that case, the curing reaction is repeated twice or more for one whiteboard. Therefore, there is a problem that the number of whiteboard manufacturing steps, energy required for manufacturing, and time are increased, and productivity is greatly reduced.

  In particular, since the writing surface of the whiteboard has a large area, the curable resin applied to substantially the entire surface of the base material that becomes the basis of the writing surface is cured and reacted by, for example, heating or irradiating ultraviolet rays. This requires a large device. Therefore, it is necessary to repeat the curing reaction using such a large apparatus twice or more, which leads to excessive energy consumption.

In addition, the unevenness formed by embossing may be irregularly deformed due to heat during the second and subsequent curing reactions, etc., and may not be uniform over the entire writing surface, resulting in unevenness. There is also.
If the unevenness becomes uneven, the writing surface is mixed with a portion where the tip of the tip is slippery and a portion where the tip of the tip is slippery, which causes a problem that writing becomes difficult locally. The effect of suppressing glare and the like is also non-uniform.

In addition, the writing surface with irregularities tends to have higher ink wettability and affinity than a smooth writing surface, but when the irregularities become uneven as described above, the wettability and affinity are locally increased. There is also a possibility that an area where the property becomes too high or the ink enters the concave portion and the erasing becomes difficult is generated.
Patent Document 3 also proposes forming irregularities on the writing surface by a silk screen method or an etching method. However, since the size of the unevenness formed by these methods in the surface direction of the writing surface is as large as about 300 μm, there is a problem that the unevenness is conspicuous and it is difficult to see the written or projected image.

In Patent Document 4, a surface of a main body sheet made of a transparent thin plastic sheet is roughened by sandblasting or the like on the entire surface of a whiteboard writing surface, and then the surface is blotted with ink from a whiteboard marker pen. In order to prevent engraving and to be able to erase easily, it is described to coat with a hard coat resin.
However, when a hard coat resin having a thickness necessary for obtaining the above-described effect is coated on the roughened surface, the writing surface which is the surface of the coating, for example, in FIG. As described, it is practically difficult to faithfully reproduce the fine unevenness of the base, and the writing surface has almost lost the unevenness, and the unevenness remains very slightly on the almost smooth surface. (Patent Document 4, paragraph [0009]).

This is because the unevenness of the surface roughened by sandblasting or the like is very fine compared to the thickness of the coating with the hard coat resin, and is almost filled with the hard coat resin applied thereon. It is.
And when the unevenness | corrugation of a foundation | substrate is lost and a writing surface becomes a substantially smooth surface, it will become easy to produce problems, such as the above-mentioned sliding of a nib, reflection of light, and glare.

A coating of a curable resin in which fine particles are dispersed is applied to substantially the entire surface of the base material, which is the writing surface of the whiteboard, and is subjected to a curing reaction, whereby the writing surface has fine particles based on the particles. It has been proposed to form convex portions (for example, Patent Documents 3 and 5).
However, it is not easy to uniformly distribute the convex portions formed of the fine particles over almost the entire writing surface of the board having a large area as described above, and the distribution of the convex portions tends to be biased.

  And if the distribution of the convex part is biased, the writing surface will be mixed with a part where the brush tip is slippery and a part which is difficult to slip, causing a problem that writing becomes difficult locally, The effect of suppressing reflection and glare is also non-uniform. In addition, there may be a region where the ink wettability and affinity become too high locally, or the ink enters the concave portion and the character cannot be easily erased.

  In addition, for example, ruled lines, company names, titles, etc. may be printed on the writing surface of the whiteboard. For example, the above-mentioned printing is performed on the surface of the base material on which the writing surface is based by an arbitrary printing method. In addition, when a convex portion is formed by applying a curable resin coating material in which fine particles are dispersed as described above and performing a curing reaction, the printing below is obstructed by the fine particles and is difficult to see. There is a problem.

Japanese Patent Laid-Open No. 10-76791 Japanese Patent Laid-Open No. 63-1509098 No. 7-37912 Japanese Patent Laid-Open No. 10-250286 JP 2007-33231 A

  The object of the present invention is that the unevenness is formed almost uniformly on the entire writing surface, so that the tip of the brush is difficult to slip and writing is easy, and it is difficult to cause problems such as reflection of light and glare. The board is designed to form a white board that is easy to see written and projected images because it is fine and inconspicuous, is easy to erase, and is excellent in productivity and durability of the irregularities. Another object is to provide a white board having a writing surface made up of a sheet for use with the board sheet.

The present invention is a board for configuring the writing surface of a white board having a writing surface capable of repeated writing and erasing,
A base material containing at least a white sheet, and a coating containing two or more kinds of crosslinkable resins having different physical properties on the surface of the base material, followed by drying and cross-linking reaction, It comprises a resin layer whose surface is made uneven by phase separation of the resin component of more than seeds as the coating agent is dried, and the surface of the resin layer made uneven is a writing surface It is what.

According to the present invention, the surface of the resin layer formed on the surface of the base material, that is, substantially the entire writing surface, is contained in the coating agent that is the basis of the resin layer, and two or more types having different physical properties from each other By the phase separation accompanying the drying of the coating material, a fine and almost uniform concavo-convex shape can be obtained.
That is, in the drying step, with the drying of the coating agent and the increase in the concentration of the resin component, the two or more types of resin components that have been mixed so far phase-separate from each other based on the difference in physical properties between each other. As a result of gathering the same species, non-uniform internal stress is generated in the resin layer before crosslinking, and fine irregularities are formed on the surface, that is, the writing surface.

Therefore, the slip of the writing tip on the writing surface can be reliably prevented over substantially the entire surface by the unevenness, and writing can be facilitated.
In addition, due to the uniform unevenness, the light of the indoor lighting equipment or the external light inserted through the window is diffused and reflected on almost the entire writing surface, or the light from the projector is reflected on the writing surface. It is possible to make it difficult to perceive glare, and for example, by adjusting the drying conditions of the coating, etc., the unevenness can be made finer and less noticeable than by embossing etc., and written or projected You can also make the image easier to see.

In addition, it is possible to prevent the occurrence of a portion that is difficult to erase because the ink wettability and affinity become too high locally, and the erasing can be facilitated over substantially the entire writing surface.
In addition, the unevenness of the resin layer and the surface (writing surface) is formed by a single crosslinking reaction after the coating agent is applied and dried or simultaneously with the drying, so that the board sheet of the present invention is produced. Also excellent in properties.

In addition, the unevenness of the resin layer and the surface (writing surface) is integrally formed only by the two or more types of crosslinkable resin components and, if necessary, a cross-linked product of the cross-linking agent, so that it has durability. Further, by selectively using the resin component and the cross-linking agent that is transparent as the cross-linking agent, it is possible to increase the transparency and make it easy to see the printed substrate.
The two or more kinds of resins preferably have at least one physical property selected from the group consisting of solubility parameter (SP value), glass transition temperature Tg, surface tension, and number average molecular weight.

Among these, two or more kinds of resins having different SP values are phase-separated from each other on the basis of the difference in SP values as the coating material is dried and the concentration of the resin content is thereby increased.
The two or more kinds of resins having different glass transition temperatures Tg are, for example, lower in glass transition temperature Tg for one resin than the environmental temperature at the time of applying the coating agent, and lower in glass transition temperature Tg for the other resin. By setting the temperature higher than the environmental temperature, the latter resin component aggregates by exhibiting a glass state in which molecular motion is suppressed in the coating agent during drying, whereby the two or more types of resin components are mutually in phase. To separate.

Further, two or more kinds of resins having different surface tensions are preferentially aggregated with the drying of the coating agent and the resulting increase in the concentration of the resin, whereby the resin having the higher surface tension is aggregated. The resin components of the seeds or more are phase-separated from each other.
Further, two or more kinds of resins having different number average molecular weights are precipitated from the coating agent with the resin having the larger number average molecular weight first as the coating agent is dried and as a result, the concentration of the resin component is increased. The two or more kinds of resin components are phase-separated from each other.

In particular, it is preferable to use two or more kinds of resins having different SP values as physical properties.
Specifically, two types of silicone (meth) acrylic block copolymers and (meth) acrylic copolymers having different SP values, or unsaturated double bond-containing (meth) acrylic having different solubility parameters from each other. Three types of copolymer, polyfunctional unsaturated double bond-containing component, and polyether skeleton-containing urethane (meth) acrylate are preferred.

In particular, the former resin layer consisting of a cross-linked product of two kinds of resins, a silicone (meth) acrylic block copolymer and a (meth) acrylic copolymer, has a small surface energy, so the surface of the resin layer (writing surface) It is possible to suppress the wettability and the affinity from being excessively increased by the unevenness generated on the surface, thereby further facilitating erasing by an eraser such as felt.
It is preferable that the writing surface, that is, the uneven surface of the resin layer is further covered with a low refractive index layer. As a result, reflection of light on the writing surface, reflection and glare caused by the reflection, and the like can be further effectively suppressed, and the written or projected image can be more easily seen.

The writing surface is preferably further covered with an antifouling resin layer. As a result, it is possible to suppress the wettability and affinity of the writing surface with the uneven shape from being increased, and it is possible to further facilitate the erasing by the eraser.
The writing surface preferably has a smoothness of not less than 1200 seconds and not more than 2000 seconds in terms of Oken smoothness.

Oken-type smoothness is less than 1200 seconds, low smoothness, that is, writing surface with large irregularities, ink wettability, affinity becomes too high, or ink enters the concave portions, and easy to erase There is a risk of disappearing. In addition, printing under the resin layer may be disturbed by the unevenness and may be difficult to see.
On the other hand, on a writing surface having a high smoothness exceeding 2000 seconds, that is, a writing surface with small unevenness, the pen tip may slip, making it difficult to write.

On the other hand, by setting the Oken-type smoothness of the writing surface within the range of 1200 seconds or more and 2000 seconds or less, it is easy to erase as much as possible while maintaining good writing properties, and under the resin layer. The print can be easily viewed.
In order to adjust the Oken type smoothness within the above range, for example, the drying conditions (temperature, time, etc.) for drying after applying the coating agent that becomes the base of the resin layer on the surface of the substrate are set. What is necessary is just to make it different or to make it different in the kind, combination, compounding ratio, etc. of 2 or more types of resin components, a crosslinking agent, and a solvent mix | blended in the said coating agent.

The writing surface has a wetting tension of 28 mN / m or more and 45 mN / m or less measured in accordance with the method described in Japanese Industrial Standard JIS K6768: 1999 “Plastic-Film and Sheet-Wetting Tension Test Method”. Is preferred.
A writing surface having a wetting tension of less than 28 mN / m has too low ink wettability and is likely to cause the ink to repel, so that writing may be difficult.

On the other hand, a writing surface with a wetting tension exceeding 45 mN / m has a high ink wettability, and there is a risk that it will not be easy to erase.
In order to adjust the wetting tension within the above range, the size of the writing surface unevenness may be adjusted by the same process as the adjustment of the Oken type smoothness, or the material forming the writing surface may be changed. That's fine.

Incidentally, Patent Document 1 describes that the wetting tension of a smooth writing surface is in the range of 32 to 48 mN / m.
However, in such a smooth writing surface, even if the wetting tension is adjusted within the above range, as described above, the pen tip slips and it becomes difficult to write, light is reflected and it is difficult to see the writing, The problem that the light of the projector or the like is reflected on the writing surface and feels dazzled and the written or projected image becomes difficult to see cannot be solved.

In addition, Patent Document 3 describes that the wetting tension of the writing surface, which is an uneven surface by embossing, silk screen method, etching method, or particle dispersion as described above, is 38 to 56 mN / m. ing.
However, even if the wetting tension is adjusted within the above range, it is impossible to solve the various problems described above, which still have the uneven surface formed by the above methods.

The base material includes the white sheet whose one surface is an ink jet printable printing surface, and a transparent sheet that covers the printed surface after printing, and the resin layer is formed on the coated transparent sheet. Preferably it is formed.
With this configuration, it is possible to print on demand on one side of the white sheet by inkjet printing, and flexibly respond to the above-mentioned custom-made whiteboards with different ruled lines, company names, titles, etc. and high-mix low-volume production can do.

The printing can be protected by a transparent sheet when the resin layer is formed, and can be protected by the resin layer and the transparent sheet after the resin layer is formed.
In addition, by selectively using a resin having a transparent crosslinked product as described above, or by setting the Oken-type smoothness of the resin layer formed using the resin component to 1200 seconds or more. It is also possible to improve the transparency and make it easier to see the underlying print.

The present invention is a white board characterized in that a writing surface is constituted by the board sheet of the present invention.
According to the present invention, it is possible to obtain a whiteboard excellent in each of the above effects.

  According to the present invention, since the unevenness is formed substantially uniformly on the entire writing surface, the writing tip is hard to slip and writing is easy, and it is difficult to cause problems such as reflection of light and glare. The board is designed to form a white board that is easy to see written and projected images because it is fine and inconspicuous, is easy to erase, and is excellent in productivity and durability of the irregularities. And a white board having a writing surface constituted by the board sheet.

It is sectional drawing which expanded a part which shows the layer structure of an example of embodiment of the board | substrate sheet | seat of this invention. It is sectional drawing which expanded a part which shows the laminated constitution of the other example of embodiment of the board | substrate sheet | seat of this invention. It is sectional drawing which expanded a part which shows the laminated constitution of the other example of embodiment of the board | substrate sheet | seat of this invention. It is sectional drawing which expanded a part which shows the layer structure of the further another example of embodiment of the board | board sheet | seat of this invention.

FIG. 1 is a partially enlarged cross-sectional view showing a layer structure of an example of an embodiment of a board sheet of the present invention.
Referring to FIG. 1, a board sheet 1 of this example includes a white sheet 2 as a base material, and a resin layer 3 formed on the upper surface of the white sheet 2 in the drawing, The exposed surface of the resin layer 3 on the side opposite to the white sheet 2 side (upper side in the figure) is a writing surface 4 that can be repeatedly written and erased with a whiteboard marker pen or the like.

Among the above, the white sheet 2 includes, for example, an arbitrary resin and a white sheet. In view of dimensional stability, strength, etc., a PET white sheet or a PET sheet with discontinuous aluminum vapor deposition that looks white is preferable.
The white board may be composed only of the board sheet 1 or an arbitrary layer (not shown) such as a backing layer or a reinforcing layer on the lower surface of the white sheet 2 in the drawing. You may laminate and comprise.

  Of these, a white board having a single-layer structure composed of only a board sheet 1 using a relatively thin flexible sheet such as PET, or a white structure having a flexible backing layer laminated on the flexible board sheet 1. The board can be stored in a so-called screen shape by being wound in a roll shape. The white board constituted by using the board sheet 1 of the present invention includes not only the rigid so-called board-like thing described below but also such a screen-like thing.

On the other hand, a white board with a single layer structure consisting only of a board sheet 1 using a relatively thick rigid sheet such as PET, or a white board with a laminated structure in which a rigid reinforcing layer is laminated on the board sheet 1 The white board can be used in combination with a support frame made of a metal frame.
Further, examples of the whiteboard configured using the board sheet 1 include a reflective screen board in which the writing surface 4 of the whiteboard also serves as a projection surface such as a projector, an overhead projector, and a slide.

The backing layer and the reinforcing layer can be formed of any material.
The resin layer 3 is formed by applying a coating containing two or more kinds of crosslinkable resins having different physical properties, followed by drying and crosslinking reaction, and the two or more kinds of resins are used for drying the coating. Accordingly, the surface, that is, the writing surface 4 is made uneven by phase separation.
That is, in the drying process, as the coating agent is dried and the concentration of the resin component is increased, two or more types of resin components having different physical properties are phase-separated from each other, and the same species try to gather together. Inhomogeneous internal stress is generated in the resin layer 3, and fine irregularities are formed on the writing surface 4.

The size of the unevenness is preferably 1200 seconds or more and 2000 seconds or less, expressed by Oken type smoothness that defines the smoothness of the writing surface 4.
Oken-type smoothness is less than 1200 seconds, and the writing surface 4 with low smoothness, that is, with large unevenness, has too high ink wettability and affinity, or the ink penetrates into the recesses and is easy to erase. There is a risk that it will disappear. Moreover, when printing under the said resin layer 3, there exists a possibility that the said printing may be obstructed by the said unevenness | corrugation, and it may become difficult to see.

On the other hand, on the writing surface 4 having a high smoothness exceeding the Oken type smoothness exceeding 2000 seconds, that is, with small unevenness, there is a possibility that the pen tip slips and writing becomes difficult.
On the other hand, by setting the Oken type smoothness of the writing surface 4 within the range of 1200 seconds or more and 2000 seconds or less, it is easy to erase as much as possible while maintaining good writing properties, and the resin layer 3 The bottom print can be made easier to see.

In order to adjust the Oken-type smoothness within the above range, for example, the drying condition (for example, after applying the coating agent for the resin layer 3 on the surface of the white sheet 2 as a base material) The temperature, time, etc.) may be different, or the types, combinations, blending ratios, etc. of two or more kinds of resin, cross-linking agent, and solvent to be blended in the coating agent may be varied.
For example, when only the drying conditions are adjusted using the same coating agent, the higher the drying temperature and the longer the time, the softer the unevenness, that is, the smoothness of the writing surface 4 tends to increase. There is.

  The Oken type smoothness is a unit that serves as an index for prescribing the smoothness of the surface of a sample such as paper. For details, see “Beck smoothness” [Yamamoto, Kaita, Iwasaki, The smoothness measured using the pressure drop type smoothness measuring instrument described in the paper pamphlet, Vol. 20 No. 2 (No. 179), Paper and Pulp Technology Association, issued in February 1966] Point to. The higher the smoothness of the sample surface, the higher the numerical value, and the lower the smoothness, the lower the numerical value.

As the pressure drop type smoothness measuring instrument, for example, Oken type air permeability smoothness tester KY6 manufactured by Asahi Seiko Co., Ltd. can be used.
The writing surface 4 having the unevenness has a wetting tension of 28 mN / m or more and 45 mN / m measured according to the method described in Japanese Industrial Standard JIS K6768: 1999 “Plastic-Film and Sheet-Wetting Tension Test Method”. It is preferable that:

The writing surface 4 having a wetting tension of less than 28 mN / m has too low ink wettability and tends to cause the ink to repel, which may make writing difficult.
On the other hand, the writing surface 4 having a wetting tension of more than 45 mN / m has too high ink wettability, and there is a risk that it will not be easy to erase.
In order to adjust the wetting tension within the range, the size of the unevenness of the writing surface 4 is adjusted by the same process as the adjustment of the Oken type smoothness, or the material for forming the writing surface 4 is changed. Just do it.

Specifically, for example, as the resin component for forming the resin layer 3, the smaller the surface energy is used, the lower the wetting tension of the writing surface 4. The wetting tension of can be increased.
In addition, when the low refractive index layer 5 and the antifouling resin layer 6 are coated on the resin layer 3 as will be described later, as the material for forming these layers is used, the smaller the surface energy, the more writing surface. The wetting tension of the writing surface 4 can be increased as the wetting tension of 4 is decreased, and conversely, a material having a larger surface energy is used.

  For example, when the antifouling resin layer 6 made of an antifouling resin having a surface energy smaller than that of the resin layer 3 is generally coated on the resin layer 3, the writing surface 4 is wetted thereby. The tension can be reduced. The wet tension of the writing surface 4 can be reduced as the thickness of the antifouling resin layer 6 is increased, and the wet tension of the writing surface 4 can be increased as the thickness is reduced. This is because as the thickness of the antifouling resin layer 6 is reduced, the surface of the resin layer 3 cannot be completely covered and the influence of the resin layer 3 as a base tends to appear.

  If the thickness of the antifouling resin layer 6 is increased so that the unevenness of the resin layer 3 is filled, the wetting tension of the writing surface 4 becomes the original wetting tension of the antifouling resin and no more changes. In that case, the effect of the present invention by providing unevenness on the resin layer 3 cannot be obtained. The same applies to the low refractive index layer 5. Therefore, it goes without saying that the thickness of these layers must be set in a range in which the unevenness of the writing surface 4 is not buried.

In order to form two or more kinds of resin components in order to form the unevenness, the physical properties of the resin components that are different from each other are selected from the group consisting of SP value, glass transition temperature Tg, surface tension, and number average molecular weight. At least one of them is preferred.
Among these, two or more kinds of resins having different SP values are phase-separated from each other based on the difference in the SP values as the coating agent is dried and the concentration of the resin is increased accordingly.

As is well known, the SP value is a measure of solubility, and the larger the SP value, the higher the polarity, and the smaller the SP value, the lower the polarity.
The SP value δ of the resin content is based on the cloud point titration method of SUH, CLARKE [J. Polym. Sci. A-1, Vol. 5, 1671-1681 (1967)].

Can be obtained.
That is, 0.5 g of the resin component for obtaining the SP value is weighed in a beaker or the like, and as a good solvent for the resin component, for example, 10 ml of tetrahydrofuran (THF) is added to dissolve the resin component to prepare a solution.
Next, when the solution is kept at a liquid temperature of 20 ° C. and stirred, a burette or the like is used to make the solution cloudy when, for example, n-hexane is gradually dropped as a poor solvent for the resin. The drop amount vh (ml) of the n-hexane at the point (turbid point) was determined, and from the drop amount vh (ml) and the amount of THF vt (= 10 ml), n-hexane and THF at the cloud point were obtained. Volume fractions φh1 and φt1 are obtained.

From the volume fractions φh1 and φt1, the SP values δh and δt of n-hexane and THF, and the molecular volumes Vh and Vt (ml / mol), V
mh and δmh are obtained.
Vmh = (Vh · Vt) / (φh1 · Vt + φt1 · Vh)
δmh = φh1 · δh + φt1 · δt
Further, in place of the n-hexane, as a poor solvent having a SP value different from that of the n-hexane, for example, ion-exchanged water is used in the same manner as described above except that ion-exchanged water is dropped vd at a cloud point. (Ml) is obtained, and the volume fractions φd2 and φt2 of the ion-exchanged water and THF at the cloud point are obtained from the dripping amount vd (ml) and the THF amount vt (= 10 ml).

From the volume fractions φd2 and φt2, the SP values δd and δt of ion-exchanged water and THF, and the molecular volumes Vd and Vt (ml / mol), V
Obtain md and δmd.
Vmd = (Vd · Vt) / (φd2 · Vt + φt2 · Vd)
δmd = φd2 · δd + φt2 · δt
Then, by substituting Vmh, δmh, Vmd, and δmd into the equation (1), the SP value δ of the resin can be obtained.

It is preferable that the difference in SP value between two or more kinds of resin components used in combination for forming the surface of the resin layer 3 to be uneven is 0.5 or more. Thereby, the two or more types of resin components can be satisfactorily phase-separated by the previous mechanism, and the surface of the resin layer 3 can be made uneven.
Note that the difference in SP value is preferably 0.8 or more even in the above range, considering that two or more kinds of resin components are more preferably phase separated.

However, if the difference in SP value is too large, the affinity of two or more types of resins is extremely reduced, and the respective resin components are completely separated, and the resin layer 3 that is integrated and excellent in durability. May not be formed. For this reason, the difference in SP value is preferably 15 or less, particularly 3.6 or less.
In addition, the difference of the said SP value calculates | requires the weighted average value of SP value for each resin as SP value for the said one resin, when any one resin part is a mixture of two or more types of resin. It is preferable to set the difference between the SP value and the SP value of the other resin to be combined within the above range.

As the resin component, the composition, molecular weight, and the like can be easily changed, whereby the SP value can be adjusted relatively easily, and in particular, the resin layer 3 having excellent transparency can be formed in order to make the printing on the base easier to see ( A (meth) acrylic resin (monomer, oligomer, polymer, etc.) is preferred.
Specific examples of the (meth) acrylic resin include, for example, (meth) acrylic copolymers, unsaturated double bond-containing (meth) acrylic copolymers, silicone (meth) acrylic block copolymers, unsaturated doubles. 1 type (s) or 2 or more types, such as a bond containing silicone (meth) acryl block copolymer and polyether frame | skeleton containing urethane (meth) acrylate, are mentioned.

In addition, as the (meth) acrylic resin, one or more kinds of polyfunctional unsaturated double bond-containing monomers such as polyfunctional unsaturated double bonds having two or more functions, and oligomers and polymers thereof are also included. Can be mentioned. Such a polyfunctional saturated double bond-containing component functions as a cross-linking agent such as the above copolymer.
Among these (meth) acrylic resins, by using two or more (meth) acrylic resins having different SP values (preferably having a difference in SP value within the above range) as a resin component, The two or more kinds of resin components can be phase separated satisfactorily during drying to make the surface of the resin layer 3 uneven.

As a suitable combination of two or more kinds of resins having different SP values,
(1) Two types of silicone (meth) acrylic block copolymer and (meth) acrylic copolymer, or
(2) Any one of three types of unsaturated double bond-containing (meth) acrylic copolymer, polyfunctional unsaturated double bond-containing component, and polyether skeleton-containing urethane (meth) acrylate is preferable.

In particular, the resin layer 3 composed of a cross-linked product of two types of the above-mentioned (1) silicone (meth) acrylic block copolymer and (meth) acrylic copolymer is used for the former silicone (meth) acrylic block copolymer. Since the surface energy is small due to the action of the silicone block contained in the polymer, it suppresses excessive increase in wettability and affinity to the ink due to the unevenness generated on the surface, and erases by eraser such as felt There is an advantage that can be made easier.

  Of the two types of resin (1), the silicone (meth) acrylic block copolymer is, for example, a (meth) acrylic monomer such as cyclohexyl methacrylate or hydroxyethyl methacrylate in the presence of an azo group-containing polysiloxane compound. Examples thereof include various block copolymers having a structure in which a (meth) acryl block is connected to one or both ends of the polysiloxane chain (silicone block) by a polymerization reaction by the action of a peroxide polymerization initiator. .

Such a block copolymer has an SP value of 10.5 or more by having the block structure in which a silicone block is introduced into the main chain.
Examples of the (meth) acrylic copolymer used in combination with the silicone (meth) acrylic block copolymer include (meth) acrylic monomers such as isobornyl methacrylate, methyl methacrylate, methacrylic acid, and the like. Examples thereof include those synthesized by random copolymerization by the action of a physical polymerization initiator.

The (meth) acrylic copolymer can have an SP value of 10 or less by changing the type, combination, and proportion of the (meth) acrylic monomer that forms the (meth) acrylic copolymer.
The two kinds of resin components can be mixed with, for example, a thermosetting agent such as a melamine curing agent, a thermosetting catalyst such as para-toluenesulfonic acid, and a solvent to prepare a heat-crosslinking coating agent.

And when the coating agent is applied to the upper surface in FIG. 1 of the white sheet 2 as a base material and then dried, the two types of resin components are phase-separated based on the difference in SP value between each other, The surface of the resin layer 3 before cross-linking is made uneven, and the unevenness is fixed by subsequent cross-linking of the two kinds of resins by heating, so that the resin layer 3 having an uneven surface is formed.
As the solvent, any solvent that can dissolve or disperse the respective components satisfactorily can be used, but in order not to inhibit the phase separation due to the difference in SP value between the two kinds of resins. The resin component having a smaller SP value is close to the SP value, preferably having a difference of ± 2 or less, particularly ± 1 or less.

  Examples of such solvents include ketone solvents such as methyl ethyl ketone, acetone, methyl isobutyl ketone, and cyclohexanone; alcohol solvents such as methanol, ethanol, propanol, isopropanol, and butanol; anisole, phenetol propylene glycol monomethyl ether, ethylene glycol dimethyl ether, and ethylene. Examples thereof include one or more ether solvents such as glycol diethyl ether, diethylene glycol dimethyl ether, and diethylene glycol diethyl ether.

Moreover, you may mix | blend with the said coating agent the component which reduces the refractive index of the resin layer 3 which co-crosslinks with resin components, such as perfluoroalkyl group containing oligomer, for example.
As described above, the blending ratio of each component adjusts the size of the irregularities formed on the surface of the resin layer 3, adjusts the degree of crosslinking and the refractive index, and further adjusts the viscosity and fluidity of the coating agent. In order to adjust etc., it can set suitably.

As the unsaturated double bond-containing (meth) acrylic copolymer among the three types of resin component (2), for example, (meth) acrylic monomers such as isobornyl methacrylate, methyl methacrylate, methacrylic acid, Random copolymerization by the action of a peroxide polymerization initiator, followed by pretreatment with tetrabutylammonium bromide, hydroquinone, etc., followed by addition reaction of glycidyl methacrylate, etc. to introduce unsaturated double bonds, etc. Is mentioned.

The unsaturated double bond-containing (meth) acrylic copolymer may have an SP value of around 10 by changing the type, combination, and proportion of the (meth) acrylic monomer that forms the unsaturated double bond. it can.
In addition, as the polyfunctional unsaturated double bond-containing component, two or more functional groups copolymerizable with the unsaturated double bond-containing (meth) acrylic copolymer and the polyether skeleton-containing urethane (meth) acrylate are used. And polyfunctional monomers, oligomers and polymers thereof.

  Examples of the polyfunctional monomer include tri- or tetra (meth) acrylate of pentaerythritol, penta- or hexa (meth) acrylate of dipentaerythritol, trimethylolpropane tri (meth) acrylate, tripropylene glycol di (meth) acrylate, Examples thereof include one or more of nanoethylene glycol di (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, neopentyl glycol di (meth) acrylate, and polyethylene glycol di (meth) acrylate.

The SP value of these polyfunctional unsaturated double bond-containing components is usually 11 or more.
Furthermore, the polyether skeleton-containing urethane (meth) acrylate is synthesized, for example, by reacting a mixture of isophorone diisocyanate, polypropylene glycol, pentaerythritol triacrylate, pentaerythritol tetraacrylate, etc. in the presence of a polymerization inhibitor by the action of a catalyst. In addition, a polyether skeleton-containing urethane (meth) acrylate having acrylate groups at both ends may be used.

The polyether skeleton-containing urethane (meth) acrylate contains a polyether skeleton, so that the SP value is 10.5 or more.
The three kinds of resins can be mixed with a photopolymerization initiator and a solvent to prepare a photocrosslinkable coating agent.
Then, when the coating agent is applied to the upper surface in FIG. 1 of the white sheet 2 as a base material and then dried, the three types of resin components are phase-separated based on the difference between the SP values, The surface of the resin layer 3 before crosslinking is made uneven, and the unevenness is fixed by subsequent crosslinking of the three types of resins by irradiation with light such as ultraviolet rays, so that the resin layer 3 having an uneven surface is formed. It is formed.

As the solvent, any solvent that can dissolve or disperse each of the above components satisfactorily can be used. Specific examples include the various solvents exemplified above.
As described above, the blending ratio of each component adjusts the size of the unevenness formed on the surface of the resin layer 3, adjusts the degree of crosslinking, and further adjusts the viscosity and fluidity of the coating agent. In order to do so, it can be set as appropriate.

  When the physical property to be different from each other in order to phase separate two or more resin components is the glass transition temperature Tg, for example, the glass transition temperature Tg of one resin is lower than the environmental temperature when applying the coating, By setting the glass transition temperature Tg of the other resin to be higher than the environmental temperature, the latter resin is aggregated by exhibiting a glass state in which molecular motion is suppressed in the coating agent during drying. Thus, the two or more kinds of resin components are phase-separated from each other.

  The range of the glass transition temperature Tg for each resin is not particularly limited. For example, when the environmental temperature during coating is 20 ° C. or higher, particularly 40 ° C. or higher, and 150 ° C. or lower, particularly 120 ° C. or lower, The glass transition temperature Tg of -70 ° C or higher, particularly -60 ° C or higher, and 120 ° C or lower, particularly 80 ° C, and the glass transition temperature Tg of the other resin is 90 ° C or higher, particularly 100 ° C or higher. In addition, it is preferable to set the temperature to 200 ° C. or lower, particularly 150 ° C. or lower, and to set the difference between the glass transition temperatures Tg of both resins to 30 ° C. or higher, particularly 50 ° C. or higher and 100 ° C. or lower.

The glass transition temperature Tg of the resin component can be measured by a method similar to the method for measuring Tg by ordinary dynamic viscoelasticity using, for example, Leovibron RHEO2000, 3000 manufactured by Orientec Co., Ltd.
As the two or more kinds of resins having different glass transition temperatures Tg, those having a glass transition temperature Tg within the above-mentioned range are selected from the exemplified (meth) acrylic resins (monomers, oligomers, polymers, etc.). And they can be used in combination.

When the physical property that is different from each other in order to phase-separate two or more kinds of resins is surface tension, the resin component with the higher surface tension is increased as the coating agent is dried and the concentration of the resin component is increased accordingly. Preferentially agglomerates, whereby the two or more resin components phase separate from each other.
The range of the surface tension of each resin is not particularly limited, but the difference in surface tension between two or more resins is 1 mN / m or more, particularly 5 mN / m or more, and 70 mN / m or less, particularly 30 mN / m or less. It is preferable to set.

The surface tension of the resin component is expressed by a static surface tension measured by a ring method using, for example, a dynamometer manufactured by Big Chemie Japan Co., Ltd.
As the two or more kinds of resins having different surface tensions, a resin having a difference in surface tension within the above range is selected from the exemplified (meth) acrylic resins (monomers, oligomers, polymers, etc.), What is necessary is just to use it in combination.

When the physical properties that are different from each other in order to phase-separate two or more types of resins are number average molecular weights, the resin having the larger number average molecular weight as the coating material is dried and the concentration of the resin content is increased. The components first precipitate from the coating agent and agglomerate, whereby the two or more types of resin components are phase-separated from each other.
The range of the number average molecular weight of each resin is not particularly limited, but the difference in the number average molecular weight of two or more kinds of resins is set to 3000 or more, particularly 5000 or more, and 100,000 or less, particularly 50,000 or less. preferable.

The number average molecular weight of the resin is represented by a value obtained from the result obtained by GPC (gel permeation chromatography: polystyrene conversion) measurement.
FIG. 2 is a partially enlarged sectional view showing a layer structure of another example of the embodiment of the board sheet of the present invention.
Referring to FIG. 2, in the board sheet 1 of this example, the exposed surface of the resin layer 3 is made uneven by the mechanism, and the surface is further refracted than the resin layer 3. It is covered with the low refractive index layer 5 having a small refractive index, and the exposed surface of the low refractive index layer 5 opposite to the resin layer 3 side (upper side in the figure) is the writing surface 4. This is different from the example of FIG.

Since the other configuration is the same as that of the example of FIG.
By providing the low refractive index layer 5, reflection of light on the writing surface 4, and reflection and glare caused by the reflection can be further effectively suppressed, thereby making it easier to see the written image and the projected image. .

The refractive index of the low refractive index layer 5 may be smaller than that of the resin layer 3. However, considering that the above effect can be obtained more effectively, the refractive index is 1.35 or more, especially 1.36 or more, particularly 1. It is preferably 38 or more and 1.39 or less.
The low refractive index layer 5 has a thickness of 0.05 μm or more, particularly 0.1 μm or more, and 2 μm or less, preferably 1 μm or less, particularly 0.3 μm or less. If the thickness is less than the above range, the above-described effect due to the provision of the low refractive index layer 5 may not be sufficiently obtained. On the other hand, when the above range is exceeded, the unevenness on the surface of the resin layer 3 is filled with the low refractive index layer 5 and the writing surface 4 becomes a substantially smooth surface. There is a risk that problems such as glare and glare may occur.

In addition, the energy required for forming the low refractive index layer 5 by applying a coating agent for forming the low refractive index layer 5 to the surface of the resin layer 3 and then drying and further curing or crosslinking reaction increases. As a result, the productivity of the board sheet may be reduced.
The low refractive index layer 5 can be formed of a low refractive index resin such as methylpentene resin, diethylene glycol bis (allyl carbonate) resin, or fluorine-containing resin. A fluorine-containing resin is particularly preferable.

  The low refractive index layer 5 made of the fluorine-containing resin has a functional group that reacts with fluorine atoms by heat, light, or the like, and is cured or crosslinked by heating or light irradiation such as ultraviolet rays to generate the fluorine-containing resin. It can be formed using a precursor (monomer, oligomer, etc.). That is, a liquid coating material containing the precursor is applied to the surface of the resin layer 3 by any coating method such as spray coating, gravure coating, roll coating, or flow coating, and then heated or irradiated with light. Thus, a fluorine-containing resin can be generated by curing or crosslinking reaction, and the low refractive index layer 5 can be formed.

  As the thermosetting one of the precursors, for example, a thermosetting resin containing a fluorine-containing monomer, for example, a fluorine-containing epoxy resin in which a part or all of a polyol component is a fluorine-containing substance (particularly a diol) as a constituent monomer, Fluorine-containing unsaturated polyester resins in which part or all of the polyol and / or polycarboxylic acid components are fluorine-containing substances, fluorine-containing urethane resins in which part or all of the polyol and / or polyisocyanate components are fluorine-containing substances, etc. 1 type or 2 types or more are mentioned.

A coating agent is prepared by further blending the thermosetting precursor with a solvent or the like as necessary.
Examples of the photocrosslinkable precursors include fluorine-containing (meth) acrylic monomers such as fluorinated alkyl esters of (meth) acrylic acid, vinyl monomers such as fluoroolefins, and 1-fluoro-2- Examples thereof include di (meth) acrylates of fluorinated alkylene glycols such as di (meth) acryloyloxyethylene, or one or more of these oligomers and polymers.

A coating agent is prepared by further blending the precursor with a photopolymerization initiator, a solvent and the like.
Specific examples of the coating agent that is the basis for the low refractive index layer 5 include TT1006A manufactured by JSR Corporation, and Defensor TR-330 manufactured by DIC Corporation.
The smoothness of the writing surface 4 which is the surface of the low refractive index layer 5 is preferably 1200 seconds or more and 2000 seconds or less, expressed as Oken smoothness. The reason for this is as described above.

The wetting tension of the writing surface 4 is preferably 28 mN / m or more and 45 mN / m or less. The reason for this is as described above.
FIG. 3 is a partially enlarged cross-sectional view showing a layer structure of another example of the embodiment of the board sheet of the present invention.
Referring to FIG. 3, in the board sheet 1 of this example, the exposed surface of the resin layer 3 is made uneven by the mechanism, and the surface is further covered by the antifouling resin layer 6. It differs from the example of the previous FIG. 1 in that the exposed surface of the antifouling resin layer 6 on the opposite side (upper side in the figure) of the antifouling resin layer 6 is the writing surface 4. ing.

Since the other configuration is the same as that of the example of FIG.
By providing the antifouling resin layer 6, it is possible to suppress the wettability and affinity of the writing surface 4 with respect to the ink from being increased, and it is possible to further facilitate the eraser by the eraser.
The thickness of the antifouling resin layer 6 is preferably 0.5 μm or more, and preferably 5 μm or less. If thickness is less than the said range, there exists a possibility that the said effect by providing the antifouling resin layer 6 may not fully be acquired. On the other hand, when the above range is exceeded, the unevenness on the surface of the resin layer 3 is filled with the antifouling resin layer 6 so that the writing surface 4 becomes a substantially smooth surface. There is a risk of problems such as reflection and glare.

In addition, the energy required to form the low refractive index layer 5 is increased by applying a coating agent for the antifouling resin layer 6 to the surface of the resin layer 3 and then drying and further curing reaction. Further, the productivity of the board sheet may be reduced.
The antifouling resin layer 6 has a low surface energy, such as an acrylic resin copolymerized with a fluorine-based or silicone-based macromonomer, for example, and thus has a releasability with respect to the colorant contained in the ink for the whiteboard marker pen. It can be formed of various excellent resins.

In particular, considering that the adhesion of the antifouling resin layer 6 to the resin layer 3 is improved, the antifouling resin forming the antifouling resin layer 6 is a phase separation forming the resin layer 3. A resin that is the same or the same as or at least compatible with the at least one resin.
The antifouling resin layer 6 is a coating containing the antifouling resin or a precursor thereof (monomers, oligomers, etc.), such as a spray coating method, a gravure coating method, a roll coating method, or a flow coating method. After the coating method is applied to the surface of the resin layer 3, the coating agent can be solidified.

  The “solidification” includes not only the process of drying and solidifying the coating material, but also the process of curing or crosslinking reaction by irradiating with ultraviolet rays or heating. That is, a coating agent containing an antifouling property and a resin that is soluble or dispersible in an arbitrary solvent together with the solvent is prepared, and the coating agent is applied to the surface of the resin layer 3 by the arbitrary application method. Thereafter, the antifouling resin layer 6 made of the resin as a solid content can be formed by drying and removing the solvent in the coating.

  In addition, after applying a coating containing a curable or crosslinkable resin or its precursor to the surface of the resin layer 3, the solvent in the coating is removed by drying, and ultraviolet rays are irradiated or heated. The antifouling resin layer 6 can be formed by curing or crosslinking reaction of the resin or its precursor. In addition, the coating agent which does not contain a solvent can also be used, and a drying process can be skipped in that case.

The smoothness of the writing surface 4 which is the surface of the antifouling resin layer 6 is preferably 1200 seconds or more and 2000 seconds or less in terms of Oken smoothness. The reason for this is as described above.
The wetting tension of the writing surface 4 is preferably 28 mN / m or more and 45 mN / m or less. The reason for this is as described above.
FIG. 4 is a partially enlarged cross-sectional view showing a layer structure of still another example of the embodiment of the board sheet of the present invention.

Referring to FIG. 4, the board sheet 1 of this example has a base material in which a white sheet 8 whose upper surface in the figure is an ink jet printable print surface 7 and the printed print surface 7 after printing are bonded. The point which is provided with the transparent sheet 10 coat | covered through the agent layer 9, and the resin layer 3 is formed on the transparent sheet 10 after the said coating differs from the example of previous FIG.
The resin layer 3 itself is configured in the same manner as in the example of FIG. 1, and the exposed surface is formed into a concavo-convex shape as the writing surface 4 by the mechanism described above. The smoothness of the writing surface 4 is preferably 1200 seconds or more and 2000 seconds or less in terms of Oken smoothness. The reason for this is as described above. The wetting tension of the writing surface 4 is preferably 28 mN / m or more and 45 mN / m or less. The reason for this is as described above.

  Among the above, the white sheet 8 is a substrate made of, for example, PET or the like, in which a white receiving layer having acceptability for water-based inkjet ink is formed on the upper surface in the drawing to form the printing surface 7 Or, at least the printing surface 7 is formed of a white vinyl chloride resin that can be inkjet printed with a non-aqueous inkjet ink.

Of these, the latter white sheet 8 is formed integrally with a white vinyl chloride resin in consideration of simplifying the layer structure to improve the productivity of the board sheet 1 and reducing the manufacturing cost. It is preferable.
As the transparent sheet 10, for example, an arbitrary resin and transparent sheet or the like can be used. In view of dimensional stability, strength, etc., a transparent sheet made of PET is preferred.

The adhesive forming the adhesive layer 9 can satisfactorily bond the white sheet 8 and the transparent sheet 10, and the printing 11 on the printing surface 7 can be applied from the writing surface 4 side to the resin layer 3, the transparent sheet 10, In order to be able to be seen well through the adhesive layer 9, it is required that the transparency is as high as possible. The same applies to the resin layer 3 and the transparent sheet 10.
The board sheet 1 includes, for example, a transparent sheet 10 on which one side of a resin layer 3 is formed and a white sheet 8 that has been ink-jet printed on a printing surface 7 in advance and bonded to each other via an adhesive layer 9. Configured.

In addition, this invention is not limited to the example of each figure demonstrated above.
For example, the antifouling resin layer 6 of the example of FIG. 3 is further formed on the surface of the low refractive index layer 5 covering the surface of the resin layer 3 of the board sheet 1 of the example of FIG. It may be surface 4.
Further, for example, at least one of the low refractive index layer 5 of the example of FIG. 2 and the antifouling resin layer 6 of the example of FIG. 3 is provided on the surface of the resin layer 3 of the board sheet 1 of the example of FIG. It is good also as the writing surface 4 by forming.

  In addition, arbitrary changes can be made without departing from the scope of the present invention.

<Synthesis Example 1>
Synthesis of Silicone Acrylic Block Copolymer Azo group-containing polysiloxane compound [VPS-1001N manufactured by Wako Pure Chemical Industries, Ltd., molecular weight of polysiloxane chain 10,000, solid content 50%] 243.9 parts by mass of cyclohexyl A mixture consisting of 144.0 parts by weight of methacrylate, 43.7 parts by weight of styrene, 52.3 parts by weight of hydroxylethyl methacrylate, and 343.3 parts by weight of butyl acetate was blended and mixed to prepare a raw material solution.

Also, 270.0 parts by mass of butyl acetate was charged into a reaction vessel equipped with a stirrer, a nitrogen introduction tube, a cooling tube, a heating / temperature control device, and a dropping funnel, and nitrogen was continuously introduced from the nitrogen introduction tube. While continuously stirring using a stirrer in a nitrogen atmosphere, the liquid temperature was raised to 120 ° C.
Next, while maintaining the liquid temperature at 120 ° C. under the nitrogen atmosphere, the whole amount of the raw material solution was dropped at a constant rate over 3 hours using the dropping funnel, and then further at 120 ° C. The reaction was continued with stirring for 30 minutes.

  Next, in the nitrogen atmosphere, while maintaining the liquid temperature at 120 ° C. and further stirring, the reaction system contains butyl acetate solution containing 0.60 part by mass of t-butylperoxy-2-ethylhexanoate 15. A total amount of 0 part by mass was dropped at a constant rate over 30 minutes using the dropping funnel, and then the mixture was further reacted by stirring at 120 ° C. for 1 hour to synthesize a silicone acrylic block copolymer.

The silicone acrylic block copolymer had a number average molecular weight: 34,000, a weight average molecular weight: 125,000, an SP value: 10.8, a glass transition temperature Tg: 69 ° C., and a surface tension: 16 dyn / cm.
<Synthesis Example 2>
Synthesis of acrylic copolymer A raw material solution was prepared by mixing 280.8 parts by mass of isobornyl methacrylate, 4.2 parts by mass of methyl methacrylate, 15.0 parts by mass of methacrylic acid, and 340.0 parts by mass of propylene glycol monomethyl ether. did.

In addition, 200 parts by mass of propylene glycol monomethyl ether was charged into a reaction vessel equipped with a stirrer, a nitrogen introduction tube, a cooling tube, a heating / temperature control device, and a dropping funnel, and nitrogen was continuously introduced from the nitrogen introduction tube. The liquid temperature was raised to 110 ° C. with continuous stirring using a stirrer in a nitrogen atmosphere.
Subsequently, while maintaining the liquid temperature at 110 ° C. under the nitrogen atmosphere, the whole amount of the raw material solution was dropped at a constant rate over 3 hours using the dropping funnel, and then at 110 ° C. The reaction was continued with stirring for 30 minutes.

  Next, the propylene glycol monomethyl ether solution 120 containing 3.0 parts by mass of t-butylperoxy-2-ethylhexanoate was added to the reaction system while maintaining the liquid temperature at 110 ° C. and continuing stirring under the nitrogen atmosphere. A total amount of parts by mass was dropped at a constant rate over 30 minutes using the dropping funnel, and then a propylene glycol monomethyl ether solution 25 further containing 0.3 parts by mass of t-butylperoxy-2-ethylhexanoate. An acrylic copolymer was synthesized by dropping and reacting a total amount of 0.5 parts by mass for 30 minutes using the dropping funnel.

The acrylic copolymer had a number average molecular weight: 6,400, a weight average molecular weight: 14,800, an SP value: 9.9, a glass transition temperature Tg: 113 ° C., and a surface tension: 29 dyn / cm.
<Synthesis Example 3>
Synthesis of unsaturated double bond-containing acrylic copolymer 190 parts by mass of propylene glycol monomethyl ether was charged into a reaction vessel equipped with a stirrer, a nitrogen introduction tube, a cooling tube, a heating / temperature control device, and two dropping funnels, The liquid temperature was raised to 100 ° C. while continuously stirring using a stirrer under a nitrogen atmosphere in which nitrogen was continuously introduced from the nitrogen introduction tube.

  Next, while maintaining the liquid temperature at 100 ° C. under the nitrogen atmosphere, the mixture is composed of 187 parts by mass of isobornyl methacrylate, 3 parts by mass of methyl methacrylate, 10 parts by mass of methacrylic acid, and 200 parts by mass of propylene glycol monomethyl ether. The total amount of the polymerizable monomer mixed solution and the total amount of the polymerization initiator solution consisting of 2 parts by mass of t-butylperoxy-2-ethylhexanoate and 80 parts by mass of propylene glycol monomethyl ether were respectively added to the two dropping funnels. In addition, after dropwise addition at a constant rate over 3 hours, the mixture was further reacted at 100 ° C. for 1 hour with stirring.

Next, while maintaining the liquid temperature at 100 ° C. under the nitrogen atmosphere, the reaction system was charged with 0.2 parts by mass of t-butylperoxy-2-ethylhexanoate and 27 parts by mass of propylene glycol monomethyl ether. The total amount of the post-shot polymerization initiator solution consisting of parts was dropped at a constant rate over 1 hour using the previous dropping funnel.
Next, while maintaining the liquid temperature at 100 ° C. under the nitrogen atmosphere and continuing stirring, the reaction system was mixed with 1.5 parts by mass of tetrabutylammonium bromide, 0.2 parts by mass of hydroquinone and 5 parts by mass of propylene glycol monomethyl ether. The total amount of the mixed solution was added using the dropping funnel.

  Next, the nitrogen atmosphere was changed to air bubbling, and the total temperature of the solution consisting of 17 parts by mass of glycidyl methacrylate and 5 parts by mass of propylene glycol monomethyl ether was added to the reaction system while maintaining the liquid temperature at 100 ° C. and continuing stirring. Then, the mixture was added dropwise using the dropping funnel over 1 hour, and the mixture was further stirred at 100 ° C. for 5 hours to carry out an addition reaction, thereby synthesizing an unsaturated double bond-containing acrylic copolymer.

The unsaturated double bond-containing acrylic copolymer had a weight average molecular weight of 17,000 and an SP value of 10.0.
<Synthesis Example 4>
Synthesis of polyether skeleton-containing urethane acrylate Isophorone diisocyanate (IPDI) 666 parts by mass, polypropylene glycol (polypropylene glycol 1000, manufactured by Kishida Chemical Co., Ltd.) 2000 parts by mass, and a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (mixed weight) (Ratio 60:40) 900 parts by mass are charged in a reaction vessel, 1000 ppm of dibutyltin dilaurate is added as a catalyst, 1000 ppm of hydroquinone is added as a polymerization inhibitor, and methyl isobutyl ketone (MIBK) is added so that the solid content concentration becomes 40% by mass. Then, the temperature of the solution is raised to 80 ° C. while blowing air, and the reaction is continued for 3 hours while maintaining the temperature of the solution. A polyether skeleton-containing urethane acrylate having the following structure was synthesized.

The polyether skeleton-containing urethane acrylate had a weight average molecular weight of 7,000 and an SP value of 10.8.
<Example 1>
(Preparation of coating agent A for resin layer 3)
In 32 parts by mass of the silicone acrylic block copolymer (SP value: 10.8) synthesized in Synthesis Example 1 and 48 parts by mass of the acrylic copolymer (SP value: 9.9) synthesized in Synthesis Example 2, While adding 20 parts by mass of a melamine curing agent as a curing agent, 6 parts by mass of paratoluenesulfonic acid as a thermosetting catalyst, and 0.1 part by mass of a perfluoroalkyl group-containing oligomer, anisole (SP value: 9. 5) was added so that a solid content concentration might be 23 mass%, and it mixed, and the coating agent A used as the base of the resin layer 3 was prepared.

(Manufacture of board sheet 1)
The coating agent A is applied to one side of a white PET sheet having a thickness of 125 μm as the white sheet 2 so as to have a coating thickness of 5 μm, dried by heating at 70 ° C. for 1 minute, and then at 1 at 80 ° C. The board | substrate sheet | seat 1 of the 2 layer structure shown in FIG.

When the Oken type smoothness of the writing surface 4 which is the surface of the resin layer 3 was measured using the Oken type air permeability smoothness tester KY6 manufactured by Asahi Seiko Co., Ltd., it was 1300 seconds. It was.
The wetting tension of the writing surface 4 was 33 mN / m as measured according to the method described in the Japanese Industrial Standard JIS K6768: 1999 “Plastic-Film and Sheet-Wetting Tension Test Method”.

<Example 2>
(Preparation of coating material B for resin layer 3)
4 parts by mass of an unsaturated double bond-containing acrylic copolymer (SP value: 10.0) synthesized in Synthesis Example 3 and 50 parts by mass of methyl isobutyl ketone (SP value: 8.3) were charged into a reaction vessel, The following components were added with stirring in a dark room, and then mixed to prepare a coating agent B that was the basis of the resin layer 3.

Mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate (SP value: 12.1): 75 parts by mass Mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (SP value: 12.7): 25 parts by mass Synthesis Example Polyether skeleton-containing urethane acrylate synthesized in 4 (SP value: 10.8): 2 parts by mass Isopropyl alcohol (SP value: 8.5): 118 parts by mass 1-hydroxycyclohexyl phenyl ketone (photopolymerization initiator): 5 Mass part α-hydroxy {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl-1-phenyl]} propan-1-one (photopolymerization initiator): 1 part by mass (sheet for board 1 Manufacturing of)
The coating agent B is applied to one side of a white PET sheet having a thickness of 125 μm as the white sheet 2 so as to have a coating thickness of 5 μm, dried by heating at 50 ° C. for 1 minute, and then at 1 at 80 ° C. The board | substrate sheet | seat 1 of the 2 layer structure shown in FIG.

The Oken type smoothness of the writing surface 4 which is the surface of the resin layer 3 was measured in the same manner as in Example 1, and was 1500 seconds. The wetting tension of the writing surface 4 was measured in the same manner as in Example 1 and found to be 48 mN / m.
<Example 3>
TT1006A manufactured by JSR Co., Ltd. was further applied to the surface of the resin layer 3 formed in the same manner as in Example 2 so that the coating thickness was 0.3 μm, and dried by heating at 70 ° C. for 1 minute. After that, the low refractive index layer 5 was formed by further heating at 80 ° C. for 1 minute to cause a crosslinking reaction, and the board sheet 1 having a three-layer structure shown in FIG.

When the Wangken type smoothness of the writing surface 4 which is the surface of the low refractive index layer 5 was measured in the same manner as in Example 1, it was 1800 seconds. The wetting tension of the writing surface 4 was measured in the same manner as in Example 1 and was 43 mN / m.
<Example 4>
On the surface of the resin layer 3 formed in the same manner as in Example 1, a silicone-containing acrylic UV-curable resin as an antifouling resin (a synthetic polymer formed by compounding a silicone-based macromonomer during acrylic resin synthesis) 3 is applied so that the coating thickness becomes 1.0 μm, and then cured by UV irradiation to form an antifouling resin layer 6, for the board having the three-layer structure shown in FIG. Sheet 1 was produced.

The Oken-type smoothness of the writing surface 4 which is the surface of the antifouling resin layer 6 was measured in the same manner as in Example 1 and found to be 1800 seconds. The wetting tension of the writing surface 4 was measured in the same manner as in Example 1 and found to be 32 mN / m.
<Example 5>
The same coating agent A as prepared in Example 1 was applied to one side of a 125 μm-thick transparent PET sheet as the transparent sheet 10 so that the coating thickness was 5 μm, and dried by heating at 70 ° C. for 1 minute. After that, the resin layer 3 was formed by further causing a crosslinking reaction by heating at 80 ° C. for 1 minute.

Also, a white vinyl chloride resin sheet printing surface 7 as a white sheet 8 prepared in advance by black printing with a non-aqueous inkjet ink is prepared, and a transparent adhesive is formed on the white sheet 8 printing surface 7. The transparent sheet 10 was bonded together with the resin layer 3 side up via the layer 9 to produce a board sheet 1 having a four-layer structure shown in FIG.
The Oken-type smoothness of the writing surface 4 which is the surface of the resin layer 3 was measured in the same manner as in Example 1 and found to be 1300 seconds. Further, the wetting tension of the writing surface 4 was measured in the same manner as in Example 1, and found to be 33 mN / m.

<Example 6>
A board sheet 1 having a four-layer structure shown in FIG. 4 was produced in the same manner as in Example 5 except that the drying condition of the coating agent A used as the resin layer 3 was changed to 60 ° C. for 1 minute.
The Oken type smoothness of the writing surface 4 which is the surface of the resin layer 3 was measured in the same manner as in Example 1, and was 1200 seconds. Further, the wetting tension of the writing surface 4 was measured in the same manner as in Example 1, and found to be 33 mN / m.

<Example 7>
A board sheet 1 having a four-layer structure shown in FIG. 4 was produced in the same manner as in Example 5 except that the drying condition of the coating A serving as the base of the resin layer 3 was 1 minute at 75 ° C.
The Oken-type smoothness of the writing surface 4 which is the surface of the resin layer 3 was measured in the same manner as in Example 1 and found to be 2000 seconds. Further, the wetting tension of the writing surface 4 was measured in the same manner as in Example 1, and found to be 33 mN / m.

<Example 8>
A board sheet 1 having a four-layer structure shown in FIG. 4 was produced in the same manner as in Example 5 except that the drying condition of the coating A serving as the base of the resin layer 3 was 1 minute at 40 ° C.
The Oken type smoothness of the writing surface 4 which is the surface of the resin layer 3 was measured in the same manner as in Example 1 and found to be 980 seconds. Further, the wetting tension of the writing surface 4 was measured in the same manner as in Example 1, and found to be 33 mN / m.

<Example 9>
A board sheet 1 having a four-layer structure shown in FIG. 4 was produced in the same manner as in Example 5 except that the drying condition of the coating A serving as the base of the resin layer 3 was 1 minute at 80 ° C.
The Oken-type smoothness of the writing surface 4 which is the surface of the resin layer 3 was measured in the same manner as in Example 1, and was 2500 seconds. Further, the wetting tension of the writing surface 4 was measured in the same manner as in Example 1, and found to be 33 mN / m.

<Example 10>
On the surface of the resin layer 3 formed in the same manner as in Example 2, a silicone-containing acrylic ultraviolet curable resin as an antifouling resin (a synthetic polymer obtained by compounding a silicone macromonomer during synthesis of the acrylic resin) 3 is applied so that the coating thickness becomes 0.3 μm and then cured by irradiation with ultraviolet rays to form an antifouling resin layer 6. Sheet 1 was produced.

The Oken-type smoothness of the writing surface 4 which is the surface of the antifouling resin layer 6 was measured in the same manner as in Example 1 and found to be 1800 seconds. The wetting tension of the writing surface 4 was measured in the same manner as in Example 1 and found to be 45 mN / m.
<Example 11>
A board sheet 1 having a three-layer structure shown in FIG. 3 was produced in the same manner as in Example 4 except that the coating thickness of the coating material used as the basis of the antifouling resin layer 6 was 1.2 μm.

The Oken-type smoothness of the writing surface 4 which is the surface of the antifouling resin layer 6 was measured in the same manner as in Example 1 and found to be 1900 seconds. Further, the wetting tension of the writing surface 4 was measured in the same manner as in Example 1 and found to be 28 mN / m.
<Example 12>
A board sheet 1 having a three-layer structure shown in FIG. 3 was produced in the same manner as in Example 4 except that the coating thickness of the coating agent used as the basis of the antifouling resin layer 6 was 1.4 μm.

The Oken type smoothness of the writing surface 4 which is the surface of the antifouling resin layer 6 was measured in the same manner as in Example 1 and found to be 2000 seconds. The wetting tension of the writing surface 4 was measured in the same manner as in Example 1 and found to be 26 mN / m.
<Comparative example 1>
The writing surface of the conventional whiteboard described in Patent Document 3 was reproduced, and a white PET sheet having a thickness of 125 μm was prepared as a base material.

In addition, a coating agent C containing an acrylic ultraviolet curable resin and having resin particles with an average particle size of 5 μm dispersed therein is prepared, and the coating agent C is applied to substantially the entire surface of the substrate by a roll coating method. For a board having a conventional writing surface in which a resin layer having a convex portion formed by the resin particles is formed by coating the resin so that the coating thickness is 2 g / m ² , irradiating ultraviolet rays to cure the resin. A sheet was produced.

The Wangken smoothness of the writing surface was measured in the same manner as in Example 1 and found to be 750 seconds. Further, the wetting tension of the writing surface 4 was measured in the same manner as in Example 1 and found to be 36 mN / m.
<Comparative example 2>
The writing surface of the conventional whiteboard described in Patent Document 1 was reproduced, and a white PET sheet having a thickness of 125 μm was prepared as a base material.

A coating D containing an acrylic ultraviolet curable resin is applied to substantially the entire surface of the base material by a spray coating method so that the coating thickness is 8 g / m ^2, and the resin is irradiated with ultraviolet rays. After semi-curing, it was embossed under heat and pressure using an embossing roll to form fine irregularities on the writing surface.
Then, after embossing, the resin was further cured by irradiating with ultraviolet rays to produce a board sheet having a conventional writing surface on which a resin layer having irregularities by the embossing was formed.

The Wangken smoothness of the writing surface was measured in the same manner as in Example 1 and was 600 seconds. Further, the wetting tension of the writing surface 4 was measured in the same manner as in Example 1, and found to be 34 mN / m.
<Comparative Example 3>
The same coating material C containing resin particles as that prepared in Comparative Example 1 was applied to one side of a transparent PET sheet having a thickness of 125 μm as a transparent sheet so that the coating thickness was 2 g / m ^2. Irradiation was performed to cure the resin, and the same writing surface provided with a resin layer having convex portions made of resin particles was formed as in Comparative Example 1.

In addition, as in Example 4, a white vinyl chloride resin sheet printed as a white sheet was prepared by black printing with a non-aqueous inkjet ink in advance, and the white sheet was printed with a transparent surface. Through the adhesive layer, the transparent sheet was laminated with the resin layer side up to produce a board sheet.
The Wangken smoothness of the writing surface was measured in the same manner as in Example 1 and was 780 seconds. Further, the wetting tension of the writing surface 4 was measured in the same manner as in Example 1 and found to be 36 mN / m.

<Writing test>
Ten subjects used a whiteboard marker pen to write on the writing surface of the board sheet produced in each of the above Examples and Comparative Examples, and the writing ease was evaluated. And the ease of writing was determined from the results according to the following criteria.
○: All 10 people evaluated that they could write without any problems. Easy to write.

Δ: 1 to 2 out of 10 people felt that writing was a little difficult and difficult to write, but others evaluated that they could write without problems. Normal level of ease of writing.
X: At least 1 out of 10 people evaluated that there was a problem with writing. Poor writing ability.
<Erasability test>
Made on the substantially entire writing surface of the board sheet produced in each of the examples and comparative examples, using a whiteboard marker pen, after 1 hour, after 3 hours, and after 24 hours, respectively. The ease of erasing when erasing using the eraser was evaluated according to the following criteria.

Yu: I was able to erase without any problems.
Good: I was able to erase it cleanly, although not as good.
Possible: Some parts were difficult to erase.
Impossible: Sometimes it was difficult to erase completely.
And the easiness of erasure of the board | board sheet | seat manufactured by each Example and the comparative example was comprehensively evaluated on the basis of the following Table 1.

<Durability test>
The writing surface of the board sheet produced in each of the above Examples and Comparative Examples was obtained by combining a clock meter manufactured by Yasuda Seiki Seisakusho Co., Ltd. with felt as a friction element, load 500 g, and 100,000 reciprocations. After the rubbing test under the above conditions, the writing ease test and the erasure ease test were performed again.

Durability is evaluated for at least one of the ease of writing and ease of erasing (×), and durability for both ease of writing and erasure is unchanged (○ ).
<Light reflection test>
The reflection of light when the front surface was projected using a projector onto the writing surface of the board sheet produced in each of the above Examples and Comparative Examples was observed, and the reflection of light was evaluated according to the following criteria.

A: There was no reflection of light and no glare was felt.
○: There was a slight reflection of light, but almost no glare.
(Triangle | delta): There was reflection of light and felt glare.
X: Reflection of light was conspicuous and strong glare was felt.
(↑↑ There is no △ in the examples and comparative examples, but △ is provided for balance with other evaluations. Please check.)
<Print visibility test>
From the writing surface side of the board sheet produced in Examples 4 to 8 and Comparative Example 3, a resin densitometer (Macbeth RD914 manufactured by Gretag Macbeth Co., Ltd.) is used on the printed surface through a resin layer and a transparent sheet. The black print reflection density was measured, and the print visibility was evaluated according to the following criteria.

○: Reflection density 0.7 or more. Good print visibility.
Δ: Reflection density of 0.5 or more and less than 0.7. Print visibility normal level.
X: The reflection density is less than 0.5. Print visibility is poor.
The above results are shown in Tables 2-4.

  From the results of Examples 1 to 12 and Comparative Example 1 in Tables 2 to 4, the conventional board sheet provided with the convex portions by the resin particles is easy to write or erase, or is a glare by reflection of light. It has been found that the effect of reducing the thickness is insufficient. Further, it was found that the resin particles easily fall off and the durability is insufficient. Further, from the results of Examples 5 to 9 and Comparative Example 3, it was also found that the printing on the base was disturbed by the resin particles and was difficult to see.

Moreover, from the results of Examples 1 to 12 and Comparative Example 2, the conventional board sheet provided with unevenness by embossing is also effective in reducing the glare due to the ease of writing and erasing, or the reflection of light. It turned out to be insufficient.
On the other hand, from the results of Examples 1 to 12, the board sheet provided with unevenness due to the resin layer separation is excellent in ease of writing and erasing, and reduces the glare due to light reflection. In addition to being excellent in durability, it was also found that the printing on the base was easier to see than before.

  In addition, from the results of Examples 1 to 4, it is possible to obtain a resin layer having the same effect by using any of the ABs as a coating agent for the resin layer. It has been found that the formation of the refractive index layer can further reduce the glare caused by the reflection of light, and the formation of an antifouling resin layer on the resin layer can further improve the ease of erasure.

In addition, from the results of Examples 5 to 9, the Wangken smoothness of the writing layer which is the surface of the resin layer is preferably 1200 seconds or more and 2000 seconds or less in order to further improve each of the above characteristics. understood.
Moreover, from the results of Examples 2 and 10, the wetting tension of the writing surface 4 is reduced by coating the antifouling resin layer 6 made of an antifouling resin having a surface energy smaller than that of the resin component forming the resin layer 3. It has been found that it is possible to improve the ease of erasing and that the wetting tension is 45 mN / m or less.

  Furthermore, from the results of Examples 4, 11, and 12, the greater the thickness of the antifouling resin layer 6 is, the smaller the wetting tension of the writing surface 4 is, and the wetting tension is 28 mN / m or more. It was found that it is preferable for improving the ease of writing.

1 Board sheet 2 White sheet 3 Resin layer 4 Writing surface 5 Low refractive index layer 6 Antifouling resin layer 7 Printing surface 8 White sheet 9 Adhesive layer 10 Transparent sheet 11 Printing

Claims (10)

A board for configuring the writing surface of a whiteboard having a writing surface capable of repeated writing and erasing,
A base material containing at least a white sheet, and a coating containing two or more kinds of crosslinkable resins having different physical properties on the surface of the base material, followed by drying and cross-linking reaction, It comprises a resin layer whose surface is made uneven by phase separation of the resin component of more than seeds as the coating agent is dried, and the surface of the resin layer made uneven is a writing surface A board sheet.   2. The board sheet according to claim 1, wherein the two or more kinds of resin components are different from each other in at least one physical property selected from the group consisting of a solubility parameter, a glass transition temperature, a surface tension, and a number average molecular weight. .   The board sheet according to claim 1, wherein the resin component is two types of silicone (meth) acrylic block copolymers and (meth) acrylic copolymers having different solubility parameters.   The resin component includes three types of unsaturated double bond-containing (meth) acrylic copolymer, polyfunctional unsaturated double bond-containing component, and polyether skeleton-containing urethane (meth) acrylate having different solubility parameters. The board sheet according to claim 1 or 2.   5. The board sheet according to claim 1, wherein substantially the entire writing surface is further covered with a low refractive index layer having a refractive index smaller than that of the resin layer.   The board sheet according to claim 1, wherein substantially the entire writing surface is further covered with an antifouling resin layer.   The board sheet according to any one of claims 1 to 6, wherein the writing surface has Oken smoothness of 1200 seconds or more and 2000 seconds or less.   The board sheet according to any one of claims 1 to 7, wherein the writing surface has a wetting tension of 28 mN / m or more and 45 mN / m or less.   The base material includes the white sheet whose one surface is an ink jet printable printing surface, and a transparent sheet that covers the printed surface after printing, and the resin layer is formed on the coated transparent sheet. The board sheet according to any one of claims 1 to 8, which is formed.   A whiteboard, wherein a writing surface is constituted by the board sheet according to claim 1.

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