JPH08258405A - Ohp sheet for ink-jet recording - Google Patents

Abstract

PURPOSE: To obtain an OHP sheet which has an appropriate surface smoothness and surface unevenness, a good water resisting property, storage stability, printability, transparency, an anti-blocking property, and scratch resistance by using a polyvinyl acetal resin and organic polymer particles and arranging D/t, Beck smoothness, and a number of surface-exposed particles in a range. CONSTITUTION: An ink layer containing polyvinyl acetal resin and organic polymer fine particles is formed on a light transmitting substrate. The ratio (D/t) between the particle size (D) of the organic polymer fine particles and the thickness (t) of the ink receiving layer is 1.2-2.2, the Bekk smoothness of the surface of the ink receiving layer is 300-6000sec, and the number of organic polymer fine particles exposed to the surface of the ink receiving layer is 10-700/mm<2> .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an OHP sheet for ink jet recording.

[0002]

2. Description of the Related Art The ink jet recording system is low in noise, capable of high-speed recording, multi-coloring, compact printer device, and recording recording on both dedicated recording paper and plain paper. Therefore, it is widely used in various printing devices such as facsimiles, printers, computer terminals, etc., and occupies one field of important information devices which have been rapidly spreading in recent years.

On the other hand, in recent years, a method of directly recording and printing information from a computer on a so-called overhead projector (OHP) sheet has been put into practical use, and an ink jet recording method is also adopted as this recording method. The OHP sheet used in this method has a structure in which an ink receiving layer is formed on a light transmissive substrate.

This OHP sheet for ink jet recording (hereinafter sometimes simply referred to as "OHP sheet").
The following six items are examples of the characteristics required for the above.

High transparency. The ink can be absorbed into the ink receiving layer quickly, and there is no color stain such as yellow, magenta, cyan, and black, and the saturation is high and a clear color tone can be reproduced. When performing multicolor recording by combining inks, each ink component is quickly absorbed even if ink dots overlap on the same surface of the recording paper, and the recording surface does not get dirty even at high speed recording, and sufficient ink absorption Must have speed and ink absorption capacity. It is water resistant and does not cause image bleeding or bleeding even if water adheres to it. The OHP sheets are stacked in a paper feed case such as an inkjet printer, but even when the OHP sheets are superposed in this way, no blocking occurs and the OHP sheets are rubbed against each other, etc. Not be scratched. No fading will occur even if the printed matter is saved.

In order to satisfy these conditions,
For example, JP-A-59-174381 proposes to use a water-soluble resin such as polyvinyl alcohol or carboxymethyl cellulose in the ink receiving layer of an OHP sheet. Further, JP-A-58-89391 proposes to crosslink the water-soluble resin in the ink receiving layer in order to improve water resistance.

[0007]

However, when a water-soluble resin such as polyvinyl alcohol or carboxymethyl cellulose is used in the ink receiving layer, the transparency of the entire OHP sheet and the printing characteristics of the ink are good, but the water resistance is poor. There is a problem that burrs are generated on the fracture surface when cutting into a predetermined size due to sufficient film strength of the ink receiving layer. Further, a water-soluble resin of the ink receiving layer crosslinked has good water resistance, but has a problem that the absorbability of the ink and the temporal stability after printing are deteriorated. Further, there is a problem in handling such that the ink receiving layer and the substrate may be scratched by rubbing the OHP sheets with each other during feeding to the printer.

The present invention solves the above-mentioned conventional problems, and has transparency, printing characteristics, water resistance, storage stability and scratch resistance,
Inkjet recording OHP with excellent blocking resistance
The purpose is to provide a sheet.

[0009]

The OHP sheet for ink jet recording of the present invention is an OHP sheet for ink jet recording having an ink receiving layer containing a polyvinyl acetal resin and organic polymer particles on a light transmissive substrate. Therefore, the ratio (D / t) of the particle diameter (D) of the organic polymer fine particles to the film thickness (t) of the ink receiving layer is 1.2 to 2.2.
And the Bekk smoothness of the surface of the ink receiving layer is 300 to 6
The number of organic polymer fine particles exposed on the surface of the ink receiving layer (hereinafter sometimes referred to as “the number of surface exposed particles”) is 10 to 700 particles / mm ² for 000 sec.

That is, the inventor of the present invention has conducted extensive studies to improve the surface properties of the OHP sheet for ink jet recording and the resin contained in the ink receiving layer, in particular, the blocking resistance and the abrasion resistance. It has been found that an OHP sheet for inkjet recording satisfying all the above requirements can be provided by setting the D / t, Beck's smoothness, and the number of surface-exposed particles defined in the present invention within the ranges. Was completed.

In the present invention, the number of exposed particles can be measured by observing the surface with a scanning electron microscope, and is represented by the number of organic polymer fine particles per 1 mm ^{2 of} sheet area.

The polyvinyl acetal resin used as the binder resin of the ink receiving layer in the present invention is obtained by reacting polyvinyl alcohol with an aldehyde to form an acetal. In this case, polyvinyl acetate may be used as a starting material, and saponification and acetalization may be performed concurrently. As an acetalization method, a conventionally known method such as a dissolution method, a precipitation method or a homogeneous method can be adopted.

The polyvinyl alcohol used as a raw material for the polyvinyl acetal resin according to the present invention is not limited in any way, but generally has a degree of polymerization of 300 to 450.
0, preferably 500 to 4500, is used. The higher the degree of polymerization, the better the ink fixability and water resistance of the ink receiving layer of the OHP sheet obtained.
Although the degree of saponification of polyvinyl alcohol is arbitrary, it is usually 80.0 to 99.5 mol%.

On the other hand, examples of aldehydes condensed with polyvinyl alcohol include aliphatic aldehydes such as formaldehyde, acetaldehyde, butyraldehyde, hexylaldehyde, octylaldehyde and decylaldehyde; benzaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4 -Methylbenzaldehyde, other alkyl-substituted benzaldehydes, chlorobenzaldehyde, other halogen-substituted benzaldehydes, aromatic aldehydes such as phenylacetaldehyde, β-phenylpropionaldehyde, and other phenyl-substituted alkylaldehydes, as well as hydroxy groups and alkoxy groups on aromatic rings. , Aromatic aldehydes having substituents such as amino groups and cyano groups. Further, it may be an aldehyde having a condensed aromatic ring such as naphthaldehyde or anthraldehyde. Among these, aromatic aldehydes are particularly preferably used because a resin having good fixability, water resistance, and transparency can be obtained.

The degree of acetalization of the polyvinyl acetal resin used in the present invention is preferably in the range of 2 to 40 mol%, more preferably 3 to 30 mol%, and particularly preferably 5 to 20 mol%. . If the degree of acetalization is too low, the fixability of the ink of the ink receiving layer to be formed is good, but the water resistance may decrease, and conversely,
If the degree of acetalization is too high, the water resistance will be good, but the ink fixability will decrease.

Here, the degree of acetalization means that the number of moles of acetal groups contained in the polyvinyl acetal resin is A, the number of moles of acetyl groups is B, and the number of moles of hydroxyl groups is C.
Is the value represented by A / (A + B + C) × 100 (mol%).

Generally, several or more OHP sheets are handled in piles during distribution, storage, or in a paper feed case of a printer. At that time, in order to prevent the stacked sheets from blocking each other, fine particles (filler) are added to the ink receiving layer for the purpose of forming appropriate irregularities on the sheet surface.

The OHP sheet for ink jet recording of the present invention contains organic polymer fine particles as a filler in the ink receiving layer. Specific examples thereof include fillers made of acrylic resin, styrene resin, urea-formaldehyde resin, benzoguanamine resin, silicone resin, fluororesin and the like. Of these, acrylic resin fine particles are particularly preferable from the viewpoint of transparency and the like.

The particle shape of the filler used is preferably spherical as much as possible. When the particle shape of the filler is spherical, the transparency of the receiving layer is high and scratches are less likely to occur.

In the present invention, the particle diameter of the organic polymer particles used as a filler is such that D / t is 1.2 to 2.2, where D is the particle diameter and t is the thickness of the ink receiving layer. It should be in the range. If D / t is less than 1.2, the OHP sheets that are stacked in the paper feed case or the like cause blocking, which causes a trouble during printing. On the other hand, when it exceeds 2.2, there arises a problem that the surface of the OHP sheet is scratched by rubbing the OHP sheets with each other.

Regarding the surface smoothness of the ink receiving layer of the OHP sheet of the present invention, the Beck's smoothness is 300 to 60.
Within the range of 00 sec. This surface smoothness is specifically controlled by the particle size of the filler, that is, the organic polymer fine particles, and the addition amount thereof. Bekk smoothness of less than 300 sec means that the particle size of the additive filler is large or the additive amount is large.
There is a problem of scratches on the surface of the P sheet. On the contrary, 6000s
If it exceeds ec, the surface may be too smooth and blocking may occur.

In the present invention, the number of organic polymer fine particles of the filler exposed on the surface of the ink receiving layer is in the range of 10 to 700 per 1 mm ² of the OHP sheet. If the number of exposed particles is less than 10 particles / mm ² , blocking occurs, and if it exceeds 700 particles / mm ² , blocking is improved but transparency of the OHP sheet is lowered.

The compounding amount of the organic polymer fine particles as the filler satisfies the above-mentioned Beck's smoothness and the number of surface exposed particles, and the surface smoothness, blocking resistance,
In order to improve the transparency, it is preferably about 0.1 to 10% by weight with respect to the polyvinyl acetal resin. The ink receiving layer usually has a thickness t of 3
It is formed so as to be in the range of ˜20 μm. Therefore, as the organic polymer fine particles, those having a particle size of 5 to 40 μm are generally used.

Various additives may be added to the ink receiving layer according to the present invention within the range not impairing the object of the present invention. For example, glycerin, polyethylene glycol, or a surfactant may be used as the adsorbability improving agent for the aqueous ink, and an ultraviolet absorber, a pH adjusting agent, or the like may be used as the ink filling resistance improving agent.

Examples of the light-transmitting substrate used in the present invention include plastic films such as polyester, celluloid and polyvinyl chloride.

Any method may be used to form a film of a polyvinyl acetal resin containing organic polymer fine particles on such a light-transmitting substrate to form an ink receiving layer.
A method of applying the coating liquid by a bar coater method, a roll coater method, a blade coater method or the like and then drying it is employed.

The water-based ink used in the OHP sheet for ink jet recording of the present invention is optional,
Usually, a water-soluble dye, a wetting agent, a dye-solubilizing agent, water, a water-miscible organic solvent or the like is used.

[0028]

The polyvinyl acetal resin is used as the binder resin of the ink receiving layer, the organic polymer fine particles are used as the filler, and the D / t specified in the present invention,
By satisfying Beck's smoothness and the number of surface exposed particles, appropriate surface smoothness and appropriate surface irregularities are imparted,
Excellent in water resistance, storage stability, printing characteristics, and transparent,
An OHP sheet for inkjet recording having excellent blocking resistance and scratch resistance can be obtained.

[0029]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist.

Example 1 Polyvinyl acetal resin (trade name "ESREC KX-
1 "Sekisui Chemical Co., Ltd .: solid content 8%, acetalization degree 8 mol% 1225 parts by weight, polymer acrylic resin particles (trade name" BR89 "Mitsubishi Rayon Co., Ltd .: central particle size) 20 μm) 2 parts by weight was added to carry out a dissolution operation, and then a valve homogenizer (APV Gaulin I) was used.
NC. (Manufacturing) to perform a dispersion operation at a pressure of 200 kg / cm ² to obtain a paint. This paint was applied on a corona-treated surface of a polyethylene terephthalate film "T600" manufactured by Diafoil Co., Ltd. by a bar coater so that the film thickness after drying would be 10 μm to prepare an OHP sheet.

The produced OHP sheet was evaluated according to the following evaluation methods, and the results are shown in Table 1. The Beck smoothness of the ink receiving layer was measured by the JIS P 8119 method, and the number of surface exposed particles was measured by electron microscope observation.
A "560C" manufactured by Hewlett Packard Co., Ltd. was used as a commercially available inkjet printer for printing characteristics and other evaluations.

[Water resistance] One hour after ink jet recording, the OHP sheet is immersed in tap water for 1 minute and then immediately pulled up, and then the state of the ink image is observed. ◯, the case where the ink receiving layer runs off was determined as x.

[Printing Characteristics] Printed dots after ink jet recording were observed with a microscope. The print dots are circular,
When four color inks were overlaid and recorded, those having a clear image without ink flowing out were evaluated as ◯, and other than that were evaluated as x.

[Blocking test] An OHP sheet was placed on a glass plate so that the surface of the ink receiving layer faced downward, and a 1 kg weight was placed as a weight, and 60
It was allowed to stand for 20 days under the temperature and humidity conditions of 90 ° C. and 90% RH. Then, the sticking of the sheets was observed. When the sheet surface was stuck, it was judged as ×, and when sticking could not be confirmed, it was judged as ○.

[Abrasion resistance test] An OHP sheet was placed on a glass plate so that the surface of the ink receiving layer faced downward, a 1 kg weight was prepared, and this was used as an OH weight.
The P sheet was rubbed parallel to the longitudinal direction. Scraping is OHP
The sheet was fixed to glass and the glass was moved once at a speed of 160 mm / min, and then the degree of scratches on the recording surface was observed. The case where the scratch was clearly seen was judged as X, and the case where the scratch could not be confirmed with the naked eye was judged as O.

Example 2 An OHP sheet was prepared in the same manner as in Example 1 except that the coating material was applied so that the film thickness after drying was 15 μm.
The same evaluation was performed and the results are shown in Table 1.

Example 3 Polymer acrylic resin particles having an average particle size of 11 μm (trade name “MR13HG” manufactured by Soken Chemical Co., Ltd.) were used.
OHP was prepared in the same manner as in Example 1 except that 0 part by weight was used.
A sheet was prepared and evaluated in the same manner, and the results are shown in Table 1.

Example 4 An OHP sheet was prepared and evaluated in the same manner as in Example 3 except that the coating material was applied so that the film thickness after drying was 6 μm, and the results are shown in Table 1. It was

Example 5 Polymer acrylic resin particles having an average particle size of 7 μm (trade name “MR7HG” manufactured by Soken Chemical Industry Co., Ltd.) were 1.0
An OHP sheet was prepared in the same manner as in Example 1 except that the coating material was applied so as to have a film thickness after drying of 5 μm by weight, and the same evaluation was performed. The results are shown in Table 1.

Comparative Example 1 An OHP sheet was prepared in the same manner as in Example 1 except that the coating material was applied so that the film thickness after drying was 20 μm.
The same evaluation was performed and the results are shown in Table 1.

Comparative Example 2 An OHP sheet was prepared and evaluated in the same manner as in Example 1 except that the coating material was applied so that the film thickness after drying was 5 μm, and the results are shown in Table 1. It was

Comparative Example 3 An OHP sheet was prepared in the same manner as in Example 3 except that the coating material was applied so that the film thickness after drying was 20 μm.
The same evaluation was performed and the results are shown in Table 1.

Comparative Example 4 An OHP sheet was prepared and evaluated in the same manner as in Example 5 except that the coating material was applied so that the film thickness after drying was 3 μm, and the results are shown in Table 1. It was

Comparative Example 5 Example 4 was repeated except that silica particles (trade name "Silica Micro Bead P1505" manufactured by Catalysts & Chemicals Industry Co., Ltd .: average particle size 10.0 μm) were used in place of the polymer acrylic resin particles. An OHP sheet was prepared in the same manner as above and evaluated in the same manner, and the results are shown in Table 1.

Comparative Example 6 As the binder resin, polyethylene oxide (trade name "PEO-3") was used instead of the polyvinyl acetal resin.
An OHP sheet was prepared in the same manner as in Example 1 except that Sumitomo Seika Chemical Co., Ltd. was used, and the same evaluation was performed.
The results are shown in Table 1.

[0046]

[Table 1]

From Table 1, it is clear that the present invention provides an OHP sheet for ink jet recording, which has good water resistance, printing characteristics, blocking resistance and abrasion resistance.

[0048]

As described above in detail, the OHP sheet for ink jet recording of the present invention is excellent in water resistance, printing characteristics and storage stability, has high transparency, and can be superposed in a printer or the like. It has high practical value with no blocking or scratches.

Claims (1)

[Claims] 1. An OHP sheet for ink jet recording comprising an ink receiving layer containing a polyvinyl acetal resin and organic polymer fine particles provided on a light transmissive substrate.
The ratio (D / t) of the particle size (D) of the organic polymer particles to the film thickness (t) of the ink receiving layer is 1.2 to 2.2,
Beck smoothness of the ink receiving layer surface is 300 to 6000 s
ec, the number of organic polymer particles exposed on the surface of the ink receiving layer is 10 to 700 / mm ² , and the OHP sheet for inkjet recording is characterized.