JPS5850343B2 - Projection sheet with excellent writing properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a projection sheet that exhibits excellent writing properties with respect to pencils and water-based writing instruments, and also has excellent transparency.

Conventionally, films of polyester, polyvinyl chloride, polypropylene, acetate, and the like have been used as projection sheets for overhead projectors and the like, either as they are or after being subjected to corona discharge treatment.

However, although these films have good writability with oil-based writing instruments, they have poor writability with water-based writing instruments, making them completely useless for writing with a pencil.

As a solution to these drawbacks of conventional projection sheets, ultrafine powder is dispersed in a binder resin and applied as a thin film layer to the surface of a transparent film (Japanese Patent Laid-Open No. 49-827
No. 73).

However, providing a transparent film with a thin film layer in which ultrafine powder is dispersed in a binder resin improves writability, but has the disadvantage that light transmittance inevitably decreases.

In order to improve this light transmittance, based on the phenomenon that when a film of water or oil is applied to the rough surface of frosted glass, the rough surface becomes obtuse or smooth, improving light transmission.
It has been considered to add liquid surfactants, oil agents, etc.

However, although these do improve the light transmittance, they have the disadvantage that the thin film layer becomes soft and the writing performance of a pencil or water-based writing instrument is poor.

As a result of various studies, we found that in order to increase the light O transmittance without deteriorating the writing performance of pencils or water-based writing instruments, it is necessary to select additives that do not reduce the hardness of the thin film and are hydrophilic. There is.

The inventors have discovered a higher fatty acid alkali metal salt that fully satisfies these conditions, leading to the present invention.

That is, the present invention provides a writing thin film layer which is coated on the surface of a transparent film and whose main components are ultrafine powder and a binder resin, in which a heavy fatty acid alkali metal salt with a weight ratio of 2 to 10 is added to the binder resin. The present invention further improves the light transmittance and the writability of a water-based writing instrument while maintaining the writability of a projection sheet pencil with excellent writability, which is characterized by its inclusion in the thin film layer.

The transparent film used in the present invention is highly transparent, such as polystyrene, polyvinyl chloride, polyester, polycarbonate, and acetate film (JIS K671
A film having a visible light transmittance of 80 or higher) and a relatively stiff thickness of 30 to 300 microns is used.

The ultrafine powder used in the present invention is coated on a transparent film to provide writing properties, and includes carbonates of alkaline earth metals, sulfates, silicas such as finely divided silicic acid, synthetic silicates, calcium silicate, alumina, etc. , alumina hydrate, etc., polystyrene ultrafine powder spheres, organic powders such as microcrystalline cellulose, etc., used alone or as a mixture of two or more.

The ultrafine powder has an average diameter of primary particles of the ultrafine powder in the range of 1 to 100 mμ, preferably 10 to 50 mμ, and a refractive index (ASTMD s 42 ) of 1.
．． Those in the range of 4 to 1.7 are preferred.

The bonding resin used in the present invention is for firmly bonding the ultrafine powder to the transparent film, and is a substantially transparent resin having a refractive index similar to that of the transparent film and the ultrafine powder.

These binding resins include natural resins such as rosins, tammers, copal, shellac, and giltstone, maleic acid resins, phenolic resins, acrylic resins, polyvinyl alcohol, and cellulose polymers. Used as a mixture of more than one species.

Furthermore, the higher fatty acid alkali metal salts used in the present invention are salts of higher fatty acids such as lauric acid, myristic acid, palmitic acid, and stearic acid and alkali metals such as sodium and potassium, and are highly hydrophilic and solid at room temperature. something is used.

Here, the carbon number of the higher fatty acid is 1O~21, preferably 12~18, and the lower fatty acid alkali metal salt with a low molecular weight lower than this range is used for writing purposes in the same way as adding synthetic surfactants. This is undesirable because it tends to lower the hardness of the thin film and reduce pencil writing properties.

Furthermore, higher fatty acid alkali metal salts with too high molecular weights are less effective in improving the writability of water-based writing instruments.

The composition of the ultrafine powder, the binding resin, and the alkali metal salt of higher fatty acid is such that the ultrafine powder and the alkali metal salt of higher fatty acid are each blended in an amount of 2 to 10% by weight with respect to the binding resin.

It is preferable that the blending ratio of this ultrafine powder and higher fatty acid alkali metal salt is approximately equal. The writing performance and light transmittance of the writing instrument are poor.

Furthermore, if the added amounts of the ultrafine powder and the higher fatty acid alkali metal salt are each 10% by weight or more, it becomes difficult to apply these compositions to form a thin film layer on the surface of the transparent film.

The method of coating these compounded compositions on a transparent film to form a thin film layer is to dissolve or disperse the compounded composition in an appropriate solvent together with a small amount of auxiliary agents such as dispersants and surfactants, and to form a thin film layer with a solid content of 10 ~30% by weight coating composition and none;
An effective method is to apply the film onto the surface using a roll coating method, an air knife coating method, or the like, and then evaporate the solvent.

The solvent used may be one or a mixture of two or more commonly used solvents such as aromatics, ketones, esters, aliphatic hydrocarbons, and alcohols.

The amount of the writing thin film formed on the transparent film is preferably 0.5 to 3 g/m as a solid content, because if the coating amount is too small, the writing properties will be poor, and if it is too large, the transparency will be poor.

Furthermore, by subjecting the projection sheet of the present invention obtained as described above to a level treatment (corona discharge treatment) that is commonly performed, the writing properties of the water-based writing instrument can be further improved.
Alternatively, a mount printed with ruled lines may be stacked on the non-coated side of the projection sheet and fixed on one side to improve handling, such as improving writing workability on the sheet.

On the projection sheet obtained according to the present invention, calligraphy and drawings can be written not only with ordinary oil-based writing instruments but also with water-based writing instruments such as India ink or water-based paints, or with a pencil.

Furthermore, in the case of writing in thin lines with a pencil, the projected image on an OHP or the like is enlarged 30 to 50 times, so the light shielding properties tend to deteriorate.

However, when an image is drawn directly on the projection sheet with a pencil or the like and near-infrared rays are irradiated with a thermal copying machine, the pencil image area absorbs the light and generates heat, etching that part of the pencil image area of the projection sheet. The area reflects diffusely and prevents light from passing through, so when combined with shading with a pencil or carbon black, almost no light passes through. Therefore, when projected with an overhead projector, etc., an extremely clear and high-contrast projected image can be obtained. Invented.

Example 1 A thin film agent having the following composition ratio was applied to a 100μ thick biaxially stretched polystyrene film (light transmittance (JIS K6714: 95%)) using a commonly used gravure roll coating machine. .

The gravure roll used for coating was 180 wire 45μ.
The coating speed was 30 bottles/min.

The coating amount after drying was L59/m2.

<Coating composition> Logitsu modified phenolic resin 20 parts by weight Ethyl cellulose 2 Finely divided silicic acid (particle size 15-18μ) l Potassium laurate
1 Polymer nonionic surfactant
2 〃Xylene 25 〃n-
Butyl alcohol 25 Isopropyl alcohol 25 25 cr of the obtained sheet
rLX25α was cut, and writing on the coated surface with a pencil (hardness B) showed good writing properties, comparable to those without the addition of potassium laurate, and the projected image with an overhead projector was clear, and the light transmittance was low. 82
Approximately 1 liter compared to when potassium laurate is not added.
o% (relative) light transmission improved.

Furthermore, when calligraphy was written using India ink on the coated surface of the projection sheet, a clear calligraphy image was obtained without repelling the ink at all, and the image projected by the overhead projector was also extremely clear.

Example 2 The following composition was applied under the same conditions as in Example 1 to a 75 μm thick polystyrene film (96% light transmittance) obtained by the inflation method.

<Coating composition> Rosin-modified maleic acid resin 20 parts by weight Finely divided silicic acid (particle size 15-18771μ) 1 Ethyl cellulose 2 Sodium stearate 2 Nonionic surfactant
l〃Xylene 10//
Isopropyl alcohol 90 The obtained sheet was heated to 23crI1. When the coated surface was cut into ×26C1rL and written with a pencil (hardness B), it showed good writing properties similar to actual case 1, and the light transmittance was 84 coefficients, which was about 100% higher than when no sodium stearate was added. 13
% (relative) light transmission was improved.

Furthermore, the above projection sheet with the pencil drawings was irradiated with light and heat using a commercially available thermal copying machine (trade name: Trapen Up, manufactured by Riso Kagaku Kogyo) to etch the pencil image area, and then projected using an overhead projector, which resulted in extremely clear images. A projection image with strong contrast was obtained.

Claims (1)

[Scope of Claims] 1. In a writing thin film layer coated on the surface of a transparent film, the main components of which are ultrafine powder and a binder resin, a fatty acid alkali metal with a weight ratio of 2 to 10 to the binder resin. A projection sheet with excellent writability, characterized in that salt is contained in the thin film layer. 2 Carbon number 10-21. Claim 1, characterized in that it is a higher fatty acid alkali metal salt comprising preferably 12 to 18 higher fatty acids such as lauric acid, myristic acid, palmitic acid, and stearic acid and an alkali metal such as sodium and potassium. A projection sheet with excellent writing properties as described in the section.