JPH0358501B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a diazo photosensitive paper for copying, and more particularly, the present invention relates to a paper substrate, a sizing layer formed on at least one surface of the paper substrate, and a photodegradable diazonium compound formed on the sizing layer. In a diazo photosensitive paper for copying, the sizing layer contains a latex type thermoplastic resin binder of 35 to 70% by weight based on solid content, and 20 to 50% of a latex-type thermoplastic resin binder.
silica gel particles having an average particle diameter of 0.5 to 20 microns and a pore volume of 0.2 to 3.0 ml/g and 0.05 to 35% by weight of a carboxylate type water-soluble polymer; The present invention relates to a photosensitive paper for diazo copying characterized by: After exposing a one-component diazo photosensitive layer containing a photosensitive diazonium salt and developing with an alkaline solution containing a coupler, or after exposing a two-component diazo photosensitive layer containing a photosensitive diazonium salt and a coupler, The diazo copying method, which involves developing with ammonia-steam or alkaline liquid, is widely practiced as a low-cost copying method. However, in the photosensitive papers used in these diazo copying methods, dye-forming components such as photosensitive diazonium salts or couplers, as well as the formed diazo dye itself, have a strong tendency to permeate into the paper substrate. Compared to the amount of forming components used and the amount of diazo dye actually formed during development,
This method has the disadvantage that the density of the image formed is still not sufficiently high. In order to improve this shortcoming,
It has long been widely practiced to provide a sizing layer (precoat layer) on the surface of a paper substrate and provide a diazo photosensitive layer on this sizing layer. This sizing composition typically consists of a combination of a silica filler and an organic binder, and various water-soluble resins and water-dispersible resins are used as the organic binder. . The effect of this sizing layer is to prevent permeation of photosensitive diazonium salts and the like into the paper substrate, increasing density, contrast, and apparent sensitivity, and increasing the effective surface area of the photosensitive layer. These effects can be divided into two main types: the effect of increasing density and contrast due to the pigment effect caused by retaining the dye on the particle surface, but it is practically difficult to expect these two effects at the same time. That is, when the latter pigment effect is expected, there is a problem of seepage during application of the photosensitive layer composition, while on the other hand, when the former seepage prevention effect is expected, it becomes difficult to expect the latter pigment effect. The present inventors believe that when forming a sizing layer (precoat layer) by combining a specific silica gel particle latex-type thermoplastic resin binder and a carboxylate-type water-soluble polymer described in detail below in a specific quantitative ratio, It has been found that an optimum combination of the anti-bleeding effect and the pigment effect can be obtained, and that a photosensitive paper for diazo copying can be obtained which has excellent density, contrast and apparent sensitivity of the formed image. In FIG. 1 showing the cross-sectional structure of the photosensitive paper for diazo copying of the present invention, this photosensitive paper includes a paper substrate 1, sizing layers 2a and 2b applied to the surface of the paper substrate,
and a photosensitive layer 3 containing a photodegradable diazonium compound provided on one sizing layer 2a. In the photosensitive paper of the present invention, the sizing layer contains a latex-type thermoplastic resin binder of 20 to 80% by weight, particularly 35 to 70% by weight on a solid basis, and 10 to 80% by weight of a latex type thermoplastic resin binder.
% by weight, especially 20 to 70% by weight of silica gel particles with an average particle size of 0.5 to 20μ and a pore volume of 0.2 to 3.0 ml/g, and 0.03 to 40% by weight, especially
A distinctive feature is that it consists of a composition containing 0.05 to 20% by weight of a carboxylate type water-soluble polymer. In this sizing composition, the silica gel particles mainly act to increase the specific surface of the photosensitive layer and give a pigment effect to the dye formed, and the silica gel particles also improve the texture of the photosensitive paper. It also acts to improve its writing characteristics. The silica gel particles used in the present invention have a porous network structure in which primary particles of silicic acid ranging from several millimicrons to tens of millimicrons are tertiary connected by chemical bonds such as siloxane bonds.
Compared to other silica-based fillers, it is characterized by a significantly larger pore volume, ie, 0.2 to 3.0 ml/g, and a relatively larger final particle size. Because of this characteristic, when this silica gel particle is used to form a sizing layer, it can be used to form a sizing layer with a particle size of 0.02
~20μ colloidal silica or particle size 10 to 20
Significantly improves the density of the azo dye image formed compared to when using silica particles that exist alone and do not form pores, such as vapor-phase silica (Aerosil) of about mμ size. This fact will become immediately clear by referring to the example below. The exact reason for this significant increase in concentration is not fully clear, but the silica gel particles described above effectively adsorb and retain diazonium salts and couplers on their surfaces, and are formed by development. This is thought to be due to the fact that the azo dye is supported on silica gel particles having a relatively large particle size, resulting in a further increase in the pigment effect or hiding power. If the amount of silica gel particles is less than the above range, the above-mentioned effects will be unsatisfactory, while if it is more than the above range, the permeation of the photosensitive composition will be large and the sizing layer will easily peel off. . On the other hand, latex-type thermoplastic resin exists in the coating solution in the form of spherical particles with an emulsion size, that is, a particle size of 0.1 to 10 microns, and this resin is present between the silica gel particles and between the silica gel particles and the paper substrate. , which exhibits the effect of providing excellent binding properties without inhibiting the pigment effect. This characteristic is thought to be due to the fact that even after the sizing film is formed, the remains of the emulsion particles remain. When the amount of the latex resin is less than the above range, the binding of the silica gel particles tends to be unsatisfactory, and when it is more than the above range, both the pigment effect and the seepage prevention effect tend to be unsatisfactory. Latex-type thermoplastic resin binders include those conventionally known as latex-type or emulsion-type adhesives, such as polyvinyl acetate latex, vinyl acetate-vinyl chloride copolymer latex, acrylic resin emulsion, and styrene-acrylic copolymer. Although a combined emulsion, a vinyl chloride-acrylic copolymer emulsion, etc. can be used, the latex resin that can be used in the present invention is of course not limited to these. Including the carboxylate type water-soluble polymer in this sizing composition prevents the diazonium salt from permeating into the paper substrate, reducing the amount of photosensitive layer coated, and improving the apparent sensitivity and image quality. provides significant benefits in improving density and contrast. That is, a sizing layer consisting of a latex-type thermoplastic resin binder and silica gel particles is unsatisfactory in that the diazonium salt still tends to seep into the paper substrate during application of the photosensitive layer. On the other hand, when a carboxylate type water-soluble polymer is blended into the composition according to the present invention, such a tendency to percolate is significantly suppressed.
Although the exact reason for this is unknown, the inventors of the present invention assume that it is as follows. That is, since the carboxylate water-soluble polymer is a polymer having a carboxyl group, it acts as a cation exchanger, and the sizing layer containing it acts as a kind of cation exchange membrane. On the other hand, photodegradable diazonium compounds are almost always used in the form of double salts with zinc chloride for their stabilization.
It is believed that the sizing layer according to the present invention captures the diazonium salt that tends to permeate into the paper substrate due to the above-mentioned cation exchange effect, thereby providing excellent barrier properties. When the amount of the carboxylate type water-soluble polymer is less than the above range, such barrier properties become unsatisfactory, while when it is more than the above range, the pigment effect of the sizing layer tends to be lost. Examples of carboxylate type water-soluble polymers include water-soluble polymers having an alkali metal salt carboxyl group in the main chain or side chain of the polymer chain, such as carboxymethyl cellulose (Na salt), carboxymethyl starch (Na salt), Examples include sodium alginate, sodium salt of vinyl ether-maleic anhydride copolymer, sodium polyacrylate, and sodium polymethacrylate. These carboxylate type water-soluble polymers have carboxyl groups of 50 to 1100 meq/100g polymer, especially 100 to 600 meq/100g polymer, in terms of barrier properties.
It is desirable to contain the amount of 100g polymer,
In addition, it is desirable for the pH of the aqueous solution to be in the range of 6 to 8 from the viewpoint of stability of image quality. In the photosensitive paper of the present invention, the basis weight of the paper base (paper
The weight (Kg) per area of 880 mm x 1100 mm can vary over a wide range, but anything from as thin as 50 Kg to relatively thick as 68 Kg may be used for the purposes of the present invention. In order to provide a sizing layer on this paper substrate, a coating liquid with a solid content concentration of 10 to 60% by weight is prepared from the above-mentioned composition, and a coating amount of this coating liquid as solid content is 0.5 to 4.0 g. /m ² , especially 1.5 to 2.0g/m ²
The coating is carried out by means known per se, such as a coating roller, an air knife coater, a bar coater, a blade coater, a reverse coater, a hard coater, spraying, and dip coating. This coating composition may contain one or more additives known per se, such as plasticizers, solubilizers or dispersants, organic solvents, and the like. A diazo photosensitive layer composition known per se is then provided on this sizing layer. As the photosensitive diazonium salt contained in this diazo photosensitive layer, any diazonium salt can be used as long as it is photodegradable and can be coupled with a coupler used in the diazo copying method under normal development conditions. can. As the acid stabilizer to be contained in the diazo photosensitive layer, any organic or inorganic acid such as sulfosalicylic acid, p-toluenesulfonic acid, citric acid,
Tartaric acid, oxalic acid, sulfamic acid, maleic acid, phosphoric acid, etc. are used. In the case of a two-component diazo photosensitizer composition, a coupler is contained in addition to the above-mentioned essential components. Such couplers are also well known per se, and any compound capable of coupling with the above-mentioned diazonium salts can be used. In addition to the above-mentioned essential components, the diazo photosensitive composition used in the present invention may contain compounding agents known per se, such as wetting agents, stabilization aids, development accelerators, extenders, dispersants, pigments, etc. Each of these components is dissolved or dispersed in a solvent such as water to prepare a coating composition. Representative examples of this prescription are as follows. (1) Two-component diazo photosensitizer composition Diazonium salt 0.1 to 4.0% Coupler 0.1 to 5.0% Acid stabilizer 2 to 10.0% Development accelerator 2 to 10.0% Extender 0 to 10.0% Dispersant 0 to 1.0% Color element 0 Solvent remaining amount (2) One-component diazo photosensitizer composition Diazonium salt 0.1 to 4.0% Acid stabilizer 2.0 to 10.0% Stabilizer 0 to 10.0% Extender 0 to 10.0% Pigment 0 to 0.003% Solvent Medium Remaining Amount The coating amount of the photosensitive composition described above varies depending on the type of substrate and the development method, but generally speaking, the coating amount of the diazonium salt is 0.05 to 0.05.
It may be 0.2 g/m ² , particularly in the range of 0.075 to 0.15 g/m ² . Image exposure and development of this photosensitive layer is easily carried out by means known per se, for example exposure is carried out through the document using light from a light source such as a fluorescent lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, etc.; is ammonia
Dry development using water vapor, semi-dry development or wet development using an organic or inorganic base can be applied. The invention is illustrated by the following example. Example 1 The following composition liquid was applied to white base paper for photosensitive paper and dried.
A precoat layer with a coating weight of 1.7 g/m ² was formed. Sodium alginate 0.2g Polyvinyl acetate emulsion (solid content 50%)
6.0g silica gel particles (particle size 3.3μ, pore volume 1.60ml/
g) Add 3.0 g of water to bring the total volume to 100 ml. Furthermore, the following composition solution was coated on the precoat layer to form a photosensitive layer with a coating amount of 0.8 g/m ² . Boric acid 10g Caffeine 15g 2-hydroxy-3-naphthoic acid morpholinopropylamide 10g 4-morpholino-2,5-dibutoxybenzenediazonium chloride 1/2ZnCl 10g Zinc chloride 15g Methylene blue 0.04g Add water to bring the total amount to 1. The two-component diazo photosensitive paper produced in this way was processed using a commercially available semi-dry developing diazo copying machine (ED-800,
When developed using a special developer (manufactured by Sanda Kogyo Co., Ltd.), a copy with high density and excellent contrast was obtained. The image density at this time was 1.167. Furthermore, when this two-component diazo photosensitive paper was layered with the original and a copy was made using a commercially available dry developing (ammonia gas developing) diazo copying machine (Dynamini, manufactured by Sanda Kogyo Co., Ltd.), it was found to have high density and excellent contrast. A copy was obtained. The image density at this time is
It was 1.347. In addition, semi-dry developing diazo copying machine (ED-800,
(manufactured by Sanda Kogyo Co., Ltd.), the printing speed of the photosensitive paper was set to be constant (scale 9), the image density of the image area and the non-image area was measured, and the difference in density was calculated. The results are shown in Table 1. Comparative Example A two-component diazo photosensitive paper was prepared in the same manner as in Example 1, except that vapor phase silica (Aerosil, particle size 10 mμ) was used instead of silica gel particles as the precoat layer, and it was used for semi-dry development. When developed with a diazo copying machine (ED-800, manufactured by Sanda Kogyo Co., Ltd.) using a special developer, an image with a lower density than that of Example 1 and which was difficult to see was obtained. The image density at this time was 1.117. Furthermore, when development was carried out using ammonia gas in the same manner as in Example 1, an image with a low image density of 1.268 was obtained. Further, in the same manner as in Example 1, the image density of the image area and non-image area of the copy was measured at a constant printing speed (scale 9), and the difference in density was calculated. The results are shown in Table 1.

【table】

[Table] From Table 1, it was found that the diazo photosensitive paper of the present invention was also excellent in color development sensitivity.

[Brief explanation of drawings]

FIG. 1 shows the structure of the diazo copying photosensitive paper of the present invention. Reference number 1 is paper substrate, 2
a and 2b are sizing layers, and 3 is a photosensitive layer, respectively.

Claims (1)

[Scope of Claims] 1. A diazo copying photosensitive paper comprising a paper substrate, a sizing layer formed on at least one surface of the paper substrate, and a photosensitive layer containing a photodegradable diazonium compound formed on the sizing layer. , the sizing layer comprises 35 to 70% by weight of a latex-type thermoplastic resin binder, 20 to 50% by weight of a latex-type thermoplastic resin binder, an average particle size of 0.5 to 20 microns, and an average particle size of 0.2 to 20 microns, based on solids content.
1. A diazo photosensitive paper for copying, comprising a composition containing silica gel particles having a pore volume of 3.0 ml/g and 0.05 to 35% by weight of a carboxylate type water-soluble polymer.