JPH02154252A - Base for photographic paper - Google Patents

Abstract

PURPOSE:To obtain a base for photographic paper having high adhesion of printed picture image parts on a sheet-shaped base body to a layer coated with a polyolefin resin, and high resistance to blotting at edges by forming a printed picture image of a predetermined density on one side of the sheet- shaped base body with a water-base printing ink. CONSTITUTION:Water-base printing ink contg. a pigment consisting singly of carbon black and a binder is used for printing a base for photographic paper printed on a rear surface. Since the ink contains no white pigment nor reducer and is required only to form picture images having low density which are so low as being not detected by a mark sensor, the amt. of the carbon black pigment to be contained absolutely in the ink may be a considerably small amt. Accordingly, the amt. of the binder to be contained absolutely in order to fix the low density pigment may be also small. Such water-base printing ink has high adhesion to the sheet-shaped base body generating no choking, and a base body obtd. therefrom causes hardly blotting at the edges.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a support for photographic paper. More specifically, the present invention relates to a support for photographic paper having predetermined information printed on its negative side using special printing ink.

[Conventional technology]

Photographic paper basically consists of a support and a silver halide emulsion.
1 (photographic emulsion layer), and a protective gelatin layer.When base paper is used as the sheet-like substrate, generally both sides of the base paper are coated with polyolefin resin such as polyethylene in order to impart water resistance to the base paper. Coating is carried out using In photographic paper using such polyolefin resin-coated paper as a support, the side on which the photographic emulsion layer is coated is called the surface J, and the opposite side is called the back surface J. .

An image is formed on the surface of photographic paper. In addition, the product name, manufacturer name, etc. may be written on the back of the photographic paper as desired.
Symbol marks and the like are printed using printing ink. In particular, printing is often performed with a gravure or flexo printing machine using a printing ink containing a black dye or pigment on the back side of the base paper before it is coated with a polyolefin resin.

The printing area on the back side must have a density that allows the printed image to be clearly identified, processing liquid will not seep into the printed area during photo processing, and the mark detection device of the machine will detect it when cutting after photo processing. It is required that the concentration be such that no

When printing as described above on a sheet-like substrate using a printing ink containing an ordinary organic solvent, there are safety and hygiene problems due to the use of this organic solvent.
Additionally, if the boiling point of the solvent is high, there may be a delay in drying after printing, which may stain the bath roll.Furthermore, if the boiling point of the solvent is low, the printing ink may dry before printing and the printed image may not be printed. The solvent may cause unevenness on the support, reducing its flatness as a support for photographic paper, and the thickener added to the printing ink may not be sufficiently dissolved in the solvent. The addition of thickeners may cause the printing ink to string on the plate cylinder roll of the gravure printing press, or the printed image may have an adverse effect on the silver salt emulsion of the photographic paper. Various problems are known.

For this reason, the use of printing inks containing aqueous solvents for photographic paper supports has gradually declined, and recently, aqueous gravure or flexographic printing has been applied to photographic paper supports instead. It is becoming the mainstream printing method.

Generally, in order to produce a back-printed photographic paper support, a predetermined image is first printed on the back side of a sheet-like substrate, and after drying the image, corona is applied on the printed back side. A surface activation treatment such as discharge treatment P1 is performed, and finally a polyolefin resin composition is extruded and coated thereon. In this case, if the adhesion between the polyolefin resin coating layer and the printed portion on the back side of the sheet-like substrate is weak, the printed portion of the sheet-like substrate may be damaged due to stress in the post-process applied to the support for photographic paper. delamination occurs between the polyolefin resin coating layer and the polyolefin resin coating layer. This peeling between the eyebrows causes the printed portion to become floating, ie, blister, in a subsequent process, and the resulting support loses its commercial value.

Even if it does not reach the level of blistering, if a photographic emulsion is applied to a support with weak adhesive strength and the resulting photographic paper is subjected to photographic development processing, the cut surface of the photographic paper may If this weak adhesive area is present, the developer will seep into the photographic paper from that area, coloring it, and causing what is called sagging in the print area, which reduces the commercial value of the photographic paper. I am a member. Therefore, in a photographic paper support that has a sheet-like substrate and a printed image on the back side, good adhesion can be achieved between this printed part and the polyolefin resin coating layer formed thereon. is important.

In order to improve the adhesion between the printed portion of the sheet-like substrate and the polyolefin resin coating layer and to prevent blistering, the amount of pigment contained in the printing ink is 1/20 or less of the amount of binder, and printing The amount of binder in the ink image obtained by
No. 7-130031. However, photographic paper having such a printed ink image is also unsatisfactory in preventing edge seepage.

As mentioned above, printing on the back side of photographic paper supports is being replaced from conventional printing inks containing organic solvents to methods using water-based printing inks.

However, since the binder of water-based printing inks basically consists of an alkali-soluble resin, images printed with such water-based printing inks have the problem of being easily attacked by the developer during photographic development. .

[Problem to be solved by the invention]

The present invention provides a support for photographic paper that has good adhesion between the printed portion on the sheet-like substrate and the polyolefin resin coating layer, and that does not allow processing liquid to enter from the cut portion (edge seepage). This is what we are trying to provide.

[Means and effects for solving the problems] The support for photographic paper of the present invention has a sheet-like substrate and a coating layer formed on both surfaces of the sheet-like substrate and containing a polyolefin resin as a main component. The present invention is characterized in that a printed image of a predetermined shape is formed on at least one surface of the sheet-like substrate using an aqueous printing ink containing a pigment made only of carbon black and a binder.

In the aqueous printing ink, it is preferable that the binder is contained in an amount of 0.3 to 20 times the weight of the carbon black pigment.

The present inventors investigated in detail the composition of printing ink, printing conditions, etc. in order to obtain a support that can prevent or suppress edge seepage of photographic paper obtained when water-based printing ink is used. However, the present invention has been completed.

In general, printed images applied to photographic paper supports have a density sufficient for identification, but the density is low enough to not be detected by a cutting mark detector when cutting after photo development processing. must have.

For this reason, conventional water-based printing inks are made by diluting a mixed pigment of carbon blank black pigment and white pigment (generally titanium dioxide) with a reducer containing an extender pigment, and then mixing a binder with this to reduce the solid content. 10-25%
was commonly used. The content of the binder component relative to the weight of the pigment component (including extender pigment) is:
-a is in the range of 1 to 5 times the weight. Such conventional water-based printing inks are diluted 2 to 5 times with a mixed diluent of an alcoholic solvent and water and then used for printing.

The printing ink used in the present invention is a water-based printing ink that contains a pigment consisting only of carbon fluff and a binder, and does not contain a white pigment or a reducer, and is designed so that it will not be detected by a mark detector. Since it is only necessary to form a low-density image, the absolute amount of carbon black pigment contained in the ink can be quite small, and therefore the absolute amount of binder required to fix the low-density pigment is also small. That's a good thing.

The aqueous printing ink of the present invention has good adhesion to sheet-like substrates, does not cause chalking, and the obtained support has no or very little edge immersion.

For example, the density of an image printed on a photographic paper support (
The density difference between the non-printed area and the printed image area was measured using a microphotometer (manufactured by Union Optical Co., Ltd., MPM-174).
When measured at , it is approximately 0.03.

In order to obtain printed images with such density, in conventional water-based inks, the black pigment was diluted using a white lIl agent and a reducer whose weight was more than 10 times the weight of the carbon black pigment. Therefore, it was necessary to use Okawa's binder to fix such a large amount of pigment.

In the printing ink of the present invention, the absolute binder amount at is 1/10 of that in conventional water-based printing inks.
Therefore, the printed image portion does not substantially cause the support to sink into the support.

In addition, the printing ink of the present invention contains a white pigment and a reducer.
Since it does not contain pigments such as pigments, it is possible to easily set the pigment concentration to obtain a printed image with a desired density.

In the printing ink of the present invention, as described above, if the absolute content of the carbon blank pigment is appropriately set, the content of the binder is 0.3 to 2 of the weight of the carbon blank pigment.
It is preferable to set it in the range of 0 times, and it is more preferable to set it in the range of 0.3 to 18 times.

Paper is generally used as the sheet-like substrate of the support of the present invention, and such paper substrates can be made of various types of paper, such as natural valve paper, synthetic valve paper, mixed paper of natural valve and synthetic valve, etc. I can name paper. This base paper may contain additives such as sizing agents, fixing agents, paper strength enhancers, fillers, antistatic agents, dyes, etc. that are generally used in paper manufacturing, and may also contain surface sizing agents, surface strength agents, etc. , an antistatic agent or the like may be appropriately applied to the surface.

The sheet-like substrate usually has a weight of 100 to 300 g/n.

The polyolefin resins used to coat both sides of the sheet-like substrate include homopolymers of ethylene, α-olefins such as propylene, copolymers of two or more of the above olefins, and polymers of various types of these olefins. You can choose from a mixture of two or more types. Particularly preferred polyolefin resins are low density polyethylene, high density polyethylene, and mixtures thereof. There is no particular restriction on the molecular weight of polyolefin resin, but it is usually 20.00.
A value in the range of 0 to 200,000 is used. Each coating layer is generally applied to the paper substrate with a weight of 10 to 40 g/n.

It is already known to add various additives such as white pigments, colored pigments, fluorescent whitening agents, and antioxidants to the polyolefin resin used for the coating layer.

That is, in the present invention, there is no problem in adding these additives to the polyolefin resin coating layer on the surface side of the support sheet on which the photographic emulsion is coated.

〔Example〕

The photographic paper support of the present invention will be further explained with reference to Examples.

In the examples, printing ink preparation components were prepared with the following composition.

(a) Black component (black) Carbon black 17% (solid content weight) (b) White component (white) Titanium dioxide 35% (solid compensation! Ii) Medium 9% (〃) Volume 56% ( c) Reducer - BaSO4 13% (solid weight) Medium 17% (〃) ) Volume agent 70% (d) Diluent: Weight ratio of isopropyl alcohol to water 50:50
Mixtures 1 to 5 and -1 In each of Examples 1 to 5 and Comparative Example 1, a support for photographic paper having a printed image was prepared as follows.

Canadian Standard Freeness (JISP81)
21) Softwood bleached sulfite pulp beaten to 250d 20
% and 80% hardwood bleached sulfate pulp beaten to a freeness of 280 ttrl to produce a paper substrate having a basis weight of 170 g/%, a tightness of 1.0 g/cm, and a moisture content of 8%.

The papermaking additives (based on solid content) were as follows.

Cationized starch 2.0% alkyl ketene dimer resin 0.4% anionic polyacrylamide resin 0.1% polyamide polyamine epichlorohydrin resin 0.7% caustic soda Adjusted to pH 7.5 Furthermore, as a size press chemical, carboxyl modification Using a size press coating liquid in which PVA and sodium chloride were mixed at a weight ratio of 2:1 and dissolved in water to adjust the concentration to 5%,
This was applied to both sides of the paper substrate at a coating density of 25 g/% (solid content).

On the back side of the paper substrate thus obtained, a printing ink prepared from the above components and having the composition listed in Table 1 was diluted with the above diluent to a ratio of ink/diluent-1/3.5. 5 steps (cell depth 30μ to 10μ
A chart with μ) was printed using a gravure printing machine.

In order to keep the printing density (density difference between non-printing area and printing area) constant, a microphotometer (manufactured by Union Optical Co., Ltd., ?IP) was used.
M-174) was used to measure the print density at each step, and the portion closest to 0.030 was later used for the edge penetration test.

The printed surface was subjected to corona discharge treatment, and high density polyethylene (density -0.94 g/cd, melt index (hereinafter abbreviated as Ml) -8.0) and low density polyethylene (density = 0.94 g/cd) and low density polyethylene (density = 0.94 g/cd, melt index (hereinafter abbreviated as Ml) -8.0) were applied to the printed surface. 92g/d, MI=4.6) at a weight ratio of 1:l was melt-extruded and laminated at a resin temperature of 330°C, and the surface of the formed coating layer was matted with a cooling roll. This was then cooled to form a back side coating layer with a thickness of 30 mm.

Next, the surface side of the substrate was subjected to corona discharge treatment, and titanium dioxide (manufactured by Ishihara Sangyo Co., Ltd., A-22
Weight of high-density polyethylene (density -0.94 g/cl, MI = 8.0) and low-density polyethylene (density "" 0.918 H/cl, MI = 7) containing 0% Mixed resin with a ratio of 1:3 and a resin temperature of 3
Laminated by /8 melt extrusion at 20°C, glossy thickness 30
A surface coating layer of .mu.m was formed to obtain a photographic paper support.

In the obtained support, the adhesion between the printed image portion on the back side of the paper base and the polyolefin resin coating layer and the edge penetration property of the support were evaluated as follows.

A test piece with a length of 25 m and a length of 200 m+a was taken along the longitudinal direction of the support, and from one end surface of the test piece, only the 1 layer was removed 180° in the opposite direction along the longitudinal direction of the test piece. Peel along the direction and observe the fiber fuzz on the surface of the peeled base paper. If the paper fibers are fuzzed and peeled off from the paper waste, the adhesion is good, and there is no fuzz at the interface between the paper layer and the coating layer. If so, it was determined that the adhesion was poor, and the evaluation was performed as follows based on the area ratio of the good part.Grades 1 to 2 are practical, while grades 3 and below are not practical.

Grade 1 〃 2 〃 3 〃 4 〃 5 仝Jj Pi Yuzuki” Support the paper base so that the part of the back side printed portion of the paper base whose print density is closest to 0.030 is located at the longitudinal cutting edge of the paper base. The body was cut into a size of 80 x 120 m using an office cutter from the front side. This test piece was developed using CPK-1R18A developer manufactured by Konica ■ at 48°C for 3 minutes, and the test piece was placed between 4 pieces of filter paper.
The liquid was removed for a minute, and then fixed on a Konica CP using a 4B'CX fixer for 3 minutes using a 2Rl8A fixer.
Wash at 20°C for 1 minute, then heat at 80°C
It was dried for 1 minute and 30 seconds. All of the test adhesion area had good adhesion 〃 90% or more had good adhesion 80 〃 〃 60 〃 〃 Less than 60% had 〃 The width of the edge penetration of the printed part of the piece was measured. Edge soaking width is 1
If it exceeds III11, such a support is not practical.

Table 1 shows the obtained adhesion evaluation results and edge penetration evaluation results. Table 1 also shows the weight ratio of pigment to binder in the printing ink used in each example, and the same printing Cell depth in gravure printing that gives density (#)
is listed.

As is clear from Table 1, Examples 1 to 5 according to the present invention
The support showed good adhesion between the printed image area and the polyolefin resin coating and good resistance to edge seepage. Furthermore, as in Example 5, when the pigment/binder weight ratio in the printing ink was increased to 110.41 (
Even when the amount of binder was reduced), the resulting supports showed good adhesion and edge-wet resistance.

〔Effect of the invention〕

The support for photographic paper having a printed image of the present invention is produced by forming a printed image of a predetermined density on one side of a sheet-like substrate using an aqueous printing ink of a specific composition. It can exhibit good adhesion with the polyolefin resin coating layer and good resistance to edge seepage, and is extremely useful from a practical and economic point of view.

Claims (1)

[Scope of Claims] 1. A sheet-like substrate, and a coating layer formed on both sides of the sheet-like substrate and containing a polyolefin resin as a main component, wherein at least one surface of the sheet-like substrate contains only carbon black. With a water-based printing ink containing a pigment consisting of and a binder,
A support for photographic paper, characterized in that a printed image of a predetermined shape is formed.