JPH03200139A - Base for photographic printing paper - Google Patents

Abstract

PURPOSE:To provide the base suitable for production of photographic paper having high smoothness by decreasing the unequal thicknesses of a sheet-like base body to <=1.00 mum in the integrated value (PY volue) of the power spectrum of the sheet-like base body surface. CONSTITUTION:The base for the photographic paper having the good surface smoothness is effectively obtd. by using the sheet-like base body having the specific surface smoothness. The sheet base body having <=1.0 mum, more preferably <=0.80 mum integrated value (PY value) of the power spectrum at 1 to 12.5 mm wavelength is, thereupon, used. The measurement of the PY value is executed by using a film thickness gage, continuously measuring the unequal thicknesses of the sheet-like base body and subjecting the measured signal values obtd. in such a manner to a frequency analysis. Thus, the surface of the sheet-like base body has the excellent smoothness and is extremely useful for the production of the photographic printing paper having excellent smoothness.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a support for photographic paper, and more specifically, it relates to a support for photographic paper with good surface smoothness. .

[Conventional technology]

In recent years, as a support for photographic paper that can be rapidly developed, a water-resistant support has been developed in which a resin coating layer containing polio-fin resin as the main component is formed on both sides of a sheet-like substrate such as paper. has been put into practical use and is already widely used.

Generally available commercially available photographic papers include those with a highly glossy surface, those with a matte surface, and those with a grained surface. The surface shape of such photographic paper is such that the surface shape of the polyolefin resin coating layer on the front side of the support (on which the photographic emulsion layer is formed) becomes the surface shape of the photographic paper emulsion layer. It is something that was given to me.

Among the photographic paper surface shapes mentioned above, there are no patterns,
Photographic paper, which has a smooth, high-gloss surface, is most commonly used. In order to produce photographic paper with such a high gloss surface, the surface of the support resin coating layer on which the photographic emulsion layer is coated must have high gloss, that is, high smoothness. In order to obtain a resin coating layer with such a low surface smoothness, it is necessary that the surface of the sheet-like substrate on which it is formed has high smoothness, and that the surface of the resin coating layer is It is known to perform smoothing processing.

In general, the most common method for producing a water-resistant support is to laminate molten resin layers on both sides of a sheet-like substrate such as paper using a melt-extrusion coating layer, and then cool and solidify the molten resin layers.

In order to improve the surface smoothness of such a resin coating layer, it is necessary to increase the thickness of the resin coating layer to reduce or eliminate the influence on the surface of the resin coating layer on the sheet-like substrate surface. , and when forming the resin coating layer, it is considered that the pressure against the resin coating layer should not be excessively applied, but in reality, the effects of the above means are small, and disadvantages such as a large increase in cost are known. ing.

Furthermore, as a method for improving the surface smoothness of a sheet-like substrate, when the sheet-like substrate is calendered to improve its surface smoothness, the pressure of the calender is increased;
It is known to compress sheet-like substrates to improve their density. However, with this method, problems such as appearance defects such as "broad spots" and "white spots" are likely to occur, and smoothness is lost over time.

Furthermore, as a method for improving the surface smoothness of a sheet-like substrate, it is known to perform a tension press treatment during drying of the sheet-like substrate. However, a sufficient improvement in surface smoothness cannot be achieved with tension press treatment alone, and if this treatment is too strong, it may cause "kudake", which may actually worsen the smoothness and cause problems such as a decrease in opacity. There is.

[Problem B to be Solved by the Invention] The present invention solves the above-mentioned drawbacks of conventional supports for photographic paper, and provides a method for photographic paper that is capable of producing photographic paper having high smoothness. It is intended to provide support.

[Means and effects for solving the problem] The photographic paper support according to the present invention includes a sheet-like substrate;
It has a resin coating layer that covers both sides of the sheet-like substrate and contains a polyolefin resin as a main component,
When the thickness unevenness of the sheet-like substrate was continuously measured using a film thickness meter and the measurement signal was analyzed using a frequency analyzer, it was found that the thickness unevenness of the sheet-like substrate surface was found to be
The integral value of the power spectrum at 12.5ms+ (P
Y value) is 1, . 00m or less.

The present inventors found that in order to obtain a support for photographic paper with good surface smoothness, it is effective to use a sheet-like substrate having a specific surface smoothness, and in this case, the surface of the sheet-like substrate is the integral value of the power spectrum (partial overall value 2 PY
value) is 1.00 m or less, preferably 0.80- or less,
He later discovered that it was necessary to use a new method, and completed the present invention.

PY value is 1. If a sheet-like substrate having a surface larger than OOm is used, it becomes difficult to obtain a photographic paper with excellent surface smoothness.

The PY value of the surface of the sheet-like substrate is within the specified wavelength region, that is, 1~! It is the root mean square value of the input signal value at 2.5 mm. To measure this PY value, use a film thickness meter (
For example, the thickness unevenness of the sheet-like substrate is continuously measured using a thickness gauge (made by Anri), and the obtained measurement signal value is measured using a frequency analyzer (for example, made by Ono Saiki, trademark: C.F.
-940) by performing frequency analysis. In this case, the PY value is expressed as a voltage (Vr+++s) value, so in order to convert this into thickness unevenness (depth of peaks to valleys), this voltage value can be multiplied by 28.8 n/V.

Regarding the smoothness of the surface of the sheet-like substrate, the small wavelength range 1, 7 to
2.5 The PY value of rIlffl is 0.4 source or less,
PY value in large wavelength range 6.3-12.5mm is 0.50//
It is preferable that it is below II.

Small wavelength range 1.7-2.5 tnaOPY value 0.4 n
If it is below, the surface will have less flickering due to light with a wavelength of around 2 + nm, which is highly irritating to the human eye, and will give a sensually preferable impression. Furthermore, if the PY value in the large wavelength range 6.3 to 12.5 mm is 0.50n or less, coating unevenness (thickness) may occur when forming an emulsion layer on the surface of a support obtained from such a sheet-like substrate. Therefore, when such photographic paper is developed, uneven shading becomes noticeable in the colored image.

In order to obtain paper as a sheet-like substrate (hereinafter referred to as base paper) having the PY value specified in the present invention, it is effective to employ, for example, the following method.

The freeness of the pulp used is 200 to 400cc (
csf), preferably 250 to 350cc (
csf) is more preferable. Further, the type of pulp may be any of hardwood pulp, softwood pulp, hardwood mixed pulp, etc., and these may also be any of kraft pulp, sulfide pulp, soda pulp, etc. These pulps may include synthetic pulps, synthetic fibers, and the like.

However, it is preferable to use a pulp that contains as a main component hardwood pulp that has short fiber length and high flexibility, and contains 30% or more, preferably 50% or more of hardwood bleached kraft pulp (LBKP).

Further, when making base paper from the above-mentioned pulp, it is preferable to increase the pressure in the press part and to adjust the pressure of the tightness press and the pressure conditions of the calender.

The main purpose of the wet press in a paper machine is dewatering, and although this condition does not have a direct effect on the surface smoothness of the base paper, rapid dewatering in the press part can cause the paper layer to sag and become smooth. It has a negative effect on sexuality. For dewatering, it is necessary to provide at least two or more stages of presses to share the dewatering duties, and preferably three or more stages of presses are required. Further, it is preferable to provide a smoothing roll at the final stage of the press part.

The smoothness of the base paper can be greatly improved by providing a tension press during the drying of the base paper. Tension press position is base paper moisture 3
A position of 0 to 50% is preferable, and if the press pressure is too strong, it will cause cracking, and if it is too weak, the smoothing effect will be insufficient, so it is necessary to select it appropriately. In particular, the balance with the calendering conditions in the subsequent process is a key point in determining the smoothness of the base paper.

Furthermore, the surface smoothness of the base paper is improved by machine calendering and/or supercalendering.

This point is an important point for smoothing, including compensating for the surface of the base paper that has been roughened by the size press.

The inventor of the present application studied the conditions for smoothing and found that the following balance of pressure conditions is preferable as smoothing conditions.

Wet part 1st press pressure 20-50kg/c
m 2nd press 40-60 3rd press 60-90 Smoother 30-40 Tightness press 40-70 Machine calender 50-80 The base paper used in the present invention includes: Additives commonly used in paper manufacturing such as sizing agents, fixing agents, paper strength enhancers, fillers, antistatic agents, pH adjusters, pigments, and dyes may be included. Furthermore, a surface sizing agent, a surface paper strength agent, and an antistatic agent may be coated on the surface.

A resin coating layer containing a polyolefin resin as a main component is formed on both sides of the base paper. The polyolefin resin can be selected from α-olefin homopolymers such as polyethylene and polypropylene, α-olefin copolymers, and mixtures of these various polymers. Particularly preferred polyolefin resins include low density polyethylene,
High density polyethylene and mixtures thereof.

Various additives such as white pigments, colored pigments, optical brighteners, antioxidants, and dispersants may be added to the polyolefin resin. In the method of the present invention, these additives may also be added to the polyolefin resin coating layers formed on both sides of the photographic emulsion layer.

Additives (Examples) The present invention will be further explained below with reference to Examples, but the present invention is not limited thereto.

Actual JL example "1", cusp - "muta β" bite case - L example 1~
In each of Comparative Examples 1 to 3 and Comparative Examples 1 to 3, the wood pulps with the respective blending ratios shown in Table 1 were beaten with a deluxe finisher to the freeness shown in Table 1, and then additives with the compositions shown below were added in the respective amounts. (based on absolute dry weight of pulp) and paper was made using a Fourdrinier paper machine. In this case, the sea urchin y I breath, tension breath, and machine calender pressurization of each sample were performed under the conditions shown in Table 1.

30g of a 5% size liquid obtained by dissolving a mixture of carboxyl group-modified PVA and sodium chloride in a ratio of 2=1 in water using a size press on the base paper obtained by papermaking.
It was applied in a coating amount (solution weight) of /bo and dried. next,
This base paper was machine calendered under the linear pressure shown in Table 1 to obtain a base paper with a tsubo of 1175 g/rd and a thickness of 1751 m.

The PY value of each of the obtained base papers was measured. P
The method for measuring the Y value was as follows.

A sample was taken at 50cs* (MD force direction ) was analyzed.

Details of the film thickness meter and measurement conditions were as follows.

The frequency analysis equipment and analysis conditions were as follows.

Frequency analyzer CF-940 (@Ono side lid) human signal D
C2V, IK (1,024 points)/dual To convert the power spectrum value obtained with this device into the depth of peaks and valleys, multiply the obtained value by 28.8 (tm/■) .

Further, each of these base papers was coated with a resin as described below using the same laminator.

That is, one side of the base paper was extruded and coated with high-density polyethylene (density: 0.942, melt index: 10) to a thickness of 28 lines at a temperature of 330°C, and the other side was coated with high-density polyethylene (density: 0.942, melt index: 10). : 0.951, melt index: 9) and low density polyethylene (density:
0.918, melt index: 4), containing 10% anatase titanium dioxide, was extrusion coated to a thickness of 35 mm at a temperature of 330°C. Further, a support having a glossy surface was prepared using a cooling roll having a mirror surface.

This support was coated with black and white emulsion Liquid Light (Rockla, USA).
The smoothness of photographic paper coated with ndColloid, exposed and developed was compared and evaluated. The evaluation results are evaluated on a five-point scale, with 1 point being the best and 5 points being the worst, with 4 and 5 points being unsatisfactory as a product. The results are shown in Table 2.

From the results in Table 2, it is clear that the support for photographic paper according to the present invention has good smoothness.

Table 1: Paper making conditions Table 2 [Effects of the invention] The photographic paper support of the present invention has a sheet-like substrate surface having excellent smoothness defined by the above-mentioned PY (!), and therefore , this support is extremely useful for producing photographic paper having a photographic image surface with uneven smoothness.

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Claims (1)

[Scope of Claims] 1. A sheet-like substrate, and a resin coating layer that covers both sides of the sheet-like substrate and contains a polyolefin resin as a main component, and the thickness unevenness of the sheet-like substrate is reduced. , when measured continuously using a film thickness meter and analyzing the measurement signal using a frequency analyzer, wavelength 1 of the surface of the sheet-like substrate
The integral value of the power spectrum at ~12.5 mm (P
1. A support for photographic paper, characterized in that its Y value) is 1.00 μm or less. 2. The sheet-like substrate is paper, and is treated with at least two stages of wet press and smoother rolls, and is subjected to tension press treatment during drying, and machine calender treatment. The support for photographic paper according to claim 1. 3. The support for photographic paper according to claim 1, wherein the sheet-like substrate is paper and contains as a main component bleached hardwood pulp containing 30% or more of bleached hardwood kraft pulp.