JPH03293349A - Supporting body for photographic paper - Google Patents

Abstract

PURPOSE:To reduce the occurrence of twisting curling of a sheet of photographic paper and to lower the height of it even in the case of occurrence of it by using a original sheet with a specified elastic characteristic. CONSTITUTION:The photographic sensitive paper 1 is constituted of a paper base body 2, surface layer coated with a polyolefine resin 3a, a back layer coated with a polyolefine resin 3b and a photographic emulsion layer 4. The base body 2 is uses the original sheet with an elastic characteristic satisfying formulae 1-III. Here, Efl in the formulae expresses the elasticity in a vertical direction of a half layer 3a side of the original sheet and Ebt expresses the elasticity in a horizontal direction of a half layer 3a side of the original sheet and Ebl expresses the elasticity of in a vertical direction of a half layer 3b side of the original sheet. The basis weight of the original sheet is preferred to 100-200 g/m<2> and the layers 3a and 3b are preferred to be a resin consisting of polyethylene as a main component.

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 which is characterized by excellent resistance to torsional curling and, furthermore, even if curling occurs, the height of the curling is low.

[Prior Art] In order to speed up the development process of photographic paper, so-called water-resistant supports for photographic paper, in which polyolefin resin coating layers are formed on both sides of a base paper base, have come into widespread use. Photographic paper is manufactured by forming a photosensitive emulsion layer on one surface of such a water-resistant support using gelatin as an adhesive.

When a photographic print made from photographic paper having a water-resistant support as described above is placed on a flat surface, the central part of the print curves concavely and the peripheral part of the print lifts up. In other words, it is known to cause curling. In order to express the degree of curl in such a curled print, the height of the four corners of the print from the mounting plane is calculated by 50% of the commonly used dimensions, that is, 82 mm x 114 mm.
It is measured at RH, and the average value is used to represent the "curl height".

The curl height of commonly used prints at 50% RH is about 1 to 5 m.

In order to prevent the above-mentioned curling, the weight per unit area, thickness, or density of both polyolefin resin coating layers formed on both sides of the paper base are made to be different from each other.
A method in which curling properties in the opposite direction are imparted to the support in advance to offset the curling that occurs in the print (British Patent No. 1.
No. 269,802 and Japanese Patent Publication No. 4B-9963) are known.

However, even with such improved photographic paper, prints cannot be printed under low humidity environmental conditions (e.g., 30°C, 30% RH), such as immediately after development and drying in an automatic processor. If you put it aside, 5-30I
Curl heights of IIffl often occur. If the axis of such curl is in the same direction as the print progressing direction in the developing machine, the curl height will be 23°Cl2O
%RH, unless it becomes abnormally large, such as 20 mm or more, phenomena such as jamming or scooking that cause great difficulty in the automatic developing operation itself will not occur. However, it is preferable that the curl height is 12 mm or less. On the other hand, if the axis of the curl that occurs on the photographic paper is in a direction that intersects the direction in which the prints travel in the developing machine, and the intersection angle is large, this will not only cause problems with automatic developing operations, but also cause distortion in the resulting prints. This results in a significant reduction in its commercial value. Hereinafter, such curls will be referred to as twisted curls.

The cause of curls (including twisted curls) in photographic paper is the gelatin-containing emulsion layer formed on the photographic paper,
It is believed that this is due to the difference in shrinkage caused by drying between the polyolefin resin-coated paper substrate and the support.

That is, when dried after development or placed in a low humidity environment, the gelatin-containing emulsion layer on the surface of the photographic paper dries relatively quickly and shrinks in volume.

However, the shrinkage and volume reduction of the paper base in a support coated on both sides with a hydrophobic polyolefin resin coating layer proceed extremely slowly. For this reason, a difference in shrinkage occurs between the gelatin-containing emulsion layer and the support layer in the photographic paper, which is thought to cause curling with the gelatin-containing emulsion layer having a large amount of shrinkage on the inside. .

Regarding the occurrence of photographic paper curl during the development and drying process, the degree of twisting is determined by the drying temperature of 50 to 60°C.
Although it is relatively small when the temperature is around 70 to 80 degrees Celsius, it is recognized that it becomes significantly large.

The reason why the drying temperature affects the occurrence of curl as described above is not yet fully understood, but in general, 7
At high temperatures above 0°C, the flexural flexibility of the support layer, especially the polyolefin resin coating layer, increases (that is, the resistance to deformation decreases), and as a result, the support layer shrinks due to shrinkage of the gelatin-containing emulsion layer. This is thought to be because it curls easily.

In recent years, there has been a strong demand for automatic developing apparatuses to operate at higher speeds, and for this reason, there is a tendency for drying temperatures to gradually increase. The high temperature and high speed of the drying process in automatic development tends to increase the occurrence of curl (including twisted curl) in photographic paper prints, and there is a strong need for immediate measures to prevent the occurrence of curl. There is.

Regarding prevention of the occurrence of torsional curl as described above, it is known that the occurrence of curl can be prevented by appropriately controlling the elastic modulus characteristics of base paper, as disclosed in Japanese Patent Application Laid-Open No. 2-48. There is. However, as a result of a more detailed study of curl prevention measures, it was found that the method disclosed in JP-A-2-48 can sufficiently prevent twisting curl and achieve good results. Depending on the characteristics of the base paper, the curl height may be somewhat high, and therefore further improvement was recognized as necessary.

That is, in Example 1 described in JP-A-2-48,
The twist angle of the curl that occurred in the sample was 2°, which was good, but the curl height was 14.0 mm, which was somewhat high, and it was recognized that there was room for improvement. The curl characteristics of such a sample were determined by developing the sample at 38°C using a mini automatic processor (trademark: NPS-1, manufactured by Konica ■), fixing, washing with water, and drying at 70°C.
This is a value measured and evaluated under the conditions of 23°C and 20%.

Generally, the curl height is preferably lower in order to prevent the occurrence of scooking of prints in the developing machine, and
In terms of the appearance of the print, it is preferable to keep the curl height as low as possible, preferably 13 mm or less, preferably 12.0 mm or less.

[Problem to be solved by the invention]

The present invention addresses the problems of conventional photographic paper supports, namely, when they are coated with a gelatin-containing emulsion to form a photographic paper and stored in a low humidity environment, or when drying after development, especially at high temperatures. This is intended to solve the problem that when dried, curls (including twisted curls) often occur, making development operations difficult and reducing product value.

In particular, the present invention aims to provide a photographic paper support that is less likely to cause twisting curls and has a low curl height even if curls occur.

[Means for Solving the Problems and Their Effects] The support for photographic paper of the present invention includes a base made of base paper and a polyolefin resin coating layer laminated on both sides of this base, wherein the base paper has the following: Relational expressions (I), (n) and (■)
: 1.3≦E tt / E bt≦3.4
(1) EfI/Ebz≧1.0
(U) and 0.95≦Eft/Ebt≦1.05 (I[[) [However, in the above formula, Efl represents the longitudinal elastic modulus of the front half of the base paper, and Ebt represents the Eft represents the elastic modulus in the horizontal direction of the back side half of the base paper, Eft represents the horizontal elastic modulus of the front side half of the base paper, and Eb7 represents the longitudinal elasticity of the back side half of the base paper. represents the rate. ] It is characterized by having elastic properties that satisfy the following.

The base paper for photographic paper is generally manufactured on a paper machine, usually a Fourdrinier machine, which has a paper dewatering wire (sukiy4) and a press drying felt (blanket), and the paper that comes into contact with the wire during this papermaking process It has a surface (denoted as wire contact surface) and an opposite surface that is in contact with felt (felt contact surface).

In addition, a water-resistant coating layer made of polyolefin resin is formed on both sides of the substrate made of base paper, and a polyolefin resin coating layer containing titanium dioxide is usually formed on one side (generally the front surface) of the substrate. A polyolefin resin coating layer is formed on the opposite side (generally the back side).

In the cross-sectional view showing the structure of the photographic paper shown in FIG.
The photographic paper 1 includes a paper base 2, a polyolefin resin surface coating layer 3a (front side) formed on both surfaces thereof, a polyolefin resin back coating layer 3b (back side), and a surface coating layer 3a formed on the paper base 2. It includes a photographic emulsion layer 4.

Now, we will discuss the paper base 2 by dividing it into the front side half 2a and the back side half 2b (of course, the paper base 2 is not usually made by dividing into the above two halves and making them together, but ) In other words, the photographic paper support 5 is the paper base 2.
It is also formed by front and back side coating layers 3a and 3b.

Next, the occurrence of curl in photographic paper will be explained using FIG. 2.3.

In FIGS. 2 and 3, when the curled photographic paper 1 is placed on the horizontal surface 6, both side edges 7a and 7b of the photographic paper l are
, 7c, 7d are at the height h (rIIm) from the horizontal surface 6
It becomes higher by (h++hz+h++h4). If the width between both curled edges of this photographic paper 1 is Wp (Illffl), then the curl height of this photographic paper 1 is (h, +h z
It can be expressed as f h s + h 4)/4. Further, the curl axis of the photographic paper is represented by the center line Y-Y' of the portion of the photographic paper 1 that is in contact with the horizontal surface 6. Curl axis Y-Y
' may be parallel to, perpendicular to, or oblique to the traveling direction axis x-x' of the photographic paper. Second
In the figure and FIG. 3, the x-x' axis and the Y-Y' axis intersect at a twist angle θ.

Generally, when processing roll photographic paper with an automatic processor,
The curl axis of the cut photographic paper is parallel to, perpendicular to, or oblique to the traveling direction of the photographic paper, regardless of the direction of the cut. The curl axes in this oblique manner are called torsional curl axes, and this oblique angle will be referred to as the twist angle.

The present inventors have conducted extensive research into what factors determine the direction of the curl axis that occurs in photographic paper, and have found that the most important factor is the nature of the paper layer that forms the core layer of the support. I found out.

That is, the curl that occurs on photographic paper immediately after development or immediately after exposure to a low humidity environment, which is the issue of the present invention, is the curl that occurs after the photographic paper has been sufficiently conditioned, or It was found that the cause of curling is different from the curling that occurs on baryta photographic paper. In curling that occurs in humidity-controlled photographic paper or conventional baryta photographic paper, the expansion and contraction of the base paper due to the inflow and outflow of moisture is the main cause of curl formation, along with the expansion and contraction of the gelatin layer that forms the emulsion layer. Immediately after drying of photographic paper with a water-resistant support coated with a resin with low moisture permeability such as polyolefin, or when curling occurs due to being left in a low humidity environment for a short period of time, the base paper The release of water from the layer is substantially lower than that of baryta paper or paper that has been thoroughly conditioned over a long period of time, whereas the gelatin-containing emulsion layer loses its elasticity as it dries. (For example, the modulus of the emulsion layer when equilibrated at 50% R11 is about 0.3 GPa and increases to about 2 GPa when equilibrated at 30% RH.) In photographic paper, the shrinkage of the emulsion layer compresses and shrinks the underlying polyolefin resin laminate layer and base paper layer. Depending on the amount of shrinkage, the size of the curl that occurs is determined, and depending on the direction in which it tends to shrink, It is thought that twisting of the curl axis occurs.

The factors that cause this twisted curl are considered to be as follows. In paper made using long-length paper machines, the orientation of pulp fibers is generally greater in the machine direction than in the cross direction. Twisted curls may occur due to uneven distribution of fiber orientation, such as the degree of fiber orientation being slightly higher in certain directions due to papermaking conditions, or due to causes such as differences in the direction of fiber orientation between the front and back sides. considered to be a thing.

It is preferable to make base paper so that the fiber orientation in the base paper is not uneven, but in reality it is difficult to achieve a uniform degree of orientation over the entire width and layer of the paper. . For example, in a low-speed Fourdrinier paper machine, in order to improve the formation of the paper, it is common to vibrate the wire at right angles to the papermaking direction, which causes the fibers to vibrate in the direction of flow of the papermaking slurry. Although the degree of orientation is alternately tilted slightly to the left and right, it is difficult to avoid such deviation in fiber orientation.

As mentioned above, the inventors of the present invention have conducted intensive studies on means that can substantially reduce the twist of the curl axis (less than 8 degrees of twist of the axis) even if there is a slight deviation in fiber orientation. It has been discovered that appropriately balancing the elastic modulus of the front half of the base paper that forms the core layer of the photographic paper and the back half of the base paper is effective in reducing or preventing the occurrence of torsional curl.

When the photographic paper 1 having the five-layer laminated structure illustrated in FIG. 1 is exposed to low humidity conditions, the emulsion layer 4 dries and...
It contracts in the same direction and its elastic modulus increases. The polyolefin resin surface coating layer 3a located below the emulsion layer 4 is
Generally, it has a relatively low elastic modulus of 0.2 to 0.3 GPa, so as the emulsion layer 4 shrinks in the same direction, the beam is compressed and contracts in the same direction, and the paper base layer 2 also has a compressive force. receive. At this time, the shrinkage of the paper base 2 due to the decrease in water content is substantially extremely small. The shrinkage of the paper base layer 2 accompanying the shrinkage of the emulsion layer 4 will be explained with reference to FIG.

When the paper base 2 having the two-layer structure 2a and 2b is subjected to compressive force due to contraction of the emulsion layer 4, the longitudinal elastic modulus Efl of the front half 2a of the paper base 2 is When the longitudinal elastic modulus Ebl of Suppresses the formation of twisted curls centered in the horizontal direction and curls in the width direction of photographic paper.

Also, the lateral elastic modulus Eb of the back side half 2b of the paper base 2
When the elastic modulus Eft of the front side half 2a in the horizontal direction is made smaller than t, the front side half 2a tends to contract, which makes curling with the longitudinal direction of the base paper as the axial direction easier to occur. By causing the base paper to curl such that the longitudinal direction is the axial direction, it is possible to prevent the occurrence of torsional curl.

That is, in order to prevent the occurrence of twisted curls, the following relational expressions (IV) and (■): EfI>EbI, that is, E tz / E bz > 1 (IV)E
rt<Ebt, that is, E□/EbL<1 (V
) It is preferable to regulate the elastic modulus in the longitudinal and lateral directions of the front half and the back half of the paper substrate so as to satisfy the following.

That is, when formula (IV) is satisfied, the paper base layer is
It is possible to prevent the occurrence of curls that have an axial direction that intersects with the longitudinal direction of the base paper, and when formula (V) is satisfied, the paper base layer can prevent the occurrence of curls that have an axial direction that is parallel to the longitudinal direction of the base paper. , thereby suppressing the occurrence of twisted curls.

From the above equations (IV) and (V), it is derived, but as a result of examining this relationship in more detail in relation to the shrinkage force of the gelatin-containing emulsion layer, the above effect can be obtained by the following relational expression (■): I discovered that it is significantly enhanced when you are satisfied. In addition, the above effects were examined in more detail from the relationship between the basis weight of the paper base layer and the thickness of the polyolefin resin coating layer. That is, it is generally preferable that the value of the longitudinal elastic modulus Erl of the surface side half of the paper substrate falls within the range of the following relational expression (): % formula % ().

In addition, the value of the transverse elastic modulus Ebt of the back side half of the paper substrate has the following relationship (VIII): 2, 8 (GPa)≦Ebt≦4.8 (GPa)
It is preferably within the range of (VIII).

In this way, Efl and Eb t of the paper base; as a result of further detailed investigation, Efl and EbLO
It has been found that when the ratio satisfies the following relationship (1), this support provides a photographic paper with excellent anti-curl properties.

1.3≦Eri/Ebt≦3.4
(I) In the above various relationships, the Eft of the base paper
and Ebt are expressed by the relational expression (V): E rt/E bt < 1
It was found that when (V) was satisfied, the occurrence of curls having a main curl axis in the longitudinal direction was promoted, and the curl height became too high. In order to reduce the curl height as much as possible, it has been found that it is effective to satisfy the following relational expression (■): Eft/E, t-1 (■). In practice, Eft and EbL of the base paper are expressed by the following relational expression (
■): 0.95<Ert/EbL<1.05
In a range that satisfies (III), the curl height tends to decrease.

Therefore, for the base paper substrate, Etz / Ebz > 1.0
By maintaining the relationship (IV), the occurrence of twisted curls can be suppressed and further 0.95 < E rt / E bt < 1.05
By maintaining the relationship (III), it is possible to suppress the occurrence of twisting curl and at the same time reduce the curl height.

The elastic modulus of the front and back sides of the base paper can be measured by the following methods a) to 2).

(b) Attach the test paper sample so that its surface is in contact with the base surface of a paper grinder (precision grinder, manufactured by Tawara Seisakusho), and use the grinder to scrape off the back side in small portions several times until the thickness of the base paper Reduce the thickness to the original thickness of about 172 mm.

(b) The surface side half thus obtained is subjected to an elastic modulus measuring device such as Tensilon, and the elastic modulus in a desired direction is measured by a conventional method.

In other words, the width of the test paper sample is 15am+, and the span length is 1
50 mm, the sample was pulled at a slow head pulling speed of 10/min, and a stress-elongation curve was created from the start of pulling to breakage. In this stress-elongation curve, the slope of a straight line (ratio of stress increase ΔT to elongation Δ!: ΔT/Δl) is measured.

The elastic modulus (E) of the sample is calculated from the following formula.

[However, in the above formula: ΔT = Stress increase in the above straight section (kg) W = Sample width (m) h = Sample thickness (m) Δi = Elongation corresponding to ΔT (mm) L = Family span length of the sample (a) G = Acceleration of gravity = 9.8 (N/kg) (c) Since it takes a long time to measure the elastic modulus of a paper sample using the above method, we have Even if a sound wave transmission velocity measuring device is used, results similar to those of the above measurement method can be obtained. The four circumferences of the paper sample prepared by grinding as described above were
What is necessary is to attach it to the measuring table using craft adhesive tape, and measure the ultrasonic transmission velocity in a predetermined direction at the center of the measuring table. Calculation of the elastic modulus of paper using this method is as follows [However, in the above formula, d = apparent density of the sample (lCg/rr'r) S = ultrasonic transmission speed (m/sec) To measure the elastic modulus Although any of the methods described in (b) and (c) above may be used, the method (c) above is advantageous from the viewpoint of reproducibility of measured values.

(d) For paper with a basis weight of 100 to 200 g/m2,
A test paper sample can be easily prepared as follows.

That is, prepare an A4 size paper sample, stick paper tape or craft tape on both sides of the paper sample along the short side edge of the paper sample, and apply approximately the thickness of the paper sample at the edge of the paper sample at that part. A cut is made at the half position using a sharp knife, and the whole paper sample is divided into two layers using the tape as a support, and each layer is used as a test paper sample for ultrasonic transmission velocity measurement.

Even if the test paper sample prepared by this method is used,
Compared to the test paper sample prepared by the method (a) above, no significant difference was observed in the measured values of ultrasonic transmission velocity.

In a support for photographic paper, when the paper base satisfies the relationships of formulas (I) and (II), the curl that occurs in the photographic paper obtained from this support is at least parallel to the machine axis direction. , or a small inclination angle, which does not cause twisting curls that would impair its commercial value.

Furthermore, if the paper substrate satisfies the relationship of formula (III), even if curling occurs, the curl height will be low.

If the paper substrate does not satisfy the relationship of formula (I[l), even if the torsional curl is reduced, the curl height will be slightly higher. Therefore, in order to reduce the torsional curl and the curl height, the above (1), (I
It is necessary to satisfy all of the relationships of formulas I) and (III).

If the above relational expressions (I), (II) and (III) are not satisfied, the curl that occurs on the obtained photographic paper is:
The inclination angle of the base paper with respect to the longitudinal direction changes unstably, or gives a twisted appearance with a large inclination angle, and also makes it difficult for the photographic paper to run inside the developing machine.

In order to obtain a base paper having an elastic modulus that satisfies the above relational expressions (1) and (II) (I[[), the papermaking process is controlled as follows, for example. In other words, the ratio between the peripheral speed of the dandy roll, which is installed in the latter half of the wire part of the Fourdrinier paper machine (for example, between the suction boxes) and is in contact with the surface layer of the paper pulp slurry, and the running speed of the wire. By adjusting D/W (hereinafter referred to as D/W), it is possible to control the ratio of the elastic modulus of the front and back sides of the base paper to be made, and the desired base paper can be obtained.

Another method is to directly control the strength of fiber orientation on the front and back sides, in which the base paper forming the front side half and the base paper forming the back side half are made separately, and then,
There is a method of manufacturing base paper by so-called paper making, in which both are pasted together to form a single sheet of base paper.For example, the jet/wire ratio of the front half of the base paper, that is, paper making from the slits of the flow box. The ratio of the flow rate of the raw material slurry to the running speed of the wire (hereinafter referred to as J/W),
It is possible to obtain a base paper having a desired ratio of front and back elastic modulus by making it larger than that of the back side half of the base paper.

Furthermore, the type of wire used in the paper making process,
Equations (1), (II) and A base paper that satisfies the relationship (II[) can be produced. However, the above-mentioned paper-making conditions must be appropriately set through preliminary experiments, etc., depending on the characteristics of the paper-making machine and paper-making method used.

To control the curl of photographic paper, especially twisted curl,
Focusing on the characteristics of the paper base of a support for photographic paper, particularly the modulus of elasticity, was completely unknown in the past. In particular, we focused on the elastic modulus of the front half of the base paper and the back half of the base paper in the dark blue and lateral directions, and calculated these as appropriate, that is, formula (1)
and (■).

The present invention is the first to propose and achieve the control of twisting curl of photographic paper and the reduction of curl height using base paper controlled to satisfy (III).

The photographic paper support of the present invention is produced by using a base paper having the above-mentioned required properties as a base, and forming a coating layer made of a polyolefin resin on both sides of the paper base.

The raw material for the filter paper substrate used in the method of the present invention can be selected from the raw materials generally used for photographic paper supports,
Examples include natural pulp, synthetic pulp, a mixture of natural pulp and synthetic pulp, and various raw materials for laminated paper. Generally, softwood pulp, hardwood pulp,
Natural pulps whose main components are softwood and hardwood mixed pulp are widely used. This base paper contains sizing agents, fixing agents, paper strength enhancers, fillers,
Additives such as pHSm conditioners, antistatic agents, and dyes may be added, and surface sizing agents, surface strength agents,
The surface may be appropriately coated with an antistatic agent, dye, or the like.

The paper substrate used has a smooth surface and usually has a weight of 50 to 300 E/m2, preferably 100 to 200 g/n.

The water-resistant thermoplastic resin used to coat both sides of the paper substrate is selected from polyolefin resins. The polyolefin resin can be selected from homopolymers of Tomoe tyrene, α-olefins such as propylene, copolymers of at least two of the above olefins, and mixtures of at least two of these various polymers. Particularly preferred polyolefin resins include low density polyethylene, high density polyethylene, linear low density polyethylene and
It is a mixture of these. There is no particular restriction on the molecular weight of polyolefin resin, but it is usually 20,000 to 200,
A value in the range of 000 is used. Each coating layer is generally one
Weight of 0-50g/m, preferably 20-40g/m
Formed on a paper substrate with a weight of 2. The polyolefin resin density on the front side is 0.918-0.9458/cili, and the polyolefin resin density on the back side is 0.936-0.95
Preferably it is 5g/crA.

The polyolefin used to coat the back side of the support (the side opposite to the side on which the emulsion layer will be applied) is usually low density polyethylene, high density polyethylene, or a mixture of low density polyethylene and high density polyethylene, which is itself melt laminated. be done. This layer is generally often matted.

A white pigment such as titanium dioxide is dispersed and mixed in the polyolefin resin used for the coating layer on the surface of the support (the surface on which the emulsion layer is provided), but in addition, colored pigments, optical brighteners, antioxidants, and Various additives such as dispersants may be added.

When forming the coating layers on the front and back sides of the support, in order to improve the flatness of developed photographic paper in the normal use environment, the density of the resin layer on the front side is generally made slightly smaller than that on the back side, or the density of the resin layer on the back side is made smaller than that on the back side. Measures such as increasing the amount of layers are used.

As is clear from the above theory, the surface of the substrate to which the resin coating layer is applied is the surface on which the photographic emulsion and titanium dioxide-containing polyolefin resin layer will be formed, regardless of the felt contact surface of the base paper and the wire contact surface. The surface on which only the polyolefin resin layer is formed is the back surface, and this front surface and the back surface have the formula (I).

It is necessary to control so as to satisfy (II) and (III).

Generally, the front and back coating layers are formed by melt-extrusion coating a polyolefin resin composition onto a paper substrate. To carry out this melt-extrusion coating method, a polyolefin resin composition is usually melt-extruded onto a running base paper for a paper substrate in the form of a single layer or multiple layers of film from a slit die of an extruder. Usually, it is preferred that the melt extrusion temperature is 280° to 350°C.

Furthermore, before coating the resin composition on the substrate, it is preferable to subject the substrate to an activation treatment such as corona discharge treatment or flame treatment.

Further, the surface of the support can also be subjected to activation treatment such as corona discharge treatment or flame treatment. In addition, if necessary, a subcoat layer for improving adhesion with the photographic emulsion may be applied on the surface resin layer, or a backcoat layer for improving printing and writability and antistatic properties on the back resin coating layer. It's okay.

In order to produce photographic paper from the support of the present invention, a photosensitive emulsion is coated on the surface resin coating layer of the support.

This emulsion may be an ordinary black-and-white emulsion or a color emulsion, and generally contains several tens of silver salts per 100 g of emulsion, and the concentration of gelatin contained therein is 4 to 8%. (weight).

The dry weight of the photographic emulsion layer on photographic paper is usually around Log/m2.

〔Example〕

The invention will be further illustrated by the following examples.

1-2, and 1-5 In each of Examples 1-2 and Comparative Examples 1-5, the following operations were performed.

(a) Canadian Standard Freeness (JIS P81) for papermaking of base paper
21-76) 20% softwood bleached sulfite pulp (NBSP) beaten to 250ml and 80% hardwood bleached sulfate pulp (LBKP) beaten to freeness 280d were mixed, and this mixed pulp was subjected to a fourdrinier paper machine. Teyonetsubo @ 170g/m2, tension 1.02g/CT1, moisture 8
% base paper was made. At this time, the following paper-making additives were used in the mixed pulp in the following amounts based on the absolute dry weight of the pulp.

Cationized starch 2.0% alkyl ketene dimer resin 0.4% anionic polyacrylamide resin 0.1% polyamide polyamine epiclor 0.7% hydrin resin Caustic soda Adjusted to pH 7.5 Next, carboxyl-modified PVA and sodium chloride To, 2
:1 weight ratio was dissolved in water as a size press agent to prepare a 5% size liquid, which was applied to both sides of the base paper at a coating amount of 25 g/nf.

In addition, during papermaking, the length of the cheeking pieces on both sides of the sliced part of the head box was set to 100 mm longer than the lip.
mm to prevent the valve slurry from spilling outside the edges on both sides, and also arranged a no-date scale to control the jet flow of the pulp slurry, and further increased the ratio of jet speed to wire speed (J/W) to 1. It was controlled to .05. In addition, under conditions such that the ratio (D/W) of the peripheral speed of the dandy roll in the latter half of the wire to the running speed of the wire becomes the value shown in papermaking conditions A to C in Table 1, Table 2 Paper was made from each sample shown in .

In addition, in Comparative Example 1, J/
Paper was made by controlling W to a fairly high value of 1.15 and setting D/W to 1.00. Among the samples shown in Table 2, samples Nα2 and 3.4 are examples in which the wire side of the above papermaking base paper is used as the front side, and samples Nα1 and 5
．． 6.7 is an example in which the felt surface is used as the front side.

Table 2 shows the measurement results of the elastic modulus ratio of each sample.

Table 1 In measuring the elastic modulus above, the base paper was approximately 300 x 21
Cut each sample into a size of 0.0mm, paste regular craft tape (width 5C111) on both sides of the base paper along the short side edges of each sample, and place it at a position of about half the thickness of the base paper at the edge of the side edge. Make a cut with a utility knife, and pull it left and right with both hands to roughly divide it in half to create a front half and a back half.

Next, from each sample, a sample with dimensions of 20C+++ x 20C1 (not including craft tape) was cut out.
This was subjected to an ultrasonic transmission velocity measuring device (Sonic Tester, manufactured by Nomura Shoji Co., Ltd., model SST-200). The sample base paper, that is, the base paper of Example 1, satisfied the relationships of formulas (1) to (III), but the base papers of Comparative Examples 1 to 5 satisfied the relationships of formulas (I) to (
III) was not satisfied. However, the base paper of Example 2, in which the felt contact surface and the wire contact surface of the base paper of Comparative Example 1 were reversed and used as the front and back surfaces, was expressed by formula (1).
-(III) was satisfied.

Incidentally, the measured values of the fiber orientation angle of each sample obtained when measuring the ultrasonic transmission speed were all within 4 degrees.

(b) Manufacture of support for photographic paper A support for photographic paper was produced as follows.

The wire side of the sized base paper was subjected to corona discharge treatment, and high-density polyethylene (density 0.94 g/d,
MI=8.0) and low density polyethylene (density 0.92g
/emit, M I = 4.6) was melt-extruded and laminated at a resin temperature of 330 °C, and cooled while applying matte molding with a cooling roll, resulting in a coating amount of 28
A back resin coating layer of g/m2 was formed.

Next, the felt surface of the base paper was subjected to corona discharge treatment, and a dispersion mixture of the high-density polyethylene and the low-density polyethylene containing 10% titanium oxide in a weight ratio of 8:2 was then applied to the felt surface at a resin temperature of 320°C. It is melt extruded and laminated,
A glossy surface resin coating layer was formed with a coating amount of 26 g/bo.

The photographic paper support of Example 2 used the same base paper as Comparative Example 1, except that a resin coating layer made of a polyethylene mixture containing titanium oxide was formed on the wire surface, and the other parts were as described above. Manufactured in a similar manner.

(c) Preparation of photographic paper (coating of photographic emulsion layer) After corona discharge treatment was applied to the surface of each of the above supports, a commercially available silver salt emulsion (
Rockland, manufactured by Colloid, product name Liquid Light)
and 2 x 10-' mol/g of gelatin hardener (HDU, Sogo Yakuhin Co., Ltd., N).

A treatment solution prepared by adding N'-hexamethylene-1,6-bis(1-aziridinecarboxamide) was added to
The coating was applied to a dry coating weight of g/nf, dried and solidified under cold air, then heated and dried at 40°C for 90 minutes, and further 4
Cured for 60 hours at 0°C, 150% RH, and 20°
The humidity was controlled at 165% RH for 2 hours.

(d) Development process The resulting photographic paper is cut into pieces with a width (horizontal direction) of 82 mm and a length (vertical direction of the base paper) of 114 mm, and is developed so that its longitudinal axis coincides with the paper feeding direction of the developing machine. The film was then subjected to development processing.

Development processing conditions (a) Developing machine: NFS-1 (trademark) manufactured by Konica ■ was used.

(b) Developed image: Konica developer CPK-18CQ.

Using P-1 (trademark), temperature 38 Performed at °C.

(c) Fixing: Konica fixer CPK-18CQ
.

P-2 (trademark) at room temperature. went.

(d) Anhydrous cleaning treatment: Anhydrous cleaning liquid CPK-1 manufactured by Konica Corporation
The test was carried out using 8CQ, P-3 (trademark) at room temperature.

(e) Drying; 70°C Sample of developed photographic paper (dimensions: 82mm x 114
(automatically cut into a plate) was immediately heated to 23°Cl2O.
The photographic paper was left in an environment of %RH for 2 hours, and the twist angle and curl height of the obtained photographic paper were measured. This twist angle is calculated by placing a curled piece of photographic paper on a horizontal surface with its concave side facing upward, and then placing the curled photographic paper on a horizontal surface with its concave side facing upward.
curl axis) and the longitudinal axis of the support.

The curl height is displayed as the average value of the heights of the four corners from the horizontal plane.

If the twist angle is 8 degrees or less, the photographic paper is evaluated to have practically good curl resistance, and it is practically preferable that the curl height is 13 mm or less.

Table 2 shows the measurement results of the twist angle and curl height of the curls generated on the photographic paper.

From the results in Table 2, only the photographic papers of Examples 1 and 2 that satisfy formulas (1) to (III) have small twist curls and low curl heights, and therefore have good curl resistance. I understand.

3 and 6 6-8 In each of Example 3 and Comparative Examples 6-8, the following operations were performed.

(b) Manufacturing of base paper Using the same pulp as in Example 1, the third
Three types of semi-base papers (1 to 3) with a basis weight of 70 g/rrf were formed according to the J/W ratio listed in the table, and after passing through the wire, these semi-base papers were combined into combinations E and F listed in Table 3.
The two layers were combined and bonded together to produce the combined base paper shown in Table 4.

In Table 4, in Samples 8 and 9 (Comparative Example 6゜7), the front half of the combined base paper was formed of half base paper 1, and in Sample 10゜11 (Example 3, Comparative Example In Example 8), the front half of the laminated base paper was formed of half base paper 2. The properties of this base paper (ultrasonic transmission speed and elastic modulus) are shown in Table 4.

Table 3 (b) Production of photographic paper support Photographic paper supports as shown in Table 4 were produced using the above two types of laminated base papers in the same manner as in Example 1.

However, the back side resin coating layer is formed of the polyethylene resin described in Example 1 with a coating amount of 25 g/m2, and the front side resin coating layer is formed of a linear low density polyethylene resin (density: 0.926 , M?=20) 40 parts and low density polyethylene resin (density: 0.918゜M
A mixture of 60 parts of I=2) and 10% titanium dioxide based on the weight of the resin was formed to give a coating weight of 35 g/nf at a resin temperature of 320°C.

(c) Production of photographic paper Photographic paper was produced in the same manner as in Example 1 using the above photographic paper support.

Table 4 shows the curl resistance of this photographic paper.

No. table No. Table (continued) tree) Note) The density of each paper base paper was 1.02.

From the results in Table 4, it can be seen that only Example 3, which satisfies formulas (I) to (II[), provides photographic paper with small torsion curl and low curl height, and therefore good curl resistance.

〔Effect of the invention〕

As specifically shown in Tables 2 and 4, even if the relational expressions (I) and (n) are satisfied, the relational expression (I[[
) was not satisfied, the effect of suppressing the occurrence of twisting curl was improved, but it was confirmed that the curl height was not reduced.

On the other hand, if all of the relational expressions (I) to (III) are satisfied, the occurrence of twisting curl in the photographic paper is prevented and the height of the curl is also reduced.

Therefore, the present invention makes it possible to provide a support for photographic paper that prevents the occurrence of torsional curl and reduces the curl height.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view showing the structure of photographic paper including the support for photographic paper of the present invention, and FIGS. 2 and 3 are
FIG. 3 is an explanatory diagram showing the curling condition of photographic paper. 1... Photographic paper, 2... Paper base layer, 3
a, 3b...Resin coating layer, 4...Photographic emulsion layer, 5
...Support, 6--Horizontal surface, 7a
, 7b, 7c, 1d=-side edge of curled photographic paper, h+, hz...height, Y-Y'...curl axis, x-x'...paper feeding direction of the developing machine Axis, θ...twist angle.

Claims (1)

[Claims] 1. The base paper includes a base paper and a polyolefin resin coating layer laminated on both sides of the base paper, and the base paper satisfies the following relational formulas (I), (II), and (III): 1 .3≦E_f_l
/E_b_t≦3.4(I)E_f_l/E_b_l
≧1.0 (II) 0.95≦E_f_t/E_b_t≦1.05 (III)
[However, in the above formula, E_f_l represents the elastic modulus in the longitudinal direction of the side half of the surface (surface on which the photographic emulsion layer is formed) of the base paper,
E_b_t represents the elastic modulus in the lateral direction of the side half of the back surface (the surface opposite to the surface on which the photographic emulsion layer is formed) of the base paper;
_f_t represents the transverse elastic modulus of the front half of the base paper, and E_b_l represents the longitudinal elastic modulus of the front half of the base paper. ] A support for photographic paper, characterized by having elastic properties satisfying the following. 2. The support according to claim 1, wherein the base paper has a basis weight of 100 to 200 g/m^2. 3. Claim 1, wherein the polyolefin resin coating layer is formed mainly of polyethylene resin.
Support described in Section. 4. The polyolefin resin coating layer has a thickness of 10 to 50 μm
The support according to claim 1, having a thickness of . 5. In the above relational expressions (I) and (II), E_f
The values of _l and E_b_t are the following relational expressions (VII) and (VIII): 6.6 (GPa)≦E_f_l≦9.61 (GPa) (
VII) 2.8 (GPa)≦E_b_t≦4.8 (GPa
) The support according to claim 1, which satisfies (VIII).