JP2736770B2 - Photographic paper support - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an improvement of a photographic printing paper support comprising a base paper having a polyolefin resin coating layer on both surfaces. BACKGROUND OF THE INVENTION A photographic printing paper support generally used in recent years has a configuration in which resin coating layers are provided on both sides of a base paper, and usually, the resin coating layer on one side is transparent. The other side of the resin coating is an opaque polyolefin containing a white pigment such as titanium dioxide. The former is called the back side, and the latter is called the front side. Photographic paper is provided with a photographic emulsion layer provided on the polyolefin coating layer on the front side. Polyolefin coating layers provided on both sides of the support are useful for imparting water resistance, curling resistance, hiding power, etc. to photographic printing paper, but polyolefin resins are inherently soft and tough. Therefore, the cutting property of the polyolefin coating layer with a blade tends to be worse than that of paper. In use, photographic paper is printed in a lab with an image from a negative film and then developed to provide a positive image. This photographic paper is cut to the specified size by a cutter, and it becomes a finished product.However, a poorly cut polyolefin layer appears on the cut surface of the cutter as a whisker, which reduces the commercial value of the photographic paper. Is easy to occur. The mechanism of generating the whisker-like polyolefin is that the polyolefin coating layer that has been subjected to the shearing force between the upper and lower blades of the cutter is not simply cut, but is cut while being stretched. Therefore, when the cutter blade is not sharp or when the polyolefin coating layer is tough, a phenomenon of poor cutting occurs. Based on such technical knowledge, a method using a polyolefin having a low average molecular weight has been attempted in order to improve the cutability of the polyolefin coating layer (for example, Japanese Patent Application Laid-Open No.
Invention with "Support for photographic paper" described in JP-A-114125. However, the coating layer made of a low-molecular-weight polyolefin has a low strength, and when rubbed with a metal part or the like when traveling in a printer or a current processing state, particularly, the surface on the back side is easily scratched. It is difficult to say that the improved technology is satisfactory. [Object of the Invention] A main object of the present invention is to provide a novel photographic printing paper support which mainly satisfies the conflicting required properties of good cuttability and scratch resistance. [Summary of the Invention] The present invention relates to a photographic printing paper support having a resin coating layer provided on the back surface of a base paper, wherein at least the resin coating layer on the back side has an intrinsic viscosity of 0.8 to 1.8 dl / g and a density of 0.940. Or
A photographic printing paper support comprising a polyolefin having a characteristic value of 0.970 g / cm ³ , a melt tension of 0.8 to 5.0 g, and a molecular weight distribution index of 3.0 to 5.0. [Effects of the Invention] The photographic printing paper manufactured using the photographic printing paper support of the present invention hardly shows a poorly cut polyolefin layer in the form of a whisker on the cut surface by a cutter, and also requires a printer or a developing device. It also has the advantage that the rear side surface is not easily damaged, especially when traveling in the processing machine. Accordingly, the photographic printing paper using the photographic printing paper support of the present invention satisfies these contradictory required characteristics, and therefore has a very high commercial value. [Detailed Description of the Invention] The photographic printing paper support of the present invention comprises a base paper and a polyolefin resin coating layer provided on both sides thereof. Base paper is made from pulp raw materials such as bleached wood pulp or a mixture of bleached wood pulp and synthetic pulp, and usually has a basis weight of 50 to 250 g / m ² . Of the polyolefin resin coating of the photographic printing paper support of the present invention, at least the back side (the side on which the photographic emulsion layer is not provided) has an intrinsic viscosity of 0.8.
~ 1.8dl / g, density 0.940 ~ 0.970g / cm ² , melt tension
It consists of a polyolefin having a characteristic value of 0.8 to 5.0 g and a molecular weight distribution index of 3.0 to 5.0. The polyolefin may be a copolymer obtained by copolymerization of two or more α-olefins, or may be a mixture of two or more polyolefins, and at least one polyolefin is obtained by copolymerization of α-olefins. It may be something like that. The definition of the intrinsic viscosity, the melt tension, and the molecular weight distribution index are as follows. Intrinsic viscosity: Measured in decalin solution at 135 ° C Melt tension: Tension when extruding polyolefin at 15 ° C / min at 170 ° C and 15 mm / min using a nozzle used for JIS-K6760 (polyethylene test method) MI measurement method Molecular weight distribution index: Intrinsic viscosity × logM M value: The shear stress of the melt flow curve (the relationship between the shear stress and the shear rate) measured at 190 ° C. using a nozzle capillary rheometer with L / D = 30 is 2.
Shearing speed at 4 × 10 ⁶ dyne The intrinsic viscosity has a correlation with the molecular weight, and greatly affects the cutting performance with a cutter and the scratch resistance when running in a printer development processor. That is, if the intrinsic viscosity is less than 0.8 dl / g, the scratch resistance is deteriorated, while if it exceeds 1.8 dl / g, the cutting property is deteriorated. Therefore, a polyolefin having an intrinsic viscosity of 0.8 to 1.8 dl / g as a range satisfying both the scratch resistance and the cutting property is preferred. Density affects the cutting properties, the density of 0.940 g / cm ³ less than the low-density side, since the crystallinity is low, resulting polyolefin is liable elongation, when cut with a cutter, the polyolefin layer of the cut surface The whisker becomes noticeable and reduces the commercial value of photographic paper. Melt tension is the most important indicator of extrusion lamination suitability of polyolefins. If the melt tension is less than 0.8 g, the width of the molten polyolefin extruded from the die of the extruder will be very narrow compared to the die width, that is, the neck-in will be large, and it will not be suitable for extrusion coating . On the other hand, if the melt strength exceeds 5.0 g, the molten polyolefin film breaks during extrusion coating at a high speed, which is not suitable for practical use. The molecular weight distribution index is a value representing the molecular weight distribution of the polyolefin, and the higher the distribution index, the wider the molecular weight distribution and the higher the scratch resistance. If the distribution index is less than 3.0, there is no effect on scratch resistance, and the neck-in at the time of extrusion coating becomes large, which is not suitable for practical use. Conversely, the distribution index is 5.
If it exceeds 0, the molten polyolefin film breaks during extrusion coating at a high speed, which is not suitable for practical use. Therefore, the optimal range of the molecular weight distribution index in the present invention is 3.0
To 5.0. When the representative polyolefins of the present invention having these characteristic values are measured by ¹³ C-NMR, they are all 5 methyl groups / 1000 c or less, and 0.5 to 5 ethyl groups / 1000 c butyl groups. 0.5 to 6 / 1000c Pentyl groups were found to be contained in 0.5 to 5 / 1000c hexyl groups in 0.5 to 3 / 1000c. In the support for photographic paper of the present invention, only the backside polyolefin coating layer that is particularly easily damaged among the polyolefin coating layers provided on both surfaces needs to be formed from the polyolefin of the present invention, while other The side (front side) of the polyolefin coating layer may be formed of another polyolefin. However, it is a matter of course that the polyolefin coating layer on the front side may also be formed from a polyolefin having the above characteristics. The thickness of the polyolefin resin coating layer is usually 15 to 60 μm
It is. It is already known that various additives such as white pigments, color pigments, fluorescent whitening agents and antioxidants are added to the polyolefin resin used for forming the resin coating layer of the polyolefin resin coated paper for photographic printing paper. Therefore, in preparing the polyolefin resin of the present invention, it is naturally possible to add such various additives, which is preferable depending on the purpose. Regarding the kind, amount and method of such various additives, for example, U.S. Pat.
No. 3833380, No. 4169188, No. 3501298, No. 3449247,
And publications such as No. 3499762. Alternatively, as described in U.S. Pat. No. 388,492, these additives can be applied onto the resin coating layer after forming the coating layer. Alternatively, U.S. Pat.Nos. 2715075, 2846727, 35
As described in publications such as No. 49406 and No. 3590107, the surface activation treatment of the resin coating layer can be performed as necessary. In order to apply the photographic emulsion to the photographic paper support of the present invention to obtain photographic paper, a method conventionally used for the production of photographic paper can be used. In addition, for the processing such as development and fixing of the photographic paper manufactured in such a manner, conventionally used techniques can be used. Regarding these conventional techniques, for example, Shinichi Kikuchi: Photochemistry (Kyoritsu Shuppan: 1973), and CEKMees “THE THEORY OF
THE PHOTOGRAPHIC PROCESS ”3rd.ed. Next, examples of the present invention and comparative examples will be described. [Evaluation Method of Photographic Paper] In Examples and Comparative Examples, the cutting performance of the photographic paper was evaluated as follows. That is, by observing the cut surface when the developed photographic printing paper is cut by a cutter usually used in a developing laboratory, by the presence or absence of a polyolefin layer stretched like a mustache, and by the number and length of the mustache, A, B,
The evaluation was made in four stages of C and D. A: No stretched mustache-like polyolefin was observed on the cut surface, and it was cut cleanly.B: Some slightly stretched mustaches were observed.C: Whiskers were found over almost the entire cut surface. Observed D: A long stretched mustache-like polyolefin coating layer is present on the entire cut surface and the commercial value is lost. Practically, A or B is preferable as a photographic printing paper. The evaluation of scratch resistance was carried out by bringing a sapphire needle with a tip with a radius of curvature of 0.025 mm into contact with the polyolefin-coated surface of the photographic paper support, and running at a speed of 30 cm / min while applying a load stepwise. The test was performed with a load that started to be damaged after running. The scratch resistance was evaluated by the following A, B, C, and D. A: The load started to be damaged at a load of 15 g or more B: The load started to be damaged at a load of less than 15 g, 10 g or more C: The load started to be damaged at a load of less than 10 g, 5 g or more D: The load was started at 5 g Those which began to be scratched at less than those which are practically satisfactory as photographic printing papers are those which have been given a rating of A or B. Example 1 The following polyolefin was extruded to a thickness of 30 μm on each of the front and back sides of a base paper having a weight of 180 g / m ² and a thickness of 170 μm made of bleached hardwood pulp to provide a polyolefin coating layer. Front side polyolefin coating layer Intrinsic viscosity: 1.1 dl / g Density: 0.923 g / cm ² Melt tension: 13 g Molecular weight distribution index: 3.6 (α-polyolefin copolymer) ¹³ C-NMR measurement result: methyl group: 0.5 / 1000 c or less ethyl group: 2.4 pieces / 1000c-butyl: 4.2 pieces / 1000c pentyl: 3.0 pieces / 1000c hexyl: 2.8 pieces / 1000c backside polyolefin coating layer intrinsic viscosity: 1.1 dl / g density: 0.928 g / cm ² melt tension: 3.5 g Molecular weight distribution index: 3.8 (mixture of 20% by weight of low-density polyolefin and 80% by weight of high-density polyolefin) ¹³ C-NMR measurement result: Methyl group: 0.5 / 1000c or less Ethyl group: 1.0 / 1000c Butyl group: 1.7 10 / 1000c Pentyl group: 1.2 / 1000c Hexyl group: 1.2 / 1000c 10 wt% of titanium dioxide pigment was added to the surface-side polyolefin coating layer. Next, a photographic emulsion layer for a normal color photographic paper having a thickness of 0.012 mm was provided on the polyolefin coating layer on the front side of the photographic paper support produced as described above to produce a photographic paper. [Example 2] A photographic paper support was produced in the same manner as in Example 1 except that the polyolefin of the polyolefin coating layer provided on the front side and the back side of the base paper was changed to the following polyolefin. To produce photographic paper. Surface polyolefin coating layer Intrinsic viscosity: 1.1 dl / g Density: 0.927 g / cm ² Melt tension: 13 g Molecular weight distribution index: 3.7 (mixture of 85% by weight of low density polyolefin and 15% by weight of high density polyolefin) ¹³ C-NMR measurement Result: Methyl group: 0.5 / 1000c or less Ethyl group: 2.3 / 1000c Butyl group: 4.1 / 1000c Pentyl group: 2.8 / 1000c Hexyl group: 2.6 / 1000c Back polyolefin coating layer Intrinsic viscosity: 1.1dl / g Density : 0.955 g / cm ² Melt tension: 2.9 g Molecular weight distribution index: 3.8 (α-polyolefin copolymer) ¹³ C-NMR measurement result: Methyl group: 0.5 / 1000 c or less Ethyl group: 1.1 / 1000 c Butyl group: 1.5 Pcs / 1000c Pentyl group: 1.2 pcs / 1000c Hexyl group: 1.1 pcs / 1000c [Comparative Example 1] Same as Example 1 except that the polyolefin of the polyolefin coating layer provided on the front and back sides of the base paper was changed to the following polyolefin. A photographic paper support is manufactured, and then the support is used. To produce a photographic paper in the. Surface side polyolefin coating layer Intrinsic viscosity: 1.1 dl / g Density: 0.923 g / cm ² Melt tension: 10 g Molecular weight distribution index: 3.6 (α-polyolefin copolymer) ¹³ C-NMR measurement result: methyl group: 0.5 / 1000 c or less ethyl group: 2.4 pieces / 1000c-butyl: 4.2 pieces / 1000c pentyl: 3.0 pieces / 1000c hexyl: 2.8 pieces / 1000c backside polyolefin coating layer intrinsic viscosity: 0.7 dl / g density: 0.947 g / cm ² melt tension: 0.5 g Molecular weight distribution index: 3.4 (mixture of 35% by weight of low-density polyolefin and 65% by weight of high-density polyolefin) ¹³ C-NMR measurement result: Methyl group: 0.5 / 1000c or less Ethyl group: 0.9 / 1000c Butyl group: 1.1 Pcs / 1000c Pentyl group: 0.9 pcs / 1000c Hexyl group: 0.8 pcs / 1000c [Evaluation of photographic paper] The photographic papers obtained in Examples 1 and 2 and Comparative Example 1 were developed, dried, cut and tested for cutability. A scratch resistance test was performed. Table 1 shows the results. From the results shown in Table 1, it can be seen from Example 1 that the resin coating layer comprising the specific polyolefin of the present invention was provided on the back side.
The photographic papers Nos. 2 and 3 were excellent in both the cutting property and the scratch resistance. On the other hand, since the low-molecular-weight polyethylene was used on the back side of the photographic paper of Comparative Example 1, the intrinsic viscosity was lowered and the cutting property was good, but the scratch resistance was insufficient. [Example 3] A base paper having a basis weight of 165 g / m ² and a thickness of 160 µm consisting of a blended article of 92% by weight of bleached hardwood pulp and 8% by weight of bleached hardwood pulp was coated with the following polyolefin having a thickness of 33 µm on the front and back sides, respectively.
And extruded to provide a polyolefin coating layer. Front polyolefin coating layer Intrinsic viscosity: 1.1 dl / g Density: 0.929 g / cm ² Melt tension: 95 g Molecular weight distribution index: 3.7 (mixture of low-density polyolefin 80% by weight and high-density polyolefin 20% by weight) ¹³ C-NMR measurement Result: Methyl group: 0.5 / 1000c or less Ethyl group: 2.2 / 1000c Butyl group: 4.0 / 1000c Pentyl group: 2.8 / 1000c Hexyl group: 3.6 / 1000c Back polyolefin coating layer Intrinsic viscosity: 0.9dl / g Density : 0.953 g / cm ² Melt tension: 3.1 g Molecular weight distribution index: 3.8 (mixture of 35% by weight of low-density polyolefin and 70% by weight of high-density polyolefin) ¹³ C-NMR measurement result: Methyl group: 0.5 / 1000c or less Ethyl Group: 1.2 / 1000c Butyl group: 1.7 / 1000c Pentyl group: 1.2 / 1000c Hexyl group: 1.2 / 1000c In the front-side polyolefin coating layer, 10% by weight of titanium dioxide pigment was added. Next, a photographic emulsion layer for a normal color photographic paper having a thickness of 0.012 mm was provided on the polyolefin coating layer on the front side of the photographic paper support produced as described above to produce a photographic paper. Example 4 A photographic paper support was produced in the same manner as in Example 3 except that the polyolefin of the polyolefin coating layer provided on the front and back sides of the base paper was changed to the following polyolefin, and then this support was used. To produce photographic paper. Front side polyolefin coating layer Intrinsic viscosity: 1.1 dl / g Density: 0.923 g / cm ² Melt tension: 13 g Molecular weight distribution index: 3.6 (α-polyolefin copolymer) ¹³ C-NMR measurement result: methyl group: 0.5 / 1000 c or less ethyl group: 2.4 pieces / 1000c-butyl: 4.2 pieces / 1000c pentyl: 3.0 pieces / 1000c hexyl: 2.8 pieces / 1000c backside polyolefin coating layer intrinsic viscosity: 1.1 dl / g density: 0.955 g / cm ² melt tension: 3.1 g Molecular weight distribution index: 3.8 (mixture of 10% by weight of low-density polyolefin and 90% by weight of high-density polyolefin) ¹³ C-NMR measurement result: Methyl group: 0.5 / 1000c or less Ethyl group: 1.1 / 1000c Butyl group: 1.5 Pcs / 1000c Pentyl group: 1.2 pcs / 1000c Hexyl group: 1.1 pcs / 1000c [Comparative Example 2] The same as Example 3 except that the polyolefin of the polyolefin coating layer provided on the front side and the back side of the base paper was changed to the following polyolefin. A photographic paper support is manufactured, and then the support is used. To prepare a paper to. Front side polyolefin coating layer Intrinsic viscosity: 1.1 dl / g Density: 0.923 g / cm ² Melt tension: 13 g Molecular weight distribution index: 3.6 (α-polyolefin copolymer) ¹³ C-NMR measurement result: methyl group: 0.5 / 1000 c or less ethyl group: 2.4 pieces / 1000c-butyl: 4.2 pieces / 1000c pentyl: 3.0 pieces / 1000c hexyl: 2.8 pieces / 1000c backside polyolefin coating layer intrinsic viscosity: 1.1 dl / g density: 0.935 g / cm ² melt tension: 8.5 g Molecular weight distribution index: 3.8 (mixture of low-density polyolefin 70% by weight and high-density polyolefin 30% by weight) ¹³ C-NMR measurement result: methyl group: 0.5 / 1000c or less ethyl group: 2.4 / 1000c butyl group: 4.2 Pcs / 1000c Pentyl group: 3.0 pcs / 1000c Hexyl group: 3.0 pcs / 1000c [Evaluation of photographic paper] The photographic papers obtained in Examples 3, 4 and Comparative Example 2 were dried after being developed and subjected to a cutting property test. A scratch resistance test was performed. Table 2 shows the results. From the results shown in Table 2, it can be seen from Example 3 that the resin coating layer comprising the specific polyolefin of the present invention was provided on the back side.
The photographic papers of No. 4 and No. 4 were excellent in both cutting properties and scratch resistance. In particular, the polyolefin used on the back surface was excellent in scratch resistance of Example 4 in which the intrinsic viscosity was high. In Comparative Example 2, the cutability was not sufficient because the density of the polyolefin used for forming the back surface coating layer was low, and was not a satisfactory level. [Comparative Examples 3 to 5] A photographic paper support was produced in the same manner as in the base paper described in Example 1 using the front-side polyolefin coating layer material described in Example 1 and the following back-side polyolefin coating layer material. did. Next, a photographic emulsion layer for a normal color photographic paper having a thickness of 0.012 mm was provided on the polyolefin coating layer on the front side of the photographic paper support in the same manner as in Example 1 to produce a photographic paper. . The photographic paper thus manufactured was evaluated by the method described above. Table 3 shows the results. From the results shown in Table 3, even if the intrinsic viscosity, density, and molecular weight distribution index are included in the ranges specified in the present invention, those having too high a melt tension have poor cutting properties (Comparative Example 3), Further, even if the intrinsic viscosity and the density are included in the range specified in the present invention, those having a melt tension and a molecular weight distribution index that deviate from the range of the present invention are not only poor in cutability, but also the coating layer on the back side. It can be seen that the scratch resistance of the sample also significantly decreased.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Yasuo Iwasaki               Fuji Photo Hui 200 Onakazato, Fujinomiya City               Lum Co., Ltd. (72) Inventor Masanobu Ishiyama               Akidai Higashi 3-chome, Ichihara City (72) Inventor Masaya Yamada               2-4-1 Akidai Nishi, Ichihara-shi                (56) References JP-A-58-95731 (JP, A)                 JP-A-57-32442 (JP, A)                 JP-A-60-168142 (JP, A)                 JP-A-58-95732 (JP, A)                 JP-A-60-150049 (JP, A)                 Japanese Patent Publication No. 44-22904 (JP, B1)

Claims (1)

(57) [Claims] In a photographic printing paper support in which a resin coating layer is provided on both sides of the base paper, at least the resin coating layer on the back surface,
Intrinsic viscosity 0.8 ~ 1.8dl / g, density 0.940 ~ 0.970g / cm
^3, melt tension of 0.8 to 5.0 g, and a molecular weight distribution index is 3.
A photographic printing paper support comprising a polyolefin having a characteristic value of 0 to 5.0. 2. The photographic printing paper support according to claim 1, wherein the polyolefin is obtained by copolymerizing two or more α-olefins. 3. The photographic printing paper support according to claim 1, wherein the polyolefin is a mixture of two or more polyolefins, and at least one of the polyolefins is obtained by copolymerizing an α-olefin.