JPH0651435A - Photographic printing void-containing polyester film - Google Patents

Abstract

PURPOSE:To provide a polyester film capable of obtaining an extremely clear and durable phtographic image, excellent in hiding property, whiteness, etc., when used as photographic printing paper by optimizing the distribution of voids. CONSTITUTION:A thermoplastic resin incompatible with polyester is mixed with a polyester and the obtained polymer mixture is at least uniaxially oriented to produce a polyester layer A having many fine voids. A layer B consisting of a thermoplastic resin is provided on at least one side of the polyester layer A, the content of voids in the region to the depth of 3mum from the layer A surface is controlled to <=8vol.% and the average void content of the whole film is adjusted to 10-50vol.%. The soln., emulsion or dispersion o the polymer material are applied on at least one side of the film to form an undercoating layer and a photographic emulsion layer is furnished on the undercoating layer to constitute a photographic printing void-contg. polyester film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention, when used for photographic printing,
The present invention relates to a void-containing polyester film for photographic printing, which contains a large amount of fine voids inside the film having improved surface peel strength, hiding power, whiteness and the like.

[0002]

2. Description of the Related Art Synthetic paper, which is a paper substitute mainly made of synthetic resin, has a higher water resistance, a higher dimensional stability in moisture absorption, and a higher dimensional stability than natural paper.
It has excellent surface stability, gloss and clarity of printing, and mechanical strength. In recent years, application development has been promoted by making use of these advantages. As a method of obtaining a film having a function similar to paper using polyester as a main raw material, a method of containing a large amount of fine voids inside the film can give a point that the film itself can be made lightweight and appropriate flexibility. ,
There is an advantage that clear printing and transfer are possible.

As a method for forming fine cavities inside a film, conventionally, a polymer that is incompatible with polyester is melt-kneaded by an extruder to obtain a sheet in which the polymer is dispersed in fine particles to obtain a sheet. A method of forming voids around fine particles by stretching is disclosed. As a polymer which is incompatible with polyester used for cavities (hereinafter referred to as cavities expressing agent), a polyolefin resin (for example, JP-A-49-13)
4755) and polystyrene resins (for example, JP-B-49-2016 and JP-B-54-29550).

Conventional void-containing polyester films have excellent properties such as light weight, concealability, and firmness. However, since they are used as photographic printing paper, they contain many fine voids. The surface peel strength was poor, and it was difficult to maintain a clear photographic image for a long period of time.

[0005]

DISCLOSURE OF THE INVENTION The present invention optimizes the disadvantage of the previous term, that is, the surface peel strength when using a void-containing film as a photographic printing paper, and the distribution of voids in the void-containing film. This provides a base material capable of maintaining a clear photographic image for a long period of time.

[0006]

That is, the present invention provides a fine cavity produced by orienting at least uniaxially a polymer mixture obtained by mixing a polyester with a thermoplastic resin incompatible with the polyester. A layer (B) made of a thermoplastic resin is provided on at least one surface of the polyester layer (A) containing a large number, and the content of voids contained in the surface layer up to 3 μm from the surface of the layer A is 8% by volume or less, And, on at least one side of the film having an average void content of the whole layer of 10% by volume or more and 50% by volume or less, a solution of a polymer material,
The present invention relates to a polyester film for photographic printing, which comprises coating an emulsion or a dispersion to form an undercoat layer, and providing a photographic emulsion layer on the undercoat layer.

The polymer mixture obtained by mixing the polyester of the present invention and the incompatible thermoplastic resin with the polyester is prepared by, for example, mixing chips of each resin, melt-kneading in an extruder, and then extruding and solidifying. Method, or a method in which both resins are kneaded in advance by a kneader and further melt-extruded by an extruder to solidify, or an incompatible thermoplastic resin is added to the polyester in the polyester polymerization step and dispersed by stirring. It can also be obtained by a method of melt-extruding and solidifying the obtained chips.

It is possible to add a colorant, a light-proofing agent, a fluorescent agent, an antistatic agent, etc. to the polymer mixture depending on the application. The obtained polymer mixture is further stretched between rolls having different speeds (roll stretching), stretching by gripping a clip and expanding (tenter stretching), or stretching by expanding by air pressure (inflation stretching) At least one axis is subjected to orientation treatment by, for example, By the orientation treatment, peeling occurs at the interface between the polyester and the void-developing agent, and voids are developed.

Therefore, the amount of the thermoplastic resin which is incompatible with the polyester and mixed with the polyester varies depending on the amount of the target voids, but is preferably 3% by weight to 35% by weight based on the total amount of the polymer mixture. . If it is less than 3% by weight, there is a limit to increase the amount of cavities generated, and the desired flexibility, lightness, and drawability cannot be obtained. Conversely, 40
If it is more than 10% by weight, the heat resistance and strength of the polyester film are significantly impaired.

The conditions for orienting the polymer mixture are closely related to the formation of cavities. Therefore, the conditions for achieving the object of the present invention include, for example, the most commonly used sequential biaxial stretching step, in which a continuous sheet of the polymer mixture is roll-stretched in the longitudinal direction and then in the width direction. In the case of the sequential biaxial stretching method in which the tenter stretching is performed, it is as follows. In roll stretching, it is preferable to set the temperature to a biaxial stretching temperature of polyester + 30 ° C. or less and a draw ratio of 1.2 to 5 times in order to generate a large number of cavities. In the tenter stretching, the temperature is 80 to 140 for stable film formation without breaking.
It is preferable that the temperature and the magnification are 1.2 to 5 times.

The void-containing film stretch-oriented is 1
When heat setting is performed at 30 ° C. or higher, preferably 180 ° C. or higher, dimensional stability at high temperature can be improved. In the present invention, a so-called composite film in which the surface layer and the central layer are laminated is preferable. The method is not particularly limited. However, in view of productivity, the raw materials for the surface layer and the center layer are extruded from different extruders, introduced into one die to obtain an unstretched sheet, and then oriented at least uniaxially. preferable.

The void-containing polyester film thus obtained has a void content of 8% by volume or less in the layer from the surface of the layer A to a depth of 3 μm, and the average void content of the entire layer is 10% by volume. % Or more is required. When the number of cavities contained in the surface layer from the surface of the layer A to a depth of 3 μm is more than 8% by volume, the surface strength is not particularly good. Further, even when the surface layer portion of the layer A having a porosity of 8% by volume or less is thinner than 3 μm, good surface strength cannot be obtained. Therefore, in the present invention, the surface layer portion of the A layer having fewer cavities than the central portion has a depth of 3 μm or more, and the cavity content rate contained therein is 8 μm.
It must be below volume%. Further, the entire layer needs to have an average void content of 10% by volume or more. When the average void content of the entire layer is 10% by volume or less, the flexibility peculiar to the void-containing polyester film becomes insufficient, and the drawing property and cushioning property also become insufficient.

In order to reduce the amount of voids only in the surface layer of the layer A, it is effective to make the dispersed particles of the thermoplastic resin in the polymer mixture finer near the surface than in the central region. It can be obtained by selecting the melt viscosity characteristics of the polyester and the thermoplastic resin and the conditions for melt extrusion from an extruder. In the film of the present invention, a solution, emulsion or dispersion of a polymer material is applied to the void-containing polyester film to form an undercoat layer, and a photographic emulsion layer is provided on at least one side of the undercoat layer. The subbing layer referred to here is for improving the adhesiveness to a polyester film having a poor coating property on a photographic emulsion containing a light-sensitive material and gelatin as a main component, and a polyester-based resin and a vinylidene chloride-based It is formed by applying a solution, emulsion or dispersion of a polymer material such as a resin on the polyester film surface.

The polyester resin for the undercoat layer is a polyester resin composed of dibasic acid and glycol and soluble in water, emulsified or dispersed. For example, the dibasic acid is 50 to 0.5 mol% of the total dicarboxylic acid. Is a sulfonic acid group-containing dicarboxylic acid, and is a polyester copolymer obtained by copolymerizing these two dicarboxylic acid components and a glycol component.

The sulfonic acid metal salt-containing dicarboxylic acid includes sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene-2,
Examples thereof include metal salts such as 7-dicarboxylic acid and 5 [4-sulfophenoxy] isophthalic acid. Particularly preferred are 5-sodium sulfoisophthalic acid and sodium sulfoterephthalic acid. These sulfonic acid metal salt-containing dicarboxylic acids are 50 to 0.5 mol%, preferably 20 to 1 mol%, based on the total dicarboxylic acid components, and when the amount exceeds 50 mol%, the dispersibility in water is improved. Also reduces the water resistance of the copolymer. The dispersibility of the polyester copolymer in water varies depending on the copolymerization composition, the kind and amount of the water-soluble organic compound, etc., but the amount of the sulfonic acid metal salt-containing dicarboxylic acid component is small unless the dispersibility in water is impaired. Better.

Examples of the usual dicarboxylic acid containing no metal sulfonate group include terephthalic acid, isophthalic acid, orthophthalic acid, and 2,6-naphthalenedicarboxylic acid. Each of these aromatic, aliphatic and alicyclic dicarboxylic acids is used. Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, and 2,6-naphthalenedicarboxylic acid. The aromatic dicarboxylic acid content is preferably 40 mol% or more of the total dicarboxylic acid component, and when it is less than 40 mol%, the mechanical strength and water resistance of the polyester copolymer are deteriorated.

As the aliphatic or alicyclic dicarboxylic acid,
Examples thereof include succinic acid, adipic acid, sebacic acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclodicarboxylic acid and 1,4-cyclohexanedicarboxylic acid. The addition of these non-aromatic dicarboxylic acid components may improve the adhesive performance, but generally the mechanical strength and water resistance of the polyester copolymer deteriorate.

The glycol component to be reacted with the dicarboxylic acid mixture is an aliphatic glycol having 2 to 8 carbon atoms, and a mixture of both, such as ethylene glycol,
Examples thereof include 1,2-propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, 1,2-cyclohexanedimethanol and p-xylylene glycol. Examples of the aliphatic diol having 4 or more carbon atoms include diethylene glycol and triethylene glycol, and examples of the polyether include polyethylene glycol, polypropylene glycol and polytetramethylene glycol. As the vinylidene chloride resin of the undercoat layer, a polyvinylidene chloride-acrylic acid ester copolymer, or an unsaturated monocarboxylic acid such as acrylic acid, methacrylic acid, or crotonic acid, or an unsaturated dicarboxylic acid is added to these copolymers. Examples include ternary and quaternary copolymers containing components. The content of vinylidene chloride in the copolymer is 70 mol% or more, particularly preferably 87 to 92 mol%. If it exceeds 92 mol%, the aqueous emulsion tends to gel and must be used as a coating agent quickly. Further, if it is less than 72 mol%, the adhesive strength with the photographic emulsifier layer is lowered.

As the polymer material constituting the undercoat layer, an acrylic resin, a polyurethane resin or the like can be used in addition to the above polyester resin and vinylidene chloride resin. To coat the polyester film with the aqueous dispersion of the above-mentioned polymer material, either unstretched, uniaxially stretched or biaxially stretched may be used, and the coating may be either in-line coating or offline coating.

The coating amount of the polymer material applied to the polyester film is 0.01 to 5 g / m ² in terms of the film after biaxial stretching. Coating amount is 0.01g /
If it is less than m ² , the adhesion to the photographic emulsion layer is not sufficient. When the coating amount exceeds 1 g / m ² , slipperiness and blocking resistance can be improved by adding fine particles of an inorganic compound or an organic compound to the aqueous dispersion.

In order to easily apply the aqueous dispersion uniformly to the polyester film, the surface tension may be lowered by adding an organic solvent such as methyl alcohol or ethyl alcohol to the aqueous dispersion. Further, the polyester film may be subjected to surface treatment, and as the surface treatment, flame treatment, ultraviolet irradiation, plasma treatment, discharge treatment such as corona treatment,
Irradiation treatment with electron beams and radiation, chemical treatment, etc. Among the above treatments, the corona discharge treatment is simple and effective in a short time.

Any known method can be applied to coat the aqueous dispersion on the surface of the polyester film. The coating method includes a roll coating method, a gravure coating method, a roll brushing method, a spray coating method and an air knife method. , The impregnation method and the curtain coating method are applied alone or in combination.

[0023]

In the present invention, the polyester is used
This is because the heat resistance and mechanical strength of the void-containing polyester film are satisfied. In the present invention, a polyester is mixed with an incompatible thermoplastic resin to the polyester to obtain a polymer mixture by dispersing fine particles of an incompatible thermoplastic resin in the polyester in the polyester, This is to form a nucleus of a cavity generated by the next alignment treatment.

In the present invention, the reason why the amount of cavities contained in the surface layer portion of layer A up to 3 μm is 8% by volume or less is to strengthen the surface strength. This is to improve. On the other hand, the average porosity of the entire layer is set to 8% by volume or more in order to obtain flexibility for clear printing and transfer.

[0025]

EXAMPLES Examples of the present invention will be described below. 1) Intrinsic viscosity of polyester Polyester was dissolved in a mixed solvent of phenol (6 parts by weight) and tetrachloroethane (4 parts by weight) and measured at 30 ° C. 2) Melt Flow Index of Polystyrene Resin Measured at 200 ° C. under a load of 5 kg according to JIS-K7210. 3) Density The film was cut into a square of 5.00 cm × 5.00 cm and the thickness was measured at 50 points, and the average thickness was t μm.
The weight was calculated up to 0.1 mg to be wg, and the weight was calculated by the following formula.

[0026]

[Equation 1]

4) Average Porosity of Film Calculated by the following formula.

[0028]

[Equation 2] However,

[0029]

[Equation 3]

[0030]

[Equation 4]

Xi in the above equation is the weight fraction of the i component, d
i represents the true specific gravity of the i component. The value of true specific gravity used in the calculations in the examples is polyethylene terephthalate 1.4.
0, general-purpose polystyrene 1.05, polypropylene 0.
91 and anatase type titanium dioxide 3.9 were used.

5) Porosity of the surface layer of the void-containing film A photograph of the surface layer near the surface of the cross section of the film was photographed with a scanning electron microscope, and the voids in the region from the surface layer to a depth of 3 μm were traced on a tracing film and painted. Was subjected to image processing by an image analyzer, and the void ratio was obtained by the area ratio, and this value was directly displayed as volume%. -Scanning electron microscope used S-510 scanning electron microscope manufactured by Hitachi Ltd.-Image analysis processor used Luzex IID (Nireco Corporation)

6) Light transmittance According to JIS-K6714, the Poick integrating sphere type H. T.
The light transmittance of the film was measured using an R meter (manufactured by Nippon Seimitsu Optical Co., Ltd.). The smaller this value is, the higher the hiding property is.

7) Surface peel strength Using cellophane tape (18 mm width, made by Nichiban), the surface peel strength was evaluated by a cellophane tape peel test. The peeling angle was in the direction of about 150 degrees while keeping the void-containing film flat. The area of the peeled void-containing film was differentiated as follows. Class 5 ... Peeled entirely Class 4 ... Mostly peeled Class 3 ... Peeled about half, Class 2 ... Peeled little Class 1 ... Peeled at all Example (1) Polymer Manufacture of Aqueous Dispersion of Material 117 parts of dimethyl terephthalate, 117 parts of dimethyl isophthalate, 103 parts of ethylene glycol, 58 parts of diethylene glycol, 0.08 part of zinc acetate and 0.08 part of antimony trioxide were charged into a reaction vessel at 40 to 220 ° C. ,
Transesterification was carried out for 3 hours, then 9 parts of 5-sodium isophthalic acid was added, and the esterification reaction was carried out at 220 to 260 ° C. for 1 hour, and then under reduced pressure (0.2 to 10).
(mmHg), polycondensation reaction is carried out for 2 hours to give a molecular weight of 180
A polyester copolymer having a softening point of 00 and a softening point of 140 ° C. was obtained.
300 parts of this polyester copolymer, 140 parts of n-butyl cellosolve, and 560 parts of water were charged into a container,
℃, stirring for about 3 hours, uniform light white solid concentration 30%
An aqueous dispersion of was obtained. Further water 450 to this aqueous dispersion
0 part and 4500 parts of ethyl alcohol were added and diluted to a solid content concentration of 3% to obtain a coating liquid. (2) Production of in-line coat film 80% by weight of polyethylene terephthalate resin having an intrinsic viscosity of 0.62 and a melt flow index of 2.0 as raw materials
g / 10 minutes 15% by weight of general-purpose polystyrene and 5% by weight of anatase type titanium dioxide having an average particle size of 0.3 μm
As the raw material of the layer, 95 wt% of polyethylene terephthalate resin as the raw material of the B layer, and 5 wt% of rutile titanium dioxide having an average particle diameter of 0.3 μm are melt extruded at 290 ° C. from a T-die by different screw extruders, Electrostatically adheres to the cooling rotating roll and solidifies, and each layer is B / A /
An unstretched sheet of the polymer mixture with B = 30/1190/30 μm was obtained. At this time, the T-die slit interval is 1.8 m
m, the average flow rate of the polymer mixture in that part is 8.8 m
/ Sec. Continue to roll stretcher 3.5 at 83 ℃
Double stretching was performed to obtain a uniaxially stretched film. This uniaxially stretched film was subjected to corona discharge treatment. The coating solution (1) was applied to this corona discharge treated surface by an air knife method, dried with hot air at 70 ° C, and then 130 ° C with a tenter.
Was stretched 3.5 times and heat-fixed at 235 ° C. while relaxing by 4% to obtain a polyester film containing a large number of cavities inside.

The apparent specific gravity is 1.16, the surface layer has a void ratio of 1% by volume, the average void ratio of the whole is 16% by volume, the light transmittance is 3%, and the thickness B / A / B = 3/119/3 μm. there were. The porosity of the layer A of the obtained film was 2% by volume, and the whole was 21% by volume. Further, the portion with few cavities was present from the surface layer to a depth of about 3 μm. The coating amount of the polyester copolymer on the polyester film is 0.0
It was 8 g / m ² . (3) Formation of photographic emulsion layer The composition of the photographic emulsion is as follows.

Liquid A: distilled water 400 cc (45 ° C.) gelatin 55 g potassium bromide 19.3 g potassium iodide 0.5 g Liquid B: distilled water 100 cc (35 ° C.) silver nitrate 25 g ammonia water (specific gravity 0.88) brown precipitate Add water until redissolved to a total volume of 150 cc.

Solution B was injected into solution A over 1 minute, and the mixture was kept at 45 ° C. for 3 minutes.
After aging for 5 minutes, it was cooled, solidified and cut. Then 15
After washing with water at ℃ for 2 hours, add 20 g of gelatin and add water to make the total emulsion amount 1.1 kg.
Aged. Then, using the above photographic emulsion fountain coater, the above in-line coated film was coated and dried. The thickness of the photographic emulsion layer after drying was 10 microns.

The polyester film obtained by the above steps was excellent in concealing property and whiteness, and the surface peeling strength was very excellent as class 1.

[0039]

The void-containing polyester film for photographic printing of the present invention is superior in water resistance, durability, discoloration resistance, dimensional stability, and mechanical properties to conventional variator papers or photographic papers containing void-containing films. In addition to being excellent, since the void distribution is optimized as compared with the conventional void-containing polyester film, the surface peel strength is excellent and a clear photographic image can be maintained for a long period of time.

Claims (1)

[Claims] 1. At least one polymer mixture in which a polyester is mixed with a thermoplastic resin incompatible with the polyester.
A layer (B) made of a thermoplastic resin is provided on at least one surface of a polyester layer (A) containing a large number of fine cavities produced by orienting to the axis, and the layer 3 from the surface of the layer A is provided.
The void content contained up to the micron is 8% by volume or less, and the average void content of the entire film is 10% by volume.
A solution, emulsion or dispersion of a polymer material is applied to at least one surface of a film having a volume ratio of 50% by volume or more to form an undercoat layer, and a photographic emulsion layer is provided on the undercoat layer. A void-containing polyester film for photographic printing.