JP3163930B2 - Recording material based on microporous thermoplastic resin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention is directed to a fine void-containing thermoplastic resin film substrate, a thermal transfer image-receiving sheet, the heat-sensitive recording paper, sublimation transfer image-receiving sheet, a recording material such as a printed sheet.

[0002]

2. Description of the Related Art Synthetic paper, which is a paper substitute made of thermoplastic resin, has higher water resistance, greater moisture absorption dimensional stability than natural paper.
It is excellent in terms of surface stability, printing gloss and sharpness, mechanical strength, and the like. In recent years, application development utilizing these advantages has been recommended.

[0003] The main raw materials of synthetic paper are polyethylene,
Thermoplastic resins such as polypropylene and polyester are used. Among them, polyester typified by polyethylene terephthalate is excellent in terms of high heat resistance and high rigidity, and can be used in a wide range of applications.

There is also known a method of adding good printability and the like to a film mainly composed of a thermoplastic resin while maintaining the characteristics of the film. Such methods include:
(1) A method in which fine cavities are contained in the inside of the film during the production of the film, and (2) a method of roughening the surface of a normal film are known. As the latter method, (2-
1) Sandplast treatment, (2-2) etching treatment,
Means such as (2-3) matting treatment (a method of laminating a matting agent together with a binder) and the like are known. Among these methods, the method (1) of including fine voids in the film reduces the weight of the obtained film, and has appropriate flexibility, good writing properties, clear printing / transfer properties, and the like. There are advantages.

[0005] As means for forming fine cavities in the film, a sheet is produced by melt-kneading a thermoplastic resin as a main raw material and a thermoplastic resin which is incompatible with the thermoplastic resin, and dispersing the thermoplastic resin into fine particles. A method has been reported in which voids are generated around fine particles by stretching a sheet.

As the main thermoplastic resin, polyester is generally used.

When a polyester is used as a main raw material, a thermoplastic resin incompatible with the thermoplastic resin as a main raw material (referred to as a cavity developing agent) used for forming a cavity is a polyolefin resin (for example, JP 1974-132
755), a polystyrene resin (for example, Japanese Patent Publication No. Sho 4)
No. 9-2016, JP-B-54-29550), polyarylate resins (for example, JP-B-58-280).
No. 97 gazette) has been proposed. Among them, polypropylene and polystyrene are particularly preferred in that cavities are easily formed, the density is low, and the cost is low.

The most common method of stretching a thermoplastic resin film containing fine voids is a biaxial stretching method in which a continuous sheet of a resin mixture is roll-stretched in the longitudinal (longitudinal) direction and then tenter-stretched in the width (horizontal) direction. It is. More specifically, when performing roll stretching (longitudinal stretching), the temperature is set to 80 to 100 ° C., and the magnification is set to 2.0 to 100% in order to develop many cavities.
5.0 and then tenter stretching (transverse stretching) at a temperature of 8
Perform at 0-140 ° C., 2.8-5.0 magnification,
It is reported that heat treatment after stretching is performed at 150 ° C. or higher. (For example, JP-A-63-168441,
JP-A-63-193938, JP-A-2-80247, JP-A-2-284929, and 3-114817
And JP-A-4-202540).

However, when the thermoplastic resin film containing fine cavities obtained by the conventional method is used as a heat-sensitive recording material, a printing sheet, or the like, it causes problems such as curling due to heat and wrinkling due to heat. It had the disadvantage of being easy.

The present inventors have found that the cavities of the thermoplastic resin film containing fine cavities obtained by the prior art tend to be longer in the horizontal direction than in the vertical direction. We came to realize that this was one of the related factors, and we examined various ways to make the cavity isotropic.

First, the lateral growth of the cavities can be suppressed by setting the temperature of the lateral stretching to 140 ° C. or higher. However, in this case, the content of the cavities is insufficient, and the thickness unevenness of the film becomes large. Substantially unsuitable. Also, a method of forming a vertically long cavity by increasing the longitudinal stretching ratio and subsequently achieving the isotropy of the cavity by subsequent transverse stretching was also attempted,
In this case, the film-forming property is deteriorated, and thus is not suitable for industrial production. Further, a method of reducing the transverse stretching ratio was considered, but also in this case, there was a problem that the thickness unevenness of the film was increased.

[0012]

SUMMARY OF THE INVENTION The present invention solves these disadvantages of the prior art thermoplastic resin film containing fine cavities, is excellent in isotropy of cavities, has little curl due to heat, and has a small thickness. Thermal transfer image receiving paper, thermal recording paper,
It is an object of the present invention to provide a recording material such as an image receiving paper for sublimation transfer and a printing sheet.

[0013]

The thermoplastic resin film containing fine cavities constituting the recording material of the present invention has an average length (L1) of cavities in a longitudinal cross section of the film and a perpendicular direction, that is, a transverse direction. Is characterized in that the ratio (L1 / L2) of the average length (L2) of the cavities in the cross section is 2/3 to 3/2, and the thickness unevenness of the film is 5% or less. In addition, the fine-cavity-containing thermoplastic resin film generally means a film having a void content of 5 to 50% by volume.

In order to produce the thermoplastic resin film containing fine cavities constituting the recording material of the present invention, a thermoplastic resin as a main raw material and a thermoplastic resin incompatible with the thermoplastic resin are formed. It is manufactured by biaxially stretching the sheet to be formed. At that time, stretching in the transverse direction is performed in two stages.
That is, initially at a stretching temperature of 100 to 140 ° C. and 2.0 to
Stretch 2.8 times, then stretch temperature 140-230 ° C
And the total stretching ratio multiplied by the initial stretching ratio is 3.
It is stretched so as to be 0 times or more.

The thermoplastic thermoplastic resin as a main raw material of the thermoplastic resin film containing fine cavities constituting the recording material of the present invention includes:
Use polyester . However, the present invention does not
Although not mentioned , polypropylene or the like can also be used.
As the polyester as the main raw material thermoplastic resin, terephthalic acid, isophthalic acid, aromatic dicarboxylic acid such as naphthalenedicarboxylic acid or an ester thereof and ethylene glycol, diethylene glycol, 1,4-butanediol, glycol such as neopentyl glycol. Polyester produced by polycondensation is used. These polyesters are prepared by directly reacting an aromatic dicarboxylic acid and a glycol, transesterifying an alkyl ester of an aromatic dicarboxylic acid with a glycol followed by polycondensation, or polymerizing a diglycol ester of an aromatic dicarboxylic acid. It is produced by a method such as condensation. Representative examples of such polyesters include polyethylene terephthalate, polyethylene butylene terephthalate, and polyethylene-2,6-naphthalate. The polyester used may be a homopolymer, or may be another polyester or a copolymer with the third component. Preferred polyesters are ethylene terephthalate units, butylene terephthalate units or ethylene-2,6-naphthalate units is 70 mol% or more, a polyester is preferably 80 mol% or more, more preferably 90 molar% or more.

The thermoplastic resin that is incompatible with the thermoplastic resin as the main raw material is a resin that is incompatible with the polyester resin.
Specifically, polystyrene-based resins, polyolefin-based resins, polyacryl-based resins, polycarbonate resins, polysulfone-based resins, cellulose-based resins, and the like can be given. In particular, polystyrene resins and polyolefin resins such as polymethylpentene and polypropylene are preferred.

For example, a polymer mixture of a thermoplastic resin as a main raw material and a thermoplastic resin incompatible with the thermoplastic resin is prepared by mixing chips of each resin, melt-kneading in an extruder, and then extruding and solidifying the mixture. method for solid-reduction melt-extruded from further extruder both resins were kneaded in advance by a kneading machine,
Was added to this to incompatible thermoplastic resin in the polymerization process of the main raw material thermoplastic resin by a method such as for solid of melt-extruding the obtained by stirring the dispersion chips, unstretched sheet-like polymer mixture is formed Is done. The resulting unstretched sheet-like polymer mixture is usually in a non-oriented or weakly oriented state. In addition, the thermoplastic resin incompatible with the thermoplastic resin of the main material is spherical in the thermoplastic resin of the main material,
It exists in a form dispersed in various shapes such as an elliptical sphere and a thread.

The amount of the thermoplastic resin which is mixed with the thermoplastic resin as the main raw material and is incompatible with the thermoplastic resin varies depending on the desired amount of cavities and the stretching temperature to be employed. To 40% by weight, particularly 6 to 35% by weight.
% By weight is preferred. If the amount is less than 3% by weight, the amount of cavities to be formed is limited, and the desired flexibility, lightness and drawing property may not be obtained. Conversely, if the amount is more than 40% by weight, the amount of cavities generated is too large. characteristics of the main raw material thermoplastic resin, sand
That is, the heat resistance, strength, stiffness and the like of the polyester film may be impaired.

The polymer mixture may contain inorganic particles, if necessary, in order to improve concealing properties, drawing properties and the like. Suitable inorganic particles include, but are not limited to, titanium dioxide, silicon dioxide, calcium carbonate, barium sulfate, aluminum oxide, kaolin, talc, zeolites, and the like.
If necessary, a crosslinking agent, a coloring agent, a light-fast agent, a fluorescent agent, an antistatic agent, and the like can be added to the polymer mixture.

A preferred method for producing a thermoplastic resin film containing fine cavities constituting the recording material of the present invention from a polymer mixture is, for example, the following method. That is, after the unstretched film formed from the polymer mixture is stretched in the longitudinal direction in the conventional manner, the transverse stretching is performed at two or more different temperatures. In the transverse stretching, first, the film is stretched at a stretching ratio of 2.0 to 2.8 times at 100 to 140 ° C.
The film is stretched at 230 ° C., preferably 160 ° C. to 230 ° C., so that the total stretching ratio of the transverse stretching multiplied by the initial ratio is 3.0 times or more. The first horizontal stretching at a low temperature mainly contributes to the formation of a cavity balanced in the vertical and horizontal directions, and the second horizontal stretching at a high temperature mainly contributes to reducing thickness unevenness. There is almost no increase in cavities in the second stretching. It does not matter if the sum of the transverse stretching ratios exceeds the longitudinal stretching ratio.

The stretched film is preferably further heat-treated. The heat treatment after the stretching is desirably performed under the following conditions. That is, heat treatment is performed at 200 ° C. or higher, preferably 220 ° C. or higher, more preferably 230 ° C. or higher after the completion of stretching. In this case, it is preferable to perform heat setting while relaxing the film by 3 to 8%. When heat setting is performed at a temperature of less than 200 ° C. or a relaxation rate of less than 3%, the heat shrinkage at 150 ° C. is less than 2%, preferably 1.
A fine void-containing thermoplastic resin film having a preferable property as a recording material of less than 7%, more preferably less than 1.5%, cannot be obtained.

By providing a coating layer on the surface of the thermoplastic resin film containing fine cavities constituting the recording material of the present invention, the wettability and adhesion of inks, coating agents and the like are improved. As a material constituting the coating layer, a polyester resin is preferable, but in addition, a urethane resin,
Substances generally known to improve the adhesiveness of a polyester film, such as polyester urethane resin and acrylic resin, can be used.

As a method for providing a coating layer, a commonly used method such as a gravure coating method, a kiss coating method, a dip method, a spray coating method, a curtain coating method, an air knife coating method, a blade coating method, a reverse roll coating method, and the like. Applicable. As the step of providing the coating layer, a method of applying the polymer layer (unstretched sheet) in advance to the surface of the polymer mixture (unstretched sheet) before performing the stretching / orientation treatment, a uniaxially stretched / oriented cavity-containing thermoplastic resin. Either a method of coating on the surface of the film and stretching and orienting the film in the perpendicular direction, or a method of applying the film on the surface of the void-containing thermoplastic resin film which has been subjected to the stretching and orientation treatment can be used.

The thermoplastic resin film containing fine cavities constituting the recording material of the present invention may be a so-called composite film in which a surface layer and a central layer are laminated. Although the method is not particularly limited, in consideration of productivity, the surface layer and the central layer are extruded from separate extruders, and these are guided to one die to obtain an unstretched sheet, and then at least uniaxially. Lamination by the so-called co-extrusion method of stretching and orienting is most preferred.

The reason why L1 / L2 is used to specify the fine void-containing thermoplastic resin film constituting the recording material of the present invention is to quantify the vertical and horizontal balance of the voids,
When this value is 2/3 to 3/2, the balance is obtained, and 2
If it is less than / 3, the cavity is horizontally long, and if it is 3/2 or more, it is vertically long. If the balance is poor, curl due to heat occurs.

The thermoplastic resin film containing fine cavities constituting the recording material of the present invention must generally contain a necessary amount of cavities for the performance as a thermoplastic resin film containing fine cavities. It is 5 to 50% by volume in terms of the void content. If the void content exceeds 50% by volume, the content of the void is too large, so that the film loses its function such as insufficient strength and curls regardless of the shape of the void. If the void content is less than 5% by volume, the void content is low and the film cannot be said to be a void-containing film anymore. Therefore, curling due to heat does not occur, but drawing properties, printability, thermal recording properties, etc. Greatly decreases.

The fine void-containing thermoplastic resin film constituting the recording material of the present invention is excellent in the isotropy of the voids compared to the conventionally reported void-containing films, and is particularly resistant to curling due to heat. Recording materials based on this material include labels, posters, cards, recording paper, broadcasting materials, video printer receiving paper, barcode labels, barcode printer receiving paper, thermal recording paper, maps, dust-free paper, display boards, and white boards. , Electronic whiteboard, photographic paper, decorative paper, wallpaper, banknotes, release paper,
Origami, calendar, magnetic card, tracing paper, slip, delivery slip, pressure-sensitive recording paper, copy paper, clinical examination paper, parabolic antenna reflector, offset stamp, PS, LB
It can be used for a P plate, a reflector for a liquid crystal display, and the like.

[0028]

In the recording material of the present invention, the average length (L1) of the cavities in the longitudinal section of the thermoplastic resin film containing fine cavities and the average (L1) of the lengths of the cavities in the perpendicular direction, that is, the transverse section ( L2) ratio (L1 / L2)
Is set to 2/3 to 3/2 in order to suppress the occurrence of curl due to heat and the like.

In the recording material of the present invention, a thermoplastic resin as a main raw material is mixed with a thermoplastic resin incompatible with the thermoplastic resin.
The polymer mixture is formed by dispersing fine particles of a thermoplastic resin incompatible with the thermoplastic resin as a main raw material, and forming a nucleus capable of generating cavities by the next stretching and orientation treatment. To make it. By stretching and orienting the polymer mixture in at least one axial direction, a large number of fine cavities can be generated in the polymer mixture. By forming cavities, the film can be reduced in weight, workability is improved, and the cost per area is reduced. In addition, flexibility is increased by containing cavity,
When printing and transferring, clear printing and printing can be performed.
Further, by containing a cavity, light opacity and whiteness can be obtained. Further, a large number of protrusions derived from the incompatible resin are also formed on the surface of the film, and writing with a pencil, a ballpoint pen or the like becomes possible.

Further, since polyester is used as a thermoplastic resin as a main raw material, a film having excellent heat resistance and mechanical strength can be obtained. Recording material The fine void-containing thermoplastic resin film obtained in the base material, generation and uneven thickness less curl due heat, writability, printability is excellent in heat resistance, mechanical strength Excellent and lightweight.

[Measurement / Evaluation Method] The measurement / evaluation method used in the present invention is described below. 1) Intrinsic viscosity of polyester The polyester was dissolved in a mixed solution of phenol (6 parts by weight) and tetrachloroethane (4 parts by weight) and measured at 30 ° C.

2) Cavity content The film was accurately cut out into a square of 5.00 × 5.00 cm, the thickness was measured at 50 points, and the average thickness was t μm.
The weight was measured up to 0.1 mg and defined as wg, and the apparent density ρ (g / cm ³ ) was calculated by the following equation.

[0033]

(Equation 1)

Next, the density of the raw materials used (g / c
m ³ ) a1, a2, a3... and raw material mass% b1,
The void content v was calculated from b2, b3,.

[0035]

(Equation 2)

3) Average value of the length of the cavity The vertical and horizontal cross sections of the film were measured with a scanning electron microscope for 100 times.
After photographing at a magnification of 0 times, the length of the cavity was measured in a direction perpendicular to the thickness direction of the film using an image analyzer. -Scanning electron microscope used Hitachi-made S-510 scanning electron microscope.・ Image analyzer used Image scanner GT-8 manufactured by Seiko Epson Corporation
000 and a personal computer Macintosh using the same software AdobePhot
An image was captured with oshop TM2.5J, and image processing was performed with the same software, UltimateTM 242.1.1.

(4) Shrinkage ratio The film was taken to a width of 10 mm and a length of 250 mm, and
Mark at mm intervals, fix under a constant tension of 5 g, and measure the mark interval Amm. Subsequently, 150 minutes under no tension for 30 minutes.
The interval B between marks after the sample was placed in an oven at an atmosphere of ° C. was measured, and the heat shrinkage was determined by the following equation.

[0038]

(Equation 3)

5) Light transmittance According to JIS-K6174, a Poick integrating sphere formula T.
The total light transmittance of the film was measured using an R meter (manufactured by Nippon Seimitsu Kogaku). The smaller the value, the higher the concealment property.

6) Presence or absence of curl due to heat An anchor layer having the following composition is provided on the surface of the film, and an image receiving layer having the following composition is provided thereon, and a color hard copy (D-D made by Seiko Denshi Kogyo KK) SCA
NCH-5504), an image from a computer was actually output. At this time, if no curl was confirmed in the output printed matter, it was evaluated as ○, and if confirmed, as ×. Anchor layer Urethane-based dry laminating agent (A-130 manufactured by Takeda Pharmaceutical Co., Ltd.) 100 parts by weight Curing agent (A-3 manufactured by Takeda Pharmaceutical Co., Ltd.) 30 parts by weight Image-receiving layer Vinyl chloride / vinyl acetate copolymer (# 1000D manufactured by Denki Kagaku Kogyo) 100 parts by weight Amino-modified silicone (X-22-343 manufactured by Shin-Etsu Chemical Co., Ltd.) 3 parts by weight Epoxy-modified silicone (KF-393 manufactured by Shin-Etsu Chemical Co., Ltd.) 3 parts by weight Methyl ethyl ketone / toluene (weight ratio 1/1) 500 parts by weight

7) Presence or absence of elephant omission If no omission is seen in the image output in 6), ○;

8) Uneven thickness of the film The film was accurately cut out into a square of 10.00 × 10.00 cm, and the thickness was measured at 100 points.
μm, maximum thickness is Tmax μm, minimum thickness is Tn
In μm, it was calculated by the following formula.

[0043]

(Equation 4)

[0044]

Next, the present invention will be described more specifically with reference to examples and comparative examples.

Example 1 Polyethylene terephthalate resin 8 having an intrinsic viscosity of 0.62
0 wt%, polystyrene for general use (T575-57U manufactured by Mitsui Toatsu Chemicals, Inc.) 15 wt%, and average particle size 0.3
5 μm anatase type titanium dioxide (Fuji Titanium Co., Ltd.)
TA-300) was introduced into a twin-screw extruder using 5% by weight as a raw material, melt-extruded from a T-die at 290 ° C., solidified electrostatically in close contact with a cooling rotary roll, and had a thickness of about 9%.
An unstretched sheet of the polymer mixture of 00 μm was obtained. This was stretched 3.5 times in the machine direction at 80 ° C. by a roll stretching machine. Then, the film was stretched 2.7 times in the transverse direction at 125 ° C. by a tenter.
The film was stretched 1.3 times in the transverse direction at 0 ° C. Then 235 ° C
Then, a heat treatment was performed while relaxing by 4% to obtain a 100 μm-thick polyester film containing a large number of fine cavities inside.

Example 2 As raw materials, 85% by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.62, 10% by weight of crystalline polypropylene (FO-50F, manufactured by Mitsui Toatsu Chemicals, Inc.), and titanium dioxide (TA-3000) 5 A void-containing polyester film was obtained in the same manner as in Example 1 except that the weight% was used.

Comparative Examples 1 and 2 Except that the mixing ratios (% by weight) of polyethylene terephthalate resin, general-purpose polystyrene and titanium dioxide used as raw materials were 92/3/5 and 55/40/5, respectively. In the same manner as in Example 1, a fine void-containing polyester film was obtained.

Comparative Examples 3, 4 and 5 The transverse stretching was performed only in one stage, and the stretching temperature was 110 ° C., respectively.
135 ° C. and 180 ° C., and the draw ratio is 3.6.
A polyester film containing fine voids was obtained in the same manner as in Example 1 except that the film was doubled.

Comparative Example 6 The procedure of Example 2 was repeated, except that the transverse stretching was performed only in one step, the stretching temperature was 180 ° C., and the stretching ratio was 3.6 times.
A polyester film containing fine voids was obtained.

Comparative Examples 7 and 8 In the same manner as in Example 1 except that the transverse stretching was performed only in one step, the stretching temperature was 125 ° C., and the stretching ratio was 2.2 times and 2.6 times, respectively. A polyester film containing fine voids was obtained. Table 1 shows the properties of the films obtained in the above examples.
Shown in

[0051]

[Table 1]

The films of Examples 1 and 2 were obtained by stretching in two stages of transverse stretching in accordance with the method specified in the present invention to a total stretching ratio of 3.5 times (2.7 × 1.3). It satisfies the conditions for isotropy and thickness unevenness of the cavity specified in the present invention, has an appropriate cavity content ratio, and has no defects such as curling due to heat. On the contrary,
The films of Comparative Examples 3 and 4 were subjected to transverse stretching only in one step.
It was obtained by the conventional method of stretching 6 times,
The cavities had a small L1 / L2, and were therefore long in the lateral direction, and were curled by heat. Further, the films of Comparative Examples 5 and 6 were produced by increasing the transverse stretching temperature in the conventional one-stage transverse stretching. However, since the formation of cavities due to the transverse stretching was small, the cavities were elongated and the content was low. Small, uneven thickness. The low content of the cavity means that the flexibility, the lightness, the drawing property, the printability and the like are poor. However, the curl due to heat is not large because the content of cavities is small. The films of Comparative Examples 7 and 8 were produced by reducing the transverse stretching ratio in conventional one-stage transverse stretching. The cavities were isotropic and no curl due to heat was observed. large. Further, the films of Comparative Examples 1 and 2 were produced by the horizontal two-stage stretching method specified in the present invention, and the cavities were isotropic. However, the former has a low void content. This means that the film no longer has sufficient functions based on the inclusion of microvoids in the film, such as flexibility, lightness, drawing properties, and printability. Also, the latter has too much void content. Therefore, although the cavity is isotropic, curl due to heat is generated, and mechanical strength etc.
It is also clear that the function as a film has been impaired.

[0053]

The hollow thermoplastic resin film constituting the recording material of the present invention has the same lightness and flexibility as the conventional hollow polyester film produced by using polystyrene, polyolefin or the like as a voiding agent. Properties, concealing properties, drawing properties, etc., and less occurrence of heat curl and the like than conventional void-containing polyester films, so that sublimation transfer recording paper, heat transfer recording paper, heat-sensitive recording material, printing sheet, Labels, posters, recording paper,
It is particularly useful for applications such as packaging materials, slips, courier delivery slips, copy paper, and pressure sensitive paper.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI C08L 77:00 (72) Inventor Toshitake Suzuki 2-1-1 Katata, Otsu-shi, Shiga Pref. Toyo Boseki Co., Ltd. (56) References Patent 3067557 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 9/00-9/42 B29C 55/00-55/30 B41M 5/38-5/40

Claims (2)

(57) [Claims] 1. A ratio (L1 / L) of an average of lengths of cavities (L1) in a longitudinal section of a film and an average of lengths of cavities (L2) in a direction perpendicular to the film, that is, in a transverse direction.
2) is a 2/3 to 3/2, the thickness unevenness of the film is not less than 5%, based on the fine void-containing polyester film, wherein the void content of 5 to 50 vol%
Transfer recording material by sublimation or heat the wood. 2. The ratio (L1 / L) of the average length (L1) of the cavities in the longitudinal section of the film to the average length (L2) of the cavities in the perpendicular or transverse section thereof.
2) is a 2/3 to 3/2, the thickness unevenness of the film is not less than 5%, based on the fine void-containing polyester film, wherein the void content of 5 to 50 vol%
Heat-sensitive recording material with product.