JPS601198B2 - Heat-sensitive stencil printing base paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a heat-sensitive stencil printing base paper which is made into a plate by flash irradiation using a xenon flash lamp or the like.

The principle of this plate-making method is clearly stated in Japanese Patent Publication No. 7623/1973 and is already widely known, but to put it simply, a base paper is superimposed on top of the manuscript (original), and then When irradiated with flash light, the light absorbed by the image area of the original turns into heat, which causes the corresponding portion of the base paper to melt and shrink, creating perforations in the base paper corresponding to the image area. Since the perforated base paper has holes corresponding to the image of the original, by applying mimeograph ink or screen printing ink thereon, it is possible to obtain printed matter corresponding to the image of the original. Now, the structure of what has been conventionally used as heat-sensitive stencil printing base paper (hereinafter simply referred to as base paper) is as shown in FIG. That is, in FIG. 1, 1 is a heat-shrinkable film, 2 is an adhesive, and 3 is a porous support. Films used on the cheek are stretched vinyl chloride/vinylidene chloride copolymer films and polypropylene films, and films used as porous supports include:
These include tissue paper and Tetoron gauze. Vinyl acetate adhesives are often used as adhesives, but recently polyamide copolymers and polyester copolymers have also been used. Now, even though it is a film that has the essential function of being perforated by flash irradiation, why do we have to go to the trouble of using an adhesive to attach a porous support such as tissue paper or Tetoron gauze? There are two possible causes:

[11] Prevents unlimited expansion of the perforation.

If only one film is used, the perforations caused by the irradiation may spread indefinitely, which would reduce the clarity of the print. When the porous support is bonded to the film, the expansion of the perforations is stopped at the bonded portion. ■ Improved strength during printing.

If only one film is used, it will easily tear during printing. For these reasons, a porous support is bonded to the film, but such bonding work is troublesome and inefficient, and of course increases manufacturing costs.

As a result of intensive research by the present inventors, we have developed a film structure that prevents the perforations from expanding indefinitely even when the film is used alone without such bonding work, and which also has sufficient strength during printing. , the present invention has been achieved. That is, the gist of the present invention is that the melting point or softening temperature is 2°C.
This heat-sensitive stencil printing base paper is characterized in that a polymer alternating array film having a structure in which two different types of polymers are alternately arranged in the width direction of the film is used as a heat-sensitive layer.

The polymer alternating array film referred to here refers to Figures 2 and 3.
The film has a cross section in the width direction as illustrated in FIGS. 4, 5, and 6. In these figures, the black portions are made of polymer A, and the white portions are made of polymer B. Of course, this is only divided into A and B for the convenience of the following explanation, and does not limit the present invention. Now, one of the important requirements constituting the present invention is that both the polymers A and B have a temperature of 2°C or higher, preferably 5°C.
They should have a difference in melting point or softening point of at least .degree. C., more preferably at least 8.degree.

For example, if the melting point of polymer A is 16,500, the melting point of polymer B is 16,300 or less, preferably 160
00 or less, more preferably 15,700 or less. Here, the melting point is measured by a scanning differential calorimeter (DSC).
It means the temperature at the peak of an endothermic peak caused by melting of crystals when a 0 female sample is placed and heated at a temperature increase rate of 1000/min. Also, the softening point is ASTM-
This is the softening point determined by D1525-65T.

When the two types of polymers used in the present invention are both crystalline polymers, both have melting points, so the temperature difference is defined as the difference in melting points. If one or both of the polymers is amorphous, there is no melting point and therefore it is not possible to take the difference in melting point, so the difference in softening point becomes the temperature difference required by the present invention. In a polymer alternating array film having a cross-sectional structure as illustrated in FIGS.
It has been found that by using materials with the above-mentioned difference in melting point or softening point, an extremely excellent heat-sensitive stencil printing base paper can be obtained. That is, even if flash irradiation is performed using only the film (ie, without bonding a porous support), a clean perforation state can be obtained and the perforations will not expand indefinitely. It also has strong strength during printing and does not tear easily, so you can print a large number of copies. If the difference in melting point (or softening point) between the two polymers is less than 2° C., there is no such advantage, and it cannot be put to practical use unless a porous support is attached. Although it is not necessarily clear why the advantages mentioned above are obtained by having such a difference in melting point (or softening point) between polymers A and B, It is presumed that the array is somewhat difficult to melt even when exposed to flash light, which prevents the perforations from expanding indefinitely and contributes to improving the strength during printing.

The larger the difference in melting point (or softening point), the better the above-mentioned advantages tend to be.
The temperature above, more preferably 8° C. or higher is required. The upper limit of this temperature difference is necessarily determined from the viewpoint of ease of manufacturing such a film, and is usually 80 oo or less, preferably 5,000 or less. It is preferable to align polymers A and B that are compatible with each other, and from that point of view, it is preferable to combine polymers of the same type, for example, polyolefins to vinyl-based polymers, polyesters, or polyamide-based polymers. Become something. Expressed in terms of the solubility index (solubility parameter), which is one of the parameters that indicates the compatibility between polymers, polymers A and B have a difference of 2 or less in the index, preferably 1 or less. The combination of these is the most practical. One of the best combinations is that of homopolymers and copolymers. Generally, the melting point (or softening point) of a copolymer is lower than that of a homopolymer due to copolymerization, so it is convenient to mediate the difference in melting point (or softening point) by the degree of copolymerization. Moreover, ``if a homopolymer and a copolymer are made of the same main structural unit, the compatibility between the two is usually very good. Therefore, a homopolymer of propylene (melting point 16,600) is used for polymer A, and a propylene homopolymer (melting point 16,600) is used for polymer B. A combination using an ethylene base copolymer (melting point 155°C), or an ethylene terephthalate-1 isophthalate copolymer (using polyethylene Q terephthalate (melting point 25820) as polymer A and copolymerizing isophthalic acid as polymer B) A combination using a melting point of 245 qo) is very preferable.Next, the combination using
The sizes of the constituent units of the cross-section of the film illustrated in the figures, that is, the polymers A and B, are also extremely important for successfully carrying out the present invention. Looking at the cross section of the film,
The maximum length in the width direction of one structural unit made of polymer A (see Figures 2 to 6) La and the shortest length from one polymer A unit to the nearest neighboring polymer A (See Figures 2 to 6. Therefore, this length is made of polymer B.) Lb is usually 1 to 400 μm, preferably 5 to 300 μm, and more preferably 10 μm. Preferably, the length ranges from ~200 Buddha kites. When La and Lb are smaller than this lower limit, the effect of preventing unlimited expansion of the perforation becomes extremely small, and the strength during printing also becomes weak. On the other hand, when La and Lb exceed the upper limit,
The resolution of the printed matter deteriorates, resulting in an unsightly printed state.
Of course, it is not necessary that all La and Lb measured in the cross section of the film fall within this range, but 60% or more of the total, preferably 80% or more of Lb must be within this range.
It is sufficient that a and Lb fall within this range. The values of La and Lb do not always need to take the same value for one cross section of the film, and the values of La and Lb may change when the cross section of the same film is changed. In other words, each constituent unit of polymers A and B is
They do not need to be regularly lined up in the cross section of the film, nor do they need to be regularly continuous in the longitudinal direction of the film. For example, one structural unit made of polymer A may have a varying thickness or a bent direction when viewed in the longitudinal direction of the film,
Moreover, it may be discontinuous in some places. In other words, the regular arrangement as illustrated in FIGS. 2 to 6 is for convenience of explanation and is not necessarily required for the present invention. A structural unit of another polymer C may be interposed between the structural units of polymers A and B, but in that case, polymer C has a melting point (or softening point) between polymers A and B. ) should have. Furthermore, both polymers A and B do not need to be a single polymer, and may be a mixture of polymers. In this case, the melting point (or softening point) of the mixture is determined by the value of the component having the highest weight ratio among the components constituting the mixture. In addition, known additives (stabilizers, ultraviolet absorbers, surfactants, lubricants, inorganic fillers, molding agents, coloring agents, glittering agents,
Pigments, plasticizers, etc.) may be added in an amount of 0.01 to 2% by weight. Next, a method for producing a stencil paper having the structure of the present invention will be explained, but the present invention is not limited to these production methods.

The easiest method is disclosed in Japanese Patent Publication No. 49-34656.
This method uses a pipe mixer or a static mixer as shown in No. Polymers A and B are melted in separate extruders and fed into a static mixer. In this mixer, polymers A and B are stacked in multiple layers by repeatedly shifting their positions with respect to each other. This multi-layered melt is fed into a film-forming die such as a fish-tilt die, so that polymers A and B overlap in the width direction to form a sheet. This is cooled and solidified by a conventional method and subjected to necessary stretching operations to form a film having a thickness of 5 to 20 ridges. Another method involves feeding polymers A and B in a molten state from separate extruders into a special die as shown in Japanese Patent Publication No. 50-1686, At the mouth manifold, A and B are arranged alternately in the width direction, and extruded into a sheet.

After cooling and solidifying this, it is biaxially stretched and, if necessary, subjected to heat treatment or surface treatment to form a film with a thickness of 5 to 20 mm. The film of the present invention manufactured through a series of relatively simple processes as described above has a cross-sectional structure as illustrated in FIGS. 2 to 6, and can be used as is as a base paper for heat-sensitive stencil printing. I can do things.

Of course, the film obtained in this way may be used by bonding a conventional porous support with an adhesive. This will be explained below using examples.
The present invention is not limited to these examples.

Example 1 Isotactic polypropylene as polymer A,
As polymer B, an isotactic propylene ethylene copolymer was used.

The composition and characteristic values of each are as follows. Polypropylene: Isotactic polypropylene randomly copolymerized with 0.8% ethylene, melt index 2.0, boiling N-heptane extraction residue 96.8% by weight,
Melting point: 160oo.

Solubility index approximately 9.2. It contains 0.5% by weight of 2,6-tert-butyl-paracresol as an antioxidant and 0.2% by weight of calcium stearate as a glutinous agent. Propylene-ethylene copolymer: 2. A random copolymerized isotactic polymer with a melt index of 5.0 and a boiling N-hebutane extraction residue of 91. % by weight, melting point 150 pm.

Solubility index approximately 9.1. Contains the same antioxidants mentioned above, but
Does not contain lubricant. These two types of polymers were each supplied to separate extruders and melt-extruded at 240 to 2700C, and both were combined at the inlet of a static mixer.

Inside this mixer, two types of polymers are laminated in multiple layers, and in this state, they are sent to a fishtail type mouthpiece to a thickness of approximately 24 mm.
It was discharged in the form of a sheet. This sheet was wound around a rotating cooling drum (drum surface temperature: 3000) and cooled and solidified. This sheet was applied to a film stretcher (manufactured by T.M. Long), and was sequentially biaxially stretched 5×6 times in all directions while heating to 140 qo. Subsequently, while maintaining tension, heat fixation was performed with hot air at 140° C. for 15 seconds. The thus obtained film having a thickness of approximately 8 mm was transparent, and its cross section in the width direction had a shape as shown in FIG.

La, which indicates the dimensions of the cross section, was approximately 20 mm, and Lb was approximately 60 mm. This film was placed on top of a manuscript containing approximately 100 Japanese characters, and a flash discharge irradiation device was used from the film side.
Using a flash of light rich in near-infrared rays (manufactured by Riso Kagaku Kogyo Co., Ltd.), the film was perforated to correspond to the letters. When this perforated film was printed on a mimeograph machine and the number of characters with blurred or missing parts was counted in the printed matter and expressed as a percentage of the total number of characters (this is called the missing rate), it was found that there was only a slight 0. .5%, which was an extremely good result. ``This film is also extremely durable during printing, and the number of sheets that can be printed before the film breaks in the printing machine (this is called the number of sheet-bearing sheets) is approximately 800.
It was 1 piece. Comparative Example 1 The ethylene copolymerization rate of polymer B in Example 1 was gradually decreased.

A film was made of a material having a different melting point from Polymer A. The method of making the film is the same as in Example 1.
Regarding these films, the defect rate and number of printed sheets were measured in the same manner as in Example 1.The results are shown below.Sample No.
Melting point difference Defective rate Number of printing sheets (OC) (Takashi Son) 1 10 0.5 8002
8 0.6 7503
5 0.9 6504 2
1.5 5005 0.5
3.4 150As is clear from this result,
It can be seen that the difference in melting point between polymer A and polymer B is 200 or more, preferably 500 or more, more preferably 8° C. or more, in order to improve the chipping rate and the number of rigid plates.

Comparative Example 2 A double-stretched polypropylene film with a thickness of about 8 cm was produced using only the polymer A used in Example 1 and following the same procedure as in Example 1.

Naturally, this film does not have the cross-sectional structure shown in FIGS. 2 to 6, but is a normal single film. The defect rate of this film was 3.6%, and the number of printed sheets was 11, which was far inferior to the product of the present invention of Example 1. Comparative Example 3 By changing the ratio of the discharge amounts of both extruders and the number of elements of the static mixer in Example 1, the dimensions of the film cross section, that is, the values of La and Lb, were changed, and the rest was carried out by the same operations. A film similar to Example 1 was made.

These films were printed in the same manner as in Example 1, and the defect rate, number of Sakaki sheets, and quality of resolution were evaluated. The results are shown below. (In addition, the quality of resolution is
They were divided into three classes, A, B, and C, by visual judgment. The printed surface, which should originally appear continuous, was labeled A when it appeared as a continuous surface, B when it appeared to have some striped pattern, and C when it was made up of a collection of completely discontinuous lines. Of course, from the point of view of the appearance and readability of printed matter, it is desirable that the scale image power be A, but even B may have practical value depending on the purpose. ) Kaoru Cod 1''a Lb defect rate Durable number of sheets Resolution (〃m) (〃m) (%) (sheets) 6 20 0.5 1.8 500
A7 20 1 1.0 700
A8 20 5 0.7 750
A9 20 10 0.5 800
A sample La Lb Defect rate Durable number of sheets Resolution number (mountain m) (mm) Cooperation G square 10 20 6
0 0.5 800 AII 20 2
00 0.6 750 AI2 20
300 0.6 720 B13 2
0 400 0.8 700 B14
20 600 1.2 650 015
0.5 60 1.7 400 A
I6 1 60 1.0 580 A
I7 5 60 0.7 700
AI8 10 60 0.6 800
AI9 20 60 0.5 800
A20 100 60 0.5 800
A21 200 60 0.7 8
00 A22 300 60 0.9
700 B23 400 60 1.0
660 B24 600 60 1
．． 6 600 From the results above, La and L, which indicate the sizes of polymer A and polymer B in the cross section of the film.
The value of b is 1 to 400, preferably 5 to 30.
It can be seen that it is extremely important for the quality of the stencil printing paper to have a 0-pitch range, more preferably a range of 10 to 200 treads.

Example 2 One side of the film obtained in Example 1 was coated with a basis weight of 10
The porous thin paper sheets were pasted together using a pinyl acetate adhesive.

When this base paper was printed in the same manner as in Example 1, the defect rate was 0.5% and the number of printed sheets was 1,500, which was very good. Example 3 Two polymers, polyethylene terephthalate (melting point 259°C) and ethylene terephthalate isophthalate copolymer (melting point 24,800) (both with solubility indexes of about 10.7) were fed into separate extruders. About 280o
After melt extrusion at o and filtering through porous metal film,
The melt streams were conducted into a pipe mixer where they were combined.

In this pipe mixer, both polymers are stacked in multiple layers by exchanging positions with each other. This multilayer melt was introduced into a die, formed into a sheet, and wound around a rotating cooling drum (temperature 70 oo) to cool and solidify. The thickness of this sheet was approximately 60 mm. This sheet 9
000 and in the longitudinal direction 3. The film was stretched by a single pitch, and then fed into a stenter heated with 105 oo of hot air, and stretched 3.2 times in the width direction. Next, it was subjected to heat treatment at 210o0 for 7 seconds in a stentter, and after both ears were cut off, it was wound up. The film thus obtained was transparent and had a thickness of about 6 mm. The cross-sectional structure of this film is shown in Figure 4, and in this figure, polymer A corresponds to polyethylene terephthalate.
Ethylene terephthalate isophthalate copolymer corresponds to polymer B, where La is 30 French and Lb
There were 40 mountains. This film was perforated and printed in the same manner as in Example 1. As a result, the defect rate was 0.6% and the number of printed sheets was 75 prints, which were excellent results.

[Brief explanation of drawings]

FIG. 1 schematically shows the cross-sectional structure of a conventionally used heat-sensitive stencil printing base paper. FIGS. 2, 3, 4, 5 and 6 schematically illustrate the cross-sectional structure of the film used as the heat-sensitive layer of the base paper of the present invention. In the figure, 1: plastic film, 2
: Adhesive, 3: Porous support, A: Some kind of polymer, B
: Polymer having a different melting point from Polymer A, La: Maximum length of polymer A in the width direction, Lb: Minimum length between adjacent polymers A. Scales 1 *Ezu Fist S Figure Winter 4 Legs Taza 1 Liu Chi et al. 10%

Claims (1)

[Claims] 1. For heat-sensitive stencil printing, characterized in that a polymer alternating arrangement film having a structure in which two types of polymers having melting points or softening temperatures different by 2°C or more are arranged alternately in the film width direction is used as a heat-sensitive layer. Base paper.