JPH07171939A - Thermal screen plate making apparatus and master thereof - Google Patents

Abstract

PURPOSE:To form perfect perforations to a master to form a sharp printing image by controlling the plate making conditions of a resistance heating element so that applied energy per one pixel at the time of the formation of a perforated image becomes a specific range. CONSTITUTION:When the thickness of a master 1 is set to (t) cm, the density thereof is set to sigmag/cm<3>, the specific heat thereof is set to Cp(J/g.K), a melting start point is set to Tm deg.C, crystal melting heat is set to X(J/g), the size of a resistance heating element 8 is set to R(Q) and the current supply time to the resistance heating element 8 is set to T(S), a control means 18 controls the plate making condition of the resistance heating element 8 so that the applied energy E(J) per one pixel of a perforated image satisfies formula (1) to form the perforated image. By such a control, perforations having a size sufficient to pass ink are opened to the master 1 and the perforations of pixels adjacent in a main scanning direction S and a sub-scanning direction F are not connected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive stencil plate-making apparatus and a master for heat-sensitive stencil which form a perforated image by using a thermal head on a master for heat-sensitive stencil consisting essentially of a thermoplastic resin film. It is a thing.

[0002]

2. Description of the Related Art A digital thermal stencil printing machine is well known as a simple printing method. The plate making apparatus in this printing apparatus is shown in FIGS. 5 and 6 (a), (b) and (c).

This plate making apparatus has a master 71 for heat-sensitive stencil.
The resistance heating elements 721 arranged in a line in the main scanning direction S
The thermal head 72 having the heat generating element is brought into contact with the master 71 in the sub-scanning direction F orthogonal to the arrangement direction of the resistance heating elements 721.
Is moved relative to the thermal head 72 by the platen roller 73, and the perforation image 91 is formed in a dot matrix manner by the selective heating of the resistance heating element 721. The master 71 on which the perforation image 91 is formed is conveyed to the conveying roller pair 76. The master 71 is cut by the rotary blade 741 of the cutter means 74, and the printing paper is continuously pressed against the master 71 by a pressing means such as a press roller. Printing is performed by allowing ink to seep out from the perforated portion 71.

The above-mentioned master is made by mixing a very thin thermoplastic resin film such as polyester (hereinafter referred to simply as "film") and synthetic fibers or Japanese paper as a porous flexible support, or a mixture of Japanese paper and synthetic fibers. It has a laminated structure in which the above are laminated together, and an overcoat layer is provided on the surface of the film for fusing with the surface of the thermal head and for preventing electrification.

Japanese Unexamined Patent Publication (Kokai) No. 4-265783 introduces a method of forming a perforated image on a master obtained by laminating a thermoplastic resin film and a porous support. Further, in JP-A-5-220919, the thickness of the thermoplastic resin film of the supportless master is 0.5 to 30 μm.
m, the melting start temperature is set to 50 to 300 ° C., and the thermal conductivity of the platen roller is set to 0.01 to 1 W / m · K.

[0006]

Since the master uses Japanese paper or the like as its support, the passage of the ink is obstructed at the part where the fibers of the Japanese paper are entangled with each other, and the ink does not transfer to the printing paper. There is a problem of so-called fiber stitches in which a fiber pattern appears on the part or fine lines are faint.
Further, since the passage of the ink is blocked by the Japanese paper at the time of printing, there is a problem that the rising of the image is bad and wasteful waste paper is generated.

[0007] Therefore, it is possible to prevent the generation of fiber stitches and improve the rise of the image by using a master consisting of only the film without using the Japanese paper or the like as the support. Although it can be done, the thickness of the film itself is about 2 to 8 μm at most, which is about 20 times thinner than the thickness of the Washi laminate master of about 40 to 50 μm, which makes the master less stiff. However, in the conventional stencil printing machine, there is a problem that the transportability is deteriorated by sticking to a guide member or a transport roller. Therefore, if the thickness of the film is increased to improve the transportability of the film, the perforation property deteriorates, resulting in a complete opening (a hole large enough to allow ink to pass) and an independent opening. (The holes of the pixels adjacent to each other in the main scanning direction and the sub scanning direction are open without being connected to each other.)
There is a problem that is not formed.

An object of the present invention is to solve the above-mentioned problems and to provide a heat-sensitive stencil plate making apparatus and a master thereof which can form a complete opening and an independent opening in the master and can obtain a clear printed image. It is in.

[0009]

The invention according to claim 1 is
A thermal head having a plurality of resistance heating elements arranged in the main scanning direction is brought into contact with the master for heat-sensitive stencil by pressing a platen roller which faces the resistance heating element and is arranged substantially parallel to the resistance heating element. In the heat-sensitive stencil plate making apparatus that moves the master relative to the thermal head in the sub-scanning direction orthogonal to the arrangement direction of the resistance heating elements, and forms a perforated image by selectively heating the resistance heating elements, The master substantially consists of a thermoplastic resin film, and the thickness of the master is t (cm),
Its density is σ (g / cm ³ ), and its specific heat is Cp {J /
(G · K)}, the melting start point is Tm (° C.), the heat of crystal fusion is X (J / g), and the size of the resistance heating element is S
(Cm ² ), the voltage applied to the resistance heating element is V
(V), where the resistance value of the resistance heating element is R (Ω) and the energization time to the resistance heating element is T (S), the applied energy E (J) per pixel when forming a perforated image
Is E = 20 (1 + k) {Cp (Tm-25) + X} σ
Control means is provided to control the plate making conditions of the resistance heating element so that St, E = (V ^{2 /} R) T, and −0.1 ≦ k ≦ 0.1 are satisfied.

[0010] According to a second aspect of the invention, the master stencil making apparatus consisting substantially only thermoplastic resin film, the master thickness t (cm) is, 2 × 10 _~ ⁴ ≦
characterized in that the range that satisfies t ≦ 10 × 10 _~ ^4.

According to a third aspect of the present invention, in a master of a heat-sensitive stencil plate-making apparatus which substantially consists of a thermoplastic resin film, the melting start point Tm (° C.) of the master is 70 ≦.
It is characterized by being in a range satisfying Tm ≦ 260.

According to a fourth aspect of the present invention, in a master of a heat-sensitive stencil plate making apparatus which is substantially composed of a thermoplastic resin film, the heat of crystal fusion X (J / g) of the master is 0≤.
It is characterized by being in a range satisfying X ≦ 50.

According to a fifth aspect of the present invention, in the heat-sensitive stencil plate making apparatus according to the first aspect, the substantial heating portion of the resistance heating element has a rectangular shape, and the pixel density thereof is r (do).
t / mm), the length a (cm) in the main scanning direction and the length b (cm) in the sub scanning direction of the resistance heating element are
0.5 ≦ b / a ≦ 1.7, 0.032 / r ≦ a ≦ 0.0
8 / r, 0.032 / r ≦ b ≦ 0.08 / r.

According to a sixth aspect of the present invention, in the heat-sensitive stencil plate making apparatus according to the first aspect, the surface of the platen roller has a thermal conductivity of 1.0 {W / (m · K)} or less, and Average roughness of the center line of the platen roller (Ra)
Is 12.5 or less.

According to a seventh aspect of the present invention, in the heat-sensitive stencil plate making apparatus according to the first aspect, the pressing force of the platen roller against the thermal head is from 65 (gf / cm) to 490.
It is characterized in that it is in a range satisfying (gf / cm).

Here, the sub-scanning direction means the direction in which the heat-sensitive stencil master is conveyed, and the main scanning direction means the direction orthogonal to the sub-scanning direction. Further, the master for heat-sensitive stencil consisting essentially of a thermoplastic resin film, in addition to those in which the master consists of only the thermoplastic resin film, those containing a minor component such as an antistatic agent in the thermoplastic resin film Further, it includes one in which one or more thin film layers such as an overcoat layer are formed on both main surfaces of the thermoplastic resin film, that is, at least one of the front surface and the back surface.

The thermoplastic resin film applied to the heat-sensitive stencil plate making apparatus of the present invention and the master thereof may be a polyester-based, nylon-based or vinyl chloride-based thermoplastic resin film. Further, a coating agent for antistatic and sticking prevention may be applied to one side or both sides of the thermoplastic resin film, or may be mixed inside the thermoplastic resin film.

In the thermal head applied to the heat-sensitive stencil plate making apparatus of the present invention, the resistance heating element is made of Ta-N system or the like, and the maximum value of the energy applied to the thermal head is within the rating of the thermal head. Anything that fits will do. Moreover, the resolution of the resistance heating element is not particularly limited. Furthermore, the control of the energy applied to the thermal head may be performed by the applied pulse width or the applied voltage. The applied energy data may be provided in a pre-registered ROM form or may be provided by an input operation of the stencil printing apparatus.

The platen roller applied to the heat-sensitive stencil plate making apparatus of the present invention includes silicone rubber, nitrile rubber,
Any rubber material such as chloroprene rubber may be used, and its hardness is preferably 25 to 60 in JIS hardness. Further, a conductive material, a heat insulating material or the like may be mixed in the rubber material, or the surface of the platen roller may be coated with a conductive material, a heat insulating material or the like.

[0020]

According to the first aspect of the invention, the control means controls the applied energy E per pixel when forming the perforated image.
(J) is E = 20 (1 + k) {Cp (Tm-25) +
X} σSt, E = (V 2 /R)T,-0.1≦k≦0.
Since the plate making conditions of the resistance heating element are controlled so as to satisfy 1, the hole of a size large enough for ink to pass through is opened in the master, and the holes of the adjacent pixels in the main scanning direction and the sub scanning direction are connected to each other. Disappear.

According to the invention of claim 2, the master is
Its thickness t a _{(cm), 2 × 10 ~} 4 ≦ t ≦ 10 × 10 ~ 4
Is formed in the range of.

According to the invention of claim 3, the master is
The melting start point Tm (° C.) is formed so as to be in the range of 70 ≦ Tm ≦ 260.

According to the invention of claim 4, the master is
The crystal fusion heat X (J / g) is formed so as to be in the range of 0 ≦ X ≦ 50.

According to the invention of claim 5, the pixel density r
(Dot / mm) and the length a of the resistance heating element in the main scanning direction
(Cm) and the length b (cm) in the sub-scanning direction are 0.5 ≦
b / a ≦ 1.7, 0.032 / r ≦ a ≦ 0.08 / r,
It is formed so as to be in a range satisfying 0.032 / r ≦ b ≦ 0.08 / r.

According to the invention of claim 6, the platen roller has a surface having a thermal conductivity of 1.0 {W / (m ·
K)} or less, the average roughness (Ra) of the center line is 1
It is formed below 2.5.

According to the invention of claim 7, the platen roller has a thermal head of 65 (gf / cm) to 49 (gf / cm).
Press with a pressing force of 0 (gf / cm).

[0027]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 100 indicates a heat-sensitive stencil plate making apparatus in a stencil printing apparatus. Heat-sensitive stencil plate making apparatus 100
Is a shaft 1s serving as a holding unit that holds the master 1, a platen roller 3 that conveys the master 1 in the sub-scanning direction F,
A thermal head 2 that extends in parallel with the platen roller 3 and is provided so as to be able to come into contact with and separate from the platen roller 3.
A control means 18 for controlling the applied energy applied to the thermal head 2, a pressing roller pair 4 for holding the master 1 and carrying the master 1 toward the master locking means 6 on the outer peripheral surface of the plate cylinder 7, It is arranged between the pressing roller pair 4 and the master locking means 6 so as to be vertically movable, and is mainly composed of a heater wire 9 for fusing the master 1. Reference numeral 5 in FIG.
Shows a guide plate for guiding the master 1 toward the master locking means 6 on the outer peripheral surface of the plate cylinder 7.

The master 1 is formed of polyester or the like having a width of 320 mm, is wound in a roll shape, and is supported by the shaft 1s so as to be able to be drawn out. The master 1 is coated with a mixed liquid of a silicon-based lubricant and an antistatic agent on the surface in contact with the thermal head 2.

The platen roller 3 is a silicon rubber to which carbon has been added and which has been electrically conductive, and has a length of 3 in the main scanning direction S.
08mm, wall thickness 5mm, outer diameter 24mm,
It is rotationally driven by a stepping motor (not shown).

The thermal head 2 has a structure shown in FIG.
As shown in (b) and (c), a plurality of resistance heating elements 8 arranged in one line in the main scanning direction S and the resistance heating elements 8 are arranged.
It is mainly configured by a holder portion 10 that holds and cools. The thermal head 2 is provided so as to come into contact with and separate from the platen roller 3 by means not shown. The thermal head 2 selectively melts and perforates the master 1 based on a digital image signal which is processed and transmitted by an A / D conversion unit and a control unit 18 of an original reading unit (not shown) to form a perforated image 11. It has the function of. In this embodiment, the thermal head 2 has a 16 DPM (dot)
/ Mm) with a rectangular resistance heating element 8 having a pixel density of 293 mm (A
4608 pieces are arranged in one row at a constant pitch over the length of (corresponding to 3), and are divided into first to fourth blocks.

The control means 18 changes the thickness of the master 1 to t (c
m), its density is σ (g / cm ³ ), and its specific heat is Cp
{J / (g · K)}, the melting start point is Tm (° C.), the heat of crystal fusion is X (J / g), the size of the resistance heating element 8 is S (cm ² ), and the resistance heating element 8 is Voltage applied to V
(V), the resistance value of the resistance heating element 8 is R (Ω), and the energization time to the resistance heating element 8 is T (S).
The applied energy E (J) per pixel is E = 2
0 (1 + k) {Cp (Tm-25) + X} σSt, E =
The perforation image 11 is formed by controlling the plate making conditions of the resistance heating element 8 so as to satisfy (V ^{2 /} R) T, −0.1 ≦ k ≦ 0.1. In the present embodiment, as shown in FIG. 3, the control unit 18 changes the applied pulse width (energization time T) as one of the applied energy E to form the punched image 11. A map of the energization time T for forming the punched image 11 shown in FIG. 3 is input to the ROM of the control unit 18 in advance. Further, when making a master having a different composition, thickness, etc., from the master 1, the ROM reading area of the control means 18 is changed or the ROM chip is replaced.

Next, the operation of the heat-sensitive stencil plate making apparatus 100 will be described below. As shown in FIG. 2A, the master 1 waits at a position slightly downstream of the pressing roller pair 4 with its tip end aligned in a direction substantially parallel to the pressing roller pair 4. ing. By pressing a plate-making start key (not shown), a plate-making command is sent to a stepping motor (not shown) and the platen roller 3 starts rotating. When the platen roller 3 rotates, the pressing roller pair 4 also starts rotating. A resistance heating element 8 of the thermal head 2 which is pressed against the platen roller 3 while sandwiching the master 1 selectively generates heat by a digital image signal which is processed and transmitted by an A / D converter and control means 18 (not shown). And the master 1 is selectively melted and perforated, as shown in FIG.
As shown in, the punched image 11 is formed.

Further rotation of the platen roller 3 and the pressing roller pair 4 causes the master 1 to be held between the pressing roller pair 4 along the guide plate 5 as shown in FIG.
When the tip of the master 1 is delivered to the master locking means 6 and reaches the master locking means 6, the master locking means 6 locks the tip of the master 1. Simultaneously with this locking operation, the plate cylinder 7 rotates and the master 1 starts to be wound around the outer peripheral surface of the plate cylinder 7. During this winding, the plate cylinder 7 is wound around the plate cylinder 7 in order to wind it around the master cylinder 1 without causing wrinkles or floating.
Master the tensile load from 0 to 2000 (gf / mm ² ) 1
To give evenly. Master 1 is transported for a predetermined length,
When the final row of the punched image 11 reaches a position slightly downstream of the heater wire 9, the rotation of the platen roller 3, the pressing roller pair 4, and the plate cylinder 7 is stopped while the master 1 is held, and the heater wire 9 causes The master 1 is melted and the plate making process ends. When the master 1 melts down, the plate cylinder 7 resumes rotation,
After the master 1 is wound around the outer peripheral surface of the plate cylinder 7, the printing process is started.

The present invention will be described below based on Examples and Comparative Examples. The thickness of the master 1 is t (cm), its density is σ (g / cm ³ ), and its specific heat is Cp {J / (g ·
K)}, its melting start point is Tm (° C.), its heat of crystal fusion is X (J / g), and the size of the resistance heating element 8 is S (c).
m ² ), the voltage applied to the resistance heating element 8 is V (V), the resistance value of the resistance heating element 8 is R (Ω), and the energization time to the resistance heating element 8 is T (S). The applied energy E (J) per pixel of 11 is E = 20 (1+
k) {Cp (Tm-25) + X} σSt, E = (V ² /
R) The plate-making conditions were set so as to satisfy T, −0.1 ≦ k ≦ 0.1.

In this equation, the thermal capacity of the thermal head 2 until the perforated portion of the master 1 is heated to the melting start point and melted, and the thermal head 2
To the master 1 in consideration of the efficiency of heat conduction from the master to the master 1. That is, data of applied energy was calculated based on various physical property values of the master 1 and various physical property values of the thermal head 2. These equations will be described below.

E = 20 (1 + k) {Cp (Tm-25) + X} σSt ・ ・ ・ Equation 1 E = (V ² / R) T ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ Formula 2 −0.1 ≦ k ≦ 0.1 ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ We energy of master 1 to open, It is based on the basic equation in thermodynamics of crystalline solids. Equation 1 is composed of two terms, the heat capacity Cp (Tm-25) σSt for heating and raising the temperature of the master 1 from room temperature (25 ° C.) to the melting start point Tm (° C.), and the melting start point Tm ( The heat capacity (corresponding to the latent heat in the crystalline solid) XσSt for the master 1 that has been heated and raised to (° C.) to change its state and melt. Therefore, the perforation energy is given by E = {Cp (Tm-25) + X} σSt.

Therefore, the perforation energy obtained by the equation 4 may be supplied from the resistance heating element 8 of the thermal head 2 to the master 1. Since the heat generation energy of the resistance heating element 8 is given by Expression 2, if the applied voltage or the applied pulse width to the thermal head 2 is defined so that (Expression 4) = (Expression 2), the master 1 is punched. It should be able to form an image. The expression 2 is based on Ohm's law.

However, since the equation 4 does not consider the heat loss at all, the perforation energy value becomes a very small value, and when the perforation energy value is set in the actual perforation plate making, the master 1 cannot be perforated. The heat loss includes a loss due to heat diffusion in the thermal head 2, a loss due to heat conduction from the thermal head 2 to the master 1, a loss due to heat diffusion in the master 1, and a heat conduction from the master 1 to the platen roller 3. There is a loss, etc. These losses are difficult to isolate, identify and quantify. Therefore, the value calculated recursively from the energy that can actually perforate the master 1 and the equation 4 is (20) in the equation 1.

In the actual perforation plate making, the perforation energy obtained by the equation 1 may be supplied from the resistance heating element 8 of the thermal head 2 to the master 1. Since the heat generation energy of the resistance heating element 8 is given by the equation 2 as described above, if the applied voltage or the applied pulse width of the thermal head 2 is defined so that (equation 1) = (equation 2), the master A perforated image 11 can be formed on the first screen.

Further, the coefficient (1 + k) of the equation 1 and the equation 3 are
The coefficient is a coefficient representing the allowable range of applied energy in consideration of variations in characteristic values of the master 1, the thermal head 2, the platen roller 3, etc., and is set to ± 10% in this embodiment.

Tables 1 to 4 show each condition of the embodiment.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

[Table 4]

In all cases of the examples shown in Tables 1 to 4, complete opening and independent opening were achieved in the master. As a comparative example, a case in which applied energy exceeding the range of the applied energy described above and a case in which applied energy lower than the range is applied will be described. The results of Examples and Comparative Examples are shown in FIG. In the figure, ∘ indicates complete opening and independent opening (example), and x indicates plate making failure (comparative example).

When the applied energy exceeding the range of the applied energy described above was applied, the master was completely opened, but the holes were connected and the independent opening was not formed. When the applied energy below the range of the applied energy was applied, the holes could not be opened, or the open ratio was low, and the open defects occurred. Therefore, a good perforated image could not be formed in any case.

Further, when the thickness of the master is less than 2 (μm), the stiffness of the master becomes weak, so that the master is frequently not fed or jammed, resulting in poor transportability. Conversely, the thickness is 10 (μ
If it exceeds m), the openability deteriorates, and it becomes necessary to set plate-making conditions exceeding the plate-making performance of the thermal head. Therefore, in order to achieve complete opening independently openings to the master, the master of the thickness t (cm) ^{_{is, 2 × 10 ~ 4 ≦ t}} ≦
It is set to 10 x 10 _~ ⁴ .

Further, a proper melting start point (° C.) of the master
Further, an experiment for obtaining the heat of crystal fusion (J / g) of the master was conducted. The results are shown in Tables 5 and 6.

[0050]

[Table 5]

[0051]

[Table 6]

From the results of the experiment shown in Table 5, when the melting start point (° C.) of the master is lower than 70 ° C., the master's porosity is improved, but the master is the environment of use of the heat-sensitive stencil plate making machine and the master's. More susceptible to storage conditions. In particular, in a high temperature environment, the master causes heat shrinkage and environmental stability deteriorates. On the contrary, the melting start point (° C) of the master is 260
If the temperature exceeds ℃, it becomes difficult for the master to melt, and there is no room for the temperature rising temperature and the temperature rising time of the resistance heating element of the thermal head, and sufficient openings cannot be formed. Therefore, the melting start point Tm (° C.) of the master is set to 70 ≦ Tm ≦ 260.

The heat of crystal fusion (J / g) of the master does not directly contribute to the opening of the master and can be regarded as a heat loss. Therefore, the smaller the better. (That is,
From the results of the experiment shown in Table 6, when the heat of crystal fusion (J / g) of the master is larger than 50 (J / g), the ratio of the heat loss increases and the porosity is increased. , The heat of crystal fusion X (J / g) of the master is 0 ≦ X
It is set to ≦ 50.

In the thermal heads used in the above-described Examples 1 to 4, the resistance heating element has a rectangular shape and the pixel density r = 16 (dot / mm). The length a ( cm) = 30 x 1
0 _to ⁴ length of resistance heating element in sub-scanning direction b (cm) = 40 × 1
0 _to ⁴ resistance heating element dot pitch in the main scanning direction = 1/16
(Mm) = 62.5 μm Dot pitch of the resistance heating element in the sub-scanning direction = 1/16
(Mm) = 62.5 μm was used.

As a comparative example, the resistance heating element has the same pixel density and a rectangular shape as that of the above-described embodiment, and the resistance heating element has a length a (cm) in the main scanning direction and a length b (cm) in the sub-scanning direction.
And used the following thermal head to make a master plate.

[0056] ^{_{a = 50 × 10 ~ 4,}} b = 55 × 10 ~ 4 a = 50 × 10 ~ 4, b = 60 × 10 ~ 4 a = 15 × 10 ~ 4, b = 10 × 10 ~ 4 Comparative Example When making a plate with the thermal head, the size of the resistance heating element, that is, the pixel size is too large, and holes are connected or conversely holes are formed, but the diameter of the holes is too small to allow sufficient ink passage. However, good plate-making results such as low print image density were not obtained. Therefore,
In order to obtain a complete opening or an independent opening, the length a of the resistance heating element in the main scanning direction and the length b of the resistance heating element in the sub scanning direction are set.
Is set to 0.5 ≦ b / a ≦ 1.7 0.032 / r ≦ a ≦ 0.08 / r 0.032 / r ≦ b ≦ 0.08 / r.

Further, the proper thermal conductivity of the surface of the platen roller and the average roughness of the center line of the platen roller (R
An experiment for determining a) was performed. The results are shown in Tables 7 and 8.

[0058]

[Table 7]

[0059]

[Table 8]

From the results of the experiment, when the thermal conductivity of the surface of the platen roller exceeds 1.0 {W / (m · K)}, the heat from the thermal head easily escapes through the master,
No holes were formed in the master. Further, when the average roughness (Ra) of the center line of the platen roller exceeds 12.5, the adhesion between the master and the thermal head becomes poor, and the heat from the thermal head becomes difficult to be effectively transmitted to the master. No holes were formed in the. Therefore, the thermal conductivity of the surface of the platen roller is 1.0 {W / (m · K)}
The average roughness (Ra) of the center line of the platen roller is set to 12.5 or less.

Further, an experiment was conducted to obtain an appropriate pressing force of the platen roller on the thermal head. The results are shown in Table 9.

[0062]

[Table 9]

From the result of the experiment, the pressing force is 65 (gf / c
If it is smaller than m), the adhesion between the master and the thermal head and the nip width of the platen roller cannot be secured,
The openness of the master deteriorated. Conversely, the pressing force is 490
When it exceeds (gf / cm), the feeding of the master in the conveying direction becomes non-uniform, and the punched image is cut or torn.
Therefore, the pressing force of the platen roller on the thermal head is set to 65 (gf / cm) to 490 (gf / cm).

[0064]

As described above, according to the present invention,
The control means determines that the applied energy E per pixel at the time of forming the punched image is E = 20 (1 + k) {Cp (Tm-2
5) + X} σSt, E = (V ^{2 /} R) T, −0.1 ≦ k
Since the plate making conditions of the resistance heating element are controlled so as to satisfy ≦ 0.1, holes having a size sufficient to allow ink to pass through are opened in the master, and holes of pixels adjacent to each other in the main scanning direction and the sub scanning direction are formed. It is possible to provide a heat-sensitive stencil plate making apparatus and a master thereof, in which clear printing images can be obtained because of no connection.

[Brief description of drawings]

FIG. 1 is a front view of a heat-sensitive stencil plate making apparatus showing an embodiment of the present invention.

2A is a plan view showing a master in the standby state of the heat-sensitive stencil plate making apparatus shown in FIG. 1, and FIG. 2B is a plan view showing a master on which a punch image is formed by the heat-sensitive stencil plate making apparatus shown in FIG. , (C) are plan views showing the fused master.

FIG. 3 is a time chart showing an applied pulse width when a perforated image is formed by the thermal stencil plate making apparatus shown in FIG.

FIG. 4 is a graph showing results of plate making conditions under various plate making conditions of Examples and Comparative Examples.

FIG. 5 is a front view of a conventional heat-sensitive stencil plate making apparatus.

6A is a plan view of the heat-sensitive stencil plate making apparatus shown in FIG. 6, and FIG. 6B is a plan view of a master in which a cutting portion is formed by cutter means in the heat-sensitive stencil plate making apparatus shown in FIG. 6A. , (C) are plan views showing the master cut along the cutting section shown in (b) of FIG.

[Explanation of symbols]

 1 Master 2 Thermal Head 3 Platen Roller 4 Pressing Roller Pair 5 Guide Plate 6 Master Locking Means 7 Plate Cylinder 8 Resistance Heating Element 9 Heater Wire 10 Holder Part 11 Perforated Image 18 Control Means S Main Scanning Direction F Sub-scanning Direction 100 Heat Sensitive Plate Plate making equipment

Claims (7)

[Claims] 1. A heat-sensitive stencil plate is provided with a thermal head having a plurality of resistance heating elements arranged in the main scanning direction, which is pressed by a platen roller which faces the resistance heating elements and is arranged substantially parallel to the resistance heating elements. Contacting the master, and moving the master relative to the thermal head in the sub-scanning direction orthogonal to the arrangement direction of the resistance heating elements,
In a heat-sensitive stencil plate making apparatus for forming a perforated image by selectively heating the resistance heating element, the master substantially consists of a thermoplastic resin film, and the thickness of the master is t (cm) and its density is σ. (G / c
m ³ ), its specific heat is Cp {J / (g · K)}, its melting start point is Tm (° C.), its heat of crystal fusion is X (J / g), and the size of the resistance heating element is S ( cm ² ), the voltage applied to the resistance heating element is V (V), the resistance value of the resistance heating element is R (Ω), and the energization time to the resistance heating element is T
(S), the applied energy E per pixel when forming a perforated image
Plate making of the resistance heating element so that (J) satisfies E = 20 (1 + k) {Cp (Tm-25) + X} σSt E = (V ² / R) T −0.1 ≦ k ≦ 0.1 A heat-sensitive stencil plate making apparatus having control means for controlling conditions. 2. A master of substantially stencil making apparatus consisting only of a thermoplastic resin film, the range of the master thickness t (cm) satisfies ^{_{2 × 10 ~ 4 ≦ t ≦}} 10 × 10 ~ 4 A master of a heat-sensitive stencil making machine characterized by being present. 3. A heat-sensitive stencil plate-making apparatus master comprising substantially only a thermoplastic resin film, wherein the melting start point Tm (° C.) of the master is in the range of 70 ≦ Tm ≦ 260. Master of stencil plate making equipment. 4. A master of a heat-sensitive stencil plate-making apparatus consisting essentially of a thermoplastic resin film, wherein the heat of crystal fusion X (J / g) of the master is in a range satisfying 0 ≦ X ≦ 50. Master of thermal stencil making machine. 5. The heat-sensitive stencil plate making apparatus according to claim 1, wherein the resistance heating element has a substantially heat-generating portion having a rectangular shape and the pixel density thereof is r (dot / mm). The length a (cm) of the element in the main scanning direction and the length b (cm) of the element in the sub scanning direction are 0.5 ≦ b / a ≦ 1.7 0.032 / r ≦ a ≦ 0.08 / r 0 A heat-sensitive stencil plate making apparatus having a range of 0.032 / r ≦ b ≦ 0.08 / r. 6. The heat-sensitive stencil plate making apparatus according to claim 1, wherein the surface of the platen roller has a thermal conductivity of 1.0 {W /
(M · K)} or less, and the average roughness (Ra) of the center line of the platen roller is 12.5 or less. 7. The heat-sensitive stencil plate making apparatus according to claim 1, wherein the pressing force of the platen roller against the thermal head is 65.
A heat-sensitive stencil plate making apparatus characterized by being in a range of (gf / cm) to 490 (gf / cm).