JP7722239B2 - Waterless offset master plate manufacturing method and manufacturing device - Google Patents

Description

The present invention relates to a method and apparatus for manufacturing a waterless offset master plate.

Waterless offset printing is a lithographic printing technique characterized by the use of an ink-repellent silicone material instead of the dampening water used in regular offset printing to repel oil-based ink. In waterless offset printing, the master plate typically consists of a plate made of aluminum or other material with a silicone film formed on its surface (Patent Document 1).

Specifically, a silicone material is continuously applied to a long, continuous sheet of material, which is then cut to individual lengths depending on the required size of the master plate. The printing pattern is then processed onto the master plate to create a printing plate, which is then wrapped around a cylindrical substrate called a plate cylinder and used in a printing press.

However, this poses the problem that the edges of the printing plate form a seam in the circumferential direction on the cylindrical substrate, making it impossible to print near this seam. To address this problem, Patent Document 2 proposes an offset master plate that changes from the conventional plate-like shape to a seamless cylindrical shape. Patent Document 2 also discloses a method of recycling printing plates by subjecting a resist pattern applied to the matte surface of a cylindrical substrate to ultrasonic cleaning, chemical cleaning, or other treatments to remove the resist pattern portion from the surface of the cylindrical substrate.

Furthermore, Patent Document 3 proposes forming seamless printing cylinders in waterless offset printing by coating the surface of the printing cylinder substrate with a silicone resin layer.

Japanese Patent Application Publication No. 05-094008 International Publication No. 2017/104327 Domestic Publication No. 2017/077825

When the substrate shape of the master plate changes from the traditional plate shape to a cylindrical shape, there are some processes in its manufacturing that make it difficult to use traditional methods. One such process is the process of forming the required functional film on the substrate. For example, when using cylindrical substrates, cylindrical substrates with different outer diameters are used depending on the size of the master plate. However, since these cannot be stacked and compacted like plate-shaped substrates during storage and transportation, master plate manufacturing is sometimes carried out at a printing company or printing manufacturer.

When master plates are manufactured at a printing company or printing manufacturer, they are produced locally in the quantity needed. Due to storage space and transportation constraints, it is preferable to repeatedly reuse the same cylindrical substrate. Reusing such cylindrical substrates requires a recycling process: the functional film formed on the surface of the cylindrical substrate is removed after use as a printing plate, and then a new functional film is formed. The silicone material used as the functional film for waterless offset master plates tends to adhere to the cylindrical substrate and is difficult to remove completely. Therefore, one recycling method involves providing an easily removable release film on the cylindrical substrate, forming a silicone film on the release film, and then peeling off the release film along with the silicone film when recycling the substrate. However, the release film formed on the surface of the cylindrical substrate must have sufficient adhesion to the cylindrical substrate to prevent plate peeling during printing. Strong adhesion to the cylindrical substrate is particularly required in the circumferential direction of the substrate, which is the direction of rotation during printing.

In other words, the release film provided for recycling cylindrical substrates must be easily peelable during the recycling process, while also adhering strongly to the cylindrical substrate and not peeling off during the printing process. These contradictory functions must be compatible. However, in the manufacture of waterless offset master plates, applying a liquid release film material to the surface of the cylindrical substrate to form a release film has not been considered as a way to achieve both easy peeling and strong adhesion to the cylindrical substrate.

In other words, the problem that this invention aims to solve is to manufacture a seamless waterless offset master plate with no seams on the surface of a cylindrical substrate that can be easily peeled off from the cylindrical substrate, making the cylindrical substrate recyclable, while maintaining a high degree of adhesion to the substrate during printing, allowing for stable printing. The objective of this invention is to provide a manufacturing method and manufacturing device for this purpose.

In order to solve the above problems, the present invention provides a method and apparatus for producing a waterless offset master plate having the following configuration.
(1) A method for manufacturing a waterless offset master plate, comprising a first application step of applying a liquid release film material to the surface of a cylindrical substrate, a first solidification step of drying and solidifying the release film material to form a release film on the surface of the cylindrical substrate, a second application step of applying a silicone film material to the surface of the release film, and a second solidification step of drying and solidifying the silicone film material, wherein the release film material has standard release characteristics after drying and solidification such that when the coating film thickness is 100 μm or less, the product of the tensile strength [N/ ^mm2 ] of the release film and the coating film thickness [mm] exceeds the adhesive strength [N/mm] of the release film, and the first application step is a step of spraying the release film material from a first applicator provided below the cylindrical substrate onto the circumferential surface of the cylindrical substrate while rotating the cylindrical substrate about its axis as a central axis, and applying the liquid release film material while adhering it to the surface of the cylindrical substrate,
The first solidification step is a step following the first application step, in which the applied release film material is dried and solidified while the cylindrical substrate is rotated, thereby shrinking the applied release film material on the cylindrical substrate and forming the release film on the cylindrical substrate. The second application step is a step in which the silicone film material is ejected from a second applicator and applied to the surface of the release film, and a laminate including at least the release film and silicone film is formed on the surface of the cylindrical substrate. This is a method for manufacturing a waterless offset master plate.

(2) The method for producing a waterless offset master plate described in (1) is characterized in that the first coating step involves moving the first applicator back and forth in the axial direction of the cylindrical substrate while rotating the cylindrical substrate, thereby spraying the release film material onto the peripheral surface of the cylindrical substrate to form a coating film.
(3) The method for producing a waterless offset master plate according to (1) or (2), wherein the viscosity of the liquid release film material is 0.01 to 1 poise.
(4) A method for producing a waterless offset master plate according to any one of (1) to (3), wherein the second coating step is started while the cylindrical substrate is rotated during the first solidification step.
(5) A method for producing a waterless offset master plate according to any one of (1) to (4), wherein the first solidification step and the second solidification step are carried out by using air generated by the rotation of the cylindrical substrate or by blowing air from an air nozzle onto the coating surface on the cylindrical substrate.

(7) A coating device comprising at least a first coating means having a fountain nozzle as a first coating nozzle for coating the peripheral surface of the cylindrical substrate with a first coating material, a second coating means having a second coating nozzle for coating the peripheral surface of the cylindrical substrate with a second coating material, a rotation drive means for rotating the cylindrical substrate around the axis of the cylinder as the central axis, a solidification means for solidifying the coating film coated on the peripheral surface of the cylindrical substrate by blowing air from an air nozzle or irradiating light, a measuring device for measuring the film thickness value of the coating film, and a controller for switching between the first and second coating means and the solidification means,
The first and second coating means are equipped with a moving means for moving the first coating nozzle and the second coating nozzle in the direction of the rotation axis of the cylindrical substrate, and further, the coating material is applied by moving the first and second coating nozzles by the moving means while the cylindrical substrate is rotated by the rotation drive means, and the second coating means starts the coating process by the second coating means after stopping the solidification means based on the measurement value of the measuring instrument, in a waterless offset master plate manufacturing apparatus.

According to the present invention, when manufacturing a seamless waterless offset master plate on the surface of a cylindrical substrate, a release film material applied to the surface of the cylindrical substrate is shrunk to form a release film on the cylindrical substrate, and then a silicone film is formed on the surface of the release layer. This laminate structure makes it easy to release the release layer from the cylindrical substrate, and maintains high adhesion to the substrate during printing, allowing for stable printing.

As a result, by using these manufacturing methods and manufacturing equipment that are compatible with cylindrical substrates, it is possible to efficiently and with high quality produce waterless offset master plates with easily peelable films.

1 is a schematic perspective view showing an embodiment of a manufacturing apparatus according to the present invention. 1 is a schematic front view showing an embodiment of a manufacturing apparatus according to the present invention. FIG. 10 is a schematic side view showing a first application step and a first solidification step. FIG. 10 is a schematic side view showing a second application step and a second solidification step. FIG. 1 is a front view showing a schematic configuration of an apparatus for drying and solidifying a coating film. FIG. 10 is a schematic perspective view showing a step of forming a laminate.

One embodiment of the present invention will be described below with reference to the drawings. The present invention will be understood based on the following description and drawings, but the embodiments of the present invention are not limited to these.

The method for producing a waterless offset master plate of the present invention includes a first coating step of coating a liquid release film material on the surface of a cylindrical substrate, a drying and solidifying step of the release film material, and a second coating step of coating a silicone film material and a drying and solidifying step of the silicone film material, thereby forming a laminate including at least the release film and the silicone film on the surface of the cylindrical substrate. The release film material of the present invention is an easily peelable material such that, when the coating film thickness is 100 μm or less, the product of the tensile strength [N/ ^mm2 ] and the coating film thickness [mm] exceeds the adhesive strength [N/mm] of the release film in standard release characteristics after drying and solidifying. The first coating step is a step of spraying the release film material from a first applicator located below the cylindrical substrate onto the circumferential surface of the cylindrical substrate while rotating the cylindrical substrate about its axis, thereby coating the liquid release film material while adhering it to the surface of the cylindrical substrate. The first solidification step is performed following the first application step, in which the applied release film material is dried and solidified while the cylindrical substrate is rotated, causing the applied release film material to shrink and form the release film on the cylindrical substrate. The second application step then involves ejecting the silicone film material from a second applicator and applying it to the surface of the release film. The release film material refers to the release material that becomes the release film, and the silicone film material refers to the silicone material that forms the silicone film. The laminate of the release film and the silicone film is sometimes called a functional film.

In the present invention, the second coating method for applying the silicone material is not limited, but in the following description of the embodiment, the second coating step will be described using a method similar to the first coating step. That is, it is a step in which the coating liquid is sprayed from a second applicator located below the cylindrical substrate, and the coating liquid is applied to the surface of the cylindrical substrate while adhering to the surface.

In this invention, the silicone material used as the functional film of the waterless offset master plate adheres easily to the cylindrical substrate and is difficult to peel off. Therefore, by providing an easily peelable release film between the cylindrical substrate and the silicone film, the cylindrical substrate can be easily peeled off. When recycling the cylindrical substrate, the release film is peeled off along with the silicone film. On the other hand, the release film formed on the surface of the cylindrical substrate must have strong adhesion to the cylindrical substrate to prevent peeling of the plate surface during printing.

The standard release properties required for the release film material of the present invention are as follows. In this specification, "standard release properties" are an index that represents the release film material based on the properties of a release layer formed thinly on a substrate by coating or other methods. A release film material with good release properties, i.e., easy release, allows the release film formed on the substrate to be easily peeled off without breaking when peeled from the substrate, and is related to the tensile strength of the release film itself and the adhesive strength between the substrate and the release film. The standard release properties of the release material used in the waterless offset master plate of the present invention are such that the tensile strength [N] of the release film is greater than the adhesion strength [N] between the substrate and the release film.

Here, the tensile strength is the material strength of the release film material in a film state: T [N/mm ² ], and can be measured using a tensile tester specified in JIS B 7721 (2018), and is expressed as T/(W·t) from the cross-sectional area [mm ² ] of the width W [mm] and the film thickness t [mm]. The adhesive strength: P [N/m] can be measured using the adhesive strength measurement method by 90-degree peeling described in JIS Z 0237 (2009), and is expressed as P/W from the width W [mm]. When the thickness of the release film, i.e., the film thickness t, is 100 μm or less, the standard release characteristics require that the easy-to-peel film material has T·W·t exceeding P·W. The standard release characteristics and the characteristics of the release film obtained by the manufacturing method of the present invention will be described in detail below.

First, the configuration of the apparatus used in the manufacturing method of the present invention will be explained with reference to the drawings.

<Configuration of manufacturing equipment>
Fig. 1 is a schematic diagram showing an example of a waterless offset master plate manufacturing apparatus 100. Fig. 2 is a front view showing in detail the coating process, which is part of the manufacturing apparatus 100 of Fig. 1, and Figs. 3 and 4 are side views of the coating process, which is also part of the manufacturing apparatus 100 of Fig. 1, with Fig. 3 showing a first coating process and a first solidification process, and Fig. 4 showing a second coating process and a second solidification process. Fig. 5 is a front view showing a drying and solidification process, which is also part of the manufacturing apparatus 100 of Fig. 1.

In Figure 1, the first application process for applying a liquid release film material includes at least a first fountain-type application nozzle 121a that sprays the coating material and a first application and recovery unit 122a that has the function of supplying and recovering the coating material, and the release film material is applied to the surface of a cylindrical substrate. The manufacturing apparatus 100 shown in Figure 1 rotates the cylindrical substrate 111 to be coated about its axis while moving the first application nozzle 121a, which dispenses the coating material, back and forth in a movement direction P that indicates the axial direction of the cylindrical substrate 111, applying coating material F to the outer peripheral surface of the substrate in layers. Then, while the cylindrical substrate 111 is rotated about its axis, an airflow is sprayed from an airflow solidification means 141 toward the coating material F on the outer peripheral surface of the substrate, drying and solidifying the coating material F.

In Figure 1, the second coating process for applying the silicone film material includes at least a second coating nozzle 121b and a second coating and recovery unit 122b, which are shown waiting away from the cylindrical substrate in Figure 1 to carry out the second coating process. Then, although not shown in Figure 1, after the first coating process and the first solidification process, the second coating nozzle 121b and the second coating and recovery unit 122b apply the silicone material onto the release film, and after the second solidification process, a silicone film is formed, resulting in the production of a waterless offset printing plate.

The manufacturing apparatus 100 in Figure 1 is shown with one airflow solidification means 141 used in the first and second solidification steps, but multiple airflow solidification means may be provided, each of which independently performs drying and solidification. Note that Figure 1 shows the airflow solidification means 141 as a slit-type nozzle with a slit-shaped airflow outlet in the axial direction of the cylindrical substrate, but other nozzle shapes may also be used.

When spraying an airflow onto the coating surface around the substrate using the airflow solidification means 141, it is preferable to spray the airflow while the cylindrical substrate is rotating so that the airflow is sprayed across the entire coating surface. This not only promotes drying of the coating with the airflow generated on the substrate surface by the rotation of the substrate, but also suppresses liquid flow in the coating due to the influence of gravity.

During this solidification process, the film thickness value of the coating film is measured using the film thickness sensor 151 shown in Figures 3 and 4, and the measured value is input into the sensor controller 152 to detect the amount of coating film adhered, control the timing of the end of the first coating process and the start of the first solidification process, and also monitor the drying and solidifying state of the coating film by measuring the change in the state of the coating film after the end of the first coating process.

For example, the measurement values captured by the sensor controller 152 are also transmitted to the interlocking operation controller 150. When the amount of coating film deposited in the first coating process reaches a level that allows for transition to the next process, the first solidification process, the interlocking operation controller 150 issues a command to transition to the first solidification process. Then, when the dried and solidified state of the coating film reaches a level that allows for transition to the next process, the second coating process, the interlocking operation controller 150 issues a command to transition to the second coating process. In the second coating process, a silicone functional layer is applied to the surface of the release film while the second coating nozzle 121b shown in FIG. 1 is moved in the axial direction of the cylindrical substrate 111. Subsequently, an airflow is sprayed from the airflow solidification means 141 shown in FIGS. 1 and 4 to dry and solidify the coating, thereby forming a laminate in which multiple functional films are layered on the cylindrical substrate.

The manufacturing apparatus 100 of the present invention may also include a rotation drive means for rotating the cylindrical substrate 111 shown in FIG. 1, a moving means for moving the coating means shown in FIG. 2 in the longitudinal direction of the substrate (the Y direction in the figure), and a film thickness detection unit consisting of a film thickness sensor 151 and a sensor controller 152 shown in FIGS. 3 and 4. The first and second coating nozzles and coating heads, the airflow solidification means 141, and the like may be linked with their respective moving means, rotating means, and film thickness detection unit.

Figures 6(a) to 6(d) show each process and how they are linked together. Figure 6(a) shows a first application process in which droplets of release film material are applied to the surface of a cylindrical substrate in a reciprocating motion, forming a layer of the material. Figure 6(b) shows a first solidification process in which the release film material is dried and solidified to form a release film on the surface of the cylindrical substrate. Figure 6(c) shows an example of a second application process in which a silicone film material is applied to the surface of the release film, and Figure 6(d) shows an example of a second solidification process in which the silicone film material is dried and solidified. Figures 6(a) to 6(d) may be controlled by an interlocking operation controller 150 to operate the processes in sequence.

Each means of the apparatus and the formation of the coating film will be described in detail below.
<Rotational driving means>
The rotation drive means shown in Figure 2 includes left and right rotation central shafts 112 and 113 that support the rotation of a cylindrical substrate 111, support tables 114 and 115 that support the rotation central shafts, an actuator 116 connected to the rotation support shafts to rotate the cylindrical substrate 111, and a rotation speed controller 117 that controls the actuator and controls the rotation speed of the cylindrical substrate 111. The rotation drive means can rotate the cylindrical substrate 111 at any rotation speed, and the rotation speed of the cylindrical substrate 111 can be set to a rotation speed suitable for coating or drying and solidifying. The rotation drive means is preferably controlled independently of the means for reciprocating or linearly moving the first coating nozzle 121a and the second coating nozzle 121b, i.e., the arrows (symbol P) in Figure 1.

<Coating means and means for moving it>
3 is a coating means used in the first coating step, and includes a first coating nozzle 121a that sprays the liquid release film material from a discharge hole and adheres it to the substrate, a first coating and recovery unit 122a that supplies the coating material and recovers any coating material that falls without adhering to the substrate, a first liquid supply pump 123a, and a first coating tank 124a that stores the coating material. The coating liquid travels from the first coating tank 124a through a flow path (not shown) in the first coating and recovery unit 122a, and can be continuously discharged at any desired discharge rate from the discharge hole of the first coating nozzle 121a at the tip of the first coating and recovery unit 122a. Here, the method of supplying the coating material Fa to the first coating nozzle 121a is not particularly limited as long as it can continuously eject the coating material Fa from the coating nozzle. In addition to a method using a metering pump for the first liquid delivery pump 123a, a pressure-feed method (not shown) can also be used in which the first coating material tank 124 is pressurized and the ejection flow rate is controlled by adjusting the pressurization pressure.

Figure 4 also shows the coating means for the second coating nozzle 121b used in the second coating process. Similar to Figure 3, this also includes a second coating and recovery unit 122b that supplies the silicone coating material, a second liquid supply pump 123b, and a second coating material tank 124b that stores the coating material. The coating material Fb can be continuously discharged at any desired rate from the discharge hole of the second coating nozzle 121b at the tip of the second coating and recovery unit 122b. As with the coating means of Figure 3, the method for supplying these coating materials is not limited to a specific method, and the shape of the second coating nozzle 121b and the method for supplying the coating material may be different from those of the coating means of Figure 3.

The movement means for each coating means shown in Figures 2, 3, and 4 includes stages 131a and 131b that support the first coating and recovery unit 122a and the second coating and recovery unit 122b, a slider 132 along which the stage moves, an actuator 133 that drives the slider, and a controller 134 that controls the actuator, and can move the first coating head 121a and the second coating head 121b at any speed in the axial direction of the cylindrical substrate 111. Here, in the first coating step of coating the release film material, the stage 131 may have an adjustment mechanism that adjusts the distance between the coating nozzle 121a in the first coating and recovery unit 122a and the cylindrical substrate 111.

Furthermore, it is preferable that the movement means for the first application nozzle 121a shown in Figure 3 and the movement means for the second application nozzle 121b shown in Figure 4 can be moved and controlled independently, but they may also share the same movement means. During the application operation, the substrate is rotated by the rotation drive means, while the application nozzle 121 is moved back and forth by these movement means. This causes the coating material to be continuously sprayed from the application nozzle 121 onto the circumferential surface of the cylindrical substrate, adhering to the circumferential surface of the substrate, and the coating material is then applied to the entire circumferential surface of the substrate, thereby forming a coating film on the circumferential surface.

The controller 134 shown in FIG. 2 may also be a controller that stores a program for linking the coating means with the movement means of the coating means to determine the return position of the reciprocating movement, and inputting position information from the movement means and executing a predetermined scan. When it is desired to change the film thickness, for example, to thin the coating film at a specific location such as the end of a cylindrical substrate, this linked operation controller 150 can control each parameter related to coating film formation based on the set position information of the movement means, such as changing the return position of the reciprocating movement.

<Solidification means for drying and solidifying the coating film>
Fig. 3 is a schematic diagram of a cylindrical substrate viewed from the side. Fig. 3 shows an airflow solidification means 141 having an outlet for discharging a slit-shaped airflow in the axial direction of the cylindrical substrate. As shown in Fig. 3, the drying and solidification means preferably maintains a constant gap in the radial direction from the peripheral surface of the cylindrical substrate.

The airflow solidification means 141 also includes an airflow injection pressure controller 142 that controls the pressure of the supplied gas, and a compressed gas supply source 143 that supplies compressed gas to the pressure controller, and is capable of continuously injecting an airflow toward the outer circumferential surface of the cylindrical substrate 111. In this case, the gas used for the airflow may be dry air or an inert gas such as nitrogen.

Furthermore, while Figure 3 shows solidification means 141 using an air flow, the solidification means is not limited to this. For example, a solidification method using a light irradiator can be used. However, solidification methods using high-temperature heating or hot air spray, which are used to remove solvents and harden resins, are not preferred for the solidification means of the present invention because they increase the temperature of the substrate and require time to return it to room temperature.

<Film thickness detection unit>
The film thickness detection unit comprises a film thickness sensor 151 and a sensor controller 152 shown in FIGS. 3 and 4 . The film thickness sensor 151 is installed facing the circumferential surface of the cylindrical substrate 111. The film thickness sensor 151 measures the film thickness value of the coating film and inputs the measured values into the sensor controller 152, thereby monitoring the coating film thickness during the coating process and the drying and solidifying state of the coating film during the solidifying process. In this case, the film thickness value measured by the film thickness sensor is preferably measured by measuring the front and back surfaces of the coating film. However, the film thickness value may also be calculated by measuring the surface height of the substrate and the coating film and calculating the film thickness value from the change in height. In this case, the film thickness value detected by the film thickness sensor 151 and the control device 152 is the average film thickness value on the circumferential surface of the cylindrical substrate 111, obtained by averaging multiple measured values measured while the cylindrical substrate 111 is rotating. However, the film thickness value may also be measured only at specific positions on the circumferential surface, and the measured value at that position may be used as the film thickness value.

In addition, in the present invention, the film thickness sensor 151 uses a confocal laser sensor, but any sensor that can measure the film thickness value in the coated film state will do, and is not limited to this.

<About coating of release film material>
A coating film is formed on a cylindrical substrate using the manufacturing apparatus 100 having the above configuration. A method for applying a release film material will now be described. In the coating material filling process, a coating material Fa, which is a sufficiently degassed release film material, is placed in the first coating material tank 124a shown in FIG. 3, and the first liquid supply pump 123a uses the first coating and recovery unit 122a, the first coating nozzle 121a, and the piping connecting the components to fill the coating material Fa. In the coating operation process, the cylindrical substrate 111 is fixed to the rotary support shafts 112 and 113 shown in FIG. 2, and then the cylindrical substrate 111 is rotated at a constant rotational speed in the manufacturing apparatus 100, with the axis of the cylinder as the central axis. At this time, the first coating nozzle 121a, which dispenses the coating material Fa, is in a standby state at the axial end of the cylindrical substrate 111. Next, the first liquid supply pump 123a is operated, and the coating material Fa is sprayed from the first coating nozzle 121a via the first coating and recovery unit 122a. At this time, by spraying the coating material Fa from below the rotating cylindrical substrate 111, some of the sprayed coating material Fa adheres to the underside of the cylindrical substrate 111, but the coating material that does not adhere falls due to gravity and is collected by the coating and recovery unit 122a. Then, by moving the coating nozzle 121 and the coating and recovery unit 122 in the axial direction of the cylindrical substrate 111, the coating material F adheres to the circumferential surface of the substrate, forming a coating film. During this coating operation, by making the movement amount of the coating nozzle 121 during one rotation of the cylindrical substrate 111 less than the width of the coating film to be adhered, the coating films overlap at the edges, forming a planar coating film.

The coating material F used in this coating operation is preferably one that can be controlled to adhere to the cylindrical substrate 111 in small amounts, has a low coating viscosity, and is highly diluted with solvent, i.e., has a low solids concentration. A preferred application range for coating is one with a coating viscosity adjusted to 0.01 P to 1 P, more preferably 0.03 P to 0.5 P. That is, in the first coating step of the present invention, the viscosity of the coating liquid of the release film material discharged from the first applicator can be in the range of 0.01 P to 1 P. More preferably, the viscosity of the coating liquid of the release film material is 0.03 P to 0.5 P. The unit of viscosity for the coating liquid is Poise.

In order to stably spray the peel-off film material Fa from the nozzle hole of the first application nozzle 121a, it is better to have a larger nozzle hole of the application nozzle 121a, and it is preferable to use a nozzle hole with a diameter of 0.1 mm or more. On the other hand, if the nozzle hole of the application nozzle 121a is too large, the discharge flow rate required for spraying becomes large, making it difficult to control the small amount of adhesion, so it is preferable that the diameter of the nozzle hole is 1 mm or less.
<About the drying and solidification of the release film and silicone film>
First, Figure 5 shows the configuration of an apparatus for drying and solidifying a coating film. Figure 5(a) shows a drying and solidifying means using solidifying means 141 using an airflow, and Figure 5(b) shows a configuration for solidifying a coating film using a light irradiator 151, which will be described later. Figures 5(a) and (b) are shown representatively for the first coating step. The coating film in the following description is a coating film coated with a release film material.

First, the drying and solidifying process will be described for the configuration shown in Figure 5(a). After a coating film is applied to the substrate by the coating means, the substrate is rotated while an airflow is sprayed from the airflow spraying means toward the circumferential surface of the cylindrical substrate, thereby accelerating the drying of the coating film and causing it to dry and solidify.

In this drying and solidifying process, it is effective to increase the temperature of the airflow by about 10 to 30°C above room temperature in order to shorten the processing time. However, if the temperature of the cylindrical substrate rises excessively after drying and solidifying, thermal distortion will occur in the cylindrical substrate, which will affect the accuracy of the pattern formation in the next process. Therefore, it is preferable to carry out the process at room temperature without increasing the temperature of the airflow.

Next, Figure 6 shows an example of a method for forming a laminate of a release film and a silicone film. The steps are performed in the following order: first application step (a), first solidification step (b), second application step (c), and second solidification step (d). After each application step is completed, an airflow is sprayed over the entire coating film to promote drying and solidification. Furthermore, the second application step can be started while the cylindrical substrate is rotating during the first solidification step. This is preferable from the perspective of further enhancing adhesion by applying a silicone layer and drying the laminate together before the release film surface has completely solidified.

In this process, the cylindrical substrate is rotated in each of steps (a) to (d), but the rotation speed does not have to be the same. For example, if the coating is performed at a rotation speed of 500 rpm and then the drying and solidification is performed at a reduced speed of 25 rpm, the coating material is more likely to level on the coating surface before solidification, resulting in the formation of a high-quality coating film without coating streaks.

Another method of drying and solidifying the coating is to use a photocurable resin, which can be easily solidified at room temperature. In this case, if a photocurable resin that does not require a diluting solvent is used, there is no need to use an air jetting means. However, since a light irradiator is required to solidify the resin, it is advisable to install a light irradiator 161 and a controller 162 that controls the irradiation time, as shown in Figure 5(b), within the device, and irradiate the substrate with light while it is rotating to solidify the coating on the substrate.

<About the release film>
In order to reuse the cylindrical substrate used for a waterless offset master plate, after the desired printing is completed, the coating film formed on the cylindrical substrate is removed, and a coating film for a new master plate is formed on the substrate again, thereby reusing the cylindrical substrate.

In offset printing, the resist film on the substrate is removed by washing and dissolving it with chemicals. However, if the silicone material used in waterless lithography is removed from a cylindrical substrate using the same method, the silicone material will adhere to the surface of the cylindrical substrate. Once adhered, the silicone material will remain in a thin layer on the surface of the cylindrical substrate, which changes the surface condition when the cylindrical substrate is reused, resulting in a decrease in the quality of the master plate.

For this reason, one method of removing the silicone material is to form a release coating (release film) on the surface of the cylindrical substrate below the silicone layer, and then peel the release film off the cylindrical substrate together with the silicone layer in a film-like form, thereby enabling stable initialization of the cylindrical substrate.

The primary function required of a release film is that it can be easily peeled from the cylindrical substrate. To achieve this, it is preferable to use a release film material with film properties that satisfy the following formula (1). Release materials that have this property are determined to have easy peelability, and release materials with such peelability properties are called easy-to-peel film materials.

When peeling a release film from a substrate, the forces acting on the film are the tensile force [N] that tries to peel the film off and the adhesion force [N] that tries to keep the film attached to the substrate. If the tensile force [N] is greater than the adhesion force [N], the film can be peeled off from the substrate.

When this relational expression is transformed into a balance of forces per unit width [1/mm], it becomes as shown in Equation (1).
Tensile strength (N/mm ² )×coating film thickness (mm)>adhesive strength (N/mm) Formula (1)
The tensile strength [N/ ^mm2 ] on the left is the maximum tensile force [N] that can be generated without the film breaking, divided by the cross-sectional area of the film [ ^mm2 ], and multiplied by the coating thickness [mm] to obtain the tensile force [N] per unit width [1/mm]. The adhesive strength [N/mm] on the right is the adhesion force [N] per unit width [1/mm].

In this formula (1), the tensile strength x coating thickness represents the film strength that the film can withstand when peeled off in its film state. If the force applied is less than this film strength, the release film will not tear and will be able to maintain its shape. Furthermore, the adhesive strength (right-hand term) represents the resistance force that arises when peeling the release film from the substrate. If the film is pulled up with a force greater than this resistance force, it can be peeled off from the substrate. In other words, with materials that satisfy formula (1), the release film can be continuously peeled off from the substrate while maintaining its shape. However, under conditions that do not satisfy formula (1), the release film will tear when peeled off, and it will take a great deal of effort to remove all of the release film from the substrate. Thus, whether a release film has easy peelability can be determined not only by whether the film material satisfies formula (1), but also by observing how the release film peels off from the substrate.

Here, each item in formula (1) will be explained. The tensile strength in the left term is the material strength of the release film material in a film state, and can be measured using a tensile tester specified in JIS B 7721 (2018). The tensile strength of the release film is preferably 20 N/mm ² or more in order to maintain the functional film as a master, and more preferably 40 N/mm ² or more in consideration of stability. Similarly, the coating film thickness in the left term is the film thickness when dried and solidified as a release film. The thicker the film thickness, the better the strength of the film. However, as the film thickness increases, the longer it takes to dry and solidify, and the higher the material costs, so an appropriate film thickness is required. The thickness of this release film is preferably 100 μm or less, and more preferably 50 μm or less in order to dry and solidify in a short time.

Next, the adhesive strength in the right column is measured based on the adhesive strength measurement method using 90-degree peeling as described in JIS Z 0237 (2009), with the substrate having the same surface roughness as the surface finish of the cylindrical substrate. Here, the surface condition of the cylindrical substrate in this disclosure is aluminum (A5052) as the base material, with an average roughness of the finished surface of Ra 1.6.

Furthermore, according to the relationship in formula (1), the smaller the adhesive strength of the release film, the greater the tendency for it to be easily peeled off, but on the other hand, the ability of the functional film to be retained on the cylindrical substrate during printing decreases. For this reason, it is desirable to have a large adhesive strength within the conditions that satisfy formula (1), but when considering the ease of manual peeling with fingers, an adhesive strength value of 0.50 N/mm or less is preferable, and 0.10 N/mm or less is even more preferable.

The adhesive strength of the release film to the cylindrical substrate is also increased by the force with which the release film tightens the cylindrical substrate, in addition to the adhesive strength with the substrate as shown in formula (1). Therefore, if you want to maintain adhesion to the substrate while using a release film material that is easier to release, you can use the shrinkage properties of the release film to shrink the release film on the cylindrical substrate, thereby increasing the holding force of the cylindrical substrate.

<About the production of waterless offset master plates>
When using a cylindrical substrate to manufacture a waterless offset master plate using the coating method and manufacturing apparatus of the present invention, a release film is formed on the surface of the substrate in a first coating step and a first solidification step, and then a silicone layer is formed on the release film in a second coating step and a second solidification step.

In more detail, in the first coating step, a coating film is formed on the cylindrical substrate while the cylindrical substrate is rotating, using an amount of release film material calculated from the film thickness after drying and solidification. During this coating, a larger amount of coating liquid is sprayed from the first coating nozzle than the amount of material needed to form the coating film, and a portion of it is deposited on the cylindrical substrate, allowing for application with a small deposition amount while maintaining the flow rate required for spraying. Controlling the deposition amount to a small amount makes it possible to form a thin film layer by the time the target film thickness is reached. The increased deposition amount reduces the likelihood of leaving traces of the spiral coating, resulting in a high-quality coated surface. For example, if the rotation of the cylindrical substrate is stopped midway, gravity will cause the coating material to flow, resulting in an uneven coating film. Therefore, it is preferable to maintain the rotation of the cylindrical substrate from start to finish during this coating film formation process.

Next, in the first coating step, when the coating thickness of the release film measured by the film thickness sensor reaches the set film thickness, the first coating step is terminated, and the first solidification step is carried out while the cylindrical substrate is kept rotating to prevent the shape of the liquid film from collapsing. In the first solidification step, room temperature air is blown onto the coating surface to promote drying, and at the same time, the liquid film shrinks and solidifies, solidifying so that the release film grips the cylindrical substrate. In this case, in addition to air blowing, the liquid film can also be solidified by using a photocurable resin as the release film material and then irradiating it with light. Resin curing by light irradiation has the advantage of minimizing the temperature rise of the substrate, as well as the advantage of completing the solidification step in a short time.

Next, the first solidification process is terminated by determining the dryness state based on the film thickness sensor measurement value, and the process then moves on to the application of the silicone film material in the second coating process. The transition from the first solidification process to the second coating process can be carried out after the release film has completely solidified in the first solidification process, but by transitioning before the release film surface has completely solidified, the master production time can be shortened and the adhesion between the release film and the silicone layer can be expected to be further improved. Furthermore, the release film is dried and solidified by further drying in the second solidification process. After the second coating process is completed, the second solidification process can be carried out to produce a waterless offset master plate having a release film and silicone layer on a cylindrical substrate.

The waterless offset printing plate manufactured in this way has a release film formed as a uniform coating on the peripheral surface of the cylindrical substrate, making it less likely for the release film to peel off during printing and resulting in high film durability.

Furthermore, when reusing the cylindrical substrate, since the release film is made of an easily peelable material, by scratching part of the film surface with a cutter or the like to create a starting point for peeling, the release film can be easily peeled off by hand from the cylindrical substrate together with the silicone layer.
In addition, in this disclosure, the functional film of the waterless offset master plate has been described as having a two-layer structure consisting of a release film and a silicone layer, but in addition to these two layers, for example, a heat-sensitive layer for forming a printing pattern between the release layer and the silicone layer may be provided, or a protective film that can be easily peeled off may be provided on the outside of the silicone layer. In this case, just as in the case of forming a silicone layer on a release film, by increasing the number of coating nozzles, coating means, and coating nozzle movement means for the coating material according to the number of coating films, a laminated film can be formed in a manner similar to the second coating step and the second solidification step.

The following examples illustrate specific aspects of the present invention. However, the present invention is not limited to these examples.

For Examples 1 and 2 and Comparative Example 1, evaluation samples of the master plate were prepared under the respective conditions, and then the durability of the functional film was evaluated assuming printing, and the peelability of the release film was evaluated assuming substrate recycling.

Durability was evaluated by pressing a rubber roller, simulating the blanket used in offset printing, against the outer surface of the master plate and running the plate for long periods of time, 50 and 100 hours, to see whether the functional film could maintain adhesion to the cylindrical substrate. Evaluations were made to determine whether the release film had lifted or peeled off from the substrate, and whether the silicone film had peeled off from the release film, and the conditions were checked visually. The evaluation criteria were "Good: ◯" if no change in the condition of the functional film occurred after the set durability time (50 hours, 100 hours); "Bad: ×" if defects such as peeling or tears were observed in the functional film; and "Slightly poor: △" if the functional film had lifted off, which was a precursor to the problem but did not reach the "×" rating.

Removability was evaluated by simulating the manual removal of the release film from the substrate. A cut was made at the end of the functional film on the cylindrical substrate, and the laminate of the release film and silicone film was peeled off from the cylindrical substrate while peeling in the circumferential direction. Peelability was evaluated as "Good: ◯" if the laminate could be easily peeled off without breaking; "Poor: ×" if the laminate was torn in three or more places and was difficult to peel; and "Slightly Poor: △" if the laminate was possible to peel off but was torn in two or fewer places and was difficult to peel off.

Example 1
Using a manufacturing apparatus similar to that shown in Figures 1-4, a laminate of a release film and a silicone film was formed on a cylindrical substrate using the procedure shown in Figure 6. A cylindrical substrate with an outer diameter of 185 mm and an axial length of 300 mm was used. In the first coating step, the amount of coating film applied was set so that a uniform, flat coating film would form on the cylindrical substrate's periphery, resulting in a film thickness of 50 μm after drying and solidifying. A fountain-type coating nozzle with an outlet diameter of 0.08 mm was used to apply the release film while the substrate was rotating at 50 rpm. In the next solidification step, the substrate rotation speed was reduced to 25 rpm, and a slit-type air nozzle was used to spray an airflow at a discharge velocity of 90 m/sec for 10 minutes while the substrate rotation speed was maintained at 25 rpm, allowing the coating to dry and solidify. In the second coating step, the rotation speed of the substrate was increased to 500 rpm, the film thickness was set to 10 μm after drying, and a fountain-type coating nozzle with an outlet diameter of 0.5 mm was used to apply the silicone film material in a spiral pattern. In the second solidification step, the rotation speed of the substrate was reduced to 25 rpm, and using the same slit-type air nozzle as used in drying the peeled film, an air flow with a discharge velocity of 90 m/sec was sprayed for 10 minutes while the rotation speed of the substrate was maintained at 25 rpm, and the coating was dried and solidified.

The results of the confirmation of the durability of the functional film and the peelability of the release film are shown in Table 1. In the durability confirmation, in Examples 1 to 3, there were no problems with lifting or peeling of the release film or peeling of the silicone film even after 100 hours had passed.

The release film material was a diluted solution of polyurethane with a solids concentration of 5 wt% and N,N-dimethylformamide as the main solvent. The liquid viscosity of the diluted solution material was 10 cP, and the adhesive strength of the film after drying and solidification was 0.10 N/mm, while the tensile strength was 40 N/ ^mm2 and the film thickness was 50 μm, making it easy to peel.

Example 2
In the first solidification step, a manufacturing apparatus with the configuration shown in Figures 1 to 4, but with the addition of the light irradiator shown in Figure 5(b), was used. A photocurable coating material was used as the release film material to form a release film and a silicone film on a cylindrical substrate. In the first coating step, a cylindrical substrate with an outer diameter of 185 mm and an axial length of 300 mm was used. When a uniform, flat coating film was formed on the circumferential surface of the cylindrical substrate, the coating amount was set so that the film thickness after solidification would be 50 μm. A fountain-type coating nozzle with an outlet diameter of Φ0.2 mm was used, and the release film was applied in a spiral pattern while the substrate was rotating at 500 rpm. Next, in the first solidification step, the rotation speed of the substrate was reduced to 25 rpm, and a light irradiator with an irradiation dose of 300 mW/ ^cm2 was used. Light irradiation was continued for 5 minutes while the rotation speed of the substrate was maintained at 25 rpm, solidifying the coating. Next, in the second coating step, the rotation speed of the substrate was increased again to 500 rpm, the liquid feed rate was adjusted with the liquid feed pump so that the film thickness after drying and solidifying would be 10 μm, and the silicone material was applied in a spiral pattern using a fountain-type application nozzle with an outlet diameter of Φ0.5 mm. Next, in the second solidification step, the rotation speed of the substrate was reduced to 25 rpm, and using a slit-type air nozzle, an air flow with an outlet velocity of 90 m/sec was continuously sprayed for 10 minutes while the rotation speed of the substrate was maintained at 25 rpm, drying and solidifying the coating film, producing a master plate with a base release layer and an upper silicone film.

The peelable film material used was a photocurable resin made from polyurethane, and the film shrinkage rate when the material solidified was 10%, the liquid viscosity was 50 cP, the adhesive strength in the film state was 0.08 N/mm, the tensile strength was 40 N/ ^mm2 , and the film thickness was 50 μm, making it easy to peel.
<Comparative Example 1>
In Example 1, the coating method for the first coating step was changed to droplet spraying using a spray, and the release film material was spirally coated to a film thickness of 50 μm. The axial movement in the spiral coating was completed in one go, and no layer coating was performed. Furthermore, after the first solidification step, the release film was dried and solidified, and a silicone layer was formed in the same manner as in Example 1.

The durability of the functional film and the releasability of the release film were confirmed using waterless offset master plates manufactured under the conditions of Examples 1-3 and Comparative Example 1. The results are shown below. To confirm durability, each master plate was set in a testing machine capable of rotating and holding the plate. While held at a rotation speed of 200 rpm, a rubber roller was pressed against the plate surface with a load of 10 kg, and the plate surface condition was visually confirmed after 50 and 100 hours. In Examples 1-3, there were no problems with lifting or peeling of the release film or peeling of the silicone film, even after 100 hours. In Comparative Example 1, however, although there was no peeling of the silicone film, cracks occurred in parts of the release film over time, and the release film broke and peeled off from the substrate before 100 hours had passed.

To check the peelability, a cut was made in the functional film of the master plate with a cutter, partially breaking the release film, and the functional film was then pulled with the fingers from that point to check whether the release film could be easily peeled off. The results of checking the durability of the functional film and the releaseability of the release film are shown below. In the peelability check, the release film could be peeled off by hand under all conditions, but in Comparative Example 1, the film was prone to tearing during peeling.

100: Waterless offset master plate manufacturing apparatus 110: Rotation drive means 111: Cylindrical substrate 112, 113: Rotation center shaft 114, 115: Support table 116: Actuator 117: Rotation speed controller 121a: First coating nozzle 121b: Second coating nozzle 122a: First coating and recovery unit 122b: Second coating and recovery unit 123a: First liquid supply pump 123b: Second liquid supply pump 124a: First coating material Tank 125b: Second coating material tank 131a: First applicator stage 131b: Second applicator stage 132: Slider 133: Actuator 134: Controller 141 for controlling movement of coating means: Airflow solidification means 142: Airflow spray pressure controller 143: Compressed gas supply source 150: Interlocking operation controller 151: Film thickness sensor 152: Sensor controller 160: Light irradiator 161: Controller for controlling irradiation time F: Coating material Fa: Coating material for first coating process Fb: Coating material for second coating process R: Rotation direction P: Reciprocating movement direction

Claims (7)

A method for manufacturing a waterless offset master plate, comprising: a first coating step of coating a liquid release film material on a surface of a cylindrical substrate; a first solidification step of drying and solidifying the release film material to form a release film on the surface of the cylindrical substrate; a second coating step of coating a silicone film material on the surface of the release film; and a second solidification step of drying and solidifying the silicone film material,
The release film material is a release film material in which, when the coating film thickness is 100 μm or less in terms of standard release characteristics after drying and solidification, the product of the tensile strength [N/mm ² ] of the release film and the coating film thickness [mm] exceeds the adhesive strength [N/mm] of the release film;
the first coating step is a step of spraying the release film material from a first applicator provided below the cylindrical substrate onto the circumferential surface of the cylindrical substrate while rotating the cylindrical substrate about its axis as a central axis, and coating the liquid release film material onto the surface of the cylindrical substrate while adhering the liquid release film material to the surface of the cylindrical substrate;
the first solidification step is a step of drying and solidifying the applied release film material while rotating the cylindrical substrate following the first application step, thereby shrinking the applied release film material on the cylindrical substrate and forming the release film on the cylindrical substrate;
the second coating step is a step of discharging the silicone film material from a second applicator and coating the silicone film material on the surface of the release film;
A method for producing a waterless offset master plate, in which a laminate including at least the release film and a silicone film is formed on the surface of a cylindrical substrate. The method for manufacturing a waterless offset master plate according to claim 1, wherein the first coating step involves moving the first applicator back and forth in the axial direction of the cylindrical substrate while rotating the cylindrical substrate, thereby spraying the release film material onto the peripheral surface of the cylindrical substrate to form a coating film. The method for producing a waterless offset master plate according to claim 1 or 2, wherein the viscosity of the liquid release film material is 0.01 to 1 poise. The method for manufacturing a waterless offset master plate according to any one of claims 1 to 3, wherein the second coating process is started while the cylindrical substrate is rotated during the first solidification process. The method for producing a waterless offset master plate according to any one of claims 1 to 4, wherein the first solidification step and the second solidification step are carried out by using air generated by rotation of the cylindrical substrate or by blowing air from an air nozzle onto the coating surface on the cylindrical substrate. The method for manufacturing a waterless offset master plate according to any one of claims 1 to 4, wherein a photocurable resin is used as the release film material, and after the release film material is applied, the substrate is rotated and irradiated with light to solidify the release film material. a first coating means having a fountain-type first coating nozzle provided below the cylindrical substrate for coating a first coating material on the peripheral surface of the cylindrical substrate; and a second coating means having a second coating nozzle for coating a second coating material on the peripheral surface of the cylindrical substrate;
a rotation drive means for rotating the cylindrical substrate about the axis of the cylinder;
a solidification means for solidifying the coating film applied to the peripheral surface of the cylindrical substrate by blowing air from an air nozzle or irradiating light;
The apparatus includes at least a measuring device for measuring a film thickness value of a coating film, and a controller for switching between the first and second coating means and the solidifying means,
The first and second coating means include a moving means for moving the first coating nozzle and the second coating nozzle in the direction of the rotation axis of the cylindrical substrate, and further, the coating material is applied by moving the first and second coating nozzles by the moving means while the cylindrical substrate is rotated by the rotation drive means, and
The second coating means stops the solidifying means based on the measurement value of the measuring device, and then starts a coating process by the second coating means.