JP2005342658A - Laser drying method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser drying method and an apparatus therefor by which drying energy efficiency is improved and compactification of the apparatus is attained, which are excellent in speeding up of switching of drying conditions and which hardly produce drying unevenness even when rapid drying is performed. <P>SOLUTION: When web-shaped matter to be dried 12 is dried by being irradiated with laser beams from a laser irradiation means 14, the laser beams are diffused by a plano-convex cylindrical lens 16A so that the luminous flux cross section of the laser beam may be spread in a web width direction of the matter to be dried 12 and further the matter to be dried 12 is moved in a longitudinal direction of the web while irradiating the matter to be dried 12 with diffused laser beams. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a laser drying method and apparatus, and in particular, a laser drying method suitable for drying an object to be dried such as a coating material in which a coating liquid is coated on a metal, plastic, paper, or a composite support thereof, or a film. And an apparatus.

  As drying methods of the drying equipment, hot air drying method in which hot air is applied to the object to be dried, infrared drying method in which infrared light from an infrared lamp is applied to the object to be dried, contact with the object to be dried on a heated roll There are heating roll drying etc. which convey and dry. Among these drying methods, a hot-air drying method is generally used for drying a coated material or a film coated on a support. As described in Patent Document 1, the hot air drying method is configured by arranging a plurality of pass rollers in an arch shape from the entrance to the exit in the tunnel-shaped dryer, while wrapping the web to the rollers, What is dried with hot air is widely used. In addition, there is a system in which dry air is supplied from the upper and lower surfaces of the web by a nozzle and the web is dried while being conveyed in a non-contact manner.

  However, the hot air drying method has a large energy loss that is effectively used for drying and has poor drying efficiency.If the hot air speed is increased to achieve high speed drying, the film surface of the coating will be disturbed, causing streaks, unevenness, etc. There is a drawback that the surface defects are easily generated. Furthermore, since a tunnel-shaped dryer for preventing hot air from escaping is required, there is a disadvantage that the apparatus becomes large. Since the infrared drying method and the heating roll method are methods for drying an object to be dried by heat conduction in the same manner as the hot air drying method, energy loss is large and the apparatus tends to be large. In addition, these drying methods using heat conduction have a drawback that even if the drying conditions are switched depending on the lot of the object to be dried, the drying conditions are not immediately changed and it takes time to switch the drying conditions.

By the way, in addition to the drying method described above, Patent Document 2 introduces a laser drying apparatus for printing. This laser drying device utilizes the fact that when the printing surface is irradiated with laser light, the printing surface is heated by the laser light. The laser light is reflected by a rotating polygon mirror so that the laser light is directed in the width direction. The printed surface of the printed material conveyed by scanning is dried.
JP-A-6-63487 JP 7-144403 A

  However, since the laser drying apparatus of Patent Document 2 scans the laser beam, when the conveyance speed of the printed material is increased and high-speed drying is performed in order to increase productivity, drying unevenness is likely to occur and surface defects are likely to occur. . In addition, there are various restrictions in drying such that the printing speed has to be lowered when the width of the printing surface, that is, the scanning width is increased.

  The present invention has been made in view of such circumstances, and is a laser drying method that is excellent in improving drying energy efficiency, downsizing the apparatus, speeding up switching of drying conditions, and hardly causing unevenness in drying even at high speed drying. And an apparatus.

  According to a first aspect of the present invention, there is provided a laser drying method for drying a material to be dried by irradiating a web-shaped material to be dried with a laser beam from a laser irradiation means. While diffusing the laser beam so that a beam cross section spreads in the web width direction of the object to be dried, and irradiating the object to be dried with the diffused laser light, either the object to be dried or the laser irradiation means is applied. The object to be dried is moved in the longitudinal direction of the web.

  According to the present invention, when the object to be dried is irradiated with laser light from the laser irradiation means, the object to be dried is heated by the laser light, and thereby the object to be dried is dried. In this way, by using laser light as a heat source for drying, compared with the conventional drying methods that dry the object to be dried by heat conduction, such as hot air drying method, infrared drying method, heating roll drying, etc., the drying energy The efficiency can be improved, the apparatus can be made compact, and the drying conditions can be switched quickly. In the present invention, since the laser beam is diffused so that the beam cross section of the laser beam spreads in the web width direction of the object to be dried, the object to be dried is irradiated with the laser beam all at once in the web width direction. Can be heated. As the shape of the light beam cross section of the diffused laser light, a shape having an extension in the web width direction such as an elliptical shape or a rectangular shape is preferable. Accordingly, unlike conventional laser drying (Patent Document 2), it is not necessary to scan the laser beam in the web width direction, and thus it is difficult to cause uneven drying in the web width direction even when drying at high speed.

  By the way, the conventional laser drying device scans spot-shaped laser light and irradiates the surface of the object to be dried one after another in the width direction, so even if the spots are continuous in the web width direction of the object to be dried Since the spot main body portion and its peripheral portion are non-uniform in terms of thermal energy, it is not possible to obtain a band-like region that is energetically uniform in the web width direction. Therefore, in the conventional laser drying apparatus, unevenness of drying is likely to occur and surface defects are likely to occur, and in particular, when high-speed drying is performed by increasing the conveyance speed of the printed material in order to increase productivity, the spot main body portion and its periphery Since unevenness in thermal energy between the portions tends to increase, drying unevenness also increases. Here, the light beam cross section refers to a cross section orthogonal to the optical axis of the laser light. Further, the drying unevenness refers to a distribution of water content or solvent content in the dried material after drying.

  A second aspect of the present invention is characterized in that, in the first aspect of the present invention, the diffused laser light is diffused so that the length in the web width direction of the cross section of the light beam of the laser beam is three times or more the length in the web longitudinal direction. This is because even if the laser drying apparatus of the present invention is configured with less than 3 times, the use as an actual apparatus becomes extremely difficult.

  A third aspect of the present invention is characterized in that, in the first or second aspect, both ends of the beam cross section of the diffused laser light in the web width direction are cut. Although this depends on the extent to which the laser beam is diffused, the energy in the end portion in the diffusion direction of the diffused laser beam is smaller than that in the central portion. Accordingly, by cutting the end portion in the laser light diffusion direction, the energy distribution accuracy in the direction in which the laser light is diffused can be improved, so that the occurrence of drying unevenness can be further suppressed.

  A fourth aspect of the present invention is the method according to the first or second aspect, wherein a plurality of the laser irradiation means are arranged in the web width direction, and a laser beam cross section of each laser irradiation means spreads in the web width direction of the object to be dried. While diffusing light, the edge part of the cross section of the light beam of the diffused laser beam is made to overlap each other on the surface of the object to be dried.

  When multiple laser irradiation means are arranged in the web width direction so that the cross section of the laser beam of each laser irradiation means spreads in the web width direction of the object to be dried, the dimension in the web width direction of the object to be dried is long Can also respond. Furthermore, by making the end portions in the web width direction of the beam cross section of the diffused laser light overlap each other on the surface of the object to be dried, the end portions in the diffusion direction of the diffused laser light are compared with the central portion. The problem of reduced energy can also be solved.

  A fifth aspect of the present invention is the lithographic printing plate according to any one of the first to fourth aspects, wherein the web-like object to be dried is a lithographic printing plate having a photosensitive layer formed on a support, and the photosensitive layer is dried with the laser beam. A laser light source having a wavelength that does not cause fogging in the photosensitive layer is used as the laser light source of the laser irradiation means.

  This is because it is possible to make the most of the fact that the laser light is monochromatic light. The photosensitive region of the photosensitive layer can be selected from a variety of laser light sources such as Yg laser, carbon dioxide laser, and He-Ne laser. By selecting a laser light source having a wavelength that is avoided, fogging of the photosensitive layer can be reliably prevented.

  According to a sixth aspect of the present invention, in order to achieve the above object, in a laser drying apparatus for drying a material to be dried by irradiating the material to be dried with a laser beam from a laser irradiation means. Either the laser diffusing means for diffusing the laser beam so that the cross section of the light beam spreads in the web width direction of the object to be dried and either the object to be dried or the laser irradiation means are moved in the longitudinal direction of the web of the object to be dried. And a moving means. A laser drying apparatus comprising the moving means.

  The sixth aspect is configured as an apparatus for performing the laser drying method according to the first aspect.

  A seventh aspect of the present invention is characterized in that, in the sixth aspect, the laser diffusing means is a plano-convex cylindrical lens or an uneven cylindrical lens.

  By using a plano-convex cylindrical lens or an uneven cylindrical lens, a spot-like laser beam can be diffused and spread in the curvature direction of the lens at the time of incidence.

  An eighth aspect of the present invention is the method according to the sixth or seventh aspect, wherein cutting means is provided between the laser diffusing means and the material to be dried to cut both ends in the web width direction of the light beam cross section of the diffused laser light. Features.

  Thereby, since the problem that the energy of the end portion in the diffusion direction of the diffused laser light is smaller than that of the central portion can be solved, the occurrence of drying unevenness can be further suppressed.

  A ninth aspect is characterized in that, in the sixth or seventh aspect, a plurality of optical systems comprising the laser irradiation means and the laser diffusion means are arranged in the web width direction of the object to be dried.

  Thereby, even when the dimension of the to-be-dried material in the web width direction is long, it can respond.

  A tenth aspect of the present invention according to the ninth aspect is the optical system according to the ninth aspect, wherein the plurality of optical systems are arranged so that end portions in a web width direction of a light beam cross section of the diffused laser light overlap each other on the surface to be dried. .

  Thereby, the problem that the energy in the end portion in the diffusion direction of the diffused laser light is smaller than that in the central portion can be solved.

  An eleventh aspect is characterized in that, in the ninth or tenth aspect, a plurality of optical systems including the laser irradiating means and the laser diffusing means are arranged in a longitudinal direction of the web of the object to be dried.

  Thereby, since the irradiation width of the laser beam with respect to the longitudinal direction of the web of the object to be dried can be increased, a long irradiation time can be secured even if the moving speed of the object to be dried is increased. Thereby, it becomes easy to respond by high-speed drying.

  According to the present invention, it is possible to provide a laser drying method and apparatus that are excellent in improving drying energy efficiency, downsizing the apparatus, and speeding up switching of drying conditions and are less likely to cause uneven drying even when high-speed drying is performed.

  Hereinafter, preferred embodiments of a laser drying method and apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a conceptual diagram of a laser drying apparatus of the present invention for carrying out the laser drying method of the present invention.

  As shown in FIG. 1, the laser drying apparatus 10 mainly includes a laser irradiation means 14 for irradiating a web-shaped object to be dried 12 with laser light, and a beam cross section of the laser light spreads in the web width direction of the object to be dried 12. Thus, the laser diffusing means 16 for diffusing the laser beam and the moving means for moving the object to be dried 12 in the longitudinal direction of the web of the object to be dried 12 are configured. The moving means is not particularly shown, but in the step of drying the web-like object to be dried 12, the object to be dried 12 is wound by winding the object to be dried 12 wound in a roll shape around a delivery machine with a winder. Is generally used (see the planographic printing plate original production line in FIG. 7). Moreover, you may provide conveyance rollers, such as a nip roller and a suction roller, between a sending machine and a winding machine. In this embodiment, the object to be dried 12 is moved. However, the object to be dried 12 is fixed, and the optical system 18 including the laser irradiation means 14 and the laser diffusion means 16 is used as the object to be dried 12. It is also possible to make it move with respect to.

  Examples of the web-like material to be dried 12 include a coated material in which a coating liquid is coated on a belt-shaped support, a film manufactured by casting, and the like. Examples of the coated material include a lithographic printing plate having a support provided with a photosensitive layer, an inkjet recording material having a support provided with an ink absorbing layer, and a magnetic recording medium having a support provided with a magnetic layer. It is not limited.

  As the support, a plastic film, a metal plate, paper, a composite support thereof, or a support obtained by applying various undercoat layers to these supports can also be used. As a metal plate, an aluminum plate, a steel plate, a copper plate, and other metal plates can be used. As the aluminum plate, pure aluminum and a material containing a trace amount of foreign elements, or a plastic film on which aluminum is laminated or vapor-deposited can be used. As the plastic film, for example, various plastic films such as olefinic films such as polyethylene and polypropylene, polyvinyl acetate, polystyrene, 6,6-nylon, polyethylene terephthalate, cellulose acetate, and acrylic films can be used. The coating solution for the coated product is not particularly limited, and an organic solvent solution or aqueous solution of a polymer compound, a pigment dispersion, a colloid solution, or the like can be used. Moreover, as a solvent of a coating liquid, various solvents, such as an organic solvent, water, or a mixed system of an organic solvent and water, can be used, and the coated material is dried by volatilizing the solvent from the coating liquid. As the organic solvent, for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, sec-butyl alcohol, acetone, benzene, cyclohexane and the like described in JP-A-62-251739 can be used. it can.

  As a laser light source of the laser irradiation means 14, those of various wavelengths generally used, for example, YAG laser (oscillation wavelength: 1.064 μm), carbon dioxide laser (oscillation wavelength: 10.6 μm), He—Ne laser. Various materials such as (oscillation wavelength: 0.4 to 0.7 μm) can be properly used according to the drying conditions of the object to be dried 12. The laser output needs to be appropriately selected according to the width of diffusing laser light, the intensity of irradiation, and the moving speed of the object to be dried 12, and can be widely used from several MW level to several thousand W level. . Further, the energy irradiated to the object to be dried 12 can be appropriately selected depending on the characteristics of the object to be dried 12, such as whether it is easily heat-denatured, whether it is a photosensitive object, whether the drying speed is fast or slow, etc. Although necessary, in general, energy in the range of 0.01 to 100 J (joule) / second can be preferably used.

  The laser drying apparatus 10 of the present invention can also be suitably used for drying a photosensitive layer when producing a photosensitive material for a lithographic printing plate or a photograph. In this case, avoid the photosensitive area of the photosensitive layer. By selecting a laser light source having a different wavelength, fogging of the photosensitive layer can be prevented during drying. In general, the photosensitive wavelength of the photosensitive layer can be designed in a specific wavelength range by selecting various materials constituting the photosensitive layer, so the material design of the photosensitive layer is changed according to the wavelength of the laser light source. Therefore, the occurrence of fog may be prevented.

  Furthermore, the laser drying apparatus 10 of the present invention can also be used in a drying process for producing a transparent resin film, and is transparent such as PET (polyethylene terephthalate), PP (polypropylene), PE (polyethylene), and acrylic. Since such a resin film has a high laser absorptivity and is heated by absorbing the laser, the solvent and water in the film can be volatilized. For example, PET and PP are known to absorb YAG fourth harmonic laser light (266 nm). Even if the resin film does not have a high laser absorption, a coating solution containing a surface modification that absorbs the wavelength of the desired laser beam or a material that absorbs the laser beam during the surface treatment of the resin film. Can be laser-dried.

  As the laser diffusing means 16, as shown in FIG. 2, a plano-convex cylindrical lens 16A having one flat surface and another convex surface, or an uneven cylindrical lens 16B having one concave surface and another convex surface is preferably used. be able to. The lens material of the cylindrical lens 16A or 16B needs to be a lens material that satisfies laser beam transparency, durability against the laser beam, optical stability in the use atmosphere such as the atmosphere, for example, a carbon dioxide laser GaAs (gallium arsenide), ZnSe (zinc selenium), Ge (germanium), or the like can be preferably used.

  The cylindrical lens 16A or 16B is disposed between the laser irradiation unit 14 and the object to be dried 12, and the laser beam is irradiated from the laser irradiation unit 14 to the object to be dried 12, whereby the cylindrical lens 16A or 16B is applied to the cylindrical lens 16A or 16B. At the time of incidence, the spot-like laser light can be diffused and spread in the direction of curvature of the cylindrical lens 16A or 16B. Thereby, as shown in FIG. 1, the laser beam can be diffused so that the beam cross section of the laser beam spreads in the web width direction of the article to be dried 12. For example, a spot-like carbon dioxide laser beam having a diameter of about 1.5 mm can be extended to about 200 mm in the curvature direction of the plano-convex cylindrical lens 16A by passing through the plano-convex cylindrical lens 16A. The width W (see FIG. 2) of the cylindrical lens 16A or 16B in the curvature direction may be selected in the range of several mm to several hundred mm depending on the width of diffusing the laser light. In this case, if the laser beam is diffused too much, the energy for heating the object to be dried 12 is dispersed and becomes small, and the drying efficiency is deteriorated. As shown in FIG. 5, the cutting means for cutting the both ends in the web width direction of the beam cross section of the diffused laser light is provided, or the ends of the plurality of laser lights diffused in the web width direction are overlapped as shown in FIG. Any of these methods can be used as appropriate.

  The laser drying apparatus 10 in FIG. 3 includes a mask having a rectangular opening 20A (aperture) long in the web width direction of the object to be dried 12 as a cutting means between the cylindrical lens 16A or 16B and the object to be dried 12. 20 is arranged. Thereby, the shape of the light beam cross section of the laser light diffused in the elliptical shape shown in FIG. 4A can be changed to the laser light having a rectangular light beam cross section shown in FIG. In this case, if the mask 20 is too far away from the object 12 to be dried, the laser beam that has passed through the opening 20A of the mask 20 wraps around the back surface (side surface of the object to be dried) of the mask 20 and the light beam cross section is widened. It is preferable to bring it close to the object to be dried 12 to the extent that it does not interfere with the drying. Further, since the mask 20 itself is heated by the laser light cut by the mask 20, the material of the mask 20 is preferably a material used as a refractory having a large heat capacity. A method of cooling the mask 20 by incorporating a cooling device inside the mask 20 can also be suitably employed.

  In FIG. 3, the mask 20 is used as a cutting means. However, by arranging a plurality of lenses between the cylindrical lens 16 </ b> A or 16 </ b> B and the object to be dried 12, the degree of diffusion and the energy distribution due to diffusion are corrected. You may make it do. The length L1 in the web width direction of the beam cross section of the diffused laser light is preferably at least three times the length L2 in the web longitudinal direction. This is because even if L2 / L1 is less than 3 times and the laser drying apparatus 10 of the present invention is configured, the use as an actual apparatus becomes extremely difficult.

  In the laser drying apparatus 10 of FIG. 5, a plurality of optical systems 18, 18, 18 including a laser irradiation unit 14 and a laser diffusion unit 16 are arranged in the web width direction of the object to be dried 12. The laser beam is diffused so that the beam cross section of the laser beam spreads in the web width direction of the object to be dried 12, and the end portions in the web width direction of the beam cross section of the diffused laser light beam overlap each other on the surface of the object to be dried 12. It is a thing. Thereby, the problem that the energy in the end portion in the diffusion direction of the diffused laser light is smaller than that in the central portion can be solved. The number of optical systems 18 arranged in the web width direction of the object to be dried 12 is not limited to three, but the dimension of the object to be dried 12 in the web width direction, the energy required for drying the object to be dried 12, etc. Can be set arbitrarily.

  5 shows a case where a plurality of optical systems 18 are arranged in the web width direction of the article to be dried 12, but a plurality of optical systems 18 may be arranged in the longitudinal direction of the web as shown in FIG. 5 and FIG. 6 may be combined.

  In the present invention, when the laser beam is guided onto the surface of the object to be dried 12, the optical system 18 is disposed at a position away from the moving line of the object to be dried 12 by arranging the mirror at an appropriate position. Is also possible. Thereby, it is not necessary to arrange the entire optical system above the moving line of the object to be dried 12, and the apparatus configuration can be made compact, and the apparatus configuration having various flexibility can be freely configured. Can do.

  The laser drying apparatus 10 of the present invention does not require a tunnel-shaped dryer for preventing hot air from escaping unlike the conventional hot air drying apparatus, but is provided with a device for removing the organic solvent and water volatilized from an object to be dried. It is preferable. For example, it is possible to suitably employ a method in which a suction hood is provided above an object to be dried that is irradiated with laser light, and the solvent and water volatilized from the object to be dried are sucked and removed. In this case, air is blown into the room where the laser drying apparatus is installed, and the volatilized solvent and water are positively excluded to the outside through the suction hood.

  FIG. 7 shows an example in which the laser drying apparatus 10 of the present invention is incorporated in a lithographic printing plate precursor production line 100 in which the present invention can be used particularly effectively.

  As shown in FIG. 7, a long support 24 wound in a roll shape is set in the delivery machine 22. The support 24 continuously delivered from the feeder 22 is subjected to surface treatment in the surface treatment unit 26. The support 24 that has been subjected to the surface treatment is provided with a backcoat layer on the back surface of the support 24 in the backcoat layer coating / drying unit 28, and then an undercoat layer on the surface of the support 24 in the undercoat coating / drying unit 30. Is formed. Next, after the photosensitive layer of the photopolymerizable composition is formed on the undercoat layer in the photosensitive layer coating / drying unit 32, the overcoat layer coating / drying unit 34 includes a water-soluble high-concentration group containing a hydrogen bonding group. An overcoat layer mainly composed of molecules is formed, and the crystallinity of the water-soluble polymer in the formed overcoat layer is controlled within a predetermined range. Next, the overcoat layer is controlled so that the moisture content of the overcoat layer falls within a predetermined range in the overcoat layer humidity control zone 36. The moisture content of the overcoat layer is measured online by the infrared moisture meter 41, and the air conditioning unit 42 of the overcoat layer humidity control zone controls the temperature and humidity of the overcoat layer humidity control zone so that the moisture content data is constant. . The original 24A of the lithographic printing plate manufactured through these steps is wound up by a winder 38.

  The laser drying apparatus 10 of the present invention is used in the drying section of the backcoat layer coating / drying section 28, the undercoat coating / drying section 30 and the photosensitive layer coating / drying section 32 of the lithographic printing plate precursor production line. Can do. In particular, in the drying section of the photosensitive layer coating / drying section 32, by selecting a laser light source having a wavelength that avoids the photosensitive area of the photosensitive layer, fogging of the photosensitive layer during drying can be prevented.

(Example 1)
Using the laser drying apparatus shown in FIG. 1, the coating material was subjected to a drying test.

  A 100 W carbon dioxide laser light source was used as the laser light source of the laser irradiation means. Further, as the laser diffusing means, a plano-convex cylindrical lens having a width (aperture) of the curvature direction of 20 mm is used, and the beam cross section of the laser beam on the surface of the coating material to be dried is 150 mm in the web width direction, the longitudinal direction of the web. A 2 mm elliptical laser beam was obtained.

その結果、乾燥後における塗布物の塗布膜はピンホール等の面欠陥がなく、塗布膜面の含水量は平均で１．２ｇ／ｍ² で十分に乾燥されていた。また、塗布物のウエブ幅方向の含水量分布は３％で小さかった。 Moreover, the coating liquid described in Table 1 was applied on a web-like aluminum plate with a wire bar coating device so that the coating width was 130 mm and the coating amount was 30 cc / m ² to obtain a coated product. While transporting the coated material in the longitudinal direction of the web, the surface of the coated material was irradiated with the laser beam for 5 seconds.

As a result, the coating film of the coated product after drying had no surface defects such as pinholes, and the moisture content of the coating film surface was 1.2 g / m ^{2 on} average and was sufficiently dried. Further, the moisture content distribution in the web width direction of the coated product was as small as 3%.

(Comparative Example 1)
A coated material was prepared in the same manner as in Example 1. This coated material was put into a drying oven and dried with hot air at 90 ° C. for 50 seconds. As a result, the coating film of the coated product after drying had no surface defects such as pinholes, and the moisture content of the coating film surface was 1.3 g / m ^{2 on} average, and was sufficiently dried. The water content distribution was 5.5%, which was larger than Example 1.

  From the comparison between Example 1 and Comparative Example 1, it can be seen that laser drying can suppress the moisture content distribution in the web width direction of the coated product, that is, drying unevenness, as compared with hot air drying.

(Example 2)
The coating solution shown in Table 1 was applied thicker than Example 1 so that the coating width was 130 mm and the coating amount was 50 cc / m ² on a web-like aluminum plate using a wire bar coating device. The coated material was dried in the drying oven used in Comparative Example 1 until it was semi-dry (slightly sticky). The water content of the coated product at this time was 5.2 g / m ² on average. This semi-dried coating was irradiated with laser light for 0.7 seconds using the same laser drying apparatus 10 as in Example 1.

As a result, the coating film of the coated product after drying had no surface defects such as pinholes, and the moisture content on the coating film surface was 1.5 g / m ^{2 on} average, and was sufficiently dried. The water content distribution in the web width direction was small at 3.5%.

(Comparative Example 2)
A coated material was prepared in the same manner as in Example 2. This coated material was put in a drying oven and dried with hot air at 90 ° C. for 50 seconds. As a result, the coating film of the coated product after drying has no surface defects such as pinholes, and the moisture content of the coating film surface is 1.5 g / m ^{2 on} average, and is dried to the same moisture content as in Example 2. However, the water content distribution in the web width direction was 6.2%, which was larger than Example 2.

  From the comparison between Example 2 and Comparative Example 2, even if laser drying is used for finish drying after drying most of the water by hot air drying, drying unevenness is more than that by hot air drying from the beginning to the end. It turns out that it can suppress.

(Example 3)
A laser having a total length of 450 mm in the web width direction using the laser drying apparatus 10 shown in FIG. 2 in which three optical systems 18 comprising laser irradiation means and laser diffusion means are arranged in the web width direction of the coating. Got the light. A 100 W carbon dioxide laser light source was used as the laser light source of the laser irradiation means 14. As the laser diffusing means 16, a plano-convex cylindrical lens is used. And the coating material whose application width is 450 mm was created by the same method as Example 1, and the laser beam was irradiated for 5 seconds.

As a result, the coating film of the coated product after drying had no surface defects such as pinholes, and the moisture content of the coating film surface was 1.28 g / m ^{2 on} average, and was sufficiently dried. Further, the moisture content distribution in the web width direction on the coating film surface was 3.6%, which was almost the same as that in Example 1. As can be seen from this result, in the case of a coating having a large coating width, even if a plurality of optical systems 18 including the laser irradiation means 14 and the laser diffusing means 16 are arranged in the web width direction of the coating, drying unevenness is caused. Does not grow.

Conceptual diagram of the laser drying apparatus of the present invention Explanatory drawing of plano-convex cylindrical lens and concavo-convex cylindrical lens This is an example of laser light diffusion, where the beam cross section is elliptical. This is an example of laser light diffusion, where the beam cross-section is rectangular. Conceptual diagram of multiple laser irradiation means arranged in the web width direction of the object to be dried Conceptual diagram of multiple laser irradiation means arranged in the longitudinal direction of the web of the object to be dried Block diagram of lithographic printing plate production line

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Laser drying apparatus, 12 ... To-be-dried object, 14 ... Laser irradiation means, 16 ... Laser diffusion means, 16A ... Plano-convex cylindrical lens, 16B ... Uneven cylindrical lens, 18 ... Optical system, 20 ... Mask, 22 ... Sending machine , 24 ... support, 24A ... lithographic printing plate raw material, 26 ... surface treatment part, 28 ... backcoat layer coating / drying part, 30 ... undercoat coating / drying part, 32 ... photosensitive layer coating / drying part, 34 ... over Coat layer application / drying section, 36 ... overcoat layer humidity control zone, 38 ... winder, 41 ... infrared moisture meter, 42 ... overcoat layer humidity control zone air conditioning unit

Claims (11)

In a laser drying method of drying a material to be dried by irradiating a web-like material to be dried with laser light from a laser irradiation means,
The laser beam is diffused so that a cross section of the laser beam spreads in the web width direction of the object to be dried, and the object to be dried or the laser irradiation means is irradiated while irradiating the object to be dried with the diffused laser light. Any one of them is moved in the longitudinal direction of the web of the material to be dried.   2. The laser drying method according to claim 1, wherein the diffused laser beam is diffused so that the length in the web width direction of the cross section of the luminous flux is not less than three times the length in the web longitudinal direction.   3. The laser drying method according to claim 1, wherein both ends of the cross section of the diffused laser beam in the web width direction are cut.   A plurality of the laser irradiation means are arranged in the web width direction, and the laser light is diffused so that a cross section of the laser beam of each laser irradiation means spreads in the web width direction of the object to be dried. 3. The laser drying method according to claim 1, wherein ends of the beam cross section in the web width direction overlap each other on the surface of the object to be dried.   The web-like material to be dried is a lithographic printing plate in which a photosensitive layer is formed on a support. The photosensitive layer is dried with the laser beam, and fog is generated in the photosensitive layer as a laser light source of the laser irradiation means. The laser drying method according to any one of claims 1 to 4, wherein one having a wavelength not to be used is used. In a laser drying apparatus for drying a material to be dried by irradiating a web-like material to be dried with laser light from a laser irradiation means,
A laser diffusing means for diffusing the laser light so that a beam cross section of the laser light spreads in the web width direction of the object to be dried;
A laser drying apparatus comprising: moving means for moving either the object to be dried or the laser irradiation means in the longitudinal direction of the web of the object to be dried.   7. The laser drying apparatus according to claim 6, wherein the laser diffusing means is a plano-convex cylindrical lens or an uneven cylindrical lens.   8. Laser drying according to claim 6 or 7, characterized in that cutting means for cutting both ends in the web width direction of the beam cross section of the diffused laser light is provided between the laser diffusing means and the object to be dried. apparatus.   The laser drying apparatus according to claim 6 or 7, wherein a plurality of optical systems comprising the laser irradiation means and the laser diffusion means are arranged in the web width direction of the object to be dried.   10. The laser drying apparatus according to claim 9, wherein the plurality of optical systems are arranged such that end portions in the web width direction of the beam cross section of the diffused laser light overlap each other on the surface to be dried.   The laser drying apparatus according to claim 9 or 10, wherein a plurality of optical systems comprising the laser irradiation means and the laser diffusion means are arranged in the longitudinal direction of the web of the object to be dried.

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