Web printing press

The present invention relates to a web printing press.

Japanese Patent Laid-Open No. 2008-308341 (reference 1) proposes a conventional web printing press. The web printing press described in reference 1 will be described with reference to FIG. 5 . A web printing press 201 includes a sheet feeding device 202 , two printing units 204 and 205 , a fixing device 206 including a thermal dryer 206 a , a cooling device 207 , and a folder 208 .

With this arrangement, a web 203 wound in a roll is fed from the sheet feeding device 202 to the printing units 204 and 205 , thereby undergoing double-sided printing. The printed web 203 is exposed to hot air from the dryer 206 a in the fixing device 206 , thereby drying the ink printed on the web 203 . At this time, upon exposure of the web 203 to hot air, a solvent in the ink transferred onto the web 203 evaporates, so the ink fixes on the paper. After that, the web 203 is wound around cylinders 207 a to 207 d , which are called chill rollers and through which cooling water passes, in the cooling device 207 , undergoes cutting and folding processing by the folder 208 , and is delivered.

On the other hand, a sheet-fed offset printing press prints/coats on a sheet using ultraviolet curing ink/varnish. This can be done using a known printing/coating method of irradiating a printed/coated sheet with ultraviolet rays from an UV (Ultraviolet) lamp to cure ultraviolet curing ink/varnish, as described in Japanese Patent laid-Open No. 54-123305 (reference 2).

In recent years, a printing/coating method which attains both energy saving and a low environmental load has been developed. In this method, ultraviolet curing ink/varnish is cured using a light-emitting diode (LED-UV) which emits light with UV wavelengths in place of a conventional UV lamp, as disclosed in Japanese Patent Laid-Open No. 2008-307891 (reference 3).

In the web printing press disclosed in reference 1 mentioned above, printing is performed using ink called thermal evaporative drying type ink (heat-set ink), and a solvent in the printed ink is forcibly evaporated and removed by hot air using a thermal drying device to fix the ink on the web. However, a web printing press prints at a speed faster than a sheet-fed offset printing press, and therefore requires a large-sized drying device in order to reliably dry the ink. Hence, the former printing press not only requires a large space for accommodation because it has a relatively large size as a whole, but also consumes a large amount of energy to activate the drying device.

The sheet-fed offset printing press disclosed in reference 2 consumes so much energy that the environmental load cannot be reduced.

In the sheet-fed offset printing press disclosed in reference 3, because light emitted by the LED-UV has an extremely narrow wavelength range (e.g., 370 nm to 380 nm), only ink/varnish which reacts to light in this narrow wavelength range can be used as ink/varnish which cures with light from the LED-UV.

It is an object of the present invention to provide a web printing press which is downsized as a whole and attains both energy saving and a low environmental load.

In order to achieve the above-mentioned object, according to the present invention, there is provided a web printing apparatus including a transfer device which transfers highly reactive ink/varnish onto a web, and a fixing device which fixes, on the web, the highly reactive ink/varnish transferred by the transfer device, wherein the fixing device comprises only a light irradiation device which irradiates the web with light in a wavelength range, in which no ozone is generated, to cure the highly reactive ink/varnish on the web without thermal drying of the web.

FIG. 1 is a side view of a web printing press according to the first embodiment of the present invention;

FIG. 2 is a sectional view of the main body of the web printing press shown in FIG. 1 ;

FIG. 3 is a graph showing the wavelength distribution of light emitted by an ozoneless lamp shown in FIG. 2 ;

FIG. 4 is a side view of a web printing press according to the second embodiment; and

FIG. 5 is a side view of a conventional web printing press.

The present invention will be described in detail below with reference to the accompanying drawings.

First Embodiment

The first embodiment of the present invention will be described first with reference to FIGS. 1 to 3 .

A web printing press 1 according to the first embodiment includes a sheet feeding device 2 which feeds a web 3 from a roll, printing units 4 and 5 (transfer devices) which print by sequentially transferring highly reactive ink onto the web 3 supplied from the sheet feeding device 2 , a fixing device 6 which fixes the ink transferred onto the web 3 by the printing units 4 and 5 , and a folder 8 which performs cutting and folding processing of the web 3 delivered from the fixing device 6 . The printing units 4 and 5 include obverse side printing units 4 A and 5 A which print on the obverse surface of the web 3 , and reverse side printing units 4 B and 5 B which print on the reverse surface of the web 3 . The fixing device 6 includes only a pair of light irradiation devices 15 A and 15 B which irradiate the web 3 with light beams having a specific wavelength to dry the ink transferred onto the two surfaces (the obverse and reverse surfaces) of the web 3 .

Each of a set of the obverse and reverse side printing units 4 A and 4 B and a set of the obverse and reverse side printing units 5 A and 5 B includes plate cylinders 11 A and 11 B which have printing plates mounted on their circumferential surfaces, inking devices 12 A and 12 B which supply highly reactive ink (highly reactive liquid) to the plate cylinders 11 A and 11 B, respectively, dampening devices 13 A and 13 B which supply dampening water to the plate cylinders 11 A and 11 B, respectively, and blanket cylinders 14 A and 14 B which are arranged in contact with the plate cylinders 11 A and 11 B, respectively. The blanket cylinder 14 A of the plate cylinder 11 A and the blanket cylinder 14 B of the plate cylinder 11 B are arranged in contact with each other.

The highly reactive ink supplied to the plate cylinders 11 A and 11 B means UV ink which cures with low light irradiation energies from the light irradiation devices 15 A and 15 B, and is also called highly reactive UV ink, high-sensitivity ink, or high-sensitivity UV ink. Such highly reactive UV ink rapidly cures with a light wavelength which has a low light irradiation energy without requiring light having wavelengths which fall within the ozone generation range and have a high light irradiation energy. Various types of inks can be used as the highly reactive ink supplied to the plate cylinders 11 A and 11 B, as long as a wavelength to which it reacts falls within the wavelength range of light beams emitted by the light irradiation devices 15 A and 15 B. The ink supplied to the plate cylinders 11 A and 11 B may be ink which reacts to light having a single wavelength, such as light emitted by an LED, or ink which reacts to light having wavelengths in a certain range.

Each of the dampening devices 13 A and 13 B includes at least four rollers which are connected in contact with each other, and two rollers which are in contact with each other among the four rollers are rotated so as to produce a counter-slip between them. In this arrangement, a given minimum necessary amount of dampening water is transferred from one roller to the other roller on the downstream side at the contact point between the two rollers. Hence, the dampening water is supplied in an amount optimum for the ink onto the plate surfaces of the printing plates mounted on the plate cylinders 11 A and 11 B to prevent excessive emulsification of the highly reactive ink supplied from the inking devices 12 A and 12 B onto these plate surfaces.

The light irradiation device 15 A includes an ozoneless lamp (to be described later) which is used for obverse surface irradiation and cures the highly reactive ink transferred onto the obverse surface of the web 3 by the obverse side printing units 4 A and 5 A. The light irradiation device 15 B includes an ozoneless lamp (to be described later) which is used for reverse surface irradiation and cures the highly reactive ink transferred onto the reverse surface of the web 3 by the reverse side printing units 4 B and 5 B. The pair of light irradiation devices 15 A and 15 B which constitute the fixing device 6 have the same structure.

The light irradiation devices 15 A and 15 B are disposed such that their irradiation surfaces (to be described later) face down and up, respectively, with the web 3 being vertically sandwiched between them. Since the light irradiation devices 15 A and 15 B have the same structure, only the light irradiation device 15 A will be described in detail with reference to FIG. 2 . The light irradiation device 15 A includes a box-shaped housing 17 having an irradiation opening 16 a formed in an irradiation surface 16 b , and an ozoneless type UV lamp (to be referred to as an ozoneless UV lamp hereinafter) 18 is fixed at the central portion of the housing 17 , as shown in FIG. 2 . Light emitted by the ozoneless UV lamp 18 is reflected by a reflecting mirror 19 and guided to the outside from the irradiation opening 16 a.

The ozoneless UV lamp 18 employs silica glass containing a small amount of impurity in an arc tube of a UV lamp serving as a discharge lamp. Silica glass containing an impurity absorbs light having wavelengths in the ozone generation range to prevent ozone generation. Hence, light emitted by the ozoneless UV lamp 18 contains no wavelength in the ozone generation range (wavelengths less than 270 nm) which includes an ozone generation wavelength of 254 nm, as shown in FIG. 3 . In contrast, light emitted by a metal halide lamp contains wavelengths in the ozone generation range. Also, an LED emits light containing no wavelength in the ozone generation range, and emits only light in the narrow wavelength range of 370 nm to 380 nm.

As shown in FIG. 2 , the light irradiation device 15 A includes a cut filter (optical filter) 20 in the irradiation opening 16 a . The cut filter 20 absorbs (cuts off) light wavelengths in the heat generation range, i.e., wavelengths more than 400 nm shown in FIG. 3 in light emitted by the ozoneless UV lamp 18 . Therefore, the light irradiation device 15 A emits light in the wavelength range of 270 nm to 400 nm upon filtering out wavelengths in both the ozone generation range and heat generation range via the irradiation surface 16 b.

In this embodiment, a discharge lamp which emits light by discharge in a gas such as neon or xenon, the vapor of a metal such as mercury, sodium, or scandium, or a gas mixture thereof is employed as the ozoneless UV lamp 18 . A light source of the light irradiation device 15 A includes no LED. The light irradiation device 15 A is defined as an ozoneless lamp which includes a discharge lamp and emits light having ultraviolet wavelengths including no ozone generation wavelength emitted by the discharge lamp.

Although an example in which the ozoneless UV lamp 18 which emits light containing no wavelength in the ozone generation range has been explained in this embodiment, a general discharge lamp which emits light containing an ozone generation wavelength may be employed in place of the ozoneless UV lamp 18 . In this case, in addition to the cut filter 20 which absorbs wavelengths in the heat generation range, another cut filter which absorbs wavelengths in the ozone generation range need only be provided in the irradiation opening 16 a . An ozoneless type UV lamp can be employed even when a cut filter which absorbs wavelengths in the ozone generation range is provided, as a matter of course. When there is no need to absorb wavelengths in the heat generation range, light from the ozoneless UV lamp 18 can be directly guided to the outside from the irradiation surface 16 b without requiring the cut filter 20 .

Also, although the wavelength range of light beams emitted by the light irradiation devices 15 A and 15 B is set to 270 nm to 400 nm, this does not limit the present invention to the condition in which the wavelength of light beams from the light irradiation devices 15 A and 15 B contains all wavelength components in this wavelength range. That is, wavelengths in an arbitrary range may be set as long as this range approximately falls within the wavelength range of 270 nm to 400 nm, so it is only necessary to set the lower limit of the wavelength to 260 nm to 300 nm and its upper limit to 380 nm to 420 nm. According to the present invention, by setting the wavelength of light beams from the light irradiation devices 15 A and 15 B to fall within the wide range of 270 nm to 400 nm, the highly reactive ink can be selected from various types of inks which react to light with a specific wavelength among a wide range of wavelengths, thus widening the range of options for ink.

A method of curing the highly reactive ink printed on the two surfaces of the web 3 by the light irradiation devices 15 A and 15 B in the web printing press 1 with the above-mentioned arrangement will be described next. Referring to FIG. 1 , the web 3 fed from the sheet feeding device 2 to the printing unit 4 undergoes double-sided printing in the process of passing between the blanket cylinder 14 A of the obverse side printing unit 4 A and the blanket cylinder 14 B of the reverse side printing unit 4 B. Subsequently, the web 3 undergoes double-sided printing in the process of passing between the blanket cylinder 14 A of the obverse side printing unit 5 A in the printing unit 5 and the blanket cylinder 14 B of the reverse side printing unit 5 B in the printing unit 5 .

The web 3 printed by the printing units 4 and 5 is irradiated with light beams from the light irradiation devices 15 A and 15 B, so the highly reactive ink transferred onto the two surfaces of the web 3 cures. At this time, because the light beams emitted by the light irradiation devices 15 A and 15 B contain no wavelength which generates ozone, no device for processing ozone is necessary. Also, because a low-power ozoneless lamp with a low light irradiation energy is employed, no cooling device is necessary, thereby making it possible to save both space and energy. Moreover, because of the use of highly reactive ink, the ink rapidly cures, so no large-sized thermal drying device is necessary, thereby making it possible to downsize the entire printing press.

In the dampening devices 13 A and 13 B, the two rollers which are in contact with each other are rotated so as to produce a counter-slip between them, so a given minimum necessary amount of dampening water is transferred from one roller to the other roller at a contact point A between them. Hence, an optimum amount of dampening water is supplied onto the plate surfaces of the printing plates mounted on the plate cylinders 11 A and 11 B to prevent excessive emulsification of the highly reactive ink supplied from the inking devices 12 A and 12 B onto these plate surfaces. This makes it possible to keep the highly reactive ink in an optimum emulsified state, thereby reliably curing the highly reactive ink despite its irradiation by the ozoneless UV lamp 18 with a low light irradiation energy.

By filtering out wavelengths in the heat generation range from light emitted by the ozoneless UV lamp 18 , the amount of heat acting on the web 3 is reduced, so thermal deformation of the web 3 is prevented. This makes it possible to improve the quality of a printing product. The web 3 on which the highly reactive ink printed on its two surfaces has cured with light beams emitted by the light irradiation devices 15 A and 15 B undergoes cutting and folding processing by the folder 8 , and is delivered.

Second Embodiment

The second embodiment of the present invention will be described next with reference to FIG. 4 .

The second embodiment is different from the first embodiment in that in the former a fixing device 16 including a pair of light irradiation devices 115 A and 115 B is provided between printing units 4 and 5 , in addition to a fixing device 6 including a pair of light irradiation devices 15 A and 15 B. The light irradiation devices 115 A and 115 B are disposed such that their irradiation surfaces face down and up, respectively, with a web 3 being vertically sandwiched between them.

In this arrangement, as for the web 3 having undergone double-sided printing by the printing unit 4 , the highly reactive ink transferred onto the two surfaces of the web 3 cures with light beams emitted by the light irradiation devices 115 A and 115 B. Next, as for the web 3 having undergone double-sided printing by the printing unit 5 , the highly reactive ink transferred onto the two surfaces of the web 3 cures with light beams emitted by the light irradiation devices 15 A and 15 B.

Although an example in which highly reactive ink is printed on the web 3 has been explained in each of the above-mentioned embodiments, the present invention may be applied to a coating unit/coating device which coats the web 3 using highly reactive varnish as a highly reactive transfer liquid. Also, although an example in which one or two pairs of light irradiation devices are provided has been explained, three or more pairs of light irradiation devices may be provided as needed.

According to the present invention, highly reactive ink/varnish rapidly cures upon irradiation with light having a specific wavelength, thus making it possible to downsize the entire printing press without requiring a large-sized thermal drying device as a fixing device. Also, highly reactive ink can sufficiently cure despite the use of a low-power ozoneless lamp, thus making it possible to provide an environment-friendly printing/coating apparatus which attains ozoneless, energy-saving printing/coating. Moreover, no device for processing ozone is necessary because of the use of ozoneless printing/coating, thus making it possible to save energy in this respect as well. Not only a cooling device for removing the generated heat but also a duct and a peripheral device are unnecessary because of the use of a low-power ozoneless lamp, thus making it possible to save space.

From the standpoint of an ink manufacturer, there is no need to develop ink assuming the use of light with limited wavelengths, such as an LED-UV. Hence, the ink manufacturer can develop ink which rapidly cures with an arbitrary wavelength among a wide range of wavelengths output from an ozoneless lamp. This means that the ink manufacturer can develop ink with good printing quality that is the original goal of ink.

By filtering out wavelengths in the heat generation range from light emitted by an ozoneless lamp, the amount of heat acting on the web is reduced, so thermal deformation of the web is prevented. This makes it possible to improve the quality of a printing product. Because highly reactive ink/varnish can be selected from various types of inks/varnishes which react to an arbitrary wavelength among a wide range of wavelengths, the range of options for ink widens.