WO2017016595A1

WO2017016595A1 - Determining print quality of web press

Info

Publication number: WO2017016595A1
Application number: PCT/EP2015/067282
Authority: WO
Inventors: Tal Rosenberg
Original assignee: Hewlett-Packard Indigo B.V.
Priority date: 2015-07-28
Filing date: 2015-07-28
Publication date: 2017-02-02

Abstract

A method is described in which an image is printed onto a main web substrate (103) by transferring the image to the main web substrate (103) via a transfer member (101). A secondary substrate (110) is then engaged with the transfer member (101) to transfer an image from the transfer member to the secondary web substrate. One or more optical parameters of the image on the secondary substrate are determined by an optical sensor (140).

Description

Determining Print Quality of Web Press

Background

[001] It is often desired to determine one or more parameters of printed output in order to evaluate print quality. In order to aid such evaluation it is known to print an image comprising one or more calibration patterns. In a sheet-fed printer, printing such an image is not problematic since a sheet of print media comprising the image is easily removed for inspection. However, in web presses, where the print media is a continuous web, the test sheet remains part of the web, requiring removal at a point of cutting and processing the web. In certain applications where the web is processed further before cutting, such as laminating or pouch making, it is desirable to avoid non-usable test pattern sections in the web which can incur additional time and material waste costs.

Brief Description of the Drawings

[002] Example implementations of the present disclosure will now be described by way of example only, with reference to the accompanying figures, in which:

[003] Figure 1 shows an illustration of an example web press according to the present disclosure; and

[004] Figure 2 shows an example method according to the present disclosure. Detailed Description

[005] Examples of the present disclosure provide a printing apparatus and method of determining print quality of a web press in which a secondary web substrate is used for printing an image to determine one or more optical parameters of the image by an optical sensor. The use of a secondary substrate avoids printing images for determining print quality on a main substrate, or a requirement to replace the main substrate with a substrate for printing test patterns thereon, especially in cases where the main substrate may not be uniform in one or more properties such as colour, texture etc. The use of an optical sensor avoids a need to print test patterns on the main substrate thereby disturbing a printed output which results in the test patterns needing to be processed out, or removed, later.

[006] Referring to Figure 1, there is shown a view of an example printing apparatus 100. The exemplary printing apparatus 100 illustrated in Figure 1 is a web press printer for printing images onto a web print medium.

[007] The printing apparatus 100 comprises an intermediate transfer member (ITM) 101 and an impression member or roller 102. The ITM 101 is provided for receiving an image formed on a photoreceptor (not shown) and transferring the image to a main web substrate 103 which is brought into contact with the ITM 101 by the impression roller or cylinder 102. The photoreceptor may be a photoreceptor sheet attached to a photo imaging plate (PIP) or drum on which the image is formed. The ITM 101 may have a transfer blanket wrapped around an outer surface thereof for receiving and transferring the image. The impression roller 102 is moveable between an engaged position, in which the web substrate 103 is brought into contact with the ITM 101, and a disengaged position in which the web substrate 103 is not contacting or free from the ITM 101. In Figure 1 the impression roller 102 is shown in the disengaged position.

[008] The printing apparatus 100 comprises a secondary web substrate 110 which is selectively contactable with the ITM 101. In the exemplary apparatus illustrated in Figure 1 the printing device 100 comprises a blanket cleaning station (BCS) 120 comprising the secondary substrate 110. The secondary substrate 110 may thus be a cleaning web 110 for cleaning the ITM 101 or the blanket wrapped there-around. The cleaning web 110 may be a transparent foil. The transparent foil may be formed of a plastic material, such as PET. Advantageously the cleaning web 110 may be of a lower cost than the main web substrate. Furthermore, the cleaning web 1 10 may be a coated film having a minimal thickness which reduces waste compared to a heavier substrate.

[009] In the example apparatus shown in Figure 1 the BCS comprises a pressure roller 121 for selectively contacting the cleaning web 110 with the ITM 101. The cleaning web 110 may, in use, contact the blanket surrounding the ITM 101. The pressure roller 121 is selectively brought into contact with the ITM 101 by means of an actuator 122 which is connected to a rotatably mounted cam 123. The cam 123 is further connected to the pressure roller 121 such that rotation of the cam 123 moves an axis of rotation of the pressure roller 121 relative to the surface of the ITM 101. In this way, extension of the actuator 122 causes the pressure roller 121 and cleaning web 110 to selectively engage or disengage contact with the ITM 101. In use, the pressure roller 121 and impression roller 102 may interlockingly engage with the ITM 101 i.e. only one of the pressure roller 121 and impression roller 102 may be arranged to engage the ITM 101 at once.

[0010] The BCS 120 may further comprise an unwind roller 124 on which the cleaning web 110 is collected and a rewind roller 125 to which the cleaning web is returned after printing. In a path of the cleaning web 110 between the unwind roller 124 and rewind roller 125 is a member having predetermined optical properties, which may be in the form of an idler 130. The cleaning web 110 is arranged to run over the idler 130 after having contacted the ITM 101. In this way a printed portion of the cleaning web 110 is moved from the ITM 101 to the idler 130. The idler 130 has predetermined optical properties such that one or more optical parameters of the image on the cleaning web 110 may be determined.

[0011] The one or more optical parameters of the image formed on the cleaning web 110 are determined by an optical sensor 140. The optical sensor 140 may be a spectrophotometer or optical densitometer. The optical sensor 140 is arranged to measure a reflectivity or transmittance of the printed image as a function of wavelength for measuring a colour of the printed image. The optical sensor 140 is arranged to measure the optical properties of the image on the cleaning web overlying the idler 130. In this way, a white background is provided by the idler 130 whilst measuring the optical properties of the printed image. The image printed on the cleaning web 110 may comprise a plurality of colour calibration patterns. That is the printed image may have a plurality of portions of predetermined colour for enabling colour reproduction of the printing apparatus 100 to be verified by the optical sensor 140. Correction may then be applied to the colour reproduction if necessary. The correction may be applied until one or more printed colours meet a required specification.

[0012] Figure 2 illustrates an example method 200 according to the present disclosure. The method is a method of determining print quality of a web press. The method 200 may be performed by a printing apparatus 100 as shown in Figure 1.

[0013] In step 210 a web press printer can be printing on a main web 103. In step 210 a printed image can be formed on a photoreceptor such as a PIP and transferred to a transfer member such as the ITM 101 shown in Figure 1. The main web 103 can be contacted with the ITM 101 by the impression roller 102 in an engaged position in step 210.

[0014] In step 220, the main web 103 can be disengaged from the ITM 101. That is, the main web 103 may be moved to no longer contact the ITM 101 thus an image present on the ITM 101 is not transferred to the main web 103. Furthermore, the main web 103 is not required to be cut. The main web 103 can be moved by the impression roller 102 moving away from the ITM 101.

[0015] In step 230, a secondary web substrate 110 can be engaged with the ITM 101.

The secondary web substrate 110 may be the cleaning web 110 of the BCS 120 shown in Figure 1. As discussed above, the cleaning web 110 may be foil. The cleaning web may be generally transparent. The cleaning web 110 of the BCS 120 may be brought into contact with the ITM 101 by movement of the pressure roller 121. When contacting the ITM 101, an image transferred to the ITM 101 from the photoreceptor can be transferred in step 240 to the cleaning web 110. Thus, in this way, the image can be printed 240 onto a portion of the cleaning web 110, rather than the main web 103.

[0016] In step 250, one or more optical properties of the image printed on the secondary web, such as the cleaning web 110, are determined by the optical sensor 140. Step 250 may comprise transporting the portion of the cleaning web 1 10 having the image printed thereon to a predetermined location with respect to the optical sensor 140. The predetermined location may overlie a member having predetermined optical properties, such as the idler 130 of the BCS 120 shown in Figure 1. As discussed above, the idler 130 may have a predetermined colour or reflectance. In particular, some examples of the idler 130 may be white for providing a white background for the image printed on the cleaning web 110. In this way, a reference background is provided for the portion of the cleaning web 110 for the optical sensor to obtain uniform measurements. The provision of a predetermined background, particularly when the cleaning web 110 can be a film, such as a transparent film, removes a need to print a white layer on which colour calibration patches are printed. The optical sensor 140 may be arranged to output data indicative of a colour or a spectrum of each colour calibration pattern printed on the cleaning web 110. Based on the output data, colour calibration may be performed to correct one or more colours output by the printing apparatus 100.

[0017] In step 260 printing upon the main web 103 may recommence. In step 260 the

BCS 120 can be removed from printing. The BCS 120 may be removed by the pressure roller 121 being removed from contact with the ITM 101. As discussed above, the pressure roller 121 can be moved, in some examples, by actuator 122 via cam 123 away from the ITM 101. Once moved away from the ITM 101 an image formed on the ITM 101 is not transferred to the cleaning web 110. The impression roller 102 can then be moved toward the ITM 101 such that the main web 103 is brought into contact with the ITM 101, or the blanket wrapped there-around, such that an image transferred to the ITM 101 can be formed on the main web substrate 103.

[0018] It will be appreciated that examples of the present disclosure can be realised in the form of hardware, software or a combination of hardware and software. Any such software may be stored in the form of volatile or non-volatile storage such as, for example, a storage device like a ROM, whether erasable or rewritable or not, or in the form of memory such as, for example, RAM, memory chips, device or integrated circuits or on an optically or magnetically readable medium such as, for example, a CD, DVD, magnetic disk or magnetic tape. It will be appreciated that the storage devices and storage media are examples of machine-readable storage that are suitable for storing a program or programs that, when executed, implement examples of the present disclosure. Accordingly, examples provide a program comprising code for implementing a system or method as claimed in any preceding claim and a machine readable storage storing such a program. Still further, examples of the present disclosure may be conveyed electronically via any medium such as a communication signal carried over a wired or wireless connection and examples suitably encompass the same.

[0019] All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

[0020] Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0021] The present disclosure is not restricted to the details of any foregoing examples. The disclosure extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. The claims should not be construed to cover merely the foregoing examples, but also any examples which fall within the scope of the claims.

Claims

1. A method of determining print quality of a web press, comprising:

printing on a main web substrate by transferring an image onto the main web substrate via a transfer member;

engaging a secondary web substrate with the transfer member to transfer an image from the transfer member to the secondary web substrate; and

determining one or more optical parameters of the image on the secondary substrate by an optical sensor.

2. The method of claim 1, further comprising disengaging the main web substrate from the transfer member prior to engaging the secondary web substrate with the transfer member.

3. The method of claim 1, further comprising transporting a portion of the secondary web substrate having the image printed thereon from the transfer member to a location proximal to the optical sensor.

4. The method of claim 3, wherein the portion of the secondary web substrate having the image printed thereon is transported to overlie a member having predetermined optical properties.

5. The method of claim 1, wherein the engaging the secondary web substrate with the transfer member comprises moving a member supporting the secondary web substrate, such that the secondary web substrate is brought into contact with the transfer member.

6. The method of claim 1, wherein the secondary web substrate is a cleaning substrate.

7. The method of claim 1, comprising engaging the main web substrate with the transfer member after transferring the image from the transfer member to the secondary web substrate.

8. A printing apparatus, comprising:

an image transfer member to transfer an image onto a continuous main substrate;

a moveable member to selectively contact a secondary substrate with the image transfer member to print an image on the secondary substrate;

an optical sensor to determine one or more optical parameters of the image on the secondary medium.

9. The printing apparatus of claim 8, wherein the optical sensor is one of a spectrophotometer and a densitometer.

10. The printing apparatus of claim 8, further comprising an idler member having a predetermined optical parameter, wherein the optical sensor is arranged to determine the optical parameter of the image on the secondary medium upon the idler member.

11. The printing apparatus of claim 8, comprising an unwind roller and a rewind roller, wherein the secondary substrate is arranged to be collected on the unwind roller until a portion having the image printed thereon is proximal to the optical sensor.

12. The printing apparatus of claim 8, comprising an impression roller arranged to selectively engage the main substrate with the image transfer member, wherein the main substrate is disengaged from the image transfer member prior to contacting a secondary substrate with the image transfer member.

13. The printing apparatus of claim 8, wherein the moveable member and the secondary substrate are formed within a blanket cleaning station of the printing apparatus.

14. The printing apparatus of claim 8, wherein the optical sensor is arranged to output data indicative of a colour of regions of the image on the secondary substrate.

15. A computer readable medium tangibly containing program instructions for causing a computer to perform the method of: printing on a main web substrate by transferring an image onto the main web substrate via a transfer member;