Method for exposure of relief precursors having multiple profiles

Abstract

A method, control means and exposure device for exposing a relief precursor P with a light source (2), the irradiated area of ​​the light source (2) covering a part of the area of ​​the precursor, whereby exposure of the entire area of ​​the precursor is performed by moving the light source and the precursor relative to each other during an exposure pass, the method comprising a step (20) of providing a mask (4) on the photosensitive layer, a first exposure step (ES1) in which the precursor is exposed during one or more exposure passes according to a first intensity profile (IP1) and a first velocity profile (SP1), and a second exposure step (ES2) in which the precursor is exposed during one or more exposure passes according to a second intensity profile (IP2) different from the first intensity profile (IP1) and a second velocity profile (SP2) different from the first velocity profile (SP1).

Description

[Technical Field]

[0001] The field of the present invention relates to apparatus and methods for exposing relief precursors, particularly printing plate precursors.

[0002] background

[0003] A relief structure can be created by transferring image information onto an image-forming layer and then removing a portion of the image-forming layer. The formed relief can then be used to transfer information onto a substrate during the printing step. An example of a relief precursor is a printing plate precursor. Digitally imageable flexible printing plate precursors are known and typically include at least a dimensional stability support layer, a photosensitive layer, and a digitally imageable mask layer. The digitally imageable mask layer can be, for example, a laser-removable layer. In the case of conventional printing plate precursors, the digitally imageable layer is replaced by a separate mask attached to the photosensitive layer.

[0004] According to existing methods, to produce a printing plate from a printing plate relief precursor, a mask is first written onto a digital image-forming layer based on the image data to be printed. Following the writing of the mask, the plate is exposed to radiation through the mask so that the photosensitive layer undergoes polymerization or crosslinking, or a reaction that alters the solubility or fluidity of the photosensitive layer in areas not covered by the mask. After exposure, residues from the unexposed parts of the mask and photosensitive layer are removed. This can be done using one or more liquids in a washing device, or by thermal development, in which the unexposed material of the photosensitive layer is liquefied and removed by a rise in temperature.

[0005] Exposure apparatuses for printing plate precursors are known. The exposure apparatus may comprise a first light source for back exposure and a second light source for front exposure. Back exposure can be performed using a pair of UV tubes. Back exposure creates a solid layer (bed) on which the relief structure is generated. Front exposure can be performed using a pair of UV tubes, a movable UV light source such as a movable laser or LED bar, or a stationary light source, such as an arrangement of tubular light sources. Some exposure apparatuses perform only front exposure or only back exposure, as required. In some cases, the exposure apparatus can expose from both sides, and embodiments of the present invention relate to such cases.

[0006] Prior art includes U.S. Patents 2018 / 0004093, 2018 / 0126721, and 2013 / 0242276, which disclose known methods for producing flexographic printing plates.

[0007] overview

[0008] An object of embodiments of the present invention is to provide an apparatus and method for exposing a relief precursor according to multiple profiles with improved efficiency and / or print quality.

[0009] According to a first aspect of the present invention, a method is provided for exposing a relief precursor with a light source, wherein the irradiation area of ​​the light source covers a portion of the region of the precursor, and exposure of the entire region of the precursor is carried out by moving the light source and the precursor relative to each other during the exposure pass. The method comprises the steps of providing a mask on the photosensitive layer of the precursor, a first step and a second step, the first step of exposing the precursor through the mask according to a first intensity profile and a first velocity profile during one or more exposure passes, and the second step of exposing the precursor through the mask according to a second intensity profile different from the first intensity profile and a second velocity profile different from the first velocity profile during one or more exposure passes.

[0010] Therefore, according to embodiments of the present invention, both the intensity profile and the speed profile can be changed between the two exposure steps. In this way, both print quality and power consumption can be controlled multivariably depending on the situation. More precise and versatile control of intensity and speed, which affect both print quality and efficiency (power consumption), is achieved by controlling the first and second exposure steps according to different profiles for both intensity and speed. In this way, a wider range of relief precursors can be produced while achieving the best print quality with the best efficiency. Depending on the characteristics of the relief precursor being exposed (reactivity, especially thickness), typically, one or more high-intensity, high-speed exposure passes can be followed by one or more low-intensity, slow exposure passes, to mitigate heat buildup while achieving high curing quality.

[0011] In a preferred embodiment, the first velocity profile is such that the velocity is substantially constant during one or more exposure passes of the first exposure step, and / or the second velocity profile is such that the velocity is substantially constant during one or more exposure passes of the second exposure step. Alternatively, at least one of the first or second velocity profile may be a time-varying profile, typically a profile in which the velocity decreases or increases over time. The profile may be changed linearly or stepwise. In this way, finer control of the exposure steps can be achieved.

[0012] In a preferred embodiment, the average pass-through speed during the first exposure step is higher than the average pass-through speed during the second exposure step. In this way, the high-speed exposure step precedes the low-speed exposure step. Typically, the high-speed exposure step is associated with a first intensity, while the low-speed exposure step is associated with a lower second intensity. Thus, the relief precursor is not heated too much during the high-speed exposure step, forming flat dots, and completes curing during the low-speed exposure step. Alternatively, the average pass-through speed during the first exposure step may be lower than the average pass-through speed during the second exposure. In this way, the low-speed exposure step precedes the high-speed exposure step. In this way, the high-intensity high-speed final exposure step can also function as a post-exposure step and therefore does not need to be performed as a post-treatment. Omitting or reducing post-treatment time reduces the total development time of the relief precursor.

[0013] In a preferred embodiment, the first intensity profile is such that the intensity is substantially constant during one or more exposure passes in the first exposure step, and / or the second first intensity profile is such that the intensity is substantially constant during one or more exposure passes in the second exposure step. Alternatively, at least one of the first or second intensity profiles may be a profile that changes over time, typically a profile in which the intensity decreases or increases over time. The profiles can be changed linearly or stepwise. In this way, finer control of the exposure steps can be achieved.

[0014] In a preferred embodiment, the average intensity during exposure in the first exposure step is higher than the average intensity during exposure in the second exposure step. In this case, the high-intensity exposure step precedes the low-intensity exposure step. Typically, the high-intensity exposure step is associated with a faster speed, while the low-intensity exposure step is associated with a lower second speed. In this way, the relief precursor forms flat dots and is not heated much during the high-intensity exposure step, while curing is completed during the low-intensity exposure step. Alternatively, the first intensity may be lower than the second intensity. In this case, the low-intensity exposure step precedes the high-intensity exposure step. In this way, the high-intensity, fast final exposure step can also function as a post-exposure step and therefore does not need to be performed as a separate post-treatment. By omitting or reducing post-treatment time, the total development time of the relief precursor is reduced.

[0015] According to a preferred embodiment, the first exposure step includes a first number of exposure passes, and / or the second exposure step includes a second number of exposure passes. In this way, another variable for controlling the exposure steps is provided. By repeating the exposure passes, the dose can be distributed between passes to further control how the exposure of the relief precursor is carried out to obtain the desired quality and efficiency.

[0016] In a preferred embodiment, the first dose applied during the first exposure step is lower than the dose applied during the second exposure step. Preferably, the first and second doses are 0.2–30 J / cm², respectively. 2 More preferably, the first dose is 0.2-20 J / cm². 2 Preferably, 0.5-18 J / cm 2 More preferably, 1-17 J / cm 2 Therefore, the second dose is 2-28 J / cm². 2 Preferably, 5-25 J / cm 2 More preferably, 10-20 J / cm 2 That is the case.

[0017] According to a preferred embodiment, the first number of exposure passes is different from the second number of exposure passes. In this way, different exposure behaviors according to different profiles can be selectively repeated. Preferably, the first number of exposure passes is higher than the second number of exposure passes. In this way, the total dose can be spread out during the exposure passes. More preferably, the first number of exposure passes is 2 or more, and the second number of exposure passes is 1.

[0018] According to a preferred embodiment, the light source is moved in an exposure cycle involving a first movement in a first direction and a second movement in a second opposite direction, and each exposure cycle includes one or two exposure passes. In this way, the exposure by the light source can be carried out while moving in one direction or both directions.

[0019] In a preferred embodiment, one or more first exposure passes of the first exposure step and one or more exposure passes of the second exposure step are carried out during movement in the same direction. Alternatively, one or more exposure passes of the first exposure step are carried out during movement in the first direction, and one or more exposure passes of the second exposure step are carried out during movement in the second opposite direction. Alternatively, one or more exposure passes of the first exposure step and / or one or more exposure passes of the second exposure step are carried out during movement in both directions. In this way, it is possible to expose separately in the first exposure step and the second exposure step and customize the exposure according to the situation (thickness, reactivity among the possible parameters to be considered).

[0020] Preferably, the average speed during the exposure passes of the first exposure step is 500 - 10000 mm / min, and the average speed during the exposure passes of the second exposure step is 10 - 1000 mm / min.

[0021] Preferably, the average intensity during the exposure passes of the first exposure step is 30 - 10000 mW / cm 2 , preferably 50 - 5000 mW / cm 2 , more preferably 50 - 2500 mW / cm 2and the average intensity during exposure in the second exposure step is 1 - 5000 mW / cm 2 , preferably 20 - 2500 mW / cm 2 , more preferably 50 - 500 mW / cm 2 .

[0022] When referring to the first intensity or the first intensity profile during one or more exposures in the first exposure step, it is intended to refer to the intensity measured by an Ophir 10A - V1.1 sensor (Ophir Optronics Solutions Ltd) having a 16 - mm diameter diaphragm arranged to be placed in a plane corresponding to the first side of the relief precursor when the relief precursor is placed in the exposure apparatus. Thus, when the exposure apparatus has a carrier structure having a support surface, for example, a glass plate having a support surface, the sensor can be set on the support surface with its measurement side directed towards the first light source. This is illustrated in FIG. 7, where the sensor S is placed on the support surface of a support structure 3 such as a glass plate, and the measurement side M of the sensor S is placed on the support surface such that the measurement side M receives the light emitted by the first light source.

[0023] When referring to the second intensity or the second intensity profile during one or more exposures of the second exposure step, it is intended to refer to the intensity between the plane corresponding to the first side of the relief precursor when the relief precursor is placed in the exposure apparatus and the second light source, at a distance of 15 mm from said plane. Thus, when the exposure apparatus comprises a support structure having a support surface, for example a glass plate, the intensity is the intensity at a distance of 15 mm above the support surface. However, since the sensor has a certain height and the distance between the second light source and the support surface is typically very small, the light intensity may have to be measured outside the exposure apparatus. Thus, the sensor may be arranged outside the exposure apparatus, but the measurement side of the sensor is positioned at a distance dm of the second light source corresponding to a distance d2(dm = d2 - 15 mm) which is 15 mm subtracted from the distance d2 between the second light source and the support surface. Also, the intensity of the second light source may be measured by an Ophir 10A-V1.1 sensor (Ophir Optronics Solutions Ltd) equipped with a diaphragm of 16 mm diameter. This is illustrated in Figure 7, where the sensor S’ is placed such that the measurement side M’ of the sensor is at a distance dm equal to the distance d2 (in the illustrated embodiment, d2 = 50 mm) minus 15 mm from the distance d2 between the second light source 2 and the support surface of the support structure 3 (i.e., dm = d2 - 15 mm = 50 mm - 15 mm = 35 mm).

[0024] Preferably, the ratio of the average speed during the exposure pass of the first exposure step to the average speed during the exposure pass of the second exposure step is higher than 1.5, preferably higher than 2, or the ratio of the second to the first speed is higher than 0.05, preferably higher than 0.08.

[0025] Preferably, the ratio of the average intensity during the exposure pass of the first exposure step to the average intensity during the exposure pass of the second exposure step is higher than 0.15, preferably higher than 0.5, more preferably higher than 1.0, or the ratio of the second to the first intensity is higher than 0.5, preferably higher than 0.7, more preferably higher than 1.

[0026] In a preferred embodiment, the third exposure step comprises exposing at a third speed and a third intensity, wherein the third speed is different from the second speed and / or the third intensity is different from the second intensity. In this way, further exposure steps for improving quality can be provided. Preferably, the third exposure step may include one or more further steps.

[0027] In a preferred embodiment, prior to the first and second exposure steps, a step is provided in which a first intensity profile, a first velocity profile, a second intensity profile, and a second velocity profile are received via a user input interface. In this way, the operator can customize the profiles.

[0028] According to a preferred embodiment, the step of providing a mask includes adding a pre-fabricated mask layer, or generating a transparent region in the mask layer which is an intrinsic layer of a precursor.

[0029] According to a preferred embodiment, the method further includes a step of back-exposing the precursor to electromagnetic radiation from the side opposite to the relief-forming side exposed before, after, or during the first and second exposure steps. Preferably, the back exposure is performed during the first and / or second exposure steps. More preferably, the method includes whether or not to perform the back exposure step during the first and / or second exposure steps based on the input first and second velocity profiles.

[0030] Preferably, the wavelength of the electromagnetic radiation is 200-2000 nm.

[0031] According to a preferred embodiment, after the second exposure step, further steps are performed selected from the group including liquid treatment, gas treatment, heat treatment, contact with a surface, removal of dissolvable or liquefiable material, exposure to electromagnetic radiation, exposure to plasma, cutting, sanding, or a combination thereof. Post-processing is thus achieved.

[0032] Preferably, the relief precursor comprises at least a dimensionally stable support layer, one or more photosensitive layers, and optionally a cover layer, an adhesive layer, a barrier layer, a protective layer, a particle layer, a mask layer, or a combination thereof.

[0033] According to another aspect of the present invention, the relief structure is obtained by the method described in any one of the preferred embodiments described above.

[0034] According to another aspect of the present invention, the use of the relief structure according to the previous aspect is provided as a flexographic printing plate, letterpress plate, relief printing plate, (flexible) printed circuit board, electronic element, microfluidic element, microfluidic engineering element, microreactor, photocell, photonic crystal, optical element, or Fresnel lens. To obtain a microfluidic element or microreactor, an additional layer is added on the formed relief, thereby creating channels and spaces.

[0035] According to yet another aspect of the present invention, a control means is provided configured to control the exposure of a relief precursor by a light source, wherein the irradiation area of ​​the light source covers a portion of the region of the precursor, and exposure of the entire region of the precursor is carried out by moving the light source and the precursor relative to each other during the exposure pass. The control means is configured to control the intensity on the surface of the precursor and the moving speed of the light source, and a first exposure step and a second exposure step are performed, the first exposure step comprising the step of exposing the precursor through a mask according to a first intensity profile and a first velocity profile during one or more exposure passes, and the second exposure step comprising the step of exposing the precursor through a mask according to a second intensity profile different from the first intensity profile and a second velocity profile different from the first velocity profile during one or more exposure passes.

[0036] In a preferred embodiment, the control means is configured to control the moving speed of the light source such that the speed of one or more exposure passes in the first exposure step is substantially constant, and / or the speed between one or more exposure passes in the second exposure step is substantially constant.

[0037] According to a preferred embodiment, the average speed during exposure in the first exposure step is higher than the average speed during exposure in the second exposure step.

[0038] In a preferred embodiment, the control means is configured to control the intensity on the surface of the precursor such that the intensity during one or more exposure passes in the first exposure step is substantially constant, and / or the intensity during one or more exposure passes in the second exposure step is substantially constant.

[0039] According to a preferred embodiment, the average intensity during exposure in the first exposure step is higher than the average intensity during exposure in the second exposure step.

[0040] According to a preferred embodiment, the first exposure step includes a first number of exposure passes, and / or the second exposure step includes a second number of exposure passes. Preferably, the first number of passes are different from the second number of passes, and more preferably, the first number of passes are higher than the second number of passes.

[0041] According to a preferred embodiment, the first dose applied during the exposure pass-through of the first exposure step is lower than the dose applied during the exposure pass-through of the second exposure step.

[0042] According to a preferred embodiment, the light source is moved in a cycle involving a first movement in a first direction and a second movement in a second opposite direction, each cycle comprising one or two exposure passes.

[0043] In another embodiment, the exposure apparatus comprises a first light source configured to expose a first side of a relief precursor; a movable second light source configured to expose a second side of the relief precursor opposite to the first side during one or more exposure passes; a moving means configured to move the second light source; and a control means according to any one of the above preferred embodiments.

[0044] Preferably, the first light source, which is a stationary light source, may comprise a plurality of LEDs or a plurality of phototubes, or a plurality of laser diodes or a combination thereof. Optionally, the first light source may include intensity control means configured to change the intensity emitted by the first light source. For example, if the first light source is an LED array, the intensity control means may be a driving means configured to drive the LED array at different power levels. Alternatively, the intensity control means may be an optical means configured to change the light intensity on the relief precursor by, for example, placing a partially absorbing, partially reflective, or partially diffracting medium between the light source and the relief precursor. Furthermore, the intensity may be changed by selecting a plate with appropriate optical properties from a plurality of plates with different optical properties and placing this plate between the first light source and the relief precursor to affect the intensity seen by the relief precursor. If different intensities are required, this plate may be replaced. In yet another embodiment, a PCB having a driving circuit for generating the required driving current for the first light source can be selected from a plurality of PCBs configured to generate different driving currents depending on the required intensity. Furthermore, the distance between the second light source and the relief precursor may be varied to affect the intensity observed by the relief precursor.

[0045] The second light source is preferably a movable light source and may comprise a plurality of LEDs or a plurality of phototubes, or a plurality of laser diodes or a combination thereof. Optionally, the second light source may comprise a plurality of LEDs. In this way, variable intensity can be achieved in a convenient manner. Optionally, the second light source may comprise intensity control means configured to change the intensity emitted by the second light source. For example, if the second light source is an LED array, the intensity control means may be a drive means configured to drive the LED array at different power levels. Alternatively, the intensity control means may be an optical means configured to change the light intensity on the relief precursor. Furthermore, the intensity may be changed by selecting a plate with appropriate optical properties from a plurality of plates with different optical properties and placing this plate between the second light source and the relief precursor to affect the intensity seen by the relief precursor. If different intensities are required, this plate may be replaced. In yet another embodiment, depending on the required intensity, a PCB having a drive circuit for generating the required drive current for the second light source can be selected from a plurality of PCBs configured to generate different drive currents. Furthermore, the distance between the second light source and the relief precursor may be varied to affect the intensity observed by the relief precursor.

[0046] According to a preferred embodiment, the exposure apparatus includes control means configured to back-expose the precursor with electromagnetic radiation from the side opposite to the relief-forming side that is exposed before, after, or during the first and second exposure steps. [Brief explanation of the drawing]

[0047] The accompanying drawings are used to illustrate currently preferred, non-limiting, exemplary embodiments of the apparatus and method of the present invention. The above and other advantages of the features and objectives of the present invention will become clearer, and the present invention will be better understood from the following detailed description when read in conjunction with the accompanying drawings. [Figure 1]Figure 1 is a schematic cross-sectional view of an exemplary embodiment of an apparatus for exposure of a relief precursor. [Figure 2] Figure 2 is a time diagram of the first exposure step of an exemplary embodiment of a method for exposing a relief precursor cursor when the second light source is exposed only while it is moving forward. [Figure 3] Figure 3 is a time diagram of the first exposure step of an exemplary embodiment of a method for exposing a relief precursor cursor when a second light source is exposed during the entire cycle of forward and backward movement. [Figure 4] Figure 4 is a flowchart of an exemplary embodiment of a method for exposure of a relief precursor. [Figure 5] Figure 5 is a table containing data according to an exemplary embodiment of the method for exposure. [Figure 6] Figure 6 is a perspective view of another exemplary embodiment of the apparatus for exposure of a relief precursor. [Figure 7] Figure 7 schematically illustrates how the intensity emitted by the first and second light sources is measured. Detailed description of the embodiment

[0048] Figure 1 schematically shows a cross-sectional view of an exposure apparatus for a relief precursor P comprising a substrate layer and at least one photosensitive layer. The apparatus comprises a first light source 1, a movable second light source 2, a transport structure 3, and a mask 4, all located on the photosensitive layer of the relief precursor P. The first light source 1 is configured to illuminate the first side of the relief precursor P, the underside, also known as the back side. The movable second light source 2 is configured to illuminate the second side of the relief precursor P, opposite to the first side. The second side is typically the uppermost side, also known as the front side of the relief precursor P.

[0049] The first light source 1 extends substantially in a plane parallel to the relief precursor P. The first light source 1 is stationary. The second light source 2 is movable back and forth in a plane parallel to the plane of the first light source 1, as indicated by arrow A1.

[0050] Preferably, the first light source 1 is configured to illuminate a first illumination region of a plane (having a width w1' in Figure 1), and the second light source is configured to illuminate a second illumination region of the plane (having a width w2' in Figure 1), the plane being positioned between the first and second light sources and on which the first side of the relief precursor P is intended to be placed. The illumination region of the plane is defined as the region where the maximum light intensity on the plane exceeds 10%. If a support structure 3 is present, the plane is corresponding to the support surface of the support structure 3. Preferably, the second illumination region (having a width w2' in Figure 1) is at least twice, more preferably at least three times, and most preferably at least five times smaller than the first illumination region (having a width w1' in Figure 1). In a typical embodiment, the first light source 1 is used to substantially illuminate the entire first side (i.e., the entire rear side) of the relief precursor P, while the second light source 2 illuminates a smaller area of ​​the second side (i.e., the upper side) of the relief precursor, typically with a higher light intensity. Preferably, the width w2' is 100 mm to 600 mm, for example, 200 mm to 400 mm. Preferably, the width w1' is 1500 mm to 3000 mm, for example, 1800 mm to 2500 mm.

[0051] The support structure 3, for example, a glass plate, is configured to support the relief precursor and is placed between the second light source 2 and the first light source 1. The transport structure 3 may be transparent to electromagnetic radiation emitted from the first light source 1.

[0052] The first light source 1 may be selected from a group including multiple LEDs, a pair of fluorescent lamps, a flash lamp, a pair of phototubes, an LCD screen, a light projection system (with movable mirrors), a sunlight collection system, and combinations thereof. The second light source 2 may be selected from a group including an LED array, a pair of fluorescent lamps, a flash lamp, a pair of phototubes arranged in a straight line, a (scanning) laser, an LCD screen, a light projection system (with movable mirrors), and combinations thereof.

[0053] Figure 1 illustrates a moving means M configured to move the second light source 2. The control means 5 may control the moving means M so that the second light source 2 exposes the entire surface of the relief precursor. The control means 5 can be configured to control the first light source 1 and to control and move the second light source 2.

[0054] In particular, the control means 5 can be configured to control the exposure by the second light source 2 to follow the received intensity profile, and to control the moving means M to move the second light source 2 according to the received velocity profile. The control means 5 can receive the intensity and velocity profiles via the operator interface 7. The operator interface 7 may be a graphical interface.

[0055] Preferably, the first light source, which is a fixed light source, may include a plurality of LEDs or a plurality of phototubes, or a plurality of laser diodes or a combination thereof. Optionally, the first light source may include intensity control means configured to change the intensity emitted by the first light source. For example, if the first light source is an LED array, the intensity control means may be a driving means configured to drive the LED array at different power levels. Alternatively, the intensity control means may be an optical means configured to change the light intensity on the relief precursor by, for example, placing a partially absorbing, partially reflective, or partially diffracting medium between the light source and the relief precursor.

[0056] The second light source may comprise multiple LEDs. In this way, variable intensity can be achieved by using an intensity control means that is configured to drive the LED array at different power levels. Alternatively, the intensity control means may be an optical means configured to change the light intensity on the relief precursor by, for example, setting a partially absorbing, partially reflective, or partially diffracting medium between the light source and the relief precursor. Additionally or alternatively, the intensity control means may control the dose seen by the relief precursor P by controlling the movement of an additional plate arranged between the light source 2 and the relief precursor P, and / or control the intensity seen by the relief precursor P by controlling the distance between the second light source 2 and the relief precursor.

[0057] According to one embodiment, once a mask 4 is provided on the photosensitive layer of the relief precursor, the control means 5 can be configured to control the second light source 2 to conform to a first intensity profile received via the operator interface 7, while controlling the moving means M to expose the relief precursor according to a first velocity profile received via the operator interface 7. In this first exposure step, the relief precursor P can be exposed through the mask 4 according to the first intensity profile and the first velocity profile. The control means can then be configured to expose the relief precursor according to a second exposure step, during which the precursor is exposed by the second light source 2 through the mask according to a second intensity profile different from the first intensity profile, while the second light source 2 is moved by the moving means M according to a second velocity profile different from the first velocity profile.

[0058] Figure 2 is a time diagram of the first exposure step of an exemplary embodiment of a method for exposing a relief precursor cursor when the second light source is exposed only during forward movement. The second light source 2 can then be moved in an exposure cycle, making a first movement in the first direction and a second movement in the second opposite direction. Each exposure cycle may include one exposure pass and one time period to return the light source to its original position.

[0059] Figure 2 shows a first exposure step ES1 comprising two cycles EC1 and EC2 as an example. During each cycle EC1, EC2, the light source can expose the relief precursor during exposure passes EP1, EP2, and for the remainder of the cycle, the light source is returned to its original position for the next cycle.

[0060] During the first exposure step ES1, the intensity I of the second light source 2 is controlled to follow a first intensity profile IP1. The first intensity profile IP1 is such that the intensity is substantially constant during exposure passes EP1 and EP2, equal to the average intensity I1, and substantially zero during the remaining cycles EC1 and EC2. Still, depending on the circumstances, other options can be considered in which the first intensity profile IP1 follows a profile that increases or decreases over time during each pass of the first exposure step or between subsequent passes of the first exposure step. It is also conceivable to increase the intensity stepwise or linearly during the passes of the first exposure step.

[0061] During the first exposure step ES1, the speed of the moving means M for moving the second light source 2 is controlled to follow a first speed profile SP1. The first speed profile SP1 is such that the speed is substantially constant while the exposure passes through EP1 and EP2, substantially equal to the average speed S1f for forward movement during the first exposure step, and substantially equal to the average speed S1b for backward movement during the remaining cycles EC1 and EC2. The backward speed S1b is usually higher than the forward speed Sf in order to minimize the duration of backward movement. Still, depending on the situation, other options can be considered in which the first speed profile SP1 follows a profile that increases or decreases over time during each pass of the first exposure step or between subsequent passes of the first exposure step. A gradual or linear increase in speed during the pass of the first exposure step can also be considered. Furthermore, both speed and intensity can have customizable profiles depending on the situation.

[0062] Figure 3 is a time diagram of the first exposure step in an exemplary embodiment of a method for exposing a relief precursor cursor when a second light source is exposed during the entire cycle of forward and backward movement.

[0063] In Figure 3, the first exposure step ES1 also includes two cycles EC1 and EC2. Furthermore, contrary to the embodiment in Figure 2, in Figure 3, the second light source 2 may expose the relief precursor throughout the entire exposure cycle, i.e., while the second light source 2 is moving forward and backward. In this case, each cycle includes two exposure passes. For example, cycle EC1 includes exposure passes EP1 and EP2, and exposure cycle EC2 includes exposure passes EP3 and EP4, where the second light source 2 is moved in the same (forward) direction between EP1 and EP3, and in opposite (backward) directions between EP2 and EP3.

[0064] Throughout the first exposure step ES1, the intensity I of the second light source 2 is controlled to follow a first intensity profile IP1, which is a substantially constant average intensity I1. Similarly, throughout the first light step ES1, the speed of the moving means M that moves the second light source 2 is controlled to follow a first speed profile SP1, which is a substantially constant average speed S1 for both forward and backward movement.

[0065] Furthermore, as with the embodiment in Figure 2, in order to customize the first exposure step to the operator's needs, other options besides a constant profile can be considered for the intensity profile, the velocity profile, or both, depending on the situation. For example, the average velocity and / or average intensity during the passage through the first exposure step can be increased in stages after a certain number of passes.

[0066] Figure 4 is a flowchart of an exemplary embodiment of the method for exposing the relief precursor.

[0067] In the first step 20, a mask 4 may be placed on the photosensitive layer of the relief precursor P. Next, in step 21, a first intensity profile IP1, a first velocity profile SP1, a second intensity profile IP2, and a second velocity profile SP2 may be received via the operator interface 7. Then, the relief precursor P may be exposed in the first exposure step ES1 according to the first intensity profile IP1 and the first velocity profile SP1, and in the second exposure step ES2 according to the second intensity profile IP2 and the second velocity profile SP2.

[0068] In exemplary embodiments, all profiles may be constant. For example, the first intensity profile IP1 and the second intensity profile IP2 may be such that the average intensity I1 during exposure in the first exposure step ES1 is higher than the average intensity I2 during exposure in the second exposure step ES2. Similarly, the first velocity profile SP1 and the second velocity profile SP2 may be such that the average velocity S1 during exposure in the first exposure step ES1 is higher than the average velocity S2 during exposure in the second exposure step ES2. However, as already mentioned above, other intensity and / or velocity profiles during the first and / or second exposure steps can also be assumed.

[0069] As defined in Figures 2 and 3, a pass means a unidirectional movement that covers the entire surface of the relief precursor in the irradiation area of ​​the second light source 2. A cycle can be defined by two consecutive passes in opposite directions. Each cycle may include one or two exposure passes. A cycle may actually include a first pass in one direction during exposure and a second pass while exposure is not performed and the second light source 2 is simply returned to its initial position (as in Figure 2). Alternatively, and preferably, a cycle may include two exposure passes, where exposure is performed during the forward and backward movement of the second light source 2 (as in Figure 3). In this scenario, the first exposure step ES1 may include a first number of passes n1, and / or the second exposure step ES2 may include a second number of passes n2. Typically, the first number of passes n1 and / or the second number of passes n2 may be received by the control means 5 via the operator interface 7. The first number of passes n1 may typically be higher than the second number of passes n2. The first dose applied during the first exposure step ES1 may also typically be lower than the dose applied during the second exposure step ES2.

[0070] Typically, the exposure method includes a first exposure step ES1 comprising a relatively fast passage of n1 of a second light source 2 at a relatively high intensity I1 and a relatively high speed S1, and a second exposure step ES2 comprising a relatively slow passage at a relatively low intensity I2 and a relatively low speed S2, where I1 > I2 and S1 > S2.

[0071] Figure 5 is a table containing data according to an exemplary embodiment of the exposure method. Two different relief precursors, labeled A and B, were exposed according to different first and second exposure steps. In these two examples, the first exposure step ES1 includes multiple high-speed passes only during forward movement, and the second exposure step ES2 includes one low-speed pass (n2=1) during forward movement. Generally, this sequence can be used to focus on first reducing oxygen inhibition in the relief precursor using high intensity to form flat dots during the first exposure step with high-speed passes, and the second exposure step with low intensity and low passes can complete curing with moderate heating of the precursor.

[0072] Furthermore, back exposure with the first light source 1 may be performed before, after, or simultaneously with the first or second exposure step. More generally, the timing and intensity of the exposure and movement steps by the first and second light sources can be controlled in any possible way, for example, by adjusting them according to the type of relief precursor. For example, while the first light source 1 is exposing at a high power level, the second light source 2 can move back and forth multiple times to adjust the timing so that each part of the relief precursor receives the same dose at the end of exposure by the first light source.

[0073] For a type A precursor with a thickness of 1.14 mm, light source 2 was used at 460 mW / cm². 2 The first two passes were at a speed of 1,000 mm / min, with a flow rate of 8.3 J / cm² per pass. 2 The procedure was carried out at the dose, followed by a test using light source 2 at 370 mW / cm². 2One pass-through was performed at a speed of 350 mm / min with a dose of 18 J / cm.

[0074] For the type B precursor with a thickness of 2.84 mm, a light source of 426 mW / cm² was used. 2 The first two passes through at a speed of 6000 mm / min with a flow rate of 1275 J / cm². 2 The procedure was carried out at the dose, and then using light source 2, 370 mW / cm² was used. 2 A single pass through at a speed of 350 mm / min with a flow rate of 18 J / cm² 2 The procedure was carried out at this dose.

[0075] Print quality was evaluated as follows: If there was no difference in ink density between the treated and untreated areas of the paper, it was indicated as low quality. If there was a strong difference in ink density between the treated and untreated areas of the paper, and the two areas were clearly separated by a boundary line, it was indicated as high quality. Results in between were categorized as mediocre quality.

[0076] Using the above exposure parameters, high-quality flat dots were obtained efficiently from both types of precursors.

[0077] Furthermore, alternative embodiments may be envisioned in which the first exposure step includes one or more slow passes and the second exposure step includes one or more fast passes. In particular, in such embodiments, the second exposure step is a high-intensity exposure that can be used to complete the curing of the relief precursor. Completion of curing is generally a separate post-processing step so that the total development time can be reduced when completion of curing is combined with the second exposure step.

[0078] Figure 6 illustrates in detail an exemplary embodiment using the same main components as in the embodiment of Figure 1, and these components will not be described again. The apparatus comprises a housing 100 having a lower housing portion 130 with a first light source and an upper housing portion 110 with an optional additional light source. The relief precursor P may be brought onto the support structure 3 manually or automatically so as to be placed between the first light source in the lower housing portion 130 and the upper housing portion 110. The apparatus comprises a second light source 2 including a movable LED bar. The movable LED bar structure 2 is movable from right to left and backward.

[0079] Furthermore, in embodiments not shown, a pretreatment unit may be provided for pretreatment of the relief precursor, the pretreatment being selected from the group including: cutting, ablation, exposure to electromagnetic radiation, and combinations thereof.

[0080] In embodiments not shown, a post-processing unit may be provided to perform post-processing on the relief precursor, such as washing, drying, post-processing exposure, heating, cooling, material removal, etc. Furthermore, in embodiments not shown, a pre-processing unit may be selected from the group including: cutting, ablation, exposure to electromagnetic radiation, and combinations thereof.

[0081] The relief precursor generally comprises a support layer and at least one photosensitive layer. The support layer may be a flexible metal, a natural or artificial polymer, paper, or a combination thereof. Preferably, the support layer is a film or sheet of a flexible metal or polymer. In the case of a flexible metal, the support layer may include a thin film, a sieve-like structure, a mesh-like structure, a woven or nonwoven fabric structure, or a combination thereof. Steel, copper, nickel, or aluminum sheets are preferred and may have a thickness of about 50–1000 μm. In the case of a polymer film, the film is dimensionally stable but flexible and can be made from, for example, polyalkylene, polyester, polyethylene terephthalate, polybutylene terephthalate, polyamide, and polycarbonate, polymers reinforced with woven fibers, nonwoven fibers, or layered fibers (e.g., glass fibers, carbon fibers, polymer fibers), or a combination thereof. Preferably, polyethylene and polyester foils are used, with a thickness of about 100–300 μm, preferably 100–200 μm.

[0082] In addition to the photosensitive layer and support layer, the relief precursor may comprise one or more further additional layers. For example, the further additional layers may be any one of the following: a directly (e.g., laser) etchable layer, a solvent or water developable layer, a heat developable layer, a mask layer, a cover layer, a barrier layer, etc. One or more adhesive layers may be placed between the different layers described above to ensure proper adhesion between the different layers.

[0083] The relief precursor may support at least one additional layer. For example, the additional layer may be any of the following: a layer that can be directly (e.g., by laser) engraved, a layer that can be developed with a solvent or water, a layer that can be developed with heat, a photosensitive layer, a cover layer, a barrier layer, or a combination of a photosensitive layer and a mask layer. Optionally, one or more additional layers may be provided on top of the additional layer. One or more adhesive layers may be placed between the different layers described above to ensure proper adhesion of the different layers. Such one or more further additional layers may include a cover layer on top of all other layers that are removed before the image-forming layer is image-formed. One or more additional layers may comprise a relief layer and an anti-halation layer between the support layer and the relief layer, or on the side of the support layer opposite the relief layer. One or more additional layers may comprise a relief layer, an image-forming layer, and one or more barrier layers between the relief layer and the image-forming layer to prevent oxygen diffusion. One or more adhesive layers may be placed between the different layers described above to ensure proper adhesion of the different layers.

[0084] In a preferred embodiment, the relief precursor includes a support layer made of a polymer material polyester and an additional layer made of a directly engravable material such as a resin material. The optional layer may be a laser ablation layer. In an exemplary embodiment, the relief precursor may include at least a dimensionally stable support layer, a relief layer and an image-forming mask layer. Optionally, further layers may be present. A cover layer may be on top of all other layers that are removed before the image-forming mask layer is imaged. A halation prevention layer may be provided between the support layer and the relief layer, and it may be placed on the opposite side of the support layer from the relief layer. One or more barrier layers to prevent oxygen diffusion may be present between the relief layer and the image-forming mask layer. One or more adhesive layers may be placed between the different layers described above to ensure proper adhesion of the different layers. One or more layers may be removable by liquid treatment. The liquid used may be the same or different for the different layers. Preferably, different liquids are used.

[0085] In a preferred embodiment, the relief precursor comprises a photosensitive layer and a mask layer. The mask layer may be removed during processing or its transparency may change to form a mask having transparent and opaque regions. The mask layer and / or barrier layer may contain materials that could cause problems during further process steps or use of the final relief, and are therefore preferably removed in a pre-cleaning section of the system. Beneath the transparent region of the mask, the photosensitive layer undergoes a change in solubility and / or fluidity upon irradiation. This change is used to generate the relief by removing a portion of the photosensitive layer in one or more subsequent steps. The change in solubility and / or fluidity can be achieved by photo-induced polymerization and / or crosslinking, which reduces the solubility of the irradiated region. In other cases, electromagnetic radiation causes the breakdown of bonds or the cleavage of protecting groups, making the irradiated region more soluble. Preferably, a method using photo-induced crosslinking and / or polymerization is employed.

[0086] Liquids that can be used to remove material from an exposed precursor include, among others, water, aqueous solutions, solvents, and combinations thereof. The properties of the liquid used are determined by the properties of the precursor used. If the layer to be removed is soluble, emulsifiable, or dispersible in water or aqueous solutions, water or aqueous solutions may be used. If the layer is soluble, emulsifiable, or dispersible in organic solvents or mixtures thereof, organic solvents or mixtures may be used. For organically developable precursors, different organic solvents or mixtures thereof may be used.

[0087] The removal of uncured material from the exposed precursor may also be carried out by heating and removal of the liquefied material with a developing material. The removal of the softened material is achieved by bringing it into continuous contact with an absorbent material. The absorbent developing material may be a nonwoven fabric of polyamide, polyester, cellulose, or inorganic fibers, on which the softening material adheres and is subsequently removed. Such methods are described, for example, in U.S. Patent No. 3,264,103, U.S. Patent No. 5,175,072, WO 96 / 14603, or WO 01 / 88615. Alternatively, WO 01 / 90818 proposes removing the uncured material by treating the exposed relief precursor with a high-temperature gas or fluid jet. Apparatus capable of carrying out the above methods is described in EP-A 469 735 and WO 01 / 18604.

[0088] Although the principles of the present invention have been described above in relation to specific embodiments, it should be understood that this description is merely illustrative and not intended to limit the scope of protection as determined by the appended claims.

Claims

1. A method for exposing a relief precursor (P) with a light source (2), wherein the irradiation area of ​​the light source (2) covers a portion of the region of the precursor, and the entire region of the precursor is exposed by moving the light source and the precursor relative to each other during exposure, and the method is Step (20) of providing a mask (4) on the photosensitive layer of the precursor (P), A first exposure step (ES1) is provided, wherein the precursor is exposed through a mask during one or more exposure passes according to a first intensity profile (IP1) and a first velocity profile (SP1). A second exposure step (ES2) is a second exposure step (ES2) in which the precursor is exposed through a mask during one or more exposure passes according to a second intensity profile (IP2) different from the first intensity profile (IP1) and a second velocity profile (SP2) different from the first velocity profile (SP1), Includes, A method wherein the average intensity (I1) during exposure in the first exposure step (ES1) is higher than the average intensity (I2) during exposure in the second exposure step (ES2).

2. The method according to claim 1, wherein the first velocity profile (SP1) is a profile such that the velocity during one or more exposure passes of the first exposure step (ES1) is substantially constant, and / or the second velocity profile (SP2) is a profile such that the velocity during one or more exposure passes of the second exposure step (ES2) is substantially constant.

3. The method according to any one of claims 1 to 2, wherein the average speed (S1) during exposure in the first exposure step (ES1) is higher than the average speed (S2) during exposure in the second exposure step (ES2).

4. The method according to any one of claims 1 to 3, wherein the first intensity profile (IP1) is a profile such that the intensity during one or more exposure passes of the first exposure step (ES1) is substantially constant, and / or the second first intensity profile (IP2) is a profile such that the intensity during one or more exposure passes of the second exposure step (ES2) is substantially constant.

5. The method according to any one of claims 1 to 4, wherein the first exposure step (ES1) has a first number of exposure passes (n1), and / or the second exposure step (ES2) has a second number of exposure passes (n2).

6. The method according to any one of claims 1 to 5, wherein the first dose irradiated during the exposure pass of the first exposure step (ES1) is lower than the second dose irradiated during the exposure pass of the second exposure step (ES2).

7. The first dose and the second dose are, respectively, 0.2–30 J / cm². ２ The method according to claim 6.

8. The first dose is 0.2 to 20 J / cm². ２ The second dose is 2 to 28 J / cm². ２ The method according to claim 7.

9. The method according to any one of claims 5 to 8, wherein the first number of exposure passes (n1) and the second number of exposure passes (n2) are different.

10. The method according to any one of claims 5 to 9, wherein the exposure pass-through of the first number (n1) is higher than the exposure pass-through of the second number (n2).

11. The method according to any one of claims 5 to 10, wherein the first number of exposure passes (n1) is 2 or more, and the second number of exposure passes (n2) is 1.

12. The method according to any one of claims 1 to 11, wherein the light source (2) is moved in an exposure cycle comprising a first movement in a first direction and a second movement in a second opposite direction, and each exposure cycle comprises one or two exposure passes.

13. The method according to any one of claims 1 to 12, wherein one or more of the first exposure passes in the first exposure step and one or more of the second exposure passes are performed while moving in the same direction.

14. The method according to any one of claims 1 to 13, wherein one or more exposure passes of the first exposure step and / or one or more exposure passes of the second exposure step are performed while moving in both directions.

15. The method according to any one of claims 1 to 14, wherein the first average speed (S1) during exposure passage in the first exposure step is in the range of 1,000 to 10,000 mm / min, and the average speed (S2) during exposure passage in the second exposure step is in the range of 10 to 1,000 mm / min.

16. The average intensity (I1) during exposure in the first exposure step is in the range of 30 to 10000 mW / cm², and the average intensity (I2) during exposure in the second exposure step is in the range of 1 to 5000 mW / cm². ２ The method according to any one of claims 1 to 15, which is within the range of claims 1 to 15.

17. The method according to any one of claims 1 to 16, wherein the ratio of the average speed during exposure in the first exposure step (S1) to the average speed during exposure in the second exposure step (S2) is greater than 1.5, or the ratio of the second average speed to the first average speed is greater than 0.

05.

18. The method according to any one of claims 1 to 17, wherein the ratio of the average intensity during exposure in the first exposure step (I1) to the average intensity during exposure in the second exposure step (I2) is greater than 0.15, or the ratio of the second average intensity to the first average intensity is greater than 0.

5.

19. The method according to any one of claims 1 to 18, further comprising the step (21) of receiving the first intensity profile (IP1), the first velocity profile (SP1), the second intensity profile (IP2), and the second velocity profile (SP2) via an operator interface (7) prior to the first exposure step (ES1) and the second exposure step (ES2).

20. The method according to any one of claims 1 to 19, wherein the step (20) of providing the mask (4) includes the step of adding a pre-fabricated mask layer, or the step of generating a transparent region in the mask layer which is an intrinsic layer of the precursor.

21. The method according to any one of claims 1 to 20, further comprising the step of back-exposing the precursor to electromagnetic radiation from the side of the precursor opposite to the side of the mask that has been exposed before, after, or between the first exposure step and the second exposure step.

22. The method according to claim 21, wherein the back exposure is performed during the first exposure step (ES1) and / or the second exposure step (ES2).

23. The method according to claim 18 or 19, further comprising whether or not to perform a back exposure step during the first exposure step and / or second exposure step (ES1, ES2) based on the input first and second speed profiles (SP1, SP2).

24. The method according to claim 21, wherein the wavelength of the electromagnetic radiation is in the range of 200 to 2000 nm.

25. The method according to any one of claims 1 to 24, wherein after the second exposure step (ES2), a further step is performed which is selected from the group including treatment with a liquid, treatment with a gas, heat treatment, contact with a surface, removal of a material that can be dissolved or liquefied, exposure to electromagnetic radiation, exposure to plasma, cutting, sanding, or a combination thereof.

26. The method according to any one of claims 1 to 25, wherein the relief precursor (P) comprises at least a dimensionally stable support layer, one or more photosensitive layers, and optionally a cover layer, an adhesive layer, a barrier layer, a protective layer, a particle layer, a mask layer, or a combination thereof.

27. A control means (5) configured to control the exposure of a relief precursor (P) by a light source (2), The irradiation area of ​​the light source (2) covers a portion of the region of the precursor, and exposure of the entire region of the precursor is performed by moving the light source and the precursor relative to each other during the exposure process, and the control means (5) controls the surface intensity of the precursor and the movement speed of the light source (2) so that the first exposure step (ES1) and the second exposure step (ES2) are performed. The first exposure step (ES1) includes the step of exposing the precursor through a mask (4) in accordance with a first intensity profile (IP1) and a first velocity profile (SP1) during one or more exposure passes, The second exposure step (ES2) includes a step of exposing the precursor through the mask (4) during one or more exposure passes according to a second intensity profile (IP2) different from the first intensity profile (IP1) and a second velocity profile (SP2) different from the first velocity profile (SP1), Control means wherein the average intensity (I1) during exposure in the first exposure step (ES1) is higher than the average intensity (I2) during exposure in the second exposure step (ES2).

28. The control means according to claim 27, configured to control the moving speed of the light source (2) such that the speed of the one or more exposure passes in the first exposure step is substantially constant, and / or the speed during the one or more exposure passes in the second exposure step is substantially constant.

29. The control means according to any one of claims 27 to 28, wherein the average speed (S1) during exposure in the first exposure step is higher than the average speed (S2) during exposure in the second exposure step.

30. A control means according to any one of claims 27 to 29, configured to control the intensity on the surface of the precursor such that the intensity of the first intensity profile (IP1) is substantially constant during the one or more exposure passes of the first exposure step, and / or the intensity of the second intensity profile (IP2) is substantially constant during the one or more exposure passes of the second exposure step.

31. The control means according to any one of claims 27 to 30, wherein the first exposure step comprises a first number of exposure passes, and / or the second exposure step comprises a second number of exposure passes.

32. The control means according to any one of claims 27 to 31, wherein the first dose irradiated during the exposure pass of the first exposure step is lower than the dose irradiated during the exposure pass of the second exposure step.

33. The control means according to any one of claims 27 to 32, wherein the light source is periodically moved with a first movement in a first direction and a second movement in the second opposite direction, and each period includes one or two exposure passes.

34. An exposure apparatus comprising: a first light source (1) configured to expose a first side of a relief precursor; a movable second light source (2) configured to expose a second side of the relief precursor opposite to the first side during one or more exposure passes; a moving means configured to move the second light source; and a control means according to any one of claims 27 to 33.

35. The exposure apparatus according to claim 34, wherein the control means is configured to back-expose the precursor to electromagnetic radiation from the side of the precursor opposite to the side of the mask that has been exposed before, after, or between the first exposure step and the second exposure step.

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