JP2001129960A - Method for obtaining heat sensitive element by spraying coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for obtaining a printing plate of high quality by atomizing a spraying solution on the receiving surface of a roughed and anodized aluminum. SOLUTION: In the method for obtaining a heat sensitive element by spraying coating, a spray factor(SF) is in a range of 48 to 70 mN/m [wherein SF=P/(d×σ), wherein SF is the spray factor (mN/m), P is a spay profile (mm), d is a distance (mm) between a spraying head and a receiving surface, and σis a surface tension (mN/m)]. The width at the half of the height of the profile is divided by the overall height (maximum density) of the profile. This quotient is called 'a profile value' (P). The profile value is determined by the pneumatic pressure of the head, the flow rat of the head and properties of the receiving surface. This value is suitably in a range of 50 to 220 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to heat sensitive elements.
The present invention relates to a method of manufacturing an iterative element by spray-coating.

[0002]

BACKGROUND OF THE INVENTION Lithographic printing is a specially prepared surface in which some areas of the surface can accept the lithographic ink while other areas do not receive the ink when wet with water. This is a method of performing printing by using.
The areas that accept ink constitute the printed image area and the areas that reject ink constitute the background area.

[0003] The photographic materials in the photolithographic arts rely on exposure on a hydrophilic background [negative wor
king)] areas or unexposed areas [positive features] are made to accept oily or greasy inks in an imagewise manner.

A conventional lithographic printing plate [also a surface lithographic plate (su
Also known as lithoplates or planographic printing plates, a support which has been rendered water-compatible or rendered water-compatible by chemical treatment is coated with a thin layer of a photosensitive composition. Is done. Coatings used for that purpose include photopolymer layers containing diazo compounds, dichromate-sensitized hydrophilic colloids and a wide variety of synthetic photopolymers. In particular, systems that have been subjected to diazo sensitization are widely used.

When such a photosensitive layer is exposed imagewise, the exposed image areas become insoluble and the unexposed areas remain soluble. Next, the plate is developed with an appropriate liquid to remove the diazonium salt or diazo resin present in the unexposed areas.

[0006] On the other hand, there is also known a method of making a printing plate by using heat-sensitive, but not light-sensitive, image-forming elements. A particular disadvantage of photosensitive imaging elements, such as those for making printing plates described above, is that they need to be shielded from light. In addition, they have a sensitivity problem in terms of storage stability and they exhibit a lower resolution. There is a clear trend in the market towards thermal printing plate precursors.

[0007] For example, Research in January 1992
h Disclosure no. No. 33303 discloses a thermosensitive image forming element comprising a support and a crosslinked hydrophilic layer containing thermoplastic polymer particles and a pigment absorbing infrared light, for example, carbon black. When the thermoplastic polymer particles are imagewise exposed to an infrared laser, they solidify in an imagewise manner such that the imaging element surface in that area receives the ink without any further development. . The drawback of such a method is that the resulting printing plate is easily damaged, since some pressure on the non-printing area can cause the area to accept ink. Further, such printing plates are critical condition (critical condition).
The lithographic printing performance shown below may be inferior,
Thus, such printing plates have little lithographic latitude.

[0008] European Patent Application Publication No. 514 145
The present invention relates to a thermal image comprising a coating comprising core-shell particles having a water-insoluble, heat-softenable core component and a shell component soluble in or swellable in an aqueous alkaline medium. A forming element is disclosed. When a red or infrared laser beam is applied in an image-wise manner to the imaging element, the selected particles are coalesced, at least to some extent, to form an image, and then the uncoalesced particles are developed in an aqueous alkaline solution. To remove selectively. Thereafter, a baking step is performed. However, the printing durability obtained by the printing plate thus obtained (printi)
ng endurance is low.

EP-A-599 510
(1) Component A which is insoluble in water and can be softened by heat
And (2) a binder or continuous phase composed of component B that is soluble or swellable in an aqueous medium, preferably an aqueous alkaline medium. Wherein at least one of components A and B contains a reactive group or a precursor thereof such that this layer undergoes insolubilization when exposed to elevated temperatures and / or actinic radiation; and (ii) A thermal imaging element comprising a substrate coated with a substance capable of absorbing and transferring the energy thus obtained to the disperse phase as heat, resulting in at least some coalescence of the coating. Is disclosed. After the imaging element has been subjected to imagewise irradiation and the imagewise irradiated plate has been developed, heating and / or irradiation of actinic radiation on the plate results in insolubilization. However, the printing durability of the printing plate thus obtained is low.

[0010] European Patent Application Publication No. 625 728
Discloses an imaging element comprising a positive-working or negative-working layer sensitive to UV and IR radiation. The layer is a resole resin,
It comprises a novolak resin, a potential Bronsted acid and an IR absorbing material. The lithographic printing plate obtained by irradiating and developing the image forming element has poor printing results.

US Pat. No. 5,340,699 is almost identical to EP-A-625 728, but discloses a method for obtaining a negative-working IR laser recording imaging element. The IR-sensitive layer comprises a resole resin, a novolak resin, a potential Bronsted acid and an IR absorbing material. The lithographic printing plate obtained by irradiating and developing the image forming element has poor printing results.

No. 4,708,925 discloses an alkali-soluble novolak resin and an onium salt.
m-salt) are disclosed. The composition may optionally contain an IR sensitizer.
The image-forming element is subjected to image-wise exposure with UV-visible or finally IR radiation, and is then subjected to a development step with an aqueous alkaline solution, resulting in a positive-working printing plate. The lithographic printing plate obtained by irradiating and developing the image forming element has poor printing results.

EP-A-96 200
No. 972.6 includes hydrophobic thermoplastic polymer particles dispersed in a resin that is insoluble in water and soluble in or swellable with alkali, and a compound capable of converting light to heat. There is disclosed a thermal imaging element comprising an imaging layer comprising a hydrophilic surface of a lithographic substrate, comprising:
The compound is present in or adjacent to the imaging layer and in the alkali swellable or soluble resin is a phenolic hydroxyl group and / or Or comprising a carboxyl group. However, if the pixel time of exposure to the thermal imaging element is short, abrasion occurs in the exposed area, resulting in:
Insufficient ink receptivity.

An image forming layer comprising hydrophobic thermoplastic polymer particles dispersed in a resin soluble or swellable with water or alkali and a compound capable of converting light into heat. A similar imaging element comprising on the hydrophilic surface of a lithographic substrate (wherein the compound is present in or adjacent to the imaging layer in a layer located therein) is, for example, EP- A- 770 494, EP-A- 770 495, EP-A- 770 496, E
PA- 770 497, EP-A-773 112, EP-A- 773 113, EP-A- 7
74 364, EP-A- 800 928, EP-A- 96 202 685, EP-A- 96 2
03 003, EP-A-96 203 004 and EP-A-96 203 633. In most of the above applications, poly (meth) acrylate latex is used as thermoplastic polymer particles, and no specific hydrophilic resin is mentioned. In most cases, carbon black or IR dyes are mentioned as compounds capable of converting light to heat.

[0015] In order to be able to process the image-forming element as described above in the production of it by pressing, IR dyes should preferably be used. The use of carbon black actually causes press smearing when removing unexposed areas. On the other hand, IR
When a dye is used, the unexposed areas do not completely dissolve when developed using a press, resulting in the formation of scum.

Lithographic printing plate precursor (lithographic)
The application of coatings used in plate making of c precursor plates has largely been performed according to coating techniques such as dip coating, cascade coating and curtain coating. The use of spray technology when applying a lithographic printing layer usually fails in terms of the level of surface quality achievable in the final product. High quality lithographic printing materials with high requirements for resolution, sensitivity and replication properties [thermoprinting plates which can be processed well or not using a press
The requirements for this are very high with regard to the surface quality of the printing plate. Such surface quality depends on the presence of lines.
f lines), general unevenness (genera)
level and the presence of mottled patterns. Such a mottled pattern, even if only slightly present, is present on a large screen (screen pl
anes) clearly appear during the printing process.

[0017]

An object of the present invention is to provide a spray-coated layer having excellent surface quality.
Required to obtain the parameters (parameters)
Is to provide.

[0018]

SUMMARY OF THE INVENTION In accordance with the present invention, a grained and anodized treatment is performed.
d) Receiving surface of aluminum
spray solution on a spray solution
a high quality printing plate is obtained by spraying the spray factor (spray f).
actor (SF) is 48 to 70 mN / m [where SF = (P / dxσ) SF: spray factor (mN / m) P: spray profile (Spray Profile)
e) (mm) d: distance (mm) between the spray head and the receiving surface (σ: surface tension (mN / m)).

[0019]

DETAILED DESCRIPTION OF THE INVENTION When attempting to define the spray profile, the solution and hardware settings are clarified to prevent the spray head from moving laterally during one revolution of the rotating drum. Spray one wire. Appropriate spray pattern
For the purpose of obtaining tern), a sufficiently swellable receiving layer comprising gelatin, polyvinylpyrrolidone and polyethylene glycol [Agfa-Gevaer
Agfajet Photo, commercially available from t)
HP Glossy 165 (trademark), an Ograde paper, was used as a substrate. As a result, the spray solution cannot flow laterally over the receiving surface and the spray pattern solidifies immediately. Using microdensitometry, the density profile of this line (dens
(Profile). In the next step, the width at half the height of the profile is divided by the overall height of this profile (maximum density). This value is called a profile value (P).

This profile value is the value of the spray head (s
depends on the air pressure of the spraying head, the flow rate of the spray head and the nature of the receiving surface.

This value is preferably in the range from 50 to 220 mm, but this value should be taken into account in connection with the given formula. The surface tension of the spray solution is preferably 2
The range is from 2 mN / m to 60 mN / m.

The spray head and a receiving member (receiver)
The distance between the living members is preferably 25.
To 100 mm.

The spray solution is preferably an aqueous solution, which may contain a surfactant, preferably a fluorosurfactant. The viscosity of the spray solution is preferably at least 1.5 mPa.s. s.

The receiving surface may be a drum having a hydrophilic surface, which can be incorporated into a printing press.

[0025] The receiving surface may be a lithographic printing surface located on a drum.

Optimum coating quality is obtained using the following spray settings: Drum speed: 200-240 rpm Spray head distance: 60-100 mm Flow rate: 6-8 ml / min Air pressure: 5.17 × 10 ⁵ − 7.24 × 10 ⁵ Pa Number of coatings: 5-7 Spray head speed: 1-2 m / min Drying temperature: 70 ° C. Spray head type: air-assisted SUJ1 A preferred spray solution has hydrophobic thermoplastic polymer particles that are hydrophilic. It is a dispersion liquid dispersed in a sexual binder. The solution preferably contains thermoplastic particles of a homopolymer or copolymer of styrene, a carboxyl group-containing hydrophilic polymer, and a compound capable of converting light into heat. Said solution suitable for use in spraying a thermal imaging element together with its exposure and development is disclosed in EP-A-982.
00 187.

The receiving element is a lithographic substrate with a hydrophilic support, ie an aluminum support which has been subjected to a roughening treatment and an anodizing treatment.

Development can be performed by exposing the imaging element obtained by spraying the spray solution onto the receiving element to an IR laser and then rinsing the element with an aqueous solution. The exposed imaging element is preferably mounted directly on a press.

The following examples illustrate the present invention but do not limit the invention. All parts and percentages are by weight unless otherwise specified.

[0030]

EXAMPLES Preparation of Spray Solution Spray Solution A A polystyrene latex, dye I and a hydrophilic binder were mixed to prepare a 2.61% by weight solution in water. After spraying and drying, the resulting layer contained 75% (w / w) of the polystyrene latex, 10% of Dye A and 15% (w / w) of Glascol E15 ™. . Glascol E15 is available from N.I.
V. Allied Colloids Belgium
Is a commercially available polyacrylic acid.

The structure of Dye I is as follows:

[0032]

Embedded image

Spray Solution B To Spray Solution A was added 5 ml of a fluorosurfactant. Spray Solution C To Spray Solution A was added 10 ml of a fluorosurfactant. Example 1 Preparation of a lithographic printing substrate An aluminum foil having a thickness of 0.30 mm was immersed in an aqueous solution containing 50 g / l of sodium hydroxide at 50 ° C., and then rinsed with deionized water. A degreasing treatment was performed. Next, 4 g / l of hydrochloric acid and 4 g of hydroboric acid were added to the foil.
/ L and 5 g / l of aluminum ions and a current density of 1200 A
/ M ² of an electrochemical surface roughening treatment using alternating current,
Average center-line roughness (average center-lin
e roughness (Ra) produced a surface microstructure of 0.5 μm.

Next, after rinsing the aluminum foil with deionized water, the aluminum foil was etched for 180 seconds using an aqueous solution of 60 ° C. containing 300 g / l of sulfuric acid, and then deionized water at 25 ° C. for 30 seconds. I rinsed.

Next, a voltage of about 1 V was applied to the foil in an aqueous solution containing 200 g / l of sulfuric acid and having a temperature of 45 ° C.
Anodizing at 0 V and a current density of 150 A / m ²
After forming an anodic oxide film of 3.00 g / m ² of Al ₂ O ₃ , this was washed with deionized water, and a solution containing polyvinyl phosphonic acid was used. Subsequent to the treatment, a post-treatment using a solution containing aluminum trichloride was performed, and the solution was treated with deionized water at 20 ° C. for 120 minutes.
After rinsing for 2 seconds, it was dried. Heat-mode image forming element
Preparation of ng element Spray solution A was sprayed onto the lithographic substrate described above. Therefore, by attaching the lithographic printing substrate to a drum,
The drum is operated at a line speed of 164 m / min.
speed). Spray nozzle (spray
Nozzle was moved laterally at a speed of 1.5 m / min to coat the imaging element. The spray nozzle was mounted such that the distance between the nozzle and the receiving substrate was 80 mm. The flow rate of the spray solution is 7m
1 / min. The air pressure at the spray head used during the spraying process was 7.58 × 10 ⁵ Pa. The final coating weight is obtained by successive spraying during the six passes of the spray head. This layer was dried during the spraying process at a temperature of 70 ° C. and for an additional 30 seconds. The spray nozzle is Spraying S
SUJ1 type air-assisted spray nozzle commercially available from systemss (Brussels, Belgium). Example 2 The same substrate as described in Example 1 was used. Preparation of Thermal Mode Imaging Element The same spray solution and procedure as described in Example 1 was used except for the following settings: flow rate of the spray solution was 4 m
1 / min and the air pressure is 6.21 × 10 ⁵ Pa
Set to. Example 3 The same substrate as described in Example 1 was used. Preparation of Thermal Mode Imaging Element The same spray solution and procedure was used as described in Example 1 except for the following settings: the distance between the spray nozzle and the receiver was set to 60 mm and the air pressure Was set to 6.21 × 10 ⁵ Pa. Example 4 The same substrate as described in Example 1 was used. Preparation of Thermal Mode Imaging Element The same spray solution and procedure as described in Example 2 was used except for the following settings: the flow rate of the spray solution was 15
It was set to ml / min. Example 5 The same substrate as described in Example 1 was used. Preparation of Thermal Mode Imaging Element The same spray solution and procedure as described in Example 2 was used except for the following settings: the flow rate of the spray solution was 10
It was set to ml / min. Example 6 The same substrate as described in Example 1 was used. Preparation of Thermal Mode Imaging Element The same spray solution and procedure as described in Example 3 was used except for the following settings: The distance between the spray nozzle and the receiver was set at 45 mm. Example 7 The same substrate as described in Example 1 was used. Preparation of Thermal Mode Imaging Element The same spray solution and procedure as described in Example 3 was used except for the following settings: The distance between the spray nozzle and the receiver was set to 35 mm. Example 8 The same substrate as described in Example 1 was used. Preparation of Thermal Mode Imaging Element 6.21 × 1 instead of 7.58 × 10 ⁵ Pa air pressure
0 ⁵ except set to Pa was sprayed spray solution B according to the procedure as described for Example 1. Example 9 The same substrate as described in Example 1 was used. Preparation of Thermal Mode Imaging Element 3.45 × 1 instead of 6.21 × 10 ⁵ Pa air pressure
0 ⁵ except set to Pa was sprayed spray solution B according to the procedure as described for Example 8. Example 10 The same substrate as described in Example 1 was used. Preparation of Thermal Mode Imaging Element Air pressure was 4.83 × 1 instead of 3.45 × 10 ⁵ Pa
0 set to ⁵ Pa to and except for the 70mm distance of the spray nozzle and the receiving member by shortening was sprayed spray solution B according to the procedure as described for Example 9. Example 11 The same substrate as described in Example 1 was used. Preparation of Thermal Mode Imaging Element Spray Solution C was sprayed according to the procedure as described in Example 9. Example 12 The same substrate as described in Example 1 was used. Preparation of Thermal Mode Imaging Element Spray Solution C was sprayed according to the procedure as described in Example 1, changing the air pressure setting to 4.83 × 10 ⁵ Pa. Example 13 The same substrate as described in Example 1 was used. Preparation of Thermal Mode Imaging Element Spray Solution C was sprayed according to the procedure as described in Example 1. Surface tension of the spray solution The surface tension of the spray solution was measured using a generally known Wilhelmy plate method. in this way,
The surface tension is calculated by measuring the force that breaks the contact between the platinum plate and the liquid surface.

[0036]

[Table 1]

Calculation of Spray Factor The spray factor (SF) is obtained by multiplying the value obtained by dividing the profile (P) by the distance (d) (mm) between the spray head and the receiver and the surface tension (σ) of the spray solution. calculate.

[0038]

[Table 2]

Surface Quality The plate after spraying and drying is visually inspected to give estimates for the presence of lines, level of uniformity and mottle behavior.

The lower the value, the better the quality in this procedure. A value of 0 means that the quality is perfect. On the other hand, a value of 5 means that the quality is very poor.

For both line presence and uniformity, 1
Is still an acceptable value. Regarding the mottled behavior,
A value of one is an unacceptable value because such mottle is visible on a large screen surface during the printing process.

[0042]

[Table 3]

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03F 7/00 503 G03F 7/00 503 7/16 501 501 7/16 501

Claims (7)

[Claims] 1. A method for obtaining a high quality printing plate by spraying a spray solution on an aluminum receiving surface which has been subjected to a surface roughening treatment and an anodizing treatment, comprising a spray factor (S)
F) from 48 to 70 mN / m [where SF = (P / dxσ) SF: spray factor (mN / m) P: spray profile (mm) d: distance between spray head and receiving surface (mm) σ : Surface tension (mN / m)]. 2. The method of claim 1, wherein said spray solution is an aqueous solution. 3. The method according to claim 1, wherein the spray solution comprises hydrophobic thermoplastic polymer particles and a compound capable of converting light to heat. 4. The method of claim 3, wherein said solution comprises a hydrophilic binder. 5. The method according to claim 1, wherein the receiving material has a roughened and anodized aluminum surface and is a drum which can be incorporated into a printing press. 6. The method according to claim 1, wherein said receiving surface is a roughened and anodized aluminum surface located on a drum. 7. The spray solution is at least 1.5 m
Pa. 7. The method according to claim 1, which has a viscosity of s.