JPH0816785B2 - Exposure method for photosensitive lithographic printing plate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for exposing a photosensitive lithographic printing plate, and more specifically, it relates to a light-emitting beam having a wavelength of 375 to 425 nm in the range of 300 to 700 nm. The present invention relates to a method for exposing a photosensitive lithographic printing plate using a light source containing 35% or more of light rays, and most of the exposure light rays are at an angle within 10 degrees with respect to the main exposure light ray axis. .

[Conventional technology]

Conventionally, the exposure in the plate making process of a photosensitive lithographic printing plate (hereinafter referred to as "PS plate") requires that the PS plate and the original image to be overlaid on the PS plate are brought into close contact with each other in order to form a clear exposure image on the PS plate. However, the so-called vacuum contact exposure method is adopted in which the PS plate and the original image are placed between the rubber sheet and the pressure-bonded glass, and a vacuum is applied between them to bring them into close contact.

However, in the case of an original picture consisting of several films,
As a so-called sticking film, a film is stuck to a transparent base with tape, but due to dust stuck between this sticking tape and the PS plate and the original film, poor adhesion occurs, so-called burning around the tape or dust. There is a problem that blurring occurs. In fact, the cause of so-called cracking rate of PS plate at the printing site is that the burning blur is the biggest cause.

In addition, when printing with the PS plate, the dot area from the plate to the printed matter increases, that is, the dot gain increases. For this reason, in positive PS plates, the dot area on the plate is reduced by utilizing thinning due to exposure, but in the case of negative PS plates,
Because of its characteristics, it causes inevitably thickening, which increases the halftone dot area on the plate. Therefore, when printing with a negative PS plate, it is desirable to keep dot thickening to a minimum by low exposure, but conversely, with low exposure, problems such as reduced printing durability and film strength may occur. It was a result that ended up.

[Object of the Invention]

Therefore, an object of the present invention is to provide an exposure method for a PS plate which has a low blurring rate and a low sagging rate.

Another object of the present invention is to provide an exposure method for obtaining a negative PS plate having little dot thickness and good printing durability and film strength.

[Structure of Invention]

The present inventors have completed the present invention as a result of various studies to achieve the above object.

The present invention is a method for exposing a photosensitive lithographic printing plate in which a photosensitive lithographic printing plate and a film original image are brought into close contact with each other and an exposure light beam is irradiated from above the film original image, and the light source of the exposure light beam emits light in a range of 375 to 425 nm. It is a light source whose light amount is 35% or more of the light amount in the range of 300 to 700 nm, and by arranging a condenser lens between the light source and the film original image, 90% or more of the light beam irradiating the film original image is the main exposure. An exposure method for a photosensitive lithographic printing plate characterized in that the angle is within 10 degrees with respect to the ray axis.

Hereinafter, the plate making method according to the present invention will be described in detail step by step.

The PS plate used in the present invention is one in which a photosensitive layer is provided on a support having a hydrophilic surface, but preferably an aluminum plate is anodized, and then a support which has been subjected to a hydrophilic treatment if necessary. A photosensitive layer is provided on the top.

The aluminum plates used include pure aluminum and aluminum alloy plates. Various aluminum alloys can be used, for example, an alloy of aluminum with a metal such as silicon, copper, manganese, magnesium, chromium, zinc, lead, bismuth, and nickel. These compositions include some iron and titanium, as well as other negligible amounts of impurities.

The aluminum plate is preferably grained, but prior to that, the surface of the aluminum plate is optionally pretreated in order to remove rolling oil from the surface and to expose a clean aluminum surface. For the former, solvents such as trichlene and surfactants are used. For the latter, a method of using an alkali etching agent such as sodium hydroxide or potassium hydroxide is widely used. As the graining method, a mechanical graining method, a chemical graining method, an electrochemical graining method (so-called electrolytic etching method) and the like are used.

The grained aluminum plate is washed with water if necessary, and then chemically etched if necessary.

The etching treatment liquid used is usually selected from an aqueous solution of a base or acid which dissolves aluminum. In this case, the etched surface must not form a coating different from aluminum or aluminum derived from the etching liquid component. Examples of preferred etching agents include sodium hydroxide, potassium hydroxide, trisodium phosphate, disodium phosphate, tripotassium phosphate, dipotassium phosphate as basic substances; sulfuric acid, persulfuric acid as acidic substances. , Phosphoric acid, hydrochloric acid and salts thereof.

Etching is performed by immersing an aluminum plate in the above-mentioned etching solution, or by applying an etching solution to the aluminum plate, and is preferably processed so that the etching amount is in the range of 0.5 to 10 g / m ² .

For the above etching, it is desirable to use an aqueous solution of a base because the etching speed is high. In this case, since sumat is generated, usually, desmut processing is performed. The acid used for desmut treatment is nitric acid, sulfuric acid,
Phosphoric acid, chromic acid, hydrofluoric acid, hydrofluoric acid, etc. are used.

The etching-treated aluminum plate is optionally washed with water and then anodized. The anodic oxidation can be performed by a method conventionally used in this field. Specifically, when a direct current or an alternating current is applied to aluminum in sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfamic acid, benzenesulfonic acid, etc., or an aqueous solution or a non-aqueous solution containing a combination of two or more of these, the aluminum support An anodized film can be formed on the body surface.

Anodizing treatment conditions vary depending on the electrolytic solution used, and thus cannot be unconditionally determined. However, in general, the concentration of the electrolytic solution is 1 to 80% by weight, the liquid temperature is 5 to 70 ° C, and the current density is 0.5
-60 amps / dm ² , voltage 1-100 V, electrolysis time 30 seconds-50
A range of minutes is suitable.

Among these anodizing treatments, in particular, British Patent No. 1,41
The method of anodizing in sulfuric acid at high current density and the method of anodizing phosphoric acid as an electrolytic bath described in U.S. Pat.No. 3,511,661 used in the invention described in US Pat. preferable.

If necessary, the aluminum support thus treated may be hydrophilized. Preferred hydrophilic treatment 1
One is treatment with an aqueous solution containing at least one group of carboxylic acid, sulfonic acid, phosphonic acid and / or its salt. Specific compounds include gum arabic, carboxymethyl cellulose, carboxyethyl cellulose, carboxymethyl hydroxyethyl cellulose, alginic acid, polyacrylic acid and acrylic acid derivatives, copolymers of vinyl methyl ether and maleic anhydride, vinyl acetate and maleic anhydride. Of polyvinyl sulfonic acid and salts thereof. These compounds may be used in combination of two or more, and if necessary, other compounds such as water-soluble metal salts (for example, zinc acetate) as described in US Pat. No. 3,860,426,
Alternatively, it may contain fine particles such as silica or titanium dioxide, or a dye for the purpose of preventing halation.

These compounds are dissolved in water and then an organic solvent is added if necessary, and this is subjected to a known method such as a dipping method,
By coating on the anodic oxide film of the aluminum plate by a roll coating method, a bar coating method, etc. and drying, and then removing the excess by washing with water if necessary, or by dipping in a heated aqueous solution and then washing and drying, A thin layer composed of such a compound is formed.

The concentration of the coating solution is preferably about 0.001 to 1% by weight, and the coating weight after drying is preferably about 1 to 1000 mg / m ² .

Still another preferred hydrophilic treatment is a method of treating with an aqueous solution of an inorganic salt. Examples of the inorganic salt include alkali metal silicates such as sodium silicate as described in the specifications of U.S. Pat.Nos. 2,714,066 and 3,181,461, and fluorinated zirconates.
The weight after treatment is preferably about 1 to 100 mg / m ² .

A photosensitive layer is provided on the lithographic printing plate support thus treated.

The photosensitive composition constituting the photosensitive layer is one whose solubility or swelling property in a developing solution changes before and after exposure, and some typical examples will be described below.

Composition consisting of diazo resin The diazo resin typified by a condensate of p-diazodiphenylamine and paraformaldehyde may be water-soluble or water-insoluble, but is preferably water-insoluble and ordinary organic compound. Those that are soluble in the solvent are used. Particularly preferred diazo compounds have two or more diazo groups in one molecule such as a condensate of p-diazodiphenylamine and formaldehyde or acetaldehyde, such as a salt with phenol or a salt with sulfonic acid. There is a compound. The diazo resin may be used alone, but is preferably used together with a binder. Since various polymer compounds are known as binders,
It can also be used for the present invention. The content of the binder in the photosensitive layer is about 40 to 95% by weight, and when the amount of the binder is large (that is, when the amount of the diazo resin is small), the photosensitivity is naturally large, but the stability with time is high. descend. The optimal amount of binder is about 70-90% by weight.

Composition Composed of o-quinonediazide Compound A particularly preferred o-quinonediazide compound is an o-naphthoquinonediazide compound, and many kinds thereof are known and can be used. These o
The quinonediazide compound may be used alone, but an alkali-soluble resin may be used in combination as a binder. Examples of the alkali-soluble resin include novolak type phenol resin and t-butylphenol formaldehyde resin, and the content of the binder in the photosensitive layer is about
50-80% by weight.

Composition Composed of Photosensitive Azide Compound A suitable photosensitive azide compound is an aromatic azide compound in which an azide group is bonded to an aromatic ring directly or through a carbonyl group or a sulfonyl group. These are those in which the azido group is decomposed by light to produce nitrene, and various reactions of nitrene cause insolubilization. A large number of photosensitive azide compounds are known and can be used for the present invention, but a binder is usually used as a composition as in the case of other photosensitive resins.

As the photosensitive composition, in addition to the main chain or side chain -CH
= A composition comprising a polymer compound containing a CH-CO- group or a photopolymer composition comprising an addition-polymerizable unsaturated compound, (a) a compound that forms a strong acid upon irradiation, and (b) a cleavage with an acid There is a high-sensitivity positive-working composition composed of a compound (for example, a polymer compound having an orthocarboxylic acid ester group: described in JP-A-56-17345 and a silyl ether polymer compound), which is used for the present invention. be able to. A large number of these photosensitive compositions have been specifically introduced in detail in the literature, and these techniques can be utilized or applied. Among these, those using negative and positive type diazo resins are particularly preferable.

The composition of the present invention can be dissolved in a solvent that dissolves the above components, applied on a support, and dried to obtain a PS plate.

A lithographic printing plate is obtained by the following processing using the PS plate thus created.

After making the photosensitive layer of the PS plate and the original film adhere in a vacuum,
Exposure is performed with an ultraviolet light source.

Most of the rays used for exposure are rays having an angle within 10 degrees with respect to the main exposure ray axis, preferably 90% or more of rays have an angle within 10 degrees, particularly preferably 8 degrees.
A ray whose angle is within degrees.

The main exposure ray axis is the direction in which the light intensity is strongest at an arbitrary point on the PS plate, and is usually the axis connecting the arbitrary point on the PS plate and the center of the light source lamp. To measure the amount of light within an angle of 10 degrees, use a cylinder with a maximum angle of 10 degrees (for example, a cylinder with a diameter of 5 cm and a height of 28.36 cm: a maximum of 10 degrees of light can enter the side wall). It is blackened, and the light intensity of a circle with a diameter of 5 cm is measured with and without the cylinder, and it is calculated from the light intensity ratio.Here, the perpendicular line from the center of the lamp to the PS plate surface is PS because of the ease of measurement. Specified as the measured value at the intersection on the plate.

Conventionally, as a PS plate exposure light source, a fluorescent lamp, a carbon arc lamp, a mercury lamp, a metal halide, etc. have been used, but since these are rod-shaped, they are not only exposed by light rays from various directions, but also Since a scattering plate is placed on the back surface and the measuring surface of the lamp to increase the exposure sensitivity,
The exposure was scattered light.

As a method of obtaining a light ray like the present invention, (1) use of parallel rays of sunlight (2) a method of increasing the distance between the light source lamp and the PS plate (3) a tube as described above in a conventional exposure apparatus (4) Method of providing a light-shielding element formed in parallel between the light source and the PS plate in the shape of a honeycomb. For example, the bright room printer "FFPRINTER series" manufactured by Utex Co., Ltd. By using the honeycomb board A, it is possible to obtain light rays within an angle of 6.3 degrees, and by using the honeycomb board B, it is possible to obtain light rays within an angle of 8.9 degrees. Bright room printer "FF
The "PRINTER (printer) series" aims to obtain a "high illuminance distribution in the entire area" by running a lamp house and to increase the reversal accuracy by "parallel rays". There is a light intensity difference in the peripheral part, and in the central part it is perpendicular to the film,
Since it becomes an oblique light ray in the peripheral part, the reversal accuracy (hair removal accuracy, enlargement of the dimension in repeated reversal of the cut mask, accuracy of matching the female and male plates of the bag character, nonuniformity of the line width in thinning and thickening, etc.) is poor. ) Is the best bright room printer.

(5) Method of making the light source into a small spherical shape and making it an ideal light source by preventing scattered light from the back surface and measurement (6) By installing a condenser lens between the light source and the PS plate, the illuminance Improved method to make the film uniform. For example, the contact reversal printers "P-607", "P-617W series", and "P-627W series" for Meituro film manufactured by Dainippon Screen Co., Ltd. The combination of high pressure mercury lamp and condenser lens can be increased. The condenser lens is used for the purpose of improving the light amount difference between the central portion and the peripheral portion as described above.

(7) A method in which the light source is a small sphere in (6) For example, specifically, the contact reversal printers for the Mei Chamber film "P-617M series" and "P-627M" manufactured by Dainippon Screen Co., Ltd.
Series "(a combination of a spherical electrodeless lamp with a diameter of 30 mm [Magnerax MD series] and a condenser lens). Regarding the Magnetics MD series, published by The Printing Society of Japan, "Printing Magazine 1984 (Vol.67) 6, P1"
1 to P18, Microwave Discharge Light Source Device ". The electrodeless lamp has a flashing life of 5 times or more by removing the electrode of the lamp that causes a decrease in light output and non-lighting. Furthermore, since the lamp is a small sphere, it is arranged as an ideal point light source. The light accuracy is improved and the light distribution is easily controlled.

Furthermore, by providing a parabolic light-reflecting surface on the back surface of the light source like the Magnerax MD series, it is possible to expose the light on the back surface and side surfaces through the condenser lens after reflection, so all light can be used effectively. You can

Among these methods, (1) is difficult to work and
It is difficult to control the exposure amount. In (2), the device becomes long and the light amount is not significantly reduced, and in (3), the exposure area is extremely reduced and only a part of the light beam is used. After all, the decrease in light intensity is large,
In (4), there is no problem in the exposed area, but as in (3), there is a large decrease in the amount of light, and in (5), there is a problem with the method of preventing scattered light (for example, in the case of absorption by a black body,
It causes a problem of heat generation) and unevenness of illuminance. On the other hand, the methods (6) and (7) are the most excellent methods because the condenser lens can be designed so that the sensitivity is minimized and the illuminance is uniform.

Conventionally, a bright room printer used a condenser lens only for the purpose of making the illuminance uniform, but unexpectedly when it was used in the PS plate, it reduced the burning blurring and prevented the dot thickening in the negative PS plate, Moreover, they have found the effect that sufficient printing durability can be obtained.

Moreover, in the case of the PS plate, it is not necessary to invert as many times as the reverse film, and the adhesion baking accuracy is not as severe as that of the reverse film, so it is sufficiently useful for the PS plate.

However, when a conventional bright room printer with a condenser lens was used, the sensitivity decreased compared to the conventional PS plate printer. This is a bright room film. The long wave side is cut by a filter to enable bright room work, and 300 to 400 nm (λmax3
Since it is a silver salt photosensitive material that has a main photosensitive area at 50 nm), a bright room printer light source has many short-wave rays, or the silver salt photosensitive material has a higher sensitivity than the PS plate, so part of the light is used. However, this is because there are many extra wavelength rays in order to obtain sufficient exposure sensitivity.

The light source used in the present invention is a light source containing 35% or more of 357 to 425 nm light with respect to the emitted light in the range of 300 to 700 nm so that sufficient exposure sensitivity can be obtained as a diazo PS plate. To do. In particular, a light source having an emission spectrum peak at 375 to 425 is preferable, and 45% or more is more preferable. In order to obtain such light rays, it is possible to use a metal halide lamp and an electrodeless lamp in which the materials used for the metal halide lamp are enclosed. Especially, a condenser lens is used between the light source that is a small sphere and the PS plate. It is preferable that a parabolic reflector is arranged on the back and side surfaces of the light source. Since the electrodeless lamp has no electrode inside the lamp, there is no problem such as a reaction between the metal and the electrode to be encapsulated, and there are few restrictions on the substance to be encapsulated and it is possible to select relatively freely, so that a desired emission spectrum can be easily obtained.

As such an exposure device, it is not a device like a bright room printer that overlaps the original film on the glass and the baking film and then adheres it with a rubber sheet, and then exposes from below, not a device that matches the usage characteristics of the PS plate That is, the original film is stacked on the PS plate and adhered with a glass frame, and then exposed from above the device. Similarly, after attaching with the glass frame, the glass frame is inverted and exposed from below inside the device. It is possible to increase the intaglio machine, etc., which exposes the PS plate for multiple exposures on one PS plate either vertically or downward.

The PS plate thus exposed is developed with a developing solution to form a lithographic printing plate.

[Effect of the present invention]

According to the present invention, the burning blurring of the PS plate is reduced, and the sagging ratio can be reduced.

Further, according to the present invention, it is possible to obtain a lithographic printing plate having a small dot thickness, good printing durability and good film strength from a negative PS plate.

〔Example〕

Hereinafter, the present invention will be described in more detail based on examples. However, the present invention is not limited to these examples. In the examples,% means% by weight.

Examples 1 to 7 and Comparative Examples a to d An aluminum plate (material 1050) having a thickness of 0.3 mm was washed with trichlene and degreased, and then its surface was grained with a nylon brush and 400 mesh of Pamisou water suspension, Washed well with water. This plate is immersed in a 25% aqueous solution of sodium hydroxide at 45 ° C for 9 seconds for etching and washing with water.
Further, it was immersed in 20% nitric acid for 20 seconds and washed with water. At this time, the etching amount on the grained surface was about 3 g / m ² . Next, this plate was provided with a DC anodic oxide coating of 3 g / m ² at a current density of 15 A / dm ² using 7% sulfuric acid as an electrolyte, and then washed with water and dried.

The following photosensitive solution was applied to the aluminum plate thus treated and dried at 100 ° C. for 2 minutes to obtain a positive PS plate.
The coating amount after drying was 2.5 g / m ² .

Photosensitive liquid Note U.S. Pat. No. 3,635,709, the one described in Example 1 Note: U.S. Pat. No. 4,123,279, the positive PS plate is used as a film original image by using various exposure apparatuses. After exposing in close contact, the positive developer DP-4 manufactured by Fuji Photo Film Co., Ltd. 800E was diluted 1 to 8 with water and developed at 25 ° C. for 40 seconds. . Table 1 shows the results.

In the table, the exposure time was 20μ when the fine line of 15μm disappeared on the plate.
The effective sensitivity on the plate was adjusted so that the thin line of m could be reproduced. In addition, the sensitivity of gray scale (density difference 0.15: manufactured by Fuji Photo Film Co., Ltd.) on the plate was also shown.

As for the blur width, a 100μ base is 5
It was put between 0% plain mesh and PS plate, and it was expressed by the distance from the base edge of the part where the halftone dot is blurred (the part where the halftone dot area is smaller than the normal part). Along with that, a small trash
Put it between the PS version and the original film to indicate the degree of burning blurring.
The evaluation was 6 ranks from (good) to F (bad). Usually, the usable level is C rank or higher.

From Table 1, those using the light rays of Examples 1 to 7 according to the present invention are the light rays of Comparative Examples a and d which have been conventionally used in the PS plate and Comparative Example b for a printer for a bright room film.
It can be seen that the blur width is narrower than that of the ray of c and the blurring is reduced. However, in Examples 1 to 3, the exposure sensitivity was extremely lowered.

Further, bright room bright printers Examples 4 and 6 equipped with a condenser lens have a relatively short exposure time as compared with Examples 1 to 3, but they are longer than PS plate printer comparative examples a and d. On the other hand, in Examples 5 and 7 using a light source containing 35% or more of light of 375 to 425 nm and having an emission spectrum peak within this range, the exposure time was about the same as that of a conventional PS plate printer. And is the best way to reduce the bokeh.

In Comparative Examples a to d, it was possible to reduce the blurring by reducing the exposure amount, but the gray scale sensitivity and the effective sensitivity were low, and the halftone dots were not fine enough. Only printed matter with poor dot reproducibility was obtained.

Examples 8 to 14 and Comparative Examples e to h An aluminum plate surface-treated in the same manner as in Example 1 was further immersed in No. 3 sodium silicate 2.5% solution at 70 ° C for 30 seconds, washed with water and dried, and the coating solution described below was applied. Was coated and dried to obtain a negative PS plate. The coating amount after drying was 2.0 g / m ² .

NOTE What is described in Example 1 in US Pat. No. 4,123,276.

This negative PS plate was exposed in the state of being brought into close contact with the original film of the film by using the exposure apparatus used in Examples 1 to 5 and Comparative Examples a to d, and then the automatic developing machine 800U manufactured by Fuji Photo Film Co., Ltd. At the same time, the negative developer DN-3C manufactured by the same company was diluted 1: 1 with water and developed at 25 ° C for 50 seconds. The results are shown in Table 2.

In the table, the exposure time is 54% of the original film with halftone dots on the plate.
The time was set so that it could be reproduced in%. In addition to that, the gray scale solid sensitivity was shown.

As for burning bokeh, small dust was put between the PS plate and the original film 50% plain net, and the blur around the dust (thickening of halftone dots around the dust) was visually judged.

The strength of the image area was determined by rubbing the exposed PS plate with DN-3C (1: 1) with a nylon brush at present. Printing durability is KOR
(Manufactured by Heidelberg).

From Table 2, those using the light rays of Examples 8 to 14 according to the present invention are compared with the light rays of Comparative Examples e and h which have been conventionally used in the PS plate and Comparative Examples f and g of a bright room film printer similar thereto. It can be seen that the film strength and the printing durability are good because the burning blur is reduced and the gray scale solid sensitivity is increased.

Further, among Examples 8 to 14, Examples 8 to 10 are examples in which the exposure time is extremely long and a conventional bright room printer is used.
Although the exposure time was long even in the cases of 11 and 13, the exposure times of Examples 12 and 14 using the light source according to the present invention were comparable to those of the conventional PS plate printer comparative examples e and h.

In Comparative Examples e to h, the film strength and the printing durability were able to be improved by increasing the exposure amount and increasing the solid sensitivity, but only the printed matter with a large halftone dot and poor tone reproducibility was obtained. Nakatsuta.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-51-100808 (JP, A) JP-A-48-89006 (JP, A) JP-A-56-97339 (JP, A) JP-A-55- 56681 (JP, A) JP 57-164595 (JP, A) JP 58-17445 (JP, A) JP 48-14404 (JP, A) JP 61-61154 (JP, A) JP-B-46-42456 (JP, B1) JP-B-61-500083 (JP, A) US Patent 3635709 (US, A)

Claims (1)

[Claims] 1. A method for exposing a photosensitive lithographic printing plate in which a photosensitive lithographic printing plate and a film original image are brought into close contact with each other and an exposure light beam is irradiated from above the film original image, in a range of 375 to 425 nm where a light source of the exposure light beam emits light. Is 35% or more of the light amount in the range of 300 to 700 nm, and by arranging a condenser lens between the light source and the film original image, 90% or more of the light rays irradiating the film original image are mainly An exposure method for a photosensitive lithographic printing plate, wherein the angle is within 10 degrees with respect to the exposure light ray axis.