JP3321952B2 - Offset printing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a case where it is necessary to reproduce the shape of a pattern to be printed as faithfully as possible in offset printing in an offset printing. Related to offset printing used in the field.

[0002] In ordinary offset printing,
Provided is a method useful in a case where the print quality needs to be particularly high, and a case where it is necessary to increase the thickness of the ink.

[0003]

2. Description of the Related Art Conventionally, various devices have been devised to faithfully print a pattern to be printed on a plate on a printing substrate. That is what is said to be a device for improving print reproducibility. In general printing, instead of controlling the size, shape, and thickness of the ink pattern on the printing substrate, a method called density management, that is, whether the overall color density is the intended value Is managed by

[0004] However, when printing technology is used in the manufacture of electrical and electronic components, density management cannot be applied. For example, when forming an etching resist pattern for manufacturing a printed circuit board by a printing method, the size and shape such as the line width of the pattern match the pattern to be printed on the plate used for the printing. It is desired. Further, the thickness of the resist ink must be sufficient to withstand the corrosive action of the etchant. That is, when printing technology is used in the production of electric and electronic components, it is required to separate and control and manage the size, shape and thickness of the ink pattern. In addition, the shape includes the ruggedness of the peripheral portion of the ink pattern, and it is required that the shape be as small as possible.

In the conventional offset printing method, it is difficult to control and manage the size, shape, and thickness of the ink pattern separately. As the thickness of the ink increases, the size of the pattern also increases. The shape also changes. The reason for this will be described later in detail, but simply speaking, the pressure at the time of printing causes the ink to be crushed and spread, but when the amount of ink is large, the degree of spread is increased. In particular, when the ink transfers from the plate to the blanket, the ink spreads significantly. This situation is shown in FIG.

FIG. 6 is a graph showing the change in the shape and size of a pattern during printing described in Kyosuke Takahashi et al., Journal of the Printing Society of Japan, Vol. 21, No. 3 (1983). It is a schematic diagram of a state. The known document states that when the ink 3 transfers from the plate 1 to the blanket 5, the size increases 1.3 times. In addition, not only the size but also the shape changes considerably. For example, even if the ink pattern on the plate is rectangular, it changes to a degree close to a circle on the blanket, and the periphery of the ink pattern 6 is jagged. . Then, in the transfer from the blanket 5 to the printing material (for example, paper) 8, the size and shape of the ink pattern hardly change from those on the blanket.

As a countermeasure against this problem, a method usually used in the conventional printing technique is a repetitive printing method. That is,
By reducing the amount of ink placed on the plate, the amount of ink placed on the substrate in one printing operation can be reduced, the amount of ink spreading due to crushing can be reduced, and the thickness of the ink can be secured by repeatedly printing. ing. However, in this method, if the thickness of the ink on the printing material increases, the next printing must be performed after the ink is cured in order to prevent crushing. There was a major drawback of lowering.

As a countermeasure sometimes used, there is a method in which the size of a pattern to be printed is reduced in advance when a printing plate is prepared. The degree of reduction is expected to be large during printing. The extent of the increase is estimated by experience and preliminary experiments. Methods of reducing the size of the pattern to be printed on the plate include a method of starting all over from design and a method of adjusting the exposure and development time at the time of preparation of the original plate or plate making. However, these methods are problematic in that they are complicated and require re-doing because they involve estimation.

In addition, the ruggedness of the peripheral portion of the ink pattern in the conventional offset printing method is too large for use in the production of electric parts and electronic parts, and a countermeasure is required. There is no definitive solution.

Further, ink adheres to a portion of the plate that is not a printing pattern, and the ink transfers to a blanket,
The image may be transferred onto a printing substrate and a defect called background stain may occur. This background dirt leads to a short circuit in an electric circuit such as a printed circuit board, so that it is necessary to prevent the occurrence of the short circuit. In this regard, in the conventional offset printing method, there is no other way but to prevent ink from adhering to a portion other than the printing pattern on the plate as a countermeasure. But,
Actually, ground stains often occur due to insufficient supply of dampening solution in the offset printing plate, and missing or worn doctors in the intaglio printing plate, and it is often difficult to take countermeasures.

For the above reasons, the offset printing method is actually used for such a purpose only when the specifications are loose. On the other hand, even in printing on ordinary paper, film, or the like, there are cases where it is desired to increase the thickness of the ink.
For example, there is a case where it is desired to make the address and name of an envelope, a letterhead, etc. look heavy. In offset printing, when the thickness of the ink is increased, the ink is crushed as described above. Therefore, conventionally, offset printing is repeated or another printing method is used. However, offset printing has advantages such as easy plate making, and there has been a demand for the development of a method that causes less collapse of the ink even when the thickness of the ink is increased.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide an offset printing method in offset printing, wherein the shape of the pattern to be printed is faithful to the shape of the pattern on the plate. For example, it is an object of the present invention to provide an offset printing method that can be used in a field where the shape of a pattern of an electric component, an electronic component, or the like is a problem, in which specifications are particularly severe.

More specifically, the first object is to provide an offset printing method characterized in that the size of an ink pattern on a printing substrate matches the size of a print pattern on a plate. A second object is to provide a printing method in which the size of the ink pattern and the thickness of the ink can be controlled independently. Thirdly, it is an object of the present invention to provide a method for reducing the deformation of the ink pattern and the roughness of the peripheral portion. Fourth, it is to provide a method for preventing background dirt. In order to achieve the above object, it is necessary to prevent the ink from being crushed and spread on the blanket, which is the problem to be solved by the present invention.

[0014]

As a means for solving the problems, in the present invention, a blanket is used in which a part or all of the blanket corresponding to the non-print pattern portion of the plate is formed to have ink repellency. In offset printing, an ink-repellent product is provided on a non-print pattern portion of a plate, transferred to a blanket, and then fixed.
Further, as another means, in a state where the ink is placed on the blanket, an ink-repellent forming substance is applied to the surface of the blanket and fixed.

Here, the fact that the blanket is ink-repellent means that the ink on the plate does not transfer to the blanket during printing. The term “transfer” means that the ink moves from the printing plate to the blanket during printing, and the term “transfer” used later means that the ink moves from the blanket to the printing material. In addition, the ink-repellent formed material is a substance having ink-repellent property under specific conditions, for example, water content, as well as a substance having ink-repellent property itself.

A plate is a plate comprising an ink-philic portion and an ink-repellent region, including a PS plate, a waterless offset plate, a trimetal plate, etc., used for normal offset printing, and an intaglio plate used for gravure offset printing. And flexographic printing plates used in dry offset printing. That is, printing using a blanket is an offset printing method, and the plate used for the printing is the plate in the present invention.

In the present invention, the printing pattern on the printing plate means a pattern of a portion of the printing plate on which ink is to be applied.
It is desirable that the size of the print pattern on the substrate is exactly the same as the size of the print pattern on the plate. However, in the present invention, when the printing pattern printed on the printing material is suitable for the purpose and satisfies the specifications even if it is not completely the same, it is expressed as "the same" in the present invention.

The ink-repellent formed product must be capable of forming a film on a blanket and has such characteristics that the film is not destroyed during printing. Materials that can be used as ink repellent products are classified according to their physical properties.
There are a substance having many hydrophilic groups and a substance which can contain a large amount of water. Examples of those suitable for use in practice are silicone resins, fluororesins, gelatin, casein, polyvinyl alcohol, gum arabic, superabsorbent resins, agar, and cellulosic resins. What dissolves in a dampening solution such as gum arabic can be used when a waterless plate is used. In addition, when a substance containing a large amount of hydrophilic groups or a substance that can contain a large amount of water is used, it is preferable to adjust the degree of swelling by including an alcohol such as glycerin together with the water. is there.

There are various methods for providing the ink-repellent region on the blanket. For example, there are a method of supplying a solution and drying to form a film, and a method of curing a stock polymerization solution on a blanket. The lift-off method is one of the powerful means. The fixing strength is 150 g / peel strength.
cm or more is required.

The time when the ink-repellent area is provided on the blanket is after the printing conditions are adjusted so that a required print pattern can be obtained. The reason is that it is necessary to adjust the printing conditions in various ways in order to fit the print pattern into the desired dimensional accuracy, size, shape, and the like. However, when doing so, the position where the ink adheres on the blanket changes, so the time to provide the ink-repellent area on the blanket is
After adjusting the printing conditions.

It is preferable to remove the ink-repellent area once formed on the blanket, since the blanket can be reused when printing another pattern. Therefore, of the above substances, those that dissolve in a solvent are preferred.

When an ink repellent product is applied to the blanket surface in a state where the ink pattern is formed on the blanket, it is important that the ink pattern is close to a desired print pattern. Therefore, when the ink pattern is formed, the amount of ink supplied to the plate is reduced, so that the ink is not crushed when the ink is transferred from the plate to the blanket, and the spread of the size is prevented as much as possible. According to experiments, when the thickness of the ink on the plate is 2 μm or less, the spread of the ink pattern on the blanket is 1 μm or less, and there is almost no problem in printing for manufacturing ordinary electric and electronic components. If the specifications are stricter, use a special ink instead of the ink actually used. The properties of specialty inks are low viscosity and high ability to form films. Basically, an ink consisting only of a resin component and a solvent component not containing a pigment component, that is, a so-called vehicle is preferable. It is preferable that the viscosity be adjusted by the solvent content to make the viscosity low (preferably 1000 to 5000 centipoise) before use.

[0023]

The size of the ink pattern formed on the blanket is limited by the ink-repellent material.
Even if the amount of ink supplied on the plate is large, the size of the ink pattern transferred to and formed on the blanket is almost the same as the size of the ink pattern on the plate, and has conventionally been generated around the ink pattern. Almost no jaggedness occurs. In addition, since the ink in the background stain portion on the plate does not transfer to the blanket, the background does not occur on the printing material.

[0024]

【Example】

(Embodiment 1) As a first embodiment, an example in which an etching resist pattern is formed by printing on a printed circuit board will be described.

The plate 1 is prepared, for example, by printing and developing a desired pattern on a PS plate (FUJI PS-PLATE FPD manufactured by Fuji Photo Film Co., Ltd.). The size of the print pattern 2 formed on the plate is as follows. Was within ± 5 μm of the designed value.

After setting this plate on a platen of a circular pressure offset printing press, and examining printing conditions such as printing pressure and printing speed with ink actually used, and setting the printing size to a specified value. Then, the ink 3 was inked on the plate 1 to a thickness of 2 μm, and in this state, a gelatin aqueous solution 4 (30 g of medium hard gelatin was added to water 2) using a dampening roll (not shown).
(3 g / m ² ) was transferred to a blanket 5 and dried. This transfer / drying step was repeated five times to form a gelatin coating 4a having a thickness of 2.5 μm on the surface of the blanket 5.

Next, the gelatin aqueous solution 4 of the plate 1 is wiped off, and a gelatin swelling solution (not shown) is
Glycerin 700ml + water 300ml + ammonia water 5
(0 ml + 12 g of hypo) was supplied to the plate 1 and transferred to the blanket 5 to make the gelatin coating 4a on the blanket 5 swell, and this portion became an ink-repellent area 4b for repelling ink.

Using the blanket 5 in which the ink-repellent area 4b is formed at the portion corresponding to the non-ink pattern portion of the plate 1 in this manner, the blanket 5 is applied to the plate under the initially set printing conditions.
When an ink having a thickness of μm was supplied and printing was performed, the size of the ink pattern 6 transferred from the plate 1 onto the blanket 5 was within the range of the designed value ± 5 μm, and the size of the resist ink pattern transferred onto the printed circuit board (not shown). The size was also the designed value ± 5 μm, and only a small amount of small jaggedness occurred around the ink pattern.

Next, the ink thickness of the plate 1 was set to 7 μm,
As a result of performing the overprinting twice, a required ink thickness (for example, 3.5 μm) was obtained, and required etching solution resistance was secured. In addition, there was almost no increase in burrs around the ink pattern.

The state of the transfer of the ink 3 from the plate 1 to the blanket 5 will be described with reference to FIG. 1 schematically showing a process. Step 1: A dampening solution 7 is supplied to the plate 1, and the ink 3
Is supplied. 3a is the ink remaining on the plate at the time of the previous printing. Step 2: The blanket 5 approaches the inked plate 1. The surface of the blanket 5 excluding the ink repellent area 4b (hereinafter, referred to as an exposed portion) also has the ink 3b remaining at the time of previous printing adhered thereto. Steps 3-4: Blanket 5 presses ink 3, whereby ink 3 protrudes to the side.

Steps 5-8: As the blanket 5 separates from the plate 1, the ink 3 in the ink-repellent area 4b of the blanket 5 is repelled and gathers at the exposed portion of the blanket 5, so that the spread of the ink pattern 6 is suppressed. Meanwhile, the thickness is secured.

After the printing was completed, the gelatin coating 4a of the blanket 5 was peeled off with a sponge (not shown) containing hot water, and another pattern was printed in the same manner. Met.

On the other hand, in printing performed using a normal blanket having no ink-repellent area 4b on the surface, the size of the printed pattern was expanded in the range of 10 to 20 μm from the designed size. In addition, in order to obtain the same ink thickness and etching resistance as in the double overprinting of the present invention, four overprints were required. However, when the overprinting was performed four times, the size of the resist ink pattern on the printed circuit board was increased by 15 to 25 μm from the design value. In addition,
The size of the ink pattern on the blanket was thicker in the range of 25 to 35 μm than the designed size, and an extremely large amount of jaggedness occurred around the ink pattern.

(Embodiment 2) As a second embodiment, an example in which a thick film circuit is formed on a ceramic substrate will be described.

As the plate, an intaglio plate having a depth of 15 μm was used. The size of the printing pattern on the plate is the designed value ± 5μ.
m until the printing conditions were set using the inks actually used.

Then, the ink on the plate and the blanket is removed, a 5% aqueous solution of polyvinyl alcohol is supplied to the plate using a doctor, and the water evaporates to a thickness of about 2 μm.
When it became, it was transferred to a blanket. After drying the polyvinyl alcohol on the blanket, the pattern of the polyvinyl alcohol was transferred and dried again from the plate to the blanket in the same manner. The size of the polyvinyl alcohol pan on the blanket was within the designed value ± 5 μm, and the film thickness after drying was 0.8 μm.

Next, a silicone resin varnish TSR144 (trade name of Toshiba Silicone Co., Ltd.) for release is sprayed onto the surface of the blanket in this state, supplied, dried, and dried to a thickness of 2 μm.
m was formed. Then, the surface of the blanket is gently rubbed with a sponge soaked in warm water to remove the polyvinyl alcohol together with the silicone resin thereon, and the silicone resin varnish TS is applied to the portion corresponding to the non-ink pattern of the plate.
With R144 remaining, an ink-repellent area was formed.

When printing was performed using actual ink under general printing conditions, the size of the ink pattern on the ceramic substrate was within the designed value ± 5 μm. When supplying ink to the intaglio with a doctor,
In some cases, the doctor was incomplete and ink remained on the convex portions of the intaglio in the form of background stains. However, some background stains did not hinder good printing at all. For this reason, the number of times the doctor is polished has been drastically reduced to 1/10 or less of the conventional one.

On the other hand, in printing performed using a normal blanket, the size of the ink pattern on the blanket is 15 to 25 μm larger than the design value, and the size of the ink pattern on the ceramic substrate is 10 to 20 μm larger than the design value. I was Also, the degree of jaggedness around the ink pattern was 3 to 10 μm.

Embodiment 3 As a third embodiment, an example in which a color filter is formed on a glass substrate will be described.

As the plate, a trimetal plate having a depth of 5 μm was used. The size of the printing pattern on the plate is the designed value ± 5μ.
m until the printing conditions were set using the inks actually used.

Then, the ink on the plate and the ink on the blanket were removed, and the treated layer of the ink in the concave portion of the plate was destroyed with diluted nitric acid, and a 10% aqueous solution of polyvinyl alcohol was supplied by a doctor. When the water had evaporated to a thickness of about 2 μm, it was transferred to a blanket. The size of the polyvinyl alcohol pattern on the blanket was the designed value ± 5 μm, and the film thickness after drying was about 0.5 μm.

The blanket surface in this state was spray-coated with a silicone rubber TSE3450 (trade name of Toshiba Silicone Co., Ltd.) to which a predetermined amount of a predetermined curing agent was added, diluted with a solvent and sprayed. Wait for the solvent to evaporate and cure to form the rubber, and after leaving it for 24 hours, for example, gently rub the blanket surface with a sponge soaked in warm water to remove the polyvinyl alcohol with the silicone rubber on it Then, the silicone rubber TSE3450 is left in a portion corresponding to the non-ink pattern of the plate,
An ink-repellent area was formed. The thickness of the silicone rubber was 2 μm. Further, the ink recesses of the plate were subjected to an ink-friendly treatment.

Then, the ink for the color filter was rolled in and printed under general printing conditions.
The thickness was within 5 μm, the ink dripping was small, and the image shape was good.

On the other hand, in printing performed using a normal blanket, the size of the ink pattern for the color filter on the blanket is 15 to 25 μm larger than the designed value.
The size of the ink pattern on the glass substrate is 1
It was 0-20 μm larger.

The blanket used in the offset printing of the present invention can be formed by the following method.

For example, as shown in FIG. 3, a lithographic plate 1 made of a PS plate is applied to a liquid (solution,
When the unpolymerized liquid and the low-polymerized liquid) are supplied using a dampening water roll, the liquid of the ink-repellent formation 4c adheres to the hydrophilic surface 1a of the plate 1 and the ink-repellent part (the required printing pattern) (Part 1) does not adhere to 1b (Step 1). When this is transferred to the surface of the blanket 5, a liquid pattern of the ink-repellent formation 4c is formed (Step 2). By curing this, the ink-repellent region 4b is formed on the surface of the blanket 5. You.

According to this method, the target blanket can be easily obtained. However, when the thickness of the liquid of the ink-repellent formation 4c is increased, the extent to which the liquid of the ink-repellent formation 4c spreads on the blanket 5 is increased. , And the ink-affinity portion 1b becomes narrow. In order to avoid this, the thickness of the ink-repellent forming liquid to be supplied to the plate 1 may be reduced, and the liquid may be repeatedly transferred to the blanket 5. Since the merit is lost, it is suitable for use in printing in which prevention of background contamination is more important than printing in which accuracy and jaggedness are important.

Further, as shown in FIG. 4, the ink 3 is arranged on the surface of the blanket 5 in a desired pattern using an appropriate plate (not shown) (step 1). Then, the ink-repellent region 4b is also formed on the surface of the blanket 5 by applying the liquid of the ink-repellent formation 4c to the blanket 5 in this state (step 2).

According to this method, the ink repellent formed product 4c
And that the ink 3 and the ink-repellent formation 4c are easily mixed with each other even after the ink 3 on the blanket 5 is cured. There is an advantage that both are not mixed if the liquid is supplied. When the ink 3 is cured, the liquid of the ink repellent composition 4c can be applied to the blanket 5 with a brush or the like.

As shown in FIG. 5, the ink 3 is arranged on the surface of the blanket 5 in a desired pattern using an appropriate plate (not shown) (step 1). Then, the entire surface of the blanket 5 in this state is coated with the liquid of the ink-repellent forming material 4c, and the liquid is cured (Step 2).

Next, the cured (including semi-cured) ink 3
A solution capable of dissolving or swelling is supplied to the blanket 5 by means such as brushing or spray coating (step 3, here schematically showing the swollen state),
The ink 3 and the film of the ink repellent material 4c hardened thereon are removed by rubbing with a brush or the like, and the ink repellent product 4c is removed.
The ink-repellent region 4b can be formed on the blanket 5 by leaving c in the pattern to be ink-printed (step 4).

Incidentally, since the present invention is not limited to the above embodiment, various modifications can be made in accordance with the gist of the claims. For example, in the embodiment, the entire surface of the blanket except for the print pattern was made ink-repellent. However, in areas where the specifications of the print pattern are not strict, ink-repellency is not necessary. It can also be a partial area of the blanket.

Further, as the ink 3 used for forming the ink-repellent area on the blanket, an ink which actually forms a resist pattern can be used. This is
The trouble of changing ink can be reduced. But,
The ink cannot be used for actual printing unless attention is paid to ink stains (dust, mixing of ink-repellent products, etc.).

In this method, if the ink repellent product is repeatedly supplied, the ink and the ink repellent product are mixed, so-called emulsification of the ink occurs, and the ink repellency of the ink repellent portion is reduced. Will not be able to achieve their goals.
To prevent this, after curing the ink on the plate,
It is necessary to supply a solution of the ink-repellent composition to the plate. Since the ink used in this step needs to be peeled off later, it is preferable to use ink that can be peeled off without affecting the ink-philic part of the plate, for example, linseed oil-based ink. Since the linseed oil-based ink can be peeled off by washing, it does not affect the ink-philic part of the PS plate.

[0056]

As described above, according to the present invention, the size of the printed pattern can be kept within the design value ± 5 μm, and the ruggedness around the pattern can be adjusted variously by the conventional offset printing method. It can be less than can be achieved for the first time. In addition, once soiling occurs, it is easy to recur, but this can be reliably prevented. In normal offset printing, the supply amount of dampening water is set higher than necessary to prevent background contamination, but if the amount of dampening water is large, the amount of water contained in the ink also increases, resulting in pinhole defects. Leads to the occurrence of On the other hand, in the present invention, the supply amount of the dampening solution can be significantly reduced as compared with the related art, and if necessary, the supply amount of the dampening solution can be reduced to the extent that a slight soiling occurs. . Therefore, the occurrence of pinhole defects can be prevented accordingly.

Further, since the ink-repellent area provided on the surface of the blanket is determined using the ink pattern on the plate or the blanket after the printing conditions have been sufficiently examined and determined in advance, a truly necessary area is required. Only the portion can be made ink-repellent. If the ink-repellent area is formed by reversing the order, the ink pattern position on the blanket changes due to changes in printing conditions, for example, printing pressure, etc., and the ink-repellent area on the formed blanket is On the contrary, it may lead to adverse effects.

The thickness of the ink-repellent portion formed on the blanket can be adjusted. Increasing the thickness can increase the thickness of the ink that can be held during that time, so that the thickness of the ink on the substrate can be increased in a single printing operation compared to normal offset printing. There is an upper limit to the thickness of the ink obtained by this method. That is, if the thickness of the ink-repellent area on the blanket is too large, the transfer of the ink from the plate to the blanket becomes unstable, and some places are not transferred. However, in practice, it may be desired to further increase the thickness of the ink on the substrate. At this time, a method that combines printing and curing is usually considered,
In the case of the present invention, another method can be adopted as described below.

That is, as another method of forming the ink-repellent area, as shown in FIG. 3, a method of arranging the ink-repellent formed material on the non-printing pattern portion of the plate and transferring it to a blanket. According to the method, the size of the pattern on the blanket where the ink is applied can be the same as or slightly smaller than the size of the pattern on the plate where the ink is applied. Therefore, if you want to increase the thickness of the ink when actually printing, this method can be used without repeating printing and curing, and the uncured ink will be crushed when transferring the ink from the blanket to the printing substrate. Even if the pattern spreads, a pattern having a size close to the design value can be printed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a first embodiment.

FIG. 2 is an explanatory view showing a procedure for forming an ink-repellent region.

FIG. 3 is an explanatory diagram for forming a blanket.

FIG. 4 is an explanatory diagram for forming a blanket.

FIG. 5 is an explanatory diagram for forming a blanket.

FIG. 6 is an explanatory view of a conventional technique.

[Explanation of symbols]

 1 plate 1a hydrophilic surface 1b ink-philic portion 2 printing pattern 3 ink 4 gelatin aqueous solution 4a gelatin coating 4b ink-repellent area 4c ink-repellent forming material 5 blanket 6 ink pattern 7 dampening water 8 printing material

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-55-100187 (JP, A) JP-A-59-147072 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 1/08 B41N 10/02

Claims (4)

(57) [Claims] In an offset printing using a blanket in which a part or all of a blanket region corresponding to a non-print pattern portion of a plate is formed to have ink repellency, an ink repellent disposed on the non-print pattern portion of the plate. An offset printing method characterized in that an ink-repellent region is formed by transferring and fixing a repellent material to a blanket. 2. The offset printing according to claim 1, wherein
An offset printing method, wherein an ink-repellent material is transferred to a blanket together with ink arranged in a printing pattern portion of a plate, and is fixed to form an ink-repellent region. 3. In offset printing using a blanket in which a part or all of a blanket region corresponding to a non-print pattern portion of a plate is formed to be ink-repellent, ink arranged in a print pattern portion of the plate transfers. The ink-repellent composition applied and cured over the entire required portion of the blanket is removed from the ink portion together with the ink removed by the liquid that dissolves or swells the cured ink, and remains on the non-ink portion to repel the ink. An offset printing method, wherein an ink area is formed. 4. In offset printing using a blanket in which a part or all of a blanket region corresponding to a non-print pattern portion of a plate is formed to be ink-repellent, a cover member disposed on a print pattern portion of the plate is used. Transferred to the blanket, the ink-repellent formation applied to the entire surface of the blanket and cured is removed from the portion of the covering member together with the covering member which is removed by the solution that dissolves or swells the covering member. An offset printing method, wherein an ink-repellent region is formed by remaining at a site.