JP4222164B2 - Offset printing paper - Google Patents

Description

  The present invention relates to an offset printing paper that can be produced with a small amount of surface treatment agent and is low in production cost, is less likely to cause trouble during production, and has good printing workability and color printing quality.

  In recent years, offset printing has become mainstream as a commercial printing method. Offset printing is a method in which a printing plate, usually called a PS plate, is prepared and dampening water and ink are supplied to the printing plate for printing. The printing plate is a lithographic plate, and the image area on the printing plate is treated to have an oleophilic surface, and the non-image area is treated to have a hydrophilic surface. When dampening water and ink are supplied to this printing plate, ink is applied to the image area and water is applied to the non-image area. The ink is transferred from the printing plate to the paper via the blanket for printing. To do.

  In this offset printing, since the ink having a relatively strong tack is used, the strength of the surface of the paper is required to be strong. In addition, if paper with a weak surface strength or water resistance is used to treat the paper surface with fountain solution, paper dust accumulates on the blanket or mixes with the ink. This causes troubles such as so-called blurring.

  As a method for dealing with the problems related to the reduction in surface strength during offset printing such as blanket piling and printing surface scuffing, an adhesive such as starch, polyvinyl alcohol or polyacrylamide resin has been used as a main component on the surface of printing paper. The surface treatment agent to be applied is applied using a roll coater such as a two-roll size press coater, a metering size press coater or a gate roll coater.

  However, in the roll coater, since the surface treatment agent is pushed into the base paper at the coater nip, the penetration of the surface treatment agent cannot be suppressed, and the actual amount of the surface treatment agent penetrating into the substrate is taken into consideration. The fact is that the coating amount must be set high.

  However, when the amount of the surface treatment agent used is increased, not only the cost is increased, but also the adhesiveness of the paper surface (commonly referred to as “Nepari”) that occurs when the paper surface is dampened with dampening water during printing tends to increase. Yes, when this dullness increases, the blanket piling especially in the non-image area is increased, or the paper surface sticks to the blanket during printing, resulting in other problems such as running performance such as wrinkles and paper breaks. There is a possibility of inducing, which is not preferable.

  Also, when applying at high speed in coating methods such as gate rolls and metering size presses, operational troubles such as coating unevenness and mist are likely to occur, especially in the high application amount area, and operability and coating surface quality are improved. There was also the weakness of getting worse.

  On the other hand, by using an internal sizing agent such as rosin emulsion sizing agent, the generation of paper dust is suppressed by increasing the sizing degree of the paper surface and suppressing the penetration of dampening water into the paper layer during offset printing. However, these internally added sizing agents tend to cause troubles due to foaming in a white water system in a high speed paper machine such as a printing paper machine. In addition, when a yield improver is used in combination with an internal sizing agent, there is a problem that the pitch in the papermaking system is taken into the paper and the whiteness of the printing paper is lowered.

In addition, a method for improving the above-mentioned blanket piling by applying a surface sizing agent to improve the contact angle of the paper surface (see Patent Document 1) has been proposed, but the improvement effect such as blanket piling is recognized. However, there are problems such as worsening of Nepari property, and in reality it is extremely difficult to solve all the problems of blanket piling, stamp face scraping, and Nepari. Cationicity by adding a cationic polymer to a method of reducing nepari with a surface treatment agent containing a substituted succinic acid as an active ingredient (see Patent Document 2) or a copolymer of a vinyl monomer and an unsaturated carboxylic acid A surface treatment agent containing an emulsion (see Patent Document 3) has also been proposed, but even if these methods are used, the amount of the surface treatment agent applied cannot be reduced, and these expensive treatment agents can be used. On the contrary, the cost is high, and it is not possible to provide an offset printing paper that is inexpensive and has good color printing suitability.
Japanese Patent Publication No. 2000-234292 Japanese Patent Application Laid-Open No. 6-192959 Japanese Patent Laid-Open No. 5-287695

In addition, a method of using a starch composition for paper coating, which is a blend of high-viscosity starch and low-viscosity starch, as a surface treatment agent (see Patent Document 4) has been proposed. It is based on the premise that it penetrates the market, has low cost effectiveness, and is not realistic.
Japanese Patent Laid-Open No. 5-195490

In recent years, a spray coating method has been proposed as a new coating method for paper and paperboard (see Patent Document 5). The spray nozzle includes a one-fluid nozzle called an airless spray system and a two-fluid nozzle called an air spray. In the one-fluid spray, paint is pressurized and sprayed at high speed from an elliptical spray nozzle. Fine paint particles are formed by the shear stress generated when the paint film comes into contact with the atmosphere, and the paint particles adhere to the substrate. This is a method of generating a coating film. The two-fluid spray has nozzles for air and paint at the tip of the nozzle. The high-pressure air flow is struck against the paint sprayed at low pressure, and the paint is refined by the impact. This is a method of controlling the shape of the film.
United States Patent No. 6063449

In these spray coating methods, there is no nip portion during coating, so there are no coating defects caused by contact between the coating surface and the coating device, and the covering properties of the base paper are excellent. (See Non-Patent Document 1 ). However, there is no application example of this spray coating method to offset printing paper, and a detailed study has not yet been made (see Non-Patent Document 2 ).

As a result of intensive research on offset printing paper having good printing workability and color printing quality with a small amount of surface treatment agent, the present inventors have used a spray coating method to obtain a dry weight of 1.0 g / m ^2. By distributing the above surface treatment agent within 10 μm from the outermost surface of the base paper, it has become possible to provide an offset printing paper having good offset printability while having a small surface treatment agent coating amount.

Offset printing paper according to the present invention, on at least one surface of the base paper, surface treatment agent coating solution on one side per dry weight the first fluid spray system mainly composed of starch or starch derivative having a viscosity of 10 to 100 mPa · s coated so as to .0~3.0g / m ^2, dried and the average penetration depth of the surface treatment agent of the coated surface obtained is equal to or is 10μm or less from the base paper the outermost surface.

As a result of intensive studies on the conditions necessary for developing good printing workability and color printing quality, the inventors have found that the dry weight of the surface treatment agent is 1.0 g / m ² within 10 μm from the outermost surface of the base paper. It has been found that the presence of the above allows fine fibers on the outermost surface of the base paper to be efficiently bonded, sufficiently exhibiting the surface strength required for offset printing, and exhibiting good printing workability and color printing quality. That is, generally, for offset printing paper, the surface treatment agent is applied in a dry weight of about 0.5 to 4 g / m ² per side, which is, for example, a coating method such as a roll coater, The coating amount includes the penetration of the surface treatment agent, and it was found that about 1.0 g / m ² within 10 μm from the outermost surface of the base paper is related to the surface strength. It has been found that, for the first time, an offset printing paper satisfying the above conditions and having the above quality can be achieved with a small amount of surface treatment agent. When the amount of the surface treatment agent within 10 μm from the outermost surface of the base paper is less than 1.0 g / m ² , the surface strength is insufficient, and troubles such as piling and peeling occur in offset printing. In addition, as a method of drying a wet coating layer, various systems, such as vapor | steam drying, gas heater drying, electric heater drying, infrared heater drying, etc. are employable, for example.

  It is important that the average surface treatment agent penetration depth of the present invention is within 10 μm from the surface. In order to obtain sufficient surface strength, it is necessary to increase the amount of the surface treatment agent that is fixed in the surface layer of the base paper, and among these, the surface treatment agent that remains in the surface layer within 10 μm from the outermost surface of the base paper in the depth direction. The amount greatly affects the surface strength. When it penetrates deeper than 10 μm, the amount of the surface treatment agent more than that actually required for obtaining the desired quality characteristics is required, and the drying load becomes large, so the economic efficiency is remarkably impaired. .

  In the offset printing paper obtained in the present invention, a surface treatment agent is applied on at least one side of a base paper by a spray method, but these apparatuses may be on-machine or off-machine. When the most common roll coater is used, the surface treatment agent is pushed into the base paper, and the surface treatment agent coating solution cannot be kept within 10 μm from the outermost surface of the base paper. Application of a treatment agent is required. As with the roll coater, it is also common for bevel type, bent type blade coaters, air knife coaters, rod blade coaters such as trailing, flexible, roll applications, fountain applications, short dwells, etc. The penetration of the surface treatment agent is large, and the surface treatment agent coating solution cannot be kept within 10 μm from the outermost surface of the base paper. In bar coaters, champ flex coaters, gravure coaters, etc., where the indentation of the surface treatment agent at the nip is relatively small, it is possible to suppress penetration by applying a high concentration surface treatment agent. However, the covering of the base paper is inferior and the coating pattern appears, resulting in poor color offset printing suitability.

  The spray coating apparatus is preferably a one-fluid spray. By using a one-fluid spray device that forms a coating layer by high-pressure jetting of the coating material, further miniaturization of the coating material can be achieved, and covering of the base paper by the coating layer is improved.

  The physical properties of the surface treatment agent coating solution are not particularly limited, but the viscosity is preferably about 10 to 100 mPa · s, and the concentration is preferably 5% or more. The viscosity is a value measured at 40 ° C. and 60 rpm measured using a B-type viscometer. When the viscosity of the surface treatment agent coating solution exceeds 100 mPa · s, it is difficult to atomize the surface treatment agent coating solution in the spray device, and there is a possibility that a coating defect due to generation of coarse particles may occur. On the other hand, when the viscosity is less than 10 mPa · s, the surface treatment agent does not stay within 10 μm from the substrate surface.

In spray coating, there is a minimum wet coating thickness at which a continuous film can be formed. In order to make the surface treatment agent 1 g / m ² or more by dry weight in the present invention, the surface treatment agent coating used is used. In accordance with the physical properties of the liquid, spray conditions such as liquid pressure and coater speed are appropriately selected. Further, in spray coating, even if the concentration of the surface treatment agent coating solution is lowered, the surface treatment agent remains within 10 μm in the depth direction from the outermost surface of the base paper as long as the viscosity is in the range of 10 mPa · s or more, but the viscosity is preferable. Even within the range, if the concentration is extremely low, a dry weight of 1 g / m ² or more may not be obtained even if spray conditions are used. For example, when the concentration of the surface treatment agent coating solution is less than 5%, it tends to be difficult to obtain a dry coating weight of 1 g / m ² or more in the surface treatment agent.

The surface treatment agent is a per side 1 to 3 g / m ² approximately by dry weight, or greater cost exceeds 3 g / m ^2, there is a possibility that poor color print quality.

When the main component of the surface treatment agent is starch and starch is not used as the internal sizing agent of the base paper, the average penetration depth of the surface treatment agent was measured using an iodine / starch reaction. . In other words, a 0.1K (KI + I ₂ ) solution was applied to two surfaces of a coated sample in advance using a # 0 Meyer bar, and a natural dried sample was prepared. Subsequently, the sample whose surface was colored by the iodine / starch reaction was cut into tomographic sections of about 5 mm × 20 μm using a microtome, and using an optical microscope (trade name: FLUOPHOT, manufactured by Nippon Optical Co., Ltd.), the magnification was 480 times. To obtain three cross-sectional images at random. Further, using this tomographic image, the depth of the colored portion from the surface of the paper layer is measured at 20 locations with a 10 μm pitch in the width direction, and an average value at a total of 60 points is calculated, and the surface treatment agent on one side of the surface is calculated. The average penetration depth was determined. Similarly, using the same tomographic image, the average penetration depth of the surface treatment agent on the other surface was determined.

  In the case where the main component of the surface treatment agent is starch and starch is also used as the internal additive sizing agent of the base paper, the amount of the internal additive sizing agent is generally within 10 μm from the outermost surface of the base paper. The coloring level obtained from the starch of the internal sizing agent and the starch of the surface treatment agent when the color is developed by the iodine / starch reaction in the above-mentioned method. Are significantly different, and the average penetration depth of the starch of the surface treatment agent in the above method can be calculated.

When the surface treatment agent is mainly composed of starch, the dry weight of the surface treatment agent can be calculated by the following method. First, a tape is applied to both sides of a paper sample, delamination is performed to divide the paper sample into two layers, and the divided paper pieces are further repeatedly delaminated to divide into a total of eight layers. For example, when divided into eight layers, the layers from one applied surface layer to the other applied surface layer are the first layer, the second layer, the third layer, ... the eighth layer, respectively. It becomes. The weight of each layer is W ₁ g / m ² , W ₂ g / m ² , W ₃ g / m ² ,... W ₈ g / m ^{2 in} order from the first layer, and the basis weight of the paper sample is Wg / m. ^{2 When the} paper thickness is D μm, W = W ₁ + W ₂ + W ₃ +... + W _{8 and} , for example, the paper thickness D ₁ corresponding to the first layer is obtained from the weight W ₁ g / m ² of the first layer. It is done. And by quantifying the amount of starch contained in the layer, it can be calculated on the dry weight of the starch, which corresponds to the depth D ₁ of the the base paper the outermost surface of the first layer.

  When starch is not used as an internal sizing agent for base paper, the calculated starch amount is the dry weight of starch as the surface treatment agent in the layer, and starch is used as an internal sizing agent for base paper. If so, the dry weight of the starch as the surface treatment agent can be calculated by the following method. That is, in the layer near the center of the sample, starch having a substantially constant concentration per pulp is detected, but this starch is an internally added starch, and this concentration of starch is uniformly distributed throughout the paper layer. It can be said. Further, by quantifying the amount of starch in the divided layers, the total amount of the dry weight of the surface treating agent and the dry weight of the internally added starch can be found. Therefore, the dry weight of the starch as the surface treatment agent can be calculated by subtracting the amount of starch used in the internal addition from the amount of starch in the layer.

The amount of starch can be quantified by a known method such as anthrone sulfate method, phenol sulfate method (see Non-Patent Document 8), biosensor method or the like. For example, in the case of the biosensor method, the starch in the filtrate obtained by treating the sample obtained by the delamination method with an amylase solution containing glucoamylase and filtering with a filter (trade name: Ecodisc 13, manufactured by Nihon Pall). By measuring the concentration with a biosensor (model: BF-2, manufactured by Oji Scientific Instruments), the amount of starch can be calculated.
Nikuni Jiro: “Starch Science Handbook”, Asakura Shoten, (1977)

Moreover, when the surface treatment agent did not contain starch, the average penetration depth of the surface treatment agent was measured as follows using the above delamination method. For example, if no surface treatment agent is confirmed in the third layer and the sixth layer, the penetration depth of the surface treatment agent from each surface can be obtained by the following equation when the density in the fault direction is assumed to be constant. The penetration depth of the surface treatment agent from one surface is D × (W ₁ + W ₂ ) / W, and the penetration depth of the surface treatment agent from the other surface is D × (W ₇ + W ₈ ). / W. Twenty such points were measured, the average value was calculated, and the average penetration depth was determined. The more layers that are divided, the more accurate the penetration depth. In addition, as an analysis method for confirming the surface treatment agent, it can be quantified by specifying monomer components by pyrolysis GC / MS (gas chromatography mass spectrometry) and comparatively analyzing those of known concentrations. .

  For example, when polyacrylamide is used as an internal sizing agent for base paper and polyacrylamide is also used as a surface treatment agent, the amount of the internal sizing agent is generally the amount used in the present invention. When the amount of the sample divided in the above delamination method is quantified, the surface treatment agent polyacrylamide is involved up to the layer close to the surface of the layer where the amount is extremely reduced. Penetration depth can be calculated as a layer. The dry weight of the polyacrylamide as the surface treatment agent can be performed in the same manner as the method for calculating the dry weight of the starch as the surface treatment agent.

  As a main component of the surface treatment agent used in the present invention, starch derivatives such as corn, potato, tapioca, wheat, rice and the like, oxidized starches thereof, dialdehyde starches, phosphate-modified starches, cationized starches, Examples thereof include adhesives such as synthetic water-soluble binders such as polyacrylamide resins and polyvinyl alcohol, and copolymer latexes such as styrene-butadiene copolymers. The polyacrylamide resin has a molecular weight of about tens of thousands to 2,000,000, and is a polymer of acrylamide, a polymer of methacrylamide, a copolymer of acrylamide and methacrylamide, or a polymer or copolymer of these. Examples thereof include a polymer obtained by partial hydrolysis and partial methylolation of the polymer. Among them, starch or starch derivatives are preferably used because they have good neppari properties and are inexpensive. In addition, a polyacrylamide resin is preferably used because of its good surface strength.

  Addition of a surface sizing agent such as a styrene-acrylic acid copolymer or a styrene-maleic acid copolymer to the above adhesive in an amount of 5 to 50% by mass is also appropriately performed for the purpose of improving the size of the surface. For the purpose of improving opacity, it is also effective to add pigments such as calcium carbonate, kaolin, white carbon, amorphous silica, titanium oxide, and plastic pigment at a ratio of 100% by mass or less with respect to the adhesive. In addition, the mass% of the adhesive selected from starch, starch derivatives, or polyacrylamide resins is preferably in the range of 30 to 100 mass% with respect to the total solid content of the surface treatment agent.

As the base paper of the offset printing paper used in the present invention, chemical pulp (NBKP, LBKP, etc.), mechanical pulp (GP, CGP, RGP, PGW, TMP, etc.), waste paper pulp (DIP, etc.), etc. are used alone or arbitrarily as raw pulp It is used by mixing at a ratio of In addition, paper-making fillers such as white carbon, clay, amorphous silica, talc, titanium oxide, and calcium carbonate are added during papermaking. Generally known publicly available paper chemicals such as a paper strength enhancer, a yield improver, a water-proofing agent, and an ultraviolet absorber are added, and paper is made with a paper machine. There are no particular limitations on the papermaking conditions of the base paper itself. In order to keep the surface treatment agent on the substrate surface, it is desirable to add an internal sizing agent during papermaking. The sizing degree of the base paper is preferably 10 seconds or more. The measuring method is JIS P 8122. In addition, as the paper machine, for example, a commercial paper machine such as a long paper machine, a gap former paper machine, a circular paper machine, a short paper machine, etc. is selected as appropriate according to the purpose. Can be used. The papermaking method may be any method such as acidic papermaking, neutral papermaking, or weak alkaline papermaking. However, in recent years, since paper preservation is required, base paper made by neutral papermaking is preferred. The base paper used for the coated paper for printing of the present invention is not particularly limited, but in general, a base paper having a basis weight in the range of about 30 to 300 g / m ² is appropriately selected according to the purpose. Select and use.

In the production of the coated paper for printing of the present invention, after the formation of the coating layer, smoothing treatment is performed in various calendar devices, such as a super calendar, soft calendar, Commonly used calendar devices such as a gloss calendar, a compact calendar, a mat super calendar, and a mat calendar can be used as appropriate. As the calender finishing conditions, the temperature of the rigid roll, the calender pressure, the number of nips, the roll speed, the paper moisture before the calender, and the like are appropriately selected according to the required quality. Furthermore, the calendar device includes an off type that is different from the coater and an on type that is integrated with the coater, but can be used in either case. The material of the calendar apparatus to be used is a roll which is mirror-finished with a metal or a hard chrome plating on the surface of a rigid roll. As the elastic roll, a roll obtained by molding a resin roll such as urethane resin, epoxy resin, polyamide resin, phenol resin, polyacrylate resin, or the like, cotton, nylon, asbestos, aramid fiber, or the like is appropriately used. It should be noted that it is of course possible to use a suitable combination of a water coating device, an electrostatic humidifying device, a steam humidifying device, etc., for humidity control and humidification of the coated paper after finishing with a calendar.

  Since it can be manufactured with a small amount of surface treatment agent, it is possible to obtain an offset printing sheet having a low manufacturing cost, hardly causing troubles during manufacturing, and having good printing workability and color printing quality.

Because it is possible to manufacture with a small amount of surface treatment agent, the manufacturing cost is low, it is difficult to cause trouble during manufacturing, and offset printing paper with good printing workability and color printing quality is provided on at least one side of the base paper. The average penetration depth of the surface treatment agent obtained by applying and drying the treatment agent solution by a dry weight of 1.0 g / m ² or more by a spray method was 10 μm or less from the paper surface.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Moreover, unless otherwise indicated, the part and% in an example show a solid content mass part and solid content mass%, respectively.
Example 1

・ Preparation of base paper 95 parts of LBKP (CSF 500 ml) bleached in multiple steps in a process consisting of oxygen-ozone-sodium hydroxide-hydrogen peroxide-chlorine dioxide and a process consisting of oxygen-ozone-sodium hydroxide-hydrogen peroxide-chlorine dioxide To 100 parts of pulp slurry consisting of 5 parts of NBKP bleached multiple times at CSF (500 ml of CSF), 0.5 parts of aluminum sulfate and cationic starch (trade name: Ace K-100, manufactured by Oji Cornstarch Co., Ltd.) ) 0.5 part, 0.1 part of alkyl ketene dimer sizing agent (trade name: Size Pine K-287, manufactured by Arakawa Chemical Co., Ltd.), 0.02 part of polyacrylamide (trade name: Polystron 851, manufactured by Arakawa Chemical Co., Ltd.) Were sequentially added to prepare a paper stock. The obtained paper stock was made with an on-top twin-wire paper machine to produce a base paper with an actual amount of 85 g / m ² . The degree of size was 20 seconds.

-Preparation of offset printing paper A 10% solid concentration aqueous solution (viscosity: 15 mPa · s) of oxidized corn starch (trade name; Ace A, manufactured by Oji Cornstarch Co., Ltd.) was used as the surface treatment agent coating solution. In addition, using a one-fluid spray nozzle (manufactured by Spraying Systems Japan Co., Ltd., chip number 650017-TC) with an equivalent orifice diameter of 0.28 mm, the dry weight per side is 1.2 g / m ² at a liquid pressure of 785 N. After coating on both sides and drying, super calender finishing was performed to obtain an offset printing paper having an actual amount of 87.4 g / m ² . The average penetration depth of the surface treatment agent was 8 μm.
Example 2

Offset printing paper with an actual amount of 88.6 g / m ^{2 in} the same manner as in Example 1 except that the liquid pressure was 1079 N and the dry weight per side was 1.8 g / m ² on both sides. Got. The average penetration depth of the surface treatment agent at this time was 8 μm.
Example 3

In Example 1, the surface treatment agent coating solution was an aqueous solution of oxidized corn starch (trade name; Ace A, manufactured by Oji Cornstarch Co., Ltd.) with a solid content concentration of 15% (viscosity: 50 mPa · s), the liquid pressure was 1079 N, An offset printing paper having an actual amount of 90 g / m ² was obtained in the same manner as in Example 1 except that 2.5 g / m ² by dry weight was applied on both sides and dried. The average penetration depth of the surface treatment agent at this time was 9 μm.
Example 4

Reference example 1
In Example 1, the surface treatment agent coating liquid is a polyacrylamide polymer (trade name: Santax NP-14, manufactured by Mitsui Chemicals), 5% solids concentration aqueous solution (viscosity: 60 mPa · s), and the liquid pressure is 1079 N. In the same manner as in Example 1 except that 1.0 g / m ² was applied on both sides by dry weight per side and dried, an offset printing paper having an actual amount of 87 g / m ² was obtained. The average penetration depth of the surface treatment agent at this time was 8 μm.

Reference example 2
In Example 1, the surface treatment agent coating solution is polyvinyl alcohol (trade name: PVA-124, manufactured by Kuraray Co., Ltd.), a solid content concentration 5% aqueous solution (viscosity: 80 mPa · s), the liquid pressure is 1079 N, and it is dried per side. An actual amount of 87.2 g / m ² offset printing paper was obtained in the same manner as in Example 1 except that 1.1 g / m ² by weight was coated on both sides and dried. The average penetration depth of the surface treatment agent at this time was 8 μm.

Reference example 3
In Example 1, the one-fluid spray nozzle was changed to a two-fluid nozzle (manufactured by Spraying Systems Japan, liquid cap 2850, air cap 67228-45 °), and 1.1 g dry weight per side at air pressure 392N. An offset printing paper having an actual amount of 87.2 g / m ² was obtained in the same manner as in Example 1 except that / m ² was coated on both sides and dried. The average penetration depth of the surface treatment agent at this time was 9 μm.

In Example 1, the solid content concentration of the oxidized corn starch aqueous solution used as the surface treatment agent coating solution was 5% (viscosity: 5 mPa · s), and 0.7 g / m ² in terms of dry weight per side was coated on both sides and dried. Otherwise, an offset printing paper having an actual amount of 86.4 g / m ² was obtained in the same manner as in Example 1. The average penetration depth of the surface treatment agent at this time was 17 μm.
Comparative Example 2

Offset printing paper with an actual amount of 86.6 g / m ^{2 in} the same manner as in Example 1 except that the liquid pressure was 392 N and the dry weight per side was 0.8 g / m ² on both sides. Got. The average penetration depth of the surface treatment agent at this time was 10 μm.
Comparative Example 3

In Example 1, the surface treatment agent coating solution was a 13% solid concentration aqueous solution (viscosity: 30 mPa · s) of oxidized corn starch (trade name; Ace A, manufactured by Oji Cornstarch Co., Ltd.), and the coating method was changed to a gate roll coater. The offset printing paper having an actual amount of 87.4 g / m ² was obtained in the same manner as in Example 1 except that 1.2 g / m ² in terms of dry weight per side was applied on both sides and dried. The average penetration depth of the surface treatment agent at this time was 22 μm.

  The following evaluation tests were performed on the nine types of offset printing paper thus obtained, and the results are shown in Table 1. The evaluation of the offset printing paper in the present invention was performed in an environment of 23 ° C. and 50% RH unless otherwise specified.

・ Average penetration depth of surface treatment agent (μm)
It was measured by the above method.

・ Dry weight (g / m ² ) of the front and back surfaces of the surface treatment agent
It was measured by the above method.

・ Blanket Piling Using an offset printing machine (Mitsubishi Lithopia L-BT3-1100), printing four colors and printing 10,000 copies, then visually judging the degree of paper dust accumulation on the blanket non-image area did.
A: Almost no generation of paper dust is observed.
○: Paper dust is slightly generated, but there is no practical problem.
Δ: The occurrence of paper dust is clearly recognized.
X: A lot of paper dust is deposited on the blanket.

-Marking of the printed surface Using the offset printing machine, after performing continuous 10,000-color black ink printing, the degree of printing on the printed surface was visually determined.
○: The ink density on the printing surface is high, and no blurring is observed.
Δ: Scratch is slightly observed, but there is no practical problem.
X: The degree of blurring is large and the ink density on the printing surface is low.

Claims (1)

On at least one surface of the base paper, surface treatment agent coating solution one fluid spray system per side by dry weight by 1.0 to 3.0 g / ^{m 2} mainly composed of starch or starch derivative having a viscosity of 10 to 100 mPa · s coated to a dried, resulting offset printing paper, wherein the average penetration depth of the surface treatment agent of the coated surface is 10μm or less from the base paper the outermost surface.