JPS63170075A - Production of ink jet recording sheet - Google Patents

Abstract

PURPOSE:To improve absorbing performance of water-color ink, resolution of an image, coloring performance of coloring matter in the ink, and to prevent foaming or cracking of a coating layer, by applying coating liquid onto a base sheet and setting a specific highest drying temperature with a specific temperature gradient. CONSTITUTION:Filling material for coating liquid includes silica, synthetic and natural zeolites, etc., and aqueous binder includes mixture of one or more kinds of water dispersion macromolecular substance such as polyvinyl alcohl, starch, vinyl acetate emulsion. Water-proof agent, optical whitening agent, viscosity regulating agent, surfactant, hardener, coloring agent, anti-foaming agent, sizing agent, anti-oxidizing agent, light-resistance improving agent, etc., may be contained. When drying conditions of the coating layer are set so that the highest drying temperature is in the range of 120-150 deg.C with temperature gradient not lower than 20 deg.C, recording characteristics such as absorbing performance and resolution of water-color ink, coloring performance of coloring matter in the ink, and dot type of a recording sheet, especially of ink jet recording sheet are improved, while cracking, forming, powdering thereof are prevented form occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing recording paper, which has particularly excellent absorbency of water-based ink, image resolution, and color development of the coloring material in the ink. The present invention relates to a method for producing a recording paper useful for inkjet use, in which the coating layer is free from foaming and cracking, the coating layer has good surface properties, and there is little powder falling off.

(Conventional Technique i) Conventionally, recording paper for inkjet has been made by (1) ordinary paper whose main component is pulp and made into a paper with a low size such as filter paper or blotting paper; (2) A paper with a large size as the base paper, coated with a porous filler with high oil absorption such as silica or zeolite, and provided with an ink absorbing layer; (3) JP-A-52-
No. 53012, JP-A-55-11829 and JP-A-5
As disclosed in Japanese Patent No. 9-38087, a coating layer is provided on a base paper of low size, etc., and the like are known.

Although recording paper (1) has excellent ink absorption, the ink penetrates deeply into the fiber layer of the paper, resulting in poor color development of the coloring material in the ink, and the ink does not adhere to the fibers on the paper surface. As a result, a phenomenon called feathering occurs, which causes the dots to become jagged instead of circular, resulting in a decrease in resolution, making it impossible to obtain high-quality images.

In the recording paper (2), the ink absorption layer is porous and uniform, so good dot shape and resolution can be obtained, but in order to provide sufficient ink absorption, it is necessary to There is also the problem that the layer must be thick, and one coat is insufficient, so multiple coats must be applied.

Also, when the coating layer dries, foaming and cracking occur in the coating layer.
Defects that degrade images are likely to occur.

Furthermore, in an attempt to improve ink absorption, if the filler-to-binder ratio (P/B) of the ink-absorbing layer is made too large, the filler may fall off, causing so-called powder drop, which may cause the paper feed roller to slip, or There were drawbacks such as clogging of inkjet nozzles.

Even if the recording paper (3) has good ink absorption, resolution, and dot shape, the color development may be insufficient, or the coating layer may not be formed uniformly because the base paper is water absorbent, and the ink may not be formed uniformly. There were problems such as local variations in inkjet recording characteristics such as absorption, resolution, dot shape, and coloring properties of coloring materials. Further, when the coating layer dries, there is a problem that foaming or cracking occurs in the coating layer.

However, with regard to these recording papers, little is known that has been studied from the aspect of manufacturing conditions, and at present, little is known about the relationship between manufacturing conditions and inkjet recording characteristics.

(Problems to be Solved by the Invention) The present invention relates to a method for manufacturing recording paper belonging to the above-mentioned recording papers (2) and (3), and relates to a method for expressing the characteristics of recording paper in a steady state as conventionally disclosed. It is difficult to produce recording paper that has inkjet recording properties such as ink absorption, resolution, color development of the coloring material in the ink, and uniformity of the coated layer surface in a well-balanced and uniform manner by using paper alone. This was achieved based on knowledge.

Therefore, an object of the present invention is to provide a method for producing a recorder for stably producing improved recording paper having inkjet suitability as described above, particularly inkjet recording paper.

(1gL of steps to solve the problem) The above object is achieved by the present invention as follows.

That is, the present invention provides a method for producing recording paper in which a coating liquid is applied to a base paper and dried, in which the drying conditions for the coating layer include a temperature gradient of 20° C. or higher, and a maximum drying temperature in the drying temperature gradient. This is a method for producing inkjet recording paper, characterized in that the temperature is in the range of 120 to 150°C.

Next, to explain the present invention in more detail, the base paper used in the present invention is a sheet containing a fibrous substance and filler if necessary, and any conventionally known coating liquid used in the present invention can be used. It mainly consists of a filler and a water-based binder. Examples of fillers include silica, synthetic and natural zeolites, calcium silicate, aluminum silicate, magnesium silicate, white carbon, calcium carbonate, barium sulfate, clay, kaolin, talc, titanium oxide, satin white, etc. Among these, silica is particularly suitable.

Examples of water-based binders include water-soluble polymers such as polyvinyl alcohol, starch, oxidized starch, cationized starch, casein, carboxymethyl cellulose, gelatin, hydroxyethyl cellulose, and SBR latex.
One type or a mixture of two or more types of water-dispersible polymers such as MBR latex and vinyl acetate emulsion are used.

In addition, water resistant agents, optical brighteners, viscosity modifiers, surfactants, curing agents, colorants, antifoaming agents, sizing agents, antioxidants,
Of course, it may contain a light resistance improver and the like.

The viscosity of the aqueous coating liquid as described above can be easily adjusted to an appropriate viscosity by adjusting the type and combination of the filler and binder, their usage ratio, their respective concentrations, the total concentration, etc.

In the present invention, generally the use ratio of filler and binder is in the range of about 20/1 to 1/3 (weight ratio), and the total solid content is in the range of about 3 to 70% by weight. Liquid is preferred.

As the coating machine used in the present invention, any conventionally known coating machine can be used, but suitable coaters for the present invention include an air knife coater and a bar coater.

The coating amount of the aqueous coating liquid is preferably such that the thickness of the coating layer when dried is 2 to 50 μm, and if it is thinner than 2 μm, it will not function as a coating layer.

In other words, when the coating amount is less than 2 μm, the ink that collides with the surface of the recording paper smears along the fibers, distorting the dot shape,
At the same time, the dye penetrates deeply into the paper, reducing the color density of the image.

On the other hand, if the coating amount exceeds 50 μm, problems such as powder falling may occur, which is not preferable. Further, in order to give the coating layer thickness or to provide a functional difference between the surface and the inside, it is of course possible to perform multilayer coating of two or more layers.

The present inventor has proposed that when preparing recording paper having a coating layer using the various materials described above, especially inkjet recording paper, the coating liquid is applied to the base paper and dried to form the coating layer. It has been found that during formation, the drying temperature conditions of the coating layer at that time have a significant effect on the recording properties and surface condition of the resulting recording paper, particularly inkjet recording paper.

That is, when the drying conditions of the coating layer are set such that the temperature gradient is 20°C or higher and the maximum drying temperature in the drying temperature gradient is in the range of 120 to 150°C, the absorbency of the water-based ink, the resolution, and the ink Recording paper that has excellent recording properties such as the color development of the coloring material inside and the dot shape, and has solved the problems of the surface of the coating layer, such as cracks in the coating layer, foaming marks, and powder falling, which were particularly problematic in the past. In particular, inkjet recording paper could be obtained.In other words, the various drying ovens commonly used in the past were
It has a total length of ~50m and is divided into 3 to 7 sections and the temperature is controlled. However, if the maximum drying temperature is less than 120℃, the drying efficiency of the coating layer is extremely poor, and the binder is This causes problems such as the P/B ratio being changed due to absorption by the air, and the surface of the coating layer becoming uneven when the amount of air is increased to improve drying efficiency.

In addition, when the maximum drying temperature exceeds 150° C., problems such as cracks on the surface of the coating layer, formation of foaming marks, and severe fall-off of filler particles may occur.

Furthermore, not only the maximum drying temperature in the drying oven but also the temperature gradient of the drying oven is an important factor, and it is necessary that the gradient is 20° C. or higher. For example, if the maximum drying temperature through a section of the drying oven is 130°C, it is necessary to have a temperature of 110°C or less in any of the drying oven sections.

More specifically, the inlet section of the drying oven is set at a relatively low temperature, e.g. 80-120°C, and the temperature gradient is set at 20
It was preferable to have a section with a maximum temperature of 120 to 150°C in the middle to rear half of the drying oven.

The temperature gradient is preferably 20°C or higher and 50°C or lower. Therefore, since the maximum drying temperature is 120-150°C, the minimum drying temperature is 70-130°C, more preferably 90°C.
~110°C, but is not limited thereto.

Furthermore, it is more preferable to lower the temperature in the section near the population to create a temperature gradient. It is also possible to create a temperature gradient such as lowering the temperature to 120 to 150°C and then gradually increasing it to 120 to 150°C.

If the temperature gradient is less than 20°C, the surface of the coating layer will be heated all at once, causing rapid foaming of water in the coating solution, or causing degassing before the surface of the coating layer becomes smooth. Bubble marks may be formed on the coated surface and cause image damage. In addition, only the surface of the paper dries rapidly, causing cracks that damage the image and worsen powder falling off when the paper is passed through.

In the manufacturing method of the present invention, as long as the coating layer is dried under the conditions of the present invention, the drying method may be a conventionally known drying method,
For example, any drying method such as a hot air drying oven or a drying drum may be used, and the surface may be further smoothed by super calendering.

(Function/Effect) According to the present invention as described above, when producing coated paper, the drying conditions of the coating layer are set to specific conditions, that is, the temperature gradient is 2.
By setting the temperature above 0℃ and the maximum drying temperature in the drying temperature gradient in the range of 120 to 150℃, it is possible to record the absorbency of water-based ink, resolution, color development of coloring material in ink, dot shape, etc. Provided is a recording paper, particularly an inkjet recording paper, which has excellent properties and solves the problems of the surface of the coating layer, such as cracking of the coating layer, foaming marks, powder falling, etc., which have been particularly problematic in the past.

Next, the method of the present invention will be explained in more detail with reference to Examples and Comparative Examples. In addition, parts and percentages in the text are based on weight unless otherwise specified.

Examples 1 to 4, Comparative Examples 1 to 3 As a base paper, a handmade sheet with a size of 20 seconds and a viscosity of 20
0 cps of water-based coating liquid with the following composition using a bar coater.
The coating was applied at a speed of 0.00 m/min to give a dry film thickness of 20 μm, and dried under the conditions listed in Table 1 below to obtain inkjet recording papers of the present invention and comparative examples.

Silica (thyroid 74, oil absorption 2) 0ml/100
g, manufactured by Fuji Davison Chemical) 15 parts Polyvinyl alcohol (PVA-17, manufactured by Kuraray) 3 parts Water 82 parts Using an inkjet printer having four colors of Y, M, C, and BK, inkjet recording was performed using the inkjet head having the following composition, and the ink absorption, resolution, and color development were evaluated.

Y (Yellow Ink C, L Direct Yellow 86 2 parts polyethylene glycol 15 parts diethylene glycol 15 parts water
70 parts M Magenta Tank C, 1, Acid Red 35 2 parts polyethylene glycol 15 parts diethylene glycol 15 parts water
70 parts Cyank C, 1, Direct Blue 199 2 parts polyethylene glycol 15 parts diethylene glycol 15 parts water
70 parts BK (black ink C, 1, food black 2 2 parts polyethylene glycol 15 parts diethylene glycol 15 parts water
70-part review JL 瑣法 (1) Ink absorption is when printing four colors of Y, M, C, and BK one on top of the other, O indicates that the ink is well absorbed, and ink overflows because the ink cannot be absorbed completely. What you put out is X,
The middle value between ○ and × was marked as △.

(2) Resolution: For BK printing, a white line of 2 dots is printed, and the one with a clear white line is ○
, The crushed one is marked as ×, and the one in between ○ and × is marked as △.

(3) Color development was determined by Macbeth Densitometer RD918.
The reflective optical density of the solid printed area of K was measured.

(4) The surface condition of the coating layer was evaluated by observing the solid printed area. Those that were good were marked as ○, and those that were not good were marked as ×.

(5) Powder removal was evaluated by writing on the surface of the coating layer with a 2H pencil.

The results are summarized in Table 2 below.

1 - (Drying conditions) Example 1 130 100 30 Example 2
125 105 20 Example 3 145
110 35 Example 4 130 50
80 Comparative Example 1 110 80 30
Comparative example 2 130 120 10 Comparative example 3
160 100 60~2 (Test results)

Claims (3)

[Claims] (1) In a recording paper manufacturing method in which a coating liquid is applied to a base paper and dried, the drying conditions for the coating layer are such that the temperature gradient is 20°C or higher, and the highest drying temperature in the drying temperature gradient is 120°C or higher. A method for producing an inkjet recording paper, characterized in that the temperature is in the range of 150°C. (2) The method for producing an inkjet recording paper according to claim (1), wherein the temperature gradient is 20°C to 50°C. (3) The method for producing an inkjet recording paper according to claim (1), wherein the filler forming the coating layer contains silica as a main component.