JPH06202371A - Electrophotographic transfer paper - Google Patents

Abstract

PURPOSE:To provide such an electrophotographic transfer paper that contains waste paper pulp by >70% of the whole pulp and has the same electrophotographic properties including troubles such as decrease in density of copy image during copying in a high humidity environment and voids in images as those of conventional electrophotographic transfer paper using fresh bleached pulp as the source material. CONSTITUTION:This transfer paper contains waste paper pulp by >=70% of the whole pulp. The surface resistance of the paper is controlled to <=5X10<13>OMEGA with 4-6% water content of the paper and >=1X10<8>OMEGA at 20 deg.C, under controlled humidity to 85% R.H. by adding a conducting agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer sheet used in an indirect electrostatic copying machine, an indirect electrostatic printer or the like.

[0002]

2. Description of the Related Art In recent years, the importance of forest resource protection has been recognized as global environmental problems have come to the surface, and as a part of countermeasures, saving the use of wood resources by using waste paper as a paper raw material has become a serious issue. In particular, for printing and information papers that are rarely used, it is desired to expand the use of recycled paper made from recycled paper.

Recent changes in copiers and printers have been remarkable, and various functions such as an increase in copy speed, compactness, double-sided copying, and multiple copying have been completed, and it has become widespread even in models having a relatively slow copying speed.
Along with this, the number of papers fed from the lateral direction is increased, and the papers are conveyed in a complicated machine, and the conditions are becoming more and more severe for the papers. However, in indirect electrophotographic copying machines,
If you use recycled paper for electrophotography that uses waste paper as a raw material, problems such as a decrease in the density of copied images and missing images often occur during copying in high-humidity environments, and copying in low-humidity environments is possible. , It has become clear that there is a lot of trouble in practical use due to frequent image disturbances and running troubles caused by static electricity when used immediately after opening. by the way,
Electrophotographic paper mixed with used paper is Japanese Patent Publication Sho 63-6867
However, there is no suggestion of means for solving the above-mentioned problems such as image quality deterioration in a high humidity environment. Further, in order to solve the problem caused by the curl after copying, Japanese Patent Laid-Open No. 55-142799 discloses a means for specifying the moisture content of the product. However, in order to solve the problem of image quality deterioration in a high humidity environment. The means of is not presented.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems in the prior art, and has been made in order to provide a recycled paper which is suitable for electrophotography and which contains used paper. Therefore, an object of the present invention is to provide a transfer sheet for electrophotography which has a conventional bleached virgin pulp as a main raw material and which is suitable for electrophotography including troubles such as a reduction in the density of a copy image and a missing image in a copy operation in a high humidity environment. There is no difference to (hereinafter, referred to as a transfer paper), and it is to provide a transfer paper for electrophotography (hereinafter referred to as a recycled paper for transfer) containing 70% or more of waste paper pulp in the total pulp.

[0005]

The recycled paper for transfer of the present invention is a paper containing 70% or more of waste paper pulp in the total pulp. 5 × 10 ¹³ Ω or less at ~ 6%, 2
0 ° C 85% R.O. H. It is characterized in that it is adjusted to 1 × 10 ⁸ Ω or more by controlling the humidity in the environment.

Further, the moisture content (Y) at the time of opening the package and 20 ° C 85% R.V. H. The relation with the equilibrium moisture content (A) meets the following equation (A-6.5 ≦ Y ≦ A-4.5), and the moisture content at the time of opening the package is 6.5% or less. Characterize.

As a result of investigating and examining the relationship with the paper characteristics under the environment where the above-mentioned copy image quality trouble occurs, the inventor of the present invention has found that the environment is high humidity (temperature 20 ° C., humidity 85% RH) for 2 hours. The surface electric resistance of the paper when the humidity is adjusted above is 1 × 10 ⁸
It has been found that problems such as a decrease in the density of the copy image and a dropout of the image can be significantly improved if the value is Ω or more.

At this time, as shown in FIG. 1, irrespective of whether the used pulp is newspaper pulp or high quality pulp paper, the waste pulp paper has surface electricity when the humidity is controlled in the same environment as the virgin chemical pulp paper. Although there is no difference in resistance, it was also discovered that the virgin mechanical pulp paper according to the above-mentioned Japanese Patent Laid-Open Publication No. 55-142799 is different from the higher virgin chemical pulp paper. This is considered to be due to the deinking agent used in the used paper processing step even though the same mechanical pulp is used. Therefore, it was also found that the control of the electric resistance required was completely different depending on whether the same mechanical pulp was virgin or waste paper. In addition, as shown in FIG. 2, newspaper pulp paper containing a large amount of mechanical pulp has a higher surface electric resistance than virgin chemical pulp paper and high-quality waste paper pulp containing no mechanical pulp at the same water content, and therefore, when the water content becomes low, copying occurs. Problems such as poor tray and sorter accommodation due to the large amount of residual static electricity when the image is scattered and the copy is discharged.

The present inventor has energetically studied the relationship between the water content of the paper and the surface electric resistance with respect to this problem. As a result, the scattering of the copy image and the defectiveness at the time of discharging the copy cause the water content of the paper to fall within the range of 4 to 6%. When, the surface electric resistance of the paper is 5
It has been found that it can be improved by adjusting to 10 ¹³ Ω or less. That is, it is possible to obtain stable image quality and runnability in the range of water content contained in the paper which is usually used in copying work. However, since it is impossible to use the same kind of waste paper as the raw material for waste paper pulp, the equilibrium moisture content differs due to the difference in the waste paper raw material type even if the moisture content at opening is specified. Since the problem of deviating from the improved electric resistance range occurs even if the electric resistance is controlled under the conditions, the present inventor has found that the equilibrium moisture fluctuation and packaging caused by the used waste paper raw material type while maintaining the improved electric resistance range. As a result of diligent research on the relationship between the moisture content at the time of opening the package, the moisture content (Y) at the time of opening the package and 85 ° C. H. The relationship with the equilibrium moisture content (A) is expressed by the following equation (A-6.5 ≦ Y ≦ A-
It was found that the range of improved electric resistance can be maintained by setting 4.5).

Even if the moisture content at the time of opening the package is such that the optimum range can be maintained, if the moisture content exceeds 6.5%, the curl after copying becomes large, and paper jams at the time of double-sided copying, trays, sorters, etc. Since the storage capacity is poor, the moisture content at the time of opening the package is adjusted to 6.5% or less to adjust the surface electric resistance of the paper within the range of the present invention to obtain a recycled paper having stable quality even in a high humidity environment. It was discovered that it was possible.

The surface electric resistance in the present invention is the JIS
It is measured according to K 6911, and conductive agents used for control include sodium chloride, potassium chloride,
Inorganic salts such as calcium chloride and sodium alginate, and polymer electrolytes such as styrene-maleic acid copolymers and quaternary ammonium salts, and organic acid salts of potassium formate and sodium bromide, and soaps, phosphates, and carboxylates. Any material that enhances the conductivity of the paper, such as a surface active agent and an electron conductive conductive material such as zinc oxide doped with aluminum oxide, tin oxide doped with antimony, and titanium oxide may be used. It is obtained by surface-coating these conductive agents with a size press of a paper machine. The paper treated with these conductive agents has a surface electric resistance of 5 × 10 ¹³ Ω or less at a water content of 4 to 6% in the paper and 85 ° C. at 20 ° C.
H. Adjust the humidity so that it is 1 × 10 ⁸ Ω or more. Therefore, the type and amount of the conductive agent can be selected so that the surface electric resistance value of the treated paper is within the above range.

In the present invention, the water content of the paper is JIS
It is measured according to P 8127, and the moisture content at the time of opening the package is controlled at 20 ° C8 of the waste paper raw material used in the dryer of the paper machine, the calender process, the cutting process, etc.
5% R. H. Adjust to the proper moisture calculated from the relationship with the equilibrium moisture. Also, in order to prevent moisture absorption and desorption during storage, it is wrapped with moisture-proof wrapping paper such as polyethylene laminated paper or polypropylene film.

Further, in order to improve the sharpness of the copy image portion, the surface roughness is reduced by calendering or the like so that the smoothness of the transfer paper (JIS P 8119) is 10 seconds or more, preferably 20 seconds or more. .

The waste paper pulp used in the present invention is used for bookbinding, printing factories, cutting sites, etc.
Reusable waste paper pulp, high quality paper, high quality coated paper, medium quality paper, medium quality coated paper, planographic printing etc. Letterpress, intaglio printing, electrophotographic method, heat-sensitive method, heat transfer method, pressure-sensitive recording method, inkjet recording method, used paper printed with carbon paper, and used paper written with water-based or oil-based ink or pencil, newspaper used paper , And deinked pulp (hereinafter abbreviated as DIP) can be used. However, in the present invention, the equilibrium water content varies depending on the type of waste paper as described above, and therefore, in order to maintain an appropriate water content when opening the package. , Sorting
Manage the types and ratios of used paper by combining them.

In the present invention, in addition to the above waste paper, virgin chemical pulp (hardwood bleached kraft pulp, softwood bleached kraft pulp, hardwood unbleached kraft pulp, softwood unbleached kraft pulp, hardwood bleached sulfite pulp, softwood bleached sulfite pulp, hardwood Unbleached sulphite pulp, softwood unbleached sulphite pulp etc.Pulp made by chemically treating wood and other fiber raw materials) or ground pulp obtained by mechanically pulping wood or chips, or chemicals on wood or chips. After impregnating, mechanically pulped chemigrand pulp, chemi-mechanical pulp, and after digesting chips until somewhat soft, may contain virgin pulp such as semi-chemical pulp pulped with a refiner . However, it is preferable to contain virgin chemical pulp in addition to the waste paper.

In the present invention, in order to control the equilibrium water content and suppress the occurrence of curl after copying, the used paper is selected and the combination of virgin pulp is blended, and the beating degree is adjusted in the preparation step.

As the filler which can be used in the recycled paper for transfer of the present invention, heavy calcium carbonate, light calcium carbonate, calcium carbonate such as chalk, kaolin,
Inorganic fillers such as calcined clay, pyrophyllite, sericite, talc, and other inorganic fillers, and organic pigments such as urea resins can be used, but the ash content (JIS-
P-8128) in consideration of the addition. When added, calcium carbonate is preferably added from the viewpoint of maintaining image quality in the electrophotographic system so that the ash content is 8% or less.

The internally added sizing agent used in the present invention is
Sulfuric acid band that can be used with sizing agents such as rosin-based sizing agents, synthetic sizing agents, petroleum resin-based sizing agents, neutral sizing agents,
An appropriate sizing agent such as cationized starch and a fixing agent for the fiber are used in combination. Desirably, a neutral sizing agent, particularly an alkenyl succinic anhydride-based sizing agent, is used from the viewpoints of running properties in an electrophotographic copying machine, printer and the like, and paper storability after copying. Furthermore, copy suitability,
Preparation of raw materials in order to impart electrophotographic suitability such as runnability,
Manufacturing conditions are controlled.

[0019]

The present invention will be described in more detail with reference to the following examples, but of course the present invention is not limited thereto.

Example 1 As shown in Example 1 of Table 1, fine printed waste paper DIP40
%, DIP 30% imitation waste paper, 70 total as waste paper pulp
%, And 30% of hardwood bleached kraft pulp (L · BKP) was blended as pulp other than waste paper. Then, an internal addition size as shown in Table 1 was blended, papermaking was carried out with a Fourdrinier paper machine using this paper material, and 1 g of starch / g was obtained by size press treatment.
m ^2, was coated such that the sodium chloride 0.2 g / m ^2, to obtain a transfer recycled paper of the present invention to adjust the packaging opening when moisture 5.0%. 20 of this recycled paper for transfer
C 85% R.C. H. The measured equilibrium water content after conditioning for 2 hours in the environment was 10.1%, and the surface electric resistance at that time was 8.1.
It was × 10 ⁸ Ω. The surface electric resistance was 2.51 × 10 ¹³ Ω when the water content of the paper was 5.0%. The copy image quality of this transfer paper in a high humidity environment was confirmed as follows. That is, this transfer paper was printed at 20.degree. H. In the environment of No. 2, left for 2 hours, single-sided copying was performed with a copying machine (FX5030, manufactured by Fuji Xerox Co., Ltd.), and image density and image loss were confirmed. In addition, 500 minutes after opening the package with the copier.
Paper jams were confirmed by running single-sided copy and double-sided copy respectively. The results are shown in Table 1. As is clear from Table 1, 20 ° C 85% R.V. H. The surface electric resistance of the environment was 8.1 × 10 ⁸ Ω, and the moisture content was 5.0% when the package was opened. As a result, there was no image deterioration even when running after high humidity conditioning, and paper jams did not occur. No recycled paper for transfer was obtained.

Example 2 As shown in Example 2 in Table 1, newspaper waste paper DIP 50%, high-quality waste paper DIP 20%, and waste paper pulp total 70%
20% of hardwood bleached kraft pulp (L · BKP) and 10% of refiner ground pulp (RGP) were blended as pulp other than waste paper. Then, an internal addition size as shown in Table 1 was blended, papermaking was carried out using a Fourdrinier paper machine using this paper material, and the starch was 1.2 g / m 2 by size press treatment.
² and potassium chloride were coated so as to be 0.1 g / m ² and the water content at opening of the package was adjusted to 6.1% to obtain a recycled paper for transfer of the present invention. 20 ° C8 of this recycled paper for transfer
5% R. H. The measured equilibrium water content after conditioning for 2 hours in the environment was 11.2%, and the surface electric resistance at that time was 1.7 × 10.
It was ⁸ Ω. The surface electric resistance was 2.8 × 10 ¹² Ω when the water content of the paper was 5.1%. This transfer sheet was evaluated in the same manner as in Example 1. The results are shown in Table 1. As is apparent from Table 1, 20 ° C. 85% R.V.
H. The surface electric resistance of the environment is 1.7 × 10 ⁸ Ω, and the moisture content is 6.1% when the package is opened. As a result, there is no image deterioration and paper jam even when running after high humidity conditioning. No recycled paper for transfer was obtained.

Example 3 As shown in Example 3 in Table 1, newspaper waste paper DIP 30%, high quality printing waste paper DIP 30%, fine white waste paper pulp 20%, and a total of 80% as waste paper pulp were added, and hardwood bleached as pulp other than waste paper. 20% of kraft pulp (L · BKP) was blended. Then, blended internal sizing, such as shown in Table 1, and papermaking in a Fourdrinier paper machine using this paper stock, with a size press, starch 1.2 g / m ^2, sodium chloride 0.2
It is coated so that it is g / m ^2, and the moisture content is 5.5 when the package is opened.
% To obtain a recycled paper for transfer of the present invention. This recycled paper for transfer has a 20% C. H. In the environment 2
The equilibrium water content after time humidity control was measured to be 10.6%, and the surface electric resistance at that time was 2.9 × 10 ⁸ Ω. Also,
Surface electric resistance is 5.0 × 10 when paper moisture is 5.5%.
It was ¹² Ω. This transfer sheet was evaluated in the same manner as in Example 1. The results are shown in Table 1. As is clear from Table 1, 20 ° C 85% R.V. H. The surface electric resistance of the environment is 2.9 × 10 ⁸ Ω, and the moisture content is 5.5% when the package is opened. As a result, there is no image deterioration and paper jam even when running after high humidity conditioning. No recycled paper for transfer was obtained.

Example 4 As shown in Example 4 of Table 1, fine printed waste paper DIP40
%, Imitation waste paper DIP 40%, total 80 as waste paper pulp
%, And 20% of hardwood bleached kraft pulp (L · BKP) was blended as pulp other than waste paper. Then, the internal addition sizes shown in Table 1 were blended, the paper stock was used to make a paper using a Fourdrinier paper machine, and the starch was 1.0
The recycle paper for transfer according to the present invention was obtained by coating so as to have g / m ² and 0.2 g / m ² of sodium chloride, and adjusting the water content when opening the package to 4.7%. 2 of this recycled paper for transfer
0 ° C 85% R.O. H. The equilibrium water content after conditioned for 2 hours was measured to be 9.9%, and the surface electric resistance at that time was 1.0.
It was × 10 ⁹ Ω. The surface electric resistance was 3.16 × 10 ¹³ Ω when the water content of the paper was 5.0%. This transfer sheet was evaluated in the same manner as in Example 1. The results are shown in Table 1. As is clear from Table 1, 20 ° C 85%
R. H. The surface electric resistance of the environment is 1.0 × 10 ⁹ Ω,
As a result of the moisture content at the time of opening the package being 4.7%, recycled transfer paper without image deterioration and paper jam even during running after high humidity conditioning was obtained.

Example 5 As shown in Example 5 of Table 2, waste paper DIP 10%, fine printing waste paper DIP 30%, imitation waste paper DIP 20%, high-quality electrophotographic paper waste paper DIP 20%, and a total of 90% as waste paper pulp, were used. 10% of hardwood bleached kraft pulp (L · BKP) was blended as the other pulp. Then, the internal addition sizes shown in Table 2 were blended, the paper stock was used to make paper with a Fourdrinier paper machine, and size press treatment was conducted to obtain 1.0 g / m ^{2 of} starch and 0.15 g / m ² of sodium chloride. ^It was coated so as to be ^2, and the water content when opening the package was adjusted to 5.3% to obtain a recycled paper for transfer of the present invention. This recycled paper for transfer has a 20% C. H. The equilibrium water content after humidity control for 2 hours was measured to be 10.3%, and the surface electric resistance at that time was 5.4 × 10 ⁸ Ω. Also, the water content of the paper is 5.
The surface electric resistance at 3% was 7.9 × 10 ¹² Ω.
This transfer sheet was evaluated in the same manner as in Example 1. The results are shown in Table 2. As is clear from Table 2, 20 ° C
85% R.I. H. Surface electric resistance of the environment is 5.4 × 10 ⁸ Ω
The effect of setting the water content to 5.3% when opening the package
Recycled paper for transfer was obtained in which there was no image deterioration even when running after high humidity conditioning and no paper jam occurred.

Example 6 As shown in Example 6 of Table 2, fine printed waste paper DIP60
%, Fine white waste paper pulp 20%, fine electrophotographic paper waste paper DI
P20% and 100% in total as waste paper pulp. Then, the internal addition sizes as shown in Table 2 are blended, the paper stock is used to make a paper by a Fourdrinier paper machine, and the size press treatment is performed.
Starch was coated at 0.6 g / m ² , PVA at 0.5 g / m ² , and sodium chloride at 0.2 g / m ^2, and the water content at the time of opening the package was adjusted to 4.9%. Recycled paper for transfer was obtained. 20 ° C 85% of this recycled paper for transfer
R. H. As a result of measuring equilibrium water content after conditioned for 2 hours in the environment, the surface electric resistance at that time was 9.8% and 6.3 × 10 ⁸ Ω. The surface electric resistance was 2.0 × 10 ¹³ Ω when the water content of the paper was 5.0%. This transfer paper is used in Example 1.
It evaluated by the method similar to. The results are shown in Table 2. Table 2
As is clear from FIG. H. The surface electric resistance of the environment was 6.3 × 10 ⁸ Ω, and the moisture content when opening the package was 4.9%. As a result, there was no image deterioration even when running after high humidity conditioning, and paper jams did not occur. No recycled paper for transfer was obtained.

Example 7 As shown in Example 7 of Table 2, newspaper waste paper DIP 60%, imitation waste paper DIP 20%, high-quality electrophotographic paper waste paper DIP20
%, 100% in total as waste paper pulp. And
An internal additive size as shown in Table 2 was blended, the paper stock was used to make a paper using a Fourdrinier paper machine, and a styrene-maleic acid copolymer was coated to 1.0 g / m ² by size press treatment. Then, the moisture content at the time of opening the package was adjusted to 6.4% to obtain a recycled paper for transfer of the present invention. This recycled paper for transfer has a 20% C. H. The equilibrium moisture content after conditioning for 2 hours in the environment was measured to be 11.4%, and the surface electric resistance at that time was 1.3 × 10 ⁸ Ω. Also, the water content of the paper is 5.5%.
The surface electric resistance at that time was 6.0 × 10 ¹¹ Ω. This transfer sheet was evaluated in the same manner as in Example 1. The results are shown in Table 2. As is clear from Table 2, 20 ° C 85
% R. H. The surface electric resistance of the environment is 1.3 × 10 ⁸ Ω, and the moisture content when opening the package is 6.4%. As a result, there is no image deterioration even when running after high humidity conditioning, and paper jams do not occur. No recycled paper for transfer was obtained.

[0027]

[Table 1]

[0028]

[Table 2]

A comparative example will be described below. Comparative Example 1 As shown in Comparative Example 1 of Table 3, newspaper DIP 30%, fine print DIP 30%, total 60% as waste paper pulp, 10% hardwood bleached kraft pulp (L · BKP) as pulp other than waste paper, 30% of refiner ground pulp (RGP) was blended. Then, the paper was made according to the formulation shown in Table 3. With respect to the obtained transfer paper, the image density, image loss, and paper jam were confirmed by the same experimental method as in Example 1. The results are shown in Table 3 below.

COMPARATIVE EXAMPLE 2 As shown in Comparative Example 2 in Table 3, 0% waste paper pulp was used, and as a pulp other than waste paper, a hardwood bleached kraft pulp (L.BK) was used.
P) was blended 100%. Then, the paper was made according to the formulation shown in Table 3. With respect to the obtained transfer paper, the image density, image loss, and paper jam were confirmed by the same experimental method as in Example 1. The results are shown in Table 3 below.

Comparative Example 3 As shown in Comparative Example 3 in Table 3, 60% of fine printing DIP, 10% of imitation DIP, and 70% in total as waste paper pulp were blended,
Hardwood bleached kraft pulp (L.
BKP) was blended at 30%. Then, the paper was made according to the formulation shown in Table 3. With respect to the obtained transfer paper, the image density, image loss, and paper jam were confirmed by the same experimental method as in Example 1. The results are shown in Table 3 below.

Comparative Example 4 As shown in Comparative Example 4 in Table 4, DIP 10% newspaper, high quality printing DIP 30%, imitation DIP 20%, high quality electrophotographic paper DIP 20%, and 90% in total as waste paper pulp were added. Hardwood bleached kraft pulp (L · BKP) was blended at 10% as the pulp. Then, the paper was made according to the formulation shown in Table 4. Example 1 of the obtained transfer paper
By the same experimental method as above, the image density, the image omission, and the paper jam were confirmed. The results are shown in Table 4 below.

Comparative Example 5 As shown in Comparative Example 5 in Table 4, used newspaper DIP 60%, high quality printed DIP 30%, high quality electrophotographic paper used paper DIP10.
%, 100% in total as waste paper pulp. And
Paper was made according to the formulation shown in Table 4. With respect to the obtained transfer paper, the image density, image loss, and paper jam were confirmed by the same experimental method as in Example 1. The results are shown in Table 4 below.

[0034]

[Table 3]

[0035]

[Table 4]

[0036]

INDUSTRIAL APPLICABILITY The recycled paper for transfer of the present invention contains 70% or more of waste paper pulp in the total pulp, but at 85 ° R. H. Control of surface electric resistance of paper humidity-controlled in the environment, water content when opening the package and 20 ° C8
5% R. H. Even if this transfer paper is used in an indirect electrophotographic copying machine, by specifying the moisture content when opening the package from the relationship of equilibrium moisture and setting the moisture content when opening the package to 6.5% or less. It can be used in the same manner as the electrophotographic transfer paper made of bleached virgin pulp. Especially, in a high humidity environment, problems such as image quality of copy and paper jam are improved as compared with the conventional transfer paper containing waste paper pulp.

[Brief description of drawings]

FIG. 1 shows the relationship between surface electric resistance and relative humidity of waste paper pulp sheets and virgin pulp sheets. The pulp sheet contains 100% each of newspaper waste paper DIP, high-quality waste paper DIP (high-quality waste paper), L-BKP and RGP, and a basis weight of 6
Paper was made at 8 g / m ² , a paper thickness of 105 μm, and no conductive agent added. The temperature of the measurement environment was all 20 ° C.

FIG. 2 shows the relationship between the surface electric resistance of the paper used in FIG. 1 and the equilibrium moisture content under each environment.

Claims (2)

[Claims] 1. A paper containing 70% or more of waste paper pulp in the total pulp, by adding a conductive agent,
Surface electric resistance is 5 × 10 ¹³ Ω or less when the water content in the paper is 4 to 6%, and 20 ° C. 85% R. H. 1 × 10 ^{8 for} humidity control under environment
Transfer paper for electrophotography, which is adjusted to Ω or more. 2. The moisture content when the package is opened conforms to the formula shown below, and the moisture content when the package is opened is 6.5.
% Or less, and the electrophotographic transfer sheet according to claim 1. A-6.5 ≦ Y ≦ A-4.5 (Y: Moisture content when opening the package,%, A: 20 ° C. 85
% R. H. Equilibrium moisture content,%)