JPS6025784B2 - Recording paper that suppresses the amount of curling - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording paper that suppresses the amount of curl, and is particularly suitable for use in pressure fixing magnetic recording or electrostatic recording using diagonal fixing rolls. It is a recording paper that suppresses the amount of paper, and is 26M in size.

-10 [where W is the metric basis weight of the paper (dyne/ground), p is the density of the paper (ta'), and G is the dynamic rigidity (dyne/ground) measured by the free-damped vibration method.] It relates to recording paper that has certain characteristics.

In the pressure fixing method of magnetic recording or electrostatic recording, toner transferred from a recording medium to paper or developed from a latent image formed on paper is passed together with paper between a pair of pressurized diagonal rolls. This method uses nip pressure to forcibly force the toner particles into the paper and fix them. Compared to the method of melting and fixing the toner using heated rolls, this method has the advantages of requiring less energy for fixing, no waiting time, no risk of fire, and no maintenance of equipment. are doing. In this case, the reason for using diagonal rolls is as follows. In FIGS. 1 and 2, a pair of lower driving metal roll 1 and upper driven metal roll 2 have their axes obliquely intersecting at an angle of 4° or less, generally 1.5°,
Paper 3 is passed perpendicular to the center line x-x of the intersection angle (
In the drawings, the intersecting angle is enlarged for convenience of explanation).

Because the rolls are crossed, pressure is applied uniformly to the paper across its width, which has the same effect as when the rolls are crowned, so that the toner is evenly deposited on the paper. At the same time, the paper is stretched from the center of the roll toward the edges during passage through the roll nip, preventing the formation of brood. However, when such diagonal rolls are used, curls occur at the four corners of the mirror paper after passing through the rolls, and when the curls become large, the paper has the disadvantage that it impairs the transportability after recording and causes trouble in sorting work.

Therefore, there is an increasing demand for recording paper that suppresses curling. The inventors of the present invention have conducted various studies on the causes and mechanisms of curl occurrence, and have found that by increasing the density and dynamic elastic modulus of paper, the occurrence of curl can be suppressed to below a certain size. This invention was completed based on. When paper is passed through the diagonal rolls, after passing through the roll nip, the paper's traveling direction changes by an angle ◇ with respect to the direction in which it enters the nip.

The refraction angle at this time is given by the following formula: n =
[(1; In a container) 2-1] - (In the formula, J is the angle at which the paper is bent after passing through the nip, 1 is 1/2 of the length of the roll, J is the diameter of the roll, and 2 is the angle of the paper after passing through the nip. Oblique angle) When calculated by substituting the actual roll length, diameter, and oblique angle values into this equation, an almost constant proportional relationship is established between 0 and ], that is, when plotted as a graph, the relationship between the two is A linear relationship is established between them.

This means that as the value of 1 increases, that is, as you move from the center of intersection of the rolls to the ends of the rolls, it becomes larger.
This means that the edges of the paper experience the greatest refraction. Furthermore, since the rolls are arranged in opposite directions on both sides of the intersection, the paper is bent in opposite directions. Due to the bending of the paper, PsinJ is generated in the bending direction and in the opposite direction at the time of bending as a component of the lo-erodynamic force P on the roll.

This component force Psin necessarily acts as a new shear force other than the shear force generated inside the paper layer due to the transmission of driving force and frictional resistance in the case of a normal pair of parallel rolls. As mentioned above, in the case of oblique rolls, the refraction angle? is 0 at the intersection center of the rolls,
This shear force Psj increases as it approaches the curled end.
n0 is also 0 at the center and gradually increases toward the curled ends. This shear force causes stresses of equal magnitude but opposite directions to act on the front and back surfaces of the paper. The vectors of this state are shown in Figures 3 to 5 for the front and back sides of the paper, respectively, where abcd and ef indicate the four corners of the front and back sides of the paper, and pq and uv are the corners below the center of the nip, respectively. A line in the xx direction is shown. As is clear from the figure, when observed from the side abfe of the paper, tension is generated on the front surface in the ab direction and on the back surface in the fe direction.

As a result, paper edge a shrinks, while the opposite paper edge e
Stretching occurs and the paper curls upward. Similarly, elongation occurs at the paper edge b, shrinkage occurs at the paper twist f, and downward curl occurs at this corner. On the opposite side, upward curls occur at the total points c and g, and downward curls occur at the end points d and h, respectively. After all, at both ends of the paper diagonal lines ac and db, the directions are the same, and the total point a
and b, d and c are curled in opposite directions, respectively.
Propeller curl occurs. The above observation was made on the side surface of the paper, but the same principle applies to the internal cross section of the paper as well, due to the stress increasing in proportion to the distance from the center of the nip, i.e. the center of the paper, to both sides. Elongation and contraction occur respectively, and these effects appear in a concentrated form at the edge of the paper. If the paper is homogeneous, the absolute values of the curls that occur at the four corners of the paper will be the same even if the directions are different. However, in reality, the size of curl that actually occurs differs due to differences in properties in the longitudinal and lateral directions due to the orientation of the paper fibers, and differences between the front and back sides.
In particular, the difference in size between a pair of curls (upward or downward) in the same direction at both ends of the diagonal line is small. However, a pair of curls in opposite directions at both the left and right ends of the paper are significantly different in size. If the upward curl is large, the downward curl is small (0 in severe cases), and the same is true for curls in the opposite direction. As described above, in the pressure fixing method, it is inevitable that propeller curl will occur at the four corners of the recording paper due to the shear force applied to the front and back sides of the paper, which is inevitably generated due to the mechanism of the diagonal rolls used. It is clear that the size of corresponds to the amount of shear deformation. Therefore, in order to suppress curling, it is sufficient to use paper with small shear deformation. There is a method to directly measure paper shear deformation, but it is complicated.

For convenience, the present inventors determined the dynamic stiffness modulus (shear modulus) of paper using an indirect method using free damped vibration of a pseudopendulum. In this method, as shown in Fig. 6, a long strip of paper S is fixed between a pair of fixed jaws J and a jaw J2 fixed to a disc-shaped inertial body 1, and is attached to the center of the upper end of the inertial body 1. A constant load is applied to the piano wire W via a pulley, and the measurement is performed using a vibration system that is tension-coupled in the axial direction. The system is placed at a constant temperature, the inertia is deflected to give the upper end of the paper a deflection angle (generally about 100 degrees), and the inertia is then released to set it free, producing damped oscillations. The logarithmic damping rate and the corresponding vibration period are measured from the recorded logarithmic output waveform. Generally, the vibration system is held in a vacuum for measurement, but in this invention, the measurement was performed at normal pressure in order to simulate curling in a pressure fixing method. From the damping curve obtained at this time, the dynamic rigidity G of the paper piece is calculated by the following formula.

G = [Left (1-o-year) Wt-1 [(4 Junior High School 2nd year) I
Q-k.

[In the formula, L is the length between the jaws of the sample paper, w is the width of the sample paper, t is the thickness of the sample (arc), Q is the logarithmic attenuation rate, and L is the inertial body. where T is the vibration period corresponding to the saw (sec), ko is the friction constant of the piano wire (dyne/gong)] The first term on the right side of the equation indicates the shape factor of the sample, and the second term indicates the stiffness coefficient of the sample paper piece.

The present inventors have diligently investigated the relationship between the size of curl and the physical properties of paper from various angles, and as a result of their research, the relationship between the size of curl and W/pG (W, p, and G are as described above) has been determined. It was found that an extremely good proportional relationship holds true.

Figure 7 shows one set of larger curl heights (fences) in the diagonal direction when W/pG x 10-lo is on the machine axis and A-row 4-size paper is passed through the diagonal rolls on the vertical axis. This is a graph plotting the average value. As is clear from the figure, there is a difference between the two.
In order to establish a linear relationship and reduce curl, W/
All you have to do is reduce pG by 4. However, it is virtually impossible to eliminate curl completely, and in reality, one must be satisfied by suppressing the size of curl to below a certain limit that does not cause problems in handling after copying. Regarding this limit value, as a result of various studies on actual pressure fixing type recording equipment, we found that if the average height of the larger curl in the diagonal direction is 2 mm or less, paper transportability, sorting characteristics, etc. are satisfied. It was confirmed that there was no problem with subsequent processing and handling. The value of W/pG corresponding to the height of the curl is 26.1×10-
It is 10. Therefore, paper having the following conditions can suppress the occurrence of curling in a pressure fixing method using diagonal rolls: <26.IXI.

-10 [In the formula, W is the metric basis weight of the paper (Ta′〆), p is the density of the paper (Y/Y), and G is the dynamic rigidity (Dyne/K) measured by the free damping vibration method] W/ In order to reduce the absolute value of pG by 4, W
It is clear that it is sufficient to reduce by 4 and to increase p and G.

Generally, from the point of view of recording performance and transportability, a paper having a basis weight (W) of 60 to 70 mm is used as a recording paper, and paper lighter than this is not preferred. On the other hand, the paper density (p) can be determined by using known means such as further pressurizing the wet process after dehydration, strengthening machine calendering after drying, and strengthening off-machine supercalendering in the papermaking process. By using it in combination with silk, it can be easily increased in price. Furthermore, it has been experimentally confirmed that the dynamic rigidity (G) of paper increases as the density increases, so if the density of paper increases, the absolute value of W/pG decreases.
Therefore, the object of the present invention can be achieved by pressurizing green paper and/or dry paper to make it compact.

This invention will be explained in more detail in the following examples.
The methods for measuring dynamic rigidity and curl size in Examples are as follows.

Sample S was a strip piece having a width IQ cape whose length direction was the paper passing direction in a dynamic rigidity measuring and recording device.

Using the simulated free damping type viscoelasticity measuring device RD-10M model manufactured by Resuga Seisakusho Co., Ltd. shown in Fig. 6, the measurement length was accurately fixed between mounting chucks J and J2 with a measuring length of 8 mm.
Attach an inertial body with an inertia rate L = 2.80 x 1 mm. The piano wire W used had a friction coefficient ko = 1.80 x 1 pidine cm, a diameter of 0.2 and a length of 73. Vibration was started by a starter coil at normal pressure and room temperature. Logarithmic decay rate Q and period T (
seconds), and based on this, the dynamic rigidity G was calculated using the above formula. Measurement of Curl Two steel rolls with a diameter of 6 mm and a length of 210 ribs were stacked one on top of the other at an oblique angle of 1.5 degrees, and pressure was applied to the roll nip by springs at both ends of the upper roll.

Driven the lower roll. A 4-size paper in A row was passed between the nips of diagonal rolls with the longitudinal direction of the paper as the passing direction. Among the curls that occurred at the four corners, the distance from the horizontal plane to the edge of the paper was measured for one set that was larger in the diagonal direction, and the average value was taken as the curl height (skin). The density of paper is JISP8
113, it was calculated from the basis weight and thickness.

Example 1 A mixed pulp of LBKP60/Eucalyptus BKP40 produced in Hokkaido was beaten to 430% CSF, and the sizing agent and sulfuric acid were added to the pulp at 0.4% and 1%, respectively, and the talc was added at an ash content of 12% in the paper. A test machine was used to make high-quality paper with a basis weight of 65 ta', and the surface was sized using a 3% oxidized starch solution using a size press.

Machine calender line pressure 102035 and 40k9'
Density 0.650.700.80 and 0 respectively
．． I got 4 types of paper of 83 evening/earth. The dynamic stiffness and curl height were measured and the results are shown in Table 1.

From Table 1 above, when the basis weight of paper is almost constant, as density p and dynamic rigidity G increase, tW/pG) decreases, even if the value is 23.5×10-10 or less. For example, the curl height was less than the desired 20 ribs.

On the other hand, sample N with W/pG=33.0×10-10
o. 1, the curl height exceeded the allowable range of 2. When the ash content is 12%, sample No. 3 and NO. 4 was particularly suitable. Example 2 Domestic LBKP85/Imported NBKP15 beaten separately
0.5% rosin size in a mixed stock of total 0' CSF
, banyl sulfate 1% (both for pulp) and talc 90%
/Titanium dioxide 10 was added with an ash content of 24%, 709/that paper was made with a test machine, and treated with a machine calender at a linear pressure of 15k9/arc (sample No. 5).

Further, the pressure gauge of the supercalender was processed once (sample No. 6) and twice (sample No. 7) with a pressure gauge reading of 25k9, and five times (sample No. 8) with a pressure gauge of 40k9', each having a density of 0.700. Spot, 0. group and 1.03 evening/
Obtained four types of ground paper. The dynamic rigidity G and curl height were measured and the results are shown in Table 2.

Table 2 In this example as well, if the paper is pressurized to make it denser, W/p
G decreased and curl height decreased.

However, when increasing the ash content of paper, the dynamic stiffness G
It was found that the rate of increase in paper density became low, and the effect of reducing curl height due to improvement in paper density became relatively small. Example 3 0.1% of a synthetic sizing agent, 0.3% of a cationic starch, 0.01% of a retention agent (all based on pulp) and calcium carbonate were added to the stock of Example 1 at an ash content of 8%. death,
A neutral paper was produced using a test machine, aiming for a basis weight of 65 sheets/pillow.

Machine calendered with linear pressure 15k9' skin (sample No.
．． 9), and once again at gauge reading 25k9' (sample N
o. 10) and twice (sample No. 11) were supercalendered. The results are shown in Table 3. Table 3 From Table 3, in the case of neutral paper with internal addition of calcium carbonate, it was necessary to make the paper even more dense, and even at 0.81 m/kg, the desired curl height was exceeded.

Sample No. 11 is paper feeding, paper ejection performance, and toner transfer;
The fixing properties were good. Example 4 0.5% sizing agent, 1% aluminum sulfate (all relative to pulp), and talc were added to the paper stock of Example 1 with an ash content of 6%, and after papermaking with a test machine, linear pressure was applied with a machine calender. A base paper having a density of 0.74 mm/base was obtained by processing with 20k9/base.

10 parts of kaolin, 8 parts of PVA, and 8 parts of polymer conductive agent
A conductive treatment composition containing Ikarito and having a solid content concentration of 15% was applied to both sides of the base paper using a test coater at a rate of about 7 coats in total.

Conductive treated paper (sample No. 12) and super calender treatment of conductive treated paper at a linear pressure of 50 kg/skin (sample No. 13)
and 150k9/Ki (Sample No. 14), and three types of paper were coated with a dielectric layer using a test coater. The coating solution was made by adding 35% and 5% fine powder of calcium carbonate and silicic anhydride to methyl methacrylic acid ester styrene copolymer, respectively, and having a solid content of 20%. was coated. The result is the 4th
Shown in the table. Also in the electrostatic recording paper having the fourth surface conductive layer and dielectric layer,
When W/pG<26.1×10-10, the curl height is 2
& A relationship of being below him was established.

Paper compaction treatment is necessary not only for the purpose of smoothing the dielectric layer but also for suppressing curling due to high density. From the above examples, in order to achieve a curl height of 2 or less, the paper must be made denser to satisfy the condition of W/pG<26.1×10-10, and the density of the paper is generally about 0.75. Evening/Status Preferably higher than 0.8 ta', in some cases about 1
．． It turns out that it is sufficient to set the value to 0 or higher. this is,
For example, conventional recording paper has an ash content of 10% and a density of 0.6 to 0.
This is in contrast to the previous 8 evenings/mass.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing the state in which paper passes between pressure rolls, Fig. 2 is a sectional view taken along line 1-1 in Fig. 1, and Figs. 3 and 4 respectively show the surface of the paper and Figure 5 shows the state of the force applied to the back side. Figure 5 is an oblique view of the paper. Figure 6 is a front view of the device for measuring free damping vibration due to friction. Figure 7 shows the relationship between curl height and W/pG. It is a graph. 1...Lower driving metal roll, 2...Upper driven metal roll, 3...Paper, S...
Strips of paper, J. ...Fixed jaw, 1.
... Disc-shaped inertial body, ... Jaw, W ......
piano wire. Figure 2 Figure 2 Figure 4 Figure 5 Figure 5 Umbrella diagram

Claims (1)

[Claims] Recording paper for pressure fixing, characterized by having properties expressed by the linear equation: W/(ρG)<26.1×10
^-^1^0 [In the formula, W is the metric basis weight of the paper (g/m^
2) ρ is the paper density (g/cm^3) and G is the dynamic rigidity (dyne/cm^2) measured by the torsional free damping vibration method.]