JPH02217862A - Transfer paper - Google Patents

Abstract

PURPOSE:To drastically decrease curling after heat fixing by specifying the longitudinal wave propagation speed ratio of the ultrasonic pulse expressed by the propagation speed in a machine direction to the ultrasonic propagation speed in a cross direction to 1.00 to 1.25. CONSTITUTION:This paper is so formed that the longitudinal wave propagation speed ratio of the ultrasonic pulses of the paper expressed by the propagation speed in the machine direction to the ultrasonic propagation speed in the cross direction is within a 1.00 to 1.25 range as a result of the investigation made in terms of the fiber orientability of the paper. The transfer paper adjusted to this range of the longitudinal wave propagation speed ratio is drastically lowered in the dehumidification shrinkage in the cross direction and is greatly decreased in the curling value after the heat fixing of the ordinary transfer paper. The results of the figure indicate that there is no directivity in the fiber arrangement as the longitudinal wave propagation speed ratio of the ultrasonic pulses is nearer 1.0. The transfer paper which is decreased in the curling after the heat fixing is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a transfer paper with reduced curl after heat fixing in a copying machine, printer, etc. (hereinafter referred to as "post-heat fixing curl").

Conventional technology When copying machines, printers, etc. heat-fix toner images on paper, heat is applied from one side of the paper, which causes the paper to curl due to dehumidification from the heated surface, resulting in paper jams and poor paper output tray storage capacity. Problems such as defects and poor sorter accommodation may occur. Curl after heat fixation can be said to be an important characteristic that greatly affects paper running performance in copiers, printers, etc.

In the past, attempts to improve the curl after heat fixation were carried out by various companies, but because the mechanism by which heat fixation (unnatural curl) occurs was unknown, effective countermeasures could not be implemented, and papermaking conditions In reality, it is necessary to deal with the problem by changing some parts of the paper, pulp softness, and dryer differential pressure.In addition, regarding improvement of transfer paper, for example, Japanese Patent Publication No. 48-96801, Japanese Patent Publication No. 51-102107 @Publication, Special Publication 1984-9
6107, etc., disclose that inorganic fibers such as glass fibers and rock wool are mixed with wood pulp fibers, and JP-A-57-204057 discloses that a large amount of organic or inorganic filler (18% or more) is mixed with wood pulp fibers. ) is disclosed to be added.

Problems to be Solved by the Invention The present inventors have made the following findings as a result of intensive research into the mechanism of occurrence of curl after heat fixing. That is, when copying or printing line images (low image density) that are commonly used as originals, the toner layer has little effect on curling after heat fixing, so the cause of curling after heat fixation is It can be limited to the characteristic values of paper. Post-heat fixing curl occurs when heat is applied to one side of the paper, causing water to evaporate from the front and back layers of the paper, causing the paper to shrink. The difference in the amount of shrinkage between the front and back layers of the paper at this time appears as curl after heat fixing. This curl after heat fixation is expressed by the following equation.

K: Curl curvature (reciprocal of curvature radius H1/5) Hl: Change in moisture content due to heat fixation on the surface layer of paper (χ) H2: Change in moisture content due to heat fixation on the back layer of paper (%) β1: Change in moisture content due to heat fixation on the back layer of paper Dehumidification shrinkage rate of surface layer (%/moisture 1% change) β
2: Dehumidification shrinkage rate of paper backing layer (%/moisture 1χ change) t:
Thickness of the curl (m) In the above equation (1), the factors that affect the curl after heat fixing are: (1) dehumidification shrinkage rate, (2) change in moisture content, and (2) thickness.

By the way, the above-mentioned Japanese Patent Publication No. 48-96801 @ Publication, Special Publication No. 51-102107 @ Publication, Special Publication No. 54-96107
In the case disclosed in the publication, the dehumidification shrinkage rate and the change in moisture content are reduced, but when inorganic fibers are blended, the strength decreases significantly, causing problems in papermaking and quality. In addition, when synthetic fibers are blended, heat resistance decreases, and problems arise such as deformation (wrinkles, waving) and shrinkage during heat fixing. Furthermore, these inorganic fibers and synthetic I! Since fiber is more expensive than wood pulp A fiber, it becomes a factor of cost increase. Further, in the case disclosed in JP-A-57-204057@, a large amount of filler is blended, which causes problems such as a decrease in stiffness and an increase in the amount of paper dust generated.

On the other hand, a measure to reduce curl after heat fixing by increasing the thickness of the paper will increase the basis weight if the density is the same, resulting in an increase in cost. Moreover, if the thickness is increased with the same basis weight, a decrease in smoothness becomes a problem.

In any case, in the prior art, there has been no effective method for significantly reducing curl after heat fixing.

The present invention has been made in view of the above-mentioned problems in the conventional technology.

Therefore, it is an object of the present invention to provide a transfer paper that exhibits less curl after heat fixing.

Means for Solving the Problems The present inventors have improved post-heat fixing curl from the viewpoint of paper's wi fiber orientation, and as a result, the longitudinal wave propagation velocity ratio of ultrasonic pulses in paper has increased from i, oo to The inventors have found that curling after heat fixing can be greatly improved if the ratio is within the range of 1.25, and have completed the present invention.

The transfer paper of the present invention is characterized in that the longitudinal wave propagation velocity ratio of ultrasonic pulses is i,oo to 1.25, preferably i,oo to 1.20.

In this specification, "longitudinal wave propagation velocity ratio of ultrasonic pulse"
means the value shown by the following formula.

Longitudinal wave propagation velocity ratio of ultrasonic pulse Ultrasonic propagation velocity in machine direction () I [)) Cross direction (
Ultrasonic propagation velocity of CD) Note that "machine direction () It)) J" means the flow direction of the paper machine, and "cross direction (C [) month" means the direction perpendicular to the flow direction of the paper machine. means direction.

The longitudinal wave propagation velocity ratio of the ultrasonic pulse in the present invention is:
It can be determined by the measurement method shown in FIG. That is, a sample 22 is placed on a bubble-containing rubber plate 21 with a thickness of 10 rmIrI, and a transmitting transducer 23 and a receiving transducer 24 are brought into contact with each other at a distance of 150 M to generate longitudinal waves of ultrasonic pulses. It is sent out from the wave transmitting section 25, received by the wave receiving section 26,
The time it takes for the sample to pass from the transmitting transducer to the receiving transducer is measured and converted to propagation velocity. The propagation velocity in both HD and C[) directions is measured for each sample, and the propagation velocity ratio is determined. In addition, in the figure, 27 is an arithmetic element, 28
is a display element.

The longitudinal wave propagation velocity ratio of the ultrasonic pulse in the present invention is 1.0
As shown in Fig. 3, the transfer paper adjusted to a range of 0 to 1.25 has a significantly smaller dehumidification shrinkage rate in the cross direction, and the ratio of the longitudinal wave propagation velocity of the ultrasonic pulse is 1.
, 35 to 1.70) can be significantly reduced after heat fixing.

Note that FIG. 3 is a graph showing the relationship between the longitudinal wave propagation velocity ratio of ultrasonic pulses and the dehumidification shrinkage rate, where the solid line means the cross direction and the dotted line means the machine direction. The longitudinal wave propagation velocity ratio of the ultrasonic pulse indicates the degree of orientation of fibers arranged in the machine direction (HD) and the cross direction (CD). The closer the longitudinal wave propagation velocity ratio propagation velocity of the pulse is to 1.0, the less directionality there is in the fiber arrangement.

In addition, "dehumidification shrinkage rate" means % dimensional change/% moisture change at the time of reversible dimensional change after repeated hot water absorption and desorption treatment under humidity of 25 to 90% RH.

FIG. 4 is a graph for explaining the dehumidification shrinkage rate in the cross direction, and shows the relationship between the moisture content and the dimensional change rate in the hot water absorption and desorption process.

The hot water absorption and desorption process is performed sequentially from codes 1 to 12, and when an almost constant relationship is reached, the % dimensional change/% moisture change during reversible dimensional changes in codes 6 to 12) is calculated as the dehumidification shrinkage rate. shall be.

Since the transfer paper of the present invention has a longitudinal wave propagation velocity ratio of ultrasonic pulses adjusted to a range of 1.00 to 1.25, preferably 1.00 to 1.20, the fiber arrangement has directionality. The fiber arrangement is the same in both the machine direction and the cross direction. Therefore, the difference in reversible dimensional change rate in the length direction and diameter direction of the fiber (diameter direction dimensional change rate = 30X length direction dimensional change rate) does not appear as a difference in the dimensional change rate of the entire sheet. , the dehumidification shrinkage rate in the cross direction is significantly smaller and is comparable to the dehumidification shrinkage rate in the machine direction.

An effective way to reduce the longitudinal wave propagation velocity ratio of ultrasonic pulses is to appropriately adjust the JET/WIRE ratio (raw material ejection degree/paper machine wire speed ratio). It is also possible to adopt methods such as reducing the tension of the paper in the machine direction during drying and the tension of the paper in the machine direction during drying with a dryer.

In the transfer paper of the present invention, it is preferable that the fiber orientation angle with respect to the longitudinal wave propagation velocity of the ultrasonic pulse is within ±10 degrees for both the machine direction fiber orientation angle and the cross direction fiber orientation angle.

In this specification, "machine direction fiber orientation angle" refers to the deviation angle of the axis where the longitudinal wave propagation velocity of the ultrasonic pulse is maximum from the machine direction axis (the axis parallel to the flow direction of the paper machine). "Cross direction fiber orientation angle" means the deviation angle of the axis where the longitudinal wave propagation velocity of the ultrasonic pulse is minimum from the cross direction axis (the axis perpendicular to the flow direction of the paper machine). .

The deviation in the direction of movement of the clock hands is represented by 10, and the deviation in the opposite direction is represented by -.

In the present invention, if the fiber orientation angle is within ±10 degrees, the longitudinal wave propagation velocity ratio of the ultrasonic pulse is 1.00 to 1.2.
Diagonal curls (hereinafter referred to as torsion curls) after heat fixing, which tend to occur on transfer paper with comparatively non-oriented fibers adjusted to a range of 5, are reduced. In other words, the transfer paper in which the longitudinal wave propagation velocity ratio of the ultrasonic pulse is adjusted in the range of i,oo to 1.25 has less directionality in the fiber arrangement, and the transfer paper absorbs less moisture.
Due to partial limitations such as paper thickness and basis weight, as well as uneven pressure and speed in the axial direction between the heat fixing roll and the pressure roll, the direction of the maximum dimensional change after heat fixation may be in the cross direction (
CO) is likely to move in the diagonal axis direction. Therefore, the fiber orientation angle has a large influence on the curl axis after heat fixation, and twisting curls about diagonal lines are likely to occur. However, if both the machine direction fiber orientation angle and the cross direction fiber orientation angle are adjusted within ±10 degrees, the above-mentioned secondary problems can be prevented.

In order to adjust both the machine direction fiber orientation angle and the cross direction fiber orientation angle within ±10 degrees, it is necessary to eject the raw material as parallel to the wire traveling direction of the paper machine as possible. This can be achieved by adjusting the opening degree, position, etc. of the slicing lip that spouts the raw material onto the wire so that it is uniform in the direction of the wire 11.

Example The present invention will be explained below with reference to Examples.

Example 1 Bleached hardwood kraft pulp was prepared to have a freeness of 480CC, containing 10% by weight of light calcium carbonate and 1% by weight of cationized starch.
% by weight, add 0.5% by weight of alkyl ketene dimer,
Using an experimental oriented paper machine (manufactured by Kumagai Rikikan), the raw material ejection speed was varied at a wire speed of 700 m/min.
52.3g/butt, 64.0g/TIi, 81.4o/
A TIi transfer paper was made.

Transfer the transfer paper obtained by the above method into 2 pieces of B5 size.
0 sheets were cut at the seam and used as a test sample.

Five test samples were taken from the above test samples, and the longitudinal wave propagation velocity ratio of the ultrasonic pulse was measured 1a (SST'-210 (Sonic
Sheet Te5ter-210) Measured using Nomura Shoji (manufactured by !1).

The average values are shown in Table 1.

Furthermore, five sheets were taken from the above test samples, and the dehumidification shrinkage rate in the cross direction was measured using an HK type expansion/contraction tester (manufactured by Honshu Paper Corporation). The average values are shown in Table 1.

The remaining 10 test samples were pretreated in an appropriate chamber so that 5 sheets had a moisture content of 5% and 5 sheets had a moisture content of 1%. ), the curl after being heated and fixed on the wire side surface (curl curvature after heat fixing) was measured by passing the paper in the horizontal direction (feeding the paper so that the short side of the paper was perpendicular to the axis of the heat fixing roll). did.

The curl curvature after heat fixing was measured as shown in FIG. That is, the center part of one side perpendicular to the curl axis of test sample F151 is suspended with a suspension tool 52 having a width of about i cm, and the curl height (h) is measured. The measured force-curvature is converted to curl curvature by the following formula:

h=γ(1-CO5(7,75/27')) Curl curvature (K)='[/r γ: radius of curvature The measurement results of curl after heat fixing are shown in Table 1. The curl after heat fixation is expressed as the average value of the curl height (h) of five test samples converted into curl curvature.

FIG. 1 shows the relationship between the longitudinal wave propagation velocity ratio of the ultrasonic pulse and the curl curvature after heat fixing for the test sample.

As is clear from Table 1 and FIG. 1, when the longitudinal wave propagation velocity ratio of the ultrasonic pulse of the test sample becomes 1.25 or less, the curl curvature after heat fixing becomes significantly small.

Further, when the longitudinal wave propagation velocity ratio of the ultrasonic pulse becomes 1.20 or less, the curl curvature after heat fixing becomes almost zero. This tendency is almost the same regardless of the raw material valve blending ratio, sample basis weight, and sample moisture content.

Example 2 Hardwood bleached kraft pulp/softwood bleached kraft pulp 5
10% by weight of calcium carbonate, 1% by weight of cationized starch, and 0.5% by weight of alkyl ketene dimer were added to pulp (Freeness 480cc) having a blending ratio of 0.0150 (weight ratio), and an experimental oriented paper machine (Kumagai Riki 11), the raw material ejection speed was varied at a wire speed of 700 m/min, 52.3Q/bottom, 64.0Q/m, 81.4
An o/rd transfer paper was made.

Transfer the transfer paper obtained by the above method into 2 pieces of B5 size.
0 sheets were cut at the seam and used as a test sample.

Regarding the test sample, the longitudinal wave propagation velocity ratio of the ultrasonic pulse, the cross-direction dehumidification shrinkage rate, and the curl curvature after heat fixing were measured in the same manner as in Example 1. The results are shown in Table 2.

FIG. 6 shows the relationship between the longitudinal wave propagation velocity ratio of the ultrasonic pulse and the curl curvature after heat fixing for the above test sample.

As is clear from Table 2 and FIG. 6, when the longitudinal wave propagation velocity ratio of the ultrasonic pulse of the test sample is 1.25 or less, the curl curvature after heat fixing becomes significantly small.

Further, when the longitudinal wave propagation velocity ratio of the ultrasonic pulse becomes 1.20 or less, the curl curvature after heat fixing becomes almost zero. This tendency is almost the same regardless of the raw material valve blending ratio, sample basis weight, and sample moisture content.

Example 3 Under the same conditions as Example 1, 52.3q/m, 64.0
g/end, 81.4 g/TIi transfer paper was made, and as shown in Figure 7, 10 pieces of B5 size sheets were cut at a fixed angle (a) from the axis parallel to the flow direction of the paper machine. , was used as the test sample.

Five samples were taken from the above test samples, and the longitudinal wave propagation velocity ratio of the ultrasonic pulse was measured using a measuring device (SST-210 manufactured by Nomura Shoji ■). The average values are shown in Table 3.

The remaining five test samples were pretreated in a suitable chamber so that the moisture content was 5%, and then transferred to an electrostatic copying machine (
9500B, manufactured by Fuji Xerox ■), with horizontal paper passing (
The torsion curl after the paper was heated and fixed on the wire side surface was measured by passing the paper so that the width direction of the paper was perpendicular to the heat fixing roll axis.

The results are shown in Table 3. Note that the torsion curl value is the average value of the values of five test samples.

The method for measuring torsion curl is shown in Figure 8 (a) and (b).
) as shown. That is, one side of the test sample 81 was suspended with the suspension tool 82, and the height (h) of the torsion curl was measured, which was defined as the torsion curl value.

From Table 3 below, it can be seen that the relationship between the fiber orientation angle and the torsion curl value after heat fixing of the test samples tends to be constant regardless of the basis weight.

Basis weight 64. Taking a test sample of Og/m as a representative example, the relationship between the fiber orientation angle and the torsion curl value after heat fixing is shown in Figure 9.2 As is clear from Figure 9, the longitudinal wave propagation of the ultrasonic pulse of the test sample When the speed ratio is 1.25 or less, the fiber orientation angle is ±
When the temperature exceeds 10 degrees, the torsion curl value after heat fixing becomes significantly large.

Example 4 Under the same conditions as Example 2, 52.3 g/TIt, 84.
OfJ/Shi, 81, 4 g/rtl transfer paper was made, and 10 pieces of B5 size sheets were cut at a fixed angle (a) from the axis parallel to the flow direction of the paper machine as shown in Fig. 7. , was used as the test sample.

Regarding the above test sample, the fiber orientation angle and the torsion curl value after heat fixing were measured in the same manner as in Example 3. The results are shown in Table 4.

From Table 4, it can be seen that the relationship between the fiber orientation angle and the torsion curl value after thermal setting of the test samples has a constant tendency regardless of the basis weight.

Basis weight 64. Taking a test sample of Oq/m as a representative example, the relationship between the fiber orientation angle and the torsion curl value after heat fixing is shown in Figure 10.2 As is clear from Figure 10, the longitudinal wave propagation of the ultrasonic pulse of the test sample When the speed ratio is 1.25 or less and the 18M orientation angle is larger than ±10 degrees, the torsion curl value after heat fixing becomes significantly large.

Effects of the Invention Since the transfer paper of the present invention has a longitudinal wave propagation velocity ratio of ultrasonic pulses of i,oo to 1.25, curling after heat fixing is significantly smaller than that of conventional transfer paper.

In addition, in the transfer paper of the present invention, when the machine direction H fiber orientation angle and the cross direction fiber orientation angle with respect to the longitudinal wave propagation velocity of the ultrasonic pulse are both within ±10 degrees, the torsion curl after heat fixing is significant. This produces the effect of becoming smaller.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the longitudinal wave propagation velocity ratio of the ultrasonic pulse and the curl curvature after heat fixing in Example 1;
Figure 2 is a graph showing the relationship between the longitudinal wave propagation velocity ratio of ultrasonic pulses and the dehumidification shrinkage rate, Figure 3 is a block diagram of the method for measuring the longitudinal wave propagation velocity of ultrasonic pulses, and Figure 4 is a graph showing the relationship between the longitudinal wave propagation velocity ratio of ultrasonic pulses and the dehumidification shrinkage rate. A graph showing dimensional changes in the cloth method due to processing, Figure 5 is an explanatory diagram explaining the method for measuring curl after heat fixing, and Figure 6 is Example 2.
Graph showing the relationship between the longitudinal wave propagation velocity ratio of the ultrasonic pulse and the curl curvature after heat fixing, Figure 7 is an explanatory diagram explaining the method for preparing the test sample, and Figure 8 shows the method for measuring the torsion curl after fixing. In the explanatory diagrams (a> top view, (b) is a side view, FIG. 9 is a graph showing the relationship between the fiber orientation angle and the torsion curl value after heat fixing in Example 3, and FIG. 10 is the graph in Example 4. This is a graph showing the relationship between the fiber orientation angle and the torsion curl value after heat fixing.Movement element, 24... Receiving wave motion element, 25... Wave transmission section, 26
... Wave receiving section, 27... Arithmetic element, 28... Display element, 51... Test sample, 52... Suspension equipment, 81...
... Test sample, 82... Suspension equipment.

Claims (2)

[Claims] (1) The longitudinal wave propagation velocity ratio of the ultrasonic pulse is 1.00 to 1.
．． A transfer paper characterized by having a size of 25. (2) A claim characterized in that both the machine direction fiber orientation angle and the cross direction fiber orientation angle are within ±10 degrees (
1) Transfer paper as described.