Method of evaluating interleaf paper, glass plate package body, and method of producing glass plate package body

Abstract

To reliably prevent the formation of stains caused by an interleaf paper on the surface of a glass plate.SOLUTION: The method of evaluating an interleaf paper used for packaging glass plates to measure the concentration of acid-soluble calcium salts contained in the interleaf paper comprises an extraction step S3 in which the interleaf paper is immersed in an acidic extraction solution, and a measurement step S4 in which the concentration of calcium ions contained in the extraction solution is measured.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for evaluating interleaf paper, a glass plate package, and a method for manufacturing a glass plate package. [Background technology]

[0002] 2. Description of the Related Art As a form for transporting or storing various glass plates, including glass substrates or cover glasses for displays or solar cells, a glass plate package is known in which glass plates and interleaf papers are alternately laminated to form a laminate, and the laminate is packaged in a loaded state on a pallet.

[0003] Here, for example, an example of a glass plate package is disclosed in Patent Document 1. In the package disclosed in this document, rectangular glass plates and interleaf papers that constitute a laminate are stacked in the front-rear direction at an inclination, and the laminate is loaded on a pallet while being supported from the rear side.

[0004] In the case of a glass plate package comprising a laminate including such a glass plate and interleaf paper, a problem may arise during storage or transportation in which components contained in the interleaf paper adhere to the glass plate as foreign matter, causing the surface of the glass plate to become dirty.

[0005] In order to remove such dirt adhering to the surface of the glass plate, a cleaning process for the glass plate may be performed. For example, Patent Document 2 describes cleaning of the glass plate using a glass plate cleaning device including an alkaline cleaning area using an alkaline cleaning liquid and a pure water cleaning area using a neutral cleaning liquid (pure water).

[0006] Patent Document 3 also discloses that the concentrations of the elements aluminum, silicon, sulfur, calcium, magnesium, iron, chlorine, sodium, potassium, phosphorus, and nickel contained in the slip paper are measured by fluorescent X-ray analysis, and slip paper having a measured concentration of at least one of these elements that is equal to or lower than a certain level is selected. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2021-46239 [Patent Document 2] JP 2015-89546 A [Patent Document 3] JP 2020-176369 A Summary of the Invention [Problem to be solved by the invention]

[0008] Among the stains derived from the interleaf paper that adhere to the glass plate, calcium salts such as calcium chloride and calcium bicarbonate are water-soluble and can be removed from the glass plate by alkaline washing or pure water washing. However, calcium salts that are difficult to dissolve in alkaline to neutral washing solutions such as calcium carbonate, calcium sulfate, and calcium phosphate are difficult to remove from the glass plate even when alkaline washing or pure water washing is performed. In order to remove these calcium salts from the glass plate, it is necessary to wash the glass plate with an acidic washing solution, but the introduction of new washing equipment is not preferable because it increases the manufacturing cost of the glass plate and increases the environmental load.

[0009] On the other hand, Patent Document 3 does not focus on acid-soluble calcium contained in the interleaf paper. In other words, since the total amount of calcium is measured in the fluorescent X-ray analysis, it is not possible to distinguish between the concentration of acid-soluble calcium salts and the concentration of calcium salts that are poorly soluble in acid. Therefore, the conventional methods still have room for improvement in terms of suppressing stains on the surface of the glass plate caused by the interleaf paper.

[0010] An object of the present invention is to reliably suppress stains on the surface of a glass plate that are caused by interleaf paper. [Means for solving the problem]

[0011] (1) The present invention, which has been invented to solve the above-mentioned problems, is a method for evaluating interleaf paper used for packaging glass sheets, which measures the concentration of acid-soluble calcium salts contained in the interleaf paper, and is characterized by comprising an extraction step of immersing the interleaf paper in an acidic extraction solution, and a measurement step of measuring the concentration of calcium ions contained in the extraction solution.

[0012] In this way, in the extraction step, among the calcium salts contained in the interleaf paper, the acid-soluble calcium salts are extracted into the extraction liquid, and as a result, by measuring the concentration of calcium ions contained in the extraction liquid in the measurement step, the concentration of the acid-soluble calcium salts can be selectively measured.

[0013] (2) In the above configuration (1), the extraction liquid preferably contains at least one acid selected from the group consisting of nitric acid, sulfuric acid, and hydrochloric acid.

[0014] (3) In the above configuration (1) or (2), it is preferable that in the extraction step, the slip sheet is immersed in an extraction liquid having a temperature of 50° C. or more and 100° C. or less.

[0015] In this way, the time required for extracting the acid-soluble calcium salt contained in the slip paper can be shortened.

[0016] (4) In any one of the above configurations (1) to (3), in the extraction step, the time for which the slip sheet is immersed in the extraction liquid is preferably from 6 hours to 12 hours.

[0017] In this way, when the interleaf paper contains an acid-soluble calcium salt, an appropriate amount of the acid-soluble calcium salt is extracted into the extraction liquid in the extraction step, making it easier to measure the calcium ion concentration in the measurement step.

[0018] (5) In any one of the above configurations (1) to (4), a cutting step is provided for cutting the interleaf paper into a predetermined size, and in the extraction step, the cut interleaf paper is immersed in an extraction liquid and the area S [mm 2 The ratio S / V of the volume of the extract to the volume V [mL] is 10 mm 2 / mL or more 20mm 2 It is preferable that the concentration is 1 / mL or less.

[0019] In this way, the slip sheet to be measured can be made small, and the amount of extraction liquid can be reduced. In addition, by setting the ratio S / V within the above-mentioned range, when the slip sheet contains an acid-soluble calcium salt, an appropriate amount of the acid-soluble calcium salt is extracted into the extraction liquid in the extraction process, and the concentration of calcium ions can be easily measured in the measurement process.

[0020] (6) The present invention, which has been invented to solve the above-mentioned problems, is a method for manufacturing a glass plate package including a laminate including glass plates and interleaf paper, and a pallet on which the laminate is loaded, and is characterized in that it includes a step of evaluating the interleaf paper using a method for evaluating the interleaf paper having any one of the configurations (1) to (5) above.

[0021] In this way, the same effects as those of the corresponding configurations already described can be obtained.

[0022] (7) The present invention, which has been invented to solve the above problems, is a glass plate package comprising a laminate including glass plates and interleaf paper, and a pallet on which the laminate is loaded, and is characterized in that when the interleaf paper cut into a rectangular shape with each side of 50 mm is immersed in 200 mL of pure water at 60°C for 60 minutes, 0.5 mL of 6 mol / L hydrochloric acid is added, the extract is maintained at 60°C and concentrated to 40 mL, and the calcium ion concentration of the extract is measured, and the calcium ion concentration is found to be 0.35 mg / L or less.

[0023] In this way, it is possible to reliably prevent the surface of the glass plate from being stained with acid-soluble calcium salts contained in the slip paper. Effect of the Invention

[0024] According to the present invention, stains on the surface of a glass plate resulting from interleaf paper can be reliably suppressed. [Brief description of the drawings]

[0025] [Figure 1] FIG. 4 is a flow diagram of an evaluation method for an interleaf sheet according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view illustrating a preparation step included in the method for evaluating an interleaf sheet according to the embodiment of the present invention. [Diagram 3] 5A to 5C are cross-sectional views for explaining an adjustment step included in the slip sheet evaluation method according to the embodiment of the present invention. [Figure 4] 5A to 5C are cross-sectional views for explaining an adjustment step included in the slip sheet evaluation method according to the embodiment of the present invention. [Diagram 5] 5 is a cross-sectional view for explaining an extraction step included in the slip sheet evaluation method according to the embodiment of the present invention. FIG. [Figure 6] FIG. 2 is a side view showing an example of a glass plate package according to the embodiment of the present invention. [Figure 7] FIG. 2 is a side view showing an example of a glass plate package according to the embodiment of the present invention. [Figure 8] FIG. 7 is an enlarged view of region X in FIG. [Figure 9] FIG. 8 is an enlarged view of a Y region in FIG. [Figure 10] FIG. 2 is a flow diagram of a method for manufacturing a glass plate package according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0027] <Evaluation method of slip sheets> As shown in FIG. 1, the method for evaluating an interleaf sheet according to the embodiment of the present invention includes, in this order, a cutting step S1, an adjusting step S2, an extracting step S3, and a measuring step S4.

[0028] As shown in Fig. 2, in the cutting step S1, a large interleaf paper 1 is cut to a predetermined size to obtain a small interleaf paper 2. Hereinafter, the large interleaf paper 1 may be referred to as a product interleaf paper, and the small interleaf paper 2 may be referred to as a test interleaf paper. The product interleaf paper 1 is the same type and size as the interleaf paper included in the laminate of the glass plate package (see Figs. 6 and 7).

[0029] For example, a tool having a cutting blade, such as scissors or a cutter, is used to cut the product interleaf paper 1. Before cutting, it is preferable to wipe off any dirt on the cutting blade with ethanol or the like.

[0030] The area of ​​the test paper 2 is 700 to 12,000 mm 2 , 1000~10000mm 2 , 1500~7500mm 2 , 2000~5000mm 2 It is preferable that the shape of the test interleaf paper 2 is not particularly limited, and may be rectangular or circular. In this embodiment, the shape of the test interleaf paper 2 is illustrated as a square. The thickness of the test interleaf paper 2 is the same as the thickness of the product interleaf paper 1, and is, for example, 0.05 to 0.10 mm, but is not limited to this thickness.

[0031] 3, in the adjusting step S2, the test interleaf 2 is immersed in the pure water 4 stored in the container 3 and left to stand for a predetermined time. In this embodiment, the predetermined time may be 60 minutes or more and 120 minutes or less. In this embodiment, in order to prevent the pure water 4 from evaporating during the adjusting step S2, after the test interleaf 2 is immersed in the pure water 4, the upper opening of the container 3 is closed with a lid 5.

[0032] In addition, in the adjustment process S2, the pure water 4 in which the test interleaf paper 2 is soaked is left to stand for a predetermined period of time, and then, as shown in FIG. 4, an acidic solution 6 is added to the pure water 4 to generate an acidic extract 7 in which the test interleaf paper 2 is soaked.

[0033] In the extraction step S3, the test interleaf paper 2 is left to stand for a predetermined time while being immersed in the extraction liquid 7. The time for immersing the test interleaf paper 2 in the extraction liquid 7 is preferably 6 hours or more and 12 hours or less, 7 hours or more and 11 hours or less, or 8 hours or more and 10 hours or less.

[0034] The temperature of the extraction liquid 7 may be room temperature, but is preferably 50°C to 100°C, 52°C to 80°C, or 55°C to 65°C in order to shorten the extraction time. When the temperature of the extraction liquid 7 is set to a predetermined temperature higher than room temperature, it is preferable to heat the test interleaf paper 2 to a predetermined temperature before immersing it in the pure water 4 in the adjustment step S2. In the extraction step S3, the lid 5 is removed from the upper end opening of the container 3, and the extraction liquid 7 is concentrated by evaporating water. When concentrating the extraction liquid 7, it may be heated by a heater 8 or the like, as shown in FIG. 5. The concentration rate when concentrating the extraction liquid 7 (volume of the extraction liquid 7 before concentration / volume of the extraction liquid 7 after concentration) can be, for example, 2 times to 10 times.

[0035] Area S of test interleaf 2 [mm 2 The ratio S / V of the volume of the extract 7 to the volume V [mL] is 10 mm 2 / mL or more 20mm 2 / mL or less, 12 to 18, or 14 to 16.

[0036] In the measurement step S4, the concentration of calcium ions contained in the extract 7 concentrated in the extraction step S3 is measured. Here, since the calcium ions contained in the extract 7 are acid-soluble calcium salts, the concentration of the acid-soluble calcium salts can be selectively measured by measuring the concentration of calcium ions. As a measuring device for measuring the concentration of calcium ions, an ICP emission spectrometer, an atomic absorption spectrometer, or the like can be used.

[0037] For example, when the calcium ion concentration measured in the measurement step S4 is equal to or lower than a predetermined threshold value (e.g., 0.35 mg / L), the same type of interleaf as the product interleaf 1 from which the test interleaf 2 was cut out can be evaluated as a "passing interleaf" that can reliably suppress calcium stains on the surface of the glass plate. On the other hand, when the calcium ion concentration measured in the measurement step S4 is higher than a predetermined threshold value (e.g., 0.35 mg / L), the same type of interleaf as the product interleaf 1 from which the test interleaf 2 was cut out can be evaluated as a "failed interleaf" that cannot reliably suppress calcium stains on the surface of the glass plate. The threshold value for determining whether the product interleaf 1 is pass or fail can be appropriately changed depending on the extraction conditions, such as the size of the test interleaf 2, the volume (amount of liquid) of the extraction liquid 7, the immersion time of the test interleaf 2, and the temperature of the extraction liquid 7, and the measurement conditions, such as the concentration rate of the extraction liquid 7.

[0038] <Glass plate packaging> The glass sheet package according to the embodiment of the present invention includes a form for packaging glass sheets in a vertical position and a form for packaging glass sheets in a horizontal position.

[0039] In the case of packaging glass plates in a vertical position, as shown in Fig. 6, a glass plate package 11 includes a stack 14 including a plurality of glass plates 12 stacked in a vertical position and product interleaf paper 13, and a vertical placement pallet 15 on which the stack 14 is loaded. Here, the "vertical position" refers to a position in which the inclination angle with respect to the horizontal plane is preferably 45° to 80°, and more preferably 60° to 75°.

[0040] The pallet 15 includes a bottom support portion 15a that supports the bottom surface of the stack 14 including the vertically oriented glass plates 12, and a rear support portion 15b that supports the rear surface of the stack 14 including the vertically oriented glass plates 12.

[0041] Although not shown in the figures, for example, a presser plate is placed on the front surface of the laminate 14, and presser bars are placed on the presser plate so as to protrude from both sides of the width direction (for example, horizontal direction) of the laminate 14, and both ends of the presser bar are fastened by fastening members so as to be pulled toward the back support portion 15b, thereby fixing the laminate 14 to the pallet 15. The method of fixing the laminate 14 to the pallet 15 is not limited to this, and any fixing method such as a belt fastener can be used. A presser member that presses the side surface of the laminate 14 may be placed to restrict the movement of the laminate 14 in the width direction. The laminate 14 may be covered with a band-shaped or bag-shaped protective film to prevent foreign matter from adhering to it.

[0042] In the case of packaging glass plates in a horizontal position, as shown in Fig. 7, a glass plate package 21 includes a stack 24 including a plurality of glass plates 22 and product interleaf paper 23 stacked in a horizontal position, and a horizontal placement pallet 25 on which the stack 24 is loaded. Here, the "horizontal position" refers to a position in which the inclination angle with respect to the horizontal plane is preferably 0° to 30°, and more preferably 0° to 15°.

[0043] The pallet 25 includes a bottom support portion 25a that supports the bottom surface of the laminate 24 including the glass plates 22 in a horizontal position.

[0044] Although not shown in the figures, for example, a presser plate is placed on the front (top) surface of the laminate 24, and presser bars are placed on the presser plate so as to protrude from both sides of the laminate 24. The both ends of the presser bar are fastened by fastening members so as to be pulled toward the bottom support portion 25a, thereby fixing the laminate 24 to the pallet 25. The method of fixing the laminate 24 to the pallet 25 is not limited to this, and any fixing method such as a belt fastener can be used. In order to restrict the lateral shift of the laminate 24, a presser member that presses the side surface of the laminate 24 may be placed. For example, a plurality of presser members are placed at different locations so as to surround the four sides of the laminate 24. The laminate 24 may be covered with a belt-shaped or bag-shaped protective film to prevent adhesion of foreign matter.

[0045] As shown in Figures 8 and 9, in the glass plate packages 11, 21, it is preferable that the product interleaving paper 13, 23 protrudes outside the glass plates 12, 22. Specifically, in the glass plate package 11 in which the glass plate 12 is packaged in a vertical position, it is preferable that the product interleaving paper 13 protrudes outside the glass plate 12 at the remaining three sides of the glass plate 12 except for the bottom side. Also, in the glass plate package 21 in which the glass plate 22 is packaged in a horizontal position, it is preferable that the product interleaving paper 23 protrudes outside the glass plate 22 at the four sides of the glass plate 22. This allows the end faces of the glass plates 12, 22 to be protected by the product interleaving paper 13, 23.

[0046] The glass plates 12, 22 are rectangular, but are not limited to this shape. The thickness of each of the glass plates 12, 22 is, for example, 0.1 to 2.0 mm, preferably 0.2 to 1.0 mm, but is not limited to this thickness. The dimensions of the glass plates 12, 22 are, for example, 550 mm x 650 mm to 3200 mm x 3600 mm, but are not limited to this dimension.

[0047] The product interleaving papers 13, 23 are rectangular, but are not limited to this shape. The thickness of each product interleaving paper 13, 23 is, for example, 0.05 to 0.10 mm, but is not limited to this thickness. The size of the product interleaving papers 13, 23 is preferably larger than the size of the glass plates 12, 22.

[0048] The product interleaving papers 13, 23 are prepared by the above-mentioned interleaving paper evaluation method. A test interleaving paper cut from the product interleaving papers 13, 23 in a rectangular shape with each side of 50 mm is immersed in 200 mL of pure water at 60° C. for 60 minutes, and then 0.5 mL of 6 mol / L hydrochloric acid is added to generate an extract. The extract is concentrated to 40 mL while maintaining the temperature at 60° C., and the calcium ion concentration of the extract is measured. The calcium ion concentration is 0.35 mg / L or less. In other words, the above-mentioned approved interleaving papers are used as the product interleaving papers 13, 23. This can reliably prevent calcium stains from occurring on the surfaces of the glass plates 12, 22 during the transportation and storage of the glass plate packages 11, 21. When measuring the calcium ion concentration in the extract, for example, an ICP emission spectrometer (iCAP6000 manufactured by Thermo Fisher Scientific) can be used.

[0049] <Method of manufacturing glass sheet package> As shown in FIG. 10, the method for manufacturing a glass plate package according to the embodiment of the present invention includes a preparation step S5 and a loading step S6.

[0050] In the preparation step S5, a plurality of glass plates 12, 22 and a plurality of product interleaf papers 13, 23 are prepared.

[0051] The glass sheets 12, 22 are manufactured by a known forming method such as a downdraw method such as an overflow downdraw method or a slot downdraw method, or a float method. In this embodiment, the glass sheets 12, 22 are manufactured by the overflow downdraw method.

[0052] As the product interleaf papers 13, 23, product interleaf papers having a calcium ion concentration below a certain level when evaluated using the above-mentioned interleaf paper evaluation method are prepared. Specifically, for example, the test interleaf paper 2 is evaluated in advance using the above-mentioned interleaf paper evaluation method, and the product interleaf papers 13, 23 having an acid-soluble calcium ion concentration below a certain level are selected. In other words, the preparation step S5 includes an evaluation step of performing the above-mentioned interleaf paper evaluation method.

[0053] When the glass plates 12 are packed in a vertical position, a stack 14 including the glass plates 12 and the product interleaving paper 13 is loaded onto a vertical-placement pallet 15 in the loading step S6 (see FIG. 6). On the other hand, when the glass plates 22 are packed in a horizontal position, a stack 24 including the glass plates 22 and the product interleaving paper 23 is loaded onto a horizontal-placement pallet 25 in the loading step S6 (see FIG. 7). Note that in the loading step S6, the glass plates 12, 22 and the product interleaving papers 13, 23 are loaded alternately onto the pallets 15, 25.

[0054] The present invention is not limited to the configuration of the above embodiment, and is not limited to the above-mentioned effects. Various modifications of the present invention are possible without departing from the spirit and scope of the present invention.

[0055] In the above embodiment, the method for evaluating the interleaf paper includes the cutting step S1. However, depending on the size of the product interleaf paper 1, the cutting step S1 may be omitted and the product interleaf paper 1 may be used as the test interleaf paper 2 as is.

[0056] In the above embodiment, the extract 7 is generated by adding hydrochloric acid to the pure water 4 in the adjustment step S2. However, nitric acid or sulfuric acid may be added instead of hydrochloric acid, or a mixed acid of these may be used. EXAMPLES

[0057] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0058] First, two types of product interleaf papers were prepared. Hereinafter, one product interleaf paper is referred to as product interleaf paper A, and the other product interleaf paper is referred to as product interleaf paper B. Then, the above-mentioned interleaf paper evaluation method was carried out for each of these product interleaf papers A and B.

[0059] In detail, first, in the cutting step, the product interleaf A was cut to obtain a rectangular test interleaf a with each side being 50 mm. Similarly, the product interleaf B was cut to obtain a rectangular test interleaf b with each side being 50 mm. Next, in the adjustment step, the test interleaf a and b were immersed in 200 mL of pure water at 60° C. for 60 minutes, and then 0.5 mL of 6 mol / L hydrochloric acid was added to generate an extract. In the extraction step, the extract was concentrated until the extract became 40 mL while maintaining it at 60° C., and acid-soluble calcium salts were extracted from the test interleaf a and b. Then, in the measurement step, the ion concentrations (mg / L) of each of the components Ca, Mg, Ba, Si, and S contained in the concentrated extract were measured using an ICP emission spectrometer (iCAP6000 manufactured by Thermo Fisher Scientific), and the ion concentrations (mg / L) of each of the components Na and K were measured using an atomic absorption spectrometer (iCE3000 manufactured by Thermo Fisher Scientific). The results are shown in Table 1. Each component shown in Table 1 is dissolved in the acidic extract, and is therefore acid-soluble. In addition, Mg, Ba, Si, S, Na, and K, other than Ca, are components that can be removed relatively easily by alkaline washing or pure water washing.

[0060] [Table 1]

[0061] Then, glass plate packages (see Fig. 6) were made by packaging glass plates in a vertical position (inclination angle to the horizontal plane: 72°) using each of the above product interleaving papers A and B, and a transportation test was carried out for each glass plate package. The glass plate package using product interleaving paper A and the glass plate package using product interleaving paper B were under the same conditions except for the type of product interleaving paper used.

[0062] In detail, the glass plate is OA-11 manufactured by Nippon Electric Glass Co., Ltd., the size of the glass plate is 2200 mm (width) × 2500 mm (height), and the thickness of the glass plate is 0.4 mm. The number of laminated glass plates is 340. In the transportation test, the glass plate was transported 400 km on land. Then, the average number of particles P1 adhering to the surface of the glass plate before the transportation test (before packaging) and the average number of particles P2 adhering to the surface of the glass plate that was unpacked after the transportation test and subjected to alkaline cleaning and pure water cleaning were counted, and the increase rate of the average number of particles before and after the transportation test ((P2-P1) / P1×100) was calculated. The results are shown in Table 2. The number of particles was counted by an image inspection device to count particles with a size of 0.3 μm or more. The number of glass plates in the table was counted from the frontmost side (the opposite side to the back support part 15b).

[0063] [Table 2]

[0064] From Table 2, it can be seen that the number of particles on the surface of the glass plate in the glass plate package using the product interleaf paper A (Ca extraction amount: 0.46 mg / L) is greater than that in the glass plate package using the product interleaf paper B (Ca extraction amount: 0.22 mg / L) before and after the transportation test. In other words, it can be seen that by packaging the glass plate using an interleaf paper with a Ca extraction amount of 0.35 mg / L or less, it is possible to suppress the increase in the amount of particles attached during transportation. In particular, the effect of suppressing the increase in the amount of particles attached is remarkable in the glass plate on the side of the back support part 15b on which the weight of the glass plate is applied. From this, it can be seen that it is preferable to use an interleaf paper with a low content of acid-soluble calcium salt as the interleaf paper. And, by using the interleaf paper evaluation method according to the present invention, it is possible to selectively measure the concentration of acid-soluble calcium salt contained in the interleaf paper and select an interleaf paper with a low content of acid-soluble calcium salt, so that it is possible to reliably remove calcium stains on the surface of the glass plate originating from the interleaf paper. [Explanation of symbols]

[0065] 1. Interleave paper (product interleave paper) 2. Interleave (Test Interleave) 3 containers 4 Pure water 5 Lid 6. Acid Solution 7 Extract 8 Heater 11,21 Glass plate packaging 12,22 Glass plate 13,23 Product interleaving paper 14,24 Laminate 15,25 palette S1 Cutting process S2 adjustment process S3 extraction process S4 Measurement process S5 Preparation process S6 Loading process

Claims

1. A method for evaluating interleaf paper used for packaging glass sheets, comprising measuring a concentration of an acid-soluble calcium salt contained in the interleaf paper, the method comprising the steps of: a step of immersing the slip paper in an acidic extraction solution, and a step of measuring a concentration of calcium ions contained in the extraction solution.

2. The method for evaluating an interleaf paper according to claim 1 , wherein the extracting solution contains at least one acid selected from the group consisting of nitric acid, sulfuric acid, and hydrochloric acid.

3. The method for evaluating an interleaf paper according to claim 1 or 2, wherein in the extraction step, the interleaf paper is immersed in the extraction liquid having a temperature of 50° C. or higher and 100° C. or lower.

4. 3. The method for evaluating an interleaf paper according to claim 1, wherein in the extraction step, the interleaf paper is immersed in the extraction liquid for a period of time of 6 hours or more and 12 hours or less.

5. a cutting step of cutting the interleaf paper into a predetermined size, In the extraction step, the cut-out slip paper is immersed in the extraction liquid, and the area S [mm ２ The ratio S / V of the volume of the extract to the volume V [mL] of the extract is 10 mm ２ / mL or more 20mm ２ The method for evaluating slip sheets according to claim 1 or 2, wherein the viscosity of the slip sheet is 0.1 to 1.0 μm / mL or less.

6. A method for manufacturing a glass plate package comprising: a laminate including a glass plate and an interleaf paper; and a pallet on which the laminate is loaded, the method comprising the steps of: A method for manufacturing a glass plate package, comprising: a step of evaluating the interleaf paper by using the interleaf paper evaluation method according to claim 1 or 2.

7. A glass plate package including a laminate including glass plates and interleaf paper, and a pallet on which the laminate is loaded, The above-mentioned interleaf paper is cut into a rectangular shape with each side being 50 mm, and is immersed in 200 mL of pure water at 60°C for 60 minutes. Then, 0.5 mL of 6 mol / L hydrochloric acid is added, and the extract is concentrated to 40 mL while maintaining the temperature at 60°C. When the calcium ion concentration of the extract is measured, the calcium ion concentration is 0.35 mg / L or less.

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