Laminate paper for glass plate, glass plate laminate, glass plate packaging body, and method for producing laminate paper for glass plate

Abstract

To provide laminate paper for a glass plate suppressed in adhesion of foreign matters to the surface of the glass plate.SOLUTION: Laminate paper for a glass plate includes pulp as a raw material, has a pair of main faces facing each other, and includes calcium-containing foreign matters on at least one face of the main faces, the foreign matters having an equivalent circle diameter of 0.3-15 μm, where, in the calcium-container foreign matters, the number ratio of those that have an arithmetic average height Sa of more than 0.1 μm is 50% or more.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Glass plates used in flat panel displays (FPDs) such as liquid crystal displays have fine electronic wiring (hereinafter sometimes simply referred to as "wiring") formed on the glass plate surface. Since even slight scratches or stains on the glass plate surface can cause defects such as broken wiring, the glass plate surface must be highly clean.

[0003] In order to improve the efficiency of transportation, such glass plates are sometimes transported in a stacked state. In this case, the glass plates are stacked with glass plate interleaf paper (hereinafter, sometimes simply referred to as "interleaf paper") interposed between them. This prevents the glass plates from coming into contact with each other during transportation, thereby preventing scratches and the like from occurring on the surfaces of the glass plates.

[0004] On the other hand, foreign matter may adhere from the slip paper to the surface of the glass plate. This includes paper dust generated from the slip paper, organic matter contained in the slip paper, and foreign matter mixed in during the slip paper manufacturing process.

[0005] Most of the foreign matter adhering to the surface of a glass plate can be removed by cleaning the glass plate before forming wiring on the surface. However, some foreign matter remains on the surface of the glass plate even after cleaning, and this may cause wiring breakage or the like. Therefore, there is a demand for an interleaving paper for glass plates that further reduces the amount of foreign matter adhering to the surface of the glass plate.

[0006] In contrast, for example, Patent Document 1 describes a method in which the ratio of aluminum-based solid inorganic substances present on the surface is 20 particles / m 2The following interleaf papers for glass plates are disclosed. Patent Document 2 also discloses interleaf papers for glass plates in which the concentration of one or more of aluminum, silicon, sulfur, calcium, magnesium, iron, chlorine, sodium, potassium, phosphorus, and nickel determined by fluorescent X-ray analysis is below a certain level. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-191180 [Patent Document 2] Japanese Patent Application Publication No. 2017-210286 Summary of the Invention [Problem to be solved by the invention]

[0008] When manufacturing glass sheet interleaf paper, a pH adjuster may be added to adjust the pH of the papermaking system. One example of a pH adjuster is calcium carbonate. Calcium carbonate is a pH adjuster that adjusts the pH of the papermaking system from neutral to alkaline.

[0009] The calcium carbonate and Ca-containing foreign matter derived therefrom are dispersed inside and on the surface of the obtained glass plate interleaf paper, but have not been considered to be a particular problem up until now. This is because the Ca-containing foreign matter is very small and the composition of the glass plate contains Ca, making it difficult to distinguish whether the Ca on the surface of the glass plate is a Ca-containing foreign matter or the glass plate itself, and therefore the problem was not properly recognized. However, in recent years, as displays have become increasingly high-definition, wiring has become finer and the size of problematic foreign matter has become smaller.

[0010] The inventors have conducted research and found that foreign matter measuring tens to hundreds of nanometers or even several micrometers to tens of micrometers can cause disconnection of wiring formed on the surface of the glass plate when it adheres to the surface of the glass plate from the glass plate interleaf paper.Furthermore, it has been found that foreign matter can be transferred from the surface of the glass plate to the conveyor, stage, etc. in the display manufacturing line, contaminating the line and causing defects in the manufacturing equipment.

[0011] To identify such foreign matter, it is common to analyze the components using, for example, an energy dispersive X-ray analyzer. However, when analyzing without knowing the target components, the analysis is often performed at a high accelerating voltage to broaden the range of elements to be measured. However, by increasing the accelerating voltage, the electron beam penetrates deeper into the glass plate, rather than remaining on the foreign matter, and this can result in the detection of the matrix composition of the glass plate. Among these, calcium is a component contained in a certain amount in the composition of glass, so even if calcium is present on the surface of the glass plate, it is not recognized as a foreign matter component and is overlooked.

[0012] Therefore, in order to identify the foreign matter itself, the present inventors performed a component analysis at a low accelerating voltage and found that the problematic foreign matter was a Ca-containing foreign matter. Furthermore, it was found that when calcium carbonate is used as a pH adjuster, the calcium-containing impurities can include calcium carbonate itself and calcium salts derived from calcium carbonate.

[0013] Therefore, an object of the present invention is to provide an interleaving paper for glass plates that suppresses adhesion of foreign matter to the surfaces of glass plates, and a method for manufacturing the same. Another object of the present invention is to provide a glass plate laminate and a glass plate package that use the above interleaving paper for glass plates. [Means for solving the problem]

[0014] As a result of further investigations into the above-mentioned problems, the present inventors have found that calcium carbonate itself and calcium salts derived from calcium carbonate, i.e., Ca-containing contaminants, are difficult to remove by cleaning when they adhere to the surface of a glass plate if they are smaller than a certain size. Specifically, it has been found that Ca-containing contaminants with an equivalent circle diameter of 15 μm or less tend to be difficult to remove even when the surface of the glass plate is cleaned. Further investigation into such Ca-containing foreign particles with an equivalent circle diameter of 15 μm or less led to the discovery of a correlation between the arithmetic mean height (surface roughness) Sa of the Ca-containing foreign particles and the ease with which they adhere to the glass plate surface, leading to the completion of the present invention.

[0015] That is, the gist of the present invention is as follows. [1] A glass sheet interleaving paper containing pulp as a raw material and having a pair of opposing main surfaces, the glass plate interleaving paper contains Ca-containing foreign matter having a circle equivalent diameter of 0.3 to 15 μm on at least one of the main surfaces, The interleaving paper for glass plates, wherein the number ratio of the Ca-containing foreign matter having an arithmetic mean height Sa of more than 0.1 μm is 50% or more. [2] 0 pieces / 5mm of the above Ca-containing foreign matter 2 Super, 50 pieces / 5mm 2 The glass plate interleaving paper according to [1] above, which includes the following: [3] The glass plate interleaving paper according to [1] or [2], wherein the Ca-containing impurities include at least one selected from the group consisting of calcium carbonate, calcium bicarbonate, calcium hydroxide, calcium sulfate, and calcium oxalate. [4] A glass plate laminate in which a plurality of glass plates are laminated with interleaving paper therebetween, A glass plate laminate, wherein the interleaf paper is the interleaf paper for glass plates according to any one of [1] to [3] above. [5] The glass plate laminate according to [4], wherein the plurality of glass plates are glass plates for flat panel displays. [6] A glass plate package comprising the glass plate laminate according to [4] or [5] above, and a packaging container for accommodating the glass plate laminate.

[0016] [7] Preparing a pulp slurry from the raw material pulp; and producing glass plate interleaf paper from the pulp slurry, A pH adjuster is added during the preparation. The pH adjuster contains inorganic particles having an equivalent circle diameter of 0.2 to 30 μm, The method for producing an interleaf paper for glass plates, wherein the proportion of particles having an arithmetic mean height Sa of more than 0.1 μm in the inorganic particles is 50% or more. [8] The method for producing interleaf paper for glass plates according to [7] above, wherein the inorganic particles are calcium carbonate. [9] The surface of the obtained glass plate interleaving paper has 0 particles / 5 mm of foreign matter derived from the inorganic particles. 2 Super, 50 pieces / 5mm 2 The method for producing glass plate interleaf paper according to [7] or [8] below. [Effects of the Invention]

[0017] According to the present invention, a glass plate interleaving paper is obtained that suppresses adhesion of foreign matter to the glass plate surfaces. As a result, glass plates transported as glass plate laminates or glass plate packages using the glass plate interleaving paper can be prevented from having fine wiring breaks caused by minute foreign matter, even when fine wiring is applied for use in high-definition displays. Furthermore, defects in manufacturing equipment due to transfer of foreign matter from the glass plate surfaces to conveyors and the like in display manufacturing lines can be prevented. DETAILED DESCRIPTION OF THE INVENTION

[0018] Preferred embodiments of the present invention will be described below. The embodiments described below are merely examples, and the present invention should not be construed as being limited to these embodiments. In this specification, the use of "to" to indicate a range of values means that the values before and after it are included as the lower and upper limits.

[0019] <Glass plate interleaf> The glass plate interleaf paper according to this embodiment contains pulp as a raw material and has a pair of opposing main surfaces. The glass plate interleaving paper contains Ca-containing impurities having a circle-equivalent diameter of 0.3 to 15 μm on at least one of the pair of main surfaces. The percentage of the number of the Ca-containing impurities having an arithmetic mean height Sa of more than 0.1 μm is 50% or more. The glass plate interleaving paper also contains 0 Ca-containing impurities having a circle-equivalent diameter of 0.3 to 15 μm per 5 mm. 2 Super, 50 pieces / 5mm 2 It is preferable to include the following:

[0020] <Ca-containing foreign matter> In this embodiment, Ca-containing impurities refer to impurities containing Ca (calcium) in their composition. Examples of Ca-containing impurities include those derived from calcium carbonate used as a pH adjuster when producing glass plate interleaf paper, those derived from calcium carbonate used as a filler or pigment when producing other paper, rather than when used directly in producing glass plate interleaf paper, those precipitated when calcium hypochlorite is used in the bleaching process of raw pulp production, and scale precipitated from calcium contained in minerals contained in water used in the process, such as spring water or river water. Among these, calcium carbonate used as a pH adjuster when producing glass plate interleaf paper is considered to be the main cause.

[0021] Specific examples of calcium-containing foreign matter include calcium carbonate itself and calcium salts derived from the calcium component, such as calcium bicarbonate, calcium hydroxide, calcium sulfate, calcium oxalate, calcium aluminosilicate, calcium aluminate, calcium silicate, calcium oxide, calcium silicate, and calcium phosphate. Preferably, the Ca-containing impurities include at least one selected from the group consisting of calcium carbonate, calcium hydrogen carbonate, calcium hydroxide, calcium sulfate, and calcium oxalate.

[0022] When calcium carbonate is used as a pH adjuster, it is nearly impossible to completely eliminate the Ca-containing impurities contained in the glass sheet interleaf paper. In this embodiment, attention is focused on Ca-containing foreign matter contained in glass plate interleaf paper having an equivalent circle diameter of 0.3 to 15 μm. This is because the inventors' investigations have revealed that Ca-containing foreign matter having an equivalent circle diameter of more than 15 μm can be easily removed by washing even if it adheres to the surface of the glass plate, and therefore is unlikely to cause disconnection of wiring or defects in the manufacturing equipment.

[0023] The above idea was arrived at as a result of specific investigations by the present inventors. That is, the present inventors scrubbed calcium carbonate having an equivalent circle diameter of 0.1 to 40 μm against a glass plate, then subjected it to alkaline scrubbing, and measured the amount of calcium carbonate that remained attached to the surface of the glass plate after scrubbing. The alkaline scrubbing was performed by varying the cleaning strength by changing the brush height. As a result, it was found that calcium carbonate having an equivalent circle diameter of 15 μm or less is difficult to remove, as described above.

[0024] The reason for this is unclear, but it is thought that, compared with forces that cause separation of the glass plate and the foreign matter, such as the impact force during cleaning, the attractive forces acting between molecules, such as electrostatic forces and van der Waals forces, become relatively stronger as the particle size decreases. Therefore, the smaller the particle, the less effective cleaning becomes in removing it. Furthermore, in the case of Ca-containing foreign matters, the equivalent circle diameter of which is 15 μm or less is difficult to remove from the glass plate surface by cleaning. From this perspective, it is thought that it is necessary to control Ca-containing foreign matters with an equivalent circle diameter of 15 μm or less.

[0025] On the other hand, foreign matter with a circle equivalent diameter of less than 0.3 μm is unlikely to cause a break due to its small size, so the glass plate interleaving paper of this embodiment targets Ca-containing foreign matter with a circle equivalent diameter of 0.3 to 15 μm.

[0026] In this specification, the "equivalent circle diameter" of Ca-containing foreign matter refers to the diameter of a circle having an area equal to the area when viewed from a direction perpendicular to the main surface of the glass plate interleaf paper. Specifically, the area of the particles is determined by image processing of an optical microscope image of the glass plate interleaf paper, and the value converted into the diameter of a circle having an area equal to that area is defined as the equivalent circle diameter. More specifically, the method used in the examples described below can be used.

[0027] In the glass plate interleaf paper according to this embodiment, of the Ca-containing foreign matters having a circle equivalent diameter of 0.3 to 15 μm on at least one of the main surfaces, the percentage of those having an arithmetic mean height Sa of more than 0.1 μm is 50% or more.

[0028] The inventors discovered that even when the number density of Ca-containing foreign particles having a circle-equivalent diameter of 0.3 to 15 μm is the same, the ease with which the Ca-containing foreign particles adhere to the glass plate surface varies depending on the surface roughness of the Ca-containing foreign particles. Specifically, calcium carbonate particles were pressed onto the surface of a glass plate, and then the surface was washed with running water, dried, and then observed. As a result, it was found that the calcium carbonate particles that remained on the surface of the glass plate mainly had an arithmetic mean height Sa of 0.1 μm or less. From the above investigation, it was found that, among the surface roughness parameters, the arithmetic mean height Sa is particularly correlated with the ease of adhesion to the glass plate surface, and that the smaller the arithmetic mean height Sa, the easier it is for particles to adhere to the glass plate surface. It was also found that an arithmetic mean height Sa of 0.1 μm is the threshold for this. Regarding the above, we believe that the smaller the arithmetic mean height Sa of Ca-containing inclusions, the greater the contact area with the glass plate surface, resulting in a stronger interaction with the glass plate, and therefore a stronger adhesive force. We actually investigated the correlation between the arithmetic mean height Sa of Ca-containing inclusions with a circle equivalent diameter of 0.3 to 15 μm and the amount of calcium adhering to the glass plate surface, and found that when the arithmetic mean height Sa of Ca-containing inclusions exceeds 0.1 μm, the amount of adhering to the glass plate surface decreases sharply.

[0029] Here, the arithmetic mean height Sa of Ca-containing foreign matter having a circle equivalent diameter of 0.3 to 15 μm means the arithmetic mean height Sa measured from the side opposite to the side adhering to the glass plate interleaf paper in the direction perpendicular to the main surface of the glass plate interleaf paper.

[0030] The arithmetic mean height Sa of Ca-containing contaminants transferred from the glass sheet interleaf and attached to the surface of the glass sheet may be measured. In this case, it is desirable to specify the arithmetic mean height Sa of the Ca-containing contaminants on the side attached to the glass sheet in the direction perpendicular to the main surface of the glass sheet. However, since Ca-containing contaminants are actually attached to the surface of the glass sheet, it is difficult to measure the arithmetic mean height Sa of the Ca-containing contaminants on the side attached to the glass sheet. Therefore, it is possible to assume that the arithmetic mean height Sa of the Ca-containing contaminants on the side attached to the glass sheet and the opposite side are approximately the same, and to regard the arithmetic mean height Sa of the Ca-containing contaminants on the side opposite to the side attached to the glass sheet as the arithmetic mean height Sa of the Ca-containing contaminants.

[0031] The arithmetic mean height Sa of a Ca-containing foreign particle means the mean absolute value of the difference in height of each point from the mean plane of the foreign particle surface, measured non-contact. Specifically, the position and area of the Ca-containing foreign matter can be measured using a laser microscope, the equivalent circle diameter can be calculated from the area, and then the arithmetic mean height Sa can be measured in accordance with ISO 25178. More specifically, the method used in the examples described below can be employed.

[0032] That is, among the Ca-containing foreign matters having a circle-equivalent diameter of 0.3 to 15 μm in the glass plate interleaf paper according to this embodiment, the number ratio of those having an arithmetic mean height Sa of more than 0.1 μm is 50% or more, preferably 50 to 100%, more preferably 60 to 100%, and even more preferably 70 to 100%. Here, from the viewpoint of suppressing adhesion to the glass plate surface, the number ratio is 50% or more, preferably 60% or more, and more preferably 70% or more. The higher the number ratio, the better, and it may be 100%, but it may also be 95% or less. The arithmetic mean height Sa of Ca-containing impurities can be adjusted by using calcium carbonate with a large arithmetic mean height Sa as the calcium carbonate used in the pH adjuster. Furthermore, the arithmetic mean height Sa of Ca-containing impurities that are reprecipitated after dissolving and becoming ions tends to be small. Therefore, the aforementioned method of reducing the amount of Ca can also be used to relatively reduce the number of Ca-containing impurities with an arithmetic mean height Sa of 0.1 μm or less.

[0033] The upper limit of the arithmetic mean height Sa of Ca-containing impurities having a circle-equivalent diameter of 0.3 to 15 μm is not particularly limited, and examples include 0.3 μm or less and 0.5 μm or less.

[0034] The glass plate interleaving paper according to this embodiment has a thickness of 0.01 mm / 5 mm and a diameter of 0.3 to 15 μm. 2 Super, 50 pieces / 5mm 2 It is preferable to include less than 0 pieces / 5mm 2 Super, 30 pieces / 5mm 2 It is particularly preferred to include the following: Here, the number of Ca-containing foreign particles with a circular equivalent diameter of 0.3 to 15 μm is 0 / 5 mm. 2 The term "excessively containing" refers to, for example, the use of calcium carbonate as a pH adjuster in the production of glass sheet interleaf paper. When calcium carbonate is used as a pH adjuster, it is nearly impossible to completely eliminate the Ca-containing impurities contained in the glass sheet interleaf paper.

[0035] When calcium carbonate is used as a pH adjuster, the pH of the glass plate interleaf paper extracted with cold water is usually neutral to alkaline, and the cold water extract pH is, for example, 6.5 to 11.0. In this specification, the cold water extraction pH of the glass plate interleaf paper is a value measured in accordance with JIS P 8133-1 (2013) as the pH value of an electrolyte solution extracted from the glass plate interleaf paper with cold water.

[0036] The number density of Ca-containing foreign particles having a circle equivalent diameter of 0.3 to 15 μm contained on at least one of the main surfaces of the glass plate interleaf paper according to this embodiment is 50 particles / 5 mm 2Preferably less than 30 pieces / 5mm 2 Less than 25 pieces / 5mm is more preferable. 2 The following is even more preferable, and the fewer the better. The number density of the Ca-containing impurities can be adjusted, for example, by adjusting the amount of calcium carbonate added as a pH adjuster, and the amount of Ca can be reduced by increasing the amount of alkaline components other than calcium carbonate. The amount of calcium carbonate added is preferably 0.1 to 5.0 mass%. To further reduce the amount of Ca, measures include not using calcium carbonate as a filler or pigment other than a pH adjuster in the process of producing glass sheet interleaf paper, reducing calcium ions by passing the water used through a filter such as an ion exchange resin, and cleaning the equipment, papermaking tools, and piping used in the process with an acidic detergent to remove calcium scale.

[0037] In this specification, the number density (number / 5 mm) of Ca-containing foreign particles having a circle equivalent diameter of 0.3 to 15 μm in the glass plate interleaving paper is 2 ) can be identified using a scanning electron microscope (SEM) and an energy dispersive X-ray analyzer attached to the SEM. More specifically, the method used in the examples described below can be employed.

[0038] In this embodiment, the shape of the Ca-containing foreign particles having a circle-equivalent diameter of 0.3 to 15 μm is not particularly limited as long as 50% or more of them have an arithmetic mean height Sa of more than 0.1 μm, and examples thereof include flat and spherical shapes.

[0039] The glass plate interleaving paper according to this embodiment may contain, on its surface, Ca-containing foreign matter other than Ca-containing foreign matter having an equivalent circle diameter of 0.3 to 15 μm, i.e., Ca-containing foreign matter having an equivalent circle diameter of less than 0.3 μm or Ca-containing foreign matter having an equivalent circle diameter of more than 15 μm.

[0040] Even if Ca-containing particles with a circle equivalent diameter of more than 15 μm adhere to the surface of a glass plate, they can be easily removed by cleaning the surface of the glass plate. 2 ) and the arithmetic mean height Sa are not particularly limited.

[0041] Like Ca-containing foreign particles with an equivalent circle diameter of 0.3 to 15 μm, Ca-containing foreign particles with an equivalent circle diameter of less than 0.3 μm are difficult to remove when they adhere to the surface of a glass plate, but as mentioned above, they are less likely to cause wire breakage. On the other hand, from the viewpoint that it cannot be said that they have no effect on wire breakage or other problems, the number density (pieces / 5 mm) of Ca-containing foreign particles with an equivalent circle diameter of less than 0.3 μm is 2 ) is preferably small, for example, 100 pieces / 5 mm 2 Preferably less than 50 pieces / 5mm 2 The lower limit is not particularly limited, but is usually 0 pieces / 5 mm 2 Ultra-low density, 0.01 pieces / 5mm 2 Super is fine too.

[0042] Furthermore, similar to Ca-containing foreign particles having an equivalent circle diameter of 0.3 to 15 μm, it is preferable that the number proportion of Ca-containing foreign particles having an arithmetic mean height Sa of 0.1 μm or more is high. Of the Ca-containing foreign particles having an equivalent circle diameter of 0.3 μm, the number proportion of Ca-containing foreign particles having an arithmetic mean height Sa of more than 0.1 μm is preferably 50 to 100%, more preferably 60 to 98%, and even more preferably 70 to 95%. Here, from the viewpoint of suppressing adhesion to the glass plate surface, this number proportion is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. The higher the number proportion, the better, and although 100% is acceptable, it is usually 98% or less, and may be 95% or less.

[0043] <Other inorganic foreign bodies> The glass plate interleaving paper according to this embodiment may contain inorganic foreign matter other than the Ca-containing foreign matter on its surface. Other inorganic foreign matter includes Fe-containing foreign matter containing Fe (iron) in its composition, Cr-containing foreign matter containing Cr (chromium) in its composition, Ni-containing foreign matter containing Ni (nickel) in its composition, Na-containing foreign matter containing Na (sodium) in its composition, K-containing foreign matter containing K (potassium) in its composition, and Al-containing foreign matter containing Al (aluminum) in its composition.

[0044] Among the above-mentioned other inorganic foreign substances, for example, Fe-containing foreign substances, Cr-containing foreign substances, and Ni-containing foreign substances are a group of inorganic foreign substances (hereinafter sometimes referred to as "Group A inorganic foreign substances.") that originate from stainless steel materials, etc., used in papermaking equipment and may be contained on the surface of glass sheet interleaf paper. If these inorganic foreign substances Group A adhere to the surface of the glass sheet, they can cause wiring breaks and manufacturing equipment defects, as can Ca-containing foreign substances, and can also cause scratches on the surface of the glass sheet.

[0045] Therefore, the number density of at least one type of inorganic foreign matter A in the glass plate interleaf paper, which has a circle equivalent diameter of 0.3 to 15 μm and is contained on at least one surface of the glass plate interleaf paper, is 10 particles / 5 mm 2 Less than 1 piece / 5mm is preferable. 2 The following is more preferable, and the fewer the better. It is more preferable that at least two of the inorganic foreign matter group A are within the above range, and it is even more preferable that all three are within the above range.

[0046] Furthermore, it was found that, similarly to the Ca-containing foreign matter, the inorganic foreign matter group A can be prevented from adhering to the glass plate surface if the arithmetic mean height Sa is a certain level or more. That is, the arithmetic mean height Sa of the inorganic foreign matter group A having a circle equivalent diameter of 0.3 to 15 μm is, for example, preferably 0.1 μm or more, more preferably 0.3 μm or more. The upper limit is not particularly limited, but is, for example, 0.5 μm or less.

[0047] Of inorganic foreign matter group A having a circle-equivalent diameter of 0.3 to 15 μm, the proportion of particles having an arithmetic mean height Sa of 0.1 μm or more is preferably 50% or more, more preferably 60% or more, and may be 100% or less, but may also be 95% or less.

[0048] Among the above-mentioned other inorganic foreign substances, for example, sodium-containing foreign substances and potassium-containing foreign substances are a group of inorganic foreign substances (hereinafter sometimes referred to as "group B inorganic foreign substances") that can be contained on the surface of glass plate interleaf paper and are derived from chemicals such as sodium hydroxide and sodium sulfide used in pulp bleaching, or sodium hydroxide, sodium carbonate, potassium hydroxide, and potassium carbonate used as pH adjusters. When a pH adjuster such as sodium hydroxide or potassium hydroxide is used, the cold water extraction pH of the obtained glass plate interleaf paper becomes, for example, about 6.5 to 11.0.

[0049] These inorganic foreign substances Group B have a higher solubility in water than Ca-containing foreign substances. Therefore, even if inorganic foreign substances Group B are contained on the surface of the glass plate interleaf paper and adhere to the surface of the glass plate, they are easily removed by washing or the like, and are not likely to aggregate, so they are unlikely to cause wiring breakage or the like. Therefore, there are no particular limitations on the degree of adhesion of inorganic foreign matter group B to the surface of the glass plate interleaf paper, the size of the equivalent circle diameter, the arithmetic mean height Sa, etc. However, this does not in any way exclude the inorganic foreign matter group B having an equivalent circle diameter of 0.3 to 15 μm from having a large arithmetic mean height Sa, for example, 0.1 μm or more, like Ca-containing foreign matter.

[0050] The amount of Ca-containing impurities in the surface of the glass plate interleaf paper can be reduced by using sodium hydroxide or potassium hydroxide alone or in combination as a pH adjuster for the inorganic foreign matter Group B. Specifically, the amount of Ca in the surface of the glass plate interleaf paper can be reduced to, for example, about 0.01 ppm by mass or more and 100 ppm by mass or less.

[0051] Among the above-mentioned other inorganic foreign matters, for example, aluminum-containing foreign matters are inorganic foreign matters that originate from pH adjusters such as aluminum sulfate and can be contained on the surface of glass plate interleaf paper. If aluminum-containing foreign matters adhere to the surface of the glass plate, they can cause wiring breaks and manufacturing equipment failures, just like calcium-containing foreign matters.

[0052] Therefore, the number density of aluminum-containing foreign particles having a circle equivalent diameter of 0.3 to 15 μm contained on at least one of the main surfaces of the glass plate interleaf paper is 50 particles / 5 mm 2Preferably less than 30 pieces / 5mm 2 The less the better.

[0053] It has also been found that, similar to the case of Ca-containing contaminants, adhesion to the glass sheet surface can be suppressed when the arithmetic mean height Sa of the Al-containing contaminants is at least a certain level. That is, the arithmetic mean height Sa of Al-containing contaminants having a circle-equivalent diameter of 0.3 to 15 μm is, for example, preferably at least 0.1 μm, more preferably at least 0.3 μm. The upper limit is not particularly limited, but is, for example, at most 0.5 μm.

[0054] Of the Al-containing foreign particles having a circle-equivalent diameter of 0.3 to 15 μm, the number ratio of those having an arithmetic mean height Sa of 0.1 μm or more is preferably 50% or more, more preferably 60% or more, and may be 100% or less, but may also be 95% or less.

[0055] The equivalent circle diameter of Al-containing contaminants can be adjusted to reduce the size of the precipitated contaminants by, for example, making the papermaking pH more acidic to make precipitation less likely in the first place, by cleaning the process and papermaking tools with acid washing to prevent the growth of coarse particles, or by cleaning with an acid-containing detergent downstream of the process for producing glass plate interleaf paper. Similarly, the arithmetic mean height Sa can be adjusted by cleaning the process, tools, and interleaf paper itself with acid washing to roughen their surfaces.

[0056] <Other ingredients> The glass plate interleaving paper according to this embodiment may contain metal elements and semi-metal elements in addition to the elements constituting the Ca-containing contaminants and other inorganic contaminants, such as boron (B), magnesium (Mg), silicon (Si), titanium (Ti), copper (Cu), zinc (Zn), and barium (Ba).

[0057] <Raw materials> The glass plate interleaf paper according to this embodiment contains pulp as a raw material. The type of raw material pulp is not particularly limited, but one having the properties required for glass plate interleaf paper is preferably used.

[0058] Examples of raw pulp include chemical pulps such as kraft pulp (KP), sulfite pulp (SP), and soda pulp (AP); mechanical pulps such as groundwood pulp (GP), thermomechanical pulp (TMP), and chemithermomechanical pulp (CTMP); semi-chemical pulps such as chemiground pulp (CGP) and semi-chemical pulp (SCP) as intermediate mechanical / chemical pulps; non-wood fiber pulps made from materials such as kenaf, mitsumata, kozo, gampi, and hemp; synthetic pulp, synthetic fiber, and recycled paper pulp (DIP).

[0059] Pulp can be bleached or unbleached, such as bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), unbleached hardwood kraft pulp (LUKP), or unbleached softwood kraft pulp (NUKP), and may contain carbon nanofibers (CNF).

[0060] Among these, since glass plate interleaf paper requires high cleanliness, bleached kraft pulp (LBKP, NBKP) is particularly preferred as the raw pulp, which has been bleached to reduce the amount of resinous components derived from lignin and the like by washing them. Pulp from which foreign matter has been removed using a cyclone cleaner or the like is also preferred.

[0061] These raw pulps may be any of recycled paper pulp, virgin pulp, and a mixture of recycled paper pulp and virgin pulp. Here, virgin pulp refers to pulp made from wood, not recycled paper pulp. In order to particularly suppress contamination of glass plates by particles and resin components, it is preferable that the weight ratio of virgin pulp to the total amount of raw material pulp (virgin pulp rate) is high, and this ratio is, for example, preferably 80% or more, preferably 90% or more, and 100%, i.e., raw material pulp consisting only of virgin pulp, is most preferable.

[0062] (density) The density of the glass plate interleaf paper according to this embodiment is determined by the basis weight (g / m 2The density is 0.4 to 1.6 g / cm. 3 is preferred, and 0.5 to 1.4 g / cm 3 More preferably, 0.6 to 1.2 g / cm 3 is more preferably 0.7 to 1.1 g / cm 3 Here, from the viewpoint of obtaining sufficient strength of the interleaf paper to prevent abnormal occurrences such as paper breakage during the manufacturing process, the density is 0.4 g / cm. 3 More than 0.5g / cm is preferable. 3 More preferably, 0.6 g / cm 3 More preferably, 0.7 g / cm 3 From the viewpoint of productivity by reducing the amount of raw material per sheet of interleaf paper, the density is preferably 1.6 g / cm. 3 Less than 1.4 g / cm is preferred 3 Less than 1.2 g / cm is more preferable. 3 More preferably, 1.1 g / cm 3 The following are particularly preferred:

[0063] <<Method for manufacturing interleaf paper for glass plates>> The method for producing glass plate interleaf paper according to this embodiment includes the following steps in order. Process 1: Preparation of pulp slurry from natural virgin wood pulp Step 2: A step of making glass plate interleaf paper from the pulp slurry obtained in step 1. Each step will be described below.

[0064] <Process 1: Pulp slurry preparation process> In step 1, a pulp slurry is prepared from the raw material pulp. Specifically, the raw material is diluted with water or the like and then appropriately beaten using a conical refiner, double disc refiner or the like to obtain a raw material liquid (pulp slurry).

[0065] A pH adjuster is added when preparing the pulp slurry. In this embodiment, the pH adjuster preferably contains inorganic particles.

[0066] The inorganic particles preferably have an equivalent circle diameter of 0.2 to 30 μm, and more preferably, the proportion of particles having an arithmetic mean height Sa of more than 0.1 μm by number is 50% or more. This prevents inorganic foreign matter originating from inorganic particles having an equivalent circle diameter of 0.3 to 15 μm from adhering to the surface of the glass plate, even if the inorganic foreign matter is present on the surface of the obtained glass plate interleaf paper.

[0067] Of the inorganic particles, the number ratio of particles having an arithmetic mean height Sa of more than 0.1 μm is 50% or more, preferably 50 to 100%, more preferably 60 to 100%, and even more preferably 70 to 100%. From the viewpoint of suppressing adhesion to the glass plate surface, the number ratio is 50% or more, preferably 60% or more, and more preferably 70% or more. The higher the number ratio, the better, and it may be 100%, but it may also be 95% or less.

[0068] In this embodiment, calcium carbonate is preferably used as the inorganic particles contained in the pH adjuster. Calcium carbonate is an inorganic particle that is poorly soluble or insoluble in a pulp slurry. As described above, the inorganic particles made of calcium carbonate preferably have an equivalent circle diameter of 0.2 to 30 μm, and the proportion of particles having an arithmetic mean height Sa of more than 0.1 μm is preferably 50% or more.

[0069] Furthermore, the upper limit of the arithmetic mean height Sa of inorganic particles having a circle-equivalent diameter of 0.2 to 30 μm is not particularly limited, and examples thereof include 0.3 μm or less and 0.5 μm or less.

[0070] By using the pulp slurry obtained by adding a pH adjuster containing inorganic particles and then passing through the subsequent step 2, an interleaf paper for glass plates is obtained which contains inorganic foreign matter on its surface with a circle-equivalent diameter of 0.3 to 15 μm, and in which the number ratio of the inorganic foreign matter having an arithmetic mean height Sa of more than 0.1 μm is 50% or more.

[0071] In addition, the density of inorganic foreign matter derived from these inorganic particles is 0 pieces / 5mm 2Super, 50 pieces / 5mm 2 Preferably less than 30 pieces / 5mm 2 The following is more preferable: 25 pieces / 5mm 2 The following is more preferable, and the fewer the amount, the better. The inorganic foreign matter can be adjusted, for example, by the concentration of inorganic particles used as a pH adjuster, that is, the pH when preparing a pulp slurry from raw pulp. When calcium carbonate is used as the inorganic particles, the inorganic foreign matter includes Ca-containing foreign matter.

[0072] pH adjusters other than calcium carbonate may be used in preparing the pulp slurry. Examples include calcium salts such as calcium bicarbonate, calcium hydroxide, calcium sulfate, and calcium oxalate. Other examples include potassium carbonate, potassium hydroxide, sodium carbonate, sodium hydroxide, and aluminum sulfate.

[0073] In preparing the pulp slurry, various chemicals other than the pH adjuster may be further added within a range that does not deteriorate the quality of the glass plate interleaf paper. Examples of chemicals include antifoaming agents, fixing agents, paper strength agents, retention aids, coagulants, surfactants, sizing agents, antistatic agents, slime control agents, dryer release agents, polyvinyl alcohol, polyacrylamide, starch, cellulose derivatives such as CMC (carboxymethyl cellulose), and fillers (talc, clay, titanium dioxide, etc.).

[0074] In beating, the beating conditions are changed depending on the type of pulp used and the characteristics of the intended glass plate interleaf, in other words, the properties of the disintegrated pulp, and either free beating, whose main effect is fiber cutting, or sticky beating, whose main effect is fiber swelling and fibrillation, can be appropriately performed.

[0075] <Process 2: Papermaking process for glass plate interleaf paper> In step 2, glass plate interleaf paper is made from the pulp slurry obtained in step 1 above. Specifically, the resulting pulp slurry is made into paper using, for example, a Fourdrinier paper machine, a cylinder paper machine, an inclined wire paper machine, or a twin wire paper machine. The wet paper is then dewatered after passing through the wet end and dried using a multi-cylinder dryer, Yankee dryer, or the like. If necessary, the above-mentioned chemicals may be applied or impregnated using a roll coater or blade coater. Various calenders such as soft calenders and super calenders may be used online or offline.

[0076] <Glass plate laminate> The glass plate laminate according to this embodiment is formed by laminating a plurality of glass plates with interleaving papers therebetween. As the interleaving paper, the interleaving paper described in the above section "Glass Plate Interleaving Paper" or the interleaving paper obtained by the method described in the above section "Method for Producing Glass Plate Interleaving Paper" can be used, and preferred aspects are also the same.

[0077] By stacking the glass plates, the efficiency of conveying the glass plates is improved. However, when the glass plates are brought into contact with each other during lamination, scratches may be formed on the surfaces of the glass plates. If such scratches occur on the surfaces of the glass plates on which electronic circuits are formed, they may cause breaks in the wiring or the like. In response to this problem, by stacking the glass plates with glass interleaf paper interposed between the glass plates, it is possible to prevent scratches from occurring on the surfaces of the glass plates on which electronic circuits are formed.

[0078] The number of laminated glass plates in the glass plate laminate according to this embodiment may be two or more, and can be appropriately changed depending on various conditions, such as the strength and size of the glass plates, the size of the packaging container, etc. Therefore, the upper limit of the number of laminated glass plates in the glass plate laminate is not particularly limited, but is, for example, 300 or less. In addition, the total mass of the glass plate laminate is, for example, 2000 kg or less. The number of interleaf sheets in the glass plate laminate is either the same as the number of laminated glass plates, or one more or one less.

[0079] The composition, shape, size, thickness, etc. of the glass plate may be appropriately changed depending on the application. For example, the large glass plate may be a glass plate having at least one side of 2400 mm or more, a specific example being a glass plate having a long side of 2400 mm or more and a short side of 2000 mm or more. The large glass plate is preferably a glass plate having at least one side of 2400 mm or more, for example, a glass plate having a long side of 2400 mm or more and a short side of 2100 mm or more, more preferably a glass plate having at least one side of 3000 mm or more, for example, a glass plate having a long side of 3000 mm or more and a short side of 2800 mm or more, more preferably a glass plate having at least one side of 3200 mm or more, for example, a glass plate having a long side of 3200 mm or more and a short side of 2900 mm or more, and particularly preferably a glass plate having at least one side of 3300 mm or more, for example, a glass plate having a long side of 3300 mm or more and a short side of 2950 mm or more.

[0080] The thickness of the glass plate is preferably 1.30 mm or less. By making the glass plate thinner, the weight per plate becomes lighter, which allows for an increase in the number of plates that can be loaded and also shortens the etching time when manufacturing liquid crystal panels, for example. The thickness of the glass plate is more preferably 0.75 mm or less, even more preferably 0.65 mm or less, and most preferably 0.55 mm or less. The thickness can also be 0.10 mm or less, or 0.05 mm or less. However, from the viewpoint of preventing deflection due to its own weight, the thickness is preferably 0.10 mm or more, and more preferably 0.20 mm or more.

[0081] The uses of the multiple glass plates in the glass plate laminate according to this embodiment are not particularly limited, but since there is little foreign matter, such as Ca-containing foreign matter, adhering from the surface of the glass plate interleaf paper, the glass plate laminate is suitable for uses requiring high surface cleanliness. Specifically, for example, glass plates for flat panel displays such as liquid crystal displays, plasma displays, and organic electroluminescence displays, and glass plates used in electronic devices such as solar cells are preferred, and glass plates for flat panel displays are more preferred. Also, glass plates for high-definition displays are more preferred.

[0082] When the glass plate is used for a display, the number of pixels is preferably 2K (1920 × 1080) or more, more preferably 4K (3840 × 2160) or more, and even more preferably 8K (7680 × 4320) or more. The greater the number of pixels, the thinner and more numerous the wiring becomes, making it more susceptible to the influence of minute foreign matter, and therefore the greater the effect of the present invention can be expected.

[0083] Glass plate packaging The glass plate package according to this embodiment includes a glass plate laminate and a packaging container for accommodating the glass plate laminate. Here, the glass plate laminate may be one described in the above "Glass Plate Laminate," and preferred embodiments thereof are also the same.

[0084] When transporting or storing glass plates, the glass plates and interleaf papers for glass plates are alternately stacked to form a laminate, which is then placed in a packaging container and packaged to form a package (glass plate package). There are two types of glass plate packages: a horizontal type in which glass plates are stacked horizontally, and a vertical type in which glass plates are stacked in an upright state at an angle. The glass plate package according to this embodiment can be applied to either type. Conventionally known glass plate packages can be used for both the vertical and horizontal stacking types. [Example]

[0085] The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. Examples 1 and 2 are working examples, and Examples 3 and 4 are comparative examples.

[0086] Example 1 Water was added to commercially available NBKP (100% virgin pulp) prepared as the raw pulp to form a slurry. Commercially available heavy calcium carbonate A (average particle size: 3.1 μm, proportion of particles with a circular equivalent diameter of 0.3 to 15 μm: 97%, proportion of particles with an arithmetic mean height Sa exceeding 0.1 μm: 80%) was then added to the raw pulp (bone-dry pulp) at a concentration of 0.75% by mass. The pulp was then beaten using a double-disc refiner to a CSF of 500 ml, yielding a pulp slurry. The resulting pulp slurry was then processed using a Fourdrinier paper machine and a multi-cylinder dryer at a papermaking speed of 400 m / min to produce glass plate interleaving paper.

[0087] Example 2 An interleaving paper for glass plates was obtained in the same manner as in Example 1, except that the amount of heavy calcium carbonate A was changed to 2.0%.

[0088] Example 3 An interleaving paper for glass plates was obtained in the same manner as in Example 1, except that heavy calcium carbonate B (average particle size: 2.1 μm, proportion of particles with a circle-equivalent diameter of 0.3 to 15 μm: 95%, proportion of particles with an arithmetic mean height Sa of more than 0.1 μm: 55%) was used instead of heavy calcium carbonate A in Example 1.

[0089] Example 4 An interleaving paper for glass plates was obtained in the same manner as in Example 1, except that heavy calcium carbonate A in Example 1 was replaced with light calcium carbonate C, a commercially available synthetic product (average particle size: 5.0 μm, proportion of particles with equivalent circle diameters of 0.3 to 15 μm: 96%, proportion of particles with an arithmetic mean height Sa of more than 0.1 μm: 45%).

[0090] "evaluation" <Cold water extraction pH> The pH value of the electrolyte solution extracted from the obtained glass plate interleaf paper with cold water was measured in accordance with JIS P 8133-1 (2013). The results are shown in Table 1.

[0091] <Ca-containing foreign matter> The amount of Ca-containing foreign matter contained on any one surface of the obtained glass plate interleaf paper was measured. Specifically, a laser microscope (Keyence, VK-X3100) and a 50x objective lens were used to measure the surface of the glass plate interleaf paper to a depth of 5 mm. 2 The above observations were performed, and the location and area of any foreign matter other than cellulose fibers were measured. The equivalent circle diameter was calculated from the area, and the arithmetic mean height Sa was determined in accordance with ISO 25178. The resulting images were then processed to obtain the shape of the foreign matter, including its circularity and kurtosis. Multi-file analysis software (Keyence Corporation) was used for all measurements.

[0092] Next, for the foreign matter observed above with a circle equivalent diameter of 0.3 to 15 μm, those containing 0.5 mass % or more of Ca (calcium) were identified as Ca-containing foreign matter using a scanning electron microscope (SEM) and a backscattered electron detector of an energy dispersive X-ray analyzer attached to the SEM (both manufactured by JEOL, IT-200). 2 Number density per 5mm 2 The results were converted to σ. The surface was coated with platinum by sputtering before analysis. The results are shown in Table 1.

[0093] In the above method, the size, shape, and Ca element content are determined, but if the above method cannot be used, measurements may be made using another method as long as the results do not differ significantly from the measured values obtained by the above method. Other techniques include changing the lens magnification of the laser microscope when measuring surface roughness, changing the field of view, or using an SEM with a three-dimensional roughness analysis function. For elemental analysis, the surface can be coated with a metal other than platinum during SEM-EDS measurement, or a low-vacuum SEM can be used without coating. Furthermore, elemental analysis can also be performed in air using laser-induced breakdown spectroscopy instead of SEM-EDS.

[0094] <Quality: Adhesion to glass surface> The resulting glass interleaf was sandwiched between two glass plates (AGC Inc., AN100). To adhere the Ca-containing impurities on the surface of the glass interleaf to the glass plate surface, the paper was placed in a thermo-hygrostat chamber at 60°C and 60% relative humidity for 20 hours, with a pressure equivalent to that of 200 glass plates. The glass plates were then removed and cleaned with a pH 12 alkaline shower and a roll brush, followed by drying with clean dry air. Mo / Cu wiring was then formed on the resulting glass plates, and the occurrence rate of wire breakage was measured to evaluate the quality of the glass interleaf. The results are shown in Table 1, and the evaluation criteria are as follows: ⊚: The amount of attached Ca-containing foreign matter was extremely small, and the incidence of wire breakage caused by the Ca-containing foreign matter was extremely low, which was extremely good. ◯: The amount of attached Ca-containing foreign matter was small, and the incidence of wire breakage caused by the Ca-containing foreign matter was low, which was good. △: A certain amount of Ca-containing foreign matter was attached, and the incidence of wire breakage caused by the Ca-containing foreign matter was moderate, so it was slightly poor. ×: The amount of adhering Ca-containing foreign matter was large, and the occurrence rate of wire breakage due to the Ca-containing foreign matter was high, resulting in a poor result.

[0095] [Table 1]

[0096] The results of Examples 1 and 4 show that even when the number density of Ca-containing foreign particles with a circle equivalent diameter of 0.3 to 15 μm, which are difficult to remove once attached to the glass plate surface, was similar, Example 1, in which the number proportion of particles with an arithmetic mean height Sa of more than 0.1 μm was 50% or more, was able to more effectively suppress adhesion to the glass plate surface than Example 4, in which the number proportion was 35%. A similar tendency was confirmed from the results of Examples 2 and 3. Furthermore, the results of Examples 1 and 2 show that when the above-mentioned number ratio is 50% or more, the smaller the number density of Ca-containing foreign matter with a circle equivalent diameter of 0.3 to 15 μm, the smaller the absolute amount of adhesion to the glass plate surface, resulting in a lower rate of wire breakage caused by Ca-containing foreign matter.

Claims

1. A glass plate interleaving paper containing pulp as a raw material and having a pair of opposing main surfaces, the glass plate interleaving paper contains Ca-containing foreign matter having a circle equivalent diameter of 0.3 to 15 μm on at least one of the main surfaces, The glass plate interleaf paper has a number ratio of 50% or more of the Ca-containing foreign matter having an arithmetic mean height Sa of more than 0.1 μm.

2. 0 pieces / 5mm of the Ca-containing foreign matter ２ Super, 50 pieces / 5mm ２ The glass plate interleaving paper according to claim 1 , comprising:

3. 3. The glass plate interleaving paper according to claim 1, wherein the Ca-containing impurities include at least one selected from the group consisting of calcium carbonate, calcium bicarbonate, calcium hydroxide, calcium sulfate, and calcium oxalate.

4. A glass plate laminate in which a plurality of glass plates are laminated with interleaving paper therebetween, A glass plate laminate, wherein the interleaf paper is the glass plate interleaf paper according to claim 1 or 2.

5. 5. The glass plate laminate according to claim 4, wherein the plurality of glass plates are glass plates for flat panel displays.

6. A glass sheet package comprising: the glass sheet laminate according to claim 4; and a packaging container that houses the glass sheet laminate.

7. preparing pulp slurry from raw pulp; and producing glass plate interleaf paper from the pulp slurry, A pH adjuster is added during the preparation. the pH adjuster contains inorganic particles having an equivalent circle diameter of 0.2 to 30 μm, the inorganic particles have an arithmetic mean height Sa of more than 0.1 μm, and the number ratio of the inorganic particles having an arithmetic mean height Sa of more than 0.1 μm is 50% or more.

8. The method for producing glass plate interleaving paper according to claim 7 , wherein the inorganic particles are calcium carbonate.

9. The surface of the obtained glass plate interleaf paper contains 0 particles / 5 mm of foreign matter derived from the inorganic particles. ２ Super, 50 pieces / 5mm ２ The method for producing glass plate interleaf paper according to claim 7 or 8, wherein:

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