Glass plate interleaving paper, glass plate laminate, glass plate package, and method for producing glass plate interleaving paper

Abstract

The present invention relates to a glass plate interleaving paper, a glass plate laminate, a glass plate package, and a method for manufacturing a glass plate interleaving paper. The present invention relates to an interleaving paper for a glass plate, the interleaving paper for a glass plate containing pulp as a raw material and having a pair of opposite main surfaces, the interleaving paper for a glass plate containing Ca-containing foreign matters having an equivalent circle diameter of 0.3-15 [mu] m on at least one surface of the main surfaces, the proportion of the number of foreign matters having an arithmetic mean height Sa of more than 0.1 [mu] m among the Ca-containing foreign matters being 50% or more.

Description

Technical Field

[0001] The present invention relates to a backing paper for glass plates, a glass plate laminate, a glass plate package, and a method for manufacturing a backing paper for glass plates. Background Art

[0002] In glass plates for flat panel displays (FPDs) such as liquid crystal displays, fine electronic wirings (hereinafter sometimes simply referred to as "wirings") are formed on the surface of the glass plates. Minute scratches and dirt present on the surface of such glass plates cause defects such as disconnection, and thus a high degree of cleanliness of the glass plate surface is required.

[0003] For the purpose of improving transportation efficiency, such glass plates are sometimes transported in a stacked state. At this time, the glass plates are stacked with a backing paper for glass plates (hereinafter sometimes simply referred to as "backing paper") interposed therebetween. Thereby, it is possible to suppress the situation where the glass plates come into contact with each other during transportation and scratches are generated on the surface of the glass plates.

[0004] On the other hand, foreign substances sometimes adhere to the surface of the glass plate from the backing paper. The foreign substances include paper powder generated from the backing paper, organic substances contained in the backing paper, foreign substances mixed in the process of manufacturing the backing paper, and the like.

[0005] Most of the foreign substances adhering to the surface of the glass plate are removed by washing before the wirings are formed on the surface of the glass plate. However, there are also foreign substances remaining on the surface of the glass plate after washing, which may cause disconnection or the like. Therefore, a backing paper for glass plates that further reduces foreign substances adhering to the surface of the glass plate is required.

[0006] In this regard, for example, Patent Document 1 discloses a backing paper for glass plates in which the proportion of aluminum-containing solid inorganic substances present on the surface is 20 or less per m 2 Further, Patent Document 2 discloses a backing paper for glass plates in which the concentration of one or more of aluminum, silicon, sulfur, calcium, magnesium, iron, chlorine, sodium, potassium, phosphorus, and nickel analyzed by fluorescent X-ray is below a certain level.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2016-191180

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2017-210286 Summary of the Invention

[0011] Problems to be Solved by the Invention

[0012] When manufacturing the backing paper for glass plates, a pH regulator is sometimes added to adjust the pH of the papermaking system. As an example of a pH regulator, calcium carbonate can be cited. Calcium carbonate is a pH regulator that adjusts the pH of the papermaking system from neutral to the alkaline range.

[0013] The above-mentioned calcium carbonate and Ca (calcium)-containing foreign substances derived from the calcium carbonate are dispersed inside and on the surface of the obtained backing paper for glass plates, but have not particularly been a problem so far.

[0014] This is because, since the above-mentioned Ca-containing foreign substances are minute and Ca is contained in the composition of the glass plate, it is difficult to distinguish whether the Ca on the glass plate surface is a Ca-containing foreign substance or the glass plate itself, and thus it cannot be accurately identified as a problem.

[0015] However, in recent years, with the development of high definition of displays, the wiring has become finer, and the size of the foreign substances that become a problem has also become smaller.

[0016] Therefore, the present inventors conducted research and found that even foreign substances of several tens of nm to several hundreds of nm and several μm to several tens of μm can cause the wiring formed on the glass plate surface to break when attached to the glass plate surface from the backing paper for glass plates. Furthermore, it was found that the foreign substances are transferred from the glass plate surface to conveyors, stages, etc. in the manufacturing production line of the display, thereby contaminating the production line and can also cause defects in the manufacturing apparatus.

[0017] In order to identify such foreign substances, for example, an energy dispersive X-ray analysis device is generally used to analyze the composition. However, when analyzing without knowing the target composition, in order to expand the range of elements to be measured, the analysis is mostly carried out under the condition of increasing the acceleration voltage.

[0018] However, by increasing the acceleration voltage, the electron beam irradiates deep into the glass plate instead of staying on the foreign substances, so sometimes the basic composition of the glass plate is also captured at the same time. Among them, since calcium is a component contained in a certain amount in the composition of the glass, even if calcium exists on the glass plate surface, it is not regarded as the component of the foreign substance and is ignored.

[0019] Therefore, in order to capture the foreign substances themselves, when the present inventors carried out the composition analysis at a low acceleration voltage, it was found that there are Ca-containing foreign substances as the foreign substances that become a problem.

[0020] In addition, it was found that when calcium carbonate is used as the pH regulator, the above-mentioned Ca-containing foreign substances can be calcium carbonate itself or calcium salts derived from calcium carbonate.

[0021] Accordingly, an object of the present invention is to provide a backing paper for a glass plate that suppresses foreign matter from adhering to the surface of the glass plate 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 using the above-mentioned backing paper for a glass plate.

[0022] Means for Solving the Problem

[0023] The present inventors further studied the above problems and found that when calcium carbonate itself or a calcium salt derived from calcium carbonate, that is, a Ca-containing foreign matter, is below a certain size, it is difficult to remove by cleaning when adhering to the surface of the glass plate. Specifically, it was found that if the Ca-containing foreign matter has an equivalent circle diameter of 15 μm or less, there is a tendency that it is difficult to remove even when the surface of the glass plate is cleaned.

[0024] Further in-depth study of such Ca-containing foreign matter with an equivalent circle diameter of 15 μm or less revealed that the arithmetic mean height (surface roughness) Sa of the Ca-containing foreign matter is related to the ease of adhesion to the surface of the glass plate, thus completing the present invention.

[0025] That is, the gist of the present invention is as follows.

[0026] [1] A backing paper for a glass plate, the backing paper for a glass plate containing pulp as a raw material and having a pair of opposite main surfaces, wherein the backing paper for a glass plate contains Ca-containing foreign matter with an equivalent circle diameter of 0.3 μm to 15 μm on at least one surface of the main surface, and the proportion of the number of foreign matters with an arithmetic mean height Sa greater than 0.1 μm in the Ca-containing foreign matter is 50% or more.

[0027] [2] The backing paper for a glass plate according to [1] above, wherein the backing paper for a glass plate contains more than 0 pieces / 5 mm 2 and less than or equal to 50 pieces / 5 mm 2 of the Ca-containing foreign matter.

[0028] [3] The backing paper for a glass plate according to [1] or [2] above, wherein the Ca-containing foreign matter contains at least one selected from the group consisting of calcium carbonate, calcium bicarbonate, calcium hydroxide, calcium sulfate, and calcium oxalate.

[0029] [4] A glass plate laminate obtained by laminating a plurality of glass plates with a backing paper layer therebetween, wherein the backing paper is the backing paper for a glass plate according to any one of [1] to [3] above.

[0030] [5] The glass plate laminate according to [4] above, wherein the plurality of glass plates are glass plates for flat panel displays.

[0031] [6]A glass plate package, wherein the glass plate package has the glass plate laminate described in [4] or [5] and a packaging container for accommodating the glass plate laminate.

[0032] [7]A method for manufacturing a separator for glass plates, which successively includes: a step of preparing a pulp slurry from pulp as a raw material, and a step of forming a separator for glass plates from the pulp slurry. A pH regulator is added during the preparation, and the pH regulator contains inorganic particles having an equivalent circle diameter of 0.2 μm to 30 μm, and the proportion of the number of particles having an arithmetic mean height Sa greater than 0.1 μm in the inorganic particles is 50% or more.

[0033] [8]The method for manufacturing a separator for glass plates according to [7] above, wherein the inorganic particles are calcium carbonate.

[0034] [9]The method for manufacturing a separator for glass plates according to [7] or [8] above, wherein there are more than 0 and less than or equal to 50 foreign matters from the inorganic particles per 5 mm on the surface of the obtained separator for glass plates. 2 and less than or equal to 50 per 5 mm 2 of foreign matter from the inorganic particles.

[0035] Advantages of the Invention

[0036] According to the present invention, a separator for glass plates with reduced foreign matter adhesion to the glass plate surface can be obtained. As a result, for glass plates transported as a glass plate laminate or a glass plate package using the above-mentioned separator for glass plates, even when fine wiring is performed for use in a high-definition display, disconnection of the wiring caused by minute foreign matter can be prevented. In addition, defects in manufacturing equipment caused by transfer of foreign matter from the glass plate surface to a conveyor belt or the like in a manufacturing line of a display can be prevented. Detailed Embodiments

[0037] Hereinafter, preferred embodiments of the present invention will be described. The embodiments shown below are examples, and the present invention should not be construed as being limited to these embodiments.

[0038] In this specification, "~" indicating a numerical range is used in the sense of including the values described before and after it as a lower limit value and an upper limit value.

[0039] 《Separator for Glass Plates》

[0040] The separator for glass plates of this embodiment contains pulp as a raw material and has a pair of opposite main surfaces.

[0041] The above-mentioned backing paper for glass plates contains Ca-containing foreign substances with an equivalent circle diameter of 0.3 μm to 15 μm on the surface of at least one of its pair of main surfaces. Among these Ca-containing foreign substances, the proportion of foreign substances with an arithmetic mean height Sa greater than 0.1 μm is 50% or more. In addition, the backing paper for glass plates preferably contains more than 0 pieces / 5 mm 2 and less than or equal to 50 pieces / 5 mm 2 of the above-mentioned Ca-containing foreign substances with an equivalent circle diameter of 0.3 μm to 15 μm.

[0042] <Ca-containing foreign substances>

[0043] The Ca-containing foreign substances in this embodiment refer to foreign substances containing Ca (calcium) in their composition. As the above-mentioned Ca-containing foreign substances, the following can be listed: foreign substances derived from calcium carbonate used as a pH regulator in the manufacture of backing paper for glass plates; foreign substances derived from calcium carbonate used as a filler or pigment in the manufacture of other papers rather than directly in the manufacture of backing paper for glass plates; foreign substances precipitated when calcium hypochlorite is used during the bleaching process in the manufacture of raw pulp; and foreign substances formed by the precipitation and scaling of calcium in minerals contained in water such as spring water and river water used in the process, etc. Among them, it is considered that calcium carbonate used as a pH regulator in the manufacture of backing paper for glass plates is the main reason, especially.

[0044] As the Ca-containing foreign substances, specifically, in addition to calcium carbonate itself, calcium salts derived from the above-mentioned calcium component can also be listed. As the calcium salts, for example, the following can be listed: calcium bicarbonate, calcium hydroxide, calcium sulfate, calcium oxalate, calcium aluminosilicate, calcium aluminate, calcium silicate, calcium oxide, calcium phosphate, etc.

[0045] Preferably, a mode can be listed in which the Ca-containing foreign substances include at least one selected from the group consisting of calcium carbonate, calcium bicarbonate, calcium hydroxide, calcium sulfate, and calcium oxalate.

[0046] When calcium carbonate is used as a pH regulator, it is almost impossible to completely eliminate the Ca-containing foreign substances contained in the backing paper for glass plates.

[0047] In this embodiment, as the Ca-containing foreign substances contained in the backing paper for glass plates, foreign substances with an equivalent circle diameter of 0.3 μm to 15 μm are focused on. This is because, according to the research of the present inventor, Ca-containing foreign substances with an equivalent circle diameter greater than 15 μm can be easily removed by cleaning even if they adhere to the glass plate surface, so they are not likely to be the main cause of wire breakage in wiring and defects in manufacturing equipment.

[0048] The above content was conceived based on the specific research results of the present inventors. That is, the present inventors wiped calcium carbonate with an equivalent circle diameter of 0.1 μm to 40 μm onto a glass plate, then performed alkaline scrub cleaning, and measured the calcium carbonate that remained attached to the surface of the glass plate after cleaning and was not removed. The alkaline scrub cleaning was performed by changing the strength of the cleaning by changing the height of the brush. As a result, as described above, it is difficult to remove calcium carbonate with an equivalent circle diameter of 15 μm or less.

[0049] Although the reason is not yet clear, it is considered that the intermolecular attractive forces such as electrostatic force and van der Waals force become relatively larger as the particle size becomes smaller, compared to the force that causes the separation of the glass plate and foreign matter, such as the impact force during cleaning. Therefore, the smaller the particle, the smaller the removal effect caused by cleaning. Moreover, in the case of Ca-containing foreign matter, the equivalent circle diameter that is difficult to remove from the surface of the glass plate by cleaning is 15 μm or less. From this point of view, it is considered necessary to control Ca-containing foreign matter with an equivalent circle diameter of 15 μm or less.

[0050] On the other hand, since foreign matter with an equivalent circle diameter of less than 0.3 μm is small, the possibility of causing wire breakage is low. Therefore, in the glass plate backing paper of the present embodiment, Ca-containing foreign matter with an equivalent circle diameter of 0.3 μm to 15 μm is targeted.

[0051] It should be noted that in this specification, the equivalent circle diameter of the Ca-containing foreign matter refers to the diameter when converted into a circle having an area equal to the area observed from the direction perpendicular to the main surface of the glass plate backing paper. Specifically, the area obtained by performing image processing on the particles from the optical microscope image of the glass plate backing paper is converted into the diameter of a circle having an area equal to this area, and the obtained value is used as the equivalent circle diameter. More specifically, the method used in the examples described later can be adopted.

[0052] In the Ca-containing foreign matter with an equivalent circle diameter of 0.3 μm to 15 μm on at least one surface of the main surface of the glass plate backing paper of the present embodiment, the proportion of the number of foreign matter with an arithmetic mean height Sa greater than 0.1 μm is 50% or more.

[0053] The present inventors found that even when the number density of Ca-containing foreign matter with an equivalent circle diameter of 0.3 μm to 15 μm is the same, the ease of attachment to the glass plate surface varies depending on the surface roughness of the Ca-containing foreign matter.

[0054] Specifically, calcium carbonate particles were pressed onto the surface of the glass plate, then the surface of the glass plate was washed with running water and dried, and the surface of the glass plate was observed. As a result, it was found that the calcium carbonate that remained attached to the surface of the glass plate without being removed was mainly calcium carbonate with an arithmetic mean height Sa of 0.1 μm or less.

[0055] From the above research, it can be seen that among the parameters related to surface roughness, the arithmetic mean height Sa is particularly related to the ease of adhesion on the glass plate surface. The smaller the arithmetic mean height Sa, the easier it is to adhere to the glass plate surface. And it is known that 0.1 μm of the arithmetic mean height Sa is its threshold value.

[0056] Regarding the above content, it is considered that the smaller the arithmetic mean height Sa of the Ca-containing foreign matter, the larger the contact area with the glass plate surface, the stronger the interaction with the glass plate, and as a result, the adhesion increases. And in fact, the correlation between the arithmetic mean height Sa of the Ca-containing foreign matter with an equivalent circle diameter of 0.3 μm to 15 μm and the adhesion amount of the Ca-containing foreign matter on the glass plate surface was studied. The result shows that when the arithmetic mean height Sa of the Ca-containing foreign matter is greater than 0.1 μm, the adhesion amount on the glass plate surface decreases sharply.

[0057] Here, the arithmetic mean height Sa of the Ca-containing foreign matter with an equivalent circle diameter of 0.3 μm to 15 μm refers to the arithmetic mean height Sa measured from the side opposite to the side where the Ca-containing foreign matter adheres to the glass plate liner paper in the direction perpendicular to the main surface of the glass plate liner paper.

[0058] It should be noted that the arithmetic mean height Sa of the Ca-containing foreign matter can also be measured from the Ca-containing foreign matter transferred from the glass plate liner paper and adhering to the glass plate surface. In this case, it is preferably stipulated to measure the arithmetic mean height Sa of the Ca-containing foreign matter on the side of the glass plate where it adheres in the direction perpendicular to the main surface of the glass plate. However, in fact, since the Ca-containing foreign matter adheres to the glass plate surface, it is difficult to measure the arithmetic mean height Sa of the Ca-containing foreign matter on the side of the glass plate where it adheres. Therefore, it can be assumed that the arithmetic mean height Sa of the Ca-containing foreign matter on the side of the glass plate where it adheres and on the opposite side is approximately the same, and the arithmetic mean height Sa on the side opposite to the side where the Ca-containing foreign matter adheres to the glass plate is regarded as the arithmetic mean height Sa of the Ca-containing foreign matter.

[0059] The arithmetic mean height Sa of the Ca-containing foreign matter refers to the average value of the absolute value of the difference between the height of each point and the average plane of the foreign matter surface measured in a non-contact manner.

[0060] Specifically, a laser microscope can be used to measure the position and area of the Ca-containing foreign matter, calculate the equivalent circle diameter from this area, and then measure the arithmetic mean height Sa according to ISO 25178. More specifically, the method used in the following examples can be adopted.

[0061] That is, in the backing paper for glass plates of the present embodiment, the proportion of foreign substances containing Ca with an equivalent circle diameter of 0.3 μm to 15 μm and an arithmetic mean height Sa greater 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 on the glass plate surface, the above-mentioned proportion is 50% or more, preferably 60% or more, and more preferably 70% or more. The higher the above-mentioned proportion, the more preferable it is, and it can be 100%, or can be 95% or less.

[0062] The arithmetic mean height Sa of the foreign substances containing Ca can be adjusted by using calcium carbonate with a large arithmetic mean height Sa as the calcium carbonate for the pH regulator. In addition, the arithmetic mean height Sa of the foreign substances containing Ca that first dissolve into ions and then precipitate again tends to become smaller. Therefore, the method of reducing the above-mentioned Ca amount can also be a method of relatively reducing the foreign substances containing Ca with an arithmetic mean height Sa value of 0.1 μm or less.

[0063] There is no particular limitation on the upper limit of the arithmetic mean height Sa of the foreign substances containing Ca with an equivalent circle diameter of 0.3 μm to 15 μm, and for example, 0.3 μm or less, 0.5 μm or less can be cited.

[0064] The backing paper for glass plates of the present embodiment preferably contains more than 0 pieces / 5 mm 2 and less than or equal to 50 pieces / 5 mm 2 of foreign substances containing Ca with an equivalent circle diameter of 0.3 μm to 15 μm on at least one surface of the main surface, and particularly preferably contains more than 0 pieces / 5 mm 2 and less than or equal to 30 pieces / 5 mm 2 of foreign substances containing Ca.

[0065] Here, the case of containing foreign substances containing Ca with an equivalent circle diameter of 0.3 μm to 15 μm and more than 0 pieces / 5 mm 2 can be cited, for example, the case of using calcium carbonate as a pH regulator in the manufacture of the backing paper for glass plates. When calcium carbonate is used as a pH regulator, it is almost impossible to completely eliminate the foreign substances containing Ca contained in the backing paper for glass plates.

[0066] When calcium carbonate is used as a pH regulator, the cold water extraction pH of the backing paper for glass plates is usually neutral to alkaline. The above-mentioned cold water extraction pH can be cited, for example, 6.5 to 11.0.

[0067] It should be noted that in this specification, the cold water extraction pH of the backing paper for glass plates is the value obtained by measuring the pH value of the electrolyte solution extracted from the backing paper for glass plates with cold water according to JIS P 8133-1 (2013).

[0068] The number density of Ca-containing foreign matters with an equivalent circle diameter of 0.3 μm to 15 μm contained in at least one surface of the main surface of the backing paper for glass plates in this embodiment is preferably 50 pieces / 5 mm 2 Hereinafter, it is more preferably 30 pieces / 5 mm 2 Hereinafter, it is further preferably 25 pieces / 5 mm 2 Hereinafter, the fewer, the more preferable.

[0069] The number density of the above-mentioned Ca-containing foreign matters can be adjusted, for example, by the addition amount of calcium carbonate used as a pH regulator, and the Ca amount can be reduced by increasing the amount of alkali components other than calcium carbonate. As the added amount of calcium carbonate, 0.1% by mass to 5.0% by mass is preferred. In order to further reduce the Ca amount, the following can be cited: within the process of manufacturing the backing paper for glass plates, calcium carbonate is not used as a filler or pigment used other than as a pH regulator; the calcium ions are reduced by passing the water used through a filter such as an ion exchange resin; the devices, papermaking utensils, and pipes used in the process are cleaned with an acidic cleaning agent to remove calcium scale, etc.

[0070] In this specification, the number density (pieces / 5 mm 2 ) of Ca-containing foreign matters with an equivalent circle diameter of 0.3 μm to 15 μm in the backing paper for glass plates can be determined by a scanning electron microscope (SEM) and an energy dispersive X-ray analysis device installed on the SEM. More specifically, the method used in the following examples can be adopted.

[0071] Regarding the shape of the Ca-containing foreign matters with an equivalent circle diameter of 0.3 μm to 15 μm in this embodiment, as long as more than 50% of them have an arithmetic mean height Sa greater than 0.1 μm, there is no particular limitation, and for example, flat shapes, spherical shapes, etc. can be cited.

[0072] The backing paper for glass plates in this embodiment may contain, on its surface, Ca-containing foreign matters other than Ca-containing foreign matters with an equivalent circle diameter of 0.3 μm to 15 μm, that is, Ca-containing foreign matters with an equivalent circle diameter less than 0.3 μm and Ca-containing foreign matters with an equivalent circle diameter greater than 15 μm.

[0073] Even if the Ca-containing foreign matters with an equivalent circle diameter greater than 15 μm adhere to the glass plate surface, they can be easily removed by cleaning the glass plate surface, so their number density (pieces / 5 mm 2 ) and arithmetic mean height Sa are not particularly limited.

[0074] Similar to the Ca-containing foreign substances with an equivalent circle diameter of 0.3 μm to 15 μm, when the Ca-containing foreign substances with an equivalent circle diameter less than 0.3 μm adhere to the surface of the glass plate, they are difficult to remove. However, as described above, the possibility of causing wire breakage is low. On the other hand, from the perspective that it cannot be asserted that there is no impact on wire breakage or any other problems, it is preferable that the number density (number / 5 mm 2 ) of the Ca-containing foreign substances with an equivalent circle diameter less than 0.3 μm is smaller. For example, it is preferably 100 or less / 5 mm 2 , and more preferably 50 or less / 5 mm 2 . In addition, there is no particular limitation on the lower limit, and it is usually greater than 0 / 5 mm 2 , and it can also be greater than 0.01 / 5 mm 2 .

[0075] In addition, similar to the Ca-containing foreign substances with an equivalent circle diameter of 0.3 μm to 15 μm, it is preferable that the proportion of the number of Ca-containing foreign substances with an arithmetic mean height Sa of 0.1 μm or more among the Ca-containing foreign substances with an equivalent circle diameter less than 0.3 μm is high. The proportion of the number of foreign substances with an arithmetic mean height Sa greater than 0.1 μm among the Ca-containing foreign substances with an equivalent circle diameter less than 0.3 μm is preferably 50% to 100%, more preferably 60% to 98%, and even more preferably 70% to 95%. Here, from the perspective of suppressing adhesion on the glass plate surface, the above-mentioned proportion is preferably 50% or more, more preferably 60% or more, and further preferably 70% or more. The higher the above-mentioned proportion, the more preferable it is, and it can be 100%, usually 98% or less, and it can also be 95% or less.

[0076] <Other inorganic foreign substances>

[0077] The glass plate backing paper of the present embodiment may contain other inorganic foreign substances on its surface in addition to the Ca-containing foreign substances.

[0078] Examples of other inorganic foreign substances include: Fe-containing foreign substances containing Fe (iron) in the composition, Cr-containing foreign substances containing Cr (chromium) in the composition, Ni-containing foreign substances containing Ni (nickel) in the composition, Na-containing foreign substances containing Na (sodium) in the composition, K-containing foreign substances containing K (potassium) in the composition, Al-containing foreign substances containing Al (aluminum) in the composition, etc.

[0079] Among the above-mentioned other inorganic foreign substances, for example, Fe-containing foreign substances, Cr-containing foreign substances, and Ni-containing foreign substances are inorganic foreign substances that can be included in the inorganic foreign substance group on the surface of the glass plate backing paper (hereinafter sometimes referred to as "inorganic foreign substance A group") derived from stainless steel materials used in the papermaking equipment. When these inorganic foreign substance A groups adhere to the glass plate surface, in addition to being the cause of wire breakage of the wiring and malfunction of the manufacturing device in the same way as the Ca-containing foreign substances, they may also be the cause of scratches on the glass plate surface.

[0080] Therefore, the number density of foreign substances with an equivalent circle diameter of 0.3 μm to 15 μm contained in at least one of the inorganic foreign substance group A on at least one surface of the main surface of the glass plate backing paper is preferably 10 pieces / 5 mm. 2 Hereinafter, it is more preferably 1 piece / 5 mm. 2 Hereinafter, the fewer the better. In addition, it is more preferable that at least two of the above-mentioned inorganic foreign substance group A are within the above range, and it is further preferable that all three are within the above range.

[0081] In addition, it is known that for the above-mentioned inorganic foreign substance group A, similar to the Ca-containing foreign substances, when the arithmetic mean height Sa is a certain value or more, adhesion on the glass plate surface can be suppressed. That is, the arithmetic mean height Sa of the inorganic foreign substance group A with an equivalent circle diameter of 0.3 μm to 15 μm is preferably 0.1 μm or more, and more preferably 0.3 μm or more. In addition, there is no particular limitation on the upper limit, for example, it is 0.5 μm or less.

[0082] In the inorganic foreign substance group A with an equivalent circle diameter of 0.3 μm to 15 μm, the proportion of the number of foreign substances with an arithmetic mean height Sa of 0.1 μm or more is preferably 50% or more, more preferably 60% or more. In addition, it can be 100%, or it can be 95% or less.

[0083] Among the above-mentioned other inorganic foreign substances, for example, Na-containing foreign substances and K-containing foreign substances are inorganic foreign substances that can be contained on the surface of the glass plate backing paper originating from chemicals such as sodium hydroxide and sodium sulfide used in pulp bleaching agents or sodium hydroxide, sodium carbonate, potassium hydroxide, and potassium carbonate used as pH regulators (hereinafter sometimes referred to as "inorganic foreign substance group B"). When using pH regulators such as sodium hydroxide and potassium hydroxide, the cold water extraction pH of the obtained glass plate backing paper is, for example, about 6.5 to about 11.0.

[0084] Compared with the Ca-containing foreign substances, these inorganic foreign substance groups B have higher solubility in water. Therefore, even if the inorganic foreign substance groups B are contained on the surface of the glass plate backing paper and adhere to the glass plate surface, they are easily removed by washing or the like, and they are not easily agglomerated, so they are not likely to cause reasons such as wire breakage of the wiring.

[0085] Therefore, there are no particular limitations on the degree of adhesion, the size of the equivalent circle diameter, the arithmetic mean height Sa, etc. of the inorganic foreign substance group B on the surface of the glass plate backing paper. Among them, the case where the arithmetic mean height Sa of the inorganic foreign substance group B with an equivalent circle diameter of 0.3 μm to 15 μm is as large as that of the Ca-containing foreign substances, for example, 0.1 μm or more, is not excluded.

[0086] For the above-mentioned inorganic foreign matter group B, by using sodium hydroxide or potassium hydroxide alone or in combination as a pH regulator, the amount of Ca-containing foreign matter contained in the surface of the backing paper for glass plates is reduced. Specifically, the Ca amount on the surface of the backing paper for glass plates can be reduced to, for example, about 0.01 mass ppm or more and about 100 mass ppm or less.

[0087] Among the above-mentioned other inorganic foreign matters, for example, Al-containing foreign matter is an inorganic foreign matter that can be contained in the surface of the backing paper for glass plates and is derived from a pH regulator such as aluminum sulfate. When the Al-containing foreign matter adheres to the surface of the glass plate, it can also cause wire breakage in the wiring and defects in the manufacturing apparatus, similarly to the Ca-containing foreign matter.

[0088] Therefore, the number density of Al-containing foreign matters having an equivalent circle diameter of 0.3 μm to 15 μm contained in at least one surface of the main surface of the backing paper for glass plates is preferably 50 or less per 5 mm 2 , more preferably 30 or less per 5 mm 2 , and the fewer, the more preferable.

[0089] In addition, it is known that when the arithmetic mean height Sa of the above-mentioned Al-containing foreign matter is a certain value or more, similar to the Ca-containing foreign matter, adhesion to the glass plate surface can be suppressed. That is, the arithmetic mean height Sa of the Al-containing foreign matter having an equivalent circle diameter of 0.3 μm to 15 μm is preferably 0.1 μm or more, more preferably 0.3 μm or more. In addition, the upper limit is not particularly limited, for example, it is 0.5 μm or less.

[0090] Among the Al-containing foreign matters having an equivalent circle diameter of 0.3 μm to 15 μm, the proportion of the number of foreign matters having an arithmetic mean height Sa of 0.1 μm or more is preferably 50% or more, more preferably 60% or more, and can be 100%, or can be 95% or less.

[0091] The equivalent circle diameter of the Al-containing foreign matter can be adjusted as follows: in order to reduce the precipitated foreign matter, for example, the papermaking pH is adjusted to be acidic, so that it is in a state where precipitation is not likely to occur originally; in order to prevent the hypertrophy of coarse particles, the process and papermaking utensils are cleaned by acid cleaning; downstream of the process of producing the backing paper for glass plates, cleaning is performed using a cleaning agent containing an acid, etc. Similarly, the arithmetic mean height Sa can also be adjusted by cleaning the process, utensils, and the backing paper itself by acid cleaning to roughen its surface.

[0092] <Other components>

[0093] In addition to containing the elements that make up the above-mentioned Ca-containing foreign substances and other inorganic foreign substances, the backing paper for glass plates of the present embodiment may also contain metal elements and metalloid elements. Specifically, examples include: B (boron), Mg (magnesium), Si (silicon), Ti (titanium), Cu (copper), Zn (zinc), Ba (barium), etc.

[0094] <Raw materials>

[0095] The backing paper for glass plates of the present embodiment contains pulp as a raw material.

[0096] There is no particular limitation on the type of raw material pulp, and pulp having the characteristics required for backing paper for glass plates is preferably used.

[0097] Examples of raw material pulp include: chemical pulps such as kraft pulp (KP), sulfite pulp (SP), and alkaline pulp (AP); mechanical pulps such as groundwood pulp (GP), thermomechanical pulp (TMP), and chemithermomechanical pulp (CTMP); semi-chemical pulps such as chemigroundwood pulp (CGP) and semi-chemical pulp (SCP) which are mechanical-chemical pulps in between; non-wood fiber pulp made from kenaf, edgeworthia, paper mulberry, gampi, hemp, etc.; synthetic pulp, synthetic fiber; deinked pulp (DIP), etc.

[0098] The pulp can be bleached or unbleached. For example, bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), unbleached hardwood kraft pulp (LUKP), and unbleached softwood kraft pulp (NUKP) can be used. In addition, carbon nanofibers (CNF) can also be contained.

[0099] Among them, since high cleanliness is required for the backing paper for glass plates, as the raw material pulp, bleached kraft pulp (LBKP, NBKP) which has been bleached and has reduced the amount of resin components and other components derived from lignin by washing is particularly preferred. In addition, pulp obtained by removing foreign substances through a cyclone dust collector or the like is also preferred.

[0100] These raw material pulps can be any one of deinked pulp, virgin pulp, and a mixture of deinked pulp and virgin pulp.

[0101] Here, virgin pulp is not pulp made from deinked pulp as a raw material, but pulp made from wood as a raw material.

[0102] In order to particularly suppress the contamination of glass plates caused by particles and resin components, it is preferred that the weight ratio of virgin pulp to the total amount of raw material pulp (virgin pulp ratio) is high. For example, the above ratio is preferably 80% or more, preferably 90% or more, and most preferably 100%, that is, the raw material pulp containing only virgin pulp.

[0103] (Density)

[0104] The density of the backing paper for glass plates in this embodiment is the value obtained by dividing the basis weight of the backing paper (g / m 2 ) by the paper thickness (μm). The above density is preferably 0.4 g / cm 3 ~1.6 g / cm 3 , more preferably 0.5 g / cm 3 ~1.4 g / cm 3 , further preferably 0.6 g / cm 3 ~1.2 g / cm 3 , even more preferably 0.7 g / cm 3 ~1.1 g / cm 3 . Here, from the viewpoint of preventing abnormalities such as paper breakage during the manufacturing process by obtaining sufficient strength of the backing paper, the above density is preferably 0.4 g / cm 3 or more, more preferably 0.5 g / cm 3 or more, further preferably 0.6 g / cm 3 or more, particularly preferably 0.7 g / cm 3 or more. In addition, from the viewpoint of improving productivity by reducing the raw materials for each backing paper, the above density is preferably 1.6 g / cm 3 or less, more preferably 1.4 g / cm 3 or less, further preferably 1.2 g / cm 3 or less, particularly preferably 1.1 g / cm 3 or less.

[0105] "Manufacturing Method of Backing Paper for Glass Plates"

[0106] The manufacturing method of the backing paper for glass plates in this embodiment sequentially includes the following processes.

[0107] Process 1: A process of preparing a pulp slurry from natural wood raw pulp as a raw material

[0108] Process 2: A process of forming a backing paper for glass plates from the pulp slurry obtained in the above Process 1

[0109] Hereinafter, each process will be described.

[0110] <Process 1: Preparation Process of Pulp Slurry>

[0111] In Process 1, a pulp slurry is prepared from the pulp as a raw material.

[0112] Specifically, the raw material is diluted with water or the like, and beating is appropriately performed using a conical refiner, a double-disc refiner, etc. to obtain a raw material liquid (pulp slurry).

[0113] A pH regulator is added during the preparation of the pulp slurry. In the present embodiment, the pH regulator preferably contains inorganic particles.

[0114] Preferably, the equivalent circle diameter of the above inorganic particles is 0.2 μm to 30 μm, and more preferably, the proportion of the number of particles with an arithmetic mean height Sa greater than 0.1 μm in the above inorganic particles satisfies 50% or more. Thus, even when the surface of the liner paper for glass plates obtained contains inorganic foreign matters from inorganic particles with an equivalent circle diameter of 0.3 μm to 15 μm, the adhesion on the glass plate surface is suppressed.

[0115] Among the above inorganic particles, the proportion of the number of particles with an arithmetic mean height Sa greater than 0.1 μm is 50% or more, preferably 50% to 100%, more preferably 60% to 100%, and still more preferably 70% to 100%. Here, from the viewpoint of suppressing the adhesion on the glass plate surface, the above proportion is 50% or more, preferably 60% or more, and more preferably 70% or more. The higher the above proportion, the more preferable it is, and it can be 100%, or it can be 95% or less.

[0116] In the present embodiment, as the inorganic particles contained in the pH regulator, calcium carbonate is preferably used. Calcium carbonate is an inorganic particle that exhibits poor solubility or insolubility in the pulp slurry. As described above, the equivalent circle diameter of the inorganic particles containing the calcium carbonate is preferably 0.2 μm to 30 μm, and the proportion of the number of particles with an arithmetic mean height Sa greater than 0.1 μm preferably satisfies 50% or more.

[0117] In addition, the upper limit of the arithmetic mean height Sa of the inorganic particles with an equivalent circle diameter of 0.2 μm to 30 μm is not particularly limited, and examples thereof may include 0.3 μm or less and 0.5 μm or less.

[0118] Using the pulp slurry obtained by adding the pH regulator containing the inorganic particles, through the subsequent process 2, a liner paper for glass plates is obtained, which contains inorganic foreign matters with an equivalent circle diameter of 0.3 μm to 15 μm on its surface and the proportion of the number of foreign matters with an arithmetic mean height Sa greater than 0.1 μm in the above inorganic foreign matters is 50% or more.

[0119] In addition, the number density of the inorganic foreign matters from the inorganic particles is preferably greater than 0 pieces / 5 mm 2 and less than or equal to 50 pieces / 5 mm 2 and more preferably 30 pieces or less / 5 mm 2 and further preferably 25 pieces or less / 5 mm 2 and the less, the more preferable. The above inorganic foreign matters can be adjusted, for example, by the concentration of the inorganic particles used as the pH regulator, that is, the pH when preparing the pulp slurry from the raw pulp.

[0120] When calcium carbonate is used as the above inorganic particles, calcium-containing foreign substances are included as the above inorganic foreign substances.

[0121] As the pH regulator used when preparing the pulp slurry, pH regulators other than calcium carbonate can be used. For example, calcium salts such as calcium bicarbonate, calcium hydroxide, calcium sulfate, and calcium oxalate can be listed. In addition, potassium carbonate, potassium hydroxide, sodium carbonate, sodium hydroxide, aluminum sulfate, etc. can also be listed.

[0122] In addition, when obtaining the pulp slurry, various chemicals other than the pH regulator can be added within the range that does not reduce the quality of the backing paper for glass plates.

[0123] As the chemicals, for example, defoamers, fixing agents, paper strength enhancers, yield improvers, coagulants, surfactants, sizing agents, antistatic agents, slime control agents, dry release agents, polyvinyl alcohol, polyacrylamide, starch, cellulose derivatives such as CMC (carboxymethyl cellulose), fillers (talc, clay, titanium dioxide, etc.), etc. can be listed.

[0124] During beating, the beating conditions can be changed according to the type of pulp used and the target backing paper for glass plates, in other words, the characteristics of the disintegrated pulp, and free beating mainly for fiber cutting (cutting), viscous beating mainly for fiber swelling and fibrillation, etc. can be appropriately carried out.

[0125] <Process 2: Process for manufacturing the backing paper for glass plates>

[0126] In Process 2, the backing paper for glass plates is manufactured from the pulp slurry obtained in the above Process 1. Specifically, for example, a Fourdrinier paper machine, a cylinder paper machine, an inclined wire paper machine, or a twin-wire paper machine is used to manufacture the obtained pulp slurry. Then, the wet paper after passing through the wet part is dehydrated, and a multi-cylinder dryer, a Yankee dryer, etc. are used to dry it. Chemicals can be coated or infiltrated using a roll coater, a knife coater, etc. as needed. In addition, various calenders such as a soft calender and a super calender can be used online or offline.

[0127] 《Glass plate laminate》

[0128] The glass plate laminate of the present embodiment is obtained by laminating multiple glass plates with a backing paper interposed therebetween. As the backing paper here, the backing paper described in the above 《Backing paper for glass plates》 or the backing paper obtained by the method described in the above 《Manufacturing method of the backing paper for glass plates》 can be used, and the preferred mode is the same.

[0129] By laminating the glass plates, the transportation efficiency of the glass plates is improved.

[0130] However, in the above lamination, when the glass plates are brought into contact with each other, there is a possibility of generating scratches on the surfaces of the glass plates. In the case where such scratches are generated on the electronic circuit formation surface of the glass plate, it may cause problems such as disconnection of the wiring.

[0131] In this regard, by laminating the glass plates with a separator paper interposed between the glass plates, it is possible to prevent the generation of scratches on the electronic circuit formation surface of the glass plate.

[0132] The number of laminated glass plates in the glass plate laminate of the present embodiment may be two or more, and can be appropriately changed according to various conditions such as the strength, size, and size of the packaging container of the glass plate. Therefore, there is no particular limitation on the upper limit of the number of laminated glass plates in the glass plate laminate, for example, it is 300 or less. In addition, the total mass of the glass plate laminate is, for example, 2000 kg or less.

[0133] In addition, the number of separator papers in the glass plate laminate can be any one of the same as the number of laminated glass plates, one more, or one less.

[0134] In addition, the composition, shape, size, thickness, etc. of the glass plate can be appropriately changed according to the use.

[0135] For example, as a large glass plate, a glass plate with at least one side being 2400 mm or more can be cited. As a specific example, a glass plate with a long side of 2400 mm or more and a short side of 2000 mm or more can be cited. The above large glass plate is preferably a glass plate with at least one side being 2400 mm or more, for example, a glass plate with a long side of 2400 mm or more and a short side of 2100 mm or more, more preferably a glass plate with at least one side being 3000 mm or more, for example, a glass plate with a long side of 3000 mm or more and a short side of 2800 mm or more, further preferably a glass plate with at least one side being 3200 mm or more, for example, a glass plate with a long side of 3200 mm or more and a short side of 2900 mm or more, and particularly preferably a glass plate with at least one side being 3300 mm or more, for example, a glass plate with a long side of 3300 mm or more and a short side of 2950 mm or more.

[0136] The thickness of the glass plate is preferably 1.30 mm or less. By making the glass plate thinner, the weight of each sheet becomes lighter, so that the number of loaded sheets can be increased, and for example, the etching time during the production of a liquid crystal panel can be shortened.

[0137] The thickness of the glass plate is more preferably 0.75 mm or less, further preferably 0.65 mm or less, and most preferably 0.55 mm or less. The thickness can also be set to 0.10 mm or less or 0.05 mm or less. However, from the viewpoint of preventing deflection caused by its own weight, the thickness is preferably 0.10 mm or more, and more preferably 0.20 mm or more.

[0138] The use of the multiple glass plates in the glass plate laminate of the present embodiment is not particularly limited. However, since there are few foreign substances such as Ca-containing foreign substances adhering to the surface of the glass plate liner paper, it is suitable for uses that require a high degree of cleanliness of the surface.

[0139] Specifically, for example, it is preferably used in glass plates for flat panel displays such as liquid crystal displays, plasma displays, and organic electroluminescent displays, and glass plates used in electronic devices such as solar cells, and more preferably in glass plates for flat panel displays. Additionally, it is more preferably a glass plate for a high-definition display.

[0140] When the glass plate is used for display purposes, the number of pixels is preferably 2K (1920×1080) or more, more preferably 4K (3840×2160) or more, and further preferably 8K (7680×4320) or more. The more the number of pixels, the thinner the wiring. Since the number of pixels increases, it is more likely to be affected by fine foreign substances. Therefore, the effects of the present invention can be further expected.

[0141] 《Glass Plate Package》

[0142] The glass plate package of the present embodiment has a glass plate laminate and a packaging container that houses the glass plate laminate. Here, the glass plate laminate can be the laminate described in the above 《Glass Plate Laminate》, and the preferred embodiments are the same.

[0143] During the transportation and storage of the glass plates, the glass plates and the glass plate liner paper are alternately laminated to form a laminate, which is then housed in a packaging container and then packaged to form a package (glass plate package).

[0144] The glass plate package has a horizontal lamination type in which the glass plates are laminated horizontally and a vertical lamination type in which the glass plates are laminated in an inclined and upright state. The glass plate package of the present embodiment can be applied to either type. Either the vertical lamination type or the horizontal lamination type can adopt a conventionally known lamination type.

[0145] Examples

[0146] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

[0147] Examples 1 and 2 are examples, and Examples 3 and 4 are comparative examples.

[0148] 《Example 1》

[0149] Water was added to commercially available NBKP (100% virgin pulp) prepared as raw material pulp to make a pulp, and commercially available heavy calcium carbonate A (average particle size: 3.1 μm, number ratio of particles with equivalent circle diameter of 0.3 μm to 15 μm: 97%, ratio of arithmetic mean height Sa greater than 0.1 μm: 80%) was further added at 0.75% by mass based on the raw material pulp (bone-dry pulp). Then, it was beaten with a double-disc refiner until the Canadian Standard Freeness (CSF) measured according to JIS P 8121-2:2012 became 500 ml, thereby obtaining a pulp slurry. The obtained pulp slurry was formed using a Fourdrinier paper machine and a multi-cylinder dryer at a forming speed of 400 m / minute, thereby obtaining a backing paper for glass plates.

[0150] 《Example 2》

[0151] A backing paper for glass plates was obtained by operating in the same manner as in Example 1 except that the amount of heavy calcium carbonate A in Example 1 was set to 2.0%.

[0152] 《Example 3》

[0153] A backing paper for glass plates was obtained by operating in the same manner as in Example 1 except that heavy calcium carbonate B (average particle size: 2.1 μm, number ratio of particles with equivalent circle diameter of 0.3 μm to 15 μm: 95%, ratio of arithmetic mean height Sa greater than 0.1 μm: 55%) was used instead of heavy calcium carbonate A in Example 1.

[0154] 《Example 4》

[0155] A backing paper for glass plates was obtained by operating in the same manner as in Example 1 except that light calcium carbonate C (average particle size: 5.0 μm, number ratio of particles with equivalent circle diameter of 0.3 μm to 15 μm: 96%, ratio of arithmetic mean height Sa greater than 0.1 μm: 45%), which is a commercially available synthetic product, was used instead of heavy calcium carbonate A in Example 1.

[0156] 《Evaluation》

[0157] <Cold water extraction pH>

[0158] For the obtained backing paper for glass plates, according to JIS P 8133-1 (2013), the pH value of the electrolyte solution extracted from the backing paper for glass plates with cold water was measured. The results are shown in Table 1.

[0159] <Ca-containing foreign matter>

[0160] The Ca-containing foreign matter contained on any one surface of the obtained backing paper for glass plates was measured.

[0161] Specifically, a laser microscope (manufactured by Keyence Corporation, VK-X3100) and a 50x objective lens were used to observe the surface of the glass plate with a thickness of 5 mm or more covered with backing paper, and the position and area of foreign substances other than cellulose fibers were measured. Then, the equivalent circle diameter was calculated from this area, and the arithmetic mean height Sa based on ISO 25178 was obtained. In addition, by performing image processing on the obtained images, the shape of the foreign substances such as roundness and kurtosis was obtained. A multi-file analysis software (manufactured by Keyence Corporation) was used in various measurements. 2 Next, for foreign substances with an equivalent circle diameter of 0.3 μm to 15 μm observed above, a scanning electron microscope (Scanning Electron Microscopy (SEM)) and a reflection electron detector of an energy dispersive X-ray analysis device (both manufactured by JEOL Ltd., IT-200) installed on the SEM were used, and foreign substances containing 0.5 mass% or more of Ca (calcium) were determined as Ca-containing foreign substances. Then, it was converted to the number density per 5 mm

[0162] (pieces / 5 mm 2 ). 2 )

[0163] It should be noted that during the measurement, the surface was coated with platinum sputtering for analysis. The results are shown in Table 1.

[0164] It should be noted that in the above method, the determination of size, shape, and the amount of Ca element was carried out. However, in cases where the above method cannot be used, it can be measured by other methods within a range not significantly different from the measured values obtained by the above method.

[0165] As other methods, specifically, the following can be listed: changing the lens magnification of the laser microscope, changing the field of view range, or using an SEM with a three-dimensional roughness analysis function during the measurement of surface roughness. In addition, in elemental analysis, it can also be in the form of coating the surface with other metals other than platinum or using a low-vacuum SEM without coating during SEM-EDS measurement. In addition, elemental analysis can also be performed using laser-induced breakdown spectroscopy in the atmosphere without using SEM-EDS.

[0166] <Quality: Adhesion on the Glass Plate Surface>

[0167] The obtained glass plate was sandwiched between two glass plates (manufactured by AGC Inc., AN100) with tissue paper. In order to make the Ca-containing foreign substances on the surface of the tissue paper for the glass plate adhere to the glass plate surface, a pressure equivalent to that of 200 glass plates was applied. The glass plate was placed in a thermo-hygrostat at a temperature of 60 °C and a relative humidity of 60% and left for 20 hours. Then, the glass plate was taken out, and the glass plate surface was cleaned under cleaning conditions including an alkaline shower with pH 12 and a roller brush, and dried with clean dry air. A wiring including Mo / Cu was formed on the obtained glass plate, and then the wire breakage incidence rate was measured to conduct a quality evaluation of the tissue paper for the glass plate.

[0168] The results are shown in Table 1, and the evaluation criteria are as follows.

[0169] ◎: The amount of Ca-containing foreign substances attached is extremely small, and the wire breakage incidence rate caused by such Ca-containing foreign substances is very low, which is very good.

[0170] ○: The amount of Ca-containing foreign substances attached is small, and the wire breakage incidence rate caused by such Ca-containing foreign substances is low, which is good.

[0171] △: The amount of Ca-containing foreign substances attached is a certain amount, and the wire breakage incidence rate caused by such Ca-containing foreign substances is at a medium level, which is slightly poor.

[0172] ×: The amount of Ca-containing foreign substances attached is large, and the wire breakage incidence rate caused by such Ca-containing foreign substances is high, which is poor.

[0173]

[0174] From the results of Example 1 and Example 4, it can be seen that although the number density of Ca-containing foreign substances with an equivalent circle diameter of 0.3 μm to 15 μm, which are difficult to remove when attached to the glass plate surface, is at the same level, Example 1 in which the proportion of the number of foreign substances with an arithmetic mean height Sa greater than 0.1 μm is 50% or more suppresses the adhesion on the glass plate surface better than Example 4 in which this proportion is 35%. The same tendency was also confirmed from the results of Example 2 and Example 3.

[0175] In addition, from the results of Example 1 and Example 2, it can be seen that when the above-mentioned proportion is 50% or more, the smaller the number density of Ca-containing foreign substances with an equivalent circle diameter of 0.3 μm to 15 μm, the smaller the absolute amount of adhesion on the glass plate surface, and the lower the wire breakage incidence rate caused by the Ca-containing foreign substances.

[0176] This application is based on Japanese Patent Application No. 2024-008789 filed on January 24, 2024, the content of which is incorporated herein by reference.

Claims

1. A backing paper for a glass plate, the backing paper for the glass plate comprising pulp as a raw material and having a pair of opposite main surfaces, wherein, the backing paper for the glass plate contains Ca-containing foreign matters with an equivalent circle diameter of 0.3 μm to 15 μm on at least one of the main surfaces, the proportion of the number of foreign matters with an arithmetic mean height Sa greater than 0.1 μm in the Ca-containing foreign matters is 50% or more.

2. The backing paper for a glass plate according to claim 1, wherein, The backing paper for the glass plate contains more than 0 pieces / 5 mm 2 and less than or equal to 50 pieces / 5 mm 2 of the Ca-containing foreign matter.

3. The backing paper for glass plates according to claim 1 or 2, wherein, The Ca-containing foreign matters include at least one selected from the group consisting of calcium carbonate, calcium bicarbonate, calcium hydroxide, calcium sulfate, and calcium oxalate.

4. The backing paper for glass plates according to claim 1 or 2, wherein, The proportion of the number of foreign matters with an arithmetic mean height Sa greater than 0.1 μm in the Ca-containing foreign matters is 70% to 100%.

5. The backing paper for glass plates according to claim 1 or 2, wherein, The backing paper for the glass plate contains more than 0 pieces / 5 mm 2 and less than or equal to 30 pieces / 5 mm 2 of the Ca-containing foreign matter.

6. A glass plate laminate, the glass plate laminate obtained by laminating a plurality of glass plates with a backing paper interposed therebetween, wherein, the backing paper is the backing paper for a glass plate according to any one of claims 1 to 5.

7. The glass laminate according to claim 6, wherein, The plurality of glass plates are glass plates for flat panel displays.

8. A glass plate package, wherein, The glass plate package has the glass plate laminate according to claim 6 or 7 and a packaging container for accommodating the glass plate laminate.

9. A method for manufacturing a backing paper for a glass plate, wherein, The manufacturing method of the backing paper for the glass plate sequentially includes: a step of preparing a pulp slurry from pulp as a raw material, and a step of forming the backing paper for the glass plate from the pulp slurry, adding a pH regulator during the preparation, the pH regulator contains inorganic particles with an equivalent circle diameter of 0.2 μm to 30 μm, the proportion of the number of particles with an arithmetic mean height Sa greater than 0.1 μm in the inorganic particles is 50% or more.

10. The manufacturing method of the backing paper for glass plates according to claim 9, wherein, The inorganic particles are calcium carbonate.

11. The manufacturing method of the backing paper for glass plates according to claim 9 or 10, wherein, On the surface of the obtained glass plate with backing paper, there are more than 0 foreign matters per 5 mm 2 and less than or equal to 50 foreign matters per 5 mm 2 from the inorganic particles.

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