Backing paper for glass sheets, glass sheet laminate, and glass sheet bale

Abstract

The present invention relates to a backing paper for a glass sheet, a glass sheet laminate, and a glass sheet bale, the backing paper for a glass sheet being characterized by a thickness of 30 μm to 150 μm, a smoothness of a major surface of at least one side of the backing paper for a glass sheet of 20 seconds or more, and a compressive elastic modulus K of 1.0 MPa to 8.5 MPa.

Description

TECHNICAL FIELD

[0001] The present application relates to a glass sheet backing paper, a glass sheet laminate, and a glass sheet bale. BACKGROUND

[0002] For example, in a glass sheet used for a flat panel display such as an LCD (Liquid Crystal Display), an OLED (Organic Light-Emitting Diode), and the like, since a fine electronic component or the like is formed on the surface of the glass sheet, a slight scratch or dirt on the surface becomes a cause of a defect such as a wire breakage. Therefore, a high cleanliness is required for the surface of the glass sheet.

[0003] The glass sheet is transported in a state in which a plurality of glass sheets are overlapped for the purpose of improving the transport efficiency. At this time, a glass sheet backing paper (hereinafter, also referred to as "backing paper") is interposed between the glass sheets, and a scratch or the like is prevented from being generated on the surface of the glass sheet during the transport.

[0004] However, since the glass sheet is laminated in a state in which the surface thereof is press-bonded to the backing paper, there is a concern that a particle such as a paper powder or a foreign matter generated from the backing paper is attached to the surface of the glass sheet, or a scratch is generated on the surface of the glass sheet mainly due to an inorganic foreign matter in the backing paper. Therefore, a glass sheet backing paper in which a particle is less likely to be attached to the surface of the glass sheet and in which a scratch generated on the glass sheet is suppressed is sought.

[0005] A glass sheet backing paper having a cured treatment portion and an uncured treatment portion is disclosed in Patent Literature 1, and it is intended to suppress the generation of a particle by making the smoothness of the cured treatment portion 20 seconds or more. In addition, in Patent Literature 2, it is intended to reduce a scratch on a glass sheet by making the smoothness 70 seconds or more.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT LITERATURE

[0008] Patent Literature 1: Japanese Patent Application Laid-Open No. 2016-34843

[0009] Patent Literature 2: Japanese Patent Application Laid-Open No. 2016-35125 SUMMARY

[0010] However, with the high definition of a display in recent years, the width and pitch of a wiring formed on the surface of a glass sheet are finer than in the past, and the quality required for the surface of the glass sheet is higher. Therefore, even if a glass sheet backing paper of Patent Literature 1 or 2 is used, there is a problem that a wire breakage or the like occurs in a wiring on a glass sheet due to the attachment of a particle to the glass sheet or a scratch generated on the surface of the glass sheet, and the quality of the glass sheet backing paper needs to be improved.

[0011] Therefore, in addition to the above-described prior art, a lot of glass sheet backing paper for suppressing the occurrence of scratches on the surface of a glass sheet has been proposed. As one example thereof, there can be cited the glass sheet backing paper disclosed in Japanese Patent Application Publication No. 2016-006240, which is limited in the content of a mineral having a prescribed Mohs hardness or more.

[0012] However, in the case of a glass sheet used in a high-fineness display, even if a backing paper in which only a prescribed Mohs hardness or less foreign matter exists is used, it can become a problem. As a result of intensive studies by the inventors and others, it has been found that even in the case where only a prescribed Mohs hardness or less foreign matter exists, since the particle strength of these foreign matters is large, scratches can sometimes occur on the glass sheet.

[0013] An object of the present application is to provide a glass sheet backing paper which, in correspondence with the high fineness of displays, can reduce the adhesion of particles to a glass sheet and suppress the occurrence of scratches on the surface of the glass sheet.

[0014] (1) The glass sheet backing paper of the present application is characterized in that the thickness is 30 μm to 150 μm, and the smoothness of the major surface of at least one side of the glass sheet backing paper is 20 seconds or more, and the compression elastic modulus K measured on the major surface is 1.0 MPa to 8.5 MPa.

[0015] (2) The glass sheet backing paper according to (1), wherein the arithmetic mean height Sa of the major surface is 2.5 μm or more.

[0016] (3) The glass sheet backing paper according to (1) or (2), wherein the maximum height Sz of the major surface is 45 μm or more.

[0017] (4) The glass sheet backing paper according to any one of (1) to (3), wherein the density of the glass sheet backing paper is 0.4 (g / cm 3 ) to 1.6 (g / cm 3 ), and the smoothness of the major surface is 20 seconds to 400 seconds.

[0018] (5) The glass sheet backing paper according to any one of (1) to (4), wherein the sheet resistance of the glass sheet backing paper is 5.0 x 10 10 (Ω / □) to 5.0 x 10 13 (Ω / □).

[0019] (6) The glass sheet backing paper according to any one of (1) to (5), wherein the compression elastic modulus K (MPa) and the number N (pieces / m 2the product of the number N (pieces / m2) of foreign matters having an average diameter of 10 μm to 50 μm and a particle strength C of 15 (MPa) or more contained in the glass sheet backing paper and the compression elastic modulus K (MPa) is 35.0 or less.

[0020] (7) The glass sheet backing paper according to any one of (1) to (6), wherein the product of the number N (pieces / m2) of foreign matters having an average diameter of 10 μm to 50 μm and a particle strength C of 15 (MPa) or more contained in the glass sheet backing paper and the compression elastic modulus K (MPa) is 15.0 or less. 2

[0021] (8) The glass sheet backing paper according to any one of (1) to (7), wherein the main surface is a surface that comes into contact with an electronic circuit formation surface of a glass sheet.

[0022] (9) A glass sheet laminate in which at least two or more glass sheets are laminated, the glass sheet laminate having the glass sheet backing paper according to any one of (1) to (8) between the glass sheets.

[0023] (10) A glass sheet package having the glass sheet laminate according to (9) and a cradle on which the glass sheet laminate is placed.

[0024] According to the present application, it is possible to provide a glass sheet backing paper that can suppress the attachment of particles to a glass sheet and the occurrence of scratches on the surface of the glass sheet in correspondence with the high refinement of displays. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a graph showing the relationship between Mohs hardness and particle strength.

[0026] Figure 2 is a conceptual view showing one embodiment of a manufacturing method of a glass sheet backing paper.

[0027] Figure 3 is a cross-sectional view showing one embodiment of a cradle on which a glass sheet is placed.

[0028] Figure 4 is a cross-sectional view showing one embodiment of a glass sheet package.

[0029] LIST OF SYMBOLS

[0030] 10... glass sheet package,

[0031] 12... glass sheet laminate

[0032] 14... glass sheet

[0033] 16... glass sheet backing paper

[0034] 18... inclined stage

[0035] 22... base​

[0036] 24 … loading table

[0037] 30 … carrier

[0038] 42 … backing paper roll

[0039] 100 … glass plate backing paper manufacturing apparatus

[0040] 112 … headbox

[0041] 114 … wire section

[0042] 116 … lower wire

[0043] 118 … upper wire

[0044] 120 … pressurizing section

[0045] 124 … dryer section

[0046] 126 … calender section

[0047] 128 … reel

[0048] 130 … large roll

[0049] 134 … cutter

[0050] 136 … winding machine DETAILED DESCRIPTION

[0051] Hereinafter, preferred embodiments of the glass plate backing paper of the present application will be described. The embodiments shown below are examples, and the present application is not construed as being limited to the explanation of these embodiments. Note that the glass plate is also referred to as a glass substrate.

[0052] The glass plate is transported in a state in which at least two or more glass plates are stacked and placed on a carrier from the viewpoint of transport efficiency. An article in which at least two or more glass plates are stacked is referred to as a glass plate stack, and an article in which the glass plate stack is placed on a carrier is referred to as a glass plate bundle.

[0053] In the glass plate stack, if the glass plates contact each other, it is possible that scratches are generated on the surfaces of the glass plates. It is known that in the case where such scratches are generated on the circuit formation surface of the glass plate, problems such as disconnection are caused. Therefore, by interposing the glass plate backing paper between the glass plates, generation of scratches on the circuit formation surface of the glass plate is prevented.

[0054] However, it is possible that particles generated from the backing paper adhere, or that scratches are generated on the surface of the glass plate mainly due to inorganic foreign matter in the backing paper. In recent years, with the high definition of displays, the width and pitch of the wiring formed on the surface of the glass plate are finer than in the past, and the quality required of the surface of the glass substrate is higher. Therefore, even if a backing paper for a glass plate that was not a problem in the past is used, problems such as disconnection of the wiring on the glass plate can occur.

[0055] The present inventors discovered that by making the smoothness of the backing paper a certain value or more, even for a high-definition display, it is possible to suppress adverse conditions due to the adhesion of particles. However, even in cases where the smoothness of the backing paper is increased to reduce the amount of adhesion of particles, scratches generated on the surface of the glass plate can sometimes become a problem. Therefore, it is required to suppress the adhesion of particles and the generation of scratches on the surface of the glass plate.

[0056] Therefore, the present inventors investigated scratches that are a cause of disconnection and the like. As a result, it was found that the cause is foreign matter with an average diameter of 10 μm or more and a particle strength C of 15 (MPa) or more. Among these, in particular, scratches generated due to foreign matter with an average diameter of 10 μm to 50 μm and a particle strength C of 15 (MPa) or more are scratches that were not a problem in the past. However, with the high definition of displays, the quality required of the surface of the glass substrate is higher, and as a result, scratches generated due to these foreign matter can also become a problem.

[0057] Note that if the foreign matter has an average diameter of less than 10 μm, it is easy to be buried in the backing paper for a glass plate, and therefore, it is considered that it is not easy to become a cause of scratching the glass plate. Also, if the foreign matter has a particle strength C of less than 15 (MPa), it is considered that even if the foreign matter is pressed into the glass plate, it is not easy to scratch. Also, even in cases where scratches are generated, the size is small, and therefore, it is considered that it is not easy to cause disconnection and the like. Therefore, it is important to make the backing paper in which foreign matter with an average diameter of 10 μm to 50 μm and a particle strength C of 15 (MPa) or more contained in the backing paper is controlled to be reduced.

[0058] The foreign matter in the backing paper is pulp that is a raw material of the backing paper; dust generated from the manufacturing device of the backing paper; and impurities contained in the water used in the production process of the backing paper, which are mixed in the backing paper without being removed by a filter or the like. Also, substances added as additives in the process of producing backing paper other than the backing paper for a glass plate remain in the surface of a roll contacted when the paper passes, and the like, and in the production of the backing paper for a glass plate, foreign matter can also be mixed in the backing paper for a reason such as adhesion to the surface of the backing paper or the like, and among the mixed foreign matter, there can be foreign matter with a particle strength C of 15 (MPa) or more. Therefore, it is difficult to completely eliminate foreign matter with an average diameter of 10 μm to 50 μm and a particle strength C of 15 (MPa) or more.

[0059] Therefore, the inventors focused on the cushioning property of the backing paper. The cushioning property of the backing paper is defined by the compressive elastic modulus K (MPa) in the thickness direction of the backing paper. The smaller the value of the compressive elastic modulus K (MPa), the higher the cushioning property, and the larger the value, the lower the cushioning property. The inventors conducted intensive studies, and as a result, found that the higher the cushioning property of the backing paper, the more the scratches caused by the foreign matter having an average diameter of 10 μm to 50 μm and a particle strength C of 15 (MPa) or more can be suppressed even when the foreign matter is mixed into the backing paper.

[0060] It is considered that this is because the higher the cushioning property of the backing paper, the more easily the foreign matter is buried in the backing paper when the glass sheets are laminated, and therefore, the scratches caused by the foreign matter having an average diameter of 10 μm to 50 μm and a particle strength C of 15 (MPa) or more are reduced.

[0061] (Pulp of raw material)

[0062] The kind of the pulp of raw material is not particularly limited, and a pulp having the properties required as the backing paper can be appropriately used. For example, 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 chemithermomechanical pulp (CGP) and semi-chemical pulp (SCP); non-wood fiber pulps using esparto, yellow poplar, mulberry, willow, hemp, and the like as raw materials; synthetic pulp, synthetic fiber, and deinked pulp (DIP) can be given. The pulp can be bleached or unbleached, and for example, bleached kraft pulp of hardwood (LBKP), bleached kraft pulp of softwood (NBKP), unbleached kraft pulp of hardwood (LUKP), and unbleached kraft pulp of softwood (NUKP) can be used. In addition, carbon nanofiber (CNF) can also be included. These pulps of raw material can be deinked pulp, virgin pulp, or a mixture of deinked pulp and virgin pulp. In order to particularly suppress the contamination and scratches of the glass sheet caused by particles and foreign matter, LBKP and NBKP subjected to bleaching treatment are particularly preferred, and further, a pulp subjected to foreign matter removal using a cyclone, a floatation device, or the like is further preferred. The foreign matter in the pulp refers to a substance other than the fiber component contained in the pulp. In the pulp, foreign matter such as compounds of SiC, ZrO2, Al2O3, TiO2, SiO2, Fe, Fe2O3, Cr, Ni, CaF2, MgO, CaCO3, Al, Cu, and the like and their alloys, resins such as aromatic polyether ketone (PEEK), polyphenylene sulfide (PPS), ultrahigh molecular weight polyethylene (UPE), and epoxy resin, and the like are sometimes mixed. It is considered that they are mixed from minerals and devices in the process from the felling of the tree to the manufacture of the pulp from the pulp chips.

[0063] (Method for manufacturing backing paper for glass sheet)

[0064] Using Figure 2 A conceptual diagram illustrating one embodiment of a manufacturing method of a backing paper for a glass sheet is shown.

[0065] In the manufacturing apparatus 100 of the backing paper for a glass sheet, a raw material slurry (a slurry-like liquid obtained by diluting and dissociating paper pulp with water) of the backing paper for a glass sheet is supplied in a sheet shape from a headbox 112 to a lower wire 116 provided to a wire section 114 after being beaten. The raw material slurry supplied to the lower wire 116 is then sandwiched by the lower wire 116 and an upper wire 118, thereby being expanded to a uniform thickness and being dewatered to become a wet paper (paper).

[0066] The lower wire 116 and the upper wire 118 of the wire section 114 are formed as a permeable film in a loop shape. Specifically, it is a loop-shaped belt made of a net of plastic or metal material, or a felt made of natural fiber or synthetic fiber.

[0067] The lower wire 116 and the upper wire 118 are hung on a plurality of rollers, and are moved in a loop shape at a predetermined speed by transmitting a driving force of a motor (not shown) to a driving roller among the plurality of rollers.

[0068] The wet paper formed by the wire section 114 is transported to a pressurizing section 120 including a pressurizing roller, a loop-shaped felt, and a pressurizing roller pair, and is further dewatered and pressurized therein.

[0069] The wet paper that has passed through the pressurizing section 120 is transported to a dryer section 124 including a plurality of rollers, and is dried in an atmosphere of, for example, about 120°C while passing through the dryer section 124.

[0070] When the wet paper is directly transported at a high speed while passing through the dryer section 124, there is a concern that the paper will be torn, and therefore the wet paper is transported while being in contact with an auxiliary member called a canvas.

[0071] The paper dried by the dryer section 124 is transported to a calender section 126, and a predetermined linear pressure is applied to the paper by sandwiching and transporting the paper using a calender roller, thereby smoothing the front and back surfaces. Various calendering such as soft calendering, hard calendering, super calendering, and hot calendering can be used in the calendering process, and is not limited to be used in-line, but can be used off-line. In addition, it can be multi-stage calendering. Note that a coater section can be provided between the dryer section 124 and the calender section 126 as needed, and a paint or the like can be applied to the surface of the smoothed paper.

[0072] The paper on which the calendering process is performed in the calender section 126 is wound on a reel 128 as a backing paper for a glass sheet, and is manufactured in a roll shape (hereinafter, a large roll 130).

[0073] The glass sheet backing paper made into the large roll 130 is usually cut to correspond to the width of the product, for example, wound into a backing paper roll 42 in which a long strip of glass sheet backing paper of a prescribed length of about 8000 m to 10000 m is wound.

[0074] The glass sheet backing paper is fed from the large roll 130, cut to a prescribed width (cut in the longitudinal direction) by the cutter 134, and wound by the winding machine 136. At the time when the glass sheet backing paper fed from the large roll 130 becomes a prescribed length, it is cut to a prescribed length (cut in the width direction) by the cutter 134, and made into the backing paper roll 42 in which a long strip of glass sheet backing paper is wound in a prescribed width.

[0075] The long strip of glass sheet backing paper wound in the backing paper roll 42 is cut into a cut piece shape (rectangular shape) corresponding to the size of the laminated glass sheet, and interposed between the laminated glass sheets.

[0076] (Thickness of backing paper)

[0077] The thickness of the backing paper can be measured according to the paper thickness measurement prescribed in JIS P8118:2014. The measurement can use, for example, an automatic lifting paper thickness meter (Kumagai Rikagaku Kogyo, TM-600).

[0078] Here, if the backing paper is too thin, even in the case where the cushioning property of the backing paper is high, foreign matter does not get buried in the backing paper, and thus, scratches are easily generated. In addition, since the strength of the backing paper becomes weak, paper dust and the like are easily generated at the time of manufacturing the backing paper, and the production efficiency is reduced. Therefore, the thickness of the glass sheet backing paper of the present application is 30 μm or more, preferably 40 μm or more, more preferably 50 μm or more, and further preferably 60 μm or more. In addition, if the backing paper is too thick, the volume and weight of the backing paper increase, and thus, the number of glass sheets that can be laminated in the carrier becomes small. Therefore, the thickness of the glass sheet backing paper of the present application is 150 μm or less, preferably 140 μm or less, more preferably 130 μm or less, and further preferably 120 μm or less.

[0079] (Compressive elastic modulus)

[0080] The compressive elastic modulus K (MPa) of the backing paper of the glass sheet according to the present application is 1.0 MPa to 8.5 MPa. The smaller the compressive elastic modulus K, the higher the cushioning property of the backing paper, and thus the scratch caused by foreign matter having an average diameter of 10 μm to 50 μm and a particle strength C of 15 (MPa) or more can be suppressed. Here, the electronic circuit formation surface is particularly required to be suppressed from being attached with particles and scratched. Therefore, if the compressive elastic modulus K (MPa) of the main surface of the side of the backing paper which contacts the electronic circuit formation surface and the portion which contacts the glass sheet is within the above range, the effect of the present application can be exerted. The compressive elastic modulus K (MPa) is more preferably 8.0 MPa or less, further preferably 5.0 MPa or less, particularly preferably 3.0 MPa or less, and most preferably 2.0 MPa or less. The lower limit of the compressive elastic modulus of the backing paper is 1.0 MPa or more. If the compressive elastic modulus of the backing paper is 1.0 MPa or more, an improvement in durability can be expected. Note that in the present specification, the compressive elastic modulus K (MPa) of the backing paper is measured by the following method.

[0081] (Measurement method of compressive elastic modulus)

[0082] The compressive elastic modulus of the backing paper can be measured using, for example, a constant pressure thickness tester (TECLOCK, PG-02J). The paper thickness when a load corresponding to a pressure PI (kPa) is applied to the substantially central portion of the backing paper is set as Tl (μm), the paper thickness when a load corresponding to a pressure P2 (kPa) is applied to the substantially central portion of the backing paper is set as T2, and the (strain) = (Tl - T2) / Tl (dimensionless) is calculated. Then, the (compressive elastic modulus) = (P2 - PI) / (strain x 10 －3 ) (MPa) is calculated. Note that in the present specification, PI = 100 (kPa), and P2 = 270 (kPa).

[0083] The compressive elastic modulus K of the backing paper can be controlled mainly by the apparent density and the density of the outermost layer of the backing paper. The apparent density is the density of a piece of paper. Generally, the greater the weight per unit area, the thicker the paper thickness, but the lower the density of the backing paper is formed by reducing the weight per unit area and increasing the thickness, and the smaller the compressive elastic modulus K, that is, there is a tendency for the cushioning property to be higher. As a method of increasing the thickness of the backing paper under the same weight per unit area, the proportion of the long fiber-containing rate of coniferous pulp in the raw material can be increased; the beating amount can be adjusted to increase the freeness of the raw material pulp; an expanding agent or the like can be added. Note that in order not to contaminate the glass sheet, the amount of the reagent such as the expanding agent added is preferably small.

[0084] As for the density of the surface layer, the pressure applied to the paper by the calendering rolls in the calendering section (hereinafter referred to as "nip pressure") is controlled. That is, the smaller the nip pressure during the calendering and conveying in the calendering section 126, the smaller the compressive elastic modulus, and a backing paper with high cushioning properties can be obtained. However, this operation is in the direction of reducing the adhesion between fibers, and there is a possibility that the increase in the particles generated by the backing paper will be caused. Therefore, it is preferable to reduce the apparent density of the backing paper, and on the other hand, to make the surface hard, and to produce a backing paper having cushioning properties as a whole. The compressive elastic modulus K is not necessarily consistent with the apparent density, but this is also affected by the density of the surface layer, and therefore, it can be inferred that the more the density difference in the paper layer direction of the backing paper is generated, the more the compressive elastic modulus K and the apparent density deviate from each other.

[0085] By increasing the temperature of the surface of the hot roll, the nip pressure, the contact time, the number of nips, and the like in the hot calendering process, a highly smooth paper can be obtained. On the other hand, the increase in the nip pressure, the contact time, and the number of nips reduces the bulkiness. Here, by applying a temperature higher than the temperature of the paper web to the hot roll, the temperature gradient in the thickness direction of the paper web becomes large, the plastic deformation of the surface of the paper layer is promoted, and the inside of the paper layer becomes less likely to be plastically deformed, and therefore, when the hot roll is at a high temperature, a backing paper with bulkiness and cushioning properties is easily produced, and is suitable for the present application. For the same reason, by reducing the temperature of the paper web before the calendering process is performed, the temperature gradient can be further increased, and is therefore further preferable. As a method of performing cooling, methods using air, water, and a cooling roll can be given. It should be noted that by applying a small amount of water to the paper web, immediately performing low-temperature drying air blowing to dry it, and taking away the heat of evaporation, the paper web can be cooled, and when the calendering process is performed, the calendering process with a large temperature gradient can be performed before capillary penetration of water into the inside of the paper layer occurs, and therefore, the inside of the paper layer can be inhibited from being plastically deformed to form bulkiness, and is therefore particularly preferable. By setting the time during which water acts to be a very short time, the process can be performed without causing roughening accompanied by the breaking of the bonds between fibers and the deformation of the fibers.

[0086] In addition, it is known that in hot soft calendering, the paper on the side of the metal hot roll and the paper on the side of the resin elastic roll differ in the degree of increase in smoothness. Such a process can particularly increase the smoothness of the surface on one side, and therefore, is suitable for obtaining a backing paper in which the surface of the backing paper is highly smooth and the entire backing paper is low in density. In one embodiment of the present application, the temperature suitable for obtaining a highly smooth paper is 25°C to 250°C. The higher the temperature, the higher the smoothing effect that can be obtained, but if it exceeds 250°C, problems such as discoloration of the paper, unevenness in the width direction of the smoothing, and the like easily occur, and in addition, the degradation of the elastic roll is accelerated. Smoothing can be performed even at less than 100°C, but the smoothing using the temperature gradient described above becomes insufficient, and therefore, particularly in the case where a backing paper with a smoothness exceeding 100 seconds is obtained, it is preferable to be 100°C or higher.

[0087] Further, in one embodiment of the present application, the nip pressure suitable for obtaining a highly smooth paper is, for example, 5 kN / m to 350 kN / m. When the nip pressure is less than 5 kN / m, the smoothing is insufficient, and when it exceeds 350 kN / m, the deterioration of the elastic roller easily occurs. Further, as a method for exerting the same effect, a paper having a plurality of densities can be joined to constitute.

[0088] By thus designing the kind of the calender treatment, the temperature and the nip pressure in the calender treatment, and the like, a backing paper having a high smoothness on the surface and a small compressive elastic modulus can be obtained.

[0089] (Smoothness)

[0090] The smoothness of the main surface of at least one side of the backing paper for a glass sheet according to the present application is 20 seconds or more. The smoothness of the backing paper indicates the unevenness of the surface of the backing paper including the height of several μm to several mm, and the unevenness of the fibers therebelow, and becomes highly smooth by causing the fibers to adhere to each other.

[0091] This can be achieved by, for example, using a pulp having a short fiber length to eliminate the voids between the fibers; enhancing beating to enhance the entanglement of the fibers; reducing the surface roughness of the drying cylinder in the drying process; improving the cleanliness; controlling the papermaking speed and the humidifying and dehumidifying environment to perform papermaking while adjusting the humidity; and increasing the nip pressure of the calender treatment. The higher the smoothness, the more the fibers adhere to each other and to foreign matter, and thus the generation of particles such as paper dust and foreign matter from the paper surface is suppressed.

[0092] In the case where the smoothness is increased by performing the calender treatment on the backing paper at a high nip pressure, the compressive elastic modulus K tends to increase because the backing paper is crushed. However, in the case where the smoothness of the backing paper is less than 20 seconds, particles easily occur. Therefore, by designing not only the nip pressure but also the kind of the calender treatment, the temperature in the calender treatment, and the like as described above, the smoothness can be made 20 seconds or more, and the compressive elastic modulus K can be made 1.0 MPa to 8.5 MPa, and both the suppression of particles and the suppression of scratches can be taken into account.

[0093] Here, the electronic circuit formation surface is particularly required to suppress contamination, that is, to suppress the adhesion of particles, in the glass sheet. Therefore, if the smoothness of the portion of the main surface of the side of the backing paper which contacts the electronic circuit formation surface and which contacts the glass sheet is 20 seconds or more, the effect of the present application can be exerted.

[0094] However, in the case where the smoothness is excessively high, the adhesion of the backing paper becomes high, and the backing paper is adhered to the glass sheet or the conveying roller due to static electricity. Therefore, for example, at the time of taking out the glass sheet from the glass sheet laminate (hereinafter, also referred to as "unpacking"), the backing paper is easily adhered to the glass sheet or the like, and the like, and thus, the smoothness of the surface of the backing paper is preferably 400 seconds or less, more preferably 100 seconds or less, further preferably 70 seconds or less, and particularly preferably 50 seconds or less. If the smoothness of the surface of the backing paper is the above upper limit or less, the occurrence of the backing paper being adhered to the glass sheet or the like at the time of unpacking can be reduced.

[0095] In the present specification, the smoothness is measured by the measurement method described in the Examples described later.

[0096] Note that the measurement position of the smoothness is not particularly limited as long as the measurement is performed at a position of the backing paper that can be in contact with the glass sheet, and the measurement is performed at, for example, the substantially central portion of the backing paper.

[0097] (Sheet Resistance (Ω / D)

[0098] The present inventors and the like have conducted intensive studies, and as a result, it has been found that the adhesion of the backing paper to the glass sheet is associated with the electrification property of the backing paper. The electrification property of the backing paper can be represented by the sheet resistance (surface resistivity) of the backing paper. The sheet resistance represents the resistance value per unit area (1 cm 2 ) of a thin film such as paper or a film. The greater the sheet resistance, the lower the conductivity, and the more easily the electrification. The sheet resistance is mainly affected by the moisture content of the backing paper, but even if the moisture content is the same, the conductivity characteristics differ depending on the state of the fibers such as the thickness, the entanglement mode, the orientation, the components contained, the thickness of the backing paper, and the like, and the value of the sheet resistance can be controlled by the combination thereof. The more the moisture content, the denser the fibers, and the smaller the sheet resistance. In addition, in order to reduce the sheet resistance, an antistatic agent can be added within a range that does not decrease the quality of the backing paper. The sheet resistance can be measured, for example, using Hiresta-UX MCP-HT800 (manufactured by Mitsubishi Chemical Analysis and Technology Corporation).

[0099] In the backing paper for a glass sheet of the present application, the sheet resistance is 5.0 x 10 13 Ω / D or less, and thus, the occurrence of the backing paper being adhered to the glass sheet or the like can be reduced. Therefore, the sheet resistance of the backing paper is preferably 5.0 x 10 13 Ω / D or less, more preferably 2.5 x 10 13 Ω / D or less, and further preferably 1.0 x 10 13 Ω / D or less. If the sheet resistance of the backing paper is the above upper limit or less, the occurrence of the backing paper being adhered to the glass sheet or the like at the time of unpacking can be further reduced.

[0100] In a case where the sheet resistance of the backing paper is too low, the backing paper does not sufficiently adhere to the glass sheet when the backing paper is filled in the vertical holder, and sometimes, an adverse condition such as peeling of the backing paper occurs. In addition, as a result of trying to reduce the sheet resistance of the backing paper and increase the water retention amount of the backing paper, sometimes, an adverse condition such as excessive adhesion of the backing paper and the glass via moisture occurs. Therefore, the sheet resistance of the backing paper for a glass sheet according to the present application is preferably 5.0 x 10 10 Ω / □ or more, more preferably 7.5 x 10 10 Ω / □ or more, further preferably 1.0 x 10 11 Ω / □ or more. If the sheet resistance of the backing paper is the above lower limit or more, it is possible to reduce the occurrence of adverse conditions such as peeling of the backing paper, excessive adhesion, and the like.

[0101] (Hard Foreign Matter Resistance Value)

[0102] The hard foreign matter resistance value is defined by the product KN of the compressive elastic modulus K (MPa) and the number N (pieces / m2) of foreign matters having an average diameter of 10 μm to 50 μm and a particle strength C of 15 (MPa) or more contained in the above-mentioned backing paper. 2

[0103] The smaller the hard foreign matter resistance value KN of the backing paper, the fewer foreign matters having an average diameter of 10 μm to 50 μm and a particle strength C of 15 (MPa) or more that become the cause of scratches, or the smaller the compressive elastic modulus K, it is possible to further reduce scratches generated on the glass sheet. The above-mentioned hard foreign matter resistance value is preferably 35.0 or less, more preferably 30.0 or less, further preferably 15.0 or less, particularly preferably 10.0 or less, and most preferably 5.0 or less. If it is desired to reduce the hard foreign matter resistance value KN, it is necessary to suppress the mixing of foreign matters in the manufacturing process, and the manufacturing cost increases. Therefore, the lower limit value of the hard foreign matter resistance value KN is preferably 0.1 or more, and more preferably 0.5 or more.

[0104] (Foreign Matter Having an Average Diameter of 10 μm to 50 μm and a Particle Strength C of 15 (MPa) or More)

[0105] In the present specification, as an evaluation of foreign matters, a particle strength is used. As an evaluation of foreign matters in the backing paper other than the particle strength, for example, there is a method using Mohs hardness, which is used in Japanese Patent Application Publication No. 2016-006240 and the like. Mohs hardness defines the hardness of an object by which scratches are generated when one object is scratched with another object, and is a scale for comparing the hardness of bulk minerals with each other. In addition, since Mohs hardness is a relative value, even if the same Mohs hardness value is used, it is not necessarily the same hardness (particle strength), and it is not possible to quantitatively express which one is more likely to generate scratches. In fact, it is not possible to know without scratching the objects with each other.

[0106] ​Here, the inventors et al. investigated the relationship between the particle strength and the Mohs hardness, and the results are shown in Table 1. Figure 1 is a chart showing the results of measuring the particle strength of a plurality of particles with respect to minerals of generally known Mohs hardness and various components considered to be the minute foreign matter in the backing paper. Figure 1 is a box plot showing the first quartile, the second quartile, the third quartile, the maximum value, the minimum value, the arithmetic mean, and the outlier.

[0107] The outlier refers to data of a number greater than the third quartile plus the quartile range (the difference between the third quartile and the first quartile) multiplied by 1.5 times, or data of a number less than the first quartile minus the quartile range multiplied by 1.5 times.

[0108] The maximum value refers to the largest value among the data excluding the outlier. The minimum value refers to the smallest value among the data excluding the outlier. In the box plot of Figure 1 , the outlier is indicated by a white circle, and the arithmetic mean is indicated by a black circle.

[0109] The inventors et al. found that, as shown in Figure 1 , the magnitude of the particle strength of the minute foreign matter approximately matches the sequence of the magnitude of the Mohs hardness, but is not necessarily consistent, and there are cases in which the value of the Mohs hardness and the value of the particle strength are reversed, and even for the same kind of particle, the deviation of the particle strength is large.

[0110] It is presumed that these are caused by the different manner of generation of each particle, the different density and orientation state of the crystallite, the presence of a void, and the like. Therefore, even in the case in which only a specific foreign matter below the Mohs hardness is present, there is a possibility that scratches are generated in the glass sheet due to the large particle strength of the foreign matter.

[0111] In such a case, even in the case in which it does not become a problem in the conventional glass sheet for a display, there is a possibility that it becomes a problem in the case of a glass sheet for a high-definition display. According to the above research, it is considered that the hardness of the minute foreign matter that generates scratches in the glass sheet is preferably represented by the particle strength, as compared to being represented by the representative value based on the Mohs hardness.

[0112] The foreign matter existing on the surface of the backing paper is observed from the thickness direction of the backing paper, the long diameter and the short diameter of the shape of the foreign matter are measured, and the average diameter of the foreign matter is the average of the sum of the measured long diameter and short diameter. As the foreign matter having a particle strength C of 15 MPa or more, there are SiC, ZrO2, Al2O3, TiO2, SiO2, Fe, Fe2O3, Cr, Ni, CaF2, MgO, CaCO3, Al, Cu, and the like, compounds and alloys thereof, resins such as PEEK, PPS, UPE, and epoxy resin, but even if the composition is the same, the particle strength varies, and thus even the above foreign matter needs to be measured for the particle strength.

[0113] As a method for reducing the number N (pieces / m 2 ) of foreign matter having an average diameter of 10 μm to 50 μm and a particle strength C of 15 (MPa) or more in the backing paper, there are a method of using a pulp having a small amount of foreign matter; a method of removing a magnetic substance using a magnetic filter; a method of removing a small ore and dust from the pulp by applying a centrifugal force; and a method of removing the foreign matter by adsorbing it to a fine bubble using a floatation device. In addition, the number N (pieces / m 2 ) of the above foreign matter can be reduced by a method of removing the foreign matter contained in the water of the raw material by filtration or the like; and a method of preventing dust from being mixed in by performing a papermaking process in a clean room in the manufacturing process of the backing paper. As the method of using a pulp having a small amount of foreign matter, there are a method of selecting a pulp having a small amount of ash, and a method of selecting a pulp having a small amount of inorganic elements measured by fluorescent X-ray.

[0114] The number N (pieces / m 2 ) of the foreign matter is preferably 10.0 or less, more preferably 5.0 or less, further preferably 1.0 or less, particularly preferably 0.1 or less, and most preferably 0.01 or less. The lower limit of the number N (pieces / m 2 ) of the foreign matter is not particularly limited, and is, for example, 1.0 x 10 －6 Even if the countermeasures for preventing the mixing of foreign matter as described above are taken, it is difficult to completely eliminate the foreign matter having an average diameter of 10 μm to 50 μm and a particle strength C of 15 (MPa) or more.

[0115] The number N (pieces / m 2) can be measured by the following method using a micro compression tester. For example, measurement is performed using a laser microscope (Keyence, VK-8500) and a micro compression tester (Shimadzu Corporation, MCT-510). The backing paper is set on a stage, and 1600 regions are measured, for example, in an area of 1 field of view of 2 mm x 1.4 mm. At this time, the measurement can be performed by moving 1 field of view at a time using the teaching function of the microscope, and the automatic measurement of the next field of view. Next, for each foreign matter in the measured region, the size is calculated from the number of pixels, and particles having an average diameter of 10 μm to 50 μm are selected. The particle strength C can be measured by placing the foreign matter on the stage of the micro compression tester, measuring the particle strength C one by one, and counting the number of particles having a particle strength C of 15 (MPa) or more, and converting the number to 1 m 2 The number N (pieces / m2) of the existing foreign matters can be measured. 2 ) can be measured.

[0116] Note that the particle strength C used here is not limited to the strength measured using the micro compression tester, and for example, can be the hardness of the particle estimated from the indentation depth using a nanoindenter, or the hardness of the particle measured using a micro Vickers hardness tester.

[0117] (arithmetic average height Sa (μm))

[0118] The arithmetic average height Sa is a parameter in which the arithmetic average height Ra of a line is extended to a plane, and represents the average of the absolute values of the differences between the average of the heights of the surface of the backing paper and the heights of the respective points. The arithmetic average height Sa is generally used in evaluating the roughness of a surface.

[0119] When the arithmetic average height Sa of the backing paper is large, there is a tendency that the smoothness of the backing paper becomes small. However, if the smoothness of the backing paper is less than 20 seconds, particles are easily generated. By making the arithmetic average height Sa of the backing paper be a certain value or more, and making the smoothness be 20 seconds or more, both the suppression of particles and the suppression of scratches can be taken into account.

[0120] Therefore, the smoothness of the backing paper is 20 seconds or more, and the arithmetic average height Sa of the main surface of at least one side of the backing paper is preferably 2.5 μm or more, and more preferably 3.0 μm or more. If the arithmetic average height Sa of the backing paper is the above lower limit or more, the foreign matters existing in the backing paper are easily buried, and the suppression of scratches caused by pressing the foreign matters can be expected. The upper limit of the arithmetic average height Sa of the backing paper is preferably 8.0 μm or less, more preferably 6.0 μm or less, and further preferably 4.0 μm or less. If the arithmetic average height Sa is the above upper limit or less, the generation of particles can be suppressed.

[0121] Here, the side of the two main surfaces of the backing paper which is in contact with the electronic circuit formation surface of the glass plate is particularly important in terms of suppressing the attachment of particles and scratches in the glass substrate. Therefore, the arithmetic mean height Sa of the side of the two main surfaces of the backing paper which is in contact with the electronic circuit formation surface of the glass plate is particularly important.

[0122] The arithmetic mean height Sa is the average of the arithmetic mean heights of the respective fields of view. The arithmetic mean height Sa can be measured using a known measuring machine such as a laser microscope (Keyence, VK-8500) or the like.

[0123] (Maximum height Sz (μm))

[0124] The maximum height indicates the distance from the highest point to the lowest point on the surface of the backing paper. The maximum height Sz is the average of the maximum heights of the respective fields of view. The maximum height Sz can be measured using a known measuring machine such as a laser microscope (Keyence, VK-8500) or the like.

[0125] When the maximum height Sz of the backing paper is large, there is a tendency for the smoothness of the backing paper to be small. However, if the smoothness of the backing paper is less than 20 seconds, particles are easily generated. By making the maximum height Sz of the backing paper be a certain value or more and making the smoothness be 20 seconds or more, it is possible to take into account both the suppression of particles and the suppression of scratches.

[0126] Therefore, the smoothness of the backing paper is 20 seconds or more, and the maximum height Sz of at least one side of the main surfaces of the backing paper is preferably 45 μm or more, more preferably 50 μm or more. If the maximum height Sz of the backing paper is the above lower limit or more, foreign matter present in the backing paper is easily buried, and it is possible to expect the suppression of scratches caused by pressing the foreign matter against the surface of the backing paper. In addition, the upper limit of the maximum height Sz of the backing paper is preferably 80 μm or less, more preferably 65 μm or less, and further preferably 54 μm or less. If the maximum height Sz is the above upper limit or less, it is possible to suppress the generation of particles.

[0127] Here, the side of the two main surfaces of the backing paper which is in contact with the electronic circuit formation surface of the glass plate is particularly important in terms of suppressing the attachment of particles and scratches in the glass substrate. Therefore, the maximum height of the side of the two main surfaces of the backing paper which is in contact with the electronic circuit formation surface of the glass plate is particularly important.

[0128] (Density of backing paper)

[0129] The density of the backing paper is a value obtained by dividing the weight per unit area (g / m 2 ) of the backing paper by the thickness (μm) of the paper. The density of the backing paper is preferably 0.4 (g / cm3 ) above, more preferably 0.5 (g / cm 3 ) above, further preferably 0.6 (g / cm 3 ) above, particularly preferably 0.7 (g / cm 3 ) above. If the density of the backing paper is above the lower limit described above, a backing paper of sufficient strength can be obtained, and thus, abnormalities such as paper dust are less likely to occur during the manufacturing process. In addition, the density of the backing paper is preferably 1.6 (g / cm 3 ) below, more preferably 1.4 (g / cm 3 ) below, further preferably 1.2 (g / cm 3 ) below, particularly preferably 1.1 (g / cm 3 ) below. If the density of the backing paper is below the upper limit described above, the amount of raw materials can be reduced, and thus, the productivity is increased.

[0130] (Glass plate laminated body)

[0131] The glass plate laminated body of the present embodiment has at least two or more glass plates laminated with the backing paper for glass plate of the present invention between the glass plates.

[0132] (Glass plate bale)

[0133] The glass plate bale of the present embodiment has a glass plate laminated body and a cradle on which the glass plate laminated body is placed, the glass plate laminated body having at least two or more glass plates laminated with the backing paper for glass plate of the present invention between the glass plates.

[0134] Figure 3 A cross-sectional view showing one embodiment of a cradle on which a glass plate is placed. Figure 4 A cross-sectional view showing one embodiment of a glass plate bale.

[0135] Figure 4 The glass plate bale 10 shown has a glass plate laminated body 12 and a cradle. The glass plate laminated body 12 has the backing paper for glass plate 16 between the glass plate 14 and another glass plate 14 adjacent thereto. Figure 3 The cradle 30 shown is a publicly known cradle for glass plate bales, and has a base 22, an inclined stage 18 provided on the upper surface of the base, and a placement stage 24. The angle θ of the placement stage 24 with respect to the inclined stage 18 is not particularly limited as long as the glass plate can be stably loaded, and is preferably 90°.

[0136] The angle γ of the inclined stage 18 is the angle of the inclined stage 18 with respect to the horizontal plane. That is, as shown in FIG. 2, the angle γ is the angle of the inclined stage 18 with respect to the horizontal plane when the inclined stage 18 is viewed from the direction of the arrow A. Figure 3In the case where the upper surface of the base 22 provided with the inclined stage 18 and the placement stage 24 is horizontal, the angle γ of the inclined stage 18 refers to the angle of the inclined stage 18 with respect to the base 22. The closer the angle γ of the inclined stage 18 is to 90°, the more space is saved, but a greater pressure is applied to the end surface of the glass plate, and thus, a breakage or the like can occur. In addition, the closer the angle γ of the inclined stage 18 is to 0°, the more the pressure applied to the glass plate is dispersed, and an end surface breakage or the like can be suppressed, but a greater space is required, and thus, the efficiency of storage and transportation decreases. In the present specification, a cradle in which the angle of the inclined stage is 10° or less is referred to as a flat-stacked cradle, and a cradle in which the angle exceeds 10° is referred to as a vertical-stacked cradle.

[0137] The cradle used can be either a flat-stacked cradle or a vertical-stacked cradle, and in the case of a large glass plate, a greater pressure is applied to the end portion of the glass plate due to the self weight of the glass plate. Therefore, in the case of a large glass plate, it is preferable to use a cradle in which the glass plate is placed in a flat-stacked state. In addition, the larger the glass plate, the greater the pressure applied to the end surface of the glass plate, and thus, the angle of the inclined stage is preferably 0° to 5°, more preferably 0° to 3°, and further preferably 0° to 1°. However, when housed in a truck or a box for transportation of the glass plate, it is sometimes not possible to house it in a flat-stacked cradle. Therefore, in order to save space, a vertical-stacked cradle can also be used.

[0138] A large glass plate refers to, for example, a glass plate in which at least one side is 2400 mm or more, and as a specific example, a glass plate in which the longer side is 2400 mm or more and the shorter side is 2000 mm or more. The above large glass plate is preferably a glass plate in which at least one side is 2400 mm or more, for example, a glass plate in which the longer side is 2400 mm or more and the shorter side is 2100 mm or more, more preferably a glass plate in which at least one side is 3000 mm or more, for example, a glass plate in which the longer side is 3000 mm or more and the shorter side is 2800 mm or more. Further preferably, it is a glass plate in which at least one side is 3200 mm or more, for example, a glass plate in which the longer side is 3200 mm or more and the shorter side is 2900 mm or more, and particularly preferably, it is a glass plate in which at least one side is 3300 mm or more, for example, a glass plate in which the longer side is 3300 mm or more and the shorter side is 2950 mm or more.

[0139] The thickness of the glass plate is preferably 1.30 mm or less. By thinning the glass plate, the weight per sheet becomes light, and thus, the number of sheets loaded can be increased, and the etching time during the production of a liquid crystal panel can be shortened. The thickness of the glass plate of the present application 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 0.10 mm or less, or 0.05 mm or less. However, from the viewpoint of preventing deflection due to the self weight, the thickness is preferably 0.10 mm or more, and more preferably 0.20 mm or more.

[0140] The glass sheet is preferably used at the time of manufacturing a display. The glass sheet has few particles such as paper powder and foreign matter present on the main surface of the glass sheet, and has few scratches on the surface of the glass sheet, and thus generation of defects such as wire breakage can be suppressed. As the display, it is preferable to be used for a substrate of a liquid crystal display, an organic EL display. In addition, the glass sheet backing paper of the present application can suppress scratches of the glass sheet, and thus the effect is remarkable in the case of being used for a high-definition display. Therefore, the number of pixels of the display glass sheet using the glass sheet backing paper of the present application is preferably 2K (1920 x 1080) or more, more preferably 4K (3840 x 2160) or more, and further preferably 8K (7680 x 4320) or more.

[0141] The glass sheet backing paper, the glass sheet laminate, and the glass sheet bale have been described in detail above, but the present application is not limited to the above-described examples, and various modifications and changes can of course be made within the scope of the gist of the present application.

[0142] Examples

[0143] The present application will be described in detail below using examples, but the present application is not limited by these examples. Examples 1 to 10 below are examples, and Examples 11 to 13 are comparative examples. In addition, in the case where not particularly described, the manufactured backing paper is measured after being conditioned in a standard state in accordance with JIS P8111:1998. Each measurement of the backing paper is performed on the backing paper before being used as a glass sheet laminate.

[0144] The smoothness is measured in accordance with JIS P8119:1998 Smoothness Test Method (Bekk method) and JIS P8155:2010 Smoothness Test Method (Wang method). In general, it is known that the smoothness of the Wang method is higher than that of the Bekk method, but the higher the smoothness of the Bekk method, the longer the measurement time, and thus in the case where it exceeds 100 seconds, the smoothness is obtained using the Wang method, and converted into the value of the Bekk method. The smoothness of Examples 2, 4, 6, 8, 9, 12, and 13 is the value obtained by converting the smoothness obtained using the Wang method into the value of the Bekk method. The smoothness of the backing paper manufactured in Examples 1 to 13 is measured at the approximately central portion of the first main surface and the second main surface of the backing paper in accordance with the above-described method, and the higher value is taken as the smoothness of the backing paper. Next, the arithmetic mean height Sa and the maximum height Sz of the main surface having the higher smoothness are measured using a laser microscope (manufactured by Keyence, VK-8500). The arithmetic mean height Sa and the maximum height Sz are each measured at the approximately central portion of the above-described main surface.

[0145] The sheet resistance was measured using a Hiresta-UX and a URS probe (MCP-HTP14). Note that, in order to measure the sample in a state in which the probe stands upright, a load of 600 g was applied to the outer periphery of the probe in a concentric cylindrical shape, and the load portion was kept at a sufficient distance from the sample so as not to affect the measurement. In a manner that imitates the MCC-A method (measurement of the Teflon (registered trademark) face side), after a 0.5 mm-thick glass plate was laid as an insulator on the non-measurement face side of the sample, the probe was placed on the central portion of the measurement face, a voltage of 1000 V was applied, and the value after 10 seconds was taken as the measurement value. Note that, in this measurement, the backing paper that had been left to stand for 15 minutes under conditions of 23°C and 50% was used. This is intended to simulate the conditions in which the backing paper is actually loaded on a glass substrate, unwound from a roll surface, and loaded. Note that, the measurement face is the major face having high smoothness among the first major face and the second major face of the backing paper.

[0146] Next, the compressive elastic modulus of the above-described backing paper was measured using a constant rate of thickness tester. Next, 1600 regions of 2.0 mm x 1.4 mm were measured using a laser microscope and a micro compression tester, the number (pieces) of foreign matter having an average diameter of 10 μm to 50 μm and a particle intensity C of 15 (MPa) or more present in the 1600 regions was counted, and the number was converted to the number of pieces per 1 m 2 The number N (pieces / m 2 ) of foreign matter present.

[0147] The glass plates manufactured in Examples 1 to 13 were formed into a size of 500 mm x 400 mm using the backing paper, and were sandwiched between glass plates having a thickness of 0.5 mm and a size of 470 mm x 370 mm, to produce a glass plate laminate in which 180 glass plates were laminated. Note that, the protruding amount of each edge of the backing paper was 15 mm. The above-described glass plates were glass plates on which both faces had been subjected to alkali cleaning after being polished with cerium oxide, and which had been dried with clean dry air after being polished. The bottom face refers to the major face that comes into contact with molten tin in a glass plate manufactured by the float method. When the glass plates were laminated, the major face having high smoothness among the first major face and the second major face of the backing paper was laminated so as to come into contact with the bottom face of the polished glass plate. Note that, the method of forming the glass plate used in the present application is not limited to the float method, and can be the down-draw method, the roll-plate method, or the like, and can also be a glass plate that has not been polished.

[0148] The glass plate laminates were stacked to make a glass plate bundle. Note that the tray was made of aluminum and did not have a vibration absorbing material such as rubber or a spring, or a mechanism for suppressing movement of the laminate in the vertical direction. The glass plate bundle thus made was vibrated in the vertical direction for 1 hour by a random vibration test according to JIS Z0232:2004 using a vibration tester (IMV Co., Ltd., m120 / MA1). Note that the vibration conditions were set to the conditions of the acceleration power spectral density simulating a general transportation environment (mainly roads) described in Table A.1 of the annex to JIS Z0232:2004, and the acceleration was 5.92 (m / s 2 rms). The temperature and humidity in the environment were set to 25 ± 2°C and 50 ± 5%, respectively.

[0149] After the vibration test, the glass plates located above the third glass plate from the bottom of the glass plate bundle were removed from the bottom of the glass plate bundle, and the glass plates were cleaned and evaluated for the amount of particle adhesion and scratches on the bottom surface using a foreign matter inspection machine.

[0150] Measurement and Evaluation of Particle Adhesion and Scratches on the Surface of the Glass Plate

[0151] The bottom surface of the glass plate removed from the bundle was passed through a cleaning machine at a speed of 3 m / min. The cleaning machine was a showering machine in which 2 rows of shower pipes through which pure water (ion-exchanged water) flowed at a piping pressure of 1 MPa and a flow rate of 20 L / min were provided, and the nozzles of the outlet had an equal sector shape. The glass plate was dried by a gas knife that sprayed clean dry air, and the cleaned glass plate was obtained. The cleaned glass plate was measured using an FPD foreign matter inspection machine (Toray Engineering Co., Ltd., HS-830e) in the Normal (1.0 μm) mode, and the number of particles was obtained. Note that the number of particles was measured for at least 3 glass plates for each test condition, and the average value was used as the number of particles for each test condition. Note that the foreign matter inspection machine generally includes scratches in addition to convex adhesion, and in this specification, the convex adhesion is referred to as particles, and the concave defects are referred to as scratches.

[0152] The adhesion of particles was measured before the laminate was made and after the vibration using an FPD foreign matter inspection machine, and the difference in the number of particles was used to evaluate the adhesion. The evaluation criteria were as follows.

[0153] A: The difference in the number of particles was less than 20,000 pieces / m 2 .

[0154] B: The difference in the number of particles was 20,000 pieces / m 2 to less than 50,000 pieces / m 2 .

[0155] C: The difference in particle count is 50,000 / m³. 2 above.

[0156] For scratch resistance on the glass plate, the foreign object inspection machine (FPD) was used for observation, and the following evaluation criteria were used for evaluation.

[0157] A: The number of scratches on the bottom surface of the glass plate is less than 0.5 per m. 2 .

[0158] B: The number of scratches on the bottom surface of the glass plate is 0.5 per m. 2 More than or less than 3.0 pieces / m 2 .

[0159] C: The number of scratches on the bottom surface of the glass plate is 3.0 / m. 2 More than or less than 10.0 pieces / m 2 .

[0160] D: The number of scratches on the bottom surface of the glass plate is 10.0 / m. 2 above.

[0161] (Determination of compressive elastic modulus K (MPa))

[0162] The device, which has a load mounting section in the constant pressure thickness measuring instrument (TECLOCK, PG-02J) to allow arbitrary load setting, is used without any other changes. It should be noted that the minimum thickness reading is 1 μm. First, the paper thickness when a load equivalent to pressure P1 (kPa) is applied to approximately the center of the liner paper with a pressure head diameter of 5 mm is defined as T1 (μm), and the paper thickness when a load equivalent to pressure P2 (kPa) is applied to approximately the center of the liner paper is defined as T2. The strain is calculated as (T1 - T2) / T1 (dimensionless). Next, the compressive modulus K is calculated as (P2 - P1) / (strain × 10⁻¹⁰). －3 (MPa). It should be noted that here P1 = 100 (kPa) and P2 = 270 (kPa).

[0163] It should be noted that the compressive modulus of elasticity is determined by pressing the pressure head against the smoother surfaces of the first and second main surfaces of the liner paper.

[0164] The number N (pieces / m²) of foreign objects with an average diameter of 10μm to 50μm and a particle strength C of 15 (MPa) or higher 2 (determination)

[0165] The base paper was placed on the stage of a laser microscope (Keyence, VK-8500), and the end portion was fixed with tape so that the base paper would not warp. In the approximate center portion of the base paper, 1600 regions were measured in regions of 2.0 mm x 1.4 mm, the size was calculated from the number of pixels, and particles having an average diameter of 10 μm to 50 μm were selected. The measurement can be automatic measurement in which the field of view is moved by one field of view each time measurement is performed, and the next field of view is measured, using the teaching function of the microscope. The particles were placed on the stage of a micro compression tester (Shimadzu Corporation, MCT-510). Note that the micro compression tester uses a diamond flat indenter having a diameter of 50 μm, a test force resolution of 5 μN, and a displacement amount resolution of 0.01 μm. The shape of the particles was confirmed using the microscope attached to the test machine, the major axis and the minor axis were measured, and the average diameter was calculated as the average of the sum. The test force was applied to the above particles at a test force of 20 mN and a load rate of 0.44 mN / sec, and the point at which the average diameter after compression was 10% less than the average diameter before compression was set as the 10% compression point. Using the test force at this time, the formula Cx=2.48 x (test force at 10% compression point) / (average particle diameter) 2 was used to calculate the particle strength C. Then, the number of particles having a particle strength C of 15 (MPa) or more was counted, and the number N (pieces / m 2 ) of foreign matter was calculated.

[0166] Note that, in general, the point at which a test force of 15 (MPa) or more is applied and the particle is broken (the point at which the particle is sharply pressed into the indenter due to the breaking of the particle, the test force is substantially constant, and only the displacement amount greatly changes) is set as the breaking point, and using the test force at this time, Cs=2.48 x (test force at breaking point) / (average particle diameter) 2 is used to calculate the particle strength C. This is the case in many cases.

[0167] However, in the case of particles in which Cx calculated using the test force at the 10% compression point is around 15 (MPa), the breaking point of the particle is not detected, and therefore, in this specification, Cx is calculated using the test force at the 10% compression point, and this value is used as the particle strength C. In addition, in the case in which the breaking point of the particle is observed before the 10% compression point is reached, the shape of the particle changes greatly at this time, and therefore, in this case, the particle strength uses the value of Cs.

[0168] Example 1

[0169] A pulp slurry of NBKP 100% was beaten with a twin-disc refiner, and a raw material slurry was sprayed on a Fourdrinier former at a paper stock concentration of 1% at a weight per unit area shown in Table 1, and a paper layer was formed, and dried in a multi-cylinder dryer. As the raw material water, purified water treated with a 40-μm filter was used. Then, a heat soft calendering treatment was performed at a temperature of 100°C and a nip pressure of 10 (kN / m). The resulting base paper had a weight per unit area of 45.1 g / m 2 , a thickness of 80 μm, a density of 0.53 (g / cm 3 ), a smoothness of the first main surface of 25 seconds, and a smoothness of the second main surface of 23 seconds.

[0170] (Example 2)

[0171] A heat soft calendering treatment was performed at a temperature of 150°C with a temperature gradient, and at a nip pressure of 120 (kN / m) with a heat gradient, and otherwise, the base paper was obtained in the same manner as in Example 1.

[0172] (Example 3)

[0173] The raw material was composed of NBKP 50% and LBKP(A) 50% as shown in Example 1, a filter for water was a filter with an opening diameter of 20 μm, and as the calendering treatment, a hard calendering was performed at a nip pressure of 30 (kN / m), and otherwise, the base paper was obtained in the same manner as in Example 1.

[0174] (Example 4)

[0175] A raw material system composed of the pulp and water shown in Example 3 was used, and as the calendering treatment, a heat soft calendering was performed at a temperature of 150°C and a nip pressure of 150 (kN / m), and otherwise, the base paper was obtained in the same manner as in Example 1.

[0176] (Example 5)

[0177] A filter for water was a filter with an opening diameter of 5 μm, and the calendering treatment was performed at a nip pressure of 50 (kN / m), and otherwise, the base paper was obtained in the same manner as in Example 3.

[0178] (Example 6)

[0179] A raw material system composed of the pulp and water shown in Example 5 was used, and after a cooling treatment with water and a low-temperature air blow before the calendering treatment, as the calendering treatment, a heat soft calendering was performed at a temperature of 200°C and a nip pressure of 170 (kN / m), and otherwise, the base paper was obtained in the same manner as in Example 1.

[0180] (Example 7)

[0181] After the raw material slurry was papered, drying was performed with a Yankee dryer, and no calendering treatment was performed, and otherwise, the base paper was obtained in the same manner as in Example 1.

[0182] Example 8

[0183] The raw material was composed of the NBKP 50% and the LBKP(B) 50% shown in Example 1, and a filter having an opening diameter of 40 μm was used as the water filter. Other than this, the backing paper was obtained in the same manner as in Example 4. Note that the LBKP(A) and the LBKP(B) were bleached kraft pulps from different kinds of wood.

[0184] Example 9

[0185] The papermaking speed was reduced by 20%, and a drying roll at 150°C was provided before the backing paper was wound up, and drying treatment was performed to reduce the moisture content. Other than this, the backing paper was obtained in the same manner as in Example 6.

[0186] Example 10

[0187] Moisture treatment was performed before the backing paper was wound up to increase the moisture content. Other than this, the backing paper was obtained in the same manner as in Example 1.

[0188] Example 11

[0189] The raw material pulp was papered without performing calendering treatment. Other than this, the backing paper was obtained in the same manner as in Example 1.

[0190] Example 12

[0191] A raw material system composed of the pulp shown in Example 8 and water was used, and papermaking was performed using a raw material pulp beaten in such a manner as to have a freeness of 200 mL CSF. Then, a wet paper was produced using a moisture imparting device, and supercalendering treatment was performed at a temperature of 150°C and a nip pressure of 200 kN / m for 10 stages to obtain a backing paper as a glassine paper.

[0192] Example 13

[0193] A raw material system composed of the pulp shown in Example 3 and water was used, and the papermaking speed was reduced by 20%. Then, as the calendering treatment, treatment was performed at a temperature of 100°C and a nip pressure of 350 kN / m. Other than this, the backing paper was obtained in the same manner as in Example 1.

[0194] [Table 1]

[0195]

[0196] <Results>

[0197] Table 1 shows the measurement results and evaluation results. According to Table 1, in the case where the smoothness is 20 seconds or more, the adhesiveness of the particles is all A or B. On the other hand, in the case where the smoothness is less than 20 seconds, the adhesion amount of the particles is all C. In addition, in the case where the compressive elastic modulus K is 8.5 MPa or less, the scratch resistance is all A or B. On the other hand, in the case where the compressive elastic modulus K exceeds 8.5 MPa, the scratch resistance is C or D.

[0198] This application is based on Japanese Patent Application No. 2020-195392 filed on November 25, 2020, and Japanese Patent Application No. 2021-187432 filed on November 17, 2021, the contents of which are incorporated herein by reference.

Claims

1. A backing paper for glass plates, with a thickness of 30μm to 150μm. The smoothness of at least one side of the main surface of the glass plate using the backing paper is greater than 20 seconds. The compressive modulus K measured on the main surface is 1.0 MPa to 8.5 MPa. The product of the compressive modulus K and the number N of foreign objects in the glass plate backing paper with an average diameter of 10μm to 50μm and a particle strength C of 15MPa or higher, i.e., the hard foreign object resistance value KN, is 35.0 or less. The unit of the compressive modulus K is MPa, and the unit of the number of foreign objects N is particles / m. 2 .

2. The glass plate backing paper according to claim 1, wherein, The arithmetic mean height Sa of the main surface is greater than 2.5 μm.

3. The glass plate backing paper according to claim 1 or 2, wherein, The maximum height Sz of the main surface is 45 μm or more.

4. The glass plate backing paper according to claim 1 or 2, wherein, The density of the backing paper used for the glass plate is 0.4 g / cm³. 3 ~1.6g / cm 3 , The smoothness of the main surface is between 20 seconds and 400 seconds.

5. The glass plate backing paper according to claim 1 or 2, wherein, The resistivity of the paper backing used for the glass plate is 5.0 × 10⁻⁶. 10 Ω / □~5.0×10 13 Ω / □.

6. The glass plate backing paper according to claim 1 or 2, wherein, The product of the compressive modulus K and the number N of foreign objects in the glass plate backing paper with an average diameter of 10μm to 50μm and a particle strength C of 15MPa or higher, i.e., the hard foreign object resistance value KN, is 15.0 or less. The unit of the compressive modulus K is MPa, and the unit of the number of foreign objects N is particles / m. 2 .

7. The glass plate backing paper according to claim 1 or 2, wherein, The main surface is the surface that is in contact with the electronic circuitry of the glass plate.

8. A glass plate laminate comprising at least two glass plates, wherein the glass plate laminate has a glass plate backing paper as described in claim 1 or 2 between the glass plates.

9. A glass plate bundle comprising the glass plate stack as described in claim 8 and a bracket for holding the glass plate stack.

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