JPWO2019188974A1 - Insertion paper for glass plates and its manufacturing method - Google Patents

Abstract

The present invention is a glass plate interleaving paper made from wood pulp, wherein the presence ratio of foreign substances having a moth hardness of 4 or more existing on one surface is less than 10 per 1000 m2, and the foreign substances on one surface. The difference between the abundance ratio of the foreign matter and the abundance ratio of the foreign matter on the other surface is 4 or less per 1000 m2. INDUSTRIAL APPLICABILITY According to the present invention, it is possible to solve a problem caused by a difference in the state of the front and back surfaces of a glass plate interleaving paper.

Description

The present invention provides paper for wrapping glass plates and paper for wrapping glass plates in the process of stacking, storing, and transporting a plurality of glass plates for flat panel displays such as liquid crystal displays, plasma displays, and organic electroluminescence (organic EL) displays. It relates to paper sandwiched between glass plates and the manufacture of these papers.

Generally, in a storage process in which a plurality of glass plates for flat panels and displays are stacked and stored, a distribution process in which glass plates are transported by a truck or the like, the glass plates are impacted and come into contact with each other to cause scratches. In order to prevent the glass surface from being contaminated by contaminants from the outside world, a paper called interleaving paper is sandwiched between the glass plates.

Since glass plates for flat panel displays are used for high-definition displays compared to general window glass plates for buildings and window glass plates for vehicles, the glass surface contains impurities contained in the paper surface as much as possible. It is required to maintain a clean surface, and to have excellent flatness for high-speed response and widening of the viewing angle.

As the interleaving paper used for such applications, some interleaving papers that can prevent cracking of the glass plate and scratches on the surface and interleaving papers that do not contaminate the glass surface have already been proposed. For example, Patent Document 1 discloses a method of forming a fluorine coating film on the surface of a slip sheet. Further, Patent Document 2 is an interleaving paper in which a polyethylene-based resin foam sheet and a polyethylene-based resin film are bonded together, and Patent Document 3 is a paper made of pulp containing 50% by mass or more of bleached chemical pulp. Therefore, there is a glass interleaving paper containing a specific alkylene oxide adduct and water-soluble polyether-modified silicone, and Patent Document 4 specifies the amount of resin in the paper and considers contamination of the glass surface. Each of the interleaving papers for glass plates using the raw materials is disclosed.

Japanese Unexamined Patent Publication No. 2012-188785 Japanese Unexamined Patent Publication No. 2010-24257 Japanese Unexamined Patent Publication No. 2008-208478 JP-A-2006-44674

For example, when manufacturing a color filter substrate in an array process, which is one of the manufacturing processes of a TFT liquid crystal display, if the glass plate surface has cracks, scratches, etc., or the glass surface is contaminated, problems such as disconnection occur. It is known. The color filter substrate is produced by forming a thin film such as a semiconductor film, an ITO film (transparent conductive film), an insulating film, and an aluminum metal film on a glass plate by sputtering, vacuum deposition, etc., but the surface of the glass plate is cracked. This is because the presence of scratches and contaminants causes disconnection in the circuit pattern formed from the thin film and short circuit due to defects in the insulating film. Further, in the production of the color filter substrate, a pattern is formed on the glass plate by photolithography. If cracks, scratches, or contaminants are present on the glass plate surface at the time of resist coating in this step, the resist film after exposure or development is present. Pinholes occur in the glass, resulting in disconnection or short circuit. A similar problem has been confirmed in the manufacture of organic EL displays. Since an organic EL display is manufactured by forming thin films such as ITO anode, organic light emitting layer, and cathode on a glass substrate by sputtering, vapor deposition, printing, etc., cracks, scratches, and contaminants that hinder the thin film are formed on the glass substrate surface. If it exists, there is a problem that it does not emit light.

It was difficult to identify the causes of cracks, scratches, and contamination of such glass plates, but one of the causes is present on the surface of the glass plate interleaving paper, or glass from the surface of the glass plate interleaving paper. It has been found to be a fine foreign substance that transfers to the surface of the plate.

Further, it has been found that one of such foreign substances is a foreign substance having a Mohs hardness of 4 or more.

By the way, when sandwiching the interleaving paper for glass plates between the glass plates, if there is a difference in the physical state of the front and back surfaces of the interleaving paper, care should be taken so that the specific surface of the interleaving paper comes into contact with the surface of the glass plate. There may be a need. For example, a glass plate for a flat panel display has fine circuits and the like formed on its surface, so that even a small amount of foreign matter is particularly repelled from its adhesion and cracks and scratches caused by the foreign matter. If more foreign matter is present on one surface of such a glass plate interleaving paper than on the other surface, there is a risk that the foreign matter may crack or scratch the surface of the glass plate, or the foreign matter may be transferred to the surface of the glass plate. Therefore, care should be taken to bring the interleaving paper into contact with the surface of the glass plate so that the surface with few foreign substances is in contact with the surface of the glass plate, not the surface with many foreign substances. In this case, it is conceivable to sandwich two sheets of interleaving paper between the glass plates and face the surface of each interleaving paper with the smaller amount of foreign matter toward the glass plate, but the amount of interleaving paper used increases. , The weight of the laminate of the interleaving paper and the glass plate increases, which is not preferable in terms of handling.

An object of the present invention is to solve the above-mentioned problems caused by the difference in the state of the front and back surfaces of the interleaving paper for a glass plate. In particular, an object of the present invention is to provide a glass plate interleaving paper on which either the front or the back surface may be brought into contact with the glass plate.

Therefore, as a result of diligent studies, the present inventors have reduced the amount of foreign matter having a moth hardness of 4 or more existing on the surface of the glass plate interleaving paper, and also reduced the amount of foreign matter having a moth hardness of 4 or more on the front and back surfaces of the interleaving paper. It was found that it is possible to suppress the difference in the state of the front and back surfaces of the glass plate interleaving paper by suppressing the difference in the abundance ratio of the glass plate, and to provide the glass plate interleaving paper in which either the front or back surface may be in contact with the glass plate. The present invention has been completed.

The first aspect of the present invention is a glass plate interleaving paper made from wood pulp.
The presence ratio of foreign substances having a Mohs hardness of 4 or more on one surface is less than 10 per 1000 m ² .
The difference between the abundance ratio of the foreign matter on one surface and the abundance ratio of the foreign matter on the other surface is within 4 per 1000 m ² .
It is a slip paper for glass plates.

The foreign matter preferably contains a metal oxide or an inorganic silicon oxide. The inorganic silicon oxide is preferably silicon dioxide.

More preferably, the foreign matter is one or more selected from the group consisting of iron oxide, copper, quartz, fused quartz, titanium oxide, glass pieces, crystal pieces, magnesium oxide and sand.

The volume of the foreign matter is preferably less than 2 × ^10-5 mm ³ .

The basis weight of the interleaving paper for glass plates of the present invention is preferably ²⁰ to 100 g / m ² .

The thickness of the interleaving paper for a glass plate of the present invention is preferably 0.030 to 0.130 mm.

The water content of the interleaving paper for glass plates of the present invention is preferably 2 to 10% by mass.

The glass is preferably for display. The display is preferably a TFT liquid crystal display or an organic EL display.

The present invention also relates to a laminate of the glass plate interleaving paper and the glass plate.

The second aspect of the present invention is the method for producing the interleaving paper for a glass plate.
Slurry preparation process, which prepares a slurry of wood pulp,
A sheet forming step of forming the slurry into a sheet,
Wet paper preparation step of dehydrating the sheet to form wet paper,
At least a drying step of drying the wet paper to obtain the interleaving paper is included.
The present invention relates to a manufacturing method in which dehydration is performed from both sides of the sheet in the wet paper preparation step.

It is preferable to perform the dehydration by suction.

It is preferable that the difference between the dehydration rate of the suction on one surface of the sheet and the dehydration rate of the suction on the other surface is 10% or less of the dehydration rate of the suction on the other surface.

The manufacturing method preferably includes an additional suction step of further sucking both sides of the interleaving paper after the drying step.

The interleaving paper for glass plates of the present invention has a small amount of foreign matter having a Mohs hardness of 4 or more on the front surface, and the difference in the abundance ratio of foreign matter having a Mohs hardness of 4 or more on the front and back surfaces of the interleaving paper is suppressed. The difference in the presence state of foreign matter having a Mohs hardness of 4 or more on the front and back surfaces of the glass plate interleaving paper is suppressed. Therefore, either of the front and back surfaces of the glass plate interleaving paper of the present invention may be brought into contact with the glass plate. As a result, the interleaving paper for glass plates of the present invention is excellent in handleability.

Further, the interleaving paper for glass plates is originally wound into a roll and shipped, but in the wound state, the front surface and the back surface of the interleaving paper come into contact with each other, so that, for example, there are few foreign substances having a Mohs hardness of 4 or more on the front surface. If there are many foreign substances with a Mohs hardness of 4 or more on the back surface, even if the front surface of the interleaving paper is brought into contact with the front surface of the glass plate, foreign substances with a Mohs hardness of 4 or more on the back surface of the interleaving paper will be present in the wound state. It may be transferred to the surface and the cleanliness of the surface may be deteriorated.

However, the glass plate interleaving paper of the present invention suppresses the transfer of foreign matter having a Mohs hardness of 4 or more from one surface of the interleaving paper to the other surface even when it is wound into a roll. There is no need to worry about a decrease in the cleanliness of the interleaving paper surface due to winding in a roll shape, that is, an increase in the abundance ratio of foreign substances having a Mohs hardness of 4 or more.

Further, since the amount of foreign matter having a Mohs hardness of 4 or more existing on the surface of the glass plate interleaving paper of the present invention is small, cracks, scratches, etc. occur on the glass plate surface even if the interleaving paper comes into contact with the glass plate surface. In addition, it is possible to effectively suppress or avoid the transfer of foreign matter having a Mohs hardness of 4 or more from the interleaving paper to the glass plate. In this way, by reducing or avoiding problems such as cracks and scratches on the surface of the glass plate and suppressing or avoiding the transfer of foreign substances having a Mohs hardness of 4 or more to the glass plate, for example, a TFT liquid crystal display. It is possible to prevent circuit disconnection of a color film or the like in a manufacturing process of a display or the like.

The first aspect of the present invention is a glass plate interleaving paper made from wood pulp.
The presence ratio of foreign substances having a Mohs hardness of 4 or more on one surface is less than 10 per 1000 m ² .
The difference between the abundance ratio of the foreign matter on one surface and the abundance ratio of the foreign matter on the other surface is within 4 per 1000 m ² .
It is a slip paper for glass plates.

The fact that the number of foreign substances having a Morse hardness of 4 or more existing on the surface of the glass plate interleaving paper of the present invention is less than 10 per 1000 m ² means that the glass plate interleaving paper of the present invention exists alone, that is, the present invention. This means that the abundance ratio of the foreign matter present on the surface of the interleaving paper in the state where the interleaving paper for the glass plate is not laminated with the glass plate is less than 10 per 1000 m ² . However, in a state where the glass plate interleaving paper of the present invention is in contact with or pressed against the glass plate, that is, in a state where the glass plate interleaving paper of the present invention is laminated with the glass plate, the interleaving paper It is preferable that the abundance ratio of the foreign matter present on the surface is less than 10 per 1000 m ² .

The wood pulps that can be used in the present invention are softwood bleached kraft pulp (NBKP), hardwood bleached kraft pulp (LBKP), softwood bleached sulphite pulp (NBSP), softwood bleached sulphite pulp (LBSP), and thermomechanical pulp (TMP). It is a single or mixed wood pulp such as. Mainly this wood pulp, and if necessary, non-wood pulp such as hemp, bamboo, straw, kenaf, 楮, sansho and cotton, modified pulp such as cationized pulp and marcelized pulp, rayon, vinylon, nylon, Synthetic fibers such as acrylic and polyester, chemical fibers, and microfibrillated pulp can be used alone or in combination. However, if the pulp contains a large amount of resin, the resin may have adverse effects such as soiling the surface of the glass plate. Therefore, chemical pulp with as little resin as possible, such as softwood bleached kraft pulp, is used alone. It is preferable to do so. Further, high-yield pulp such as crushed wood pulp is not preferable because it contains a large amount of resin. It should be noted that mixing synthetic fibers and chemical fibers improves sword cutting performance and improves workability when flattening interleaving paper, but caution is required because recyclability deteriorates in terms of waste treatment. ..

The form of the wood pulp is not particularly limited, and any form such as a sheet, a block, or flakes can be taken. Sheet pulp can be obtained using, for example, a pulp machine having four steps of wire part, press part, dry part and finishing. In the wire part, pulp fibers are made from paper using a long net or a vacuum filter, and in the press part, they are dehydrated using a roll press. In the dry part, it is dried with a cylinder dryer, a fructo dryer, etc., and finally both ends of the sheet pulp are cut off and wound on a roll. Such a method is described in detail in the "Pulp and Paper Manufacturing Technology Series" published by the Pulp and Paper Technology Association and the "Pulp and Paper Manufacturing Technology Complete Book". The block-shaped pulp can be obtained by laminating the sheet-shaped pulp, for example, and the flake-shaped pulp can be obtained by crushing the sheet-shaped pulp, for example.

The thickness of the sheet pulp is preferably 0.7 to 1.5 mm, more preferably 0.9 to 1.3 mm, and even more preferably 1.0 to 1.2 mm. ..

The basis weight of the pulp sheet is preferably 400~1300g / ^{m 2,} more preferably from 500~1200g / ^{m 2,} more preferably from 500~1100g / ^{m 2,} 500~1000g / more preferably ^m is ^2, more preferably from a 700～1000G / ^{m 2.}

In the interleaving paper for glass plates of the present invention, the abundance ratio of foreign substances having a Mohs hardness of 4 or more on one surface is limited to less than 10 per 1000 m ² . The number of foreign substances having a Mohs hardness of 4 or more existing on one surface of the glass plate interleaving paper is preferably 8 pieces / 1000 m ² or less, more preferably 6 pieces / 1000 m ² or less, and 4 pieces. It is even more preferably less than / 1000m ^{2 and even} more preferably 3 pieces / 1000m ² or less, even more preferably 2 pieces / 1000m ² or less, and 1 piece / 1000m ² or less. Especially preferable.

In the interleaving paper for glass plates of the present invention, the difference between the abundance ratio of foreign substances having a Mohs hardness of 4 or more on one surface and the abundance ratio of foreign substances having a Mohs hardness of 4 or more on the other surface is within 4 per 1000 m ^2. and it is preferably not less than 3 per 1000 m ^2, more preferably within 2 per 1000 m ^2, and still more preferably from not exceed one per 1000 m ^2. That is, in the interleaving paper for glass plates of the present invention, the proportion of foreign matter having a Mohs hardness of 4 or more on one surface is within the above specific range from the abundance ratio of foreign matter having a Mohs hardness of 4 or more on the other surface. It is preferable that it does not fluctuate significantly.

Here, the "presence ratio" means the number of foreign substances having a Mohs hardness of 4 or more per unit area on the surface of the interleaving paper. For example, a plurality of locations on the surface of the interleaving paper for a glass plate are enlarged by an electron microscope. It can be determined by observing and averaging the number of foreign substances having a Mohs hardness of 4 or more observed at the site. Alternatively, as another method, the surface of a predetermined area of the glass plate interleaving paper is sufficiently washed with water, an acidic solution or a basic solution, and the foreign matter having a Mohs hardness of 4 or more that has fallen off is counted. The abundance ratio of can be determined.

The interleaving paper for glass plates of the present invention has a small amount of foreign matter having a Mohs hardness of 4 or more on the front surface, and the fluctuation of the abundance ratio of foreign matter having a Mohs hardness of 4 or more on the front and back surfaces of the interleaving paper is suppressed. As a result, the difference in the physical state of the front and back surfaces of the glass plate interleaving paper is suppressed. Therefore, in the interleaving paper for glass plates of the present invention, the abundance ratio of foreign substances having a Mohs hardness of 4 or more on the surface does not differ significantly between the front and back surfaces of the interleaving paper. Therefore, in the interleaving paper for a glass plate of the present invention, either the front or the back surface may be in contact with the glass plate.

The foreign substance having a Mohs hardness of 4 or more in the present invention may be particles made of either an inorganic substance or an organic substance, and inorganic particles are preferable. Examples of the foreign matter include metal oxides having a Mohs hardness of 4 or more or inorganic silicon oxides. The metal constituting the metal oxide is not particularly limited as long as the moth hardness of the oxide is 4 or more. For example, an element of a Group 2 element such as magnesium, a Group 4 element such as titanium, or iron. 8th group elements such as. As the inorganic silicon oxide, silicon dioxide is preferable. Examples of the foreign matter having a Mohs hardness of 4 or more include oxidized minerals. Examples of the foreign matter having a Mohs hardness of 4 or more include iron oxide, copper, quartz, fused silica (quartz glass), titanium oxide, glass pieces, crystal pieces, magnesium oxide, sand and the like. The sand is mainly composed of amphibole having a Mohs hardness of 5.5, feldspar having a Mohs hardness of 6, and quartz having a Mohs hardness of 7. Therefore, the Mohs hardness of sand is 4 or more, typically 7. The Mohs hardness is an index of hardness expressed in 10 stages, and the hardness relative to the standard substance is determined by rubbing the corresponding standard substance and the substance to be measured and whether or not it is scratched. This is the evaluated value. The standard substances are, in order from soft (Mohs hardness 1) to hard (Mohs hardness 10), 1: talc, 2: gypsum, 3: calcite, 4: fluorite, 5: apatite, 6: long stone, 7: quartz. , 8: Topaz, 9: Corundum, 10: Diamond. To measure the Mohs hardness, two plates with a smooth surface and a known Mohs hardness are prepared, a foreign substance to be measured is sandwiched between the two plates, and both plates are rubbed together to check for scratches on the plate surface.

Most of the foreign substances that are easily contained in the interleaving paper for glass plates and may damage the surface of the glass plate are derived from raw materials, especially quartz having a Mohs hardness of 7, molten quartz, sand and crystal. On the other hand, it is often a piece of magnesium oxide having a Mohs hardness of 6, titanium oxide and iron oxide, copper having a Mohs hardness of 5 to 8, and a glass piece having a Mohs hardness of 4 to 7.

In the present invention, the volume of the foreign matter is preferably controlled to less than 0.00002Mm ^3, less than 0.00001mm ³ is more preferable. Unlike dirt, foreign matter exists as a three-dimensional object on the surface or inside of the interleaving paper and causes problems. In particular, when the size of the foreign matter is 0.00002 mm ³ or more, there is a high possibility that the foreign matter comes into contact with the surface of the glass plate and leaves scratches or cracks when the interleaving paper for the glass plate is used. For example, when a glass plate interleaving paper and a glass plate are laminated, foreign matter existing on the interleaving paper surface may be pressed by the weight of the glass plate, but if the size of the foreign matter is small, the interleaving paper may be pressed. Since foreign matter is buried in the paper, the possibility of damaging the surface of the glass plate is reduced. Since the foreign matter is a three-dimensional object as described above, it can be visually recognized as a scratch generated when the glass or the interleaving paper for the glass plate moves, especially when the projected area is small but the height is high. There is a risk of leaving scratches. On the contrary, if the projected area is large even if the height is low, the surface of the glass plate may be damaged, which is also not preferable.

The average particle size of the sphere volume equivalent diameter of the foreign matter is preferably 30 μm or less, more preferably 20 μm or less, further preferably 10 μm or less, still more preferably 5 μm or less. It is particularly preferably 1 μm or less. The sphere volume equivalent diameter is the diameter of the sphere when foreign particles are converted into spheres of the same volume, and can be measured by a laser diffraction method or the like.

Glass plate for inserting paper of the present invention preferably has a basis weight of 20 to 100 g / ^{m 2,} more preferably 30~90g / ^{m 2,} still more preferably 40 and 80 g / ^{m 2.} If it is less than 20 g / m ² , it becomes difficult to maintain the minimum air permeation resistance (5 seconds or more), and when only the glass plate interleaving paper is sucked and removed after use on the glass plate, it is sucked up to the glass plate body. There is a risk that it will end up. Further, if it is less than 20 g / m ² , the back of the glass plate interleaving paper itself becomes weak and the handleability deteriorates, which is not preferable. Further, when the basis weight exceeds 100 g / m ² , the flexibility of the interleaving paper for the glass plate is impaired and the handleability is deteriorated. In addition, since the glass plate interleaving paper is used for the purpose of transporting the used glass plate, protecting it during storage, and preventing scratches and stains, it is disadvantageous in terms of cost to increase the basis weight more than necessary. Workability is also reduced.

The thickness of the interleaving paper for a glass plate of the present invention is preferably 0.030 to 0.130 mm, more preferably 0.040 to 0.120 mm, and even more preferably 0.050 to 0.110 mm. If it is less than 0.030 mm, the protective effect during transportation and storage of the glass plate used is reduced, which is not preferable. In particular, it becomes difficult to fully exert the cushioning function as a slip sheet, and the thickness may be too thin, so that the paper may be easily torn. Further, if it exceeds 0.130 mm, the thickness of the laminate of the glass plate and the interleaving paper for the glass plate increases, so that problems such as storage space and transportation are expected to occur.

The water content of the interleaving paper for a glass plate of the present invention is preferably 2 to 10% by mass, more preferably 3 to 9% by mass, and even more preferably 4 to 8% by mass. If the water content is less than 2% by mass, the glass plate interleaving paper itself tends to be charged with static electricity, and a blocking phenomenon due to static electricity occurs between the glass plate and the paper plate, which is not preferable. On the other hand, if the water content exceeds 10% by mass, the dimensional stability may deteriorate due to the blocking phenomenon with the glass plate due to excessive water content and the decrease in water content during use.

The surface electrical resistance value of the glass plate interleaving paper of the present invention (based on JIS K 6911 1995) is determined after the interleaving paper has been adjusted for 24 hours or more under the conditions of a temperature of 23 ° C. and a relative humidity of 50%. When measured under the same conditions, it is preferably in the range of 1 × 10 ⁸ to 1 × 10 ¹³ Ω, more preferably in the range of 5 × 10 ^{8 to} 5 × 10 ¹² Ω, and 1 × 10 ⁹ to 1. The range of × 10 ¹² Ω is even more preferable. The surface resistivity is less than 1 × 10 ⁸ Ω, the adhesion of the glass plate and the slip sheet is lowered, there is a possibility that the handling becomes poor. Furthermore, the fact that the surface electrical resistance is less than 1 × 10 ⁸ Ω means that moisture and conductive material (such as surfactants) is added more than necessary. Excessive moisture can adversely affect the dimensional stability of the glass plate interleaving paper, and since most of the conductive substances are organic substances, these substances are transferred to the surface of the glass plate that comes into contact with them. It may cause problems such as dirt. On the other hand, when the surface electrical resistance value of the glass plate interleaving paper becomes a high resistance value exceeding 1 × 10 ¹³ Ω, it becomes easy to be charged with static electricity, and the interleaving paper adheres to the contacting glass plate surface and the handleability is remarkably improved. May hinder. As a method of adjusting the surface electrical resistance value to a desired range, for example, moisture adjustment by drying or the like can be mentioned.

The interleaving paper for glass plates of the present invention may contain short fibers having a fiber length of 200 μm or less, but since the short fibers may attract foreign substances, the content of the short fibers is the absolute dry weight of the interleaving paper. On the other hand, it is preferably 4.5% by weight or less, more preferably 4.0% by weight or less, even more preferably 3.5% by weight or less, and particularly preferably 3.0% by weight or less. Here, "fiber length" does not mean the average fiber length. Therefore, all short fibers having a fiber length of 200 μm or less have a fiber length of 200 μm or less. In other words, the maximum fiber length of the short fibers is 200 μm or less. Here, the fiber length refers to the length of the fiber when the fiber is in a straight stretched state.

The average fiber diameter of the short fibers is preferably 10 μm to 50 μm, more preferably 12 μm to 40 μm, and even more preferably 15 μm to 30 μm.
The "average fiber diameter" here means that a predetermined number of fibers are randomly selected from each electron microscope image by magnifying and observing a plurality of locations on the surface of the glass plate interleaving paper with an electron microscope. It means the average fiber diameter obtained by measuring and averaging the diameter of the fiber. The number of fibers to be selected is 100 or more, preferably 150 or more, more preferably 200 or more, and even more preferably 300 or more.

Abundance of the short fibers in the glass plate for slip sheet surface of the present invention is preferably from 50 lines 600 present / cm ^2, more preferably from 60 present 500 present / cm ^2, 70 present - More preferably, it is 400 lines / cm ² . When the abundance of the short fibers is relatively small, the amount of foreign matter attracted by the short fibers can be reduced.

In the interleaving paper for glass plates of the present invention, the difference between the abundance of the short fibers on one surface and the short fibers on the other surface is 15% or less of the abundance of the short fibers on the other surface. It is preferably 12% or less, and even more preferably 10% or less. That is, in the interleaving paper for glass plates of the present invention, it is preferable that the abundance of short fibers on one surface does not fluctuate significantly from the abundance of short fibers on the other surface to the extent that it falls within the above specific range. Here, the "abundance amount" means the number of the short fibers on the surface of the interleaving paper. For example, a plurality of locations on the surface of the interleaving paper for a glass plate are magnified and observed with an electron microscope and observed at the locations. It can be determined by averaging the number of short fibers produced. It can also be determined by selecting short fibers of 200 μm or less from the fibers that have fallen by rubbing a predetermined area with a sheet or the like with the surface of the interleaving paper facing downward and obtaining the number per unit area. Further, it can also be determined by dividing the interleaving paper into two sheets at the center in the thickness direction to form two very thin sheets, slurry each paper, and measure the number of short fibers of 200 μm or less in the slurry. .. Alternatively, as another method, the abundance of short fibers can be determined by sufficiently washing the surface of the glass plate interleaving paper with water and subjecting the fallen fibers to a fiber length measuring machine.

The interleaving paper for a glass plate of the present invention can be produced based on a usual method such as a papermaking method.

A second aspect of the present invention is a method for producing a slip sheet for a glass plate.
Slurry preparation process, which prepares a slurry of wood pulp,
A sheet forming step of forming the slurry into a sheet,
Wet paper preparation step of dehydrating the sheet to form wet paper,
At least a drying step of drying the wet paper to obtain the interleaving paper is included.
This is a manufacturing method in which dehydration is performed from both sides of the sheet-like slurry in the wet paper preparation step.

In order to reduce the number of foreign substances with a moth hardness of 4 or more existing on the surface of the glass plate interleaving paper to less than 10 per 1000 m ² , the examination and management of raw materials for papermaking such as pulp, papermaking chemicals, fillers, etc. It is important to control a series of processes including the whole process from the preparation process of the raw material to the finishing process, but it is particularly preferable that the wood pulp used as the raw material of the interleaving paper does not contain a large amount of foreign matter.

Usually, various foreign substances are contained in wood pulp. For example, foreign matter derived from wood, which is a raw material for wood pulp, foreign matter derived from cooking chemicals during pulp production, foreign matter derived from chemicals used in unbleached cleaning processes, metal foreign matter derived from used paper raw materials, or used in each process. The cause is foreign matter derived from water. Therefore, in the present invention, it is preferable to wash and carefully select the pulp that is the raw material of the interleaving paper for the glass plate to remove foreign substances from the pulp as much as possible in advance.

Generally, in the process of pulp production, the pulp obtained by evaporating wood chips is delignin-treated, and then the pulp is washed and further bleached. Therefore, it is preferable to first remove foreign substances from the chips and wash them at the stage of wood chips. For example, it is preferable to remove foreign matter such as metal and sand with a known foreign matter removing system such as a tip washer. Further, in the pulp manufacturing process, the purpose of cleaning after cooking is to remove the cooking chemical solution, the lignin decomposition product, and the colored component remaining in the pulp liquid, but it is also possible to remove foreign substances at the same time. For example, a known method such as a countercurrent cleaning method using various cleaning devices such as a vacuum filter cleaning machine, a pressure drum type filter cleaning machine, a press type cleaning machine and a diffuser cleaning machine can be adopted. In particular, in order to remove foreign substances and improve the cleanliness of pulp, it is preferable to increase the amount of washing water used or to adopt a multi-stage washing method having two or more stages of rinsing washing. It is more preferable not to use substances that cause foreign substances as chemicals such as surfactants, pH adjusters, pitch control agents, chelating agents, and defoaming agents used during cleaning. For example, a mineral oil-based defoaming agent used as a defoaming agent can cause mineral-based foreign matter in a glass plate interleaving paper, so the amount of the mineral oil-based defoaming agent used can be reduced, or other defoaming agents can be used. It is preferable to substitute it.

After the cleaning step, there is a bleaching step, and it is preferable to remove foreign substances as much as possible here as well. For example, a cleaning device may be installed for each bleaching stage. A known washing machine can be used here as well, and for example, a pressure diffuser, a diffusion washer, a pressure drum washer, a horizontal long net type washer, a press washing machine and the like can be used. In particular, by using a plurality of these, various foreign substances can be removed to a high degree. Although chemicals such as alkalis, acids, chelating agents, surfactants, and antifoaming agents can be added to the washing water, it is preferable not to use those that cause foreign substances. In addition, it is preferable to take measures to prevent foreign matter from being mixed in between each process. Further, it is even more preferable to combine the iron removal methods described later.

When used paper pulp is used as a raw material in the present invention, it is preferable to remove foreign substances at a high level with a pulper, a screen, a cleaner, or the like in the used paper pulp manufacturing process.

In the slurry preparation step, a slurry of wood pulp can be prepared by a conventionally known method. For example, in the slurry preparation step, the cellulose fibers constituting the wood pulp are disintegrated into an aqueous suspension to prepare a slurry.

In addition, as long as the performance of the present invention is not impaired, adhesives, fungicides, defoamers, fillers, wet paper strength enhancers, dry paper strength enhancers, sizing agents, etc. Coloring agents, fixing agents, yield improving agents, slime control agents and the like can be added. When adding these chemicals, it is preferable to take great care not to mix insects and dust.

When the slurry is prepared, the effect of increasing the paper interlayer strength can be expected by advancing the beating of the wood pulp. However, if the number of fine fibers increases as the beating progresses, there is a risk of causing inconveniences such as attracting foreign substances and generating paper dust during use as interleaving paper, so it is not preferable to advance the beating degree more than necessary. .. The preferred beating degree in the present invention is 300 to 650 mlc. s. f. Is.

In the sheet forming step of forming the slurry into a sheet, the slurry can be formed into a sheet by a conventionally known method. For example, by discharging the slurry onto a flat wire (for example, a long net paper machine), or by scooping a sheet from the slurry with a wire wound around a cylindrical cylinder (for example, a circular net paper machine). , You can get the sheet.

By the way, as a possibility that foreign matter is mixed in the interleaving paper, there is also a possibility that foreign matter is mixed in the papermaking process. For example, it may be mixed with paper chemicals, or the materials of various devices may fall off and be mixed with paper. As a method for removing foreign substances in the papermaking process, a dust remover such as a cleaner or a screen device or other cleaning device may be used. In the present invention, known devices can be used for these removal methods, for example, centrifugal cleaners, extra-weight cleaners, medium-concentration cleaners, lightweight cleaners, hole screens, slit screens, Janson screens, flat screens, and other cleaning machines. Can be used. In addition, foreign matter may be mixed into the pipes of paper and white water, so it is advisable to keep the pipes clean at all times.

Iron, which is one of the causes of foreign matter, becomes iron oxide with high moth hardness due to iron powder and iron rust mixed in from the piping of pulp manufacturing equipment and papermaking machines due to friction and corrosion and oxidation. Is preferably removed selectively. For example, each equipment may be made of a material other than iron, a highly magnetic material such as a magnet may be installed in the system to selectively remove iron, or an adsorbent that selectively adsorbs iron may be used. It is preferable to arrange it on the outlet side of each facility. The selective removal method by installing a high magnetic material enables removal of not only iron but also other magnetic materials.

In this way, for example, by using wood pulp with a small amount of foreign matter as a raw material and carefully removing foreign matter in the papermaking process, foreign matter having a moth hardness of 4 or more existing on the surface of the interleaving paper for a glass plate is 1000 m. It is possible to produce less than 10 glass plate interleaving papers per ² .

In the second aspect of the present invention, dehydration is performed from both sides of the sheet in the wet paper preparation step of dehydrating the sheet to form a wet paper. As a result, foreign substances having a Mohs hardness of 4 or more contained in the sheet are effectively removed from both sides of the sheet. Therefore, the difference between the abundance ratio of foreign substances having a Mohs hardness of 4 or more on one surface and the abundance ratio of foreign substances having a Mohs hardness of 4 or more on the other surface can be set to 4 or less per 1000 m ² .

The dehydration method is arbitrary, and conventionally known methods can be used. For example, the sheet can be dehydrated by pressing it with a roll. However, in order to effectively remove foreign substances having a Mohs hardness of 4 or more, it is preferable to carry out the dehydration by suction.

In the step of dehydrating from both sides of the sheet, for example, the sheet extending in the horizontal direction may be sandwiched between the top and bottom by a net and sucked in the vertical direction by a suction device to dehydrate, but due to the influence of gravity, the dehydration may be performed in the upward direction. There is a difference between the suction force to and the downward suction force, and foreign matter with a moth hardness of 4 or more remains on the sheet surface on the upward suction side compared to the sheet surface on the downward suction side. Since there is a risk, it is preferable to sandwich a sheet extending in the vertical direction with a net and suck it in the left-right direction to dehydrate it. In this case, it is preferable to maintain the wet paper so that the moving direction is the vertical direction or an inclination range within 30 ° from the vertical direction.

The difference between the suction dehydration rate (dehydration rate) on one surface of the sheet and the suction dehydration rate (dehydration rate) on the other surface is 10 of the suction dehydration rate (dehydration rate) on the other surface. % Or less is preferable. That is, in the method for producing the interleaving paper for a glass plate of the present invention, it is preferable that suction from both sides of the sheet is performed with substantially the same suction force.

The sheet forming step and the wet paper preparation step may be carried out individually by using separate devices, but may be carried out continuously or partially overlapping in the same device. For example, in the wire part of a paper machine, the slurry may be placed on a wire (net) to form a sheet and dehydrated to form a wet paper.

In the drying step, the wet paper can be dried to obtain the interleaving paper by a conventionally known method using a dryer roll or the like.

In order to further remove foreign substances having a Mohs hardness of 4 or more that may remain on the surface of the interleaving paper, the method for producing the interleaving paper for a glass plate of the present invention further sucks both sides of the interleaving paper after the drying step. Is preferably included.

In addition, processing such as calender processing, super calender processing, soft nip calendar processing, embossing, etc. may be performed during and / or after papermaking of the interleaving paper for glass plate. The surface properties and thickness can be adjusted by processing.

By the production method of the second aspect of the present invention, the interleaving paper for a glass plate of the first aspect of the present invention can be efficiently produced.

The interleaving paper for glass plates of the present invention is used by being inserted between the glass plates. For example, the interleaving paper for glass plates is typically inserted one by one between a plurality of glass plates to form a laminated body as a whole, and the laminated body is a target for storage and transportation. Further, the glass plate alone or the laminate may be wrapped using the glass plate interleaving paper of the present invention. Therefore, the present invention has an aspect of a method for protecting a glass plate, which includes a step of arranging (particularly inserting) the interleaving paper for the glass plate between the glass plates.

The glass plate is not particularly limited, but is preferably a glass plate for a flat panel display such as a plasma display panel, a liquid crystal display panel (particularly a TFT liquid crystal display panel), and an organic EL display panel. Fine electrodes, partition walls, etc. are formed on the surface of the glass plate for flat panel display. However, by using the glass plate interleaving paper of the present invention, cracks and scratches that become problems of the glass plate, and Since the transfer of foreign matter to the glass plate is suppressed or avoided, even if fine electrodes, partition walls, etc. are formed on the surface of the glass plate, the inconvenience caused by the foreign matter can be suppressed or avoided, and as a result. In addition, display defects can be suppressed or avoided.

In particular, as the size of a display increases, the size and weight of a glass plate for a flat panel display are increasing, and the interleaving paper for a glass plate of the present invention covers the surface of such a large to heavy glass plate. Can be well protected. In particular, since the interleaving paper for a glass plate of the present invention contains an extremely small amount of foreign matter having a Mohs hardness of 4 or more, the occurrence of cracks and scratches on the surface of the glass plate is reduced or avoided even when pressed by a heavy glass plate. In addition, the transfer of foreign matter to the surface of the glass plate is suppressed or avoided. Therefore, the interleaving paper for glass plates of the present invention can be suitably used for glass plates for flat panel displays where surface cleanliness is particularly required.

Moreover, since the difference in the abundance ratio of foreign substances having a Mohs hardness of 4 or more on the front and back surfaces of the interleaving paper for glass plates of the present invention is suppressed, either the front or back surface may be brought into contact with the glass plate. Therefore, the interleaving paper for glass plates of the present invention is excellent in handleability. For example, it is not necessary to sandwich two sheets of interleaving paper between the glass plates and to face the surface of each interleaving paper, whichever has the smaller amount of foreign matter, toward the glass plate. Further, even when the paper is wound into a roll, there is no need to worry about deterioration of the cleanliness of the paper sheet surface due to the transfer of foreign matter having a Mohs hardness of 4 or more from one surface of the paper sheet to the other surface. ..

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the scope of the present invention is not limited to the Examples.

[Manufacturing of wood pulp]
In a coniferous bleached kraft pulp manufacturing apparatus consisting of a cooking step, a washing step, an oxygen delignin reaction step, and a multi-step bleaching bleaching step with chlorine dioxide and hydrogen peroxide, 10,000 to the pulp transfer line after the multi-step bleaching step. A metal removing device in which a plurality of Gaussian magnet bars were arranged was provided to remove metallic foreign substances such as iron present in the pulp slurry. Coniferous bleached kraft pulp A was obtained by the above steps.

On the other hand, softwood bleached kraft pulp B was obtained in the same manner as above except that the in-line box with the magnet bar was not used.

[Example 1]
As wood pulp, 80 parts by mass of softwood bleached kraft pulp A and 20 parts by mass of softwood bleached kraft pulp B were prepared, and these were separated to give a beating degree of 520 mlc. s. f. Polyacrylamide (trade name: Polystron 1254, manufactured by Arakawa Chemical Industry Co., Ltd.) was added to the slurry prepared in the above as a paper strength enhancer by 0.4 parts by mass with respect to the total pulp mass, and a pulp slurry having a concentration of 0.4% by mass was added. Was tuned. This was made using a long net paper machine equipped with an on-top former in the wire part, and dehydrated from both sides of the wet paper by the on-top former to obtain a glass plate interleaving paper with a basis weight of 55 g / m ² . ..

[Example 2]
A glass plate interleaving paper having a basis weight of 55 g / m ² was obtained in the same manner as in Example 1 except that 0.7 parts by mass of polyacrylamide was added.

[Comparative Example 1]
A glass plate interleaving paper having a basis weight of 55 g / m ² was obtained by the same method as in Example 1 except that the on-top former was not used.

[Comparative Example 2]
A glass plate interleaving paper having a basis weight of 55 g / m ² was obtained by the same method as in Example 1 except that 50 parts by mass of softwood bleached kraft pulp A and 50 parts by mass of softwood bleached kraft pulp B were used.

[Measurement of foreign matter with Mohs hardness of 4 or more]
Foreign substances on each surface were identified by observing the front and back surfaces of the glass plate interleaving papers of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 with a stereomicroscope of 100 times. Furthermore, the material of the foreign matter was identified using an X-ray diffraction microscope. Among the foreign substances, the number of foreign substances made of a material having a Mohs hardness of 4 or more was specified and converted per 1000 m ² .

The abundance ratio of foreign substances having a Mohs hardness of 4 or more on the front and back surfaces of the glass plate interleaving papers of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 was as follows. In Example 1, the front surface was 5 pieces / 1000 m ² and the back surface was 1 piece / 1000 m ² . In Example 2, the front surface was 9 pieces / 1000 m ² and the back surface was 5 pieces / 1000 m ² . In Comparative Example 1, the front surface was 13 pieces / 1000 m ² and the back surface was 6 pieces / 1000 m ² . In Comparative Example 2, the front surface was 7 pieces / 1000 m ² and the back surface was 2 pieces / 1000 m ² .

[Transport test]
Urethane foam is laid on the glass mounting surface on the L-shaped stand that is made of aluminum and has an angle of 75 degrees, and from the mounting surface for vertically mounting the glass plate and the rear end of the mounting surface. Insert a glass plate interleaving paper between 120 glass plates of size 680 mm x 880 mm x 0.7 mm and each glass plate toward the backrest surface extending in the vertical direction, and lean against the backrest surface so that it is parallel to the backrest surface. A fixed strip-shaped belt was hung from the rear end to the backrest surface over the entire circumference to fix the glass plate. The entire surface of the gantry set as described above was covered with a packaging material in order to prevent dust and dirt from entering from the outside. After that, a truck transportation test was conducted. As for the transportation test conditions, the test was carried out at a transportation distance of 1000 km (stored in an environment of 40 ° C. × 95% RH for 5 days during transportation).

The glass plate interleaving papers of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 were subjected to the above transportation test. In the above transportation test, when forming an array of liquid crystal panels using a glass plate in which the interleaving papers of Examples 1 and 2 are in contact with each other, even if either the front or back surface of the interleaving paper is brought into contact with the glass plate. No disconnection of the color film was observed. On the other hand, in the above transportation test, when forming an array of liquid crystal panels using the glass plate in which the glass plate interleaving paper of Comparative Example 2 is in contact, when the glass plate in which the back surface of the interleaving paper is in contact is used, No disconnection of the color film was observed, but when a glass plate in which the surface of the interleaving paper was in contact was used, the disconnection of the color film was observed. On the other hand, in the above transportation test, when forming an array of liquid crystal panels using a glass plate in which the glass plate interleaving paper of Comparative Example 1 is in contact, any of the front and back surfaces of the interleaving paper is brought into contact with the glass plate. Also, disconnection of the color film was observed.

Claims (15)

It is a glass plate interleaving paper made from wood pulp.
The presence ratio of foreign substances having a Mohs hardness of 4 or more on one surface is less than 10 per 1000 m ² .
The difference between the abundance ratio of the foreign matter on one surface and the abundance ratio of the foreign matter on the other surface is within 4 per 1000 m ² .
Interleaving paper for glass plates. The interleaving paper for a glass plate according to claim 1, wherein the foreign matter contains a metal oxide or an inorganic silicon oxide. The interleaving paper for a glass plate according to claim 2, wherein the inorganic silicon oxide is silicon dioxide. The combination for a glass plate according to claim 1, wherein the foreign matter is one or more selected from the group consisting of iron oxide, copper, quartz, fused silica, glass pieces, crystal pieces, magnesium oxide, titanium oxide and sand. paper. The interleaving paper for a glass plate according to any one of claims 1 to 4, wherein the volume of the foreign matter is less than 2 × ^10-5 mm ³ . The interleaving paper for a glass plate according to any one of claims 1 to 5, which has a basis weight of 20 to 100 g / m ² . The interleaving paper for a glass plate according to any one of claims 1 to 6, which has a thickness of 0.030 to 0.130 mm. The interleaving paper for a glass plate according to any one of claims 1 to 7, wherein the water content is 2 to 10% by mass. The interleaving paper for a glass plate according to any one of claims 1 to 8, which is used for a glass plate for a display. The interleaving paper for a glass plate according to claim 9, wherein the display is a TFT liquid crystal display or an organic EL display. A laminate composed of the interleaving paper for a glass plate and the glass plate according to any one of claims 1 to 10. The method for manufacturing a glass plate interleaving paper according to any one of claims 1 to 10.
Slurry preparation process, which prepares a slurry of wood pulp,
A sheet forming step of forming the slurry into a sheet,
Wet paper preparation step of dehydrating the sheet to form wet paper,
At least a drying step of drying the wet paper to obtain the interleaving paper is included.
A manufacturing method in which dehydration is performed from both sides of the sheet in the wet paper preparation step. The production method according to claim 12, wherein the dehydration is performed by suction. The production according to claim 13, wherein the difference between the dehydration rate of the suction on one surface of the sheet and the dehydration rate of the suction on the other surface is 10% or less of the dehydration rate of the suction on the other surface. Method. The manufacturing method according to claim 13 or 14, further comprising an additional suction step of sucking both sides of the interleaving paper after the drying step.