TWI701195B - Glass plate-interleaving paper and manufacturing method thereof - Google Patents

Abstract

The present invention relates to an interleaving paper for glass plates, the raw material of which is wood pulp, wherein the existing rate of foreign substances with a Mohs hardness of 4 or more on one surface is less than 10 per 1000 m² and the difference between the existing rates of the foreign substances on one surface and the other surface is within 4 per 1000 m². The interleaving paper according to the present invention can solve problems derived from the difference in the conditions of the front and back surfaces of an interleaving paper for glass plates.

Description

Spacer paper for glass plate and manufacturing method thereof

The present invention relates to a paper for packaging glass plates in the process of laminating several glass plates used in flat panel displays such as liquid crystal displays, plasma displays, and organic electroluminescence (organic EL) displays, and storing and transporting them, and Paper sandwiched between glass plates, and the manufacture of such paper.

Generally speaking, in the storage process where several glass plates used in flat panel displays are stacked and stored, and the distribution process where the glass plates are transported by rails, etc., in order to prevent the glass plates from being impacted and contacting each other and causing scratches, and, The surface of the glass is contaminated by pollutants from outside, and paper called spacer paper is sandwiched between the glass plates.

Compared with ordinary building window glass panels, vehicle window glass panels, etc., flat panel display glass panels are used for high-definition displays. Therefore, the glass surface is required to be kept as clean as possible without the impurities contained in the paper surface. In order to achieve high-speed responsiveness and widen the viewing angle, excellent flatness is required.

As spacer paper for this purpose, several kinds of spacer paper have been proposed that can prevent the glass plate from cracking or surface damage without polluting the glass surface. For example, Patent Document 1 discloses a method of forming a fluorine-plated film on the surface of spacer paper. In addition, Patent Document 2 discloses a spacer paper laminated with a polyethylene resin foam sheet and a polyethylene resin film; Patent Document 3 discloses a paper made of bleached chemical pulp containing 50% by mass or more. A paper made of pulp is a glass spacer paper containing a specific alkylene oxide adduct and a water-soluble polyether modified polysiloxane; in Patent Document 4, it is disclosed that the The amount of resin composition uses spacer paper for glass plates that takes into account the contamination of the glass surface.

[Prior Technical Literature] [Patent Literature]

[Patent Document 1] JP 2012-188785 A

[Patent Document 2] JP 2010-242057 A

[Patent Document 3] JP 2008-208478 A

[Patent Document 4] JP 2006-44674 A

For example, it is known that when the color filter substrate of the array step, which is one of the manufacturing steps of TFT liquid crystal display, is produced, there will be problems such as breakage, damage, etc. on the surface of the glass plate, or when the glass surface is contaminated. . The reason is that the color filter substrate is formed on a glass plate by sputtering or vacuum evaporation, etc., and thin films such as semiconductor film, ITO film (transparent conductive film), insulating film, and aluminum metal film are made. If there are cracks, damages, and contaminants on the surface, the circuit pattern formed by the thin film will have a disconnection or a short circuit due to the defect of the insulating film. In addition, in the production of the color filter substrate, the pattern is formed by photoetching on the glass plate, but if there are cracks, damages, or contaminants on the glass plate surface when the resist is applied in this step, the exposure Or pinholes may occur in the resist film after development, resulting in disconnection or short circuit. The same problem has also been confirmed in the manufacture of organic EL displays. The organic EL display is formed on a glass substrate by sputtering, vapor deposition, or printing to produce ITO anodes, organic light-emitting layers, cathodes and other thin films. Therefore, if there are substances on the surface of the glass substrate that hinder the cracking, damage, and pollution of the thin films, Will produce the problem of no light.

It is difficult to identify the causes of cracks, damages, and contamination of such glass plates, but it has been determined that one of the causes is fine foreign matter, which is present on the surface of the glass plate spacer paper or from the glass plate spacer The surface of the paper is transferred to the surface of the glass plate.

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

In addition, when the spacer paper for the glass plate is sandwiched between the glass plates, when there is a difference in the physical state of the front and back surfaces of the spacer paper, it is sometimes necessary to consider the specific surface of the spacer paper and the surface of the glass plate. contact. For example, for glass plates for flat-panel displays, in order to form fine circuits on the surface, even a small amount of foreign matter is particularly prevented from adhesion or cracking and damage caused by the foreign matter. If there are more foreign objects on one surface of the spacer paper than on the other surface, the risk of cracking or damage to the surface of the glass plate caused by the foreign objects, or the risk of the foreign objects being transferred to the surface of the glass plate is increased, so it should be considered to make foreign objects The surface of the glass plate is in contact with the surface of the glass plate in a way that the surface with fewer surfaces is not more foreign objects. In this case, consider sandwiching two pieces of spacer paper between the glass plates, so that the surface of each spacer paper with a small amount of foreign matter facing the glass plate will increase the amount of spacer paper used. The weight of the laminated body of the glass plate increases, so the handling is not good.

The problem of the present invention is to solve the above-mentioned problem caused by the difference in the state of the front and back of the spacer paper for glass plates. In particular, the subject of the present invention is to provide a spacer paper for glass plates whose front and back surfaces can contact the glass plate.

Therefore, after diligent research, the inventor found that it is possible to provide a spacer paper for glass plates by reducing the amount of foreign matter with a Mohs hardness of 4 or more present on the surface of the spacer paper for glass plates and suppressing the spacer paper The difference in the existence ratio of foreign matter with Mohs hardness of 4 or more on the front and back can suppress the difference in the state of the front and back of the spacer paper for the glass plate, so that either the front or the back can be in contact with the glass plate , Thereby completing the present invention.

The first aspect of the present invention is a spacer paper for glass plates, which uses wood pulp as a raw material, and the proportion of foreign matter with a Mohs hardness of 4 or more present on a surface is less than 10 per 1000 m ² . The difference between the above-mentioned foreign matter existence ratio and the above-mentioned foreign matter existence ratio on the other surface is within 4 per 1000 m ² .

It is preferable that the above-mentioned foreign matter contains a metal oxide or an inorganic silicon oxide. Preferably, the above-mentioned inorganic silicon oxide is silicon dioxide.

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

Preferably, the volume of the above-mentioned foreign body is less than 2×10 ^-5 mm ³ .

Preferably, the basis weight of the spacer paper for glass plates of the present invention is 20-100 g/m ² .

Preferably, the thickness of the spacer paper for the glass plate of the present invention is 0.030 to 0.130 mm.

Preferably, the water content of the spacer paper for glass plates of the present invention is 2-10% by mass.

Preferably, the above-mentioned glass is used for a display. Preferably, the above-mentioned display is a TFT liquid crystal display or an organic EL display.

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

The second aspect of the present invention relates to a manufacturing method, which is a method of manufacturing the above-mentioned spacer paper for glass plates, at least comprising: a slurry preparation step, which prepares wood pulp slurry; and a sheet formation step, which combines the above-mentioned slurry Formed into a sheet; a wet paper preparation step, which dehydrates the above-mentioned sheet to form a wet paper; and a drying step, which dries the above-mentioned wet paper to obtain the above-mentioned spacer paper; and in the above-mentioned wet paper preparation step is performed from both sides of the above-mentioned sheet Dehydrated.

Preferably, the above-mentioned dehydration is performed by suction.

Preferably, the difference between the dehydration ratio of the suction on one surface of the sheet and the dehydration ratio of the suction on the other surface is 10% or less of the dehydration ratio of the suction on the other surface.

Preferably, the manufacturing method described above includes an additional suction step of further suctioning both sides of the spacer paper after the drying step.

In the spacer paper for glass plates of the present invention, the amount of foreign matter with a Mohs hardness of 4 or more on the surface is relatively small, and the ratio of foreign matter with a Mohs hardness of 4 or more on the front and back of the spacer paper is different. Suppressing the difference in the existence of foreign matter with Mohs hardness of 4 or more between the front and back of the spacer paper for glass plates is suppressed. Therefore, any one of the front and back of the spacer paper for glass plates of the present invention can be in contact with the glass plate. Thereby, the spacer paper for glass plates of the present invention has excellent operability.

In addition, the spacer paper for glass plates is originally rolled into a roll and shipped. In the wound state, the front and back of the spacer are in contact with each other. Therefore, for example, there are few foreign objects with a Mohs hardness of 4 or more on the front. When there are many foreign objects with Mohs hardness of 4 or more on the back, even if the front side of the spacer paper is to be in contact with the surface of the glass plate, the foreign objects with the Mohs hardness of 4 or more on the back of the spacer paper in the rolled state It will be transferred to the front, and the cleanliness of the front may be reduced.

However, even if the spacer paper for glass plates of the present invention is rolled into a roll shape, it can suppress the transfer of foreign matter with a Mohs hardness of 4 or more from one surface of the spacer paper to the other surface, so there is no need to worry about being rolled. Taking it into a roll shape reduces the cleanliness of the front side of the spacer paper, that is, the proportion of foreign matter with a Mohs hardness of 4 or more increases.

Furthermore, in the spacer paper for glass plates of the present invention, the amount of foreign matter with a Mohs hardness of 4 or more present on the surface is small, so even if the spacer paper contacts the surface of the glass plate, it can reduce or even avoid cracks on the surface of the glass plate. , Damage, etc., and can effectively prevent or even avoid the transfer of foreign matter with a Mohs hardness of 4 or more from the spacer paper to the glass plate. By reducing or even avoiding the problems of cracks and damages on the surface of the glass plate, it also prevents or even avoids the transfer of foreign matter with a Mohs hardness of 4 or higher to the glass plate. For example, in the manufacturing steps of TFT liquid crystal displays, it can prevent color The circuit of the film is broken.

The first aspect of the present invention is a spacer paper for glass plates, which uses wood pulp as a raw material, and the proportion of foreign matter with a Mohs hardness of 4 or more present on a surface is less than 10 per 1000 m ² . The difference between the above-mentioned foreign matter existence ratio and the above-mentioned foreign matter existence ratio on the other surface is within 4 per 1000 m ² .

The so-called foreign matter with Mohs hardness of 4 or higher existing on the surface of the spacer paper for glass plates of the present invention does not reach 10 per 1000 m ² means that the spacer paper for glass plates of the present invention exists alone, that is, the glass plate of the present invention In the state where the spacer paper is not laminated with the glass plate, the ratio of the above-mentioned foreign matter existing on the surface of the spacer paper is less than 10 per 1000 m ² . Among them, it is preferable that the spacer paper for the glass plate of the present invention is in contact with the glass plate or pressed against the glass plate, that is, when the spacer paper for the glass plate of the present invention is laminated with the glass plate, the surface of the spacer paper The ratio of the above-mentioned foreign matter present is less than 10 per 1000 m ² .

The wood pulps that can be used in the present invention are conifer bleached kraft pulp (NBKP), hardwood bleached kraft pulp (LBKP), conifer bleached sulfite pulp (NBSP), hardwood bleached sulfite pulp (LBSP), thermomechanical pulp (TMP) and other wood pulp used alone or mixed. The wood pulp can be used as the main body, and if necessary, hemp, bamboo, straw, non-wood pulp such as kenaf, chrysanthemum or cotton, cationized pulp, mercerized pulp and other modified pulp, rayon, pooh Synthetic fibers or chemical fibers such as nylon, nylon, acrylic, polyester, or microfibrillated pulp are added separately or mixed together. However, if the pulp contains more resin components, the resin components may cause adverse effects such as contaminating the surface of the glass plate. Therefore, it is better to use chemical pulp with less resin components as much as possible, such as conifer bleached kraft pulp . In addition, high-yield pulp like shredded wood pulp contains a lot of resin components and is therefore not preferable. In addition, if synthetic fiber and chemical fiber are mixed, the cutting performance is improved, and the workability when forming the spacer paper into a lithographic plate is improved. However, in terms of waste disposal, the reusability is deteriorated, so be careful.

The form of the wood pulp is not particularly limited, and it can take any form of sheet, block, or flake. The sheet-like pulp can be obtained by using a pulp machine equipped with 4 steps, for example, a wire part, a pressing part, a drying part, and a post-processing. The wire part uses a Fourdrinier wire or vacuum filter to make paper from the pulp fiber, and the extrusion part uses a roller press for dehydration. The drying part uses a drum dryer or a Fläkt dryer to dry, and finally cuts off the two ends of the sheet pulp and winds it into a roll. This method is described in detail in the "Pulp Manufacturing Technology Series" and "Pulp Manufacturing Technology Book" published by the Pulp Technology Association. In addition, the block-shaped pulp can be obtained, for example, by laminating the aforementioned sheet-like pulp, and the flake-shaped pulp can be obtained, for example, by pulverizing the aforementioned sheet-like pulp.

The thickness of the above-mentioned sheet-like 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 above-mentioned sheet pulp is preferably 400~1300g/m ² , more preferably 500~1200g/m ² , still more preferably 500~1100g/m ² , and still more preferably 500~1000g/m ² , It is still more preferably 700 to 1000 g/m ² .

In the spacer paper for glass plates of the present invention, the proportion of foreign substances with a Mohs hardness of 4 or higher on one surface is limited to less than 10 per 1000 m ² . The number of foreign objects with a Mohs hardness of 4 or more on the surface of the spacer paper for glass plates is preferably 8/1000m ² or less, more preferably 6/1000m ² or less, and still more preferably 4 /1000m ² or less, still more preferably 3 pieces/1000m ² or less, still more preferably 2 pieces/1000m ² or less, particularly preferably 1 piece/1000m ² or less.

In the spacer paper for glass plates of the present invention, the difference between the proportion of foreign matter with a Mohs hardness of 4 or higher on one surface and the proportion of foreign matter with a Mohs hardness of 4 or higher on the other surface is per 1000 m ² less than 4, preferably less per 1000m ² to 3, more preferably 1000m ² per 2 or less, and further more preferably 1000m ² or less per 1. That is, in the spacer paper for glass plates of the present invention, it is preferable that the ratio of foreign matter with a Mohs hardness of 4 or more on one surface is not lower than the ratio of foreign matter with a Mohs hardness of 4 or more on the other surface. The difference between the two changes greatly within the above-mentioned specific range.

Here, the so-called "existence ratio" refers to the number of foreign objects with a Mohs hardness of 4 or more per unit area on the surface of the spacer paper. For example, the surface of the spacer paper for glass plates can be magnified and observed by using an electron microscope. , And determine the average number of foreign objects with a Mohs hardness of 4 or more observed at the site. Or as another method, the surface of a specified area of the spacer paper for the glass plate is sufficiently cleaned with water or acid solution or alkaline solution, and the foreign matter with Mohs hardness of 4 or more that has fallen off is counted, and the Mohs can be determined by this method. The proportion of foreign matter with a hardness of 4 or more.

In the spacer paper for glass plates of the present invention, the amount of foreign matter with a Mohs hardness of 4 or more on the surface is small, and the ratio of foreign matter with a Mohs hardness of 4 or more on the front and back of the spacer can be suppressed Variation, thereby, can suppress the difference in physical state between the front and back of the spacer paper for glass plates. Therefore, in the spacer paper for glass plates of the present invention, there is no significant difference in the proportion of foreign matter with a Mohs hardness of 4 or more between the front and back of the spacer paper. Therefore, for the spacer paper for glass plates of the present invention, either of the front and back surfaces can be in contact with the glass plate.

The foreign matter having a Mohs hardness of 4 or more in the present invention may be particles composed of inorganic or organic substances, and inorganic particles are preferred. Examples of the aforementioned foreign matter include metal oxides or inorganic silicon oxides having a Mohs hardness of 4 or more. The metal constituting the metal oxide is not particularly limited as long as the Mohs hardness of the oxide is 4 or more, and examples include group 2 elements such as magnesium, group 4 elements such as titanium, and group 8 elements such as iron. As the inorganic silicon oxide, silicon dioxide is preferred. Examples of the foreign matter having a Mohs hardness of 4 or more include oxide 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 flakes, quartz flakes, magnesium oxide, and sand. Sand is mainly composed of hornblende with Mohs hardness of 5.5, feldspar with Mohs hardness of 6 and quartz with Mohs hardness of 7. Therefore, the Mohs hardness of sand is 4 or more, typically 7. The so-called Mohs hardness refers to the hardness index expressed in 10 grades, which is obtained by rubbing the corresponding standard material with the material to be measured, and comparing the hardness relative to the standard material according to whether there is damage. The value. The standard materials from soft (Mohs hardness of 1) to hard (Mohs hardness of 10) are: 1: talc, 2: gypsum, 3: calcite, 4: fluorite, 5: apatite, 6: feldspar , 7: Quartz, 8: Topaz, 9: Corundum, 10: Diamond. The method of measuring the Mohs hardness is to prepare two plates with a smooth surface and a known Mohs hardness, sandwich the foreign matter to be measured between the two plates, rub the two plates against each other to check whether the surface of the plate is damaged.

The foreign matter is easily contained in the spacer paper for the glass plate. Among them, the foreign matter that may damage the surface of the glass plate is mostly derived from raw materials, especially quartz, fused silica, sand and quartz flakes with a Mohs hardness of 7 In the case of magnesium oxide, titanium oxide, and iron oxide with a hardness of 6, copper with a Mohs hardness of 5-8, and glass sheets with a Mohs hardness of 4-7.

In the present invention, the volume of the foreign matter is preferably controlled to less than 0.00002 mm ³ , more preferably less than 0.00001 mm ³ . Foreign matter is different from dirt. It exists as a three-dimensional object on the surface or inside of the spacer paper and causes problems. In particular, if the size of the foreign matter becomes 0.00002 mm ³ or more, when the spacer paper for glass plates is used, there is a tendency that the foreign matter contacts the surface of the glass plate and leaves damage or cracks. For example, when the glass plate is laminated with spacer paper and the glass plate, the foreign matter on the surface of the spacer paper may be squeezed due to the weight of the glass plate. However, if the size of the foreign matter is small, the foreign matter will also be squeezed. It will be buried in the paper of the spacer paper, so the possibility of damage to the surface of the glass plate is reduced. Furthermore, as mentioned above, the foreign object is a three-dimensional object, so especially when its projected area is small but has a certain height, it may be seen as a scratch when moving the glass or glass plate spacer paper. Risk of injury. Conversely, when the height is low but the projected area is large, it may damage the surface of the glass plate, so it is still not good.

The average particle diameter of the spherical volume equivalent diameter of the foreign matter is preferably 30 μm or less, more preferably 20 μm or less, still more preferably 10 μm or less, still more preferably 5 μm or less, and particularly preferably 1 μm or less. The so-called equivalent diameter of the ball volume refers to the diameter of the ball when the particles of the foreign matter are converted into a ball of the same volume, which can be measured by the laser diffraction method.

The basis weight of the spacer paper for glass plates of the present invention is preferably 20-100 g/m ² , more preferably 30-90 g/m ² , and still more preferably 40-80 g/m ² . If it is less than 20 g/m ² , it is difficult to maintain the lower limit of air permeability (5 seconds or more). After use, the glass plate may be sucked to remove the spacer paper for the glass plate, and the suction may spread to the glass plate body. Furthermore, if it is less than 20 g/m ² , the toughness of the spacer paper for glass plates itself becomes weak, and the workability also becomes poor, which is not preferable. In addition, if the basis weight exceeds 100 g/m ² , the flexibility of the spacer paper for glass plates is impaired, and the workability deteriorates. In addition, the purpose of using spacer paper for glass plates is to protect the glass plates used during transportation and storage to prevent damage and contamination. Therefore, increasing the basis weight beyond necessary is disadvantageous in terms of cost, and workability is also reduced.

The thickness of the spacer paper for glass plates 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 0.030mm, the protective effect of the glass plate used during transportation and storage is reduced, which is not good. In particular, it is difficult to fully exert the cushioning function as a spacer, and there is also a risk of being easily damaged due to the thickness being too thin. In addition, if it exceeds 0.130 mm, the thickness of the laminate of the glass plate and the spacer paper for the glass plate will increase, which is expected to cause problems in storage space or transportation.

The water content of the spacer paper for glass plates of the present invention is preferably 2-10% by mass, more preferably 3-9% by mass, and still more preferably 4-8% by mass. If the water content is less than 2% by mass, the spacer paper for the glass plate itself is prone to static electricity, and adhesion between the glass plate and the glass plate caused by static electricity will occur, which is not good. In addition, if the water content exceeds 10% by mass, there is a risk of adhesion to the glass plate due to excessive water, or deterioration of dimensional stability due to reduction of water during use.

Regarding the surface resistance value of the spacer paper for glass plates of the present invention (according to JIS K 6911 1995), the spacer paper is subjected to humidity conditioning for more than 24 hours under the conditions of a temperature of 23°C and a relative humidity of 50%, and then under the same conditions In the next measurement, 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 still more preferably 1×10 ⁹ to 1×10 Within the range of ¹² Ω. When the surface resistance value is less than 1×10 ⁸ Ω, the adhesion between the glass plate and the spacer paper is reduced, and the workability may deteriorate. Furthermore, the expression that the surface resistance value is less than 1×10 ⁸ Ω means that water or a conductive substance (such as a surfactant) is added more than necessary. Excessive moisture may have a bad influence on the dimensional stability of the spacer paper for glass plates. In addition, most of the conductive materials are organic materials, so these materials are transferred to the surface of the glass plate to cause pollution and other problems. Yu. On the other hand, if the surface resistance value of the spacer paper for glass plates becomes a high resistance value exceeding 1×10 ¹³ Ω, it is easy to be charged with static electricity, and the spacer paper may be in close contact with the surface of the glass plate in contact, which may significantly hinder operability. As a method of adjusting the surface resistance value within a desired range, for example, moisture adjustment by drying or the like can be mentioned.

The spacer paper for glass plates of the present invention may also contain short fibers having a fiber length of 200 μm or less, but the short fibers may pull foreign matter out, so the content of the short fibers is preferably relative to the absolute dry mass of the spacer paper It is 4.5% by weight or less, more preferably 4.0% by weight or less, still more preferably 3.5% by weight or less, and particularly preferably 3.0% by weight or less. Here, the "fiber length" refers to the average fiber length. Therefore, for short fibers having a fiber length of 200 μm or less, all of them have a fiber length of 200 μm or less. In other words, the maximum fiber length of the aforementioned short fibers is 200 μm or less. Here, the term "fiber length" refers to the length of the fiber when the fiber is drawn straight.

The average fiber diameter of the aforementioned 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.

Furthermore, the "average fiber diameter" here refers to the magnified observation of multiple parts on the surface of the spacer paper for the glass plate using an electron microscope, and randomly selects a specified number of fibers from each electron microscope image, and determines the selected fibers The average fiber diameter is obtained by averaging it. The number of fibers to be screened is 100 or more, preferably 150 or more, more preferably 200 or more, and even more preferably 300 or more.

The amount of short fibers on the surface of the spacer paper for glass plates of the present invention is preferably 50 to 600 fibers/cm ² , more preferably 60 to 500 fibers/cm ² , and even more preferably 70 to 400 fibers/cm ² cm ² . If the amount of short fibers is relatively small, the amount of foreign matter drawn by the short fibers can be reduced.

In the spacer paper for glass plates of the present invention, the difference between the amount of the short fibers on one surface and the short fibers on the other surface is preferably 15% or less of the amount of the short fibers on the other surface. It is preferably 12% or less, and more preferably 10% or less. That is, in the spacer paper for glass plates of the present invention, it is preferable that the amount of short fibers on one surface does not greatly vary to such an extent that it falls within the above-mentioned specific range according to the amount of short fibers on the other surface. Here, the so-called "existing amount" refers to the number of the aforementioned short fibers on the surface of the spacer paper. For example, it can be observed by magnifying a number of parts on the surface of the spacer paper for glass plates with an electron microscope, and observing that part The number of short fibers is determined by averaging. In addition, it is also possible to select short fibers of 200 μm or less from the fibers that fall down to a predetermined area by rubbing the front side of the spacer paper with a sheet, etc., and obtain the number per unit area. Furthermore, it can be determined by dividing the spacer paper into two parts in the center of the thickness direction to form two very thin paper, pulping each paper and measuring the number of short fibers of 200 μm or less in the slurry. Or as another method, the surface of the spacer paper for glass plates is sufficiently washed with water, and the fallen fibers are measured by a fiber length measuring machine, thereby determining the amount of short fibers.

The spacer paper for glass plates of the present invention can be manufactured based on common methods such as papermaking methods.

The second aspect of the present invention is a manufacturing method, which is a method of manufacturing spacer paper for glass plates, at least comprising: a slurry preparation step, which prepares a slurry of wood pulp; and a sheet formation step, which forms the slurry into Sheet form; wet paper preparation step, which dehydrates the above-mentioned sheet to form wet paper; and a drying step, which dries the above-mentioned wet paper to obtain the above-mentioned spacer paper; and in the above-mentioned wet paper preparation step, it is performed from both sides of the sheet-like slurry Dehydrated.

In order to reduce the number of foreign objects with a Mohs hardness of 4 or higher on the surface of the spacer paper for glass plates to less than 10 per 1,000 m ² , the focus is on the research and management of paper-making raw materials such as pulp, paper-making chemicals, and fillers as raw materials , And a series of steps management from the preparation step of the raw material during the papermaking to the post-processing step, and it is especially preferable to make the wood pulp as the raw material of the spacer paper free of many foreign substances.

Generally, wood pulp contains various foreign substances. For example, foreign matter from wood used as a raw material for wood pulp, foreign matter from cooking chemicals in pulp manufacturing, foreign matter from chemicals used in the unbleached cleaning step, metal foreign matter from waste paper raw materials, or foreign matter from various steps Foreign matter in the water used. Therefore, in the present invention, it is preferable to clean and select the pulp that is a raw material of spacer paper for glass plates, and to remove foreign matter from the pulp as much as possible in advance.

Generally speaking, in the pulp manufacturing process, after the pulp obtained by cooking wood chips is delignified, the pulp is washed and then bleached. Therefore, it is better to first remove and clean the debris from the wood debris. For example, it is preferable to remove foreign matter such as metal and sand in a known foreign matter removal system such as a debris scrubber. In addition, in the pulp manufacturing step, the purpose of cleaning after cooking is to remove the cooking liquid, lignin decomposition products, and colored components remaining in the pulp liquid, but it can also remove foreign matter at the same time. For example, well-known methods such as a convection cleaning method using various cleaning devices such as a vacuum filter, a pressurized drum filter, a pressure cleaning machine, and a diffusion cleaning machine can be used. In order to remove foreign matter and improve the cleanliness of the pulp, it is particularly preferable to increase the amount of washing water used, or to adopt a multi-stage washing method with more than 2 rinsing stages. Furthermore, as chemicals used in cleaning such as surfactants, pH adjusters, spacing control agents, chelating agents, defoamers, etc., it is better not to use substances that can cause foreign matter. For example, mineral oil-based defoamers used as defoamers may cause mineral foreign matter in spacer paper for glass sheets. Therefore, it is better to suppress the use of mineral oil-based defoamers or substitute other defoamers. use.

There is a bleaching step after the above-mentioned cleaning step, and it is preferable to remove foreign matter as much as possible here. For example, a cleaning device is provided for each stage of bleaching. A well-known washing machine can also be used here, for example, a high-pressure diffuser, a diffusion washing machine, a pressure drum washing machine, a horizontal fourdrinier washing machine, a pressure washing machine, etc. can be used. Especially by using a plurality of the above-mentioned washing machines, various foreign substances can be highly removed. Furthermore, chemicals such as alkalis, acids, chelating agents, surfactants, defoamers, etc. can also be added to the washing water, and it is preferable not to use chemicals that can cause foreign matter. In addition, it is preferable to adopt a strategy to prevent foreign matter from being mixed between steps. Moreover, it is more preferable to use the following iron component removal method in combination.

When waste paper pulp is used as a raw material in the present invention, it is preferable to use a beater, a sieve, a cleaner, etc. to remove foreign matter at a high level in the waste paper pulp manufacturing step.

In the above slurry preparation step, a previously known method can be used to prepare wood pulp slurry. For example, in the aforementioned slurry preparation step, the cellulose fibers constituting the wood pulp are depolymerized and used as an aqueous suspension to prepare the slurry.

In addition, within the range that does not impair the performance of the present invention, adhesives, anti-mold agents, defoamers, fillers, wet paper strength enhancers, dry paper strength enhancers, sizing agents, Coloring agent, fixing agent, yield enhancer, viscosity control agent, etc. Furthermore, care should be taken when adding these chemicals to prevent insects, dirt, etc. from being mixed in.

When preparing the above-mentioned slurry, if wood pulp beating is performed, the effect of increasing the strength between paper layers can be expected. However, if the fine fibers are increased by beating, the following problems may occur, that is, foreign matter is pulled out, or paper dust is generated during use as a spacer paper, so it is not good to increase the beating degree more than necessary. The preferred beating degree in the present invention is 300~650mlc.s.f.

In the sheet forming step of forming the above-mentioned slurry into a sheet shape, a previously known method can be used for sheet formation. For example, by spitting out the above-mentioned slurry onto a flat wire (for example, a Fourdrinier paper machine), or using a wire wound into a cylindrical tube to take a sheet from the slurry (for example, a cylinder paper machine) Available films.

In addition, as the possibility of foreign matter being mixed in the spacer paper, mixing in the papermaking step can also be cited. For example, the case where it is mixed into paper-making chemicals, or the case where the raw materials of various devices fall off and mixed into paper, etc. are mentioned. As a method for removing foreign matter in this papermaking step, dust removal devices such as cleaners or screen devices and other cleaning devices can be used. In the present invention, such removal methods can use well-known devices, such as centrifugal cleaners, special weight cleaners, medium concentration cleaners, lightweight cleaners, porous screens, slit screens, vibrating screens, flat screens, And other washing machines. In addition, foreign matter may be mixed into the pipes of paper or white water, so it is better to keep the pipes clean at all times.

Furthermore, with regard to the iron component that is one of the causes of foreign matter, iron powder or rust is mixed and oxidized from the pulp manufacturing equipment or paper machine piping due to friction or corrosion, thereby becoming iron oxide with high Mohs hardness. Therefore, it is preferable to selectively remove the iron component. For example, it is preferable to use a material other than iron for each device, or install a high-magnetic material such as a magnet in the system to selectively remove the iron component, or arrange an adsorption material that selectively adsorbs iron in the above-mentioned devices. Exit side. The method of selective removal by high-magnetic material can not only remove iron, but also other magnetic materials.

In this way, for example, by using wood pulp with less foreign matter as a raw material, and carefully removing foreign matter in the papermaking step, it is possible to produce foreign matter with a Mohs hardness of 4 or higher on the surface of spacer paper for glass plates per 1000 m ² Spacer paper for glass plates less than 10 pieces.

In the second aspect of the present invention, in the wet paper preparation step of dehydrating the above-mentioned sheet to form a wet paper, dehydration is performed from both sides of the sheet. Thereby, foreign matter with Mohs hardness of 4 or more contained in the above-mentioned sheet can be effectively removed from both sides of the sheet. Therefore, the difference between the proportion of foreign substances with a Mohs hardness of 4 or higher on one surface and the proportion of foreign substances with a Mohs hardness of 4 or higher on the other surface can be within 4 per 1000 m ² .

The above-mentioned dehydration method is arbitrary, and previously known methods can be used. For example, dehydration can be performed by pressing the sheet with a roller. However, in order to effectively remove foreign matter with a Mohs hardness of 4 or more, it is preferable to perform the above-mentioned dehydration by suction.

The step of dehydrating from both sides of the sheet can also be dehydrated by sucking the sheet up and down by a suction device in a state where the sheet extending in the horizontal direction is clamped from top to bottom with a net, but due to the influence of gravity , There will be a difference between the suction force in the upward direction and the suction force in the downward direction, so that the surface of the sheet on the side that is sucked in the upward direction remains compared to the surface of the sheet on the side that is sucked in the downward direction. Since there is a risk of foreign matter with a Mohs hardness of 4 or more, it is preferable to use a net to sandwich the sheet extending in the vertical direction and to suck the sheet in the left and right directions for dehydration. In this case, it is preferable to maintain the moving direction of the wet paper in the vertical direction or a tilt range within 30° from the vertical direction.

Preferably, the difference between the dehydration ratio (dehydration rate) of the suction on one surface of the sheet and the dehydration ratio (dehydration rate) of the suction on the other surface is the dehydration ratio of the suction on the other surface (dehydration rate) Rate) below 10%. That is, in the manufacturing method of the spacer paper for glass plates of the present invention, it is preferable to perform suction from both sides of the sheet with substantially the same suction force.

The above-mentioned sheet forming step and wet paper preparation step may be performed individually using different devices, or may be performed continuously or partially overlapping in the same device. For example, it is also possible to place the slurry on the wire (mesh) at the same time in the wire part of the paper machine, to sheet it, and to dewater it to form a wet paper.

In the drying step, the spacer paper can be obtained by drying the wet paper by a previously known method using a drying drum or the like.

In order to further remove foreign matter that may remain on the surface of the spacer paper with a Mohs hardness of 4 or higher, the method for manufacturing spacer paper for glass plates of the present invention preferably includes further extracting both sides of the spacer paper after the drying step. Suction is an additional suction step.

Furthermore, during and/or after papermaking of spacer paper for glass plates, calendering treatment, super calendering treatment, soft calendering treatment, embossing, etc. can also be processed. Through processing, the surface and thickness can be adjusted.

By the manufacturing method of the second aspect of the present invention, the spacer paper for glass plates of the first aspect of the present invention can be efficiently manufactured.

The spacer paper for glass plates of the present invention can be inserted between glass plates and used. For example, it is more typical to insert the above-mentioned spacer paper for glass plates one by one between a plurality of glass plates to form a laminate as a whole, and use the laminate as an object for storage and transportation. Moreover, you may use the spacer paper for glass plates of this invention to package a single glass plate or the said laminated body. Therefore, the present invention has an aspect of a method for protecting a glass plate, which includes a step of arranging (especially inserting) spacer paper for the glass plate between the glass plates.

The glass plate is not particularly limited, but a glass plate for flat panel displays such as plasma display panels, liquid crystal display panels (especially TFT liquid crystal display panels), and organic EL display panels are preferred. Fine electrodes, partition walls, etc. are formed on the surface of the glass plate for flat panel displays. However, by using the spacer paper for glass plates of the present invention, the problem of breakage or damage of the glass plate and the transfer of foreign matter to the glass plate can be suppressed or even avoided. The problem is that even if fine electrodes, partitions, etc. are formed on the surface of the glass plate, the defects caused by the foreign matter can be suppressed or even avoided, and as a result, the defects of the display can be suppressed or even avoided.

Along with the enlargement of displays, the size and weight of glass plates for flat panel displays have increased, but the spacer paper for glass plates of the present invention can particularly well protect the surface of such large or heavy glass plates. In particular, in the spacer paper for glass plates of the present invention, the content of foreign matter with a Mohs hardness of 4 or more is extremely small, so even if it is squeezed by a heavy glass plate, it can reduce or even avoid cracking or damage on the surface of the glass plate. It can prevent or even prevent the transfer of foreign matter to the surface of the glass plate. Therefore, the spacer paper for glass plates of the present invention can be preferably used for glass plates for flat panel displays that particularly require surface cleanability.

In addition, the spacer paper for glass plates of the present invention can suppress the difference in the existence ratio of foreign matter having a Mohs hardness of 4 or more between the front and back of the spacer paper, so that either the front and the back can contact the glass plate. Therefore, the spacer paper for glass plates of the present invention has excellent operability. For example, it is not necessary to sandwich two pieces of spacer paper between the glass plates and make the surface of each spacer paper which has a smaller amount of foreign matter facing the glass plate. Moreover, even if it is wound into a roll shape, there is no need to worry about the deterioration of the surface cleanliness of the spacer paper caused by the transfer of foreign matter with a Mohs hardness of 4 or more from one surface of the spacer paper to the other surface.

[Example]

Hereinafter, examples and comparative examples are used to explain the present invention more specifically, but the scope of the present invention is not limited to the examples.

[Manufacture of wood pulp]

In the conifer bleached kraft pulp manufacturing device composed of a cooking step, a cleaning step, a deoxylignin reaction step, and a multi-stage bleaching step using chlorine dioxide and hydrogen peroxide, the pulp conveying line after the multi-stage bleaching step is installed A metal removal device with multiple 10,000 Gauss magnetic rods arranged to remove metal foreign matter such as iron components in the pulp slurry. Through the above steps, a conifer bleached kraft pulp A is obtained.

On the other hand, except that the in-line box equipped with the above-mentioned magnetic rods is not used, the other methods are the same as the above, to obtain the conifer bleached kraft pulp B.

[Example 1]

As wood pulp, 80 parts by mass of conifer bleached kraft pulp A and 20 parts by mass of conifer bleached kraft pulp B were prepared, and the pulp was depolymerized to prepare a pulp with a beating degree of 520 mlc.sf. The addition was 0.4 relative to the total mass of the pulp. Part by mass of polypropylene amide (trade name: Polystron 1254, manufactured by Arakawa Chemical Industry Co., Ltd.) was used as a paper strength enhancer to prepare a pulp slurry with a concentration of 0.4% by weight. Use a Fourdrinier paper machine equipped with an on top former in the wire section to make paper, and use the on top former to dehydrate both sides of the wet paper to obtain a basis weight of 55g/m ² Spacer paper for glass plates.

[Example 2]

A spacer paper for glass plates having a basis weight of 55 g/m ² was obtained by the same method as in Example 1 except for adding 0.7 parts by mass of polypropylene amide.

[Comparative Example 1]

A spacer paper for glass plates with a basis weight of 55 g/m ² was obtained by the same method as in Example 1 except that the laminating machine was not used.

[Comparative Example 2]

Except that 50 parts by mass of coniferous bleached kraft pulp A and 50 parts by mass of coniferous bleached kraft pulp B were used, the other methods were the same as in Example 1, to obtain spacer paper for glass plates with a basis weight of 55 g/m ² .

[Measurement of foreign matter with Mohs hardness of 4 or more]

The front and back surfaces of the spacer paper for glass plates of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were observed with a 100-fold stereo microscope to identify foreign matter on each surface. Furthermore, an X-ray diffraction microscope was used to identify the material of the foreign matter. Specify the number of the above-mentioned foreign objects made of materials with a Mohs hardness of 4 or more, and convert them to how many per 1000m ² .

On the front and back surfaces of the spacer paper for glass plates of Example 1, Example 2, Comparative Example 1, and Comparative Example 2, the existence ratio of foreign matter with a Mohs hardness of 4 or more is as follows. In Example 1, the front side is 5 pieces/1000m ² , and the back side is 1 piece/1000m ² . In Example 2, the front side is 9 pieces/1000m ² and the back side is 5 pieces/1000m 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 is 7 pieces/1000m ² , and the back surface is 2 pieces/1000m ² .

[Transportation test]

Spread foamed polyurethane on the glass mounting surface on the aluminum L-shaped stand that forms an angle of 75 degrees, facing the mounting surface for placing the glass plate in the vertical direction and the rear end of the mounting surface On the back side extending in the vertical direction, insert spacer paper for the glass plate between 120 glass plates with a size of 680mm×880mm×0.7mm and each glass plate, and erect it parallel to the back side, and fix it on The belt-shaped conveyor belt of the stand is erected from the rear end to the back side all the way to fix the glass plate. In order to prevent dust and dirt from entering, the entire surface of the stand set as described above is covered with packaging materials. After that, a transport test on the track was implemented. The transportation test condition is that the transportation distance is 1000km (during transportation, it is stored in an environment of 40℃×95%RH for 5 days). The above-mentioned conveyance test was performed on the spacer paper for glass plates of Example 1, Example 2, Comparative Example 1, and Comparative Example 2. In the above-mentioned transport test, when the glass plate in contact with the spacer paper of Example 1 and Example 2 is used to form an array of liquid crystal panels, there is no situation when either of the front and back of the spacer paper is in contact with the glass plate. See broken thread of color film. On the other hand, in the above-mentioned transport test, when the glass plate in contact with the spacer paper for the glass plate of Comparative Example 2 was used to form an array of liquid crystal panels, no color film was seen when the glass plate in contact with the back of the spacer paper was used. However, when using the glass plate in contact with the front surface of the spacer, the color film is broken. On the other hand, in the above-mentioned transport test, when the glass plate contacted with the spacer paper for the glass plate of Comparative Example 1 is used to form an array of liquid crystal panels, when either the front or back of the spacer paper is in contact with the glass plate Disconnection of the color film was seen.

Claims (15)

A spacer paper for glass plates, which is made of wood pulp as the raw material, and the proportion of foreign objects with Mohs hardness of 4 or higher on a surface is less than 10 per 1000 m ² , and the presence of the above-mentioned foreign objects on a surface The difference between the ratio and the ratio of the foreign matter on the other surface is within 4 per 1000 m ² . The spacer paper for a glass plate according to claim 1, wherein the foreign matter includes a metal oxide or an inorganic silicon oxide. The spacer paper for glass plates according to claim 2, wherein the inorganic silicon oxide is silicon dioxide. The spacer paper for glass plates according to claim 1, wherein the foreign matter is one selected from the group consisting of iron oxide, copper, quartz, fused silica, glass flakes, quartz flakes, magnesium oxide, titanium oxide, and sand Above. The spacer paper for glass plates according to any one of claims 1 to 4, wherein the volume of the above-mentioned foreign matter does not reach 2×10 ^-5 mm ³ . The spacer paper for glass plates according to any one of claims 1 to 4, the basis weight of which is 20-100 g/m ² . The spacer paper for glass plates described in any one of claims 1 to 4 has a thickness of 0.030 to 0.130 mm. The spacer paper for glass plates according to any one of claims 1 to 4, which has a water content of 2-10% by mass. The spacer paper for glass plates according to any one of claims 1 to 4, which is used for glass plates for displays. The spacer paper for a glass plate according to claim 9, wherein the display is a TFT liquid crystal display or an organic EL display. A laminated body composed of the spacer paper for glass plates described in any one of claims 1 to 10 and a glass plate. A manufacturing method, which is a method for manufacturing the spacer paper for glass plates according to any one of claims 1 to 10, at least comprising: a slurry preparation step, which prepares wood pulp slurry; and a sheet formation step, which combines the above The slurry is formed into a sheet shape; a wet paper preparation step, which dehydrates the aforementioned sheet to form a wet paper; and a drying step, which dries the aforementioned wet paper to obtain the aforementioned spacer paper; and in the aforementioned wet paper preparation step, from the aforementioned sheet Dehydrate both sides. The manufacturing method according to claim 12, wherein the dehydration is performed by suction. The manufacturing method according to claim 13, wherein the difference between the dehydration ratio of the suction on one surface of the sheet and the dehydration ratio of the suction on the other surface is the difference of the dehydration ratio of the suction on the other surface 10% or less. The manufacturing method according to claim 13 or 14, which includes an additional suction step of further suctioning both sides of the spacer paper after the drying step.