JP7684013B2 - Surface protection sheet and method for producing same - Google Patents

Description

The present invention relates to a surface protection sheet used to protect the surfaces of glass, metal, etc.

During the manufacturing, storage, and transportation of glass products, metal products, products with a mirror-like luster, and the like, various types of surface protection sheets are used to protect the surfaces of the products in order to avoid or reduce physical damage such as scratches on the surfaces of the products, or to prevent the surfaces of the products from becoming contaminated.

For example, in the case of glass plates, during the storage process when multiple glass plates are stacked and stored, or during the distribution process when they are transported by truck or the like, the glass plates are subjected to impact and come into contact with each other, causing scratches, and in order to prevent the glass surface from being contaminated by foreign matter from the outside world, paper known as interleaf paper is sandwiched between the glass plates.

However, the surface of a glass plate in contact with the slip paper can be contaminated not only by foreign matter from the outside world, but also by foreign matter contained in the slip paper. Therefore, as a slip paper that does not contaminate the surface of a glass plate, for example, Patent Document 1 proposes a glass slip paper in which the adhesive substances contained in the slip paper are made non-adhesive by using a specific substance. Furthermore, in addition to foreign matter contained in the slip paper, polyvalent ions such as aluminum ions derived from aluminum sulfate contained in the slip paper as a papermaking chemical also adsorb anionic substances and coarsen them, leading to contamination of the glass plate.

Patent Document 2 also proposes glass interleaving paper in which a water-soluble polymer is applied to the interleaving paper surface as a means of reducing contamination of the glass plate surface caused by foreign matter contained in the interleaving paper.

JP 2007-131965 A Japanese Patent Application Publication No. 09-170198

The objective of the present invention is to provide a surface protection sheet that can prevent or reduce the transfer of foreign matter or harmful ions from a surface protection sheet such as interleaf paper to the surface of an object to be protected such as a glass plate.

As a result of intensive research, the inventors discovered that in a surface protection sheet having a paper base material made from wood pulp, the presence of cellulose nanofibers on the surface of the paper base material can suppress the transfer of foreign matter or harmful ions from the surface of the surface protection sheet to the object to be protected, such as a glass plate, and thus completed the present invention.

The first aspect of the present invention is a method for producing a cellular membrane comprising the steps of:
It has a paper base material made from wood pulp,
The surface protection sheet comprises cellulose nanofibers on at least a portion of the surface of the paper substrate.

The fiber diameter of the cellulose nanofibers is preferably 3 to 100 nm.

The fiber length of the cellulose nanofibers is preferably 100 nm to 100 μm.

The surface strength of the surface protection sheet of the present invention is preferably 8 or more.

It is preferable that the surface protection sheet of the present invention has a surface layer, and that the surface layer contains the cellulose nanofiber.

The thickness of the surface layer is preferably 3 to 100 nm.

It is preferable that the cellulose nanofibers are present in the surface layer at a ratio of 30 to 100% by mass based on the mass of the surface layer.

In the surface protection sheet of the present invention, it is preferable that the cellulose nanofibers are present in a ratio of 0.04 to 4 parts by mass per 100 parts by mass of the wood pulp.

The surface protective sheet of the present invention preferably has a basis weight of 20 to 100 g/ ^m2 .

The thickness of the surface protection sheet of the present invention is preferably 15 to 200 μm.

The surface protective sheet of the present invention is preferably used for glass plates for displays. In this case, the surface protective sheet of the present invention can be glass interleaving paper.

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

The present invention also relates to a surface protection sheet according to the first aspect of the present invention, and a laminate comprising a glass plate.

The present invention also relates to a method for protecting glass plates, comprising the step of placing the surface protection sheet of the first aspect of the present invention between a plurality of glass plates.

A second aspect of the present invention is a method for producing a composition comprising the steps of:
The method for producing a surface protection sheet includes a step of applying a composition containing at least cellulose nanofibers to at least one surface of a paper substrate made of wood pulp.

The surface protection sheet produced according to the second aspect of the present invention can have the characteristics of the surface protection sheet according to the first aspect of the present invention.

The surface protection sheet of the present invention can prevent or reduce the transfer of foreign matter or harmful ions from the surface protection sheet to the surface of the object to be protected, such as a glass plate, with which the surface protection sheet comes into contact.

In particular, the present invention can prevent or reduce the transfer of foreign matter or harmful ions from the surface protection sheet to the surface of the object to be protected, even if the surface protection sheet contains foreign matter or harmful ions.

When the surface protective sheet of the present invention is used as paper for wrapping glass plates and/or as paper to be sandwiched between glass plates, it can provide good protection for the surfaces of the glass plates. Therefore, by using the surface protective sheet of the present invention as glass interleaving paper, scratches and/or contamination of the surfaces of the glass plates can be avoided or reduced.

Furthermore, the surface protection sheet of the present invention can have excellent surface strength due to the presence of cellulose nanofibers.

In the present invention, in a surface protection sheet having a paper base material made from wood pulp, the presence of cellulose nanofibers on the surface of the paper base material suppresses the transfer of foreign matter and harmful ions from the surface of the surface protection sheet to the object to be protected, such as a glass plate.

In the present invention, even if the paper substrate contains sticky or hard foreign matter, the presence of cellulose nanofibers on the surface reduces the contact area between the foreign matter and the surface of the object to be protected, thereby preventing or reducing adhesion of the foreign matter to the surface of the object to be protected or scratching of the surface. Moreover, since cellulose nanofibers are made of cellulose like wood pulp, they have excellent affinity with the paper substrate and there is little concern about transfer to the surface of the object to be protected.

The surface protective sheet of the present invention can be suitably used to package glass plates and/or to be sandwiched between glass plates. Therefore, the surface protective sheet of the present invention is useful as glass interleaving paper (interleaving paper for glass plates). The glass plate is preferably a glass plate for flat panel displays such as liquid crystal displays (particularly TFT liquid crystal displays), plasma displays, and organic electroluminescence (organic EL) displays.

Compared to general architectural window glass sheets and vehicle window glass sheets, etc., glass sheets for flat panel displays are used for high-definition displays, so the glass surface must be as clean as possible with no impurities, and it must also have excellent flatness to achieve high-speed response and a wide viewing angle.

Contamination of the glass plate surface can cause defects in flat panel displays. For example, in the manufacturing process of TFT liquid crystal displays, elements such as very fine wiring and electrodes are produced on the surface of a substrate made of a glass plate by sputtering, vacuum deposition, photolithography, etc. In that case, it is known that if the surface of the glass plate is contaminated, such very fine electrical circuits will be disconnected and/or short-circuited, and defects will occur in the manufactured elements. In addition, in the manufacturing process of TFTs, if contaminants are present on the surface of the glass plate substrate, the fine lines formed on the surface will be disconnected and/or short-circuited. For example, in the manufacturing process of color filters, which is one of the manufacturing processes of TFT liquid crystal displays, a resist pattern is formed on the surface of a glass plate by photolithography, but if contaminants are present on the glass plate surface during the resist coating in this process, pinholes will occur in the resist film after exposure or development, resulting in defects such as disconnections in the color filter pattern. Similar problems have also been confirmed in the manufacturing of organic EL displays. Organic EL displays are made by forming thin films of ITO anodes, organic light-emitting layers, cathodes, etc. on a glass plate substrate using methods such as sputtering, deposition, and printing, so if there is a substance on the surface of the glass plate substrate that inhibits the thin films, there will be a problem of non-emission of light.

Although it was difficult to identify the cause of contamination of such glass plates, it was found that one of the causes was minute foreign matter that was transferred from the surface of the glass plate interleaving paper to the surface of the glass plate.

Therefore, by using the surface protection sheet of the present invention as glass interleaving paper, it is possible to reduce defects in flat panel displays such as TFT liquid crystal displays and organic EL displays that are caused by the transfer of foreign matter present on the surface of the interleaving paper to the surface of the glass plate.

The first aspect of the present invention is a surface protection sheet comprising a paper substrate made from wood pulp, in which cellulose nanofibers are present on at least a portion of the surface of the paper substrate, and which is preferably an interleaving paper for glass plates.

The wood pulp that can be used in the present invention is a single or mixed wood pulp such as softwood bleached kraft pulp (NBKP), hardwood bleached sulfite pulp (LBKP), softwood bleached sulfite pulp (NBSP), hardwood bleached sulfite pulp (LBSP), and thermomechanical pulp (TMP). This wood pulp is the main component, and as necessary, non-wood pulp such as hemp, bamboo, straw, kenaf, paper mulberry, mitsumata, and cotton, modified pulp such as cationic pulp and mercerized pulp, synthetic fibers such as rayon, vinylon, nylon, acrylic, and polyester, and chemical fibers, or microfibrillated pulp can be used alone or in combination. However, if the pulp contains a large amount of resin, the resin may have a negative effect such as staining the surface of the object to be protected such as a glass plate, so it is preferable to use a chemical pulp with as little resin as possible, such as softwood bleached kraft pulp, alone. Also, high-yield pulp such as groundwood pulp is not recommended because it contains a lot of resin. Mixing synthetic or chemical fibers improves the cutting properties and improves the workability when turning the interleaf into a plate, but care must be taken as this reduces recyclability in terms of waste disposal.

The form of the wood pulp is not particularly limited, and it can be any form such as a sheet, a block, or a flake. The sheet pulp can be obtained, for example, by using a pulp machine equipped with four processes: a wire part, a press part, a dry part, and a finishing part. In the wire part, the pulp fibers are made into paper using a long wire or a vacuum filter, and in the press part, dewatering is performed using a roll press. In the dry part, the pulp is dried using a cylinder dryer or a fractal dryer, and finally, both ends of the sheet pulp are cut off and wound on a roll. This type of method is described in detail in the "Paper and Pulp Manufacturing Technology Series" and "Paper and Pulp Manufacturing Technology Complete Book" published by the Paper and Pulp Technology Association. Note that the block pulp can be obtained, for example, by stacking the sheet pulp, and the flake pulp can be obtained, for example, by crushing the sheet pulp.

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 sheet-like pulp is preferably 400 to 1300 g/ ^m2 , more preferably 500 to 1200 g/ ^m2 , even more preferably 500 to 1100 g/ ^m2 , even more preferably 500 to 1000 g/ ^m2 , and even more preferably 700 to 1000 g/ ^m2 .

The surface protection sheet of the present invention includes a paper substrate made from wood pulp. The surface protection sheet of the present invention typically includes one paper substrate, but may include multiple paper substrates as necessary. The wood pulp includes cellulose fibers, but the fibers are not cellulose nanofibers. Therefore, the cellulose fibers derived from wood pulp included in the paper substrate are not cellulose nanofibers.

The paper substrate is preferably in the form of a sheet. The thickness of the sheet-like paper substrate is preferably 10 to 130 μm, more preferably 20 to 120 μm, even more preferably 30 to 110 μm, and even more preferably 40 to 100 μm.

The paper base material is made from wood pulp. Therefore, it is preferable that the paper base material is not made from regenerated cellulose.

The paper base material may contain other components as necessary in addition to the cellulose fibers derived from wood pulp. Examples of other components include paper strength enhancers or fixing agents such as starch, polyacrylamide, polyamine polyamide epichlorohydrin, sizing agents, fillers, drainage yield improvers, water resistance agents, fixing agents, defoamers, slime control agents, etc., and these can be used alone or in combination of two or more.

The surface protective sheet of the present invention comprises cellulose nanofibers on at least a portion of the surface of the paper substrate. That is, in the surface protective sheet of the present invention, cellulose nanofibers are present on at least a portion of the surface of the paper substrate.

Cellulose nanofibers are fine fibers made of cellulose, and in the present invention, for example, those with a width (fiber diameter) of 2 to 300 nm and a length of 1 to 500 μm can be used.

The width of the cellulose nanofiber is preferably 2 to 200 nm, more preferably 3 to 100 nm, even more preferably 4 to 50 nm, and even more preferably 4 to 20 nm. The fiber diameter is preferably an average fiber diameter. Here, "average fiber diameter" means the number average of the fiber diameters of the cellulose nanofibers. The average fiber diameter can be obtained, for example, by magnifying and observing multiple locations on the surface of the surface protection sheet with an electron microscope, randomly selecting a predetermined number of fibers from each electron microscope image, and measuring and averaging the diameters of the selected fibers. The number of fibers selected is 100 or more, preferably 150 or more, more preferably 200 or more, and even more preferably 300 or more.

The length (fiber length) of the cellulose nanofiber is preferably 10 nm to 300 μm, more preferably 50 nm to 200 μm, even more preferably 100 nm to 100 μm, and even more preferably 150 nm to 50 μm. The fiber length here refers to the length of the fiber when the fiber is stretched straight. The fiber length is preferably the average fiber length. The "average fiber length" here means the number average of the fiber lengths of the cellulose nanofiber. The average fiber length can be obtained, for example, by magnifying and observing multiple locations on the surface of the surface protection sheet with an electron microscope, randomly selecting a predetermined number of fibers from each electron microscope image, and measuring and averaging the lengths of the selected fibers. The number of fibers selected is 100 or more, preferably 150 or more, more preferably 200 or more, and even more preferably 300 or more.

Cellulose nanofibers can be produced, for example, according to Japanese Patent No. 3036354 (Method for producing microfibrillated cellulose), Japanese Patent No. 2967804 (Ultrafine fibrillated cellulose and its production method, and method for producing coated paper and dyed paper using ultrafine fibrillated cellulose), or Japanese Patent Application Publication No. 2008-169497 (Method for producing nanofibers and nanofibers). However, it is not limited to the wet grinding method as in the above three examples, and a dry grinding method is also used. In addition, cellulose nanofibers can also be produced by a method using chemical modification, as in Japanese Patent Application Publication No. 2009-263652 (Method for producing cellulose nanofibers) and International Publication No. 2009/069641 (Cellulose nanofibers and their production method, cellulose nanofiber dispersion), but is not limited to these TEMPO oxidation methods. The average degree of polymerization of the cellulose nanofibers used in the present invention is preferably 600 or more and 30,000 or less, more preferably 600 or more and 5,000 or less, and even more preferably 800 or more and 5,000 or less.

The raw materials for cellulose nanofibers include, for example, chemical pulps such as bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), and bleached hardwood sulfite pulp (NBSP); mechanical pulps such as groundwood pulp (GP) and thermomechanical pulp (TMP); wood pulps such as bast fiber pulp from paper mulberry, gampi, and mitsumata; non-wood pulps such as cotton pulp, hemp, kenaf, rice, bagasse, and bamboo; biocelluloses such as bacterial cellulose; powdered cellulose, microcrystalline cellulose, modified cellulose, and regenerated cellulose.

The cellulose nanofibers used in the present invention may be modified, and examples of the types of modification include modification by TEMPO oxidation, cationic modification, anionic neutralization after cationic modification, hydrophobic modification, etc. The modification may be performed on the raw material of the cellulose nanofiber either before or after the production of the cellulose nanofiber.

The cellulose nanofibers are preferably present on 50% or more of the surface of the paper substrate, more preferably 70% or more, even more preferably 90% or more, and particularly preferably present on the entire surface of the paper substrate. When the paper substrate is in sheet form, the cellulose nanofibers are preferably present on 50% or more of at least one of the front and back surfaces of the paper substrate, more preferably 70% or more, even more preferably 90% or more, and particularly preferably present on the entire surface of the surface. Furthermore, when the paper substrate is in sheet form, the cellulose nanofibers are preferably present on 50% or more of the total surface area of both the front and back surfaces of the paper substrate, more preferably 70% or more, even more preferably 90% or more, and particularly preferably present on the entire surface of both the front and back surfaces.

In the surface protection sheet of the present invention, the cellulose nanofibers can be present in a ratio of 0.01 to 10 parts by mass per 100 parts by mass of the wood pulp, preferably 0.02 to 8 parts by mass, more preferably 0.04 to 4 parts by mass, and even more preferably 0.05 to 3 parts by mass.

The amount of the cellulose nanofibers present in the surface protection sheet of the present invention is not particularly limited, but can be, for example, 0.01 to 10 g/ ^m2 , preferably 0.01 to 5 g/ ^m2 , and more preferably 0.1 to 3 g/ ^m2 .

Cellulose nanofibers have a high affinity with paper substrates, which are also made of cellulose, and are firmly held to the surface of the paper substrate. This prevents the cellulose nanofibers from detaching from the surface of the paper substrate and transferring.

In addition, because cellulose nanofibers are hydrophilic, they can prevent hydrophobic foreign matter from adhering to the surface protection sheet.

In one aspect of the present invention, the surface protective sheet of the present invention has a surface layer, and the surface layer contains cellulose nanofibers. The surface layer is preferably present on at least one surface of the paper substrate, preferably on both the front and back surfaces, and it is more preferable that the paper substrate and the surface layer are in contact with each other. The surface layer can function as a protective layer for the paper substrate.

The thickness of the surface layer is not particularly limited, but can be, for example, 2 to 300 nm. The thickness of the surface layer is preferably 2 to 200 nm, more preferably 3 to 100 nm, and even more preferably 4 to 50 nm.

The cellulose nanofibers may be present in the surface layer in a proportion of 10 to 100% by mass based on the mass of the surface layer, and the proportion is preferably 20 to 100% by mass, more preferably 30 to 100% by mass, and even more preferably 40 to 100% by mass. When the cellulose nanofibers in the surface layer are present in a proportion of 100% by mass based on the mass of the surface layer, the surface layer consists only of cellulose fibers.

The surface layer may contain other components, if necessary, in addition to the cellulose nanofibers. Examples of other components include paper strength enhancers or fixing agents such as starch, polyacrylamide, and polyamine polyamide epichlorohydrin, sizing agents, fillers, drainage yield improvers, water-resistant agents, fixing agents, defoamers, and slime control agents. These can be used alone or in combination of two or more.

Due to the high crystallinity of cellulose, cellulose nanofibers can form a film on the surface of the paper substrate, forming a relatively hard surface layer. In addition, due to the high specific surface area of cellulose nanofibers and the large number of hydroxyl groups that cellulose possesses, cellulose nanofibers can form a relatively strong surface layer. This allows the surface layer to have suitable physical properties as a protective layer.

When the fiber diameter (width) of the cellulose nanofiber is smaller than the wavelength of visible light, the layer made up of the cellulose nanofiber can be transparent because it does not scatter visible light. This can improve the appearance of the surface protection sheet of the present invention.

The foreign matter that is of concern in this invention is minute foreign matter that contaminates the surface of the object to be protected, such as a glass plate.

The foreign matter may be an organic substance, such as a resin like polyvinyl alcohol, or an inorganic substance, such as aluminum sulfate, and may be either sticky or non-sticky, and may be either hard or soft.

The foreign matter may be either solid or liquid. The size of the foreign matter is not particularly limited, but is usually so small that it cannot be seen with the naked eye. The size of the foreign matter targeted by the present invention is, for example, 0.1 μm to 50 μm, preferably 0.1 μm to 40 μm, and more preferably 0.1 μm to 30 μm. Here, "size" refers to the volume average (median) particle size. The volume average particle size can be measured, for example, by a laser diffraction scattering method.

The foreign matter may contain a hydrophobic substance. However, the foreign matter may consist only of a hydrophobic substance.

The hydrophobic substance is not particularly limited. The hydrophobic substance is preferably non-volatile and is more preferably selected from the group consisting of oils (excluding silicone oils, e.g., aliphatic hydrocarbons, vegetable oils, animal oils, synthetic glycerides, aliphatic alcohols, fatty acids, esters of aliphatic alcohols and/or fatty acids), resins (excluding silicone), silicones, pitch, rubber, and talc, particularly talc adsorbed with hydrophobic foreign matter, and even more preferably selected from the group consisting of silicones and talc (particularly talc adsorbed with hydrophobic foreign matter).

Aliphatic hydrocarbons include, for example, linear or branched hydrocarbons, in particular mineral oils (such as liquid paraffin), paraffin, petrolatum, naphthalene, etc.; hydrogenated polyisobutene, isoeicosane, polydecene, perleam, and other hydrogenated polyisobutenes and decene/butene copolymers; and mixtures thereof.

Examples of other aliphatic hydrocarbons include linear or branched, or optionally cyclic, C ₆ -C ₁₆ lower alkanes. Examples that may be mentioned include hexane, undecane, dodecane, tridecane and isoparaffins, such as isohexadecane and isodecane.

Examples of vegetable oils include, for example, linseed oil, camellia oil, macadamia nut oil, sunflower oil, apricot oil, soybean oil, arara oil, hazelnut oil, corn oil, olive oil, avocado oil, camellia oil, castor oil, safflower oil, jojoba oil, almond oil, grape seed oil, sesame oil, peanut oil, and mixtures thereof.

Examples of animal oils include mink oil, squalene, perhydrosqualene and squalane.

An example of a synthetic glyceride is caprylic/capric triglyceride.

The fatty acids should be in acid form (i.e. not in the form of a salt, to avoid soap), may be saturated or unsaturated, contain from 6 to 30 carbon atoms, in particular from 9 to 30 carbon atoms, and are optionally substituted, in particular with one or more hydroxyl groups (in particular with 1 to 4). If the fatty acid is unsaturated, the compound may contain from 1 to 3 conjugated or non-conjugated carbon-carbon double bonds. The fatty acids are, for example, chosen from myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid and isostearic acid.

The term "aliphatic alcohol" as used herein means any saturated, linear or branched _C8 to _C30 alcohol, optionally substituted, especially with one or more hydroxyl groups (especially 1 to 4).

Of the fatty alcohols, _C12 - _C22 fatty alcohols are preferred, and _C16 - _C18 saturated fatty alcohols are more preferred. Among these, mention may be made of lauryl alcohol, cetyl alcohol, stearyl alcohol, isostearyl alcohol, oleyl alcohol, behenyl alcohol, undecyl alcohol, myristyl alcohol, and mixtures thereof.

As examples of esters of fatty acids and/or fatty alcohols, mention may in particular be made of esters of saturated or unsaturated, linear or branched C ₁ -C ₂₆ aliphatic mono- or polyacids, and esters of saturated or unsaturated, linear or branched C ₁ -C ₂₆ aliphatic mono- or polyhydric alcohols, the total carbon number of the ester being preferably 10 or more.

The resin (excluding silicone) is not particularly limited as long as it is hydrophobic. Examples of the resin include thermoplastic resins such as polyolefin, polystyrene, poly(meth)acrylate, polyacrylamide, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polyester, polycarbonate, polyamide, and polyimide, thermosetting resins such as polyurethane, melamine resin, and urea resin, and mixtures thereof.

Examples of silicones include silicone oils. Silicone oils are hydrophobic and may have any of cyclic, linear, and branched molecular structures. The kinetic viscosity of silicone oils at 25° C. is usually in the range of 0.65 to 100,000 ^{mm 2} /s, but may be in the range of 0.65 to 10,000 mm ² /s.

Examples of silicone oils include linear organopolysiloxanes, cyclic organopolysiloxanes, and branched organopolysiloxanes.

Ｒ^１ _{（４－ｃ）}Ｓｉ（ＯＳｉＲ^１ _３）_ｃ （３）

（式中、
Ｒ^１は、それぞれ独立して、水素原子、水酸基、或いは、置換若しくは非置換の一価炭化水素基、アルコキシ基で示される基から選択される基であり、
ａは、０～１０００の整数であり、
ｂは３～１００の整数であり、
ｃは１～４の整数、好ましくは２～４の整数である）
で表されるオルガノポリシロキサンが挙げられる。 Examples of the linear organopolysiloxane, cyclic organopolysiloxane, and branched organopolysiloxane include those represented by the following general formulas (1), (2), and (3):

R ¹ ₃ SiO-(R ¹ ₂ SiO) _a -SiR ¹ ₃ (1)

R ¹ _(4-c) Si(OSiR ¹ ₃ ) _c (3)

(In the formula,
R ¹ 's are each independently a group selected from a hydrogen atom, a hydroxyl group, or a substituted or unsubstituted monovalent hydrocarbon group or an alkoxy group;
a is an integer from 0 to 1000;
b is an integer from 3 to 100;
c is an integer from 1 to 4, preferably an integer from 2 to 4.
Examples of organopolysiloxanes include those represented by the following formula:

The substituted or unsubstituted monovalent hydrocarbon group is typically a substituted or unsubstituted monovalent saturated hydrocarbon group having 1 to 30 carbon atoms, preferably 1 to 10 carbon atoms, and more preferably 1 to 4 carbon atoms; a substituted or unsubstituted monovalent unsaturated hydrocarbon group having 2 to 30 carbon atoms, preferably 2 to 10 carbon atoms, and more preferably 2 to 6 carbon atoms; or a monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms, and more preferably 6 to 12 carbon atoms.

Examples of monovalent saturated hydrocarbon groups having 1 to 30 carbon atoms include linear or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl, as well as cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl.

Examples of monovalent unsaturated hydrocarbon groups having 2 to 30 carbon atoms include linear or branched alkenyl groups such as vinyl, 1-propenyl, allyl, isopropenyl, 1-butenyl, 2-butenyl, pentenyl, and hexenyl; cycloalkenyl groups such as cyclopentenyl and cyclohexenyl; cycloalkenylalkyl groups such as cyclopentenylethyl, cyclohexenylethyl, and cyclohexenylpropyl; and alkynyl groups such as ethynyl and propargyl.

Examples of monovalent aromatic hydrocarbon groups having 6 to 30 carbon atoms include aryl groups such as phenyl, tolyl, xylyl, and mesityl. Phenyl is preferred. In this specification, the term "aromatic hydrocarbon group" includes not only groups consisting of aromatic hydrocarbons, but also groups consisting of a combination of aromatic hydrocarbons and saturated aliphatic hydrocarbons. Examples of groups consisting of a combination of aromatic hydrocarbons and saturated hydrocarbons include aralkyl groups such as benzyl and phenethyl.

The hydrogen atoms on the monovalent hydrocarbon group may be substituted with one or more substituents, and the substituents are selected from the group consisting of organic groups including, for example, halogen atoms (fluorine, chlorine, bromine, and iodine atoms), hydroxyl groups, carbinol groups, epoxy groups, glycidyl groups, acyl groups, carboxyl groups, amino groups, methacryl groups, mercapto groups, amide groups, and oxyalkylene groups. Specific examples include 3,3,3-trifluoropropyl groups, 3-chloropropyl groups, 3-hydroxypropyl groups, 3-(2-hydroxyethoxy)propyl groups, 3-carboxypropyl groups, 10-carboxydecyl groups, and 3-isocyanatopropyl groups.

Examples of alkoxy groups include methoxy, ethoxy, and propoxy groups, with methoxy and ethoxy groups being preferred, and methoxy being more preferred.

More specifically, linear organopolysiloxanes include dimethylpolysiloxanes with trimethylsiloxy groups blocked at both molecular chain ends (dimethyl silicones with low viscosities of 2 mPa·s or 6 mPa·s, etc., to high viscosities of 1,000,000 mPa·s, etc.), organohydrogenpolysiloxanes, methylphenylpolysiloxanes with trimethylsiloxy groups blocked at both molecular chain ends, dimethylsiloxane-methylphenylsiloxane copolymers with trimethylsiloxy groups blocked at both molecular chain ends, Diphenylpolysiloxane capped with trimethylsiloxy groups at both molecular chain ends, dimethylsiloxane-diphenylsiloxane copolymer capped with trimethylsiloxy groups at both molecular chain ends, trimethylpentaphenyltrisiloxane, phenyl(trimethylsiloxy)siloxane, methylalkylpolysiloxane capped with trimethylsiloxy groups at both molecular chain ends, dimethylpolysiloxane-methylalkylsiloxane copolymer capped with trimethylsiloxy groups at both molecular chain ends, Methylsiloxy group-blocked dimethylsiloxane/methyl(3,3,3-trifluoropropyl)siloxane copolymer, α,ω-dihydroxypolydimethylsiloxane, α,ω-diethoxypolydimethylsiloxane, 1,1,1,3,5,5,5-heptamethyl-3-octyltrisiloxane, 1,1,1,3,5,5,5-heptamethyl-3-dodecyltrisiloxane, 1,1,1,3,5,5,5-heptamethyl-3-hexadecyltrisiloxane, Examples include tristrimethylsiloxymethylsilane, tristrimethylsiloxyalkylsilane, tetrakistrimethylsiloxysilane, tetramethyl-1,3-dihydroxydisiloxane, octamethyl-1,7-dihydroxytetrasiloxane, hexamethyl-1,5-diethoxytrisiloxane, hexamethyldisiloxane, octamethyltrisiloxane, higher alkoxy-modified silicone, higher fatty acid-modified silicone, dimethiconol, etc.

Cyclic organopolysiloxanes include hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), 1,1-diethylhexamethylcyclotetrasiloxane, phenylheptamethylcyclotetrasiloxane, 1,1-diphenylhexamethylcyclotetrasiloxane, 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, 1,3,5,7-tetracyclohexyltetramethylcyclotetrasiloxane, tris(3,3,3-trifluoropropyl)trimethylcyclotrisiloxane, 1,3,5,7-tetra(3-methacryloxypropyl)tetramethyl Examples include cyclotetrasiloxane, 1,3,5,7-tetra(3-acryloxypropyl)tetramethylcyclotetrasiloxane, 1,3,5,7-tetra(3-carboxypropyl)tetramethylcyclotetrasiloxane, 1,3,5,7-tetra(3-vinyloxypropyl)tetramethylcyclotetrasiloxane, 1,3,5,7-tetra(p-vinylphenyl)tetramethylcyclotetrasiloxane, 1,3,5,7-tetra[3-(p-vinylphenyl)propyl]tetramethylcyclotetrasiloxane, 1,3,5,7-tetra(N-acryloyl-N-methyl-3-aminopropyl)tetramethylcyclotetrasiloxane, and 1,3,5,7-tetra(N,N-bis(lauroyl)-3-aminopropyl)tetramethylcyclotetrasiloxane.

Examples of branched organopolysiloxanes include methyltristrimethylsiloxysilane, ethyltristrimethylsiloxysilane, propyltristrimethylsiloxysilane, tetrakistrimethylsiloxysilane, and phenyltristrimethylsiloxysilane.

Preferred examples of silicone oils in the present invention include dimethylpolysiloxane, diethylpolysiloxane, methylphenylpolysiloxane, polydimethyl-polydiphenylsiloxane copolymer, polymethyl-3,3,3-trifluoropropylsiloxane, etc. Dimethylpolysiloxane is a typical example of silicone in the present invention.

The silicone oil in the present invention may be a modified silicone oil. Examples of modified silicone oils include polyoxyalkylene-modified silicone oils.

Polyoxyalkylene-modified silicone oil is a silicone oil in which polyoxyalkylene groups are bonded to the molecule via silicon-carbon bonds, and is preferably water-soluble at room temperature, specifically at 25°C, and more preferably is nonionic.

The polyoxyalkylene-modified silicone oil is specifically a copolymer of a silicone oil made of linear or branched siloxane and a polyoxyalkylene, and there are various types, but the one represented by the following formula (4) is particularly preferred.

R ² ₃ SiO-(R ¹ ₂ SiO) _d -(R ¹ ASiO) _e -SiR ² ₃ (4)

(In the formula,
Each R ¹ is independently the same as above,
Each ^R2 is independently ^R1 or A;
Each A is independently a group represented by R ³ G, R ³ is a substituted or unsubstituted divalent hydrocarbon group, G is a polyoxyalkylene group containing at least one alkylene oxide having 2 to 5 carbon atoms, such as ethylene oxide or propylene oxide,
d represents an integer of 1 to 500;
and e represents an integer of 1 to 50.

Examples of substituted or unsubstituted divalent hydrocarbon groups include linear or branched divalent hydrocarbon groups having 1 to 30 carbon atoms, specifically linear or branched alkylene groups having 1 to 30 carbon atoms, such as methylene, dimethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, heptamethylene, and octamethylene; alkene groups having 2 to 30 carbon atoms, such as vinylene, allylene, butenylene, hexenylene, and octenylene; Examples of the divalent hydrocarbon group include an alkylene group having 1 to 30 carbon atoms, such as an aryl group, an arylene group having 6 to 30 carbon atoms, such as a phenylene group or a diphenylene group, an alkylenearylene group having 7 to 30 carbon atoms, such as a dimethylenephenylene group, and groups in which the hydrogen atoms bonded to the carbon atoms of these groups are at least partially substituted with a halogen atom such as fluorine, a hydroxyl group, or an organic group including a carbinol group, an epoxy group, a glycidyl group, an acyl group, a carboxyl group, an amino group, a methacryl group, a mercapto group, an amide group, or an oxyalkylene group. The divalent hydrocarbon group is preferably an alkylene group having 1 to 30 carbon atoms, more preferably an alkylene group having 1 to 6 carbon atoms, and more preferably an alkylene group having 3 to 5 carbon atoms.

（式中、
ｘは２０～１６０であり、ｙは１～２５であり、ｘ／ｙの値は５０～２であり、
Ａは、例えば－（ＣＨ_２）_３Ｏ－（ＣＨ_２ＣＨ_２Ｏ）_ｍ－（ＣＨ_２ＣＨ_２ＣＨ_２Ｏ）_ｎ－Ｒ^４であり、ｍは７～４０、ｎは０～４０、ｍ＋ｎの値は少なくとも１であり、グラフト重合されたものでもランダム重合されたものでもよく、Ｒ^４は水素原子又は上記置換若しくは非置換の一価炭化水素基を表す。好適には、ｍは７～３０、ｎは０～３０である） For example, specific examples of polyoxyalkylene-modified silicone oils include the following:

(In the formula,
x is 20 to 160, y is 1 to 25, and the value of x/y is 50 to 2;
A is, for example, -(CH ₂ ) ₃ O-(CH ₂ CH ₂ O) _m -(CH ₂ CH ₂ CH ₂ O) _n -R ⁴ , where m is 7 to 40, n is 0 to 40, and the value of m+n is at least 1. A may be graft polymerized or random polymerized, and R ⁴ represents a hydrogen atom or the above-mentioned substituted or unsubstituted monovalent hydrocarbon group. Preferably, m is 7 to 30 and n is 0 to 30.

Modified silicone oils include, for example, aminoalkyl-modified silicone oils.

Aminoalkyl-modified silicone oil is a silicone oil in which aminoalkyl groups are bonded to the molecule via silicon-carbon bonds, and preferably has a viscosity of 10 to 100,000 cs at room temperature, specifically 25°C.

The aminoalkyl silicone oil includes those in which, in the above formula (4), G is replaced by the formula: -(NR ⁴ CH ₂ CH ₂ ) _z NR ⁴ ₂ (wherein R ⁴ is independently as defined above, and z is a number in the range of 0≦z≦4).

In the present invention, when the foreign matter is silicone, the amount of silicone contained in the surface protection sheet is preferably 0.5 ppm or less, more preferably 0.4 ppm or less, even more preferably 0.3 ppm or less, even more preferably 0.2 ppm or less, and particularly preferably 0.1 ppm or less, based on the bone dry mass of the surface protection sheet. If silicone is present in an amount exceeding 0.5 ppm, for example, in situations requiring very high-definition displays such as mobile terminals, breaks in color films, etc. caused by trace amounts of silicone transferred to the surface of a glass plate are noticeable due to their high definition, and there is a high risk that the film will be judged to be of poor quality. In addition, in the present invention, "bone dry" means a state in which substantially no moisture is present in the object to be dried due to drying.

The foreign matter may have a hardness of 4 or more on the Mohs scale. The foreign matter with a Mohs hardness of 4 or more may be particles made of either an inorganic or organic substance, and inorganic particles are preferred. Examples of the foreign matter include metal oxides or inorganic silicon oxides with a Mohs hardness of 4 or more. The metal constituting the metal oxide is not particularly limited as long as the oxide has a Mohs hardness of 4 or more, and examples of the metal include elements of Group 2 elements such as magnesium, elements of Group 4 elements such as titanium, and elements of Group 8 elements such as iron. Silicon dioxide is preferred as the inorganic silicon oxide. Examples of the foreign matter with a Mohs hardness of 4 or more include oxide minerals. Examples of the foreign matter with a Mohs hardness of 4 or more include iron oxide, copper, quartz, fused quartz (quartz glass), titanium oxide, glass chips, quartz chips, magnesium oxide, sand, and the like. Sand is mainly composed of amphibole with a Mohs hardness of 5.5, feldspar with a Mohs hardness of 6, and quartz with a Mohs hardness of 7. Therefore, the Mohs hardness of sand is 4 or more, typically 7. Mohs hardness is a hardness index expressed on a 10-point scale, and is a value obtained by rubbing the material being measured against a corresponding standard material and evaluating the hardness of the material relative to the standard material based on whether scratches are left. The standard materials are, in order from softest (Mohs hardness 1) to hardest (Mohs hardness 10), 1: talc, 2: gypsum, 3: calcite, 4: fluorite, 5: apatite, 6: feldspar, 7: quartz, 8: topaz, 9: corundum, and 10: diamond. The Mohs hardness is measured by preparing two smooth plates with known Mohs hardness, placing the foreign object to be measured between the two plates, and rubbing the two plates together to check for scratches on the plate surface.

The harmful ions that are problematic in the present invention are multivalent ions such as aluminum ions. Harmful ions may be cationic or anionic. Ions with high valences tend to adsorb counter-ion substances and become coarse. If harmful ions are transferred to the glass plate and become coarse, they can cause breaks and/or short circuits when fine wiring or electrodes are installed on the surface of the glass plate during the display manufacturing process, resulting in defects.

Examples of cationic polyvalent ions include, for example, Ca2 ⁺ , Al3 ⁺ , Mg2 ⁺ , Ba2 ⁺ , Cu2 ⁺ , Fe2 ⁺ , Fe3 ⁺ , and Zn2 ⁺ .

Examples of anionic polyvalent ions include SO ₄ ²⁻ , CO ₃ ²⁻ , PO ₄ ³⁻ , and S ²⁻ .

The thickness of the surface protective sheet of the present invention is preferably 15 to 200 μm, more preferably 20 to 200 μm, even more preferably 20 to 180 μm, even more preferably 30 to 150 μm, and even more preferably 45 to 135 μm.

The surface protective sheet of the present invention has a basis weight of preferably 20 to 100 g/ ^m2 , more preferably 25 to 75 g/ ^m2 , and even more preferably 30 to 70 g/ ^m2 .

The surface protection sheet of the present invention can have excellent surface strength due to the presence of cellulose nanofibers. The surface strength of the surface protection sheet of the present invention is preferably 8 or more, more preferably 9 or more, even more preferably 10 or more, even more preferably 11 or more, and even more preferably 12 or more. If the surface strength is less than 8, the fibers such as wood pulp and cellulose nanofibers constituting the sheet are likely to fall off, and as a result, there is a risk that the fibers or foreign matter may contaminate or scratch the surface of the object to be protected such as a glass plate. In addition, by providing cellulose nanofibers or a surface layer containing them as in the present invention, it is possible to increase the surface strength and also capture foreign matter. This is due to the crystallinity and high specific surface area of the cellulose nanofibers and the viscosity of the dispersion liquid.

The surface protection sheet of the present invention preferably has a mean deviation (MMD) of the coefficient of friction of the surface measured by the KES method of 0.022 or less, preferably 0.020 or less, more preferably 0.019 or less, even more preferably 0.018 or less, and even more preferably 0.017 or less. MMD is the mean deviation value of the coefficient of friction measured by using a friction tester (KES-SE manufactured by Kato Tech Co., Ltd.) to bring a 10 mm square friction element made of a bundle of piano wires with a diameter of 0.5 mm into contact with the surface of a paper fixed under a tension of 20 g/cm at a contact pressure of 50 g/cm ² and moving the sample 2 cm in the same direction as the direction in which the tension is applied at a sample moving speed of 0.1 cm/sec. If this MMD is large, it means that the coefficient of friction of the sheet surface varies greatly depending on the position on the sheet surface, and microscopically, it means that the sheet surface has many minute irregularities. By providing the sheet surface with fine irregularities in this way, the coefficient of friction between the surface of the surface protection sheet and the surface of the object to be protected, such as a glass plate, is reduced, and the removal operation when removing the surface protection sheet from the surface of the object to be protected is facilitated. If the MMD exceeds 0.022, the fine irregularities on the surface increase, and the surface protection sheet and the surface of the object to be protected are more likely to get caught together, which is not preferable. The MMD is, for example, preferably 0.001 to 0.022, more preferably 0.002 to 0.020, and even more preferably 0.004 to 0.019.

The method for producing the surface protection sheet of the present invention is not particularly limited, but it can be produced, for example, by applying cellulose nanofibers to the surface of a paper substrate produced based on a papermaking method.

A second aspect of the present invention is a method for producing a surface protection sheet, comprising:
The method includes a step of applying a composition containing at least cellulose nanofibers to at least one surface of a paper substrate made of wood pulp.

The paper base material can be produced by a conventional papermaking method. For example, the paper base material can be produced by
a slurry preparation step of preparing a wood pulp slurry;
a sheet forming step of forming the slurry into a sheet;
A wet paper preparation step of dewatering the sheet to form a wet paper;
The paper substrate can be produced through a drying step in which the wet paper is dried to obtain the paper substrate.

In the slurry preparation step, a wood pulp slurry can be prepared by a conventional method. For example, in the slurry preparation step, the cellulose fibers that make up the wood pulp are disaggregated in water to form an aqueous suspension, and the slurry is prepared.

In addition, to the above slurry, adhesives, antifungal agents, defoamers, fillers, wet strength agents, dry strength agents, sizing agents, colorants, fixing agents, retention agents, slime control agents, etc. can be added as necessary, so long as the performance of the present invention is not impaired. Note that when adding these chemicals, it is preferable to take great care to prevent insects, debris, etc. from being mixed in.

In the sheet forming process, the slurry is turned into a sheet, and the sheet can be formed by a conventional method. For example, the slurry can be discharged onto a flat wire (e.g., a Fourdrinier paper machine) or the sheet can be scooped up from the slurry with a wire wound around a cylindrical cylinder (e.g., a cylinder paper machine).

The dehydration method in the wet paper preparation process is arbitrary, and conventionally known methods can be used. For example, a method of making paper using a twin-wire papermaking machine such as an on-top former or a gap former can be used. Adjustment in the press part is also possible, and for example, the sheet can be dehydrated by pressing it with a roll.

The sheet forming process and the wet paper preparation process may be carried out separately using separate equipment, or may be carried out continuously or partially overlapping in the same equipment. For example, in the wire part of a papermaking machine, the slurry may be placed on a wire (mesh) and formed into a sheet while being dewatered to form a wet paper.

In the drying step, the wet paper can be dried using a conventional method such as a dryer roll to obtain the paper base material.

In addition, during and/or after the paper base material is made, processing such as calendaring, super calendaring, soft nip calendaring, embossing, etc. can be performed. Processing can adjust the surface properties and thickness.

In the process of applying a composition containing at least cellulose nanofibers to at least one surface of the paper substrate, the composition may be one containing the cellulose nanofibers described above.

The composition is preferably an aqueous dispersion of cellulose nanofibers. That is, the proportion of water in the composition is preferably 50% by weight or more, more preferably 70% by weight or more, and even more preferably 90% by weight or more. In addition to cellulose nanofibers, the composition may contain other components as necessary. Examples of other components include paper strength enhancers or fixing agents such as starch, polyacrylamide, and polyamine polyamide epichlorohydrin, sizing agents, fillers, drainage yield improvers, water-resistant agents, fixing agents, defoamers, slime control agents, etc., and these can be used alone or in combination of two or more.

The concentration of cellulose nanofibers in the composition is not particularly limited as long as it can be applied, but can be, for example, 0.1 to 5% by weight, 0.3 to 3% by weight, or 0.5 to 1% by weight.

The coating can be carried out by a conventional method such as a blade coater, an air knife coater, or cast coating. It can also be carried out using a size press device, for example.

The manufacturing method of the second aspect of the present invention makes it possible to efficiently manufacture the surface protection sheet of the first aspect of the present invention.

The surface protection sheet of the present invention is used by contacting its surface with the surface of the object to be protected, such as glass or metal. The surface protection sheet of the present invention can be used as interleaving paper for glass plates that is inserted between laminated glass plates, as well as for general surface protection applications for glass products, metal products, and products with a mirror gloss.

When the surface protective sheet of the present invention is used as glass plate interleaf paper, the glass plate interleaf paper of the present invention is placed between glass plates. For example, the glass plate interleaf paper is typically inserted one by one between multiple glass plates, and the whole is made into a laminate, and the laminate is the object of storage and transportation. In addition, the glass plate interleaf paper of the present invention may be used to package a single glass plate or the laminate. Thus, the present invention has an aspect of a method for protecting glass plates, which includes a step of placing (particularly, inserting) the glass plate interleaf paper between glass plates.

The glass plate used in the glass plate protection method of the present invention is not particularly limited, but as described above, it is preferably a glass plate for flat panel displays such as plasma display panels, liquid crystal display panels (particularly TFT liquid crystal display panels), and organic EL display panels. Fine lines and elements such as fine electrodes and partitions are formed on the surface of glass plates for flat panel displays. By using the glass plate interleaving paper of the present invention, the transfer of problematic fine foreign matter or harmful ions to the glass plate is suppressed or avoided. Therefore, even if fine lines and elements are formed on the surface of the glass plate, the inconvenience caused to the lines and elements by the foreign matter or harmful ions can be suppressed or avoided, and as a result, defects in the display can be suppressed or avoided.

The glass plate interleaving paper of the present invention can be suitably used for glass plates for flat panel displays, which require particularly clean surfaces. In particular, as displays become larger, the size and weight of glass plates for flat panel displays increases, and the glass plate interleaving paper of the present invention can provide excellent protection for the surfaces of such large or heavy glass plates.

The present invention will be described in more detail below using examples and comparative examples, but the scope of the present invention is not limited to the examples.

(1) Glass transfer test (transport test)
A urethane foam was laid on the glass placement surface on an aluminum L-shaped stand with a 75 degree angle, and 120 glass plates with a size of 680 mm x 880 mm x 0.7 mm were placed on the placement surface for placing the glass plate vertically and the backrest surface extending vertically from the rear end of the placement surface, with a surface protection sheet inserted between each glass plate, and the glass plates were placed parallel to the backrest surface, and a belt-like belt fixed to the stand was hung from the rear end to the backrest surface all around to fix the glass plates. The stand set up as described above was covered entirely with packaging materials to prevent the intrusion of dust and other foreign matter from the outside. Then, a transportation test was carried out by truck. The transportation test conditions were a transportation distance of 1000 km (storage for 5 days in an environment of 40°C x 95% RH during transportation).

(2) Surface Strength The surface strength was measured in accordance with JAPAN TAPPI No. 1.

[Example 1]
A waste paper raw material from newspapers and magazines was prepared, and the raw material was beaten to obtain a 0.4% concentration slurry adjusted to 300 ml csf. When this was used for papermaking using a Fourdrinier papermaking machine, a 1 wt % dispersion of cellulose fine fibers (WMa-10002 manufactured by Sugino Machine Co., Ltd.) was applied to the slurry using a size press coater so that the solid content application amount was 0.5 g/ ^m2 , and a surface protection sheet with a basis weight of 50 g/ ^m2 was obtained.

[Example 2]
In a manufacturing apparatus for softwood bleached kraft pulp, which includes a cooking step, a washing step, an oxygen delignification reaction step, and a multi-stage bleaching step using chlorine dioxide and hydrogen peroxide, an appropriate amount of stock solution of a silicone-based defoaming agent "SN DEFORMER 551K" (manufactured by San Nopco) was continuously added as an antifoaming agent used in the washing liquid of the drum washer immediately after removing knots after the cooking step. In addition, an appropriate amount of "SN DEFORMER 551K" was also added as an antifoaming agent added to the wash press in the press washing step. When papermaking was performed using a fourdrinier papermaking machine with the softwood bleached kraft pulp thus obtained as a raw material, a 1% by weight dispersion of cellulose fine fibers (WMa-10002 manufactured by Sugino Machine Co., Ltd.) was applied with a size press coater so that the solid content application amount was 0.5 g/m ² , and a surface protection sheet with a basis weight of 50 g/m ² was obtained.

[Comparative Example 1]
A surface protection sheet having a basis weight of 50 g/m ² was obtained in the same manner as in Example 1, except that the cellulose fine fibers were not applied using the size press coater.

[Comparative Example 2]
A surface protection sheet having a basis weight of 50 g/m ² was obtained in the same manner as in Example 2, except that the cellulose fine fibers were not applied using the size press coater.

[Comparative Example 3]
A surface protection sheet having a basis weight of 50 g/ ^m2 was obtained in the same manner as in Example 2, except that instead of applying cellulose fine fibers with a size press coater in Example 2, polyvinyl alcohol (Kuraray Poval 28-98, manufactured by Kuraray Co., Ltd.) was applied to give a solid application amount of 0.5 g/ ^m2 .

The transfer of the surface protection sheets obtained in Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3 to a glass plate was confirmed by a transport test. When the glass plate using the surface protection sheets of Example 1 and Example 2 was used to form an array of liquid crystal panels, no breaks in the color film were observed. On the other hand, when the glass plate using the surface protection sheets of Comparative Example 1, Comparative Example 2, and Comparative Example 3 was used to form an array of liquid crystal panels, breaks in the color film were observed. The results are shown in Table 1. Furthermore, in Comparative Example 3, polyvinyl alcohol was transferred to the glass plate, and contamination of the glass plate was also confirmed by visual inspection. Furthermore, the results of the surface strength of each Example and Comparative Example were as shown in Table 1.

As is clear from Table 1, Examples 1 and 2, which have cellulose nanofibers on the surface, have superior surface strength to Comparative Examples 1 and 2, which do not have cellulose nanofibers on the surface. This reduces the risk that the cellulose fibers constituting the sheet will fall off the surface of the sheet and contaminate or damage the surface of the glass plate. In addition, the cellulose nanofibers can capture foreign matter.

Claims (14)

It has a paper base material made from wood pulp,
The paper substrate is provided with cellulose nanofibers on at least a portion of the surface thereof,
A glass plate interleaving paper having a surface strength of 8 or more as measured in accordance with JAPAN TAPPI No. 1 . The glass plate interleaving paper according to claim 1, wherein the fiber diameter of the cellulose nanofibers is 3 to 100 nm. The glass plate interleaving paper according to claim 1 or 2, wherein the fiber length of the cellulose nanofibers is 100 nm to 100 μm. The glass plate interleaving paper has a surface layer,
The glass plate interleaving paper according to claim 1 , wherein the surface layer contains the cellulose nanofibers. The glass plate interleaving paper according to claim 4 , wherein the surface layer has a thickness of 3 to 100 nm. The glass plate interleaving paper according to claim 4 or 5 , wherein the cellulose nanofibers are present in the surface layer in an amount of 30 to 100 mass% based on the mass of the surface layer. The glass plate interleaving paper according to any one of claims 1 to 6 , wherein the cellulose nanofibers are present in a ratio of 0.04 to 4 parts by mass per 100 parts by mass of the wood pulp. The glass plate interleaving paper according to any one of claims 1 to 7 , having a basis weight of 20 to 100 g/ ^m2 . The glass plate interleaving paper according to any one of claims 1 to 8 , having a thickness of 15 to 200 µm. The glass plate interleaving paper according to any one of claims 1 to 9 , which is used for glass plates for displays. The glass plate interleaving paper according to claim 10 , wherein the display is a TFT liquid crystal display or an organic EL display. A laminate comprising the glass plate interleaving paper according to any one of claims 1 to 11 and a glass plate. A method for protecting glass plates, comprising a step of placing the glass plate interleaving paper according to claim 1 between a plurality of glass plates. A method for producing interleaving paper for glass plates, the method comprising the step of applying a composition containing at least cellulose nanofibers to at least one surface of a paper base material made of wood pulp, the surface strength of which is 8 or more as measured in accordance with JAPAN TAPPI No. 1 .