Surface protection sheet and method for manufacturing the same

Abstract

To provide a surface protective sheet capable of avoiding or reducing a foreign matter from transferring from the surface protective sheet to a surface of a protection object.SOLUTION: A surface protective sheet comprises a paper base material formed of wood pulp as a raw material and a cellulose nanofiber on at least a part surface of the paper base material.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a surface protection sheet used for surface protection of glass, metal, etc.

Background Art

[0002] In the process of manufacturing, storing, and transporting glass products, metal products, products with a mirror finish, etc., in order to avoid or reduce physical damage such as scratches on the surface of the product, or contamination of the surface of the product, various surface protection sheets are used to protect the surface of the product.

[0003] For example, in the case of a glass plate, in the storage process of stacking a plurality of glass plates for storage, the distribution process of transporting them by a truck or the like, the glass plates come into contact with each other under impact and scratches are generated, and in order to prevent the glass surface from being contaminated by foreign substances from the outside, paper called interleaving paper is sandwiched between the glass plates.

[0004] However, not only foreign substances from the outside but also foreign substances contained in the interleaving paper may contaminate the surface of the glass plate in contact with the interleaving paper. Therefore, as an interleaving paper that does not contaminate the surface of the glass plate, for example, Patent Document 1 proposes a glass interleaving paper in which the adhesive substance contained in the interleaving paper is made non-adhesive by a specific substance. Furthermore, in addition to foreign substances contained in the interleaving paper, polyvalent ions such as aluminum ions derived from aluminum sulfate contained as a papermaking chemical in the interleaving paper also adsorb anionic substances and coarsen, leading to contamination of the glass plate.

[0005] Also, Patent Document 2 proposes a glass interleaving paper in which a water-soluble polymer is applied to the surface of the interleaving paper as a means for reducing contamination of the glass plate surface by foreign substances contained in the interleaving paper.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] An object of the present invention is to provide a surface protection sheet capable of avoiding or reducing the transfer of foreign substances or harmful ions from the surface of a surface protection sheet such as a laminate paper to the surface of an object to be protected such as a glass plate. [Means for Solving the Problems]

[0008] As a result of intensive studies, the present inventor has found that in a surface protection sheet having a paper substrate made of wood pulp, the presence of cellulose nanofibers on the surface of the paper substrate can suppress the transfer of foreign substances or harmful ions from the surface of the surface protection sheet to an object to be protected such as a glass plate, and thus completed the present invention.

[0009] A first aspect of the present invention is a surface protection sheet comprising a paper substrate made of wood pulp, wherein at least a part of the surface of the paper substrate is provided with cellulose nanofibers.

[0010] The fiber diameter of the cellulose nanofibers is preferably 3 to 100 nm.

[0011] The fiber length of the cellulose nanofibers is preferably 100 nm to 100 μm.

[0012] The surface strength of the surface protection sheet of the present invention is preferably 8 or more.

[0013] It is preferable that the surface protection sheet of the present invention has a surface layer, and the surface layer contains the cellulose nanofibers.

[0014] The thickness of the surface layer is preferably 3 to 100 nm.

[0015] It is preferable that the cellulose nanofiber is present in the surface layer at a ratio of 30 to 100% by mass based on the mass of the surface layer.

[0016] In the surface protection sheet of the present invention, it is preferable that the cellulose nanofiber is present in a ratio of 0.04 to 4 parts by mass with respect to 100 parts by mass of the wood pulp.

[0017] The basis weight of the surface protection sheet of the present invention is preferably 20 to 100 g / m 2 2.

[0018] The thickness of the surface protection sheet of the present invention is preferably 15 to 200 μm.

[0019] The surface protection sheet of the present invention is preferably used for a glass plate for a display. In this case, the surface protection sheet of the present invention can be a glass backing paper.

[0020] The display is preferably a TFT liquid crystal display or an organic EL display.

[0021] The present invention also relates to a laminate comprising the surface protection sheet of the first aspect of the present invention and a glass plate.

[0022] The present invention also relates to a method for protecting a glass plate, which includes a step of disposing the surface protection sheet of the first aspect of the present invention between a plurality of glass plates.

[0023] The second aspect of the present invention is A method for manufacturing a surface protection sheet, which includes a step of applying a composition containing at least cellulose nanofibers to at least one surface of a paper base material made of wood pulp.

[0024] The surface protection sheet manufactured according to the second aspect of the present invention can have the characteristics of the surface protection sheet of the first aspect of the present invention.

Advantages of the Invention

[0025] The surface protection sheet of the present invention can avoid or reduce the transfer of foreign substances or harmful ions from the surface protection sheet to the surface of an object to be protected such as a glass plate with which the surface protection sheet comes into contact.

[0026] In particular, even if the surface protection sheet contains foreign substances or harmful ions, the present invention can avoid or reduce the transfer of the foreign substances or harmful ions from the surface protection sheet to the surface of the object to be protected.

[0027] When the surface protection sheet of the present invention is used as paper for wrapping a glass plate and / or paper sandwiched between glass plates, the surface of the glass plate can be well protected. Therefore, by using the surface protection sheet of the present invention as glass interleaving paper, damage and / or contamination of the surface of the glass plate can be avoided or reduced.

[0028] Furthermore, due to the presence of cellulose nanofibers, the surface protection sheet of the present invention can have excellent surface strength.

Embodiments for Carrying Out the Invention

[0029] In the present invention, in a surface protection sheet including a paper base material made from wood pulp, by causing cellulose nanofibers to exist on the surface of the paper base material, the transfer of foreign substances and harmful ions from the surface of the surface protection sheet to an object to be protected such as a glass plate is suppressed.

[0030] And in the present invention, even if the paper base material contains sticky or hard foreign substances, since cellulose nanofibers exist on its surface, the contact area between the foreign substances and the surface of the object to be protected decreases, so that the adhesion of foreign substances to the surface of the object to be protected or damage to the surface can be prevented or reduced. Moreover, since cellulose nanofibers are made of cellulose like wood pulp, they have excellent affinity with the paper base material, and there is little concern about transfer to the surface to be protected.

[0031] The surface protection sheet of the present invention can preferably be used for wrapping a glass plate and / or sandwiching between glass plates. Therefore, the surface protection sheet of the present invention is useful as a glass interleaving paper (interleaving paper for glass plates). As the glass plate, a glass plate for a flat panel display such as a liquid crystal display (particularly a TFT liquid crystal display), a plasma display, an organic electroluminescence (organic EL) display, etc. is preferable.

[0032] Since a glass plate for a flat panel display is used for a high-definition display as compared with a general window glass plate for construction, a window glass plate for vehicles, etc., it is required that the glass surface maintains a clean surface with as few impurities as possible, and that it has excellent flatness for high-speed responsiveness and wide viewing angle.

[0033] Contamination of the glass plate surface can cause problems in a flat panel display. For example, in the manufacturing process of a TFT liquid crystal display, elements such as very fine wirings and electrodes are formed on the surface of a substrate made of a glass plate by sputtering, vacuum evaporation, photolithography, etc. At that time, if the surface of the glass plate is contaminated, it is known that disconnection and / or short circuit may occur in such a very fine electric circuit, or defects may occur in the fabricated elements. Also, in the manufacturing process of a TFT, if a contaminant exists on the surface of the glass plate substrate, the fine lines formed on the surface are disconnected and / or short-circuited. For example, in the manufacturing process of a color filter, which is one of the manufacturing processes of a TFT liquid crystal display, a resist pattern is formed on the surface of the glass plate by photolithography. However, if a contaminant exists on the glass plate surface during resist coating in this process, pinholes are generated in the resist film after exposure or development, and as a result, defects such as disconnection of the color filter pattern occur. And similar problems have also been confirmed in the manufacturing of an organic EL display. Since an organic EL display is fabricated by forming thin films such as an ITO anode, an organic light-emitting layer, and a cathode on a glass plate substrate by sputtering, evaporation, printing, etc., if a substance that inhibits the thin film exists on the surface of the glass plate substrate, a problem of non-light emission occurs.

[0034] Although it has been difficult to identify the cause of such contamination of the glass plate, it has been found that one of the causes is fine foreign matter that transfers from the surface of the interleaving paper for the glass plate to the surface of the glass plate.

[0035] Therefore, by using the surface protection sheet of the present invention as an interleaving paper for glass, it is possible to reduce defects in flat panel displays such as TFT liquid crystal displays and organic EL displays, which are caused by the transfer of foreign matter present on the surface of the interleaving paper to the surface of the glass plate.

[0036] A first aspect of the present invention is a surface protection sheet including a paper base material made from wood pulp, wherein cellulose nanofibers are present on at least a part of the surface of the paper base material, and preferably it is an interleaving paper for a glass plate.

[0037] The wood pulp that can be used in the present invention is a single or mixed one of wood pulps such as softwood kraft pulp (NBKP), hardwood kraft pulp (LBKP), softwood sulfite pulp (NBSP), hardwood sulfite pulp (LBSP), and thermomechanical pulp (TMP). Based on this wood pulp, if necessary, non-wood pulps such as hemp, bamboo, straw, kenaf, paper mulberry, trifoliate orange, and cotton, modified pulps such as cationized pulp and mercerized pulp, synthetic fibers and chemical fibers such as rayon, vinylon, nylon, acrylic, and polyester, or microfibrillated pulp can be used alone or in combination. However, if the pulp contains a large amount of resin, the resin may have an adverse effect such as soiling the surface of the object to be protected such as a glass plate. Therefore, it is preferable to use a chemical pulp with as little resin as possible, for example, softwood kraft pulp alone. Also, high-yield pulps such as groundwood pulp are not preferable because they contain a large amount of resin. In addition, when synthetic fibers or chemical fibers are mixed, the cutting property is improved and the workability when making the interleaving paper into a flat plate is improved, but attention is required because the recyclability deteriorates in terms of waste treatment.

[0038] The form of the wood pulp is not particularly limited and can take any form such as sheet, block or flake. The sheet-like pulp can be obtained, for example, using a pulp machine having four processes: a wire part, a press part, a dry part, and a finishing part. In the wire part, the pulp fibers are formed into paper using a fourdrinier or a vacuum filter, etc., and in the press part, dehydration is performed using a roll press. In the dry part, it is dried using a cylinder dryer, a fractal dryer, etc., and finally, both ends of the sheet-like pulp are cut off and wound around a roll. Such methods are described in detail in "Paper Pulp Manufacturing Technology Series" and "Encyclopedia of Paper Pulp Manufacturing Technology" published by the Paper Pulp Technology Association. Note that the block-like pulp can be obtained, for example, by laminating the above-mentioned sheet-like pulp, and the flake-like pulp can be obtained, for example, by pulverizing the above-mentioned sheet-like pulp.

[0039] The thickness of the 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.

[0040] The basis weight of the sheet-like pulp is preferably 400 to 1300 g / m 2 and more preferably 500 to 1200 g / m 2 and even more preferably 500 to 1100 g / m 2 and even more preferably 500 to 1000 g / m 2 and even more preferably 700 to 1000 g / m 2 and even more preferably.

[0041] The surface protection sheet of the present invention includes a paper base material made of wood pulp. The number of paper base materials included in the surface protection sheet of the present invention is usually one, but may include a plurality of paper base materials as required. The wood pulp contains cellulose fibers, but the fibers are not cellulose nanofibers. Therefore, the cellulose fibers derived from the wood pulp contained in the paper base material are not cellulose nanofibers.

[0042] The form of the paper substrate is preferably sheet-like. The thickness of the sheet-like paper substrate is preferably 10 to 130 μm, more preferably 20 to 120 μm, still more preferably 30 to 110 μm, and even more preferably 40 to 100 μm.

[0043] The paper substrate uses wood pulp as a raw material. Therefore, it is preferable that the paper substrate is not made from recycled cellulose.

[0044] In addition to the cellulose fibers derived from wood pulp, the paper substrate may contain other components as necessary. Examples of other components include paper strength enhancers or fixing agents such as starch, polyacrylamide, polyamine polyamide epichlorohydrin, sizing agents, fillers, drainage aids, water resistance agents, fixing agents, defoaming agents, slime control agents, etc. These can be used alone or in combination of two or more.

[0045] The surface protection sheet of the present invention is provided with cellulose nanofibers on at least a part of the surface of the paper substrate. That is, in the surface protection sheet of the present invention, cellulose nanofibers are present on at least a part of the surface of the paper substrate.

[0046] Cellulose nanofibers are fine cellulose fibers. In the present invention, for example, those having a width (fiber diameter) of 2 to 300 nm and a length of 1 to 500 μm can be used.

[0047] The width of the cellulose nanofibers is preferably from 2 to 200 nm, more preferably from 3 to 100 nm, still more preferably from 4 to 50 nm, and yet more preferably from 4 to 20 nm. The fiber diameter is preferably the average fiber diameter. Herein, the "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 a plurality of 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, measuring the diameters of the selected fibers, and averaging them. The number of fibers to be selected is 100 or more, preferably 150 or more, more preferably 200 or more, and yet more preferably 300 or more.

[0048] The length (fiber length) of the cellulose nanofibers is preferably from 10 nm to 300 μm, more preferably from 50 nm to 200 μm, still more preferably from 100 nm to 100 μm, and yet more preferably from 150 nm to 50 μm. Herein, the fiber length refers to the length of the fiber when the fiber is stretched straight. The fiber length is preferably the average fiber length. Herein, the "average fiber length" means the number average of the fiber lengths of the cellulose nanofibers. The average fiber length can be obtained, for example, by magnifying and observing a plurality of 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, measuring the lengths of the selected fibers, and averaging them. The number of fibers to be selected is 100 or more, preferably 150 or more, more preferably 200 or more, and yet more preferably 300 or more.

[0049] Cellulose nanofibers can be produced, for example, according to Japanese Patent No. 3036354 (Method for producing microfibrillated cellulose), Japanese Patent No. 2967804 (Method for producing ultrafine fibrillated cellulose, method for producing coated paper and dyed paper using ultrafine fibrillated cellulose), or Japanese Patent Application Laid-Open 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 be produced by a method involving chemical modification, such as Japanese Patent Application Laid-Open No. 2009-263652 (Method for producing cellulose nanofibers) and International Publication No. 2009 / 069641 (Cellulose nanofibers and method for producing the same, cellulose nanofiber dispersion), but it 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.

[0050] As raw materials for cellulose nanofibers, for example, chemical pulps such as hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), and hardwood bleached sulfite pulp (NBSP), mechanical pulps such as groundwood pulp (GP) and thermomechanical pulp (TMP), wood pulps, bast fiber pulps such as kozo, gampi, and mitsumata, cotton pulp, non-wood pulps such as hemp, kenaf, rice, bagasse, and bamboo, biocelluloses such as bacterial cellulose, powdered cellulose, microcrystalline cellulose, modified cellulose, and regenerated cellulose can be used.

[0051] 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, anion neutralization after cationic modification, and hydrophobization modification. Such modification may be carried out either before or after the production of cellulose nanofibers with respect to the raw materials of cellulose nanofibers.

[0052] The cellulose nanofibers are preferably present in an amount of 50% or more, more preferably 70% or more, still more preferably 90% or more, and particularly preferably on the entire surface of the paper substrate. When the paper substrate is in the form of a sheet, it is preferably present in an amount of 50% or more, more preferably 70% or more, still more preferably 90% or more, and particularly preferably on the entire surface of at least one of the front and back surfaces of the paper substrate. Further, when the paper substrate is in the form of a sheet, it is preferably present in an amount of 50% or more, more preferably 70% or more, still more preferably 90% or more, and particularly preferably on the entire surfaces of both the front and back surfaces of the paper substrate, based on the total surface area of both surfaces.

[0053] In the surface protection sheet of the present invention, the cellulose nanofibers can be present in a proportion of 0.01 to 10 parts by mass, preferably 0.02 to 8 parts by mass, more preferably 0.04 to 4 parts by mass, and still more preferably 0.05 to 3 parts by mass, based on 100 parts by mass of the wood pulp.

[0054] The amount of the cellulose nanofibers present in the surface protection sheet of the present invention is not particularly limited, but for example, it can be present in a proportion of 0.01 to 10 g / m 2 preferably 0.01 to 5 g / m 2 more preferably 0.1 to 3 g / m 2 is more preferred.

[0055] The cellulose nanofibers also have a high affinity with the paper substrate composed of cellulose and are firmly held on the surface of the paper substrate. Therefore, the cellulose nanofibers are suppressed from separating and transferring from the surface of the paper substrate.

[0056] In addition, since the cellulose nanofibers are hydrophilic, it is possible to suppress the adhesion of hydrophobic foreign substances to the surface protection sheet.

[0057] In one aspect of the present invention, the surface protection sheet of the present invention includes 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 more preferably the paper substrate and the surface layer are in contact. The surface layer can function as a protective layer for the paper substrate.

[0058] The thickness of the surface layer is not particularly limited, but for example, it can be 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.

[0059] In the surface layer, the cellulose nanofibers can be present in a proportion of 10 to 100% by mass based on the mass of the surface layer. 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.

[0060] In addition to cellulose nanofibers, the surface layer may contain other components as needed. Examples of other components include paper strength enhancers or fixing agents such as starch, polyacrylamide, polyamine polyamide epichlorohydrin, sizing agents, fillers, drainage improvers, water resistance agents, fixing agents, defoaming agents, slime control agents, etc. These can be used alone or in combination of two or more.

[0061] Due to the high crystallinity of cellulose, cellulose nanofibers can form a film on the surface of the paper substrate to form a relatively hard surface layer. Also, due to the high specific surface area of cellulose nanofibers and the numerous hydroxyl groups of cellulose, cellulose nanofibers can form a relatively strong surface layer. Thereby, the surface layer can have physical properties suitable as a protective layer.

[0062] When the fiber diameter (width) of the cellulose nanofiber is smaller than the wavelength of visible light, the cellulose nanofiber does not scatter visible light, so that the layer formed by the cellulose nanofibers can be transparent. Thereby, the appearance of the surface protection sheet of the present invention can be improved.

[0063] The foreign matter that is a problem in the present invention is fine foreign matter that contaminates the surface of an object to be protected such as a glass plate.

[0064] The foreign matter may be an organic substance such as a resin such as polyvinyl alcohol or an inorganic substance such as aluminum sulfate, may be either adhesive or non-adhesive, and may be either hard or soft.

[0065] The foreign matter may be either solid or liquid. Also, the size of the foreign matter is not particularly limited, but is usually so fine that it cannot be visually recognized. 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, the "size" means the volume average (median) particle diameter. The volume average particle diameter can be measured, for example, by the laser diffraction scattering method.

[0066] The foreign matter may contain a hydrophobic substance. Note that the foreign matter may consist only of a hydrophobic substance.

[0067] 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, for example, aliphatic hydrocarbons, vegetable oils, animal oils, synthetic glycerides, aliphatic alcohols, fatty acids, esters of aliphatic alcohols and / or fatty acids), resins (excluding silicones), silicones, pitch, rubber, and talc, and even more preferably selected from the group consisting of silicones and talc (particularly talc adsorbed with hydrophobic foreign matter).

[0068] Examples of aliphatic hydrocarbons include, for example, linear or branched hydrocarbons, particularly mineral oil (such as liquid paraffin), paraffin, petrolatum, i.e., petroleum jelly, naphthalene, etc.; hydrogenated polyisobutene, isoeicosane, polydecene, pearl lene, etc., hydrogenated polyisobutenes and decene / butene copolymers; and mixtures thereof.

[0069] Examples of other aliphatic hydrocarbons include linear or branched, or optionally cyclic, C 6 ~C 16 lower alkanes. Examples that can be mentioned include hexane, undecane, dodecane, tridecane and isoparaffins, such as isohexadecane and isodecane.

[0070] 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, southernwood oil, castor oil, safflower oil, jojoba oil, almond oil, grape seed oil, sesame oil, peanut oil, and mixtures thereof.

[0071] Examples of animal oils include, for example, mink oil, squalene, perhydrosqualene and squalane.

[0072] Examples of synthetic glycerides include, for example, caprylic / capric triglyceride.

[0073] The fatty acid should be in the acidic form (i.e., not in the form of a salt to avoid becoming soap), and can be saturated or unsaturated, contain 6 to 30 carbon atoms, particularly 9 to 30 carbon atoms, and optionally, particularly, be substituted with one or more hydroxyl groups (particularly 1 to 4). When the fatty acid is unsaturated, the compound can contain 1 to 3 conjugated or non-conjugated carbon-carbon double bonds. Fatty acids are selected from, for example, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid and isostearic acid.

[0074] The term "aliphatic alcohol" as used herein means any saturated, straight-chain or branched C 8 ~C 30 alcohol, optionally substituted with one or more hydroxyl groups (especially 1 to 4).

[0075] Among the aliphatic alcohols, C 12 ~C 22 aliphatic alcohols are preferred, and C 16 ~C 18 saturated aliphatic alcohols are more preferred. Examples thereof include lauryl alcohol, cetyl alcohol, stearyl alcohol, isostearyl alcohol, oleyl alcohol, behenyl alcohol, undecyl alcohol, myristyl alcohol, and mixtures thereof.

[0076] Examples of esters of fatty acids and / or aliphatic alcohols include esters of saturated or unsaturated, straight-chain or branched C 1 ~C 26 aliphatic monoacids or polyacids, and esters of saturated or unsaturated, straight-chain or branched C 1 ~C 26 aliphatic monohydric alcohols or polyhydric alcohols, and the total carbon number of the esters is preferably 10 or more.

[0077] Resins (excluding silicone) are not particularly limited as long as they are hydrophobic. Examples of resins include thermoplastic resins such as polyolefin, polystyrene, poly(meth)acrylate, polyacrylamide, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polyester, polycarbonate, polyamide, polyimide, etc., thermosetting resins such as polyurethane, melamine resin, urea resin, etc., and mixtures thereof.

[0078] Examples of silicone include silicone oil. Silicone oil is hydrophobic, and its molecular structure may be cyclic, linear, or branched. The kinematic viscosity of silicone oil at 25°C is usually in the range of 0.65 to 100,000 mm 2 / s, but it may also be in the range of 0.65 to 10,000 mm 2 / s.

[0079] Examples of silicone oil include linear organopolysiloxane, cyclic organopolysiloxane, and branched organopolysiloxane.

[0080] Examples of linear organopolysiloxane, cyclic organopolysiloxane, and branched organopolysiloxane include the following general formulas (1), (2), and (3): R 1 3 SiO-(R 1 2 SiO) a -SiR 1 3 (1)

Chemical formula

[0081] 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, 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, more preferably 2 to 6 carbon atoms; or a monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms, more preferably 6 to 12 carbon atoms.

[0082] Examples of the monovalent saturated hydrocarbon group having 1 to 30 carbon atoms include linear or branched alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, etc., and cycloalkyl groups such as cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, etc.

[0083] Examples of the monovalent unsaturated hydrocarbon group having 2 to 30 carbon atoms include linear or branched alkenyl groups such as vinyl group, 1-propenyl group, allyl group, isopropenyl group, 1-butenyl group, 2-butenyl group, pentenyl group, hexenyl group, etc.; cycloalkenyl groups such as cyclopentenyl group, cyclohexenyl group, etc.; cycloalkenylalkyl groups such as cyclopentenylethyl group, cyclohexenylethyl group, cyclohexenylpropyl group, etc.; and alkynyl groups such as ethynyl group, propargyl group, etc.

[0084] Examples of the monovalent aromatic hydrocarbon group having 6 to 30 carbon atoms include aryl groups such as phenyl group, tolyl group, xylyl group, mesityl group, etc. Phenyl group is preferred. In the present specification, the aromatic hydrocarbon group includes not only a group consisting only of aromatic hydrocarbons but also a group in which an aromatic hydrocarbon and an aliphatic saturated hydrocarbon are combined. Examples of the group in which an aromatic hydrocarbon and a saturated hydrocarbon are combined include aralkyl groups such as benzyl group, phenethyl group, etc.

[0085] The hydrogen atom on the above-mentioned monovalent hydrocarbon group may be substituted by one or more substituents, and the substituents include, for example, a halogen atom (fluorine atom, chlorine atom, bromine atom, and iodine atom), a hydroxyl group, 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, an oxyalkylene group, and other organic groups. Specifically, a 3,3,3-trifluoropropyl group, a 3-chloropropyl group, a 3-hydroxypropyl group, a 3-(2-hydroxyethoxy)propyl group, a 3-carboxypropyl group, a 10-carboxydecyl group, a 3-isocyanatopropyl group, etc. can be mentioned.

[0086] Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, etc., but a methoxy group or an ethoxy group is preferred, and a methoxy group is more preferred.

[0087] More specifically, examples of the linear organopolysiloxane include dimethylpolysiloxane blocked at both molecular chain ends with trimethylsiloxy groups (dimethyl silicone with low viscosity such as 2 mPa·s and 6 mPa·s to high viscosity such as 1,000,000 mPa·s), organohydrogenpolysiloxane, methylphenylpolysiloxane blocked at both molecular chain ends with trimethylsiloxy groups, dimethylsiloxane·methylphenylsiloxane copolymer blocked at both molecular chain ends with trimethylsiloxy groups, diphenylpolysiloxane blocked at both molecular chain ends with trimethylsiloxy groups, dimethylsiloxane·diphenylsiloxane copolymer blocked at both molecular chain ends with trimethylsiloxy groups, trimethylpentaphenyltrisiloxane, phenyl(trimethylsiloxy)siloxane, methylalkylpolysiloxane blocked at both molecular chain ends with trimethylsiloxy groups, dimethylpolysiloxane·methylalkylsiloxane copolymer blocked at both molecular chain ends with trimethylsiloxy groups, dimethylsiloxane·methyl(3,3,3-trifluoropropyl)siloxane copolymer blocked at both molecular chain ends with trimethylsiloxy groups, 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, tris(trimethylsiloxy)methylsilane, tris(trimethylsiloxy)alkylsilane, tetrakis(trimethylsiloxy)silane, tetramethyl-1,3-dihydroxydisiloxane, octamethyl-1,7-dihydroxytetrasiloxane, hexamethyl-1,5-diethoxytetrasiloxane, hexamethyldisiloxane, octamethyltrisiloxane, higher alkoxy-modified silicone, higher fatty acid-modified silicone, dimethiconol, and the like.

[0088] Examples of 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)tetramethylcyclotetrasiloxane, 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, 1,3,5,7 - tetra(N,N - bis(lauroyl)-3 - aminopropyl)tetramethylcyclotetrasiloxane, and the like.

[0089] Examples of branched organopolysiloxanes include methyltris(trimethylsiloxy)silane, ethyltris(trimethylsiloxy)silane, propyltris(trimethylsiloxy)silane, tetrakis(trimethylsiloxy)silane, phenyltris(trimethylsiloxy)silane, and the like.

[0090] As the silicone oil in the present invention, dimethylpolysiloxane, diethylpolysiloxane, methylphenylpolysiloxane, polydimethyl-polydiphenylsiloxane copolymer, polymethyl-3,3,3-trifluoropropylsiloxane, etc. are preferable. As the silicone in the present invention, dimethylpolysiloxane is typical.

[0091] The silicone oil in the present invention may be a modified silicone oil. Examples of the modified silicone oil include polyoxyalkylene-modified silicone oil.

[0092] The polyoxyalkylene-modified silicone oil is a silicone oil in which a polyoxyalkylene group is bonded via a silicon-carbon bond in the molecule, preferably shows water solubility at normal temperature, specifically 25 °C, and more preferably is nonionic.

[0093] Specifically, the polyoxyalkylene-modified silicone oil is, for example, a copolymer of a silicone oil composed of linear or branched siloxane and polyoxyalkylene, and there are various types, but those represented by the following formula (4) are particularly preferable. R 2 3 SiO-(R 1 2 SiO) d -(R 1 ASiO) e -SiR 2 3 (4) (In the formula, R 1 are each independently the same as above, R 2 are each independently R 1 or A, A is each independently a group represented by R 3 G, R 3is a substituted or unsubstituted divalent hydrocarbon group, G represents a polyoxyalkylene group containing at least one alkylene oxide having 2 to 5 carbon atoms such as ethylene oxide and propylene oxide, d represents an integer from 1 to 500, e represents an integer from 1 to 50).

[0094] Examples of the substituted or unsubstituted divalent hydrocarbon group 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 group, dimethylene group, trimethylene group, tetramethylene group, pentamethylene group, hexamethylene group, heptamethylene group, octamethylene group; alkenylene groups having 2 to 30 carbon atoms such as vinylene group, arylene group, butenylene group, hexenylene group, octenylene group; arylene groups having 6 to 30 carbon atoms such as phenylene group, diphenylene group; alkylene arylene groups having 7 to 30 carbon atoms such as dimethylene phenylene group; and groups in which at least part of the hydrogen atoms bonded to the carbon atoms of these groups are substituted with organic groups containing halogen atoms such as fluorine, hydroxyl groups, or carbinol groups, epoxy groups, glycidyl groups, acyl groups, carboxyl groups, amino groups, methacryl groups, mercapto groups, amide groups, oxyalkylene groups, etc. 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 even more preferably an alkylene group having 3 to 5 carbon atoms.

[0095] For example, specific examples of the polyoxyalkylene-modified silicone oil can include the following.

Chemical formula

[0096] Examples of the modified silicone oil include aminoalkyl-modified silicone oil.

[0097] Aminoalkyl-modified silicone oil is a silicone oil in which an aminoalkyl group is bonded through a silicon-carbon bond in the molecule, and preferably shows a viscosity of 10 to 100,000 cs at normal temperature, specifically 25°C.

[0098] As the aminoalkyl silicone oil, in the above formula (4), G is substituted with the formula: -(NR 4 CH 2 CH 2 ) z NR 4 2 (wherein R 4 are each independently as described above, and z is a number from 0 ≤ z ≤ 4).

[0099] 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, still more preferably 0.3 ppm or less, still more preferably 0.2 ppm or less, and particularly preferably 0.1 ppm or less with respect to the absolutely dry mass of the surface protection sheet. When there is silicone in an amount exceeding 0.5 ppm, in a scene that requires a very high-definition display such as a mobile terminal, for example, a disconnection point such as a color film caused by a trace amount of silicone transferred to the surface of a glass plate is highly conspicuous, so the possibility of being judged as a quality defect increases. In the present invention, "absolutely dry" means a state in which substantially no moisture exists in the object to be dried due to drying.

[0100] Foreign substances can have a Mohs hardness of 4 or more. The foreign substances with a Mohs hardness of 4 or more may be particles made of either inorganic or organic substances, and inorganic particles are preferred. Examples of the foreign substances 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 elements of Group 2 such as magnesium, elements of Group 4 such as titanium, and elements of Group 8 such as iron. Silicon dioxide is preferred as the inorganic silicon oxide. Examples of the foreign substances with a Mohs hardness of 4 or more include oxide minerals. Particularly, examples of the foreign substances with a Mohs hardness of 4 or more include iron oxide, copper, quartz, fused quartz (quartz glass), titanium oxide, glass pieces, crystal pieces, magnesium oxide, sand, etc. Sand mainly consists of hornblende 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. The Mohs hardness is an index representing hardness in 10 levels. It is a value obtained by rubbing a standard substance corresponding to each level and the substance to be measured and relatively evaluating the hardness of the substance to be measured with respect to the standard substance based on whether scratches are formed. The standard substances are, in order from soft (Mohs hardness 1) to hard (Mohs hardness 10), 1: talc, 2: gypsum, 3: calcite, 4: fluorite, 5: apatite, 6: feldspar, 7: quartz, 8: topaz, 9: corundum, 10: diamond. The method for measuring the Mohs hardness is to prepare two plates with a known Mohs hardness and a smooth surface, sandwich the foreign substance to be measured between the two plates, rub the two plates against each other, and check for the occurrence of scratches on the plate surface.

[0101] Harmful ions that are problematic in the present invention are polyvalent ions such as aluminum ions. The harmful ions may be cationic or anionic. Ions with a high valence tend to adsorb counter-ion substances and coarsen. When harmful ions transfer to the glass plate and coarsen, it causes disconnection and / or short circuit and becomes a cause of defects when fine wirings and electrodes are installed on the glass plate surface in the display manufacturing process.

[0102] Examples of cationic polyvalent ions include, for example, Ca 2+ 、Al3+ , Mg 2+ , Ba 2+ , Cu 2+ , Fe 2+ , Fe 3+ , Zn 2+ may be mentioned.

[0103] Examples of anionic polyvalent ions include, for example, SO 4 2- , CO 3 2- , PO 4 3- , S 2- may be mentioned.

[0104] The thickness of the surface protection sheet of the present invention is preferably 15 to 200 μm, more preferably 20 to 200 μm, still more preferably 20 to 180 μm, still more preferably 30 to 150 μm, and still more preferably 45 to 135 μm.

[0105] The basis weight of the surface protection sheet of the present invention is preferably 20 to 100 g / m 2 , more preferably 25 to 75 g / m 2 , and still more preferably 30 to 70 g / m 2 .

[0106] Due to the presence of cellulose nanofibers, the surface protection sheet of the present invention can have excellent surface strength. 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. When the surface strength is less than 8, fibers such as wood pulp and cellulose nanofibers constituting the sheet are likely to fall off, and as a result, the fibers and foreign substances may contaminate or scratch the surface of the object to be protected such as a glass plate. In addition, by providing a cellulose nanofiber or a surface layer containing the same as in the present invention, there is an effect of increasing the surface strength and an effect of capturing foreign substances. This is due to the crystallinity of cellulose nanofibers, the high specific surface area, and the viscosity of its dispersion liquid.

[0107] The surface protection sheet of the present invention preferably has an average deviation (MMD) of the coefficient of friction on the surface 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. For MMD, using a friction feel tester (KES-SE manufactured by Kato Tech Co., Ltd.), a 10 mm square friction element composed of a bundle of piano wires with a diameter of 0.5 mm is placed on the surface of the paper fixed with a tension of 20 g / cm at 50 g / cm 2It is the average deviation value of the coefficient of friction measured by moving 2 cm at a sample moving speed of 0.1 cm / second in the same direction as the direction in which the tension is applied while contacting with the contact pressure. If this MMD is large, it means that the coefficient of friction on the sheet surface varies greatly depending on the position on the sheet surface. Microscopically, it means that there are many minute irregularities on the sheet surface. By providing such minute irregularities on the sheet surface, 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 becomes small, and the removal operation when removing the surface protection sheet from the surface of the object to be protected becomes easy. If MMD exceeds 0.022, the minute irregularities on the surface increase, and the snagging between the surface of the surface protection sheet and the surface of the object to be protected increases, which is not preferable. MMD is preferably, for example, from 0.001 to 0.022, more preferably from 0.002 to 0.020, and even more preferably from 0.004 to 0.019.

[0108] The manufacturing method of the surface protection sheet of the present invention is not particularly limited. For example, it can be manufactured by applying cellulose nanofibers to the surface of a paper base material manufactured based on the papermaking method.

[0109] The second aspect of the present invention is a method for manufacturing a surface protection sheet, including a step of applying a composition containing at least cellulose nanofibers to at least one surface of a paper base material made of wood pulp.

[0110] The paper base material can be manufactured by a normal papermaking method. For example, the paper base material, a slurry preparation step of preparing a slurry of wood pulp, a sheet forming step of forming the slurry into a sheet shape, a wet paper preparation step of dehydrating the sheet to form wet paper, a drying step of drying the wet paper to obtain the paper base material can be manufactured through.

[0111] In the slurry preparation step, a slurry of wood pulp can be prepared by a conventionally known method. For example, in the slurry preparation step, the cellulose fibers constituting the wood pulp are disintegrated in water to form an aqueous suspension to prepare a slurry.

[0112] Also, within a range not impairing the performance of the present invention, an adhesive, a fungicide, an antifoaming agent, a filler, a wet paper strength enhancer, a dry paper strength enhancer, a sizing agent, a colorant, a fixing agent, a yield improver, a slime control agent, etc. can be added to the above slurry as necessary. Note that it is preferable to take great care so that insects, dust, etc. do not mix in when adding these chemicals.

[0113] In the sheet forming step of forming the slurry into a sheet shape, sheeting can be performed by a conventionally known method. For example, the slurry can be discharged onto a flat wire (for example, a Fourdrinier paper machine), or a sheet can be scooped from the slurry with a wire wound around a cylindrical cylinder (for example, a cylinder mold paper machine) to obtain a sheet.

[0114] The dehydration method in the wet paper preparation step is arbitrary, and a conventionally known method can be used. For example, a method of papermaking using a twin-wire paper machine such as an on-top former or a gap former can be mentioned. Also, adjustment in the press part is conceivable. For example, the sheet can be dehydrated by pressing it with a roll.

[0115] The sheet forming step and the wet paper preparation step may be performed individually using separate apparatuses, or may be continuously or partially overlappingly performed in the same apparatus. For example, in the wire part of a paper machine, the slurry may be placed on a wire (mesh) to form a sheet while being dehydrated to form a wet paper.

[0116] In the drying step, the wet paper can be dried by a conventionally known method using a dryer roll or the like to obtain the paper base material.

[0117] In addition, calendering, supercalendering, soft nip calendering, embossing, or other processing may be performed during and / or after the papermaking of the paper substrate. The surface properties and thickness can be adjusted by the processing.

[0118] In the step of applying a composition containing at least cellulose nanofibers to at least one surface of the paper substrate, a composition containing the cellulose nanofibers described above can be used.

[0119] 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. The composition may contain other components as necessary in addition to cellulose nanofibers. Examples of other components include paper strength enhancers or fixing agents such as starch, polyacrylamide, polyamine polyamide epichlorohydrin, sizing agents, fillers, drainage aids, water resistance agents, fixing agents, defoaming agents, slime control agents, etc. These can be used alone or in combination of two or more.

[0120] The concentration of cellulose nanofibers in the composition is not particularly limited as long as coating is possible, and can be, for example, 0.1 to 5% by weight, 0.3 to 3% by weight, or 0.5 to 1% by weight.

[0121] The coating can be carried out by a conventionally known method such as a blade coater, an air knife coater, or cast coating. Also, for example, it can be carried out using a size press device.

[0122] By the manufacturing method of the second aspect of the present invention, the surface protection sheet of the first aspect of the present invention can be efficiently manufactured.

[0123] The surface protection sheet of the present invention is used by bringing its surface into contact with the surface of an object to be protected, such as glass or metal. The surface protection sheet of the present invention can be used not only as interleaving paper for glass plates inserted between laminated glass plates, but also for general surface protection applications of glass products, metal products, and products having a mirror finish.

[0124] When the surface protection sheet of the present invention is used as interleaving paper for glass plates, the interleaving paper for glass plates of the present invention is disposed between glass plates for use. For example, the interleaving paper for glass plates is typically inserted one by one between a plurality of glass plates and, as a whole, forms a laminate, and the laminate becomes an object for storage and transportation. Further, a single glass plate or the laminate may be packaged using the interleaving paper for glass plates of the present invention. Therefore, the present invention has an aspect of a method for protecting glass plates including the step of disposing (particularly inserting) the above-described interleaving paper for glass plates between glass plates.

[0125] The glass plates used in the method for protecting glass plates of the present invention are not particularly limited, but as described above, they are preferably glass plates 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, fine electrodes, elements such as partition walls, etc. are formed on the surface of the glass plate for flat panel displays. By using the interleaving paper for glass plates of the present invention, the transfer of fine foreign matters or harmful ions that cause problems 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 inconveniences occurring in the lines and elements due to the foreign matters or harmful ions can be suppressed or avoided, and as a result, the defects of the display can be suppressed or avoided.

[0126] The interleaving paper for glass plates of the present invention can be suitably used for glass plates for flat panel displays that particularly require surface cleanliness. In particular, with the increase in the size of displays, the size and weight of glass plates for flat panel displays have increased, but the interleaving paper for glass plates of the present invention can well protect the surface of such large or heavy glass plates.

Example

[0127] Hereinafter, the present invention will be described more specifically using examples and comparative examples, but the scope of the present invention is not limited to the examples.

[0128] (1) Transfer test to glass (transport test) Foamed urethane was laid on the glass placement surface of an L-shaped gantry made of aluminum with an angle of 75 degrees. A placement surface for vertically placing the glass plate and a backrest surface extending vertically from the rear end of the placement surface were provided. 120 glass plates with a size of 680 mm × 880 mm × 0.7 mm and a surface protection sheet were inserted between each glass plate, and they were leaned against the backrest surface in parallel and fixed by hanging a belt-shaped belt fixed to the gantry over the entire circumference from the rear end to the backrest surface. The gantry set as described above was covered entirely with packaging materials to prevent the entry of dust and dirt from the outside. Thereafter, a transport test by truck was carried out. The transport test conditions were a transport distance of 1000 km (stored for 5 days in an environment of 40°C × 95% RH during transportation).

[0129] (2) Surface strength The surface strength was measured in accordance with JAPAN TAPPI No.1.

[0130] [Example 1] Old paper raw materials derived from newspapers and magazines were prepared, and the raw materials were beaten to prepare a 0.4% concentration slurry adjusted to 300 ml c.s.f. When this was used for papermaking using a Fourdrinier paper machine, a 1 wt% dispersion of cellulose microfibers (WMa-10002 manufactured by Sugino Machine Limited) was applied by a size press coater so that the solid content coating amount was 0.5 g / m 2 and a surface protection sheet with a basis weight of 50 g / m 2 was obtained.

[0131] [Example 2] In a manufacturing apparatus for softwood kraft pulp consisting of a cooking process, a washing process, an oxygen delignification reaction process, and a multi-stage bleaching process using chlorine dioxide and hydrogen peroxide, an appropriate amount of the stock solution of a silicone-based defoaming agent "SN Deformer 551K" (manufactured by San Nopco Ltd.) was continuously added as a defoaming agent to the cleaning liquid of a drum washer immediately after removing knots after the cooking process. Also, an appropriate amount of the same "SN Deformer 551K" was added as a defoaming agent to the wash press in the press washing process. When papermaking was carried out using a Fourdrinier paper machine with the softwood kraft pulp thus obtained as a raw material, a 1 wt% dispersion of cellulose microfibrils (WMa-10002 manufactured by Sugino Machine Ltd.) was applied by a size press coater so that the solid content coating amount became 0.5 g / m 2 and a surface protection sheet with a basis weight of 50 g / m 2 was obtained.

[0132] [Comparative Example 1] A surface protection sheet with a basis weight of 50 g / m 2 was obtained in the same manner as in Example 1, except that cellulose microfibrils were not applied by the size press coater in Example 1.

[0133] [Comparative Example 2] A surface protection sheet with a basis weight of 50 g / m 2 was obtained in the same manner as in Example 2, except that cellulose microfibrils were not applied by the size press coater in Example 2.

[0134] [Comparative Example 3] A surface protection sheet with a basis weight of 50 g / m 2 was obtained in the same manner as in Example 2, except that polyvinyl alcohol (Kuraray Poval 28-98 manufactured by Kuraray Co., Ltd.) was applied so that the solid content coating amount became 0.5 g / m 2 instead of applying cellulose microfibrils by the size press coater in Example 2.

[0135] When the transfer of the surface protection sheets obtained in Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3 to the glass plate was confirmed by a transport test, no disconnection of the color film was observed during the array formation of the liquid crystal panel using the glass plate with the surface protection sheets of Example 1 and Example 2. On the other hand, during the array formation of the liquid crystal panel using the glass plate with the surface protection sheets of Comparative Example 1, Comparative Example 2, and Comparative Example 3, disconnection of the color film was observed. The results are shown in Table 1. Furthermore, in Comparative Example 3, polyvinyl alcohol had transferred to the glass plate, and contamination of the glass plate was also visually confirmed. Also, the results of the surface strength of each example and comparative example were as shown in Table 1.

[0136]

Table 1

[0137] As is clear from Table 1, Examples 1 and 2 having cellulose nanofibers on the surface are superior in surface strength to Comparative Examples 1 and 2 in which cellulose nanofibers do not exist on the surface, respectively. Thereby, the risk that the cellulose fibers constituting the sheet fall off from the surface of the sheet and contaminate or damage the surface of the glass plate can be reduced. Also, the effect of capturing foreign substances by the cellulose nanofibers can be obtained.

Claims

1. It comprises a paper base material made of wood pulp, Cellulose nanofibers are provided on at least a part of the surface of the paper base material, A backing paper for a glass plate having a surface strength of 8 or more measured in accordance with JAPAN TAPPI No.

1.

2. The backing paper for a glass plate according to claim 1, wherein the fiber diameter of the cellulose nanofibers is 3 to 100 nm.

3. The backing paper for a glass plate according to claim 1 or 2, wherein the fiber length of the cellulose nanofibers is 100 nm to 100 μm.

4. The backing paper for a glass plate has a surface layer, The backing paper for a glass plate according to any one of claims 1 to 3, wherein the surface layer contains the cellulose nanofibers.

5. The backing paper for a glass plate according to claim 4, wherein the thickness of the surface layer is 3 to 100 nm.

6. The backing paper for a glass plate according to claim 4 or 5, wherein 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.

7. The backing paper for a glass plate 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 with respect to 100 parts by mass of the wood pulp.

8. The basis weight is 20 to 100 g / m ２ The interleaving paper for a glass plate according to any one of claims 1 to 7, wherein the basis weight is 20 to 100 g / m

9. The backing paper for a glass plate according to any one of claims 1 to 8, having a thickness of 15 to 200 μm.

10. The backing paper for a glass plate according to any one of claims 1 to 9, which is used for a glass plate for a display.

11. The backing paper for a glass plate according to claim 10, wherein the display is a TFT liquid crystal display or an organic EL display.

12. A laminate comprising the backing paper for a glass plate according to any one of claims 1 to 11 and a glass plate.

13. A method for protecting a glass plate, comprising the step of disposing the backing paper for a glass plate according to any one of claims 1 to 11 between a plurality of glass plates.

14. A method for producing a backing paper for a glass plate having a surface strength of 8 or more measured in accordance with JAPAN TAPPI No. 1, 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.

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