JP6954210B2 - Seat - Google Patents

Description

The present invention relates to a sheet having a pearly appearance.

Various techniques are known for sheets having a pearly appearance on a paper base material.
For example, a pearl-like printed matter in which a printing ink layer composed of a mixed ink of white ink and medium is arranged on a base material having a metallic luster is disclosed (Patent Document 1). Further, there is disclosed a pearl-like coated paper in which a white pigment coating layer is provided on at least one surface of a sheet-like material made of wood fiber, and a coating layer containing a pearl pigment is coated on the white pigment coating layer. 2).

JP-A-2017-094500 Japanese Patent No. 5348734

However, in Patent Document 1, a vapor deposition step of laminating a metal vapor deposition layer on a paper substrate is required in order to obtain a substrate having a metallic luster, and the production of a sheet is complicated. Further, in Patent Document 2, it is necessary to provide a plurality of layers containing pigments in order to impart a pearly tone to the paper base material, and there is a problem that the amount of coating on the entire sheet increases.
Further, Patent Documents 1 and 2 exhibit a pearl tone by using a pigment such as titanium oxide-coated mica or a metal, and do not disclose a technique for expressing a pearl tone appearance regardless of the pigment.

Therefore, it is an object of the present invention to provide a sheet having a pearly appearance regardless of pigments.

As a result of diligent studies to solve the above problems, the present inventors have come up with the following invention and found that the problems can be solved.
That is, the present invention is as follows.

[1] Absolute reflectance in the wavelength region of 380 to 780 nm, which has a paper substrate and a fine fibrous cellulose-containing layer, and is measured in accordance with JIS Z 8722: 2009 on the surface of the fine fibrous cellulose-containing layer side. A sheet having a ripple amplitude of 0.10% or more.
[2] The sheet according to the above [1], wherein the applied amount of the fine fibrous cellulose-containing layer is 0.1 g / m ² or more and 1.2 g / m ^{2 or less.}
[3] The sheet according to the above [1] or [2], wherein the degree of polymerization of the fine fibrous cellulose contained in the fine fibrous cellulose-containing layer is 400 or more and 800 or less.
[4] The sheet according to any one of the above [1] to [3], wherein the content of the pearl pigment in the entire sheet is 10% by mass or less.
[5] The sheet according to any one of [1] to [4] above, wherein the fine fibrous cellulose-containing layer further contains a binder.
[6] The sheet according to the above [5], wherein the fine fibrous cellulose-containing layer is an ink receiving layer.
[7] The sheet according to any one of [1] to [6] above, wherein the content ratio of the fine fibrous cellulose in the fine fibrous cellulose-containing layer is 60% by mass or more.
[8] The above-mentioned [1] to [7], wherein the arithmetic mean roughness Ra measured according to JIS B 0601: 2013 on the surface on the side of the fine fibrous cellulose-containing layer is 100 nm or less. Sheet.
[9] The above-mentioned [1] to [8], wherein the 75 ° mirror surface gloss measured in accordance with JIS P 8142: 2005 on the surface on the side of the fine fibrous cellulose-containing layer is 30% or more. Sheet.
[10] The sheet according to any one of [1] to [9] above, wherein the oil resistance by the kit method measured according to the TAPPI UM-557 method is 1st grade or higher.

According to the present invention, it is possible to provide a sheet having a pearly appearance regardless of pigments.

FIG. 1 is a graph showing the relationship between the amount of NaOH added to the fiber raw material having a phosphoric acid group and the electrical conductivity in the production example.

The sheet of the present invention has a paper substrate and a fine fibrous cellulose-containing layer, and the surface of the fine fibrous cellulose-containing layer side surface is absolutely measured in the wavelength region of 380 to 780 nm measured in accordance with JIS Z 8722: 2009. It is characterized in that the ripple amplitude of the reflectance is 0.10% or more.
That is, the sheet of the present invention has a fine fibrous cellulose-containing layer (hereinafter, also referred to as “CNF-containing layer”), and the ripple amplitude of the absolute reflectance on the surface of the CNF-containing layer is 0.10% or more. Therefore, it has a pearly appearance regardless of the pigment.

In order to make the ripple amplitude 0.10% or more, the amount of the CNF-containing layer applied, the degree of polymerization of the fine fibrous cellulose, the fine fibrous cellulose contained in the coating liquid forming the CNF-containing layer, and if necessary, This can be achieved by appropriately controlling the content ratio and the like of the binder and the like to be blended, and appropriately selecting other conditions on the manufacturing method such as the coating method.
Further, in the sheet of the present invention, by using a high-viscosity coating liquid for forming the CNF-containing layer, it becomes difficult for the fine fibrous cellulose in the coating liquid to permeate into the paper base material, and the surface of the paper base material. Fine fibrous cellulose stays in the paper to give a pearly appearance. The high-viscosity coating liquid can be adjusted by appropriately controlling the content ratio of the fine fibrous cellulose contained in the coating liquid and the binder to be blended as needed.
Here, the "imparted amount" of the CNF-containing layer means ^{the amount (g / m 2} ) per unit area of the CNF-containing layer provided on the paper substrate. When CNF-containing layers are provided on both sides of the paper base material, the "impartment amount" of the CNF-containing layer is the amount per unit area of the CNF-containing layer provided on one surface of the paper base material. Represents.

As described above, since the fine fibrous cellulose in the coating liquid does not easily permeate into the paper base material, the CNF-containing layer does not have to permeate into the paper base material in the sheet of the present invention, and the CNF-containing layer does not have to permeate into the paper base material. A part of the paper may have penetrated into the paper substrate.
When a part of the CNF-containing layer permeates into the paper base material in the sheet of the present invention, it is preferable that the fine fibrous cellulose permeates into the paper base material less, and 50% of the thickness of the CNF-containing layer. The above is more preferably located above the surface of the paper substrate. In the above case, in the sheet of the present invention, a part of the CNF-containing layer and a part of the paper base material, that is, the permeated portion of the CNF-containing layer into the paper base material are present so as to overlap each other.

Further, the sheet of the present invention can be expected to have effects other than the pearl-like appearance.
As an effect other than the pearly appearance, the surface of the CNF-containing layer is highly smooth, and the high smoothness produces a mirror-like luster. When the CNF-containing layer further contains a binder, the CNF-containing layer functions as an ink receiving layer, and printability is exhibited on the sheet.
Further, since the voids on the surface of the paper base material are filled with the fine fibrous cellulose, the effect of preventing the penetration of oil droplets is produced, and the sheet of the present invention can also exhibit oil resistance. Further, the sheet of the present invention does not exhibit a pearl tone by using a pearl pigment such as titanium oxide-coated mica or a metal, and the CNF-containing layer can give the sheet a pearl tone appearance regardless of the pigment. Because it can be made, it is also excellent in recyclability.

[Paper base material]
The paper base material constituting the sheet of the present invention is not particularly limited as long as it can secure the air permeability to the extent that water vapor generated when the coating liquid containing fine fibrous cellulose can be cast-coated. The paper base material used in the present invention includes single-gloss paper, high-quality paper, medium-quality paper, copy paper, art paper, coated paper, kraft paper, paperboard, white paperboard, newspaper paper, coating base paper, liner paper, and medium. Examples thereof include core paper, glassin, and stencil paper.
The basis weight of the paper substrate is not particularly limited, it is preferably 15~300g / m ^2, and more preferably 20 to 200 g / m ^2. When the basis weight of the paper base material is 15 g / m ² or more, CNF can be sufficiently captured and a pearl-like appearance can be expressed on the sheet. Further, when the basis weight of the paper base material is 300 g / m ² or less, the productivity of the sheet of the present invention can be improved.

[Fine fibrous cellulose-containing layer]
The CNF-containing layer constituting the sheet of the present invention can be directly or indirectly provided on the paper base material, but it is preferable to directly provide the CNF-containing layer on the paper base material without interposing another layer. .. Even if the CNF-containing layer is provided directly on the paper substrate, the CNF can remain on the surface of the paper substrate as described above, so that the sheet of the present invention exhibits a pearly appearance. A base layer or an aluminum vapor deposition layer may be provided between the paper base material and the CNF layer as long as the effects of the present invention are not impaired. By providing the base layer and the aluminum vapor deposition layer, an optical interface having a large difference in refractive index is formed, and it is possible to strengthen optical interference due to backside reflection.
The CNF-containing layer may be provided on only one of one side and the other side of the paper substrate, or may be provided on both sides, and is determined according to the application. be able to.
Further, the CNF-containing layer may be provided in a plurality of layers on at least one side of the paper substrate as long as it has a desired ripple amplitude. Further, the CNF-containing layer may be formed by a plurality of CNF-containing layers on one side of the paper base material.

(Fine fibrous cellulose)
The fiber width of CNF contained in the CNF-containing layer is preferably 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, further preferably 2 nm or more and 50 nm or less, and 2 nm or more and 10 nm or less. Is particularly preferred. By setting the fiber width of CNF to 2 nm or more, it is possible to suppress the dissolution of cellulose molecules in water and to more easily exhibit the effects of improving strength, rigidity and dimensional stability of CNF. CNF is, for example, single fibrous cellulose.

The average fiber width of the fine fibrous cellulose is measured as follows, for example, using an electron microscope. First, an aqueous suspension of fine fibrous cellulose having a concentration of 0.05% by mass or more and 0.1% by mass or less is prepared, and this suspension is cast on a hydrophilized carbon film-coated grid for TEM observation. Use as a sample. If it contains wide fibers, an SEM image of the surface cast on the glass may be observed. Next, observation is performed using an electron microscope image at a magnification of 1000 times, 5000 times, 10000 times, or 50,000 times depending on the width of the fiber to be observed. However, the sample, observation conditions and magnification should be adjusted so as to satisfy the following conditions.
(1) A straight line X is drawn at an arbitrary position in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y that intersects the straight line perpendicularly is drawn in the same image, and 20 or more fibers intersect the straight line Y.

The width of the fiber intersecting the straight line X and the straight line Y is visually read with respect to the observation image satisfying the above conditions. In this way, at least three sets of observation images of surface portions that do not overlap each other are obtained. Next, for each image, the width of the fiber intersecting the straight line X and the straight line Y is read. As a result, at least 20 fibers × 2 × 3 = 120 fibers are read. Then, the average value of the read fiber widths is taken as the average fiber width of the fine fibrous cellulose.
The average fiber width of the fine fibrous cellulose contained in the CNF-containing layer is, for example, 1000 nm or less. The average fiber width of the fine fibrous cellulose is, for example, preferably 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, further preferably 2 nm or more and 50 nm or less, and 2 nm or more and 10 nm or less. Is particularly preferable. By setting the average fiber width of the fine fibrous cellulose to 2 nm or more, it is possible to suppress the dissolution of the fine fibrous cellulose in water as a cellulose molecule, and to more easily exhibit the effects of the fine fibrous cellulose to improve strength, rigidity and dimensional stability. be able to. The fine fibrous cellulose is, for example, monofibrous cellulose.

The fiber length of the fine fibrous cellulose is not particularly limited, but is preferably 0.1 μm or more and 1000 μm or less, more preferably 0.1 μm or more and 800 μm or less, and 0.1 μm or more and 600 μm or less. More preferred. By setting the fiber length within the above range, destruction of the crystal region of the fine fibrous cellulose can be suppressed. It is also possible to set the slurry viscosity of the fine fibrous cellulose in an appropriate range. The fiber length of the fine fibrous cellulose can be obtained by, for example, image analysis by TEM, SEM, or AFM.

The fine fibrous cellulose preferably has an I-type crystal structure. Here, the fact that the fine fibrous cellulose has an I-type crystal structure can be identified in the diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ = 1.5418 Å) monochromatic with graphite. Specifically, it can be identified by having typical peaks at two positions, 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less.
The ratio of the type I crystal structure to the fine fibrous cellulose is, for example, preferably 30% or more, more preferably 40% or more, and further preferably 50% or more. As a result, even better performance can be expected in terms of heat resistance and low coefficient of linear thermal expansion. The crystallinity is determined by a conventional method from the X-ray diffraction profile measured and the pattern (Seagal et al., Textile Research Journal, Vol. 29, p. 786, 1959).

The axial ratio (fiber length / fiber width) of the fine fibrous cellulose is not particularly limited, but is preferably 20 or more and 10000 or less, and more preferably 50 or more and 1000 or less. By setting the axial ratio to the above lower limit value or more, it is easy to form a sheet containing fine fibrous cellulose. In addition, sufficient viscosity can be easily obtained when the solvent dispersion is produced. By setting the axial ratio to the above upper limit value or less, for example, when treating fine fibrous cellulose as an aqueous dispersion, it is preferable in that handling such as dilution becomes easy.
The fine fibrous cellulose in the present embodiment has, for example, both a crystalline region and a non-crystalline region. In particular, fine fibrous cellulose having both a crystalline region and a non-crystalline region and having a high axial ratio is realized by a method for producing fine fibrous cellulose, which will be described later.

The fine fibrous cellulose in the present embodiment preferably has, for example, at least one of an ionic substituent and a nonionic substituent. From the viewpoint of improving the dispersibility of the fibers in the dispersion medium and increasing the defibration efficiency in the defibration treatment, it is more preferable that the fine fibrous cellulose has an ionic substituent. The ionic substituent can include, for example, either one or both of an anionic group and a cationic group. Further, as the nonionic substituent, for example, an alkyl group, an acyl group and the like can be included. In this embodiment, it is particularly preferable to have an anionic group as an ionic substituent.
The fine fibrous cellulose may not be subjected to a treatment for introducing an ionic substituent.

Examples of the anionic group as an ionic substituent include a phosphate group or a substituent derived from a phosphate group (sometimes simply referred to as a phosphate group), a carboxyl group or a substituent derived from a carboxyl group (simply referred to as a carboxyl group). It may be at least one selected from a sulfone group or a substituent derived from a sulfone group (sometimes simply referred to as a sulfone group), and at least one selected from a phosphate group and a carboxyl group. It is more preferably a seed, especially a phosphate group.

The phosphoric acid group is, for example, a divalent functional group obtained by removing a hydroxyl group from phosphoric acid. Specifically, it is a group represented by _{−PO 3} H _2. Substituents derived from phosphoric acid groups include substituents such as salts of phosphoric acid groups and phosphoric acid ester groups. The substituent derived from the phosphoric acid group may be contained in the fine fibrous cellulose as a group in which the phosphoric acid group is condensed (for example, a pyrophosphate group).
The substituent derived from the phosphoric acid group or the phosphoric acid group is, for example, a substituent represented by the following formula (1).

In formula (1), a, b and n are natural numbers (where a = b × m). At least one of ^{α 1} , α ² , ..., α ^{n and α'is O −} , and the rest is either R or OR. All of each α ⁿ and α'may be O ⁻ . When n is 2 or more and α'is R or OR, at least one of ^{each α n is O −} and the rest is R or OR. When n is 2 or more and α'is O ⁻ , each α ⁿ may be all R, all may be OR, and at least one is O ⁻ and the rest is R or. It may be OR. R is independently a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched chain hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, an unsaturated-branched chain. Hydrocarbon groups, aromatic groups, and inducing groups thereof.
Examples of the saturated-linear hydrocarbon group include, but are not limited to, a methyl group, an ethyl group, an n-propyl group, an n-butyl group and the like. Examples of the saturated-branched chain hydrocarbon group include an i-propyl group and a t-butyl group, but are not particularly limited. Examples of the saturated-cyclic hydrocarbon group include, but are not limited to, a cyclopentyl group, a cyclohexyl group and the like. Examples of the unsaturated-linear hydrocarbon group include a vinyl group, an allyl group and the like, but are not particularly limited. Examples of the unsaturated-branched chain hydrocarbon group include an i-propenyl group and a 3-butenyl group, but the group is not particularly limited. Examples of the unsaturated-cyclic hydrocarbon group include, but are not limited to, a cyclopentenyl group, a cyclohexenyl group and the like. Examples of the aromatic group include a phenyl group and a naphthalene group, but the group is not particularly limited.
The derivative in R is a functional group in which at least one of functional groups such as a carboxyl group, a hydroxyl group, or an amino group is added or substituted with respect to the main chain or side chain of the various hydrocarbon groups. However, there is no particular limitation. The number of carbon atoms constituting the main chain of R is not particularly limited, but is preferably 20 or less, and more preferably 10 or less. By setting the number of carbon atoms constituting the main chain of R to 20 or less, it is possible to prevent the molecule of the phosphorus oxo acid group containing R from becoming too large, and to maintain good permeability to the fiber raw material. It can contribute to the improvement of the yield of fine fibrous cellulose.
β ^{b +} is a monovalent or higher cation composed of an organic substance or an inorganic substance. Examples of monovalent or higher cations composed of organic substances include aliphatic ammonium or aromatic ammonium, and examples of monovalent or higher valent cations composed of inorganic substances include alkali metal ions such as sodium, potassium, and lithium. Examples thereof include cations of divalent metals such as calcium and magnesium, hydrogen ions, and the like, but the present invention is not particularly limited. These may be applied alone or in combination of two or more. The monovalent or higher cation composed of an organic substance or an inorganic substance is preferably sodium or potassium ion which is hard to yellow when the fiber raw material containing β is heated and is easily industrially used, but is not particularly limited.

The amount of the ionic substituent introduced into the fibrous cellulose is, for example, 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, and 0.50 mmol / g per 1 g (mass) of the fibrous cellulose. It is more preferably / g or more, and particularly preferably 1.00 mmol / g or more. The amount of the ionic substituent introduced into the fibrous cellulose is preferably 3.65 mmol / g or less, more preferably 3.50 mmol / g or less per 1 g (mass) of the fibrous cellulose, for example, 3 It is more preferably 0.00 mmol / g or less. By setting the amount of the ionic substituent introduced within the above range, it is possible to facilitate the miniaturization of the fiber raw material and enhance the stability of the fine fibrous cellulose.
Here, the denominator in the unit mmol / g indicates the mass of fibrous cellulose when the counter ion of the ionic substituent is a hydrogen ion (H ^+).

The amount of the ionic substituent introduced into the fine fibrous cellulose can be measured by, for example, a conductivity titration method. In the measurement by the conductivity titration method, the introduction amount is measured by determining the change in conductivity while adding an alkali such as an aqueous sodium hydroxide solution to the obtained slurry containing fine fibrous cellulose.
A more specific method for measuring the amount of the ionic substituent introduced into the fine fibrous cellulose is as described in the production example described later.

As a method for producing fine fibrous cellulose by introducing an ionic substituent into the fibrous cellulose, a known technique can be used. For example, fine fibrous cellulose in which an ionic substituent is introduced through an ionic substituent introduction step, a washing step, an alkali treatment step (neutralization step), and a defibration treatment step for introducing an ionic substituent into a fiber raw material. Can be obtained as an aqueous dispersion containing.
A more specific production method for introducing an ionic substituent into the fibrous cellulose to make it finer is as described in the production example described later.

The degree of polymerization of the fine fibrous cellulose contained in the CNF-containing layer is preferably 400 or more, more preferably 420 or more, and further preferably 440 or more. The degree of polymerization of the fine fibrous cellulose contained in the CNF-containing layer is preferably 800 or less, more preferably 700 or less, still more preferably 600 or less, still more preferably 550 or less, and even more preferably 500 or less. With the same amount of fine fibrous cellulose applied, the smaller the numerical value of the degree of polymerization of fine fibrous cellulose, the larger the ripple amplitude of the above-mentioned absolute reflectance tends to be. However, if the degree of polymerization of the fine fibrous cellulose becomes too small, it becomes difficult to adjust the coating liquid to a high viscosity, and there is a possibility that a desired pearl-like appearance cannot be obtained. When the degree of polymerization is within the above range, it is easy to adjust the ripple amplitude of the absolute reflectance to 0.10% or more, and it is suitable for expressing the pearly appearance of the sheet.
The degree of polymerization of the fine fibrous cellulose can be easily controlled within the above preferable range by appropriately selecting the raw material and the production conditions of the fine fibrous cellulose. Such production conditions are not particularly limited, but for example, the conditions in the ionic substituent introduction step are adjusted, the defibration treatment conditions in the defibration treatment step are adjusted, and the type of the defibration treatment apparatus is selected. It can be adjusted by adjusting.
Further, the degree of polymerization of the fine fibrous cellulose can be measured according to Tappi T230, and more specifically, it is as in the examples described later.

The content ratio of the fine fibrous cellulose in the CNF-containing layer may be specified so as to satisfy a preferable amount of the fine fibrous cellulose described later, but is preferably 60% by mass or more, more preferably 65% by mass or more, still more preferably. May be 70% by mass or more and 100% by mass. When the fine fibrous cellulose content is 60% by mass or more, it is possible to satisfactorily develop a pearly appearance even if the amount of the CNF-containing layer applied is small.

(binder)
By containing the binder, the CNF-containing layer can exhibit the properties of an ink receiving layer while having a pearly appearance.
Examples of the binder include water-soluble polymers and water-insoluble polymers.
Examples of the water-soluble polymer include cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose, natural polysaccharides such as dextrin, mannan, chitosan, arabinogalactan, glycogen, inulin, pectin and hyaluronic acid, and their oligomers. Modified products: Synthetic water-soluble resins such as polyacrylic acid, polymethacrylic acid, polyethylene glycol, and polyvinyl alcohol are exemplified.
Examples of the water-insoluble polymer include starch purified from natural plants, hydroxyethylated starch, oxidized starch, etherified starch, phosphoric acid esterified starch, enzyme-modified starch, and starch such as cold water-soluble starch obtained by flush-drying them. And modified starch; natural proteins such as gelatin, casein, soybean lecithin, collagen and their modified products; synthetic water-insoluble which is each (co) polymer of styrene-butadiene type, acrylic type, polyvinyl acetate, ethylene-vinyl acetate and the like. Resin is exemplified.
The binder may be used in a state of being dissolved in water by heating or adjusting the pH, or may be used in a state of being dispersed in water using a surfactant or the like.
These binders may be used alone or in combination of two or more.

Among the above-mentioned binders, modified starch, cellulose derivative, natural protein, synthetic water-soluble resin, and synthetic water-insoluble are preferable from the viewpoint of printability such as surface strength of CNF-containing layer, ink fillability, and ink sharpness. Resins, more preferably oxidized starch, carboxymethyl cellulose, casein, polyvinyl alcohol, and styrene-butadiene copolymers, more preferably styrene-butadiene copolymers.

When the CNF-containing layer contains a binder, the content of the binder in the CNF-containing layer is preferably 45% by mass or less, more preferably 40% by mass or less, still more preferably 35% by mass or less, still more preferably 30% by mass. It is as follows. When the CNF-containing layer contains a binder, the content of the binder in the CNF-containing layer is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, still more preferably 20. By mass or more, more preferably 25% by mass or more. When the content of the binder in the CNF-containing layer is within the above range, the sheet of the present invention is suitable for achieving both a pearly appearance and printability.

(Amount of CNF-containing layer added)
In the sheet of the present invention, the amount of the CNF-containing layer applied is preferably 1.2 g / m ² or less, more preferably 1.0 g / m ² or less, still more preferably 0.8 g / m ² or less, still more preferably. It is 0.5 g / m ² or less. The amount of the CNF-containing layer applied is preferably 0.1 g / m ² or more, more preferably 0.2 g / m ² or more, still more preferably 0.3 g / m ² or more, still more preferably 0.4 g / m / or more. It is m ² or more. When the amount of the CNF-containing layer applied is within the above range, the appearance of the sheet can be easily adjusted to a pearl tone. From the viewpoint of thinning the sheet, the amount of the CNF-containing layer applied can be, for example, 0.28 g / m ² or less.

(Amount of CNF added in CNF-containing layer)
Further, in the sheet of the present invention, the amount of CNF applied in the CNF-containing layer is preferably 1.2 g / m ² or less, more preferably 1.0 g / m ² or less, still more preferably 0.8 g / m ² or less. Is. The amount of CNF applied in the CNF-containing layer is preferably 0.1 g / m ² or more, more preferably 0.2 g / m ² or more, and further preferably 0.3 g / m ² or more. When the amount of the CNF-containing layer applied is within the above range, the appearance of the sheet can be easily adjusted to a pearl tone.
The amount of CNF applied in the CNF-containing layer is the dry mass of CNF contained in the CNF-containing layer provided on the paper base material, and the amount of CNF applied per one side of the paper base material.

(Mass ratio of CNF and binder)
When the CNF-containing layer contains a binder, the mass ratio b / a of the binder content b to the CNF content a in the CNF-containing layer is such that the sheet has a pearly appearance, and has surface strength and ink inking property. , And from the viewpoint of improving printability such as ink sharpness, it is preferably 5/95 to 40/60, more preferably 10/90 to 35/65, and even more preferably 10/90 to 30/70.

When the CNF-containing layer contains a binder, the total content of the CNF and the binder in the CNF-containing layer is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, and further. It is preferably 80% by mass or more, and may be 100% by mass. When the total content of the CNF and the binder is 50% by mass or more, it is easy to obtain printability such as surface strength, ink inking property, and ink sharpness while the sheet has a pearly appearance.

(Other ingredients)
In addition to the CNF and the binder, the CNF-containing layer may contain other components as needed.
The other components are not particularly limited as long as the effects of the present invention are not impaired, but are released from a mold release agent such as microcrystalline wax, a wetting agent such as a surfactant, colloidal silica, a dispersant, an antifoaming agent, and an antiseptic. Viscosity improvers, colorants, lubricants, water resistant agents and the like can be mentioned. These other components may be used alone or in combination of two or more.
Further, the sheet of the present invention can contain a pearl pigment within a range that does not impair the effects of the present invention, but from the viewpoint of recyclability, the content of the pearl pigment in the entire sheet is preferably 10% by mass or less. It is more preferably 5% by mass or less, further preferably less than 0.5% by mass, and particularly preferably substantially absent (that is, 0% by mass).
Examples of the pearl pigment include known pearl pigments such as those in which the surface of an inorganic substance such as titanium oxide-coated mica and titanium oxide-coated talc is coated with a metal oxide.

[Other layers]
As described above, the sheet of the present invention can be provided with a CNF-containing layer on one side or both sides of the paper base material, but has characteristics such as high smoothness and high gloss, printability and oil resistance while having a pearly appearance. From the viewpoint of being able to express the above, it is preferable that the CNF-containing layer is the outermost surface.
When the CNF-containing layer is provided on only one side of the paper base material, another layer can be provided on the other side of the paper base material depending on the use of the sheet. Examples of the other layer include an adhesive layer and a release agent layer, and a sheet having a so-called label type (also referred to as a sticker or a seal type) structure may be used.

[Ripple amplitude]
In the sheet of the present invention, the ripple amplitude of the absolute reflectance in the wavelength region of 380 to 780 nm measured according to JIS Z 8722: 2009 on the surface on the CNF-containing layer side is 0.10% or more. When the ripple amplitude of the absolute reflectance is less than 0.10%, it is difficult to develop a good pearly appearance on the sheet. The ripple amplitude of the absolute reflectance is preferably 0.20% or more, more preferably 0.30% or more, still more preferably 0.50% or more, still more preferably 1.00% or more. In order to set the ripple amplitude in a preferable range, the amount of the CNF-containing layer applied, the degree of polymerization of the fine fibrous cellulose, the fine fibrous cellulose contained in the coating liquid forming the CNF-containing layer, and if necessary, blended. It is preferable to adjust by appropriately controlling the content ratio of the binder and the like, and appropriately selecting other conditions on the manufacturing method such as the coating method.
More specific measurement conditions for the ripple amplitude of the absolute reflectance are as described in Examples described later.

The sheet of the present invention tends to easily develop a pearly appearance by controlling the ripple amplitude within a specific range as described above. This is because by adjusting the ripple amplitude, the optical interference caused by the difference in the refractive index between the CNF layer and the paper substrate can be controlled within an appropriate range, and it can be involved in the development of pearl tone. Guessed.
In the present invention, the difference between the maximum reflectance and the minimum reflectance of the ripple (waveform) of the absolute reflectance spectrum in the wavelength region of 380 to 780 nm measured in accordance with JIS Z 8722: 2009 on the surface on the CNF-containing layer side ( That is, when the ripple amplitude) is 0.10% or more, it can be evaluated that the pearl-like appearance is likely to be developed, and the pearl-like appearance tends to become stronger as the ripple amplitude becomes larger.

The ripple amplitude of the absolute reflectance is a value when the sheet of the present invention is not colored with a colorant such as a pigment. However, even if the sheet of the present invention is colored with a colorant, it is possible to specify the ripple amplitude of the absolute reflectance.
For example, in the case of a colored sheet in which a CNF-containing layer containing no colorant is provided on a colored paper base material, the surface of the colored paper base material on the CNF-containing layer side is based on the measured value of the absolute reflectance of the colored paper base material itself. The ripple amplitude can be obtained by subtracting the measured value of the base from the measured value of the absolute reflectance of.
Further, in the case of a colored sheet containing a colorant only in the CNF-containing layer, the ripple amplitude of the absolute reflectance may be obtained for a sheet similar to the colored sheet except that the colorant is not contained, or the colorant. The absolute reflectance may be corrected in consideration of the absorption wavelength of.

[Arithmetic mean roughness]
In the sheet of the present invention, the arithmetic mean roughness Ra measured according to JIS B 0601: 2013 on the surface on the CNF-containing layer side is preferably 100 nm or less. As described above, the sheet of the present invention can make it difficult for the CNF in the coating liquid to permeate into the paper base material, so that the CNF stays on the surface of the paper base material and can cover the surface irregularities of the paper base material. Furthermore, by adopting the rewet casting method described later as the method for producing the sheet of the present invention, it is possible to achieve excellent smoothness in which Ra is preferably 100 nm or less.
The value of Ra achieved depends on the type of paper base material and its basis weight. For example, when the paper base material is single-gloss paper and a CNF-containing layer is provided on the glossy surface side, the Ra is 30 nm or less, 20 nm or less, and so on. It is also possible to make it 15 nm or less, and further 10 nm or less. When the paper base material is woodfree paper, the Ra can be 30 nm or less, 20 nm or less, 19 nm or less, and further 18 nm or less. The lower limit of Ra cannot be unequivocally specified from the type of paper base material and its basis weight, but is usually about 2 nm or more.

[Glossiness]
In the sheet of the present invention, the 75 ° mirror surface gloss measured in accordance with JIS P 8142: 2005 on the CNF-containing layer side surface is preferably 30% or more, more preferably 50% or more, still more preferably 60% or more. , More preferably 70% or more, even more preferably 80% or more, even more preferably 90% or more, still more preferably 95% or more.
The mirror glossiness is determined by appropriately controlling the content of each component contained in the coating liquid forming the CNF-containing layer, appropriately selecting other manufacturing method conditions such as the coating method, and the like. Can be adjusted more. As described above, the sheet of the present invention can be expected to produce a mirror-like gloss represented by the above-mentioned specific mirror gloss while having a pearl-like appearance.

[Printability]
As described above, the sheet of the present invention can exhibit printability such as surface strength, ink inking property, and ink sharpness by further containing a binder in the CNF-containing layer, and can be used as an ink receiving layer. It can be expected to have the properties of.
That is, the CNF-containing layer in the sheet of the present invention can be suitably used as an ink receiving layer, and when the CNF-containing layer contains a binder, the sheet of the present invention is particularly suitable for offset printing. ..
The above-mentioned "ink sharpness" is one of the indexes indicating printability, and is the difference in saturation between the printed portion and the unprinted portion, the color development of the ink adhering to the printed sheet, and the printing surface. It means the vividness of luster.

[Oil resistance]
The sheet of the present invention can exhibit oil resistance. The oil resistance of the sheet of the present invention can be evaluated by the oil resistance by the kit method measured according to the TAPPI UM-557 method. The oil resistance of the sheet of the present invention measured by the above kit method is preferably 1st grade or higher, which indicates that oil resistance is exhibited, more preferably 6th grade or higher, and 7th grade or higher. Is even more preferable. It is considered that the oil resistance of the sheet of the present invention is exhibited because the CNF in the CNF-containing layer fills the voids on the surface of the paper substrate.
The oil resistance according to the above kit method that can be used as oil resistant paper is usually 5th grade or higher.

[Sheet manufacturing method]
As the method for producing the sheet of the present invention, a known production method may be adopted, but in order to obtain the effect of the present invention, the following production method is preferably adopted.
That is,
A step of applying a coating liquid containing fine fibrous cellulose to at least one surface of a paper base material to provide a fine fibrous cellulose-containing layer (coating step).
A step of drying or semi-drying the fine fibrous cellulose-containing layer (drying or semi-drying step),
A step of re-wetting the surface of the fine fibrous cellulose-containing layer with a re-wetting liquid (re-wetting step), and a step of re-wetting.
A step of crimping the surface of the fine fibrous cellulose-containing layer with a cast drum (crimping step),
It is a method of manufacturing a sheet having sequentially.

The casting method, which is one of the film-forming methods for film sheets, includes (i) a wet casting method in which a coating liquid is applied and immediately pressed onto a cast drum, and (ii) a coating liquid is applied, dried or semi-finished. After drying, a rewetting liquid is applied, and then a rewet casting method is applied to a cast drum. (Iii) After applying a coating liquid, a gelling agent is applied to form a gel, and then a gel is cast. The casting method and the like are known. Among these casting methods, it is preferable that (ii) the rewet casting method is adopted as the method for producing the sheet of the present invention.
When the (iii) gelation casting method is adopted in the production of the sheet of the present invention, the outermost surface of the sheet is exposed because the gelling agent is applied on the coating liquid containing the fine fibrous cellulose. It is no longer a fine fibrous cellulose, and it is difficult to develop a pearly appearance of the sheet. Further, in the gelation casting method, the amount of coating is increased, and it becomes difficult to thin the sheet by reducing the amount of the CNF-containing layer applied while obtaining the effect of the present invention, for example. Further, in (i) the wet casting method, it is difficult to adjust the wetting and set the conditions in order to express the pearly appearance of the sheet, and the workability may be inferior. On the other hand, (ii) the rewet casting method is suitable for producing the sheet of the present invention having a pearly appearance because it is relatively easy to adjust the wetting and is excellent in productivity. Further, if the rewet casting method is used, high smoothness and high gloss of the CNF-containing layer can be easily realized, and further, the thin film of the sheet of the present invention can be realized.

(Coating liquid containing fine fibrous cellulose)
The content ratio of the fine fibrous cellulose in the fine fibrous cellulose-containing coating liquid (hereinafter, also simply referred to as “coating liquid”) is preferably 0.5% by mass or more, more preferably 0.5% by mass or more in terms of solid content. It is 0.8% by mass or more, more preferably 1.0% by mass or more. The content ratio of the fine fibrous cellulose in the coating liquid is preferably 4.0% by mass or less, more preferably 3.5% by mass or less, still more preferably 3.0% by mass or less in terms of solid content. Even more preferably, it is 2.5% by mass or less. When the content ratio of the fine fibrous cellulose in the coating liquid is within the above range, the fine fibrous cellulose is suppressed from penetrating into the paper substrate and stays on the surface while having a viscosity suitable for coating. This makes it possible to develop a pearly appearance on the sheet even with a small amount of application, and further, the CNF-containing layer can easily realize high smoothness and high gloss.

From the viewpoint of imparting printability to the CNF-containing layer, the coating liquid preferably further contains a binder, and can also contain other components used as needed.
When a styrene-butadiene copolymer is used as the binder, the styrene-butadiene copolymer latex can be contained in the raw material of the coating liquid. The content ratio of the binder in the coating liquid is preferably adjusted so as to be the preferable content (solid content) of the binder in the CNF-containing layer described above in the description of the sheet of the present invention.

(Coating process)
In this step, the coating liquid is applied so that the amount of the CNF-containing layer applied to at least one surface of the paper substrate is preferably 0.1 g / m ² or more and 1.2 g / m ^{2 or less in terms of solid content.} To paint. A more preferable amount of the CNF-containing layer is the same as that described above in the description of the sheet of the present invention. Further, as described above in the description of the sheet of the present invention, the added amount is the total dry mass including CNF and the binder as well as other components contained as necessary, and the paper base material. It is the amount of the CNF-containing layer per one side of the above.
As the coating machine for applying the coating liquid, for example, a bar coater, a roll coater, a gravure coater, a die coater, a curtain coater, an air doctor coater and the like can be used, but the coating machine is not particularly limited. A bar coater is preferable from the viewpoint of being able to uniformly apply a viscous coating liquid, but the present invention is not particularly limited thereto.

(Drying or semi-drying process)
In this step, a dried or semi-dried CNF-containing layer is formed by drying or semi-drying the coating liquid coated on the paper substrate.
The drying method is not particularly limited, but a method of heating and drying with hot air, infrared rays, far infrared rays or near infrared rays (heat drying method) and a method of vacuum drying (vacuum drying method) can be applied. Although the heat drying method and the vacuum drying method may be combined, the heat drying method is usually applied. Drying with infrared rays, far infrared rays, or near infrared rays can be performed using an infrared device, a far infrared device, or a near infrared device, but is not particularly limited. The heating temperature in the heat drying method is not particularly limited, but is preferably 40 to 120 ° C, more preferably 60 to 110 ° C. When the heating temperature is 40 ° C. or higher, the dispersion medium in the coating liquid can be rapidly volatilized, and when the heating temperature is 120 ° C. or lower, the cost required for heating can be suppressed and the discoloration due to heat of CNF can be suppressed.

(Rewetting process)
In this step, the CNF-containing layer that has been dried or semi-dried by the above step is re-wetted. The rewetting liquid is not particularly limited, but it is preferable to use water. Further, in water, a polyethylene emulsion generally used as a mold release agent, fatty acid salts and derivatives thereof, microcrystalline wax, funnel oil and the like may be dissolved or dispersed. Before rewetting the CNF-containing layer, a smoothing treatment such as super calendar or brushing can be performed.

(Crimping process)
In this step, the surface of the re-wet CNF-containing layer is crimped with a cast drum by the re-wetting step.
The cast drum may be a general cast drum having a chrome-plated layer that is mirror-polished on the surface of the drum body made of steel or casting, and is a special cast drum such as a nickel-plated layer under the chrome-plated layer. It may be provided with a layer. Moreover, the cast drum may be used by heating.

[Use]
Since the sheet of the present invention has a pearl-like appearance, it is suitable for applications requiring design such as wrapping paper.
Further, the sheet of the present invention may have characteristics such as high gloss and high smoothness, surface strength, ink penetration, ink sharpness and other printability, and oil resistance while having a pearly appearance.
Therefore, the sheet of the present invention can be used for wrapping paper, stickers, labels, boxes and envelopes in the packaging field and the distribution field, wrapping paper and containers for foods containing oil and fat components, paper for inkjet printers, etc. due to the above characteristics. ..

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In the following Examples and Comparative Examples, "parts" means "parts by mass" unless otherwise specified.

<Paper base material>
In each Example and Comparative Example, single glossy paper (basis weight 30 g / m ² ) was used as the paper base material.
<Fine fibrous cellulose>
As the fine fibrous cellulose used in each Example and Comparative Example, those produced by the following production examples were used.

[Manufacturing Example 1]
(Preparation of phosphate group-introduced cellulose fiber)
As a raw material pulp, softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solid content 93% by mass, basis weight 208 g / m ² sheets, separated and measured according to JIS P 8121 has a Canadian standard drainage degree (CSF) of 700 ml. )It was used. The raw material pulp was phosphorylated as follows. First, a mixed aqueous solution of ammonium dihydrogen phosphate and urea is added to 100 parts by mass (absolute dry mass) of the raw material pulp to obtain 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water. To obtain a chemical-impregnated pulp. Next, the obtained chemical-impregnated pulp was heated in a hot air dryer at 165 ° C. for 200 seconds to introduce a phosphoric acid group into the cellulose in the pulp to obtain a phosphorylated pulp. Then, the obtained phosphorylated pulp was washed. The washing treatment is carried out by repeating the operation of pouring 10 L of ion-exchanged water into 100 g (absolute dry mass) of phosphorylated pulp, stirring the pulp dispersion liquid so that the pulp is uniformly dispersed, and then filtering and dehydrating the pulp. went. When the electrical conductivity of the filtrate became 100 μS / cm or less, the washing end point was set. Next, the phosphorylated pulp after washing was neutralized as follows. First, the washed phosphorylated pulp was diluted with 10 L of ion-exchanged water, and then a 1N aqueous sodium hydroxide solution was added little by little with stirring to obtain a phosphorylated pulp slurry having a pH of 12 or more and 13 or less. .. Next, the phosphorylated pulp slurry was dehydrated to obtain a phosphorylated pulp that had been neutralized. Next, the phosphorylated pulp after the neutralization treatment was subjected to the above-mentioned washing treatment. The infrared absorption spectrum of the phosphorylated pulp thus obtained was measured using FT-IR. As a result, ^{absorption based on the phosphate group was observed around 1230 cm -1} , and it was confirmed that the phosphate group was added to the pulp. Further, when the obtained phosphorylated pulp was tested and analyzed by an X-ray diffractometer, it was found at two positions, 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less. A typical peak was confirmed, and it was confirmed that it had cellulose type I crystals.

(Preparation of fine fibrous cellulose dispersion 1)
Ion-exchanged water was added to the obtained phosphorylated pulp to prepare a slurry having a solid content concentration of 2% by mass. This slurry was treated twice with a wet atomizing device (manufactured by Sugino Machine Limited, Starburst) at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion 1 containing fine fibrous cellulose. By X-ray diffraction, it was confirmed that this fine fibrous cellulose maintained the cellulose type I crystal. Moreover, when the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, it was 3 to 5 nm.
The amount of phosphoric acid group (strong acid group amount) measured by the measuring method described later was 1.45 mmol / g. The degree of polymerization of the fine fibrous cellulose measured by the measuring method described later was 680.

[Measurement of phosphate group amount]
The amount of phosphoric acid group of the fine fibrous cellulose is a fibrous form prepared by diluting a fine fibrous cellulose dispersion containing the target fine fibrous cellulose with ion exchange water so that the content is 0.2% by mass. The measurement was performed by treating the cellulose-containing slurry with an ion exchange resin and then performing titration with an alkali.
In the treatment with the ion exchange resin, a strongly acidic ion exchange resin (Amberjet 1024; manufactured by Organo Corporation, conditioned) having a volume of 1/10 is added to the fine fibrous cellulose-containing slurry, and the mixture is shaken for 1 hour. , The resin and the slurry were separated by pouring on a mesh having a mesh size of 90 μm.
In the titration using alkali, a 0.1 N sodium hydroxide aqueous solution is added to the fine fibrous cellulose-containing slurry treated with an ion exchange resin once every 30 seconds by 50 μL, and the electric conductivity exhibited by the slurry is exhibited. This was done by measuring the change in the value of the degree. For the amount of phosphoric acid group (mmol / g), the amount of alkali (mmol) required in the region corresponding to the first region shown in FIG. 1 of the measurement results is divided by the solid content (g) in the slurry to be titrated. Was calculated.

[Measurement of degree of polymerization of fine fibrous cellulose]
The degree of polymerization of the fine fibrous cellulose was measured according to Tappi T230. That is, after measuring the viscosity (referred to as η1) measured by dispersing the fine fibrous cellulose to be measured in a dispersion medium and the blank viscosity (referred to as η0) measured only with the dispersion medium, the specific viscosity (η _sp ). , The intrinsic viscosity ([η]) was measured according to the following formula.
η _SP = (η1 / η0) -1
[Η] = η _{sp / (} c (1 + 0.28 × _{η sp} ))
Here, c in the formula indicates the concentration of fine fibrous cellulose at the time of viscosity measurement.
Further, the degree of polymerization (DP) of the fine fibrous cellulose was calculated from the following formula.
DP = 1.75 x [η]
Since this degree of polymerization is the average degree of polymerization measured by the viscosity method, it is sometimes called "viscosity average degree of polymerization".

[Manufacturing Example 2]
In Production Example 1, the fine fibrous cellulose dispersion 2 was obtained in the same manner as in Production Example 1 except that the degree of polymerization of the fine fibrous cellulose was adjusted to 590.

[Manufacturing Example 3]
In Production Example 1, the fine fibrous cellulose dispersion 3 was obtained in the same manner as in Production Example 1 except that the degree of polymerization of the fine fibrous cellulose was adjusted to 499.

[Manufacturing Example 4]
In Production Example 1, the fine fibrous cellulose dispersion 4 was obtained in the same manner as in Production Example 1 except that the degree of polymerization of the fine fibrous cellulose was adjusted to 459.

<Making a coating sheet>
[Example 1]
The dispersion liquid obtained by adjusting the concentration of the fine fibrous cellulose dispersion liquid 1 obtained in Production Example 1 is used as the coating liquid, and the amount of the CNF-containing layer applied (coating amount) to the glossy surface side of the paper substrate by a bar coater. ) Was applied so that the solid content was 0.25 g / m ^2, and the mixture was blown and dried at 105 ° C. Water was applied to the dried sheet, and then the sheet was pressure-bonded to a heated mirror-finished drum and dried to obtain a sheet by the rewet casting method.

[Example 2]
A sheet was obtained in the same manner as in Example 1 except that the amount of fine fibrous cellulose applied was 0.5 g / m ^2.
[Example 3]
A sheet was obtained in the same manner as in Example 1 except that the amount of fine fibrous cellulose applied was 0.8 g / m ^2.

[Example 4]
A sheet was obtained in the same manner as in Example 2 except that the fine fibrous cellulose dispersion 2 obtained in Production Example 2 was used instead of the fine fibrous cellulose dispersion 1.
[Example 5]
A sheet was obtained in the same manner as in Example 2 except that the fine fibrous cellulose dispersion 3 obtained in Production Example 3 was used instead of the fine fibrous cellulose dispersion 1.
[Example 6]
A sheet was obtained in the same manner as in Example 2 except that the fine fibrous cellulose dispersion 4 obtained in Production Example 4 was used instead of the fine fibrous cellulose dispersion 1.

[Example 7]
The fine fibrous cellulose dispersion 1 and SBR latex (manufactured by JSR Corporation, OJ3000F) obtained in Production Example 1 above so that the amount of fine fibrous cellulose is 90 parts and the amount of styrene-butadiene copolymer (SBR) is 10 parts. ) Was mixed to prepare a coating solution.
Using the coating liquid prepared above, the glossy surface side of the paper substrate was coated with a bar coater so that the amount of the CNF-containing layer applied (coating amount) was 0.5 g / m ^{2 in} terms of solid content, and 105 It was blown dry at ° C. Water was applied to the dried sheet, and then the sheet was pressure-bonded to a heated mirror-finished drum and dried to obtain a sheet by the rewet casting method.
[Example 8]
A sheet was obtained in the same manner as in Example 7 except that it was changed to 80 parts of fine fibrous cellulose and 20 parts of SBR.
[Example 9]
A sheet was obtained in the same manner as in Example 7 except that it was changed to 70 parts of fine fibrous cellulose and 30 parts of SBR.

[Example 10]
A sheet was obtained in the same manner as in Example 9 except that 30 parts of SBR was changed to 30 parts of polyvinyl alcohol (PVA) (manufactured by Kuraray Co., Ltd., PVA105).
[Example 11]
A sheet was obtained in the same manner as in Example 9 except that 30 parts of SBR was changed to 30 parts of oxidized starch (Ace A manufactured by Oji Cornstarch).
[Example 12]
A sheet was obtained in the same manner as in Example 9 except that 30 parts of SBR were changed to 30 parts of casein (ALACID LIC CASEIN manufactured by Fonterra).
[Example 13]
A sheet was obtained in the same manner as in Example 9 except that 30 parts of SBR was changed to 30 parts of carboxymethyl cellulose (CMC) (Cerogen 4H, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.).

[Comparative Example 1]
The paper substrate was used as it was.
[Comparative Example 2]
A sheet was obtained in the same manner as in Example 1 except that the amount of the CNF-containing layer applied ^{was changed to 1.5 g / m 2.}
[Comparative Example 3]
A sheet was obtained in the same manner as in Example 7 except that the parts were changed to 50 parts of CNF and 50 parts of SBR.
[Comparative Example 4]
A sheet was obtained in the same manner as in Example 10 except that the parts were changed to 50 parts of CNF and 50 parts of PVA.
[Comparative Example 5]
A sheet was obtained in the same manner as in Example 11 except that the content was changed to 50 parts of CNF and 50 parts of oxidized starch.
[Comparative Example 6]
Sheets were obtained in the same manner as in Example 12 except that they were changed to 50 parts of CNF and 50 parts of casein.
[Comparative Example 7]
A sheet was obtained in the same manner as in Example 13 except that the parts were changed to 50 parts of CNF and 50 parts of CMC.

<Evaluation method>
The sheets prepared in Examples and Comparative Examples were evaluated according to the following evaluation methods. The results of each evaluation are shown in Table 1.
(1) Ripple amplitude (%)
Based on JIS Z 8722: 2009, using an automatic absolute reflectance measurement system (manufactured by JASCO Corporation, device name: V-770, accessory device: ARMN-920), incident angle 5 °, detection angle 0 °, polarized light The absolute reflectance of the coated surface (CNF-containing layer side surface) in the wavelength region of 380 to 780 nm was measured under the condition of the element 45 °. The difference between the maximum reflectance and the minimum reflectance of the measured absolute reflectance was calculated as the ripple amplitude.
(2) Pearl-like appearance (visual)
The obtained sheet was visually evaluated for the presence or absence of a pearl-like appearance.
2: Has a pearl-like appearance 1: Does not have a pearl-like appearance

(3) Smoothness (Ra)
Using a scanning probe microscope (Multimode8-HR, manufactured by Bruker AX), the cutoff value was 0.08 mm, and the arithmetic mean roughness Ra of the coated surface (CNF-containing layer side surface) was set in accordance with JIS B 0601: 2013. (Nm) was measured.
(4) Mirror gloss (75 ° gloss)
In accordance with JIS P 8142: 2005, the glossiness of the coated surface (the surface on the CNF-containing layer side) at a light incident angle of 75 ° was measured using a glossiness meter (manufactured by Murakami Color Technology Research Institute).

(5) Offset printing suitability For the coated surface (CNF-containing layer side surface) of the obtained sheet, use an RI printing tester (Ming Seisakusho Co., Ltd., RI-1) to test ink (T & K TOKA Co., Ltd., Best One Paper). Printing was performed using the test SD50 red BT-13), and the coating layer strength (surface strength), ink inking property, and ink sharpness were visually evaluated. The evaluation criteria are as follows.
In Examples 1 to 6 and Comparative Example 2, since the CNF-containing layer was peeled off, the coating layer strength and the ink sharpness were not evaluated.

(Coating layer strength (surface strength))
4: Good with no picking at all 3: Almost no picking and no problem in practical use 2: Picking occurs but practically acceptable level 1: Many picking occurs and practically unacceptable level (Ink picking property)
4: Ink adheres to the entire sample 3: Ink shading / fading is slightly seen 2: Ink shading / fading is seen 1: Ink does not adhere to the entire sample (ink sharpness)
4: Ink develops vivid color and gloss is good 3: Ink develops vivid color and gloss is slightly good 2: Ink develops vivid color but gloss is slightly poor 1: Ink develops vivid color but gloss Is bad

(6) Oil resistance The oil resistance of the coated surface (the surface on the CNF-containing layer side) was measured according to the TAPPI UM-557 method (kit method). An oil resistance grade 0 indicates that oil resistance is not exhibited, and an oil resistance grade 1 or higher indicates that oil resistance is exhibited. In addition, general oil-resistant paper shows grade 5 or higher.

From Examples 1 to 6, it can be seen that a sheet having a pearly appearance can be obtained regardless of the pigment by adjusting the amount of the CNF-containing layer applied and the degree of polymerization of the fine fibrous cellulose. Further, from Examples 7 to 13, the sheets containing the binder in the CNF-containing layer showed good offset printing suitability, suggesting the applicability to practical use.

Due to the above characteristics, the sheet of the present invention can be used for wrapping paper, boxes and envelopes in the packaging field and distribution field, wrapping paper and containers for foods containing oil and fat components, inkjet printers and the like.

Claims (10)

It has a paper substrate and a fine fibrous cellulose-containing layer, and the ripple amplitude of the absolute reflectance in the wavelength region of 380 to 780 nm measured in accordance with JIS Z 8722: 2009 on the surface on the side of the fine fibrous cellulose-containing layer. A sheet that is 0.10% or more. The sheet according to claim 1, wherein the amount of the fine fibrous cellulose-containing layer applied is 0.1 g / m ² or more and 1.2 g / m ^{2 or less.} The sheet according to claim 1 or 2, wherein the degree of polymerization of the fine fibrous cellulose contained in the fine fibrous cellulose-containing layer is 400 or more and 800 or less. The sheet according to any one of claims 1 to 3, wherein the content of the pearl pigment in the entire sheet is 10% by mass or less. The sheet according to any one of claims 1 to 4, wherein the fine fibrous cellulose-containing layer further contains a binder. The sheet according to claim 5, wherein the fine fibrous cellulose-containing layer is an ink receiving layer. The sheet according to any one of claims 1 to 6, wherein the content ratio of the fine fibrous cellulose in the fine fibrous cellulose-containing layer is 60% by mass or more. The sheet according to any one of claims 1 to 7, wherein the arithmetic average roughness Ra measured in accordance with JIS B 0601: 2013 on the surface on the side of the fine fibrous cellulose-containing layer is 100 nm or less. The sheet according to any one of claims 1 to 8, wherein the 75 ° mirror surface gloss measured in accordance with JIS P 8142: 2005 on the surface on the side of the fine fibrous cellulose-containing layer is 30% or more. The sheet according to any one of claims 1 to 9, wherein the oil resistance by the kit method measured according to the TAPPI UM-557 method is 1st grade or higher.

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