WO2019117175A1 - Sheet and method for manufacturing sheet - Google Patents

Abstract

The present invention provides a sheet and a method for manufacturing the same, the sheet having a paper base and a microfibrous-cellulose-containing layer, the amount imparted of the microfibrous cellulose-containing layer being 2.0 g/m² or less, and the arithmetic mean roughness Ra of the surface on the microfibrous-cellulose-containing-layer side being 20 nm or less, as measured according to JISB 0601:2001. The surface is very smooth regardless of there being a small amount imparted of the layer containing microfibrous cellulose, and it is possible to provide a highly glossy sheet and a method for manufacturing the same.

Description

Sheet and method of manufacturing sheet

The present invention relates to a sheet having a fine fibrous cellulose-containing layer and a method for producing the sheet. The invention also relates to a sheet having a pearly appearance.

By providing a fine fibrous cellulose-containing layer on a paper substrate, development of a sheet provided with various physical properties such as printability, oil resistance, gas barrier properties, and gloss is being conducted.
For example, Patent Literatures 1 and 2 disclose coated paper which is provided with a coating layer containing fine fibrous cellulose, a pigment and the like on a paper substrate and is excellent in printability, smoothness, glossiness and the like. Further, Patent Document 3 describes an oil resistant paper which is provided with a coated layer containing fine fibrous cellulose on a paper base, has oil resistance, and has both water vapor permeability and opacity. Further, Patent Document 4 describes a sheet material in which fine fibrous cellulose penetrates a paper substrate at a specific depth and is excellent in gas barrier properties and the like. In addition, Patent Document 5 shows a silver halide photographic image, provided with an ink receiving layer containing fine fibrous cellulose, colloidal silica as a pigment, and an aqueous binder resin such as styrene-butadiene resin latex as a binder, by a gelation casting method. A cast coated paper for ink jet recording having a glossiness is described.
Moreover, various techniques are known regarding the sheet | seat which gave the pearl appearance to the paper base material.
For example, a pearl-like printed matter is disclosed in which a printing ink layer composed of a mixed ink of white ink and medium is disposed on a substrate having a metallic gloss (Patent Document 6). Further, a pearl-like coated paper is disclosed in which a white pigment coating layer is provided on at least one side of a sheet material made of wood fibers, and a coating layer containing a pearl pigment is coated thereon (Patent Document 1) 7).

International Publication No. 2010/113805 International Publication No. 2011/01706 JP, 2011-074535, A Patent No. 6171674 JP, 2011-073368, A Unexamined-Japanese-Patent No. 2017-094500 Patent 5348734 gazette

Although patent documents 1 and 2 describe that the smoothness and glossiness of coated paper are excellent, further improvement of these physical properties is desired. Patent Document 3 does not describe at all the smoothness, and Patent Document 4 describes that the superiority in the smoothness improving effect is thin, and the sheet described in any of Patent Documents 3 and 4 has smoothness and It is difficult to say that it is excellent in glossiness.
According to Patent Document 5, the coating amount of the ink receiving layer is preferably 5 to 30 g / m ² in terms of solid content, so that excellent smoothness can be obtained with a small amount of the fine fibrous cellulose layer applied. Needs improvement.
Accordingly, Patent Documents 1 to 5 have surfaces having high smoothness and high gloss so that the arithmetic average roughness Ra is nano level despite the small amount of the layer containing fine fibrous cellulose being applied. The sheet is not described.
Further, Patent Documents 1 and 5 disclose that coated paper or the like excellent in printability such as ink receptivity and ink drying property and having high glossiness can be provided. However, Patent Documents 1 and 5 do not disclose that the color and gloss of the ink attached to the coated paper after printing is good and looks vivid.
Furthermore, in patent document 6, in order to obtain the base material which has metallic luster, the vapor deposition process which laminates | stacks a metal vapor deposition layer on a paper base material is required, and manufacture of a sheet | seat is complicated. Moreover, in patent document 7, in order to provide a pearliness to a paper base material, it is necessary to provide multiple layers containing a pigment, and there exists a problem to which the coating amount of the whole sheet | seat increases.
Further, Patent Documents 6 and 7 exhibit a pearly appearance by using a pigment or metal such as titanium oxide-coated mica, and do not disclose a technique for expressing a pearlescent appearance regardless of the pigment.

A first object of the present invention is to provide a sheet having a high surface smoothness and a high gloss despite the small amount of the layer containing fine fibrous cellulose and a method for producing the same.
Moreover, the 2nd subject of this invention is providing the sheet and sheet manufacturing method which are excellent in the ink definition after printing.
Furthermore, the third object of the present invention is to provide a sheet having a pearly appearance regardless of the pigment.

As a result of earnest studies to solve the above problems, the present inventors have conceived of the present invention described below and found that the problems can be solved.
That is, the present invention is as follows.

A first invention [1] A paper base and a fine fibrous cellulose-containing layer, wherein the amount of the fine fibrous cellulose-containing layer applied is 2.0 g / m ² or less, the fine fibrous cellulose-containing layer A sheet whose arithmetic mean roughness Ra measured according to JIS B 0601: 2001 on the side surface is 20 nm or less.
[2] The sheet according to [1] above, wherein the content ratio of the fine fibrous cellulose in the fine fibrous cellulose-containing layer is 55% by mass or more.
[3] The sheet according to the above [1] or [2], wherein the 75 ° specular glossiness measured according to JIS P 8142: 2005 of the fine fibrous cellulose-containing layer side surface is 30% or more.
[4] The sheet according to any one of the above [1] to [3], wherein the oil resistance according to the kit method measured according to the TAPPI UM-557 method is a first grade or higher.
[5] At least one surface of the paper substrate is coated with the fine fibrous cellulose-containing coating solution so that the amount of the fine fibrous cellulose-containing layer applied is 2.0 g / m ² or less in terms of solid content. Providing a fine fibrous cellulose-containing layer,
Drying or semi-drying the fine fibrous cellulose-containing layer,
Rewetting the surface of the fine fibrous cellulose-containing layer with a rewetting liquid;
Pressure-bonding the surface of the fine fibrous cellulose-containing layer with a cast drum,
The manufacturing method of the sheet which has sequentially.
[6] The production of the sheet according to the above [5], wherein the arithmetic mean roughness Ra measured according to JIS B 0601: 2001 of the fine fibrous cellulose-containing layer side surface after the pressure bonding step is 20 nm or less Method.

Second Invention [1] A paper base material and a fine fibrous cellulose-containing layer, wherein the fine fibrous cellulose-containing layer contains fine fibrous cellulose and a binder, and the fine fibrous cellulose-containing layer side surface A sheet having a 75 ° specular gloss of 50% or more measured in accordance with JISP 8142: 2005.
[2] A step of applying a coating liquid containing fine fibrous cellulose and a binder to at least one surface of a paper substrate to provide a fine fibrous cellulose-containing layer,
Drying or semi-drying the fine fibrous cellulose-containing layer,
Rewetting the surface of the fine fibrous cellulose-containing layer with a rewetting liquid;
Pressure-bonding the surface of the fine fibrous cellulose-containing layer with a cast drum,
Sequentially
A method for producing a sheet having a 75 ° specular gloss of 50% or more measured according to JIS P 8142: 2005 on the fine fibrous cellulose-containing layer side surface after the pressure bonding step.

Third Invention [1] A paper base having a fine fibrous cellulose-containing layer, and the fine fibrous cellulose-containing layer side surface in a wavelength region of 380 to 780 nm measured according to JIS Z 8722: 2009 A sheet whose absolute reflectance ripple amplitude is 0.10% or more.
[2] The sheet according to [1] above, 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.
[3] The sheet according to [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 the above [1] to [4], wherein the fine fibrous cellulose-containing layer further contains a binder.
[6] The sheet according to [5], wherein the fine fibrous cellulose-containing layer is an ink receiving layer.
[7] The sheet according to any one of the above [1] to [6], wherein the content of the fine fibrous cellulose in the fine fibrous cellulose-containing layer is 60% by mass or more.
[8] The method according to any one of the above [1] to [7], wherein arithmetic mean roughness Ra measured according to JIS B 0601: 2013 on the side of the fine fibrous cellulose-containing layer is 100 nm or less Sheet.
[9] The film according to any one of the above [1] to [8], wherein the 75 ° specular glossiness measured according to JIS P 8142: 2005 of the fine fibrous cellulose-containing layer side is 30% or more Sheet of paper.
[10] The sheet according to any one of the above [1] to [9], wherein the oil resistance according to the kit method measured according to the TAPPI UM-557 method is a first grade or higher.

According to the first aspect of the present invention, it is possible to provide a sheet having a high surface smoothness and high gloss despite the small amount of the layer containing fine fibrous cellulose and a method for producing the same.
Further, according to the second aspect of the present invention, it is possible to provide a sheet and a sheet manufacturing method which are excellent in ink definition after printing.
Furthermore, according to the third invention, it is possible to provide a sheet having a pearl-like appearance regardless of the pigment.

FIG. 1 is a graph showing the relationship between the amount of dropped NaOH and the conductivity of the fiber material having a phosphate group in the production example.

Hereinafter, preferred embodiments of the present invention will be described in detail.

Embodiment of First Invention (First Embodiment)
<Sheet>
The first sheet of the present invention has a paper base and a fine fibrous cellulose-containing layer, and the amount of the fine fibrous cellulose-containing layer applied is 2.0 g / m ² or less, and the fine fibrous cellulose-containing layer Arithmetic mean roughness Ra measured based on JISB 0601: 2001 of the layer side surface is characterized by being 20 nm or less.
Here, the "applying amount" of the fine fibrous cellulose-containing layer (hereinafter sometimes referred to as "CNF-containing layer") is the unit area of the fine fibrous cellulose-containing layer provided on the paper substrate. Mean amount (g / m ² ). When the CNF-containing layer is provided on both sides of the paper substrate, the "applied amount" of the CNF-containing layer is the amount per unit area of the CNF-containing layer provided on one side of the paper substrate. Show.
In the first sheet of the present invention, although the amount of the fine fibrous cellulose-containing layer applied is 2.0 g / m ² or less, a highly smooth sheet can be obtained by appropriately controlling the conditions such as the sheet manufacturing method. It can be realized. As the above conditions, for example, the selection of the coating method, setting the coating conditions such as the coating speed and the coating temperature appropriately, the selection of the components of the coating liquid, and the content ratio of each component are optimized. It can be considered that a highly smooth sheet can be realized by this. In particular, by appropriately controlling the content ratio of each component contained in the coating liquid, it is possible to obtain a high viscosity coating liquid which hardly penetrates into the paper substrate. And, by setting it as a high viscosity coating liquid, it becomes difficult for the fine fibrous cellulose (hereinafter sometimes referred to as "CNF") in the coating liquid to penetrate into the paper substrate, and the paper substrate surface is finely divided. Since fibrous cellulose remains, it is presumed that a high smooth CNF-containing layer can be provided even with a small amount of application.

As described above, since the fine fibrous cellulose in the coating liquid hardly penetrates the paper substrate, the CNF-containing layer may not penetrate into the paper substrate in the sheet of the present invention, and the CNF-containing layer A portion of the may penetrate into the paper substrate.
When a part of the CNF-containing layer penetrates into the paper substrate in the sheet of the first invention, it is preferable that the penetration of the fine fibrous cellulose into the paper substrate is small, and the thickness of the CNF-containing layer More preferably, 50% or more of the above is 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 substrate, that is, the penetrating part of the CNF-containing layer into the paper substrate are present mutually overlapping.
In addition, as an effect other than the high smoothness of the first present invention, it can be mentioned that the sheet surface has high smoothness to produce gloss. Furthermore, since the pores of the paper substrate surface 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.

[Paper base material]
The paper base material constituting the sheet of the first invention of the present invention has such permeability that water vapor generated when cast coating a coating liquid containing fine fibrous cellulose or a coating liquid containing CNF and a binder can permeate It is not particularly limited as long as it can be secured. The paper base used in the present invention includes single-glossy paper, high-quality paper, medium-quality paper, copy paper, art paper, coated paper, kraft paper, paperboard, white paperboard, newsprint paper, coated base paper, liner paper Examples include core paper, glassine, and paper.
The basis weight of the paper substrate is not particularly limited, but is preferably 15 to 300 g / m ² , and more preferably 20 to 200 g / m ² . When the basis weight of the paper base is 15 g / m ² or more, fine fibrous cellulose can be sufficiently captured, excellent smoothness can be exhibited, and excellent ink definition can be exhibited. A pearly appearance can also be developed on the sheet. In addition, when the basis weight of the paper substrate is 300 g / m ² or less, the productivity of the sheet of the present invention can be made favorable.

[Fine fibrous cellulose-containing layer]
The CNF-containing layer constituting the sheet of the present invention is preferably provided on a paper substrate. For example, the CNF-containing layer can be provided directly on the paper substrate without passing through the other layers. Even if the CNF-containing layer is provided directly on the paper substrate, as described above, the fine fibrous cellulose can be retained on the surface of the paper substrate, so a highly smooth sheet can be obtained.
The CNF-containing layer may be provided on only one of the one side and the other side of the paper substrate, or may be provided on both sides, depending on the application. Can.
If the application amount of the CNF-containing layer on one side of the paper substrate is 2.0 g / m ² or less, a plurality of CNF-containing layers may be provided on at least the one side. Moreover, the CNF containing layer may be comprised so that the provision amount may be 2.0 g / m < ² > or less with several CNF containing layer in the single side | surface of a paper base material. In addition, if the application amount of the CNF-containing layer on one side of the paper substrate is 2.0 g / m ² or less, the application amount of the CNF-containing layer on the other side is more than 2.0 g / m ² , It is also good.

(Fine fibrous cellulose)
The fiber width of the fine fibrous cellulose 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, still more preferably 2 nm or more and 50 nm or less, and 2 nm or more and 10 nm It is particularly preferred that By setting the fiber width of the fine fibrous cellulose to 2 nm or more, it is possible to suppress dissolution in water as cellulose molecules and to more easily express the effect of improving the strength, rigidity, and dimensional stability by the fine fibrous cellulose. Can. The fine fibrous cellulose is, for example, monofibrillar cellulose.

The average fiber width of the fine fibrous cellulose is measured, for example, using an electron microscope as follows. First, an aqueous suspension of fine fibrous cellulose with 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 Let it be a sample. If wide fibers are included, an SEM image of the surface cast on glass may be observed. Next, observation with an electron microscope image is performed at a magnification of 1000 times, 5000 times, 10000 times or 50000 times depending on the width of the fiber to be observed. However, the sample, observation conditions and magnification are adjusted to satisfy the following conditions.
(1) One straight line X is drawn at an arbitrary position in the observation image, and 20 or more fibers cross the straight line X.
(2) Draw a straight line Y intersecting perpendicularly with the straight line in the same image, and 20 or more fibers cross the straight line Y.

The width of the fiber intersecting the straight line X and the straight line Y is visually read for the observation image satisfying the above conditions. In this way, three or more sets of observation images of surface portions not overlapping each other at least are obtained. Then, for each image, the width of the fiber intersecting the straight line X and the straight line Y is read. Thereby, a fiber width of at least 20 × 2 × 3 = 120 is read. And let the average value of the read fiber width be the average fiber width of CNF.
The average fiber width of CNF contained in the CNF-containing layer is, for example, 1000 nm or less, and more preferably, for example, 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, and 2 nm or more and 50 nm or less Is more preferable, and 2 nm or more and 10 nm or less is particularly preferable. By setting the average fiber width of CNF to 2 nm or more, dissolution in water as a cellulose molecule can be suppressed, and the effect of improving the strength, rigidity, and dimensional stability by CNF can be more easily exhibited. CNF is monofibrillar cellulose, for example.

The fiber length of the fine fibrous cellulose is not particularly limited, but is preferably 0.1 μm to 1000 μm, for example, and more preferably 0.1 μm to 800 μm, and preferably 0.1 μm to 600 μm. More preferable. By setting the fiber length within the above range, it is possible to suppress the destruction of the crystalline region of the fine fibrous cellulose. It also becomes possible to make the slurry viscosity of fibrous cellulose into a suitable range. In addition, the fiber length of fine fibrous cellulose can be calculated | required from the image analysis by TEM, SEM, and AFM, for example.

The fine fibrous cellulose preferably has a type I crystal structure. Here, the fact that the fine fibrous cellulose has a type I crystal structure can be identified in a diffraction profile obtained from a wide angle X-ray diffraction photograph using CuKα (λ = 1.5418 Å) monochromatized with graphite. Specifically, it can be identified from having typical peaks at two positions of 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less.
The proportion of crystal form I in fine fibrous cellulose is, for example, preferably 30% or more, more preferably 40% or more, and still more preferably 50% or more. Thereby, further excellent performance can be expected in terms of heat resistance and low linear thermal expansion. With regard to the degree of crystallinity, the X-ray diffraction profile is measured, and the pattern is determined by a conventional method (Seagal et al., Textile Research Journal, 29: 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 prepared. By setting the axial ratio to the above upper limit value or less, for example, when handling fine fibrous cellulose as a water dispersion, it is preferable in that handling such as dilution is facilitated.
The fine fibrous cellulose in the present embodiment has, for example, both a crystalline region and an amorphous region. In particular, fine fibrous cellulose having both crystalline regions and noncrystalline regions and having a high axial ratio is realized by the method of producing fine fibrous cellulose 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. It is more preferable that fibrous cellulose has an ionic substituent from a viewpoint of improving the dispersibility of the fiber in a dispersion medium, and raising the disintegration efficiency in a disintegration process. The ionic substituent can include, for example, one or both of an anionic group and a cationic group. Moreover, as a non-ionic substituent, an alkyl group, an acyl group, etc. can be included, for example. In the present embodiment, it is particularly preferable to have an anionic group as the ionic substituent.
In addition, the process which introduce | transduces an ionic substituent does not need to be performed to the fine fibrous cellulose.

As an anionic group as an ionic substituent, for example, 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) And at least one selected from a sulfone group or a substituent derived from a sulfone group (sometimes referred to simply as a sulfone group), and at least one selected from a phosphoric acid group and a carboxyl group It is more preferably a species, and particularly preferably a phosphate group.

The phosphoric acid group is, for example, a divalent functional group corresponding to phosphoric acid with a hydroxyl group removed. Specifically, it is a group represented by -PO ₃ H ₂ . The substituent derived from the phosphate group includes a substituent such as a salt of a phosphate group and a phosphate ester group. In addition, the substituent originating in a phosphoric acid group may be contained in fine fibrous cellulose as group (for example, pyrophosphoric acid group) which the phosphoric acid group condensed.
The phosphate group or the substituent derived from the phosphate group is, for example, a substituent represented by the following formula (1).

In formula (1), a, b and n are natural numbers (however, a = b × m). alpha ^1, alpha ^2, at least one of · · ·, alpha ⁿ and alpha 'is O ^- a and the remainder is either R or OR. All the alpha ⁿ and alpha 'is O ^- may be a. When n is 2 or more and α 'is R or OR, at least one of each α ⁿ is O 2 ^- and the remainder is R or OR. n is equal to or greater than 2, alpha 'is O ^- when it is may be a respective alpha ⁿ are all R, may be all OR, at least one O ^- remaining in the R or It may be OR. R each independently represents a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, an unsaturated-branched chain Hydrocarbon groups, aromatic groups, and derivatives thereof.
Examples of the saturated-linear hydrocarbon group include methyl group, ethyl group, n-propyl group, and n-butyl group, but are not particularly limited. Examples of the saturated-branched hydrocarbon group include i-propyl group and t-butyl group, but are not particularly limited. The saturated-cyclic hydrocarbon group may, for example, be a cyclopentyl group or a cyclohexyl group, but is not particularly limited. Examples of the unsaturated-linear hydrocarbon group include, but are not particularly limited to, a vinyl group, an allyl group and the like. Examples of unsaturated-branched hydrocarbon groups include i-propenyl group and 3-butenyl group, but are not particularly limited. Examples of the unsaturated-cyclic hydrocarbon group include, but are not particularly limited to, cyclopentenyl group, cyclohexenyl group and the like. Examples of the aromatic group include, but are not particularly limited to, a phenyl group or a naphthalene group.
In addition, as the derivative in R, at least one of functional groups such as a carboxyl group, a hydroxyl group, or an amino group is added or substituted to the main chain or side chain of the various hydrocarbon groups. Although a group is mentioned, it is not limited in particular. 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 maintain good permeability to the fiber material, It can contribute to the improvement of the yield of fine fibrous cellulose.
β ^{b +} is a monovalent or more cation composed of an organic substance or an inorganic substance. The monovalent or more monovalent cations of organic substances include aliphatic ammonium or aromatic ammonium, and the monovalent or more monovalent cations of inorganic substances include ions of alkali metals such as sodium, potassium or lithium, Examples thereof include cations of divalent metals such as calcium or magnesium, or hydrogen ions, but not particularly limited. These can also be applied combining 1 type or 2 or more types. The monovalent or more monovalent cation composed of an organic substance or an inorganic substance is preferably an ion of sodium or potassium which is not easily yellowed when the fiber material containing β is heated and which is industrially easy to use, but is not particularly limited.

The introduction amount of the ionic substituent to the fibrous cellulose is, for example, preferably 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, and more preferably 0.50 mmol per 1 g (mass) of fibrous cellulose. It is more preferable that it is / g or more, and it is particularly preferable that it is 1.00 mmol / g or more. Further, the introduction amount of an ionic substituent such as a phosphoric acid group to fibrous cellulose is, for example, preferably 3.65 mmol / g or less per 1 g (mass) of fibrous cellulose, and is 3.50 mmol / g or less. Is more preferable, and 3.00 mmol / g or less is more preferable. By making the introduction amount of the ionic substituent within the above range, it is possible to facilitate the miniaturization of the fiber raw material, and it is possible to 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 introduction amount of the ionic substituent to the fine fibrous cellulose can be measured, for example, by the conductivity titration method. In the measurement by the conductivity titration method, the introduced amount is measured by determining the change in conductivity while adding an alkali such as an aqueous solution of sodium hydroxide to the obtained slurry containing fine fibrous cellulose.
A more specific measuring method of the ionic substituent introduction amount to the fine fibrous cellulose is as described in the production example described later.

A well-known technique can be used as a method of introduce | transducing an ionic substituent into fibrous cellulose and manufacturing a fine fibrous cellulose. For example, fine fibrous cellulose in which an ionic substituent is introduced through an ionic substituent introduction step of introducing an ionic substituent into a fiber raw material, a washing step, an alkali treatment step (neutralization step), and a defibration treatment step Can be obtained as an aqueous dispersion containing
A more specific production method of introducing an ionic substituent into fibrous cellulose and refining it is as described in the production example described later.
Moreover, the obtained fine fibrous cellulose containing aqueous dispersion can be used as a fine fibrous cellulose containing coating liquid mentioned later.

The content ratio of the fine fibrous cellulose in the CNF-containing layer may be specified so as to satisfy the preferable amount of fine fibrous cellulose described later, but is preferably 55% by mass or more, and more preferably 63% by mass or more. More preferably, it is 66 mass% or more, and 100 mass% may be sufficient. When the content of the fine fibrous cellulose is 55% by mass or more, high smoothness can be easily achieved even if the amount of the CNF-containing layer applied is small.

(Styrene-Butadiene Copolymer)
The CNF-containing layer can further contain a styrene-butadiene copolymer (SBR) from the viewpoint of improving the printability such as the surface strength and the ink receptivity of the CNF-containing layer.
The content ratio of the styrene-butadiene copolymer in the CNF-containing layer is preferably 1% by mass or more, more preferably 5% by mass or more, and further preferably 15% by mass or more from the viewpoint of improvement in printability. More preferably, it is 25% by mass or more from the viewpoint of improving the In addition, the content ratio of the styrene-butadiene copolymer in the CNF-containing layer is preferably less than 45% by mass, more preferably from the viewpoint of balance between the low CNF-containing layer content and high smoothness and printability. Is less than 37% by mass, more preferably less than 34% by mass.

(Other ingredients)
The CNF-containing layer may contain other components in addition to the fine fibrous cellulose and the optionally contained styrene-butadiene copolymer.
The other components are not particularly limited as long as the effects of the present invention are not impaired, but they may be release agents such as microcrystalline wax, wetting agents such as surfactants, colloidal silica, dispersants, antifoams, preservatives, Viscosity modifiers, colorants, lubricants, water resistance agents, etc. may be mentioned. These other components may be used alone or in combination of two or more.

(Amount of CNF-containing layer)
In the sheet of the present invention, the application amount of the CNF-containing layer is 2.0 g / m ² or less, preferably 1.7 g / m ² or less, more preferably 1.4 g / m ² or less, still more preferably 1.1 g / M ² or less, more preferably 0.9 g / m ² or less. By setting the application amount to 2.0 g / m ² or less, high smoothness can be realized. The amount of the CNF-containing layer applied is preferably 0.1 g / m ² or more, more preferably 0.25 g / m ² or more, still more preferably 0.3 g / m ² or more, from the viewpoint of obtaining a high smoothness effect. Still more preferably, it is 0.4 g / m ² or more. From the viewpoint of thinning the sheet, the amount of the CNF-containing layer may be, for example, 0.28 g / m ² or less.
The application amount of the CNF-containing layer is the total dry mass including the styrene-butadiene copolymer and other components contained as needed in addition to the fine fibrous cellulose, and per one side of the paper substrate Of the CNF-containing layer.

Further, in the sheet of the present invention, the amount of the fine fibrous cellulose content to be applied is preferably 2.0 g / m ² or less, more preferably 1.7 g / m ² or less, from the viewpoint of obtaining a high smoothness effect. Preferably it is 1.4 g / m ² or less, more preferably 1.1 g / m ² or less, particularly preferably 0.9 m ² or less. Further, the amount of fine fibrous cellulose to be applied is preferably 0.1 g / m ² or more, more preferably 0.25 g / m ² or more, still more preferably 0.3 g / m ² from the viewpoint of achieving the effect of high smoothness. The above, more preferably 0.4 g / m ² or more. From the viewpoint of thinning the sheet, it is also possible to set the content of the fine fibrous cellulose in the application amount of the CNF-containing layer to, for example, 0.28 g / m ² or less. The application amount of the fine fibrous cellulose is the dry mass of the fine fibrous cellulose contained in the CNF-containing layer provided on the paper substrate, and is the application amount per one side of the paper substrate.

[Other layer]
The sheet of the present invention can be provided with a CNF-containing layer on one side or both sides of the paper substrate as described above, but it has high smoothness and high gloss and can have properties such as oil resistance and printability. The CNF-containing layer is preferably the outermost surface.
In addition, when the CNF-containing layer is provided only on one side of the paper base, the other side of the paper base can be provided with another layer depending on the use of the sheet. The other layer may, for example, be a pressure-sensitive adhesive layer or a release agent layer, and may be a sheet having a so-called label type (also referred to as a sticker or seal type) structure.

[Arithmetic mean roughness Ra]
The first sheet of the present invention has an arithmetic average roughness Ra of 20 nm or less measured in accordance with JIS B 0601: 2001 on the surface of the CNF-containing layer side. In the sheet of the present invention, the fine fibrous cellulose in the coating liquid penetrates the paper substrate despite the small amount of CNF-containing layer applied, so the fine fibrous cellulose remains on the surface of the paper substrate, and the paper The surface irregularities of the substrate can be covered. As a result, it is possible to achieve smoothness higher than the surface of the paper substrate, and to achieve excellent smoothness that the above-mentioned Ra is 20 nm or less.
Although the value of Ra varies depending on the type of paper substrate and its basis weight, for example, when the paper substrate is a single-gloss paper and a CNF-containing layer is provided on the glossy surface side, the Ra is 15 nm or less, and 10 nm or less. It is also possible. Moreover, when the paper base material is high quality paper, it is also possible to set the above-mentioned Ra to 19 nm or less, and further 18 nm or less. The lower limit of the above Ra can not be unambiguously specified from the type of paper substrate and its basis weight, but is usually about 2 nm or more.

[Glossiness]
In the sheet of the first invention, the 75 ° specular glossiness measured according to JIS P 8142: 2005 of the surface on the CNF-containing layer side is preferably 30% or more, more preferably 80% or more, still more preferably It is 83% or more, more preferably 85% or more, and particularly preferably 90% or more. Since the sheet of the present invention has high smoothness as described above, it can also exhibit the above-mentioned excellent glossiness.

[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 according to the kit method measured according to the TAPPIUM-557 method. The oil resistance of the sheet of the present invention measured by the above-mentioned kit method is a first grade or more showing oil resistance expression, preferably a sixth grade or more, more preferably a seventh grade or more. . The oil resistance of the sheet of the present invention is considered to be due to the fact that the fine fibrous cellulose in the CNF-containing layer fills the voids of the paper substrate surface.
The oil resistance according to the above-mentioned kit method that can be used as oil-resistant paper is usually fifth grade or higher.

[Printing aptitude]
In the sheet of the present invention, when the CNF-containing layer further contains a styrene-butadiene copolymer as described above, it is possible to improve the printability such as the surface strength and the ink receptivity. That is, the CNF-containing layer in the sheet of the present invention can be suitably provided as an ink receiving layer.

<Production method of sheet>
The method for producing a sheet of the present invention is
The fine fibrous cellulose-containing coating liquid is applied to at least one surface of the paper substrate so that the amount of the fine fibrous cellulose-containing layer applied is 2.0 g / m ² or less in terms of solid content, and the fine fibers are Forming a cellulose-containing layer (coating step),
Drying or semi-drying the fine fibrous cellulose-containing layer (drying or semi-drying step),
Rewetting the surface of the fine fibrous cellulose-containing layer with a rewetting liquid (rewetting step);
A step of pressing the surface of the fine fibrous cellulose-containing layer with a cast drum (pressure bonding step),
In order.

As a casting method which is one of the film forming methods for film sheets, (i) a wet casting method in which a coating liquid is applied and pressure-bonded to a casting drum immediately, (ii) coating a coating liquid, drying or semi-coating After drying, after applying the rewetting liquid, rewet casting method of pressing on the cast drum, (iii) Coating liquid coating, gelation is applied after applying gelation agent and gelation The casting method etc. are known. Among these cast methods, it is preferable to adopt (ii) rewet cast method as a method of producing the sheet of the present invention.
In the production of the sheet of the present invention (iii) When the gelation casting method is adopted, the coating solution containing fine fibrous cellulose is applied and then the gelling agent is applied thereon to make the outermost surface of the sheet fine. It is not fibrous cellulose, and it is difficult to develop high smoothness and glossiness thereby. Further, in the gelation casting method, the coating amount is also large, and it is difficult to obtain the effect of the present invention in which the sheet is highly smooth even though the amount of the CNF-containing layer applied is small. In addition, in (i) the wet casting method, in order to express desired high smoothness, it is difficult to adjust the wetting and setting the conditions, and there is a possibility that the workability is also inferior. On the other hand, (ii) Rewet casting is relatively easy to adjust the wettability and is excellent in productivity, and the surface is even if the amount of CNF-containing layer applied is as small as 2.0 g / m ² or less in terms of solid content. It is possible to produce sheets with CNF-containing layers that are highly smooth and even highly glossy.

[Fine fibrous cellulose-containing coating solution]
The content ratio of the fine fibrous cellulose in the fine fibrous cellulose-containing coating solution (hereinafter sometimes referred to simply as "coating solution") is preferably 0.5% by mass or more, more preferably 0 in terms of solid content. .8 mass% or more, more preferably 1.0 mass% or more. The content ratio 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, still more preferably 2.5% by mass or less in terms of solid content. It is. If it is in the above-mentioned range, while having viscosity suitable for coating, penetration of fine fibrous cellulose into a paper base material can be suppressed and it can be made to remain on the surface, and it is highly smooth even with a small amount of application. CNF containing layer can be provided.

The fine fibrous cellulose-containing coating solution preferably further contains a styrene-butadiene copolymer from the viewpoint of improving the printability such as the surface strength and the ink receptivity of the CNF-containing layer. The coating liquid may contain a styrene-butadiene copolymer latex as a styrene-butadiene copolymer. The content ratio of the styrene-butadiene copolymer latex in the coating liquid is the same as the preferable content ratio (solid content) of the styrene-butadiene copolymer in the CNF-containing layer described above in the description of the sheet of the present invention. It is preferable to adjust.
The coating solution is preferably an aqueous dispersion containing the fine fibrous cellulose described above in the description of the sheet of the present invention, a styrene-butadiene copolymer used as needed, and other components.

[Coating process]
In this step, the coating liquid is applied to at least one surface of the paper substrate such that the amount of the CNF-containing layer applied is 2.0 g / m ² or less in terms of solid content. The preferred application amount of the CNF-containing layer is the same as that described above in the description of the sheet of the present invention. In addition, in the same manner as described above in the description of the sheet of the present invention, the above-mentioned application amount is the total dry including the styrene-butadiene copolymer and other components optionally contained in addition to the fine fibrous cellulose. It is mass and also the amount of CNF containing layer per side of the paper substrate.
As a coating machine which applies a coating liquid, a bar coater, a roll coater, a gravure coater, a die coater, a curtain coater, an air doctor coater etc. can be used, for example, It does not specifically limit. Although a bar coater is preferable from the viewpoint of uniformly applying a viscous coating liquid, it 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 applied on the paper substrate.
The drying method is not particularly limited, but it may be either a non-contact drying method or a method of drying while restraining the sheet, or a combination thereof. For example, the drying process may be a two-step process including, but not limited to, a non-contacting first drying process and a subsequent second drying process of drying while restraining the sheet.

The non-contact drying method is not particularly limited, but a method of heating and drying by hot air, infrared rays, far infrared rays or near infrared rays (heat drying method), a method of vacuum drying (vacuum drying method) may be applied. Although the heat drying method and the vacuum drying method may be combined, the heat drying method is usually applied. Drying by infrared light, far infrared light or near infrared light can be performed using an infrared light device, a far infrared light device or a near infrared light device, but is not particularly limited. The heating temperature in the heating and drying method is not particularly limited, but is preferably 40 to 120 ° C., and more preferably 60 to 110 ° C. If the heating temperature is 40 ° C. or higher, the dispersion medium in the coating liquid can be volatilized quickly, and if it is 120 ° C. or lower, suppression of the cost required for heating and suppression of color change due to heat of the fine fibrous cellulose it can.

[Rewet process]
In this step, the dried or semi-dried CNF-containing layer is rewetted in the above step. The rewetting liquid is not particularly limited, but it is preferable to use water. In water, polyethylene emulsion generally used as a releasing agent, salts and derivatives of fatty acids, microcrystalline wax, funnel oil, etc. may be dissolved or dispersed. In addition, before re-wetting a CNF containing layer, smoothing treatments, such as a super calender and brushing, can also be performed.

[Crimping process]
In this step, the surface of the rewetted CNF-containing layer is crimped by a cast drum by the rewetting step.
The cast drum may be a general cast drum having a chrome plated layer polished to a mirror surface on the surface of a drum main body made of steel or casting, etc. A layer may be provided. In addition, the cast drum may be used by heating.

<Use>
The sheet of the first invention and the sheet produced by the production method of the first invention have high smoothness and gloss, and can also have physical properties such as oil resistance and printability.
Therefore, the sheet of the present invention and the sheet produced by the production method of the present invention are, from the above-mentioned characteristics, wrapping paper, seal, label, box or envelope in the field of packaging and distribution And ink jet printer paper.

Embodiment of Second Invention (Second Embodiment)
<Sheet>
The sheet of the second present invention has a paper base and a fine fibrous cellulose-containing layer, and the fine fibrous cellulose-containing layer contains fine fibrous cellulose and a binder, and the fine fibrous cellulose-containing layer side surface It is characterized in that the 75 ° specular glossiness measured in accordance with JISP 8142: 2005 of is 50% or more.
In the second sheet of the present invention, the fine fibrous cellulose-containing layer (hereinafter sometimes referred to as "CNF-containing layer") comprises fine fibrous cellulose (hereinafter sometimes referred to as "CNF") and a binder. When the surface on the CNF-containing layer side contains the above-mentioned specular gloss, the definition of the ink is excellent.
The above-mentioned specular gloss is achieved by appropriately controlling the content of each component contained in the coating liquid forming the CNF-containing layer, and by appropriately selecting the other manufacturing method conditions such as the coating method. Be done. Furthermore, since the coating liquid containing CNF forming the CNF-containing layer and the binder hardly penetrates the paper substrate, and the CNF and the binder stay on the paper substrate surface, the CNF-containing layer exhibits the above-mentioned specular gloss. In addition to the above, the ink receiving layer can also have the properties as an ink receiving layer, and as a result, the excellent color of the ink attached to the sheet after printing, the gloss and the like are good, and an excellent ink definition of giving a vivid impression is expressed.
In the present invention, “ink definition” is one of the indicators showing printability, and the difference in the saturation between the printed portion and the unprinted portion, the color development and printing of the ink attached to the sheet after printing Means the vividness of the surface gloss etc.

As described above, in the present invention, since the coating liquid hardly penetrates the paper substrate, the CNF-containing layer may not penetrate into the paper substrate, and a part of the CNF-containing layer is in the paper substrate. It may penetrate to
In the sheet of the present invention, when a part of the CNF-containing layer penetrates into the paper substrate, the CNF-containing layer preferably penetrates less into the paper substrate, and 50% of the thickness of the CNF-containing layer More preferably,% or more is 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 substrate, that is, the penetrating part of the CNF-containing layer into the paper substrate are present mutually overlapping.

The second sheet of the present invention can also exhibit effects other than ink definition.
As an effect other than ink definition, the sheet of the present invention can also be realized to be excellent in, for example, high smoothness, surface strength, and ink receptivity. Furthermore, since the voids of the paper substrate surface are filled with CNF, the effect of preventing the penetration of oil droplets is produced, and the sheet of the present invention can also exhibit oil resistance.

[Paper base material]
The paper substrate constituting the sheet of the second invention may be the same as that described in the first embodiment, and is produced when a coating liquid containing CNF and a binder is cast coated. It is not particularly limited as long as it can ensure the permeability to the extent that water vapor can permeate. The basis weight of the paper substrate is also not particularly limited, and the preferred range is the same as that of the paper substrate in the first embodiment. If the basis weight of the paper substrate is 15 g / m ² or more, CNF can be sufficiently captured and excellent ink definition can be exhibited. On the other hand, if the basis weight is 300 g / m ² or less, this The productivity of the inventive sheet can be improved.

[Fine fibrous cellulose-containing layer]
The CNF-containing layer constituting the second sheet of the present invention can be provided directly or indirectly on the paper substrate, but the CNF-containing layer is provided directly on the paper substrate without any other layer. Is preferred. Even if the CNF-containing layer is provided directly on the paper substrate, the sheet of the present invention exhibits excellent ink definition because the CNF and the binder can stay on the surface of the paper substrate as described above.
The CNF-containing layer may be provided on only one of the 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.
In addition, a plurality of CNF-containing layers may be provided on at least one side of the paper substrate. Moreover, the CNF containing layer may be comprised by the several CNF containing layer in the single side | surface of a paper base material.

(Fine fibrous cellulose)
As the fine fibrous cellulose, those similar to those described in the first embodiment can be used.
The content of CNF in the CNF-containing layer may be specified so as to satisfy the preferable application amount of CNF described later, and although the range of the preferable content varies depending on the type of binder used, preferably 45% by mass or more, more preferably Is 50% by mass or more, more preferably 55% by mass or more. If the CNF content is 45% by mass or more, it is suitable for achieving the specific specular glossiness in the present invention, and it is easy to obtain a better ink definition. The CNF content is preferably 95% by mass or less, more preferably 90% by mass or less, still more preferably 85% by mass or less, still more preferably 80% by mass or less, still more preferably 75% by mass or less . If the CNF content is 95% by mass or less, in addition to the excellent ink definition, the excellent surface strength and ink receptivity of the CNF-containing layer can be easily obtained.

Further, as described above, in the present invention, the preferable content of CNF in the CNF-containing layer differs depending on the type of binder contained in the CNF-containing layer. When the binder is, for example, a water-insoluble polymer such as styrene-butadiene copolymer, oxidized starch, and casein, the content of CNF in the CNF-containing layer is usually about 40% by mass or more, preferably The content is 45% by mass or more, more preferably 50% by mass or more, still more preferably 55% by mass or more, still more preferably 60% by mass or more, and still more preferably 65% by mass or more. If the CNF content is 45% by mass or more, it is suitable for achieving the specific specular glossiness in the present invention, and it is easy to obtain a better ink definition. The CNF content when the binder is a water-insoluble polymer is preferably 95% by mass or less, more preferably 90% by mass or less, still more preferably 85% by mass or less, still more preferably 80% by mass or less More preferably, it is 75 mass% or less. If the CNF content is 95% by mass or less, in addition to the excellent ink definition, it is easy to obtain the excellent surface strength and ink receptivity of the CNF-containing layer.

When the binder is a water-soluble polymer such as polyvinyl alcohol and carboxymethyl cellulose, the content of CNF in the CNF-containing layer is preferably 35% by mass or more, more preferably 40% by mass or more, and further preferably Is 45% by mass or more, more preferably 50% by mass or more, still more preferably 55% by mass or more. If the CNF content is 35% by mass or more, it is suitable for achieving the specific specular glossiness in the present invention, and it is easy to obtain a more excellent ink definition. The CNF content when the binder is a water-soluble polymer is preferably 95% by mass or less, more preferably 90% by mass or less, still more preferably 85% by mass or less, still more preferably 80% by mass or less More preferably, it is 75 mass% or less. If the CNF content is 95% by mass or less, it is easy to obtain excellent surface strength and ink receptivity of the CNF-containing layer, in addition to excellent ink definition.

(binder)
The CNF-containing layer can exhibit the property as an ink receiving layer and the excellent ink definition by containing a binder. When the CNF-containing layer does not contain a binder, the surface strength of the CNF-containing layer of the sheet is insufficient, and the ink does not adhere and the effect of the present invention can not be obtained.

Examples of the binder include water-soluble polymers and water-insoluble polymers.
Examples of water-soluble polymers include cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose, dextrin, mannan, chitosan, arabinogalactan, glycogen, inulin, pectin, natural polysaccharides such as pectin and hyaluronic acid, and oligomers thereof Examples of the modified body include synthetic water-soluble resins such as polyacrylic acid, polymethacrylic acid, polyethylene glycol, and polyvinyl alcohol.
Examples of water-insoluble polymers include starches purified from natural plants, hydroxyethylated starches, oxidized starches, oxidized starches, etherified starches, phosphated starches, enzyme-modified starches and starches such as cold water-soluble starches obtained by flash-drying them. And modified starches; natural proteins such as gelatin, casein, soy lecithin, collagen etc. and modified products thereof; each water (co) polymers such as styrene-butadiene type, acrylic type, polyvinyl acetate, ethylene-vinyl acetate etc. synthetic water insoluble Resin is illustrated.
The binder may be used in the state of being dissolved in water by heating or pH adjustment, or may be used in the 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, preferred are modified starch, cellulose derivative, natural protein, synthetic water-soluble resin, and synthetic water, from the viewpoints of excellent ink definition and printability such as surface strength and ink receptivity of CNF-containing layer. Insoluble resins are more preferably oxidized starch, carboxymethylcellulose, casein, polyvinyl alcohol, and styrene-butadiene copolymer, more preferably styrene-butadiene copolymer.

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, still more preferably 25% by mass or more It is. When the content of the binder is 5% by mass or more, a specific specular glossiness can be easily achieved, and an excellent ink definition can be easily expressed. Furthermore, the balance between the ink definition, the surface strength and the ink receptivity can be easily obtained.
Further, the upper limit of the content of the binder in the CNF-containing layer varies depending on the type of the binder, and may be appropriately determined in the range satisfying the specific specular glossiness in the present invention, but preferably 55% by mass or less, more preferably It is 50% by mass or less, more preferably 45% by mass or less. If the upper limit of the content is within the above range, it is possible to easily achieve the specific specular glossiness in the present invention, and it becomes easy to develop excellent ink definition.

As described above, the upper limit of the preferred content of the binder in the CNF-containing layer in the present invention varies depending on the type of binder. When the binder is a water-insoluble polymer, for example, at least one selected from oxidized starch, casein, and a styrene-butadiene copolymer, the upper limit of the content of the binder in the CNF-containing layer is usually 60% by mass It is less than about, preferably 55% by mass or less, more preferably 50% by mass or less, still more preferably 45% by mass or less, still more preferably 40% by mass or less, still more preferably 35% by mass or less. The lower limit of the binder content in the CNF-containing layer when the binder is a water-insoluble polymer is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass as described above. The content is more preferably 20% by mass or more, still more preferably 25% by mass or more. If the content is within the above range, it is possible to easily achieve the specific specular glossiness in the present invention, and it becomes easy to develop excellent ink definition.

On the other hand, when the binder is a water-soluble polymer, for example, at least one selected from carboxymethylcellulose and polyvinyl alcohol, the content of the binder in the CNF-containing layer is 60% by mass or more, even if it is specified in the present invention The specular gloss of the toner can be satisfied, and the expression of excellent ink definition can be expected. Specifically, when the binder is at least one selected from, for example, carboxymethylcellulose and polyvinyl alcohol, the upper limit of the binder content in the CNF-containing layer may be 65% by mass or less, preferably 60% by mass or less More preferably, it is 55 mass% or less, More preferably, it is 50 mass% or less, More preferably, it is 45 mass% or less. The lower limit of the binder content in the CNF-containing layer when the binder is a water-soluble polymer is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 15% by mass, as described above. The content is more preferably 20% by mass or more, still more preferably 25% by mass or more.

(Amount of CNF-containing layer)
In the sheet of the second invention, the application amount of the CNF-containing layer is preferably 5.0 g / m ² or less, more preferably 3.0 g / m ² or less, still more preferably 2.0 g / m ² or less More preferably, it is 1.7 g / m ² or less, still more preferably 1.4 g / m ² or less, still more preferably 1.1 g / m ² or less, still more preferably 0.9 g / m ² or less. When the application amount of the CNF-containing layer is 5.0 g / m ² or less, it is easy to realize excellent ink definition, further high gloss and smoothness. Moreover, the application amount of the CNF-containing layer is preferably 0.1 g / m ² or more, more preferably 0.25 g / m ² or more, still more preferably 0.3 g / m ² or more, still more preferably 0.4 g / M ² or more. When the application amount of the CNF-containing layer is 0.1 g / m ² or more, excellent ink definition can be easily realized. From the viewpoint of thinning the sheet, the amount of the CNF-containing layer may be, for example, 0.28 g / m ² or less.

Here, the “applied 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 the CNF-containing layer is provided on both sides of the paper substrate, the "applied amount" of the CNF-containing layer is the amount per unit area of the CNF-containing layer provided on one side of the paper substrate. Represent.
In addition, the application amount of the CNF-containing layer is the total dry mass including other components described later optionally contained in addition to the CNF and the binder, and the amount of the CNF-containing layer per one side of the paper substrate It is.

In the sheet of the second invention, the application amount of CNF in the CNF-containing layer is preferably 4.75 g / m ² or less from the viewpoint of excellent ink sharpness, high glossiness and smoothness. preferably 2.85 g / ^{m 2} or less, more preferably 1.9 g / ^{m 2} or less, still more preferably 1.6 g / ^{m 2} or less, still more preferably 1.3 g / ^{m 2} or less, more preferably more 1 .0g / ^{m 2} or less, still more preferably 0.85 g / ^{m 2} or less. Further, the application amount of the CNF has excellent ink sharpness, further a high gloss and smoothness of the aspect, preferably 0.045 g / ^{m 2} or more, more preferably 0.1 g / ^{m 2} or more, more preferably It is 0.14 g / m ² or more, more preferably 0.18 g / m ² or more.
The application amount of CNF in the CNF-containing layer is the dry mass of CNF contained in the CNF-containing layer provided on the paper substrate, and is the application amount per one side of the paper substrate.

(Mass ratio of CNF to binder)
The mass ratio b / a of the content b of the binder to the content a of CNF in the CNF-containing layer varies depending on the type of the binder, but the ink definition, gloss and smoothness, and surface strength and surface strength From the viewpoint of improving printability such as ink receptivity, preferably 5/95 to 55/45, more preferably 10/90 to 50/50, still more preferably 15/85 to 50/50, still more preferably 15/85 to 45/55, still more preferably 20/80 to 45/55.

As described above, in the present invention, the preferred range of the mass ratio b / a varies depending on the type of the binder more specifically. When the binder is a water-insoluble polymer, for example, at least one selected from oxidized starch, casein, and styrene-butadiene copolymer, the ink definition, gloss and smoothness, and surface strength The range of the mass ratio b / a is preferably 5/95 to 55/45, more preferably 10/90 to 50/50, still more preferably 15 from the viewpoint of improving printability such as ink receptivity and ink receptivity. / 85 to 50/50, still more preferably 15/85 to 45/55, still more preferably 20/80 to 45/55, still more preferably 20/80 to 40/60, still more preferably 20/80 To 35/65, even more preferably 25/75 to 35/65.

When the binder is a water-soluble polymer, for example, at least one selected from carboxymethylcellulose and polyvinyl alcohol, the definition of the ink, the gloss and smoothness, and the surface strength and the ink receptivity of the ink The mass ratio b / a is preferably 5/95 to 65/35, more preferably 5/95 to 60/40, still more preferably 5/95 to 55 /, from the viewpoint of improving printability such as 45, still more preferably 10/90 to 50/50, still more preferably 15/85 to 50/50, still more preferably 15/85 to 45/55, still more preferably 20/80 to 45/55. is there.

The sheet of the second invention of the present invention can easily achieve the specific specular glossiness in the present invention by adjusting the content ratio of CNF and binder in the CNF-containing layer, and extremely excellent ink definition is obtained. Be Moreover, if mass ratio b / a is the said range, it will become easy to adjust the coating liquid which forms a CNF containing layer to high viscosity. A coating solution of high viscosity does not easily penetrate into the paper substrate, and in particular, CNF generally easily penetrates into the paper substrate. It is also preferable from the viewpoint of keeping it. As described above, when the mass ratio b / a is in the above range, the CNF and the binder in the coating liquid can be more easily retained on the surface of the paper substrate, even if the amount of the CNF-containing layer is small. The CNF-containing layer is imparted with glossiness and properties as an ink receiving layer, so that extremely excellent ink definition can be exhibited, and further high gloss and high smoothness, and excellent in surface strength and ink receptivity, etc. It is possible to form a CNF-containing layer which is printable and has well-balanced properties.

The total content of CNF and 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 still more preferably 80% by mass or more. It may be mass%. If the total content of the CNF and the binder is 50% by mass or more, excellent ink definition is easily obtained.

(Other ingredients)
The CNF-containing layer can contain other components as needed in addition to the CNF and the binder.
The other components are not particularly limited as long as the effects of the present invention are not impaired, but they may be release agents such as microcrystalline wax, wetting agents such as surfactants, colloidal silica, dispersants, antifoams, preservatives, Viscosity modifiers, colorants, lubricants, water resistance agents, etc. may be mentioned. These other components may be used alone or in combination of two or more.

[Other layer]
The sheet of the second invention of the present invention can be provided with a CNF-containing layer on one side or both sides of the paper base as described above, but it has excellent ink definition and further has high gloss and high smoothness, printability From the viewpoint of properties such as oil resistance, the CNF-containing layer is preferably the outermost surface.
In addition, when the CNF-containing layer is provided only on one side of the paper base, the other side of the paper base can be provided with another layer depending on the use of the sheet. The other layer may, for example, be a pressure-sensitive adhesive layer or a release agent layer, and may be a sheet having a so-called label type (also referred to as a sticker or seal type) structure.

[Glossiness]
In the sheet of the second invention, the 75 ° specular glossiness measured according to JIS P 8142: 2005 of the CNF-containing layer side surface is 50% or more, preferably 60% or more, more preferably 70% The above, more preferably 80% or more.
The specular glossiness appropriately controls the content of each component contained in the coating liquid forming the CNF-containing layer as described above, and appropriately selects the conditions on other manufacturing methods such as the coating method. Is achieved by the method of Further, the above preferable aspect of mirror glossiness can also be realized by optimizing the method.
The sheet of the present invention is excellent in ink definition such that the ink after printing is vividly developed while exhibiting the excellent glossiness represented by the specific specular glossiness.

[Arithmetic mean roughness Ra]
The sheet of the present invention preferably has an arithmetic mean roughness Ra measured according to JIS B 0601: 2013 on the CNF-containing layer side surface of 100 nm or less. The sheet of the present invention can make it difficult for the CNF in the coating liquid to penetrate into the paper substrate as described above, so the CNF can be retained on the surface of the paper substrate and can cover the surface irregularities of the paper substrate. Furthermore, by adopting the rewet casting method described later as a method for producing the sheet of the present invention, excellent smoothness with the above Ra preferably of 100 nm or less can be achieved.
Although the value of Ra achieved varies depending on the type of paper substrate and its basis weight, for example, when the paper substrate is a single-gloss paper and a CNF-containing layer is provided on the glossy surface side, the above Ra is 30 nm or less and 20 nm or less, The thickness may be 15 nm or less, and further 10 nm or less. In addition, when the paper base material is high quality paper, the Ra may be 30 nm or less, 20 nm or less, 19 nm or less, or 18 nm or less. The lower limit of the above Ra can not be unambiguously specified from the type of paper substrate and its basis weight, but is usually about 2 nm or more.

[Printing aptitude]
The sheet of the second invention of the present invention is excellent in the definition of the ink, and preferably can improve the printability such as the surface strength and the ink receptivity, by having the CNF-containing layer. That is, the CNF-containing layer in the sheet of the present invention can be suitably used as an ink receiving layer. In particular, the sheet of the present invention is suitable for offset printing.

[Oil resistance]
The second sheet of the present invention can develop oil resistance. The oil resistance of the second sheet of the present invention can be evaluated by the oil resistance according to the kit method measured according to the TAPPIUM-557 method. The oil resistance of the sheet of the present invention measured by the above-mentioned kit method is preferably a first grade or more showing that oil resistance is expressed, more preferably a sixth grade or more, and a seventh grade or more Is more preferred. The oil resistance of the sheet of the present invention is considered to be due to the CNF in the CNF-containing layer filling the voids of the paper substrate surface.
The oil resistance according to the above-mentioned kit method that can be used as oil-resistant paper is usually fifth grade or higher.

<Production method of sheet>
Although the manufacturing method of the sheet | seat of 2nd this invention may employ | adopt a well-known manufacturing method, in order to acquire the effect of this invention, the following manufacturing methods are employ | adopted suitably.
That is, the same method as that described in the method for producing the sheet of the first invention can be used, and specifically, the coating step, the drying or semi-drying step, the rewetting step, and the pressure bonding step are sequentially performed. Have
It is a manufacturing method of a sheet whose 75-degree specular glossiness measured based on JIS P 8142: 2005 of the surface by the side of the fine fiber cellulose content layer after the process of pressure-bonding is 50% or more.

As a casting method which is one of the film forming methods for film sheets, (i) a wet casting method in which a coating liquid is applied and pressure-bonded to a casting drum immediately, (ii) coating a coating liquid, drying or semi-coating After drying, after applying the rewetting liquid, rewet casting method of pressing on the cast drum, (iii) Coating liquid coating, gelation is applied after applying gelation agent and gelation The casting method etc. are known. Among these cast methods, it is preferable to adopt (ii) rewet cast method as a method of producing the sheet of the present invention.
In the production of the sheet of the present invention (iii) When the gel cast method is adopted, the coating solution containing CNF is coated, and then the sheet outermost surface is coated with CNF and a binder. It is difficult to develop excellent ink definition. In addition, in the gelation casting method, the coating amount also increases, and for example, it is difficult to thin the sheet by reducing the amount of the CNF-containing layer while obtaining the effects of the present invention. In addition, in (i) the wet casting method, in order to develop excellent ink definition, setting of wet adjustment and conditions is difficult, and there is a possibility that the workability is inferior. On the other hand, (ii) the rewet casting method is relatively easy to adjust wetness, is excellent in productivity, is preferable in achieving the above-mentioned mirror glossiness, and is preferable for producing the sheet of the present invention excellent in ink definition. Preferred. In addition, with the rewet casting method, high smoothness of the CNF-containing layer can be easily realized, and further, thinning of the sheet of the present invention can also be realized.

[Fine fibrous cellulose-containing coating solution]
The fine fibrous cellulose-containing coating solution (hereinafter sometimes referred to simply as "coating solution") may be the same as in the first embodiment, and the content ratio of CNF in the coating solution Is within the above range, CNF and the binder can be retained on the surface of the paper substrate while suppressing the penetration of the coating liquid into the paper substrate while having a viscosity suitable for coating, which is excellent A CNF containing layer can be provided having ink definition.

It is preferable that the said coating liquid is an aqueous dispersion containing CNF mentioned above in description of the sheet | seat of this invention, a binder, and the other component used as needed.
When a styrene-butadiene copolymer is used as a binder, a styrene-butadiene copolymer latex can be contained in the raw material of the coating liquid. The content ratio of the styrene-butadiene copolymer latex in the coating liquid is the preferable mass ratio of the binder content to the CNF content and the preferable content of the binder in the CNF-containing layer described above in the description of the sheet of the present invention It is preferable to adjust so that it may become solid content amount.

[Coating process]
In this step, the coating liquid is applied to at least one surface of the paper substrate such that the amount of CNF-containing layer applied is preferably 5.0 g / m ² or less in terms of solid content. More preferable application amounts of the CNF-containing layer are the same as those described above in the description of the sheet of the present invention. In addition, in the same manner as described above in the description of the sheet of the present invention, the application amount is a total dry mass including other components optionally contained in addition to CNF and a binder, and a paper substrate Amount of CNF-containing layer per side of the
As a coating machine which coats a coating liquid, the thing similar to what was described in the first embodiment can be used.
Also, the drying or semi-drying step, the re-wetting step, and the pressure-bonding step can be the same steps as those described in the first embodiment.

<Use>
The sheet of the present invention and the sheet produced by the production method of the present invention have excellent ink definition and further have high gloss and high smoothness, printability such as surface strength and ink receptivity, oil resistance, etc. Can also have the following characteristics.
Therefore, the sheet of the present invention and the sheet produced by the production method of the present invention are, from the above-mentioned characteristics, wrapping paper, seal, label, box or envelope in the field of packaging and distribution And ink jet printer paper.

Embodiment of Third Invention (Third Embodiment)
The sheet of the present invention has a paper base and a fine fibrous cellulose-containing layer, and the absolute reflection of the fine fibrous cellulose-containing layer side surface in the wavelength range of 380 to 780 nm measured in accordance with JIS Z 8722: 2009. It is characterized in that the ripple amplitude of the rate is 0.10% or more.
That is, the sheet of the present invention has a fine fibrous cellulose-containing layer (hereinafter sometimes 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 In this case, it has a pearly appearance regardless of the pigment.

In order to make the ripple amplitude 0.10% or more, the amount of CNF-containing layer applied, the degree of polymerization of the fine fibrous cellulose, the fine fibrous cellulose contained in the coating liquid for 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, or by appropriately selecting the other manufacturing method conditions such as the coating method.
In the sheet of the present invention, by using a coating solution having a high viscosity to form a CNF-containing layer, fine fibrous cellulose in the coating solution hardly penetrates the paper substrate, and the paper substrate surface The fine fibrous cellulose remains on the surface to develop a pearly appearance. The above-mentioned 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 etc. which is blended according to need.
Here, the “applied 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 the CNF-containing layer is provided on both sides of the paper substrate, the "applied amount" of the CNF-containing layer is the amount per unit area of the CNF-containing layer provided on one side of the paper substrate. Show.

As described above, since the fine fibrous cellulose in the coating liquid hardly penetrates the paper substrate, the CNF-containing layer may not penetrate into the paper substrate in the sheet of the present invention, and the CNF-containing layer A portion of the may penetrate into the paper substrate.
In the sheet of the present invention, when a part of the CNF-containing layer penetrates into the paper base, it is preferable that the penetration of the fine fibrous cellulose into the paper base is small, 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 case described above, in the sheet of the present invention, a part of the CNF-containing layer and a part of the paper substrate, that is, the penetrating part of the CNF-containing layer into the paper substrate are present mutually overlapping.

Further, the sheet of the present invention can also be expected to have effects other than the pearly appearance.
As an effect other than the above-mentioned pearly appearance, it can be mentioned that the surface of the CNF-containing layer is highly smooth and highly smooth to produce specular gloss. When the CNF-containing layer further contains a binder, the CNF-containing layer functions as an ink receiving layer, and the printability of the sheet is developed.
Furthermore, since the pores of the paper substrate surface 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 pearly appearance by using a pearl pigment such as titanium oxide-coated mica or a metal, and the sheet can exhibit a pearlescent appearance on the sheet by the CNF-containing layer regardless of the pigment. Because it can, it is also excellent in recyclability.

[Paper base material]
The paper base material which comprises the sheet | seat of this invention can use the thing similar to what was demonstrated in 1st embodiment. The basis weight of the paper substrate is also not particularly limited, and the preferred range is the same as that of the paper substrate in the first embodiment. If the basis weight of the paper substrate is 15 g / m ² or more, CNF can be captured sufficiently and a pearly appearance can be developed on the sheet, while if the basis weight is 300 g / m ² or less, this The productivity of the inventive sheet can be improved.

[Fine fibrous cellulose-containing layer]
The CNF-containing layer constituting the sheet of the present invention can be provided directly or indirectly on the paper substrate, but it is preferable to provide the CNF-containing layer directly on the paper substrate without any other layer. . Even if the CNF-containing layer is provided directly on the paper substrate, the sheet of the present invention exhibits a pearly appearance because the CNF can stay on the surface of the paper substrate as described above. In the range which does not impair the effect of the present invention, a foundation layer or an aluminum deposition layer may be provided between the paper base and the CNF layer. By providing the base layer and the aluminum deposition layer, an optical interface having a large difference in refractive index is formed, and optical interference due to back surface reflection can be intensified.
The CNF-containing layer may be provided on only one of the 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.
Also, multiple CNF-containing layers may be provided on at least one side of the paper substrate as long as the desired ripple amplitude is obtained. Moreover, the CNF containing layer may be comprised by the several CNF containing layer in the single side | surface of a paper base material.

(Fine fibrous cellulose)
As the fine fibrous cellulose, those similar to those used in the first embodiment and the second embodiment can be used.

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 still more 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, still more preferably 500 or less. If the applied amount of the fine fibrous cellulose is the same, the ripple amplitude of the above-mentioned absolute reflectance tends to increase as the numerical value of the degree of polymerization of the fine fibrous cellulose decreases. However, when the degree of polymerization of the fine fibrous cellulose is too small, it is difficult to adjust the coating liquid to a high viscosity, and there is a possibility that the desired pearly appearance can not be obtained. If the said polymerization degree is in the said range, it is easy to adjust the ripple amplitude of absolute reflectance to 0.10% or more, and it is suitable for expressing the pearly appearance of a sheet | seat.
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. 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 device is selected. It can be adjusted by
Moreover, although the polymerization degree of fine fibrous cellulose can be measured based on Tappi T230, it is specifically, it is as the Example mentioned later.

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

(binder)
The CNF-containing layer can exhibit the property as an ink receiving layer while having a pearl-like appearance by containing a binder.
Examples of the binder include water-soluble polymers and water-insoluble polymers.
Examples of water-soluble polymers include cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose, dextrin, mannan, chitosan, arabinogalactan, glycogen, inulin, pectin, natural polysaccharides such as pectin and hyaluronic acid, and oligomers thereof Examples of the modified body include synthetic water-soluble resins such as polyacrylic acid, polymethacrylic acid, polyethylene glycol, and polyvinyl alcohol.
Examples of water-insoluble polymers include starches purified from natural plants, hydroxyethylated starches, oxidized starches, oxidized starches, etherified starches, phosphated starches, enzyme-modified starches and starches such as cold water-soluble starches obtained by flash-drying them. And modified starches; natural proteins such as gelatin, casein, soy lecithin, collagen etc. and modified products thereof; each water (co) polymers such as styrene-butadiene type, acrylic type, polyvinyl acetate, ethylene-vinyl acetate etc. synthetic water insoluble Resin is illustrated.
The binder may be used in the state of being dissolved in water by heating or pH adjustment, or may be used in the 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, preferred are modified starches, cellulose derivatives, natural proteins, synthetic water-soluble resins, and synthetic water-insoluble resins from the viewpoint of printability such as surface strength of CNF-containing layer, ink receptivity and ink definition. Resins, more preferably oxidized starch, carboxymethyl cellulose, casein, polyvinyl alcohol, and styrene-butadiene copolymer, more preferably styrene-butadiene copolymer.

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 below. The content of the binder in the CNF-containing layer when the CNF-containing layer contains a binder 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. If 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)
In the sheet of the present invention, the application amount of 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, still more preferably It is 0.5 g / m ² or less. Moreover, the application amount of the CNF-containing layer is preferably 0.1 g / m ² or more, more preferably 0.2 g / m ² or more, further preferably 0.3 g / m ² or more, still more preferably 0.4 g / m ² m ² or more. If the application amount of the CNF-containing layer is within the above range, it is easy to adjust the appearance of the sheet to be pearly. From the viewpoint of thinning the sheet, the amount of the CNF-containing layer may be, for example, 0.28 g / m ² or less.

(Amount of CNF in CNF-containing layer)
In the sheet of the present invention, the application amount of CNF 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 It is. Moreover, the application amount of CNF in the CNF-containing layer is preferably 0.1 g / m ² or more, more preferably 0.2 g / m ² or more, and still more preferably 0.3 g / m ² or more. If the application amount of the CNF-containing layer is within the above range, it is easy to adjust the appearance of the sheet to be pearly.
The application amount of CNF in the CNF-containing layer is the dry mass of CNF contained in the CNF-containing layer provided on the paper substrate, and is the application amount per one side of the paper substrate.

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

When the CNF-containing layer contains a binder, the total content of CNF and 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 more Preferably it is 80 mass% or more, and 100 mass% may be sufficient. If 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 receptivity, and definition of ink while the sheet has a pearly appearance.

(Other ingredients)
The CNF-containing layer can contain other components as needed in addition to the CNF and the binder.
The other components are not particularly limited as long as the effects of the present invention are not impaired, but they may be release agents such as microcrystalline wax, wetting agents such as surfactants, colloidal silica, dispersants, antifoams, preservatives, Viscosity modifiers, colorants, lubricants, water resistance agents, etc. may be mentioned. These other components may be used alone or in combination of two or more.
In addition, the sheet of the present invention can contain a pearl pigment within the range not impairing the effects of the present invention, but the content of the pearl pigment in the entire sheet is preferably 10% by mass or less from the viewpoint of recyclability. More preferably, it is 5% by mass or less, still more preferably less than 0.5% by mass, particularly preferably substantially non-containing (ie, 0% by mass).
Examples of the pearl pigment include known pearl pigments such as those obtained by coating the surface of an inorganic substance such as titanium oxide-coated mica and titanium oxide-coated talc with a metal oxide.

[Other layer]
The sheet of the present invention can be provided with a CNF-containing layer on one side or both sides of the paper substrate as described above, but it has characteristics of high smoothness and high gloss, printability and oil resistance while having a pearly appearance. The CNF-containing layer is preferably the outermost surface from the viewpoint of expression of
In addition, when the CNF-containing layer is provided only on one side of the paper base, the other side of the paper base can be provided with another layer depending on the use of the sheet. The other layer may, for example, be a pressure-sensitive adhesive layer or a release agent layer, and may be a sheet having a so-called label type (also referred to as a sticker or seal type) structure.

[Ripple amplitude]
The sheet of the present invention has an absolute reflectance ripple amplitude of 0.10% or more on the CNF-containing layer side surface in a wavelength range of 380 to 780 nm measured in accordance with JIS Z 8722: 2009. When the ripple amplitude of the absolute reflectance is less than 0.10%, it is difficult for the sheet to have a good pearl appearance. The ripple amplitude of the absolute reflectance is preferably 0.20% or more, more preferably 0.30% or more, further preferably 0.50% or more, and still more preferably 1.00% or more. In order to make the above-mentioned ripple amplitude a preferable range, the amount of CNF-containing layer applied, the degree of polymerization of the fine fibrous cellulose, the fine fibrous cellulose contained in the coating liquid for forming the CNF-containing layer and It is preferable to adjust by appropriately controlling the content ratio of the binder or the like, or by appropriately selecting the other manufacturing method conditions such as the coating method.
The more specific measurement conditions of the ripple amplitude of the said absolute reflectance are as having described in the Example mentioned 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 refractive index at the interface between the CNF layer and the paper substrate can be controlled to an appropriate range, and it can be involved in the occurrence of pearly tone. It is 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 range of 380 to 780 nm measured according to 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 pearly appearance is likely to be developed, and the pearly tone tends to become stronger as the ripple amplitude becomes larger.

In addition, the ripple amplitude of the said absolute reflectance is a value in case the sheet | seat of this invention is not colored by coloring agents, 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 above-mentioned absolute reflectance.
For example, in the case of a colored sheet provided with a CNF-containing layer containing no colorant on a colored paper substrate, the CNF-containing layer side surface in the colored sheet is based on the measured value of the absolute reflectance of the colored paper substrate itself. The ripple amplitude can be determined by subtracting the measured value of the base from the measured value of the absolute reflectance of
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 determined for the same sheet as 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
The arithmetic mean roughness Ra of the third inventive sheet is similar to that described in the second embodiment. That is, arithmetic mean roughness Ra measured based on JISB 0601: 2013 of the CNF containing layer side surface is preferably 100 nm or less. The preferred range is also the same as that described in the second embodiment.

[Glossiness]
In the third sheet of the present invention, the 75 ° specular glossiness measured on the CNF-containing layer side surface in accordance with JIS P 8142: 2005 is preferably 30% or more, more preferably 50% or more, still more preferably 60% or more, still more preferably 70% or more, still more preferably 80% or more, still more preferably 90% or more, still more preferably 95% or more.
The above-mentioned specular gloss is a method such as appropriately controlling the content of each component contained in the coating liquid forming the CNF-containing layer, and appropriately selecting the other manufacturing method conditions such as the coating method, etc. It can be adjusted more. Thus, the sheet of the present invention can be expected to have a pearlescent appearance while producing a specular gloss represented by the above specific specular gloss.

[Printing aptitude]
In the third sheet of the present invention, when the CNF-containing layer further contains a binder as described above, it becomes possible to express printability such as surface strength, ink receptivity and ink definition, and the ink It can be expected to have properties as a receptive layer.
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 definition" is one of the indicators showing the printability, and the difference in the saturation between the printed portion and the unprinted portion, the color of the ink attached to the sheet after printing, and the printed surface Means the vividness of the gloss etc.

[Oil resistance]
The third sheet of the present invention can develop oil resistance. The oil resistance of the third sheet of the present invention can be evaluated by the oil resistance according to 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-mentioned kit method is preferably a first grade or more showing that oil resistance is expressed, more preferably a sixth grade or more, and a seventh grade or more Is more preferred. The oil resistance of the sheet of the present invention is considered to be due to the CNF in the CNF-containing layer filling the voids of the paper substrate surface.
The oil resistance according to the above-mentioned kit method that can be used as oil-resistant paper is usually fifth grade or higher.

[Sheet manufacturing method]
As a method for producing the third sheet of the present invention, the same method as that described in the second embodiment can be used. That is, it is a manufacturing method of a sheet which has a coating process, a drying or semi-drying process, a rewetting process, and a pressure bonding process one by one. The casting method is also the same as the method described in the second embodiment.

[Fine fibrous cellulose-containing coating solution]
As the fine fibrous cellulose-containing coating solution (hereinafter sometimes referred to simply as "coating solution"), the same one as in the first embodiment can be used, and the content ratio of CNF in the coating solution If it is in the above-mentioned range, the penetration of fine fibrous cellulose into the paper base material can be suppressed to be retained on the surface while having a viscosity suitable for coating, and the sheet can be provided even with a small amount of application. In addition, the CNF-containing layer is likely to realize high smoothness and high gloss.

The coating liquid preferably further contains a binder from the viewpoint of imparting printability to the CNF-containing layer, and may contain other components used as needed.
When a styrene-butadiene copolymer is used as a binder, a 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 to at least one surface of the paper substrate such that the amount of CNF-containing layer applied is preferably 5.0 g / m ² or less in terms of solid content. More preferable application amounts of the CNF-containing layer are the same as those described above in the description of the sheet of the present invention. In addition, in the same manner as described above in the description of the sheet of the present invention, the application amount is a total dry mass including other components optionally contained in addition to CNF and a binder, and a paper substrate Amount of CNF-containing layer per side of the
As a coating machine which coats a coating liquid, the thing similar to what was described in the first embodiment can be used. Also, the drying or semi-drying step, the re-wetting step, and the pressure-bonding step can be the same steps as those described in the first embodiment.

[Use]
Since the sheet of the present invention has a pearl appearance, it is suitable for applications requiring a design such as wrapping paper.
Furthermore, the sheet of the present invention may have properties such as printability such as high gloss and high smoothness, surface strength, ink receptivity and ink definition, and oil resistance while having a pearly appearance.
Therefore, the sheet of the present invention can be used for wrapping paper, seals, labels, boxes and envelopes in the field of packaging and distribution, food wrapping paper and containers containing fat and oil components, paper for inkjet printers, etc. .

[1] Hereinafter, the first invention will be specifically described by way of examples and comparative examples, but the first invention is not limited thereto.
In Examples of the first invention, the second invention, and the third invention and the comparative examples below, "part" means "part by mass" unless otherwise specified.

<Paper base>
The following paper substrates A and B were used in each example and comparative example.
Paper base material A: Glossy paper (basis weight 30 g / m ² )
Paper base material B: high quality paper (basis weight 64 g / m ² )

<Fine fibrous cellulose>
The fine fibrous cellulose used in each Example and Comparative Example was one produced according to the following production example.
[Production example]
(Preparation of phosphate group introduced cellulose fiber)
As raw material pulp, soft wood kraft pulp made by Oji Paper Co., Ltd. (solid content 93% by mass, basis weight 208 g / m ^{2 in} sheet form, disintegrated into Canadian standard freeness (CSF) of 700 ml as measured according to JISP 8121) used. The raw material pulp was subjected to a phosphorylation treatment as follows. First, a mixed aqueous solution of ammonium dihydrogen phosphate and urea is added to 100 parts by mass (dry mass) of the above-mentioned raw material pulp to make 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, 150 parts by mass of water The solution was adjusted to obtain a chemical solution impregnated pulp. Next, the chemical-impregnated pulp obtained was heated for 200 seconds with a hot air drier at 165 ° C. to introduce a phosphoric acid group to the cellulose in the pulp to obtain a phosphorylated pulp. Next, the resulting phosphorylated pulp was subjected to a washing treatment. The washing process is performed by repeating the operation of filtering and dewatering the pulp dispersion obtained by pouring 10 L of ion-exchanged water with respect to 100 g (absolute dry mass) of phosphorylated pulp so that the pulp can be uniformly dispersed. went. When the electric conductivity of the filtrate became 100 μS / cm or less, it was regarded as the washing end point. Next, neutralization treatment was performed on the washed phosphorylated pulp as follows. First, after diluting the phosphorylated pulp after washing with 10 L of ion exchanged water, a phosphated pulp slurry having a pH of 12 or more and 13 or less was obtained by gradually adding 1N aqueous sodium hydroxide solution while stirring. . Next, the phosphorylated pulp slurry was dewatered to obtain a phosphorylated pulp subjected to neutralization treatment. Next, the above-mentioned washing treatment was performed on the phosphorylated pulp after the neutralization treatment. The infrared absorption spectrum of the phosphorylated pulp thus obtained was measured using FT-IR. As a result, absorption attributable to phosphate groups was observed at around 1230 cm ^-1 , confirming that phosphate groups were added to the pulp. Moreover, when the obtained phosphorylated pulp was tested and analyzed by an X-ray diffractometer, it was found at two positions of 2θ = 14 ° or more and 17 ° or less and 2θ = 22 or more and 23 ° or less A typical peak was confirmed and confirmed to have cellulose type I crystals.

(Preparation of Fine Fibrous Cellulose Dispersion)
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 at a pressure of 200 MPa with a wet atomization apparatus (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion containing fine fibrous cellulose. It was confirmed by X-ray diffraction that this fine fibrous cellulose maintained cellulose type I crystals. The fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 3 to 5 nm.
In addition, the amount of phosphate groups (the amount of strongly acidic groups) measured by the measurement method described later was 1.45 mmol / g.

[Measurement of phosphate group amount]
The phosphoric acid group content of the fine fibrous cellulose is prepared by diluting the fine fibrous cellulose dispersion containing the fine fibrous cellulose to be treated with ion exchanged water so that the content is 0.2% by mass. The cellulose-containing slurry was treated with an ion exchange resin and then measured by titration with an alkali.
The treatment with the ion exchange resin is carried out by adding 1/10 strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, conditioned) to the above-mentioned fine fibrous cellulose-containing slurry and shaking it for 1 hour It was carried out by pouring on a mesh of 90 μm mesh to separate resin and slurry.
In addition, titration using an alkali is carried out by adding an aqueous solution of 0.1 N sodium hydroxide to the fibrous cellulose-containing slurry after treatment with an ion exchange resin, while adding 50 μL each once for every 30 seconds. This was done by measuring the change in the value of. The amount of phosphate group (mmol / g) is obtained by dividing the amount of alkali (mmol) required in the region corresponding to the first region shown in FIG. 1 among the measurement results by the solid content (g) in the slurry to be titrated. Calculated.

<Production of coated sheet>
Example 1
Using the dispersion obtained by adjusting the concentration of the fine fibrous cellulose dispersion obtained by the above production example as a coating liquid, the application amount (coating amount) of the CNF-containing layer on the glossy surface side of the substrate A by a bar coater It applied so that it might be set to 0.25 g / m < ² > in solid content amount, and it air-dried at 105 degreeC. Water was applied to the sheet in a dry state, and then the sheet was pressure-bonded to a heated mirror drum and dried to obtain a sheet by a rewet cast method.

Example 2
A sheet was obtained in the same manner as in Example 1 except that the solid content of the fine fibrous cellulose was set to 0.5 g / m ² .
[Example 3]
A sheet was obtained in the same manner as Example 1, except that the solid content of the fine fibrous cellulose was changed to 0.8 g / m ² .
Example 4
A sheet was obtained in the same manner as in Example 1 except that the solid content of the fine fibrous cellulose was set to 1.5 g / m ² .

Comparative Example 1
The base material A was used as it was.
Comparative Example 2
A sheet was obtained in the same manner as in Example 1 except that the solid content of the fine fibrous cellulose was changed to 0.2 g / m ² .

[Example 5]
A sheet was obtained in the same manner as in Example 1 except that the substrate B was used.
[Example 6]
A sheet was obtained in the same manner as in Example 5 except that the solid content of the fine fibrous cellulose was set to 0.5 g / m ² .
[Example 7]
A sheet was obtained in the same manner as Example 5, except that the solid content of the fine fibrous cellulose was changed to 0.8 g / m ² .
Comparative Example 3
The base material B was used as it was.

Example 8
The coating solution is prepared by mixing the fine fibrous cellulose dispersion obtained by the above production example with SBR latex (OJ3000F manufactured by JSR Corporation) so that fine fibrous cellulose is 90 parts and SBR is 10 parts. did.
Using the coating solution prepared above, coat with a bar coater on the glossy surface side of the substrate A so that the application amount (coating amount) of the CNF-containing layer is 0.5 g / m ^{2 in} solid content, 105 Blow dry at ° C. Water was applied to the sheet in a dry state, and then the sheet was pressure-bonded to a heated mirror drum and dried to obtain a sheet by a rewet cast method.
[Example 9]
A sheet was obtained in the same manner as in Example 8 except that 80 parts of fine fibrous cellulose and 20 parts of SBR were changed.
[Example 10]
A sheet was obtained in the same manner as in Example 8 except that 70 parts of fine fibrous cellulose and 30 parts of SBR were changed.
[Example 11]
A sheet was obtained in the same manner as in Example 8 except that the amount was changed to 60 parts of fine fibrous cellulose and 40 parts of SBR.

Comparative Example 4
A sheet was obtained in the same manner as in Example 8 except that 50 parts of fine fibrous cellulose and 50 parts of SBR were changed.
Comparative Example 5
A sheet was obtained in the same manner as in Example 8 except that the amount was changed to 40 parts of fine fibrous cellulose and 60 parts of SBR.

<Evaluation method>
The sheets produced in Examples and Comparative Examples were evaluated according to the following evaluation methods.
(1) Smoothness (Ra)
Arithmetic mean roughness Ra (nm) of the coated surface was measured according to JIS B 0601: 2001 using a scanning probe microscope (Multimode 8-HR, manufactured by Bruker AX).
(2) Specular glossiness (75 ° glossiness)
The white paper glossiness of the coated surface (surface on the CNF-containing layer side) at a light incident angle of 75 ° was measured using a gloss meter (manufactured by Murakami Color Research Laboratory) in accordance with JIS P8142: 2005.
(3) Offset printing suitability About the obtained sheet, using RI printing tester (manufactured by Akira Mfg. Co., RI-1), print with test ink (manufactured by T & K TOKA, SD50 red BT-13 for best one paper test) The coating layer strength and the ink fixability were visually evaluated. Evaluation criteria are as follows.
(Coated layer strength)
○: Picking hardly occurs and there is no problem in practical use △: Picking occurs, a level requiring considerable limitation in practical use ×: A large amount of picking occurs, practically unacceptable level (ink receptivity )
○: Ink adheres to the whole sample Δ: Light and dark of the ink is observed, Ink is slightly blurred ×: There is an unprinted portion due to the ink being faded (4) Oil resistance TAPPI UM-557 method (kit According to the method, the oil resistance of the coated surface was measured. An oil resistance of 0 indicates that oil resistance is not expressed, and an oil resistance of 1 or more indicates that oil resistance is expressed. In addition, general oil-resistant paper shows fifth grade or more.

[result]
As is clear from Table 1, the sheets of Examples 1 to 11 obtained by applying the coating liquid containing fine fibrous cellulose and using the rewet casting method have a small amount of CNF-containing layer, It exhibited high smoothness with Ra of 20 nm or less and high glossiness with a specular gloss of 80% or more.
Moreover, the coating liquid which mixed the fine fibrous cellulose dispersion and SBR was coated, and the sheet | seat of Examples 8-11 obtained by the rewet cast method has shown the favorable offset printing aptitude, Applicability is suggested.

[2] Next, the second invention will be described in more detail by way of examples and comparative examples, but the second invention is not limited by these examples.
<Production of coated sheet>
[Example 12]
The CNF dispersion obtained by the above production example and SBR latex (JSR Co., Ltd., OJ3000F) are mixed and coated so that CNF is 90 parts and styrene-butadiene copolymer (SBR) as binder is 10 parts. The solution was prepared.
Using the coating solution prepared above, the application amount of the CNF-containing layer (referred to as “application amount” in Table 2) by the bar coater on the glossy surface side of the paper substrate A is 0.5 g / m ^{2 in} solid content And dried by air at 105.degree. Water was applied to the sheet in a dry state, and then the sheet was pressure-bonded to a heated mirror drum and dried to obtain a sheet by a rewet cast method.
[Example 13]
A sheet was obtained in the same manner as in Example 12 except that 80 parts of CNF and 20 parts of SBR were used.
Example 14
A sheet was obtained in the same manner as in Example 12 except that 70 parts of CNF and 30 parts of SBR were used.
[Example 15]
A sheet was obtained in the same manner as in Example 12 except that CNF was changed to 60 parts and SBR to 40 parts.
[Example 16]
A sheet was obtained in the same manner as in Example 12 except that CNF 50 parts and SBR 50 parts were changed.

[Example 17]
A sheet was obtained in the same manner as in Example 12 except that CNF was changed to 50 parts, and SBR of 10 parts was changed to 50 parts of polyvinyl alcohol (PVA) (manufactured by Kuraray, PVA 105).
[Example 18]
A sheet was obtained in the same manner as in Example 12 except that CNF was changed to 50 parts, and SBR of 10 parts was changed to 50 parts of oxidized starch (Ace A, manufactured by Oji Cornstarch Co., Ltd.).
[Example 19]
A sheet was obtained in the same manner as in Example 12 except that CNF was changed to 50 parts and SBR 10 parts was changed to 50 parts of casein (manufactured by Fonterra, ALACID LACTIC CASEIN).
Example 20
A sheet was obtained in the same manner as in Example 12 except that CNF was changed to 50 parts, and SBR of 10 parts was changed to 50 parts of carboxymethylcellulose (CMC) (Daiichi Kogyo Seiyaku Co., Ltd., Serogen 4H).
[Example 21]
A sheet was obtained in the same manner as in Example 12 except that CNF was changed to 40 parts, and SBR of 10 parts was changed to 60 parts of polyvinyl alcohol (PVA) (manufactured by Kuraray, PVA 105).
[Example 22]
A sheet was obtained in the same manner as in Example 12 except that CNF was changed to 40 parts, and SBR of 10 parts was changed to 60 parts of carboxymethylcellulose (CMC) (Daiichi Kogyo Seiyaku Co., Ltd., Serogen 4H).

Comparative Example 6
Paper substrate A was used as it was.
Comparative Example 7
A sheet was obtained in the same manner as in Example 12 except that 40 parts of CNF and 60 parts of SBR were used.
Comparative Example 8
A sheet was obtained in the same manner as in Example 12 except that CNF was changed to 30 parts and SBR to 70 parts.
Comparative Example 9
A sheet was obtained in the same manner as in Example 12 except that CNF was changed to 20 parts and SBR to 80 parts.

Comparative Example 10
A sheet was obtained in the same manner as in Example 12 except that CNF was changed to 40 parts and SBR 10 parts was changed to 60 parts of oxidized starch (Ace A, manufactured by Oji Cornstarch Co., Ltd.).
Comparative Example 11
A sheet was obtained in the same manner as in Example 12 except that CNF was changed to 40 parts, and SBR was changed to 10 parts casein (manufactured by Fonterra, ALACID LACTIC CASEIN) to 60 parts.
Comparative Example 12
A sheet was obtained in the same manner as in Example 12 except that CNF was changed to 100 parts and SBR to 0 parts.
In addition, in the evaluation of offset printability described later, since the sheet of Comparative Example 12 did not have the ink attached, it was not possible to carry out the evaluation on the ink sharpness and the coated layer strength.

<Evaluation method>
The sheets produced in Examples and Comparative Examples were evaluated according to the following evaluation methods.
(1) Specular glossiness (75 ° glossiness)
The white paper glossiness of the coated surface (surface on the CNF-containing layer side) at a light incident angle of 75 ° was measured using a gloss meter (manufactured by Murakami Color Research Laboratory) in accordance with JIS P8142: 2005.

(2) Offset printing suitability About the obtained sheet, it is printed with the test ink (made by T & K TOKA, SD50 red BT-13 for best one paper test) by RI printing test machine (made by Akira Mfg. Co., RI-1) The ink definition, the strength of the coated layer (surface strength) and the ink receptivity were visually evaluated. Evaluation criteria are as follows.
(Ink definition)
4: The ink is vividly colored, the gloss is good 3: the ink is vividly colored, the gloss is slightly good 2: the ink is vividly colored, but the gloss is somewhat poor 1: the ink is vividly colored, but the gloss is Is not good (coated layer strength (surface strength))
4: Picking does not occur at all, good 3: Picking does not occur almost, and there is no problem in practical use 2: Picking occurs, but practically acceptable level 1: A lot of picking occurs and it is unacceptable in practical use Ink receptivity)
4: Ink adheres to the whole sample 3: Slightness or faintness of the ink is observed 2: Slightness or faintness of the ink is observed 1: The ink does not adhere to the whole sample

(3) Smoothness (Ra)
Arithmetic mean roughness Ra (nm) of the coated surface was measured according to JIS B 0601: 2013, using a scanning probe microscope (manufactured by Bruker AX, Multimode 8-HR), with a cutoff value of 0.08 mm.
(4) Oil Resistance The oil resistance of the coated surface was measured in accordance with the TAPPI UM-557 method (kit method). Oil resistance level 0 indicates that oil resistance is not expressed, and oil resistance level 1 or higher indicates that oil resistance is expressed. In addition, general oil-resistant paper shows fifth grade or more.

 

 

[result]
From Table 2, the sheets of Examples 12 to 22 obtained by mixing and coating CNF and a binder in specific proportions and obtained by the rewet casting method have the requirement that the 75 ° specular glossiness in the present invention is 50% or more. It can be seen that the ink of the present invention can be exhibited by exhibiting excellent ink definition. On the other hand, Comparative Examples 7 to 12 which do not satisfy the above-described specular gloss in the present invention are inferior in ink definition, and Comparative Example 12 which does not contain a binder in the CNF-containing layer does not adhere to ink, and all Comparative Examples It can be seen that the effect of can not be obtained.
Furthermore, from the examples, by controlling the mixing ratio of CNF and binder, offset printability is shown to be well-balanced with ink sharpness, surface strength and ink receptivity, and show high smoothness and oil resistance. It turned out that a sheet could be obtained, suggesting the applicability to practical use.

[3] Next, the third invention will be described in more detail by way of examples and comparative examples, but the third invention is not limited by these examples.
<Paper base>
In each of the examples and the comparative examples, single-glossy paper (basis weight: 30 g / m ² ) was used as the paper substrate.
<Fine fibrous cellulose>
The fine fibrous cellulose used in each Example and Comparative Example was one produced according to the following production example.

Production Example 1
(Preparation of phosphate group introduced cellulose fiber)
A phosphate group-introduced cellulose fiber was produced in the same manner as the production example.

(Preparation of Fine Fibrous Cellulose Dispersion 1)
In the preparation of the phosphate group-introduced cellulose fiber, 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 at a pressure of 200 MPa with a wet atomization apparatus (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion 1 containing fine fibrous cellulose. It was confirmed by X-ray diffraction that this fine fibrous cellulose maintained cellulose type I crystals. The fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 3 to 5 nm.
In addition, the amount of phosphate groups (the amount of strongly acidic groups) measured by the above-mentioned measurement method was 1.45 mmol / g. Moreover, the polymerization degree of the fine fibrous cellulose measured by the measuring method mentioned later was 680.

[Determination 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, the specific viscosity (η _sp ) is measured after measuring the viscosity (referred to as η1) measured by dispersing the fine fibrous cellulose to be measured in the dispersion medium and the blank viscosity (referred to as 00) measured only with the dispersion medium. The intrinsic viscosity ([η]) was measured according to the following formula.
η _SP = (η1 / η0) -1
[Η] = _{sp sp / (} c (1 + 0.28 x _{sp sp} ))
Here, c in the formula indicates the concentration of fine fibrous cellulose at the time of viscosity measurement.
Furthermore, the degree of polymerization (DP) of the fine fibrous cellulose was calculated from the following formula.
DP = 1.75 × [η]
This degree of polymerization is sometimes referred to as "viscosity average degree of polymerization" because it is the average degree of polymerization measured by the viscosity method.

Production Example 2
A 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 in Production Example 1.

[Production Example 3]
A 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 in Production Example 1.

Production Example 4
A 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 in Production Example 1.

<Production of coated sheet>
[Example 23]
Using the dispersion prepared by adjusting the concentration of the fine fibrous cellulose dispersion 1 obtained in the above Production Example 1 as a coating liquid, the amount of the CNF-containing layer applied to the glossy surface side of the paper substrate by a bar coater ) Was applied at a solid content of 0.25 g / m ² and blown dry at 105 ° C. Water was applied to the sheet in a dry state, and then the sheet was pressure-bonded to a heated mirror drum and dried to obtain a sheet by a rewet cast method.

[Example 24]
A sheet was obtained in the same manner as in Example 23, except that the amount of fine fibrous cellulose applied was 0.5 g / m ² .
[Example 25]
A sheet was obtained in the same manner as in Example 23, except that the amount of fine fibrous cellulose applied was 0.8 g / m ² .

[Example 26]
A sheet was obtained in the same manner as in Example 24 except that the fine fibrous cellulose dispersion 2 obtained in the above Production Example 2 was used instead of the fine fibrous cellulose dispersion 1.
[Example 27]
A sheet was obtained in the same manner as in Example 24 except that the fine fibrous cellulose dispersion 3 obtained in the above Production Example 3 was used instead of the fine fibrous cellulose dispersion 1.
[Example 28]
A sheet was obtained in the same manner as in Example 24, except that the fine fibrous cellulose dispersion 4 obtained in the above Production Example 4 was used instead of the fine fibrous cellulose dispersion 1.

[Example 29]
Fine fibrous cellulose dispersion 1 obtained by the above-mentioned Preparation Example 1 and SBR latex (JSR Corporation OJ3000F) so that fine fibrous cellulose is 90 parts and styrene-butadiene copolymer (SBR) is 10 parts ) Were mixed to prepare a coating solution.
Using the coating solution prepared above, coat with a bar coater on the glossy surface side of the paper substrate so that the applied amount (coating amount) of the CNF-containing layer is 0.5 g / m ^{2 in} solid content, 105 Blow dry at ° C. Water was applied to the sheet in a dry state, and then the sheet was pressure-bonded to a heated mirror drum and dried to obtain a sheet by a rewet cast method.
[Example 30]
A sheet was obtained in the same manner as in Example 29, except that 80 parts of fine fibrous cellulose and 20 parts of SBR were changed.
Example 31
A sheet was obtained in the same manner as in Example 29, except that 70 parts of fine fibrous cellulose and 30 parts of SBR were changed.

[Example 32]
A sheet was obtained in the same manner as in Example 31 except that 30 parts of SBR was changed to 30 parts of polyvinyl alcohol (PVA) (manufactured by Kuraray, PVA 105).
[Example 33]
A sheet was obtained in the same manner as in Example 31 except that 30 parts of SBR was changed to 30 parts of oxidized starch (Ace A, manufactured by Oji Cornstarch Co., Ltd.).
[Example 34]
A sheet was obtained in the same manner as Example 31 except that 30 parts of SBR was changed to 30 parts of casein (manufactured by Fonterra, ALACID LACTIC CASEIN).
[Example 35]
A sheet was obtained in the same manner as Example 31 except that 30 parts of SBR was changed to 30 parts of carboxymethylcellulose (CMC) (Daiichi Kogyo Seiyaku Co., Ltd., Serogen 4H).

Comparative Example 13
The paper base was used as it was.
Comparative Example 14
A sheet was obtained in the same manner as in Example 23, except that the amount of CNF-containing layer applied was changed to 1.5 g / m ² .
Comparative Example 15
A sheet was obtained in the same manner as in Example 29 except that CNF 50 parts and SBR 50 parts were changed.
Comparative Example 16
A sheet was obtained in the same manner as in Example 32, except that 50 parts of CNF and 50 parts of PVA were used.
Comparative Example 17
A sheet was obtained in the same manner as in Example 33 except that 50 parts of CNF and 50 parts of oxidized starch were used.
Comparative Example 18
A sheet was obtained in the same manner as in Example 34 except that 50 parts of CNF and 50 parts of casein were used.
Comparative Example 19
A sheet was obtained in the same manner as in Example 35 except that 50 parts of CNF and 50 parts of CMC were used.

<Evaluation method>
The sheets produced in Examples and Comparative Examples were evaluated according to the following evaluation methods. Each evaluation result is shown in Table 3.
(1) Ripple amplitude (%)
According to JIS Z 8722: 2009, using an automatic absolute reflectance measurement system (manufactured by JASCO Corporation, device name: V-770, attached device: ARMN-920), incident angle 5 °, detection angle 0 °, polarizer The absolute reflectance of the coated surface (surface on the CNF-containing layer side) in the wavelength region of 380 to 780 nm was measured under the condition of 45 °. The difference between the maximum reflectance and the minimum reflectance of the measured absolute reflectance was calculated as the ripple amplitude.
(2) Pearl appearance (visual)
The resulting sheet was visually evaluated for the presence or absence of a pearly appearance.
2: Have a pearly appearance 1: Do not have a pearly appearance

(3) Smoothness (Ra)
Using a scanning probe microscope (manufactured by Bruker AX, Multimode 8-HR), the cutoff value is 0.08 mm, and the arithmetic average roughness Ra of the coated surface (surface on the CNF-containing layer side) according to JIS B 0601: 2013 nm) was measured.
(4) Specular glossiness (75 ° glossiness)
The glossiness of the coated surface (surface on the CNF-containing layer side) at a light incident angle of 75 ° was measured using a gloss meter (manufactured by Murakami Color Research Laboratory) in accordance with JIS P8142: 2005.

(5) Offset printing aptitude The coated surface (CNF-containing layer side surface) of the obtained sheet was tested with an RI printing tester (RI-1 manufactured by Akira Mfg. Co., Ltd.) as a test ink (T & K TOKA manufactured by Best One Paper) Printing was carried out using test SD50 red BT-13), and the coating layer strength (surface strength), the ink receptivity, and the ink definition were visually evaluated. Evaluation criteria are as follows.
In Examples 23 to 28 and Comparative Example 14, since the peeling of the CNF-containing layer occurred, the evaluation of the coated layer strength and the ink definition was not performed.

(Coated layer strength (surface strength))
4: Picking does not occur at all, Good 3: Picking does not occur almost, and there is no problem in practical use 2: Picking occurs, but practically acceptable level 1: Many picking occurs, practically unacceptable level (Inking property)
4: Ink adheres to the whole sample 3: Slightness or faintness of ink is observed 2: Slightness or faintness of ink is observed 1: Ink does not adhere to the whole sample (ink sharpness)
4: The ink is vividly colored, the gloss is good 3: the ink is vividly colored, the gloss is slightly good 2: the ink is vividly colored, but the gloss is somewhat poor 1: the ink is vividly colored, but the gloss is Is bad

(6) Oil Resistance The oil resistance of the coated surface (surface on the CNF containing layer side) was measured in accordance with the TAPPI UM-557 method (kit method). Oil resistance level 0 indicates that oil resistance is not expressed, and oil resistance level 1 or higher indicates that oil resistance is expressed. In addition, general oil-resistant paper shows fifth grade or more.

 

 

From Examples 23 to 28, it is understood that by adjusting the application amount of the CNF-containing layer and the polymerization degree of the fine fibrous cellulose, it is possible to obtain a sheet having a pearly appearance regardless of the pigment. Further, from Examples 29 to 35, the sheet containing the binder in the CNF-containing layer showed good offset printability, suggesting the applicability to practical use.

The sheet of the present invention and the sheet produced by the production method of the present invention are used for wrapping paper, boxes and envelopes in the field of packaging and distribution, food wrapping paper and containers containing fat and oil components, ink jet printers, etc. be able to.

Claims (29)

It has a paper base material and a fine fibrous cellulose-containing layer, and the amount of the fine fibrous cellulose-containing layer applied is 2.0 g / m ² or less, according to JIS B 0601: 2001 of the surface of the fine fibrous cellulose-containing layer side. Sheet whose arithmetic mean roughness Ra measured according to is 20 nm or less. It has a paper base material and a fine fibrous cellulose-containing layer, and the fine fibrous cellulose-containing layer contains fine fibrous cellulose and a binder, in accordance with JISP 8142: 2005 of the fine fibrous cellulose-containing layer side surface A sheet whose 75 ° specular gloss to be measured is 50% or more. It has a paper base material and a fine fibrous cellulose-containing layer, and the ripple amplitude of the absolute reflectance in the wavelength range of 380 to 780 nm measured according to JIS Z 8722: 2009 on the surface of the fine fibrous cellulose-containing layer side is 0 .10% or more sheet. The sheet | seat of Claim 1 whose content rate of the fine fibrous cellulose in the said fine fibrous cellulose containing layer is 55 mass% or more. The sheet | seat of Claim 1 or 4 whose 75 degree specular glossiness measured based on JISP8142: 2005 of the said fine fibrous cellulose containing layer side is 30% or more. The sheet | seat of Claim 2 whose arithmetic mean roughness Ra measured based on JISB0601: 2013 of the said fine fibrous cellulose containing layer side surface is 100 nm or less. The sheet according to claim 2 or 6, wherein the amount of the fine fibrous cellulose-containing layer applied is 5.0 g / m ² or less. The sheet according to claim 2, 6 or 7, wherein the binder is at least one selected from the group consisting of modified starch, cellulose derivatives, natural proteins, synthetic water-soluble resins, and synthetic water-insoluble resins. The sheet according to any one of claims 2 and 6 to 8, wherein the binder is a water-insoluble polymer, and the content of the fine fibrous cellulose in the fine fibrous cellulose-containing layer is 45% by mass or more. The binder is a water-insoluble polymer, and the mass ratio b / a of the content b of the binder to the content a of fine fibrous cellulose in the fine fibrous cellulose-containing layer is 5/95 to 55/45. A sheet according to any of claims 2 and 6-9. The sheet according to any one of claims 2 and 6 to 8, wherein the binder is a water-soluble polymer, and the content of the fine fibrous cellulose in the fine fibrous cellulose-containing layer is 35% by mass or more. The binder is a water-soluble polymer, and the mass ratio b / a of the content b of the binder to the content a of fine fibrous cellulose in the fine fibrous cellulose-containing layer is 5/95 to 65/35. A sheet according to any one of claims 2, 6-8 and 11. The sheet according to any one of claims 2 and 6 to 12, wherein the fine fibrous cellulose-containing layer is an ink receiving layer. The sheet according to claim 3, 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 3 or 14, 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 claim 3, 14 or 15, wherein the content of pearl pigment in the whole sheet is 10% by mass or less. The sheet according to any one of claims 3 and 14 to 16, wherein the fine fibrous cellulose-containing layer further contains a binder. The sheet according to claim 17, wherein the fine fibrous cellulose-containing layer is an ink receiving layer. The sheet according to any one of claims 3 and 14 to 18, wherein the content 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 3 and 14 to 19, wherein an arithmetic mean roughness Ra measured according to JIS B 0601: 2013 of the fine fibrous cellulose-containing layer side surface is 100 nm or less. The sheet according to any one of claims 3 and 14 to 20, wherein a 75 ° specular glossiness measured according to JIS P 8142: 2005 of the fine fibrous cellulose-containing layer side is 30% or more. The sheet according to any one of claims 1 to 21, wherein the oil resistance according to the kit method measured according to the TAPPI UM-557 method is a grade 1 or higher. The fine fibrous cellulose-containing coating liquid is applied to at least one surface of the paper substrate so that the amount of the fine fibrous cellulose-containing layer applied is 2.0 g / m ² or less in terms of solid content, and the fine fibers are Providing a cellulose-containing layer,
Drying or semi-drying the fine fibrous cellulose-containing layer,
Rewetting the surface of the fine fibrous cellulose-containing layer with a rewetting liquid;
Pressure-bonding the surface of the fine fibrous cellulose-containing layer with a cast drum,
The manufacturing method of the sheet which has sequentially. The method for producing a sheet according to claim 23, wherein an arithmetic mean roughness Ra measured according to JIS B 0601: 2001 of the fine fibrous cellulose-containing layer side surface after the pressure bonding step is 20 nm or less. A step of applying a coating solution containing fine fibrous cellulose and a binder to at least one surface of a paper substrate to provide a fine fibrous cellulose-containing layer,
Drying or semi-drying the fine fibrous cellulose-containing layer,
Rewetting the surface of the fine fibrous cellulose-containing layer with a rewetting liquid;
Pressure-bonding the surface of the fine fibrous cellulose-containing layer with a cast drum,
Sequentially
A method for producing a sheet having a 75 ° specular gloss of 50% or more measured according to JIS P 8142: 2005 on the fine fibrous cellulose-containing layer side surface after the pressure bonding step. The manufacturing method of the sheet | seat of Claim 25 whose arithmetic mean roughness Ra measured based on JISB0601: 2013 of the fine fibrous cellulose containing layer side surface after the process to pressure-bond is 100 nm or less. The manufacturing method of the sheet | seat of Claim 25 or 26 which coats the said coating liquid so that the provision amount of the said fine fibrous cellulose containing layer will be 5.0 g / m < ² > or less in conversion of solid content. The mass ratio b / a of the content b of the binder to the content a of the fine fibrous cellulose in the coating liquid is 5/95 to 55/45, and the binder is a water-insoluble polymer. 27. The method for producing a sheet according to any one of to 27. The mass ratio b / a of the content b of the binder to the content a of the fine fibrous cellulose in the coating liquid is 5/95 to 65/35, and the binder is a water-soluble polymer. 27. The method for producing a sheet according to any of 27

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