WO2023013632A1

WO2023013632A1 - Laminate, anchoring agent for surface protective layer, anchor sheet, layered sheet, and application thereof

Info

Publication number: WO2023013632A1
Application number: PCT/JP2022/029635
Authority: WO
Inventors: 紅酒井
Original assignee: 王子ホールディングス株式会社
Priority date: 2021-08-02
Filing date: 2022-08-02
Publication date: 2023-02-09
Also published as: JP2023021952A

Abstract

The present invention addresses the problem of providing a laminate having a surface protective layer in which the hardness thereof is sufficiently enhanced. The present invention pertains to a laminate which includes a substrate, a fiber layer, and a surface protective layer in the stated order, and in which the fiber layer contains a fibrous cellulose having a fiber width of not more than 1000 nm, and the contained amount of the fibrous cellulose is 15 mass% or more with respect to the total solid content mass of the fiber layer.

Description

Laminate, anchor agent for surface protective layer, anchor sheet, laminated sheet and its application

The present invention relates to laminates, anchoring agents for surface protective layers, anchor sheets, laminated sheets, and applications thereof.

In recent years, attention has been focused on materials that use reproducible natural fibers due to the growing awareness of the need to replace petroleum resources and the environment. Among natural fibers, fibrous cellulose having a fiber diameter of 10 μm or more and 50 μm or less, particularly wood-derived fibrous cellulose (pulp) has been widely used mainly as paper products.

As fibrous cellulose, fine fibrous cellulose with a fiber diameter of 1 μm or less is also known. Further, development of a sheet containing such fine fibrous cellulose, a hard coat layer containing fine fibrous cellulose, and the like is underway.

For example, Patent Document 1 discloses a resin glass plate including a transparent resin substrate and a hard coat layer formed on the transparent resin substrate, wherein the hard coat layer contains cellulose nanofibers and is a thermosetting silicone polymer. Disclosed is a resin glass plate formed of a material. Patent Document 2 discloses a laminated sheet comprising a substrate and a hard coat layer provided on one surface of the substrate, wherein the hard coat layer contains an active energy ray-curable monomer and nanocellulose. disclosed. Further, Patent Document 3 discloses an antiglare film comprising an antiglare hard coat layer having composite particles and a binder matrix on a transparent substrate, wherein the composite particles are core particles containing at least one type of polymer. and a coating layer composed of micronized cellulose on the surface of the core particles.

Thus, a laminate is known in which a hard coat layer is provided on a base material. In these laminates, it has been studied to incorporate fine fibrous cellulose into the hard coat layer for the purpose of increasing the hardness and scratch resistance of the hard coat layer.

WO2017/195350 JP 2019-81877 A JP 2020-192765 A

As described above, in a laminate in which a surface protective layer such as a hard coat layer is provided on a substrate, the surface protective layer may contain fine fibrous cellulose in order to increase the hardness of the surface protective layer. being considered. However, in conventional laminates, the addition of fine fibrous cellulose sometimes does not sufficiently increase the hardness of the surface protective layer, and further improvement has been expected.

Therefore, in order to solve such problems of the prior art, the present inventors conducted studies with the aim of providing a laminate in which the hardness of the surface protective layer is sufficiently increased. Another object of the present invention is to provide a surface protective layer anchoring agent, an anchor sheet, and a laminate sheet which are used in the production of such a laminate.

Specifically, the present invention has the following configurations.

[1] Having a base material, a fiber layer and a surface protective layer in this order,
The fiber layer contains fibrous cellulose with a fiber width of 1000 nm or less,
A laminate in which the content of fibrous cellulose is 15% by mass or more with respect to the total solid mass of the fiber layer.
[2] The laminate according to [1], wherein the fiber layer and the surface protective layer are directly laminated.
[3] The laminate according to [1] or [2], wherein the fiber layer has a thickness of 50 µm or less.
[4] The laminate according to any one of [1] to [3], wherein the fiber layer has a thickness of 0.1 μm to 25 μm.
[5] The laminate according to any one of [1] to [4], which has a haze of 10% or less.
[6] The laminate according to any one of [1] to [5], wherein the fiber layer includes an adhesion aid and/or a structure derived from the adhesion aid.
[7] The laminate according to [6], wherein the adhesion aid is at least one selected from silane coupling agents and isocyanate compounds.
[8] The laminate according to any one of [1] to [7], wherein the surface protective layer includes an adhesion aid and/or a structure derived from the adhesion aid.
[9] The laminate according to [8], wherein the adhesion aid is at least one selected from silane coupling agents and isocyanate compounds.
[10] The laminate according to any one of [1] to [9], wherein the pencil hardness of the surface on the surface protective layer side of the laminate is 2H or more.
[11] For pencil hardness 6B = 1, 5B = 2, 4B = 3, 3B = 4, 2B = 5, B = 6, HB = 7, F = 8, H = 9, 2H = 10, 3H = 11, Numerical values are assigned as 4H = 12, 5H = 13, 6H = 14, 7H = 15, 8H = 16, and 9H = 17. When Q is the numerical value of the pencil hardness of the surface on the side of the surface protective layer in the control laminate obtained by directly laminating the protective layer,
The laminate according to any one of [1] to [10], wherein PQ≧1.
[12] The laminate according to any one of [1] to [11], wherein the surface of the fiber layer has a pencil hardness of F or higher.
[13] The laminate according to any one of [1] to [12], wherein the fibrous cellulose has an ionic substituent.

[14] An anchoring agent for a surface protective layer, containing fibrous cellulose with a fiber width of 1000 nm or less.
[15] An anchor sheet for surface protection layer lamination, containing fibrous cellulose having a fiber width of 1000 nm or less, wherein the content of the fibrous cellulose is 15% by mass or more relative to the total solid mass of the anchor sheet.
[16] The anchor sheet of [15], which has a thickness of 50 µm or less.
[17] The anchor sheet of [15] or [16], which has a thickness of 0.1 μm to 25 μm.
[18] The anchor sheet according to any one of [15] to [17], whose surface has a pencil hardness of F or higher.

[19] comprising a substrate and a fibrous layer;
The fiber layer contains fibrous cellulose with a fiber width of 1000 nm or less,
A laminated sheet in which the content of fibrous cellulose is 15% by mass or more relative to the total solid mass of the fiber layer.
[20] The laminated sheet of [19], wherein the fiber layer has a thickness of 50 µm or less.
[21] The laminated sheet of [19] or [20], wherein the fiber layer has a thickness of 0.1 to 25 μm.
[22] The laminated sheet according to any one of [19] to [21], wherein the surface of the fiber layer has a pencil hardness of F or higher.
[23] The laminated sheet according to any one of [19] to [22], which is for laminating a surface protective layer.
[24] comprising a substrate and a fibrous layer;
The fiber layer contains fibrous cellulose with a fiber width of 1000 nm or less,
The content of fibrous cellulose is 15% by mass or more with respect to the total solid mass of the fiber layer,
A laminated sheet for laminating a surface protective layer.

[i] A surface protective agent containing fibrous cellulose with a fiber width of 1000 nm or less.
[ii] A sheet containing fibrous cellulose with a fiber width of 1000 nm or less,
A sheet for surface protection, wherein the content of fibrous cellulose is 15% by mass or more relative to the total solid mass of the sheet.
[iii] The surface protection sheet according to [ii], which has a thickness of 50 µm or less.
[iv] The surface protection sheet according to [ii] or [iii], which has a thickness of 0.1 to 25 μm.
[v] The surface protection sheet according to any one of [ii] to [iv], having a pencil hardness of F or higher on the surface.

(A) A method for producing an anchor sheet provided under a surface protective layer, comprising mixing fibrous cellulose with a fiber width of 1000 nm or less.
(B) Use of fibrous cellulose with a fiber width of 1000 nm or less for manufacturing an anchor sheet provided under the surface protective layer.
(C) Use of an anchor sheet containing fibrous cellulose with a fiber width of 1000 nm or less for protecting the surface of the laminate.
(D) A method for protecting the surface of a laminate, comprising laminating an anchor sheet containing fibrous cellulose with a fiber width of 1000 nm or less under the surface protective layer.
(E) A method for protecting the surface of a laminate, comprising applying an anchoring agent containing fibrous cellulose having a fiber width of 1000 nm or less.

(A') A method for producing a surface protection sheet, comprising mixing fibrous cellulose with a fiber width of 1000 nm or less.
(B') Use of fibrous cellulose with a fiber width of 1000 nm or less for producing a surface protection sheet provided on a substrate.
(C') Use of a sheet containing fibrous cellulose with a fiber width of 1000 nm or less for protecting the surface of the laminate.
(D') A method for protecting the surface of a laminate, comprising laminating a sheet containing fibrous cellulose having a fiber width of 1000 nm or less on a substrate.
(E') A method for protecting the surface of a substrate, comprising applying a surface protecting agent containing fibrous cellulose having a fiber width of 1000 nm or less.

According to the present invention, it is possible to obtain a laminate in which the hardness of the surface protective layer is sufficiently increased.

FIG. 1 is a cross-sectional view illustrating the configuration of the laminate of this embodiment. FIG. 2 is a graph showing the relationship between the amount of dropped NaOH and the pH for a fibrous cellulose-containing slurry having a phosphorous acid group. FIG. 3 is a graph showing the relationship between the dropping amount of NaOH and the pH for a fibrous cellulose-containing slurry having carboxyl groups.

The present invention will be described in detail below. Although the constituent elements described below may be described based on representative embodiments and specific examples, the present invention is not limited to such embodiments. In this specification, the numerical range represented by "-" means a range including the numerical values described before and after "-" as lower and upper limits.

(Laminate)
This embodiment has a substrate, a fiber layer and a surface protective layer in this order, the fiber layer contains fibrous cellulose with a fiber width of 1000 nm or less, and the content of fibrous cellulose is the total solid mass of the fiber layer. It relates to a laminate that is 15% by mass or more with respect to the In this specification, fibrous cellulose having a fiber width of 1000 nm or less is sometimes referred to as fine fibrous cellulose or CNF.

FIG. 1 is a cross-sectional view for explaining the configuration of the laminate of this embodiment. As shown in FIG. 1, the laminate 10 of this embodiment has a substrate 2, a fiber layer 6, and a surface protection layer 8 in this order. In the laminate 10, another layer such as an adhesive layer may be provided between the base material 2 and the fiber layer 6 and between the fiber layer 6 and the surface protective layer 8, and the layers are directly in contact with each other. It may be a laminated configuration. In this embodiment, an adhesive layer may be provided between the base material 2 and the fiber layer 6, but the fiber layer 6 and the surface protective layer 8 are directly laminated in contact with each other. is preferred. No other layer such as an adhesive layer is provided between the fiber layer 6 and the surface protective layer 8, and the fiber layer 6 and the surface protective layer 8 are directly laminated in contact with each other, so that the surface of the surface protective layer 8 Hardness is enhanced more effectively.

Because the laminate of this embodiment has the above configuration, the surface protective layer exhibits excellent hardness. Specifically, compared to a laminate (control laminate) in which a surface protective layer is directly laminated on a substrate, a laminate having a substrate, a fiber layer, and a surface protective layer in this order is used to protect the surface. The pencil hardness of the layer can be increased. Thus, in the present embodiment, the pencil hardness of the surface protective layer can be increased by providing a fiber layer containing a predetermined amount or more of fine fibrous cellulose between the substrate and the surface protective layer. The pencil hardness of the surface protective layer is a value measured according to JIS K 5600-5-4:1999.

The degree of increase in pencil hardness of the surface protective layer is 6B = 1, 5B = 2, 4B = 3, 3B = 4, 2B = 5, B = 6, HB = 7, F = 8, H = 9, 2H with respect to pencil hardness. = 10, 3H = 11, 4H = 12, 5H = 13, 6H = 14, 7H = 15, 8H = 16, 9H = 17. P, when the numerical value of the pencil hardness of the surface on the surface protective layer side in the laminate (control laminate) in which the surface protective layer is formed directly on the base material is Q, when PQ ≥ 1, it is good. It can be determined that there is

The pencil hardness of the surface on the surface protective layer side of the laminate of the present embodiment is preferably 2H or higher, more preferably 3H or higher, and even more preferably 4H or higher. Although the upper limit of the pencil hardness of the surface of the laminate on the surface protection layer side is not particularly limited, it is preferably 9H or less, for example. The pencil hardness of the surface protective layer in the laminate is measured according to JIS K 5600-5-4:1999.

By the way, in the prior art, in order to increase the hardness of a surface protective layer such as a hard coat layer, it has been considered to contain fine fibrous cellulose in the surface protective layer. Since most of the constituent components are hydrophobic, a sufficient amount of fine fibrous cellulose cannot be blended into the surface protective layer, and as a result, there is a problem that the hardness of the surface protective layer cannot be sufficiently increased. rice field. On the other hand, in the present embodiment, instead of blending fine fibrous cellulose in the surface protective layer, a fiber layer containing fine fibrous cellulose is separately provided directly below the surface protective layer, so that the It is possible to increase the hardness of the applied surface protective layer. In the present embodiment, the hardness of the surface protective layer was successfully increased by providing a separate layer (fiber layer) instead of intentionally blending the fine fibrous cellulose into the surface protective layer whose hardness is to be increased. be. Such an effect is exhibited more remarkably when a fiber layer with a relatively high surface hardness is provided on a base material with a relatively low surface hardness, and a surface protective layer is further provided thereon.

The haze of the laminate of this embodiment is preferably 10% or less, more preferably 5% or less, and even more preferably 3% or less. The lower limit of the haze of the laminate is not particularly limited, and may be 0%. The haze of the laminate is a value measured using a haze meter in accordance with JIS K 7136:2000. As the haze meter, for example, HM-150 manufactured by Murakami Color Research Laboratory Co., Ltd. can be used.

The total light transmittance of the laminate of this embodiment is preferably 80% or more, more preferably 85% or more. Here, the total light transmittance of the laminate is a value measured using a haze meter in accordance with JIS K 7361-1:1997. As the haze meter, for example, HM-150 manufactured by Murakami Color Research Laboratory Co., Ltd. can be used.

Although the overall thickness of the laminate is not particularly limited, it is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more. Also, the total thickness of the laminate is preferably 10000 μm or less, more preferably 6000 μm or less, and even more preferably 4000 μm or less. It is preferable to appropriately adjust the thickness of the laminate according to its use. The thickness of the laminate can be measured with a constant pressure thickness gauge (PG-02, manufactured by TECLOCK CORPORATION).

(fiber layer)
The fiber layer contains fibrous cellulose (fine fibrous cellulose) with a fiber width of 1000 nm or less. The content of fine fibrous cellulose in the fiber layer is preferably 15% by mass or more, more preferably 20% by mass or more, and 25% by mass or more relative to the total solid mass of the fiber layer. is more preferred. The upper limit of the content of fine fibrous cellulose in the fiber layer is not particularly limited, and may be 100% by mass. By setting the content of fine fibrous cellulose in the fiber layer within the above range, the hardness of the surface protective layer in the laminate can be increased more effectively.

The thickness of the fiber layer may be 0.01 μm or more, 0.05 μm or more, 0.1 μm or more, 0.3 μm or more, or 0.5 μm or more. 0.7 μm or more, 1 μm or more, 3 μm or more, 5 μm or more, 10 μm or more, or 50 μm or more may be The upper limit of the thickness of the fiber layer may be, for example, 500 µm or less. By setting the thickness of the fiber layer within the above range, the hardness of the surface protective layer in the laminate can be more effectively increased.

On the other hand, the thickness of the fiber layer may be 200 μm or less, 150 μm or less, 100 μm or less, 75 μm or less, or 50 μm or less. Depending on the application of the laminate, the thickness of the fiber layer is preferably 50 μm or less, more preferably 25 μm or less, even more preferably less than 25 μm, and even more preferably 10 μm or less. It is more preferably 5 μm or less. By reducing the thickness of the fiber layer, it is preferably used, for example, for optical members that require flexibility. Also, by reducing the thickness of the fiber layer, yellowing of the laminate can be more effectively suppressed, and the impact resistance of the laminate can be enhanced. The thickness of the fiber layer may be 0.01 μm or more, 0.05 μm or more, or 0.1 μm or more. The thickness of the fiber layer is preferably 0.01 μm to 500 μm, more preferably 0.05 μm to 200 μm, even more preferably 0.1 μm to 150 μm, and particularly preferably 0.1 μm to 25 μm. When used for an optical member or the like that requires flexibility, the thickness of the fiber layer is preferably 0.1 to 150 μm, more preferably 1 to 100 μm, even more preferably 5 to 50 μm, even more preferably 10 to 50 μm. Here, the thickness of the fiber layer constituting the laminate is measured by cutting out a cross section of the laminate with an ultramicrotome UC-7 (JEOL Ltd.) and observing the cross section with an electron microscope, a magnifying glass, or visually. is the value to be

The basis weight of the fiber layer is preferably 1.4 g/m ² or more, more preferably 7 g/m ² or more, even more preferably 10 g/m ² or more. Also, the basis weight of the fiber layer is preferably 300 g/m ² or less, more preferably 250 g/m ² or less, and even more preferably 200 g/m ² or less.

The density of the fiber layer is preferably 1.0 g/cm ³ or higher, more preferably 1.2 g/cm ³ or higher, and even more preferably 1.4 g/cm ³ or higher. Also, the density of the fiber layer is preferably 2.0 g/cm ³ or less, more preferably 1.8 g/cm ³ or less, and even more preferably 1.7 g/cm ³ or less.

The density of the fiber layer is calculated from the basis weight and thickness of the fiber layer. The basis weight of the fiber layer is a value calculated according to the following method after cutting the laminate with an ultramicrotome UC-7 (manufactured by JEOL Ltd.) so that only the fiber layer remains. A fiber layer cut into a size of 50 mm square or more is conditioned at 23° C. and a relative humidity of 50% for 24 hours, then weighed and divided by the area of the cut fiber layer to calculate the basis weight. do. When the fiber layer contains optional components other than fine fibrous cellulose, the density of the fiber layer is the density containing the optional components other than fine fibrous cellulose.

In this embodiment, the fibrous layer is preferably a non-porous layer. Here, that the fiber layer is non-porous means that the density of the entire fiber layer is 1.0 g/cm ³ or more. If the density of the entire fiber layer is 1.0 g/cm ³ or more, it means that the porosity contained in the fiber layer is suppressed to a predetermined value or less, and is distinguished from porous sheets and layers. .
The non-porous fiber layer is also characterized by having a porosity of 15% by volume or less. The porosity of the fiber layer referred to here is simply obtained by the following formula (a).
Formula (a): Porosity (volume%) = {1-B / (M × A × t)} × 100
Here, A is the area of the fiber layer (cm ² ), t is the thickness of the fiber layer (cm), B is the mass of the fiber layer (g), and M is the density of solids constituting the fiber layer.

The pencil hardness of the fiber layer is preferably F or higher, more preferably H or higher, and even more preferably 2H or higher. Moreover, the fiber layer preferably has a pencil hardness of 9H or less. The pencil hardness of the fiber layer is measured according to JIS K 5600-5-4:1999.

<Fine fibrous cellulose>
The fiber layer contains fibrous cellulose with a fiber width of 1000 nm or less. The fiber width of the fibrous cellulose is preferably 100 nm or less, more preferably 50 nm or less, still more preferably 20 nm or less, even more preferably 10 nm or less, and particularly preferably 8 nm or less. . Further, the fiber width of the fibrous cellulose is preferably 2 nm or more. By setting the fiber width of the fibrous cellulose within the above range, the dispersibility of the fibrous cellulose can be more effectively enhanced, and a high-strength and highly transparent fiber layer can be easily obtained.

The fiber width of fibrous cellulose can be measured, for example, by electron microscope observation. The average fiber width of fibrous cellulose is, for example, 1000 nm or less. The average fiber width of the fibrous cellulose is, for example, preferably 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, even more preferably 2 nm or more and 50 nm or less, and 2 nm or more and 20 nm or less. More preferably, it is particularly preferably 2 nm or more and 10 nm or less. By setting the average fiber width of fibrous cellulose to 2 nm or more, it becomes easier to suppress dissolution in water as cellulose molecules. The fibrous cellulose is, for example, single fibrous cellulose.

The average fiber width of fibrous cellulose is measured, for example, using an electron microscope as follows. First, an aqueous suspension of 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 to form a sample for TEM observation. and SEM images of surfaces cast on glass may be observed if they contain wide fibers. Then, an electron microscope image is observed at a magnification of 1,000, 5,000, 10,000, or 50,000 times depending on the width of the fiber to be observed. However, the sample, observation conditions and magnification are adjusted so as to satisfy the following conditions.
(1) A single straight line X is drawn at an arbitrary point in the observed image, and 20 or more fibers intersect the straight line X.
(2) Draw a straight line Y that intersects the straight line perpendicularly in the same image, and 20 or more fibers intersect the straight line Y.
Widths of fibers intersecting the straight lines X and Y are visually read from the observation image satisfying the above conditions. In this way, at least three sets of observed images of surface portions that do not overlap each other are obtained. Then, for each image, the width of the fiber that crosses straight line X and straight line Y is read. This gives at least 20 x 2 x 3 = 120 fiber width readings. Then, the average value of the read fiber widths is taken as the average fiber width of the fibrous cellulose.

Although the fiber length of the fibrous cellulose is not particularly limited, it is preferably 0.1 μm or more and 1000 μm or less, more preferably 0.1 μm or more and 800 μm or less, and further preferably 0.1 μm or more and 600 μm or less. preferable. By setting the fiber length within the above range, destruction of the crystalline regions of the fibrous cellulose can be suppressed. Moreover, it becomes possible to make the slurry viscosity of fibrous cellulose into an appropriate range. The fiber length of fibrous cellulose can be determined by image analysis using, for example, TEM, SEM, and AFM.

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

Although the axial ratio (fiber length/fiber width) of the fibrous cellulose is not particularly limited, it is preferably 20 or more and 10000 or less, more preferably 50 or more and 1000 or less. A sheet containing fine fibrous cellulose can be easily formed by making the axial ratio equal to or higher than the above lower limit. By setting the axial ratio to the above upper limit or less, handling such as dilution becomes easier, for example, when fibrous cellulose is treated as a dispersion liquid, which is preferable.

The fibrous cellulose in this embodiment has, for example, both a crystalline region and an amorphous region. In particular, fine fibrous cellulose having both a crystalline region and an amorphous region and having a high axial ratio is realized by a method for producing fine fibrous cellulose, which will be described later.

The fibrous cellulose preferably has an ionic substituent. When the fibrous cellulose has an ionic substituent, the dispersibility of the fibrous cellulose in the dispersion medium can be improved, and the defibration efficiency in the fibrillation treatment can be increased. The ionic substituents can include, for example, either one or both of an anionic group and a cationic group. In this embodiment, it is particularly preferable to have an anionic group as an ionic substituent. The ionic substituent is preferably a group introduced into fibrous cellulose via an ester bond or an ether bond, more preferably a group introduced into fibrous cellulose via an ester bond. In this case, the ester bond is preferably formed by dehydration condensation between the hydroxyl group of the fibrous cellulose and the compound serving as the ionic substituent.

The anionic group includes, for example, a phosphate group or a substituent derived from a phosphate group (sometimes simply referred to as a phosphate group), a carboxy group or a substituent derived from a carboxy group (sometimes simply referred to as a carboxy group). , a sulfur oxoacid group or a substituent derived from a sulfur oxoacid group (sometimes simply referred to as a sulfur oxoacid group), a xanthate group or a substituent derived from a xanthate group (sometimes simply referred to as a xanthate group), a phosphonic group or A substituent derived from a phosphone group (sometimes simply referred to as a phosphon group), a phosphine group or a substituent derived from a phosphine group (sometimes simply referred to as a phosphine group), a sulfone group or a substituent derived from a sulfone group (sometimes simply referred to as a sulfone group) group), carboxyalkyl group (including carboxymethyl group and carboxyethyl group), and the like. Among them, the anionic group is a phosphate group, a substituent derived from a phosphate group, a carboxy group, a substituent derived from a carboxy group, a carboxyalkyl group, a sulfur oxo acid group, and a substituent derived from a sulfur oxo acid group. It is preferably at least one selected from the group consisting of a phosphorus oxo acid group, a substituent derived from a phosphorus oxo acid group, a carboxy group, a substituent derived from a carboxy group, a sulfur oxo acid group, and a sulfur oxo acid group derived from It is more preferably at least one selected from the group consisting of substituents, and particularly preferably a phosphorous acid group or a substituent derived from a phosphorous acid group. By introducing a phosphorus oxoacid group as an anionic group, the dispersibility of fibrous cellulose can be further enhanced, for example, even under alkaline or acidic conditions, and as a result, a highly rigid and highly transparent fiber layer can be obtained. more likely to be

Examples of cationic groups include ammonium groups, phosphonium groups, and sulfonium groups. Among them, the cationic group is preferably an ammonium group.

A phosphorous acid group or a substituent derived from a phosphorous acid group is, for example, a substituent represented by the following formula (1). A plurality of types of substituents represented by the following formula (1) may be introduced into each fibrous cellulose. In this case, the plural introduced substituents represented by the following formula (1) may be the same or different.

In formula (1), a, b and n are natural numbers, and m is an arbitrary number (where a=b×m). At least one of n α and α' is O 2 ^- , and the rest are R or OR. Note that all of α and α' may be O ^{2 −} . All of the n αs may be the same or different. β ^b+ is a monovalent or higher cation composed of an organic substance or an inorganic substance.

Each R is 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 hydrocarbon group A hydrogen group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or a derivative group thereof. Also, in formula (1), n is preferably 1.

The saturated straight-chain hydrocarbon group includes, but is not particularly limited to, a methyl group, an ethyl group, an n-propyl group, an n-butyl group, and the like. The saturated-branched hydrocarbon group includes i-propyl group, t-butyl group and the like, but is not particularly limited. The saturated cyclic hydrocarbon group includes, but is not particularly limited to, a cyclopentyl group, a cyclohexyl group, and the like. The unsaturated straight-chain hydrocarbon group includes, but is not particularly limited to, a vinyl group, an allyl group, and the like. The unsaturated-branched hydrocarbon group includes i-propenyl group, 3-butenyl group and the like, but is not particularly limited. The unsaturated-cyclic hydrocarbon group includes, but is not limited to, a cyclopentenyl group, a cyclohexenyl group, and the like. The aromatic group includes, but is not particularly limited to, a phenyl group, a naphthyl group, or the like.

In addition, the derivative group in R is selected from functional groups such as carboxy group, carboxylate group (—COO ⁻ ), hydroxy group, amino group and ammonium group for the main chain or side chain of the above various hydrocarbon groups. functional groups to which at least one type is added or substituted, but are not particularly limited. Although the number of carbon atoms constituting the main chain of R is not particularly limited, it is preferably 20 or less, more preferably 10 or less. By setting the number of carbon atoms constituting the main chain of R within the above range, the molecular weight of the phosphorous acid group can be set within an appropriate range, facilitating penetration into the fiber raw material and increasing the yield of fibrous cellulose. can also In addition, when a plurality of R are present in the formula (1) or when a plurality of types of substituents represented by the above formula (1) are introduced into the fibrous cellulose, the plurality of Rs present are the same. There may be or may be different.

β ^b+ is a monovalent or higher cation composed of an organic substance or an inorganic substance. An organic onium ion can be mentioned as a cation having a valence of 1 or more composed of an organic substance. Organic onium ions include, for example, organic ammonium ions and organic phosphonium ions. Examples of organic ammonium ions include aliphatic ammonium ions and aromatic ammonium ions, and examples of organic phosphonium ions include aliphatic phosphonium ions and aromatic phosphonium ions. Examples of monovalent or higher-valent cations composed of inorganic substances include ions of alkali metals such as sodium, potassium, or lithium, ions of divalent metals such as calcium or magnesium, hydrogen ions, and ammonium ions. In addition, when a plurality of β ^b+ are present in the formula (1) or when a plurality of types of substituents represented by the above formula (1) are introduced into the fibrous cellulose, the plurality of β ^b+ are each They may be the same or different. As the cation having a valence of 1 or more composed of an organic substance or an inorganic substance, sodium or potassium ions are preferable, but are not particularly limited, because they do not easily turn yellow when fiber raw materials containing β ^b+ are heated and are easily industrially available. .

More specifically, the phosphoric acid group or the substituent derived from the phosphoric acid group includes a phosphoric acid group (—PO ₃ H ₂ ), a salt of a phosphoric acid group, a phosphorous acid group (phosphonic acid group) (—PO ₂ H ₂ ), salts of phosphite group (phosphonic acid group). In addition, the phosphoric acid group or the substituent derived from the phosphoric acid group includes a condensed phosphoric acid group (e.g., pyrophosphate group), a condensed phosphonic acid group (e.g., polyphosphonic acid group), a phosphoric acid ester group ( For example, it may be a monomethyl phosphate group, a polyoxyethylene alkyl phosphate group), an alkylphosphonic acid group (eg, a methylphosphonic acid group), or the like.

Further, the sulfur oxoacid group (a sulfur oxoacid group or a substituent derived from a sulfur oxoacid group) is, for example, a substituent represented by the following formula (2). A plurality of substituents represented by the following formula (2) may be introduced into each fibrous cellulose. In this case, the plural introduced substituents represented by the following formula (2) may be the same or different.

In the above structural formula, b and n are natural numbers, p is 0 or 1, and m is an arbitrary number (where 1=b×m). In addition, when n is 2 or more, multiple p may be the same number or may be different numbers. In the above structural formula, β ^b+ is a monovalent or higher cation composed of an organic substance or an inorganic substance. An organic onium ion can be mentioned as a cation having a valence of 1 or more composed of an organic substance. Organic onium ions include, for example, organic ammonium ions and organic phosphonium ions. Examples of organic ammonium ions include aliphatic ammonium ions and aromatic ammonium ions, and examples of organic phosphonium ions include aliphatic phosphonium ions and aromatic phosphonium ions. Examples of monovalent or higher-valent cations composed of inorganic substances include ions of alkali metals such as sodium, potassium, or lithium, ions of divalent metals such as calcium or magnesium, hydrogen ions, and ammonium ions. When multiple types of substituents represented by the above formula (2) are introduced into fibrous cellulose, the multiple β ^b+ may be the same or different. As the cation having a valence of 1 or more composed of an organic substance or an inorganic substance, sodium or potassium ions are preferable, but are not particularly limited, because they do not easily turn yellow when fiber raw materials containing β ^b+ are heated and are easily industrially available. .

The amount of the ionic substituent introduced into fibrous cellulose is, for example, preferably 0.05 mmol/g or more, more preferably 0.10 mmol/g or more, more preferably 0.20 mmol per 1 g (mass) of fibrous cellulose. /g or more, more preferably 0.40 mmol/g or more, and particularly preferably 0.60 mmol/g or more. In addition, the amount of the ionic substituent introduced into fibrous cellulose is, for example, preferably 5.20 mmol/g or less, more preferably 3.65 mmol/g or less per 1 g (mass) of fibrous cellulose. 00 mmol/g or less, more preferably 2.50 mmol/g or less, and particularly preferably 2.00 mmol/g or less. Here, the denominator in units of mmol/g indicates the mass of fibrous cellulose when the counter ion of the ionic substituent is hydrogen ion (H ⁺ ). By setting the amount of the ionic substituent to be introduced within the above range, the fiber raw material can be easily made finer, and the stability of the fibrous cellulose can be enhanced. Also, by setting the amount of the ionic substituent to be introduced within the above range, it becomes easier to obtain a laminate having high hardness and high transparency.

The amount of the ionic substituent introduced into fibrous cellulose may be, for example, less than 0.50 mmol/g per 1 g (mass) of fibrous cellulose, may be 0.40 mmol/g or less, or may be 0.40 mmol/g or less. It may be 30 mmol/g or less, 0.25 mmol/g or less, or 0.15 mmol/g or less. The fibrous cellulose in which the content (introduction amount) of the ionic substituent is within the above range may be obtained through, for example, a substituent removal treatment step as described below. That is, the fibrous cellulose contained in the fiber layer may be fibrous cellulose after substituent removal treatment. By using fibrous cellulose after substituent removal treatment as fibrous cellulose, yellowing of the fiber layer and laminate can be more effectively suppressed, and in particular, yellowing in a high-temperature and high-humidity environment can be more effectively prevented. can be effectively suppressed.

The amount of ionic substituents introduced into fibrous cellulose can be measured, for example, by a neutralization titration method. In the measurement by the neutralization titration method, the introduced amount is measured by determining the pH change while adding an alkali such as an aqueous sodium hydroxide solution to the obtained slurry containing the fibrous cellulose.

FIG. 2 is a graph showing the relationship between the pH and the amount of NaOH added to a fibrous cellulose-containing slurry having a phosphorous acid group as an ionic substituent. The amount of phosphorus oxoacid groups introduced into fibrous cellulose is measured, for example, as follows.
First, a slurry containing fibrous cellulose is treated with a strongly acidic ion exchange resin. In addition, before the treatment with the strongly acidic ion exchange resin, a defibration treatment similar to the fibrillation treatment step described below may be performed on the object to be measured, if necessary.
Next, while adding sodium hydroxide aqueous solution, the change in pH is observed to obtain a titration curve as shown in the upper part of FIG. The titration curve shown in the upper part of FIG. 2 plots the measured pH against the amount of alkali added, and the titration curve shown in the lower part of FIG. 2 plots the pH against the amount of alkali added. The increment (differential value) (1/mmol) is plotted. In this neutralization titration, two points where the increment (the differential value of the pH with respect to the amount of alkali dropped) are maximized are confirmed in the curve obtained by plotting the measured pH against the amount of alkali added. Among these, the maximum point of the increment obtained first when the alkali is first added is called the first end point, and the maximum point of the increment obtained next is called the second end point. The amount of alkali required from the start of titration to the first end point is equal to the first dissociated acid amount of fibrous cellulose contained in the slurry used for titration, and the amount of alkali required from the first end point to the second end point The amount is equal to the second dissociated acid amount of fibrous cellulose contained in the slurry used for titration, and the amount of alkali required from the start of titration to the second end point is equal to the amount of fibrous cellulose contained in the slurry used for titration. equal to the total dissociated acid content of A value obtained by dividing the amount of alkali required from the start of titration to the first end point by the solid content (g) in the slurry to be titrated is the amount of phosphorus oxoacid group introduced (mmol/g). In addition, when simply referring to the amount of phosphorus oxoacid groups introduced (or the amount of phosphorus oxoacid groups), it means the amount of the first dissociated acid.
In FIG. 2, the region from the start of titration to the first end point is called the first region, and the region from the first end point to the second end point is called the second region. For example, when the phosphoric acid group is a phosphoric acid group and the phosphoric acid group causes condensation, the weakly acidic group amount (second dissociated acid amount) in the phosphoric acid group is apparently decreased, and the first region The amount of alkali required for the second region is less than the amount of alkali required for the second region. On the other hand, the amount of strongly acidic groups (the amount of first dissociated acid) in the phosphorus oxoacid group coincides with the amount of phosphorus atoms regardless of the presence or absence of condensation. In addition, when the phosphorous acid group is a phosphorous acid group, the weakly acidic group does not exist in the phosphorous acid group, so the amount of alkali required for the second region is reduced, or the amount of alkali required for the second region is may be zero. In this case, the titration curve has one point at which the pH increment is maximum.

In addition, since the denominator of the amount of introduced phosphate groups (mmol/g) indicates the mass of the acid-form fibrous cellulose, the amount of phosphate groups possessed by the acid-form fibrous cellulose (hereinafter referred to as the phosphate group amount (acid form)). On the other hand, when the counter ion of the phosphooxy acid group is substituted with an arbitrary cation C so as to have a charge equivalent, the denominator is converted to the mass of fibrous cellulose when the cation C is the counter ion. Thus, the amount of phosphate groups (hereinafter referred to as the amount of phosphate groups (type C)) possessed by fibrous cellulose whose counter ion is cation C can be determined.
That is, it is calculated by the following formula.
Phosphorus oxo acid group amount (C type) = Phosphorus oxo acid group amount (acid type) / {1 + (W-1) × A / 1000}
A [mmol/g]: Total amount of anions derived from phosphate groups possessed by fibrous cellulose (total dissociated acid amount of phosphate groups)
W: Formula weight per valence of cation C (for example, 23 for Na and 9 for Al)

FIG. 3 is a graph showing the relationship between the amount of dropped NaOH and pH for a dispersion containing fibrous cellulose having a carboxyl group as an ionic substituent. The amount of carboxyl groups introduced into fibrous cellulose is measured, for example, as follows.
First, a dispersion containing fibrous cellulose is treated with a strongly acidic ion exchange resin. In addition, before the treatment with the strongly acidic ion exchange resin, a defibration treatment similar to the fibrillation treatment step described below may be performed on the object to be measured, if necessary.
Next, while adding sodium hydroxide aqueous solution, the change in pH is observed to obtain a titration curve as shown in the upper part of FIG. The titration curve shown in the upper part of FIG. 3 plots the measured pH against the amount of added alkali, and the titration curve shown in the lower part of FIG. 3 plots the pH against the amount of added alkali. The increment (differential value) (1/mmol) is plotted. In this neutralization titration, in the curve plotting the measured pH against the amount of alkali added, one point where the increment (the differential value of pH with respect to the amount of alkali dropped) is maximum was confirmed. 1 end point. Here, the region from the start of titration to the first end point in FIG. 3 is called the first region. The amount of alkali required in the first region is equal to the amount of carboxyl groups in the dispersion used for titration. Then, the amount of alkali (mmol) required in the first region of the titration curve is divided by the solid content (g) in the dispersion containing the fibrous cellulose to be titrated to obtain the amount of carboxyl groups introduced (mmol / g).

In addition, since the denominator of the amount of introduced carboxy groups (mmol/g) is the mass of the acid-type fibrous cellulose, the amount of carboxy groups possessed by the acid-type fibrous cellulose (hereinafter referred to as the amount of carboxy groups (acid-type )). On the other hand, when the counterion of the carboxy group is substituted with an arbitrary cation C so as to have a charge equivalent, the denominator is converted to the mass of fibrous cellulose when the cation C is the counterion. , the amount of carboxy groups (hereinafter referred to as the amount of carboxy groups (C type)) possessed by fibrous cellulose whose counter ion is cation C can be obtained. That is, it is calculated by the following formula.
Carboxy group amount (C type) = carboxy group amount (acid form) / {1 + (W-1) x (carboxy group amount (acid form)) / 1000}
W: Formula weight per valence of cation C (for example, 23 for Na and 9 for Al)

When measuring the amount of ionic substituents by the titration method, if the amount of 1 drop of aqueous sodium hydroxide solution is too large, or if the titration interval is too short, the amount of ionic substituents will be lower than the original value. may not be obtained. As a suitable drop amount and titration interval, for example, it is desirable to titrate 10 to 50 μL of 0.1N sodium hydroxide aqueous solution every 5 to 30 seconds. In order to eliminate the influence of carbon dioxide dissolved in the fibrous cellulose-containing slurry, for example, it is desirable to measure while blowing an inert gas such as nitrogen gas into the slurry from 15 minutes before the start of titration to the end of titration.

The amount of sulfur oxoacid group or sulfone group introduced into fibrous cellulose is determined by wet ashing fibrous cellulose with perchloric acid and concentrated nitric acid, diluting it at an appropriate ratio, and measuring the amount of sulfur by ICP emission spectrometry. can be calculated by The sulfur oxoacid group content or sulfone group content (unit: mmol/g) is obtained by dividing the sulfur content by the absolute dry weight of the fibrous cellulose tested.

The amount of xanthate groups introduced into fibrous cellulose can be measured by the Bredee method as follows. First, 40 mL of a saturated ammonium chloride solution was added to 1.5 parts by mass (absolute dry mass) of fibrous cellulose, mixed well while crushing the sample with a glass rod, and left for about 15 minutes. 25) and wash thoroughly with saturated ammonium chloride solution. Next, the sample is placed in a 500 mL tall beaker together with the GFP filter paper, 50 mL of 0.5 M sodium hydroxide solution (5° C.) is added, stirred, and allowed to stand for 15 minutes. After adding the phenolphthalein solution until the solution turns pink, 1.5 M acetic acid is added and the point at which the solution turns from pink to colorless is taken as the neutralization point. After neutralization, 250 mL of distilled water is added and well stirred, and 10 mL of 1.5 M acetic acid and 10 mL of 0.05 mol/L iodine solution are added using a whole pipette. Then, this solution is titrated with a 0.05 mol/L sodium thiosulfate solution, and the amount of xanthate groups is calculated from the following equation from the titration amount of sodium thiosulfate and the absolute dry mass of fibrous cellulose.
Xanthate group amount (mmol/g) = (0.05 x 10 x 2-0.05 x sodium thiosulfate titer (mL))/1000/absolute dry mass of fibrous cellulose (g)

The amount of cationic groups to be introduced into fibrous cellulose can be calculated by the following formula after performing trace nitrogen analysis.
(Amount of cationic groups) [mmol/g]=(Amount of nitrogen) [g]/14×1000/(Amount of fine fibrous cellulose tested) [g]

<Manufacturing process of fine fibrous cellulose>
<Textile raw material>
Microfibrous cellulose is produced from fibrous raw materials containing cellulose. The fibrous raw material containing cellulose is not particularly limited, but pulp is preferably used because it is readily available and inexpensive. Pulp includes, for example, wood pulp, non-wood pulp, and deinked pulp. Examples of wood pulp include, but are not limited to, hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolving pulp (DP), soda pulp (AP), unbleached kraft pulp (UKP). ) and chemical pulp such as oxygen bleached kraft pulp (OKP), semi-chemical pulp such as semi-chemical pulp (SCP) and chemigroundwood pulp (CGP), groundwood pulp (GP) and thermomechanical pulp (TMP, BCTMP) A mechanical pulp etc. are mentioned. Non-wood pulps include, but are not limited to, cotton-based pulps such as cotton linters and cotton lints, and non-wood-based pulps such as hemp, straw, and bagasse. The deinked pulp is not particularly limited, but includes, for example, deinked pulp made from waste paper. The pulp of this embodiment may be used alone or in combination of two or more. Among the above pulps, wood pulp and deinked pulp are preferred, for example, from the viewpoint of availability. In addition, among wood pulps, the cellulose ratio is high and the yield of fine fibrous cellulose at the time of defibration is high, and the decomposition of cellulose in the pulp is small, and fine fibrous cellulose of long fibers with a large axial ratio can be obtained. From the point of view, for example, chemical pulp is more preferable, and kraft pulp and sulfite pulp are more preferable. The use of fine fibrous cellulose of long fibers with a large axial ratio tends to increase the viscosity.

As fiber raw materials containing cellulose, for example, cellulose contained in sea squirts and bacterial cellulose produced by acetic acid bacteria can be used. Fibers formed by straight-chain nitrogen-containing polysaccharide polymers such as chitin and chitosan can also be used instead of fiber raw materials containing cellulose.

<Phosphorus oxoacid group introduction step>
The process for producing fine fibrous cellulose preferably includes an ionic substituent introduction process, and examples of the ionic substituent introduction process include a phosphorus oxoacid group introduction process. In the phosphorus oxoacid group-introducing step, at least one compound selected from compounds capable of introducing a phosphorus oxoacid group (hereinafter also referred to as "compound A") is added to cellulose by reacting with a hydroxyl group possessed by a fiber raw material containing cellulose. It is a step of acting on a fiber raw material containing. Through this step, the phosphate group-introduced fiber is obtained.

In the phosphorus oxoacid group-introducing step according to the present embodiment, the reaction between the fiber material containing cellulose and compound A is performed in the presence of at least one selected from urea and derivatives thereof (hereinafter also referred to as "compound B"). may On the other hand, the reaction between the cellulose-containing fiber raw material and the compound A may be carried out in the absence of the compound B.

An example of a method of allowing the compound A to act on the fiber raw material in the presence of the compound B is a method of mixing the compound A and the compound B with the fiber raw material in a dry state, a wet state, or a slurry state. Among these, it is preferable to use a fiber raw material in a dry state or a wet state, and it is particularly preferable to use a fiber raw material in a dry state, because the uniformity of the reaction is high. Although the form of the fiber material is not particularly limited, it is preferably in the form of cotton or a thin sheet, for example. The compound A and the compound B can be added to the fiber raw material in the form of a powder, a solution dissolved in a solvent, or a melted state by heating to a melting point or higher. Among these, it is preferable to add in the form of a solution dissolved in a solvent, particularly in the form of an aqueous solution, since the uniformity of the reaction is high. Moreover, the compound A and the compound B may be added simultaneously to the fiber raw material, may be added separately, or may be added as a mixture. The method for adding the compound A and the compound B is not particularly limited, but when the compound A and the compound B are in the form of a solution, the fiber raw material may be immersed in the solution to absorb the liquid and then taken out, or the fiber raw material may be taken out. The solution may be added dropwise to the Further, the necessary amount of compound A and compound B may be added to the fiber raw material, or after adding excessive amounts of compound A and compound B to the fiber raw material, the excess compound A and compound B are removed by pressing or filtering. may be removed.

The compound A used in the present embodiment may be any compound having a phosphorus atom and capable of forming an ester bond with cellulose. Salts, phosphoric anhydride (diphosphorus pentoxide) and the like can be mentioned, but are not particularly limited. Phosphoric acid of various purities can be used, for example, 100% phosphoric acid (orthophosphoric acid) or 85% phosphoric acid can be used. Phosphorous acid includes 99% phosphorous acid (phosphonic acid). Dehydration-condensed phosphoric acid is obtained by condensing two or more molecules of phosphoric acid by dehydration reaction, and examples thereof include pyrophosphoric acid and polyphosphoric acid. Phosphates, phosphites and dehydrated condensed phosphates include lithium salts, sodium salts, potassium salts and ammonium salts of phosphoric acid, phosphorous acid or dehydrated condensed phosphoric acids. It can be a degree of harmony. Among these, the introduction efficiency of the phosphate group is high, the fibrillation efficiency is easily improved in the fibrillation step described later, the cost is low, and it is easy to apply industrially. salt, potassium phosphate, ammonium phosphate or phosphorous acid, sodium phosphite, potassium phosphite, ammonium phosphite, phosphoric acid, sodium dihydrogen phosphate, Disodium hydrogen phosphate, ammonium dihydrogen phosphate, or phosphorous acid, sodium phosphite, sodium hydrogen phosphite are more preferred.

The amount of compound A added to the fiber raw material is not particularly limited. For example, when the amount of compound A added is converted to the phosphorus atomic weight, the amount of phosphorus atoms added to the fiber raw material (absolute dry mass) is 0.5% by mass or more. It is preferably 100% by mass or less, more preferably 1% by mass or more and 50% by mass or less, and even more preferably 2% by mass or more and 30% by mass or less. By setting the amount of phosphorus atoms added to the fiber raw material within the above range, the yield of fine fibrous cellulose can be further improved. On the other hand, by setting the amount of phosphorus atoms added to the fiber raw material to be equal to or less than the above upper limit, it is possible to balance the effect of improving the yield and the cost.

The compound B used in this embodiment is at least one selected from urea and its derivatives as described above. Compound B includes, for example, urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, and 1-ethylurea. From the viewpoint of improving the uniformity of the reaction, compound B is preferably used as an aqueous solution. From the viewpoint of further improving the uniformity of the reaction, it is preferable to use an aqueous solution in which both compound A and compound B are dissolved.

The amount of compound B added to the fiber raw material (absolute dry mass) is not particularly limited, but is preferably 1% by mass or more and 500% by mass or less, more preferably 10% by mass or more and 400% by mass or less, More preferably, it is 100% by mass or more and 350% by mass or less.

In the reaction between the fiber raw material containing cellulose and compound A, in addition to compound B, for example, amides or amines may be included in the reaction system. Examples of amides include formamide, dimethylformamide, acetamide, dimethylacetamide and the like. Examples of amines include methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine and hexamethylenediamine. Among these, triethylamine in particular is known to work as a good reaction catalyst.

In the phosphorus oxoacid group-introducing step, it is preferable to heat-treat the fiber raw material after adding or mixing the compound A or the like to the fiber raw material. As the heat treatment temperature, it is preferable to select a temperature that can efficiently introduce phosphorus oxoacid groups while suppressing thermal decomposition and hydrolysis reaction of the fiber. The heat treatment temperature is, for example, preferably 50° C. or higher and 300° C. or lower, more preferably 100° C. or higher and 250° C. or lower, and even more preferably 130° C. or higher and 200° C. or lower. In addition, for the heat treatment, equipment having various heat media can be used, for example, a stirring dryer, a rotary dryer, a disk dryer, a roll heater, a plate heater, a fluidized bed dryer, and a band dryer. A mold drying device, a filter drying device, a vibrating fluidized drying device, a flash drying device, a vacuum drying device, an infrared heating device, a far infrared heating device, a microwave heating device, and a high frequency drying device can be used.

In the heat treatment according to the present embodiment, for example, the compound A is added to a thin sheet-like fiber raw material by a method such as impregnation, and then heated, or the fiber raw material and the compound A are heated while kneading or stirring with a kneader or the like. method can be adopted. This makes it possible to suppress unevenness in the concentration of the compound A in the fiber raw material, and to more uniformly introduce the phosphorous acid groups to the surface of the cellulose fibers contained in the fiber raw material. This is because when water molecules move to the surface of the fiber material during drying, the dissolved compound A is attracted to the water molecules by surface tension and similarly moves to the surface of the fiber material (that is, the concentration unevenness of the compound A is It is thought that this is due to the fact that it is possible to suppress the occurrence of

In addition, the heating device used for the heat treatment always removes the moisture retained by the slurry and the moisture generated due to the dehydration condensation (phosphorylation) reaction between the compound A and the hydroxyl groups contained in the cellulose etc. in the fiber raw material. It is preferable that the device can be discharged to the outside of the device system. As such a heating device, for example, an air-blowing oven can be used. By constantly draining the water in the device system, it is possible to suppress the hydrolysis reaction of the phosphate ester bond, which is the reverse reaction of phosphorylation, and to suppress the acid hydrolysis of the sugar chains in the fiber. can. Therefore, it is possible to obtain fine fibrous cellulose having a high axial ratio.

The heat treatment time is, for example, preferably 1 second or more and 300 minutes or less, more preferably 1 second or more and 1000 seconds or less, and 10 seconds or more and 800 seconds or less, after water is substantially removed from the fiber raw material. is more preferable. In the present embodiment, the amount of phosphorus oxoacid groups to be introduced can be set within a preferable range by setting the heating temperature and the heating time within appropriate ranges.

The phosphorus oxoacid group-introducing step may be performed at least once, but may be performed repeatedly two or more times. By performing the phosphorus oxoacid group-introducing step two or more times, many phosphorus oxoacid groups can be introduced into the fiber raw material.

The amount of phosphorus oxoacid groups introduced in the step of introducing phosphorus oxoacid groups is, for example, preferably 0.05 mmol/g or more, more preferably 0.10 mmol/g or more, per 1 g (mass) of fine fibrous cellulose. It is more preferably 0.20 mmol/g or more, still more preferably 0.40 mmol/g or more, and particularly preferably 0.60 mmol/g or more. In addition, the amount of phosphorus oxoacid groups introduced in the phosphorus oxoacid group-introducing step is, for example, preferably 5.20 mmol/g or less, more preferably 3.65 mmol/g or less per 1 g (mass) of fine fibrous cellulose. , 3.00 mmol/g or less. By setting the amount of the phosphorus oxoacid group to be introduced within the above range, the fiber raw material can be easily refined, the stability of the fine fibrous cellulose can be enhanced, and a highly rigid and highly transparent laminate can be easily obtained. .

In addition, in the production process of fine fibrous cellulose, when a substituent removal treatment step as described later is provided, the amount of phosphorous acid groups possessed by the finally obtained fine fibrous cellulose is, for example, 1 g of fine fibrous cellulose per (mass) may be less than 0.50 mmol/g, may be 0.40 mmol/g or less, may be 0.30 mmol/g or less, or may be 0.25 mmol/g or less It may be 0.15 mmol/g or less.

<Carboxy Group Introduction Step>
The production process of fine fibrous cellulose may include, for example, a carboxyl group introduction process as an ionic substituent introduction process. In the step of introducing a carboxy group, the fiber raw material containing cellulose is subjected to oxidation treatment such as ozone oxidation, oxidation by the Fenton method, TEMPO oxidation treatment, a compound having a carboxylic acid-derived group or a derivative thereof, or a carboxylic acid-derived group. This is done by treating the compound with an acid anhydride or a derivative thereof.

The compound having a carboxylic acid-derived group is not particularly limited. Examples include tricarboxylic acid compounds. Derivatives of compounds having a carboxylic acid-derived group are not particularly limited, but include, for example, imidized acid anhydrides of compounds having a carboxy group and derivatives of acid anhydrides of compounds having a carboxy group. Examples of imidized acid anhydrides of compounds having a carboxyl group include, but are not particularly limited to, imidized dicarboxylic acid compounds such as maleimide, succinimide and phthalimide.

The acid anhydride of the compound having a group derived from carboxylic acid is not particularly limited. acid anhydrides; In addition, the acid anhydride derivative of the compound having a group derived from carboxylic acid is not particularly limited. Acid anhydrides in which at least some of the hydrogen atoms are substituted with substituents such as alkyl groups and phenyl groups can be mentioned.

In the carboxyl group introduction step, when TEMPO oxidation treatment is performed, it is preferable to perform the treatment under the condition that the pH is 6 or more and 8 or less. Such treatment is also referred to as neutral TEMPO oxidation treatment. Neutral TEMPO oxidation treatment includes, for example, sodium phosphate buffer (pH=6.8), pulp as a fiber raw material, and TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) as a catalyst. This can be done by adding sodium hypochlorite as a nitroxy radical, sacrificial reagent. Furthermore, coexistence of sodium chlorite enables efficient oxidation of aldehydes generated in the process of oxidation to carboxyl groups. Moreover, the TEMPO oxidation treatment may be performed under the condition that the pH is 10 or more and 11 or less. Such treatment is also called alkali TEMPO oxidation treatment. Alkaline TEMPO oxidation treatment can be performed, for example, by adding a nitroxy radical such as TEMPO as a catalyst, sodium bromide as a cocatalyst, and sodium hypochlorite as an oxidizing agent to pulp as a fiber raw material. .

The amount of carboxy groups to be introduced in the carboxy group introduction step varies depending on the type of substituents. For example, when introducing carboxy groups by TEMPO oxidation, the amount should be 0.05 mmol/g or more per 1 g (mass) of fine fibrous cellulose. is preferably 0.10 mmol/g or more, more preferably 0.20 mmol/g or more, even more preferably 0.40 mmol/g or more, and 0.60 mmol/g or more is particularly preferred. In addition, the amount of carboxy groups introduced in the carboxy group introduction step is preferably 2.5 mmol/g or less, more preferably 2.20 mmol/g or less, and further preferably 2.00 mmol/g or less. preferable. In addition, when the substituent is a carboxymethyl group, it may be 5.8 mmol/g or less per 1 g (mass) of fine fibrous cellulose. By setting the amount of carboxyl groups to be introduced within the above range, the fiber raw material can be easily made finer, and the stability of the fibrous cellulose can be enhanced. Also, by setting the amount of carboxyl groups to be introduced within the above range, it becomes easier to obtain a laminate having high hardness and high transparency.

In addition, in the production process of fine fibrous cellulose, when a substituent removal treatment step as described later is provided, the amount of carboxy groups possessed by the finally obtained fine fibrous cellulose is, for example, 1 g of fine fibrous cellulose ( mass) may be less than 0.50 mmol/g, may be 0.40 mmol/g or less, may be 0.30 mmol/g or less, or may be 0.25 mmol/g or less , 0.15 mmol/g or less.

<Sulfur oxoacid group introduction step>
The step of producing fine fibrous cellulose may include, for example, a step of introducing a sulfur oxoacid group as the step of introducing an ionic substituent. In the step of introducing sulfur oxo acid groups, cellulose fibers having sulfur oxo acid groups (sulfur oxo acid group-introduced fibers) can be obtained by reacting hydroxyl groups of the fiber raw material containing cellulose with sulfur oxo acids.

In the sulfur oxoacid group introduction step, in place of compound A in the <phosphorus oxoacid group introduction step> described above, a compound that can introduce a sulfur oxoacid group by reacting with a hydroxyl group possessed by a fiber raw material containing cellulose is selected. At least one compound (hereinafter also referred to as "compound C") is used. Compound C is not particularly limited as long as it has a sulfur atom and is capable of forming an ester bond with cellulose, and includes sulfuric acid or its salts, sulfurous acid or its salts, and sulfate amides. Sulfuric acid of various purities can be used, for example, 96% sulfuric acid (concentrated sulfuric acid) can be used. Sulfurous acid includes 5% sulfurous acid water. Sulfates or sulfites include lithium, sodium, potassium, ammonium salts, etc. of sulfates or sulfites, which can be of varying degrees of neutralization. As the sulfate amide, sulfamic acid or the like can be used. In the sulfur oxoacid group-introducing step, it is preferable to use compound B in the same manner as in <phosphorus oxoacid group-introducing step>.

In the step of introducing sulfur oxo acid groups, it is preferable to heat-treat the cellulose raw material after mixing the cellulose raw material with an aqueous solution containing sulfur oxo acid and urea and/or a urea derivative. As the heat treatment temperature, it is preferable to select a temperature at which sulfur oxoacid groups can be efficiently introduced while suppressing thermal decomposition and hydrolysis reaction of the fiber. The heat treatment temperature is preferably 100° C. or higher, more preferably 120° C. or higher, and even more preferably 150° C. or higher. The heat treatment temperature is preferably 300° C. or lower, more preferably 250° C. or lower, and even more preferably 200° C. or lower.

In the heat treatment step, it is preferable to heat until the water content is substantially gone. For this reason, the heat treatment time varies depending on the amount of water contained in the cellulose raw material, sulfur oxo acid, and the added amount of the aqueous solution containing urea and/or urea derivatives, but for example, 10 seconds or more and 10000 seconds or less. preferably. For the heat treatment, equipment having various heat media can be used, such as hot air dryers, stirring dryers, rotary dryers, disk dryers, roll type heaters, plate type heaters, and fluidized bed dryers. , a band-type drying device, a filter drying device, a vibrating fluidized drying device, a flash drying device, a vacuum drying device, an infrared heating device, a far infrared heating device, a microwave heating device, and a high frequency drying device can be used.

The amount of sulfur oxoacid groups introduced in the step of introducing sulfur oxoacid groups is preferably 0.05 mmol/g or more, more preferably 0.10 mmol/g or more, and 0.20 mmol/g or more. is more preferable, 0.40 mmol/g or more is even more preferable, and 0.60 mmol/g or more is particularly preferable. The amount of sulfur oxo acid groups introduced in the step of introducing sulfur oxo acid groups is preferably 5.00 mmol/g or less, more preferably 3.00 mmol/g or less. By setting the amount of sulfur oxoacid groups to be introduced within the above range, the fiber raw material can be easily refined, and the stability of the fibrous cellulose can be enhanced. Also, by setting the amount of the sulfur oxoacid group to be introduced within the above range, it becomes easier to obtain a laminate having high hardness and high transparency.

In addition, in the production process of fine fibrous cellulose, when a substituent removal treatment step as described later is provided, the amount of sulfur oxo acid groups possessed by the finally obtained fine fibrous cellulose is, for example, per 1 g (mass) may be less than 0.50 mmol/g, may be 0.40 mmol/g or less, may be 0.30 mmol/g or less, or may be 0.25 mmol/g or less; may be 0.15 mmol/g or less.

<Xanthate group introduction step (xanthate esterification step)>
The step of producing fine fibrous cellulose may include a step of introducing a xanthate group as the step of introducing an ionic substituent. In the xanthate group-introducing step, a cellulose fiber having a xanthate group (a xanthate group-introduced fiber) is obtained by substituting a xanthate group represented by the following formula (3) for a hydroxyl group of a fiber raw material containing cellulose.
- OCSS ^- M ⁺ (3)
Here, M ⁺ is at least one selected from hydrogen ions, monovalent metal ions, ammonium ions, and aliphatic or aromatic ammonium ions.

In the xanthate group-introducing step, first, alkali treatment is performed by treating the fiber raw material containing cellulose with an alkali solution to obtain alkali cellulose. Examples of the alkaline solution include an aqueous alkali metal hydroxide solution and an aqueous alkaline earth metal hydroxide solution. Among them, the alkaline solution is preferably an aqueous alkali metal hydroxide solution such as sodium hydroxide or potassium hydroxide, and particularly preferably an aqueous sodium hydroxide solution. When the alkaline solution is an aqueous alkali metal hydroxide solution, the concentration of the alkali metal hydroxide in the aqueous alkali metal hydroxide solution is preferably 4% by mass or more, more preferably 5% by mass or more. Further, the alkali metal hydroxide concentration in the aqueous alkali metal hydroxide solution is preferably 9% by mass or less. By setting the alkali metal hydroxide concentration to the above lower limit or more, cellulose mercerization can be sufficiently advanced, and the amount of by-products generated during the subsequent xanthate formation can be reduced. As a result, The yield of the xanthate group-introduced fiber can be increased. Thereby, the fibrillation process mentioned later can be performed more effectively. In addition, by setting the alkali metal hydroxide concentration to the above upper limit or less, it is possible to suppress the penetration of the aqueous alkali metal hydroxide solution into the crystalline region of cellulose while promoting mercerization. The crystalline structure of the mold is easily maintained, and the yield of fine fibrous cellulose can be further increased.

The duration of the alkali treatment is preferably 30 minutes or longer, more preferably 1 hour or longer. Also, the alkali treatment time is preferably 6 hours or less, more preferably 5 hours or less. By setting the alkali treatment time within the above range, the final yield can be increased and the productivity can be increased.

It is preferable that the alkali cellulose obtained by the above alkali treatment is then subjected to solid-liquid separation to remove as much of the aqueous solution as possible. As a result, the water content during the subsequent xanthate treatment can be reduced, and the reaction can be promoted. As a solid-liquid separation method, a general dehydration method such as centrifugation or filtration can be used. The concentration of the alkali metal hydroxide contained in the alkali cellulose after solid-liquid separation is preferably 3% by mass or more and 8% by mass or less with respect to the total mass of the alkali cellulose after solid-liquid separation.

In the xanthate group-introducing step, the xanthate-forming treatment step is performed after the alkali treatment. In the xanthate treatment step, alkali cellulose is reacted with carbon disulfide (CS ₂ ) to convert (-O ^- Na ⁺ ) groups to (-OCSS ^- Na ⁺ ) groups to obtain xanthate group-introduced fibers. In the above description, the metal ions introduced into the alkali cellulose are represented by Na ⁺ , but similar reactions proceed with other alkali metal ions.

In the xanthate treatment, it is preferable to supply 10% by mass or more of carbon disulfide relative to the absolute dry mass of cellulose in the alkali cellulose. In addition, in the xanthate-forming treatment, the contact time between carbon disulfide and alkali cellulose is preferably 30 minutes or longer, more preferably 1 hour or longer. Xanthate formation proceeds rapidly when carbon disulfide comes into contact with alkali cellulose, but it takes time for carbon disulfide to penetrate into the interior of alkali cellulose, so the reaction time is preferably within the above range. On the other hand, the contact time between the carbon disulfide and the alkali cellulose should be 6 hours or less, whereby the alkali cellulose mass after dehydration is sufficiently permeated, and the reactable xanthate is almost completely formed. can be completed.

The reaction temperature in the xanthate-forming treatment is preferably 46°C or lower. By setting the reaction temperature within the above range, decomposition of alkali cellulose can be easily suppressed. Further, by setting the reaction temperature within the above range, uniform reaction is facilitated, so that the generation of by-products can be suppressed, and furthermore, the removal of the generated xanthate groups can be suppressed.

<Oxidation step with chlorine-based oxidizing agent (second carboxyl group introduction step)>
The step of producing fine fibrous cellulose may include an oxidation step using a chlorine-based oxidizing agent as the step of introducing an ionic substituent. In the oxidation step using a chlorine-based oxidizing agent, a carboxyl group is introduced into the fiber raw material by adding the chlorine-based oxidizing agent to a fiber raw material having hydroxyl groups in a wet or dry state and performing a reaction.

　Chlorine-based oxidizing agents include hypochlorous acid, hypochlorite, chlorous acid, chlorite, chloric acid, chlorate, perchloric acid, perchlorate, and chlorine dioxide. The chlorine-based oxidizing agent is preferably sodium hypochlorite, sodium chlorite, or chlorine dioxide from the viewpoints of introduction efficiency of substituents, defibration efficiency, cost, and ease of handling. When the chlorine-based oxidizing agent is added, it may be added as a reagent (solid or liquid) to the fiber raw material as it is, or it may be dissolved in an appropriate solvent and added.

The concentration of the chlorine-based oxidizing agent in the solution in the oxidation step using the chlorine-based oxidizing agent is preferably 1% by mass or more and 1,000% by mass or less, and is preferably 5% by mass or more and 500% by mass in terms of effective chlorine concentration. It is more preferably 10% by mass or more and 100% by mass or less. The amount of the chlorine-based oxidizing agent added to 100 parts by mass of the fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 10 parts by mass or more and 10,000 parts by mass or less, and 100 parts by mass. It is more preferable that the content is 5,000 parts by mass or more and 5,000 parts by mass or less.

The reaction time with the chlorine-based oxidizing agent in the oxidation step with the chlorine-based oxidizing agent may vary depending on the reaction temperature, but is preferably, for example, 1 minute or more and 1,000 minutes or less, and 10 minutes or more and 500 minutes or less. More preferably, the time is 20 minutes or more and 400 minutes or less. The pH during the reaction is preferably 5 or more and 15 or less, more preferably 7 or more and 14 or less, and even more preferably 9 or more and 13 or less. Moreover, at the start of the reaction, the pH during the reaction is preferably kept constant (for example, pH 11) by appropriately adding hydrochloric acid or sodium hydroxide. After the reaction, excess reaction reagents, by-products and the like may be washed with water and removed by filtration or the like.

<Carboxyalkylation step (third carboxy group introduction step)>
The production process of fine fibrous cellulose may include a carboxyalkylation process as an ionic substituent introduction process. A compound having a reactive group and a carboxyl group (compound E _C ) as an essential component, an alkali compound as an optional component, and a compound B selected from the above-mentioned urea and its derivatives are added to a fiber having a hydroxyl group in a wet or dry state. A carboxyl group is introduced into the fiber raw material by adding it to the raw material and reacting it.

Examples of reactive groups include halogenated alkyl groups, vinyl groups, epoxy groups (glycidyl groups), and the like.
As the compound E _C , monochloroacetic acid, sodium monochloroacetate, 2-chloropropionic acid, 3-chloropropionic acid, and sodium 2-chloropropionate can be used from the viewpoints of introduction efficiency of substituents, and thus fibrillation efficiency, cost, and ease of handling. , sodium 3-chloropropionate is preferred.
Furthermore, as an optional component, it is preferable to use compound B in the same manner as in the above-described <Phosphorus oxoacid group-introducing step>, and the amount added is preferably as described above.

When compound E _C is added, it may be added as a reagent (solid or liquid) to the fiber raw material as it is, or it may be dissolved in an appropriate solvent and added. It is preferable that the fiber raw material is converted to alkali cellulose in advance or is converted to alkali cellulose simultaneously with the reaction. The method of alkali cellulose conversion is as described above.

The temperature during the reaction is, for example, preferably 50°C or higher and 300°C or lower, more preferably 100°C or higher and 250°C or lower, and even more preferably 130°C or higher and 200°C or lower.

The amount of the compound _E to be added to 100 parts by mass of the fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 2 parts by mass or more and 10,000 parts by mass or less, and 5 parts by mass. It is more preferable that the amount is 1,000 parts by mass or less.

The reaction time may vary depending on the reaction temperature, but is preferably, for example, 1 minute or more and 1,000 minutes or less, more preferably 3 minutes or more and 500 minutes or less, and 5 minutes or more and 400 minutes or less. is more preferred. After the reaction, excess reaction reagents, by-products and the like may be washed with water and removed by filtration or the like.

<Phosphonic group or phosphine group introduction step (phosphoalkylation step)>
The step of producing fine fibrous cellulose may include a step of introducing a phosphonic group or a phosphine group (phosphoalkylation step) as the step of introducing an ionic substituent. In the phosphoalkylation step, a compound having a reactive group and a phospho group or a phosphine group (compound E _A ) as an essential component, an alkali compound as an optional component, and a compound B selected from the aforementioned urea and its derivatives are wetted. Alternatively, a phosphonic group or a phosphine group is introduced into the fiber raw material by adding it to the fiber raw material having hydroxyl groups in a dry state and performing a reaction.

Examples of reactive groups include halogenated alkyl groups, vinyl groups, epoxy groups (glycidyl groups), and the like.
Compound _EA includes, for example, vinylphosphonic acid, phenylvinylphosphonic acid, phenylvinylphosphinic acid and the like. Compound _EA is preferably vinylphosphonic acid from the viewpoints of the efficiency of introduction of substituents, the efficiency of fibrillation, the cost, and the ease of handling.
Furthermore, as an optional component, it is preferable to use compound B in the same manner as in the above-described <Phosphorus oxoacid group-introducing step>, and the amount added is preferably as described above.

When compound _EA is added, it may be added as a reagent (solid or liquid) to the fiber raw material as it is, or it may be dissolved in an appropriate solvent and added. It is preferable that the fiber raw material is converted to alkali cellulose in advance or is converted to alkali cellulose simultaneously with the reaction. The method of alkali cellulose conversion is as described above.

The amount of Compound E _A added to 100 parts by mass of the fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 2 parts by mass or more and 10,000 parts by mass or less, and 5 parts by mass. It is more preferable that the amount is 1,000 parts by mass or less.

The reaction time may vary depending on the reaction temperature, but is preferably, for example, 1 minute or more and 1,000 minutes or less, more preferably 10 minutes or more and 500 minutes or less, and 20 minutes or more and 400 minutes or less. is more preferred. After the reaction, excess reaction reagents, by-products and the like may be washed with water and removed by filtration or the like.

<Sulfone group introduction step (sulfoalkylation step) (second sulfone group introduction step)>
The ionic substituent introduction step may include a sulfone group introduction step (sulfoalkylation step). In the sulfoalkylation, a compound (compound E _B ) having a reactive group and a sulfone group as essential components, an alkali compound as an optional component, and a compound B selected from the above-mentioned urea and its derivatives are mixed in a wet or dry state. The sulfone group is introduced into the fiber raw material by reacting with the fiber raw material having a hydroxyl group.

Examples of reactive groups include halogenated alkyl groups, vinyl groups, epoxy groups (glycidyl groups), and the like.
Compound E _B includes sodium 2-chloroethanesulfonate, sodium vinylsulfonate, sodium p-styrenesulfonate, 2-acrylamido-2-methylpropanesulfonic acid and the like. Above all, the compound _EB is preferably sodium vinyl sulfonate from the viewpoints of the efficiency of introduction of substituents, the efficiency of fibrillation, the cost, and the ease of handling.
Furthermore, as an optional component, it is preferable to use compound B in the same manner as in the above-described <Phosphorus oxoacid group-introducing step>, and the amount added is preferably as described above.

When compound _EB is added, it may be added as a reagent (solid or liquid) to the fiber raw material as it is, or it may be dissolved in an appropriate solvent and added. It is preferable that the fiber raw material is converted to alkali cellulose in advance or is converted to alkali cellulose simultaneously with the reaction. The method of alkali cellulose conversion is as described above.

The amount of Compound E _B added to 100 parts by mass of the fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 2 parts by mass or more and 10,000 parts by mass or less, and 5 parts by mass. It is more preferable that the amount is 1,000 parts by mass or less.

The reaction time may vary depending on the reaction temperature, but is preferably, for example, 1 minute or more and 1,000 minutes or less, more preferably 10 minutes or more and 500 minutes or less, and 15 minutes or more and 400 minutes or less. is more preferred. After the reaction, excess reaction reagents, by-products and the like may be washed with water and removed by filtration or the like.

<Cationic group introduction step (cationization step)>
A compound having a reactive group and a cationic group (compound E _D ) as an essential component, an alkali compound as an optional component, and a compound B selected from the above-mentioned urea and its derivatives, in a wet or dry state, having a hydroxyl group Cationic groups are introduced into the fiber raw material by reacting with the fiber raw material.

Examples of reactive groups include halogenated alkyl groups, vinyl groups, epoxy groups (glycidyl groups), and the like.
Cationic groups include an ammonium group, a phosphonium group, a sulfonium group, and the like. Among them, the cationic group is preferably an ammonium group.
As the compound E _D , glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrimethylammonium chloride, and the like are preferable from the viewpoints of introduction efficiency of substituents, defibration efficiency, cost, and ease of handling.
Furthermore, as an optional component, it is also preferable to use compound B in the above-described <Phosphorus oxoacid group-introducing step> in the same manner. It is preferable that the amount to be added is also as described above.

When compound E _D is added, it may be added as it is as a reagent (solid or liquid) to the fiber raw material, or it may be added after being dissolved in an appropriate solvent. It is preferable that the fiber raw material is converted to alkali cellulose in advance or is converted to alkali cellulose simultaneously with the reaction. The method of alkali cellulose conversion is as described above.

The amount of compound E _D added to 100 parts by mass of the fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 2 parts by mass or more and 10,000 parts by mass or less, and 5 parts by mass. It is more preferable that the amount is 1,000 parts by mass or less.

<Washing process>
In the method for producing fine fibrous cellulose according to the present embodiment, the ionic substituent-introduced fiber can be subjected to a washing step, if necessary. The washing step is performed by washing the ionic substituent-introduced fiber with, for example, water or an organic solvent. Further, the washing step may be performed after each step described later, and the number of washings performed in each washing step is not particularly limited.

<Alkali treatment process>
When producing fine fibrous cellulose, the fiber raw material may be subjected to alkali treatment between the ionic substituent introduction step and the fibrillation treatment step described later. The method of alkali treatment is not particularly limited, but includes, for example, a method of immersing the ionic substituent-introduced fiber in an alkali solution.

The alkaline compound contained in the alkaline solution is not particularly limited, and may be an inorganic alkaline compound or an organic alkaline compound. In the present embodiment, it is preferable to use, for example, sodium hydroxide or potassium hydroxide as the alkaline compound because of its high versatility. Moreover, the solvent contained in the alkaline solution may be either water or an organic solvent. Among them, the solvent contained in the alkaline solution is preferably water or a polar solvent including a polar organic solvent exemplified by alcohol, and more preferably an aqueous solvent including at least water. As the alkaline solution, for example, an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution is preferable because of its high versatility.

Although the temperature of the alkaline solution in the alkaline treatment step is not particularly limited, it is preferably, for example, 5°C or higher and 80°C or lower, more preferably 10°C or higher and 60°C or lower. The immersion time of the ionic substituent-introduced fiber in the alkali solution in the alkali treatment step is not particularly limited, but is preferably 5 minutes or more and 30 minutes or less, more preferably 10 minutes or more and 20 minutes or less. The amount of the alkaline solution used in the alkaline treatment is not particularly limited, but for example, it is preferably 100% by mass or more and 100000% by mass or less, and 1000% by mass or more and 10000% by mass with respect to the absolute dry mass of the ionic substituent-introduced fiber. The following are more preferable. When the fibrous cellulose has anionic groups, the alkali treatment may include neutralization and/or ion exchange of the anionic groups. In this case, the temperature of the alkaline solution is preferably room temperature.

In order to reduce the amount of alkaline solution used in the alkali treatment step, the ionic substituent-introduced fiber may be washed with water or an organic solvent after the ionic substituent introduction step and before the alkali treatment step. After the alkali treatment step and before the fibrillation treatment step, it is preferable to wash the alkali-treated ionic substituent-introduced fibers with water or an organic solvent from the viewpoint of improving handleability.

<Acid treatment step>
When producing fine fibrous cellulose, the fiber raw material may be subjected to an acid treatment between the step of introducing an ionic substituent and the later-described fibrillation treatment step. For example, an ionic substituent introduction step, an acid treatment, an alkali treatment and a fibrillation treatment may be performed in this order.

The acid treatment method is not particularly limited, but includes, for example, a method of immersing the fiber raw material in an acidic liquid containing an acid. Although the concentration of the acid liquid used is not particularly limited, it is preferably 10% by mass or less, more preferably 5% by mass or less. Moreover, the pH of the acidic liquid to be used is not particularly limited. Examples of acids contained in the acid solution include inorganic acids, sulfonic acids, and carboxylic acids. Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, phosphoric acid and boric acid. Examples of sulfonic acid include methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid and the like. Carboxylic acids include, for example, formic acid, acetic acid, citric acid, gluconic acid, lactic acid, oxalic acid, and tartaric acid. Among these, it is particularly preferable to use hydrochloric acid or sulfuric acid.

The temperature of the acid solution in the acid treatment is not particularly limited, but is preferably 5°C or higher and 100°C or lower, more preferably 20°C or higher and 90°C or lower. The immersion time in the acid solution in the acid treatment is not particularly limited, but is preferably 5 minutes or more and 120 minutes or less, more preferably 10 minutes or more and 60 minutes or less. The amount of the acid solution used in the acid treatment is not particularly limited. is more preferred. When the fine fibrous cellulose has cationic groups, the acid treatment may include neutralization and/or ion exchange of the cationic groups. In this case, the temperature of the acid solution is preferably room temperature.

<Fibrillation treatment>
By defibrating the ionic substituent-introduced fibers in the fibrillation treatment step, fine fibrous cellulose can be obtained. In the defibration treatment process, for example, a fibrillation treatment device can be used. The fibrillation treatment device is not particularly limited, but for example, a high-speed fibrillator, a grinder (stone mill type pulverizer), a high pressure homogenizer, an ultra-high pressure homogenizer, a high pressure impact type pulverizer, a ball mill, a bead mill, a disk refiner, a conical refiner, and a biaxial refiner. A kneader, a vibration mill, a homomixer under high-speed rotation, an ultrasonic disperser, a beater, or the like can be used. Among the above defibration equipment, it is more preferable to use a high-speed fibrillation machine, a high-pressure homogenizer, and an ultrahigh-pressure homogenizer, which are less affected by the grinding media and less likely to cause contamination.

In the fibrillation treatment step, for example, the ionic substituent-introduced fibers are preferably diluted with a dispersion medium to form a slurry. As the dispersion medium, one or more selected from organic solvents such as water and polar organic solvents can be used. The polar organic solvent is not particularly limited, but alcohols, polyhydric alcohols, ketones, ethers, esters, aprotic polar solvents and the like are preferable. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, isobutyl alcohol and the like. Examples of polyhydric alcohols include ethylene glycol, propylene glycol and glycerin. Ketones include acetone, methyl ethyl ketone (MEK), and the like. Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether and the like. Examples of esters include ethyl acetate and butyl acetate. Aprotic polar solvents include dimethylsulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone (NMP) and the like.

The solid content concentration of fine fibrous cellulose during defibration can be set as appropriate. Further, the slurry obtained by dispersing the ionic substituent-introduced fiber in the dispersion medium may contain a solid content other than the ionic substituent-introduced fiber, such as urea having hydrogen bonding properties.

<Nitrogen removal treatment step>
The step of producing fine fibrous cellulose may further include a step of reducing the amount of nitrogen introduced into the fibrous cellulose and the amount of nitrogen present in the system (nitrogen removal treatment step). By reducing the nitrogen content, it is possible to obtain fine fibrous cellulose that can further suppress coloration. The nitrogen removal treatment step may be provided after the defibration treatment step, but is preferably provided before the fibrillation treatment step.

In the nitrogen removal treatment step, it is preferable to adjust the pH of the slurry containing the ionic substituent-introduced fiber to 10 or higher and perform heat treatment. In the heat treatment, the liquid temperature of the slurry is preferably 50° C. or higher and 100° C. or lower, and the heating time is preferably 15 minutes or longer and 180 minutes or shorter. When adjusting the pH of the slurry containing the ionic substituent-introduced fiber, it is preferable to add an alkali compound that can be used in the alkali treatment step described above to the slurry.

After the nitrogen removal treatment process, the ionic substituent-introduced fiber can be washed if necessary. The washing step is performed by washing the ionic substituent-introduced fiber with, for example, water or an organic solvent. Moreover, the number of washings performed in each washing step is not particularly limited.

<Substituent removal treatment step>
The method for producing fine fibrous cellulose may include a step of removing at least part of the substituent from fine fibrous cellulose having a substituent and having a fiber width of 1000 nm or less. Through such steps, it is possible to obtain fine fibrous cellulose with a small fiber width, although the amount of substituent introduced is low. In this specification, the step of removing at least part of the substituents from the fine fibrous cellulose is also referred to as a substituent removal treatment step.

Examples of the substituent-removing treatment step include a step of heat-treating fine fibrous cellulose having a substituent and a fiber width of 1000 nm or less, an enzyme treatment step, an acid treatment step, and an alkali treatment step. These may be carried out singly or in combination. Among them, the substituent removal treatment step is preferably a heat treatment step or an enzyme treatment step. Through the above treatment step, at least a portion of the substituents are removed from the fine fibrous cellulose having the substituents and a fiber width of 1000 nm or less, for example, the amount of the substituent introduced is less than 0.5 mmol/g. of fine fibrous cellulose can be obtained.

The substituent removal treatment step is preferably performed in a slurry state. That is, in the substituent removal treatment step, a slurry containing fine fibrous cellulose having a substituent and a fiber width of 1000 nm or less is subjected to heat treatment, enzyme treatment, acid treatment, and alkali treatment. etc. is preferable. By carrying out the substituent removal treatment step in a slurry form, it is possible to prevent residual coloring substances caused by heating or the like during the substituent removal treatment, and added or generated acids, alkalis, salts, and the like. Thereby, coloring of a fiber layer or a laminated body can be suppressed. In addition, when the salt derived from the removed substituent is removed after the substituent removal treatment, it is possible to increase the salt removal efficiency.

When a slurry containing fine fibrous cellulose having a substituent and a fiber width of 1000 nm or less is subjected to the substituent removal treatment, the concentration of the fine fibrous cellulose in the slurry is 0.05% by mass or more. It is preferably 0.1% by mass or more, more preferably 0.2% by mass or more. The concentration of fine fibrous cellulose in the slurry is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less. By setting the concentration of the fine fibrous cellulose in the slurry within the above range, the substituent removal treatment can be performed more efficiently. Furthermore, by setting the concentration of the fine fibrous cellulose in the slurry within the above range, it is possible to prevent the residual coloring matter caused by heating during the substituent removal treatment, and the acid, alkali, salt, etc. added or generated. can. Thereby, coloring of a fiber layer or a laminated body can be suppressed. In addition, when the salt derived from the removed substituent is removed after the substituent removal treatment, it is possible to increase the salt removal efficiency.

When the substituent-removing treatment step is a step of heat-treating fine fibrous cellulose having a substituent and a fiber width of 1000 nm or less, the heating temperature in the heat-treating step is preferably 40° C. or higher. , more preferably 50° C. or higher, and even more preferably 60° C. or higher. The heating temperature in the heat treatment step is preferably 250° C. or lower, more preferably 230° C. or lower, and even more preferably 200° C. or lower. Above all, when the substituent of the fine fibrous cellulose to be subjected to the substituent removal treatment step is a phosphorous acid group, the heating temperature in the heat treatment step is preferably 80° C. or higher, more preferably 100° C. or higher. More preferably, it is 120° C. or higher.

When the substituent removal treatment step is a heat treatment step, the heating device that can be used in the heat treatment step is not particularly limited, but hot air heating device, steam heating device, electric heating device, hydrothermal heating device, thermal heating device. , infrared heating device, far infrared heating device, microwave heating device, high frequency heating device, stirring drying device, rotary drying device, disk drying device, roll type heating device, plate type heating device, fluidized bed drying device, band type drying device , a filtration drying apparatus, a vibrating fluidized drying apparatus, a flash drying apparatus, and a vacuum drying apparatus can be used. From the viewpoint of preventing evaporation, the heating is preferably performed in a closed system, and from the viewpoint of increasing the heating temperature, it is preferably performed in a pressure-resistant device or container. The heat treatment may be batch treatment, batch continuous treatment, or continuous treatment.

When the substituent removal treatment step is a step of enzymatically treating fine fibrous cellulose having a substituent and a fiber width of 1000 nm or less, in the enzymatic treatment step, depending on the type of substituent, phosphate ester It is preferable to use a hydrolase, a sulfate ester hydrolase, or the like.

In the enzymatic treatment step, the enzyme is preferably added so that the enzyme activity per 1 g of fine fibrous cellulose is 0.1 nkat or more, more preferably 1.0 nkat or more, and 10 nkat or more. It is more preferable to add the enzyme so that the Further, the enzyme is preferably added so that the enzyme activity is 100,000 nkat or less, more preferably 50,000 nkat or less, and more preferably 10,000 nkat or less, per 1 g of fine fibrous cellulose. More preferred. After adding the enzyme to the fine fibrous cellulose dispersion (slurry), it is preferable to carry out the treatment at a temperature of 0° C. or more and less than 50° C. for 1 minute or more and 100 hours or less.

After the enzymatic reaction, a step of deactivating the enzyme may be provided. As a method for deactivating the enzyme, an acid component or an alkaline component is added to the enzyme-treated slurry to deactivate the enzyme. A method of deactivation can be mentioned.

When the substituent-removing treatment step is a step of acid-treating fine fibrous cellulose having a substituent and a fiber width of 1000 nm or less, the acid-treating step includes acid that can be used in the acid treatment step described above. It is preferred to add the compound to the slurry.

When the substituent-removing treatment step is a step of treating with an alkali fine fibrous cellulose having a substituent and a fiber width of 1000 nm or less, the step of treating with an alkali includes an alkali that can be used in the above-described alkali treatment step. It is preferred to add the compound to the slurry.

In the substituent removal treatment step, it is preferable that the substituent removal reaction proceeds uniformly. In order to proceed the reaction uniformly, for example, the slurry containing fine fibrous cellulose may be stirred, or the specific surface area of the slurry in contact with the heating medium may be increased. As a method for agitating the slurry, a mechanical shear may be applied from the outside, or the self-agitation may be promoted by increasing the feeding speed of the slurry during the reaction.

A spacer molecule may be added in the substituent removal treatment step. Spacer molecules act as spacers to get between adjacent fibrous celluloses, thereby providing fine spaces between the fine fibrous celluloses. By adding such a spacer molecule in the substituent-removing treatment step, aggregation of the fine fibrous cellulose after the substituent-removing treatment can be suppressed. Thereby, the transparency of the fiber layer or laminate can be more effectively improved.

The spacer molecule is preferably a water-soluble organic compound. Examples of water-soluble organic compounds include sugars, water-soluble polymers, and urea. Specifically, trehalose, urea, polyethylene glycol (PEG), polyethylene oxide (PEO), carboxymethylcellulose, polyvinyl alcohol (PVA) and the like can be mentioned. Examples of water-soluble organic compounds include alkyl methacrylate/acrylic acid copolymer, polyvinylpyrrolidone, sodium polyacrylate, propylene glycol, dipropylene glycol, polypropylene glycol, isoprene glycol, hexylene glycol, 1,3-butylene glycol, and polyacrylamide. , xanthan gum, guar gum, tamarind gum, carrageenan, locust bean gum, quince seed, alginic acid, pullulan, carrageenan, pectin, cationic starch, raw starch, oxidized starch, etherified starch, esterified starch, starches such as amylose, glycerin , diglycerin, polyglycerin, hyaluronic acid, and metal salts of hyaluronic acid can also be used.

Also, known pigments can be used as spacer molecules. For example, kaolin (including clay), calcium carbonate, titanium oxide, zinc oxide, amorphous silica (including colloidal silica), aluminum oxide, zeolite, sepiolite, smectite, synthetic smectite, magnesium silicate, magnesium carbonate, magnesium oxide, diatomaceous earth, Examples include styrene plastic pigments, hydrotalcite, urea resin plastic pigments, benzoguanamine plastic pigments, and the like.

<pH adjustment step>
When the above-described substituent-removing treatment step is performed in the form of a slurry, a step of adjusting the pH of the slurry containing fine fibrous cellulose may be provided before the substituent-removing treatment step. For example, when an ionic substituent is introduced into cellulose fibers and the counter ion of this ionic substituent is Na ⁺ , the slurry containing fine fibrous cellulose after fibrillation exhibits weak alkalinity. If heating is performed in this state, monosaccharides, which are one of the coloring factors, may be generated due to decomposition of cellulose, so it is preferable to adjust the pH of the slurry to 8 or less, more preferably 6 or less. preferable. In addition, since monosaccharides may also be generated under acidic conditions, the pH of the slurry is preferably adjusted to 3 or higher, more preferably 4 or higher.

Further, when the fine fibrous cellulose having a substituent is a fine fibrous cellulose having a phosphate group, from the viewpoint of improving the efficiency of removing the substituent, phosphorus of the phosphate group should be in a state of being susceptible to nucleophilic attack. is preferred. Cellulose -OP (=O) (-OH ⁺ ) (-O-Na ⁺ ) with a degree of neutralization of 1 is susceptible to nucleophilic attack. Preferably, the pH of the slurry is adjusted to 3 or more and 8 or less, more preferably 4 or more and 6 or less.

Although the means for adjusting the pH is not particularly limited, for example, an acid component or an alkali component may be added to the slurry containing fine fibrous cellulose. The acid component may be either an inorganic acid or an organic acid. Examples of inorganic acids include sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid. Organic acids include formic acid, acetic acid, citric acid, malic acid, lactic acid, adipic acid, sebacic acid, stearic acid, maleic acid, succinic acid, tartaric acid, fumaric acid, gluconic acid and the like. The alkali component may be an inorganic alkali compound or an organic alkali compound. Examples of inorganic alkali compounds include lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, lithium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, sodium carbonate, and sodium hydrogen carbonate. Organic alkaline compounds include ammonia, hydrazine, methylamine, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, butylamine, diaminoethane, diaminopropane, diaminobutane, diaminopentane, diaminohexane, cyclohexylamine, aniline, tetramethyl ammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide, pyridine, N,N-dimethyl-4-aminopyridine and the like.

In addition, in the pH adjustment step, ion exchange treatment may be performed to adjust the pH. For the ion exchange treatment, a strongly acidic cation exchange resin or a weakly acidic ion exchange resin can be used. By treating with an appropriate amount of cation exchange resin for a sufficient period of time, a slurry containing fine fibrous cellulose at a desired pH can be obtained. Furthermore, in the pH adjustment step, the addition of an acid component or an alkali component and the ion exchange treatment may be combined.

<Salt removal treatment step>
After the substituent-removing treatment step, it is preferable to perform a treatment for removing salts derived from the removed substituents. By removing the salt derived from the substituent, it becomes easier to obtain fine fibrous cellulose capable of suppressing coloration. Although the means for removing the salt derived from the substituent is not particularly limited, washing treatment can be mentioned, for example. The washing treatment is performed, for example, by washing the fine fibrous cellulose aggregated by the substituent removal treatment with water or an organic solvent. From the viewpoint of more effectively suppressing yellowing, the washing treatment is preferably performed by filtration dehydration, centrifugal dehydration, or centrifugation.

<Uniform dispersion treatment step>
After the substituent-removing treatment step, a step of uniformly dispersing the fine fibrous cellulose obtained through the substituent-removing treatment may be provided. By subjecting the fine fibrous cellulose to the substituent-removing treatment, at least a part of the fine fibrous cellulose aggregates. The uniformly dispersing treatment step is a step of uniformly dispersing the aggregated fine fibrous cellulose.

In the uniform dispersion treatment process, for example, high-speed fibrillation machine, grinder (stone mill type crusher), high pressure homogenizer, high pressure collision type crusher, ball mill, bead mill, disc refiner, conical refiner, twin screw kneader, vibration mill, under high speed rotation A homomixer, an ultrasonic disperser, a beater, or the like can be used. Among the uniform dispersion treatment apparatuses, it is more preferable to use a high-speed defibrator and a high-pressure homogenizer.

The treatment conditions in the uniform dispersion treatment step are not particularly limited, but it is preferable to increase the maximum moving speed of the fine fibrous cellulose during treatment and the pressure during treatment. The peripheral speed of the high-speed defibrator is preferably 20 m/sec or higher, more preferably 25 m/sec or higher, and even more preferably 30 m/sec or higher. A high-pressure homogenizer can be used more preferably than a high-speed defibrator because the maximum moving speed of fine fibrous cellulose during treatment and the pressure during treatment are higher. In the high-pressure homogenizer treatment, the pressure during treatment is preferably 1 MPa or higher, more preferably 10 MPa or higher, even more preferably 50 MPa or higher, and particularly preferably 100 MPa or higher. In the high-pressure homogenizer treatment, the pressure during treatment is preferably 350 MPa or less, more preferably 300 MPa or less, and even more preferably 250 MPa or less.

In addition, in the uniform dispersion treatment step, the spacer molecules described above may be newly added. By adding such a spacer molecule in the uniform dispersion treatment step, uniform dispersion of the fine fibrous cellulose can be carried out more smoothly. Thereby, the transparency of the fiber layer or laminate can be more effectively improved.

As described above, a fine fibrous cellulose dispersion for forming a fiber layer is obtained.

<Resin component>
The fiber layer may further contain a resin component in addition to the fine fibrous cellulose described above. The resin component contained in the fiber layer is preferably a hydrophilic polymer or a hydrophilic low-molecular weight compound, and more preferably a hydrophilic polymer component.

Hydrophilic polymers include polyethylene glycol, polyethylene oxide, casein, dextrin, starch, modified starch, polyvinyl alcohol, modified polyvinyl alcohol (such as acetoacetylated polyvinyl alcohol), polyvinyl butyral, polyethylene oxide, polyvinylpyrrolidone, polyvinyl methyl ether, Polyacrylic acid salts, polyacrylamide, acrylic acid alkyl ester copolymers, urethane copolymers, cellulose derivatives (hydroxyethyl cellulose, carboxyethyl cellulose, carboxymethyl cellulose, etc.) and the like can be mentioned. The fiber layer may also contain spacer molecules used in the above-described substituent removal treatment step and the like. Among them, from the viewpoint of improving the transparency of the fiber layer and the laminate, the hydrophilic polymer is preferably polyvinyl alcohol or a cellulose derivative. Moreover, by using a cellulose derivative as the hydrophilic polymer, it is possible to improve the transparency of the fiber layer and the laminate, and more effectively suppress yellowing.

When the fiber layer contains polyvinyl alcohol, the degree of saponification of polyvinyl alcohol is preferably 99.9% or less, more preferably 99% or less, and even more preferably 95% or less. Moreover, the degree of saponification of polyvinyl alcohol is preferably 85% or more. By including polyvinyl alcohol having a degree of saponification within the above range in the fiber layer, the transparency of the fiber layer can be more effectively increased, and as a result, a laminate having higher transparency can be obtained. .

When a cellulose derivative is blended in the fiber layer, the weight-average molecular weight of the cellulose derivative is determined from the viewpoint of forming the fiber layer by suppressing shape stability and gelation as the fiber layer, and high tensile modulus and high tensile elongation. From the ^viewpoint of compatibility of the degree of heat and ^the viewpoint of suppressing yellowing before and after heating, ^the , and preferably 2.8×10 ⁵ or less, more preferably 2.6×10 ⁵ or less. The weight average molecular weight of the cellulose derivative is measured by a gel permeation chromatography method (GPC-MALLS method) using a light scattering method.

The cellulose derivative is preferably a water-soluble cellulose ether from the viewpoint of enhancing affinity with fine fibrous cellulose and from the viewpoint of being easily added to a slurry of fine fibrous cellulose (fine fibrous cellulose dispersion). preferable. Here, being water-soluble means that 1 g or more is dissolved in 100 g of water at 20°C. Cellulose ether is a general term for cellulose derivatives obtained by etherifying the hydroxyl group of cellulose. Preferred examples of water-soluble cellulose ethers include methylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, carboxyethylcellulose and the like. Moreover, the water-soluble cellulose ether is preferably a nonionic water-soluble cellulose ether from the viewpoint of suppressing yellowing of the fiber layer due to heating. Examples of nonionic water-soluble cellulose ethers include methylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose and the like. The nonionic water-soluble cellulose ether preferably has at least one functional group selected from the group consisting of methoxy and hydroxypropoxy groups, more preferably selected from the group consisting of methylcellulose and hydroxypropylmethylcellulose. , and hydroxypropyl methylcellulose are more preferred.

When the cellulose derivative is methylcellulose, the degree of methoxy group substitution is preferably 0.5 or more, more preferably 0.8 or more, still more preferably 1.0 or more, still more preferably 1.2 or more, and particularly preferably It is 1.5 or more, and preferably 3.0 or less, more preferably 2.6 or less, even more preferably 2.2 or less, and even more preferably 2.0 or less.

When the cellulose derivative is hydroxypropylmethylcellulose, the preferred range of the degree of substitution of methoxy groups is the same as the degree of substitution of methoxy groups in methylcellulose described above. The degree of substitution of the hydroxypropoxy group is preferably 0.08 or more, more preferably 0.10 or more, still more preferably 0.12 or more, still more preferably 0.15 or more, and particularly preferably 0.18 or more. Yes, and preferably 0.50 or less, more preferably 0.40 or less, even more preferably 0.35 or less, and even more preferably 0.30 or less.

The weight average molecular weight of the hydrophilic polymer may be 10,000 or more, preferably 50,000 or more, and more preferably 100,000 or more. Also, the weight average molecular weight of the hydrophilic polymer is preferably 8,000,000 or less, more preferably 5,000,000 or less.

Hydrophilic low molecules include glycerin, sorbitol, ethylene glycol, and the like. As used herein, a hydrophilic low molecular weight molecule has a weight average molecular weight of less than 10,000.

The content of the resin component is preferably 5% by mass or more, more preferably 10% by mass, and further preferably 15% by mass or more, based on the total solid mass contained in the fiber layer. It is preferably 20% by mass or more, and particularly preferably 20% by mass or more. In addition, the content of the resin component is preferably 95% by mass or less, more preferably 90% by mass or less, and 80% by mass or less with respect to the total solid mass contained in the fiber layer. is more preferred. By setting the content of the resin component within the above range, it becomes easier to obtain a highly rigid and highly transparent fiber layer and laminate.

<Adhesion aid>
The fibrous layer may optionally contain an adhesion aid and/or a structure derived from the adhesion aid. Examples of adhesion promoters include compounds containing at least one selected from the group consisting of isocyanate groups, carbodiimide groups, epoxy groups, oxazoline groups, amino groups and silanol groups, and organosilicon compounds. Examples of organic silicon compounds include condensates of silane coupling agents and silane coupling agents. Among them, the adhesion aid is preferably at least one selected from silane coupling agents and isocyanate compounds (compounds containing an isocyanate group). When the adhesion aid is a silane coupling agent, the fiber layer contains a structure derived from the silane coupling agent, and when the adhesion aid is an isocyanate compound, the fiber layer contains It contains a structure that

Examples of isocyanate compounds include polyisocyanate compounds and polyfunctional isocyanates. Specific examples of polyisocyanate compounds include aromatic polyisocyanates having 6 to 20 carbon atoms excluding carbon atoms in the NCO group, aliphatic polyisocyanates having 2 to 18 carbon atoms, and 6 to 15 carbon atoms. Alicyclic polyisocyanates, aralkyl polyisocyanates having 8 to 15 carbon atoms, modified products of these polyisocyanates, and mixtures of two or more thereof can be mentioned. Among them, alicyclic polyisocyanates having 6 to 15 carbon atoms, that is, isocyanurates, are preferably used.

Specific examples of alicyclic polyisocyanates include isophorone diisocyanate (IPDI), dicyclohexylmethane-4,4'-diisocyanate (hydrogenated MDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, bis(2-isocyanatoethyl). -4-cyclohexene-1,2-dicarboxylate, 2,5-norbornane diisocyanate, 2,6-norbornane diisocyanate and the like.

The silane coupling agent may have a functional group other than an alkoxysilyl group, or may have no other functional group. Functional groups other than alkoxysilyl groups include vinyl groups, epoxy groups, styryl groups, methacryloxy groups, acryloxy groups, amino groups, ureido groups, mercapto groups, sulfide groups, and isocyanate groups. The silane coupling agent used in this embodiment is preferably a silane coupling agent containing a methacryloxy group.

Specific examples of silane coupling agents having a methacryloxy group in the molecule include methacryloxypropylmethyldimethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropyltriethoxysilane, 1,3-bis(3-methacryloxypropyl)tetramethyldisiloxane and the like. Among them, at least one selected from methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane and 1,3-bis(3-methacryloxypropyl)tetramethyldisiloxane is preferably used. The silane coupling agent preferably contains 3 or more alkoxysilyl groups.

When the fiber layer contains an adhesion aid and/or a structure derived from the adhesion aid, the amount of the adhesion aid added in the manufacturing process of the fiber layer is It is preferably 0.1% by mass or more, more preferably 0.5% by mass or more. Also, the amount of adhesion aid added is preferably 40% by mass or less, more preferably 35% by mass or less, relative to the total solid mass contained in the fiber layer.

<Optional component>
The fiber layer may contain other optional components in addition to the components described above. Optional components include, for example, paper strength agents, surfactants, organic ions, inorganic stratiform compounds, inorganic compounds, leveling agents, preservatives, antifoaming agents, organic particles, lubricants, antistatic agents, and UV protection agents. , dyes, pigments, stabilizers, magnetic powders, alignment promoters, plasticizers, dispersants, anti-coloring agents, polymerization inhibitors, pH adjusters and the like.

Examples of organic ions include tetraalkylammonium ions and tetraalkylphosphonium ions. Tetraalkylammonium ions include, for example, tetramethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion, tetrabutylammonium ion, tetrapentylammonium ion, tetrahexylammonium ion, tetraheptylammonium ion, tributylmethylammonium ion, lauryltrimethyl ammonium ion, cetyltrimethylammonium ion, stearyltrimethylammonium ion, octyldimethylethylammonium ion, lauryldimethylethylammonium ion, didecyldimethylammonium ion, lauryldimethylbenzylammonium ion, tributylbenzylammonium ion; Tetraalkylphosphonium ions include, for example, tetramethylphosphonium ion, tetraethylphosphonium ion, tetrapropylphosphonium ion, tetrabutylphosphonium ion, and lauryltrimethylphosphonium ion. Moreover, tetra-n-propylonium ion and tetra-n-butylonium ion can also be mentioned as examples of tetrapropylonium ion and tetrabutylonium ion, respectively.

(Surface protective layer)
The surface protective layer constituting the laminate is preferably a hard coat layer. Specifically, the surface protective layer is preferably an active energy ray-curable resin layer, a silicone resin layer, or an inorganic layer.

The active energy ray-curable resin layer is a layer containing a polymer obtained by polymerizing an active energy ray-curable monomer. Examples of the active energy ray-curable monomer include monomers having a polymerizable unsaturated group, and examples of the polymerizable unsaturated group include a vinyl group, an allyl group, and a (meth)acryloyl group. . Among them, the sexual energy ray-curable monomer is preferably a monomer having a (meth)acryloyl group. Moreover, it is preferable that the active energy ray-curable monomer has two or more polymerizable unsaturated groups. In addition, in this specification, a (meth)acryloyl group means including both an "acryloyl group" and a "methacryloyl group."

Specific examples of active energy ray-curable monomers include urethane (meth)acrylates, acrylic (meth)acrylates, epoxy (meth)acrylates, polyether (meth)acrylates, polyester (meth)acrylates, acrylic acid esters, and the like. mentioned. These active energy ray-curable monomers may be used singly or in combination of two or more.

When the surface protective layer is an active energy ray-curable resin layer, the resin coating liquid forming the active energy ray-curable resin layer contains a solvent and a photopolymerization initiator in addition to the active energy ray-curable monomer. is preferred. The photopolymerization initiator is preferably one that accelerates the polymerization reaction of the active energy ray-curable monomer with light having a wavelength of 380 to 700 nm. In this case, a resin coating liquid for forming an active energy ray-curable resin layer is applied onto the fiber layer, and if necessary, the solvent is volatilized by heating and drying, and then the active energy ray (for example, ultraviolet rays) is irradiated. Thus, a surface protective layer can be formed. It is preferable to adjust the irradiation amount of the active energy ray within a range in which the photopolymerization initiator generates radicals.

The silicone-based resin layer is a layer formed by curing a silicone-based coating liquid containing a silane compound. Specifically, a coating liquid containing a silane compound is applied onto the fiber layer, and heat treatment is performed to crosslink and condense the silane compound, thereby forming the surface protective layer.

The material constituting the inorganic layer is not particularly limited, but for example, aluminum, silicon, magnesium, zinc, tin, nickel, titanium; or mixtures thereof. Among others, the inorganic layer is selected from the group consisting of titanium oxide, aluminum oxide, silicon oxide (silicon dioxide), silicon nitride, aluminum nitride, silicon oxycarbide, silicon oxynitride, silicon oxycarbide, aluminum oxycarbide and aluminum oxynitride. preferably contains at least one selected from the group consisting of titanium oxide, aluminum oxide and silicon dioxide. In addition, the inorganic layer may contain a mixture of these.

The surface protective layer may contain an adhesion aid and/or a structure derived from the adhesion aid as an optional component. As the adhesion aid, the adhesion aid described above can be used as appropriate, and the adhesion aid is preferably at least one selected from silane coupling agents and isocyanate compounds (compounds containing isocyanate groups). When the adhesion aid is a silane coupling agent, the surface protective layer contains a structure derived from the silane coupling agent, and when the adhesion aid is an isocyanate compound, the surface protective layer contains an isocyanate compound. includes structures derived from

When the surface protective layer contains an adhesion aid and/or a structure derived from the adhesion aid, the amount of the adhesion aid added in the manufacturing process of the surface protective layer is equal to the total solid mass contained in the surface protective layer. On the other hand, it is preferably 0.1% by mass or more, more preferably 0.5% by mass or more. Also, the amount of adhesion aid added is preferably 40% by mass or less, more preferably 35% by mass or less, relative to the total solid mass contained in the surface protective layer.

The surface protective layer may contain other optional components in addition to the components described above. Optional components include, for example, surfactants, inorganic stratiform compounds, inorganic compounds, leveling agents, preservatives, antifoaming agents, organic particles, lubricants, antistatic agents, UV protection agents, dyes, pigments, stabilizers, Magnetic powders, orientation accelerators, plasticizers, dispersants, anti-coloring agents, polymerization inhibitors, pH adjusters and the like.

The thickness of the surface protective layer is preferably 0.01 µm or more, more preferably 0.1 µm or more, and even more preferably 1 µm or more. The thickness of the surface protective layer is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less. By setting the thickness of the surface protective layer within the above range, a laminate having high hardness and high transparency can be obtained. Here, the thickness of the surface protective layer constituting the laminate is determined by cutting out a cross section of the laminate with an ultramicrotome UC-7 (JEOL Ltd.) and observing the cross section with an electron microscope, a magnifying glass, or visually. It is the measured value.

(Base material)
The base material that constitutes the laminate includes a resin base material (excluding the active energy ray-curable resin layer described above), a paper base material, a glass base material (including quartz glass), and other base materials normally used in semiconductors. can be used. Among them, the substrate is preferably a resin substrate, and preferably a layer containing a natural resin or a synthetic resin as a main component. Here, the main component refers to a component that is contained in an amount of 50% by mass or more with respect to the total mass of the substrate.

Examples of natural resins that make up the base material include rosin-based resins such as rosin, rosin esters, and hydrogenated rosin esters. Synthetic resins constituting the substrate include, for example, polycarbonate resins, polyester resins, polyethylene terephthalate resins, polyethylene naphthalate resins, polyethylene resins, polypropylene resins, polyimide resins, polystyrene resins, urethane resins, acrylic resins, fluororesins, and ABS resins. , cellulose acetate resin and the like. Also, the substrate may contain two or more of these resins, such as a polymer alloy. Among them, the base material is preferably a resin base material, and is preferably a resin base material containing at least one selected from the group consisting of polycarbonate resin, polyethylene terephthalate resin, polyethylene naphthalate resin, acrylic resin and polypropylene resin. More preferably, the resin substrate contains at least one selected from polycarbonate resin and polyethylene terephthalate resin.

Examples of polycarbonate resins that make up the base material include aromatic polycarbonate-based resins and aliphatic polycarbonate-based resins. Specific polycarbonate-based resins for these are known, and include, for example, the polycarbonate-based resins described in JP-A-2010-023275.

The base material may contain an adhesion aid and/or a structure derived from the adhesion aid as an optional component. As the adhesion aid, the adhesion aid described above can be used as appropriate.

A surface treatment may be applied to the fiber layer side of the base material. Examples of surface treatment methods include corona treatment, plasma discharge treatment, UV irradiation treatment, electron beam irradiation treatment, and flame treatment. Among them, the surface treatment is preferably at least one selected from corona treatment and plasma discharge treatment. The plasma discharge treatment is preferably vacuum plasma discharge treatment.

The base material may contain optional components other than the synthetic resin as long as the effects of the present invention are not impaired. Examples of optional components include known components used in the field of resin films, such as fillers, pigments, dyes, and ultraviolet absorbers.

The pencil hardness of the substrate is preferably H or less, more preferably HB or less, and even more preferably B or less. The pencil hardness of the substrate is preferably 3B or more. The pencil hardness of the substrate is measured according to JIS K 5600-5-4:1999.

The thickness of the substrate is preferably 10 µm or more, more preferably 20 µm or more, and even more preferably 50 µm or more. Also, the thickness of the substrate is preferably 10000 μm or less, more preferably 6000 μm or less, and even more preferably 4000 μm or less. It is preferable to select the thickness of the substrate according to various uses. Here, the thickness of the base material constituting the laminate is measured by cutting out the cross section of the laminate with an ultramicrotome UC-7 (JEOL Ltd.) and observing the cross section with an electron microscope, a magnifying glass, or visually. is the value to be

(adhesive layer)
The laminate of the present embodiment may include an adhesive layer between the fiber layer and the base material. The adhesive layer may be provided between the fiber layer and the surface protective layer. are directly laminated in contact with each other.

The adhesive layer is a layer whose main component is natural resin or synthetic resin. Here, the main component refers to a component contained in an amount of 50% by mass or more with respect to the total mass of the adhesive layer. The content of the resin is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and 90% by mass with respect to the total mass of the adhesive layer. It is particularly preferable that it is above. In addition, the content of the resin may be 100% by mass, or may be 95% by mass or less.

Natural resins and synthetic resins include resins that can be used in the base material. Among them, the synthetic resin constituting the adhesive layer is preferably at least one selected from the group consisting of polycarbonate resin, acrylic resin and polypropylene resin. As the resin constituting the adhesive layer, one kind may be used alone, or a copolymer obtained by copolymerizing or graft-polymerizing a plurality of resin components may be used. Also, it may be used as a blend material in which a plurality of resin components are mixed by a physical process.

Examples of polycarbonate resins that make up the adhesive layer include aromatic polycarbonate resins and aliphatic polycarbonate resins. Specific polycarbonate-based resins for these are known, and include, for example, the polycarbonate-based resins described in JP-A-2010-023275.

Examples of polypropylene resins that make up the adhesive layer include acid-modified polypropylene resins and chlorinated polypropylene resins. Among them, an acid-modified polypropylene resin is preferable, and a maleated polypropylene resin or a maleic anhydride-modified polypropylene resin is more preferable.

As the acrylic resin constituting the adhesive layer, it is preferable to use a (meth)acrylic acid ester polymer from the viewpoint of improving adhesion and mechanical strength and improving transparency. Among them, the (meth)acrylic acid ester polymer is preferably a composite of silica particles and/or a compound having a silanol group and the (meth)acrylic acid ester polymer. By using the composite as the (meth)acrylic acid ester polymer, the adhesive strength of the adhesive layer can be increased more effectively.

The (meth)acrylic acid ester polymer may be a polymer obtained by graft-polymerizing a synthetic resin other than (meth)acrylic resin such as epoxy resin and urethane resin onto (meth)acrylic resin. A copolymer obtained by copolymerizing an acid ester and another monomer may also be used. However, the molar fraction of monomers other than the (meth)acrylic acid ester in the (meth)acrylic acid ester polymer is 50 mol % or less. Further, the content of the synthetic resin other than the graft-polymerized (meth)acrylic resin is 50% by mass or less in the (100% by mass) of the (meth)acrylic acid ester polymer.

The adhesive layer may contain an adhesion aid and/or a structure derived from the adhesion aid. As the adhesion aid, the adhesion aid described above can be used as appropriate, and the adhesion aid is preferably at least one selected from silane coupling agents and isocyanate compounds (compounds containing isocyanate groups). When the adhesion aid is a silane coupling agent, the adhesive layer contains a structure derived from the silane coupling agent, and when the adhesion aid is an isocyanate compound, the adhesive layer contains It contains a structure that

When the adhesive layer contains an adhesion aid and/or a structure derived from the adhesion aid, the amount of the adhesion aid added in the manufacturing process of the adhesive layer is, with respect to the total solid mass contained in the adhesive layer, It is preferably 0.1% by mass or more, more preferably 0.5% by mass or more. Also, the amount of adhesion aid added is preferably 40% by mass or less, more preferably 35% by mass or less, relative to the total solid mass contained in the adhesive layer.

The thickness of the adhesive layer is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more. The thickness of the adhesive layer is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 10 μm or less, and particularly preferably 5 μm or less. By setting the thickness of the adhesive layer within the above range, the adhesion between the fiber layer and the substrate can be more effectively enhanced. Here, when an adhesive layer is provided between the fiber layer and the base material, the thickness of the adhesive layer is determined by cutting out a cross section of the laminate with an ultramicrotome UC-7 (JEOL Ltd.), and examining the cross section with an electron microscope. It is a value measured by observing with a magnifying glass or visually.

When the laminate of the present embodiment has an adhesive layer, the relationship is the thickness of the base material > the thickness of the adhesive layer. By setting the thickness of the base material and the thickness of the adhesive layer in the above relationship, it is possible to obtain a laminate in which the adhesion between the fiber layer and the base material is further enhanced and the hardness of the surface protective layer is sufficiently increased.

The thickness ratio of the substrate and the adhesive layer (thickness of the substrate/thickness of the adhesive layer) is preferably 5 or more, more preferably 10 or more, and even more preferably 20 or more. The upper limit of the thickness ratio is not particularly limited, and is appropriately set according to the application and the thickness of the base material.

(arbitrary layer)
The laminate of the present embodiment may have optional layers in addition to the layers described above. As optional layers, for example, a decorative layer (decorative layer), a metal layer, etc. may be provided.

(Laminate manufacturing method)
A method for producing a laminate includes a step of forming a substrate on one side of a fibrous layer containing fibrous cellulose having a fiber width of 1000 nm or less, and a step of forming a surface protective layer on the other side of the fibrous layer. , (formation method 1). In addition, the method for producing a laminate includes a step of forming a fiber layer containing fibrous cellulose having a fiber width of 1000 nm or less on a substrate, and an exposed surface of the fiber layer (opposite to the surface on which the substrate is laminated) forming a surface protective layer on the side surface) (formation method 2). Formation method 2 can reduce the heat load applied to the fiber layer, so that the transparency and yellowing resistance of the fiber layer and laminate can be further enhanced.

<Fiber layer forming step>
The step of forming a fibrous layer containing fibrous cellulose with a fiber width of 1000 nm or less includes a step of obtaining a fibrous cellulose dispersion (hereinafter also referred to as slurry) and coating the fibrous cellulose dispersion on a substrate. It includes a coating step or a papermaking step of papermaking the fibrous cellulose dispersion. Thereby, the fiber layer mentioned above will be obtained. In addition, in the formation method 2 of the above-described laminate manufacturing method, a step of forming a fiber layer containing fibrous cellulose having a fiber width of 1000 nm or less on the base material is provided. Therefore, when forming the fiber layer, It is preferable to provide a step of coating the fibrous cellulose dispersion on the substrate constituting the laminate.

A surface treatment may be applied to the surface of the fiber layer obtained through the fiber layer forming process. Examples of surface treatment methods include corona treatment, plasma discharge treatment, UV irradiation treatment, electron beam irradiation treatment, and flame treatment. Among them, the surface treatment is preferably at least one selected from corona treatment and plasma discharge treatment. The plasma discharge treatment is preferably vacuum plasma discharge treatment.

<<Coating process>>
In the coating step, for example, a fibrous cellulose dispersion (slurry) is applied onto a substrate, dried, and a fiber sheet formed by peeling from the substrate to obtain a fiber layer. Further, by using a coating device and a long base material, it is possible to continuously produce a fiber sheet to be a fiber layer.

The material of the base material used in the coating step is not particularly limited, but a material having high wettability with respect to the fibrous cellulose dispersion (slurry) can suppress shrinkage of the fiber sheet during drying. It is preferable to select one from which the fiber sheet formed after drying can be easily peeled off. Among them, a resin film or plate or a metal film or plate is preferable, but is not particularly limited. For example, resin films and plates such as polypropylene, acrylic, polyethylene terephthalate, vinyl chloride, polystyrene, polycarbonate, and polyvinylidene chloride, metal films and plates such as aluminum, zinc, copper, and iron plates, and those whose surfaces have been oxidized. , a stainless steel film or plate, a brass film or plate, or the like can be used.

In the coating process, when the viscosity of the slurry is low and it spreads on the base material, a dam frame is fixed on the base material in order to obtain a fiber sheet with a predetermined thickness and basis weight. You may The frame for damming is not particularly limited, but it is preferable to select, for example, one that allows the ends of the fiber sheet adhered after drying to be easily peeled off. From such a point of view, a molded resin plate or metal plate is more preferable. In this embodiment, for example, resin plates such as polypropylene plates, acrylic plates, polyethylene terephthalate plates, vinyl chloride plates, polystyrene plates, polycarbonate plates, and polyvinylidene chloride plates, and metal plates such as aluminum plates, zinc plates, copper plates, iron plates, etc. , and those whose surfaces have been oxidized, and those obtained by molding a stainless steel plate, a brass plate, or the like can be used.
The coating machine for coating the slurry on the base material is not particularly limited, but for example, a roll coater, gravure coater, die coater, curtain coater, air doctor coater, etc. can be used. A die coater, a curtain coater, and a spray coater are particularly preferable because the thickness of the fiber sheet can be made more uniform.

The slurry temperature and the ambient temperature when the slurry is applied to the substrate are not particularly limited, but are preferably 5° C. or higher and 80° C. or lower, more preferably 10° C. or higher and 60° C. or lower, and 15° C. It is more preferably 50° C. or higher, and particularly preferably 20° C. or higher and 40° C. or lower. If the coating temperature is at least the above lower limit, the slurry can be more easily coated. When the coating temperature is equal to or lower than the above upper limit, volatilization of the dispersion medium during coating can be suppressed.

In the coating step, the finished basis weight of the fiber sheet is preferably 1.4 g/m ² or more and 300 g/m 2 or less, more preferably 7 g/m ² ^or more and 200 g/m ² or less. More preferably, the slurry is applied to the substrate so as to have a coating weight of 10 g/m ² or more and 200 g/m ² or less. By coating so that the basis weight is within the above range, a fiber sheet having more excellent strength can be obtained.

As described above, the coating step includes the step of drying the slurry applied onto the substrate. The step of drying the slurry is not particularly limited, but may be performed by, for example, a non-contact drying method, a method of drying while restraining the fiber sheet, or a combination thereof.

The non-contact drying method is not particularly limited, but for example, a method of drying by heating with hot air, infrared rays, far infrared rays, or near infrared rays (heat drying method), or a method of drying in a vacuum (vacuum drying method) is applied. can do. Although the heat drying method and the vacuum drying method may be combined, the heat drying method is usually applied. Drying with infrared rays, far-infrared rays, or near-infrared rays is not particularly limited.

Although the heating temperature in the heat drying method is not particularly limited, it is preferably 20°C or higher and 150°C or lower, and more preferably 25°C or higher and 105°C or lower. If the heating temperature is equal to or higher than the above lower limit, the dispersion medium can be rapidly volatilized. Moreover, if the heating temperature is equal to or lower than the above upper limit, it is possible to suppress the cost required for heating and suppress discoloration of fibrous cellulose due to heat.

<<Papermaking process>>
The papermaking process is performed by papermaking the slurry using a papermaking machine. The paper machine used in the papermaking process is not particularly limited, but examples thereof include continuous paper machines such as fourdrinier, cylinder, and inclined paper machines, and multi-layer paper machines combining these. In the paper-making process, a known paper-making method such as hand-making may be adopted.

The papermaking process is carried out by filtering the slurry with a wire and dehydrating it to obtain a fibrous sheet in a wet paper state, then pressing and drying this fibrous sheet. The filter cloth used for filtering and dewatering the slurry is not particularly limited, but it is more preferable that, for example, fibrous cellulose does not pass through and the filtration rate does not become too slow. Such a filter cloth is not particularly limited, but for example, a fiber sheet, a woven fabric, or a porous membrane made of an organic polymer is preferable. Although the organic polymer is not particularly limited, non-cellulose organic polymers such as polyethylene terephthalate, polyethylene, polypropylene, and polytetrafluoroethylene (PTFE) are preferred. In this embodiment, for example, a polytetrafluoroethylene porous film having a pore size of 0.1 μm or more and 20 μm or less, or a polyethylene terephthalate or polyethylene fabric having a pore size of 0.1 μm or more and 20 μm or less can be used.

A method for producing a fibrous sheet from a slurry includes, for example, a slurry containing fibrous cellulose, which is discharged onto the upper surface of an endless belt, and a water squeezing section for squeezing a dispersion medium from the discharged slurry to form a web, and drying the web. and a drying section to produce a fibrous sheet. An endless belt is provided from the water squeezing section to the drying section, and the web produced in the water squeezing section is conveyed to the drying section while being placed on the endless belt.

The dehydration method used in the papermaking process is not particularly limited, but includes, for example, dehydration methods commonly used in paper manufacturing. Among these, the method of dehydrating with a fourdrinier, a circular net, an inclined wire, or the like and then further dehydrating with a roll press is preferable. The drying method used in the papermaking process is not particularly limited, but includes, for example, methods used in the manufacture of paper. Among these, a drying method using a cylinder dryer, Yankee dryer, hot air drying, near-infrared heater, infrared heater, or the like is more preferable.

<Base material forming step>
Formation method 1 in the method for producing a laminate includes a step of forming a substrate on one surface of a fiber layer containing fibrous cellulose having a fiber width of 1000 nm or less. In this case, the resin layer is formed by laminating a resin film or resin sheet on one side of the fiber layer, or by applying a resin coating liquid on one side of the fiber layer and drying by heating. preferably. Among them, the substrate forming step is preferably a step of laminating a resin film or resin sheet on one surface of the fiber layer and performing hot pressing.

<Surface protective layer forming step>
The laminate manufacturing method includes a step of forming a surface protective layer on the other side of the fiber layer (the side opposite to the side on which the substrate is laminated).

When the surface protective layer is an active energy ray-curable resin layer or a silicone resin layer, it is preferable to form the surface protective layer (cured layer) by applying a resin coating liquid onto the fiber layer. A known coating apparatus can be used to apply the resin coating liquid. Coating devices include, for example, blade coaters, air knife coaters, roll coaters, bar coaters, gravure coaters, micro gravure coaters, rod blade coaters, lip coaters, die coaters and curtain coaters. At this time, it is preferable to apply the surface protective layer so that it has a predetermined thickness.

When the surface protective layer is an active energy ray-curable resin layer, an active energy irradiation step is provided after applying the resin coating liquid. Examples of active energy rays include ultraviolet rays, electron rays, visible rays, X-rays, and ion rays, which are appropriately selected according to the monomers, photopolymerization initiators, and the like contained in the resin coating liquid. Among them, the active energy rays are preferably ultraviolet rays, and the active energy irradiation step is preferably the ultraviolet irradiation step.

As the ultraviolet light source, for example, a high-pressure mercury lamp, a low-pressure mercury lamp, an extra-high pressure mercury lamp, a metal halide lamp, a UV LED lamp, a carbon arc, a xenon arc, an electrodeless ultraviolet lamp, or the like can be used. The irradiation output of ultraviolet rays is preferably such that the integrated light amount is 100 to 10000 mJ/cm ² , more preferably 500 to 5000 mJ/cm ² .

When the surface protective layer is a silicone-based resin layer, it is preferable to provide a heating step after applying the resin coating liquid.

When the surface protective layer is an inorganic layer, the inorganic layer can be formed using, for example, chemical vapor deposition (CVD) or physical vapor deposition (PVD). Specific examples of the CVD method include plasma CVD using plasma, catalytic chemical vapor deposition (Cat-CVD) in which a material gas is catalytically thermally decomposed using a heated catalyst, and the like. Specific examples of PVD methods include vacuum deposition, ion plating, ion-assisted deposition, molecular beam deposition, and sputtering.

Also, as a method for forming the inorganic layer, an atomic layer deposition (ALD) method can be adopted. The ALD method is a method of forming a thin film in units of atomic layers by alternately supplying raw material gases of elements constituting a film to be formed to a surface on which a layer is to be formed. Although it has the disadvantage of a slow deposition rate, it has the advantage over the plasma CVD method that even surfaces with complicated shapes can be covered cleanly, and a thin film with few defects can be deposited. In addition, the ALD method has the advantage that the film thickness can be controlled on the order of nanometers, and that it is relatively easy to cover a wide surface. Furthermore, the ALD method is expected to improve the reaction rate, lower the temperature of the process, and reduce unreacted gas by using plasma.

(Anchor agent for surface protective layer/anchor sheet/laminate sheet)
The present embodiment may relate to an anchoring agent for a surface protective layer containing fibrous cellulose having a fiber width of 1000 nm or less and an anchor sheet formed from the anchoring agent.
The anchoring agent is used to form an anchor sheet (fiber layer), and the anchor sheet constitutes the fiber layer in the laminate. In this embodiment, the fiber layer is a base layer for increasing the hardness of the surface protective layer, and the fiber layer also functions as an anchor layer provided between the surface protective layer and the substrate.

Further, the present embodiment may relate to a method for manufacturing an anchor sheet provided under the surface protective layer, which includes mixing fibrous cellulose having a fiber width of 1000 nm or less. It may also relate to the use of fibrous cellulose with a fiber width of 1000 nm or less for manufacturing an anchor sheet, and the use of an anchor sheet containing fibrous cellulose with a fiber width of 1000 nm or less for protecting the surface of a laminate. may be related to Furthermore, the present embodiment may relate to a method for protecting the surface of a laminate, including laminating an anchor sheet containing fibrous cellulose with a fiber width of 1000 nm or less under the surface protective layer, wherein the fiber width is 1000 nm. It may also relate to a method for protecting the surface of a laminate including applying an anchoring agent containing fibrous cellulose as described below.

The anchor sheet (fiber layer) formed from the surface protective layer anchoring agent described above is an anchor sheet for bonding the surface protective layer, and the anchor sheet increases the hardness of the surface protective layer, It also works to enhance the adhesion of the base material. The anchor sheet contains fibrous cellulose with a fiber width of 1000 nm or less, and the content of fibrous cellulose in the anchor sheet is 15% by mass or more with respect to the total solid mass of the anchor sheet.

The thickness of the anchor sheet may be 200 μm or less, 150 μm or less, 100 μm or less, 75 μm or less, or 50 μm or less. Depending on the application, the thickness of the anchor sheet is preferably 50 µm or less, more preferably 25 µm or less, even more preferably less than 25 µm, still more preferably 10 µm or less, and 5 µm or less. More preferably. By reducing the thickness of the anchor sheet, it is preferably used, for example, for optical members that require flexibility. In addition, yellowing can be more effectively suppressed by reducing the thickness of the anchor sheet. The thickness of the anchor sheet may be 0.01 μm or more, 0.05 μm or more, or 0.1 μm or more. The thickness of the anchor sheet is preferably 0.01 μm to 500 μm, more preferably 0.05 μm to 200 μm, even more preferably 0.1 μm to 150 μm, and particularly preferably 0.1 μm to 25 μm. When used for optical members that require flexibility, the thickness of the anchor sheet is preferably 0.1 to 150 μm, more preferably 1 to 100 μm, even more preferably 5 to 50 μm, even more preferably 10 to 50 μm.

The pencil hardness of the anchor sheet is preferably F or higher, more preferably H or higher, and even more preferably 2H or higher. Further, the anchor sheet preferably has a pencil hardness of 9H or less. The pencil hardness of the anchor sheet is measured according to JIS K 5600-5-4:1999.

The basis weight and density of the anchor sheet are preferably in the same ranges as those of the fiber layer described above.

In addition, the present embodiment may also relate to a laminated sheet for laminating a surface protective layer containing a base material and a fiber layer. Here, the fibrous layer contains fibrous cellulose with a fiber width of 1000 nm or less, and the content of fibrous cellulose is 15% by mass or more with respect to the total solid mass of the fibrous layer. A laminate sheet containing the substrate and the fiber layer described above is a sheet capable of increasing the hardness of the surface protective layer, and is useful for laminating the surface protective layer.

The thickness of the fiber layer may be 200 μm or less, 150 μm or less, 100 μm or less, 75 μm or less, or 50 μm or less. Depending on the application of the laminate, the thickness of the fiber layer is preferably 50 μm or less, more preferably 25 μm or less, even more preferably less than 25 μm, and even more preferably 10 μm or less. It is more preferably 5 μm or less. By reducing the thickness of the fiber layer, it is preferably used, for example, for optical members that require flexibility. Also, by reducing the thickness of the fiber layer, yellowing of the laminate can be more effectively suppressed, and the impact resistance of the laminate sheet can be enhanced. The thickness of the fiber layer may be 0.01 μm or more, 0.05 μm or more, or 0.1 μm or more. The thickness of the fiber layer is preferably 0.01 μm to 500 μm, more preferably 0.05 μm to 200 μm, even more preferably 0.1 μm to 150 μm, and particularly preferably 0.1 μm to 25 μm. When the laminated sheet is used for an optical member or the like that requires flexibility, the thickness of the fiber layer is preferably 0.1 to 150 μm, more preferably 1 to 100 μm, even more preferably 5 to 50 μm, even more preferably 10 to 50 μm. . Here, the thickness of the fiber layer constituting the laminated sheet is measured by cutting out a cross-section of the laminate with an ultramicrotome UC-7 (JEOL Ltd.) and observing the cross-section with an electron microscope, a magnifying glass, or visually. is the value to be

The pencil hardness of the fiber layer is preferably F or higher, more preferably H or higher, and even more preferably 2H or higher. Moreover, the fiber layer preferably has a pencil hardness of 9H or less. The pencil hardness of the anchor sheet is measured according to JIS K 5600-5-4:1999.

The basis weight and density of the fiber layers in the laminated sheet are preferably in the same ranges as those of the fiber layers in the laminate described above.

(Surface protective agent/Surface protective sheet/Method for producing surface protective sheet)
This embodiment may relate to a surface protective agent containing fibrous cellulose having a fiber width of 1000 nm or less. Further, the present embodiment is a sheet containing fibrous cellulose having a fiber width of 1000 nm or less, wherein the content of the fibrous cellulose is 15% by mass or more with respect to the total solid mass of the sheet. It may relate to a seat. The surface protective layer described above may be formed on the surface protective sheet, or the surface protective sheet may be disposed on the outermost surface of the laminate to form the surface protective layer.

Conventionally, a laminate is known in which a surface protective layer containing fine fibrous cellulose is provided on a base material. was expected. In this embodiment, by using a predetermined fibrous cellulose, the hardness of the surface protective layer containing fine fibrous cellulose is also successfully increased.

The thickness of the surface protection sheet may be 200 µm or less, 150 µm or less, 100 µm or less, 75 µm or less, or 50 µm or less. Depending on the application, the thickness of the surface protection sheet is preferably 50 µm or less, more preferably 25 µm or less, even more preferably less than 25 µm, even more preferably 10 µm or less, and 5 µm. The following are more preferable. By reducing the thickness of the surface protection sheet, it is preferably used for optical members that require flexibility, for example. In addition, yellowing can be more effectively suppressed by reducing the thickness of the surface protection sheet. The thickness of the surface protection sheet may be 0.01 μm or more, 0.05 μm or more, or 0.1 μm or more. The thickness of the surface protection sheet is preferably 0.01 μm to 500 μm, more preferably 0.05 μm to 200 μm, still more preferably 0.1 μm to 150 μm, and particularly preferably 0.1 μm to 25 μm. When used for optical members or the like that require flexibility, the thickness of the surface protection sheet is preferably 0.1 to 150 μm, more preferably 1 to 100 μm, even more preferably 5 to 50 μm, even more preferably 10 to 50 μm.

The pencil hardness of the surface protection sheet is preferably F or higher, more preferably H or higher, and even more preferably 2H or higher. Moreover, it is preferable that the pencil hardness of the surface protection sheet is 9H or less. The pencil hardness of the surface protection sheet is measured according to JIS K 5600-5-4:1999.

Further, the present embodiment includes a method for producing a surface protection sheet, which includes mixing fibrous cellulose with a fiber width of 1000 nm or less, and a fiber width of 1000 nm or less for producing a surface protection sheet provided on a substrate. use of fibrous cellulose, use of a sheet containing fibrous cellulose with a fiber width of 1000 nm or less for protecting the surface of the laminate, laminating a sheet containing fibrous cellulose with a fiber width of 1000 nm or less on a substrate and a surface protection method for a substrate, which includes applying a surface protective agent containing fibrous cellulose having a fiber width of 1000 nm or less.

(Application)
The laminate of this embodiment has high transparency, and the surface on the side of the surface protective layer exhibits high hardness. Therefore, the laminate of the present embodiment is suitable for optical films and resin glasses. More specifically, the laminate of the present embodiment is preferably used as optical films used in various optical display devices, window materials, interior materials, and exterior materials for various vehicles and buildings. Therefore, the present invention may also relate to an optical film including the laminate described above, or a resin glass including the laminate described above.

In addition, the laminate of the present embodiment is also suitable for applications such as electronic device substrates, home appliance members, packaging materials, and gas barrier materials.

The features of the present invention will be described more specifically below with reference to examples and comparative examples. The materials, amounts used, proportions, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed to be limited by the specific examples shown below.

<Production Example A1>
As raw material pulp, softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solid content 93% by mass, basis weight 245 g / m ² sheet, disaggregated and Canadian standard freeness measured according to JIS P 8121-2: 2012 (CSF) of 700 ml) was used.

This raw material pulp was subjected to phosphorus oxo oxidation treatment as follows. First, a mixed aqueous solution of ammonium dihydrogen phosphate and urea is added to 100 parts by mass (absolute dry mass) of the raw material pulp to obtain 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water. A chemical-impregnated pulp was obtained by adjusting as follows. Next, the resulting chemical solution-impregnated pulp was heated in a hot air dryer at 165° C. for 250 seconds to introduce phosphoric acid groups into cellulose in the pulp to obtain phosphorylated pulp.

Next, the obtained phosphorylated pulp was washed. In the washing treatment, a pulp dispersion liquid obtained by pouring 10 L of ion-exchanged water into 100 g (absolute dry mass) of phosphorylated pulp is stirred so that the pulp is uniformly dispersed, and then filtration and dehydration are repeated. gone. The washing was finished when the electric conductivity of the filtrate became 100 μS/cm or less.

Next, the washed phosphorylated pulp was neutralized as follows. First, the washed phosphorylated pulp was diluted with 10 L of ion-exchanged water, and then a 1N sodium hydroxide aqueous solution was added little by little while stirring to obtain a phosphorylated pulp slurry having a pH of 12 or more and 13 or less. . Next, the phosphorylated pulp slurry was dehydrated and washed to obtain neutralized phosphorylated pulp.

An infrared absorption spectrum was measured for the obtained phosphorylated pulp using FT-IR. As a result, an absorption based on P=O of the phosphate group was observed near 1230 cm ^-1 , confirming that the phosphate group was added to the pulp. In addition, when the obtained phosphorylated pulp was tested and analyzed with an X-ray diffraction device, it was found that the A typical peak was confirmed, confirming that it had cellulose type I crystals.

Ion-exchanged water was added to the obtained phosphorylated pulp to prepare a slurry with a solid content concentration of 2% by mass. This slurry was treated six times with a wet atomization device (Starburst, manufactured by Sugino Machine Co., Ltd.) at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion (A) containing fine fibrous cellulose.

It was confirmed by X-ray diffraction that the obtained fine fibrous cellulose maintained cellulose type I crystals. Further, when the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, it was 3 to 5 nm. The phosphate group content (first dissociated acid content) measured by the measurement method described in [Measurement of phosphate group content] described later was 1.45 mmol/g. The total amount of dissociated acid was 2.45 mmol/g.

<Production Example B1>
Fine fibrous cellulose dispersion containing phosphorous acid pulp and fine fibrous cellulose was performed in the same manner as in Production Example A1 except that 33 parts by mass of phosphorous acid (phosphonic acid) was used instead of ammonium dihydrogen phosphate. A liquid (B) was obtained.

An infrared absorption spectrum was measured for the obtained phosphorous oxidized pulp using FT-IR. As a result, an absorption based on P=O of a phosphonic acid group, which is a tautomer of a phosphite group, was observed near 1210 cm ⁻¹ , indicating that a phosphite group (phosphonic acid group) was added to the pulp. was confirmed. In addition, when the obtained phosphorous acid pulp was tested and analyzed with an X-ray diffractometer, two positions near 2θ = 14° or more and 17° or less and 2θ = 22° or more and 23° or less were found. A typical peak was confirmed in , and it was confirmed to have cellulose type I crystals.

It was confirmed by X-ray diffraction that the obtained fine fibrous cellulose maintained cellulose type I crystals. Further, when the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, it was 3 to 5 nm. The amount of phosphite groups (first dissociated acid amount) of the resulting fine fibrous cellulose measured by the measurement method described in [Measurement of amount of phosphooxy acid groups] described later was 1.51 mmol/g. . The total amount of dissociated acid was 1.54 mmol/g.

<Production Example C1>
The same operation as in Production Example A1 was performed except that 38 parts by mass of amidosulfuric acid (sulfamic acid) was used instead of ammonium dihydrogen phosphate and the heating time was extended to 20 minutes. A fibrous cellulose dispersion (C) was obtained.

An infrared absorption spectrum was measured for the obtained sulfated pulp using FT-IR. As a result, absorption due to S=O of the sulfate group was observed near 1220-1260 cm ^-1 , confirming that the sulfate group was added to the pulp. Further, when the obtained sulfated pulp was tested and analyzed with an X-ray diffraction device, it was found that there were two positions near 2θ = 14° to 17° and 2θ = 22° to 23°. A typical peak was confirmed, confirming that it had cellulose type I crystals.

It was confirmed by X-ray diffraction that the obtained fine fibrous cellulose maintained cellulose type I crystals. Further, when the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, it was 3 to 5 nm. The fine fibrous cellulose thus obtained had a sulfur oxoacid group content of 1.47 mmol/g measured by the measurement method described in [Measurement of sulfur oxoacid group content and sulfone group content] described later.

<Production Example D1>
Softwood kraft pulp (undried) manufactured by Oji Paper Co., Ltd. was used as raw material pulp. The raw material pulp was subjected to alkali TEMPO oxidation treatment as follows.

First, the raw pulp equivalent to 100 parts by mass of dry mass, 1.6 parts by mass of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl), 10 parts by mass of sodium bromide, and 10000 parts by mass of water distributed in parts. Then, a 13% by mass sodium hypochlorite aqueous solution was added to 10 mmol per 1.0 g of pulp to initiate the reaction. During the reaction, a 0.5 M sodium hydroxide aqueous solution was added dropwise to maintain the pH at 10 or more and 10.5 or less, and the reaction was considered completed when no change in pH was observed.

Next, the obtained TEMPO oxidized pulp was washed. The washing treatment is performed by dehydrating the pulp slurry after TEMPO oxidation to obtain a dehydrated sheet, pouring 5000 parts by mass of ion-exchanged water, stirring to uniformly disperse, and then filtering and dehydrating repeatedly. rice field. The washing was finished when the electric conductivity of the filtrate became 100 μS/cm or less.

This dehydrated sheet was subjected to a post-oxidation treatment of the remaining aldehyde groups as follows. The dehydrated sheet equivalent to 100 parts by mass of dry mass was dispersed in 10000 parts by mass of 0.1 mol/L acetate buffer (pH 4.8). Next, 113 parts by mass of 80% by mass sodium chlorite was added, and the mixture was immediately sealed, followed by reaction at room temperature for 48 hours while stirring at 500 rpm using a magnetic stirrer to obtain a pulp slurry.

Next, the obtained post-oxidized TEMPO oxidized pulp was washed. The washing treatment is carried out by dehydrating the post-oxidized pulp slurry to obtain a dehydrated sheet, pouring 5000 parts by mass of ion-exchanged water, stirring to uniformly disperse, and then filtering and dehydrating repeatedly. rice field. The washing was finished when the electric conductivity of the filtrate became 100 μS/cm or less.

When the obtained TEMPO oxidized pulp was tested and analyzed with an X-ray diffraction device, it was found to be typical at two positions near 2θ = 14° or more and 17° or less and 2θ = 22° or more and 23° or less. A peak was confirmed, and it was confirmed to have cellulose type I crystals.

Ion-exchanged water was added to the obtained TEMPO oxidized pulp to prepare a slurry with a solid concentration of 2% by mass. This slurry was treated six times with a wet atomization device (Starburst, manufactured by Sugino Machine Co., Ltd.) at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion (D) containing fine fibrous cellulose.

It was confirmed by X-ray diffraction that the obtained fine fibrous cellulose maintained cellulose type I crystals. Further, when the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, it was 3 to 5 nm. The carboxy group content of the obtained fine fibrous cellulose measured by the measurement method described in [Measurement of carboxy group content] described later was 1.80 mmol/g.

<Production Example E1>
[Hypochlorous acid oxidation]
A sheet of softwood bleached kraft pulp (NBKP) (solid content concentration 90% by mass) is processed with a hand mixer (Labo Milcer PLUS, manufactured by Osaka Chemical Co., Ltd.) at a rotation speed of 20000 rpm for 15 seconds to form a flocculent. Fluffing pulp (solid content concentration 90% by mass) was prepared. Next, sodium hypochlorite pentahydrate was added to the ion-exchanged water to prepare an aqueous solution having a sodium hypochlorite solid content concentration of 22% by mass. 9000 parts by mass of a 22% by mass sodium hypochlorite aqueous solution was added to 100 parts by mass of cotton-like fluffing pulp, and the mixture was reacted for 2 hours while adjusting the temperature to 30°C in a hot bath to obtain a carboxy group-introduced pulp. The pH was maintained at 11 by appropriately adding 1N sodium hydroxide aqueous solution during the reaction.

Next, the obtained carboxy group-introduced pulp was washed. The washing treatment was carried out by repeating an operation of filtering and dehydrating a pulp dispersion liquid obtained by pouring ion-exchanged water into the obtained carboxy group-introduced pulp, stirring the pulp so that the pulp is uniformly dispersed, and then filtering and dehydrating the pulp. The washing was finished when the electric conductivity of the filtrate became 100 μS/cm or less.

When the obtained carboxyl group-introduced pulp was tested and analyzed with an X-ray diffractometer, it was found to be typical at two positions near 2θ = 14° or more and 17° or less and 2θ = 22° or more and 23° or less. A specific peak was confirmed, and it was confirmed to have cellulose type I crystals.

Ion-exchanged water was added to the resulting carboxy group-introduced pulp to prepare a slurry with a solid content concentration of 2% by mass. This slurry was treated six times with a wet atomization device (Starburst, manufactured by Sugino Machine Co., Ltd.) at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion (E) containing fine fibrous cellulose.

It was confirmed by X-ray diffraction that the obtained fine fibrous cellulose maintained cellulose type I crystals. Further, when the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, it was 3 to 5 nm. The carboxy group content of the resulting fine fibrous cellulose measured by the measurement method described in [Measurement of carboxy group content] described later was 0.70 mmol/g.

<Production Example F1>
[Maleic acid esterification]
A sheet of softwood bleached kraft pulp (NBKP) (solid content concentration 90% by mass) is processed with a hand mixer (Labo Milcer PLUS, manufactured by Osaka Chemical Co., Ltd.) at a rotation speed of 20000 rpm for 15 seconds to form a flocculent. Fluffing pulp (solid content concentration 90% by mass) was prepared. An autoclave was charged with 100 parts by mass of cotton-like fluffing pulp and 50 parts by mass of maleic anhydride and treated at 150° C. for 2 hours to obtain a carboxy group-introduced pulp.

An infrared absorption spectrum was measured for the resulting carboxy group-introduced pulp using FT-IR. As a result, absorption due to carboxy groups was observed near 1580 and 1720 cm ⁻¹ , confirming maleic acid esterification. In addition, when the carboxy group-introduced pulp was tested and analyzed with an X-ray diffraction device, typical A peak was confirmed, and it was confirmed to have cellulose type I crystals.

Ion-exchanged water was added to the resulting carboxy group-introduced pulp to prepare a slurry with a solid content concentration of 2% by mass. This slurry was treated six times with a wet atomization device (Starburst, manufactured by Sugino Machine Co., Ltd.) at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion (F) containing fine fibrous cellulose.

It was confirmed by X-ray diffraction that the obtained fine fibrous cellulose maintained cellulose type I crystals. Further, when the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, it was 3 to 5 nm. The carboxy group content of the resulting fine fibrous cellulose measured by the measurement method described in [Measurement of carboxy group content] described later was 1.22 mmol/g.

<Production Example G1>
[Carboxyethylation]
As raw material pulp, softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solid content 93% by mass, basis weight 245 g / m ² sheet, disaggregated and Canadian standard freeness measured according to JIS P 8121-2: 2012 (CSF) of 700 ml) was used.

To 100 parts by mass (absolute dry mass) of this raw material pulp was added a chemical solution consisting of 250 parts by mass of 12N NaOH aqueous solution, 163 parts by mass of 2-chloropropionic acid, and 140 parts by mass of ion-exchanged water (553 parts by mass in total). An impregnated pulp was obtained. Next, the resulting chemical solution-impregnated pulp was heated in a hot air dryer at 165° C. for 10 minutes to introduce carboxyethyl groups (carboxy groups) into the cellulose in the pulp to obtain carboxy group-introduced pulp.

Next, the washed carboxyl group-introduced pulp was neutralized as follows. First, after diluting the washed carboxy group-introduced pulp with 10 L of deionized water, a 1 N sodium hydroxide aqueous solution was added little by little while stirring to prepare a carboxy group-introduced pulp slurry having a pH of 12 or more and 13 or less. Obtained. Next, the carboxyl group-introduced pulp slurry was dewatered and washed to obtain neutralized carboxyl group-introduced pulp.

When the carboxy group-introduced pulp was tested and analyzed with an X-ray diffraction device, typical peaks were observed at two positions near 2θ = 14° or more and 17° or less and 2θ = 22° or more and 23° or less. was confirmed, and it was confirmed to have cellulose type I crystals.

Ion-exchanged water was added to the resulting carboxy group-introduced pulp to prepare a slurry with a solid content concentration of 2% by mass. This slurry was treated six times with a wet atomization device (Starburst, manufactured by Sugino Machine Co., Ltd.) at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion (G) containing fine fibrous cellulose.

It was confirmed by X-ray diffraction that the obtained fine fibrous cellulose maintained cellulose type I crystals. Further, when the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, it was 3 to 5 nm. The carboxy group content of the resulting fine fibrous cellulose measured by the measurement method described in [Measurement of carboxy group content] described later was 1.41 mmol/g.

<Production Example H1>
[Sulfoethylation]
As raw material pulp, softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solid content 93% by mass, basis weight 245 g / m ² sheet, disaggregated and Canadian standard freeness measured according to JIS P 8121-2: 2012 (CSF) of 700 ml) was used.

To 100 parts by mass (absolute dry mass) of this raw material pulp, a chemical solution consisting of 180 parts by mass of a 2N NaOH aqueous solution and 780 parts by mass of a 25% by mass sodium vinylsulfonate aqueous solution (total of 960 parts by mass) was added to obtain a chemical solution-impregnated pulp. Obtained. Next, the resulting chemical solution-impregnated pulp was heated in a hot air dryer at 165° C. for 16 minutes to introduce sulfoethyl groups (sulfone groups) into the cellulose in the pulp to obtain sulfoethyl group-introduced pulp (sulfone group-introduced pulp).

Next, the obtained sulfoethyl group-introduced pulp was washed. The washing treatment was carried out by repeating an operation of filtering and dehydrating a pulp dispersion liquid obtained by pouring ion-exchanged water into the resulting sulfoethyl group-introduced pulp, stirring the pulp to uniformly disperse the pulp, and then filtering and dehydrating the pulp. The washing was finished when the electric conductivity of the filtrate became 100 μS/cm or less.

When the sulfoethyl group-introduced pulp was tested and analyzed with an X-ray diffraction device, typical peaks were observed at two positions near 2θ = 14° or more and 17° or less and 2θ = 22° or more and 23° or less. was confirmed, and it was confirmed to have cellulose type I crystals.

Ion-exchanged water was added to the resulting sulfoethyl group-introduced pulp to prepare a slurry with a solid content concentration of 2% by mass. This slurry was treated six times with a wet atomization device (Starburst, manufactured by Sugino Machine Co., Ltd.) at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion (H) containing fine fibrous cellulose.

It was confirmed by X-ray diffraction that the obtained fine fibrous cellulose maintained cellulose type I crystals. Further, when the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, it was 3 to 5 nm. Regarding the obtained fine fibrous cellulose, the sulfoethyl group content (sulfone group content) measured by the measuring method described in [Measurement of sulfur oxoacid group content and sulfone group content] described later was 1.48 mmol/g. was.

<Manufacturing Example J1>
[Cationization treatment]
As raw material pulp, softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solid content 93% by mass, basis weight 245 g / m ² sheet, disaggregated and Canadian standard freeness measured according to JIS P 8121-2: 2012 (CSF) of 700 ml) was used.

To 100 parts by mass (absolute dry mass) of this raw material pulp, 180 parts by mass of a 1N NaOH aqueous solution and a cationizing agent (Catiomaster G, manufactured by Yokkaichi Gosei Co., Ltd., glycidyltrimethylammonium chloride, pure content 73.1% by mass, moisture content 20) were added. .2% by mass) 325 parts by mass (505 parts by mass in total) of the chemical solution was added to obtain a chemical solution-impregnated pulp. Next, the resulting chemical solution-impregnated pulp was heated in a hot air dryer at 165° C. for 12 minutes to introduce cationic groups into the cellulose in the pulp to obtain cationic group-introduced pulp.

Next, the resulting cationic group-introduced pulp was washed. The washing treatment was carried out by repeating an operation of filtering and dehydrating a pulp dispersion obtained by pouring ion-exchanged water into the obtained cationic group-introduced pulp, stirring the pulp so that the pulp is uniformly dispersed, and then filtering and dehydrating. The washing was finished when the electric conductivity of the filtrate became 100 μS/cm or less.

Next, the cationic group-introduced pulp after washing was neutralized as follows. First, the cationic group-introduced pulp after washing was diluted with 10 L of deionized water, and then 1N hydrochloric acid was added little by little while stirring to obtain a cationic group-introduced pulp slurry having a pH of 1 or more and 2 or less. Next, the cationic group-introduced pulp slurry was dehydrated and washed to obtain a neutralized cationic group-introduced pulp.

When the cationic group-introduced pulp was tested and analyzed with an X-ray diffractometer, there were typical peaks at two positions near 2θ = 14° or more and 17° or less and 2θ = 22° or more and 23° or less. was confirmed, and it was confirmed to have cellulose type I crystals.

Ion-exchanged water was added to the resulting cationic group-introduced pulp to prepare a slurry with a solid concentration of 2% by mass. This slurry was treated six times with a wet atomization device (Starburst, manufactured by Sugino Machine Co., Ltd.) at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion (J) containing fine fibrous cellulose.

It was confirmed by X-ray diffraction that the resulting fine fibrous cellulose maintained cellulose type I crystals. Further, when the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, it was 3 to 5 nm. The obtained fine fibrous cellulose was subjected to trace nitrogen analysis, and the cationic group content was calculated according to the following formula and found to be 1.45 mmol/g.
(Amount of cationic groups) [mmol/g]=(Amount of nitrogen) [g]/14×1000/(Amount of fine fibrous cellulose tested) [g]

<Production example K1>
[Preparation of Substituent Removal Treated Cellulose]
<Nitrogen removal treatment>
Ion-exchanged water was added to the phosphorylated pulp produced in Production Example A1 to prepare a slurry having a solid content concentration of 4% by mass. A 48% by mass sodium hydroxide aqueous solution was added to the slurry to adjust the pH to 13.4, and the slurry was heated at a liquid temperature of 85° C. for 1 hour. After that, the pulp slurry is dehydrated, and the pulp dispersion obtained by pouring 10 L of ion-exchanged water into 100 g (absolute dry weight) of phosphorylated pulp is stirred so that the pulp is uniformly dispersed, followed by filtration and dehydration. was repeated to remove excess sodium hydroxide. The removal was terminated when the electric conductivity of the filtrate became 100 μS/cm or less. The amount of introduced carbamide groups measured in [Measurement of Carbamide Group Amount] described later was 0.01 mmol/g.

The phosphorus oxyoxidized pulp thus obtained was subjected to infrared absorption spectrum measurement using FT-IR. As a result, an absorption based on P=O of the phosphate group was observed near 1230 cm ^-1 , confirming that the phosphate group was added to the pulp. Moreover, it was confirmed by X-ray diffraction that the obtained fine fibrous cellulose maintained cellulose type I crystals. The phosphate group content (first dissociated acid content) measured by the measurement method described in [Measurement of phosphate group content] described later was 1.35 mmol/g. The total amount of dissociated acid was 2.30 mmol/g.

<Fibrillation treatment>
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 six times with a wet atomization device (Starburst, manufactured by Sugino Machine Co., Ltd.) at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion containing fine fibrous cellulose.

<Substituent removal treatment (high temperature heat treatment)>
The fine fibrous cellulose dispersion was placed in a pressure vessel and heated at a liquid temperature of 160° C. for 15 minutes until the amount of phosphate groups reached 0.08 mmol/g. This operation confirmed the formation of fine fibrous cellulose aggregates.

<Washing treatment of slurry after removal of substituents>
After the heating, the same amount of ion-exchanged water as the slurry was added to the slurry to obtain a slurry having a solid content concentration of about 1% by mass, and after stirring the slurry, the slurry was washed by repeating the operation of filtering and dehydrating. . When the electric conductivity of the filtrate became 10 μS/cm or less, ion-exchanged water was added again to obtain a slurry of about 1% by mass, and the slurry was allowed to stand for 24 hours. From there, the operation of filtering and dehydrating was repeated, and the washing was finished when the electrical conductivity of the filtrate became 10 μS/cm or less. Ion-exchanged water was added to the obtained fine fibrous cellulose aggregate to obtain a slurry after removal of substituents. The solid content concentration of this slurry was 1.7% by mass.

<Uniform dispersion of slurry after removal of substituents>
Ion-exchanged water was added to the obtained slurry after removing the substituents to obtain a slurry having a solid content concentration of 1.0% by mass, and then a wet atomization apparatus (Starburst manufactured by Sugino Machine Co., Ltd.) was used at a pressure of 200 MPa. After three treatments, a substituent-removed fine fibrous cellulose dispersion (K) containing substituent-removed fine fibrous cellulose was obtained. Further, when the number average fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, it was 4 nm.

<Example 1-1>
(Dissolution of polyvinyl alcohol)
Acetoacetyl group-modified polyvinyl alcohol (manufactured by Mitsubishi Chemical Corporation, Gohsenex TMZ-200) was added to ion-exchanged water so as to make 12% by mass, and dissolved by stirring at 95° C. for 1 hour. A polyvinyl alcohol aqueous solution was obtained by the above procedure.

(Formation of fiber layer)
The fine fibrous cellulose dispersion liquid (A) and the polyvinyl alcohol aqueous solution were each diluted with ion-exchanged water so that the solid content concentration was 0.6% by mass. Next, 30 parts by mass of the diluted polyvinyl alcohol aqueous solution was mixed with 70 parts by mass of the diluted fine fibrous cellulose dispersion (A) to obtain a mixture (A-1). Further, the mixed liquid was measured so that the finished basis weight of the sheet was 70 g/m ² and spread on a commercially available acrylic plate. A damming frame (inner dimensions: 250 mm×250 mm, height: 5 cm) was arranged on the acrylic plate so as to obtain a predetermined basis weight. After that, it was dried in a drier at 70° C. for 24 hours to form a fiber layer (fine fibrous cellulose-containing layer).

(Laminate formation method 1)
(Formation of adhesive layer)
A silane-modified acrylic resin (Compoceran AC601, manufactured by Arakawa Chemical Industries, Ltd.) was applied to the surface of the fiber layer with a bar coater so as to have a thickness of 3 μm. Then, it was heated at 100° C. for 1 hour to form an adhesive layer. After forming the adhesive layer, the fiber layer having the adhesive layer formed thereon was obtained by peeling from the acrylic plate. The thickness of the fiber layer was 50 μm, and the thickness of the adhesive layer was 3 μm.

(Lamination with base material)
A 50 μm-thick polycarbonate base material (manufactured by Teijin Limited, Pure Ace) is attached to the adhesive layer surface of the fiber layer on which the adhesive layer is formed, and pressed with a small heat press at 160 ° C. and 10 MPa for 15 minutes. A laminated sheet of substrate/adhesive layer/fiber layer was obtained.

(Formation of surface protective layer)
An ultraviolet curable resin (A) (tripentaerythritol acrylate) was diluted with toluene to obtain a solution having a solid content of 20% by mass. Furthermore, a polymerization initiator (Omnirad 184; manufactured by IGM Resins B.V.) was added to the solution in an amount of 15 parts by mass with respect to 100 parts by mass of the ultraviolet curable resin (A). This resin solution was applied to the surface of the fiber layer of the laminated sheet with a bar coater so as to have a thickness of 3 μm, and then heated at 100° C. for 5 minutes. A belt conveyor type exposure device (manufactured by Eyegraphic Co., Ltd., ECS-401GX, with an IR cut filter) equipped with a metal halide lamp (manufactured by Eyegraphic Co., Ltd., M04-L41) is equipped with an illuminance meter (manufactured by Ushio Denki Co., Ltd., UIT-150). -A, the sensor part is UVD-C365, the sensitivity wavelength range is 310 to 390 nm), and after setting the illuminance to 160 mW/cm ² and the integrated light amount to 1000 mJ/cm ² , the UV curable resin side of the laminated sheet is turned up. It was cured by irradiating it with ultraviolet light to obtain a laminate of base material/adhesive layer/fiber layer/surface protective layer.

<Examples 1-2 to 1-6>
A laminate was obtained in the same manner as in Example 1-1, except that the thickness of the fiber layer was changed to the thickness shown in Table 1.

<Example 1-7>
A laminate was obtained in the same manner as in Example 1-1 except that a polycarbonate substrate (manufactured by Takiron C.I. Co., Ltd.) having a thickness of 5 mm (5000 μm) was used as the substrate.

<Example 1-8>
A laminate was obtained in the same manner as in Example 1-7, except that the thickness of the fiber layer was 10 μm.

<Example 1-9>
A polyethylene terephthalate film (Lumirror S-10, thickness 50 μm, manufactured by Toray Industries, Inc.) was cut into a size of 210 mm×297 mm, and placed in a corona surface reforming device (TEC-4AX, manufactured by Kasuga Denki Co., Ltd.). Then, corona discharge treatment was performed at a treatment output of 60 W and a treatment speed of 1 m/min. The above corona discharge treatment was repeated 20 times to obtain a surface-treated polyethylene terephthalate film having a hydrophilic surface. A laminate was obtained in the same manner as in Example 1-1, except that this surface-treated polyethylene terephthalate film was used as the substrate.

<Example 1-10>
A laminate was obtained in the same manner as in Example 1-9, except that the thickness of the fiber layer was 10 μm.

<Example 1-11>
In (Formation of surface protective layer), a laminate was prepared in the same manner as in Example 1-1, except that the amount of the polymerization initiator added was 3 parts by mass with respect to 100 parts by mass of the ultraviolet curable resin (A). Obtained.

<Example 1-12>
In (Formation of surface protective layer), a laminate was prepared in the same manner as in Example 1-1, except that the amount of the polymerization initiator added was 5 parts by mass with respect to 100 parts by mass of the ultraviolet curable resin (A). Obtained.

<Example 1-13>
In (Formation of surface protective layer), a laminate was prepared in the same manner as in Example 1-1, except that the amount of the polymerization initiator added was 35 parts by mass with respect to 100 parts by mass of the ultraviolet curable resin (A). Obtained.

<Example 1-14>
A laminate was obtained in the same manner as in Example 1-1, except that an ultraviolet curable resin (B) (manufactured by Nippon Kako Toryo Co., Ltd., NXD-001A, containing a polymerization initiator) was used as the surface protective layer.

<Example 1-15>
A laminate was obtained in the same manner as in Example 1-3, except that the ultraviolet curable resin (B) was used as the surface protective layer.

<Example 1-16>
As a surface protective layer, a film of SiO ₂ was formed using an ion beam sputtering device (manufactured by Hakuto Co., Ltd.). Specifically, the laminated sheet of base material/adhesive layer/fiber layer obtained in Example 1-1 was placed in an ion beam sputtering apparatus so that the fiber layer faced up, and was evacuated. After heating for a period of time, it was allowed to cool, and film formation was carried out while the temperature was lowered as much as possible. Based on the SiO ₂ film formation rate of 9.65 nm/min on the silicon substrate by ion beam sputtering, the film formation time was set so as to obtain the desired film thickness, and an inorganic layer film of 200 nm was laminated on the fiber layer. , to obtain a laminate.

<Example 1-17>
A laminate was obtained in the same manner as in Example 1-3, except that a laminate sheet having an inorganic layer film formed by the same method as in Example 1-16 was used as the surface protective layer.

<Example 1-18>
To 99 parts by mass of the mixture (A-1) in Example 1-1, 1 part by mass of a silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., KBM-503) diluted to 0.6% by mass was added and mixed. A liquid (A-1') was obtained. A laminate was obtained in the same manner as in Example 1-1, except that the mixed liquid (A-1′) was used instead of the mixed liquid (A-1).

<Example 1-19>
In Example 1-1, the resin solution after adding the polymerization initiator was added so that the amount of the silane coupling agent added was 1 part by mass with respect to 100 parts by mass of the ultraviolet curable resin (A). A solution was obtained. A laminate was obtained in the same manner as in Example 1-1, except that this was used as the resin for forming the surface protective layer.

<Example 1-20>
In Example 1-19, instead of the silane coupling agent, an isocyanate compound (manufactured by Showa Denko Co., Ltd., Karenz BEI) was added so as to be 15 parts by mass with respect to 100 parts by mass of the ultraviolet curable resin (A). A resin solution was obtained. A laminate was obtained in the same manner as in Example 1-1 except that this resin was used for forming the surface protective layer.

<Example 1-21>
After Example 1-1 (lamination with the substrate), the silica-modified acrylate resin was applied to the other side of the laminated sheet in the same manner as in Example 1-1. A surface protective layer is formed on one side of this adhesive layer in the same manner as in Example 1-1 (formation of surface protective layer), and a laminate consisting of a substrate/adhesive layer/fiber layer/adhesive layer/surface protective layer. got a body

<Example 1-22>
In Example 1-20, a polycarbonate resin (Mitsubishi Gas Chemical Co., Ltd., Iupizeta FPC-2136) was used instead of the silica-modified acrylate resin, and an isocyanate compound was added as an adhesion aid in an amount of 15 parts per 100 parts by mass of the polycarbonate resin. A laminate was obtained in the same manner as in Example 1-20, except that the one added in parts by mass was used as the adhesive layer-forming coating solution.

<Example 1-23>
A laminate was formed according to the following (Laminate formation method 2).
(Laminate formation method 2)
(Formation of adhesive layer)
A silane-modified acrylic resin (Compoceran AC601, manufactured by Arakawa Chemical Industries, Ltd.) was diluted with methyl ethyl ketone to obtain a solution with a solid content of 20% by mass. A silane-modified acrylic resin was applied as an adhesive layer onto a polycarbonate substrate having a thickness of 50 μm and dried at 100° C. for 1 hour to form an adhesive layer.

(Formation of fiber layer)
A damming frame (inner dimensions: 250 mm x 250 mm, height: 5 cm) was placed on the adhesive layer of the base material on which the adhesive layer was formed, and the finished basis weight of the fiber layer was adjusted to 70 g/ ^m2 . Mixture (A) was weighed and developed. After that, it was dried at 70° C. for 24 hours, and after drying, the damming frame was removed to obtain a base material/fiber layer laminated sheet.

(Formation of surface protective layer)
The fiber layer surface of the laminated sheet was coated with the UV curable resin (A) to a thickness of 3 μm with a bar coater and dried at 100° C. for 5 minutes. A belt conveyor type exposure device (manufactured by Eyegraphic Co., Ltd., ECS-401GX, with an IR cut filter) equipped with a metal halide lamp (manufactured by Eyegraphic Co., Ltd., M04-L41) is equipped with an illuminance meter (manufactured by Ushio Denki Co., Ltd., UIT-150). -A, the sensor part is UVD-C365, the sensitivity wavelength range is 310 to 390 nm), and after setting the illuminance to 160 mW/cm ² and the integrated light amount to 1000 mJ/cm ² , the UV curable resin side of the laminated sheet is turned up. The laminate was cured by irradiating it with ultraviolet light to obtain a laminate of base material/fiber layer/surface protective layer.

<Example 2-1>
In Example 1-1 (formation of fiber layer), 50 parts by mass of the polyvinyl alcohol aqueous solution after dilution was added to 50 parts by mass of the fine fibrous cellulose dispersion (A) after dilution to 0.6% by mass. to obtain a mixture (A-2). A laminate was obtained in the same manner as in Example 1-1, except that the mixed liquid (A-2) was used instead of the mixed liquid (A-1).

<Example 2-2>
A laminate was obtained in the same manner as in Example 1-3, except that the mixed solution (A-2) was used.

<Example 2-3>
A laminate was obtained in the same manner as in Example 1-7, except that the mixed solution (A-2) was used.

<Example 2-4>
A laminate was obtained in the same manner as in Example 1-8, except that the mixed solution (A-2) was used.

<Example 2-5>
A laminate was obtained in the same manner as in Example 1-9, except that the mixed solution (A-2) was used.

<Example 2-6>
A laminate was obtained in the same manner as in Example 1-10, except that the mixed solution (A-2) was used.

<Examples 3-1 to 3-6>
In Example 1-1 (formation of fiber layer), 70 parts by mass of the polyvinyl alcohol aqueous solution after dilution was added to 30 parts by mass of the fine fibrous cellulose dispersion (A) after dilution to 0.6% by mass. to obtain a mixture (A-3). Examples 2-1 to 2-2 except that the mixture (A-3) was used instead of the mixture (A-2) in each of Examples 2-1 to 2-6 (formation of the fiber layer). A laminate was obtained in the same manner as in -6.

<Example 4-1>
(Dissolution of cellulose ether)
Methyl cellulose (manufactured by Shin-Etsu Chemical Co., Ltd., Metolose 65SH-1500, weight average molecular weight: 2.2 × 10 ⁵ , degree of substitution (methoxy group): 1.8, number of moles of substitution (hydroxypropoxy group): 0.15) was added so as to be 2% by mass, and the solution was dissolved by stirring at room temperature for 1 hour. A cellulose ether aqueous solution was obtained by the above procedure.
Next, the cellulose ether aqueous solution was diluted with ion-exchanged water so that the solid content concentration was 0.6% by mass. In Example 1-1 (formation of fiber layer), instead of the diluted polyvinyl alcohol aqueous solution, the diluted cellulose ether aqueous solution was used to obtain a mixed solution (A-4). A laminate was obtained in the same manner as in Example 1-1, except that the mixed solution (A-4) was used instead of the mixed solution (A-1).

<Examples 4-2 to 4-6>
In each of Examples 2-1 to 2-6 (formation of fiber layer), Examples 2-2 to 2-2 except that the mixture (A-4) was used instead of the mixture (A-2). A laminate was obtained in the same manner as in -6.

<Examples 5-1 to 5-6>
In Example 1-1 (formation of fiber layer), 70 parts by mass of the diluted cellulose ether aqueous solution was added to 30 parts by mass of the fine fibrous cellulose dispersion (A) diluted to 0.6% by mass. to obtain a mixture (A-5). In each of Examples 2-1 to 2-6 (formation of fiber layer), Examples 2-1 to 2-2 except that the mixture (A-5) was used instead of the mixture (A-2). A laminate was obtained in the same manner as in -6.

<Examples 6-1 to 6-8>
In Example 1-1 (Formation of fibrous layer), instead of the fine fibrous cellulose dispersion (A), the fine fibrous cellulose dispersion (fine fibrous cellulose dispersion (B) to ( A laminate was obtained in the same manner as in Example 1-1, except that J)) was used.

<Examples 7-1 to 7-6>
In Examples 4-1 to 4-6 (Formation of fibrous layer), the fine fibrous cellulose dispersion (K) was used instead of the fine fibrous cellulose dispersion (A), and the cellulose ether after dilution was used. Laminates were obtained in the same manner as in Examples 4-1 to 4-6, except that diluted polyvinyl alcohol was used instead.

<Examples 8-1 to 8-6>
Examples 4-1 to 4-6 except that the fine fibrous cellulose dispersion (K) was used in place of the fine fibrous cellulose dispersion (A) in Examples 4-1 to 4-6 (formation of the fibrous layer). A laminate was obtained in the same manner as in 4-6.

<Comparative Example 1>
A laminate was obtained in which a surface protective layer was directly formed on a 50 μm-thick polycarbonate base material according to the procedure of Example 1-1 (Formation of surface protective layer) (Laminate forming method 3).

<Comparative Example 2>
A laminate was obtained in the same manner as in Comparative Example 1 except that polyethylene terephthalate having a thickness of 50 μm described in Examples 1-9 was used as the substrate.

<Comparative Example 3>
In the neutralization treatment of Production Example A1, the same operation as in Production Example A1 was performed except that 40% by mass concentration of tetrabutylammonium hydroxide was used instead of sodium hydroxide, and 2% by mass concentration of fine fibrous cellulose A dispersion was obtained. The fine fibrous cellulose had tetrabutylammonium ions (TBA ⁺ ) as counterions. In Example 1-1 (formation of surface protective layer), the fine fibrous cellulose dispersion was added so that the fine fibrous cellulose content was 4 parts by mass with respect to 100 parts by mass of the ultraviolet curable resin (A). , a microfibrous cellulose-containing UV curable resin was prepared. Then, a laminate having a surface protective layer formed directly on the substrate was obtained in the same manner as in Comparative Example 1, except that this fine fibrous cellulose-containing ultraviolet curable resin was used to form the surface protective layer.

<Comparative Example 4>
In Example 1-1 (formation of fiber layer), 90 parts by mass of the polyvinyl alcohol aqueous solution after dilution is added to 10 parts by mass of the fine fibrous cellulose dispersion (A) after dilution to 0.6% by mass. to obtain a mixture (A-6). A laminate was obtained in the same manner as in Example 1-1, except that the mixed solution (A-6) was used instead of the mixed solution (A-1) in Example 1-1.

<Measurement and evaluation>
[Measurement of Phosphorus Acid Group Amount]
In the measurement of the phosphate group content (phosphoric acid group or phosphite group content), ion-exchanged water is first added to the target fine fibrous cellulose to prepare a slurry having a solid content concentration of 0.2% by mass. bottom. The obtained slurry was treated with an ion-exchange resin and then titrated with an alkali for measurement.
The ion-exchange resin treatment is carried out by adding 1/10 by volume of a strongly acidic ion-exchange resin (Amberjet 1024; Organo Co., Ltd., conditioned) to the fine fibrous cellulose-containing slurry and shaking for 1 hour. , by pouring it onto a mesh with an opening of 90 μm to separate the resin and the slurry.
In the titration with alkali, 0.1 N sodium hydroxide aqueous solution is added to the fine fibrous cellulose-containing slurry after treatment with the ion exchange resin, and 10 μL of 0.1 N sodium hydroxide solution is added every 5 seconds. was measured. The titration was performed while nitrogen gas was blown into the slurry from 15 minutes before the start of the titration. In this neutralization titration, two points where the increment (the differential value of the pH with respect to the amount of alkali added) are maximized are observed in the curve obtained by plotting the measured pH against the amount of alkali added. Among these, the maximum point of the increment obtained first when the alkali is first added is called the first end point, and the maximum point of the increment obtained next is called the second end point (Fig. 2). The amount of alkali required from the start of titration to the first end point is equal to the amount of first dissociated acid in the slurry used for titration. Also, the amount of alkali required from the start of titration to the second end point is equal to the total amount of dissociated acid in the slurry used for titration. The amount of alkali (mmol) required from the start of titration to the first end point was divided by the solid content (g) in the slurry to be titrated to obtain the amount of phosphate group (mmol/g).

[Measurement of Sulfur Oxoacid Group Amount and Sulfone Group Amount]
The amount of sulfur oxoacid groups or the amount of sulfone groups was measured as follows. The obtained fine fibrous cellulose (solid content obtained by heating and drying the dispersion) is wet ashed using perchloric acid and concentrated nitric acid, diluted by an appropriate ratio, and the amount of sulfur is measured by ICP emission analysis. It was measured. The amount of sulfur oxoacid groups or the amount of sulfone groups (unit: mmol/g) was obtained by dividing this amount of sulfur by the absolute dry mass of the fine fibrous cellulose tested.

[Measurement of carboxy group content]
The amount of carboxy groups in fine fibrous cellulose can be determined by adding deionized water to a fine fibrous cellulose dispersion containing target (maleated, TEMPO oxidized, hypochlorous acid oxidized or carboxyethylated) fine fibrous cellulose. , the content was set to 0.2% by mass, treated with an ion-exchange resin, and then titrated with an alkali.
The treatment with an ion-exchange resin is carried out by adding 1/10 by volume of a strongly acidic ion-exchange resin (Amberjet 1024; manufactured by Organo Co., Ltd., conditioned) to a slurry containing 0.2% by mass of fine fibrous cellulose, followed by shaking for 1 hour. After being treated, the slurry was separated from the resin by pouring it onto a mesh with an opening of 90 μm.
In addition, the titration using an alkali was performed by measuring the change in the pH value of the slurry while adding a 0.1N sodium hydroxide aqueous solution to the fibrous cellulose-containing slurry after treatment with the ion-exchange resin. . Observing the change in pH while adding an aqueous sodium hydroxide solution yields a titration curve as shown in FIG. As shown in FIG. 3, in this neutralization titration, there is one point where the increment (differential value of pH with respect to the amount of alkali added) is maximum in the curve plotting the measured pH against the amount of alkali added. Observed. The maximum point of this increment is called the first end point. Here, the region from the start of titration to the first end point in FIG. 3 is called the first region. The amount of alkali required in the first region is equal to the amount of carboxyl groups in the slurry used for titration. Then, by dividing the alkali amount (mmol) required in the first region of the titration curve by the solid content (g) in the fine fibrous cellulose-containing slurry to be titrated, the introduction amount of the carboxy group (mmol/g ) was calculated.
The amount of carboxyl groups introduced (mmol/g) described above is the amount ^of substituents per 1 g of mass of fibrous cellulose (hereinafter referred to as the amount of carboxyl groups (acid type)).

[Measurement of carbamide group content]
The introduction amount of carbamide groups in fibrous cellulose (pulp) can be calculated by freeze-drying a slurry containing fibrous cellulose and further pulverizing the sample, and analyzing a trace amount of nitrogen. The introduction amount (mmol/g) of carbamide groups per unit mass of fibrous cellulose is obtained by dividing the nitrogen content (g/g) per unit mass of fibrous cellulose obtained by trace nitrogen analysis by the atomic weight of nitrogen. can be calculated.

[Thickness of fiber layer or adhesive layer]
A cross-section of the laminate is cut out with an ultramicrotome UC-7 (manufactured by JEOL Ltd., UC-7), and the fiber layer or adhesive layer of the cross-section is observed with an electron microscope, a magnifying glass, or visually, and measured. The value was taken as the thickness of the fiber layer or adhesive layer.

[Thickness of surface protective layer]
When the surface protective layer is a resin layer such as modified acrylate, the value measured according to the method for measuring (thickness of fiber layer or adhesive layer) was used as the thickness of the surface protective layer.
When the surface protective layer is an inorganic layer such as silica, a stylus type step thickness meter (P-6, manufactured by KLA Tencor) is used to measure the difference in film thickness between the inorganic layer film formation treated surface and the non-treated surface. was measured, and the difference was taken as the thickness of the surface protective layer.

[Haze]
According to JIS K 7136:2000, the haze of the laminate was measured using a haze meter (HM-150, manufactured by Murakami Color Research Laboratory Co., Ltd.).

[exterior]
Based on the appearance of a laminate having a surface protective layer formed directly on a substrate (control laminate), the appearance was evaluated according to the following evaluation method.
A: Compared to the standard, the increase in yellowness (ΔYI) is less than 2. B: Compared to the standard, the increase in yellowness (ΔYI) is 2 or more. Based on K 7373:2006, it was measured using Color Cute i (manufactured by Suga Test Instruments Co., Ltd.), and the increase in yellowness (ΔYI value) was calculated by the following formula.
ΔYI = (YI of laminates prepared in Examples and Comparative Examples) - (YI of control laminate)

[Pencil hardness]
The pencil hardness of the fiber layer and surface protective layer was measured according to JIS K 5600-5-4:1999. For the measurement, a pencil for pencil scratch value test manufactured by Mitsubishi Pencil Co., Ltd. was used. The measurement of the pencil hardness of the fiber layer was performed after (lamination with the base material) in the examples.

[Increase in Pencil Hardness of Surface Protective Layer]
The degree of increase in pencil hardness of the surface protective layer is 6B = 1, 5B = 2, 4B = 3, 3B = 4, 2B = 5, B = 6, HB = 7, F = 8, H = 9, 2H with respect to pencil hardness. = 10, 3H = 11, 4H = 12, 5H = 13, 6H = 14, 7H = 15, 8H = 16, 9H = 17, and the pencil hardness of the surface protective layer in each example / comparative example P is the value, and Q is the value of the pencil hardness of the surface protective layer of the layered product (control layered product) in which the surface protective layer was formed directly on the base material.
A: PQ≧1 B: PQ≦0

In the examples, the pencil hardness of the surface protective layer was increased compared to the laminate in which the surface protective layer was provided directly on the base material. On the other hand, no increase in the pencil hardness of the surface protective layer was observed in the comparative examples.

2 base material 6 fiber layer 8 surface protective layer 10 laminate

Claims

Having a base material, a fiber layer and a surface protective layer in this order,
The fiber layer contains fibrous cellulose with a fiber width of 1000 nm or less,
The laminate, wherein the content of the fibrous cellulose is 15% by mass or more with respect to the total solid mass of the fiber layer.
The laminate according to claim 1, wherein the fiber layer and the surface protective layer are directly laminated.
The laminate according to claim 1, wherein the fiber layer has a thickness of 50 µm or less.
The laminate according to claim 1, wherein the fiber layer has a thickness of 0.1 μm to 25 μm.
The laminate according to any one of claims 1 to 4, which has a haze of 10% or less.
The laminate according to any one of claims 1 to 4, wherein the fiber layer includes an adhesion aid and/or a structure derived from the adhesion aid.
The laminate according to claim 6, wherein the adhesion aid is at least one selected from silane coupling agents and isocyanate compounds.
The laminate according to any one of claims 1 to 4, wherein the surface protective layer includes an adhesion aid and/or a structure derived from the adhesion aid.
The laminate according to claim 8, wherein the adhesion aid is at least one selected from silane coupling agents and isocyanate compounds.
The laminate according to any one of claims 1 to 4, wherein the surface of the laminate on the side of the surface protective layer has a pencil hardness of 2H or more.
6B=1, 5B=2, 4B=3, 3B=4, 2B=5, B=6, HB=7, F=8, H=9, 2H=10, 3H=11, 4H=12 for pencil hardness , 5H = 13, 6H = 14, 7H = 15, 8H = 16, and 9H = 17, and the numerical value of the pencil hardness of the surface on the surface protective layer side in the laminate is P, and the base material has the above When Q is the numerical value of the pencil hardness of the surface on the side of the surface protective layer in the control laminate obtained by directly laminating the surface protective layer,
5. The laminate according to any one of claims 1 to 4, wherein PQ≧1.
The laminate according to any one of claims 1 to 4, wherein the surface of the fiber layer has a pencil hardness of F or higher.
The laminate according to any one of claims 1 to 4, wherein the fibrous cellulose has an ionic substituent.
An anchoring agent for a surface protective layer containing fibrous cellulose with a fiber width of 1000 nm or less.
An anchor sheet for surface protective layer lamination, containing fibrous cellulose having a fiber width of 1000 nm or less, and having a content of the fibrous cellulose of 15% by mass or more relative to the total solid mass of the anchor sheet.
The anchor sheet according to claim 15, which has a thickness of 50 µm or less.
The anchor sheet according to claim 15, which has a thickness of 0.1 μm to 25 μm.
The anchor sheet according to any one of claims 15 to 17, wherein the surface has a pencil hardness of F or higher.
including a substrate and a fiber layer,
The fiber layer contains fibrous cellulose with a fiber width of 1000 nm or less,
The laminated sheet, wherein the content of the fibrous cellulose is 15% by mass or more with respect to the total solid mass of the fiber layer.
The laminated sheet according to claim 19, wherein the fiber layer has a thickness of 50 µm or less.
The laminated sheet according to claim 19, wherein the fiber layer has a thickness of 0.1 to 25 µm.
The laminated sheet according to any one of claims 19 to 21, wherein the surface of the fiber layer has a pencil hardness of F or higher.
Use of an anchor sheet containing fibrous cellulose with a fiber width of 1000 nm or less to protect the surface of the laminate.
A method for protecting the surface of a laminate, comprising laminating an anchor sheet containing fibrous cellulose having a fiber width of 1000 nm or less under a surface protective layer.