JP2021016982A - Manufacturing method of structure - Google Patents

Abstract

To provide a method for simply obtaining a structure to which a three-dimensional structure of a base material is transferred.SOLUTION: A manufacturing method of a structure to which a three-dimensional structure of a base material surface is transferred includes, in this order, the steps of: obtaining a laminate including a sheet in a wet state mounted on the base material surface having the three-dimensional structure; drying the sheet in a state of being mounted on the base material; and obtaining the structure to which the three-dimensional structure of the base material surface is transferred, by peeling the sheet from the laminate. The sheet comprises fine fibrous cellulose having a fiber width of 1,000 nm or less.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a structure to which the three-dimensional structure of the substrate surface is transferred.

Conventionally, by transferring various surface shapes to a sheet, the sheet is decorated and the sheet is processed into various three-dimensional shapes.
In addition, the transparent synthetic polymer sheet is one of the base materials having excellent strength and workability, and is used as various sheet base materials. The synthetic polymer sheet having an uneven structure on the surface is antireflection. It is widely used as an optical element such as a sheet and a diffraction grating.
In Patent Document 1, the molten thermoplastic resin is extruded into a sheet shape, and while the extruded sheet-like material is taken up, the surface shape of the molding roll is transferred to both surfaces of the sheet-like material to form a groove shape. A method for producing a resin sheet having a checkered pattern that has both a shaping rate and a linearity of the checkered pattern is described.
Further, in Patent Document 2, the molding resin is applied to a base material having an uneven shape on the surface, and the molding resin is pressed against the molding mold. By semi-curing the molding resin, transferring the antireflection uneven shape formed on the molding mold to the surface of the molding resin, and further curing the molding resin. A method for producing an antireflection film is described in which the surface shape of the molding resin is deformed according to the uneven shape of the surface of the base material.

JP-A-2018-1330881 Japanese Unexamined Patent Publication No. 2013-210504

In the method for producing a resin sheet described in Patent Document 1, the surface shape of the molding roll is transferred, but it is difficult to transfer the surface shape of various articles with heating. Further, in Patent Document 2, it cannot be said that it is a simple method because it involves a curing step.
An object of the present invention is to provide a method for easily obtaining a structure to which the three-dimensional structure of a base material is transferred.

The present inventors have found that the above problems can be solved by using a sheet containing fine fibrous cellulose in a wet state.
That is, the present invention relates to the following <1> to <10>.
<1> A step of obtaining a laminate in which a wet sheet is placed on the surface of a base material having a three-dimensional structure, a step of drying the sheet in a state of being placed on the base material, and a step of drying the sheet from the laminate. A step of peeling to obtain a structure to which the three-dimensional structure of the surface of the base material is transferred is obtained in this order, and the sheet contains fine fibrous cellulose having a fiber width of 1,000 nm or less. A method for manufacturing a structure to which the three-dimensional structure of is transferred.
<2> The manufacturing method according to <1>, wherein the three-dimensional structure of the surface of the base material is an uneven structure on the surface of the base material.
<3> The manufacturing method according to <2>, wherein the depth of the concave portion or the height of the convex portion of the uneven structure is 5 nm or more.
<4> The manufacturing method according to <2> or <3>, wherein the depth of the concave portion or the height of the convex portion of the uneven structure is equal to or less than the thickness of the sheet.
<5> The production method according to any one of <2> to <4>, wherein the uneven structure has periodicity.
<6> The production method according to any one of <1> to <5>, wherein the content of the fine fibrous cellulose in the sheet is 5% by mass or more in the solid content.
<7> The production according to any one of <1> to <6>, wherein the surface of the base material is formed of a material selected from metal, silicon, ceramics, plastic, glass, rubber, and a biomaterial. Method.
<8> The method according to any one of <1> to <7>, wherein the wet sheet contains an aqueous solvent of 15 parts by mass or more and 10,000 parts by mass or less with respect to 100 parts by mass of the dry mass of the sheet. Manufacturing method.
<9> The production method according to any one of <1> to <8>, wherein the film thickness of the sheet is 10 μm or more and 10,000 μm or less.
<10> The production method according to any one of <1> to <9>, wherein the moisture content of the sheet after drying is less than 15%.

According to the present invention, it is possible to provide a method for easily obtaining a structure to which the three-dimensional structure of a base material is transferred.

FIG. 1 is a graph showing the relationship between the amount of NaOH added dropwise and the pH of a slurry containing fine fibrous cellulose having a phosphoric acid group. FIG. 2 is a graph showing the relationship between the amount of NaOH added dropwise and the pH of a slurry containing fine fibrous cellulose having a carboxy group. FIG. 3 is a cross-sectional view and a bird's-eye view showing the three-dimensional structure of the surface of the base material used in Example 1. FIG. 4 is an optical micrograph of the structure obtained in Example 1. FIG. 5 is a cross-sectional view and a bird's-eye view showing the three-dimensional structure of the surface of the base material used in Example 2.

[Manufacturing method of structure]
In the method for producing a structure to which the three-dimensional structure of the surface of the base material of the present invention is transferred (hereinafter, also simply referred to as "manufacturing method"), a wet sheet is placed on the surface of the base material having the three-dimensional structure. A step of obtaining the finished laminate (hereinafter, also referred to as "step 1"), a step of drying the sheet while it is placed on a base material (hereinafter, also referred to as "step 2"), and peeling the sheet from the laminate. Then, a step of obtaining a structure to which the three-dimensional structure of the surface of the base material is transferred (hereinafter, also referred to as “step 3”) is performed in this order, and the sheet is a fine fiber having a fiber width of 1,000 nm or less. Tertiary cellulose (hereinafter, also simply referred to as "fine fibrous cellulose" or "CNF") is contained. According to the production method of the present invention, it is possible to obtain a structure to which the three-dimensional shape of the base material is transferred without the need for heating or pressurization with a pressurizing roll. In the following description, the sheet containing fine fibrous cellulose used in the present invention is also referred to as "fine fibrous cellulose-containing sheet", "CNF-containing sheet", or simply "sheet".
The detailed reason for obtaining the above-mentioned effects is unknown, but some of them are considered as follows. Sheets containing fine fibrous cellulose have high water absorption and are characterized by absorbing moisture and expanding. When the fine fibrous cellulose-containing sheet is placed on the surface of a base material having a three-dimensional structure, the swollen sheet is deformed along the three-dimensional structure of the surface of the base material, and the sheet is placed on the base material. It is considered that by drying the sheet, the drying proceeds while maintaining the surface shape, and the three-dimensional structure of the substrate surface is transferred.
Hereinafter, the present invention will be described in more detail.

<Base material>
The base material is not particularly limited as long as it is a base material having a three-dimensional structure on its surface. The three-dimensional structure of the surface of the base material is not limited to the uneven structure of the surface of the base material, and may be a three-dimensional structure such as a bowl shape, a spherical shape, or a triangular roof shape.
Among these, in the production method of the present invention, since the fine three-dimensional structure of the base material surface can be transferred to the sheet, the three-dimensional structure of the base material surface is on the base material surface. It is preferably an uneven structure. From the viewpoint of precisely transferring the three-dimensional structure to the sheet, the depth of the concave portion or the height of the convex portion is preferably 5 nm or more, more preferably 10 nm or more, still more preferably 20 nm or more, still more preferably 50 nm or more. And, preferably 300 μm or less, more preferably 100 μm or less, still more preferably 50 μm or less.
When the three-dimensional structure of the surface of the base material is an uneven structure on the surface of the base material, the depth of the concave portion or the height of the convex portion is equal to or less than the thickness of the CNF-containing sheet from the viewpoint of precisely transferring the uneven shape. Is preferable.

In the present invention, the shape of the uneven structure on the surface of the base material is not particularly limited, but according to the production method of the present invention, a structure in which the three-dimensional structure of the fine base material surface is transferred can be obtained. It is preferable that the structure is uneven. As a result, the structure to which the three-dimensional structure of the surface of the base material is transferred can be used as an optical element such as a diffraction grating or a reflection lattice sheet.
Therefore, it is particularly preferable that the three-dimensional structure of the surface of the base material is an uneven structure having periodicity.

The material of the base material is not particularly limited, but from the viewpoint of placing the sheet in the wet state, it is preferable that the surface shape does not change by placing the sheet in the wet state.
Specifically, the surface of the substrate is preferably formed of a material selected from metals, silicon, ceramics, plastics, glass, rubber, and biomaterials. Examples of biomaterials include skins, teeth, organs, and the like of human bodies and animals.

<Sheet containing fine fibrous cellulose>
The fine fibrous cellulose-containing sheet preferably contains at least fine fibrous cellulose and, in addition, a water-soluble polymer.
Each component contained in the fine fibrous cellulose-containing sheet will be described below.

[Fine fibrous cellulose]
The fine fibrous cellulose is a fibrous cellulose having a fiber width of 1,000 nm or less. The fiber width of the fibrous cellulose can be measured by, for example, observation with an electron microscope.
The fiber width of the fine fibrous cellulose is 1,000 nm or less. The fiber width of the fine fibrous cellulose is, for example, preferably 2 nm or more and 1,000 nm or less, more preferably 2 nm or more and 100 nm or less, further preferably 2 nm or more and 50 nm or less, and 2 nm or more and 10 nm or less. Is particularly preferred. By setting the fiber width of the fine fibrous cellulose to 2 nm or more, it is possible to suppress the dissolution of the fine fibrous cellulose in water as a cellulose molecule, and to make it easier to exhibit the effects of the fine fibrous cellulose on improving strength, rigidity and dimensional stability. Can be done.

The average fiber width of the fine fibrous cellulose is, for example, 1,000 nm or less. The average fiber width of the fine fibrous cellulose is preferably 2 nm or more and 1,000 nm or less, more preferably 2 nm or more and 100 nm or less, further preferably 2 nm or more and 50 nm or less, and 2 nm or more and 10 nm or less. Is particularly preferred. By setting the average fiber width of the fine fibrous cellulose to 2 nm or more, it is possible to suppress the dissolution of the fine fibrous cellulose in water as a cellulose molecule, and to more easily exhibit the effects of the fine fibrous cellulose to improve strength, rigidity and dimensional stability. be able to. The fine fibrous cellulose is, for example, monofibrous cellulose.

The average fiber width of the fine fibrous cellulose is measured as follows, for example, using an electron microscope. First, an aqueous suspension of fibrous cellulose having a concentration of 0.01% 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 prepare a sample for TEM observation. And. If it contains wide fibers, an SEM image of the surface cast on the glass may be observed. Next, observation is performed using an electron microscope image at a magnification of 1,000 times, 5,000 times, 10,000 times, or 50,000 times depending on the width of the fiber to be observed. However, the sample, observation conditions and magnification should be adjusted so as to satisfy the following conditions.
(1) A straight line X is drawn at an arbitrary position in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y that intersects the straight line perpendicularly is drawn in the same image, and 20 or more fibers intersect the straight line Y.

The width of the fiber intersecting the straight line X and the straight line Y is visually read with respect to the observation image satisfying the above conditions. In this way, at least three sets of observation images of surface portions that do not overlap each other are obtained. Next, for each image, the width of the fiber intersecting the straight line X and the straight line Y is read. As a result, at least 20 fibers × 2 × 3 = 120 fibers are read. Then, the average value of the read fiber widths is taken as the average fiber width of the fibrous cellulose.

The fiber length of the fine fibrous cellulose is not particularly limited, but is preferably 0.1 μm or more and 1,000 μm or less, more preferably 0.1 μm or more and 800 μm or less, and 0.1 μm or more and 600 μm or less. Is even more preferable. By setting the fiber length within the above range, destruction of the crystal region of the fine fibrous cellulose can be suppressed. Further, it is possible to set the slurry viscosity of the fine fibrous cellulose in an appropriate range. The fiber length of the fine fibrous cellulose can be obtained by, for example, image analysis by TEM, SEM, or AFM.

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

The axial ratio (fiber length / fiber width) of the fine fibrous cellulose is not particularly limited, but is preferably 20 or more and 10,000 or less, and more preferably 50 or more and 1,000 or less. By setting the axial ratio to the above lower limit value or more, it is easy to form a sheet containing fine fibrous cellulose. In addition, sufficient viscosity can be easily obtained when the solvent dispersion is produced. By setting the axial ratio to the above upper limit value or less, for example, when treating fine fibrous cellulose as an aqueous dispersion, it is preferable in that handling such as dilution becomes easy.

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

Examples of the anionic group as an ionic group include a phosphoric acid group or a substituent derived from a phosphoric acid group (sometimes simply referred to as a phosphoric acid group), a carboxy group or a substituent derived from a carboxy group (simply referred to as a carboxy group). (Sometimes), and at least one selected from a sulfone group or a substituent derived from a sulfone group (sometimes simply referred to as a sulfone group), preferably at least one selected from a phosphoric acid group and a carboxy group. It is more preferably a species, especially a phosphorusoxo acid group.

The phosphoric acid group or the substituent derived from the phosphoric acid group is, for example, a substituent represented by the following formula (1).
The phosphorus oxo acid group is, for example, a divalent functional group obtained by removing a hydroxy group from phosphoric acid. Specifically, it is a group represented by −PO ₃ H ₂ . Substituents derived from a phosphorus oxo acid group include substituents such as a salt of a phosphorus oxo acid group and a phosphorus oxo acid ester group. The substituent derived from the phosphoric acid group may be contained in the fine fibrous cellulose as a group in which the phosphoric acid group is condensed (for example, a pyrophosphate group). Further, the phosphorous acid group may be, for example, a phosphorous acid group (phosphonic acid group), and the substituent derived from the phosphorous acid group is a salt of a phosphorous acid group, a phosphorous acid ester group, or the like. May be good.

In the formula (1), a, b and n are natural numbers, and m is an arbitrary number (where a = b × m). Of α ¹ , α ² , ..., α ⁿ and α', a are O ⁻ , and the rest are either R or OR. It is also possible that all of each α ⁿ and α'are O ⁻ . R is a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched chain hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, and an unsaturated-branched chain hydrocarbon, respectively. A hydrogen group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or an inducing group thereof. In addition, α in the formula (1) may be a group derived from a cellulose molecular chain.

Examples of the saturated-linear hydrocarbon group include, but are not limited to, a methyl group, an ethyl group, an n-propyl group, an n-butyl group and the like. Examples of the saturated-branched chain hydrocarbon group include an i-propyl group and a t-butyl group, but are not particularly limited. Examples of the saturated-cyclic hydrocarbon group include, but are not limited to, a cyclopentyl group, a cyclohexyl group and the like. Examples of the unsaturated-linear hydrocarbon group include, but are not limited to, a vinyl group, an allyl group and the like. Examples of the unsaturated-branched chain hydrocarbon group include an i-propenyl group and a 3-butenyl group, but are not particularly limited. Examples of the unsaturated-cyclic hydrocarbon group include, but are not limited to, a cyclopentenyl group, a cyclohexenyl group and the like. Examples of the aromatic group include, but are not limited to, a phenyl group, a naphthyl group and the like.
Further, as the inducing group in R, a functional group in which at least one of functional groups such as a carboxy group, a hydroxy group, or an amino group is added or substituted with respect to the main chain or side chain of the above-mentioned various hydrocarbon groups. The group is mentioned, but it is not particularly limited. The number of carbon atoms constituting the main chain of R is not particularly limited, but is preferably 20 or less, and more preferably 10 or less. By setting the number of carbon atoms constituting the main chain of R to the above range, the molecular weight of the phosphorus oxo acid group can be set to an appropriate range, the penetration into the fiber raw material is facilitated, and the yield of the fine cellulose fiber is increased. You can also do it.

β ^{b +} is a monovalent or higher cation composed of an organic substance or an inorganic substance. Examples of monovalent or higher cations composed of organic substances include aliphatic ammonium or aromatic ammonium, and examples of monovalent or higher valent cations composed of inorganic substances include alkali metal ions such as sodium, potassium, and lithium. Examples thereof include cations of divalent metals such as calcium and magnesium, hydrogen ions, and the like, but the present invention is not particularly limited. These may be applied alone or in combination of two or more. The monovalent or higher cation composed of an organic substance or an inorganic substance is preferably sodium or potassium ion which is hard to yellow when the fiber raw material containing β is heated and is easily industrially used, but is not particularly limited.

The amount of the ionic group introduced into the fine fibrous cellulose is preferably 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, and more preferably 0.20 mmol / g or more per 1 g (mass) of the fine fibrous cellulose. It is more preferably 50 mmol / g or more, and particularly preferably 1.00 mmol / g or more. The amount of the ionic group introduced into the fine fibrous cellulose is preferably 5.20 mmol / g or less, more preferably 3.65 mmol / g or less per 1 g (mass) of the fine fibrous cellulose, for example. It is more preferably 3.50 mmol / g or less, and even more preferably 3.00 mmol / g or less. By setting the amount of the ionic group introduced within the above range, it is possible to facilitate the miniaturization of the fiber raw material and enhance the stability of the fine fibrous cellulose. Further, by setting the amount of the ionic group introduced within the above range, good properties can be exhibited in various applications such as a thickener for fine fibrous cellulose.
Here, the denominator in the unit mmol / g indicates the mass of the fine fibrous cellulose when the counter ion of the ionic group is a hydrogen ion (H ⁺ ).

The amount of the ionic group introduced into the fine fibrous cellulose can be measured by, for example, a neutralization titration method. In the measurement by the neutralization titration method, the introduction amount is measured by determining the change in pH while adding an alkali such as an aqueous sodium hydroxide solution to the obtained slurry containing fine fibrous cellulose.
FIG. 1 is a graph showing the relationship between the amount of NaOH added dropwise to fine fibrous cellulose having a phosphoric acid group and pH.

FIG. 1 is a graph showing the relationship between the amount of NaOH added dropwise and the pH of a slurry containing fine fibrous cellulose having a phosphoric acid group. The amount of the phosphorus oxo acid group introduced into the fine fibrous cellulose is measured, for example, as follows.
First, the slurry containing fine fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, the defibration treatment similar to the defibration treatment step described later may be performed on the measurement target before the treatment with the strongly acidic ion exchange resin.
Next, the change in pH is observed while adding an aqueous sodium hydroxide solution, and a titration curve as shown in the upper part of FIG. 1 is obtained. The titration curve shown in the upper part of FIG. 1 plots the measured pH with respect to the amount of alkali added, and the titration curve shown in the lower part of FIG. 1 plots the pH with respect to the amount of alkali added. The increment (differential value) (1 / mmol) is plotted. In this neutralization titration, two points are confirmed in which the increment (differential value of pH with respect to the amount of alkali dropped) becomes maximum in the curve plotting the measured pH with respect to the amount of alkali added. Of these, the maximum point of the increment obtained first when alkali is 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 was equal to the amount of first dissociated acid of the fine fibrous cellulose contained in the slurry used for titration, and was required from the first end point to the second end point. The amount of alkali is equal to the amount of second dissociating acid of the fine fibrous cellulose contained in the slurry used for titration, and the amount of alkali required from the start to the second end point of titration is contained in the slurry used for titration. Equal to the total dissociated acid content of the fibrous cellulose. Then, the 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 oxo acid group introduced (mmol / g). The amount of phosphorus oxo acid group introduced (or the amount of phosphorus oxo acid group) simply means the amount of the first dissociated acid.
In FIG. 1, the region from the start of titration to the first end point is referred to as a first region, and the region from the first end point to the second end point is referred to as a second region. For example, when the phosphoric acid group is a phosphoric acid group and the phosphoric acid group causes condensation, the amount of weakly acidic groups in the phosphoric acid group (also referred to as the second dissociated acid amount in the present specification) is apparently It decreases, and the amount of alkali required for the second region is smaller than the amount of alkali required for the first region. On the other hand, the amount of strongly acidic groups in the phosphorus oxo acid group (also referred to as the first dissociated acid amount in the present specification) is the same as the amount of phosphorus atoms regardless of the presence or absence of condensation. Further, when the phosphorous acid group is a phosphorous acid group, the weakly acidic group does not exist in the phosphorous acid group, so that the amount of alkali required for the second region is reduced or the amount of alkali required for the second region is reduced. May be zero. In this case, the titration curve has one point where the pH increment is maximized.
Since the denominator of the above-mentioned phosphorus oxo acid group introduction amount (mmol / g) indicates the mass of the acid-type fine fibrous cellulose, the phosphorus oxo acid group amount (hereinafter, phosphorus oxo acid) possessed by the acid-type fine fibrous cellulose It is called the base amount (acid type)). On the other hand, when the counterion of the phosphorus oxo acid group is replaced with an arbitrary cation C so as to have a charge equivalent, the denominator is converted to the mass of fine fibrous cellulose when the cation C is a counterion. By doing so, the amount of phosphorus oxo acid groups (hereinafter, the amount of phosphorus oxo acid groups (C type)) possessed by the fine fibrous cellulose in which the cation C is a counterion can be obtained.
That is, it is calculated by the following formula.
Amount of phosphorus oxo acid group (C type) = Amount of phosphorus oxo acid group (acid type) / {1+ (W-1) x A / 1,000}
A [mmol / g]: Total anion amount derived from the phosphoric acid group of the fine fibrous cellulose (the sum of the strong acid group amount and the weakly acidic group amount of the phosphoric acid group).
W: Formula unit of cation C per valence (for example, Na is 23, Al is 9)

In the measurement of the amount of phosphorus oxo acid groups by the titration method, if the amount of one drop of the sodium hydroxide aqueous solution is too large or the titration interval is too short, the amount of phosphorus oxo acid groups will be lower than the original value. It may not be obtained. As an appropriate dropping amount and titration interval, for example, it is desirable to titrate 10 to 50 μL of a 0.1 N sodium hydroxide aqueous solution every 5 to 30 seconds. Further, in order to eliminate the influence of carbon dioxide dissolved in the fine 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. ..

FIG. 2 is a graph showing the relationship between the amount of NaOH added dropwise to fine fibrous cellulose having a carboxy group and pH.
The amount of the carboxy group introduced into the fine fibrous cellulose is measured, for example, as follows.
First, the slurry containing fine fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, the defibration treatment similar to the defibration treatment step described later may be performed on the measurement target before the treatment with the strongly acidic ion exchange resin. Next, the change in pH is observed while adding an aqueous sodium hydroxide solution to obtain a titration curve as shown in FIG. If necessary, the same defibration treatment as the defibration treatment step described later may be performed on the measurement target.
As shown in FIG. 2, in this neutralization titration, there is one point in which the increment (differential value of pH with respect to the amount of alkaline drop) becomes maximum in the curve plotting the measured pH with respect to 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. 2 is referred to as a first region. The amount of alkali required in the first region is equal to the amount of carboxy groups in the slurry 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 fine fibrous cellulose-containing slurry to be titrated, so that the amount of carboxy group introduced (mmol / g). ) Was calculated.
The above-mentioned amount of carboxy group introduced (mmol / g) is the amount of substituents per 1 g of mass of fine fibrous cellulose when the counterion of the carboxy group is hydrogen ion (H ⁺ ) (hereinafter, the amount of carboxy group (hereinafter, carboxy group amount). It is called (acid type)).

Since the denominator of the above-mentioned carboxy group introduction amount (mmol / g) is the mass of the acid-type fine fibrous cellulose, the carboxy group amount of the acid-type fine fibrous cellulose (hereinafter, the carboxy group amount (hereinafter, carboxy group amount) It is called (acid type)). On the other hand, when the counterion of the carboxy group is replaced with an arbitrary cation C so as to have a charge equivalent, the denominator is converted to the mass of fine fibrous cellulose when the cation C is a counterion. This makes it possible to determine the amount of carboxy group (hereinafter, carboxy group amount (C type)) (mmol / g) possessed by the fine fibrous cellulose in which the cation C is a counter ion.
That is, it is calculated by the following formula.
Carboxylic acid group amount (C type) = Carboxylic acid group amount (acid type) / {1+ (W-1) x (carboxyl group amount (acid type)) / 1000}
W: Formula unit of cation C per valence (for example, Na is 23, Al is 9)

In the measurement of the amount of substituents by the titration method, if the titration interval of the aqueous sodium hydroxide solution is too short, the amount of substituents may be lower than the original amount. Therefore, an appropriate titration interval, for example, 0.1 N hydroxide. It is desirable to titrate 10 to 50 μL of the aqueous sodium solution every 5 to 30 seconds.
Further, the above-mentioned measurement of the amount of phosphorus oxo acid group and the measurement of the amount of carboxy group described later are described as the measurement of the amount of phosphorus oxo acid group and the amount of carboxy group of fine fibrous cellulose, but the same applies to the ionic group-introduced fiber. It is measurable.

The content of the fine fibrous cellulose in the solid content of the fine fibrous cellulose-containing sheet is excellent in strength and transparency, and is preferably 5% by mass or more, more preferably from the viewpoint of transferring the three-dimensional structure of the base material. Is 10% by mass or more, more preferably 15% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, still more preferably 85% by mass or less.

[Manufacturing method of fine fibrous cellulose]
(Fiber raw material containing cellulose)
Fine fibrous cellulose is produced from a fiber raw material containing cellulose.
The fiber raw material containing cellulose is not particularly limited, but pulp is preferably used because it is easily available and inexpensive. Examples of pulp include wood pulp, non-wood pulp, and deinked pulp. The wood pulp is not particularly limited, but is, for example, broadleaf kraft pulp (LBKP), coniferous kraft pulp (NBKP), sulfite pulp (SP), dissolved pulp (DP), soda pulp (AP), and unbleached kraft pulp (UKP). ) And chemical pulp such as oxygen bleached kraft pulp (OKP), semi-chemical pulp such as semi-chemical pulp (SCP) and chemiground wood pulp (CGP), crushed wood pulp (GP) and thermomechanical pulp (TMP, BCTMP), etc. Examples include mechanical pulp. The non-wood pulp is not particularly limited, and examples thereof include cotton pulp such as cotton linter and cotton lint, and non-wood pulp such as hemp, straw and bagasse. The deinking pulp is not particularly limited, and examples thereof include deinking pulp made from used paper. As the pulp of the present embodiment, one of the above types may be used alone, or two or more types may be mixed and used.
Among the above pulps, for example, wood pulp and deinked pulp are preferable from the viewpoint of availability. Further, among wood pulp, long fiber fine fibrous cellulose having a large cellulose ratio and a high yield of fine fibrous cellulose during defibration treatment and a large axial ratio with less decomposition of cellulose in the pulp can be obtained. From the viewpoint, for example, chemical pulp is more preferable, and kraft pulp and sulfite pulp are further preferable. When long fiber fine fibrous cellulose having a large axial ratio is used, the viscosity tends to increase.
As the fiber raw material containing cellulose, for example, cellulose contained in ascidians and bacterial cellulose produced by acetobacter can be used.
Further, instead of the fiber raw material containing cellulose, a fiber formed by a linear nitrogen-containing polysaccharide polymer such as chitin or chitosan can also be used.

In order to obtain the above-mentioned fine fibrous cellulose into which an ionic group has been introduced, an ionic group introduction step, a washing step, and an alkali treatment step (neutralization step) in which the ionic group is introduced into the above-mentioned fiber raw material containing cellulose ), It is preferable to have the defibration treatment step in this order, and the acid treatment step may be provided instead of the washing step or in addition to the washing step. Examples of the ionic group introduction step include a phosphorus oxo acid group introduction step and a carboxy group introduction step. Each will be described below.

(Ionic group introduction process)
-Linoxo acid group introduction process-
In the phosphorus oxo acid group introduction step, at least one compound (hereinafter, also referred to as “compound A”) selected from compounds capable of introducing a phosphorus oxo acid group by reacting with a hydroxyl group of a fiber raw material containing cellulose is introduced into cellulose. It is a step of acting on a fiber raw material containing. By this step, a phosphorus oxo acid group-introduced fiber can be obtained.
In the phosphorus oxo acid group introduction step according to the present embodiment, the reaction between the fiber raw material containing cellulose and Compound A is carried out in the presence of at least one selected from urea and its derivatives (hereinafter, also referred to as “Compound B”). You may. On the other hand, the reaction of the fiber raw material containing cellulose with the compound A may be carried out in the absence of the compound B.
As an example of the method of allowing the compound A to act on the fiber raw material in the coexistence with the compound B, there 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. Of these, since the reaction uniformity is high, 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. The form of the fiber raw material is not particularly limited, but is preferably cotton-like or thin sheet-like, for example. Examples of the compound A and the compound B include a method of adding the compound A and the compound B to the fiber raw material in the form of a powder or a solution dissolved in a solvent, or in a state of being heated to a melting point or higher and melted. Of these, since the reaction has high uniformity, it is preferable to add the mixture in the form of a solution dissolved in a solvent, particularly in the form of an aqueous solution. Further, the compound A and the compound B may be added to the fiber raw material at the same time, may be added separately, or may be added as a mixture. The method of 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 dropped into the water. Further, the required amounts of Compound A and Compound B may be added to the fiber raw material, or after the excess amounts of Compound A and Compound B are added to the fiber raw material, respectively, the excess Compound A and Compound B are added by pressing or filtering. It may be removed.

The compound A used in this embodiment may be a compound having a phosphorus atom and capable of forming an ester bond with cellulose, and may be phosphoric acid or a salt thereof, phosphoric acid or a salt thereof, dehydration-condensed phosphoric acid or a salt thereof. Examples thereof include salts and anhydrous phosphoric acid (diphosphorus pentoxide), but the present invention is not particularly limited. As the phosphoric acid, those having various puritys can be used, and for example, 100% phosphoric acid (normal phosphoric acid) or 85% phosphoric acid can be used. Examples of phosphorous acid include 99% phosphorous acid (phosphonic acid). The dehydration-condensed phosphoric acid is one in which two or more molecules of phosphoric acid are condensed by a dehydration reaction, and examples thereof include pyrophosphoric acid and polyphosphoric acid. Examples of phosphates, phosphates, and dehydration-condensed phosphates include lithium salts, sodium salts, potassium salts, and ammonium salts of phosphoric acid, phosphorous acid, or dehydration-condensed phosphoric acid, and these are among various types. It can be a sum.
Of these, phosphoric acid and phosphoric acid have high efficiency of introducing a phosphoric acid group, are likely to improve the defibration efficiency in the defibration step described later, are low in cost, and are easy to apply industrially. A sodium salt, a potassium salt of phosphoric acid, or an ammonium salt of phosphoric acid is preferable, and phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, or ammonium dihydrogen phosphate is more preferable.
The amount of compound A added to the fiber raw material is not particularly limited, but for example, when the amount of compound A added is converted to the phosphorus atomic weight, the amount of phosphorus atom 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 further 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 addition amount of the phosphorus atom to the fiber raw material to be equal to or less than the above upper limit value, the effect of improving the yield and the cost can be balanced.

Compound B used in this embodiment is at least one selected from urea and its derivatives as described above. Examples of compound B include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, 1-ethylurea and the like.
From the viewpoint of improving the uniformity of the reaction, compound B is preferably used as an aqueous solution. Further, 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, and more preferably 10% by mass or more and 400% by mass or less. It is more preferably 100% by mass or more and 350% by mass or less.

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

In the phosphorus oxo acid group introduction step, it is preferable to add or mix the compound A or the like to the fiber raw material and then heat-treat the fiber raw material. As the heat treatment temperature, it is preferable to select a temperature at which a phosphorus oxo acid group can be efficiently introduced while suppressing the 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 further preferably 130 ° C. or higher and 200 ° C. or lower. In addition, equipment having various heat media can be used for the heat treatment, for example, a stirring drying device, a rotary drying device, a disk drying device, a roll type heating device, a plate type heating device, a fluidized layer drying device, and a band. A mold drying device, a filtration drying device, a vibration flow drying device, an air flow 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, compound A is added to a thin sheet-shaped fiber raw material by a method such as impregnation and then heated, or the fiber raw material and compound A are heated while kneading or stirring with a kneader or the like. Can be adopted. This makes it possible to suppress uneven concentration of the compound A in the fiber raw material and more uniformly introduce the phosphorus oxo acid group onto the surface of the cellulose fiber contained in the fiber raw material. This is because when the water molecules move to the surface of the fiber raw material due to drying, the dissolved compound A is attracted to the water molecules by the surface tension and also moves to the surface of the fiber raw material (that is, the concentration unevenness of the compound A is caused. It is considered that this is due to the fact that it can be suppressed.
Further, the heating device used for the heat treatment always keeps the water content retained by the slurry and the water content generated by the dehydration condensation (phosphate esterification) reaction between the compound A and the hydroxyl group contained in the cellulose or the like in the fiber raw material. It is preferable that the device can be discharged to the outside. Examples of such a heating device include a ventilation type oven and the like. By constantly discharging the water in the apparatus system, in addition to being able to suppress the hydrolysis reaction of the phosphate ester bond, which is the reverse reaction of phosphate esterification, it is also possible to suppress the acid hydrolysis of the sugar chain in the fiber. it can. Therefore, it is possible to obtain fine fibrous cellulose having a high axial ratio.
The heat treatment time is 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 the water is substantially removed from the fiber raw material. Is more preferable. In the present embodiment, the amount of the phosphorus oxo acid group introduced can be within a preferable range by setting the heating temperature and the heating time within an appropriate range.

The phosphorus oxo acid group introduction step may be performed at least once, but may be repeated twice or more. By performing the phosphorus oxo acid group introduction step two or more times, many phosphorus oxo acid groups can be introduced into the fiber raw material. In the present embodiment, as an example of a preferable embodiment, there is a case where the phosphorus oxo acid group introduction step is performed twice.

The amount of the phosphorus oxo acid group introduced into the fiber raw material is, for example, 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, and 0.50 mmol / g / g per 1 g (mass) of fine fibrous cellulose. It is more preferably g or more, and particularly preferably 1.00 mmol / g or more. Further, the amount of the phosphorus oxo acid group introduced into the fiber raw material is preferably 5.20 mmol / g or less, more preferably 3.65 mmol / g or less per 1 g (mass) of fine fibrous cellulose, for example. It is more preferably 00 mmol / g or less. By setting the amount of the phosphorus oxo acid group introduced within the above range, it is possible to facilitate the miniaturization of the fiber raw material and enhance the stability of the fine fibrous cellulose.

-Carboxylic acid group introduction process-
The carboxy group introduction step has an oxidation treatment such as ozone oxidation, oxidation by the Fenton method, TEMPO oxidation treatment, a compound having a group derived from carboxylic acid or a derivative thereof, or a group derived from carboxylic acid with respect to the fiber raw material containing cellulose. This is done by treating with an acid anhydride of the compound or a derivative thereof.
The compound having a group derived from a carboxylic acid is not particularly limited, but for example, a dicarboxylic acid compound such as maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric acid, adipic acid, itaconic acid, citric acid, aconitic acid and the like. Examples include tricarboxylic acid compounds. The derivative of the compound having a group derived from carboxylic acid is not particularly limited, and examples thereof include an imide of an acid anhydride of a compound having a carboxy group and a derivative of an acid anhydride of a compound having a carboxy group. The imide of the acid anhydride of the compound having a carboxy group is not particularly limited, and examples thereof include an imide of a dicarboxylic acid compound such as maleimide, succinateimide, and phthalateimide.

The acid anhydride of the compound having a group derived from carboxylic acid is not particularly limited, but for example, a dicarboxylic acid compound such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, itaconic anhydride and the like. Acid anhydride can be mentioned. The derivative of the acid anhydride of the compound having a group derived from carboxylic acid is not particularly limited, but for example, a compound having a carboxy group such as dimethylmaleic acid anhydride, diethylmaleic acid anhydride, diphenylmaleic acid anhydride and the like. Examples thereof include those in which at least a part of hydrogen atoms of the acid anhydride is substituted with a substituent such as an alkyl group or a phenyl group.

When the TEMPO oxidation treatment is carried out in the carboxy group introduction step, it is preferable to carry out the treatment under conditions of pH 6 or more and 8 or less, for example. Such a treatment is also referred to as a neutral TEMPO oxidation treatment. The neutral TEMPO oxidation treatment includes, for example, sodium phosphate buffer (pH = 6.8), pulp as a fiber raw material, TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl) as a catalyst, and the like. This can be done by adding a nitroxy radical and sodium hypochlorite as a sacrificial reagent. Further, by coexisting sodium chlorite, the aldehyde generated in the oxidation process can be efficiently oxidized to the carboxy group.
Further, the TEMPO oxidation treatment may be carried out under the condition that the pH is 10 or more and 11 or less. Such a treatment is also referred to as an alkaline TEMPO oxidation treatment. The alkaline TEMPO oxidation treatment can be carried out, for example, by adding a nitroxy radical such as TEMPO as a catalyst, sodium bromide as a co-catalyst, and sodium hypochlorite as an oxidizing agent to pulp as a fiber raw material. ..
The amount of carboxy group introduced into the fiber raw material varies depending on the type of substituent, but for example, when introducing a carboxy group by TEMPO oxidation, it is preferably 0.10 mmol / g or more per 1 g (mass) of fine fibrous cellulose. , 0.20 mmol / g or more, more preferably 0.50 mmol / g or more, and particularly preferably 0.90 mmol / g or more. Further, it 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. 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.

(Washing process)
In the method for producing fine fibrous cellulose in the present embodiment, a washing step can be performed on the ionic group-introduced fibers as needed. The washing step is performed by washing the ionic group-introduced fibers with, for example, water or an organic solvent. Further, the cleaning step may be performed after each step described later, and the number of cleanings performed in each cleaning step is not particularly limited.

(Alkaline treatment (neutralization treatment) process)
When producing fine fibrous cellulose, an alkali treatment (neutralization treatment) may be performed on the fiber raw material between the ionic group introduction step and the defibration treatment step described later. The alkaline treatment method is not particularly limited, and examples thereof include a method of immersing the ionic group-introduced fiber in an alkaline 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, for example, sodium hydroxide or potassium hydroxide is preferably used as the alkaline compound because of its high versatility. Further, 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 a polar solvent containing water or a polar organic solvent exemplified by alcohol, and more preferably an aqueous solvent containing at least water. As the alkaline solution, for example, an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide is preferable because of its high versatility.
The temperature of the alkaline solution in the alkaline treatment step is not particularly limited, but is preferably 5 ° C. or higher and 80 ° C. or lower, and more preferably 10 ° C. or higher and 60 ° C. or lower. The immersion time of the ionic group-introduced fiber in the alkaline solution in the alkali treatment step is not particularly limited, but is preferably 5 minutes or more and 30 minutes or less, and 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 is preferably 100% by mass or more and 100,000% by mass or less, and 1000% by mass or more and 10,000% by mass or less, for example, with respect to the absolute dry mass of the ionic group-introduced fiber. Is more preferable.

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

(Acid treatment process)
When producing fine fibrous cellulose, the fiber raw material may be subjected to acid treatment between the step of introducing an ionic group and the defibration treatment step described later. For example, the ionic group introduction step, the acid treatment step, the alkali treatment step, and the defibration treatment step may be performed in this order.
The acid treatment method is not particularly limited, and examples thereof include a method of immersing the fiber raw material in an acidic liquid containing an acid. The concentration of the acidic liquid used is not particularly limited, but is preferably, for example, 10% by mass or less, and more preferably 5% by mass or less. The pH of the acidic solution used is not particularly limited, but is preferably 0 or more and 4 or less, and more preferably 1 or more and 3 or less. As the acid contained in the acidic solution, for example, an inorganic acid, a sulfonic acid, a carboxylic acid or the like can be used. Examples of the inorganic acid include sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chloric acid, chloric acid, perchloric acid, phosphoric acid, boric acid and the like. Examples of the sulfonic acid include methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid and the like. Examples of the carboxylic acid include formic acid, acetic acid, citric acid, gluconic acid, lactic acid, oxalic acid, tartaric acid and the like. 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, and 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, and 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, but is preferably 100% by mass or more and 100,000% by mass or less, and 1000% by mass or more and 10,000% by mass or less, for example, with respect to the absolute dry mass of the fiber raw material. Is more preferable.

(Defibration processing process)
Fine fibrous cellulose can be obtained by defibrating the ionic group-introduced fiber in the defibration treatment step.
In the defibration treatment step, for example, a defibration treatment apparatus can be used. The defibrating apparatus is not particularly limited, but for example, a high-speed defibrator, a grinder (stone mill type crusher), a high-pressure homogenizer or an ultra-high pressure homogenizer, a high-pressure collision type crusher, a ball mill, a bead mill, a disc type refiner, a conical refiner, and a twin shaft. A kneader, a vibration mill, a homomixer under high speed rotation, an ultrasonic disperser, or a beater can be used. Among the above-mentioned defibration processing devices, it is more preferable to use a high-speed defibrator, a high-pressure homogenizer, and an ultra-high-pressure homogenizer, which are less affected by crushed media and less likely to cause contamination.

In the defibration treatment step, for example, it is preferable to dilute the ionic group-introduced fiber with a dispersion medium to form a slurry. As the dispersion medium, one or more selected from water and an organic solvent such as a polar organic solvent can be used. The polar organic solvent is not particularly limited, but for example, 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, glycerin and the like. Examples of 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 monon-butyl ether, propylene glycol monomethyl ether and the like. Examples of the esters include ethyl acetate, butyl acetate and the like. Examples of the aprotic polar solvent include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone (NMP) and the like.

The solid content concentration of the fine fibrous cellulose during the defibration treatment can be appropriately set.
Further, the slurry obtained by dispersing the phosphorus oxo acid group-introduced fiber in the dispersion medium may contain a solid content other than the phosphorus oxo acid group-introduced fiber such as urea having a hydrogen bond property.

[Water-soluble polymer]
In the present invention, the fine fibrous cellulose-containing sheet preferably contains a water-soluble polymer.
Examples of the water-soluble polymer include carboxyvinyl polymer; polyvinyl alcohol; alkyl methacrylate / acrylic acid copolymer; polyvinylpyrrolidone; sodium polyacrylate; polyalkylene glycol such as polyethylene glycol and polypropylene glycol; polyacrylamide; xanthan gum, guar gum, tamarind. Thickening polymers such as gum, carrageenan, locust bean gum, quince seeds, alginic acid, metal salts of alginic acid, purulan, carrageenan, and starch; cellulose derivatives such as carboxymethyl cellulose, methyl cellulose, and hydroxyethyl cellulose; Examples of starches such as cationized starch, raw starch, oxidized starch, etherified starch, esterified starch, and amylose; glycerins such as polyglycerin; hyaluronic acid, metal salts of hyaluronic acid, and the like can be mentioned.
Among these, polyethylene glycol (PEG) and polyvinyl alcohol are among the water-soluble polymers from the viewpoint of obtaining a fine fibrous cellulose-containing sheet having excellent transparency and flexibility and excellent transferability of the three-dimensional structure on the surface of the base material. (PVA), modified polyvinyl alcohol (modified PVA) and polyethylene oxide (PEO) are preferred.

The content of the water-soluble polymer in the solid content of the fine fibrous cellulose-containing sheet is excellent in strength and transparency, and is preferably 5% by mass or more, more preferably from the viewpoint of transferring the three-dimensional structure of the base material. Is 10% by mass or more, more preferably 15% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, still more preferably 85% by mass or less.

[Manufacturing method of fine fibrous cellulose-containing sheet]
In the present embodiment, the fine fibrous cellulose-containing sheet can be obtained, for example, by carrying out the sheet forming step described later using the liquid composition containing the fine fibrous cellulose and the water-soluble polymer described above. Can be done.

In addition to fine fibrous cellulose and water-soluble polymers, the sheet includes, for example, surfactants, organic ions, coupling agents, inorganic layered compounds, inorganic compounds, leveling agents, preservatives, antifoaming agents, organic particles, etc. It may contain one or more selected from lubricants, antistatic agents, UV protective agents, dyes, pigments, stabilizers, magnetic powders, orientation promoters, plasticizers, dispersants, and cross-linking agents.
The sheet may contain a solvent. Examples of the solvent include organic solvents such as water and polar organic solvents, which are exemplified as dispersion media in the defibration treatment step.

The content of the solvent containing water in the sheet is, for example, preferably 0.5% by mass or more, more preferably 1% by mass or more, and 5% by mass or more, based on the total mass of the sheet. Is even more preferable. This makes it possible to impart flexibility to the sheet. On the other hand, the content of the solvent in the sheet is more preferably 15% by mass or less with respect to the total mass of the sheet, for example. As a result, a sheet having excellent transferability of the surface shape of the base material can be obtained only when it is in a wet state.

The solvent contained in the sheet is preferably water.
The water content (mass%) in the sheet can be calculated, for example, by the following procedure. First, a 100 mm square sheet is humidity-controlled for 24 hours under the conditions of a temperature of 23 ° C. and a relative humidity of 50%, and then the mass W0 of the sheet is measured. Next, the sheet is dried in a constant temperature dryer at 105 ° C. for 16 hours, and then the mass W1 of the sheet is measured. From the measured mass, the content of the solvent in the sheet is calculated according to the following formula 2.
(Equation 2) ... Water content in the sheet = (1-W1 / W0) x 100

In the present invention, it is preferable that the sheet has excellent transparency. As a result, when the periodic uneven structure on the surface of the base material is transferred to the sheet, the obtained structure is suitable for use as an optical member.
The haze of the sheet is, for example, preferably 10% or less, more preferably 5% or less, further preferably 3% or less, and even more preferably 1% or less. On the other hand, the lower limit of the haze of the sheet is not particularly limited and may be, for example, 0%. Here, the haze of the sheet is a value measured using, for example, a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute Co., Ltd.) in accordance with JIS K 7136.
The total light transmittance of the sheet is, for example, preferably 80% or more, more preferably 85% or more, and further preferably 90% or more. On the other hand, the upper limit of the total light transmittance of the sheet is not particularly limited and may be, for example, 100%. Here, the total light transmittance of the sheet is a value measured using, for example, JIS K 7361 and a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute Co., Ltd.).

In the present invention, the thickness of the fine fibrous cellulose-containing sheet is preferably 10 μm or more, preferably 10 μm or more, from the viewpoint of obtaining a structure in which the three-dimensional structure of the base material is transferred, which is excellent in transparency, strength and flexibility. 20 μm or more, more preferably 30 μm or more, still more preferably 40 μm or more, and preferably 10,000 μm or less, more preferably 1,000 μm or less, still more preferably 500 μm or less, still more preferably 300 μm or less, even more preferably. Is 200 μm or less, more preferably 150 μm or less.

The basis weight of the sheet is not particularly limited, but is preferably 10 g / m ² or more, more preferably 20 g / m ² or more, and further preferably 30 g / m ² or more. The basis weight of the sheet is not particularly limited, but is preferably 200 g / m ² or less, and more preferably 150 g / m ² or less. Here, the basis weight of the sheet can be calculated in accordance with, for example, JIS P 8124.
The density of the sheet is not particularly limited, but is preferably 0.1 g / cm ³ or more, more preferably 0.5 g / cm ³ or more, and further preferably 0.8 g / cm ³ or more. preferable. The density of the sheet is not particularly limited, but is preferably 5.0 g / cm ³ or less, more preferably 3.0 g / cm ³ or less, and 1.7 g / cm ³ or less. Is even more preferable. Here, the density of the sheet can be calculated by measuring the thickness and mass of the sheet after adjusting the humidity of a 50 mm square sheet under the conditions of 23 ° C. and 50% RH for 24 hours.

<Manufacturing process of fine fibrous cellulose-containing sheet>
The sheet manufacturing step preferably includes a coating step of coating a slurry containing at least fine fibrous cellulose on a substrate, or a papermaking step of making the slurry. As a result, a fine fibrous cellulose-containing sheet containing fine fibrous cellulose can be obtained. As described above, the fine fibrous cellulose-containing sheet preferably contains a water-soluble polymer in addition to the fine fibrous cellulose.

[Coating process]
In the coating step, for example, a slurry containing fine fibrous cellulose is applied onto a base material, and the sheet formed by drying the slurry is peeled off from the base material to obtain a sheet. Further, by using a coating device and a long base material, sheets can be continuously produced.
The material of the base material used in the coating process is not particularly limited, but a material having high wettability to the composition (slurry) may be able to suppress shrinkage of the sheet during drying, but is formed after drying. It is preferable to select a sheet that can be easily peeled off. Of these, 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 acrylic, polyethylene terephthalate, vinyl chloride, polystyrene, polypropylene, polycarbonate, and polyvinylidene chloride, metal films and plates of aluminum, zinc, copper, and iron plates, and their surfaces are oxidized. , Stainless film or plate, brass film or plate, etc. can be used.
In the coating process, when the viscosity of the slurry is low and it develops on the base material, a dammed frame is fixed on the base material to obtain a 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, a frame in which the end portion of the sheet that adheres after drying can be easily peeled off. From this point of view, a resin plate or a metal plate molded is more preferable. In the present embodiment, for example, a resin plate such as an acrylic plate, a polyethylene terephthalate plate, a vinyl chloride plate, a polystyrene plate, a polypropylene plate, a polycarbonate plate, a polyvinylidene chloride plate, or a metal plate such as an aluminum plate, a zinc plate, a copper plate, or an iron plate. , And those whose surfaces are oxidized, stainless steel plates, brass plates and the like can be used.
The coating machine for coating the slurry on the base material is not particularly limited, and for example, a roll coater, a gravure coater, a die coater, a curtain coater, an air doctor coater, or the like can be used. A die coater, a curtain coater, and a spray coater are particularly preferable because the thickness of the sheet can be made more uniform.

The slurry temperature and the atmospheric temperature (hereinafter, the slurry temperature and the atmospheric temperature are collectively referred to as “coating temperature”) when the slurry is applied to the substrate are not particularly limited, but are, for example, 5 ° C. or higher and 80 ° C. or lower. It is preferably 10 ° C. or higher and 60 ° C. or lower, more preferably 15 ° C. or higher and 50 ° C. or lower, and particularly preferably 20 ° C. or higher and 40 ° C. or lower. When the coating temperature is equal to or higher than the above lower limit, the slurry can be coated more easily. When the coating temperature is not more than the above upper limit value, volatilization of the dispersion medium during coating can be suppressed.
In the coating step, it is preferable to coat the substrate with the slurry so that the finished basis weight of the sheet and the thickness of the sheet are within the above-mentioned preferable ranges. By coating so that the basis weight and thickness are within the above ranges, a sheet having more excellent transparency, strength and flexibility can be obtained.

As described above, the coating step includes a step of drying the slurry coated on the substrate. The step of drying the slurry is not particularly limited, but is performed by, for example, a non-contact drying method, a method of drying while fixing the sheet, or a combination thereof.
The non-contact drying method is not particularly limited, and for example, a method of heating and drying with hot air, infrared rays, far infrared rays or near infrared rays (heat drying method) or a method of vacuum drying (vacuum drying method) is applied. can do. The heat drying method and the vacuum drying method may be combined, but the heat drying method is usually applied. Drying with infrared rays, far infrared rays, or near infrared rays is not particularly limited, but can be performed using, for example, an infrared device, a far infrared device, or a near infrared device.
The heating temperature in the heat drying method is not particularly limited, but is preferably 20 ° C. or higher and 150 ° C. or lower, and more preferably 25 ° C. or higher and 105 ° C. or lower. When the heating temperature is at least the above lower limit value, the dispersion medium can be rapidly volatilized. Further, when the heating temperature is not more than the above upper limit value, it is possible to suppress the cost required for heating and the discoloration due to heat of the fibrous cellulose.

[Papermaking process]
The papermaking process is performed by making a slurry with a paper machine. The paper machine used in the paper making process is not particularly limited, and examples thereof include continuous paper machines such as a long net type, a circular net type, and an inclined type, and a multi-layer paper making machine combining these. In the papermaking process, a known papermaking method such as handmaking may be adopted.
The papermaking process is performed by filtering and dehydrating the slurry with a wire to obtain a wet paper sheet, and then pressing and drying the sheet. The filter cloth used for filtering and dehydrating 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 sheet made of an organic polymer, a woven fabric, or a porous membrane is preferable. The organic polymer is not particularly limited, but non-cellulosic organic polymers such as polyethylene terephthalate, polyethylene, polypropylene, and polytetrafluoroethylene (PTFE) are preferable. In the present embodiment, for example, a porous membrane of polytetrafluoroethylene having a pore size of 0.1 μm or more and 20 μm or less, polyethylene terephthalate having a pore size of 0.1 μm or more and 20 μm or less, a polyethylene woven fabric, or the like can be mentioned.

In the papermaking process, a method of producing a sheet from a slurry is, for example, a water-squeezing section in which a slurry containing fine fibrous cellulose is discharged onto the upper surface of an endless belt and a dispersion medium is squeezed from the discharged slurry to generate a web. This can be done using a manufacturing apparatus that includes a drying section that dries the web to produce a sheet. An endless belt is arranged from the watering section to the drying section, and the web generated in the watering 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, and examples thereof include a dehydration method usually used in the production of paper. Among these, a method of dehydrating with a long net, a circular net, an inclined wire or the like and then further dehydrating with a roll press is preferable. Further, the drying method used in the papermaking process is not particularly limited, and examples thereof include a method used in the production of paper. Among these, a drying method using a cylinder dryer, a Yankee dryer, hot air drying, a near infrared heater, an infrared heater, or the like is more preferable.

<Manufacturing method of structure>
As described above, the method for producing a structure to which the three-dimensional structure of the base material of the present invention is transferred has the following steps 1 to 3 in this order.
Step 1: Obtaining a laminate in which a wet sheet is placed on the surface of a base material having a three-dimensional structure Step 2: Step of drying the sheet while placed on the base material Step 3: Laminating the sheets Steps for obtaining a structure to which the three-dimensional structure of the base material is transferred by peeling from the body Each step will be described below.

[Step 1]
In step 1, a wet fine fibrous cellulose-containing sheet is placed on the surface of a base material having a three-dimensional structure to obtain a laminate.
In step 1, a dry state of the fine fibrous cellulose-containing sheet may be placed on the surface of the base material and then put into a wet state, but the fine fibrous cellulose-containing sheet is put into a wet state in advance and then a group having a three-dimensional structure. It is preferable to obtain a laminate by placing it on the surface of the material.

The method of moistening the fine fibrous cellulose-containing sheet is not particularly limited, and any method such as a method of spray-coating water or a method of immersing in a water bath may be used. Among these, the method of immersing in a water bath is preferable from the viewpoint of sufficiently evenly moistening the state.
The water to be used is not particularly limited, such as tap water, ion-exchanged water, and distilled water, but ion-exchanged water or distilled water is preferable from the viewpoint of obtaining a structure having more excellent transparency.
From the viewpoint of transferring the three-dimensional structure of the substrate, the wet sheet is preferably an aqueous medium, preferably 15 parts by mass or more, more preferably 50 parts by mass or more, based on 100 parts by mass of the dry mass of the sheet. It is preferably contained in an amount of 150 parts by mass or more, more preferably 500 parts by mass or more. Further, from the viewpoint of shortening the drying step and the shape stability of the wet sheet, the wet sheet is preferably an aqueous medium based on 100 parts by mass of the dry mass of the sheet, preferably 10,000. It is less than or equal to parts by mass, more preferably less than 5,000 parts by mass, still more preferably less than 3,000 parts by mass.

In step 1, it is preferable to place the fine fibrous cellulose-containing sheet between the base material and the fine fibrous cellulose-containing sheet so that a gap such as air does not occur.
In the present invention, the wet state of the fine fibrous cellulose-containing sheet tends to adhere to the base material by its own weight, and therefore does not necessarily require a crimping step. However, in step 1, the laminated body on which the sheet is placed is formed. After obtaining the material, before step 2, crimping may be performed for the purpose of removing bubbles between the base material and the sheet and further improving the adhesion.

(Step 2)
In step 2, the sheet is dried while being placed on the base material.
The drying temperature in step 2 is preferably 10 ° C. or higher from the viewpoint of suppressing the shrinkage of the sheet and the occurrence of cracks and obtaining a structure in which the three-dimensional structure of the base material is precisely transferred, and from the viewpoint of productivity. It is preferably 20 ° C. or higher, more preferably 25 ° C. or higher, and preferably 200 ° C. or lower, more preferably 150 ° C. or lower, still more preferably 125 ° C. or lower, still more preferably 100 ° C. or lower, still more preferably 80 ° C. or lower. It is below ° C. Drying may be carried out at room temperature.
The drying time in step 2 is preferably 1 minute or longer, more preferably 3 minutes or longer, from the viewpoint of suppressing shrinkage and cracking of the laminated body, obtaining a laminated body having excellent flexibility, and productivity. It is more preferably 10 minutes or more, and preferably 48 hours or less, more preferably 24 hours or less, still more preferably 12 hours or less, still more preferably 6 hours or less.
The drying method is not particularly limited, but it may be left to dry, or it may be a method used in the production of paper. Examples of the method used in the production of paper include a cylinder dryer, a Yankee dryer, hot air drying, and an infrared heater.

(Step 3)
Step 3 is a step of peeling the sheet from the laminated body to obtain a structure to which the three-dimensional structure of the base material is transferred.
The method of peeling the sheet is not particularly limited, but it is preferable to peel the sheet so that the three-dimensional structure of the base material is maintained. The water content of the sheet at the time of peeling is preferably 25% by mass or less, more preferably 20% by mass or less, still more preferably 15% by mass or less, and peeling, from the viewpoint of retaining the transferred three-dimensional structure. From the viewpoint of suppressing cracking of the sheet at the time, it is preferably 0.1% by mass or more, more preferably 1% by mass or more, and further preferably 3% by mass or more.

[Characteristics of structure]
The structure of the present invention is preferably excellent in transparency, and the total light transmittance of the structure is preferably 80% or more, more preferably 85% or more, still more preferably 90% or more. The upper limit of the total light transmittance of the structure is not particularly limited, and may be, for example, 100%. Here, the total light transmittance of the structure is a value measured using, for example, JIS K 7361 and a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute Co., Ltd.).

The structure of the present invention can be used for various purposes as a transparent structure having excellent transparency and flexibility. For example, it can be used for optical applications such as a sheet having a diffraction grating and a reflection grating.

The features of the present invention will be described in more detail with reference to Examples and Comparative Examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed as limited by the specific examples shown below.

[Manufacturing Example 1]
[Preparation of phosphorylated pulp]
As raw material pulp, softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solid content 93% by mass, basis weight 208 g / m ² sheets, disintegrated and measured according to JIS P 8121 Canadian standard drainage degree (CSF)) 700 ml) was used. The 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. To obtain a chemical-impregnated pulp. Next, the obtained chemical-impregnated pulp was heated in a hot air dryer at 165 ° C. for 200 seconds to introduce a phosphoric acid group into the cellulose in the pulp to obtain a phosphorylated pulp.

Then, the obtained phosphorylated pulp was washed. In the washing treatment, the pulp dispersion 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. Was done by. When the electrical conductivity of the filtrate became 100 μS / cm or less, the washing end point was set.
Next, the phosphorylated pulp after washing was neutralized as follows. First, the washed phosphorylated pulp was diluted with 10 L of ion-exchanged water, and then a 1N aqueous sodium hydroxide solution was added little by little with stirring to obtain a phosphorylated pulp slurry having a pH of 12 or more and 13 or less. .. Next, the phosphorylated pulp slurry was dehydrated to obtain a phosphorylated pulp that had been neutralized.

Next, the phosphorylated pulp after the neutralization treatment was subjected to the above washing treatment. The infrared absorption spectrum of the phosphorylated pulp thus obtained was measured using FT-IR. As a result, absorption based on the phosphate group was observed around 1230 cm ^-1 , and it was confirmed that the phosphate group was added to the pulp.
Further, when the obtained phosphorylated pulp was tested and analyzed by an X-ray diffractometer, it was found at two positions, 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less. A typical peak was confirmed, and it was confirmed that it had cellulose type I crystals.

[Fiber processing]
Ion-exchanged water was added to the obtained phosphorylated pulp to prepare a slurry having a solid content concentration of 2% by mass. This slurry was treated twice with a wet atomizing device (manufactured by Sugino Machine Limited, Starburst) at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion 1 containing fine fibrous cellulose. By X-ray diffraction, it was confirmed that the fine fibrous cellulose maintained the cellulose type I crystal. The fiber width of the fine fibrous cellulose was measured using a transmission electron microscope as described below and found to be 3 to 5 nm. The amount of phosphorus oxo acid groups (first dissociated acid amount) measured by the measuring method described later was 1.45 mmol / g.

[Measurement of fiber width]
The fiber width of the fine fibrous cellulose was measured by the following method.
The supernatant of the fine fibrous cellulose dispersion obtained by treatment with a wet atomizing device is mixed with water so that the concentration of the fine fibrous cellulose is 0.01% by mass or more and 0.1% by mass or less. It was added dropwise to the diluted and hydrophilized carbon grid film. This was dried, stained with uranyl acetate, and observed with a transmission electron microscope (JEOL-2000EX, manufactured by JEOL Ltd.).

[Measurement of phosphorus oxo acid group amount]
The amount of phosphorus oxo acid groups in the fine fibrous cellulose is a fibrous form prepared by diluting a fine fibrous cellulose dispersion containing the target fine fibrous cellulose with ion exchange water so that the content is 0.2% by mass. The measurement was carried out by treating the cellulose-containing slurry with an ion exchange resin and then performing titration with an alkali.
In the treatment with the ion exchange resin, a strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, conditioned) with a volume of 1/10 is added to the fibrous cellulose-containing slurry, and the slurry is shaken for 1 hour. , The resin and the slurry were separated by pouring on a mesh having a mesh size of 90 μm.
In the titration using alkali, the change in pH value indicated by the slurry is measured while adding 10 μL of a 0.1 N sodium hydroxide aqueous solution to the fibrous cellulose-containing slurry treated with an ion exchange resin every 5 seconds. I went by doing. The titration was carried out while blowing nitrogen gas into the slurry from 15 minutes before the start of the titration. In this neutralization titration, two points are observed where the increment (differential value of pH with respect to the amount of alkali dropped) becomes maximum in the curve plotting the measured pH with respect to the amount of alkali added. Of these, the maximum point of the increment obtained first when alkali is added is called the first end point, and the maximum point of the increment obtained next is called the second end point (FIG. 1). The amount of alkali required from the start of the titration to the first end point is equal to the amount of the first dissociated acid in the slurry used for the titration. Further, the amount of alkali required from the start of titration to the second end point becomes 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 divided by the solid content (g) in the slurry to be titrated was defined as the amount of phosphorus oxo acid groups (mmol / g).

[Example 1]
[Preparation of fine fibrous cellulose-containing sheet]
The concentration of the fine fibrous cellulose dispersion obtained in Production Example 1 was adjusted by adding ion-exchanged water so that the solid content concentration was 0.5% by mass.
Next, 20 parts by mass of a 0.5% by mass aqueous solution of polyethylene oxide (PEO-18 manufactured by Sumitomo Seika Chemical Co., Ltd.) was added to 100 parts by mass of this fine fibrous cellulose dispersion to obtain a coating liquid. It was.

Next, the coating liquid is weighed so that the finished basis weight of the obtained sheet (layer composed of the solid content of the coating liquid) is 75 g / m ² , and the coating liquid is applied to a commercially available acrylic plate at 50 ° C. It was dried in a constant temperature dryer. A metal frame for damming (a gold frame having an inner dimension of 180 mm × 180 mm and a height of 5 cm) was placed on the acrylic plate so as to have a predetermined basis weight. Next, the dried sheet was peeled off from the acrylic plate to obtain a fine fibrous cellulose-containing sheet 1. The thickness of the fibrous cellulose-containing sheet 1 (sheet 1) was 50 μm.
The haze of the obtained sheet 1 was 0.7%.

[Preparation of structure]
On a polycarbonate plate (base material, FIG. 3) in which grooves having a groove depth of 70 nm and a groove-to-groove spacing of 740 nm are periodically carved, distilled water is absorbed to bring the sheet 1 into a wet state. It was placed and brought into close contact. The wet sheet 1 absorbed 2,000 parts by mass of distilled water with respect to 100 parts by mass of dry mass.
The sheet 1 was placed on the base material and allowed to stand in the air at room temperature for 20 minutes to evaporate water from the sheet 1, and then the sheet was peeled off from the polycarbonate plate.
As a result, a structure 1 was obtained in which a periodic groove structure having substantially the same size as the groove structure carved on the polycarbonate plate was transferred. FIG. 4 is an optical micrograph of the obtained structure 1. When white light was applied to the surface of the sheet having this uneven structure and reflected, the white light was dispersed, and it was possible to visually observe from purple, which is a short wavelength component in the visible light region, to red, which is a long wavelength component. That is, it was found that the obtained structure 1 (sheet) has a periodic groove structure.

[Example 2]
A silicon wafer (base material, FIG. 5) having a square groove having a depth of 5 μm and a side of 15 μm and a groove pattern array having a groove center-to-center distance of 20 μm, having a thickness of 50 μm obtained by absorbing distilled water. The fine fibrous cellulose-containing sheet 1 was placed and brought into close contact with the sheet 1.
After evaporating water from the sheet in the same manner as in Example 1, the sheet was peeled off from the silicon wafer. As a result, a sheet-like structure 2 was obtained in which the structure of the square groove pattern array carved on the surface of the silicon wafer was transferred to the sheet. When the structure 2 is irradiated with a laser beam of 632.8 nm in the vertical direction, the white paper placed perpendicular to the laser beam across the structure 2 has a diffraction pattern from the groove pattern array of the structure 2. It was also shown that the structure 2 has a groove pattern array.

According to the present invention, it is possible to provide a method for easily obtaining a structure having excellent transparency and strength and having the three-dimensional structure of the substrate surface transferred to the structure. The manufacturing method of the present invention is expected to be useful as a manufacturing method for structures having various surface shapes, particularly as a manufacturing method for structures having fine surface shapes.

Claims (10)

A step of obtaining a laminate in which a wet sheet is placed on the surface of a base material having a three-dimensional structure.
A step of drying the sheet while it is placed on the base material and a step of peeling the sheet from the laminated body to obtain a structure to which the three-dimensional structure of the base material surface is transferred are provided in this order.
The sheet contains fine fibrous cellulose having a fiber width of 1,000 nm or less.
A method for producing a structure in which the three-dimensional structure of the surface of a base material is transferred. The manufacturing method according to claim 1, wherein the three-dimensional structure of the surface of the base material is an uneven structure on the surface of the base material. The manufacturing method according to claim 2, wherein the depth of the concave portion or the height of the convex portion of the uneven structure is 5 nm or more. The manufacturing method according to claim 2 or 3, wherein the depth of the concave portion or the height of the convex portion of the uneven structure is equal to or less than the thickness of the sheet. The production method according to any one of claims 2 to 4, wherein the uneven structure has periodicity. The production method according to any one of claims 1 to 5, wherein the content of the fine fibrous cellulose in the sheet is 5% by mass or more in the solid content. The production method according to any one of claims 1 to 6, wherein the surface of the base material is formed of a material selected from metal, silicon, ceramics, plastic, glass, rubber, and a biomaterial. The production method according to any one of claims 1 to 7, wherein the wet sheet contains an aqueous solvent of 15 parts by mass or more and 10,000 parts by mass or less with respect to 100 parts by mass of the dry mass of the sheet. The production method according to any one of claims 1 to 8, wherein the film thickness of the sheet is 10 μm or more and 10,000 μm or less. The production method according to any one of claims 1 to 9, wherein the moisture content of the sheet after drying is less than 15%.