Negative radiation-sensitive sheets and patterned sheets

Abstract

The present invention addresses the problem of providing: a negative-tone radiation-sensitive sheet on which a fine pattern can be formed, and which has excellent transparency; and a patterned sheet which is produced by removing at least a portion of a light-unexposed area in the negative-tone radiation-sensitive sheet throughout in the thickness direction.　The negative-tone radiation-sensitive sheet according to the present invention comprises at least a radiation-sensitive composition and fine fibrous cellulose having a fiber width of 1,000 nm or less, in which the radiation-sensitive composition contains a polymerizable unsaturated bond and also contains a compound (X) having a Hansen solubility parameter (HSP) distance to water of 36 MPa0.5 or less and a polarity term (dP) of 10 MPa0.5 or more.

Description

[Technical Field]

[0001] The present invention relates to a negative-working radiation-sensitive sheet and a patterned sheet in which at least a portion of the unexposed areas of the negative-working radiation-sensitive sheet have been removed. [Background technology]

[0002] In the development of electronic devices, with the demand for finer and denser circuit configurations, there is a demand for substrates that allow for fine patterning. Furthermore, with the growing awareness of the need to utilize renewable resources, the application of compounds derived from plant materials, such as cellulose nanofibers, to various applications is being considered. Patent Document 1 discloses a fiber-reinforced composite material that contains fibers with an average fiber diameter of 4 to 200 nm and a matrix material, and has a light transmittance of 60% or more for wavelengths of 400 to 700 nm when converted to a thickness of 50 μm, with the aim of providing a fiber-reinforced composite material that always maintains high transparency without being affected by temperature conditions, wavelength, etc., and that is imparted with various functions by combining the fibers and matrix material.

[0003] Furthermore, Patent Document 2 discloses a photosensitive composite sheet that contains a photosensitive resin and a photosensitizer in a porous cellulose sheet, and that satisfies at least the following requirements. Requirement 1: The air resistance of the cellulose porous sheet is 1 s / 100 ml or more and 400,000 s / 100 ml or less, Requirement 2: The photosensitive resin contains at least one of a polymerizable compound, an alkali-soluble resin, and a resin in which a photofunctional group of the resin is protected with a protecting group, Requirement 3: When the photosensitive composite sheet has a thickness of 50 μm, the light transmittance at wavelengths of 280 nm to 433 nm is 10% or more. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-60680 [Patent Document 2] Japanese Patent Application Publication No. 2018-132655 Summary of the Invention [Problem to be solved by the invention]

[0005] The sheet described in Patent Document 1 has a problem in that it is difficult to form a fine pattern, and the sheet described in Patent Document 2 has a problem in that it has low transparency. An object of the present invention is to provide a negative-working radiation-sensitive sheet that is capable of forming a fine pattern and has excellent transparency, and a patterned sheet obtained by removing at least a portion of the unexposed areas of the negative-working radiation-sensitive sheet. Another object of the present invention is to provide a patterned sheet obtained by removing at least a portion of the radiation-sensitive composition in the unexposed areas of the negative-working radiation-sensitive sheet across the entire thickness direction. [Means for solving the problem]

[0006] The present inventors have found that the above-mentioned problems can be solved by a negative-working radiation-sensitive sheet containing a radiation-sensitive composition containing a specific compound and fine fibrous cellulose, and have thus completed the present invention. That is, the present invention provides the following: <1> ~ <12> Regarding. <1> A negative radiation-sensitive sheet containing at least a radiation-sensitive composition and fine fibrous cellulose having a fiber width of 1,000 nm or less, wherein the radiation-sensitive composition contains a polymerizable unsaturated bond and has a Hansen solubility parameter (HSP) distance with water of 36 MPa. 0.5 or less and polarity term (dP) is 10 MPa 0.5 A negative radiation-sensitive sheet containing the compound (X) described above. <2> the radiation-sensitive composition contains a photopolymerization initiator; <1> 1. A negative-working radiation-sensitive sheet according to claim 1. <3> the content of the radiation-sensitive composition in the solid content of the negative-type radiation-sensitive sheet is 30% by mass or more; <1> or <2> 1. A negative-working radiation-sensitive sheet according to claim 1. <4> The compound (X) has at least one of a (meth)acryloyloxy group and a (meth)acrylamide group. <1> ~ <3> 10. The negative radiation-sensitive sheet according to any one of the above items. <5> The fine fibrous cellulose has anionic groups. <1> ~ <4> 10. The negative radiation-sensitive sheet according to any one of the above items. <6> The fine fibrous cellulose has a phosphorus oxo acid group or a group derived from a phosphorus oxo acid group. <1> ~ <5> 10. The negative radiation-sensitive sheet according to any one of the above items. <7> The radiation-sensitive composition is soluble in at least one of water, alcohol, and a mixed solvent thereof. <1> ~ <6> 10. The negative radiation-sensitive sheet according to any one of the above items. <8> The negative radiation-sensitive sheet has a total light transmittance of 70% or more. <1> ~ <7> 10. The negative radiation-sensitive sheet according to any one of the above items. <9> the haze of the negative radiation-sensitive sheet is 10% or less; <1> ~ <8> 10. The negative-working radiation-sensitive sheet according to any one of the above items. <10> <1> ~ <9> 10. A patterned sheet in which at least a portion of the unexposed areas of the negative-working radiation-sensitive sheet according to any one of 1 to 8 have been removed. <11> <1> ~ <9> 1. A patterned sheet, in which at least a portion of the radiation-sensitive composition in the unexposed areas of the negative-working radiation-sensitive sheet according to any one of 1 to 8 has been removed across the entire thickness thereof. <12> <1> ~ <9> 1. A radiation-sensitive composition for use in the negative-working radiation-sensitive sheet according to any one of claims 1 to 9. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a negative-type radiation-sensitive sheet that can form a fine pattern and has excellent transparency, and a patterned sheet in which at least a portion of the unexposed areas of the negative-type radiation-sensitive sheet has been removed.Furthermore, it is possible to provide a patterned sheet in which at least a portion of the radiation-sensitive composition in the unexposed areas of the negative-type radiation-sensitive sheet has been removed across the entire thickness direction. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a graph showing the relationship between the amount of NaOH dropped onto a slurry containing fibrous cellulose having phosphorus oxo acid groups and pH. [Figure 2] FIG. 2 is a graph showing the relationship between the amount of NaOH dropped onto a slurry containing fibrous cellulose having a carboxy group and the pH. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Negative radiation-sensitive sheet] The negative-type radiation-sensitive sheet (hereinafter simply referred to as "radiation-sensitive sheet" or "sheet") of the present invention contains at least a radiation-sensitive composition and fine fibrous cellulose (hereinafter simply referred to as fine fibrous cellulose) having a fiber width of 1,000 nm or less, and the radiation-sensitive composition contains a polymerizable unsaturated bond and has a Hansen solubility parameter (HSP) distance with water of 36 MPa. 0.5 or less and polarity term (dP) is 10 MPa 0.5 The compound (X) is as above. According to the present invention, a radiation-sensitive sheet capable of forming a fine pattern and having excellent transparency can be obtained. Furthermore, according to the present invention, a patterned sheet can be obtained in which at least a portion of the radiation-sensitive composition in the unexposed areas has been removed across the entire thickness direction. Although the detailed reasons why the above-mentioned effects are obtained are unclear, part of the reason is thought to be as follows. In the present invention, instead of providing a radiation-sensitive layer on a substrate, the radiation-sensitive sheet itself has excellent shape stability and functions as a substrate. When a radiation-sensitive layer is provided on a substrate, problems such as curling due to differences in the thermal expansion coefficient between the substrate and the radiation-sensitive layer and light reflection at the interface may occur, but in the present invention, such problems do not occur. Furthermore, sheets containing fine fibrous cellulose have extremely high transparency, and since the fiber width is 1,000 nm or less, it is believed that fine patterns can be formed. Furthermore, when a radiation-sensitive layer (resist) is provided on the substrate, after patterning, regions where the radiation-sensitive layer (resist) is present and regions where it is not present are generated, resulting in unevenness in the film thickness. On the other hand, in the present invention, after exposure, at least a portion of the exposed or unexposed portions of the radiation-sensitive composition is removed, but mainly only the radiation-sensitive composition is removed, and the fine fibrous cellulose remains in the sheet form, so patterning can be performed without unevenness in the overall film thickness. Furthermore, by using a specific compound (X), removal of the unexposed radiation-sensitive composition is facilitated, and removal across the entire thickness of the sheet becomes possible. As a result, the removed portions form a front-to-back through-type pattern, which is expected to find applications as a sensor that effectively detects gases or liquids passing through the removed portions, or as a dye for color filters or conductive portions of touch panels by dyeing the removed portions of the radiation-sensitive composition. The present invention will be described in further detail below.

[0010] The terms used in this specification have the following meanings: A numerical range expressed by "~" means a range that includes both ends of the range. "(Meth)acrylic" is a general term for "acrylic" and "methacrylic", and refers to acrylic and methacrylic individually. The same applies to "(meth)acryloyl", "(meth)acryloyloxy", "(meth)acrylic acid", "(meth)acrylate", and "(meth)acrylamide".

[0011] <Fine fibrous cellulose> The radiation-sensitive sheet of the present invention contains fine fibrous cellulose. Fine fibrous cellulose is fibrous cellulose with a fiber width of 1,000 nm or less. The fiber width of fibrous cellulose can be measured, for example, by observation using 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, even more preferably 2 nm or more and 50 nm or less, and particularly preferably 2 nm or more and 10 nm or less. By making the fiber width of the fine fibrous cellulose 2 nm or more, it is possible to suppress the dissolution of the cellulose molecules in water, and more easily realize the effects of the fine fibrous cellulose, such as improved strength, rigidity, and dimensional stability.

[0012] 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, even more preferably 2 nm or more and 50 nm or less, and particularly preferably 2 nm or more and 10 nm or less. By making the average fiber width of the fine fibrous cellulose 2 nm or more, it is possible to suppress the dissolution of the cellulose molecules in water, and more easily realize the effects of the fine fibrous cellulose, such as improved strength, rigidity, and dimensional stability. The fine fibrous cellulose is, for example, monofilament cellulose.

[0013] The average fiber width of fine fibrous cellulose is measured, for example, using an electron microscope as follows. First, an aqueous suspension of fibrous cellulose with a concentration of 0.05% by mass or more and 0.1% by mass or less is prepared, and this suspension is cast onto a hydrophilically treated carbon film-coated grid to prepare a sample for TEM observation. When wide fibers are included, SEM images of the surface cast onto glass may be observed. Next, electron microscope images are observed at magnifications of 1,000x, 5,000x, 10,000x, or 50,000x, depending on the width of the fibers to be observed. However, the sample, observation conditions, and magnification must be adjusted to meet the following conditions. (1) Draw a line X at any point in the observed image, and 20 or more fibers intersect with the line X. (2) Draw a line Y that intersects the line perpendicularly within the same image, and 20 or more fibers intersect the line Y.

[0014] For observation images that satisfy the above conditions, the widths of the fibers intersecting with lines X and Y are visually read. In this way, three or more sets of observation images of at least the surface portions that do not overlap each other are obtained. Next, for each image, the widths of the fibers intersecting with lines X and Y are read. In this way, the widths of at least 20 fibers x 2 x 3 = 120 fibers are read. The average value of the read fiber widths is then taken as the average fiber width of the fibrous cellulose.

[0015] The fiber length of the fine fibrous cellulose is not particularly limited, but is preferably 0.1 μm to 1,000 μm, more preferably 0.1 μm to 800 μm, and even more preferably 0.1 μm to 600 μm. By setting the fiber length within the above range, destruction of the crystalline regions of the fine fibrous cellulose can be suppressed. It also becomes possible to set the slurry viscosity of the fine fibrous cellulose within an appropriate range. The fiber length of the fine fibrous cellulose can be determined, for example, by image analysis using TEM, SEM, or AFM.

[0016] The fine fibrous cellulose preferably has a type I crystal structure. The fact that the fine fibrous cellulose has a type I crystal structure can be identified from a diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ=1.5418 Å) monochromated with graphite. Specifically, the cellulose can be identified from the presence of typical peaks at two positions, around 2θ=14° to 17° and around 2θ=22° to 23°. The proportion of type I crystal structure in the fine fibrous cellulose is, for example, preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more. This allows for even better performance in terms of heat resistance and low linear thermal expansion coefficient. The degree of crystallinity can be determined by measuring an X-ray diffraction profile and using the pattern in a conventional manner (Seagal et al., Textile Research Journal, Vol. 29, p. 786, 1959).

[0017] The axial ratio (fiber length / fiber width) of the fine fibrous cellulose is not particularly limited, but is preferably 20 to 10,000, and more preferably 50 to 1,000. By setting the axial ratio at or above the lower limit, it is easy to form a sheet containing the fine fibrous cellulose. Furthermore, sufficient viscosity is easily obtained when a solvent dispersion is prepared. Setting the axial ratio at or below the upper limit is preferable, for example, because it makes handling, such as dilution, easier when treating the fine fibrous cellulose as an aqueous dispersion.

[0018] 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 may include, for example, either or both of an anionic group and a cationic group. Furthermore, the nonionic group may include, for example, an alkyl group and an acyl group. In this embodiment, it is particularly preferable that the ionic group include an anionic group. The fine fibrous cellulose does not need to be subjected to a treatment for introducing ionic groups.

[0019] Examples of anionic groups as ionic groups include phosphorus oxoacid groups or substituents derived from phosphorus oxoacid groups (sometimes simply referred to as phosphorus oxoacid groups), carboxy groups or substituents derived from carboxy groups (sometimes simply referred to as carboxy groups), sulfur oxoacid groups or substituents derived from sulfur oxoacid groups (sometimes simply referred to as sulfur oxoacid groups), xanthate groups, phosphonic groups, phosphine groups, sulfonic groups, and carboxyalkyl groups. Among these, the anionic group is preferably at least one selected from the group consisting of phosphorus oxoacid groups, substituents derived from phosphorus oxoacid groups, carboxy groups, sulfur oxoacid groups, substituents derived from sulfur oxoacid groups, carboxymethyl groups, carboxyethyl groups, and sulfonic groups; more preferably at least one selected from the group consisting of phosphorus oxoacid groups, substituents derived from phosphorus oxoacid groups, carboxy groups, sulfur oxoacid groups, and substituents derived from sulfur oxoacid groups; and particularly preferably a phosphorus oxoacid group. By introducing a phosphorus oxoacid group as an anionic group, the dispersibility of fibrous cellulose can be further improved, for example, even under alkaline or acidic conditions, making it easier to obtain a high-strength, highly transparent sheet. Examples of cationic groups as ionic groups include ammonium groups, phosphonium groups, sulfonium groups, etc. Among these, the cationic group is preferably an ammonium group.

[0020] The phosphorus oxo acid group or the substituent derived from the phosphorus oxo acid group is, for example, a substituent represented by the following formula (1). A plurality of types of substituents represented by the following formula (1) may be introduced into each fibrous cellulose. In this case, the plurality of introduced substituents represented by the following formula (1) may be the same or different.

[0021] [ka]

[0022] In formula (1), a, b, and n are natural numbers, and m is an arbitrary number (where a=b×m). At least one of the n α and α' is O. - and the rest are R or OR. Note that all of α and α' are O - The n α's may all be the same or may be different. b+ is a cation of one or more valences consisting of organic or inorganic substances.

[0023] R is a hydrogen atom, a saturated linear hydrocarbon group, a saturated branched hydrocarbon group, a saturated cyclic hydrocarbon group, an unsaturated linear hydrocarbon group, an unsaturated branched hydrocarbon group, an unsaturated cyclic hydrocarbon group, an aromatic group, or a group derived therefrom. In formula (1), n ​​is preferably 1.

[0024] Examples of saturated linear hydrocarbon groups include, but are not limited to, methyl, ethyl, n-propyl, or n-butyl groups. Examples of saturated branched hydrocarbon groups include, but are not limited to, i-propyl or t-butyl groups. Examples of saturated cyclic hydrocarbon groups include, but are not limited to, cyclopentyl or cyclohexyl groups. Examples of unsaturated linear hydrocarbon groups include, but are not limited to, vinyl or allyl groups. Examples of unsaturated branched hydrocarbon groups include, but are not limited to, i-propenyl or 3-butenyl groups. Examples of unsaturated cyclic hydrocarbon groups include, but are not limited to, cyclopentenyl or cyclohexenyl groups. Examples of aromatic groups include, but are not limited to, phenyl or naphthyl groups.

[0025] Furthermore, examples of the derivative group in R include, but are not limited to, functional groups in which at least one functional group selected from the group consisting of a carboxy group, a carboxylate group (—COO—), a hydroxy group, an amino group, and an ammonium group is added to or substituted on the main chain or side chain of the above-mentioned hydrocarbon groups. 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 within the above range, the molecular weight of the phosphorus oxoacid group can be set within an appropriate range, facilitating penetration into the fiber raw material and increasing the yield of finely divided cellulose fibers. When multiple Rs are present in formula (1) or when multiple types of substituents represented by formula (1) are introduced into the fibrous cellulose, the multiple Rs may be the same or different.

[0026] β b+ is a monovalent or higher cation made of an organic or inorganic substance. Examples of monovalent or higher cations made of an organic substance include organic onium ions. Examples of organic onium ions include organic ammonium ions and organic phosphonium ions. Examples of organic ammonium ions include aliphatic ammonium ions and aromatic ammonium ions, and examples of organic phosphonium ions include aliphatic phosphonium ions and aromatic phosphonium ions. Examples of monovalent or higher cations made of an inorganic substance include ions of alkali metals such as sodium, potassium, or lithium, ions of divalent metals such as calcium or magnesium, hydrogen ions, ammonium ions, etc. It should be noted that in formula (1), β b+ When a plurality of β b+ may be the same or different. The monovalent or higher cations made of organic or inorganic substances include β b+ Sodium or potassium ions are preferred because they are less likely to yellow when the fiber material containing the cation is heated and are easy to use industrially, but there is no particular limitation.

[0027] More specifically, examples of the phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group include a phosphate group (-POH), a salt of a phosphate group, a phosphorous acid (phosphonic acid) group (-POH), and a salt of a phosphite (phosphonic acid) group. The phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group may also be a group in which a phosphate group is condensed (e.g., a pyrophosphate group), a group in which a phosphonic acid is condensed (e.g., a polyphosphonic acid group), a phosphate ester group (e.g., a monomethyl phosphate group, a polyoxyethylene alkyl phosphate group), an alkyl phosphonic acid group (e.g., a methylphosphonic acid group), etc.

[0028] <Sulfur oxoacid> The sulfur oxoacid group (a sulfur oxoacid group or a substituent derived from a sulfur oxoacid group) is, for example, a substituent represented by the following formula (2). A plurality of substituents represented by the following formula (2) may be introduced into each fibrous cellulose. In this case, the introduced plurality of substituents represented by the following formula (2) may be the same or different.

[0029] [ka]

[0030] In the above structural formula, b and n are natural numbers, p is 0 or 1, and m is an arbitrary number (where 1 = b × m). When n is 2 or more, multiple p's may be the same number or different numbers. In the above structural formula, β b+is a monovalent or higher cation composed of an organic or inorganic substance. Examples of the monovalent or higher cation composed of an organic substance include organic onium ions. Examples of the organic onium ions include organic ammonium ions and organic phosphonium ions. Examples of the organic ammonium ions include aliphatic ammonium ions and aromatic ammonium ions, and examples of the organic phosphonium ions include aliphatic phosphonium ions and aromatic phosphonium ions. Examples of the monovalent or higher cation composed of an inorganic substance include ions of alkali metals such as sodium, potassium, or lithium, ions of divalent metals such as calcium or magnesium, hydrogen ions, ammonium ions, etc. Note that when multiple types of substituents represented by the above formula (2) are introduced into the fibrous cellulose, the multiple β b+ may be the same or different. The monovalent or higher cations made of organic or inorganic substances include β b+ Sodium or potassium ions are preferred because they are less likely to yellow when the fiber material containing the cation is heated and are easy to use industrially, but there is no particular limitation.

[0031] The amount of ionic groups introduced into the fine fibrous cellulose is, for example, preferably 0.10 mmol / g or more per gram (mass) of fine fibrous cellulose, more preferably 0.20 mmol / g or more, even more preferably 0.50 mmol / g or more, and particularly preferably 1.00 mmol / g or more. The amount of ionic groups introduced into the fine fibrous cellulose is, for example, preferably 5.20 mmol / g or less per gram (mass) of fibrous cellulose, more preferably 3.65 mmol / g or less, even more preferably 3.50 mmol / g or less, and even more preferably 3.00 mmol / g or less. By controlling the amount of ionic groups introduced within the above range, it is possible to facilitate the refinement of the fiber raw material and improve the stability of the fine fibrous cellulose. Furthermore, by controlling the amount of ionic groups introduced within the above range, excellent properties can be exhibited in various applications, such as a thickener for fine fibrous cellulose. Here, the denominator in the unit mmol / g is the value of the counter ion of the ionic group being a hydrogen ion (H + ) indicates the mass of the fine fibrous cellulose when

[0032] The amount of ionic groups introduced into the fibrous cellulose can be measured, for example, by neutralization titration, which involves measuring the change in pH while adding an alkali such as an aqueous sodium hydroxide solution to a slurry containing the obtained fibrous cellulose. FIG. 1 is a graph showing the relationship between the amount of NaOH added dropwise to fibrous cellulose having phosphorus oxo acid groups and pH.

[0033] 1 is a graph showing the relationship between the amount of NaOH added dropwise to a slurry containing fibrous cellulose having phosphorus oxo acid groups and pH. The amount of phosphorus oxo acid groups introduced into the fibrous cellulose is measured, for example, as follows. First, a slurry containing fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, the measurement object may be subjected to a defibration treatment similar to the defibration treatment step described below before the treatment with the strongly acidic ion exchange resin. Next, the change in pH is observed while adding aqueous sodium hydroxide solution, and a titration curve like the one shown in the upper part of Figure 1 is obtained. The titration curve shown in the upper part of Figure 1 plots the measured pH against the amount of alkali added, while the titration curve shown in the lower part of Figure 1 plots the pH increment (derivative value) (1 / mmol) against the amount of alkali added. In this neutralization titration, two points of maximum increment (derivative value of pH with respect to the amount of alkali added) are confirmed on the curve plotting the measured pH against the amount of alkali added. Of these, the first maximum increment obtained after starting to add alkali is called the first endpoint, and the next maximum increment obtained is called the second endpoint. The amount of alkali required from the start of titration to the first endpoint is equal to the amount of first dissociated acid from the fibrous cellulose contained in the slurry used for titration; the amount of alkali required from the first endpoint to the second endpoint is equal to the amount of second dissociated acid from the fibrous cellulose contained in the slurry used for titration; and the amount of alkali required from the start of titration to the second endpoint is equal to the total amount of dissociated acid from the fibrous cellulose contained in the slurry used for titration. The amount of alkali required from the start of titration to the first endpoint divided by the solids content (g) in the slurry to be titrated is the amount of phosphorus oxo acid groups introduced (mmol / g). Note that the term "amount of phosphorus oxo acid groups introduced" (or "amount of phosphorus oxo acid groups") simply refers to the amount of first dissociated acid. In Figure 1, the region from the start of titration to the first endpoint is referred to as Region 1, and the region from the first endpoint to the second endpoint is referred to as Region 2. For example, if the phosphorus oxoacid group is a phosphate group and this phosphate group undergoes condensation, the apparent amount of weakly acidic groups in the phosphorus oxoacid group (also referred to herein as the second dissociated acid amount) decreases, and the amount of alkali required in Region 2 is less than the amount required in Region 1. On the other hand, the amount of strongly acidic groups in the phosphorus oxoacid group (also referred to herein as the first dissociated acid amount) corresponds to the amount of phosphorus atoms regardless of whether condensation occurs. Furthermore, if the phosphorus oxoacid group is a phosphite group, the phosphorus oxoacid group no longer contains weakly acidic groups, and the amount of alkali required in Region 2 is reduced or may even be zero. In this case, there is only one point on the titration curve where the pH increment is maximized. The above-mentioned amount of introduced phosphorus oxoacid groups (mmol / g) indicates the amount of phosphorus oxoacid groups in the acid-form fibrous cellulose (hereinafter referred to as the amount of phosphorus oxoacid groups (acid form)) because the denominator indicates the mass of the acid-form fibrous cellulose. On the other hand, when the counter ions of the phosphorus oxoacid groups are substituted with an arbitrary cation C so as to be charge equivalent, the amount of phosphorus oxoacid groups in the fibrous cellulose with the cation C as the counter ion (hereinafter referred to as the amount of phosphorus oxoacid groups (C form)) can be determined by converting the denominator to the mass of the fibrous cellulose when the cation C is the counter ion. That is, it is calculated using the following formula. Amount of phosphorus oxoacid group (C type) = Amount of phosphorus oxoacid group (acid type) / {1 + (W - 1) × A / 1000} A [mmol / g]: total amount of anions derived from phosphorus oxoacid groups in fibrous cellulose (sum of the amount of strong acidic groups and weak acidic groups in phosphorus oxoacid groups) W: Formula weight per valence of cation C (for example, Na is 23, Al is 9)

[0034] FIG. 2 is a graph showing the relationship between the amount of NaOH added dropwise to fibrous cellulose having carboxy groups and pH. The amount of carboxyl groups introduced into the fibrous cellulose can be measured, for example, as follows. First, a slurry containing fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, the measurement object may be subjected to a defibration treatment similar to the defibration treatment step described below before treatment with the strongly acidic ion exchange resin. Next, a sodium hydroxide aqueous solution is added while observing the change in pH, and a titration curve such as that shown in FIG. 2 is obtained. If necessary, the measurement object may be subjected to a defibration treatment similar to the defibration treatment step described below. As shown in Figure 2, in this neutralization titration, a single point is observed where the increment (the differential value of pH with respect to the amount of alkali added) reaches a maximum on the curve plotting the measured pH against the amount of alkali added. This maximum increment is called the first endpoint. Here, the region from the start of the titration to the first endpoint in Figure 2 is called the first region. The amount of alkali required in the first region is equal to the amount of carboxyl groups in the slurry used for titration. The amount of alkali introduced (mmol / g) was calculated by dividing the amount of alkali (mmol) required in the first region of the titration curve by the solids content (g) in the fine fibrous cellulose-containing slurry to be titrated. The amount of carboxyl groups introduced (mmol / g) is calculated based on the amount of carboxyl groups introduced (mmol / g) when the counter ions of the carboxyl groups are hydrogen ions (H + ) (hereinafter referred to as the amount of carboxy groups (acid type)) per 1 g of fibrous cellulose.

[0035] The above-mentioned amount of carboxy groups introduced (mmol / g) indicates the amount of carboxy groups in the acid-form fibrous cellulose (hereinafter referred to as the amount of carboxy groups (acid form)) because the denominator is the mass of the acid-form fibrous cellulose. On the other hand, when the counter ions of the carboxy groups are substituted with any cation C so as to be charge equivalent, the amount of carboxy groups in the fibrous cellulose with the cation C as the counter ion (hereinafter referred to as the amount of carboxy groups (C form)) (mmol / g) can be determined by converting the denominator to the mass of the fibrous cellulose when the cation C is the counter ion. That is, it is calculated using the following formula. Amount of carboxyl group (C type) = Amount of carboxyl group (acid type) / {1 + (W - 1) × (Amount of carboxyl group (acid type)) / 1000} W: Formula weight per valence of cation C (for example, Na is 23, Al is 9)

[0036] The amount of sulfur oxoacid groups introduced into the fine fibrous cellulose is determined by wet ashing the obtained fibrous cellulose using perchloric acid and concentrated nitric acid, diluting it at an appropriate ratio, and measuring the amount of sulfur by ICP emission spectrometry. The amount of sulfur divided by the bone dry mass of the fibrous cellulose sample is taken as the amount of sulfur oxoacid groups (unit: mmol / g).

[0037] When measuring the amount of substituents by titration, adding too many drops of sodium hydroxide or titrating too quickly can result in lower than expected amounts of substituents, leading to inaccurate values. For example, a suitable amount and interval is recommended: titrating 10-50 μL of 0.1 N sodium hydroxide every 5-30 seconds. To eliminate the influence of carbon dioxide dissolved in the fibrous cellulose-containing slurry, it is recommended to perform measurements while blowing an inert gas such as nitrogen into the slurry from 15 minutes before the start of titration until the end of titration. The measurement of the amount of ionic groups by the above-mentioned method is applied to fine fibrous cellulose with a fiber width of 1,000 nm or less. When measuring the amount of ionic groups in pulp fibers with a fiber width of more than 1,000 nm, the pulp fibers are first refined before measurement.

[0038] [Method for producing fine fibrous cellulose] (cellulose-containing fiber materials) Fine fibrous cellulose is produced from a fiber raw material containing cellulose. Although the cellulose-containing fiber raw material is not particularly limited, pulp is preferably used because of its ease of availability and low cost. Examples of pulp include wood pulp, non-wood pulp, and deinked pulp. Examples of wood pulp include, but are not limited to, chemical pulps such as hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolving pulp (DP), soda pulp (AP), unbleached kraft pulp (UKP), and oxygen-bleached kraft pulp (OKP), semi-chemical pulps such as semi-chemical pulp (SCP) and chemi-ground wood pulp (CGP), and mechanical pulps such as groundwood pulp (GP) and thermomechanical pulp (TMP, BCTMP). Examples of non-wood pulp include, but are not limited to, cotton-based pulps such as cotton linters and cotton lint, and non-wood pulps such as hemp, straw, bamboo, and bagasse. The deinked pulp is not particularly limited, but may be, for example, deinked pulp made from recycled paper. The pulp of this embodiment may be one of the above types alone or a mixture of two or more types. Among the above pulps, wood pulp and deinked pulp are preferred from the viewpoint of ease of availability. Furthermore, among wood pulps, chemical pulp is more preferred, and kraft pulp and sulfite pulp are even more preferred, from the viewpoint of a high cellulose content, a high yield of fine fibrous cellulose during defibration treatment, and small decomposition of cellulose in the pulp to obtain long-fiber fine fibrous cellulose with a large axial ratio. Note that the use of long-fiber fine fibrous cellulose with a large axial ratio tends to increase viscosity. As a fiber raw material containing cellulose, for example, cellulose contained in sea squirts and bacterial cellulose produced by acetic acid bacteria can be used. Furthermore, instead of fiber raw materials containing cellulose, fibers formed from linear nitrogen-containing polysaccharide polymers such as chitin and chitosan can also be used.

[0039] To obtain the fine fibrous cellulose into which the above-mentioned ionic groups have been introduced, it is preferable to have an ionic group introduction step for introducing ionic groups into the above-mentioned cellulose-containing fiber raw material, a washing step, an alkali treatment step (neutralization step), and a defibration treatment step in this order, and an acid treatment step may be included instead of or in addition to the washing step. Examples of the ionic group introduction step include a phosphorus oxo acid group introduction step, a carboxy group introduction step, a sulfur oxo acid group introduction step, a xanthate group introduction step, a phosphonic or phosphine group introduction step, and a sulfonic group introduction step. Each of these steps will be explained below.

[0040] (Ionic group introduction step) -Phosphorus oxoacid group introduction process- The phosphorus oxo acid group introduction step involves reacting a cellulose-containing fiber raw material with at least one compound (hereinafter also referred to as "compound A") selected from compounds capable of introducing phosphorus oxo acid groups by reacting with hydroxyl groups in the cellulose-containing fiber raw material, thereby obtaining a phosphorus oxo acid group-introduced fiber. In the phosphate group introduction step according to this embodiment, the reaction of the cellulose-containing fiber raw material with compound A may be carried out in the presence of at least one selected from urea and its derivatives (hereinafter also referred to as "compound B"). Alternatively, the cellulose-containing fiber raw material with compound A may be reacted in the absence of compound B. One example of a method for reacting compound A with a fiber raw material in the presence of compound B is to mix compound A and compound B with a fiber raw material in a dry, wet, or slurry state. Among these methods, using a dry or wet fiber raw material is preferred because of the high uniformity of the reaction, and using a dry fiber raw material is particularly preferred. The form of the fiber raw material is not particularly limited, but is preferably a cotton-like or thin sheet form. Compound A and compound B can be added to the fiber raw material in the form of a powder, a solution dissolved in a solvent, or a melted state heated to or above their melting point. Among these methods, adding compound A and compound B in the form of a solution dissolved in a solvent, especially an aqueous solution, is preferred because of the high uniformity of the reaction. Compound A and compound B may be added to the fiber raw material simultaneously, separately, or as a mixture. The method for adding compound A and compound B is not particularly limited. When compound A and compound B are in solution form, the fiber raw material may be immersed in the solution and allowed to absorb the liquid before being removed, or the solution may be added dropwise to the fiber raw material. Alternatively, the required amounts of compound A and compound B may be added to the fiber raw material, or excess amounts of compound A and compound B may be added to the fiber raw material, and then the excess compound A and compound B may be removed by squeezing or filtration.

[0041] The compound A used in this embodiment may be any compound that has a phosphorus atom and can form an ester bond with cellulose, and examples thereof include, but are not limited to, phosphoric acid or a salt thereof, phosphorous acid or a salt thereof, dehydrated condensed phosphoric acid or a salt thereof, and phosphoric anhydride (diphosphorus pentoxide). Phosphoric acid can be used with various purities, such as 100% phosphoric acid (orthophosphoric acid) or 85% phosphoric acid. Phosphorous acid can be, for example, 99% phosphorous acid (phosphonic acid). Dehydrated condensed phosphoric acid is formed by the condensation of two or more molecules of phosphoric acid through a dehydration reaction, and examples thereof include pyrophosphoric acid and polyphosphoric acid. Phosphates, phosphites, and dehydrated condensed phosphates include lithium salts, sodium salts, potassium salts, and ammonium salts of phosphoric acid, phosphorous acid, or dehydrated condensed phosphoric acid, and these can be neutralized to various degrees. Among these, phosphoric acid, sodium salts of phosphoric acid, potassium salts of phosphoric acid, and ammonium salts of phosphoric acid are preferred, and phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, and ammonium dihydrogen phosphate are more preferred, from the viewpoints of high efficiency in introducing phosphate groups, easier improvement of defibration efficiency in the defibration step described below, low cost, and ease of industrial application. 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 into the amount of phosphorus atoms, the amount of phosphorus atoms added to the fiber raw material (bone dry mass) is preferably 0.5% by mass or more and 100% by mass or less, more preferably 1% by mass or more and 50% by mass or less, and even more preferably 2% by mass or more and 30% by mass or less. By setting the amount of phosphorus atoms added to the fiber raw material within the above range, the yield of fine fibrous cellulose can be further improved. On the other hand, by setting the amount of phosphorus atoms added to the fiber raw material to the above upper limit or less, a balance can be achieved between the effect of improving the yield and costs.

[0042] As described above, the compound B used in this embodiment is at least one selected from urea and its derivatives. Examples of the compound B include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, and 1-ethylurea. From the viewpoint of improving the uniformity of the reaction, it is preferable to use an aqueous solution of compound B. Furthermore, 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 relative to the fiber raw material (bone dry mass) is not particularly limited, but is preferably, for example, 1% by mass or more and 500% by mass or less, more preferably 10% by mass or more and 400% by mass or less, and even more preferably 100% by mass or more and 350% by mass or less.

[0043] In the reaction of a fiber material containing cellulose with compound A, the reaction system may contain, in addition to compound B, amides or amines, for example. Examples of amides include formamide, dimethylformamide, acetamide, and dimethylacetamide. Examples of amines include methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, and hexamethylenediamine. Among these, triethylamine is known to act as a particularly good reaction catalyst.

[0044] In the phosphorus oxo acid group introduction step, it is preferable to add or mix compound A or the like with the fiber raw material and then heat-treat the fiber raw material. The heat treatment temperature is preferably selected so that the phosphorus oxo acid group can be efficiently introduced while suppressing thermal decomposition and hydrolysis of the fiber. The heat treatment temperature is preferably, for example, from 50°C to 300°C, more preferably from 100°C to 250°C, and even more preferably from 130°C to 200°C. Furthermore, various types of equipment having heat transfer media can be used for the heat treatment, including, for example, a stirring dryer, a rotary dryer, a disk dryer, a roll-type heater, a plate-type heater, a fluidized-bed dryer, a band-type dryer, a filtration dryer, a vibration fluidized-bed dryer, a flash dryer, a reduced-pressure dryer, an infrared heater, a far-infrared heater, a microwave heater, and a high-frequency dryer.

[0045] In the heat treatment according to this embodiment, for example, compound A may be added to a thin sheet-like fiber raw material by impregnation or other methods, followed by heating, or heating while kneading or stirring the fiber raw material and compound A in a kneader or the like. This makes it possible to suppress unevenness in the concentration of compound A in the fiber raw material and more uniformly introduce phosphate groups onto the surface of the cellulose fibers contained in the fiber raw material. This is thought to be because, when water molecules move to the surface of the fiber raw material as it dries, dissolved compound A is attracted to the water molecules by surface tension, preventing it from migrating to the surface of the fiber raw material in the same way (i.e., causing unevenness in the concentration of compound A). Furthermore, the heating device used for the heat treatment is preferably one that can constantly discharge, to the outside of the system, moisture contained in the slurry and moisture generated during the dehydration condensation (phosphorylation) reaction between compound A and hydroxyl groups contained in cellulose or the like in the fiber raw material. Examples of such heating devices include an oven with a blower system. Constantly discharging moisture from the system not only suppresses the hydrolysis of phosphate ester bonds, which is the reverse reaction of phosphate esterification, but also suppresses acid hydrolysis of sugar chains in the fiber. This makes it possible to obtain fine fibrous cellulose with a high axial ratio. The heat treatment time is, for example, preferably from 1 second to 300 minutes after the water content has been substantially removed from the fiber raw material, more preferably from 1 second to 1,000 seconds, and even more preferably from 10 seconds to 800 seconds. In this embodiment, the amount of phosphorus oxo acid groups introduced can be kept within a preferred range by setting the heating temperature and heating time within appropriate ranges.

[0046] The phosphorus oxo acid group introduction step may be carried out at least once, but may also be carried out twice or more. By carrying out the phosphorus oxo acid group introduction step twice or more, a large number of phosphorus oxo acid groups can be introduced into the fiber raw material. In the present embodiment, a preferred example is when the phosphorus oxo acid group introduction step is carried out twice.

[0047] The amount of phosphorus oxoacid groups introduced into the fiber raw material is, for example, preferably 0.10 mmol / g or more per gram (mass) of fine fibrous cellulose, more preferably 0.20 mmol / g or more, even more preferably 0.50 mmol / g or more, and particularly preferably 1.00 mmol / g or more. The amount of phosphorus oxoacid groups introduced into the fiber raw material is, for example, preferably 5.20 mmol / g or less per gram (mass) of fine fibrous cellulose, more preferably 3.65 mmol / g or less, and even more preferably 3.00 mmol / g or less. By keeping the amount of phosphorus oxoacid groups introduced within the above range, it is possible to facilitate the micronization of the fiber raw material and improve the stability of the fine fibrous cellulose.

[0048] -Carboxy group introduction process- The carboxyl group introduction process is carried out by treating a fiber raw material containing cellulose with an oxidation treatment such as ozone oxidation, oxidation by the Fenton method, or TEMPO oxidation treatment, or with a compound having a carboxylic acid-derived group or a derivative thereof, or an acid anhydride of a compound having a carboxylic acid-derived group or a derivative thereof. Examples of compounds having a group derived from carboxylic acid include, but are not limited to, dicarboxylic acid compounds such as maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric acid, adipic acid, and itaconic acid, and tricarboxylic acid compounds such as citric acid and aconitic acid. Examples of derivatives of compounds having a group derived from carboxylic acid include, but are not limited to, imidized products of acid anhydrides of compounds having carboxy groups, and derivatives of acid anhydrides of compounds having carboxy groups. Examples of imidized products of acid anhydrides of compounds having carboxy groups include, but are not limited to, imidized products of dicarboxylic acid compounds such as maleimide, succinimide, and phthalimide.

[0049] Acid anhydrides of compounds having a group derived from carboxylic acid include, but are not limited to, acid anhydrides of dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, itaconic anhydride, etc. Furthermore, derivatives of acid anhydrides of compounds having a group derived from carboxylic acid include, but are not limited to, acid anhydrides of compounds having carboxy groups such as dimethylmaleic anhydride, diethylmaleic anhydride, diphenylmaleic anhydride, etc. in which at least some of the hydrogen atoms have been substituted with a substituent such as an alkyl group or a phenyl group.

[0050] When TEMPO oxidation treatment is performed in the carboxyl group introduction step, it is preferable to perform the treatment under conditions of pH 6 or higher and 8 or lower. This type of treatment is also called neutral TEMPO oxidation treatment. Neutral TEMPO oxidation treatment can be performed, for example, by adding pulp as the fiber raw material, a nitroxy radical such as TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) as a catalyst, and sodium hypochlorite as a sacrificial reagent to a sodium phosphate buffer solution (pH = 6.8). Furthermore, by adding sodium chlorite, aldehydes generated during the oxidation process can be efficiently oxidized to carboxyl groups. The TEMPO oxidation treatment may also be carried out under conditions of a pH of 10 to 11. This type of treatment is also called 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 carboxyl groups introduced into the fiber raw material varies depending on the type of substituent. For example, when carboxyl groups are introduced by TEMPO oxidation, the amount is preferably 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, even more preferably 0.50 mmol / g or more, and particularly preferably 0.90 mmol / g or more per gram (mass) of fine fibrous cellulose. Also, the amount is preferably 2.5 mmol / g or less, more preferably 2.20 mmol / g or less, and even more preferably 2.00 mmol / g or less. Alternatively, when the substituent is a carboxymethyl group, the amount may be 5.8 mmol / g or less per gram (mass) of fine fibrous cellulose.

[0051] -Sulfur oxoacid group introduction process- The process for producing fine fibrous cellulose may include, for example, a sulfur oxoacid group introduction step as an ionic substituent introduction step, in which hydroxyl groups in a cellulose-containing fiber raw material react with sulfur oxoacids to obtain cellulose fibers having sulfur oxoacid groups (sulfur oxoacid group-introduced fibers).

[0052] In the sulfur oxo acid group introduction step, instead of compound A in the above-described <Phosphorus oxo acid group introduction step>, at least one compound (hereinafter also referred to as "compound C") selected from compounds capable of introducing sulfur oxo acid groups by reacting with hydroxyl groups in cellulose-containing fiber raw materials is used. Compound C may be any compound containing a sulfur atom and capable of forming an ester bond with cellulose, including, but not limited to, sulfuric acid or its salts, sulfurous acid or its salts, and sulfuric acid amides. Sulfuric acid of various purities can be used, for example, 96% sulfuric acid (concentrated sulfuric acid). Sulfurous acid can be 5% aqueous sulfurous acid. Sulfates or sulfites include lithium, sodium, potassium, and ammonium salts of sulfates or sulfites, which can be neutralized to various degrees. Sulfamic acid or the like can be used as the sulfuric acid amide. In the sulfur oxo acid group introduction step, it is preferable to use compound B in the above-described <Phosphorus oxo acid group introduction step> as well.

[0053] In the sulfur oxoacid group introduction step, the cellulose raw material is preferably mixed with an aqueous solution containing a sulfur oxoacid and urea and / or a urea derivative, and then the cellulose raw material is subjected to a heat treatment. The heat treatment temperature is preferably selected so that the sulfur oxoacid groups can be efficiently introduced while suppressing thermal decomposition and hydrolysis of the fiber. The heat treatment temperature is preferably 100°C or higher, more preferably 120°C or higher, and even more preferably 150°C or higher. The heat treatment temperature is preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower.

[0054] In the heat treatment step, heating is preferably carried out until substantially all moisture is removed. Therefore, the heat treatment time varies depending on the amount of moisture contained in the cellulose raw material and the amount of aqueous solution containing sulfur oxoacid and urea and / or a urea derivative added, but is preferably set to, for example, 10 seconds or more and 10,000 seconds or less. For the heat treatment, various devices having a heat medium can be used, such as an agitator dryer, rotary dryer, disk dryer, roll-type heater, plate-type heater, fluidized-bed dryer, band-type dryer, filtration dryer, vibration fluidized dryer, flash dryer, reduced-pressure dryer, infrared heater, far-infrared heater, microwave heater, or high-frequency dryer.

[0055] The amount of sulfur oxoacid groups introduced into the cellulose raw material is preferably 0.05 mmol / g or more, more preferably 0.10 mmol / g or more, even more preferably 0.20 mmol / g or more, even more preferably 0.50 mmol / g or more, and particularly preferably 0.90 mmol / g or more. Furthermore, the amount of sulfur oxoacid groups introduced into the cellulose raw material is preferably 5.00 mmol / g or less, more preferably 3.00 mmol / g or less. By keeping the amount of sulfur oxoacid groups introduced within the above range, it is possible to easily pulverize the fiber raw material and improve the stability of the fibrous cellulose.

[0056] -Oxidation step using a chlorine-based oxidizing agent (second carboxyl group introduction step)- The process for producing fine fibrous cellulose may include, for example, an oxidation step using a chlorine-based oxidizing agent as a step for introducing an ionic substituent. In the oxidation step using a chlorine-based oxidizing agent, the chlorine-based oxidizing agent is added to a wet or dry fiber raw material having a hydroxyl group to cause a reaction, thereby introducing a carboxyl group into the fiber raw material.

[0057] Examples of chlorine-based oxidizing agents include hypochlorous acid, hypochlorites, chlorous acid, chlorites, chloric acid, chlorates, perchloric acid, perchlorates, chlorine dioxide, etc. From the viewpoints of efficiency of introducing substituents, and therefore defibration efficiency, cost, and ease of handling, sodium hypochlorite, sodium chlorite, and chlorine dioxide are preferred. The chlorine-based oxidizing agent may be added to the fiber raw material as a reagent as it is, or may be dissolved in an appropriate solvent and then added.

[0058] The reaction temperature in the oxidation step using a chlorine-based oxidizing agent is, for example, preferably 10°C or higher and 100°C or lower, more preferably 15°C or higher and 80°C or lower, and even more preferably 20°C or higher and 60°C or lower.

[0059] The concentration of the chlorine-based oxidizing agent in the solution in the oxidation step using the chlorine-based oxidizing agent is, for example, converted into an effective chlorine concentration, preferably from 1% by mass to 1,000% by mass, more preferably from 5% by mass to 500% by mass, and even more preferably from 10% by mass to 100% by mass. The amount of chlorine-based oxidizing agent added per 100 parts by mass of fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 10 parts by mass or more and 10,000 parts by mass or less, and even more preferably 100 parts by mass or more and 5,000 parts by mass or less.

[0060] The reaction time with the chlorine-based oxidizing agent in the oxidation step using the chlorine-based oxidizing agent may vary depending on the reaction temperature, but is preferably, for example, from 1 minute to 1,000 minutes, more preferably from 10 minutes to 500 minutes, and even more preferably from 20 minutes to 400 minutes. The pH during the reaction is preferably 5 or more and 15 or less, more preferably 7 or more and 14 or less, and even more preferably 9 or more and 13 or less. At the start of the reaction and during the reaction, the pH is preferably maintained constant (for example, pH 11) by appropriately adding hydrochloric acid or sodium hydroxide. After the reaction, excess reaction reagents, by-products, etc. may be washed and removed with water by filtration or the like.

[0061] -Xanthate group introduction process (xanthogen acid esterification process)- The process for producing fine fibrous cellulose may include, for example, a xanthate group introduction process (hereinafter also referred to as a xanthation process) as an ionic substituent introduction process. In the xanthation process, carbon disulfide and an alkali compound are added to a wet or dry fiber raw material having a hydroxyl group to cause a reaction, thereby introducing a xanthate group into the fiber raw material. Specifically, carbon disulfide is added to a fiber raw material that has been converted into alkali cellulose by the method described below, and the reaction is carried out.

[0062] <Alkali cellulose> When introducing ionic functional groups into a fiber raw material, it is preferable to convert the cellulose contained in the fiber raw material into alkali cellulose by treating the cellulose with an alkaline solution. This treatment causes ionic dissociation of some of the hydroxyl groups in the cellulose, thereby increasing its nucleophilicity (reactivity). The alkaline compound contained in the alkaline solution is not particularly limited and may be an inorganic alkaline compound or an organic alkaline compound. Due to their high versatility, it is preferable to use, for example, sodium hydroxide, potassium hydroxide, tetraethylammonium hydroxide, or tetrabutylammonium hydroxide. The conversion into alkali cellulose may be carried out simultaneously with the introduction of ionic functional groups, before the introduction, or at both stages.

[0063] The solution temperature at the start of alkali cellulose formation is preferably 0°C or higher and 50°C or lower, more preferably 5°C or higher and 40°C or lower, and even more preferably 10°C or higher and 30°C or lower.

[0064] The alkaline solution concentration is preferably 0.01 mol / L to 4 mol / L in molar concentration, more preferably 0.1 mol / L to 3 mol / L in molar concentration, and even more preferably 1 mol / L to 2.5 mol / L in molar concentration. In particular, when the treatment temperature is less than 10° C., the concentration is preferably 1 mol / L to 2 mol / L in molar concentration.

[0065] The treatment time for alkali cellulose formation is preferably 1 minute or more, more preferably 10 minutes or more, and even more preferably 30 minutes or more, and the alkali treatment time is preferably 6 hours or less, more preferably 5 hours or less, and even more preferably 4 hours or less.

[0066] By adjusting the type of alkaline solution, treatment temperature, concentration, and immersion time as described above, it is possible to suppress the penetration of the alkaline solution into the crystalline regions of cellulose, making it easier to maintain the crystalline structure of cellulose type I, and increasing the yield of fine fibrous cellulose.

[0067] When the introduction of ionic functional groups and the conversion to alkali cellulose are not carried out simultaneously, the alkali cellulose obtained by the alkali treatment is preferably subjected to solid-liquid separation and water removal using a common deliquoring method such as centrifugation or filtration. This improves the reaction efficiency in the subsequent ionic functional group introduction step. The cellulose fiber concentration after solid-liquid separation is preferably 5% to 50%, more preferably 10% to 40%, and even more preferably 15% to 35%.

[0068] -Phosphonic or phosphine group introduction step (phosphoalkylation step)- The process for producing fine fibrous cellulose may include, as an ionic substituent introduction step, a phosphonic or phosphine group introduction step (phosphoalkylation step). In the phosphoalkylation step, a compound having a reactive group and a phosphonic or phosphine group (compound E) is used as an essential component. A ), an optional alkali compound, and a compound B selected from the above-mentioned urea and its derivatives are added to a wet or dry fiber raw material having hydroxyl groups and reacted to introduce phosphonic or phosphine groups into the fiber raw material.

[0069] Examples of the reactive group include a halogenated alkyl group, a vinyl group, and an epoxy group (glycidyl group). Compound EA Examples of suitable vinyl phosphonic acids include vinyl phosphonic acid, phenyl vinyl phosphonic acid, phenyl vinyl phosphinic acid, etc. Vinyl phosphonic acid is preferred from the viewpoints of the efficiency of introducing a substituent, and hence the defibration efficiency, cost, and ease of handling. Furthermore, as an optional component, it is also preferable to use the compound B in the above-mentioned <Phosphorus oxo acid group introduction step> in the same manner, and the amount added is also preferably as described above.

[0070] Compound E A The reagent may be added to the fiber raw material as is, or may be dissolved in an appropriate solvent and then added. The fiber raw material is preferably converted into alkali cellulose in advance or simultaneously with the reaction. The method for converting into alkali cellulose is as described above.

[0071] The temperature during the reaction is, for example, preferably 50°C or higher and 300°C or lower, more preferably 100°C or higher and 250°C or lower, and even more preferably 130°C or higher and 200°C or lower.

[0072] Compound E A The amount added per 100 parts by mass of the fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 2 parts by mass or more and 10,000 parts by mass or less, and even more preferably 5 parts by mass or more and 1,000 parts by mass or less.

[0073] The reaction time may vary depending on the reaction temperature, but is preferably, for example, from 1 minute to 1,000 minutes, more preferably from 10 minutes to 500 minutes, and even more preferably from 20 minutes to 400 minutes. After the reaction, excess reaction reagents, by-products, etc. may be washed and removed with water by filtration or the like.

[0074] -Sulfonic acid group introduction step (sulfoalkylation step)- The process for producing fine fibrous cellulose may include, for example, a sulfonic acid group introduction step (sulfoalkylation step) as an ionic substituent introduction step. In the sulfoalkylation, a compound having a reactive group and a sulfonic acid group (compound E) is used as an essential component. B ) and, as an optional component, an alkaline compound, and the aforementioned compound B selected from urea and its derivatives are added to a wet or dry fiber raw material having a hydroxyl group and reacted to introduce a sulfonic acid group into the fiber raw material.

[0075] Examples of the reactive group include a halogenated alkyl group, a vinyl group, and an epoxy group (glycidyl group). Compound E B Examples of suitable sulfonates include sodium 2-chloroethanesulfonate, sodium vinylsulfonate, sodium p-styrenesulfonate, 2-acrylamido-2-methylpropanesulfonic acid, etc. Among these, sodium vinylsulfonate is preferred from the standpoints of the efficiency of introducing substituents, and therefore the defibration efficiency, cost, and ease of handling. Furthermore, as an optional component, it is also preferable to use the compound B in the above-mentioned <Phosphorus oxo acid group introduction step> in the same manner, and the amount added is also preferably as described above.

[0076] Compound E B The reagent may be added to the fiber raw material as is, or may be dissolved in an appropriate solvent and then added. The fiber raw material is preferably converted into alkali cellulose in advance or simultaneously with the reaction. The method for converting into alkali cellulose is as described above.

[0077] The temperature during the reaction is, for example, preferably 50°C or higher and 300°C or lower, more preferably 100°C or higher and 250°C or lower, and even more preferably 130°C or higher and 200°C or lower.

[0078] Compound E BThe amount added per 100 parts by mass of the fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 2 parts by mass or more and 10,000 parts by mass or less, and even more preferably 5 parts by mass or more and 1,000 parts by mass or less.

[0079] The reaction time may vary depending on the reaction temperature, but is preferably, for example, from 1 minute to 1,000 minutes, more preferably from 10 minutes to 500 minutes, and even more preferably from 15 minutes to 400 minutes. After the reaction, excess reaction reagents, by-products, etc. may be washed and removed with water by filtration or the like.

[0080] -Carboxyalkylation step (third carboxy group introduction step)- The process for producing fine fibrous cellulose may include, for example, a carboxyalkylation step as an ionic substituent introduction step. C ), an optional alkaline compound, and the aforementioned compound B selected from urea and its derivatives are added to a wet or dry fiber raw material having a hydroxyl group and reacted to introduce a carboxyl group into the fiber raw material.

[0081] Examples of the reactive group include a halogenated alkyl group, a vinyl group, and an epoxy group (glycidyl group). Compound E C As the chloroisothiazolinone, monochloroacetic acid, sodium monochloroacetate, 2-chloropropionic acid, 3-chloropropionic acid, sodium 2-chloropropionate, and sodium 3-chloropropionate are preferred from the standpoints of efficiency in introducing substituents, and therefore defibration efficiency, cost, and ease of handling. Furthermore, as an optional component, it is also preferable to use the compound B in the above-mentioned <Phosphorus oxo acid group introduction step> in the same manner, and the amount added is also preferably as described above.

[0082] Compound E CThe reagent may be added to the fiber raw material as is, or may be dissolved in an appropriate solvent and then added. The fiber raw material is preferably converted into alkali cellulose in advance or simultaneously with the reaction. The method for converting into alkali cellulose is as described above.

[0083] The temperature during the reaction is, for example, preferably 50°C or higher and 300°C or lower, more preferably 100°C or higher and 250°C or lower, and even more preferably 130°C or higher and 200°C or lower.

[0084] Compound E C The amount added per 100 parts by mass of the fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 2 parts by mass or more and 10,000 parts by mass or less, and even more preferably 5 parts by mass or more and 1,000 parts by mass or less.

[0085] The reaction time may vary depending on the reaction temperature, but is preferably, for example, from 1 minute to 1,000 minutes, more preferably from 3 minutes to 500 minutes, and even more preferably from 5 minutes to 400 minutes. After the reaction, excess reaction reagents, by-products, etc. may be washed and removed with water by filtration or the like.

[0086] -Cationic group introduction step (cationization step)- As an essential component, a compound having a reactive group and a cationic group (compound E D ), an optional alkaline compound, and the aforementioned compound B selected from urea and its derivatives are added to a wet or dry fiber raw material having hydroxyl groups and reacted to introduce cationic groups into the fiber raw material.

[0087] Examples of the reactive group include a halogenated alkyl group, a vinyl group, and an epoxy group (glycidyl group).

[0088] Compound E DAs the alkyl group, glycidyl trimethyl ammonium chloride, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, etc. are preferred from the viewpoints of the efficiency of introducing substituents, and therefore the defibration efficiency, cost, and ease of handling.

[0089] Furthermore, it is also preferable to use the compound B in the above-mentioned <Phosphorus oxo acid group introduction step> as an optional component in the same manner. The amount added is also preferably as described above.

[0090] Compound E D The reagent may be added to the fiber raw material as is, or may be dissolved in an appropriate solvent and then added. The fiber raw material is preferably converted into alkali cellulose in advance or simultaneously with the reaction. The method for converting into alkali cellulose is as described above.

[0091] The temperature during the reaction is, for example, preferably 50°C or higher and 300°C or lower, more preferably 100°C or higher and 250°C or lower, and even more preferably 130°C or higher and 200°C or lower.

[0092] Compound E D The amount added per 100 parts by mass of the fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 2 parts by mass or more and 10,000 parts by mass or less, and even more preferably 5 parts by mass or more and 1,000 parts by mass or less.

[0093] The reaction time may vary depending on the reaction temperature, but is preferably, for example, from 1 minute to 1,000 minutes, more preferably from 5 minutes to 500 minutes, and even more preferably from 10 minutes to 400 minutes. After the reaction, excess reaction reagents, by-products, etc. may be washed and removed with water by filtration or the like.

[0094] (Cleaning process) In the method for producing fine fibrous cellulose according to the present embodiment, the ionic group-introduced fibers may be subjected to a washing step as needed. The washing step is carried out by washing the ionic group-introduced fibers with water or an organic solvent, for example. The washing step may be carried out after each step described below, and the number of washing steps carried out in each washing step is not particularly limited.

[0095] (Alkali treatment process) When producing fine fibrous cellulose, the fiber raw material may be subjected to an alkali treatment between the ionic group introduction step and the defibration step described below. The alkali treatment method is not particularly limited, but an example thereof is a method of immersing the ionic group-introduced fiber in an alkali solution. The alkaline compound contained in the alkaline solution is not particularly limited and may be an inorganic alkaline compound or an organic alkaline compound. In this embodiment, it is preferable to use, for example, sodium hydroxide or potassium hydroxide as the alkaline compound because of their high versatility. The solvent contained in the alkaline solution may be either water or an organic solvent. Among these, the solvent contained in the alkaline solution is preferably water or a polar solvent including a polar organic solvent such as an alcohol, and more preferably an aqueous solvent including at least water. As the alkaline solution, for example, an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution is preferable because of their high versatility. The temperature of the alkaline solution in the alkaline treatment step is not particularly limited, but is preferably from 5°C to 80°C, and more preferably from 10°C to 60°C. The immersion time of the ionic group-introduced fiber in the alkaline solution in the alkaline treatment step is not particularly limited, but is preferably from 5 minutes to 30 minutes, and more preferably from 10 minutes to 20 minutes. The amount of alkaline solution used in the alkaline treatment is not particularly limited, but is preferably from 100% by mass to 100,000% by mass, and more preferably from 1,000% by mass to 10,000% by mass, based on the absolute dry mass of the ionic group-introduced fiber. When the fine fibrous cellulose has anionic groups, the alkali treatment may be a neutralization treatment or ion exchange treatment of the anionic groups. In this case, the temperature of the alkali solution is preferably room temperature.

[0096] In order to reduce the amount of alkaline solution used in the alkaline treatment step, the ionic group-introduced fiber may be washed with water or an organic solvent after the ionic group-introducing step and before the alkaline treatment step. From the viewpoint of improving handleability, it is preferable to wash the alkaline-treated ionic group-introduced fiber with water or an organic solvent after the alkaline treatment step and before the defibrating treatment step.

[0097] (Acid treatment process) When producing fine fibrous cellulose, the fiber raw material may be subjected to an acid treatment between the step of introducing ionic groups and the defibration treatment step described below. For example, the ionic group introduction step, acid treatment step, alkali treatment step, and defibration treatment step may be performed in this order. The acid treatment method is not particularly limited, but examples include a method of immersing the fiber raw material in an acid-containing acid solution. The concentration of the acid solution used is not particularly limited, but is preferably 10% by mass or less, and more preferably 5% by mass or less. The pH of the acid solution used is also not particularly limited, but is preferably 0 to 4, and more preferably 1 to 3. Examples of the acid contained in the acid solution include inorganic acids, sulfonic acids, and carboxylic acids. Examples of inorganic acids include sulfuric acid, nitric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, phosphoric acid, and boric acid. Examples of sulfonic acids include methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and trifluoromethanesulfonic acid. Examples of carboxylic acids include formic acid, acetic acid, citric acid, gluconic acid, lactic acid, oxalic acid, and tartaric acid. Among these, hydrochloric acid or sulfuric acid is particularly preferred. The temperature of the acid solution in the acid treatment is not particularly limited, but is preferably from 5°C to 100°C, and more preferably from 20°C to 90°C. The immersion time in the acid solution in the acid treatment is not particularly limited, but is preferably from 5 minutes to 120 minutes, and more preferably from 10 minutes to 60 minutes. The amount of the acid solution used in the acid treatment is not particularly limited, but is preferably from 100% to 100,000% by mass, and more preferably from 1,000% to 10,000% by mass, based on the absolute dry mass of the fiber raw material. When the fine fibrous cellulose has cationic groups, the acid treatment may be a neutralization treatment or ion exchange treatment of the cationic groups. In this case, the temperature of the acid solution is preferably room temperature.

[0098] (Defibrillation process) By subjecting the ionic group-introduced fibers to defibration treatment in a defibration treatment step, fine fibrous cellulose can be obtained. In the defibration treatment step, for example, a defibration treatment device can be used. The defibration treatment device is not particularly limited, but examples that can be used include a high-speed defibrator, grinder (stone mill-type grinder), high-pressure homogenizer, ultra-high-pressure homogenizer, high-pressure collision grinder, ball mill, bead mill, disk-type refiner, conical refiner, twin-screw kneader, vibration mill, homomixer under high-speed rotation, ultrasonic disperser, or beater. Among the above defibration treatment devices, it is more preferable to use a high-speed defibrator, high-pressure homogenizer, or ultra-high-pressure homogenizer, which are less affected by the grinding media and have less risk of contamination.

[0099] In the defibration process, it is preferable to dilute the ionic group-introduced fibers with a dispersion medium to form a slurry. The dispersion medium can be one or more selected from water and organic solvents such as polar organic solvents. The polar organic solvent is not particularly limited, but examples thereof include alcohols, polyhydric alcohols, ketones, ethers, esters, and aprotic polar solvents. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, and isobutyl alcohol. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, and glycerin. Examples of ketones include acetone and methyl ethyl ketone (MEK). Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, and propylene glycol monomethyl ether. Examples of esters include ethyl acetate and butyl acetate. Examples of aprotic polar solvents include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), and N-methyl-2-pyrrolidinone (NMP).

[0100] The solid content concentration of the fine fibrous cellulose during the defibration treatment can be appropriately set. The slurry obtained by dispersing the phosphorus oxo acid group-introduced fibers in a dispersion medium may contain solid components other than the phosphorus oxo acid group-introduced fibers, such as urea having hydrogen bonding properties.

[0101] From the viewpoint of transparency of the radiation-sensitive sheet and enabling the formation of fine patterns, the content of fine fibrous cellulose in the solid content of the radiation-sensitive sheet is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and is preferably 70% by mass or less, more preferably 60% by mass or less, even more preferably 55% by mass or less, even more preferably 50% by mass or less, and particularly preferably 45% by mass or less. As the fine fibrous cellulose, a fine fibrous cellulose containing an ionic group, which will be described later, and an unmodified fine fibrous cellulose may be used in combination.

[0102] <Radiation sensitive composition> The negative-working radiation-sensitive sheet of this embodiment contains a radiation-sensitive composition. In this embodiment, the radiation-sensitive composition contains a polymerizable unsaturated bond and has a Hansen solubility parameter (HSP) distance with water of 36 MPa. 0.5 or less and polarity term (dP) is 10 MPa 0.5 The composition contains the compound (X) as described above. In addition to the compound (X), the composition preferably contains a polymerization initiator, and more preferably contains a photopolymerization initiator. The solubility of compound (X) in a solvent decreases when the radiation-sensitive compound is irradiated. That is, compound (X) has the property of polymerizing and / or crosslinking due to the action of reactive active species such as radicals generated from the radiation-sensitive compound upon irradiation. The radiation-sensitive compound imparts radiation-sensitivity to the radiation-sensitive composition. The radiation-sensitive compound is a compound that generates reactive species upon exposure to radiation. Here, radiation includes at least visible light, ultraviolet light, far ultraviolet light, electron beams (charged particle beams), and X-rays. Among these, ultraviolet light is preferred. The radiation-sensitive compound is preferably an acid generator, a polymerization initiator, or a combination thereof, more preferably a polymerization initiator, and even more preferably a photopolymerization initiator. When an acid generator is used, a negative radiation-sensitive composition can be obtained by adding other additive components.

[0103] [Compound (X)] Compound (X) contains a polymerizable unsaturated bond and has a Hansen solubility parameter (HSP) distance with water of 36 MPa. 0.5 or less and polarity term (dP) is 10 MPa 0.5 That's all. Examples of the polymerizable unsaturated bond include a carbon-carbon double bond (hereinafter also referred to as an ethylenically unsaturated bond) and a carbon-carbon triple bond, and among these, an ethylenically unsaturated bond is preferred. The ethylenically unsaturated bond is preferably derived from a (meth)acryloyloxy group or a (meth)acrylamide group, more preferably derived from an acryloyloxy group or an acrylamide group, and even more preferably derived from an acrylamide group. That is, compound (X) preferably has at least one of a (meth)acryloyloxy group and a (meth)acrylamide group, more preferably has at least one of an acryloyl group and an acrylamide group, and even more preferably has an acrylamide group. Furthermore, the number of polymerizable unsaturated bonds that compound (X) has in one molecule may be 1 or more, preferably 2 or more, and is preferably 8 or less, more preferably 6 or less, and even more preferably 4 or less.

[0104] (HSP distance and polarity terms) In order to make the sheet transparent even when the content of the radiation-sensitive composition is increased, the radiation-sensitive composition must not only be water-soluble but also have extremely high affinity for water. The Hansen solubility parameter (HSP) is widely used as an index of affinity with water. HSP expresses the solubility of a substance using three vectors: dispersion term (dD), polar term (dP), and hydrogen bonding term (dH). The shorter the distance between these vectors, the higher the compatibility between substances with similar HSPs. The HSP distance (Ra) between substance 1 and substance 2 is expressed by the following (Equation 1): Ra = {4 × (dD1 - dD2) 2 +(dP1-dP2) 2 +(dH1-dH2) 2} 0.5 (Formula 1) Here, dD1, dP1, and dH1 represent the dispersion term, polar term, and hydrogen bonding term of substance 1, respectively, and dD2, dP2, and dH2 represent the dispersion term, polar term, and hydrogen bonding term of substance 2, respectively. When substance 1 is water and substance 2 is compound (X), it can show affinity with water. The HSP distance can be calculated by determining the HSP of each substance using Hansen Solubility Parameters in Practice (HSPiP (software name) 5th Edition Ver. 5.2.07) and calculating according to (Equation 1). When substance 1 is water, dD1 = 15.6 MPa. 0.5 , dP1=16.0MPa 0.5 , dH1=42.3MPa 0.5 is. In the radiation-sensitive sheet of the present invention, it is preferable that the compound (X) has a high affinity for water, and the HSP distance between the compound (X) and water is 36 MPa or less. 0.5 or less, preferably 35 MPa 0.5 The lower limit of the HSP is not particularly limited, but from the viewpoint of availability and molecular design of the compound (X), it is preferably 20 MPa. 0.5 More preferably, 25 MPa 0.5 More preferably, 30 MPa 0.5 That's all. In addition, compound (X) has a polarity term (dP) of Hansen solubility parameter of 10 MPa. 0.5 or more, preferably 11 MPa 0.5 More preferably, 12 MPa 0.5 The upper limit of the polarity term (dP) is not particularly limited, but from the viewpoint of availability and molecular design of the compound (X), it is preferably 30 MPa. 0.5 Less than or equal to 25 MPa, preferably 0.5 or less, more preferably 20 MPa 0.5 The polarity term of the Hansen solubility parameter for water is 16.0 MPa. 0.5 is.

[0105] Compound (X) is not particularly limited as long as it has a polymerizable unsaturated bond and the above-mentioned HSP distance and dP, but is preferably soluble in water, alcohol, or a mixed solvent thereof, more preferably soluble in water, methanol, or ethanol, and particularly preferably soluble in water. Compound (X) is soluble in water, alcohol, or a mixed solvent thereof, and therefore has high affinity with the fine fibrous cellulose dispersion, and the radiation-sensitive composition in the unexposed areas can be easily removed with a developer, thereby providing a patterned sheet from which the radiation-sensitive composition in the unexposed areas has been removed throughout the thickness direction.

[0106] The compound (X) includes not only compounds generally called polymers, but also lower molecular weight compounds, so-called oligomers and monomers. That is, compound (X) is not particularly limited as long as it has a polymerizable unsaturated bond and has a predetermined HSP distance and dP, and is a compound whose solubility in a solvent decreases due to a reaction induced by reactive species such as radicals generated from the radiation-sensitive compound upon irradiation. Among these, compound (X) is preferably a compound whose solubility in a solvent decreases due to a polymerization reaction induced by radicals generated from the radiation-sensitive compound.

[0107] When compound (X) is a polymer compound, examples of the backbone structure include polyalkylene glycols (polyethylene glycol, polypropylene glycol, etc.), cellulose derivatives (hydroxyethyl cellulose, carboxyethyl cellulose, carboxymethyl cellulose, etc.), casein, dextrin, polyvinyl alcohol, modified polyvinyl alcohols (acetoacetylated polyvinyl alcohol, ethylene-vinyl alcohol copolymer, ethylene oxide-modified polyvinyl alcohol, etc.), polyalkylene oxides (polyethylene oxide, etc.), polyvinylpyrrolidone, polyvinyl methyl ether, polyacrylates, polyacrylamide, acrylic acid ester copolymers, urethane copolymers, polyhydroxystyrene copolymers, polyalkyleneimines, etc. Among the above, structures containing polyethylene glycol, polyethylene oxide, polyvinyl alcohol, modified polyvinyl alcohol, polyacrylamide, acrylic acid ester copolymers, and polyalkyleneimines are particularly preferred. When compound (X) is a polymer, compound (X) has a polymerizable unsaturated bond in addition to the above-described skeletal structure, and therefore compound (X) is a compound that polymerizes via the polymerizable unsaturated bond.

[0108] As described above, the compound (X) used in the negative radiation-sensitive sheet has a polymerizable unsaturated group in addition to the above-mentioned skeletal structure. Examples of the polymerizable unsaturated group include an acryloyloxy group, a methacryloyloxy group, an acrylamide group, and a methacrylamide group, and it is particularly preferable to use the group in combination with a photopolymerization initiator as the radiation-sensitive compound. For example, when a portion of the radiation-sensitive sheet is irradiated with radiation, the non-irradiated portion of the sheet does not undergo a crosslinking reaction via polymerization of polymerizable unsaturated groups such as acryloyloxy groups, resulting in high solubility in a developer, etc. On the other hand, in the irradiated portion (exposed portion), radicals generated by the photoreaction of the photopolymerization initiator catalyze a crosslinking reaction via polymerization of polymerizable unsaturated groups, thereby suppressing solubility in a developer, etc. In other words, the radiation-sensitive sheet can usually exhibit negative radiation sensitivity.

[0109] When the radiation-sensitive sheet is a negative type, it is preferable to use an oligomer or monomer having a lower molecular weight as the compound (X). From the viewpoint of obtaining a desired HSP distance, the compound (X) preferably has an ether bond, an amide bond, an ester bond, or an amino group (—NH—). Suitable examples of compound (X) include the following compounds:

[0110] [ka]

[0111] In this embodiment, when the radiation-sensitive sheet is a negative type, in addition to the compound (X), a compound having an HSP distance of 36 MPa 0.5 and polarity term (dP) is greater than 10 MPa 0.5 A polymerizable unsaturated compound satisfying at least one of the following conditions (hereinafter also referred to as "other polymerizable unsaturated compounds") may be used in combination. The other polymerizable unsaturated compound is an unsaturated compound that polymerizes by irradiating the radiation-sensitive sheet with radiation in the presence of the radiation-sensitive compound in the radiation-sensitive composition. Such other polymerizable unsaturated compound is not particularly limited, but for example, a polyfunctional (meth)acrylic acid ester having two or more functional groups is preferred from the viewpoints of good polymerizability and improved strength of the radiation-sensitive sheet formed. The other polymerizable unsaturated compounds may be used alone or in combination of two or more.

[0112] When the radiation-sensitive composition contains other polymerizable unsaturated compounds, the content of the other polymerizable compounds is preferably 100 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 30 parts by mass or less, and still more preferably 10 parts by mass or less, relative to 100 parts by mass of compound (X).

[0113] Among other polymerizable unsaturated compounds, examples of the bifunctional (meth)acrylic acid esters include ethylene glycol di(meth)acrylate, dipropylene glycol diacrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol diacrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, etc. Examples of commercially available products of these compounds include, by trade name, Aronix (registered trademark) M-220 and M-240 (both manufactured by Toagosei Co., Ltd.), KAYARAD (registered trademark) HX-220 and R-604 (both manufactured by Nippon Kayaku Co., Ltd.), Viscoat 260 (manufactured by Osaka Organic Chemical Industry Co., Ltd.), and Light Acrylate 1,9-NDA (manufactured by Kyoeisha Chemical Co., Ltd.).

[0114] Among the other polymerizable unsaturated compounds, examples of the tri- or higher functional (meth)acrylic acid esters include trimethylolpropane tri(meth)acrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate; a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate; Ethylene oxide-modified pentaerythritol tetraacrylate, tri(2-(meth)acryloyloxyethyl)phosphate, succinic acid-modified pentaerythritol triacrylate, succinic acid-modified dipentaerythritol pentaacrylate, tripentaerythritol heptaacrylate, tripentaerythritol octaacrylate, isocyanuric acid EO-modified diacrylate, isocyanuric acid EO-modified triacrylate; An example is a mixture of an EO-modified isocyanuric acid diacrylate and an EO-modified isocyanuric acid triacrylate.

[0115] Furthermore, among other polymerizable unsaturated compounds, examples of polyfunctional (meth)acrylic acid esters include polyfunctional urethane acrylate compounds obtained by reacting a compound having a linear alkylene group and an alicyclic structure and having two or more isocyanate groups with a compound having one or more hydroxyl groups and three, four, or five (meth)acryloyloxy groups in the molecule. Examples of commercially available trifunctional or higher functional (meth)acrylic acid esters include, by trade name, Aronix (registered trademark) M-309, M-400, M-405, and M-450 (all manufactured by Toagosei Co., Ltd.), KAYARAD (registered trademark) TMPTA, DPHA, DPCA-20, DPCA-30, DPCA-60, and DPEA-12 (all manufactured by Nippon Kayaku Co., Ltd.), and Viscoat 295 (manufactured by Osaka Organic Chemical Industry Ltd.).

[0116] The molecular weight of compound (X) (weight average molecular weight when it has a molecular weight distribution) is not particularly limited, but from the viewpoint of enabling fine patterning and obtaining the desired HSP and dP, it is sufficient if it is 100 or more, preferably 120 or more, and more preferably 150 or more. In addition, the molecular weight (weight average molecular weight) of compound (X) is preferably 100,000 or less, and more preferably 10,000 or less. The weight average molecular weight can be measured, for example, by using GPC.

[0117] <Radiation sensitive compounds> In the present invention, the radiation-sensitive composition preferably contains a photopolymerization initiator as the radiation-sensitive compound. [Photopolymerization initiator] A photopolymerization initiator (hereinafter also simply referred to as "polymerization initiator") is a component that responds to radiation and generates active species capable of initiating polymerization of a polymerizable compound. By including a polymerization initiator, the radiation-sensitive composition of this embodiment can exhibit, for example, negative radiation sensitivity to alkaline developers. Examples of photopolymerization initiators include photoradical polymerization initiators. Photopolymerization initiators can initiate a crosslinking reaction of a compound having a polymerizable group upon exposure to radiation such as visible light, ultraviolet light, far ultraviolet light, electron beams, and X-rays. A preferred photopolymerization initiator is, for example, a photopolymerization initiator that generates the most radicals when exposed to ultraviolet light, particularly around 365 nm. Examples of the photoradical polymerization initiator include O-acyloxime compounds, acetophenone compounds, biimidazole compounds, acylphosphine oxide compounds, etc. These compounds can be used alone or in combination of two or more.

[0118] Examples of the O-acyloxime compound include 1-[4-(phenylthio)-2-(O-benzoyloxime)], 1,2-octanedione-1-[4-(phenylthio)-2-(O-benzoyloxime)], ethanone-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime), 1-[9-ethyl-6-benzoyl-9H-carbazol-3-yl]-octan-1-one oxime-O-acetate, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-ethan-1-one oxime-O-benzoate, 1-[9-n-butyl-6-(2-ethylbenzoyl)-9H-carbazol-3-yl]-ethan-1-one oxime-O-acetate, 1-[9-n-butyl-6-(2-ethylbenzoyl)-9H-carbazol-3-yl]-ethan-1-one oxime-O-benzoate, 1-[9-n-butyl-6-(2-ethylbenzoyl)-9H-carbazol-3-yl]-ethan-1-one oxime-O-acetyloxime ...

[0033] Examples thereof include ethanone-O-benzoate, ethanone-1-[9-ethyl-6-(2-methyl-4-tetrahydrofuranylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime), ethanone-1-[9-ethyl-6-(2-methyl-4-tetrahydropyranylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime), ethanone-1-[9-ethyl-6-(2-methyl-5-tetrahydrofuranylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime), ethanone-1-[9-ethyl-6-{2-methyl-4-(2,2-dimethyl-1,3-dioxolanyl)methoxybenzoyl}-9H-carbazol-3-yl]-1-(O-acetyloxime).

[0119] Examples of the acetophenone compound include an α-aminoketone compound and an α-hydroxyketone compound. Examples of α-aminoketone compounds include 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one, and 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one. Examples of α-hydroxyketone compounds include 1-phenyl-2-hydroxy-2-methylpropan-1-one, 1-(4-i-propylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-1-{4-[2-(2-hydroxyethoxy)ethoxy]phenyl}-2-methylpropan-1-one, and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone.

[0120] Examples of biimidazole compounds include 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, 2,2'-bis(2,4-dichlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, and 2,2'-bis(2,4,6-trichlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole. Examples of the acylphosphine oxide compound include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and lithium phenyl(2,4,6-trimethylbenzoyl)phosphinate.

[0121] Among these, the photopolymerization initiator is preferably an acetophenone compound, more preferably an α-hydroxyketone compound, from the viewpoints of affinity with the fine fibrous slurry used in producing the radiation-sensitive sheet and solubility in the developer. By including a photopolymerization initiator in the radiation-sensitive sheet, for example, when a part of the radiation-sensitive sheet is irradiated with radiation, the solubility of the irradiated part (exposed part) in a developer or the like can be reduced. In other words, the radiation-sensitive sheet can exhibit negative radiation sensitivity.

[0122] The content of the photopolymerization initiator in the radiation-sensitive composition of this embodiment is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and preferably 40 parts by mass or less, more preferably 20 parts by mass or less, relative to 100 parts by mass of compound (X). By using the photopolymerization initiator in this range, excellent radiation sensitivity can be imparted. Furthermore, by setting the content of the photopolymerization initiator in this range, a radiation-sensitive sheet containing the radiation-sensitive composition of this embodiment can exhibit negative radiation sensitivity even at a low exposure dose.

[0123] From the viewpoint of enabling fine patterning, the content of the radiation-sensitive composition in the solid content of the radiation-sensitive sheet is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 45% by mass or more, even more preferably 50% by mass or more, and particularly preferably 55% by mass or more, and is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less.

[0124] The radiation-sensitive composition is preferably dissolved in at least one of water, alcohol, or a mixed solvent thereof, which is preferable because it facilitates the coating or papermaking process described below. The radiation-sensitive composition being soluble in at least one of water, alcohol, or a mixed solvent thereof means that 1 g or more of the radiation-sensitive composition is soluble in 100 g of water, an alcohol having 1 to 6 carbon atoms (preferably an alcohol having 1 to 4 carbon atoms, more preferably an alcohol having 1 to 3 carbon atoms), or a mixed solvent of water and an alcohol having 1 to 6 carbon atoms at 25°C and atmospheric pressure. Dissolving the radiation-sensitive composition in at least one of water, alcohol, and a mixed solvent is preferable because it has high affinity with the fine fibrous cellulose, making it possible to prepare a uniform coating solution or papermaking slurry, and it is also preferable because it makes it easy to remove the unexposed areas with a developer, making it possible to obtain a patterned sheet from which the radiation-sensitive composition has been removed across the entire thickness direction.

[0125] In addition, from the viewpoint of providing a radiation-sensitive composition that dissolves in at least one of water, alcohol, or a mixed solvent thereof, the radiation-sensitive sheet of the present invention is preferably a negative type. By providing a negative type radiation-sensitive sheet, a low-molecular-weight, hydrophilic monomer or oligomer can be selected as the radiation-sensitive composition, and the radiation-sensitive composition can be made soluble in water, alcohol, or a mixed solvent thereof.

[0126] <Other ingredients> The radiation-sensitive sheet of the present invention may contain other components in addition to the above-mentioned fine fibrous cellulose, compound (X), and radiation-sensitive compound (for example, acid generator, photopolymerization initiator). Examples of other components include hydrophilic polymers, monofunctional polymerizable unsaturated compounds, wet strength agents, organic ions, crosslinking agents, surfactants, coupling agents, inorganic layered compounds, inorganic compounds, leveling agents, preservatives, antifoaming agents, organic particles, lubricants, antistatic agents, UV absorbers, dyes, pigments, stabilizers, magnetic powders, orientation promoters, plasticizers, and dispersants.

[0127] (Hydrophilic polymer) The radiation-sensitive sheet of the present invention may contain a hydrophilic polymer. The hydrophilic polymer refers to a polymer compound having a weight-average molecular weight of 5,000 or more and a solubility of 1 g or more in 100 mL of ion-exchanged water at normal pressure and 25°C. The hydrophilic polymer does not include the above-mentioned resin for the radiation-sensitive composition, and does not have an acid-decomposable group or a radical-polymerizable group whose solubility in a solvent changes significantly due to an acid or radical generated by irradiating the radiation-sensitive compound with radiation.

[0128] The hydrophilic polymer is preferably a hydrophilic oxygen-containing organic compound (excluding the above-mentioned cellulose fiber). The hydrophilic oxygen-containing organic compound preferably has an SP value of 9.0 or more, for example. Examples of hydrophilic polymers used in the present invention include polyalkylene glycols (polyethylene glycol, polypropylene glycol, etc.), cellulose derivatives (hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, methyl cellulose, carboxyethyl cellulose, carboxymethyl cellulose, etc.), proteins such as casein, starches (dextrin, cationized starch, raw starch, oxidized starch, etherified starch, esterified starch, amylose, etc.), polyvinyl alcohol, modified polyvinyl alcohol (acetoacetylated polyvinyl alcohol, ethylene-vinyl alcohol copolymer, ethylene oxidized polyvinyl alcohol, etc.), polyalkylene oxides (polyethylene oxy Examples of suitable polyols include polyvinylpyrrolidone, polyvinyl methyl ether, polyacrylates (sodium polyacrylate, etc.), polycations (polyacrylamide, polyethyleneimine, etc.), polyanions, amphoteric polymers, alkyl acrylate copolymers, urethane copolymers, thickening polysaccharides (xanthan gum, guar gum, tamarind gum, locust bean gum, quince seed, alginic acid, metal salts of alginic acid, pullulan, carrageenan, saccharin, pectin, etc.), polyesters, modified polyesters, modified polyimides, glycerins such as polyglycerin, hyaluronic acid, metal salts of hyaluronic acid, carboxyvinyl polymers, alkyl methacrylates, acrylic acid copolymers, and polyacrylates (sodium polyacrylate, etc.). Among the above, polyethylene glycol, polyethylene oxide, polyvinyl alcohol, and modified polyvinyl alcohol are particularly preferred.

[0129] The weight-average molecular weight of the hydrophilic polymer is not particularly limited as long as it is 5,000 or more, but from the viewpoint of the shape stability of the radiation-sensitive sheet and enabling fine patterning, it is preferably 10,000 or more, more preferably 15,000 or more, and even more preferably 20,000 or more. The weight-average molecular weight of the hydrophilic polymer is preferably 8 million or less, more preferably 5 million or less, even more preferably 1 million or less, and even more preferably 100,000 or less. The weight average molecular weight can be measured, for example, by using GPC.

[0130] The content of the hydrophilic polymer in the solid content of the radiation-sensitive sheet is preferably 15% by mass or less, more preferably 13% by mass or less, and even more preferably 10% by mass or less, and 0% by mass or more, from the viewpoint of enabling shape stability of the radiation-sensitive sheet and fine patterning. In one aspect of this embodiment, it is also preferable that the radiation-sensitive sheet does not contain a hydrophilic polymer.

[0131] (Monofunctional polymerizable unsaturated compound) Examples of the monofunctional polymerizable unsaturated compound include (meth)acrylic acid esters, such as 2-hydroxyethyl (meth)acrylate, diethylene glycol monoethyl ether (meth)acrylate, ω-carboxypolycaprolactone monoacrylate, etc. Examples of commercially available products of these compounds include trade names such as Aronix (registered trademark) M-101A, M-111, M-113, and M-5300 (all manufactured by Toagosei Co., Ltd.).

[0132] (wet strength agent) Wet strength agents are chemicals that prevent the paper from losing strength when it gets wet. When added to pulp fibers that tend to loosen in water, they help maintain the bonds between the pulp fibers even when wet, making them less likely to loosen, thereby increasing the paper's strength. Examples of wet strength agents include polyamine polyamide epihalohydrin, melamine formaldehyde resin, and urea formaldehyde resin. Polyamine polyamide epichlorohydrin is synthesized by adding epichlorohydrin to a main chain formed by condensing a polyacid and a polyethylene polyamine. Polyamine polyamide epichlorohydrin can be used over a wide pH range and can achieve high wet strength at low addition levels. Melamine formaldehyde resin is synthesized by adding formaldehyde to melamine and then acid condensing the mixture. Urea-formaldehyde resin is synthesized by adding formaldehyde to urea and then partially crosslinking the resulting mixture. Among these, polyamine polyamide epihalohydrin is preferred from the viewpoint of obtaining a sheet having low water absorption and linear thermal expansion coefficient and excellent transparency. Among polyamine polyamide epihalohydrins, polyamine polyamide epichlorohydrin is more preferred.

[0133] (organic ions) Examples of organic ions include tetraalkylammonium ions and tetraalkylphosphonium ions. Examples of tetraalkylammonium ions include tetramethylammonium ions, tetraethylammonium ions, tetrapropylammonium ions, tetrabutylammonium ions, tetrapentylammonium ions, tetrahexylammonium ions, tetraheptylammonium ions, tributylmethylammonium ions, lauryltrimethylammonium ions, cetyltrimethylammonium ions, stearyltrimethylammonium ions, octyldimethylethylammonium ions, lauryldimethylethylammonium ions, didecyldimethylammonium ions, lauryldimethylbenzylammonium ions, and tributylbenzylammonium ions. Examples of tetraalkylphosphonium ions include tetramethylphosphonium ions, tetraethylphosphonium ions, tetrapropylphosphonium ions, tetrabutylphosphonium ions, and lauryltrimethylphosphonium ions. Examples of tetrapropylonium ions and tetrabutylonium ions include tetra-n-propylonium ions and tetra-n-butylonium ions, respectively.

[0134] <Method for manufacturing radiation-sensitive sheet> The radiation-sensitive sheet of the present invention can be obtained by preparing an aqueous dispersion (slurry) containing fine fibrous cellulose, a radiation-sensitive composition, and other components, and forming the dispersion into a sheet. The method for forming the sheet is not particularly limited, but it is preferably obtained by a coating process in which the slurry is coated on a substrate, dried, and the formed sheet is peeled off from the substrate, or a papermaking process in which the slurry is made into paper. Alternatively, a radiation-sensitive sheet may be continuously produced by using a coating device and a belt-shaped substrate. Among these, it is more preferable to obtain the sheet by a coating process.

[0135] The material of the substrate used in the coating process is not particularly limited, but a material with high wettability to the slurry is preferred from the viewpoint of suppressing shrinkage of the sheet during drying, and it is also preferable that the sheet formed after drying can be easily peeled off. Resin films and plates, and metal films and plates are preferred examples, but are not particularly limited. Specific examples include resin films and plates such as acrylic, polyethylene terephthalate, vinyl chloride, polystyrene, polypropylene, polycarbonate, and polyvinylidene chloride; metal films and plates such as aluminum, zinc, copper, and iron plates; and those with oxidized surfaces; stainless steel films and plates; and brass films and plates.

[0136] If the viscosity of the slurry is low and the slurry spreads on the substrate during the coating process, a frame for blocking may be fixed to the substrate to obtain a radiation-sensitive sheet of the desired thickness and basis weight. The type of frame for blocking is not particularly limited, but it is preferable to select one that allows the edge of the sheet to be easily peeled off after drying. From this perspective, molded resin or metal plates are more preferable. In this embodiment, resin plates such as acrylic plates, polyethylene terephthalate plates, vinyl chloride plates, polystyrene plates, polypropylene plates, polycarbonate plates, and polyvinylidene chloride plates, metal plates such as aluminum plates, zinc plates, copper plates, and iron plates, and plates with their surfaces oxidized, as well as molded stainless steel plates, brass plates, and the like, can be used.

[0137] The coating machine for coating the substrate with the slurry is not particularly limited, and examples thereof include a roll coater, gravure coater, die coater, curtain coater, air doctor coater, etc. Die coaters, curtain coaters, and spray coaters are particularly preferred because they can make the thickness of the sheet more uniform.

[0138] The slurry temperature and ambient temperature when applying the slurry to the substrate are not particularly limited, but are preferably, for example, from 5°C to 80°C, more preferably from 10°C to 60°C, even more preferably from 15°C to 50°C, and particularly preferably from 20°C to 40°C. If the application temperature is above the lower limit, the slurry can be applied more easily. If the application temperature is below the upper limit, evaporation of the dispersion medium during application and side reactions due to heat can be suppressed.

[0139] The method for drying the slurry coated on the substrate is not particularly limited, but examples include a non-contact drying method, a method in which the sheet is dried while being restrained, or a combination of these. The non-contact drying method is not particularly limited, but for example, a method of drying by heating with hot air, infrared rays, far infrared rays, or near infrared rays (heat drying method), or a method of drying by vacuum (vacuum drying method) can be applied. Although the heat drying method and the vacuum drying method can be combined, the heat drying method is usually applied. Drying by infrared rays, far infrared rays, or near infrared rays can be carried out using, for example, an infrared device, a far infrared device, or a near infrared device, but is not particularly limited. The heating temperature in the heat drying method is not particularly limited, but is preferably 20°C or higher, more preferably 40°C or higher, and preferably 150°C or lower, more preferably 120°C or lower, and even more preferably 100°C or lower. If the heating temperature is equal to or higher than the above lower limit, the dispersion medium can be quickly evaporated. On the other hand, if the heating temperature is equal to or lower than the above upper limit, it is possible to reduce the cost required for heating and to suppress discoloration and side reactions of the fibrous cellulose due to heat.

[0140] The papermaking process is carried out by making paper from the slurry using a papermaking machine. The papermaking machine used in the papermaking process is not particularly limited, but examples include continuous papermaking machines such as Fourdrinier, cylinder, and tilting types, and multi-layer papermaking machines that combine these. In the papermaking process, known papermaking methods such as handmaking may also be used. The papermaking process involves filtering and dewatering the slurry with a wire to obtain a wet sheet, which is then pressed and dried. The filter cloth used to filter and dewater the slurry is not particularly limited, but it is preferable that it does not allow fibrous cellulose, hydrophilic resins, and radiation-sensitive compositions to pass through and that the filtration rate does not become too slow. Such filter cloths are not particularly limited, but are preferably sheets, woven fabrics, or porous membranes made of organic polymers. The organic polymer is not particularly limited, but is preferably a non-cellulose organic polymer such as polyethylene terephthalate, polyethylene, polypropylene, or polytetrafluoroethylene (PTFE). In this embodiment, examples include porous membranes made of polytetrafluoroethylene with a pore size of 0.1 μm to 20 μm, and woven fabrics made of polyethylene terephthalate or polyethylene with a pore size of 0.1 μm to 20 μm.

[0141] In the papermaking process, a method for producing a sheet from the slurry can be carried out using, for example, a production apparatus including a water squeezing section in which the slurry is discharged onto an endless belt and the dispersion medium is squeezed out of the discharged slurry to produce a web, and a drying section in which the web is dried to produce a sheet. An endless belt is disposed between the water squeezing section and the drying section, and the web produced in the water squeezing section is transported to the drying section while still on the endless belt.

[0142] The dehydration method used in the papermaking process is not particularly limited, but examples thereof include dehydration methods commonly used in paper manufacturing. Among these, methods in which dehydration is performed using a Fourdrinier, cylinder, or inclined wire, followed by further dehydration using a roll press, are preferred. Furthermore, the drying method used in the papermaking process is not particularly limited, but examples thereof include methods used in paper manufacturing. Among these, drying methods using a cylinder dryer, Yankee dryer, hot air dryer, near-infrared heater, infrared heater, etc. are more preferred.

[0143] <Characteristics of radiation-sensitive sheets> From the viewpoint of shape stability and enabling fine patterning, the thickness of the radiation-sensitive sheet is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 25 μm or more, and is preferably 1,000 μm or less, more preferably 500 μm or less, even more preferably 100 μm or less. The coating amount and paper making amount may be adjusted appropriately so that the thickness of the radiation-sensitive sheet falls within the above range.

[0144] The radiation-sensitive sheet of the present invention preferably has excellent light transmittance, with a total light transmittance of preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more, and is 100% or less, and from the viewpoint of ease of production, preferably 99.5% or less. The total light transmittance is measured using a haze meter in accordance with JIS K 7361-1:1997.

[0145] Furthermore, the radiation-sensitive sheet of the present invention preferably has excellent transparency, and the haze is preferably 10% or less, more preferably 3% or less, and even more preferably 2% or less, and is 0% or more, and from the viewpoint of ease of production, is preferably 0.1% or more. The haze is measured using a haze meter in accordance with JIS K 7136:2000.

[0146] <Patterned Sheet> The patterned radiation-sensitive sheet of the present invention is obtained by exposing the radiation-sensitive sheet of the present invention described above and removing (developing) the unexposed areas to form a pattern. The radiation is usually irradiated by selectively exposing at least a portion of the radiation-sensitive sheet through a photomask or the like using, for example, a contact aligner, a stepper, or a scanner. The light source for exposure is not particularly limited, and examples include known exposure techniques such as a high-pressure mercury lamp, a metal halide lamp, an ultra-high-pressure mercury lamp, a KrF excimer laser, an ArF excimer laser, an EUV irradiation device, a soft X-ray irradiation device, an electron lithography device, etc. A post-exposure bake (PEB) step may be included. Among the radiations to be irradiated onto the radiation-sensitive sheet, radiation with a wavelength of 313 nm or more is preferred, and radiation containing 365 nm ultraviolet rays is particularly preferred. Therefore, as the exposure light source, a high-pressure mercury lamp, a metal halide lamp, or an ultra-high-pressure mercury lamp, which can irradiate radiation with a wavelength of 313 nm or more including 365 nm ultraviolet rays, is more preferred. By using these exposure light sources, a relatively high transmittance can be obtained even for a sheet with a thickness of 10 μm or more in the wavelength range of 313 nm or more, and the back side of the radiation-sensitive sheet can be fully exposed without reducing the amount of light. The exposure dose is preferably 10 mJ / cm2, as measured by an illuminance meter (OAI model 356, manufactured by OAI Optical Associates Inc.) at a wavelength of 365 nm. 2 More than 1,000mJ / cm 2 Less than or equal to 100 mJ / cm 2 More than 800mJ / cm 2 The following is the result.

[0147] As the developing method, for example, shower developing method, spray developing method, immersion developing method, puddle developing method, etc. may be adopted. As the developer, an alkaline developer, water, or a water-miscible organic solvent can be used. Examples of alkaline developers include aqueous alkaline solutions in which at least one alkaline compound such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene is dissolved. The alkaline developer is preferably an aqueous TMAH solution, and the concentration of the alkaline developer is preferably 0.1% by mass or more and 2.38% by mass or less, and more preferably 0.4% by mass or less and 2.38% by mass or less. Examples of water-miscible organic solvents include alcohols such as methanol, ethanol, 1-propanol, isopropyl alcohol (IPA), t-butanol, and 1-methoxy-2-propanol (PGME); polyhydric alcohols such as ethylene glycol and glycerin; ketones such as acetone; ethers such as tetrahydrofuran; esters such as ethyl acetate and methyl acetate; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; sulfoxides such as dimethyl sulfoxide, etc. These may be used alone or in combination of two or more. As the water-miscible organic solvent, alcohols such as ethanol, IPA, and PGME are preferred. The content of the organic solvent in the organic solvent developer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 99% by mass or more. Examples of components other than the organic solvent in the organic solvent developer include water and silicone oil. Of these, water is preferred as the developer, and pure water is more preferred. After development, the formed pattern may be further rinsed (washed) with a rinse solution.

[0148] The patterned sheet has excellent transparency, and furthermore, the radiation-sensitive composition has been removed throughout the entire thickness of the sheet, and the removed portions form a front-to-back through-pattern, which is expected to find applications as a sensor that effectively detects gases or liquids passing through the removed portions, or as a dye for color filters or conductive portions for touch panels by dyeing the removed portions of the radiation-sensitive composition. [Example]

[0149] The features of the present invention will be explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0150] <Production Example 1> [Production of Fine Fibrous Cellulose Dispersion (1)] The raw pulp used was softwood kraft pulp (solid content 93% by mass, basis weight 245 g / m) manufactured by Oji Paper Co., Ltd. 2 A sheet-like product with a Canadian Standard Freeness (CSF) of 700 mL when disintegrated according to JIS P 8121-2:2012 was used. This raw pulp was subjected to phosphorus oxo-oxidation treatment as follows. First, a mixed aqueous solution of ammonium dihydrogen phosphate and urea was added to 100 parts by mass (bone dry mass) of the raw pulp to adjust the composition to 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. The obtained chemical-impregnated pulp was then heated in a hot air dryer at 165°C for 250 seconds to introduce phosphorus oxo acid groups into the cellulose in the pulp, yielding phosphorus oxo-oxidized pulp 1.

[0151] Next, the obtained phosphorus oxo-oxidized pulp 1 was subjected to a washing treatment. The washing process was carried out by pouring 10 L of ion-exchanged water over 100 g of phosphorus oxidized pulp (bone dry mass), stirring the resulting pulp dispersion until the pulp was uniformly dispersed, and then repeatedly filtering and dehydrating the pulp. The washing was completed when the electrical conductivity of the filtrate reached 100 μS / cm or less.

[0152] Next, the washed phosphorus oxy-oxidized pulp was neutralized as follows. First, the washed phosphorus oxidized pulp was diluted with 10 L of ion-exchanged water, and then a 1 N aqueous solution of sodium hydroxide was added little by little while stirring to obtain a phosphorus oxidized pulp slurry with a pH of 12 to 13. Next, the phosphorus oxidized pulp slurry was dewatered to obtain a phosphorus oxidized pulp that had been subjected to a neutralization treatment. Next, the neutralized phosphorus oxidized pulp was subjected to the above-mentioned washing treatment to obtain phosphorus oxidized pulp A.

[0153] The infrared absorption spectrum of the obtained phosphorus oxy-oxidized pulp A was measured using FT-IR. -1 Absorption due to P=O of phosphate groups was observed near the pulp, confirming that phosphate groups had been added to the pulp. In addition, the obtained phosphorus oxo-oxidized pulp A was analyzed using an X-ray diffractometer, and typical peaks were confirmed at two positions, around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming that it had a cellulose type I crystalline structure.

[0154] Ion-exchanged water was added to the obtained phosphorus oxo-oxidized pulp A to prepare a slurry with a solids concentration of 2% by mass. This slurry was treated twice at a pressure of 200 MPa in a wet pulverization device (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion (1) containing fine fibrous cellulose. X-ray diffraction confirmed that this fine fibrous cellulose maintained the cellulose type I crystal structure. The fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 2 to 5 nm. The amount of phosphorus oxoacid groups (amount of first dissociated acid) was 1.45 mmol / g. The total amount of dissociated acid was 2.45 mmol / g.

[0155] <Production Example 2> [Production of fine fibrous cellulose dispersion (2)] The same procedure as in Production Example 1 was carried out except that 33 parts by mass of phosphorous acid (phosphonic acid) was used instead of ammonium dihydrogen phosphate, to obtain phosphorus oxo-oxidized pulp B and fine fibrous cellulose dispersion (2).

[0156] The infrared absorption spectrum of the obtained phosphorus oxy-oxidized pulp B was measured using FT-IR. -1 Absorption due to P=O of the phosphonic acid group, which is a tautomer of the phosphorous acid group, was observed near the nucleus, confirming that a phosphorous acid group (phosphonic acid group) had been added to the pulp.

[0157] In addition, the obtained phosphorus oxo-oxidized pulp B was analyzed using an X-ray diffractometer, and typical peaks were confirmed at two positions, around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming that it had a cellulose type I crystalline structure.

[0158] X-ray diffraction confirmed that the obtained fine fibrous cellulose maintained the cellulose type I crystal structure. Furthermore, the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 2 to 5 nm. Furthermore, for the fine fibrous cellulose dispersion (2), the amount of phosphorous acid groups introduced into the cellulose (amount of first dissociated acid) and the total amount of dissociated acid were 1.51 mmol / g and 1.54 mmol / g, respectively.

[0159] <Production Example 3> [Production of fine fibrous cellulose dispersion (3)] The same procedure as in Production Example 1 was carried out, except that 38 parts by mass of amidosulfuric acid was used instead of ammonium dihydrogen phosphate and the heating time in the hot air dryer was 19 minutes, to obtain sulfated pulp and fine fibrous cellulose dispersion (3).

[0160] The infrared absorption spectrum of the obtained sulfated pulp was measured using FT-IR. -1 Absorption due to sulfate groups was observed in the vicinity, confirming that sulfate groups had been added to the pulp.

[0161] In addition, the obtained sulfated pulp was analyzed using an X-ray diffractometer, and typical peaks were confirmed at two positions, around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming that it had a cellulose type I crystalline structure.

[0162] X-ray diffraction confirmed that the obtained fine fibrous cellulose maintained the cellulose type I crystal structure. Furthermore, the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 2 to 5 nm. Furthermore, the amount of sulfate groups introduced into the cellulose in the fine fibrous cellulose dispersion (3) was 1.12 mmol / g.

[0163] <Production Example 4> [Production of fine fibrous cellulose dispersion (4)] The raw material pulp used was softwood kraft pulp (undried) manufactured by Oji Paper Co., Ltd. This raw material pulp was subjected to alkaline TEMPO oxidation treatment as follows. First, 100 parts by weight of the raw pulp (dry mass equivalent), 1.6 parts by weight of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl), and 10 parts by weight of sodium bromide were dispersed in 10,000 parts by weight of water. Next, 13 parts by weight of aqueous sodium hypochlorite solution was added to 1.0 g of pulp to give a concentration of 3.8 mmol to initiate the reaction. During the reaction, 0.5 M aqueous sodium hydroxide solution was added dropwise to maintain the pH at 10 to 10.5. The reaction was considered complete when no further change in pH was observed.

[0164] The resulting TEMPO oxidized pulp was then subjected to a washing treatment. The washing process was carried out by dehydrating the pulp slurry after TEMPO oxidation to obtain a dehydrated sheet, pouring 5,000 parts by mass of ion-exchanged water into the sheet, stirring to disperse the material evenly, and then filtering and dehydrating the sheet. The washing was completed when the electrical conductivity of the filtrate reached 100 μS / cm or less.

[0165] In addition, the obtained TEMPO-oxidized pulp was analyzed using an X-ray diffractometer, and typical peaks were observed at two positions, around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming that it had a cellulose type I crystalline structure.

[0166] Ion-exchanged water was added to the obtained TEMPO-oxidized pulp to prepare a slurry with a solids concentration of 2% by mass. This slurry was treated twice at a pressure of 200 MPa in a wet pulverization device (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion (4) containing fine fibrous cellulose.

[0167] For the fine fibrous cellulose dispersion (4), the amount of carboxyl groups introduced into the cellulose was 1.30 mmol / g.

[0168] <Method for measuring fiber width and ionic group content of fine fibrous cellulose> [Fiber width measurement] The fiber width of the fine fibrous cellulose was measured by the following method. The supernatant of the fine fibrous cellulose dispersion was diluted with water so that the concentration of the fine fibrous cellulose was 0.01% by mass or more and 0.1% by mass or less, and the diluted solution was dropped onto a hydrophilized carbon grid membrane. After drying, the membrane was stained with uranyl acetate and observed under a transmission electron microscope (JEOL-2000EX, manufactured by JEOL Ltd.).

[0169] [Measurement of phosphorus oxoacid group content] The amount of phosphorus oxoacid groups in the fine fibrous cellulose was measured by treating a slurry containing the fine fibrous cellulose with an ion exchange resin after diluting the dispersion containing the target fine fibrous cellulose with ion exchange water to a content of 0.2 mass% and then titrating it with an alkali. Treatment with ion exchange resin was carried out by adding 1 / 10 by volume of a strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, conditioned) to the above-mentioned fine fibrous cellulose-containing slurry, shaking for 1 hour, and then pouring it onto a mesh with 90 μm openings to separate the resin from the slurry. In addition, alkali titration was performed by measuring the change in the pH of a slurry containing fine fibrous cellulose after ion exchange resin treatment while adding 10 μL of 0.1 N sodium hydroxide solution every 5 seconds. Nitrogen gas was bubbled through the slurry for 15 minutes before the start of the titration. In this neutralization titration, two maximum points of increment (the derivative of pH with respect to the amount of alkali added) were observed on the plot of pH versus the amount of alkali added. The first maximum point of increment after starting the alkali addition is called the first endpoint, and the second maximum point is called the second endpoint (Figure 1). The amount of alkali required from the start of the titration to the first endpoint is equal to the amount of first dissociated acid in the slurry used for titration. The amount of alkali required from the start of the titration to the second endpoint is equal to the total amount of dissociated acid in the slurry used for titration. The amount of alkali (mmol) required from the start of titration to the first endpoint was divided by the solid content (g) in the slurry to be titrated, and the value was taken as the amount of phosphate groups (mmol / g).

[0170] [Measurement of sulfur oxoacid group content] The amount of sulfur oxoacid groups was measured by wet ashing the obtained fibrous cellulose with perchloric acid and concentrated nitric acid, diluting it at an appropriate ratio, and then measuring the amount of sulfur by ICP emission spectrometry. The amount of sulfur divided by the bone dry mass of the fibrous cellulose sample was taken as the amount of sulfur oxoacid groups (unit: mmol / g).

[0171] [Measurement of carboxyl group content] The amount of carboxyl groups in the fine fibrous cellulose was measured in the same manner as in [Measurement of the amount of phosphorus oxoacid groups], except that 50 μL of 0.1 N aqueous sodium hydroxide solution was added to the fine fibrous cellulose-containing slurry after treatment with the ion exchange resin once every 30 seconds. The amount of carboxyl groups (mmol / g) was calculated by dividing the amount of alkali (mmol) required in the region corresponding to the first region shown in Figure 2 by the solid content (g) in the slurry to be titrated.

[0172] <Production Example 5> [Production of Radiation-Sensitive Composition (1)] N,N'-{[(2-acrylamido-2-[(3-acrylamidopropoxy)methyl]propane-1,3-diyl)bis(oxy)]bis(propane-1,3-diyl)}diacrylamide (Fujifilm Wako Pure Chemical Industries, Ltd., FOM-03006, Hansen solubility parameter polarity term dP 15.9 MPa) 0.5 , HSP distance with water 31.6MPa 0.5 A mixture of 1.0 part by mass of 4-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (manufactured by Tokyo Chemical Industry Co., Ltd.) and 0.1 part by mass of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone was dissolved in purified water to a concentration of 0.5% by mass. The mixture was then filtered through a Millipore filter with a pore size of 0.5 μm to prepare a radiation-sensitive composition (1).

[0173] <Production Example 6> [Production of Radiation-Sensitive Composition (2)] N,N',N"-triacryloyldiethylenetriamine (Fujifilm Wako Pure Chemical Industries, Ltd., FOM-03007, Hansen solubility parameter polarity term dP 16.8 MPa) 0.5 , HSP distance with water 34.9MPa 0.5 A mixture of 1.0 part by mass of 4-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (manufactured by Tokyo Chemical Industry Co., Ltd.) and 0.1 part by mass of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone was dissolved in purified water to a concentration of 0.5% by mass. The mixture was then filtered through a Millipore filter with a pore size of 0.5 μm to prepare radiation-sensitive composition (2).

[0174] <Production Example 7> [Production of Radiation-Sensitive Composition (3)] N,N'-Diacryloyl-4,7,10-trioxa-1,13-tridecanediamine (Fujifilm Wako Pure Chemical Industries, Ltd., FOM-03008, Hansen solubility parameter polarity term dP 12.7 MPa) 0.5 , HSP distance with water 34.0MPa 0.5A mixture of 1.0 part by mass of 4-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (manufactured by Tokyo Chemical Industry Co., Ltd.) and 0.1 part by mass of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone was dissolved in purified water to a concentration of 0.5% by mass. The mixture was then filtered through a Millipore filter with a pore size of 0.5 μm to prepare radiation-sensitive composition (3).

[0175] <Production Example 8> [Production of Radiation-Sensitive Composition (4)] N,N'-Diacryloylethylenediamine (Tokyo Chemical Industry Co., Ltd., E1086, Hansen solubility parameter polarity term dP 16.8 MPa) 0.5 , HSP distance with water 32.3MPa 0.5 A mixture of 1.0 part by mass of 4-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (manufactured by Tokyo Chemical Industry Co., Ltd.) and 0.1 part by mass of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone was dissolved in purified water to a concentration of 0.5% by mass. The mixture was then filtered through a Millipore filter with a pore size of 0.5 μm to prepare radiation-sensitive composition (4).

[0176] <Production Example 9> [Production of Radiation-Sensitive Composition (5)] Dipentaerythritol hexaacrylate (DPHA) (manufactured by Shin-Nakamura Chemical Co., Ltd., NK Ester A-DPH, Hansen solubility parameter polarity term dP 1.3 MPa) 0.5 , HSP distance with water 36.6MPa 0.5 A mixture of 1.0 part by mass of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (manufactured by Tokyo Chemical Industry Co., Ltd.) and 0.1 part by mass of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone was dissolved in 1-methoxy-2-propanol to a concentration of 0.5% by mass. The mixture was then filtered through a Millipore filter with a pore size of 0.5 μm to prepare radiation-sensitive composition (5).

[0177] Example 1 Ion-exchanged water was added to the fine fibrous cellulose dispersion (1) having a solid content concentration of 2.0% by mass to prepare a fine fibrous cellulose dispersion (A) having a solid content concentration of 0.5% by mass. To 30 parts by mass of the obtained fine fibrous cellulose dispersion (A), 70 parts by mass of the radiation-sensitive composition (1) solution was added and stirred. 2 The mixed solution was measured so that the weight of the mixture was 150 mm, spread on a commercially available acrylic plate, and dried in a dryer at 50°C for 24 hours. A 150 mm square blocking plate was placed on the acrylic plate to achieve the specified basis weight. A radiation-sensitive sheet was obtained by the above procedure. The resulting radiation-sensitive sheet had a thickness of 50 μm.

[0178] <Example 2> A radiation-sensitive sheet was obtained in the same manner as in Example 1, except that the amount of the radiation-sensitive composition (1) solution was 80 parts by mass relative to 20 parts by mass of the fine fibrous cellulose dispersion (A).

[0179] Example 3 A radiation-sensitive sheet was obtained in the same manner as in Example 1, except that the amount of the radiation-sensitive composition (1) solution was 60 parts by mass relative to 40 parts by mass of the fine fibrous cellulose dispersion (A).

[0180] Example 4 Polyvinyl alcohol (PVA) (Poval 105, manufactured by Kuraray Co., Ltd., polymerization degree: 500, saponification degree: 98-99 mol%) was added to ion-exchanged water to a concentration of 0.5 mass%, and the mixture was stirred at 95°C for 1 hour to dissolve, yielding an aqueous polyvinyl alcohol solution.

[0181] (Production of radiation-sensitive sheets) A radiation-sensitive sheet was obtained in the same manner as in Example 1, except that the amount of the polyvinyl alcohol aqueous solution was 8 parts by mass, and the amount of the radiation-sensitive composition (1) solution was 70 parts by mass, relative to 22 parts by mass of the fine fibrous cellulose dispersion (A).

[0182] <Example 5> A radiation-sensitive sheet was obtained in the same manner as in Example 1, except that the radiation-sensitive composition (2) was used instead of the radiation-sensitive composition (1).

[0183] Example 6 A radiation-sensitive sheet was obtained in the same manner as in Example 1, except that the radiation-sensitive composition (3) was used instead of the radiation-sensitive composition (1).

[0184] Example 7 A radiation-sensitive sheet was obtained in the same manner as in Example 1, except that the radiation-sensitive composition (4) was used instead of the radiation-sensitive composition (1).

[0185] Example 8 Ion-exchanged water was added to the fine fibrous cellulose dispersion (2) having a solid content concentration of 2.0% by mass to prepare a fine fibrous cellulose dispersion (B) having a solid content concentration of 0.5% by mass. A radiation-sensitive sheet was obtained in the same manner as in Example 1, except that the fine fibrous cellulose dispersion (B) was used instead of the fine fibrous cellulose dispersion (A).

[0186] Example 9 Ion-exchanged water was added to the fine fibrous cellulose dispersion (3) having a solid content concentration of 2.0% by mass to prepare a fine fibrous cellulose dispersion (C) having a solid content concentration of 0.5% by mass. A radiation-sensitive sheet was obtained in the same manner as in Example 1, except that the fine fibrous cellulose dispersion (C) was used instead of the fine fibrous cellulose dispersion (A).

[0187] Example 10 Ion-exchanged water was added to the fine fibrous cellulose dispersion (4) having a solid content concentration of 2.0% by mass to prepare a fine fibrous cellulose dispersion (D) having a solid content concentration of 0.5% by mass. A radiation-sensitive sheet was obtained in the same manner as in Example 1, except that the fine fibrous cellulose dispersion (D) was used instead of the fine fibrous cellulose dispersion (A).

[0188] <Comparative Example 1> A radiation-sensitive sheet was obtained in the same manner as in Example 1, except that the amount of the polyvinyl alcohol aqueous solution was 14 parts by mass, and the amount of the radiation-sensitive composition (5) solution was 50 parts by mass, relative to 36 parts by mass of the fine fibrous cellulose dispersion (A).

[0189] <Comparative Example 2> A radiation-sensitive sheet was obtained in the same manner as in Example 4, except that the radiation-sensitive composition (5) was used instead of the radiation-sensitive composition (1).

[0190] <Comparative Example 3> The radiation-sensitive composition (1) solution was applied onto a polyethylene terephthalate film (Lumirror U48, manufactured by Toray Industries, Inc., thickness 38 μm) using a bar coater, and dried in a dryer at 50° C. for 24 hours. The thickness of the resulting laminate of the polyethylene terephthalate film and the radiation-sensitive composition (1) layer was 50 μm.

[0191] [Measurement method] <Total light transmittance of the sheet> The total light transmittance of the radiation-sensitive sheet before exposure was measured using a haze meter (HM-150, manufactured by Murakami Color Research Laboratory Co., Ltd.) in accordance with JIS K 7361-1: 1997. The results are shown in Table 1.

[0192] <Sheet haze> The haze of the radiation-sensitive sheet before exposure was measured in accordance with JIS K 7136: 2000 using a haze meter (HM-150, manufactured by Murakami Color Research Laboratory Co., Ltd.). The results are shown in Table 1.

[0193] <Patterning onto sheets> A radiation-sensitive sheet or a laminate of a polyethylene terephthalate film and a radiation-sensitive composition (1) layer was placed in an exposure device equipped with a metal halide lamp (manufactured by iGraphics Co., Ltd., model iGrandage ECS-4011GX / N, wavelength 200 to 450 nm). Next, a photomask (manufactured by Toppan Printing Co., Ltd., synthetic quartz, L / S = 400 / 400, 1,100 / 1,100 μm) was placed on the sheet. At this time, a shim tape (manufactured by Misumi Group Holdings Co., Ltd., thickness 500 μm, made of SUS) was used to ensure a gap of 500 μm between the substrate for pattern formation and the photomask. Next, the intensity of the radiation at a wavelength of 365 nm was measured using an illuminance meter (OAI model 356, manufactured by OAI Optical Associates Inc.) to obtain a value of 500 mJ / cm 2 After setting the value so that the value was 0.01, exposure was performed using an exposure device.

[0194] The exposed sheet was then developed by dipping it in pure water for 3 minutes. As a result, a patterned sheet was obtained in which the resin for the radiation-sensitive composition had been removed only from the unexposed areas of the sheet.

[0195] Next, a pure solution of Acid Red 92 was dropped evenly onto one side of this sheet using a dropper, and after 3 minutes, the sheet was dipped in pure water for 3 minutes to wash. As a result, a sheet was obtained in which Acid Red 92 was impregnated only in the area where the resin for the radiation-sensitive composition had been removed.

[0196] The sheet was observed under an optical microscope, and if a pattern was formed at both L / S = 400 / 400 μm and 1,100 / 1,100 μm, it was rated "A." If a pattern was not formed at L / S = 400 / 400 μm but a pattern was formed at L / S = 1,100 / 1,100 μm, it was rated "B." If a pattern was not formed at L / S = 400 / 400 μm or 1,100 / 1,100 μm, it was rated "C." The results are shown in Table 1.

[0197] <Dyeing depth of sheet> This sheet was embedded in epoxy resin and then cross-sectional sections were prepared using a microtome. Ten of these cross-sectional sections were prepared and the depth of staining was observed under an optical microscope at 1,000x magnification. If an average of 90% or more of the thickness of the radiation-sensitive sheet or the laminate of the polyethylene terephthalate film and the radiation-sensitive composition (1) layer was stained, it was evaluated as "A." If an average of 50% to less than 90% of the thickness was stained, it was evaluated as "B." If an average of less than 50% was stained, it was evaluated as "C." The results are shown in Table 1. In addition, in Examples 1 to 10, at least one of the ten pieces was dyed 100% relative to the thickness of the radiation-sensitive sheet, and the radiation-sensitive composition was removed throughout the entire thickness direction. On the other hand, in Comparative Examples 1 to 3, not a single piece was dyed 100% relative to the thickness of the radiation-sensitive sheet or the laminate of the polyethylene terephthalate film and the radiation-sensitive composition (1) layer.

[0198] <Sheet curl> Cut this sheet into a length of 100mm x width of 100mm, and call its four corners "vertex A," "vertex B," "vertex C," and "vertex D." Also, call its four sides "side AB," "side BC," "side CD," and "side DA." The sheet was placed on a glass substrate, and sides BC and CD were fixed with tape. The distance from the glass substrate to vertex A was measured and designated d1. Similarly, when sides CD and DA were fixed with tape, the distance from the glass substrate to vertex B was measured and designated d2. When sides AB and DA were fixed with tape, the distance from the glass substrate to vertex C was measured and designated d3. When sides AB and BC were fixed with tape, the distance from the glass substrate to vertex D was measured and designated d4. If the average value of d1 to d4 was less than 10 mm, it was evaluated as "A." If it was 10 mm or more but less than 20 mm, it was evaluated as "B." If it was 20 mm or more, it was evaluated as "C." The results are shown in Table 1.

[0199] <Adhesion of Acid Red 92> Adhesion was evaluated using the cross-cut method in accordance with JIS K 5600-5-6:1999. If peeling of the cross-cut area was less than 15%, it was rated "A", if it was 15% or more but less than 65%, it was rated "B", and if peeling was 65% or more or if the dyed area could not be formed and the test itself could not be performed, it was rated "C".

[0200] [Table 1]

[0201] According to the results of the Examples and Comparative Examples, the patterned sheets obtained in Examples 1 to 10 had high total light transmittance, low haze, and excellent transparency. They also had excellent patterning properties. Furthermore, an average of 50% or more of the radiation-sensitive composition in the unexposed areas was removed in the thickness direction, and at least a portion of the radiation-sensitive composition was removed across the entire thickness direction. Furthermore, curling was suppressed and adhesion was excellent. On the other hand, as exemplified in Comparative Examples 1 and 2, when a radiation-sensitive composition not specified in claim 1 was used, phase separation occurred between the cellulose and the composition, resulting in high haze, and the poor homogeneity of the sheet caused by the phase separation reduced the reproducibility of pattern formation (Comparative Example 2). This phase separation could be improved by reducing the amount of radiation-sensitive composition used, but at the same time, the amount of developable components (unexposed radiation-sensitive composition) was reduced, making it impossible to form a pattern all the way to the bottom of the sheet, resulting in a reduced dyeing depth (Comparative Example 1). Furthermore, as exemplified in Comparative Example 3, when the sheet did not contain a cellulose dispersion, all of the unexposed areas were developed, resulting in the problem of not being able to form dyed areas. [Industrial Applicability]

[0202] The present invention provides a radiation-sensitive sheet that can be finely patterned. The patterned sheet obtained by exposing and developing the radiation-sensitive sheet has excellent transparency. Furthermore, the radiation-sensitive composition is removed throughout the entire thickness of the sheet, and the removed portions form a front-to-back through-type pattern. This is expected to find applications as a sensor that effectively detects gases or liquids that pass through the removed portions, or as a dye for color filters or conductive portions of touch panels by dyeing the removed portions of the radiation-sensitive composition.

Claims

1. A negative-type radiation-sensitive sheet containing at least a radiation-sensitive composition and fine fibrous cellulose having a fiber width of 1,000 nm or less, The radiation-sensitive composition contains a polymerizable unsaturated bond and has a Hansen solubility parameter (HSP) distance with water of 36 MPa. ０．５ or less and polar term (dP) is 12 MPa ０．５ Compound (X) Negative radiation-sensitive sheet.

2. 2. The negative-working radiation-sensitive sheet according to claim 1, wherein the radiation-sensitive composition contains a photopolymerization initiator.

3. 3. The negative-working radiation-sensitive sheet according to claim 1, wherein the content of the radiation-sensitive composition in the solid content of the negative-working radiation-sensitive sheet is 30% by mass or more.

4. 4. The negative radiation-sensitive sheet according to claim 1, wherein the compound (X) has at least one of a (meth)acryloyloxy group and a (meth)acrylamide group.

5. 5. The negative-working radiation-sensitive sheet according to claim 1, wherein the fine fibrous cellulose has an anionic group.

6. 6. The negative-working radiation-sensitive sheet according to claim 1, wherein the fine fibrous cellulose has a phosphorus oxo acid group or a group derived from a phosphorus oxo acid group.

7. 7. The negative radiation-sensitive sheet according to claim 1, wherein the radiation-sensitive composition is soluble in at least one of water, alcohol, and a mixed solvent thereof.

8. 8. The negative-working radiation-sensitive sheet according to claim 1, wherein the negative-working radiation-sensitive sheet has a total light transmittance of 70% or more.

9. 9. The negative-working radiation-sensitive sheet according to claim 1, wherein the haze of the negative-working radiation-sensitive sheet is 10% or less.

10. 10. A patterned sheet, wherein at least a part of the unexposed areas of the negative-working radiation-sensitive sheet according to any one of claims 1 to 9 have been removed.

11. 10. A patterned sheet, comprising the negative radiation-sensitive sheet according to claim 1, wherein at least a portion of the radiation-sensitive composition in the unexposed areas has been removed across the entire thickness of the sheet.

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