JP6514487B2 - Sheet manufacturing method - Google Patents

Description

  The present invention relates to a method of producing a sheet from a dispersion of cellulose fibers and the like. More specifically, the production method of the present invention includes means for effectively performing the step of concentrating and / or drying the dispersion to form a sheet when producing a sheet from the dispersion of cellulose fibers and the like. The present invention is useful, for example, in the production of transparent fine cellulose fiber-containing sheets used for substrates for organic EL, liquid crystal display, and the like.

  BACKGROUND ART In recent years, materials using renewable natural fibers have attracted attention due to the substitution of petroleum resources and environmental awareness. Among natural fibers, wood-derived cellulose fibers (pulp) have been widely used mainly as paper products. Further, fine cellulose fibers having a fiber diameter of 1 μm or less are also known, and a sheet containing fine cellulose fibers has advantages such as high transparency, high elastic modulus, low linear expansion coefficient, and flexible properties, Application to various applications is considered.

  In producing a cellulose-containing sheet from a dispersion of cellulose fibers, a drying step is carried out, and the drying method is roughly classified into two. One method is a method widely adopted in the production of paper, and is a method of press-dehydrating cellulose fibers separated by filtration from a dispersion, and then drying them by drying (see, for example, Patent Documents 1 and 2). Another method is a method widely adopted mainly in the production of a film, in which a dispersion or solution is cast on a substrate and then dried by drying (see, for example, Patent Document 2).

  On the other hand, a technology has been developed in which conductive nanoparticles are sintered on a heat-sensitive substrate by irradiating high-energy pulsed light, heating only a limited region in or near the surface layer, and heating. For example, Patent Document 4 relates to the use of a high power pulsed photon source to process nanoparticles with minimal impact on the substrate, including exposing the nanomaterial to pulsed emission. We propose a method of sintering etc. Patent Document 5 discloses that a composition containing metal oxide particles having a flat shape, a reducing agent, and a binder resin is applied onto a substrate, dried and deposited, and the composition deposited on the substrate is irradiated with light. Alternatively, it proposes a method of producing a conductive pattern formed by reducing the metal oxide particles by microwave heating. Further, Patent Document 6 mixes a metal salt and / or a metal complex with a specific reducing agent to prepare a composition for forming a metal pattern, prints this composition on a substrate, and emits pulsed light, It is proposed to form a metal pattern (conductive pattern).

  On the other hand, Patent Document 7 utilizes pulsed light irradiation in addition to sintering of conductive nanoparticles, and as a method for drying the remaining water after cleaning the surface of the object to be treated, It is proposed to emit light with high light intensity by pulse. In addition, Patent Document 8 is a heat treatment method of performing pretreatment for film formation treatment on a substrate, wherein a surface of the substrate is irradiated with flash light to dry the moisture adhering to the surface. suggest.

JP, 2010-168716, A International Publication 2012/011559 International Publication 2012/128107 Japanese Patent Application Publication No. 2008-522369 JP, 2013-196881, A JP, 2014-31577, A JP 2004-275843 A JP, 2012-84755, A

  In the drying method through filtration for producing conventional cellulose-containing sheets, selection of filter media is difficult. In detail, when the filter material has a large diameter, fine cellulose fibers fall off, and when the filter material has a small diameter, it is clogged and the dewatering performance is significantly reduced. Further, in the method of drying the dispersion cast on the substrate, the drying load is large, and there is a limit in efficiently drying in a short time. In detail, since the viscosity of the dispersion of the fine cellulose fiber is high, the solid concentration of the dispersion is generally set to about 3% by mass at the time of sheet formation, and a large amount of water must be evaporated at the time of drying. There is a problem of having to

  On the other hand, although the methods of Patent Documents 7 and 8 use pulsed light irradiation to evaporate a relatively small amount of water, pulsed light irradiation is used to instantaneously raise the temperature of the substrate. It is only In order to sheet the solid content dispersed in the dispersion medium, it is not for concentrating and / or drying the dispersion, and no irradiation condition of pulsed light suitable for sheeting has been studied.

  In forming a sheet from a dispersion of solid content such as cellulose fiber containing a relatively large amount of water, a method capable of concentrating and / or drying the dispersion in a short time is desired.

The present invention provides the following.
[1] A method for producing a sheet, comprising the steps of irradiating a liquid containing solid content coated on a substrate with pulsed light, concentrating the liquid and / or drying to obtain a sheet containing solid content .
[2] A method for producing a fiber-containing sheet, comprising applying a pulse light to a liquid containing fibers coated on a substrate to concentrate and / or dry the liquid to obtain a fiber-containing sheet.
[3] The production method according to 1 or 2, wherein the irradiation is performed in multiple cycles, and each cycle includes one or more irradiations.
[4] The manufacturing method according to 3, wherein the irradiation in the second and subsequent cycles is performed with an irradiation dose less than 100% of the irradiation dose in the immediately preceding cycle.
[5] The manufacturing method according to any one of 1 to 4, wherein the substrate contains an inorganic material.
[6] The production method according to any one of 1 to 5, wherein the substrate comprises a heat-resistant plastic material.
[7] The substrate is
The manufacturing method according to any one of 1 to 6, which comprises an upper layer composed of a transparent substrate that transmits pulse light, and a lower layer composed of a colored substrate that absorbs and / or reflects pulse light.
[8] The production method according to any one of 1 to 7, wherein the liquid contains a filler that absorbs and / or reflects pulsed light.
[9] The production method according to 8, wherein the filler is any one selected from the group consisting of carbon, metal and metal oxide.
[10] The method for producing a cellulose fiber-containing sheet according to any one of 2 to 9, wherein the fiber is a fiber into which a substituent having electrostatic and / or steric functionality is introduced.
[11] The production method according to any one of 2 to 10, wherein the fiber is a cellulose fiber having an average fiber width of 2 to 1000 nm.
[12] The cellulose fiber is a cellulose fiber into which at least one selected from the group consisting of a group derived from phosphoric acid, a group derived from carboxylic acid and a group derived from sulfuric acid is introduced, and the introduced amount of the substituent is 0 It is 01-3.0 mmol / g, The manufacturing method of 11 characterized by the above-mentioned.
[13] A method for producing a product using the obtained sheet, comprising the steps defined in any one of 1 to 12.

  According to the present invention, in forming a sheet containing cellulose fibers and the like, the drying step can be efficiently performed in a short time. In addition, it can produce a sheet with a good appearance.

  “Parts” and “%” represent proportions based on mass (parts by mass, mass%) unless otherwise specified. The numerical range “X to Y” includes the values at both ends unless otherwise noted. "A and / or B" refers to at least one of A and B unless otherwise specified, and may be A alone or B alone, or both A and B. It may be.

  The present invention comprises the steps of: irradiating a liquid containing solids with a solid content coated on a substrate with a pulse light, and concentrating and / or drying the liquid to obtain a sheet containing solids; Provide a way. Concentration and / or drying refers to treatment that evaporates the solids dispersion medium or solvent and does not change the nature of the solids. Concentration and / or drying is a process different from calcination in that it causes changes in the nature of the solids, such as calcinations not only volatilize the dispersion medium or solvent but also imparts conductivity to the solids. The sheet formed in the present invention may be expressed as a film, membrane, thin plate, paper, non-woven fabric, etc., but after being formed on the substrate, it is finally used after being separated from the substrate And after being formed on a base material, it may be used in a form complexed with the base material. It does not contain conductive patterns or coatings fired on the substrate. One of the typical embodiments of the present invention is a cellulose-containing sheet comprising the steps of: irradiating a liquid containing cellulose fibers with pulsed light and concentrating and / or drying the liquid to obtain a cellulose fiber-containing sheet It is a manufacturing method. In the following, the invention may be described by way of an embodiment of producing a cellulose fiber-containing sheet, but the description is also applicable to other embodiments unless otherwise stated. Alternatively, those skilled in the art can implement other embodiments based on the description.

[Solid Containing Liquid]
When it is called liquid containing solid content, the state in which solid content is contained in liquid does not matter. The solid content may be partially or wholly dispersed, or part or all of the solid content may be dissolved. The liquid containing solids may be a dispersion of solids and / or a solution of solids.

<Raw material solids, fiber>
The solid content as a raw material of the sheet of the present invention is not particularly limited. For example, it may be organic or inorganic. In one preferred embodiment, the solid content comprises an organic matter. The solids may be fibers. Although it does not specifically limit as a fiber raw material, For example, semi-synthetic fiber, a regenerated fiber, etc. are mentioned, such as an organic fiber, an inorganic fiber, a synthetic fiber. Examples of organic fibers include, but are not limited to, fibers derived from natural products such as cellulose, carbon fibers, pulp, chitin, chitosan and the like. Examples of inorganic fibers include, but are not limited to, glass fibers, rock fibers, metal fibers and the like. Examples of synthetic fibers include, but are not limited to, nylon, vinylon, vinylidene, polyester, polyolefin (for example, polyethylene, polypropylene and the like), polyurethane, acrylic, polyvinyl chloride, aramid and the like. Semi-synthetic fibers include, but are not limited to, acetate, triacetate, promix, and the like. Examples of the regenerated fiber include, but not limited to, rayon, cupra, polynozic rayon, lyocell, tencel and the like.

  Further, the fiber raw material used in the present invention is not particularly limited, but it is desirable to contain a hydroxyl group or an amino group because introduction of a substituent described later becomes easy.

  The fiber material is not particularly limited, but it is preferable to use pulp in terms of availability and low cost. The pulp is selected from wood pulp, non-wood pulp and deinked pulp. Examples of wood pulp include hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), soda pulp (AP), unbleached kraft pulp (UKP), oxygen bleached kraft pulp (OKP), etc. Chemical pulp etc. are mentioned. Also, semi-chemical pulp such as semi-chemical pulp (SCP), chemiground wood pulp (CGP), mechanical pulp such as ground pulp (GP), thermo-mechanical pulp (TMP, BCTMP), etc. may be mentioned, but not particularly limited. . Non-wood pulps include cotton-based pulps such as cotton linters and cotton lint, non-wood-based pulps such as hemp, straw and bagasse, celluloses isolated from ascidians and seaweeds, chitin, chitosan and the like, but are not particularly limited . Examples of the deinked pulp include, but not particularly limited to, deinked pulp made from waste paper. The pulp of the present invention may be used alone or in combination of two or more. Among the above-mentioned pulps, wood pulps containing cellulose and deinked pulps are preferable in terms of availability. Among wood pulps, chemical pulp has a large ratio of cellulose, so the yield of fine cellulose fibers is high at the time of fiber refining (fibrillation), and decomposition of cellulose in the pulp is small, and fine fibers of long fibers having a large axial ratio Although it is especially preferable at the point from which a cellulose fiber is obtained, it does not specifically limit. Among them, kraft pulp and sulfite pulp are most preferably selected, but are not particularly limited. A sheet containing fine cellulose fibers of long fibers having a large axial ratio can obtain high strength.

  The fiber width is not particularly limited, but may be, for example, 1 to 1000 nm, preferably 2 to 1000 nm, more preferably 2 to 500 nm, and still more preferably 3 to 100 nm. When the fiber width of the fine fiber is less than 1 nm, the molecule is dissolved in water, so that the physical properties (strength, rigidity, dimensional stability) as the fine fiber can not be expressed. On the other hand, if it exceeds 1000 nm, it can not be said that it is a fine fiber, and the physical properties (strength, rigidity, dimensional stability) as a fine fiber can not be obtained.

  In applications where transparency is required for the sheet, when the fiber width exceeds 30 nm, it approaches 1/10 of the wavelength of visible light, and when combined with a matrix material, refraction and scattering of visible light are likely to occur at the interface, Transparency tends to decrease. Therefore, the fiber width is not particularly limited, but is preferably 2 nm to 30 nm, and more preferably 2 to 20 nm. Composites obtained from such fine fibers as described above generally have high strength because they form a compact structure, and high transparency can also be obtained because there is little scattering of visible light.

The fiber width is measured as follows. A fine fiber-containing slurry having a concentration of 0.05 to 0.1% by mass is prepared, and the slurry is cast on a hydrophilized carbon film-coated grid to obtain a sample for TEM observation. In the case of containing wide fibers, an SEM image of the surface cast on glass may be observed. Observation with an electron microscope image is performed at a magnification of 1000 times, 5000 times, 10000 times, 20000 times or 50000 times depending on the width of the fiber to be constructed. However, the sample, observation conditions and magnification are adjusted to satisfy the following conditions.
(1) One straight line X is drawn at an arbitrary position in the observation image, and 20 or more fibers cross the straight line X.
(2) Draw a straight line Y intersecting perpendicularly with the straight line in the same image, and 20 or more fibers cross the straight line Y.
With respect to the observation image satisfying the above conditions, the width of the fiber intersecting with the straight line X and the straight line Y is visually read. Thus, three or more sets of images of at least non-overlapping surface portions are observed, and for each image, the width of the fiber intersecting the straight line X and the straight line Y is read. Thus, a fiber width of at least 20 x 2 x 3 = 120 is read. The fiber width in the present invention is an average value of the fiber widths read in this manner.

  The fiber length is not particularly limited, but is preferably 0.1 μm or more. If the fiber length is less than 0.1 μm, it is difficult to obtain the strength improvement effect when the fine fiber is combined with the resin. The fiber length can be determined from image analysis of TEM, SEM, AFM. The said fiber length is a fiber length which occupies 30 mass% or more of a fine fiber.

  The axial ratio of fibers (fiber length / fiber width) is not particularly limited, but is preferably in the range of 20 to 10,000. If the axial ratio is less than 20, it may be difficult to form the base sheet layer. When the axial ratio exceeds 10000, the viscosity of the slurry becomes high, which is not preferable.

<Dispersion medium>
Although it does not specifically limit as a dispersion medium or solvent used for the liquid containing solid content, Water and / or an organic solvent can be used. The organic solvent is not particularly limited, but preferably has polarity, and examples thereof include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol and t-butyl alcohol. Furthermore, ketones such as acetone and methyl ethyl ketone (MEK), ethers such as diethyl ether and tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethyl acetamide (DMAc) and the like can be mentioned. The dispersion medium may be used alone or in combination of two or more. In addition to the above water and polar organic solvent, a nonpolar organic solvent may be used as long as the dispersion stability of the solid content is not impaired.

  Even when using an organic solvent, it is preferable to use it in combination with water. Organic solvents used in combination with water include alcohol solvents (methanol, ethanol, propanol, butanol etc.), ketone solvents (acetone, methyl ethyl ketone etc.), ether solvents (diethyl ether, ethylene glycol dimethyl ether, tetrahydrofuran etc.), acetate solvents Polar solvents such as solvents (ethyl acetate etc.) are preferred.

<Introduction of substituent>
If necessary, substituents having electrostatic and / or steric functionality are introduced into the raw material solids. The method for introducing a substituent having electrostatic and / or steric functionality into the fiber is not particularly limited, and a dry or wet fiber raw material is mixed with a compound that reacts with the fiber raw material. It is possible to introduce the said substituent into a fiber raw material by carrying out. A heating method is particularly effective to promote the reaction upon introduction. Although the heat processing temperature in introduction of a substituent is not specifically limited, It is preferable that it is a temperature zone which thermal decomposition, hydrolysis, etc. of this fiber raw material do not occur easily. For example, when a fiber raw material containing cellulose as a fiber raw material is selected, it is preferably 250 ° C. or less from the viewpoint of thermal decomposition temperature, and heat treated at 100 to 170 ° C. from the viewpoint of suppressing hydrolysis of cellulose. preferable.

  It does not specifically limit as a compound which reacts with a fiber raw material. For example, a compound having a group derived from phosphoric acid, a compound having a group derived from carboxylic acid, a compound having a group derived from sulfuric acid, a compound having a group derived from sulfonic acid, a compound having an alkyl group having 10 or more carbon atoms, an amine And the like. Preferred are compounds having at least one selected from the group consisting of a group derived from phosphoric acid, a group derived from carboxylic acid and a group derived from sulfuric acid from the viewpoint of ease of handling and reactivity with fibers. It is more preferable that these compounds form an ester or / and an amide with a fiber, but it is not particularly limited.

Although the introduction amount (by titration method) of the substituent in the substituent-introduced fiber is not particularly limited, 0.005α to 0.11α is preferable per 1 g (mass) of fiber, and 0.01α to 0.08α is more preferable. When the introduction amount of the substituent is less than 0.005α, it is difficult to make the fiber material finer (fibrillation) in the step (b) described later. If the introduced amount of the substituent exceeds 0.11α, the fiber may be dissolved. Here, α is an amount (unit: mmol / g) in which a functional group to which a compound reactive with the fiber material can react, such as a hydroxyl group or an amino group, is contained per 1 g of the fiber material. In addition, the measurement of the introduction amount (titration method) of the substituent on the fiber surface can be carried out by the following method, unless otherwise specified:
A fine fiber-containing slurry containing a solid content of about 0.04 g in bone dry mass is fractionated and diluted to about 50 g with ion exchanged water. While stirring this solution, measure the change of the value of electric conductivity when 0.01 N aqueous sodium hydroxide solution is added dropwise, and the amount of 0.01 N aqueous sodium hydroxide solution dropped when the value becomes minimum. , And the dropping amount at the titration end point. The amount of substituents X on the cellulose surface is represented by X (mmol / g) = 0.01 (mol / l) × V (ml) / W (g). Here, V: a dropping amount (ml) of a 0.01 N aqueous solution of sodium hydroxide, and W: solid content (g) contained in the fine cellulose fiber-containing slurry.

  When the substituent to be introduced is at least one selected from the group consisting of a group derived from phosphoric acid, a group derived from carboxylic acid, and a group derived from sulfuric acid, the amount of introduced substituent is not particularly limited. It can be set to 001 to 5.0 mmol / g. It is good also as 0.005-4.0 mmol / g, and good also as 0.01-2.0 mmol / g.

  When a compound having a group derived from phosphoric acid is used as the compound that reacts with the fiber raw material, it is not particularly limited, but it is composed of phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, polyphosphonic acid or salts or esters thereof It is at least one selected from the group. Among these, compounds having a phosphoric acid group are preferable because they are low in cost, easy to handle, and can further improve the refining (disintegration) efficiency by introducing a phosphoric acid group into the fiber raw material, but are not particularly limited. .

The compound having a phosphoric acid group is not particularly limited, but includes phosphoric acid, lithium dihydrogen phosphate which is a lithium salt of phosphoric acid, dilithium hydrogen phosphate, trilithium phosphate, lithium pyrophosphate and lithium polyphosphate . Furthermore, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate and sodium polyphosphate which are sodium salts of phosphoric acid can be mentioned. Furthermore, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate and potassium polyphosphate which are potassium salts of phosphoric acid can be mentioned. Furthermore, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium polyphosphate and the like which are ammonium salts of phosphoric acid can be mentioned.
Among these, phosphoric acid, a sodium salt of phosphoric acid, a potassium salt of phosphoric acid, and an ammonium salt of phosphoric acid are preferable from the viewpoint of high efficiency of phosphoric acid group introduction and industrially easy application, sodium dihydrogenphosphate And disodium hydrogen phosphate are more preferable, but not particularly limited.

  Moreover, although it is preferable to use a compound as aqueous solution from the uniformity of reaction, and the introduction | transduction efficiency of group derived from phosphoric acid being high, it is not specifically limited. The pH of the aqueous solution of the compound is not particularly limited, but is preferably 7 or less because the efficiency of introducing a phosphoric acid group is high. Although the pH of 3 to 7 is particularly preferable from the viewpoint of suppressing the hydrolysis of fibers, it is not particularly limited.

  When a compound having a group derived from a carboxylic acid is used as a compound which reacts with a fiber material, it is not particularly limited, but a compound having a carboxyl group, an acid anhydride of a compound having a carboxyl group and derivatives thereof It is at least one selected.

  The compound having a carboxyl group is not particularly limited, and examples thereof include 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. .

  The acid anhydride of the compound having a carboxyl group is not particularly limited, but acid anhydrides of dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, itaconic anhydride and the like can be mentioned. Be

  Although it does not specifically limit as a derivative of the compound which has a carboxyl group, The imidate of the acid anhydride of the compound which has a carboxyl group, The derivative of the acid anhydride of the compound which has a carboxyl group is mentioned. Although it does not specifically limit as an imide compound of the acid anhydride of the compound which has a carboxyl group, The imidate of dicarboxylic acid compounds, such as maleimide, a succinimide, phthalimide, is mentioned.

  The acid anhydride derivative of the compound having a carboxyl group is not particularly limited. For example, at least a part of hydrogen atoms of an acid anhydride of a compound having a carboxyl group such as dimethylmaleic anhydride, diethylmaleic anhydride, diphenylmaleic anhydride and the like have a substituent (for example, an alkyl group, a phenyl group, etc. And the like.

  Among compounds having a group derived from a carboxylic acid, maleic anhydride, succinic anhydride and phthalic anhydride are preferable because they are industrially easily applied and gasified easily, but are not particularly limited.

  When a compound having a group derived from sulfuric acid is used as the compound that reacts with the fiber raw material, it is not particularly limited, but it is at least one selected from the group consisting of sulfuric anhydride, sulfuric acid and salts and esters thereof. Among these, sulfuric acid is preferable because it is low in cost and sulfuric acid is introduced into the fiber raw material to further improve the refining (disintegration) efficiency, although not particularly limited.

  By introducing a substituent into the fiber raw material, the dispersibility of the fiber in the solution can be improved, and the disintegration efficiency can be improved.

<Alkali treatment>
If necessary, an alkali treatment may be performed after introducing a substituent having electrostatic and / or steric functionality and before the mechanical treatment step described later. By alkali treatment, cations can be supplied to the phosphate group introduced into the fiber to be easily salted. Moreover, alkali treatment is preferable from the viewpoint of improving the yield of fibers.

  The method of the alkali treatment is not particularly limited. For example, it can be carried out by immersing the phosphate group-introduced cellulose fiber in an alkaline solution.

The alkali compound contained in the alkali solution may be an inorganic alkali compound or an organic alkali compound.
Examples of inorganic alkali compounds are hydroxides, carbonates and phosphates of alkali metals or alkaline earth metals. More specific examples are lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium carbonate, lithium hydrogen carbonate, lithium carbonate, potassium carbonate, potassium hydrogen carbonate, sodium carbonate, sodium hydrogen carbonate, calcium carbonate, lithium phosphate Potassium phosphate, trisodium phosphate, disodium hydrogen phosphate, calcium phosphate and calcium hydrogen phosphate.
Examples of organic alkali compounds are ammonia, aliphatic amines, aromatic amines, aliphatic ammonium, aromatic ammonium, heterocyclic compounds, and their hydroxides, carbonates or phosphates. More specific examples are ammonia, hydrazine, methylamine, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, butylamine, diaminoethane, diaminopropane, diaminobutane, diaminobutane, diaminopentane, diaminohexane, cyclohexylamine, aniline, tetramer Methyl ammonium hydroxide, tetraethyl ammonium hydroxide, tetrapropyl ammonium hydroxide, tetrabutyl ammonium hydroxide, benzyltrimethyl ammonium hydroxide, pyridine, N, N-dimethyl-4-aminopyridine, ammonium carbonate, ammonium hydrogen carbonate, phosphoric acid Hydrogen 2 ammonium.

  The solvent in the alkaline solution is not particularly limited, and water and / or an organic solvent can be used. Those having polarity (polar organic solvents such as water and alcohol) are preferable, and aqueous solvents containing water are more preferable. Particularly preferred examples of the alkaline solution are aqueous sodium hydroxide solution or aqueous potassium hydroxide solution.

  The pH at 25 ° C. of the alkaline solution in which the phosphate group-introduced cellulose is immersed can be set as appropriate, but is preferably 9 or more, more preferably 10 or more, and further preferably 11 or more. preferable. It is because the yield of cellulose fiber becomes higher. In any case, the pH of the alkaline solution at 25 ° C. is preferably 14 or less. When the pH exceeds 14, the handleability of the alkaline solution is reduced.

  The phosphated cellulose fiber may be washed prior to the alkali treatment step to reduce the amount of alkaline solution used. Water and / or organic solvents can be used for washing. In addition, after the alkali treatment, the alkali-treated phosphated cellulose fiber may be washed with water and / or an organic solvent to improve the handleability before mechanical treatment described below.

<Machine processing>
The dispersion of fibers can be produced by further subjecting the fibers in the dispersion medium to a refining (fibrillation) process using a fibrillation treatment apparatus. The defibration treatment apparatus is not particularly limited. For example, high-speed fibrillation machines, grinders (miller mills), high-pressure homogenizers and ultra-high pressure homogenizers, Creamix, high-pressure collision mills, ball mills, bead mills, disc refiners, conical refiners, etc. may be mentioned. In addition, a twin-screw kneader, a vibration mill, a homomixer under high-speed rotation, an ultrasonic dispersion machine, a beater, an apparatus for wet grinding, and the like can be appropriately used.

<Solid concentration>
The solid content concentration of the liquid containing the solid content is not particularly limited, but is preferably 0.1 to 20% by mass, and more preferably 0.5 to 10% by mass. It is preferable that it is 0.1-20 mass% in the case of the refinement | miniaturization (fibrillation) process of the fiber in a dispersion liquid, and it is more preferable that it is 0.5-10 mass%. If the solid content concentration is above the lower limit value, the efficiency of the defibration treatment is improved, and if it is below the above upper limit value, clogging in the defibration treatment apparatus can be prevented.

  The solid content concentration of the fibers in the dispersion (sometimes referred to as slurry) after the micronization (fibrillation) treatment is not particularly limited, but is preferably 0.02 to 10% by mass, and 0.1 to 5 More preferably, it is mass%. If the content of the fine fiber is in the above-mentioned range, the handling and the dispersion stability at the time of coating described later are excellent. When solid content is a fiber, it is 1.5-7.5 mass%, it is preferable that it is 2.0-7.0 mass%, and it is more preferable that it is 2.3-6.0 mass%. Most preferably, it is 2.5-5.0 mass%. Here, the fiber concentration is the concentration of the total amount of fibers. When the fiber concentration is less than the lower limit value, a fiber-containing sheet may not be formed. Even when the fiber-containing sheet can be formed, the thickness becomes nonuniform, and it becomes difficult to obtain a fiber-containing sheet having a necessary thickness. On the other hand, when the fiber concentration exceeds the above upper limit value, the viscosity becomes too high and it becomes difficult to obtain a coated state.

  When the liquid containing solid content contains fine cellulose fibers, the viscosity of the fine cellulose fiber-containing liquid can be 300 to 30,000 mPa · s, preferably 500 to 15,000 mPa · s, and 1,000 to 10,000 mPa · s. More preferable. The viscosity in the present invention is a value measured at 23 ° C. using a B-type viscometer in accordance with JIS K 7117-1. When the viscosity of the fine cellulose fiber-containing liquid is less than the lower limit value, the fine cellulose fiber-containing sheet may not be formed. Even when the fine cellulose fiber-containing sheet can be formed, the thickness becomes nonuniform, and it is difficult to obtain a fine cellulose fiber-containing sheet having a necessary thickness. On the other hand, when the viscosity of the fine cellulose fiber exceeds the above upper limit value, the viscosity becomes too high and it becomes difficult to obtain a coated state. The viscosity can be adjusted by the cellulose fiber concentration, the average fiber width of fine cellulose fibers, the average fiber length of fine cellulose fibers, the amount of anionic groups or cationic groups of fine cellulose fibers, the type of dispersion medium, and the like. For example, the higher the cellulose fiber concentration, the smaller the average fiber width of the fine cellulose fibers, the longer the average fiber length of the fine cellulose fibers, the larger the amount of anionic or cationic groups of the fine cellulose fibers, the viscosity Will be higher.

  The liquid containing fine cellulose fibers may contain a surfactant. When the surfactant is contained in the liquid containing the fine cellulose fiber, the surface tension is lowered, the wettability to the process substrate can be enhanced, and the fine cellulose fiber-containing sheet can be formed more easily. Specifically, the surface tension of the fine cellulose fiber-containing liquid is preferably 25 to 45 mN / m, more preferably 27 to 40 mN / m, and most preferably 30 to 38 mN / m. If the surface tension of the fine cellulose fiber-containing liquid is equal to or more than the lower limit value, it is possible to prevent the drying property of the fine cellulose fiber-containing liquid from being lowered by the surfactant which easily holds water. The wettability of the fine cellulose fiber-containing liquid to the process substrate can be sufficiently improved.

  As surfactant, although nonionic surfactant, anionic surfactant, and cationic surfactant can be used, when cellulose is anionic, nonionic surfactant, anionic surfactant When cellulose is cationic, nonionic surfactant and cationic surfactant are preferable.

<Other ingredients>
The liquid containing solid content can also be prepared by mixing at least one or more of the above-mentioned fine fibers and fibers other than the above-mentioned fine fibers (hereinafter referred to as "additional fibers"). Examples of the additional fibers include, but are not particularly limited to, inorganic fibers, organic fibers, synthetic fibers and the like, semi-synthetic fibers, and regenerated fibers. Examples of inorganic fibers include, but are not limited to, glass fibers, rock fibers, metal fibers and the like. Examples of organic fibers include, but are not limited to, fibers derived from natural products such as cellulose, carbon fibers, pulp, chitin, chitosan and the like. Examples of synthetic fibers include, but are not limited to, nylon, vinylon, vinylidene, polyester, polyolefin (eg, polyethylene, polypropylene etc.), polyurethane, acrylic, polyvinyl chloride, aramid etc. Semi-synthetic fibers include, but are not limited to, acetate, triacetate, promix, and the like. Examples of the regenerated fiber include, but not limited to, rayon, cupra, polynozic rayon, lyocell, tencel and the like. The additional fibers can be subjected to treatments such as chemical treatment and defibration treatment as required. When the additional fiber is treated with chemical treatment or defibration treatment, it may be mixed with the fine fiber and then treated with chemical treatment, defibration treatment or the like, or the additional fiber may be chemically treated with disintegration treatment. It can be mixed with the fine fiber after being subjected to a treatment such as treatment. When the additional fiber is mixed, the addition amount of the additional fiber in the total amount of the fine fiber and the additional fiber is not particularly limited, but is preferably 50% by mass or less, more preferably 40% by mass or less, further preferably 30 It is less than mass%. Particularly preferably, it is at most 20% by mass.

  A hydrophilic polymer may be added to the liquid containing solid content. The hydrophilic polymer is not particularly limited. For example, polyethylene glycol, cellulose derivatives (hydroxyethyl cellulose, carboxyethyl cellulose, carboxymethyl cellulose etc.), casein, dextrin, starch, modified starch etc. may be mentioned. In addition, polyvinyl alcohol and modified polyvinyl alcohol (acetoacetylated polyvinyl alcohol and the like) can be mentioned. Furthermore, polyethylene oxide, polyvinyl pyrrolidone, polyvinyl methyl ether, polyacrylates, polyacrylamide, alkyl acrylate copolymer, urethane copolymer and the like can be mentioned.

  Also, instead of hydrophilic polymers, hydrophilic low molecular weight compounds can also be used. The hydrophilic low molecular weight compound is not particularly limited. For example, glycerin, erythritol, xylitol, sorbitol, galactitol, mannitol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol and the like can be mentioned. The addition amount in the case of adding a hydrophilic polymer or a hydrophilic low molecular weight compound is not particularly limited. For example, the amount is 1 to 200 parts by mass, preferably 1 to 150 parts by mass, more preferably 2 to 120 parts by mass, and still more preferably 3 to 100 parts by mass with respect to 100 parts by mass of the solid content of the fine fiber.

[Irradiation of pulse light to liquid containing solid content]
In the present invention, the pulse light is irradiated to the liquid containing the solid content coated on the substrate.

<Base material>
A well-known thing can be used as a base material. The material of the substrate includes, for example, plastic materials, glass, metals, metal oxides, metal nitrides, wood or composites thereof. Specific examples of preferable materials are soda glass, borosilicate glass, silica glass, quartz glass, etc .; copper plate, silver plate, iron plate, aluminum plate etc .; alumina, sapphire, zirconia, titania, yttrium oxide, indium oxide, ITO (indium tin Oxides), IZO (indium zinc oxide), nesa (tin oxide), ATO (antimony-doped tin oxide), fluorine-doped tin oxide, zinc oxide, AZO (aluminum-doped zinc oxide), gallium-doped zinc oxide, etc. . Although various plastic materials can be used if thermal deformation can be prevented by examining the irradiation conditions, heat resistant materials, specifically, materials having a heat resistant temperature of 100 ° C. or more, are generally used. It can be used preferably. More specifically, polycarbonate, polysulfone, ABS resin, acrylic resin, styrene resin, vinyl chloride, polyester (polyethylene terephthalate), polyacetal, polyetherimide, polyether ketone, cellulose derivative and the like can be mentioned. The base material may be used alone or in combination of two or more. The base material is preferably one having high wettability to a liquid containing solid content, from the viewpoint that shrinkage of the sheet can be suppressed during drying, but the formed sheet can be easily peeled off It is preferable to select

  The substrate is preferably in the form of a plate from the viewpoint of easily maintaining the state in which the liquid containing the solid content is applied and capable of uniformly irradiating the pulsed light, but is not particularly limited. For example, it may be cylindrical.

  Examples of particularly preferred substrates are any selected from the group consisting of glass plates, polycarbonate plates, copper plates, silver plates and combinations thereof.

  The substrate can also be a multilayer structure. One of the preferred embodiments is an upper layer composed of a transparent substrate that transmits pulse light and a lower layer composed of a colored substrate that absorbs and / or reflects pulse light. Examples of transparent substrates that transmit pulsed light are glass plates and plastic plates. The example of the colored base material which absorbs and / or reflects pulsed light is a metal plate, and a copper plate and a silver plate can be mentioned as a more specific example. A particularly preferable example is one having a two-layer structure in which the upper layer is a glass plate and the lower layer is a copper plate or a silver plate. The transparent substrate means a substrate having a total light transmittance of 85% or more.

<Coating>
The liquid containing the solid content is coated on the substrate, refers to a state in which the liquid containing the solid content is thinly spread on the substrate, and the method therefor is not particularly limited. The substrate may be immersed in a liquid containing solid content, or the liquid containing solid content may be applied to the substrate or sprayed. Known methods and apparatus for coating can be suitably used. Specifically, for example, a film applicator, a double roll coater, a slit coater, an air knife coater, a wire bar coater, a blade coater, a doctor coater, a squeeze coater, a reverse roll coater, a transfer roll coater, an extrusion coater, a curtain coater, a dip coater , Die coater, gravure roll, slide hopper, coating method by spray coating, screen printing method, dip coating method, spin coating method, inkjet method and the like. It is preferable to control the thickness of the liquid containing solid content.

  Although the application amount of the liquid containing the solid content on the substrate can be appropriately adjusted according to the thickness of the target sheet, concentration and / or drying by pulse light irradiation can be effectively performed. The coating thickness is preferably 0.0005 to 5 mm, more preferably 0.005 to 4 mm, and still more preferably 0.05 to 3 mm. Such a coating thickness is particularly suitable for obtaining a sheet of 1 to 100 μm using a liquid containing 0.5 to 5.0% by mass of solid content. By laminating the sheets, thicker sheets can be obtained.

  In the case of coating, it is preferable to stir the liquid containing solid content from several minutes before the start of coating to the start of coating. The liquid containing the solid content tends to be nonuniform when left to stand, but if the stirring step is included, the liquid containing the solid content immediately before coating can be made uniform. Therefore, uniform sheets can be more easily obtained. As a specific example of a stirring process, the method of stirring the liquid containing solid content by a suitable means is mentioned in the tank which stores the liquid containing solid content before coating.

  Although a coating temperature is not specifically limited, It is preferable that it is 20-45 degreeC, It is more preferable that it is 25-40 degreeC, It is more preferable that it is 27-35 degreeC. If the coating temperature is at least the lower limit value, the liquid containing the solid content can be easily applied, and if it is at the upper limit value or less, volatilization of the dispersion medium during coating can be suppressed.

<Irradiation conditions>
The liquid containing the solid content coated as described above is subjected to pulsed light irradiation under appropriate conditions, concentrated and / or dried to obtain a sheet.

The light source used in the pulsed light irradiation is not particularly limited, and examples thereof include a mercury lamp, a metal halide lamp, a xenon (Xe) lamp, a chemical lamp, and a carbon arc lamp. Examples of radiation include electron beams, X-rays, ion beams, and far-infrared rays. In addition, g-ray, i-ray, Deep-UV light, high density energy beam (laser beam) are also used.
Specific examples thereof include scanning exposure with an infrared laser, high-intensity flash exposure such as a xenon (Xe) discharge lamp, and infrared lamp exposure. More preferably, pulsed light irradiation is performed by a flash lamp (in particular, a Xe flash lamp).

  The pulse width of the pulsed light, that is, the time of one irradiation, can be set variously, although it depends on other conditions. The pulse width can be, for example, 0.5 μsec to 1 sec, preferably 5 μsec to 50 msec, and more preferably 50 μsec to 5 msec. If it is shorter than 0.5 μs, concentration and / or drying may not proceed, and if it is longer than 1 second, thermal degradation of the substrate, blistering due to boiling of the dispersion medium, coloration due to heat of solid content may occur. I am concerned.

The irradiation energy of the pulsed light is preferably 1 mJ / cm ^{2 to} 100 J / cm ² , and 10 mJ / cm ² from the viewpoint of efficiently performing concentration and / or drying of the liquid containing solid content. more preferably to 50 J / cm ^2, further preferably ^{100mJ / cm 2 ~10J / cm 2} .

  The irradiation of pulsed light can be performed repeatedly. In the case of repeated implementation, there is a time zone in which light is not irradiated between a certain light irradiation time and the next light irradiation time. In the case of repetitive implementation, the number of iterations and the frequency can be set as appropriate. The number of repetitions can be, for example, 1 to 1000 times. It is preferable to set it as 2-500 times, and it is more preferable to set it as 3-250 times. The repetition frequency can be, for example, 1 to 100 Hz. The frequency is preferably 2 to 50 Hz, and more preferably 3 to 25 Hz. If the number of repetitions is too large, there is concern that the substrate may be thermally deteriorated, blistering due to boiling of the dispersion medium, or coloring due to heat of solid content. There are also similar concerns if the frequency is too low.

  In the case of irradiation, a plurality of cycles may be performed with one irradiation or a predetermined number of repeated irradiations as one cycle. In one cycle, irradiation of the same irradiation energy (or light quantity) may be repeated, or irradiation of different irradiation energy (or light quantity) may be performed. From the viewpoint of simplifying condition setting and operation, it is preferable to repeat irradiation of the same irradiation energy (or light quantity) in one cycle.

  The number of cycles is not particularly limited, and may be performed until the liquid containing solids to a desired degree is concentrated and / or dried. The number of cycles can be, for example, 1 to 50 times, preferably 2 to 30 times, and more preferably 3 to 15 times.

  An irradiation stop time may be provided between one cycle and the subsequent cycle. Thereby, the light irradiation device can be cooled. The irradiation stop time is not particularly limited, but may be, for example, 1 to 100 seconds, preferably 2 to 50 seconds, and more preferably 3 to 25 seconds. Providing the irradiation stop time is also preferable from the viewpoint of thermal deterioration of the substrate, generation of blisters due to boiling of the dispersion medium, and prevention of coloring due to heat of solid content.

  In addition, the irradiation in the second and subsequent cycles is performed with an irradiation dose that is less than 100% of the irradiation dose in the previous cycle, such that the irradiation in the second cycle is performed with the irradiation dose smaller than the irradiation dose in the first cycle. You may implement. As a result, blistering due to boiling of the dispersion medium and coloring due to heat of solid content can be effectively prevented. The irradiation amount in the immediately preceding cycle refers to the irradiation energy (or one light amount) of pulsed light in the immediately preceding cycle. Specifically, the energy of irradiation in the second and subsequent cycles can be, for example, 95% or less of the irradiation energy in the immediately preceding cycle, preferably 90% or less, and more preferably 85% or less Preferably, 80% or less is more preferable. When the cycle is performed three or more times, the degree to which the amount is smaller than the previous cycle may be changed. For example, the irradiation in the second cycle may be performed with energy less than 85% of the irradiation in the first cycle, and the irradiation in the third cycle may be performed with energy less than 80% of the irradiation in the second cycle it can.

A particularly preferred example of irradiation is the following set:
Cycle 1) pulse width 300 to 600 μsec, irradiation energy 570 to 1150 mJ / cm ² , repetition frequency 40 to 80 times, repetition frequency 3 to 7 Hz;
Cycle 2) 5 to 20 seconds after the end of cycle 1, after setting the irradiation stop time, pulse width 300 to 600 μsec, 80% irradiation energy of cycle 1, repetition frequency 40 to 80 times, repetition frequency 3 to 7 Hz;
Cycle 3) 5 to 20 seconds after the end of cycle 2, after setting the irradiation stop time, pulse width 300 to 600 μsec, 78 to 79% of irradiation energy of cycle 2, repetition frequency 40 to 80, repetition frequency 3 to 3 7 Hz;
Cycle 4) 5 to 20 seconds after the end of cycle 3, after setting the irradiation stop time, pulse energy of 300 to 600 μsec, 76 to 77% of irradiation energy of cycle 3, repetition frequency 40 to 80, repetition frequency 3 to 3 7 Hz;
Cycle 5) 5 to 20 seconds after the end of cycle 4, after setting the irradiation stop time, pulse width 300 to 600 μsec, 70 to 76% of irradiation energy of cycle 4, concentration and / or drying to the desired extent (For example, repetition frequency 100 to 140 times), repetition frequency 3 to 7 Hz.

  The atmosphere in which the light irradiation is performed is not particularly limited, and examples thereof include an air atmosphere, an inert atmosphere, and a reducing atmosphere. Note that the inert atmosphere is an atmosphere filled with an inert gas such as argon, helium, neon, or nitrogen, and the reducing atmosphere is a reduction of hydrogen, carbon monoxide, formic acid, alcohol, etc. It refers to the atmosphere where the sex gas is present.

  The relatively high energy pulsed light irradiation can heat the liquid containing the coated solid content in a very short time in a concentrated manner. Therefore, the time for drying can be shortened compared to when drying is performed by the existing drying method. Further, as an advantage of using pulsed light, it can be mentioned that the appearance of the obtained sheet is good. In other drying methods, wrinkles and cracks may occur due to shrinkage during drying, but irradiation of pulsed light under appropriate conditions can keep the appearance of the sheet good.

  Furthermore, when obtaining a transparent fine cellulose containing sheet, it is known that the haze tends to be reduced by using pulsed light. Therefore, when preparing the transparent fine cellulose fiber-containing sheet, the transparency of the sheet can be maintained while shortening the time for drying.

  When it is intended to prepare a sheet using a fiber into which a substituent having electrostatic and / or steric functionality is introduced as a fiber material, the fiber is compared to the case where no substituent is introduced. Concentration and / or drying of the contained solution may be more difficult. However, by using pulsed light, even in such a case, the time for drying can be shortened compared to when drying is performed by the existing drying method.

  The end point of concentration and / or drying can be appropriately determined based on, for example, the state by visual observation, the sheet weight, the change rate of the sheet weight, and the like.

<Use of filler>
The liquid containing solid content may contain a filler. The use of fillers may allow for more efficient concentration and / or drying. An example where the use of a filler is effective is when a plastic material is used as the substrate.

  The filler is not particularly limited as long as it is made of a material capable of absorbing and / or reflecting the pulsed light to be irradiated. It may be organic or inorganic. It is preferable to use one selected from the group consisting of carbon, metals and metal oxides. More specifically, metal fillers such as silver powder, gold powder, copper powder and nickel powder, alumina, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, magnesium oxide, calcium oxide, magnesium oxide, Inorganic fillers such as aluminum oxide, aluminum nitride, crystalline silica, amorphous silica, boron nitride, titania, glass, iron oxide and ceramic, and organic fillers such as carbon and rubber fillers, glass, inorganic minerals, etc. It can be used without particular limitation regardless of the type and shape.

  The filler can be used properly depending on the desired function. For example, the metal filler imparts electrical conductivity, thermal conductivity and thixotropy to the resin composition, and the nonmetallic inorganic filler imparts thermal conductivity, low thermal expansion and low hygroscopicity to the resin layer. In addition, the organic filler imparts toughness and the like to the resin layer.

  These metal fillers, inorganic fillers or organic fillers can be used alone or in combination of two or more. Among them, metal fillers, inorganic fillers or insulating fillers are preferable. The conductivity, the thermal conductivity, the low moisture absorption property and the insulation required for the adhesive material for a semiconductor device are imparted. Further, among the inorganic fillers or the insulating fillers, silica fillers are more preferable. It has good dispersibility in resin varnish and can impart high adhesion when heated.

  The average particle size of the filler (refer to the cumulative 50% particle size unless otherwise specified. The same shall apply hereinafter) is not particularly limited, but those having a particle size of 100 μm or less can be used. More preferably, the average particle size is 50 μm or less. The lower limit of the average particle size is not particularly limited, but is preferably 0.001 μm or more from the viewpoint of handleability.

  The amount of filler added is determined according to the characteristics or function to be imparted. 0.1 mass part-200 mass% of a filler are preferable with respect to 100 mass parts of fibers, and 1 mass%-100 mass% are more preferable. By increasing the amount of filler, the intended function can be effectively improved.

  The timing of the addition to the liquid containing the solid content of the filler and the method of mixing may be appropriate. For the mixing, a disperser such as a common stirrer, a grinder, a triple roll, and a ball mill can be appropriately used.

[Other steps]
The method for producing a sheet of the present invention may include other steps other than the above.

<Desorption process>
The method for producing a sheet of the present invention may include the step of removing all or part of the introduced substituents after sheeting the fibers.

An alcohol can be used when removing a substituent. It is preferable to use a polyhydric alcohol from the viewpoint of high ability to separate. Polyhydric alcohol refers to alcohol having two or more OH groups. When a polyhydric alcohol is used, it is preferable to use one having an OH / C ratio of 0.15 or more. More preferably, it is 0.2 or more. The “OH / C ratio” refers to the number of OH groups per carbon (C) atom contained in the molecule, for example, the OH / C ratio of ethylene glycol (C ₂ H ₆ O ₂ ) is 1, and diethylene glycol The OH / C ratio of (C ₄ H ₁₀ O ₃ ) is 0.67.

  Examples of polyhydric alcohols having an OH / C ratio of 0.2 or more include ethylene glycol, diethylene glycol, propylene glycol (1,2-propanediol), glycerin (glycerol, 1,2,3-propanetriol) It is. Other examples are pentanediol, octanediol, decanediol, sugar alcohols (eg sorbitol, lactitol, maltitol, mannitol, xylitol).

  Although the usage-amount of alcohol is not specifically limited as long as detachment | desorption of a substituent can fully be performed, it can be suitably determined based on sheet weight. Also when using any alcohol, 1-100 mass parts of alcohol can be used with respect to 1 mass part of sheets, for example. If the amount of alcohol used is less than 1 part by mass with respect to 1 part by mass of the sheet, desorption may not be sufficiently performed.

  The temperature for the desorption step is not particularly limited as long as the substituent can be sufficiently eliminated, but may be 140 ° C. or higher, preferably 160 ° C. or higher, and more preferably 170 ° C. or higher. However, it is preferable to select a temperature at which the decomposition of the fiber raw material is suppressed, and is not particularly limited. For example, when cellulose is used as the fiber raw material, it is 250 ° C. or less, more preferably 200 ° C. or less. In addition, at the time of heating, additives such as an acid or a base may be added as appropriate.

  The time for the removal step is not particularly limited as long as the removal of the substituent can be sufficiently performed. For example, when using glycerin which is a polyhydric alcohol having an OH / C ratio of 1 as the alcohol and carried out at 180 ° C., it can be 10 to 120 minutes, preferably 15 to 90 minutes, and more preferably 15 to 60 minutes. preferable. The same can be said for other alcohols.

  The elimination step can be carried out until the introduced substituent is eliminated to the desired degree. The amount of the substituent after elimination is not particularly limited, and is, for example, 70% or less, preferably 50% or less, more preferably 30% or less at the time of introduction. Alternatively, the desorption step can be carried out until the amount of introduction of substituents of the sheet after desorption is 0.7 mmol / g or less. It is preferable to carry out until it becomes 0.5 mmol or less, It is more preferable to carry out until it becomes 0.1 mmol / g or less, and it is more preferable to carry out until it becomes 0.047 mmol / g. The smaller the content of substituents, the more the yellowing and the like can be suppressed when the sheet is heated. In the present invention, when a sheet is referred to as a substituent introduction amount, it refers to a value measured by X-ray fluorescence analysis unless otherwise specified. In the measurement, if necessary, a sheet with a known amount of introduced substituent can be prepared, and the characteristic X-ray intensity of an appropriate atom can be plotted against the amount of introduced substituent to prepare and use a calibration curve. .

<Neutralization degree change process>
In one embodiment of the present invention, a phosphate group is introduced as a substituent having electrostatic and / or steric functionality to the fiber material. In this case, it may have a step of changing the degree of neutralization of the substituent-introduced fiber before making the slurry after the mechanical treatment into a state of being applied to the substrate. When the phosphate group is introduced into the fiber, the degree of neutralization is usually 2 (also referred to as the degree of neutralization 100%).

For example, when a phosphoric acid group is introduced into a cellulose fiber using sodium salt of phosphoric acid and alkali treatment is performed with sodium hydroxide, the state of neutralization degree 2 (100% neutralization degree) after introduction is cellulose -O-P (= O) ( - O - Na +) (- O - Na +) is represented as. In the case of performing substituent removal using an alcohol in step (d), it is preferable that the electron pair on the hydroxyl group possessed by the alcohol be susceptible to nucleophilic attack on the phosphorus of the phosphate group. When the degree of neutralization is 2 (100% degree of neutralization), the phosphate group has a strong negative charge and is less susceptible to nucleophilic attack. The cellulose -O-P (= O) ( - O - H +) in the state of (- ^- O H ⁺⁾ and the degree of neutralization represented 0 (neutralization degree of 0%), hydrogen between phosphate groups Bonding becomes strong, making it difficult to attack nucleophiles. Therefore, by changing the degree of neutralization, the influence of the negative charge amount of the phosphate group and the hydrogen bond between the phosphate groups can be reduced, and the desorption efficiency of the substituent is improved. In this specification, the case where cellulose fiber is used as an example of fiber may be described as an example, but those skilled in the art can apply the description to the case where other types of fiber are used. I can understand.

Although the means to change the degree of neutralization is not particularly limited, for example, ion exchange treatment may be carried out by using fine fibers having a degree of neutralization of 2 (100% degree of neutralization) as a suspension. The ion exchange treatment is also preferable from the viewpoint that a desired effect is sufficiently obtained and the operation is simple. In the ion exchange treatment, a cation exchange resin is used. In addition, H ⁺ ion is usually used as a counter ion. By treating with an appropriate amount of cation exchange resin for a sufficient time, fine fibers with a degree of neutralization of 0 (degree of neutralization 0%) can be obtained. Mixing the obtained fine fibers of degree of neutralization 0 (degree of neutralization 0%) with fine fibers of degree of neutralization 2 (degree of neutralization 100%) without changing the degree of neutralization at an appropriate ratio Thus, fine fibers with various degrees of neutralization between 0 (degree of neutralization 0%) and 2 (degree of neutralization 100%) can be obtained.

  In the ion exchange treatment, either a strongly acidic ion exchange resin or a weakly acidic ion exchange resin can be used, but it is preferable to use a strongly acidic one. Specifically, a styrene resin or an acrylic resin into which a sulfonic acid group or a carboxy group is introduced can be used. The shape of the ion exchange resin is not particularly limited, and various materials such as fine particles (granular particles), membranes, fibers, liquids, etc. can be used, but from the viewpoint of efficiently treating the fine fiber suspension. Is preferably granular. As a specific example, commercially available Amberjet 1020, 1024, 1060, 1220 (Organo Co., Ltd.) may be mentioned. Other examples include Amberlite IR-200C, IR-120B (above, Tokyo Organic Chemical Co., Ltd.), Levatit SP 112, S100 (manufactured by Bayer), GEL CK 08 P (Mitsubishi Chemical), Dowex 50W- X8 (Dow Chemical) and the like.

 Specifically, in the ion exchange treatment, a particulate ion exchange resin and a fiber suspension (slurry) were mixed, and the ion exchange resin was brought into contact with the fine fibers for a certain time while stirring and shaking as necessary. Then, by separating the ion exchange resin and the slurry.

  When treating with an ion exchange resin, the concentration of the solid content of the slurry and the ratio to the ion exchange resin are not particularly limited, and can be appropriately designed by those skilled in the art from the viewpoint of efficiently performing ion exchange. The concentration may be such that processing for forming a sheet is easy in the subsequent steps. Specifically, the concentration of the slurry is preferably 0.05 to 5% by mass. When the concentration is too low, processing takes time, and conversely, when the concentration is too high, a sufficient ion exchange effect can not be obtained, which is not preferable. When a slurry having such a concentration range is used, for example, a strongly acidic ion exchange resin having an apparent density of 800 to 830 g / L-R, a water holding capacity of 36 to 55%, and a total exchange capacity of 1.8 eq / L-R is used. . At this time, 1/50 to 1/5 ion exchange resin can be used with respect to the slurry volume 1. The treatment time is also not particularly limited, and can be appropriately designed by those skilled in the art from the viewpoint of efficiently performing ion exchange. For example, it can process for 0.25 to 4 hours.

  Step (e) can be carried out until the degree of neutralization is altered to the desired degree. Also, as described above, the degree of neutralization is adjusted by mixing fibers of degree of neutralization 2 (degree of neutralization 100%) with fibers of degree of neutralization 0 (degree of neutralization 0%) at an appropriate ratio. May be In any case, the degree of neutralization can be 0 (degree of neutralization 0%) to 2 (degree of neutralization 100%), 0.3 (degree of neutralization 15%) to 2 (neutralization) The degree is preferably 100%, and more preferably 0.3 (degree of neutralization 15%) to 1.7 (degree of neutralization 85%).

<Others>
In the present invention, if necessary, a washing step, a foreign matter removing step, a purification step by centrifugation etc., and a desalting step may be adopted, but it is not particularly limited. The desalting step is preferred in that the purity of the fiber is increased. When the desalting step is performed, the means is not particularly limited, and washing by filtration method, dialysis, ion exchange and the like can be mentioned.

[Characteristics of Sheet Obtained by the Manufacturing Method of the Present Invention]
<Appearance>
The production method of the present invention is capable of concentrating and / or drying a solution containing solid content in a short time by using pulsed light, but has the advantage that the appearance of the obtained sheet is excellent. There is also. The evaluation of the appearance can be based on whether or not cracking is observed, since cracking is not practical in various applications if the sheet is susceptible to cracking. The appearance can be judged visually.

  When fine cellulose fibers are used as a raw material, the resulting sheet can have desirable characteristics as an optical material even in terms of total light transmittance and haze value. The measuring method and preferable range of these characteristics are demonstrated below.

<Total ray transmittance>
In the present invention, the term "total light transmittance (%)" refers to a value measured by C light using a haze meter in accordance with JIS K7105 unless otherwise specified.

  The total light transmittance of the sheet produced according to the present invention can be 80% or more. In a preferred embodiment, it can be 82% or more, and in a more preferred embodiment, it can be 90% or more.

<Haze>
In the present invention, the term “haze value” refers to a value measured by C light using a haze meter in accordance with JIS K7136 unless otherwise specified. Haze is an index relating to the transparency of a sheet and represents turbidity (cloudiness). It is determined from the ratio of diffuse transmission light to total light transmission light, and can also be affected by the surface roughness.

  The haze value of the sheet produced according to the present invention can be 2 or less. In a preferred embodiment, it may be 1.2 or less, and in a more preferred embodiment, it may be 1.0 or less.

<Others>
In the production method of the present invention, the sheet obtained by carrying out introduction of a substituent, elimination step, change of degree of neutralization, lamination of organic and / or inorganic material, etc. has yellowness and linear thermal expansion coefficient And excellent water vapor permeability etc. can be achieved. In addition, a sheet excellent in surface roughness, surface hardness, bending test (mandrel method) and the like can be obtained. Methods of evaluating these properties are well known to those skilled in the art.

[Use of sheet]
Examples of applications of the sheet obtained by the production method of the present invention include a display element, a lighting element, a solar cell or window material, or a panel or substrate for these. More specifically, if the sheet obtained is transparent, it is suitable for use as a flexible display, a touch panel, a liquid crystal display, a plasma display, an organic EL display, a field emission display, a display such as a rear projection television, or an LED element There is. Moreover, it is suitable for using as a solar cell substrate, such as a silicon system solar cell, a dye-sensitized solar cell. Furthermore, they are suitable for use as window materials for automobiles, railway vehicles, aircraft, houses, office buildings, factories and the like. What is not transparent can be used as a structural material. In particular, suitable as glazing, interior materials, outer plates, bumpers, automobiles, railway vehicles, aircraft materials, PC cases, home appliance parts, packaging materials, construction materials, civil engineering materials, marine materials, other industrial materials, etc. It can be used for Examples of products using sheets include computers using the above-described display elements or displays, tablet terminals, mobile phones; light bulbs using lighting elements, lighting (light fixtures and lighting devices), induction lights, for liquid crystal panels Backlights, flashlights, bicycle headlights, car interior lights and meter lamps, traffic lights, height lighting inside and outside buildings, home lighting, school lighting, medical lighting, factory lighting, plant cultivation lights, Lighting for image lighting, lighting in 24-hour or late-night stores such as convenience stores, lighting in a refrigerator / freezer; homes, buildings, automobiles, railway cars, aircraft, home appliances, etc. using window materials and structural materials I can mention the one.

  EXAMPLES The present invention will be more specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1
<Preparation of phosphate group introduced cellulose fiber>
A solid solution consisting of urea, sodium phosphate (molar ratio of phosphorus atom to sodium atom Na / P = 1.45), and water is impregnated with 1000 g of unripened softwood kraft pulp (manufactured by Oji Holdings Co., Ltd.) at bone-dry mass, It squeezed and squeezed out excess chemical | medical solution, and obtained the chemical | medical solution impregnation pulp. The chemical solution-impregnated pulp contained 1000 g of pulp, 950 g of urea, 400 g of sodium phosphate as phosphorus atom, and 1200 g of water as bone dry mass. The chemical-impregnated pulp was dried and heated in an oven heated to 150 ° C. to introduce phosphoric acid groups into the pulp. The substituent introduction amount was 0.74 mmol / g (by titration). After pouring 25 L of ion-exchanged water into the drug solution impregnated pulp which has been subjected to the drying and heating steps, stirring and uniformly dispersing, the step of dewatering by filtration and obtaining a dewatered sheet was repeated twice. Next, the obtained dewatered sheet was diluted with 25 L of ion exchanged water, and 1N aqueous sodium hydroxide solution was added little by little while stirring to obtain a pulp slurry having a pH of 11 to 13. Thereafter, the pulp slurry is dewatered to obtain a dewatered sheet, and then 25 L of ion-exchanged water is poured again, and after stirring and uniformly dispersing, the step of dewatering by filtration and obtaining the dewatered sheet is repeated twice. A phosphate-modified cellulose fiber was obtained.

<Machine processing>
Ion-exchanged water was added to the pulp obtained after washing and dewatering to make a 1.0 mass% pulp suspension. This pulp suspension was passed 5 times at an operating pressure of 120 MPa with a high pressure homogenizer ("Panda Plus 2000" manufactured by NiroSoavi). Furthermore, a cellulose fiber dispersion was obtained by passing 5 times at a pressure of 245 MPa with a wet atomization device ("Altimizer" manufactured by Sugino Machine Co., Ltd.). The average fiber width of the cellulose fibers in the cellulose fiber dispersion was 4.2 nm.

<Coating of cellulose fiber dispersion to coated substrate>
The cellulose fiber dispersion was coated on a silver plate (size 100 mm × 100 mm, thickness 1 mm) using a film applicator (“Baker film applicator” manufactured by TQC Corporation). The application width of the film applicator was 60 mm, and the gap (application thickness) was 2 mm. In addition, the 5 cm square marked line was previously entered in the silver plate, and coating was performed so that the whole inside of a marked line might be coat | covered with a cellulose fiber dispersion.

<Drying of cellulose fiber dispersion by light irradiation>
The silver plate coated with the cellulose fiber dispersion was allowed to stand within the effective irradiation range of a pulse light irradiation apparatus ("Pulse Forge 3300" manufactured by Novacentric, light source: xenon lamp). The processing conditions of the pulsed light irradiation apparatus were set to the following light irradiation A to light irradiation E, and light irradiation was performed.
Light irradiation A) Light irradiation was performed by setting pulse width 450 μsec, setting voltage 280 V, irradiation energy 860 mJ / cm ² , repetition frequency 60 times, repetition frequency 5 Hz. The irradiation time of the light irradiation A was 12 seconds, and the integrated light amount was 51.6 J / cm ² .
Light irradiation B) A light irradiation stop time for cooling the light sintering apparatus is set for 10 seconds from the end of light irradiation A, pulse width 450 μs, setting voltage 260 V, irradiation energy 688 mJ / cm ² , repetition number 60 times, repetition repeatedly The light was set at a frequency of 5 Hz. The irradiation time of the light irradiation B was 12 seconds, and the integrated light amount was 41.3 J / cm ² .
Light irradiation C) 10 seconds after the completion of light irradiation B, after setting the irradiation stop time for cooling the light sintering apparatus, pulse width 450 μs, setting voltage 240 V, irradiation energy 542 mJ / cm ² , repetition number 60 times, repetition repeatedly The light was set at a frequency of 5 Hz. The irradiation time of the light irradiation C was F12579MK12 seconds, and the integrated light amount was 32.5 J / cm ² .
Light irradiation D) 10 seconds after the completion of light irradiation C After setting the irradiation stop time for cooling the light sintering apparatus, pulse width 450 μs, setting voltage 220 V, irradiation energy 419 mJ / cm ² , repetition frequency 60 times, repetition repeatedly The light was set at a frequency of 5 Hz. The irradiation time of the light irradiation D was 12 seconds, and the integrated light amount was 25.1 J / cm ² .

Light irradiation E) 10 seconds after the completion of light irradiation D, after setting the irradiation stop time for cooling the light sintering apparatus, pulse width 450 μs, setting voltage 200 V, irradiation energy 317 mJ / cm ² , repetition frequency 120 times, repetition repeatedly The light was set at a frequency of 10 Hz. The irradiation time of the light irradiation E was 12 seconds, and the integrated light amount was 38.4 J / cm ² .
The light irradiation E was repeated until the drying completion of the cellulose fiber dispersion liquid coated on the silver plate, and the cellulose fiber containing sheet was obtained. The point in time when the moisture of the cellulose fiber dispersion coated in the marked line was completely volatilized visually was regarded as the end of drying. As in the case of the light irradiation A to D, in the repeated process of the light irradiation E, the irradiation stop time for cooling of the light sintering apparatus is set to 10 seconds between the irradiation completion and the next irradiation. The cellulose fiber-containing sheet was separated from the silver plate and used for evaluation of sheet properties. The thickness of the obtained cellulose fiber-containing sheet was 13 μm.

Example 2
In Example 1, the coated substrate was a copper plate (size 100 mm × 100 mm, thickness 1 mm) when the cellulose fiber dispersion was applied to the coated substrate. A cellulose fiber-containing sheet was obtained in the same manner as in Example 1 except the above. The copper plate was immersed in a 10% aqueous hydrochloric acid solution for 2 minutes to remove the oxide film on the surface, washed with ion exchanged water, and used for coating of a cellulose fiber dispersion. The thickness of the obtained cellulose fiber-containing sheet was 13 μm.

[Example 3]
In Example 1, the coated substrate was a glass plate (size 100 mm × 100 mm, thickness 1 mm) when the cellulose fiber dispersion was applied to the coated substrate. A cellulose fiber-containing sheet was obtained in the same manner as in Example 1 except the above. The glass plate is coated with a silane compound ("KBM-3103" manufactured by Shin-Etsu Chemical Co., Ltd.) and heated with a hot plate set at a temperature of 50 ° C for 15 minutes to give a water-repellent treatment and then cellulose fiber dispersion. The solution was used for coating. The thickness of the obtained cellulose fiber-containing sheet was 13 μm.

Example 4
In Example 1, the coated substrate was a polycarbonate plate (size 100 mm × 100 mm, thickness 3 mm) when the cellulose fiber dispersion was applied to the coated substrate. A cellulose fiber-containing sheet was obtained in the same manner as in Example 1 except the above. The thickness of the obtained cellulose fiber-containing sheet was 13 μm.

[Example 5]
In Example 3, at the time of drying of the cellulose fiber dispersion by light irradiation, a copper plate (dimension 100 mm × 100 mm, thickness 1 mm) was placed under the glass plate coated with the cellulose fiber dispersion, and light irradiation was performed. A cellulose fiber-containing sheet was obtained in the same manner as in Example 3 except the above. The thickness of the obtained cellulose fiber-containing sheet was 13 μm.

[Example 6]
In Example 4, at the time of drying of the cellulose fiber dispersion by light irradiation, a copper plate (dimension 100 mm × 100 mm, thickness 1 mm) was placed under the polycarbonate plate coated with the cellulose fiber dispersion, and light irradiation was performed. A cellulose fiber-containing sheet was obtained in the same manner as in Example 4 except the above. The thickness of the obtained cellulose fiber-containing sheet was 13 μm.

[Example 7]
In Example 2, when the cellulose fiber dispersion was dried by light irradiation, a copper plate (dimension 100 mm × 100 mm, thickness 1 mm) was placed under the copper plate coated with the cellulose fiber dispersion, and light irradiation was performed. A cellulose fiber-containing sheet was obtained in the same manner as in Example 2 except the above. The thickness of the obtained cellulose fiber-containing sheet was 13 μm.

[Example 8]
In Example 3, at the time of drying of the cellulose fiber dispersion by light irradiation, a glass plate (dimension 100 mm × 100 mm, thickness 1 mm) was placed under the glass plate coated with the cellulose fiber dispersion, and light irradiation was performed. . A cellulose fiber-containing sheet was obtained in the same manner as in Example 3 except the above. The thickness of the obtained cellulose fiber-containing sheet was 13 μm.

[Example 9]
In Example 4, 1 part by mass copper powder (Kanto Chemical Co., Ltd., particle size 45 μm or less) is added to the cellulose fiber dispersion with respect to 100 parts by mass of solid content in the cellulose fiber dispersion, and then added to a polycarbonate plate The coating was done. A cellulose fiber-containing sheet was obtained in the same manner as in Example 4 except the above. The thickness of the obtained cellulose fiber-containing sheet was 14 μm.

[Example 10]
In Example 9, the addition amount of the copper powder was 10 parts by mass with respect to 100 parts by mass of the solid content in the cellulose fiber dispersion. A cellulose fiber-containing sheet was obtained in the same manner as in Example 9 except for the above. The thickness of the obtained cellulose fiber-containing sheet was 17 μm.

[Example 11]
In Example 9, the addition amount of copper powder was 100 parts by mass with respect to 100 parts by mass of the solid content in the cellulose fiber dispersion. A cellulose fiber-containing sheet was obtained in the same manner as in Example 9 except for the above. The thickness of the obtained cellulose fiber-containing sheet was 25 μm.

[Example 12]
In Example 11, particles to be added were silver powder (manufactured by Kanto Chemical Co., Ltd., particle size 45 μm or less). A cellulose fiber-containing sheet was obtained in the same manner as in Example 11 except for the above. The thickness of the obtained cellulose fiber-containing sheet was 25 μm.

Comparative Example 1
The silver plate coated with the cellulose fiber dispersion in the same manner as in Example 1 was allowed to stand in a blowing oven set at a temperature of 100 ° C. Then, it hold | maintains until the completion | finish of drying of the cellulose fiber dispersion liquid coated on the silver plate, and obtained the cellulose fiber containing sheet. The point in time when the moisture of the cellulose fiber dispersion coated in the marked line was completely volatilized visually was regarded as the end of drying. The cellulose fiber-containing sheet was separated from the silver plate and used for evaluation of sheet properties. The thickness of the obtained cellulose fiber-containing sheet was 13 μm.

Comparative Example 2
In Comparative Example 1, the coated substrate was a copper plate (size 100 mm × 100 mm, thickness 1 mm) when the cellulose fiber dispersion was applied to the coated substrate. The copper plate was immersed in a 10% aqueous hydrochloric acid solution for 2 minutes to remove the oxide film on the surface, washed with ion exchanged water, and used for coating of a cellulose fiber dispersion. A cellulose fiber-containing sheet was obtained in the same manner as in Comparative Example 1 except the above. The thickness of the obtained cellulose fiber-containing sheet was 13 μm.

Comparative Example 3
In Comparative Example 1, the coated substrate was a glass plate (size 100 mm × 100 mm, thickness 1 mm) when the cellulose fiber dispersion was applied to the coated substrate. The glass plate is coated with a silane compound ("KBM-3103" manufactured by Shin-Etsu Chemical Co., Ltd.) and heated with a hot plate set at a temperature of 50 ° C for 15 minutes to give a water-repellent treatment and then cellulose fiber dispersion. The solution was used for coating. A cellulose fiber-containing sheet was obtained in the same manner as in Comparative Example 1 except the above. The thickness of the obtained cellulose fiber-containing sheet was 13 μm.

Comparative Example 4
In Comparative Example 1, the coated substrate was a polycarbonate plate (dimension 100 mm × 100 mm, thickness 1 mm) when the cellulose fiber dispersion was applied to the coated substrate. A cellulose fiber-containing sheet was obtained in the same manner as in Comparative Example 1 except the above. The thickness of the obtained cellulose fiber-containing sheet was 13 μm.

Comparative Example 5
The silver plate coated with the cellulose fiber dispersion in the same manner as in Example 1 is kept within the effective irradiation range of an infrared heater (“far-red ceramic heater S-I type” manufactured by Sakaguchi Electric Heat Co., Ltd.) preheated at 120 V output. Placed. The distance between the infrared heater and the silver plate was 6 cm. The surface temperature of the infrared heater at this time was 250.degree. Then, it hold | maintains until the completion | finish of drying of the cellulose fiber dispersion liquid coated on the silver plate, and obtained the cellulose fiber containing sheet. The point in time when the moisture of the cellulose fiber dispersion coated in the marked line was completely volatilized visually was regarded as the end of drying. The cellulose fiber-containing sheet was separated from the silver plate and used for evaluation of sheet properties. The thickness of the obtained cellulose fiber-containing sheet was 13 μm.

Comparative Example 6
In Comparative Example 5, the coated substrate was a copper plate (size 100 mm × 100 mm, thickness 1 mm) when the cellulose fiber dispersion was applied to the coated substrate. The copper plate was immersed in a 10% aqueous hydrochloric acid solution for 2 minutes to remove the oxide film on the surface, washed with ion exchanged water, and used for coating of a cellulose fiber dispersion. A cellulose fiber-containing sheet was obtained in the same manner as in Comparative Example 5 except the above. The thickness of the obtained cellulose fiber-containing sheet was 13 μm.
Comparative Example 7
In Comparative Example 5, the coated substrate was a glass plate (size 100 mm × 100 mm, thickness 1 mm) when the cellulose fiber dispersion was applied to the coated substrate. The glass plate is coated with a silane compound ("KBM-3103" manufactured by Shin-Etsu Chemical Co., Ltd.) and heated with a hot plate set at a temperature of 50 ° C for 15 minutes to give a water-repellent treatment and then cellulose fiber dispersion. The solution was used for coating. A cellulose fiber-containing sheet was obtained in the same manner as in Comparative Example 5 except the above. The thickness of the obtained cellulose fiber-containing sheet was 13 μm.
Comparative Example 8
In Comparative Example 5, the coated substrate was a polycarbonate plate (size 100 mm × 100 mm, thickness 1 mm) when the cellulose fiber dispersion was applied to the coated substrate. A cellulose fiber-containing sheet was obtained in the same manner as in Comparative Example 5 except the above. The thickness of the obtained cellulose fiber-containing sheet was 13 μm.

[Evaluation]
<Method>
The cellulose fiber-containing sheets produced in Examples 1 to 12 and Comparative Examples 1 to 8 were evaluated according to the following evaluation method.

(1) Required drying time In Examples 1 to 12, the time required from the start of light irradiation A to the end of drying was taken as the required drying time of the cellulose fiber-containing sheet. In addition, in all of light irradiation A-light irradiation E, since irradiation stop time of 10 seconds is set from the completion of light irradiation to the start of next light irradiation, drying required time is irradiation of light irradiation A-light irradiation E It is the sum of the total time and the total of the irradiation stop time.
In Comparative Examples 1 to 4, the time required from the standing in the oven to the end of drying was taken as the drying required time for the cellulose fiber-containing sheet.
In Comparative Examples 5 to 8, the time required from the standing to the end of the effective irradiation range of the far infrared heater to the end of drying was taken as the drying required time of the cellulose fiber-containing sheet.

(2) Total light transmittance The total light transmittance was measured using a haze meter ("HM-150" manufactured by Murakami Color Research Laboratory, Inc.) in accordance with JIS Standard K7361.

(3) Haze The haze was measured using a haze meter ("HM-150" manufactured by Murakami Color Research Laboratory, Inc.) in accordance with JIS K7136.

(4) Goodness or Bad of Appearance The quality of the appearance of the cellulose fiber-containing sheet was evaluated based on the following judgment criteria.
○: no cracks observed ×: cracks observed

<Result>
The results are shown in Tables 1-2.

In Examples 1 to 4 in which the cellulose fiber dispersion was dried by irradiation with pulse light, the required drying time was shorter than in Comparative Examples 1 to 8 in which drying was performed by the existing drying method.
In addition, the cellulose fiber-containing sheets obtained in Examples 1 to 4 have a tendency that the total light transmittance slightly decreases relative to the cellulose fiber-containing sheets obtained in Comparative Examples 1 to 8, but the haze is not Tended to decline. It was found that the drying required time can be shortened while maintaining the transparency of the cellulose fiber-containing sheet by performing the drying by irradiation with pulse light.
Furthermore, the crack which generate | occur | produced in Comparative example 1-3 and 5-7 was not recognized in the cellulose fiber containing sheet | seat obtained in Examples 1-4, and the external appearance was favorable.

  From the results of Examples 5 and 6, it was found that the drying time of the cellulose fiber dispersion can be shortened by placing a colored substrate which absorbs and / or reflects pulse light under a transparent coated substrate. . From the results of Examples 7 and 8, it was found that the effect of shortening the drying required time confirmed in Examples 5 and 6 was not due to the reduction of the distance from the light source.

Furthermore, it turned out that the drying required time can be shortened by adding the filler which absorbs and / or reflects pulse light to a cellulose fiber dispersion from the result of Examples 9-12.

Claims (13)

A method for producing a fiber-containing sheet, comprising the steps of: irradiating a liquid containing a fiber coated on a substrate with pulsed light to concentrate and / or dry the liquid to obtain a fiber-containing sheet ; The method wherein the fibers are organic fibers, synthetic fibers, semi-synthetic fibers or regenerated fibers. The method according to claim 1, wherein the irradiation is performed in multiple cycles, and each cycle includes one or more irradiations. The method according to claim 2, wherein the irradiation in the second and subsequent cycles is performed at an irradiation dose less than 100% of the irradiation dose in the immediately preceding cycle. A method for producing a sheet, comprising the steps of: irradiating a liquid containing solids with a solid content coated on a substrate with a pulse light and concentrating and / or drying the liquid to obtain a sheet containing solids. A method in which irradiation is performed for a plurality of cycles, and each cycle includes one or more irradiations, and the irradiation in the second and subsequent cycles is performed with an irradiation dose that is less than 100% of the irradiation dose in the previous cycle. The manufacturing method of any one of Claims 1-4 in which a base material contains an inorganic material. The method according to any one of the preceding claims, wherein the substrate comprises a heat resistant plastic material. The substrate is
The manufacturing method according to any one of claims 1 to 6, comprising an upper layer composed of a transparent substrate that transmits pulse light, and a lower layer composed of a colored substrate that absorbs and / or reflects pulse light. . The manufacturing method according to any one of claims 1 to 7, wherein the liquid contains a filler that absorbs and / or reflects pulsed light. The method according to claim 8, wherein the filler is any one selected from the group consisting of carbon, metals and metal oxides. A method for producing a fiber-containing sheet, comprising the steps of: irradiating a liquid containing a fiber coated on a substrate with a pulse light and concentrating and / or drying the liquid to obtain a fiber-containing sheet; Is a fiber into which a substituent having electrostatic and / or steric functionality has been introduced. A method for producing a fiber-containing sheet, comprising the steps of: irradiating a liquid containing a fiber coated on a substrate with a pulse light and concentrating and / or drying the liquid to obtain a fiber-containing sheet; Is a cellulose fiber whose average fiber width is 2 to 1000 nm. The cellulose fiber is a cellulose fiber into which at least one selected from the group consisting of a group derived from phosphoric acid, a group derived from carboxylic acid, and a group derived from sulfuric acid is introduced, and the introduction amount of the substituent is 0.01 to 3 The production method according to claim 11, characterized in that it is 0 mmol / g. The manufacturing method of a product using the obtained sheet | seat including the process defined in any one of Claims 1-12.