JP5998339B2 - Light transmissive Japanese paper for LED lighting - Google Patents

Description

Detailed Description of the Invention

The present invention relates to a light-transmissive Japanese paper that reduces the attenuation of light from LED lighting fixtures and light sources such as light from outside.

In recent years, LEDs with low power consumption and low heat generation have become widespread as light sources for illuminators. Especially since the earthquake off the Pacific coast of Tohoku and the accident at the Fukushima Daiichi nuclear power plant, the demand for power-saving LEDs has increased rapidly as a power-saving measure. It was. Although it has begun to be used in many interior illuminators, in particular in this field, the sharpness of LED light, which points to human eyes, is disliked, and improvements have been demanded.
As one of them, the use of Japanese paper has been studied, but there is a drawback that the light transmittance is 20% or less. Although it is conceivable to make the paper thin in order to increase the light transmittance, in addition to being easily broken, there is a drawback that the visibility of the bright spot of the LED is high. Although it is possible to use milky white acrylic, the amount of transmitted light is significantly attenuated as in Japanese paper. As a means for solving these problems, resin-made light diffusion sheets have been developed and sold.

In Patent Document 1, a light diffusing film having a light diffusing layer formed on one surface of a base material layer is used, and a pattern in which black lines are arranged at equal intervals on a translucent member is used. On the surface of the light diffusion layer, a method has been proposed in which irregularities having an average interval S between local peaks of 12 to 30 μm are formed.

In Patent Document 2, a light diffusion layer comprising a base film, a translucent resin, and translucent fine particles dispersed in the translucent resin, and the surface of the resin coating layer formed in a flat film shape A light diffusing film having the following has been proposed. Since the fine irregularities and particles have the effect of refracting light, it is possible to diffuse the light, and if these resin light diffusion sheets are used, the light of the LED is diffused and the presence of the LED becomes difficult to understand. A gentle light.

In Patent Document 3, a step of forming a plurality of short fibers into a prefilm by a dry nonwoven fabric method, and applying a coating solution for forming a transparent resin by solidification or curing on at least one side of the prefilm obtained in the previous step, There has been proposed a method of forming a light diffusion film by solidifying or curing an applied coating solution.

JP2009-300870 JP2011-033400A JP 2010-152189 A

Problems to be solved by the invention

The resin-made light diffusion films described in Patent Documents 1 to 3 have high light transmittance and excellent light diffusion performance, but uniform and inorganic light is not preferred. In particular, natural materials with a moderate unevenness such as Japanese paper are preferred because they are not suitable for spaces that produce healing and peace of mind or Japanese style. However, in the case of Japanese paper, although the light diffusion performance is excellent, the light transmission property is low. Therefore, although it is good for human-friendly light, it is not suitable as a light diffusion material for a lighting device.
In addition, the above-described light diffusing film has a complicated manufacturing process and thus increases the cost. In addition, the light diffusing film is not breathable, and therefore cannot dissipate the heat generated when the LED emits light. There were problems such as causing troubles.

  Even in applications other than lighting equipment, the light-off glass is damaged by the earthquake off the Pacific coast of Tohoku, causing damage to people by falling, and light, flexible, and highly safe light transmission other than glass that is not broken or broken by dropping There is a need for sexual materials.

Therefore, the present invention is a simple manufacturing process that can diffuse the light of the LED without damaging the atmosphere in the interior lighting using the LED having a large power saving effect and soften the light of the LED. An object of the present invention is to provide a light-transmitting Japanese paper having air permeability for dissipating generated heat. Another object of the present invention is to provide a light-transmitting Japanese paper that can reduce the attenuation of light from a light source when the Japanese paper is replaced with a window glass as a light source or used indoors as a shoji paper or a partition.

Means for solving the problem

Single or multiple types of cellulosic natural fibers and single or multiple fiber diameters of 20 μm or more and 100 μm or less, length of 10 mm or more and 20 mm or less, cross-sectional shape of circle, pseudo circle, ellipse, flat shape It is a sheet-like structure in which fibers are laminated at random in the fiber direction. The sheet-like structure has a light transmittance of more than 30% and less than 50% , a haze value of 90% or more, and a density of 0.2 g / cm ^{3 to} 0.3 g / cm ³ , Gurley air resistance is 1.5 s or less, and stiffness is 0.5 mN to 1 mN

Effect of the invention

  Even if the light-breaking glass, which has a risk of breaking when an earthquake occurs, is changed to Japanese paper that does not cause damage to humans, if the light-transmitting Japanese paper of the present invention is used, light is not greatly attenuated. Further, the present invention provides an illuminator that diffuses light that pierces the eyes of the LED, softens the light of the LED, and is friendly to humans. In particular, in an interior lighting device, an illumination with a Japanese paper-like atmosphere is provided by using the light-transmitting Japanese paper of the present invention without using an inorganic resin sheet.

  Next, the present invention will be described in detail with reference to embodiments, but the present invention is not construed as being limited to these descriptions. As long as the effect of the present invention is exhibited, the embodiment may be variously modified.

  The present invention uses light-transmitting short fibers as a main fiber, blends cellulose-based natural fibers, and forms a sheet by a papermaking process, so that the interior of an LED using an LED having a large power saving effect can be used without impairing the atmosphere. It is a light transmissive Japanese paper that can diffuse light, soften the light of the LED, and reduce the attenuation of light entering from the outdoors.

<Light transmissive fiber (main fiber)>
The light-transmitting fibers (main fibers) used for manufacturing the light-transmitting Japanese paper may be any material having a high light-transmitting property. For example, polyester fibers such as polyethylene terephthalate and polybutylene terephthalate, polymethyl methacrylate, polyacrylonitrile, etc. Acrylic fiber, polyamide fiber such as nylon 6 and nylon 66, polyolefin fiber, polyimide fiber, polyacetal fiber, polyether fiber, polystyrene fiber, polycarbonate fiber, polyester amide fiber, polyphenylene sulfide fiber, polyvinyl chloride fiber, polyether ester fiber , Polyvinyl acetate fiber, polyvinyl butyral fiber, polyvinyl fluoride fiber, polyvinylidene fluoride fiber, ethylene-vinyl acetate copolymer fiber, styrene-acryl copolymer fiber, etc. That. These fibers may be used singly or in combination with a plurality of materials, and may have a material configuration that can obtain high light transmittance even when other materials are added.

<Form of light transmissive fiber>
The form of the light-transmitting fiber used in the present invention can be either a monofilament or a multifilament, but considering the light diffusibility and light transmittance of the light-transmitting Japanese paper, the monofilament is preferred.

<Cross-sectional shape of light transmissive fiber>
The cross-sectional shape of the light-transmitting fibers used in the present invention can be any of round shapes such as circles, pseudo circles, and ellipses, flat shapes, and irregular cross-section shapes such as triangles and cross shapes. In consideration of the light diffusibility and light transmittance of Japanese paper, those having a round or flat cross section are preferred.

<Raw polymer additive for light transmissive fiber>
Bright material that does not contain a matting agent such as titanium oxide is used as a raw material polymer for the light-transmitting fiber.

<Short fiber diameter of light transmitting fiber>
The single fiber diameter of the light transmissive fiber used in the present invention is preferably 10 μm or more and 120 μm or less. The smaller the single fiber diameter of the light-transmitting fiber, the greater the light diffusibility, and the effect of reducing the bright spot unevenness of the LED when used in a lamp shade for LED lighting is as follows. The short fiber diameter is less than 20 μm. When the light-transmitting fibers are produced, the short fibers are hardened and uniform dispersibility cannot be obtained, so that the freeness of the fibers is deteriorated and the working efficiency is lowered. In addition, the larger the single fiber diameter of the light transmissive fiber, the greater the light transmittance and the effect of increasing the total light transmittance of the sheet. However, when the single fiber diameter exceeds 120 μm, the texture of the sheet deteriorates and the entire sheet becomes worse. The light diffusibility tends to be non-uniform.
If the short fiber diameter of the light transmissive fiber used in the present invention is 10 μm or more and 120 μm or less, it is not necessary to have a single fiber diameter, and it is also possible to use a combination of fibers having a plurality of fiber diameters. By combining light transmissive fibers having different fiber diameters, the light transmittance, light diffusibility, texture, strength, and the like of the sheet can be adjusted to arbitrary physical properties.

<Fiber length of light transmissive fiber>
The fiber length of the light transmissive fiber used in the present invention is preferably 1 mm or more and 20 mm or less. When the fiber length is less than 1 mm, the drainage of the pulp may be deteriorated, which is not preferable. Conversely, if the fiber length exceeds 20 mm, the texture of the sheet may be impaired, which is not preferable. Moreover, the light transmissive fiber used in the present invention may be used in combination with a plurality of light transmissive fibers having a fiber length of 1 mm to 20 mm. By combining light transmissive fibers having different fiber lengths, the light transmissive property, light diffusibility, texture, and strength of the sheet can be adjusted to arbitrary physical properties.

<Basis weight and density of light transmissive Japanese paper>
The basis weight of the light transmissive Japanese paper of the present invention can be appropriately designed in the range of 50 g / m ² or more and 150 g / m ² or less according to the application. Further, the density of the light transmissive Japanese paper can be appropriately designed in the range of 0.1 g / cm ³ or more and 0.6 g / cm ³ or less according to the application.

<Cellulose fiber>
The cellulosic fibers used in the present invention are mixed for the purpose of giving a texture like Japanese paper or general paper, or improving the light diffusibility and strength of the sheet. Such Japanese paper fibers and pulp fiber materials include typical Japanese paper fibers such as cocoons, cocoons, and husks, chemical pulps such as softwood kraft pulp, hardwood kraft pulp, sulfite pulp, stone grind pulp, thermomechanical pulp, etc. It can be appropriately selected and blended from general paper pulp such as recycled pulp obtained from mechanical pulp, newspaper, coated paper, fine paper and the like, and non-wood pulp such as kenaf, bamboo and hemp.

<Constituent fibers other than cellulosic fibers>
In addition to the above-mentioned cellulose fibers, binder fibers such as polyolefin fibers, polyester fibers, low melting point polyamide fibers, and polyvinyl alcohol fibers can be mixed as long as the effects of the present invention are not impaired. Examples of such binder fibers include those composed only of a heat-sealing component and those having a core-sheath structure in which the heat-sealing component is configured as a sheath. Polyolefin synthetic pulp made of polyethylene or polypropylene having multi-branched fiber properties suitable for a wet papermaking process using a general-purpose paper machine is preferable. Moreover, the thing excellent in the adhesiveness by heat fusion with a wood pulp by the heating at the time of shaping | molding is preferable, and the polyolefin synthetic pulp whose melting | fusing point is 100-180 degreeC is used suitably. If necessary, inorganic fibers such as glass fibers, carbon fibers and metal fibers, and semi-synthetic fibers such as rayon fibers and triacetate fibers can be blended. These fibers may be used alone or in combination of two or more.

<Blending ratio of light transmitting fiber>
The mixing ratio of the main fibers, which are light-transmitting fibers, and the pulp fibers and the Japanese paper fibers is preferably 40% or more and 90% or less by weight. If the blending ratio of the main fibers is less than 40%, high light transmittance may not be obtained. Further, when the blending ratio of the main fiber is 90% or more, workability is remarkably lowered, and the uniformity of the Japanese paper may be lost in appearance.

<Freeness of mixed pulp>
The freeness of the mixed pulp of the single or plural light-transmitting short fibers used as the main fiber and the single or plural cellulose-based natural fibers used as the secondary fibers is preferably 200 to 700 cc (CSF). ). The free pulp degree of the mixed pulp is the method described in JIS P 8121: 1995 “Pulp Freeness Test Method” when disaggregated according to the method described in JIS P 8220: 1998 “Pulp-Disaggregation Method”. It is preferable that the Canadian standard freeness according to the above is adjusted to 200 to 700 cc (CSF), and more preferably 300 to 500 cc (CSF). When the Canadian standard freeness is less than 200 cc (CSF), the dewaterability is lowered, so that the pulp constituting the base paper is difficult to be oriented in the Z-axis direction, and the paper strength is likely to be lowered and the productivity is lowered. There is a risk. Further, if the Canadian standard freeness exceeds 700 cc (CSF), there is a possibility that the paper strength is weak because the degree of beating is small. Furthermore, the formation of the base paper is easily disturbed, and it is difficult not only to obtain a uniform formation, but also the gaps between the pulp fibers are likely to be uneven, resulting in unevenness in the light diffusibility and light transmission of the light transmissive Japanese paper. There is a fear.

<Additives for light transmissive Japanese paper>
Further, in the production of the light transmissive Japanese paper of the present invention, a sizing agent, a yield improver, a paper strength improver, a bulk improver, a fixing agent, an antifoaming agent, as long as the light diffusibility and light transmittance are not affected. Antioxidants, UV absorbers, matting agents, light stabilizers, fluorescent agents, pigments, dyes, colorants, flame retardants, antibacterial agents, conductivity imparting agents, hydrophilic agents, water absorbing agents, moisture absorbing agents, water repellents, One or more thickeners, thickeners, plasticizers, lubricants, fragrances, metal particles, inorganic particles, crystal nucleating agents and the like can be added.

<Air permeability resistance of light transmissive Japanese paper>
The light-transmitting Japanese paper of the present invention is a mixture of single or multiple light-transmitting short fibers as main fibers and single or multiple cellulose-based natural fibers as secondary fibers, and the fiber direction is randomly determined by a papermaking process. By laminating to each other, a space through which air flows is secured between the fibers, and good air permeability is provided. As for the air permeability, the Gurley air resistance described in JIS P 8117 is preferably 20 s or less, and more preferably 2 s or less. By providing such ventilation characteristics, even when light transmissive Japanese paper is used for ordinary lighting fixtures, heat generated from the light source inside the fixture is released to the outside by ventilation, preventing overheating of the lighting fixture. Can do.

<Stiffness of light transmissive Japanese paper>
The light-transmitting Japanese paper of the present invention preferably has a Taber stiffness described in JIS P 8125 of 0.3 mN · m to 3 mN · m. If the Taber stiffness is less than 0.3 mN · m, tears and wrinkles are likely to occur, and the moldability when molded as a lamp shade for LED lighting may deteriorate. On the other hand, if the Taber stiffness is greater than 3 mN · m, the flexibility of Japanese paper may be impaired.

  Hereinafter, examples will be described in order to more specifically illustrate the features of the present invention, but the present invention is not limited to these examples. The method for evaluating the characteristics of the light transmissive short fibers and the light transmissive Japanese paper is as follows.

(Cross-sectional shape of light transmissive fiber, fiber diameter)
Observation of the cross-sectional shape of the light-transmitting fiber and measurement of the fiber diameter were performed using a scanning electron microscope.

(Gurley air resistance)
It was measured by the method described in JIS P 8117.

(Basis weight)
It was measured by the method described in JIS P 8124.

(Total light transmittance, haze value)
Using a spectrophotometer (U-4000 manufactured by Hitachi, Ltd.), the total light transmittance in the visible light region of the light-transmissive Japanese paper was measured. Further, the diffuse transmittance was measured, and the haze value of the light transmissive Japanese paper was calculated.

(Taber stiffness)
It was measured by the method described in JIS P 8125.

(Japanese paper texture)
It was evaluated whether there was a texture of Japanese paper by visual inspection.

(Luminance unevenness, visibility of bright spots)
Place the light transmissive Japanese paper on the LED light source (manufactured by Nichia Corporation) at a height of 100 mm, and check that there is no luminance unevenness of the light transmissive Japanese paper by visual inspection. We evaluated whether we could confirm.

A polyethylene terephthalate (PET) fiber (manufactured by Unitika Ltd., 110 dtex / 1f) was cut to a fiber length of 10 mm, and 25 g of the cut PET fiber was immersed in 2 L of a nonionic surfactant aqueous solution having the following composition and stirred for 15 minutes. Boiled. The PET fibers were taken out, washed with water, and then dried for 3 hours with a dryer at 80 ° C. to obtain main fibers. Wood pulp (NBKP) adjusted to CSF 750 cc as an auxiliary fiber was mixed with the obtained main fiber so that the mass ratio of main fiber / auxiliary fiber = 60/40, and a pulp disaggregator (manufactured by Kumagai Riki Kogyo Co., Ltd.). Stir for 2 minutes at 3000 rpm. The obtained paper was paper-made using a square sheet machine (manufactured by Kumagai Riki Kogyo Co., Ltd.) to obtain a 250 × 200 mm wet paper. After pressing the wet paper with a pressure of 300 kPa, the wet paper was dried at a temperature of 105 ° C. with a rotary drier (manufactured by Kumagai Riki Kogyo Co., Ltd.), and a PET short fiber / wood pulp mixed paper with a basis weight of 100 g / m ² Obtained.
Nonionic surfactant aqueous solution composition Nonionic surfactant (manufactured by Nikka Chemical, trade name Sunmall WX-24) 0.1% by weight
Sodium carbonate 0.1% by weight

A PET short fiber / wood pulp mixed paper having a basis weight of 100 g / m ² was obtained in the same manner as in Example 1 except that the mass ratio was main fiber / subfiber = 40/60.

A PET short fiber / wood pulp mixed paper with a basis weight of 100 g / m ² was obtained in the same manner as in Example 1 except that TETRON 56T-24-915 manufactured by Toray Industries, Inc. was used as the PET fiber.

PET having a basis weight of 100 g / m ^{2 in} the same manner as in Example 1 except that PET fiber in which the main fiber used in Example 1 and the main fiber used in Example 3 were mixed at a ratio of 1: 1 was used as the main fiber. A short fiber / wood pulp mixed paper was obtained.

A lamp shade was prepared using the PET short fiber / wood pulp mixed paper obtained in Example 1, and the distance from the light source to the light source in which LEDs (manufactured by Nichia Corporation) were arranged at 15 mm intervals was 15 mm. A lamp shade was installed so as to produce an LED lighting device. The brightness of the obtained lighting device, whether the light is suitable for a Japanese space, luminance unevenness, visibility of bright spots, and the like were evaluated visually.

Comparative Example 1

A PET short fiber / wood pulp mixed paper with a basis weight of 100 g / m ² was obtained in the same manner as in Example 1 except that TETRON 56T-36-NS92 manufactured by Toray Industries, Inc. was used as the PET fiber.

Comparative Example 2

A PET short fiber / wood pulp mixed paper with a basis weight of 100 g / m ² was obtained in the same manner as in Example 1 except that PET fiber (manufactured by Unitika Ltd., 110 dtex / 1f) was cut to a fiber length of 30 mm.

Comparative Example 3

A PET short fiber / wood pulp mixed paper having a basis weight of 100 g / m ² was obtained in the same manner as in Example 1 except that the mass ratio was main fiber / subfiber = 20/80.

Comparative Example 4

A PET short fiber / wood pulp mixed paper was obtained in the same manner as in Example 1 except that the basis weight was 200 g / m ² .

The PET short fiber / wood pulp mixed papers obtained in Examples 1 to 4 have high light transmission with a total light transmittance of 30% or more in the visible light region, and air permeability is 2 s or less and air permeability, It can be confirmed that it has flexibility, moldability, and texture like Japanese paper, has no uneven brightness, and has low visibility of bright spots.

Moreover, when the lamp shade produced in Example 5 was evaluated, the PET short fiber / wood pulp mixed paper produced in Example 1 was used as a lamp shade, so that it had a warm appearance suitable for a Japanese space in addition to a bright appearance. It was confirmed that an LED lighting device showing light, no luminance unevenness, and low visibility of bright spots was obtained. In addition, when the members of Comparative Examples 1 and 2 are installed instead of Example 1, the lighting device is very dark in Comparative Example 1, and the bright spot of the LED is dazzling in Comparative Example 2, which is suitable as a lighting device. Absent.

The light-transmitting Japanese paper of the present invention allows LED light to be diffused without impairing the atmosphere in interior lighting using LEDs with a large power-saving effect, and can soften the light of the LEDs, for example, as a light diffusion sheet for LED lighting It can be used. In addition, it is possible to reduce the attenuation of light entering from the outside, and it can be used in many fields of industry as interior components such as curtains and blinds and space components such as partitions and partitions.

Schematic plan view of light transmissive Japanese paper

1 Light-transmissive Japanese paper 2 Light-transmissive fiber 3 Cellulose natural fiber

Claims (1)

Single or multiple types of cellulosic natural fibers and single or multiple fiber diameters of 20 μm or more and 100 μm or less, length of 10 mm or more and 20 mm or less, cross-sectional shape of circle, pseudo circle, ellipse, flat shape It is a sheet-like structure in which fibers are laminated at random in the fiber direction. The sheet-like structure has a light transmittance of more than 30% and less than 50% , a haze value of 90% or more, and a density of 0.2 g / Light-transmitting Japanese paper for LED illumination having a cm ³ or more and 0.3 g / cm ³ or less, a Gurley air resistance of 1.5 s or less, and a stiffness of 0.5 mN or more and 1 mN or less.

Images