JP2014185404A - Light permeable sheet and light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light permeable sheet with flexible feeling like leather comprising a light permeable part and a shading part, and a light emitting device using the sheet.SOLUTION: A light permeable sheet comprising a filmy light permeable part that a part of fiber of a non-woven fabric consisting of intertwining thermoplastic resin fiber is fusion-bonded by heat to a thickness direction, and a shading part that the fiber is not be filmy around the light permeable part, is used.

Description

  The present invention relates to a light transmissive sheet used as a surface design material for display panels such as various home appliances and automobile indicators, sneakers, clothing and various miscellaneous products, and a light emitting device using the same.

  Conventionally, a sheet having a translucent part having a patterned outline such as a character or a pattern and a light-shielding part around the translucent part, and by irradiating a backlight from the back surface, the character of the translucent part There are known light-transmitting sheets for displaying patterns and patterns.

  For example, in Patent Document 1 below, a pattern layer divided into a light transmitting part and a light shielding part is formed on a base sheet, and the pattern layer is a decorative film for backlighting formed by applying ink. Disclose. Moreover, the following patent document 2 discloses an internally illuminated signboard in which a light-transmitting part and a light-shielding part are provided by forming a patterned printing layer on the surface of the cloth width. As a light-transmitting sheet having a light-transmitting part and a light-shielding part as described above, a method for forming a light-shielding part by applying ink has been widely known.

  Further, Patent Document 3 below is an illumination having a leather feel, in which at least an adhesive layer, a translucent plastic film, and a translucent colored layer are laminated on one surface of a synthetic leather having a cutout portion. Disclosed decorative sheet for functional parts. According to the technique disclosed in Patent Document 3, a part of the synthetic leather is cut out to impart translucency to the sheet, and a non-cutout portion of the synthetic leather can form a light-shielding portion having a leather feel. .

JP 2000-343899 A JP 2011-133585 A JP 2003-71956 A

  In the case of a light-transmitting sheet as disclosed in Patent Document 3, a light-transmitting portion is formed by cutting out synthetic leather. However, such a light-transmitting sheet has a problem that it takes time to cut out. It was. Moreover, the synthetic leather itself cut out from such a translucent part can only function as a light-shielding part that is laminated on a translucent plastic film, and since a plastic film is required as a base material, it is a supple leather. It was difficult to maintain such a texture.

  An object of the present invention is to provide a light-transmitting sheet including a light-transmitting part and a light-shielding part and having a supple texture similar to leather, and a light-emitting device using the same.

  The light-transmitting sheet of the present invention includes a light-transmitting portion that is a region formed by film-bonding a part of a non-woven fabric obtained by entanglement of fibers made of a thermoplastic resin in the thickness direction, and a light A light-shielding portion that is a region where the fibers around the transmission portion are not formed into a film. The portion of the nonwoven fabric in which the fibers are formed into a film forms a light transmitting portion having a light guiding property because there are few fiber interfaces and voids. On the other hand, the portion of the nonwoven fabric that is not made into a film shields light in order to diffusely reflect the light. Such a light-transmitting sheet is a light-transmitting sheet that retains the flexibility of the nonwoven fabric because the light-shielding portion around the light-transmitting portion maintains the nonwoven fabric structure.

  Further, when the C light source is used as the light source and the total light transmittance of the light transmitting portion measured by the single beam method is 5% or more and the total light transmittance of the light shielding portion is 1% or less, This is preferable in that the light emitted from the transmission part can be clearly seen.

  Moreover, when the total light transmittance of a light transmissive part is 10 times or more of the total light transmittance of a light-shielding part, it is preferable from the point which can light-emit the light transmissive part more clearly.

In addition, when the apparent density of the entangled fibers forming the light shielding part is 0.45 g / cm ³ or more and the thickness of the light shielding part is 1.5 times or more the thickness of the light transmission part, sufficient light A light transmissive portion having transparency can be formed.

  Moreover, when the fiber of the surface of a light-shielding part is raised or raised, it is preferable from the point which can provide the leather-like appearance like a suede tone or a nubuck tone on the surface.

  Moreover, when the leather silver surface-like resin layer is formed in the surface of the light-shielding part, it is preferable from the point which can provide the leather-like appearance of a silver surface tone on the surface.

  Moreover, when the area ratio which the light-shielding part occupies when viewed from above is 50% or more, it is preferable from the viewpoint that the supple texture of the nonwoven fabric can be sufficiently maintained.

  Moreover, when the fiber is dye | stained, it is preferable from the point from which the colored translucent sheet | seat rich in design property is obtained.

  Moreover, when a fiber contains the ultrafine fiber of the thermoplastic resin whose single fiber fineness is 0.9 dtex or less and a glass transition temperature is 130 degrees C or less, it is preferable from the point which heat-fuses fibers and makes it easy to form a film. Examples of such thermoplastic resins include thermoplastic resins containing isophthalic acid-modified polyethylene terephthalate.

  Moreover, the light-emitting device of the present invention is a light-emitting device including any of the light-transmitting sheets as described above and a backlight that illuminates from one surface of the light-transmitting sheet. According to such a light emitting device, only the light transmission part is selectively transmitted by transmitting light only to the light transmission part of the light transmissive sheet having the outline of characters and patterns and the light transmission sheet having the light shielding part. Can emit light.

  According to the present invention, it is possible to obtain a light-transmitting sheet having a supple texture and a light emitting device having a supple texture on the surface.

FIG. 1A is a schematic top view of the light transmissive sheet 10 of the present embodiment, and FIG. 1B is a schematic cross-sectional view taken along the line II ′ of FIG. FIG. 2 is an explanatory diagram for explaining an embossing process for manufacturing a light transmissive sheet. FIG. 3 is a schematic perspective view of the light emitting device 20 including the light transmissive sheet 10. FIG. 4 is a scanning electron microscope (SEM) image of the light transmitting portion on the surface of the light transmissive sheet manufactured in Example 1. FIG. 5 is a scanning electron microscope (SEM) image of the cross section of the light transmitting portion of the light transmitting sheet manufactured in Example 1. FIG. 6 is a SEM image of a cross section of the light shielding portion of the light transmissive sheet manufactured in Example 1. FIG. 7 is an SEM image of a cross section of the embossed portion of the light transmissive sheet manufactured in Comparative Example 1.

  1A and 1B are schematic views of a light-transmitting sheet 10 according to the present embodiment, in which FIG. 1A is a schematic top view, and FIG. 1B is a schematic cross-sectional view taken along the line II ′ of FIG. In FIG. 1, 1 is a nonwoven fabric in which fibers made of a thermoplastic resin are entangled, and 2 is a light transmission part formed by thermally fusing part of the fibers forming the nonwoven fabric 1 into a film. Reference numeral 3 denotes a light-shielding portion that is a region in which fibers forming the nonwoven fabric remain entangled, and reference numeral 4 denotes a raised fiber formed by raising the surface of the nonwoven fabric 1.

  The light-transmitting sheet 10 is formed by forming a film by thermally fusing a part of the fibers forming the nonwoven fabric 1 in the thickness direction, and erasing most of the fiber outline to form a light-transmitting portion 2 serving as a light guide. Have. With such a light transmissive portion 2, light can be transmitted from one surface of the light transmissive sheet 10 to the other surface. On the other hand, the portion where the fibers forming the nonwoven fabric are maintained as they are becomes the light shielding portion 3 that blocks the light by irregularly reflecting the light by the fiber interface or the gap interface.

  A base material mainly composed of a nonwoven fabric has been conventionally used as a base material for producing artificial leather having a leather-like texture. By applying napping or raising treatment to the surface of the non-woven fabric, the texture and appearance of suede-like or nubuck-like leather can be imparted, and a leather-like resin layer of leather is formed on the surface of the non-woven fabric. Thus, the texture and appearance of the leather with silver can be imparted. In the light transmissive sheet 10 of the present embodiment, for example, as shown in FIG. 1, the surface of the light-shielding portion 3 in which the state in which the fibers forming the nonwoven fabric are entangled is maintained as it is, and the napped fibers are subjected to napping treatment. By forming 4, the texture and appearance of a suede-like or nubuck-like leather can be imparted. In addition, as described later, instead of performing napping treatment or raising treatment on the surface of the nonwoven fabric, a silver-tone texture and appearance of leather are provided by forming a silver-tone resin layer on the surface of the light shielding portion. Also good.

  The light-transmitting sheet of this embodiment is a light-transmitting sheet by manufacturing a nonwoven fabric, preferably a nonwoven fabric of ultrafine fibers, and heat-pressing a part of the nonwoven fabric to soften or melt the fibers to form a film. It is manufactured by the process of forming the transmission part. Hereinafter, the light transmissive sheet of the present embodiment will be described in detail along an example of a specific manufacturing method thereof.

  In the manufacturing method of the light transmissive sheet of this embodiment, a nonwoven fabric is manufactured first. As a nonwoven fabric, the nonwoven fabric containing the fiber which makes a film by fusing the fiber of the thickness direction by heat press is preferable, and the nonwoven fabric containing the entanglement of the ultrafine fiber of a thermoplastic resin is specifically preferable.

  In addition, the nonwoven fabric including the entangled body of ultrafine fibers is an entangled body of a bundle of ultrafine fibers formed by converging a plurality of ultrafine fibers, and the nonwoven fabric is hot-pressed because the fiber structure is dense. This is particularly preferable from the viewpoint that the fibers are easily fused to form a film.

  For example, (1) a web manufacturing process for manufacturing a fiber web made of sea-island type composite fibers by melt spinning, and (2) a plurality of the obtained fiber webs are stacked and entangled. A web entanglement step for forming a web entanglement sheet by combining, (3) a wet heat shrinkage treatment step for shrinking the web entanglement sheet with heat and moisture, and if necessary, to maintain morphological stability. 4) A polymer elastic body impregnation step for impregnating and applying a polymer elastic body such as polyurethane as a binder, and (5) an ultrafine fiber forming step for converting the sea-island type composite fibers in the web entangled sheet into ultrafine single fibers. .

(1) Web manufacturing process In this process, first, a web made of sea-island type composite fibers is manufactured by melt spinning. The sea-island type composite fiber is a fiber that forms a fiber bundle-like ultrafine fiber composed of island components by extracting or decomposing and removing sea components at an appropriate later stage.

  The web is, for example, a so-called spunbond method, a sea-island type composite fiber is spun using a melt spinning method, and this is collected on a net without cutting to form a long fiber web, Examples thereof include a method of collecting short fibers cut into a desired fiber length (for example, 18 to 110 mm) and stapled to form a short fiber web. Among these, the long fiber web is preferable from the viewpoint that the fibers can be dense and the cross section of the fibers is small, so that the fibers can be heat-sealed to form a film.

  Here, the long fiber means that it is not a short fiber cut by a predetermined length. The length of the long fiber is preferably 100 mm or more, and more preferably 200 mm or more from the viewpoint of sufficiently increasing the fiber density of the ultrafine single fiber. When the length of the ultrafine single fiber is too short, it tends to be difficult to increase the density of the fiber. Although an upper limit is not specifically limited, For example, when the fiber entanglement body derived from the nonwoven fabric manufactured by the spunbond method is contained, several m, several hundred m, several km or more continuously spun The fiber length may be used. Further, these fibers may be mixed with several kinds of fibers instead of single. In the present embodiment, the case of producing a long fiber web will be described in detail as a representative example.

  Examples of the thermoplastic resin constituting the island component of the sea-island composite fiber include polyester resins such as polyethylene terephthalate (PET), polytrimethylene terephthalate, polybutylene terephthalate (PBT), and polyester elastomer; polyamide 6, polyamide 66, Examples thereof include polyamide resins such as polyamide 610, aromatic polyamide, and polyamide elastomer; acrylic resins; transparent or translucent fibers formed from a synthetic resin having fiber-forming ability such as olefin resins. These may be used alone or in combination of two or more.

  The glass transition temperature (Tg) of the thermoplastic resin forming the ultrafine fiber is not particularly limited as long as the fiber can be formed into a film. For example, it is 130 ° C. or lower, and further 120 ° C. or lower by hot pressing the nonwoven fabric. This is preferable because the fiber surface is easily softened or melted in the step of forming the film. Specific examples of the thermoplastic resin having a Tg of 130 ° C. or lower include a thermoplastic resin containing modified polyethylene terephthalate. The Tg is measured by, for example, using a dynamic viscoelasticity measuring apparatus (for example, FT Leospectra DDVIV manufactured by Rheology Co., Ltd.) to fix a test piece having a width of 5 mm and a length of 30 mm between chucks with a spacing of 20 mm. It is obtained by measuring the dynamic viscoelastic behavior under the conditions of 30 to 250 ° C., a temperature rising rate of 3 ° C./min, a strain of 5 μm / 20 mm, and a measurement frequency of 10 Hz.

  Examples of the modified polyethylene terephthalate include modified polyethylene terephthalate containing an asymmetric aromatic carboxylic acid such as isophthalic acid, phthalic acid, and 5-sodium sulfoisophthalic acid and an aliphatic dicarboxylic acid such as adipic acid as a copolymerization component in a predetermined ratio. preferable. More specifically, modified polyethylene terephthalate containing 2 to 12 mol% of isophthalic acid unit as a monomer component is particularly preferable.

  On the other hand, specific examples of the thermoplastic resin constituting the sea component include, for example, polyvinyl alcohol resin, polyethylene, polypropylene, polystyrene, ethylene propylene copolymer, ethylene vinyl acetate copolymer, styrene ethylene copolymer styrene acrylic copolymer. Polymer, and the like. Of these, polyvinyl alcohol resins, particularly ethylene-modified polyvinyl alcohol resins, are preferred because they easily shrink during wet heat treatment or hot water treatment.

  The spunbond method is preferably used for spinning the sea-island composite fibers and forming the long fiber web. Specifically, sea-island type composite fibers are continuously ejected from individual nozzle holes onto a conveyor belt-shaped mobile net using a composite spinning nozzle in which a large number of nozzle holes are arranged in a predetermined pattern. And depositing while cooling using a high-speed air stream. By such a method, a long fiber web is formed. The long fiber web formed on the net is preferably subjected to a fusing treatment that suppresses the web so as not to form a film in order to impart form stability. As a specific example of the fusion process, for example, a hot press process can be cited. As a heat press process, the method of using a calender roll and applying a predetermined pressure and temperature, for example, can be employed. The temperature at which the hot press treatment is performed is 10 ° C. or more lower than the melting point of the component constituting the sea component of the sea-island type composite fiber, and the fiber surfaces are appropriately fused while maintaining the fiber form without forming the fiber into a film. It is preferable from the point which can be made.

The basis weight of the long fiber web after hot pressing is preferably in the range of 20 to 60 g / m ² . By being in the range of 20 to 60 g / m ² , good form retention can be maintained in the next stacking step.

(2) Web entanglement process Next, a web entanglement sheet | seat is formed by overlapping about 4-100 sheets of the obtained webs, and making it entangle. The web entangled sheet is formed by performing an entanglement treatment on the web using a known nonwoven fabric manufacturing method such as needle punching or high-pressure water flow treatment. Hereinafter, the entanglement process by the needle punch will be described in detail.

First, a silicone oil agent or a mineral oil oil agent such as a needle breakage prevention oil agent, an antistatic oil agent or an entanglement improving oil agent is applied to the web. Then, the entanglement process which entangles a fiber three-dimensionally with a needle punch is performed. By performing the needle punching process, a web entangled sheet having a high fiber density and hardly causing the fiber to come off can be obtained. The basis weight of the web-entangled sheet is appropriately selected according to the target thickness, and specifically, for example, a range of 500 to 2000 g / m ² is preferable from the viewpoint of excellent handleability.

(3) Heat shrinkage treatment step Next, the web entangled sheet is thermally shrunk to increase the fiber density and the degree of entanglement of the web entangled sheet. Specific examples of the heat shrink treatment include, for example, a method in which the web entangled sheet is continuously contacted with water vapor, or water is applied to the nonwoven fabric, and then the water applied to the nonwoven fabric is heated by electromagnetic waves such as heated air and infrared rays. Methods and the like. Moreover, while further densifying the non-woven fabric densified by the heat shrink treatment, further heat press treatment is performed as necessary for the purpose of fixing the form of the non-woven fabric or smoothing the surface. Further, the fiber density may be increased.

  As a change in the basis weight of the web-entangled sheet in the heat shrinking treatment step, it is 1.1 times (mass ratio) or more, further 1.3 times or more and 2 times or less, compared to the basis weight before the shrinking treatment, Is preferably 1.6 times or less.

(4) Polymer elastic body impregnation step For the purpose of enhancing the morphological stability of the web entangled sheet, the web entangled sheet is subjected to the polymer elasticity before or after the ultra-fine fiberization treatment of the web entangled sheet. It is preferable to impregnate the body.

  Specific examples of the polymer elastic body include, for example, a polyurethane elastic body, an acrylic elastic body, a polyamide elastic body such as a polyamide elastomer, a polyester elastic body such as a polyester elastomer, a polystyrene elastic body, a polyolefin elastic body, etc. Is mentioned. Among these, polyurethane-based elastic bodies are particularly preferable because they are excellent in flexibility and fullness.

  The content of the polyurethane-based elastic body is preferably 5 to 40% by mass, more preferably 8 to 35% by mass, and particularly preferably 10 to 20% with respect to the total amount with the nonwoven fabric to be formed. . When the content of the polyurethane-based elastic body is less than 5% by mass, sufficient shape stability cannot be imparted, and when it exceeds 40% by mass, the soft texture is lowered and the film tends to be difficult to form. There is.

  As the polymer elastic body, there are a foam type polymer elastic body and a non-foam type elastic body. However, in the method for producing a light-transmitting sheet of this embodiment, a non-foam type polymer such as a non-foam polyurethane is used. The elastic body is preferable in that voids remaining in the film can be reduced when the fiber is fused to form a film.

  As a method of impregnating and imparting a non-foaming type polyurethane to the web entangled sheet, after immersing the web entangled sheet in a bath filled with an aqueous polyurethane emulsion, a predetermined impregnation state is obtained with a press roll or the like. A dip nip method in which the process of squeezing is performed once or a plurality of times is preferably used. As other methods, a bar coating method, a knife coating method, a roll coating method, a comma coating method, a spray coating method, or the like may be used.

  Examples of polyurethane aqueous emulsions include polymer polyols such as polyethylene glycol, non-yellowing diisocyanates such as aliphatic or alicyclic diisocyanates having no aromatic ring, other organic diisocyanates, and active hydrogen atoms as necessary. Components containing so-called chain extenders such as hydrazine, piperazine, hexamethylene diamine, isophorone diamine and derivatives thereof, ethylene triamine, and the like, which are two low molecular weight compounds, in an emulsion polymerization method, a melt polymerization method, A known thermoplastic polyurethane obtained by polymerization by a bulk polymerization method, a solution polymerization method or the like is preferable.

  Then, the web entangled sheet is impregnated into the web entangled sheet and solidified by a dry method or a wet method for drying and solidifying the polyurethane, whereby the polyurethane can be impregnated and fixed on the web entangled sheet. In order to crosslink the solidified polyurethane, it is also preferable to perform a heat treatment after the solidification and drying.

(5) Ultrafine fiber formation process The sea-island type composite fiber in the web-entangled sheet is converted into a fiber bundle-like ultrafine fiber by extracting or decomposing and removing sea components with water or a solvent. For example, in the case of a sea-island type composite fiber using a water-soluble resin such as a polyvinyl alcohol-based resin as a sea component, the sea component is removed by a hot water heat treatment with water, an alkaline aqueous solution, an acidic aqueous solution or the like.

  In this step, when the ultrafine fiber is formed by dissolving and removing sea components from the sea-island type composite fiber, the ultrafine fiber is greatly crimped. By this crimping, the fiber density becomes more dense and a high fiber density nonwoven fabric is obtained.

  The ultrafine fiber preferably has a single fiber fineness of 0.01 to 0.9 dtex, further 0.05 to 0.5 dtex, and particularly 0.07 to 0.1 dtex. When the fineness of the ultrafine fiber is too high, it tends to be difficult to form a film. The ultrafine fibers are preferably present in the form of, for example, 5 to 200, further 10 to 50, and particularly 10 to 30 ultrafine fibers forming a fiber bundle. In this way, the ultrafine fibers are present in the form of a fiber bundle, whereby a high fiber density nonwoven fabric can be obtained.

  A nonwoven fabric is obtained by the above processes. The non-woven fabric obtained in this way is finished after being dried and then sliced into a plurality of pieces in the direction perpendicular to the thickness direction or ground to adjust the thickness and the surface condition. Further, a suede-like or nubuck-like nonwoven fabric can be obtained by buffing the surface layer of the nonwoven fabric with sandpaper or the like and raising or raising the surface. Also, finishing treatments such as sag softening treatment, reverse seal brushing treatment, antifouling treatment, hydrophilic treatment, lubricant treatment, softener treatment, antioxidant treatment, ultraviolet absorber treatment, fluorescent agent treatment, flame retardant treatment, etc. May be applied.

  The nonwoven fabric is dyed as necessary. For dyeing, disperse dyes, reactive dyes, acid dyes, metal complex dyes, sulfur dyes, sulfur vat dyes, and other dyes are selected appropriately according to the type of fiber, and fibers such as padder, jigger, circular, and wince are selected. A known dyeing machine usually used for dyeing is used. For example, when the ultrafine fiber is a polyester-based ultrafine fiber, it is preferably dyed by high-temperature high-pressure dyeing using a disperse dye.

The basis weight of the nonwoven fabric including the entangled body of fiber bundles formed in this manner is not particularly limited, but is preferably 100 to 1800 g / m ² , and more preferably 200 to 900 g / m ^2. . Also, the apparent density of the nonwoven fabric is not particularly limited. For example, the density is 0.45 g / cm ³ or more, and further 0.45 to 0.70 g / cm ³ is obtained by forming a dense nonwoven fabric. It is preferable from the point that spots become low and are easily formed into a film. When the apparent density is too low, it becomes difficult to form a film uniformly due to the presence of dense and sparse parts of the fiber, and when it is too high, the soft texture tends to be lowered.

  Moreover, although the thickness of a nonwoven fabric is not specifically limited, For example, it is preferable that it is 0.3-3 mm, Furthermore, 0.5-2 mm, Especially 0.5-1 mm.

  Next, the process of heat-pressing and heat-bonding a part of the fibers in the nonwoven fabric thus formed will be described.

  FIG. 2 is an explanatory diagram for explaining a state when the nonwoven fabric 1 is partially hot-pressed with the embossing roll 6. The embossing roll 6 has a plurality of protrusions 6a formed in a dot shape, and is arranged to face the back roll 7 while maintaining a certain clearance. The embossing roll 6 and the back roll 7 are heated and controlled to a temperature that sufficiently softens or melts the fibers forming the nonwoven fabric 1 and forms a film that is crimped with embossing. The embossing roll 6 and the back roll 7 rotate in the direction of the arrow, and the nonwoven fabric 1 is sandwiched by the clearance between the embossing roll 6 and the back roll 7 and continuously conveyed in the direction of the white arrow. In such a process, the portion heat-pressed by the protrusion 6a of the nonwoven fabric 1 is formed into a film, and the light transmission portion 2 is formed. At this time, when a polymer elastic body is contained as a binder, the polymer elastic body is also integrated with the fiber to form a film. And the part which was not hot-pressed by the protrusion 6a becomes the light-shielding part 3.

  Conventionally, there has been known a method of embossing for the purpose of partially crimping a non-woven fabric or imparting a pattern to the surface. However, the crimped part formed by such a method has fibers bonded only on the surface. The fiber surface was partially suppressed and adhered in a state where the fiber surface contour was clearly left. On the other hand, in the manufacture of the light-transmitting sheet of the present embodiment, the fibers are fused so that the pressure-bonded portion of the nonwoven fabric is formed into a film so as to transmit light in the thickness direction. The fiber film formation in the present embodiment means a state in which the fibers are fused on the surface and the fiber outline is unclear when the cross section is observed with a scanning electron microscope.

  More specifically, the light transmission part formed into a film is a light source using a C light source, and the total light transmittance measured by the single beam method is 5% or more, further 7% or more, especially 10% or more. It is preferable that In such a case, it can be said that the fiber is formed into a film. In addition, the light transmittance of the light-transmitting part formed as a film is 10 times or more, and further 30 times or more the total light transmittance of the light-shielding part of the nonwoven fabric that is not formed into a film. A state having transmittance is preferable.

  In addition, it is preferable that the light transmitting portion has a small gap because light diffusion is reduced and light transmittance is improved. The porosity of the light transmission part is preferably 15% or less, more preferably 10% or less. The lower limit of the porosity of the total light transmittance is preferably 0%. However, when the nonwoven fabric is hot-pressed to form a film, usually some voids may inevitably remain. The void ratio can be obtained from the SEM image of the area ratio of the void in the 90% region in the thickness direction from the pressed side of the light transmission portion.

  As the nonwoven fabric, it is preferable to use a dense nonwoven fabric having a total light transmittance of 1% or less and low light transmittance or no light transmittance. According to such a non-woven fabric, it is possible to leave a light-shielding part having a light-shielding property in which fibers are not formed into a film around the light-transmitting part. Therefore, a light-transmitting sheet having design properties can be easily formed by forming a light-transmitting portion or a light-shielding portion having an outline such as a character or a pattern.

The conditions for heat-sealing the fibers forming the nonwoven fabric in the thickness direction are appropriately selected and set according to the type, fineness, thickness, etc. of the fibers forming the nonwoven fabric. As an example, it is an entangled body of ultrafine fibers having a fineness of 0.01 to 0.09 dtex made of modified polyethylene terephthalate having a Tg of 130 ° C. or less, and a nonwoven fabric with an apparent density of 0.45 to 0.7 g / cm ³ . Was used, the surface temperature of the embossing roll was set to a temperature about 40 to 100 ° C. higher than Tg, and the embossing roll was passed at a speed of 1.0 to 5.0 m / min and a pressure of 0.5 to 3.0 MPa. In this case, a light transmission part having a porosity of 15% or less and a light transmittance of 5% or more can be easily formed.

  Moreover, when using an embossing roll, the height difference (engraving depth) of the protrusion of the embossing roll is 2.0 mm or more, further 3.0 mm or more, and particularly 5.0 mm or more to form a light transmission part. It is preferable from the viewpoint that sufficient pressure can be easily applied only to the portion to be applied.

  The ratio of the light transmission part and the light shielding part in the light transmissive sheet is not particularly limited, but when the area ratio occupied by the light shielding part when viewed from the top is 50% or more, further 70% or more, It is preferable from the viewpoint that the supple texture can be sufficiently maintained.

  In the present embodiment, the method for forming the light transmission part on the nonwoven fabric using the embossing roll has been described in detail. However, the method for forming the light transmission part is not limited to such a method, for example, hot pressing with an embossing die. May be formed. Further, in the thickness direction, the surface opposite to the pressed side may not be formed into a film because heat is not sufficiently transmitted. In such a case, the light transmittance may be improved by removing an unfilmed portion by grinding or slicing.

  Moreover, although the light transmissive sheet 10 described above has a raised surface such as a suede tone or a nubuck tone obtained by raising the surface of the light shielding portion 4, the surface of the light shielding portion is used instead of such a surface. By forming a silver surface layer, a light transmissive sheet having a silver surface can be produced.

  The method for forming the silver layer is not particularly limited. For example, after applying a coating solution containing a colored resin component for forming a silver surface layer by patterning so as to cover a portion other than the light transmitting portion of the light transmitting sheet on the release sheet, drying or wet coagulation is performed. Thus, a patterned silver surface layer film is formed. And after pasting together such a silver surface layer film through an adhesive layer so as to cover a portion other than the light transmitting portion of the nonwoven fabric in which the light transmitting portion is formed, there is a method using a dry surface forming method to peel the release sheet Can be mentioned. As another method, a coating liquid containing a resin component for forming a silver surface layer is directly applied to the surface so as to cover a portion other than the light transmission portion of the nonwoven fabric by a roll coater or a spray coater, and then dried or dried. Examples thereof include a wet surface-forming method that is formed by wet solidification.

  The resin component for forming the silver surface layer is not particularly limited. Specific examples thereof include various polyurethane resins such as polycarbonate polyurethane resins, polyester polyurethane resins, and polyether polyurethane resins, acrylic resins, polyurethane acrylic composite resins, polyvinyl chloride, and synthetic rubbers. . Among these, polyurethane resins are preferable from the viewpoint of excellent adhesiveness, mechanical properties such as wear resistance and flex resistance.

  Although the thickness of a silver surface layer is not specifically limited, It is preferable that it is 10-500 micrometers, Furthermore, 20-150 micrometers, Especially 40-120 micrometers.

  The light-transmitting sheet obtained in this way is a sheet that is arranged on the surface of a backlight of a display panel such as various home appliances and automobile indicators, or selectively transmits light, or sneakers, clothing, It is preferably used as a surface design material that allows sunlight to pass through various sundry products.

  FIG. 3 shows an example of the light emitting device 20 provided with the light transmissive sheet 10. In the light emitting device 20, the light transmissive sheet 10 is disposed so as to cover the surface of the backlight device 11 that emits surface light. Light emitted from the backlight device 11 is shielded by the shielding part 3 of the light-transmitting sheet 10, and is transmitted from each light transmitting part 2 formed in a dot shape to emit light as indicated by arrows. Since the fibers on the surface of the shielding portion 3 of the light transmissive sheet 10 are raised, such a light emitting device 20 has a suede or nubuck texture of leather.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited at all by the Example.

[Example 1]
Individually melted ethylene-modified polyvinyl alcohol as the sea component thermoplastic resin and isophthalic acid-modified polyethylene terephthalate (content of isophthalic acid unit of 6.0 mol%) having a Tg of 110 ° C as the island component thermoplastic resin. I let you. Then, each molten resin was supplied to a plurality of spinning nozzles in which a large number of nozzle holes were arranged in parallel so as to form a cross-section in which 25 island components having a uniform cross-sectional area were distributed in the sea component. . At this time, it supplied, adjusting pressure so that the mass ratio of a sea component and an island component might become sea component / island component = 25/75. And the molten fiber was discharged from the nozzle hole set to the nozzle | cap | die temperature of 260 degreeC.

The molten fiber discharged from the nozzle holes is drawn by an air jet / nozzle type suction device in which the pressure of the airflow is adjusted so that the average spinning speed is 3700 m / min, and the average fineness is 2.1 dtex. The sea-island composite long fiber was spun. The spun sea-island composite long fibers were continuously deposited on the movable net while being sucked from the back of the net. The amount of deposition was adjusted by adjusting the moving speed of the net. And in order to suppress the fuzz on the surface, the sea-island type composite long fibers deposited on the net were lightly pressed with a 42 ° C. metal roll. Then, the sea-island type composite long fibers were peeled from the net and hot-pressed by passing between a lattice-pattern metal roll having a surface temperature of 75 ° C. and a back roll. In this way, a long fiber web having a basis weight of 34 g / m ² in which the fibers on the surface were temporarily fused in a lattice shape was obtained.

Next, after spraying an oil agent mixed with an antistatic agent on the surface of the obtained long fiber web, 10 sheets of the long fiber web are overlapped using a cross wrapper device, and the total basis weight is 340 g / m ² . A web was prepared, and a needle breakage oil was sprayed. And the three-dimensional entanglement process was carried out by needle punching the overlap web. Specifically, a 6 barb needle with a distance of 3.2 mm from the needle tip to the first barb was used, and needle punching was performed alternately at 3300 punches / cm ² from both sides of the laminate at a needle depth of 8.3 mm. . The area shrinkage rate by this needle punching treatment was 68%, and the basis weight of the entangled web after needle punching was 415 g / m ² .

The resulting entangled web was densified by a wet heat shrinkage treatment as follows. Specifically, water at 18 ° C. is uniformly sprayed on the entangled web by 10% by mass, and left in a state where no tension is applied for 3 minutes in an atmosphere at a temperature of 70 ° C. and a relative humidity of 95%. The apparent fiber density was improved by heat and heat shrinkage. The area shrinkage rate by the wet heat shrinkage treatment was 45%, the basis weight of the densified entangled web was 750 g / m ² , and the apparent density was 0.52 g / cm ³ . The apparent density was adjusted to 0.60 g / cm ³ by dry-heat roll pressing to further densify the entangled web.

  Next, the densified entangled web was impregnated with a non-foaming type polyurethane emulsion as follows. A densified entangled web was impregnated with a water-based polyurethane emulsion (solid content concentration 30%) mainly composed of polycarbonate / ether-based polyurethane. Then, moisture was dried in a drying furnace at 150 ° C., and non-foamed polyurethane was crosslinked. A polyurethane entangled web composite having a polyurethane / entangled web mass ratio of 18/82 was thus formed.

  Next, the polyurethane entangled web composite is immersed in hot water at 95 ° C. for 20 minutes to extract and remove sea components contained in the sea-island composite long fibers, and dried in a drying furnace at 120 ° C. An intermediate sheet of a substrate having a thickness of about 1.0 mm was obtained. And the obtained sheet | seat was divided into 2 to the thickness direction, and it ground to 0.45 mm, and obtained the base material containing a nonwoven fabric. And the surface side was brushed with 400th sandpaper to finish it in a suede tone. Then, the obtained suede-like base material was subjected to liquid dyeing at 130 ° C. for 1 hour using a blue disperse dye to perform reduction and neutralization treatment. The fiber dropped and frayed during dyeing, and the color was good.

The apparent density of the nonwoven fabric contained in the obtained base material was 0.53 g / cm ³ , and the mass ratio of the nonwoven fabric / polyurethane was 78/22. Moreover, the fineness of the ultrafine fibers forming the nonwoven fabric was 0.08 dtex.

Next, the obtained base material was embossed using an embossing roll in which a plurality of dots having a carving depth of 3.0 mm and a radius of 3.0 mm were uniformly dispersed at an area ratio of 30%. The embossing conditions were as follows: the surface temperature of the embossing roll was 185 ° C., the pressure was 0.98 MPa (10 kgf / cm ² ), and the embossing roll speed was 1.5 m / min. In this way, a light transmissive sheet was obtained.

  FIG. 4 shows a scanning electron microscope (SEM) image of the surface of the translucent part of the surface of the obtained light-transmitting sheet, and FIG. 5 shows an SEM image of the cross section. FIG. 6 shows an SEM image of the cross section of the light shielding portion of the light transmissive sheet. As shown in FIG.4 and FIG.5, in the translucent part, the fibers are fused and the outline of the fiber is unclear, and the fiber structure of the nonwoven fabric is lost. On the other hand, as shown in FIG. 6, the fiber structure of the nonwoven fabric is maintained in the cross section of the light shielding portion.

  And the total light transmittance and the porosity of the embossed part and the non-embossed part of the light-transmitting sheet were evaluated as follows.

(Total light transmittance)
A stainless steel light-shielding plate with a small hole with a diameter of 2.5 mm and a light-transmitting sheet are bonded together and set in a haze meter (equipment model name: “HV-1”) manufactured by Suga Test Instruments Co., Ltd. Using a C light source as the light source, the local total light transmittance (%) per small hole was measured by a single beam method.

(Porosity)
The porosity was calculated using the SEM photograph of the cross section in the thickness direction of the obtained sheet as described above. Specifically, the area ratio of the voids in the 90% region in the thickness direction from the pressed side of the sheet was calculated from the weight of the void portion with respect to the entire region of the photograph. In addition, the measurement took the average value of the result of a total of ten samples which selected five pieces uniformly from each direction of the cross section cut | disconnected from two directions orthogonal to each other.

  The results are shown in Table 1.

[Example 2]
In Example 1, instead of using isophthalic acid-modified polyethylene terephthalate having a Tg of 110 ° C. as the island component thermoplastic resin, isophthalic acid modified polyethylene terephthalate having a Tg of 100 ° C. was used as the island component thermoplastic resin. A light transmissive sheet was obtained in the same manner as in Example 1 except that it was used. And it evaluated similarly. The results are shown in Table 1.

[Example 3]
In Example 1, the same conditions as in Example 1 were applied except that the embossing conditions were changed to an embossing roll surface temperature of 185 ° C., a pressure of 1.47 MPa (15 kgf / cm ² ), and an embossing roll speed of 2.0 m / min. A light transmissive sheet was obtained. And it evaluated similarly. The results are shown in Table 1.

[Comparative Example 1]
In Example 1, a sheet was obtained in the same manner as in Example 1 except that the embossing conditions were changed to an embossing roll surface temperature of 185 ° C., a pressure of 0.29 MPa, and an embossing roll speed of 1.5 m / min. And it evaluated similarly. The results are shown in Table 1. An SEM image of the cross section of the embossed portion on the surface of the sheet is shown in FIG. As shown in FIG. 7, the embossed part of the obtained sheet was not formed into a film.

[Comparative Example 2]
In Example 1, instead of impregnating the non-foaming polyurethane, the polyurethane foam / entanglement was carried out by impregnating with a DMF solution (20% solids) of polyurethane to form the foaming polyurethane and wet coagulating it. A polyurethane entangled web composite having a web mass ratio of 18/82 was formed. A sheet was obtained in the same manner as in Example 1 except for the above changes. And it evaluated similarly. The results are shown in Table 1.

[Comparative Example 3]
In Example 1, instead of using isophthalic acid-modified polyethylene terephthalate having a Tg of 110 ° C. as the island component thermoplastic resin, polyamide 6 having a Tg of 47 ° C. was used as the island component thermoplastic resin. A sheet was obtained in the same manner as in Example 1 except that it was dyed with a metal-containing dye instead of dyeing with. And it evaluated similarly. The results are shown in Table 1.

[Comparative Example 4]
In Example 1, instead of isophthalic acid-modified polyethylene terephthalate (content of isophthalic acid unit 6.0 mol%), polyethylene terephthalate not modified with isophthalic acid was used as the island component thermoplastic resin. In the same manner as in No. 1, a sheet was obtained. And it evaluated similarly. The results are shown in Table 1.

  The light-transmitting sheets obtained in Examples 1 to 3 according to the present invention each had a total light transmittance of 5% or more in the light-transmitting portion. In addition, the supple texture of leather was maintained. Further, as shown in FIG. 5, the translucent part was fused to such an extent that the fiber structure becomes unclear. On the other hand, the sheet obtained in Comparative Example 1 embossed under conditions that impart shape stability while maintaining the fiber structure of the nonwoven fabric had no translucency in the embossed portion. Also, in the case of Comparative Example 2 embossed using a nonwoven fabric impregnated with foamed polyurethane, the embossed portion was not translucent. Also, in the case of Comparative Example 3 embossed using a nonwoven fabric formed from polyamide 6, the embossed part was not translucent. Furthermore, in the case of the comparative example 4 which used the nonwoven fabric formed from the polyethylene terephthalate which has not modified | denatured isophthalic acid and was embossed, the melt | fusion of fibers becomes inadequate and an embossed part is not formed into a film, but translucency There was no sex.

  The light-transmitting sheet obtained in the present invention is preferably used for a light-emitting device that is disposed on the surface of a backlight of a display panel such as various home appliances and automobile indicators and selectively transmits light. Moreover, it is preferably used as a surface design material that does not include a light-emitting device for sneakers, clothing, and various miscellaneous goods and that allows sunlight to selectively pass therethrough.

DESCRIPTION OF SYMBOLS 1 Nonwoven fabric 2 Light transmission part 3 Light-shielding part 4 Napped fiber 6 Embossing roll 6a Protrusion 7 Back roll 10 Light transmissive sheet 11 Backlight apparatus 20 Light emitting apparatus

Claims (11)

  A light transmitting portion which is a region formed by film-forming a part of the nonwoven fabric which is an entangled body of fibers made of a thermoplastic resin in the thickness direction, and the fiber around the light transmitting portion is a film A light-transmitting sheet, comprising: a light-shielding portion that is a region that has not been converted into a light.   The total light transmittance of the light transmission part measured by a single beam method using a C light source as a use light source is 5% or more, and the total light transmittance of the light shielding part is 1% or less. Light transmissive sheet.   3. The light transmissive sheet according to claim 1, wherein a total light transmittance of the light transmission portion is 10 times or more of a total light transmittance of the light shielding portion. The apparent density of the entangled body of fibers forming the light shielding part is 0.45 g / cm ³ or more, and the thickness of the light shielding part is 1.5 times or more of the thickness of the light transmission part. The light transmissive sheet according to any one of the above.   The light-transmitting sheet according to any one of claims 1 to 4, wherein the surface of the light-shielding portion has the fibers raised or raised.   The light-transmitting sheet according to any one of claims 1 to 4, wherein a leather silver surface resin layer is formed on a surface of the light shielding portion.   The light-transmitting sheet according to any one of claims 1 to 6, wherein an area ratio of the light-shielding portion when viewed from above is 50% or more.   The light-transmitting sheet according to claim 1, wherein the fibers are dyed.   The light-transmitting sheet according to any one of claims 1 to 8, wherein the fiber includes an ultrafine fiber of a thermoplastic resin having a single fiber fineness of 0.9 dtex or less and a glass transition temperature of 130 ° C or less.   The light transmissive sheet according to claim 9, wherein the thermoplastic resin contains isophthalic acid-modified polyethylene terephthalate.   A light emitting device comprising: the light transmissive sheet according to claim 1; and a backlight that illuminates from one surface of the light transmissive sheet.