JP2009155427A - White film for optical duct - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a white film for an optical duct, used in a light guide section of the optical duct system, which can carry visible light suitable for illumination efficiently and evenly, and is lightweight, and in the production of which no organic solvent having the risk of sick house syndrome is used. <P>SOLUTION: This white film for the optical duct has an average reflectance of &ge;96.0%, and is used for the optical duct. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a white film for an optical duct that is used as a reflecting material that constitutes a light guide portion of an optical duct system.

  The optical duct system is a system that guides outdoor light indoors and irradiates it indoors. In general, an optical duct system includes a daylighting unit, a light guide unit, and a light emitting unit. Outdoor natural light is taken into the duct by the daylighting unit, conveyed indoors by the light guide unit, and irradiated indoors as diffused light from the light emitting unit.

  It is said that 1/3 to 1/4 of the energy consumed by office buildings is for lighting. Despite the abundance of natural light outdoors during the day, most of the office buildings are fully lit with electricity. If natural light can be used effectively in the building, the power consumption during the day can be greatly reduced, which can greatly contribute to the leveling of the power load as well as energy saving.

  In the past, in order to use natural light in buildings, it has been used windows and top lights. However, in recent office buildings with deep depths, the lighting from the window surface is effective in a small area of about 2 to 3 meters at most from the window surface, and other areas do not depend on lighting by electric power. Did not get.

The light duct system requires indoor natural light during the daytime from the building's outer wall and rooftop, and the interior is made of a highly reflective material that reflects the light inside the duct. Since light is transported to various places and used for illumination, natural light can be used efficiently even in regions where it is difficult to use light with windows and top lights.
Conventionally, a high-reflectance mirror has been used for the light guide portion of the optical duct system, for example, a high-reflectance mirror made of an aluminum material has been used.

JP 2007-115417 A JP 2007-167734 A JP 2005-268156 A

  However, when a mirror is used for the light guide section, since the specular reflection is strong and the diffuse reflection is small, it is difficult to carry sunlight uniformly indoors and to diffuse it uniformly. In addition, since ultraviolet rays are also conveyed, there is a problem that the interior of the interior is discolored and deteriorated by the ultraviolet rays. Furthermore, even when a light aluminum material is used as the mirror, a sturdy support for supporting the mirror is required, which increases the weight of the optical duct system, and particularly high-rise buildings that are required to be reduced in weight. This is difficult to adopt in ordinary detached houses.

  In addition, when a metal or plastic plate painted with white paint is used for the light guide, there is a risk of developing sick house syndrome due to the organic solvent contained in the paint as a solvent, not only for residential buildings but also for office use. Even a building is not desirable.

The present invention provides a white light duct for use in a light guide part of a light duct system that efficiently and uniformly conveys visible light suitable for illumination, is lightweight, and does not use an organic solvent that may cause sick house syndrome. It is an object to provide a film.
Furthermore, an object of the present invention is to provide a white film for an optical duct that does not convey ultraviolet rays that cause indoor deterioration, in addition to the above problems.

  That is, this invention is a white film for optical ducts which consists of a white film with an average reflectance of 96.0% or more with a wavelength of 400-700 nm, and is used for an optical duct.

  According to the present invention, there is provided a white film for a light duct used for a light guide portion of a light duct system that is light and does not use an organic solvent while efficiently and uniformly conveying visible light suitable for illumination. Can do. Furthermore, according to this invention, the white film for optical ducts which does not convey an ultraviolet-ray, showing the said effect can be provided.

Hereinafter, the present invention will be described in detail.
[White film]
A white film can be obtained by blending a whitening agent with a thermoplastic resin to form a film. As the whitening agent, a white pigment or a void forming substance can be used. When using a white pigment, a white film can be obtained simply by blending with a thermoplastic resin. As this white pigment, for example, titanium dioxide and zinc oxide can be used.
When a void forming substance is used, a void forming substance is blended in the thermoplastic resin and stretched to obtain a film containing many voids. Light is diffusely reflected at the interface between the voids present in the film and the constituent resin of the film, and the film exhibits a white color and becomes a white film.

[Thermoplastic resin]
For example, polyester, polyolefin, or polystyrene can be used as the thermoplastic resin. Of these, polyester is preferred because of its high mechanical strength.
Examples of the polyester include polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate. Of these, polyethylene terephthalate is preferable.

  As the polyester, a copolyester is preferably used in order to obtain an appropriate stretchability. The ratio of the copolymerization component is preferably 1 to 20 mol%, more preferably 3 to 17 mol%, still more preferably 3 to 15 mol% per total dicarboxylic acid component. By copolymerizing the copolymer component within this range, a film can be obtained with good film forming properties even if a large amount of resin incompatible with inorganic particles, organic particles, or polyester is added.

  Polyolefins include polyethylene, polypropylene, poly-3-methylbutene-1, poly-4-methylpentene-1, polyvinyl t-butane, 1,4-trans-poly-2,3-dimethylbutadiene, polyvinylcyclohexane, polystyrene. , Polyfluorostyrene, cellulose acetate cellulose propionate, and polychlorotrifluoroethylene. Among these, polyethylene, polypropylene, and polymethylpentene are preferable because the resin itself is highly transparent, so that the absorption of light can be suppressed and the reflectance can be improved.

[Void-forming substance]
As the void-forming substance, for example, inorganic particles and organic particles can be used, and a resin incompatible with the thermoplastic resin constituting the white film, that is, an incompatible resin can be used.

[Inorganic particles]
As the particles, inorganic particles are preferable from the viewpoint of weather resistance, and white inorganic particles are particularly preferable. For example, barium sulfate, silicon dioxide, or calcium carbonate can be used.
The average particle diameter of the void-forming substance inorganic particles is preferably 0.1 to 10.0 μm, more preferably 0.2 to 8.0 μm, and particularly preferably 0.3 to 6.0 μm. By using a particle having a particle size in this range, it is possible to obtain a white film having good dispersibility, hardly causing particle aggregation, and having a smooth surface and appropriate gloss.

  When polyester is used as the thermoplastic resin of the white film, the content of the void-forming substance in the white film is preferably 31 to 60% by weight, more preferably 35%, based on a total of 100% by weight of the polyester and void-forming substance in the white film. It is -55 weight%, Most preferably, it is 40-50 weight%. By containing a void-forming substance in this range, it is possible to obtain bright illumination light when used in a light duct with high reflectivity, and it is difficult to break during production, bending, and installation, a white film for a light duct Can be obtained.

As the inorganic particles and organic particles of the void-forming substance, the particle size distribution is 15.0 μm or less, further 13.0 μm or less, particularly 12.0 μm or less as a 90% volume particle size (D90) integrated from the small particle size side. It is preferable to use certain particles. By using these particles, filter clogging does not occur, aggregates do not appear as surface defects on the film, and a white film free from surface defects can be obtained with high productivity.
The inorganic particles may have a plate shape or a spherical particle shape. The inorganic particles may be subjected to a surface treatment for improving dispersibility.

[Organic particles]
When organic particles are used as the void-forming substance, organic particles made of a resin that is incompatible with the thermoplastic resin of the film are used. For example, when polyester is used as the thermoplastic resin of the film, resin particles incompatible with polyester are used as the void forming substance. As the organic particles, polytetrafluoroethylene is particularly preferable because of its high melting point and thermal stability.

  The average particle diameter of the organic particles is preferably 0.1 to 10 μm, more preferably 0.2 to 8.0 μm, and particularly preferably 0.3 to 6.0 μm. When the average particle size is within this range, a white film having good dispersibility, hardly causing particle aggregation, a smooth film surface, and appropriate gloss can be obtained.

  When polyester is used as the thermoplastic resin of the white film, the content of the organic particles in the white film is preferably 1 to 60% by weight, more preferably 3% per 100% by weight of the total of the polyester and organic particles of the white film. It is -55 weight%, Most preferably, it is 5-50 weight%. By using in this range, it is possible to obtain a white film for a light duct that has high reflectivity, can obtain bright illumination light when used in a light duct, and is not easily broken during film production or bending. it can.

[Incompatible resin]
The incompatible resin varies depending on the type of the thermoplastic resin of the film. Therefore, here, a case where polyester is used as the thermoplastic resin of the film will be described as an example.
Examples of resins incompatible with polyester include polyolefin, polystyrene, poly-3-methylbutene-1, poly-4-methylpentene-1, polyethylene, polypropylene, polyvinyl t-butane, and 1,4-trans-poly-2. , 3-dimethylbutadiene, polyvinylcyclohexane, polystyrene, polyfluorostyrene, cellulose acetate cellulose propionate, polychlorotrifluoroethylene can be used. Among these, polypropylene and polymethylpentene are preferable because the resin itself is highly transparent, and light reflectance can be minimized and high reflectance can be obtained.

  When an incompatible resin is used, the blending amount is preferably 3 to 50% by weight, more preferably 4 to 45% by weight, particularly preferably 5 to 40% by weight per 100% by weight of the total amount of the polyester and the incompatible resin. %. By using in this range, a film having a high reflectance can be stably formed, and the film can be produced with high productivity.

  Next, the case where polyolefin is used as the thermoplastic resin for the film will be described. Examples of resins that are incompatible with polyolefin include polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate. The blending amount is preferably 3 to 50% by weight, more preferably 4 to 45% by weight, and particularly preferably 5 to 40% by weight per 100% by weight of the total amount of the polyolefin and the incompatible resin. By using in this range, a film having a high reflectance can be stably formed, and the film can be produced with high productivity.

[Reflectance and optical density]
The white film in the present invention is a film having an average reflectance of a wavelength of 400 to 700 nm of 96.0% or more, more preferably 96.5% or more, and particularly preferably 97.0% or more. When the average reflectance is within this range, light can be conveyed with high efficiency, and sufficient brightness can be obtained.
The white film in the present invention is a film having an optical density of preferably 0.8 or more, more preferably 0.9 or more, and particularly preferably 1.0 or more. By providing this optical density, when used in an optical duct, light does not leak in the optical duct, and light can be conveyed with high efficiency.

[Glossiness]
The glossiness of at least one side of the white film in the present invention is preferably 5 to 100%, more preferably 5 to 90%, and particularly preferably 5 to 80%. By using a white film having a glossiness in this range as the light guide portion of the optical duct, light can be efficiently conveyed by diffuse reflection, and no brightness spots are produced.

[Film thickness]
The thickness of the white film in the present invention is preferably 25 to 350 μm, more preferably 40 to 300 μm, and particularly preferably 50 to 250 μm. When the thickness is within this range, a sufficient reflectance can be obtained. Even if the thickness exceeds 350 μm, the reflectance cannot be further increased, which is uneconomical.

[Weight per area]
The white film in the present invention has a weight per area of the reflecting surface of preferably 50 to 500 g / m ² , more preferably 100 to 400 g / m ² , and particularly preferably 120 to 350 g / m ² . By being in this range of weight, it is possible to obtain high safety when an earthquake occurs. On the other hand, if a heavy object such as a metal reflector is used, it is dangerous to drop when an earthquake occurs, and it is necessary to reinforce the installation location, which increases the construction cost.

[Production method]
Hereinafter, as an example of a method for producing a white film for an optical duct according to the present invention, a method for producing an A / B laminated white film will be described. First, a polymer melted from a die is extruded onto a casting drum by a simultaneous multilayer extrusion method using a feed block to obtain a laminated unstretched sheet. That is, a polymer melt for forming the A layer and a polymer melt for forming the B layer are laminated so as to be A layer / B layer using a feed block, and are developed on a die and extruded. At this time, the polymer laminated by the feed block maintains the laminated form. The unstretched sheet extruded from the die is cooled and solidified on a casting drum to form an unstretched film.

  This unstretched film is heated by, for example, roll heating or infrared heating, and stretched in the longitudinal direction to obtain a longitudinally stretched film. This stretching is preferably performed by utilizing the difference in peripheral speed between two or more rolls. The stretching temperature is, for example, a temperature equal to or higher than the glass transition point (Tg), preferably a temperature higher by Tg to 160 ° C. The stretching ratio is preferably 2.2 to 4.0 times, more preferably 2.3 to 3.9 times in both the longitudinal direction and the direction orthogonal to the longitudinal direction (hereinafter referred to as “lateral direction”). By setting it as this range, there are few thickness spots of the film obtained, and there are few fractures also during film forming of a film.

  By stretching, peeling occurs at the interface between the thermoplastic resin of the film and the inorganic or organic particles or incompatible resin contained in the film, and fine voids are formed in the film, resulting in a white, highly reflective film. Obtainable.

  The film after the longitudinal stretching can subsequently be subjected to a process of transverse stretching, heat setting, and thermal relaxation to form a biaxially oriented film. These processes are preferably performed while the film is running. The transverse stretching starts from a temperature higher than the glass transition point (Tg) and is performed while raising the temperature to a temperature higher by 5 to 160 ° C. than Tg. Although the temperature rise in the transverse stretching process may be continuous or stepwise (sequential), the temperature is usually raised sequentially. For example, the transverse stretching zone of the tenter is divided into a plurality along the film running direction, and the temperature is raised by flowing a heating medium having a predetermined temperature for each zone. The magnification of transverse stretching is, for example, 2.5 to 4.5 times, preferably 2.8 to 3.9 times. By being this range, there are few thickness spots of the film obtained, and there are few fractures also during film forming.

  The film after transverse stretching is preferably heat-treated at a constant width or a width reduction of 10% or less at a temperature (Tm-20 to Tm-130) while holding both ends to reduce the thermal shrinkage rate. When the temperature is higher than this, the flatness of the film is deteriorated, and the thickness unevenness is unfavorable. On the other hand, if the heat treatment temperature is lower than (Tm-130) ° C., the thermal shrinkage rate may increase. In addition, in order to adjust the heat shrinkage in the process of returning the film temperature to room temperature after heat setting, both ends of the gripped film are cut off at (Tm-20 to Tm-130) ° C. Can be adjusted and relaxed in the vertical direction. As a means for relaxing, the speed of the roll group on the tenter exit side is adjusted. As the rate of relaxation, the speed of the roll group is reduced with respect to the film line speed of the tenter, preferably 0.1 to 2.5%, more preferably 0.2 to 2.3%, particularly preferably 0.3. The film is relaxed by performing a speed reduction of ˜2.0% (this value is referred to as “relaxation rate”), and the longitudinal heat shrinkage rate is adjusted by controlling the relaxation rate. Further, the width of the film in the horizontal direction can be reduced in the process until both ends are cut off, and a desired heat shrinkage rate can be obtained.

  In the above manufacturing method, the sequential biaxial stretching method is described. However, in order to generate voids in the film, the uniaxial stretching method may be employed, and the simultaneous biaxial stretching method is employed. May be.

Hereinafter, the present invention will be described in detail by way of examples. Each characteristic value was measured by the following method.
(1) Average reflectance An integrating sphere was attached to a spectrophotometer (Shimadzu UV-3101PC), and the reflectance when BaSO ₄ white plate was 100% was measured over a wavelength range of 400 to 700 nm, and 2 nm from the obtained chart. The reflectance was read at intervals, and the average reflectance at a wavelength of 400 to 700 nm was calculated. When the reflectance was different between one surface and the other surface, the reflectance was measured using the surface with the higher reflectance as the reflecting surface.

(2) Optical density It measured using the optical density meter TR927 (transmission) by a Macbeth company. An OSRAM lamp 12V / 50W was used as the light source.

(3) Glossiness of film Using “Multi-Gloss 268” manufactured by Minolta, the film was measured according to JIS K7105 with an incident angle and a light receiving angle of 60 °.

(4) Creation of optical duct Using the white film of an Example, the white film of a comparative example, or a reflecting plate, the cylindrical optical duct of 30 cm x 100 cm and length 5m was created. At this time, the reflection surface was arranged on the inner surface of the optical duct. With one end of the light duct as a daylighting part, a light emitting part was provided by cutting out a square shape with a size of 30 cm × 30 cm on the wall surface constituting the lower side of the light duct at a position 4 m from the daylighting part. At this time, the center of the square of the light emitting part was set at a position 4 m from the daylighting part.

(5) Brightness and brightness spots Using a luminometer (Lux-meter ANA-315, manufactured by Tokyo Koden), a 10 cm square area at a position 1 m directly below the light emitting part The illuminance was measured. The average value of illuminance was defined as brightness, and the difference between the maximum value of illuminance and the minimum value of illuminance was defined as brightness spots. The unit is lx.

(6) Apparent specific gravity of the film The film was cut into a 100 × 100 mm square, and a thickness of 10 points was measured with a dial gauge attached thereto, and an average thickness d (μm) was calculated. Moreover, this film was weighed with a direct balance, and the weight w (g) was read to a unit of 10 ⁻⁴ g. The apparent specific gravity was calculated from the average thickness d and the weight w. The apparent specific gravity is w / d × 100.

(7) Stretchability of film Stretchability was evaluated according to the following criteria during film formation.
○: Stable film formation for 1 hour or more ×: Breakage occurs before 1 hour elapses, and stable film formation cannot be performed.

(8) Thickness of each layer of film A sample was cut into a triangle, fixed in an embedded capsule, and then embedded in an epoxy resin. Then, after embedding the embedded sample with a microtome (ULTRACUT-S), a cross section parallel to the longitudinal direction was made into a thin film section having a thickness of 50 nm, and then observed and photographed with a transmission electron microscope at an acceleration voltage of 100 kv. The thickness of each layer was measured and the average thickness was determined.

(9) Glass transition point (Tg) and melting point (Tm) of the resin
Using a differential scanning calorimeter (TA Instruments 2100 DSC), the measurement was performed at a heating rate of 20 m / min.

(10) Average particle size of particles The particle size was measured using a laser scattering particle size distribution analyzer SALD-7000 manufactured by Shimadzu Corporation. Before dispersion, the barium sulfate particle powder was weighed so as to correspond to a 5 wt% slurry concentration, stirred for 10 minutes with a mixer (eg National MXV253 type cooking mixer), and cooled to room temperature. , And supplied to a flow cell type supply device. Then, in the supply device, ultrasonic treatment was performed for 30 seconds for defoaming (the strength of the ultrasonic treatment was 60% from the position showing the MAX value of the knob of the ultrasonic treatment device), and then the measurement was performed. . The 50% volume particle size (D50) was determined from the particle size distribution measurement result, and this was used as the average particle size.

[Example 1]
132 parts by weight of dimethyl terephthalate, 18 parts by weight of dimethyl isophthalate (12 mol% based on the acid component of the polyester), 98 parts by weight of ethylene glycol, 1.0 part by weight of diethylene glycol, 0.05 part by weight of manganese acetate, 0 parts of lithium acetate .012 parts by weight were charged into a rectifying column and a flask equipped with a distillation condenser, and heated to 150 to 235 ° C. with stirring to distill methanol to conduct a transesterification reaction. After the methanol was distilled off, 0.03 part by weight of trimethyl phosphate and 0.04 part by weight of germanium dioxide were added, and the reaction product was transferred to the reactor. Subsequently, while stirring, the pressure in the reactor was gradually reduced to 0.5 mmHg and the temperature was raised to 290 ° C. to carry out a polycondensation reaction. Using this polyester resin for layers A and B, a master batch of barium sulfate was prepared and adjusted to the addition amount shown in Table 1.

Using these raw materials, supply them to two extruders each heated to 270 ° C, and use a two-layer feed block device in which layer A polymer and layer B polymer are A / B in layer A and layer B Then, the sheet was formed into a sheet shape from a die while maintaining the laminated state. Further, an unstretched film obtained by cooling and solidifying the sheet with a cooling drum having a surface temperature of 25 ° C. was heated at the described temperature, stretched in the longitudinal direction (longitudinal direction), and cooled by a roll group at 25 ° C. Subsequently, while holding both ends of the longitudinally stretched film with clips, the film was guided to a tenter and stretched in a direction perpendicular to the longitudinal direction (lateral direction) in an atmosphere heated to 125 ° C. Thereafter, heat setting is performed in the tenter at the temperature shown in the table, the longitudinal direction is relaxed and the width is set in the horizontal direction under the conditions shown in Table 2, and the mixture is cooled to room temperature. The light is a biaxially stretched film having a total thickness of 188 μm. A white film for duct was obtained.
Using this optical duct white film, an optical duct was created and evaluated. The results are shown in Table 2.

[Examples 2 to 10]
Film formation was carried out under the conditions shown in the columns of Examples 2 to 10 in Table 1 to obtain a white film for an optical duct having a total thickness of 188 μm. An optical duct was created using the obtained white film for an optical duct and evaluated. The results are shown in Table 2. Both were excellent in brightness and brightness spots.

[Examples 11 and 12]
Films were formed under the conditions shown in the columns of Examples 11 and 12 in Table 1 to obtain a white film for an optical duct having a total thickness of 188 μm. An optical duct was created using the obtained white film for an optical duct and evaluated. The results are shown in Table 2. Both were excellent in brightness and brightness spots.

[Comparative Examples 1 and 2]
A film was formed under the conditions described in the table to produce a film having a total thickness of 188 μm. An optical duct was created using the obtained film and evaluated. The results are shown in Table 2.

[Comparative Examples 3 to 5]
An optical duct was created using the reflector shown in the table and evaluated. The results are shown in Table 2.
All of the comparative examples were light ducts having poor brightness or large brightness spots.

The white film for optical ducts of the present invention can be suitably used as a reflective material used for a light guide part of an optical duct system.
The white film for an optical duct of the present invention can be used as a light guide part of an optical duct by bending the side to be used as a reflective surface inward, for example, by bending it into a rectangular tube shape with a side of about 50 cm. it can. Furthermore, an optical duct can be created by installing a daylighting unit at one end of the duct and appropriately installing a light emitting unit on the wall surface of the duct.

It is the optical duct created for evaluation in an Example and a comparative example.

Claims (2)

  A white film for a light duct comprising a white film having an average reflectance of 96.0% or more at a wavelength of 400 to 700 nm and used for a light duct.   The white film for an optical duct according to claim 1, wherein the glossiness of the white film is 5 to 100%.

Images