JP2013232406A - White film and lamp unit using the same, liquid crystal display device, and lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lamp unit capable of lessening color change of an LED light source and having high luminance, in a backlight device having the LED light source arranged on its side face.SOLUTION: A lamp unit uses a white film in which a discharged amount of hydrogen sulfide is 20×10mol/g or less when the white film is processed for four hours under a condition of temperature of 80°C and relative humidity of 95% or less, and/or a white film in which a discharged amount of sulfur oxides is 1.0×10mol/g or below when the white film is processed for four hours under a condition of temperature of 80°C and relative humidity of 95% or less.

Description

  The present invention relates to a lamp unit, a liquid crystal display device, and an illumination device using a white film and an LED (Light Emitting Diode) light source.

  In recent years, the use of liquid crystal displays has been dramatically expanded, and liquid crystal televisions for thin screens with a depth of 150 mm or less and large screens of 26 inches or more use LED light sources that can reduce power consumption and increase output. A method is used, and an advantageous method for thinning is adopted in which the LED light source is arranged on the side surface or the front surface. In addition to liquid crystal display devices, LED light sources are used in many fields such as lighting fixtures and lighting signs. Many of the appliances using LED light sources use a reflector to efficiently use light.

In response to the recent demands for increased heat generation and improved blue light extraction efficiency, LEDs have been used as a sealing material in place of epoxy resins that may cause yellowing over time. Silicone resins are more expensive than epoxy resins but are less likely to discolor due to heat. Silicone itself is an effective solution with little discoloration due to heat, but has the disadvantage of high gas permeability. Silicone has few ionic impurities and is excellent in adhesion, so it does not cause corrosion due to moisture, but sulfur and sulfide easily penetrate silicone and react with the silver-plated substrate in the LED to blacken. There is a problem of waking up. For this reason, it has been required that other members used in devices using LED light sources, such as reflectors, diffusers, and prism sheets, do not generate sulfur and sulfide-containing gases depending on the usage environment.
On the other hand, the reflector is required to have more excellent light reflection performance (also simply referred to as “reflectivity”) in order to improve luminance. As a method for making the film exhibit light reflection performance, an incompatible resin is added to the matrix resin and formed into a sheet shape, and in the process of stretching this, the incompatibility of the incompatible resin is used to make the film interior. A method in which a large number of voids are formed and light is reflected using the voids, a method in which white inorganic particles are contained in the film and light is reflected by using particles, and inorganic particles are added to the matrix resin to form a sheet. Stretching to form a large number of voids at the interface between the inorganic particles and the matrix resin, using the voids to reflect light, and adding a foaming agent in the matrix resin, foaming when molded into a sheet or after molding There are known methods such as a method of reflecting light using the generated gap or a method of combining them. For example, since a barium sulfate particle is easy to form a fine space | gap and is excellent also in concealment property, the reflector which made this contain in polyester is used preferably (refer patent documents 1-3).

JP 2000-037835 A JP 2005-125700 A JP 2006-015674 A

In recent years, there has been a trend toward higher integration of LEDs and compaction of the lamp unit itself, and heat generation from the electric circuit system, and the usage environment has become high. For this reason, the influence of the action of water vapor that exists in daily life and the problem that a minute amount of gas such as a gas containing sulfur reacts with the silver-plated substrate in the LED to cause blackening cannot be ignored. That is, it is desired to prevent the deterioration of the sealing material that protects the LED light emitting part under such a severe environment and the deterioration of the substrate, element, or mirror part of the LED light emitting part. Further, in order to effectively use the light generated from the LED light source, it is necessary to use a reflecting plate having high reflection efficiency.
An object of the present invention is to eliminate the above-described problems. That is, it is to provide a white film having high light reflection performance without deteriorating the constituent members of the LED, and to provide a lamp unit and an illumination device with less LED degradation.

(1) A lamp unit including at least an LED light source, a white film containing inorganic particles, and a housing for holding the LED light source and the white film, wherein the white film is an LED in the following LED chip discoloration test. A lamp unit, wherein the ΔL value of the chip is less than 5,
[LED chip discoloration test]
The L value, a value, and b value of the central part of LED chip “NSSW157T” manufactured by Nichia Corporation are measured using a micro-surface spectral color difference meter VSS400 (manufactured by Nippon Denshoku Industries Co., Ltd.), and wet heat treatment The previous L value, a value, and b value are used. The measurement diameter was 0.5 mmφ. Thereafter, 100 g of the LED chip and a white film sample cut to a 10 mm square were weighed and sealed in a glass container with a total capacity of 1000 ml together with a filter paper containing an amount of water calculated to have a relative humidity of 95%. And wet heat treatment at 80 ° C. for 24 hours. After the treatment, the mixture was allowed to cool to room temperature, and the L value, a value, and b value of the central portion of the LED chip taken out from the container were measured to obtain the L value, a value, and b value after the wet heat treatment. From these values, ΔL, Δa, and Δb values were obtained from the following formulas (1) to (3).
ΔL value = (L value before wet heat treatment) − (L value after wet heat treatment) (1)
Δa value = (a value before wet heat treatment) − (a value after wet heat treatment) (2)
Δb value = (b value before wet heat treatment) − (b value after wet heat treatment) (3)
(2) The lamp unit according to (1), wherein the inorganic particles contained in the white film are barium sulfate or titanium oxide,
(3) The lamp unit according to (1) or (2), wherein the amount of hydrogen sulfide discharged when the white film is treated at a temperature of 80 ° C. and a relative humidity of 95% for 4 hours is 20 × 10 ⁻¹² mol / g or less. ,
(4) Any of (1) to (3), wherein the white film has a sulfur oxide emission amount of 1.0 × 10 ⁻⁹ mol / g or less when treated at a temperature of 80 ° C. and a relative humidity of 95% for 4 hours. Lamp unit as described in
(5) A liquid crystal display device using the lamp unit according to any one of (1) to (4),
(6) A lighting device using the lamp unit according to any one of (1) to (4),
(7) A white film containing inorganic particles, wherein the ΔL value of the LED chip in the following LED chip discoloration test is less than 5,
[LED chip discoloration test]
The L value, a value, and b value of the central part of LED chip “NSSW157T” manufactured by Nichia Corporation are measured using a micro-surface spectral color difference meter VSS400 (manufactured by Nippon Denshoku Industries Co., Ltd.), and wet heat treatment The previous L value, a value, and b value are used. Thereafter, 100 g of the LED chip and a white film sample cut to a 10 mm square were weighed and sealed in a glass container with a total capacity of 1000 ml together with a filter paper containing an amount of water calculated to have a relative humidity of 95%. And wet heat treatment at 80 ° C. for 24 hours. After the treatment, the mixture was allowed to cool to room temperature, and the L value, a value, and b value of the central portion of the LED chip taken out from the container were measured to obtain the L value, a value, and b value after the wet heat treatment. From these values, ΔL, Δa, and Δb values were obtained from the following formulas (1) to (3).
ΔL value = (L value before wet heat treatment) − (L value after wet heat treatment) (1)
Δa value = (a value before wet heat treatment) − (a value after wet heat treatment) (2)
Δb value = (b value before wet heat treatment) − (b value after wet heat treatment) (3)
(8) The white film according to (7), wherein the inorganic particles contained in the white film are barium sulfate or titanium oxide,
(9) The amount of hydrogen sulfide discharged when treated for 4 hours at a temperature of 80 ° C. and a relative humidity of 95% measured using 100 g of the white film is 20 × 10 ⁻¹² mol / g or less (7) or (8) A white film as described in
(10) The white film according to any one of (7) to (9), containing 5% by weight or more of barium sulfate particles, containing bubbles in the film, and having a specific gravity of 1.0 or less,
It is.

  According to the present invention, it is possible to provide a white film having a high light reflectance without deteriorating the constituent members of the LED, and to provide a lamp unit that has a long life and a small color change at the time of lighting. Furthermore, it is possible to provide a liquid crystal display device and a lighting device that have a long life and are small in color change and brightness change during lighting.

  As a result of intensive studies on the problem, the present inventors have found that it is effective to use an inorganic particle-containing reflector as a reflector in the effective use of light. The present inventors have found that it has a great influence on the service life and have come to make the present invention.

  In other words, inorganic particles can be prepared from naturally occurring ones or artificially synthesized. Naturally, naturally occurring ones can be synthesized naturally, or even if they are artificially synthesized. Since it is necessary to use many chemicals such as bleaching agents, neutralizing agents, and surfactants, small amounts of impurities such as sulfur and chlorine are inevitably contained. Particularly in industrially produced particles, some impurities still remain in the purification process.

  As a result of intensive studies by the present inventors, it has been found that such impurities, particularly volatile impurities, have an adverse effect on the life of the LED light source and cause an adverse effect such as coloring. Thus, it has been found that a lamp unit having a long life and hardly causing discoloration can be obtained by using a white film having an LED chip ΔL value of less than 5 in the LED chip discoloration test described below.

Hereinafter, the present invention will be described in detail.
The lamp unit of the present invention includes a white film containing at least an LED light source and inorganic particles. An LED light source consumes less power, while a white film containing inorganic particles is excellent in light reflection efficiency and concealment as described later.

The type of the LED light source is not particularly limited, but it is common to adopt a configuration in which a plurality of white LEDs are arranged or an array configuration in which a plurality of R, G, and B single-color LEDs are arranged. This is preferable because of its advantages.
Moreover, the liquid crystal display device and illumination device of the present invention are a liquid crystal display device and illumination device using the lamp unit.

  The white film of the present invention contains inorganic particles. The inorganic particles can be obtained as small-diameter particles, and can be dispersed in a matrix resin, which is advantageous in that the particles can be used efficiently in light reflection. Inorganic particles have high light reflectivity by themselves, or are dispersed in a matrix resin to form a sheet and can be further stretched to reflect light with voids generated between the matrix resin. Although there is no particular limitation, white particles are preferable, and those having a high refractive index are preferable from the viewpoint of light reflection. Examples of the inorganic particles include silica, colloidal silica, calcium carbonate, aluminum silicate, calcium phosphate, alumina, magnesium carbonate, zinc carbonate, titanium oxide, zinc oxide (zinc white), antimony oxide, cerium oxide, zirconium oxide, and tin oxide. , Lanthanum oxide, magnesium oxide, barium carbonate, zinc carbonate, basic lead carbonate (lead white), barium sulfate, calcium sulfate, lead sulfate, zinc sulfide, mica, mica titanium, talc, clay, kaolin, etc. Can be mentioned. Of these, barium sulfate and titanium oxide are preferred. One kind of inorganic particles or two or more kinds of inorganic particles may be used.

  Barium sulfate particles can be easily contained in a large amount in the resin, and fine bubbles can be easily formed between the resin and the resin in the film stretching process, so that more bubbles can be formed and high light reflection performance can be obtained. Is preferable. Moreover, since it is excellent also in concealment property, it is preferable.

  The barium sulfate particles contained in the white film are preferably particles having a secondary particle number average particle size of 0.1 to 2 μm. More preferably, it is 0.4-0.8 micrometer. If a product within the above range is used, the degree of dispersion can be increased, so that it can have an appropriate gap size and excellent reflectivity, and also can be formed into a film without blocking the filter. Excellent and does not affect the stretchability, so that the productivity can be improved.

The content of sulfide ions (S ²⁻ ) in the barium sulfate particles is preferably 5 ppm or less, more preferably 1.6 ppm or less, and most preferably 0.16 ppm or less. By setting the content of sulfide ions in barium sulfate to the above or less, the amount of hydrogen sulfide generated under high temperature and high humidity can be reduced. Sulfide ions in barium sulfate can be achieved by enhancing the cleaning of the particles.

  As a method for producing barium sulfate particles, a method of producing from barium chloride and sulfuric acid is preferable because the content of sulfide is small, but from the viewpoint of obtaining productivity and particles having a small particle size, a method of producing from barium sulfide and sulfuric acid. Is more preferable. The barium sulfate particles are preferably washed sufficiently to remove hydrogen sulfide remaining undissolved in the liquid and unreacted barium sulfide.

  The barium sulfate particles include barium sulfate having a surface coated with an organic layer (Japanese Patent Publication No. 2009-527452), and barium sulfate obtained by treating the particle surface with an organic phosphorus compound having a chelating ability (Japanese Patent Laid-Open No. 9-9 / 1990). The surface treatment may be performed with an organic material as in the case of Japanese Patent No. 156924), but discoloration may occur when performing an aging treatment. Further, by applying a technique for attaching a barium salt of sulfur oxide to the surface of the barium sulfate particles (Japanese Patent Laid-Open No. 2-160619) or a technique for attaching barium carbonate to the surface of the barium sulfate particles (Japanese Patent Laid-Open No. 2-239115). However, since many barium salts other than barium sulfate are water-soluble and toxic, they may be unsuitable for use in the present invention in which aging treatment is performed under high temperature and high humidity conditions. In addition, as for surface modification of barium sulfate, the surface of barium sulfate is coated with at least one of zinc oxide, cerium oxide, and titanium oxide (Japanese Patent Laid-Open No. 10-8028). Although it is possible to apply technology to coat the surface with an inorganic substance such as a metal oxide or metal salt, the light reflection / absorption characteristics and adhesiveness with the resin change, and the light reflection / absorption characteristics of white films and the inclusion of bubbles The rate may not be controllable, which is not preferable.

  Next, the matrix resin for the white film will be described. The matrix resin of the white film is not particularly limited as long as it can disperse inorganic particles and the resin itself is transparent and colorless, but a polyester resin is preferably used from the viewpoint of moldability and productivity. The polyester resin refers to a polymer having an ester bond in the main chain, but a polyester resin having a structure in which a dicarboxylic acid and a diol are polycondensed is preferable. As the dicarboxylic acid component, for example, an aromatic dicarboxylic acid, terephthalic acid, Examples include isophthalic acid, 5-sodium sulfoisophthalic acid, phthalic acid, diphenic acid and ester derivatives thereof, and aliphatic dicarboxylic acids include adipic acid, sebacic acid, dodecadioic acid, eicoic acid, dimer acid and ester derivatives thereof. Examples of the alicyclic dicarboxylic acid include 1,4-cyclohexanedicarboxylic acid and ester derivatives thereof. Examples of the diol component include ethylene glycol, propanediol, butanediol, neopentyl glycol, pentanediol, hexanediol, Kutanjioru, decanediol, cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyethylene glycol, tetramethylene glycol and polyethylene glycol, and the like polyethers such as polytetramethylene glycol may be mentioned as typical examples. These may be used alone or in combination of two or more. Further, trimellitic acid, pyromellitic acid and ester derivatives thereof may be copolymerized in a small amount as long as the film does not affect moldability. Considering the mechanical strength, heat resistance, production cost, etc. of the film, it is preferable to use polyethylene terephthalate as a basic structure. The basic configuration in this case means that 50% by weight or more of the polyester resin is an ethylene terephthalate unit.

  Moreover, as long as the object of the present invention is not impaired, the polyester resin may contain 5% by weight or less of a resin compatible with other polyester resins other than the polyester resin.

  In addition, when the resin constituting the white film is polyester, if necessary, olefinic resins such as polyethylene, polypropylene, polybutene, polymethylpentene, styrene resins, polyacrylate resins, polycarbonate resins, polyacrylonitrile resins, polyphenylenes Incompatible components such as sulfide resins and fluorine resins may be added. These may be homopolymers or copolymers, and two or more incompatible resins may be used in combination. Among these, polyolefins such as polypropylene, polymethylpentene and cycloolefin copolymer having a small critical surface tension are preferable, and polymethylpentene and cycloolefin copolymer are particularly preferably used. Since the incompatible component is dispersed in the polyester and stretched in the film forming process to form bubbles, the light reflection performance of the white film can be improved.

  The white film may utilize the refractive index of the inorganic particles, but it is desirable that the white film reflect the light by containing voids. The void content is preferably 5 to 50%, more preferably 10 to 45%, and still more preferably 15 to 40% in terms of the area ratio in the vertical cross section with respect to the film surface. If the bubble content is less than 5%, the light reflection performance may be insufficient, which is not preferable. On the other hand, if the bubble content is higher than 50%, the strength of the film may decrease, which is not preferable.

  The bubble content is obtained by the following method. Using a microtome, a white film width direction and a longitudinal film cross section were cut out, platinum-palladium was deposited, and then the target area was 2000 times to ~ with a field emission scanning electron microscope “JSM-6700F” manufactured by JEOL Ltd. Observation is performed at an arbitrary magnification of 3000 times to obtain a cross-sectional observation photograph. A transparent film or sheet is overlaid on the obtained cross-sectional photograph, and the part corresponding to the bubbles is painted with oil-based ink or the like. Note that the inorganic particles and incompatible resin present in the bubbles are considered to be part of the bubbles. Next, using an image analyzer (manufactured by Nireco Corporation: “Luzex” (registered trademark) IID), an area ratio (%) of bubbles in the region (to ensure a sufficient observation area) is obtained, The average value in the longitudinal direction is defined as the bubble content. In addition, when the longitudinal direction and the width direction are unclear, the measurement may be performed by cutting a cross section of the sample at two orthogonal surfaces.

  Further, the white film used in the lamp unit of the present invention needs to have an L value difference (ΔL) of less than 5 before and after wet heat treatment in an LED chip discoloration test described later. Further, it is preferably less than 3, more preferably less than 1.5. A ΔL value of 5 or more is not preferable because the luminance of the lamp unit may decrease or the color change may increase. The method of making the ΔL value less than 5 can be achieved by removing volatile impurities from the particles as described later.

  Moreover, the difference (Δa) in the a value before and after the wet heat treatment is preferably less than 5, more preferably less than 3. Further, the difference (Δb) in the b value before and after the wet heat treatment is preferably less than 5, more preferably less than 3. Since the color change of the color tone is small, the color tone change of the entire lamp unit can be reduced. As a method for setting the Δa value and Δb value in the above ranges, a method using a silicone resin as an LED sealing material can be mentioned.

In addition, one form of the white film that can be suitably used in the present invention is that the amount of hydrogen sulfide discharged when the white film is treated at a temperature of 80 ° C. and a relative humidity of 95% for 4 hours is 20 × 10 ⁻¹² mol / g or less. Is more preferably 10 × 10 ⁻¹² mol / g or less, still more preferably 5 × 10 ⁻¹² mol / g or less. By being below the above range, it is possible to suppress changes in light intensity and color tone without deteriorating the constituent members of the LED under the usage environment of the lamp unit. The amount of hydrogen sulfide discharged when the white film is treated at 80 ° C. and 95% RH for 4 hours is more preferably 0.2 × 10 ⁻¹² mol / g or more. To make the range lower than the above range is not preferable because it may be disadvantageous in terms of cost, for example, special treatment is required for the particles. The amount of hydrogen sulfide referred to in the present invention was converted to the amount (g) of white film of hydrogen sulfide amount (mol) discharged from the white film for 4 hours under air adjusted to a temperature of 80 ° C. and a relative humidity of 95%. Value. The method of setting the amount of discharged hydrogen sulfide within the above range can be achieved by reducing the sulfur component contained in the inorganic particles used in the white film. For example, when the inorganic particles are barium sulfate particles, this can be achieved by using barium sulfate having a low sulfide content using the methods described in JP-A-60-137823 and JP-A-2009-7213. . However, when the cost of barium sulfate cannot be increased, when halogen such as barium chloride cannot be contained, when the above production method cannot be used to make the particle size and shape desired, This method can also be achieved. That is, there is a method of aging treatment of barium sulfate particles, a master chip compounded with barium sulfate, or a film containing barium sulfate. In order to achieve a sufficient reflectance, it is preferable to subject the barium sulfate particles to an aging treatment under high temperature and high humidity. As conditions for the aging treatment, 50 ° C. or higher, more preferably 60 ° C. or higher, more preferably 70 ° C. or higher, relative humidity (hereinafter also referred to as RH) 70% or higher, more preferably 80% RH or higher, more preferably 90% RH or more, and the aging period is 12 hours or more, more preferably 24 hours or more, and further preferably 1 week or more. It is particularly effective to make the humidity high. If the temperature, humidity and short time are lower than this, hydrogen sulfide or sulfur oxide may remain, which is not preferable. Moreover, since the aging time may be disadvantageous in terms of cost, the aging period is preferably within 2 weeks. Further, in another embodiment of the white film of the present invention, the amount of sulfur oxide discharged when the white film is treated at a temperature of 80 ° C. and a relative humidity of 95% for 4 hours is 1.0 × 10 ⁻⁹ mol / g or less. Preferably, it is 0.5 × 10 ⁻⁹ mol / g or less, more preferably 0.25 × 10 ⁻⁹ mol / g or less. By being less than the said range, a light intensity change and a color tone change can be suppressed, without degrading the structural member of LED. Moreover, it is more preferable that the discharge amount of sulfur oxide when the white film is processed at a temperature of 80 ° C. and 95% RH for 4 hours is 0.01 × 10 ⁻⁹ mol / g or more. In order to make the range lower than the above range, it may be disadvantageous in terms of cost. In the present invention, sulfur oxide refers to sulfur monoxide and sulfur dioxide. The amount of sulfur oxide discharged refers to a value converted per white film amount (g) of sulfur oxide amount (mol) discharged from the white film for 4 hours under air adjusted to a temperature of 80 ° C. and a relative humidity of 95%. As a method of setting the amount of sulfur oxide to be discharged within the above range, a method similar to the above method relating to hydrogen sulfide can be used.

[Configuration of white film]
The white film of the present invention may be a film composed of a single layer or a film composed of a plurality of layers, but has a structure in which the surface layer (A) is laminated on at least one of the core layers (B) containing bubbles inside. preferable. High rigidity may be obtained by laminating the surface layer (A) on at least one of the polyester layers (B). The white film of the present invention may be composed of any number of layers. For example, a two-layer structure of A / B, a three-layer structure of A / B / A, or a structure of four or more layers may be used. A layer structure is preferred. Moreover, it is preferable that the surface layer (A) and the core layer (B) are stretched in a biaxial direction after being laminated at once in a film production line by a coextrusion method. Furthermore, you may perform re-longitudinal stretching and / or re-lateral stretching as needed.

  In addition, in order to impart easy adhesion and antistatic properties to the white film of the present invention, various coating liquids are applied using known techniques, and bead coating is used to impart surface slipperiness. A layer may be provided, or a hard coat layer or the like may be provided to improve impact resistance, and an appropriate additive in an amount that does not impair the effects of the present invention, if necessary, for example, a heat stabilizer Further, an oxidation resistance stabilizer, an ultraviolet absorber, an ultraviolet stabilizer, an organic lubricant, an organic fine particle, a filler, a nucleating agent, a dye, a dispersant, a coupling agent and the like may be blended.

  As for the thickness of the white film of this invention, 100-450 micrometers is preferable. The main light reflection performance is expressed by the bubbles in the film, and when the thickness of the film is less than 100 μm, both the reflectance and the rigidity may be inferior. Moreover, when the thickness of a film exceeds 450 micrometers, it may be inferior in terms of film forming stability and cost.

  The relative reflectance at a wavelength of 560 nm of at least one surface of the white film measured by the method described later is preferably 95% or more, more preferably 100% or more. If it is less than 95%, sufficient reflectance may not be obtained when it is used as a backlight of a liquid crystal display or a reflector of a lighting fixture. Examples of a method for bringing the relative reflectance into the above range include a method of containing 25% or more of barium sulfate particles and a thickness of the white film of 200 μm or more. However, the method is not limited to this, and a known method can be used.

  Hereinafter, as an example of the method for producing the white film of the present invention, a method for producing a white film using barium sulfate particles will be described as an example, but the present invention is not construed as being limited thereto.

  As a method for producing barium sulfate particles, a method of producing from barium chloride and sulfuric acid is preferable because the content of sulfide is small, but from the viewpoint of obtaining productivity and particles having a small particle size, a method of producing from barium sulfide and sulfuric acid. Is more preferable. The barium sulfate particles are preferably washed sufficiently to remove hydrogen sulfide remaining undissolved in the liquid and unreacted barium sulfide.

  In order to remove volatile impurities economically and efficiently, the barium sulfate particles are aged in an environment of temperature 50 ° C. or higher and humidity 70% RH for 12 hours or more, and then in an environment of temperature 80 ° C. to 100 ° C. and humidity 30% RH or lower. It is extremely effective to dry for 12 hours or more. Further, it is preferable to dry the polymer as necessary.

  The obtained barium sulfate particles and polymer are put into a single or twin screw extruder and melt kneaded, and the melt kneaded polymer is introduced into a die. The unstretched sheet extruded from the die is cooled and solidified by a casting drum to form an unstretched film.

  This unstretched film is heated to a temperature equal to or higher than the glass transition temperature (Tg) of the polymer by roll heating and, if necessary, infrared heating, and stretched in the longitudinal direction (hereinafter referred to as the longitudinal direction) to obtain a longitudinally stretched film. This stretching is performed by utilizing the difference in peripheral speed between two or more rolls. The ratio of longitudinal stretching is preferably 2 to 6 times, more preferably 3 to 4 times, although it depends on the required characteristics of the application. If it is less than 2 times, the reflectance may be low, and if it exceeds 6 times, breakage may easily occur during film formation. The film after longitudinal stretching is then subjected to stretching, heat setting, and thermal relaxation in the direction perpendicular to the longitudinal direction (hereinafter referred to as the transverse direction) to form a biaxially oriented film. While running. At this time, preheating and stretching temperature for transverse stretching are preferably performed at a glass transition temperature (Tg) or higher (Tg + 20 ° C.) of the polymer. The transverse stretching ratio is preferably 2.5 to 6 times, more preferably 3 to 4 times, although it depends on the required characteristics of the application. If it is less than 2.5 times, the reflectance may be low. If it exceeds 6 times, breakage may easily occur during film formation. In order to complete the crystal orientation of the obtained biaxially stretched laminated film and to give flatness and dimensional stability, heat treatment is continued in the tenter at a temperature of 180 to 230 ° C. for 1 to 60 seconds, and uniform. After cooling slowly, it is cooled to room temperature and wound on a roll.

  In addition, the case where the film is stretched by the sequential biaxial stretching method has been described in detail here, but the white film of the present invention may be stretched by any of the sequential biaxial stretching method and the simultaneous biaxial stretching method. If necessary, after the biaxial stretching, re-longitudinal stretching and / or re-lateral stretching may be performed.

The lamp unit of the present invention can be used as a planar light emitting device in a liquid crystal display device. The planar light emitting device may be either an edge type or a direct type, but the edge type planar light emitting device is preferable from the viewpoint of thinning. An edge-type planar light emitting device used for a liquid crystal display device is provided on a light guide plate, a linear light emitting unit including a plurality of LED chips provided on a light incident end surface of the light guide plate, and a back surface of the light guide plate. It is comprised by the reflecting plate which consists of a white film, and the case which covers them. In addition, an optical film such as a diffusion film or a prism sheet may be provided in the case as necessary.
The lamp unit of the present invention can also be used as illumination. Although it does not specifically limit as a structure of LED lighting, It consists of a LED chip, a white film, and a case, and may be comprised from a light guide, a reflective sheet, a diffusion sheet, and a lens by the form.

  Hereinafter, the present invention will be described in detail by way of examples. Each characteristic value was measured by the following method.

(1) After freezing the thickness film of each layer, a cross section was cut out along the longitudinal direction and the width direction with a microtome (ULTRACUT-S), and the cross section was cut into a field emission scanning electron microscope “JSM-” manufactured by JEOL Ltd. The length in the thickness direction of each polyester layer was measured from a cross-sectional photograph taken by magnifying 4000 times using 6700F ″, and the thickness of each layer was determined by calculating back from the magnification. In determining the thickness of each polyester layer, a total of 50 cross-sectional photographs arbitrarily selected from different measurement visual fields in the cut surface cut out in the longitudinal direction and the width direction were used, and the average value was calculated. . In addition, when the longitudinal direction and the width direction are unknown, a cut surface cut in two mutually perpendicular directions is measured.

(2) A state in which a φ60 integrating sphere 130-0632 (Hitachi Ltd.) (inner surface made of barium sulfate) and a 10 ° inclined spacer are attached to a relative reflectance spectrophotometer U-3410 (Hitachi Ltd.) The light reflectance at 560 nm was determined. The light reflectance was measured on both the front and back surfaces, and the higher value was taken as the relative reflectance of the film. A part number 210-0740 (aluminum oxide) manufactured by Hitachi Instrument Service Co., Ltd. was used as the standard white plate.

(3) Sulfur oxide emissions and hydrogen sulfide emissions when treated for 4 hours at 80 ° C and 95% relative humidity (under high temperature and high humidity) Samples are left for 48 hours in a room with a room temperature of 23 ° C and a humidity of 65% RH The moisture content in the film is adjusted. 100 g of a sample was weighed in a room with a room temperature of 23 ° C. and a humidity of 65% RH, and placed in a eggplant flask having a total volume of 650 ml together with a filter paper soaked with water in order to adjust the relative humidity at 80 ° C. to 95%. Heated at 80 ° C. for 4 hours. An appropriate amount of water was used according to the temperature, humidity, and sample volume. After heating, the mixture was allowed to cool to room temperature, and the gas concentration in the eggplant flask was measured using a gas detector tube. The measurable range was 0.05 ppm or more. From the measured gas concentration Q (volume fraction) and the volume V (L) of the space obtained by subtracting the sample volume in the flask, the gas discharge amount R (mol / g) per 1 g of the sample was obtained using the following formula. . R = V × Q / (24.3 × 100). The gas detector tube used was a gas detector tube manufactured by Gastec Corporation (objects: hydrogen sulfide and sulfur dioxide). Sulfur monoxide was combined with oxygen in the flask to form sulfur dioxide, and the detected amount calculated from the sulfur dioxide gas detector tube was defined as the amount of sulfur oxide discharged by combining the generated sulfur monoxide and sulfur dioxide.

(5) Specific gravity A sample obtained by cutting a white film into a size of 50 mm × 60 mm was subjected to JIS K7112 Method A (underwater substitution method) using a high-precision electronic hydrometer SD-120L (Mirage Trading Co., Ltd.). ). The measurement was performed under conditions of a temperature of 23 ° C. and a relative humidity of 65%.

(6) Bubble content rate Using a microtome, the cross section of the white film in the width direction and the longitudinal direction was cut out, and after platinum-palladium was deposited, the field emission scanning electron microscope “JSM-6700F” manufactured by JEOL Ltd. was used. The target region was observed at an arbitrary magnification between 2000 times and 3000 times to obtain a cross-sectional observation photograph. A transparent film or sheet was superimposed on the obtained cross-sectional photograph, and the portion corresponding to the bubbles was painted with oil-based ink or the like. Note that the inorganic particles and incompatible resin present in the bubbles are considered to be part of the bubbles. Next, using an image analyzer (manufactured by Nireco Co., Ltd .: “Luzex” (registered trademark) IID), the area ratio (%) of the bubbles in the region was determined, and the area ratio of the bubbles determined for the five visual fields in the longitudinal direction The average value of the bubble area ratios obtained for the five visual fields in the width direction was defined as the bubble content. In addition, when the longitudinal direction and the width direction are unclear, the measurement may be performed by cutting a cross section of the sample at two orthogonal surfaces.

(7) LED chip discoloration test The L value, a value, and b value of the central part of LED chip “NSSW157T” manufactured by Nichia Corporation are measured, and set as the L value, a value, and b value before wet heat treatment. . Thereafter, 100 g of a sample obtained by cutting the LED chip and a white film formed into a 10 mm square was weighed, and put into a glass container having a total volume of 1000 ml together with a filter paper containing an amount of water calculated so that the relative humidity was 95%. The mixture was sealed and wet-heat treated at 80 ° C. for 24 hours. After the treatment, the mixture was allowed to cool to room temperature, and the L value, a value, and b value of the central portion of the LED chip taken out from the container were measured to obtain the L value, a value, and b value after the wet heat treatment. From these values, ΔL, Δa, and Δb values were obtained from the following formulas (1) to (3).

ΔL value = (L value before wet heat treatment) − (L value after wet heat treatment) (1)
Δa value = (a value before wet heat treatment) − (a value after wet heat treatment) (2)
Δb value = (b value before wet heat treatment) − (b value after wet heat treatment) (3)
(8) L, a, b value measurement method Using a micro surface spectral color difference meter VSS400 (manufactured by Nippon Denshoku Industries Co., Ltd.), the light source D65 and the measurement diameter of 0.5 mmφ were set to JIS Z-8722 (2000). The color difference L value, a value, and b value according to JIS K-7105 (1981) were determined under the same optical conditions.

[Raw materials]
(1) Polyester resin (a)
Using terephthalic acid as the acid component and ethylene glycol as the glycol component, adding to the polyester pellets that can obtain antimony trioxide (polymerization catalyst) to 300 ppm in terms of antimony atoms, performing a polycondensation reaction, limiting viscosity Polyethylene terephthalate pellets (PET) having 0.63 dl / g and carboxyl end group amount of 40 equivalents / ton were obtained. When the heat of crystal fusion was measured using a differential thermal analyzer, it was 4.186 J / g or more, which is a crystalline polyester resin. It was 250 degreeC when melting | fusing point Tm of this resin was measured.

(2) Copolyester resin (b)
As other additives, isophthalic acid copolymerized PET was used. PET obtained by copolymerizing 17.5 mol% of isophthalic acid as a dicarboxylic acid component. When the heat of crystal fusion was measured using a differential thermal analyzer, it was less than 4.186 J / g, indicating amorphousness.

(3) Inorganic particles (c)
7L of 110g / L sulfuric acid aqueous solution and 120L / 120g / L barium sulfide aqueous solution 12L were stirred in a reaction bath at 50 ° C, hydrogen sulfide was removed by suction with a blower, and the pH was adjusted to 7 with sodium hydroxide aqueous solution. did. The obtained slurry was filtered with a filter, and the barium sulfate was further washed with water and dried with a spray dryer to obtain a barium sulfate powder having a number average particle size of 0.5 μm.

Example 1
The inorganic particles (c) are subjected to a wet heat treatment at 80 ° C. and a relative humidity of 95% for the time shown in Table 1, and then the raw materials having the composition shown in Table 1 are vacuum dried at a temperature of 180 ° C. for 3 hours and then supplied to the extruder. Then, after melt extrusion at a temperature of 280 ° C., the mixture was filtered through a 30 μm cut filter and then introduced into a T-die composite die.

  Next, in the T-die composite die, the surface layer (A) is merged so as to be laminated (A / B / A) on both surface layers of the core layer (B), and then co-extruded into a sheet to form a molten laminated sheet. The melt-laminated sheet was closely cooled and solidified by an electrostatic application method on a drum maintained at a surface temperature of 25 ° C. to obtain an unstretched laminated film. Subsequently, the unstretched laminated film was preheated with a roll group heated to a temperature of 70 ° C., and then stretched at a magnification shown in Table 1 in the longitudinal direction (longitudinal direction) while being irradiated from both sides with an infrared heater. A uniaxially stretched film was obtained by cooling with a roll group at a temperature of ° C. Then, while holding the both ends of the uniaxially stretched film with clips, lead to a preheating zone of 110 ° C in the tenter and dry 5% slightly stretched, and then continuously in the heating zone of 120 ° C in the direction perpendicular to the longitudinal direction (horizontal Direction) at a magnification of Table 1. Subsequently, heat treatment at the temperature shown in Table 1 was performed in the heat treatment zone in the tenter, and after uniform cooling, the film was wound on a roll, and the thickness of the surface layer (A) and the core layer (B) having air bubbles inside was increased. A white film of A / B / A3 layer of 5/290/5 (μm) was obtained.

  The characteristics of the white film thus obtained are as shown in Table 1, and have a high relative reflectance and a small ΔL value.

(Examples 2, 3, 5-9)
In the same manner as in Example 1, using the raw materials and conditions shown in Table 1, the thickness of the surface layer (A) and the core layer (B) having bubbles inside was 5/290/5 (μm) A / A white laminated polyester film of B / A3 layer was obtained. The characteristics of the obtained white film are as shown in Table 1, and the ΔL value in the LED chip discoloration test was also small.

Example 4
The raw materials having the composition shown in Table 1 were vacuum-dried at a temperature of 180 ° C. for 3 hours and then supplied to the extruder. Thereafter, in the same manner as in Example 1, the surface layer (A) and the core layer (B) having bubbles inside The laminated polyester film of A / B / A3 layer whose thickness is 5/290/5 (micrometer) was obtained. This film was wet-heated at 80 ° C. and a relative humidity of 95% for the time shown in Table 1 to obtain a white film. The characteristics of the obtained white film were as shown in Table 1, and the relative reflectance was high and the ΔL value was also small.

(Comparative Example 1)
In the same manner as in Example 1, using the raw materials and conditions shown in Table 1, the thickness of the surface layer (A) and the core layer (B) having bubbles inside was 5/290/5 (μm) A / A white laminated polyester film of B / A3 layer was obtained. The characteristics of the obtained white film are as shown in Table 1. The relative reflectance showed a high value but a large ΔL value.

(Comparative Example 2)
The inorganic particles (c) are wet-heat treated at a temperature of 80 ° C. and a humidity of 95% RH for the time shown in Table 1, and then the raw materials having the composition shown in Table 1 are vacuum-dried at a temperature of 180 ° C. for 3 hours and then supplied to the extruder. Then, after melt extrusion at a temperature of 280 ° C., the mixture was filtered through a 30 μm cut filter and then introduced into a T-die composite die. Thereafter, in the same manner as in Example 1, a laminated polyester film having an A / B / A3 layer in which the thickness of the surface layer (A) and the core layer (B) having bubbles inside was 5/290/5 (μm) was obtained. Obtained.
The characteristics of the white film thus obtained are as shown in Table 1. The relative reflectance was high, but the ΔL value in the LED chip discoloration test was large.

(Comparative Example 3)
The inorganic particles (c) are heat-treated at a temperature of 80 ° C. in the drying atmosphere for the time shown in Table 1, and then the raw materials having the composition shown in Table 1 are vacuum-dried at a temperature of 180 ° C. for 3 hours and then supplied to the extruder. After melt extrusion at a temperature of 280 ° C., the mixture was filtered through a 30 μm cut filter and then introduced into a T-die composite die. Thereafter, in the same manner as in Example 1, a laminated polyester film having an A / B / A3 layer in which the thickness of the surface layer (A) and the core layer (B) having bubbles inside was 5/290/5 (μm) was obtained. Obtained.
The characteristics of the white film thus obtained are as shown in Table 1. The relative reflectance was high, but the ΔL value in the LED chip discoloration test was large.

(Example 10)
The reflective film of the backlight of the 32-inch television (KDL-32EX550) manufactured by Sony Corporation was removed, and the white film of Example 1 was installed instead, and the front luminance was measured. Further, it was left in a constant temperature and humidity chamber at a temperature of 80 ° C. and a humidity of 95% RH for 24 hours with the TV turned on, and after taking out, it was cooled to room temperature and its front luminance was measured. The front luminance was measured by using a luminance meter (Chroma luminance meter BM-7 / FAST (Topcon Co., Ltd.)) and measuring the luminance and color tone at a measurement distance of 500 mm from the front of the center of the backlight. As a result of calculating the luminance and color tone change rate before and after the constant temperature and humidity treatment, the luminance and color tone change rate was 100%, and there was no change.
Luminance change rate = (Brightness of backlight after constant temperature and humidity treatment) / (Brightness of backlight before constant temperature and humidity treatment) × 100 (%)
Color tone change rate = (color tone of backlight after constant temperature and humidity treatment (x value)) / (color tone of backlight before constant temperature and humidity treatment (x value)) × 100 (%).

(Comparative Example 4)
Similarly to Example 10, the white film of Comparative Example 1 was incorporated in the backlight, and the luminance and color tone change rate before and after the constant temperature and humidity treatment were calculated in the same manner. As a result, the luminance change rate was 92%, the color tone change rate was 103%, and the change was large.

(Example 11)
A total of nine LEDs were arranged at intervals of 100 mm each in three rows and three rows on the inner bottom of a 300 mm × 300 mm square of a case of width 300 mm height 300 mm thickness 100 mm. A power supply device was attached so that the light emission voltage of each LED was 3.5 V and the current was 300 mA, and the white film of Example 1 in which the LED portion was hollowed was attached to the bottom surface. Moreover, the white film of Example 1 was affixed also to 4 side surfaces inside 300 mm x 100 mm. Moreover, the 300 mm x 300 mm square upper surface of the case was made into the opening part, and the illuminating device which installed the diffuser plate there was created. As a result of measuring the change rate of the front luminance and the color tone in the same manner as in Example 10, the luminance and color tone change rate was 100%, and there was no change.

  It can be suitably used as a backlight unit for LED lighting or liquid crystal display devices.

Claims (10)

At least a lamp unit including an LED light source, a white film containing inorganic particles, and a housing for holding the LED light source and the white film, wherein the white film is a ΔL of the LED chip in the LED chip discoloration test described below. A lamp unit having a value of less than 5.
[LED chip discoloration test]
The L value, a value, and b value of the central part of LED chip “NSSW157T” manufactured by Nichia Corporation are measured using a micro-surface spectral color difference meter VSS400 (manufactured by Nippon Denshoku Industries Co., Ltd.), and wet heat treatment The previous L value, a value, and b value are used. The measurement diameter was 0.5 mmφ. Thereafter, 100 g of the LED chip and a white film sample cut to a 10 mm square were weighed and sealed in a glass container with a total capacity of 1000 ml together with a filter paper containing an amount of water calculated to have a relative humidity of 95%. And wet heat treatment at 80 ° C. for 24 hours. After the treatment, the mixture was allowed to cool to room temperature, and the L value, a value, and b value of the central portion of the LED chip taken out from the container were measured to obtain the L value, a value, and b value after the wet heat treatment. From these values, ΔL, Δa, and Δb values were obtained from the following formulas (1) to (3).
ΔL value = (L value before wet heat treatment) − (L value after wet heat treatment) (1)
Δa value = (a value before wet heat treatment) − (a value after wet heat treatment) (2)
Δb value = (b value before wet heat treatment) − (b value after wet heat treatment) (3) The lamp unit according to claim 1, wherein the inorganic particles contained in the white film are barium sulfate or titanium oxide. The lamp unit according to claim 1 or 2, wherein the amount of hydrogen sulfide discharged when the white film is treated at a temperature of 80 ° C and a relative humidity of 95% for 4 hours is 20 x 10 ^-12 mol / g or less. The lamp according to any one of claims 1 to 3, comprising a white film having a sulfur oxide emission amount of 1.0 x 10 ^-9 mol / g or less when treated at a temperature of 80 ° C and a relative humidity of 95% for 4 hours. unit. A liquid crystal display device using the lamp unit according to claim 1. The illuminating device using the lamp unit in any one of Claims 1-4. A white film containing inorganic particles, wherein the LED chip has a ΔL value of less than 5 in the following LED chip discoloration test.
[LED chip discoloration test]
The L value, a value, and b value of the central part of LED chip “NSSW157T” manufactured by Nichia Corporation are measured using a micro-surface spectral color difference meter VSS400 (manufactured by Nippon Denshoku Industries Co., Ltd.), and wet heat treatment The previous L value, a value, and b value are used. Thereafter, 100 g of the LED chip and a white film sample cut to a 10 mm square were weighed and sealed in a glass container with a total capacity of 1000 ml together with a filter paper containing an amount of water calculated to have a relative humidity of 95%. And wet heat treatment at 80 ° C. for 24 hours. After the treatment, the mixture was allowed to cool to room temperature, and the L value, a value, and b value of the central portion of the LED chip taken out from the container were measured to obtain the L value, a value, and b value after the wet heat treatment. From these values, ΔL, Δa, and Δb values were obtained from the following formulas (1) to (3).
ΔL value = (L value before wet heat treatment) − (L value after wet heat treatment) (1)
Δa value = (a value before wet heat treatment) − (a value after wet heat treatment) (2)
Δb value = (b value before wet heat treatment) − (b value after wet heat treatment) (3) The white film according to claim 7, wherein the inorganic particles contained in the white film are barium sulfate or titanium oxide. The white film according to claim 7 or 8, wherein a hydrogen sulfide discharge amount is 20 × 10 ^-12 mol / g or less when treated with 100 g of the white film at a temperature of 80 ° C. and a relative humidity of 95% for 4 hours. . The white film according to any one of claims 7 to 9, comprising 5% by weight or more of barium sulfate particles, containing bubbles in the film, and having a specific gravity of 1.0 or less.