JP4750405B2 - Aliphatic polyester resin reflective film and reflector - Google Patents

Description

  The present invention relates to an aliphatic polyester-based resin reflection film and a reflection plate including the reflection film, and more particularly to a reflection film used for a reflection plate of a liquid crystal display device, a lighting fixture, a lighting signboard, and the like.

  In recent years, reflective films have been used in fields such as reflectors for liquid crystal display devices, projection screens and planar light source members, reflectors for luminaires, and reflectors for lighting signs. For example, reflecting plates for liquid crystal displays, in order to improve the performance of the backlight unit by supplying as much light as possible to the liquid crystal due to the demand for larger screens and advanced display performance, the reflective performance of the reflective unit is high. There is a need for films.

  In addition, as a display device such as a notebook computer, a liquid crystal display device including a backlight unit and a liquid crystal display element that can be thinned and easily view an image is used. For such a backlight unit, an edge light system is often used in which a linear light source such as a fluorescent tube is provided at one end of a light-transmitting light guide plate. In many of the edge light systems, one surface of the light guide plate is partially covered with a light diffusing substance, and the entire surface is further covered with a reflective material to constitute a surface light source. Such a reflective material is required to have high reflection performance.

  As a reflective film, a white sheet (for example, see Patent Document 1) formed by adding titanium oxide to an aromatic polyester resin is known, but it does not have high light reflectivity as required. It was. In addition, there is one in which fine voids are formed in a sheet by stretching a sheet formed by adding a filler to an aromatic polyester resin, and light scattering reflection is caused (for example, see Patent Document 2). However, it did not have high light reflectivity as required. Furthermore, since the aromatic ring contained in the molecular chain of the aromatic polyester resin forming these absorbs ultraviolet rays, the film deteriorates and yellows due to ultraviolet rays emitted from a light source such as a liquid crystal display device, and the reflection film There was a drawback that the light reflectivity was lowered.

  In recent years, a reflective film subjected to a bending process or the like is sometimes used by being incorporated in a liquid crystal display device. In this case, the reflective film is required to have good shape-retaining properties showing the property that the shape when folded can be retained. However, the conventional reflective film has a drawback of poor shape retention.

JP 2002-138150 A JP-A-4-239540

  The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to have excellent light reflectivity, and yellowing with use or light reflectivity may decrease with use. The object of the present invention is to provide a reflective film that is excellent in shape retention.

  The aliphatic polyester-based resin reflective film of the present invention is a reflective film formed from a resin composition containing an aliphatic polyester-based resin and a fine powder filler, and the yellowness (YI value) of the reflective film is 3 Less than .6.

  Here, the fine powder filler may be at least one selected from the group consisting of calcium carbonate, barium sulfate, titanium oxide, and zinc oxide.

In the present invention, the titanium oxide preferably has a vanadium content of 5 ppm or less.
The surface of the titanium oxide is preferably coated with at least one inert inorganic oxide selected from the group consisting of silica, alumina, and zirconia.

  Content of the said fine powder filler can be 10 mass% or more and 60 mass% or less in the said resin composition.

In the present invention, the aliphatic polyester resin may have a refractive index of less than 1.52.
The aliphatic polyester resin is preferably a lactic acid polymer.
The aliphatic polyester resin may have a yellowness (YI value) of 20 or less.

  The aliphatic polyester-based resin reflective film of the present invention can have voids so that the void ratio inside the film is 50% or less.

  In the present invention, a film formed by melt-forming a resin composition containing an aliphatic polyester resin and the fine powder filler can be stretched 1.1 times or more in at least one uniaxial direction.

Moreover, it is preferable that the reflectance of the film surface with respect to the light of wavelength 550nm is 95% or more.

The reflecting plate of the present invention is characterized by including any of the above aliphatic polyester resin reflecting films.

  According to the present invention, it is possible to obtain a reflective film that has high light reflectivity, does not deteriorate with time, and has excellent shape retention. In addition, by coating the reflective film of the present invention on a metal plate or resin plate, an excellent reflective plate used for liquid crystal display devices, lighting fixtures, lighting signs, etc., which is well balanced with respect to characteristics such as light reflectivity, etc. Obtainable.

BEST MODE FOR CARRYING OUT THE INVENTION

  The present invention will be described in detail below. In the present invention, even when referred to as “film”, “sheet” is included, and even when referred to as “sheet”, “film” is included.

  The aliphatic polyester-based resin reflective film of the present invention is formed from a resin composition containing an aliphatic polyester-based resin and a fine powder filler as main components. However, this aliphatic polyester-based resin reflective film has a yellowness (YI value) of less than 3.6 and preferably less than 3.5. If the yellowness is less than 3.6, the liquid crystal display or the like in which this reflective film is incorporated has good color without being yellowish.

  In the present invention, the yellowness (YI value) of the film may be adjusted by any method as long as it is less than 3.6. However, the yellowness of the film is, for example, a base for forming an aliphatic polyester resin reflective film. It is considered that it varies depending on the type of resin, impurities contained in the film, and the type and amount of metal. In the present invention, the yellowness (YI value) of the base resin is preferably 20 or less. If a reflective film is formed using such a base resin, it becomes easy to make the yellowness of a reflective film less than 3.6.

  The yellowness (YI value) depends on the measurement method (measurement method). Therefore, it is possible to formally reduce the yellowness (YI value) by reducing the thickness of the film, but the thickness of the film If the thickness is made thinner, the reflectance generally decreases. In the present invention, even if the film has the same thickness without reducing the thickness of the film, by controlling the type and impurities of the base resin to lower the yellowness (YI value), the color is improved. Thus, the reflectance can be improved.

  The base resin constituting the reflective film of the present invention preferably has a refractive index (n) of less than 1.52. In the present invention, an aliphatic polyester resin having a refractive index (n) of less than 1.52 is used. It is preferable to use it.

  A reflective film containing a fine powder filler in the film exhibits light reflectivity by utilizing refractive scattering at the interface between the base resin and the fine powder filler. This refractive scattering effect increases as the difference in refractive index between the base resin and the fine powder filler increases. Therefore, as the base resin, it is preferable to use a resin having a small refractive index so that the refractive index difference from the fine powder filler is large. Therefore, the aromatic resin containing an aromatic ring and having a refractive index of about 1.55 or more. It is preferable to use an aliphatic polyester having a refractive index of less than 1.52, rather than an aliphatic polyester, and among the aliphatic polyesters, it is preferable to use a lactic acid polymer having a low refractive index (refractive index of less than 1.46). .

  The aliphatic polyester-based resin does not absorb ultraviolet rays because it does not contain an aromatic ring in the molecular chain. Therefore, since the reflective film is not deteriorated or yellowed by being exposed to ultraviolet light or by ultraviolet light emitted from a light source such as a liquid crystal display device, the reflectance of the film does not decrease.

  As the aliphatic polyester resin, those chemically synthesized, those fermented and synthesized by microorganisms, and mixtures thereof can be used. Chemically synthesized aliphatic polyester resins include poly-ε-caprolactam obtained by ring-opening polymerization of lactone, polyethylene adipate obtained by polymerizing dibasic acid and diol, polyethylene azelate, polytetramethylene succinate. Nate, cyclohexanedicarboxylic acid / cyclohexanedimethanol condensation polymer, polylactic acid obtained by polymerizing hydroxycarboxylic acid, polyglycol, etc., and a part of the ester bond of the above aliphatic polyester, for example, 50% of the ester bond Examples include aliphatic polyesters in which the following are replaced with amide bonds, ether bonds, urethane bonds, and the like. Examples of the aliphatic polyester resin fermented and synthesized by microorganisms include polyhydroxybutyrate, a copolymer of hydroxybutyrate and hydroxyvalerate, and the like.

  In the present invention, the lactic acid polymer refers to a homopolymer of D-lactic acid or L-lactic acid or a copolymer thereof, and specifically, poly (D-lactic acid) whose structural unit is D-lactic acid. And poly (L-lactic acid) whose structural unit is L-lactic acid, and poly (DL-lactic acid) which is a copolymer of L-lactic acid and D-lactic acid, and a mixture thereof.

  The lactic acid polymer can be produced by a known method such as a condensation polymerization method or a ring-opening polymerization method. For example, in the condensation polymerization method, D-lactic acid, L-lactic acid, or a mixture thereof can be directly subjected to dehydration condensation polymerization to obtain a lactic acid polymer having an arbitrary composition. Further, in the ring-opening polymerization method, lactide, which is a cyclic dimer of lactic acid, is subjected to ring-opening polymerization in the presence of a predetermined catalyst while using a polymerization regulator or the like as necessary, and lactic acid having an arbitrary composition. A polymer can be obtained. The lactide includes L-lactide, which is a dimer of L-lactic acid, D-lactide, which is a dimer of D-lactic acid, and DL-lactide, which is a dimer of D-lactic acid and L-lactic acid, By mixing and polymerizing these as necessary, a lactic acid polymer having an arbitrary composition and crystallinity can be obtained.

  In the lactic acid polymer used in the present invention, the constituent ratio of D-lactic acid and L-lactic acid is D-lactic acid: L-lactic acid = 100: 0 to 85:15, or D-lactic acid: L- Lactic acid is preferably 0: 100 to 15:85, more preferably D-lactic acid: L-lactic acid = 99.5: 0.5 to 95: 5, or D-lactic acid: L-lactic acid = 0. .5: 99.5-5: 95.

  A lactic acid polymer having a composition ratio of D-lactic acid and L-lactic acid of 100: 0 or 0: 100 exhibits very high crystallinity, has a high melting point, and tends to be excellent in heat resistance and mechanical properties. That is, when the film is stretched or heat-treated, the resin is crystallized to improve heat resistance and mechanical properties, which is preferable.

  On the other hand, a lactic acid-based polymer composed of D-lactic acid and L-lactic acid is preferable because flexibility is imparted and film forming stability and stretching stability are improved. Therefore, considering the balance between the heat resistance of the resulting reflective film, molding stability, and stretching stability, the lactic acid-based polymer used in the present invention has a component ratio of D-lactic acid and L-lactic acid of D -Lactic acid: L-lactic acid = 99.5: 0.5 to 95: 5 or D-lactic acid: L-lactic acid = 0.5: 99.5 to 5:95 is more preferable.

  A lactic acid-type polymer mixes L-lactic acid and D-lactic acid, and produces | generates three types of dimers, LL-lactide, DL-lactide, and DD-lactide. Therefore, when polymerization is performed at 260 ° C. using tin octylate as a catalyst, LL-lactide and DD-lactide become polymers, but DL-lactide remains as a residual sample. This remaining DL-lactide is used for the next polymerization.

  For example, when poly (L-lactic acid) is the target product, the D form is discolored due to an excessive thermal history due to composition adjustment during polymerization. Therefore, when the thermal history is large, the degree of discoloration of the D-form also increases, and as a result, the yellowness of the obtained target polymer increases. Therefore, in order to reduce the yellowness (YI value) of the poly (L-lactic acid) -based lactic acid polymer to 20 or less, it is desirable that the content of D-form is small. By setting the molar ratio to less than 2.2%, a yellowness (YI value) of 20 or less can be achieved. The same applies to the content of L-form in the case of poly (D-lactic acid), and the molar ratio of L-lactic acid is preferably less than 2.2%.

  In addition, examples of factors that control the lactic acid yellowness (YI) include residual catalyst, monomer purity, oligomers, metal components such as iron and zinc, and the like. For example, it has been confirmed that when a lactic acid polymer having a high yellowness (YI) is washed with a solvent such as acetone, the yellowness (YI) can be reduced. This is presumably because components such as residual catalyst were eluted.

  In the present invention, lactic acid polymers having different copolymerization ratios of D-lactic acid and L-lactic acid may be blended. In this case, what is necessary is just to make it the value which averaged the copolymerization ratio of D-lactic acid and L-lactic acid of a some lactic acid-type polymer in the said range. By blending a homopolymer of D-lactic acid and L-lactic acid and a copolymer, it is possible to balance the difficulty of bleeding and the expression of heat resistance.

  The lactic acid polymer used in the present invention preferably has a high molecular weight. For example, the weight average molecular weight is preferably 50,000 or more, more preferably 60,000 or more and 400,000 or less, and more preferably 100,000 or more. , 300,000 or less is particularly preferable. When the weight average molecular weight of the lactic acid polymer is less than 50,000, the obtained film may be inferior in mechanical properties.

  The resin composition forming the reflective film of the present invention contains a fine powder filler. Examples of the fine powder filler used in the present invention include organic fine powder and inorganic fine powder.

  As the organic fine powder, it is preferable to use at least one selected from the group consisting of cellulose powders such as wood powder and pulp powder, polymer beads, and polymer hollow particles.

  Inorganic fine powders include calcium carbonate, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium sulfate, titanium oxide, zinc oxide, magnesium oxide, calcium oxide, alumina, aluminum hydroxide, hydroxyapatite, silica, mica, talc It is preferable to use at least one selected from the group consisting of kaolin, clay, glass powder, asbestos powder, zeolite, silicate clay and the like.

  In consideration of the light reflectivity of the obtained film, it is preferable to use a film having a large refractive index difference from the base resin constituting the film, that is, to use an inorganic fine powder having a large refractive index. Specifically, it is more preferable to use calcium carbonate, barium sulfate, titanium oxide, or zinc oxide having a refractive index of 1.6 or more, and it is particularly preferable to use titanium oxide having a refractive index of 2.5 or more. . In view of the long-term durability of the obtained film, it is preferable to blend barium sulfate that is stable against acids and alkalis.

  Titanium oxide has a high refractive index and can increase the difference in refractive index from the base resin. Therefore, the film has a high reflection performance and low light transmission with a smaller amount than when a filler other than titanium oxide is used. Can be granted. If titanium oxide is used, a film having high reflection performance and low light transmittance can be obtained even if the film is thin.

  Examples of the titanium oxide used in the present invention include titanium oxide having crystal structures such as anatase type and rutile type. From the viewpoint of increasing the difference in refractive index with the base resin constituting the film, titanium oxide having a refractive index of 2.7 or more is preferable. For example, titanium oxide having a rutile crystal structure is used. preferable. The greater the difference in refractive index, the greater the light refracting / scattering action at the interface between the base resin and titanium oxide, making it easier to impart light reflectivity to the film.

  In order to impart high light reflectivity to the film, it is necessary to use titanium oxide having a small light absorption ability for visible light. In order to reduce the light absorption ability of titanium oxide, it is preferable that the amount of the coloring element contained in titanium oxide is small. For example, if titanium oxide having a vanadium content of 5 ppm or less is used, a reflective film having high light reflectivity can be obtained. In addition, from the viewpoint of reducing the light absorption ability, it is preferable that the coloring element contained in titanium oxide, such as iron, niobium, copper, and manganese, is also small.

  Titanium oxide produced by the chlorine process has high purity. According to this production method, titanium oxide having a vanadium content of 5 ppm or less can be obtained. In the chlorine process, rutile ore mainly composed of titanium oxide is reacted with chlorine gas in a high-temperature furnace at about 1,000 ° C. to first generate titanium tetrachloride. Subsequently, high purity titanium oxide can be obtained by burning this titanium tetrachloride with oxygen. In addition, although there is a sulfuric acid process as an industrial manufacturing method of titanium oxide, since titanium oxide obtained by this method contains a large amount of colored elements such as vanadium, iron, copper, manganese, niobium, etc., visible light Increases the light absorption capacity for.

  The surface of the titanium oxide used in the present invention is preferably coated with an inert inorganic oxide. By coating the surface of titanium oxide with an inert inorganic oxide, the photocatalytic activity of titanium oxide can be suppressed, and the light resistance of the film can be increased. As the inert inorganic oxide, it is preferable to use at least one selected from the group consisting of silica, alumina, and zirconia. If these inert inorganic oxides are used, the light resistance of the film can be enhanced without impairing the high light reflectivity exhibited when titanium oxide is used. Further, it is more preferable to use two or more kinds of inert inorganic oxides in combination, and among them, a combination in which silica is essential is particularly preferable.

  Alternatively, in order to improve the dispersibility of titanium oxide in the resin, the surface of titanium oxide is made of at least one inorganic compound selected from the group consisting of siloxane compounds, silane coupling agents, and the like, polyols, polyethylene glycols, and the like. You may surface-treat with the at least 1 sort (s) of organic compound chosen from the group which consists of.

  The titanium oxide used in the present invention preferably has a particle size of 0.1 μm or more and 1 μm or less, and more preferably 0.2 μm or more and 0.5 μm or less. If the particle size of titanium oxide is 0.1 μm or more, the dispersibility in the aliphatic polyester resin is good, and a homogeneous film can be obtained. Moreover, since the interface of aliphatic polyester-type resin and a titanium oxide will be formed densely if the particle size of a titanium oxide is 1 micrometer or less, high light reflectivity can be provided to a reflective film.

  When a fine powder filler other than titanium oxide is used, in order to improve the dispersibility of the fine powder filler in the resin, a silicon compound, a polyhydric alcohol compound, an amine compound, a fatty acid, and a fatty acid are used. Surface treatment can be performed with an ester or the like.

  Such a fine powder filler preferably has an average particle size of 0.05 μm or more and 15 μm or less, and more preferably an average particle size of 0.1 μm or more and 10 μm or less. When the average particle diameter of the fine powder filler is 0.05 μm or more, light scattering reflection occurs with the roughening of the film, so that the reflection directivity of the obtained film becomes small. Moreover, if the average particle diameter of the fine powder filler is 15 μm or less, the interface between the aliphatic polyester resin and the fine powder filler is densely formed, so that a high light reflectivity can be imparted to the reflective film. .

  The fine powder filler such as titanium oxide is preferably dispersed and blended in the aliphatic polyester resin. Further, the content of the fine powder filler is 10% by mass or more and 60% by mass in the resin composition for forming the reflective film in consideration of the light reflectivity expression, mechanical properties, productivity, etc. of the film. % Or less, more preferably 10% by mass or more and less than 55% by mass, and particularly preferably 20% by mass or more and 50% by mass or less. If the content of the fine powder filler is 10% by mass or more in the resin composition, a sufficient area of the boundary surface between the resin and the fine powder filler can be secured, so that the reflective film has high light reflection. Sex can be imparted. Moreover, if content of a fine powder filler is 60 mass% or less, the mechanical property required for a film can be ensured.

  The aliphatic polyester resin reflective film of the present invention preferably has voids inside the film in view of reflectance. The porosity of the film (the ratio of voids in the film) is preferably 50% or less, and more preferably in the range of 5% or more and 50% or less. In particular, from the viewpoint of improving the reflectance, the porosity is preferably 20% or more, and most preferably 30% or more. If the porosity exceeds 50%, the mechanical strength of the film may be reduced, and the film may be broken during film production, or durability such as heat resistance may be insufficient during use. For example, a void can be formed inside the film by adding a fine powder filler or the like and stretching.

  If titanium oxide having a vanadium content of 5 ppm or less is used, high light reflectivity can be achieved even if the porosity present in the film is low. For example, there is no void in the film. Even high light reflectivity can be achieved. This is presumably due to the high refractive index and high hiding power of titanium oxide. Further, if the amount of filler used can be reduced, the number of voids formed by stretching is also reduced. Therefore, if such a titanium oxide is used, the number of voids existing in the film can be reduced, so that the mechanical properties of the film can be improved while maintaining high reflection performance. Alternatively, even when the amount of filler used is large, if the amount of stretching is reduced to reduce the number of voids, the mechanical properties can be improved as in the case where the amount of filler used is reduced. Thus, reducing the number of voids present in the film is advantageous in terms of improving the dimensional stability of the film. If high reflection performance is ensured even with a thin wall, it can be used, for example, as a reflective film for small and thin liquid crystal displays such as notebook computers and mobile phones.

  In the present invention, the aliphatic polyester resin reflective film preferably has a surface reflectance of 95% or more, and more preferably 97% or more, for light having a wavelength of 550 nm. If the reflectance is 95% or more, the reflective film exhibits good reflective properties, and a liquid crystal display or the like incorporating this reflective film does not have a yellowish screen and has good color.

  It is preferable that the reflective film retains excellent reflectance even after being exposed to ultraviolet rays. As described above, the aliphatic polyester-based resin reflective film of the present invention uses an aliphatic polyester-based resin that does not contain an aromatic ring in the molecular chain as the base resin. Sex can be maintained.

  By the way, in recent years, liquid crystal displays have been used not only for personal computer displays but also for car navigation systems for automobiles, compact TVs for vehicles, and the like, and those that can withstand high temperatures and high humidity have become necessary. Therefore, it is preferable to add a hydrolysis inhibitor to the aliphatic polyester-based resin reflective film for the purpose of imparting durability.

Examples of the hydrolysis inhibitor preferably used in the present invention include carbodiimide compounds. Preferred examples of the carbodiimide compound include those having a basic structure represented by the following general formula.

-(N = C = N-R-) _n-

In the formula, n represents an integer of 1 or more, and R represents an organic bond unit. For example, R can be either aliphatic, alicyclic, or aromatic. In addition, n is generally an appropriate integer selected from 1 to 50. When n is 2 or more, two or more R may be the same or different.

  Specifically, for example, bis (dipropylphenyl) carbodiimide, poly (4,4′-diphenylmethanecarbodiimide), poly (p-phenylenecarbodiimide), poly (m-phenylenecarbodiimide), poly (tolylcarbodiimide), poly ( Examples of the carbodiimide compound include diisopropylphenylenecarbodiimide), poly (methyl-diisopropylphenylenecarbodiimide), poly (triisopropylphenylenecarbodiimide), and the like. These carbodiimide compounds may be used alone or in combination of two or more.

  In this invention, it is preferable to add 0.1-3.0 mass parts of carbodiimide compounds with respect to 100 mass parts of aliphatic polyester-type resin which comprises a film. If the addition amount of the carbodiimide compound is 0.1 parts by mass or more, the hydrolysis resistance improving effect is sufficiently exhibited in the obtained film. Moreover, if the addition amount of a carbodiimide compound is 3.0 mass parts or less, the degree of coloring of the film obtained will be few and high light reflectivity will be obtained.

  Also, for example, in a car parked under the hot sun in the summer, car navigation systems for cars, compact TVs for vehicles, etc. will be exposed to high temperatures, and the surroundings of the light source lamp will become hot when the liquid crystal display device is used for a long time. Will be exposed. Therefore, a reflective film used for a liquid crystal display such as a car navigation system or a liquid crystal display device is required to have a heat resistance of about 110 ° C. For example, when the reflective film is left for 5 minutes at a temperature of 120 ° C., the thermal shrinkage of the film is preferably 10% or less, and more preferably 5% or less. If the heat shrinkage rate of the film is greater than 10%, the film may shrink over time when used at high temperatures. Also, if the reflective film is laminated on a steel plate, only the film will be deformed. May end up. A film that has undergone large shrinkage has a smaller surface that promotes reflection, and the voids inside the film are smaller, so the reflectivity decreases.

  In order to prevent thermal shrinkage, it is desirable to completely proceed with crystallization of the film. Since it is difficult to completely crystallize the aliphatic polyester-based resin reflective film only by performing biaxial stretching, in the present invention, it is preferable to perform heat setting after stretching the film. By promoting crystallization of the film, heat resistance can be imparted to the film and hydrolysis resistance can be improved.

  In the present invention, an antioxidant, a light stabilizer, a heat stabilizer, a lubricant, a dispersant, a UV absorber, a white pigment, a fluorescent whitening agent, and other additions within a range not impairing the effects of the present invention. An agent can be added.

  The aliphatic polyester-based resin reflective film of the present invention can be decomposed by microorganisms or the like when disposed in landfills, and does not cause various problems associated with disposal. The aliphatic polyester resin is hydrolyzed by microorganisms or the like in the soil after the ester bond is hydrolyzed in the soil and the molecular weight is reduced to about 1,000.

  On the other hand, aromatic polyester resins have high intramolecular bond stability, and hydrolysis of the ester bond portion hardly occurs. Therefore, the aromatic polyester-based resin does not decrease in molecular weight even when buried in the soil, and does not biodegrade by microorganisms or the like. As a result, there are problems such as remaining in the soil for a long time, promoting the shortening of the landfill site for waste disposal, and damaging the natural landscape and the living environment of wild animals and plants.

  Below, although an example is given and demonstrated about the manufacturing method of the aliphatic polyester-type resin reflective film of this invention, it is not limited to the following manufacturing method at all.

  First, a fine powder filler is blended with the aliphatic polyester-based resin, and further, a hydrolysis inhibitor, other additives and the like are blended as necessary to prepare a resin composition. Specifically, a fine powder filler is added to the aliphatic polyester resin, a hydrolysis inhibitor is added as necessary, and the mixture is mixed with a ribbon blender, tumbler, Henschel mixer, etc. Alternatively, the resin composition can be obtained by kneading using a twin screw extruder or the like at a temperature equal to or higher than the melting point of the resin (for example, 170 ° C. to 230 ° C. in the case of polylactic acid). Alternatively, a resin composition can be obtained by adding a predetermined amount of an aliphatic polyester resin, a fine powder filler, a hydrolysis inhibitor, or the like with a separate feeder or the like. Alternatively, a so-called master batch in which a fine powder filler, a hydrolysis inhibitor, etc. are blended in a high concentration in an aliphatic polyester resin is prepared in advance, and this master batch and the aliphatic polyester resin are mixed and desired A resin composition having a concentration of

  Next, the resin composition thus obtained is melted and formed into a film. For example, after drying the resin composition, the resin composition is supplied to an extruder and heated to a temperature equal to or higher than the melting point of the resin to melt. Or you may supply a resin composition to an extruder, without drying, but when not drying, it is preferable to use a vacuum vent at the time of melt-extrusion. Conditions such as the extrusion temperature need to be set in consideration of a decrease in molecular weight due to decomposition. For example, in the case of polylactic acid, the extrusion temperature is preferably in the range of 170 ° C to 230 ° C. . Thereafter, the melted resin composition is extruded from the slit-shaped discharge port of the T die, and is solidified on a cooling roll to form a cast sheet.

  The reflective film of the present invention is melt-formed using a resin composition comprising an aliphatic polyester resin and a fine powder filler, and then stretched at least 1.1 times in a uniaxial direction. Is preferred. By extending | stretching, since the space | gap which made the fine powder filler a nucleus is formed inside a film, the light reflectivity of a film can further be improved. This is presumably because the interface between the resin and the voids and the interface between the voids and the fine powder filler are newly formed, and the effect of refractive scattering generated at the interface is increased.

  The reflective film of the present invention is preferably stretched to 5 times or more as an area magnification, and more preferably 7 times or more. If the cast sheet is stretched so that the area magnification is 5 times or more, a porosity of 5% or more can be realized inside the film, and a porosity of 20% or more is realized by stretching 7 times or more. It is possible to achieve a porosity of 30% or more by stretching 7.5 times or more.

  The stretching temperature when stretching the cast sheet is preferably a temperature within the range of the glass transition temperature (Tg) of the resin to (Tg + 50 ° C.). For example, in the case of polylactic acid, it is 50 ° C. or higher and 90 ° C. or lower. It is preferable that If the stretching temperature is within this range, the film can be stably carried out without being broken at the time of stretching, and the stretching orientation is increased, and as a result, the porosity is increased, so that a film having a high reflectance is obtained. Easy to obtain.

  The aliphatic polyester-based resin reflective film of the present invention is formed by, for example, appropriately selecting a stretching ratio and stretching to form voids inside the film. This is because the aliphatic polyester-based resin and titanium oxide are stretched during stretching. This is because the stretching behavior differs from that of fine powder fillers such as. In other words, if the stretching is performed at a stretching temperature suitable for the aliphatic polyester resin, the aliphatic polyester resin serving as the matrix is stretched, but the fine powder filler tries to remain as it is, so the aliphatic polyester resin. And the fine powder filler are peeled off to form voids.

It is preferable that the reflective film of the present invention is further stretched in the biaxial direction. By biaxially stretching, the porosity is further increased, and the light reflectivity of the film can be further increased.
Further, if the film is stretched uniaxially, the formed voids are only in a fibrous form extending in one direction, but by biaxially stretching, the voids are in a disk-like form stretched in both vertical and horizontal directions. . That is, by biaxially stretching, the peeling area at the interface between the resin and the fine powder filler is increased, and the whitening of the film proceeds. As a result, the light reflectivity of the film can be enhanced. Furthermore, since biaxial stretching eliminates anisotropy in the shrinking direction of the film, the heat resistance of the reflective film can be improved, and the mechanical strength of the film can be increased.

  The stretching order of biaxial stretching is not particularly limited. For example, simultaneous biaxial stretching or sequential stretching may be used. After melt film formation using a stretching facility, the film may be stretched in the MD (film take-off direction) by roll stretching, and then stretched in the TD (direction perpendicular to the MD) by tenter stretching, or tubular stretching. For example, biaxial stretching may be performed.

  In the present invention, in order to impart heat resistance and dimensional stability to the aliphatic polyester-based resin reflective film, it is preferable to perform heat setting after stretching. The treatment temperature for heat-setting the film is preferably 90 to 160 ° C, more preferably 110 to 140 ° C. The processing time required for heat setting is preferably 1 second to 5 minutes. Moreover, although there is no limitation in particular about extending | stretching equipment etc., it is preferable to perform the tenter extending | stretching which can perform a heat setting process after extending | stretching.

  The thickness of the aliphatic polyester-based resin reflective film of the present invention is not particularly limited, but is usually 30 μm to 500 μm, and is preferably in the range of about 50 μm to 500 μm in view of practical handling. In particular, as a reflective film for small and thin reflectors, the thickness is preferably 30 μm to 100 μm. If a reflective film having such a thickness is used, it can also be used for small and thin liquid crystal displays and the like such as notebook computers and mobile phones.

  In addition, the reflective film of the present invention may have a single layer configuration, but may also have a multilayer configuration in which two or more layers are laminated.

  A reflector used in a liquid crystal display or the like can be formed using the aliphatic polyester resin reflective film of the present invention. For example, a reflective plate can be formed by coating an aliphatic polyester-based resin reflective film on a metal plate or a resin plate. This reflecting plate is useful as a reflecting plate used for liquid crystal display devices, lighting fixtures, lighting signs, and the like. Below, an example is given and demonstrated about the manufacturing method of such a reflecting plate.

  As a method of coating the reflective film on a metal plate or a resin plate, a method using an adhesive, a method of heat fusion without using an adhesive, a method of bonding via an adhesive sheet, a method of extrusion coating, etc. There is no particular limitation. For example, a reflective film can be bonded by applying an adhesive such as polyester, polyurethane, or epoxy to the surface of the metal plate or resin plate on the side where the reflective film is bonded. In this method, using commonly used coating equipment such as a reverse roll coater and a kiss roll coater, the adhesive film thickness after drying on the surface of a metal plate or the like to which the reflective film is bonded is about 2 to 4 μm. Apply an adhesive so that Next, the coated surface is dried and heated by an infrared heater and a hot-air heating furnace, and while maintaining the surface of the plate at a predetermined temperature, immediately using a roll laminator, the reflective film is coated and cooled, thereby cooling the reflective plate. Can get. In this case, when the surface of the metal plate or the like is held at 210 ° C. or lower, the light reflectivity of the reflecting plate can be maintained high. In addition, it is preferable that the surface temperature of a metal plate etc. is 160 degreeC or more.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples, and various applications are possible without departing from the technical idea of the present invention. In addition, the measured value and evaluation which are shown to an Example were performed as shown below. Here, the film take-up (flow) direction is indicated by MD, and its orthogonal direction is indicated by TD.

(Measurement and evaluation method)
(1) Refractive index The refractive index of resin was measured based on A method of JIS K-7142.

(2) Vanadium content in titanium oxide (ppm)
Titanium oxide was decomposed with hydrofluoric acid in a microwave sample decomposition apparatus, and the obtained solution was quantitatively analyzed using an ICP emission spectroscopic analysis apparatus.

(3) Average particle size Using a powder specific surface measuring instrument (transmission method) of model “SS-100” manufactured by Shimadzu Corporation, 3 g of sample was filled into a sample cylinder having a cross-sectional area of 2 cm ² and a height of 1 cm. The air permeation time of 20 cc with a 500 mm water column was calculated.

(4) Porosity (%)
Measure the density of the film before stretching (denoted as “unstretched film density”) and the density of the film after stretching (denoted as “stretched film density”), and assign it to the following formula to determine the porosity of the film. Asked.

Porosity (%) =
{(Unstretched film density−Stretched film density) / Unstretched film density} × 100

(5) Yellowness (YI value)
Yellowness was measured based on JIS K-7103. The measurement was performed using a spectrocolorimeter (“SC-T”, manufactured by Suga Test Instruments Co., Ltd.). The yellowness was measured not only for the reflective film but also for the yellowness of the base resin.

(6) Reflectance (%)
An integrating sphere was attached to a spectrophotometer (“U-4000”, manufactured by Hitachi, Ltd.), and the reflectance with respect to light having a wavelength of 550 nm was measured. Before the measurement, the photometer was set so that the reflectance of the alumina white plate was 100%.

(7) Hydrolysis resistance After the film was left for 1000 hours in a constant temperature and humidity chamber maintained at a temperature of 60 ° C. and a relative humidity of 95% RH, the weight average molecular weight of the aliphatic polyester resin constituting the film was measured. . The measured value was substituted into the following formula to obtain the molecular weight retention rate (%), and the hydrolysis resistance was evaluated based on the following evaluation criteria. However, the symbols “◯” and “Δ” are above the practical level.

Molecular weight retention (%) = (weight average molecular weight after standing / weight average molecular weight before standing) × 100

Evaluation criteria:
○ When the molecular weight retention is 90% or more △ When the molecular weight retention is 60% or more and less than 90% × When the molecular weight retention is less than 60%

(8) Yellowing prevention property The film is irradiated with ultraviolet rays for 1,000 hours in a sunshine weather meter tester (without intermittent spraying of water). Thereafter, the surface of the film was observed with the naked eye, and by visual judgment, the white color of the film surface was indicated as “white”, and the yellowish color was indicated as “yellow”.
Moreover, according to the measuring method of said (6), the reflectance (%) of the film after ultraviolet irradiation was also measured.

(9) Shape retention The shape retention was evaluated by a deadfold property test shown below.
A sample film having a width of 20 mm and a length of 150 mm is cut out with the longitudinal direction of the film as the width direction and the orthogonal direction as the length direction. One short side of the sample film is held, and the other short side (the other end) that is not held is located at a position 30 mm from the other end, and the straight line at this position is a fold mountain (or a fold valley). Bend 180 degrees so that a load of 0.15 MPa is applied. After applying a load of 0.15 MPa for 0.5 seconds, immediately remove the load, open the folded part, return the other end to the original position by hand, release the hand, and measure the held bending angle To do. That is, the protractor measures the angle at which the other end is separated from the original position when the hand is released. This value is 180 degrees at the maximum and 0 degree at the minimum. The larger this value, the better the deadfold property, that is, the better the shape retention.

(10) Reflector plate workability Each of the three items of right-angle bending (R = 0 mm), screw contact bending, and well-shaped Eriksen (5 mm) was evaluated based on the following evaluation criteria.
Evaluation criteria:
○ No film peeling × Film peeling

(11) Reflector reflectance The reflectance (%) of the reflector was measured according to the measurement method of (6) above.

[Example 1]
(Preparation of resin composition)
Pellets of a lactic acid polymer having a weight average molecular weight of 200,000 (NW4032D: manufactured by Cargill Dow Polymer Co., Ltd., D-form content: 1.5%) and titanium oxide having an average particle size of 0.25 μm (Taipaque PF-711; Ishihara Sangyo) (Made by Co., Ltd.) was mixed at a ratio of 50% by mass / 50% by mass to form a mixture. After adding 3 parts by mass of a hydrolysis inhibitor (bis (dipropylphenyl) carbodiimide) to 100 parts by mass of this mixture, the mixture was pelletized using a twin screw extruder to produce a so-called master batch. . This master batch and the lactic acid-based polymer were mixed at a ratio of 40% by mass / 60% by mass to prepare a resin composition. Thereafter, the resin composition was supplied to an extruder heated to 220 ° C.

(Production of film)
From the extruder, the molten resin composition was extruded into a sheet using a T-die and cooled and solidified to form a film. The obtained film was stretched biaxially at a temperature of 65 ° C., 2.5 times in MD and 2.8 times in TD, and then heat treated at 140 ° C. to obtain a reflective film having a thickness of 250 μm. About the obtained reflective film, yellowness (YI), porosity, reflectance before ultraviolet irradiation and reflectance after ultraviolet irradiation, yellowing prevention, hydrolysis resistance, and shape retention were measured and evaluated. . The results are shown in Table 2. The yellowness (YI value) of the base resin and the yellowness (YI value) of the reflective film were the values shown in Table 1.

[Example 2]
As shown in Table 1, in Example 1, instead of titanium oxide having an average particle size of 0.25 μm (Typaque PF-711; manufactured by Ishihara Sangyo Co., Ltd.), titanium oxide having an average particle size of 0.24 μm ( A reflective film having a thickness of 250 μm was obtained in the same manner as in Example 1 except that Typaque R-630 (manufactured by Ishihara Sangyo Co., Ltd.) was used. About the obtained reflective film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2. The yellowness (YI value) of the base resin and the yellowness (YI value) of the reflective film were the values shown in Table 1.

[Example 3]
As shown in Table 1, in Example 1, instead of titanium oxide having an average particle size of 0.25 μm (Typaque PF-711; manufactured by Ishihara Sangyo Co., Ltd.), barium sulfate having an average particle size of 0.7 μm ( B-55; manufactured by Sakai Chemical Industry Co., Ltd.), except that the resin composition was prepared by mixing the master batch and the lactic acid polymer in a proportion of 60% by mass: 40% by mass. In the same manner as in Example 1, a reflective film having a thickness of 250 μm was obtained. About the obtained reflective film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2. The yellowness (YI value) of the base resin and the yellowness (YI value) of the reflective film were the values shown in Table 1.

[Example 4]
As shown in Table 1, in Example 1, instead of titanium oxide having an average particle size of 0.25 μm (Typaque PF-711; manufactured by Ishihara Sangyo Co., Ltd.), calcium carbonate having an average particle size of 0.15 μm ( A reflective film having a thickness of 250 μm was obtained in the same manner as in Example 1 except that StaVigot-15A (manufactured by Shiraishi Calcium Co., Ltd.) was used. About the obtained reflective film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2. The yellowness (YI value) of the base resin and the yellowness (YI value) of the reflective film were the values shown in Table 1.

[Example 5]
As shown in Table 1, a reflective film having a thickness of 188 μm was obtained in the same manner as in Example 1 except that the sheet thickness was changed from 250 μm to 188 μm. About the obtained reflective film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2. The yellowness (YI value) of the base resin and the yellowness (YI value) of the reflective film were values shown in Table 1.

[Example 6]
In Example 1, instead of stretching 2.5 times to MD and 2.8 times to TD, biaxial stretching was performed 3 times to MD and 3.2 times to TD, and the sheet thickness was changed to 100 μm. A reflective film having a thickness of 100 μm was obtained in the same manner as Example 1. About the obtained reflective film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2. The yellowness (YI value) of the base resin and the yellowness (YI value) of the reflective film were the values shown in Table 1.

[Example 7]
As shown in Table 1, in Example 1, instead of pellets of a polylactic acid polymer (NW4032D) having a weight average molecular weight of 200,000, a polylactic acid polymer (NW5040D; Cargill Dow) having a weight average molecular weight of 200,000 was used. A reflective film having a thickness of 250 μm was obtained in the same manner as in Example 1 except that a pellet made of Polymer Co., Ltd. (D body content: 2.2%) was washed with acetone. About the obtained reflective film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2. The yellowness (YI value) of the base resin and the yellowness (YI value) of the reflective film were the values shown in Table 1.

[Comparative Example 1]
As shown in Table 1, in Example 1, in place of the lactic acid polymer (NW4032D: manufactured by Cargill Dow Polymer), a lactic acid polymer having a weight average molecular weight of 200,000 (NW5040D: manufactured by Cargill Dow Polymer, D A reflective film having a thickness of 250 μm was obtained in the same manner as in Example 1 except that pellets having a body content of 2.2% were used. About the obtained reflective film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.
The yellowness (YI value) of the base resin and the yellowness (YI value) of the reflective film were the values shown in Table 1.

[Comparative Example 2]
As shown in Table 1, in Example 2, instead of a lactic acid polymer (NW4032D: manufactured by Cargill Dow Polymer), a lactic acid polymer having a weight average molecular weight of 200,000 (NW5040D: manufactured by Cargill Dow Polymer, D A reflective film having a thickness of 250 μm was obtained in the same manner as in Example 2 except that pellets having a body content of 2.2% were used. About the obtained reflective film, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.
The yellowness (YI value) of the base resin and the yellowness (YI value) of the reflective film were the values shown in Table 1.

[Example 8]
The reflective film obtained in Example 1 was coated with a galvanized steel plate (thickness 0.45 mm) to produce a reflective plate. That is, first, a commercially available polyester-based adhesive was applied to the surface of the galvanized steel sheet to which the reflective film was bonded so that the adhesive film thickness after drying was about 2 to 4 μm. Next, the coated surface is dried and heated with an infrared heater and a hot air heating furnace, and while maintaining the surface temperature of the steel plate at 180 ° C., the roll laminator is used to immediately coat and cool the reflective film to obtain a reflective plate. It was. The resulting reflector was measured and evaluated for processability and reflectance. The results are shown in Table 3.

[Example 9]
In Example 8, a reflecting plate was obtained in the same manner as in Example 8 except that the surface temperature of the steel sheet was kept at 220 ° C. instead of being kept at 180 ° C. About the obtained reflecting plate, the same measurement and evaluation as Example 8 were performed. The results are shown in Table 3.

  As is clear from Table 1 and Table 2, the reflective films of the present invention of Examples 1 to 7 have a high light reflectivity with a yellowness (YI value) of less than 3.6 and a reflectance of 95% or more. It has been found that it has high definition. In addition, the reflective films of Examples 1 to 7 have a reflectance of 93% or more even after the ultraviolet irradiation test, and the color is evaluated to be white and excellent in yellowing prevention. It was. Among them, Example 1 and Examples 3 to 7 were excellent in that the reflectance before ultraviolet irradiation (initial reflectance) was 97% or more and the reflectance after ultraviolet irradiation was 95%. Moreover, the film of Examples 1-7 is evaluation more than a practical level also about hydrolysis resistance. That is, it was found that the reflective films of the present invention of Examples 1 to 7 gave excellent results in all evaluations.

  On the other hand, the reflective films of Comparative Examples 1 and 2 have a yellowness (YI value) of 3.7 or more and a reflectance of less than 95%, and the reflective films of Examples 1 to 7 with respect to light reflectivity. It turned out to be inferior.

  Further, as is apparent from Table 3, it was found that the reflector of Example 8 was very excellent because the adhesion required for processing and high light reflectivity were maintained. Moreover, it turned out that the reflecting plate of Example 8 is superior to the reflecting plate of Example 9 in terms of maintaining light reflectivity.

  That is, according to the present invention, it is possible to obtain a reflective film having excellent light reflectivity, which does not turn yellow over time or does not deteriorate light reflectivity, and has excellent shape retention. . Moreover, since the reflective film of this invention uses aliphatic polyester-type resin as base resin, it has biodegradability.

  Although it is used for a reflective film and a reflective plate used for a liquid crystal display device, a lighting fixture, a lighting signboard, etc., it can also be used as a reflective film in these similar fields. Moreover, it can utilize also as a reflective film in which high reflectivity is requested | required, and a reflective film in which thinness is requested | required.

Claims (11)

A reflective film formed from a resin composition containing an aliphatic polyester-based resin and a fine powder filler , wherein the aliphatic polyester-based resin is a copolymer of L-lactic acid and D-lactic acid, A lactic acid polymer in which the molar ratio of D-lactic acid in the polymer is less than 2.2%, or a lactic acid polymer in which the molar ratio of L-lactic acid is less than 2.2%, and the reflection An aliphatic polyester-based resin reflective film, wherein the yellowness (YI value) of the film is less than 3.6.   2. The aliphatic polyester resin reflective film according to claim 1, wherein the fine powder filler is at least one selected from the group consisting of calcium carbonate, barium sulfate, titanium oxide and zinc oxide.   The aliphatic polyester resin reflective film according to claim 2, wherein the titanium oxide has a vanadium content of 5 ppm or less.   The surface of the titanium oxide is coated with at least one inert inorganic oxide selected from the group consisting of silica, alumina, and zirconia. Aliphatic polyester resin reflective film.   The aliphatic polyester resin reflection according to any one of claims 1 to 4, wherein the content of the fine powder filler is 10% by mass or more and 60% by mass or less in the resin composition. the film.   The aliphatic polyester-based resin reflective film according to claim 1, wherein the aliphatic polyester-based resin has a refractive index of less than 1.52. The aliphatic polyester-based resin reflective film according to any one of claims 1 to 6 , wherein the aliphatic polyester-based resin has a yellowness (YI value) of 20 or less. The aliphatic polyester-based resin reflective film according to any one of claims 1 to 7 , wherein the aliphatic polyester-based resin reflective film has voids so that a void ratio in the film is 50% or less. A film made of the resin composition containing an aliphatic polyester series resin and the fine powder filler to melt film from claim 1, wherein the stretching at least one axial direction to 1.1 times or more 8 The aliphatic polyester-type resin reflective film of any one of Claims. The aliphatic polyester resin reflective film according to any one of claims 1 to 9 , wherein the reflectance of the film surface with respect to light having a wavelength of 550 nm is 95% or more. Reflector, characterized in that it comprises an aliphatic polyester resin reflective film according to claim 1, any one of 10.