JP2007031529A - Aliphatic polyester resin reflective film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aliphatic polyester reflective film which has an excellent reflective performance and is used for a reflection plate for a liquid crystal display and the like. <P>SOLUTION: The aliphatic polyester reflective film has a layer A consisting of a resin composition A containing an aliphatic polyester resin, a particulate filler and a liquid additive (e. g. paraffin process oil or a plasticizer). The film has a high reflective performance, is not liable to lose the reflectance by ultraviolet absorption and excellent in yellowing resistance. In particular the addition of the liquid additive prevents deterioration of the performance due to thermal degradation during manufacture, which leads to further improvement in the reflectance. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  In recent years, reflectors have been used in many fields such as liquid crystal display devices, projection screens, planar light source members, lighting fixtures, and lighting signs. In particular, in the field of liquid crystal display devices, the size of the devices and the advancement of display performance have progressed, and in order to improve the performance of the backlight unit by supplying as much light as possible to the liquid crystal, further reflection performance is achieved with a reflective film. Is required.

  On the other hand, notebook computers and the like are becoming thinner, and those liquid crystal display devices that include a backlight unit and a liquid crystal display element that can be reduced in thickness and that allow easy viewing of images are used. Many of such backlight units constitute a surface light source by partially covering one surface of a light-transmitting light guide plate with a light diffusing material and further covering the entire surface with a reflective film. The reflective film used in this application is required to have particularly high reflection performance.

  As a reflection film of this type, a white sheet formed by adding titanium oxide to an aromatic polyester resin, for example, is conventionally known (see Patent Document 1), but is required for a liquid crystal display device as described above. It was difficult to achieve high reflection performance.

  Also disclosed is a construction 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. However, it has been difficult to realize the high reflection performance required for the liquid crystal display device (see Patent Document 2). In addition, since the aromatic ring contained in the molecular chain of the aromatic polyester resin absorbs ultraviolet rays, the film is deteriorated and yellowed by ultraviolet rays emitted from a light source such as a liquid crystal display device, and the light reflectivity of the reflective film is increased. There was also a problem of gradual decline.

  In order to solve such problems, the present inventors have developed a reflective film formed by adding a fine powder filler such as titanium oxide to an aliphatic polyester resin (Patent Document 3).

JP 2002-138150 A JP-A-4-239540 WO200404077

  An object of the present invention is to provide a new reflective film having even better reflective performance.

  The aliphatic polyester-based resin reflective film of the present invention includes an A layer composed of a resin composition A containing an aliphatic polyester-based resin, a fine particle filler, and a liquid additive (for example, paraffinic process oil or plasticizer). An aliphatic polyester resin reflective film (hereinafter referred to as “reflective film”) is proposed.

  The reflective film of the present invention has the characteristics of having high light reflection characteristics (reflectance) and being excellent in yellowing prevention property with little decrease in reflectivity due to ultraviolet absorption, such as a metal plate or a resin plate. Reflective plates used for liquid crystal display devices (for example, backlight units of notebook computers, etc.), lighting fixtures, lighting signs, etc. that are well-balanced with respect to characteristics such as light reflectivity. Can be formed.

In general, “sheet” is a thin product by definition in JIS, and generally its thickness is small and flat instead of length and width, and “film” is generally compared to length and width. A thin flat product whose thickness is extremely small and whose maximum thickness is arbitrarily limited, and is usually supplied in the form of a roll (Japanese Industrial Standard JISK6900). However, since the boundary between the sheet and the film is not clear and it is not necessary to distinguish the two in terms of the present invention, in the present invention, even when the term “film” is used, the term “sheet” is included and the term “sheet” is used. In some cases, “film” is included.
In addition, the expression “main component” in the present invention includes the meaning of allowing other components to be contained within a range that does not hinder the function of the main component, unless otherwise specified. Although the content ratio of the main component is not particularly specified, the main component (when two or more components are main components, the total amount thereof) is 50% by mass or more, preferably 70% by mass in the composition. Above all, particularly preferably 90% by mass or more (including 100%).
Further, in this specification, when “X to Y” (X and Y are arbitrary numbers) is described, it means “X or more and Y or less” unless otherwise specified.

  Hereinafter, an example of an embodiment of the present invention will be described in detail.

  An aliphatic polyester-based resin reflective film (hereinafter referred to as “the present reflective film”) according to the present embodiment is an A composed of a resin composition A containing an aliphatic polyester-based resin, a fine particulate filler, and a liquid additive as main components. A reflective film provided with a layer.

  The reflective film can be formed as a single-layer reflective film consisting of only the A layer, or a multilayer reflective film including the A layer, for example, in addition to the A layer, for example, an aliphatic polyester resin and fine powder It can also be formed as a reflective film having a laminated structure comprising a B layer made of a resin composition B containing a filler, and preferably has a structure in which the B layer is laminated on both sides of the A layer. It is a reflective film. First, the A layer and the B layer will be described.

<A layer>
A layer is a layer which consists of the resin composition A which contains an aliphatic polyester-type resin, a particulate filler, and a liquid additive as a main component.

(A-layer aliphatic polyester resin)
Since the aliphatic polyester-based resin does not contain an aromatic ring in the molecular chain, it is possible to prevent ultraviolet absorption by using the aliphatic polyester-based resin as the base resin for the A layer. Therefore, the film is not deteriorated or yellowed by being exposed to ultraviolet rays or by receiving ultraviolet rays emitted from a light source such as a liquid crystal display device, and the reduction in light reflectivity of the film is suppressed. be able to.

As the aliphatic polyester resin, those chemically synthesized, those fermented and synthesized by microorganisms, or a mixture thereof can be used.
Chemically synthesized aliphatic polyester resins include polyε-caprolactam obtained by ring-opening polymerization of lactone, polyethylene adipate, polyethylene azelate, polytetramethylene succinate obtained by polymerizing dihydrochloric acid and diol. Nate, cyclohexanedicarboxylic acid / cyclohexanedimethanol condensation polymer, lactic acid polymer obtained by polymerizing hydroxycarboxylic acid, polyglycol, etc., or a part of ester bond of the aliphatic polyester, for example, 50 of ester bond Aliphatic polyester in which% or less is replaced with an amide bond, ether bond, urethane bond or the like.
Examples of aliphatic polyester resins fermented and synthesized by microorganisms include polyhydroxybutyrate, a copolymer of hydroxybutyrate and hydroxyvalerate, and the like.

  Among the aliphatic polyester resins, it is preferable to use an aliphatic polyester resin having a refractive index (n) of less than 1.52 as the base resin for the A layer. That is, if a layer comprising an aliphatic polyester resin having a refractive index (n) of less than 1.52 and a fine powder filler is provided, refractive scattering at the interface between the base resin and the fine powder filler is used. Thus, light reflectivity can be realized. Since the refractive scattering effect increases as the refractive index of the base resin and the fine powder filler increases, the base resin preferably has a low refractive index. From this viewpoint, the refractive index is less than 1.46 ( A low lactic acid polymer, which is generally about 1.45), is the most preferred example.

  Examples of the lactic acid polymer include homopolymers of D-lactic acid or L-lactic acid or copolymers thereof. Specifically, poly (D-lactic acid) whose structural unit is D-lactic acid, poly (L-lactic acid) whose structural unit is L-lactic acid, and a copolymer of L-lactic acid and D-lactic acid. Poly (DL-lactic acid) or a mixture thereof can be exemplified.

  By the way, lactic acid has two types of optical isomers, that is, L-lactic acid and D-lactic acid as described above, and the crystallinity differs depending on the ratio of these two types of structural units. For example, a random copolymer having a ratio of L-lactic acid to D-lactic acid of about 80:20 to 20:80 has a low crystallinity, and becomes a transparent complete amorphous polymer that softens near a glass transition point of 60 ° C. On the other hand, a random copolymer having a ratio of L-lactic acid to D-lactic acid of about 100: 0 to 80:20 or about 20:80 to 0: 100 has a glass transition point of 60 as in the case of the copolymer described above. Although it is about ° C., the crystallinity is high.

In the present reflective film, the DL ratio in the lactic acid polymer, that is, the content 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 = 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 content ratio of D-lactic acid and L-lactic acid of 100: 0 or 0: 100 tends to exhibit very high crystallinity, a high melting point, and excellent 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 in that respect. On the other hand, a lactic acid-based polymer composed of D-lactic acid and L-lactic acid is preferable in that respect because flexibility is imparted and film forming stability and stretching stability are improved. Considering the balance between the heat resistance, molding stability and stretching stability of the resulting reflective film, the composition ratio of D-lactic acid and L-lactic acid is D-lactic acid: L-lactic acid = 99.5: 0.5. It can be said that -95: 5 or D-lactic acid: L-lactic acid = 0.5: 99.5-5: 95 is more preferable.

  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. In addition, 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 a lactic acid system 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 addition, you may blend the lactic acid-type polymer from which the copolymerization ratio of D-lactic acid and L-lactic acid differs. In this case, it is preferable to adjust so that the average value of the copolymerization ratios of D-lactic acid and L-lactic acid of a plurality of lactic acid polymers falls within the range of the DL ratio.

Moreover, the lactic acid-type polymer can also use the copolymer of lactic acid and other hydroxycarboxylic acid. At this time, as "other hydroxycarboxylic acid units" to be copolymerized, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, Examples thereof include bifunctional aliphatic hydroxycarboxylic acids such as 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, and 2-hydroxycaproic acid, and lactones such as caprolactone, butyrolactone, and valerolactone.
Further, the lactic acid-based polymer may be a non-aliphatic carboxylic acid such as terephthalic acid and / or a non-aliphatic diol such as an ethylene oxide adduct of bisphenol A, lactic acid and / or Alternatively, a hydroxycarboxylic acid other than lactic acid may be included.

  The lactic acid polymer preferably has a high molecular weight. For example, the weight average molecular weight is preferably 50,000 or more, more preferably 60,000 to 400,000, and more preferably 100,000 to 300,000. Particularly preferred. 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.

(Fine powder filler of layer A)
Examples of the fine powder filler in the A layer include organic fine powder and inorganic fine powder.

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

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

  Among these, fine powder fillers that have a large refractive index difference from the aliphatic polyester resin and can provide excellent reflection performance are preferable. From this viewpoint, it is preferable to use inorganic fine powder having a large refractive index. Specifically, calcium carbonate, barium sulfate, titanium oxide or zinc oxide having a refractive index of 1.6 or more is preferable, and titanium oxide having a refractive index of 2.5 or more is particularly preferable. In view of the long-term durability of the obtained film, barium sulfate that is stable against acids and alkalis is particularly preferable.

  Titanium oxide has a significantly higher refractive index than other fine organic powders, and can significantly increase the difference in refractive index from aliphatic polyester resins, making it more than using other fillers. With a small blending amount, high reflection performance and low light transmittance can be imparted to the film. Further, by using titanium oxide, a reflective film having high reflection performance and low light transmittance can be obtained even if the film is thin.

  As the titanium oxide, a crystalline titanium oxide such as anatase type or rutile type is preferable. From the viewpoint of increasing the refractive index difference from the base resin, titanium oxide having a refractive index of 2.7 or more is preferable. From this viewpoint, it is preferable to use rutile-type titanium oxide. 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.

  Moreover, in order to give high light reflectivity to a film, it is required that it is a titanium oxide with small light absorption ability with respect to 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. From this viewpoint, titanium oxide having a niobium content of 500 ppm or less is preferable.

Titanium oxide produced by the chlorine process has high purity, and according to this production method, titanium oxide having a niobium content of 500 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 1000 ° C. to first generate titanium tetrachloride. Subsequently, high purity titanium oxide can be obtained by burning this titanium tetrachloride with oxygen.

The titanium oxide used as the fine powder filler is preferably one whose surface is 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 (durability when irradiated with light) of the film can be improved. .
The inert inorganic oxide for coating the surface of titanium oxide is preferably at least one selected from the group consisting of alumina, silica and zirconia. If it coat | covers with these inert inorganic oxides, the light resistance of a film can be improved, without impairing the high reflective performance obtained by a titanium oxide. Further, it is more preferable to use a combination of two or more of the above-mentioned inert inorganic oxides in combination. Among them, silica and other inert inorganic oxides (for example, alumina and zirconia) are used in combination. It is particularly preferred to coat.

  In order to improve dispersibility in the base resin, the surface of titanium oxide is at least one inorganic compound selected from siloxane compounds, silane coupling agents, and the like, and at least one selected from polyols, polyethylene glycols, and the like. You may make it surface-treat with an organic compound.

The average particle diameter of the titanium oxide to be added is preferably 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. Further, when the particle size is 1 μm or less, the interface between the aliphatic polyester resin and titanium oxide is formed more densely, so that more excellent light reflectivity can be imparted to the reflective film.

Even when a fine powder filler other than titanium oxide is used, surface treatment with a silicon compound, a polyhydric alcohol compound, an amine compound, a fatty acid, a fatty acid ester, etc. is performed in order to improve dispersibility in the base resin. You may make it do.
In addition, the fine powder filler other than titanium oxide preferably has an average particle size of 0.05 μm or more and 15 μm or less, and more preferably 0.1 μm or more and 10 μm or less. If the average particle size of the fine powder filler is 0.05 μm or more, light scattering reflection occurs with the rough surface of the film, so that the reflection directivity of the resulting film becomes smaller. Moreover, if the average particle size of the fine powder filler is 15 μm or less, the interface between the aliphatic polyester resin and the fine powder filler is formed more densely, so that more excellent light reflectivity is imparted to the reflective film. can do.

  Any fine powder filler other than titanium oxide or titanium oxide is preferably dispersed and blended in the aliphatic polyester resin.

The content of the fine powder filler may be 10% by mass or more and 60% by mass or less of the resin composition A constituting the A layer in consideration of light reflectivity, mechanical properties, productivity, and the like of the film. It is particularly preferably 10% by mass or more and less than 55% by mass, and more preferably 20% by mass or more and 45% by mass or less.
If the content of the fine powder filler is 10% by mass or more, the area of the interface between the base resin and the fine powder filler can be sufficiently secured, so that a higher light reflectivity can be imparted to the film. it can. Moreover, if content of a fine powder filler is 60 mass% or less, the mechanical property required for a film can be ensured.

  In addition, the present inventors tried to add a large amount of fine powder filler to the A layer for the purpose of further improving the reflectivity, but by adding a large amount of particles, the melt viscosity becomes high, The expected improvement in reflectivity was not seen. However, by adding a liquid additive to the A layer and lowering the melt viscosity, even if a large amount of fine powder filler is added, the melt viscosity does not increase, and the reflectance is improved by increasing the fine powder filler, It becomes possible to obtain a synergistic effect with the improvement of the reflectance by lowering the melt viscosity and suppressing the shearing heat generation, and it is possible to realize even higher light reflection characteristics.

(Liquid additive)
As the liquid additive, various known materials that are liquid or pasty at room temperature can be suitably used. Specific examples of the components are plasticizers and softeners. Examples of softeners include petroleum softeners such as paraffinic process oils, naphthenic process oils, and aromatic process oils, and ethylene-α-olefin copolymer. Examples include mineral oil softeners such as oligomers, gilsonite and asphalt, vegetable softeners such as olive oil, soybean oil, castor oil and linseed oil, and aliphatics such as oleic acid and ricinoleic acid. Of these, paraffinic process oil and plasticizer are preferable.
It has been confirmed that the reflectance of the reflective film can be improved by adding such a liquid additive. This is probably because the melt viscosity in the extruder is lowered, and as a result, shear heat generation can be avoided, and both the base resin and the fine particulate filler can prevent the performance from being deteriorated due to thermal deterioration or the like. It is done.
When paraffinic process oil is added, in addition to the above merits, it is incompatible with aliphatic polyester resins and does not lower the glass transition point (Tg) of aliphatic polyester resins, thus affecting heat resistance. It is not colored, and there is no coloration. Moreover, since it is pushed out at the interface between the resin and the fine particle filler during stretching, it becomes easy to form a void at the interface between the resin and the fine particle filler, and the reflectance is improved by the void. There is also an advantage that it is easy to obtain.

(Plasticizer)
The plasticizer is an additive having a function of lowering and softening the glass transition temperature (Tg) of the resin to be added, but the plasticizer used in this embodiment is compatible with the aliphatic polyester resin. From the viewpoint of biodegradability, those composed of one or a combination of two or more having a molecular weight of 2,000 or less selected from the compounds shown in the following (A) to (H) are preferable.

(A) H ₆ C ₃ (OH) ₃ -n (OOCCH ₃ ) _n (where 0 <n ≦ 3)
This is glycerol monoacetate, diacetate or triacetate, and a mixture thereof may be used, but n is preferably close to 3.
(B) Glycerin alkylate (the alkyl group may have 2 to 20 carbon atoms and a hydroxyl group residue)
Examples thereof include glycerin tripropionate and glycerin tributyrate.
(C) Ethylene glycol alkylate (the alkyl group has 1 to 20 carbon atoms and may have a hydroxyl group residue).
For example, ethylene glycol diacetate etc. are mentioned.
(D) Polyethylene glycol alkylate having 5 or less ethylene repeating units (the alkyl group may have 1 to 12 carbon atoms and a hydroxyl group residue).
Examples thereof include diethylene glycol monoacetate and diethylene glycol diacetate.
(E) Aliphatic monocarboxylic acid alkyl ester (the alkyl group has 1 to 20 carbon atoms)
For example, butyl stearate etc. are mentioned.
(F) Aliphatic dicarboxylic acid alkyl ester (the alkyl group may have 1 to 20 carbon atoms and a residue of a carboxyl group), among which those having a number average molecular weight of 100 to 2000 are preferable.
Specific examples include di (2-ethylhexyl) adipate and di (2-ethylhexyl) azelate.
(G) Aliphatic tricarboxylic acid alkyl ester (the alkyl group may have 1 to 20 carbon atoms and a carboxyl group residue).
For example, citric acid trimethyl ester and the like can be mentioned.
(H) Natural fats and oils and derivatives thereof Examples include soybean oil, epoxidized soybean oil, castor oil, tung oil, and rapeseed oil.

<B layer>
B layer is a layer which consists of the resin composition B which contains an aliphatic polyester-type resin and a fine powder filler as a main component.

(B layer aliphatic polyester resin)
As the base resin of the B layer, the resin described as the aliphatic polyester-based resin of the A layer can be used, and among them, a lactic acid-based polymer similar to the A layer is preferable.
However, the aliphatic polyester resin of the A layer and the aliphatic polyester resin of the B layer may be the same resin or different resins.

(Fine powder filler for layer B)
As the fine powder filler in the B layer, the fine powder filler described as the fine powder filler in the A layer can be used, and among them, titanium oxide similar to the A layer is preferable.
However, the fine powder filler of the A layer and the fine powder filler of the B layer may be the same type or different types.

The content of the fine powder filler is 10% by mass or more and 60% by mass or less in the resin composition B constituting the B layer in consideration of light reflectivity, mechanical properties, productivity, etc. of the film. Is preferably 10% by mass or more and less than 55% by mass, and more preferably 20% by mass or more and 45% by mass or less.
If the content of the fine powder filler is 10% by mass or more, the area of the interface between the base resin and the fine powder filler can be sufficiently secured, so that a higher light reflectivity can be imparted to the film. it can. Moreover, if content of a fine powder filler is 60 mass% or less, the mechanical property required for a film can be ensured.

(Other ingredients)
The resin composition A and the resin composition B may contain other resins and other additives as long as the functions of the main components are not hindered. For example, hydrolysis inhibitors, antioxidants, light stabilizers, heat stabilizers, lubricants, dispersants, ultraviolet absorbers, white pigments, optical brighteners, and other additives can be added.
Among these, for the purpose of imparting durability, it is preferable to add a hydrolysis inhibitor, which will be described in detail below.

  In recent years, liquid crystal display devices 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 reflective film containing the aliphatic polyester resin for the purpose of imparting durability.

A carbodiimide compound can be mentioned as a preferred example of the hydrolysis inhibitor.
As a carbodiimide compound, what has the basic structure of the following general formula can be mentioned as a preferable thing, for example.
-(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, 2 or more R may be the same or different.

  Specific examples of the carbodiimide compound include bis (dipropylphenyl) carbodiimide, poly (4,4′-diphenylmethanecarbodiimide), poly (p-phenylenecarbodiimide), poly (m-phenylenecarbodiimide), poly (tolylcarbodiimide), and poly (tolylcarbodiimide). (Diisopropyl phenylene carbodiimide), poly (methyl-diisopropyl phenylene carbodiimide), poly (triisopropyl phenylene carbodiimide), etc., and these monomers are mentioned. These carbodiimide compounds may be used alone or in combination of two or more.

The carbodiimide compound is preferably added at a ratio of 0.1 to 3.0 parts by mass with respect to 100 parts by mass of the aliphatic polyester resin that is the base resin of the resin composition A or B.
When the added 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, there will be little coloring of the film obtained and high light reflectivity can be obtained.

(Internal void)
In this reflective film, the inside of a film (in A layer and B layer) may have a space | gap, and a reflectance can further be raised with the space | gap inside a film.

The porosity of the reflective film (ratio occupied by voids in the film) is preferably 50% or less, particularly preferably in the range of 5% or more and 50% or less. Among these, from the viewpoint of improving the reflectance, the porosity is preferably 20% or more, and particularly preferably 30% or more. When the porosity exceeds 50%, it is assumed that the mechanical strength of the film is lowered and the film is broken during the production of the film, or the durability such as heat resistance is insufficient at the time of use.
Such voids in the film can be formed, for example, by adding a fine powder filler to the film and stretching it.

However, when titanium oxide having a niobium content of 500 ppm or less is used as the fine powder filler, it has a sufficiently high light reflectivity even if the porosity existing inside the film is low or there is no void. The following effects can also be obtained.
That is, when titanium oxide having a niobium content of 500 ppm or less is used, the amount of filler used can be reduced, and the number of voids formed by stretching is also reduced, while maintaining high reflection performance. The mechanical properties of the film can also be improved. In addition, the dimensional stability of the film can be improved by reducing the number of voids existing inside the film. Furthermore, high reflection performance can be ensured even with a thin wall, and it is particularly suitable as a reflective film for small and thin liquid crystal displays such as notebook personal computers and mobile phones.

<Configuration of reflective film>
As described above, the reflective film can be formed as a single-layer reflective film composed of only the A layer, or a multilayered reflective film including the A layer, for example, an aliphatic layer, for example, an aliphatic film. It can also be formed as a reflective film having a laminated structure including a B layer made of a resin composition B containing a polyester-based resin and a fine powder filler. That is, a two-layer structure composed of A layer / B layer, a three-layer structure composed of B layer / A layer / B layer or A layer / B layer / A layer, 4 composed of B layer / A layer / B layer / A layer It can be formed as a layer structure or a multilayer structure having more layers. Moreover, it can also form as a laminated structure provided with layers other than A layer and B layer. A configuration in which the B layer is laminated on both sides of the A layer, for example, B layer / A layer / B layer is preferable. With such a laminated structure, the reflectance can be further increased by the A layer, while bleeding out due to the liquid additive contained in the A layer can be prevented.

In the case of the above laminated structure, particularly B layer / A layer / B layer, the thickness ratio of each layer is preferably 1: 20: 1 or smaller than the ratio of A layer, and 1: 1: 1 or this. It is preferable that the ratio of the A layer is larger. Among them, it is more preferable that the ratio of the A layer is 1: 15: 1 or smaller, and it is more preferable that the ratio of the A layer is 1: 2: 1 or larger.
If the ratio of the thickness of each A layer and the B layer is greater than 1: 1, the effect of reducing the melt viscosity is sufficiently exhibited.

(Film thickness)
Although the thickness of this reflective film is not specifically limited, Usually, it is 30 micrometers-500 micrometers, and when the handleability in practical use is considered, it is preferable to exist in the range of about 50 micrometers-500 micrometers. 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.

<Characteristics of reflective film>
(Reflectance)
The reflective film preferably has a surface reflectance of 95% or more with respect to light having a wavelength of 550 nm, and more preferably 98% or more. If the reflectance is 95% or more, good reflection characteristics are exhibited, and a liquid crystal display or the like incorporating this reflection film has a clear color without a yellowish screen.
Here, the reflectance means the reflectance of the surface on the light irradiation side (reflection use surface side).

  The present reflective film has a feature that it can maintain the excellent reflectance as described above even after being exposed to ultraviolet rays. As described above, since the present reflective film uses an aliphatic polyester resin that does not contain an aromatic ring in the molecular chain as the base resin, the film is not deteriorated by ultraviolet rays, and excellent reflectivity can be maintained.

(Heat shrinkage)
The reflective film has a thermal shrinkage rate of preferably 10% or less, more preferably 5% or less when left for 5 minutes at a temperature of 120 ° C.
In a car parked under the hot summer sun, car navigation systems for automobiles, in-car small televisions, and the like are exposed to high temperatures. Further, when the liquid crystal display device is used for a long time, the periphery of the light source lamp is exposed to a high temperature. Therefore, the reflective film used for liquid crystal displays such as car navigation systems and liquid crystal display devices is required to have heat resistance at about 120 ° C., and the thermal contraction rate of the film when left at 120 ° C. for 5 minutes. If it is 10% or less, the film does not shrink over time when used at a high temperature, and even when the reflective film is laminated on a steel plate or the like, only the film may be deformed. Absent. A film having a large shrinkage causes a reduction in the reflectance of the film due to a decrease in the surface that promotes reflection or a decrease in the gap inside the film.

  As described above, in order to suppress the thermal shrinkage of the film, that is, to reduce the thermal shrinkage rate, it is desirable to completely advance the crystallization of the film. However, in the case of an aliphatic polyester-based resin reflective film, it is difficult to completely advance crystallization of the film only by performing biaxial stretching. Therefore, it is preferable to perform heat setting treatment after stretching the film. By promoting crystallization of the film, heat resistance can be imparted to the film, and hydrolysis resistance can also be improved.

(Biodegradable)
The reflective film is also capable of being decomposed by microorganisms or the like when landfilled and does not cause various problems associated with disposal. The aliphatic polyester-based resin is hydrolyzed by microorganisms or the like in the soil after the ester bond portion is hydrolyzed in the soil and the molecular weight is reduced to about 1,000.
On the other hand, the aromatic polyester-based resin has high intramolecular bond stability, and hydrolysis of the ester bond portion hardly occurs. Therefore, even if the aromatic polyester-based resin and the polypropylene-based resin are landfilled, the molecular weight does not decrease and biodegradation by microorganisms or the like does not occur. As a result, it remains in the soil for a long period of time, and promotes shortening of the landfill site for waste disposal, and causes problems such as damage to the natural landscape and the living environment of wild animals and plants.

(Production method)
Hereinafter, an example of a method for producing the present reflective film (here, a reflective film having a three-layer structure including B layer / A layer / B layer) will be described, but the present invention is not limited to the following production method.

First, a resin composition comprising a predetermined amount of a fine powder filler, a liquid additive in the case of the resin composition A, a hydrolysis inhibitor, and other additives as required, in the aliphatic polyester resin. Articles A and B are prepared respectively.
Specifically, a fine powder filler to an aliphatic polyester resin, further adding a hydrolysis inhibitor, if necessary, other additives, etc., kneading with a ribbon blender, tamper or Henschel mixer, Using a single or twin screw extruder, etc., the resin is melted at a temperature equal to or higher than the melting point of the aliphatic polyester resin (for example, 170 ° C. to 230 ° C. in the case of a lactic acid polymer). Further, a liquid additive is added by adding a liquid from a vent groove or an injection groove in the middle of the extruder, and extruded to produce resin compositions A and B, respectively. However, the liquid additive may be mixed with the aliphatic polyester resin in advance, or the aliphatic polyester resin, the liquid additive, the fine powder filler, the hydrolysis inhibitor and the like are separately provided as feeders, etc. The resin compositions A and B may be respectively produced by adding a predetermined amount. In addition, in the case of the fine powder filler, resin composition A, a so-called master batch is prepared by blending a liquid additive, other additives, etc. in an aliphatic polyester resin in a high concentration, and this master patch. And an aliphatic polyester resin may be mixed to produce resin compositions A and B having desired concentrations, respectively.

Next, the resin compositions A and B obtained as described above are melted by respective extruders, extruded into a sheet shape, and laminated.
For example, after each of the resin composition A and the resin composition B is dried, the resin composition A and the resin composition B are respectively supplied to an extruder and heated to a temperature equal to or higher than the melting point of the resin to be melted. At this time, the resin composition A and the resin composition B may be supplied to the extruder without being dried, but when not being dried, it is preferable to use a vacuum vent during 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, the extrusion temperature is set within a range of 170 ° C. to 230 ° C. in the case of a lactic acid polymer. It is preferable to do this. Thereafter, the melted resin composition A and resin composition B are respectively extruded from the slit-shaped discharge port of the T-die and laminated in three layers (B layer / A layer / B layer). And cast to form a cast sheet.

By the way, although this reflective film can express sufficient reflectance with the material composition, it obtains much more excellent reflectance by strictly adjusting the conditions of kneading and extrusion in the above production method. It is possible. That is, by setting the resin temperature of the kneaded resin (measured at the mouthpiece outlet) when kneading and extruding the aliphatic polyester-based resin and fine particulate filler such as titanium oxide to a temperature condition consisting of a predetermined temperature range. Higher reflectance can be expressed.
Specifically, the resin temperature of the kneaded resin measured by a contact thermometer at the outlet of the die is 230 ° C. or lower, more preferably 210 ° C. or lower, and particularly preferably 200 ° C. or lower. Thus, the reflectance can be further increased.
Although the clear reason for this is not clarified, by suppressing the resin temperature at the time of kneading to 230 ° C. or lower, not only the thermal deterioration of the resin itself is reduced, but also the deterioration of the fine particle filler such as titanium oxide. Specifically, it is speculated that the deterioration of the surface treatment portion can be particularly suppressed. In particular, finely particulate fillers that have been subjected to various surface treatments, for example, inorganic compounds composed of alumina, silica, zirconia, etc., silicon compounds, polyhydric alcohol compounds, amine compounds, fatty acids to improve dispersibility , Fatty acid ester, siloxane compound, silane coupling agent, fine particle filler coated with an organic compound consisting of polyol and polyethylene glycol, etc., this surface-treated portion is used when the resin composition is extruded. It is presumed that the reflectivity of the reflective film will decrease under temperature conditions higher than 230 ° C. due to deterioration and decomposition under the influence of temperature conditions.

  In addition, the lower limit of the resin temperature of the kneaded resin to be extruded is not particularly limited, and is preferably selected according to the type of the aliphatic polyester resin used. Although it depends on the melting point and melt viscosity of the resin, generally, the melting point of the kneaded resin is preferably 20 ° C. or higher. For example, when a lactic acid-based polymer is used, the melting point of the resin varies depending on the composition ratio of D-lactic acid and L-lactic acid, but is approximately 150 to 160 ° C., and therefore is measured by a contact thermometer at the mouthpiece outlet. The resin temperature of the kneaded resin is preferably 170 ° C. or higher, and more preferably 180 ° C. or higher. When the melting point of the kneaded resin is lower than + 20 ° C., there is a high possibility that the kneading will be insufficient, and as a result, the finely divided filler may become poorly dispersed and it may be difficult to form a uniform reflective film. is there.

As a method of controlling the resin temperature, there are a method of controlling at a set temperature of the extruder, a method of lowering melt viscosity and suppressing shearing heat generation in the extruder.
Like this reflective film, by adding liquid additives such as paraffinic process oil and plasticizer, shear heat generation can be suppressed, and thermal deterioration of the resin itself and deterioration of fine particle fillers such as titanium oxide can be suppressed. It is estimated that the light reflection characteristics can be further improved.

  In the present reflective film, it is preferable that the resin composition A and the resin composition B are melted and laminated as described above, and then the laminate is stretched at least 1.1 times in at least one uniaxial direction. By extending | stretching, since the space | gap which made the fine powder filler a nucleus is formed in a film inside, the light reflectivity of a film can further be improved. This is because when the stretching is performed at a stretching temperature suitable for the aliphatic polyester resin, the aliphatic polyester resin as a matrix is stretched, but the fine powder filler is left as it is. Because the stretching behavior of the aliphatic polyester resin and the fine powder filler is different at the time, a new interface is formed between the aliphatic polyester resin and the fine powder filler. It is considered that the reflectivity is further improved.

Further, the reflective film is preferably stretched in the biaxial direction. By biaxial stretching, a higher porosity can be obtained, and the reflectance of the film can be further improved. Moreover, if the film is only uniaxially stretched, 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 the vertical and horizontal directions. . That is, by biaxial stretching, the peeled area at the interface between the resin and the fine powder filler is increased, the whitening of the film proceeds, and as a result, the light reflectivity of the film can be further enhanced. Axial stretching eliminates anisotropy in the shrink direction of the film, so that the heat resistance of the reflective film can be improved, and further the mechanical strength can be increased.
The stretching order of biaxial stretching is not particularly limited, and 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. Biaxial stretching may be performed by stretching or the like.

  The stretching ratio is preferably 5 times or more, more preferably 7 times or more, as the area magnification. By stretching to 5 times or more in the area magnification, a porosity of 5% or more can be realized, and by stretching to 7 times or more, a porosity of 20% or more can be realized, and 7.5 times or more. A porosity of 30% or more can also be realized by stretching the film.

  The stretching temperature when stretching the cast sheet is preferably in the range of, for example, about the glass transition temperature (Tg) of the base resin of the A layer to the Tg + 50 ° C. or less. For example, the base resin of the A layer is a lactic acid polymer. In this case, the temperature is preferably 50 ° C. or higher and 90 ° C. or lower. If the stretching temperature is 50 ° C. or higher, the film does not break during stretching, and if it is 90 ° C. or lower, the stretching orientation becomes high. As a result, the porosity increases, so that a high reflectance can be obtained.

Moreover, in this reflective film, in order to provide heat resistance and dimensional stability to a film, it is preferable to heat-set after extending | 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.

(Use)
If it uses this reflective film, very high light reflectivity is realizable. Therefore, it is suitable as a reflective film for use in a reflector such as a display such as a personal computer or a television, a lighting fixture, and a lighting signboard, and is particularly suitable as a reflective film for applications requiring a reduction in thickness.
In recent years, there has been an increasing demand for lightweight, small notebook computers, in-vehicle small televisions, and the like, and thin liquid crystal panels that can cope with these demands have been demanded. Therefore, it is required to reduce the thickness of the reflective film, and the reflective film can meet this demand, and a reflective film having a total thickness of less than 100 μm can be realized.
Specifically, a reflection plate used for a liquid crystal display or the like can be formed using the reflection film, and for example, the reflection plate can be formed by laminating the reflection 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 of the manufacturing method of such a reflecting plate is demonstrated.
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-sealing without using an adhesive, a method of bonding via an adhesive sheet, or extrusion coating. There are methods and the like, and 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, commonly used coating equipment such as a reverse roll coater and a kiss roll coater is used, and 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 μm 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, the reflective film is directly coated and cooled using a roll laminator, thereby reflecting the reflective plate Can get. In this case, it is preferable to keep the surface of the metal plate or the like at 210 ° C. or lower because 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) Average particle size Using a powder specific surface measuring instrument (transmission method) of model “SS-100” manufactured by Shimadzu Corporation, 3 g of sample is 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.

(2) Niobium concentration in titanium oxide (ppm)
Nitric acid (10 mL) was added to titanium oxide (0.6 g), and the mixture was decomposed in a microwave ashing apparatus for 80 minutes, and the resulting solution was measured using an ICP emission spectroscopic analyzer.

(3) 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. Prior to the measurement, the photometer was set so that the reflectance of the alumina white plate was 100%.

[Example 1]
(Preparation of resin composition A)
Pellets of lactic acid polymer having a weight average molecular weight of 200,000 (NW4032D, Cargill Dow Polymer Co., Ltd., D isomer: L isomer = 1.5: 98.5, glass transition temperature 65 ° C.) and oxidation with an average particle size of 0.25 μm Titanium (rutile type, niobium concentration: 430 ppm; surface treatment with silica, alumina and zirconia, produced by chlorine process) was mixed at a mass ratio of 50:50 to obtain 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 is kneaded and extruded using a twin-screw extruder to form a pellet. Was made.
And this masterbatch and the said lactic acid-type polymer are mixed by the mass ratio of 40:60, and it supplies to an extruder, Paraffin type process oil (made by Idemitsu Kosan Co., Ltd .: with respect to 100 mass parts of this mixed resin: 1 part by weight of Diana Process PW32) was added from the vent groove, and kneaded and extruded by an extruder heated to 220 ° C. to prepare a resin composition A.

(Preparation of resin composition B)
Pellets of lactic acid polymer having a weight average molecular weight of 200,000 (NW4032D, Cargill Dow Polymer Co., Ltd., D isomer: L isomer = 1.5: 98.5, glass transition temperature 65 ° C.) and oxidation with an average particle size of 0.25 μm Titanium (rutile type, niobium concentration: 430 ppm; surface treatment with silica, alumina and zirconia, produced by chlorine process) was mixed at a mass ratio of 50:50 to obtain a mixture. After adding 2.5 parts by mass of a hydrolysis inhibitor (bis (dipropylphenyl) carbodiimide) to 100 parts by mass of this mixture and mixing, the mixture is kneaded using a twin-screw extruder, extruded into pellets, so-called master. A batch was made.
And this masterbatch and the said lactic acid-type polymer were mixed by the mass ratio of 60:40, and it supplied to the extruder heated at 220 degreeC, knead | mixed and extruded, and produced the resin composition B.

(Production of film)
From the extruders A and B heated to 220 ° C., the resin compositions A and B in the molten state are extruded into a sheet shape so as to have a three-layer configuration of B layer / A layer / B layer using a T die, respectively. The film was formed by cooling and solidification.
The film thus obtained was biaxially stretched 2.5 times to MD and 2.8 times to TD at a temperature of 65 ° C., and then heat-treated at 140 ° C. to obtain a thickness of 250 μm (A layer: 210 μm, B layer: 20 μm) of reflective film was obtained.
The obtained reflective film was subjected to various evaluation measurements, and the results are shown in Table 1.

[Example 2]
In Example 1, a reflective film having a thickness of 250 μm was obtained in the same manner as in Example 1 except that Idemitsu Kosan Co., Ltd .: Diana Fresia PW8 was used as the paraffinic process oil.
The obtained reflective film was subjected to various evaluation measurements, and the results are shown in Table 1.

[Example 3]
In Example 1, a reflective film having a thickness of 250 μm was obtained in the same manner as in Example 1 except that 3 parts by mass of di (2-ethylhexyl) azetate (: DOZ) was used as a plasticizer instead of paraffinic process oil. It was.
The obtained reflective film was subjected to various evaluation measurements, and the results are shown in Table 1.

[Example 4]
In Example 1, a reflective film having a thickness of 250 μm was obtained in the same manner as in Example 3, except that diisosinyl adipate (: DINA) was used as a plasticizer instead of paraffinic process oil.
The obtained reflective film was subjected to various evaluation measurements, and the results are shown in Table 1.

[Example 5]
In Example 1, a reflective film having a thickness of 250 μm was obtained in the same manner as in Example 3 except that diisodecyl adipate (: DIDA) was used instead of the paraffinic process oil.
The obtained reflective film was subjected to various evaluation measurements, and the results are shown in Table 1.

[Comparative Example 1]
In Example 1, a reflective film having a thickness of 250 μm was obtained in the same manner as in Example 1 except that the resin composition to which no paraffinic process oil was added was used.
The obtained reflective film was subjected to various evaluation measurements, and the results are shown in Table 1.

In Example 1, when the resin composition A is produced, the temperature of the extruder is set to 220 ° C. and the process oil is blended to suppress the resin temperature during kneading to at least 230 ° C. or less. That is, by blending the process oil, the shear viscosity at the time of kneading is reduced to suppress the temperature rise at the time of kneading, and the resin temperature at the time of kneading is suppressed to at least 230 ° C. or less. As a result, the thermal deterioration of the resin is suppressed, and an even higher reflectance can be realized. This is apparent when the results of Comparative Example 1 in which no process oil is blended are compared.

Claims (8)

  An aliphatic polyester-based resin reflective film comprising an A layer composed of a resin composition A containing an aliphatic polyester-based resin, a fine particulate filler, and a liquid additive.   2. The aliphatic polyester resin reflective film according to claim 1, wherein the liquid additive is a paraffinic process oil.   The aliphatic polyester resin reflective film according to claim 2, wherein the content of the paraffinic process oil is 0.1% by mass or more and 5% by mass or less of the resin composition A.   The aliphatic polyester-based resin reflective film according to claim 1, wherein the liquid additive is a plasticizer.   The aliphatic polyester-based resin reflective film according to claim 4, wherein the content of the plasticizer is 1% by mass or more and 10% by mass or less of the resin composition A.   The fat according to any one of claims 1 to 5, comprising a structure in which a B layer composed of a resin composition B containing an aliphatic polyester-based resin and a fine powder filler is laminated on both sides of the A layer. Group polyester resin reflective film.   The aliphatic polyester-based resin reflective film according to any one of claims 1 to 6, wherein the aliphatic polyester-based resin of the A layer, the B layer, or both of these layers is a lactic acid-based polymer. A reflector comprising the aliphatic polyester-based resin reflective film according to claim 1.