JPS5830745B2 - polyester resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyester resin composition,
More specifically, the present invention relates to a polyester resin composition suitable for light emitting diode display boards.

Recently, the use of light emitting diodes for display elements, optical communications, etc. has been increasing significantly.

Gallium-phosphorous (Gap) is usually used as a light emitting diode.
Many are made as PN junction diodes of intermetallic compound semiconductors such as , gallium-aluminum-phosphide (GaAlp), and gallium-arsenic-phosphide (GaAsp).

When using a light emitting diode as a display element, a segment method is usually used.

The segment method is a method in which numbers and letters are divided into several parts and the desired number or character is displayed by combining them, and each part of the number or letter is called a segment.

Each segment consists of a light emitting diode and a portion that reflects the light emitted from the light emitting diode.

Furthermore, a portion for dividing the segments and for blocking light is also required.

Normally, the reflecting portion and the shielding portion are integrally molded from the same material.

(Hereinafter, the reflective part and the shielding part will be collectively referred to as the display board.

) The characteristics required for a display board are first of all the property of efficiently reflecting the light emitted from the light emitting diode.

The emission wavelength of a light emitting diode is usually 5 due to the relationship with visibility.
00~700n77L is normal, and as a display board,
It is necessary that the reflectance in this wavelength range be high.

Since it is extremely troublesome to measure the reflectance due to light of 500 to 700n771, we investigated various alternative characteristic values and found that the L
It was found that there was an extremely good correspondence between the values.

Therefore, the inventor has set L as the first goal for such applications.
We conducted extensive research with the aim of improving the value.

The higher the L value is, the more preferable it is; however, when the L value is 93, the reflectance at a wavelength of 500 to 700 nm is about 90%, and when the L value is lower than this, the reflectance is less than 90%, which is not preferable.

Therefore, it has been found that the L value for such uses needs to be 93 or more, preferably 93.5 or more, and more preferably 94 or more.

Furthermore, in addition to reflection 1, characteristics required for display boards include resistance to impact and heat during manufacturing and use, that is, high toughness and high heat distortion temperature. It has also been found that chemical resistance, abrasion resistance, easy moldability, etc. are also required.

The inventors of the present invention conducted extensive research on resin compositions that fully satisfy these required characteristics, and found that a composition containing a specific proportion of titanium oxide in a specific crystal form with an aromatic polyester resin, particularly polybutylene terephthalate, was found to be suitable for use in light-emitting diode displays. The present invention has been achieved by discovering that the required properties for a plate are fully satisfied.

That is, in the present invention, rutile-type titanium oxide with a particle size of 0.01 to 10 μm is added in an amount of 5 parts by weight per 100 parts by weight of aromatic polyester.
This is a polyester resin composition for a light emitting diode display board, characterized in that it contains ~120 parts by weight and has an L value of 93 or more.

Here, the L value is the L value measured using a Hunter color meter using a test piece with a diameter of 50 mm and a thickness of 2X, and the larger the value, the higher the brightness.

The saturated aromatic polyester used in the present invention is a polyester having an aromatic ring in the chain unit of the polymer, and is a polyester containing an aromatic dicarboxylic acid (or its ester-forming derivative).
It is a polymer or copolymer obtained by a condensation reaction mainly consisting of diol and diol (or its ester-forming derivative).

Examples of the aromatic dicarboxylic acid component include dicarboxylic acids having a benzene nucleus such as terephthalic acid and isophthalic acid, naphthalene-1,5-dicarboxylic acid, and naphthalene-1,5-dicarboxylic acid.
These include dicarboxylic acids having a naphthalene nucleus such as 2,6-dicarboxylic acids, or ester-forming derivatives thereof.

Further, as the acid component, 20 mol % or less of dicarboxylic acids other than aromatic dicarboxylic acids (for example, adipic acid, cepatic acid) or ester-forming derivatives thereof may be substituted.

Examples of diol components include ethylene glycol,
trimethylene glycol, tetramethylene glycol,
Aliphatic glycols such as hexamethylene glycol, diethylene glycol, and cyclohexanediol, ■・4
-Diols having aromatic groups such as -bisoxyethoxybenzene and bisphenol A, or their ester-forming derivatives.

The aromatic polyester used in the present invention is not limited to one type of aromatic polyester, but may be a mixture of two or more types of aromatic polyesters.

A particularly preferred aromatic polyester is polybutylene terephthalate.

The titanium oxide used in the present invention is rutile-type titanium oxide.

Titanium oxide has rutile type and anatase type.

Anatase-type titanium oxide has a lower Mohr hardness than rutile-type titanium oxide, and has advantages such as less wear on the extruder when producing compositions using an extruder, etc., and less negative impact on the matrix. Although it is widely used because of its low light reflection properties and shielding properties, it requires a large amount of additives for the purpose of the present invention, and also has low light reflectance.

Furthermore, among rutile-type titanium oxides, those produced by the chlorine method are particularly preferably used because of their high quality stability.

The particle size of titanium oxide used in the present invention is 0.01 to 10
μ, more preferably in the range of 0.1 to 1 μ.

Particle size is 0.05% sodium hexametaphosphate solution 2
This is the weight median diameter measured by adding 5 gr of titanium oxide to 50 CC and dispersing with high speed stirring for 3 minutes, followed by centrifugal sedimentation (1000 r, p, m).

If the thread diameter of titanium oxide exceeds 10 μm, dispersion into the saturated aromatic polyester will be poor, resulting in poor L value and appearance properties of the composition molded product, as well as low toughness, which is undesirable.

If the particle size of titanium oxide is less than 0.01 micron, it is extremely difficult to produce titanium oxide itself, and the cost is also extremely high, which is undesirable.

The amount of titanium oxide used in the present invention is in the range of 5 to 120 parts by weight, preferably 10 to ioo parts by weight, per 100 parts by weight of the saturated aromatic polyester.

The amount of titanium oxide added is the amount normally added to color or hide plastics (for example, 0.5
~5 parts by weight).

If the amount of titanium oxide added is less than 5 parts by weight, it is not possible to obtain a molded composition having an L value of 93 or more, and the light shielding effect is also small, which is not preferable.

If the amount of titanium oxide added is 120 parts by weight or more, no improvement in the L value can be expected, molding becomes difficult, and the toughness is also significantly reduced.

The composition of the present invention may contain various additives, such as stabilizers, flame retardants, modifiers, moldability improvers, crystallization promoters, reinforcing agents, and the like.

Further, other thermoplastic resins or thermosetting resins may be contained in amounts within a range that does not reduce the properties aimed at by the present invention.

Compositions of the invention can be manufactured in a variety of ways.

For example, a saturated aromatic polyester and titanium oxide are placed together in an extrusion mixer to form pellets for molding.

Alternatively, the composition of the present invention may be triblended and molded by direct injection molding or transfer molding.

Hereinafter, the present invention will be explained in detail with reference to Examples.

Note that parts in the examples are parts by weight.

The intrinsic viscosity of polyester is measured at 35°C using orthochlorophenol as a solvent.

Examples 1 to 5, Comparative Example 1 ※※ 100 parts of polyethylene terephthalate (intrinsic viscosity 1°01) dried at 120°C for 5 hours and a specific titanium oxide were blended in the proportions shown in Table 1, and an extruder was used. The mixture was melt mixed and extruded at 250° C. to obtain pellets.

From the obtained pellets, use an injection molding machine to reduce the diameter to 50%.
A test piece with a thickness of 2 mm was prepared.

Next, the values of a and b were measured using a computer type color meter.

The results obtained are shown in Table 2. Regarding Example 2, molded pieces for ASTM D638 tensile test, ASTM D256 impact test, and ASTM D648 thermal deformation test were prepared using an injection molding machine, and the results of each evaluation are shown in Table 2.

Despite adding a large amount of filler such as tan, it has extremely high elongation at break and impact strength.
This is amazing.

Furthermore, it also has an extremely high heat distortion temperature.

Claims (1)

[Scope of Claims] 1. A light emitting device containing 5 to 120 parts by weight of rutile titanium oxide with a particle size of 0.01 to 10 μm per 100 parts by weight of aromatic polyester, and having an L value of 93 or more. Polyester resin composition for diode display boards. 2. The composition according to claim 1, wherein the aromatic polyester is polybutylene terephthalate.