JPH09157367A - Polyester polymer for liquid crystal display film or sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyester polymer which exhibits a high brightness of transmitted light, a low refractive index, and improved heat resistance, clarity, moldability, and dimensional stability by reacting an acid component comprising a dicarboxylic acid and/or its ester-forming deriv. with a diol component. SOLUTION: This polyester polymer, having a refractive index of 1.60 or higher, is obtd. by reacting an acid component comprising at least one dicarboxylic acid (e.g. terephthalic acid or 2,6-naphthalenedicarboxylic acid) and/or its ester-forming deriv. with a diol component contg. 10-95mol% dihydroxy compd. represented by the formula (wherein R1 is a 2-4C alkylene; and R2 to R5 are each H, a 1-7C alkyl, an aryl, or an aralkyl). 9.9-Bis[4-(2- hydroxyethoxy)phenyl]fluorene is pref. as the dihydroxy compd. from all the viewpoints of refractive index, birefringence, clarity, heat resistance, and moldability. Ethylene glycol, etc., usually used for producing a polyester is used as a diol other than the dihydroxy compd. If necessary, additives such as a lubricant are incorporated into the polymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester polymer, and more specifically to a liquid crystal display having a high refractive index, a small birefringence, excellent heat resistance, transparency, moldability, and dimensional stability. It relates to a polyester polymer suitable for a film sheet.

[0002]

2. Description of the Related Art Conventionally, plastics used for film sheets of liquid crystal displays are polycarbonate (hereinafter abbreviated as PC) or a combination of acrylic resin and polyethylene terephthalate. However, because of their low refractive index, the brightness of transmitted light is low,
It has a drawback that the light source cannot be used efficiently. In addition, since the moldability is poor, the product does not stop easily.

[0003]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made extensive studies in view of the drawbacks of the prior art, and as a result, have found that the novel polyester polymer solves these drawbacks and completed the present invention. However, the purpose is that the brightness of the transmitted light is high because of the high refractive index, and
Another object of the present invention is to provide a polyester polymer having a small birefringence, excellent heat resistance, transparency, moldability, and dimensional stability and suitable for a film sheet of a liquid crystal display.

[0004]

The above-mentioned object is characterized by comprising a dicarboxylic acid and / or its ester-forming derivative and a diol, and the diol contains a dihydroxy compound represented by the following general formula (1). And a polyester polymer for a film sheet of a liquid crystal display, and a polyester polymer for a film sheet of a liquid crystal display characterized by having a refractive index of 1.60 or more.

[0005]

Embedded image

(R ₁ is an alkylene group having 2 to 4 carbon atoms, R ₂ , R ₃ , R ₄ and R ₅ are hydrogen or an alkyl group having 1 to 7 carbon atoms, an aryl group or an aralkyl group, They may be the same or different.)

The present invention will be described in detail below.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester polymer of the present invention comprises
As described above, the polyester polymer comprises a dicarboxylic acid and / or its ester-forming derivative and a diol, and the diol contains the dihydroxy compound represented by the general formula (1).

The polyester polymer of the present invention has an intrinsic viscosity (60% by weight of phenol, 1, 1, 2,
2-tetrachloroethane in a 40% by weight mixed solution, 20 ° C
Is 0.4 or more and 0.7 or less. If the intrinsic viscosity is in this range, it is particularly excellent in moldability,
The film sheet of a liquid crystal display, which is a product, has a good stopping time.

The polyester polymer of the present invention preferably has a refractive index of 1.60 or more. Refractive index 1.60
If it is above, the transmitted light brightness of the film sheet of a liquid crystal display which is a product will become high enough.

The glass transition temperature (hereinafter abbreviated as Tg) of the polyester polymer of the present invention is preferably 100 ° C. or higher from the viewpoint of heat resistance of the prism sheet as a product. When the Tg is 100 ° C. or higher, the film sheet of the liquid crystal display, which is a product, has sufficiently high heat resistance to prevent thermal deterioration.

The use of the compound represented by the general formula (1) as a copolymerization component is a key part of the present invention, whereby the refractive index is high, the birefringence is small, the heat resistance and the transparency are high. It was found that a polyester polymer having excellent properties, moldability, and dimensional stability, which is suitable for a film sheet of a liquid crystal display, can be obtained.

It is also a key part of the present invention that the terminal group of the compound represented by the general formula (1) is an aliphatic hydroxyl group. When this is a phenolic hydroxyl group, the polyester polymer becomes rigid and crystallizes, and the moldability becomes extremely poor. Further, if it is an aliphatic hydroxyl group, the melt polycondensation method can be used, and the polyester polymer can be industrially produced at low cost, but the phenolic hydroxyl group cannot use the melt polycondensation method.

Since the compound represented by the general formula (1) has many benzene rings, the polyester polymer of the present invention has a very high refractive index of 1.60 or more.

Further, since the polarizability of the benzene rings in the main chain direction and the side chain direction is well balanced, the birefringence becomes extremely small.

Further, since it is amorphous, it has high transparency.

Since it has many benzene rings, it has a high glass transition temperature and excellent heat resistance.

The intrinsic viscosity of the polyester polymer of the present invention can be easily adjusted by changing the polymerization conditions such as the polymerization temperature and the polymerization time.

Examples of the dicarboxylic acid used for the polyester polymer of the present invention include dicarboxylic acids used for ordinary polyesters. Examples thereof include benzenedicarboxylic acid such as terephthalic acid and isophthalic acid, 2,6-naphthalenedicarboxylic acid, and the like. Naphthalenedicarboxylic acids such as 1,5-naphthalenedicarboxylic acid, biphenyldicarboxylic acids such as 2,2′-biphenyldicarboxylic acid, aliphatic dicarboxylic acids such as succinic acid and adipic acid, and alicyclic rings such as 1,4-cyclohexanedicarboxylic acid Examples thereof include group dicarboxylic acids and their derivatives, and among these, terephthalic acid is preferable from the viewpoint of refractive index and moldability. These may be used alone or in combination of two or more as needed.

Examples of the dihydroxy compound represented by the general formula (1) for use in the polyester polymer of the present invention include 9,9-bis [4- (2-hydroxyethoxy) phenyl] -fluorene and 9,9- Bis [4- (2-hydroxyethoxy) -3-methylphenyl] -fluorene, 9,9-bis [4- (2-hydroxyethoxy)-
9,9-bis [4- (2-hydroxyethoxy) -3-alkylphenyl] -fluorenes such as 3-ethylphenyl] -fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3, 9,9-Bis [4- (2-hydroxyethoxy) -3 such as 5-dimethylphenyl] -fluorene and 9,9-bis [4- (2-hydroxyethoxy) -3,5-diethylphenyl] -fluorene. ，
5-dialkylphenyl] -fluorenes, 9,9-bis [4- (2-hydroxyethoxy) -3-phenylphenyl] -fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3,5 9,9-bis [4- (2-hydroxyethoxy) -3-arylphenyl] -fluorenes such as -diphenylphenyl] -fluorene, or 9,9-bis [4- (2-hydroxyethoxy)-
3,5-diarylphenyl] -fluorenes, 9,9
-Bis [4- (2-hydroxyethoxy) -3-benzylphenyl] -fluorene, 9,9-bis [4- (2-
Hydroxyethoxy) -3,5-dibenzylphenyl]
-9,9-bis [4- (2-hydroxyethoxy) -3-aralkylphenyl] -fluorenes such as fluorene, or 9,9-bis [4- (2-hydroxyethoxy) -3,5-diaralkyl Phenyl] -fluorenes, 9,9-bis [4- (2-hydroxypropoxy)]
9,9 such as phenyl] -fluorene and 9,9-bis [4- (2-hydroxybutoxy) phenyl] -fluorene.
-Bis [4- (2-hydroxyalkoxy) phenyl]
-Including fluorenes and their derivatives,
Among them, 9,9-bis [4- (2-hydroxyethoxy) phenyl] -fluorene is preferable because it is effective in all of the refractive index, birefringence, transparency, heat resistance, and moldability.
These may be used alone or in combination of two or more as needed.

Examples of the diol to be used in the polyester polymer of the present invention, other than the dihydroxy compound represented by the general formula (1), include diols usually used in polyesters. For example, ethylene glycol, 1 Aliphatic diols such as 1,4-butanediol, alicyclic diols such as 1,4-cyclohexanedimethanol and tricyclodecanedimethylol, aromatic diols such as 1,4-benzenedimethanol, 1,1 -Bis [4- (2-hydroxyethoxy) phenyl] -cyclohexane, 1,1-bis [4- (2-hydroxyethoxy) phenyl] -1-phenylethane, 2,2-bis [4- (2-hydroxy) Ethoxy) phenyl] -4-methylpentane, 2,2-bis [4- (2-hydroxyethoxy) phenyl] Examples thereof include bisphenol derivative dihydroxy compounds such as propane and bis [4- (2-hydroxyethoxy) phenyl] -sulfone, and derivatives thereof. Among them, ethylene glycol is preferable from the viewpoints of birefringence, transparency and moldability. . These may be used alone or in combination of two or more as required.

The content of the dihydroxy compound represented by the general formula (1) in the polyester polymer of the present invention is preferably 10 mol% or more and 95 mol% or less of all diols from the viewpoint of transparency and production method. When the amount of the dihydroxy compound represented by the general formula (1) is 10 mol% or more, crystallization is less likely to occur, which is advantageous in that the transparency is good. On the other hand, when it is 95 mol% or less, there is an advantage that the polymerization rate by the melt polycondensation method is fast and the intrinsic viscosity is easily adjusted.

If desired, the polyester polymer of the present invention may contain various components such as a lubricant, a heat-resistant agent, an antistatic agent, an ultraviolet absorber and a pigment, which are usually contained in optical materials.

When the polyester polymer of the present invention is applied to a film sheet for a liquid crystal display, it includes a step of introducing raw materials, a polymerization step, a step of pelletizing the polymer, a step of refining pellets, a step of forming a prism sheet, etc. It is preferable to carry out in an environment where dust is not mixed in. The cleanliness in this case is preferably class 1000 or less.

Since the polyester polymer of the present invention uses the dihydroxy compound represented by the general formula (1) as a copolymerization component, it has a very high refractive index, a small birefringence, and is amorphous so that it is transparent. Excellent and high glass transition temperature. When the refractive index is high and the birefringence is small, when the film sheet of a liquid crystal display is used, the intensity of light passing through the sheet can be increased, that is, the brightness can be increased, and the cold cathode tube as a light source can be efficiently used. Can be used. Therefore, the power consumption of the display can be saved.
Further, the heat resistance is as high as 100 ° C. or higher, and there is no thermal deterioration during use.

[0026]

The present invention will be specifically described below with reference to examples. The refractive index, birefringence index, total light transmittance, Tg and relative luminance increase rate of the film sheet in the examples were evaluated by the following methods.

(1) Refractive index Measured with an Abbe refractometer.

(2) Birefringence index A non-oriented film having a length of 40 mm, a width of 2 mm and a thickness of 0.1 mm was heat-stretched by 40% at a temperature of Tg + 10 ° C. and a stretching rate of 20% / sec, and then rapidly cooled. The birefringence of each part was measured with an ellipsometer (light source 630 nm).

(3) Total light transmittance Measured according to JIS K7105.

(4) Tg Using a differential scanning calorimeter (Rigaku Denki DSC-8230), about 10 mg of the sample was heated at a temperature rising rate of 10 ° C./min for measurement.

(5) Relative Luminance Increasing Rate A sample sheet having a width of 100 mm, a length of 100 mm, a thickness of 140 μm, a prism angle of 90 ° and a prism pitch of 30 μm was formed, and the cold cathode tube was used as a light source to pass through the sample sheet to make a photo. A measurement system up to the diode was prepared, and evaluation was made by a relative value with the brightness of the sheet of the combination of acrylic resin and polyester of Comparative Example 1 described later as 1 being set.

Example 1 Transesterification using 1.0 mole of terephthalic acid dimethyl ester, 0.4 mole of 9,9-bis [4- (2-hydroxyethoxy) phenyl] -fluorene and 1.7 mole of ethylene glycol as a raw material. Calcium acetate as catalyst 0.0
Using 008 mol and 0.0002 mol of manganese acetate, these were charged into a reaction vessel and stirred to prepare 1
The transesterification reaction was carried out by gradually heating from 50 ° C to 230 ° C. After extracting a predetermined amount of methanol out of the system, 0.0016 mol of germanium oxide as a polymerization catalyst was colored, and phosphoric acid triethyl ester was used as an antioxidant of 0.0
Add 012 mol, gradually raise the temperature and reduce the pressure, and remove the generated ethylene glycol while heating at 27
At 0 ° C., the degree of vacuum reaches 0.5 Torr or less. While maintaining this condition, waiting for the increase in viscosity, the reaction was terminated when the torque applied for stirring reached a predetermined value, and the mixture was extruded into water to obtain pellets.

The refractive index of this polyester polymer is 1.6.
2 was extremely high, the birefringence was small as 0.0040, the total light transmittance was 90%, and the Tg was 125 ° C.
In addition, the relative increase rate of brightness when the film sheet is 1.1
It was as good as 5.

Example 2 1.0 mol of terephthalic acid dimethyl ester as a raw material,
0.7 mol of 9,9-bis [4- (2-hydroxyethoxy) phenyl] -fluorene, ethylene glycol 1.
Pellets were obtained in the same manner as in Example 1 except that 7 mol was used.

The refractive index of this polyester polymer is 1.6.
3, the birefringence was as small as 0.0019, the total light transmittance was 90%, and the Tg was 145 ° C. Further, the rate of increase in relative luminance when formed into a film sheet was good at 1.18.

Examples 3 to 5 Pellets were obtained in the same manner as in Example 1 except that the composition of the raw materials was changed as shown in Table 1, and the physical properties of the polyester polymer were evaluated. Table 1 shows the evaluation results.

Comparative Example 1 A film sheet was prepared from an acrylic resin (prism portion) and polyethylene terephthalate (substrate portion), and each physical property was evaluated. Table 1 shows the evaluation results.

Comparative Example 2 The physical properties of a commercially available PC (Novarex AD3 manufactured by Mitsubishi Kasei) were evaluated. Table 1 shows the evaluation results.

[0039]

[Table 1]

As is apparent from Table 1, Examples 1 to 5
In each case, the rate of increase in luminance was higher than in Comparative Examples 1 and 2, and in all other physical properties, the same or higher than those in Comparative Examples 1 and 2 were obtained. That is, the polyester polymer of the present invention is suitable for a film sheet of a liquid crystal display.

[0041]

As described above, the polyester polymer of the present invention has a high refractive index, a small birefringence, and is amorphous so that it has excellent transparency, and also has a high glass transition temperature and excellent heat resistance. It also has excellent moldability. Therefore, when it is used as a film sheet for a liquid crystal display, it exhibits a high rate of increase in luminance, the cold cathode tube as a light source can be used efficiently, and the power consumption of the display can be saved, which is suitable for this application.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuko Suzuki 2-23-14 Takada, Hirakata-shi, Osaka (72) Inventor Kazuro Sakurai 117-7 Nishishin-cho, Himeji-shi, Hyogo

Claims (2)

[Claims] 1. A polyester polymer for a film sheet of a liquid crystal display, comprising a dicarboxylic acid and / or an ester-forming derivative thereof and a diol, the diol containing a dihydroxy compound represented by the following general formula (1). Coalescing. Embedded image (R ₁ is an alkylene group having 2 to 4 carbon atoms, R ₂ , R
₃ , R ₄ and R ₅ represent hydrogen or an alkyl group having 1 to 7 carbon atoms, an aryl group or an aralkyl group, which may be the same or different. ) 2. The polyester polymer for a film sheet of a liquid crystal display according to claim 1, which has a refractive index of 1.60 or more.