JPS61210332A - Material for nonlinear optical element and formation of pattern - Google Patents

Abstract

PURPOSE:To obtain a patternable material for a nonlinear optical element having superior processability and stability by using a material having a specified amphipatic molecular structure. CONSTITUTION:This patternable material for a nonlinear optical element having an amphipatic molecular structure is represented by formula I (where M is hydrophobic residue contg. a polymerizable monomeric unit, A is a hydrophobic residue contg. a nonlinear optical substance, and L is a hydrophilic residue). The material patternable with high energy beams is obtd. by introducing an org. compound having a high nonlinear optical constant on the molecular level into amphipatic molecules contg. monomeric units sensitive to high energy beams and having capacity of forming a molecular oriented thin film. The material maintains the high nonlinearity of the org. compound, is hardly damaged by light,and has considerably improved mechanical strength as compared with a low molecular org. compound.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to materials for nonlinear optical elements that have particularly excellent workability and stability among various optical elements used in information processing and optical communications, and This invention relates to a method of forming a nonlinear optical pattern using a material.

[Conventional technology]

Conventionally, molecular crystals of organic compounds such as 2-methyl-4-nitroaniline (MNA) are known to have significantly large nonlinear optical constants that cannot be obtained from inorganic compounds. In addition, because the origin of optical nonlinearity is electrons within the molecule, it is presumed that high-speed switching of less than picoseconds is possible without the interference of lattice vibrations unlike inorganic compounds.

To give a specific example and compare, LiNb PO4 (KDP) and LiNb, which are already used as practical elements for wavelength conversion etc.
While it is difficult for inorganic ferroelectric crystals such as O3 to respond at high distances of picoseconds, MNA has a nonlinear optical constant more than 50 times that of KDP, and has a response of about a01 picoseconds. It is believed that high-speed switching is possible.

[Problems that the invention helps solve]

However, compared to inorganic optical materials, organic molecular crystals are weaker against mechanical, thermal, and chemical external forces and have poor processability, making it difficult to form optical waveguides on substrates, which is the basis for integration, making it practical. It has been thought that it is difficult to serve.

An object of the present invention is to provide a material for a nonlinear optical element that is superior in workability and stability than ever before, and a method for forming a nonlinear optical pattern using the material.7 [Means for solving the problems] ] To summarize the present invention, the first invention of the present invention relates to a patternable nonlinear optical element material having an amphiphilic molecular structure, which has the following general formula [I]: >L...CI) ( However, M is a hydrophobic residue containing a polymerizable monomer unit, A is a hydrophobic residue containing a nonlinear optical substance, and L is a hydrophilic residue.

The second invention of the present invention is an invention relating to a method for forming a nonlinear optical pattern, in which a crystalline molecule-oriented thin film of a patternable nonlinear optical element material is coated on a substrate, and a pattern of high-energy radiation is irradiated. , in a method of forming a nonlinear optical pattern by forming a nonlinear optical material having a desired shape at a desired position on a substrate by subsequent development, as the patternable nonlinear optical element material, the above general formula (1) is used. It is characterized by using a material with an amphipathic molecular structure represented by:

In view of the current state of organic materials for nonlinear optical elements and methods of forming nonlinear optical patterns as described above, the present inventors have conducted various studies and researches to solve the conventional problems, and as a result, they have discovered a large An organic compound having a nonlinear optical constant is introduced into an amphiphilic molecule that has a monomer unit that is sensitive to high energy rays and has the ability to form a molecularly oriented thin film, thereby creating a nonlinear optical material that can be patterned by high energy rays. The present invention was completed based on the discovery that this is extremely effective for achieving the above object.

In the material for a nonlinear optical element having an amphipathic molecular structure according to the present invention, the hydrophobic residue containing a polymerizable monomer unit represented by M has, for example, the following general formula CI! E ~ [■]: (!H, = c-c-o+aHke- ... (
II) II n (where n is an integer of 6 to 24, R represents hydrogen or a methyl group)
However, n represents an integer from 6 to 24.
Phase ... (IV) (however, t is an integer from 6 to 18, m
represents an integer from 0 to 8), but the value of n in general formula (II), n in (1), and z+m in [■] is 12 to 20s.
degree is most desirable.

In the material of the general formula (1), the hydrophobic residue containing the nonlinear optical substance represented by A is, for example, one of the following general formulas (V) to
[, IX]: (where p is an integer of 0 to 5, q is an integer of 2 to 12, R1
represents hydrogen, methyl group or ethyl group (where r is 1
~4 integer, q is an integer from 2 to 12 (however, θ and t are 1 to 12)
an integer of 18, b is the formula -IJHOO- or -00NH-
An amide group represented by R1, OH, -jOH, (wherein S and t are integers from 1 to 18) CHl-?
CTX, f-i:l0H-+0kt (where a and t are integers of 1 to 18, 2 represents an amino group), but p+(
As for the values of L%r+q and act, it is desirable that the length of this hydrophobic residue (M) is approximately equal to the length of the hydrophobic residue (M) shown in general formulas []] to [Iv]. .

In addition, as shown in the formula below, the tertiary carbon in the long chain alkyl group of general formulas [■] and [IX] is more advantageous in the formation stage of the molecular orientation film, but it is basically an optically active carbon. There is no problem even in racemic form.

The hydrophilic residue represented by L in the material of the general formula [I] can be represented by, for example, the following general formulas (X) to 0(M).
(However, R3 is the formula -0H5
Or -〇H, -OL:OH, represented by ler group, xehaCt
e, Bre, 工 e and tz CjlOa tear J" anion, Y is the formula -1:!0OCH snow OH, - or -
(represents a spacer represented by CH,-) (However, U is the number 2 or 5, R is hydrogen or a methyl group,
, is -30s or -0PO? Zwitterionic anion represented by, Y has the formula -cooca, cu! -or-〇H,-
] 1: 1) C11l-Xl aqueous group or -〇-Go-C==OH, or methyl group] A nonionic hydrophilic compound having a polymerizable heptadmer group-unit represented by ]△ (However, W is a number of 1 or 2, X is an integer from 1 to 12, x0
(Yl represents a group represented by the formula -0CO- or -Nuco-, and -CH- represents an asymmetric carbon) (However, W is a number of 1 or 2, y is an integer of 1 to 18, Yl
represents a group represented by the formula -oao- or -Naco-,
The hydrophilic residue (L) represented by -0H- indicates an asymmetric carbon is the most commonly used, but 7'? , MeKt! , general formula CX
V), (XVII O hydrophilic residue (L) is effective.

As explained above, in the patternable nonlinear optical element material having the amphiphilic molecular structure represented by the general formula (1), there are a wide variety of types and combinations of the three constituent elements M and A%L. is also optional. Those skilled in the art can appropriately implement and modify the types and combinations of M1 and L using their knowledge.

Furthermore, examples of methods for coating crystalline molecule-oriented thin films of materials for nonlinear optical elements include (1) the Langmier-Air-Projet type cumulative film production method or its improved horizontal deposition method or continuous film production method; ) Cast film orientation treatment method arrangement K (3
) vacuum evaporation method, etc.

The above-mentioned method for coating a crystalline molecule-oriented thin film becomes possible only when the material for a nonlinear optical element of the present invention comprises amphiphilic molecules.

As for specific methods for producing crystalline molecularly oriented thin films (1) to (3), the following publications may be cited as references: (1) rJ-times Langmuir-Prodgett International Conference on Films'' materials, Shin- Solid Films, 99 (
1982) (2) Shimozai, Kunitake, “Proceedings of the 52nd Polymer Symposium J”
52 (1su, 2841, (1985) (3) Mitsuya,
Each day, IEEJ Study Group Materials, P51, (1984), and Arita, Banjo, Ishiba, each day, "IEEJ Study Group Materials",
P. 59, (1984) Furthermore, examples of high-energy rays that can be used in patterning according to the present invention include deep ultraviolet rays, Function.

However, the hydrophobic residue (A) containing the nonlinear optical substance contains substances that may cause cross-linking and decomposition in response to high-energy rays, such as stilbenes and diphenylacetylenes. Setting the irradiation amount of electron beams and X-rays is important.

In the present invention, we have found irradiation conditions that minimize crosslinking and decomposition of the nonlinear optical material and allow good pattern formation.

As a basic manufacturing method of the material for nonlinear optical elements of the present invention, first, a hydrophobic residue (A) containing a nonlinear optical substance and a hydrophilic residue (L) are mixed by O-C, O-N.

A method of introducing a hydrophobic residue (M) containing a polymerizable monomer unit after coupling with a C-O bond, and A-L
After coupling, there is a method of first introducing only the hydrophobic portion of the compound to make it an amphiphilic molecule, and finally introducing the polymerizable heptad unit of M. Usually, the former method is used, but when the polymerizable seven-mer unit has high polymerizability, such as acrylic alcohol, it is desirable to use the latter method.

In an example of the method for manufacturing a nonlinear optical element of the present invention, first, (1) the Langmuir-Prodgett type cumulative film tabulation method or its improved horizontal deposition method or continuous film forming method;
) A cast film orientation treatment method and (3) a vacuum evaporation method is used to irradiate the crystalline molecular orientation film exploded on the substrate with deep ultraviolet rays, X-rays through a mask, and electron beams directly. The pattern is baked, and then developed with a suitable developing solution such as methyl ethyl ketone, xylene, or a mixed solvent of these with isopropyl alcohol or cyclohexane, etc., followed by washing and post-baking to further improve the adhesion of the pattern and to remove the solvent during development. remove.

Thus, according to the method of the present invention, a crystalline nonlinear optical material of a desired size can be placed at a desired position on a substrate. The material of the present invention has high sensitivity to high-energy rays and excellent resolution, so it can be used with sufficient productivity even in high-density optical integrated circuits.

Furthermore, since the material exhibiting nonlinearity is an organic polymer crystal solidified by polymerization, it maintains the high nonlinearity of organic matter.
Moreover, it is less susceptible to damage by light, and its mechanical strength can be significantly improved compared to low-molecular organic compounds.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to production examples and examples, but the scope of the present invention is not limited in any way by these production examples and examples.

Note that FIG. 1 is a schematic diagram showing the structure of a waveguide used for measurement of the optical material of the present invention, in which a sample is patterned on top of a tapered quartz waveguide layer.

FIG. 2 is a schematic cross-sectional view of the measuring device. The code 1 in Fig. 2 is N (1: YAG laser (λ = = 1.06μ
m1 output 1kW), 2 is a polarizer, 5 is an infrared transmission filter, 4 is a condenser lens, 5 is a mirror, 6 is a prism, 7 is a sample, 8 is a quartz waveguide layer, 9 is an infrared cutoff filter, 10 Set the interference filters (530nm, 552nm) to 11
means photomaru.

Production Example 1 Synthesis of material for nonlinear optical element having the following structure (1) CHrf
O11*trrCmi0-Br+HOmiOse%jjB
r-ichiu CH3-t-OH! 7rIC Mi C-C Mi ○-+
0HztrBr (1b) (IsL) + (
1c) (1) p-nitrophenylacetic acid (10
f) and N-methyl-N-(8-bromooctylnoamino-p-benzaldehyde (20f) at 120°C.
The mixture was heated to a temperature of 100.degree. C. and reacted for 1 hour. The product was recrystallized from 95% ethanol to obtain compound (1a). Red-orange scale-like crystals, yield *25? A compound (1b) synthesized by cross-coupling 1-bromo-1-tetradecine and 10-bromo-1-decyne under a copper catalyst is reacted with dimethylamine in an ampoule,
Compound (1c) was obtained.

(1a) (10f ) and (1c) (10f
) in dimethylformamide (20(ld)),
The reaction was carried out at 60°C for 5 hours. After cooling, the precipitated crystals were recrystallized from acetonitrile to obtain the target compound (good for drying. Red-orange scaly crystals, yield 13f. Production Example 2 Synthesis of nonlinear optical material with the following structure (2) (2a) + H
O[CH company■Br QH,=C! He-Br p-nitrophenylacetylene (7f) (!-N.

N,N-)limethyl-N-(4-iodophenyl)-tetramethylenetetramine (17f), bis() dichloride 9
Phenylphosphine) palladium ((L71F), cupric iodide (α05t) was dehydrated with diethylamine (150m
) for 18 hours at 50°C. After the reaction, the solvent was distilled off under reduced pressure, and the benzene-soluble content was purified by column croftography to obtain compound (2a). red needles,
Yield: 149 Compound (2a) (10f) and 16-promo-1-hexadecanol (9P) were dissolved in dimethylformamide (10
0g] and reacted at 60°C for 5 hours. After cooling, the precipitated crystals were recrystallized from acetonitrile to obtain compound (2).
b) was obtained.

Compound (2b) (10F) was converted to triethylamine (
(12t) was dissolved in methylene chloride (120mg) containing the mixture, and acrylic powder bromide (2t) was added dropwise under water cooling.
The reaction was allowed to proceed for 2 hours. After the mixture was cooled to room temperature and washed several times with cold water, anhydrous magnesium sulfate was added to dry it. The solvent was distilled off under reduced pressure, and the residue was recrystallized from a7ton. Red-orange waxy crystals, yield 7f Production Example 3 Synthesis of material for nonlinear optical element having the following structure (3) H0 -O-0)! ,-C! H, J (OH mountain CH3 (OH, n70==C! Br + HCE;=
('-(-OH2@000HOH, (CjH, λ, C=
a-CmiC-(-OH2i000H(31))-0CH
,0) TI3N (OH3)3p-nitrophenylacetylene (7f) and p-iodo-N-(61-carboxyoctyl)aniline (16f), bis(triphenylphosphine)palladium dichloride (I17f), iodide Cupric ((LQ4f) dehydrated diethylamine (150d)
The mixture was reacted for 14 hours at 40°C.

After the reaction, the solvent was distilled off under reduced pressure, and the benzene-soluble content was purified by column chromatography to obtain compound (3a).

Compound synthesized by cross-coupling 1-bromo-1-decyne and 11-undecyne under copper catalyst (jl))
(12f) with dicyclohexylcarbodiimide (Dc
c) and N,N-dimethylaminopyridine (DMAP
J Presence of α-glycerophos-7phatidylcholine (
10f) to obtain compound (3C).

Next, DOC (5a bar 4f) and (3a) (6t)!
, reacted in the presence of DMAP. The product was purified by column chromatography (carrier Nisilica gel, solvent: chloroform-methanol (3:2)), and the target compound (
3) was obtained. Preparation Examples 4 to 20 Red-orange powdery crystals, Ii5, were prepared according to the synthesis methods of Preparation Examples 1 to 3. Materials for Nonlinear Optical Elements (4) (Production Examples 4) to (20) (M Preparation Example) having the following structures were prepared. 20
synthesized.

Φ −o′+CHzhN(CHs)s of Some (-C!H snow resistant NH.

(H1±○HxW C=C-佽〇-H5tr coo-
1:! H-OH, -0-Co-GL-0H.

OH3÷OH, j70=o −Q=Q±aH, g co
o-aH-cH, -o-cc4cH, -7-g--NH
CO(!H-CH.

(15 Examples 1 to 20 Nonlinear optical element materials obtained in Production Examples 1 to 20 (1)
~(20) was dispersed as a monomolecular film on the water surface of a Langmuir-Prodgett membrane preparation apparatus. Surface pressure 25-45 dyn
The pressure was controlled at a constant pressure of /l+, and the quartz tapered waveguide substrate was moved up and down across the water surface to accumulate 400 monomolecular films on the waveguide substrate. Then 1 kVI Xe-H
When a rectangular pattern of 5 x 10 m+" was printed by irradiating far ultraviolet rays using a g lamp (55 mJ/,) and developing it with a chloroform-hexane (1:4) mixed solvent, the polymer in the far ultraviolet irradiated area was remained, and a nonlinear optical material with a film thickness of 1 μm and an area of 5×15+m” could be formed at a desired position on the substrate. Next, as shown in FIG. 1, the prism for incidence and detection was attached, and the experimental apparatus shown in FIG. 2 was assembled. Phase matching was achieved by moving the waveguide position of the tapered waveguide layer in the lateral direction and continuously changing the propagation constant. Table 1 shows @2 harmonic and #I3 harmonic output of each sample along with other examples.

Examples 21-40 Nonlinear optical element materials obtained in Production Examples 1-20 (1)
~(20) was monomolecularly dispersed on the water surface of a cumulative film explosion device. The surface pressure was controlled at a constant pressure of 25 to 45 ayn/cM, and 400 layers were accumulated by a horizontal deposition method in which a tapered quartz waveguide substrate was raised and lowered horizontally on the water surface. Thereafter, it was patterned according to Examples 1 to 20 and installed in a measurement system,
The generation of second and third harmonics was investigated. Table 1 shows the results.
Shown below.

Examples 41-43 Materials for nonlinear optical elements (1) obtained in Production Examples 1-5
Each of (3) was made into an ethanol solution of 10 to 50 f/A, spray-coated onto a quartz tapered waveguide substrate, and then heated at 55 to 85 C for 1 hour to align the liquid crystal.

Thereafter, it was patterned in accordance with Example 1 by 2°, installed in a measurement system, and the generation of second harmonics and third harmonics was examined. The results are shown in Table 1.

Example 44S65 Nonlinear optical element material obtained in Production Examples 1 to 20 (1)
~ (20) are each placed on a tantalum boat for vapor deposition,
It was deposited on a tapered quartz waveguide substrate at a temperature of 60 to 150°C.

The distance between the tantalum boat and the substrate was 10 crn, and the deposition rate was controlled by monitoring the change in the natural frequency of the crystal oscillator at the same height as the substrate. After that, it was patterned according to Examples 1 to 20 and installed in the measurement system, and the second
The generation of harmonics and third harmonics was investigated. The results are shown in Table 1.

Table 1 Table 1 (Continued) Table 1 (Continued) Examples 64-65 In Example 1, instead of far ultraviolet rays, X-rays (Example 6
4) A similar pattern was formed using an electron beam (Example 65). At this time, the irradiation amount of high-energy radiation necessary for pattern formation was as shown in Figure 2.

Table 2 [Effects of the Invention] As explained above, the patternable material for nonlinear optical elements according to the present invention has high sensitivity to high-energy rays, and can be effectively applied in a short time by conventional application techniques. Nonlinear optical materials can be patterned.

Furthermore, high-quality nonlinear optical patterns can be formed using current organic ultra-thin film technology and microfabrication technology.

The above has an extremely large effect on the waveguide type nonlinear optical element and ultimately on the optical integrated circuit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing the structure of a waveguide used for measuring the optical material of the present invention, and FIG. 2 is a schematic cross-sectional diagram of the measuring device. 1: Nd: YAG laser, 2: polarizer,
3: Infrared transmission filter, 4: Condensing lens, 5: Mirror, 6
: prism, 7: sample, 8: quartz waveguide layer, 9: infrared cutoff filter, 10: interference filter, 11: 7 otomaru

Claims (1)

[Claims] 1. The following general formula [I]: ▲There are mathematical formulas, chemical formulas, tables, etc.▼... [I] (However, M is a hydrophobic residue containing a polymerizable monomer unit, and A is a nonlinear 1. A patternable material for a nonlinear optical element having an amphipathic molecular structure, characterized in that it is represented by a hydrophobic residue containing an optical substance, and L represents a hydrophilic residue. 2. The residue represented by M has the following general formulas [II] to [IV]
: ▲There are mathematical formulas, chemical formulas, tables, etc.▼...[II] (However, n is an integer from 6 to 24, and R represents hydrogen or a methyl group) ▲There are mathematical formulas, chemical formulas, tables, etc.▼... [III] (However, n indicates an integer from 6 to 24) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...[IV] (However, l is an integer from 6 to 18, m is an integer from 0 to 8 The material for a nonlinear optical element according to claim 1, which is any group represented by: 3. The residue represented by A has the following general formulas [V] to [IX]
: ▲There are mathematical formulas, chemical formulas, tables, etc.▼...[V] (However, p is an integer from 0 to 3, q is an integer from 2 to 12, R_
1 indicates hydrogen, methyl group or ethyl group) ▲There are mathematical formulas, chemical formulas, tables, etc.▼... [VI] (However, r is an integer from 1 to 4, q is an integer from 2 to 12, R_
1 indicates hydrogen, methyl group or ethyl group) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...[VII] (However, s and t are integers from 1 to 18, Ab is the formula -NHC
Amide group represented by O- or -CONH-, R_1 represents hydrogen, methyl group, or ethyl group) ▲ Numerical formulas, chemical formulas, tables, etc. are available ▼... [VIII] (However, s and t are 1 to 18 ) ▲ Numerical formulas, chemical formulas, tables, etc. ▼...[IX] (However, s and t are integers from 1 to 18, z is the formula -NH_2
, -NHCH_3, -N(CH_3)_2 or ▲formula,
There are chemical formulas, tables, etc. The material for nonlinear optical elements according to claim 1, which is any group represented by ▼ (indicates an amino group). 4. The residue represented by L has the following general formulas [X] to [XV
I]: ▲There are mathematical formulas, chemical formulas, tables, etc.▼... [X] (However, R_2 is the formula -CH_3 or -CH_2-CH=
The group represented by CH_2, X^Θ is Cl^Θ, Br^Θ,
Anion represented by I^Θ or ClO_4^Θ, Y represents a spacer represented by the formula -COOCH_2CH_2- or -CH_2-) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...[X I] (However, u is the number 2 or 3, R is hydrogen or a methyl group, X
_1^Θ is a zwitterionic anion represented by -SO_3^Θ or -OPO_3^Θ, Y is the formula -COOCH_2CH_2-
or -CH_2-) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...[XII] ▲There are mathematical formulas, chemical formulas, tables, etc.▼...[XIII] ▲Mathematical formulas, chemical formulas, tables, etc. There is▼...[XIV] [However, X_2 is a formula▲There are mathematical formulas, chemical formulas, tables, etc.▼
, ▲There are mathematical formulas, chemical formulas, tables, etc.▼,▲Mathematical formulas, chemical formulas,
There are tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Zwitterionic hydrophilic groups or formulas ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, , R represents hydrogen or a methyl group) A nonionic hydrophilic group having a polymerizable monomer unit] ▲ Numerical formulas, chemical formulas, tables, etc. are available ▼... [XV] (However, w is 1 or the number of 2, x is an integer from 1 to 12, X^
Θ is an anion represented by Cl^Θ, Br^Θ, I^Θ or ClO_4^Θ, Y_1 is the formula -OCO- or -NHC
Indicates a group represented by O-, ▲There are mathematical formulas, chemical formulas, tables, etc.▼ indicates that it is an asymmetric carbon) ▲There are mathematical formulas, chemical formulas, tables, etc.▼... [XVI] (However, w is Number 1 or 2, y is an integer from 1 to 18, Y_
1 indicates a group represented by the formula -OCO- or -NHCO-, and ▲ has a mathematical formula, chemical formula, table, etc. ▼ indicates an asymmetric carbon) A material for nonlinear optical elements according to scope 1. 5. Cover the substrate with a crystalline molecule-oriented thin film of a material for nonlinear optical elements that can be patterned, irradiate the pattern with high-energy rays, and then develop the nonlinear optical material with the desired shape at the desired position on the substrate. In the method of forming a nonlinear optical pattern by forming a patternable nonlinear optical element material, the following general formula [
I]: ▲There are mathematical formulas, chemical formulas, tables, etc.▼...[I] (However, M is a hydrophobic residue containing a polymerizable monomer unit, A is a hydrophobic residue containing a nonlinear optical substance, and L is a hydrophobic residue containing a nonlinear optical substance. A method for forming a nonlinear optical pattern, characterized by using a material having an amphipathic molecular structure represented by (indicating a hydrophilic residue). 6. The method for forming a pattern according to claim 5, wherein the high-energy beam is deep ultraviolet rays, X-rays, or electron beams. 7. The pattern forming method according to claim 5 or 6, wherein the coating method is a Langmuir-Prodgett type cumulative film forming method, a horizontal deposition method or a continuous film forming method which is an improved method thereof. 8. The pattern according to claim 5 or 6, wherein the coating method is a method of direct coating, or a method of heat-treating a film formed by spin coating or spray coating from an organic solvent solution to align the liquid crystal. Formation method. 9. The pattern forming method according to claim 5 or 6, wherein the coating method is a vacuum evaporation method.