JP2002166488A - Surface-hard transparent sheet and method for producing the same - Google Patents

Abstract

[Problem] To achieve both high hardness, high transparency and moderate flexibility.
Provided are a hard surface sheet having excellent moisture resistance and a method for producing the same. A hard-surface transparent sheet comprising a transparent substrate coated with a silicon dioxide thin film containing a polyalkylene glycol methacrylate polymer, a polyalkylene glycol acrylate polymer and / or a copolymer thereof; Silane and / or trialkoxysilane, polyalkylene glycol methacrylate and
A hydrosol solution containing a polyalkylene glycol acrylate and a polymerization initiator is applied to a transparent substrate, and simultaneously with or after the coating film is dried, the polyalkylene glycol methacrylate and / or polyalkylene glycol methacrylate A method for producing a transparent sheet having a hard surface, comprising polymerizing an alkylene glycol acrylate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hard surface sheet and a method for producing the same.

[0002]

2. Description of the Related Art The surface of a transparent resin film is hardened,
BACKGROUND ART A transparent hard surface film (commonly referred to as a hard coat film, hereinafter referred to as an “HC film”) is used for various applications. The required hard properties vary depending on the application, not to mention the improvement in hardness, but also stricter requirements on transparency and durability (abrasion resistance, crack resistance, adhesion to film substrates, etc.). Has been sent. Hitherto, as a means of hardening, coating with a thermosetting or ultraviolet curable acrylic, epoxy, urethane or silicone resin has been proposed. Cured films of these resins are used, for example, as film substrates for touch panels, which are input devices such as personal computers. However, when higher transparency is required, it is no longer possible to answer it because of its limitations. Particularly, in touch panels such as portable information terminal devices, pen input type touch panels are increasing, and since a stronger printing pressure is applied to the substrate film than in the past, HC films made of these resins are no longer satisfactory. .

As a means for achieving higher transparency and higher hardness, there is a method of providing a silicon dioxide thin film.
This specific method includes a method of depositing silicon dioxide, a method of dispersing fine particles of silicon dioxide in the resin, a method of chemically decomposing polysilazane to form a silicon dioxide film, and a sol using tri- or tetraalkoxysilane. -A method of forming a film instead of silicon dioxide by a gel method,
Furthermore, there is a method in which colloidal silica is added thereto and a silicon dioxide film containing silica powder is similarly formed by a sol-gel method. However, in these methods, when the substrate is a resin film, the film has a high hardness, so that it is easily cracked when used in a bent state, and the film itself shrinks due to a temperature change. There has been a problem that phenomena such as cracks and peeling are likely to occur. Regarding cracks, even very fine cracks are not desirable because they lead to a drop in transparency at once.

In order to solve this problem, a hard surface sheet made of a silicon dioxide film containing an organic substance by a sol-gel method using a coating solution obtained by adding polyethylene glycol to a polyfunctional alkoxysilane comprising tetraalkoxysilane and trialkoxysilane. Is Japanese Patent Application No. 11-2642
No. 34, a hard film free of cracks was obtained even for a flexible resin film substrate. However, a sheet that is more excellent in moisture resistance and the like of the film is desired.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sheet which maintains high hardness, high transparency and bending resistance even after storage in a high-temperature and high-humidity environment, and a method for producing the same.

[0006]

Means for Solving the Problems The present invention provides the following 1. ~
3. About. 1. From a polymer of polyalkylene glycol methacrylate (hereinafter referred to as “PAGM”), a polymer of polyalkylene glycol acrylate (hereinafter referred to as “PAGA”) and a copolymer of polyalkylene glycol methacrylate and polyalkylene glycol acrylate on a transparent substrate A hard surface transparent sheet coated with a silicon dioxide thin film containing at least one member selected from the group consisting of: 2. A hydrosol liquid containing at least one kind of polyfunctional alkoxysilane selected from the group consisting of tetraalkoxysilane and trialkoxysilane, at least one kind selected from the group consisting of polyalkylene glycol methacrylate and polyalkylene glycol acrylate, and a polymerization initiator. Coating on a transparent substrate and drying the coated film, or simultaneously after drying the coated film, performing at least one polymerization treatment selected from the group consisting of polyalkylene glycol methacrylate and polyalkylene glycol acrylate. A method for producing a transparent sheet having a rigid surface. 3. 1. The polyalkylene glycol methacrylate or polyalkylene glycol acrylate polyethylene glycol having a molecular weight of 200 to 800. 3. The method for producing a transparent sheet having a hard surface according to item 1.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the material of a substrate to which a silicon dioxide thin film is applied is polyethylene terephthalate (PET), polyethylene naphthalate, polycarbonate, polyether sulfone, amorphous cyclic polyolefin, polymethyl methacrylate. And thermoplastic resins such as polyarylate, polyphenylene sulfide, aliphatic polyamide and polyvinyl alcohol; thermosetting resins such as epoxy, acrylic and silicone; and glass plates.

The preferable thickness of the substrate is 0.05 to 1 mm
It is about. The substrate is preferably transparent and has a total light transmittance of 80% or more.

[0009] The surface-hard transparent sheet of the present invention is defined as a generic term that includes a flexible thin film shape and a hard thick plate shape.

According to the present invention, a hydrosol solution obtained by adding a polyalkylene glycol methacrylate and / or a polyalkylene glycol acrylate and a polymerization initiator to a specific polyfunctional alkoxysilane is applied to a transparent substrate, and the coating film is formed. At the same time as drying or after drying the coating film, the polyalkylene glycol methacrylate and / or polyalkylene glycol acrylate is polymerized, whereby the moisture resistance of the film is dramatically improved. In particular, the reason why PAGM or PAGA is selected is as follows.

The polyalkylene glycol, which is the main chain portion of PAGM or PAGA, is water-soluble, so that it becomes a silicon dioxide coating dispersed at a molecular level with very good affinity. By being in this molecular dispersion state, a large effect can be exhibited even with a smaller amount of PAGM or PAGA mixed. Also, a polymer of PAGM, P
AGA polymers and their copolymers themselves are also extremely transparent, so that the transparency of a silicon dioxide film having an extremely high transparency can be maintained as it is without impairing the transparency. The presence of a PAGA polymer or a copolymer thereof has an advantage that the adhesion to a substrate such as the resin sheet is improved.

Further, after forming a coating film on a transparent substrate, simultaneously or after drying the coating film, PAGM or PAGA is (co) polymerized by using a double bond contained in these molecules. The PAGM in the membrane
Alternatively, by fixing PAGA, it is possible to prevent morphological changes such as expansion and contraction due to heat and moisture of the polyalkylene glycol in the main chain portion, which is originally low in moisture resistance, and as a result, the film can be formed even in a high-temperature and high-humidity environment. It is considered that the generation of stress of the film becomes small, the generation of cracks in the film can be prevented, and the moisture resistance of the film is improved.

PAG to be added to polyfunctional alkoxysilane
M or PAGA has a preferable limit because the water solubility decreases with an increase in the molecular weight and the compatibility with the silica component deteriorates. This upper limit is the weight average molecular weight (in the present specification, unless otherwise specified, the molecular weight indicates the weight average molecular weight)
About 10,000, preferably about 1,000, and more preferably about 800. On the other hand, the lower limit of the molecular weight is preferably about 200, preferably about 400, because if the molecular weight is small, the flexibility of the film after the polymerization treatment becomes poor and the film is easily cracked.

PAGM is an ester of methacrylic acid and polyalkylene glycol, specifically, polyethylene glycol monomethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol monomethacrylate, polypropylene glycol dimethacrylate, polyethylene glycol-polypropylene glycol monomethacrylate, Polyalkylene glycol mono- or dimethacrylates having 1 to 3 carbon atoms such as polyethylene glycol-polypropylene glycol dimethacrylate. Also, PAGA
Is an ester of acrylic acid and polyalkylene glycol, specifically, polyethylene glycol monoacrylate, polyethylene glycol diacrylate, polypropylene glycol monoacrylate, polypropylene glycol diacrylate, polyethylene glycol-polypropylene glycol monoacrylate, polyethylene glycol-polypropylene It is a mono- or diacrylate of a polyalkylene glycol having 1 to 3 carbon atoms, such as glycol diacrylate.

The polymer of PAGM according to the invention, PAGA
And / or the transparency of the silicon dioxide film itself containing these copolymers is the same as that of the glass plate (total light transmittance of 9).
5 to 97%), but about 1 to 3%, but higher than the resin base. Therefore, the sheet coated with the material does not become worse than the transparency of the substrate itself, and higher transparency can be obtained.

The surface hardness of a glass plate (generally 9H
(Before and after), but much higher than the resin substrate, so that the sheet coated with it is 1-
3H is higher.

In addition, for example, a first embodiment described later is applied to a glass plate.
Alternatively, the surface hardness of the sheet coated with the hydrosol (HC-1, HC-2) of No. 2 and heated and coated is 6 to 7H.
It is.

Next, the means for producing the hard-surface transparent sheet of the present invention will be described.

As the means, for example, a predetermined amount of PAGM
And / or PAGA and a polysol alkoxysilane hydrosol solution containing a polymerization initiator are applied to a substrate (coating), and simultaneously with or after heat drying, PAGM
Alternatively, a method of performing a PAGA polymerization treatment is a more effective method, but any method may be used as long as the object of the present invention can be efficiently achieved.

The polyfunctional alkoxysilane is a compound in which 3 to 4 alkoxy groups are bonded to silicon, and is hydrolyzed, polymerized, and linked to each other by —O—Si—O— high molecular weight (network) SiO ₂ . It becomes something.

Specifically, examples of trialkoxysilanes include those having 1 to 4 carbon atoms such as trimethoxysilane, triethoxysilane, tripropoxysilane, tributoxysilane, tri-iso-propoxysilane and tri-t-butoxysilane. And a silane tri-substituted with an alkoxy group. One remaining substituent here is a hydrogen atom, methyl,
Examples thereof include a lower alkyl group having 1 to 4 carbon atoms such as ethyl and an aromatic group such as a phenyl group, and an organic group such as methyl, ethyl and phenyl is preferable. This is because the affinity with the resin sheet is improved and the coating tends to be easy.

Examples of the tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetra-iso-propoxysilane, tetra-t-butoxysilane and the like. Substituted silanes; and oligomers thereof, such as ethyl silicate and methyl silicate.

In order to form a higher hardness silicon dioxide film by using these tri- or tetraalkoxysilanes,
Tetraalkoxysilane is preferred, but in order to form the film of good quality with good reproducibility in a more stable state, it is the case where tetraalkoxysilane and trialkoxysilane are used in combination.

The substrate to be coated is mainly a film made of a highly transparent thermoplastic resin or a thermosetting resin,
Or it is a sheet-like material, and is generally known regardless of its type. The substrate may of course be a glass plate,
In the present invention, it is preferable to use a resin sheet.

The coating is performed as follows.

First, a mixed solvent of alcohol (ethanol, methanol, isopropyl alcohol, etc.) and water is added to the tetraalkoxysilane and trialkoxysilane and mixed.

When the alcohol and water are added, the polyfunctional alkoxysilane slightly hydrolyzes, but does not substantially proceed to a gel to form a hydrosol. In order to efficiently convert from a sol to a silicon dioxide film, the amount of water must be
The mole is about 1 to 4.5 mole, preferably about 2 to 4 mole, and the alcohol is about 1 to 40 mole, preferably about 2 to 20 mole based on the mole. Here the amount of water is 2
The reason why the amount is preferably about 4 mol is as follows. Water influences the hydrolysis reaction, which tends to affect the quality of the membrane. That is, if the amount of water is equal to or less than the upper limit as described above, it is difficult for the membrane to become porous and lose its denseness, and if the amount of water is equal to or greater than the lower limit as described above, the reaction rate is low. This is preferable because the composition does not easily become unreacted or remains unreacted, and the hardness is hardly reduced. The amount of alcohol is not strictly limited because it is not directly involved in the reaction, but if the amount is not more than the above-mentioned upper limit, the reaction speed is slow, and the problem that the coating thickness is reduced is unlikely to occur. If the amount is at least the above-mentioned lower limit, problems such as a high reaction rate and rough film quality, and a large coating thickness and easy cracking are unlikely to occur.

When the tetraalkoxysilane and the trialkoxysilane are used in combination, the molar ratio is 9: 1 to 1: 1.
5: 5, preferably 8: 2 to 6: 4. This molar ratio relationship is preferable from the viewpoint of preventing a decrease in the film hardness of the silicon dioxide film, further reducing the risk of generation of cracks over time, and further improving the adhesion to the resin sheet. That is, the molar ratio indicates that tetraalkoxysilane acts on the development of high film hardness, and trialkoxysilane acts on the prevention of cracking and adhesion on the film in the presence of PAGM and / or PAGA. It is a molar ratio that is preferably set so as to achieve the desired expression.

PAGM and / or PAGA are added to polyfunctional alkoxysilane or a polyfunctional alkoxysilane solution as they are or dissolved in water and alcohol in advance, but those previously dissolved in water and alcohol are added. Is more preferable.

The amount of PAGM and / or PAGA added is
5 parts per 100 parts by weight of the polyfunctional alkoxysilane
It is preferably in the range of about 30 to 30 parts by weight, preferably about 10 to 20 parts by weight. It is preferable that the addition amount is not less than the above lower limit, since the adhesion to the resin sheet is hardly reduced and the silicon dioxide film is hardly cracked over time. Further, it is preferable that the amount of addition is equal to or less than the above upper limit, because the hardness of the silicon dioxide film is hard to decrease.

For the polymerization of the PAGM and / or PAGA, it is necessary to add a polymerization initiator. As the polymerization initiator, those generally used for radical polymerization can be used. For example, for heat treatment, benzoyl peroxide, azobisisobutyronitrile, initiators commonly used in thermal polymerization such as benzophenone, and the like, for photopolymerization,
1-hydroxy-cyclohexyl-phenyl-ketone,
Examples of the initiator usually used for photopolymerization, such as 2-hydroxy-2-methyl-1-phenyl-propan-1-one, are given. The amount of the polymerization initiator to be added is PAGM or PAGA1.
It is about 1 to 5 parts by weight with respect to 00 parts by weight. In order to accelerate the hydrolysis reaction, a commonly used acid catalyst (hydrochloric acid, sulfuric acid, acetic acid, etc.) may be added to the hydrosol solution. When acid catalyst is added, more stable performance,
It is preferable because a high quality silicon dioxide film can be formed with good reproducibility. When it is added, its amount is preferably about 0.005 to 0.05 mol, particularly preferably about 0.01 mol, per mol of the polyfunctional alkoxysilane.

When the above-mentioned predetermined components and amounts are mixed, a hydrosol solution is formed, which is first coated on a resin sheet serving as a substrate at room temperature (a generally known coating means may be used). By leaving this coating film at room temperature for a predetermined period of time, the film changes into a tough silicon dioxide film and adheres to it. Therefore, it is preferable that the coating film be dried by touch to the touch and then left at room temperature for about 1 hour to several days. Thereafter, in order to form a stronger film, it is preferable to heat and dry at a temperature as high as possible within the range of heat resistance of the substrate. The heating temperature in this case is usually about 50 to 150 ° C. The heating time can be appropriately set according to the heating temperature, and is, for example, about 1 to 3 days at 50 ° C. and about 1 to 30 minutes at 150 ° C. Other temperatures can be appropriately set according to the heating temperature with reference to the above-mentioned range.

If the thickness of the silicon dioxide film is too small, it is difficult to obtain the required surface hardness, and if it is too large, the silicon dioxide film has particularly large bending, and cracks are liable to occur in a large number of repetitions. For this reason, the final film thickness is preferably about 0.2 to 4 μm, more preferably about 0.5 to 2.5 μm. Therefore, the film thickness at the time of application is appropriately set so as to obtain such a film thickness after the drying and polymerization treatment.

In the method for producing a transparent sheet having a hard surface according to the present invention, a polymerization treatment by heat, light or the like can be carried out simultaneously with or after heating and drying the coating film. In the case of performing photopolymerization, for example, after application of the hydrosol liquid, after heating for drying the applied film, or simultaneously with the heating, ultraviolet irradiation is performed by a high-pressure mercury lamp or the like. UV irradiation energy is controlled by UV intensity (lamp output), distance between lamp and film, and irradiation time.
To the extent that the base film does not deteriorate, PAGM and P
It is necessary that the energy is sufficient for the polymerization of AGA.

In the case of polymerization by heat, after the coating film is dried, for example, at a temperature of about 100 to 150 ° C. for 30 minutes to 1 hour.
The polymerization can be carried out by heating for about 0 hours. Alternatively, when the polymerization is carried out simultaneously with the drying of the coating film, for example, the polymerization is performed at about 100 to 150 ° C. for 30 minutes to
Drying and polymerization can be performed by heating for about an hour.

When heating and drying are performed under the above-mentioned conditions in order to form a stronger film, the PAGM and / or PAGA may be partially polymerized by heat.

The effects of PAGM or PAGA are as described above. However, in actual addition, these effects may be slightly affected by the balance between the molecular weight of PAGM or PAGA and the amount added thereto. Since a difference is generated, it is preferable to carefully examine in advance including this point and set the optimum conditions.

[0038]

The present invention will be described below in more detail with reference to examples and comparative examples.

(Example 1) Tetraethoxysilane, phenyltriethoxysilane, ethanol, distilled water, and hydrochloric acid (acid catalyst) in a molar ratio of 0.8: 0.2: 2: 4:
The mixture was mixed at a ratio of 0.01 and stirred for 1 hour to obtain a hydrosol solution. Separately, for a total of 100 parts by weight of tetraethoxysilane and phenyltriethoxysilane,
10 parts by weight of polyethylene glycol dimethacrylate having a molecular weight of 400 (Blenmer PDE400 manufactured by NOF Corporation) and a photopolymerization initiator 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Darocur 1173 manufactured by Ciba Specialty Chemicals) 4 parts by weight were added to the same amount of ethanol (2 mole ratio) as the ethanol contained in the hydrosol solution, and dissolved by stirring. The resulting solution was mixed with the hydrosol solution under stirring to obtain a coating hydrosol solution (HC). -1) was prepared.

Next, a 188 μm-thick PET in roll form
On a film (surface hardness: 2H, total light transmittance: 87.0%), the above-mentioned HC-1 liquid was gravure coated by a gravure coating method, with a gravure roll number of 55, a roll rotation speed of 5 rpm, a reverse rotation, and a line speed of 3 m / min. After coating under the conditions and drying at 100 ° C. for 2 minutes in a continuous drying oven, the film was wound on a roll and left for one week to be aged. Next, the film was irradiated with ultraviolet rays at 598 mJ / m ^{2 by} a high-pressure mercury lamp while being dried in a continuous drying oven at 130 ° C. for 10 minutes.

The formed film surface is smooth, and the film thickness is 1.
The surface hardness was 2 μm and the surface hardness was 3H. 500 with magnifying microscope
Observation at a magnification revealed that no cracks in the film were observed.
The total light transmittance of the film was 90.0%.

This film was stored in a high-temperature, high-humidity environment of 60 ° C. and 90% RH for 500 hours, and the same evaluation was performed.
No abnormalities in film quality and no decrease in hardness were observed.

(Example 2) Tetraethoxysilane, phenyltriethoxysilane, ethanol, distilled water, and hydrochloric acid (acid catalyst) were mixed at a molar ratio of 0.8: 0.2: 2: 4:
The mixture was mixed at a ratio of 0.01 and stirred for 1 hour to obtain a hydrosol solution. Separately, for a total of 100 parts by weight of tetraethoxysilane and phenyltriethoxysilane,
10 parts by weight of polyethylene glycol dimethacrylate having a molecular weight of 600 (Blenmer PDE600 manufactured by NOF Corporation) and 0.4 parts by weight of a photopolymerization initiator 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184 manufactured by Ciba Specialty Chemicals) were added to the hydrosol. The solution was added to the same amount of ethanol as the ethanol contained in the solution, stirred and dissolved, and the resultant was combined with the hydrosol solution under stirring to prepare a coating hydrosol solution (HC-2).

Next, the above-mentioned HC-2 solution was applied on a 125 μm-thick transparent PET film at 1000 rpm for 20 seconds by a spin coating method. After the coating was allowed to stand at room temperature for 24 hours, the coating was heated and dried at 100 ° C. for 10 hours, and then irradiated with 598 mJ / m ² of ultraviolet light using a high-pressure mercury lamp.

The formed film surface is smooth, and the film thickness is 1.
5 μm and surface hardness was 3H. 500 with magnifying microscope
Observation at a magnification revealed that no cracks in the film were observed.
The total light transmittance of the film was 89.1%.

This film was stored in a high-temperature, high-humidity environment at 60 ° C. and 90% RH for 500 hours, and the same evaluation was performed.
No abnormalities in film quality and no decrease in hardness were observed.

Comparative Example 1 The procedure of Example 2 was repeated, except that the polyethylene glycol dimethacrylate had a molecular weight of 600.
A hydrosol solution was prepared under the same conditions except that polyethylene glycol was used, and the PET film was coated with a PET film under the same conditions as in Example 2 and thermally dried to coat the PET film with a silicon dioxide film.

The formed film surface is smooth, and the film thickness is 1.
5 μm and surface hardness was 3H. 500 with magnifying microscope
Observation at a magnification revealed that no cracks in the film were observed.
The total light transmittance of the film was 89.0%.
However, when this film was stored in a high-temperature and high-humidity environment of 60 ° C. and 90% RH for 200 hours, cracks occurred on the entire surface of the film.

The surface hardness referred to in each example is JIS-K54.
This is the pencil hardness measured by the method of No. 00.

[0050]

As described above, the moisture resistance of the hard surface transparent sheet having higher surface hardness, transparency and moderate flexibility than the resin sheet of the base is remarkably improved, and it can be used for more applications as a functional component. . In particular, it is suitable for use as a pen input type touch panel substrate or a display protection plate.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 183/04 C09D 183/04 // C08L 101: 00 C08L 101: 00 (71) Applicant 599132133 Tetsuo Yazawa Osaka 4-3-1, Shinkofudai, Toyono-cho, Toyono-gun, Fuyo-no-gun (71) Applicant 599132144 Koji Kuraoka 2-7-12-503, Mayoka, Ikeda-shi, Osaka Inventor Toshiki Okamoto 163 Morikawaramachi, Moriyama-shi, Shiga Prefecture Gunze Co., Ltd.Research and Development Department Inventor Koji Kuraoka 1-81-31 Midorioka, Ikeda-shi, Osaka F-term in Osaka Institute of Technology (F) (reference) 4F006 AA35 AB43 AB67 AB76 BA02 CA08 D A04 EA03 4F100 AH06B AK25B AK25J AK42 AK52B AL01B AL05B AT00A BA02 CA30B CC00B EH46 EH462 EJ012 EJ54 GB41 JD04 JJ03 JK12 JK13 JK17 JN01 JN01A YY00B 4J027 AC02 AC06 AJ01CA18 JA03 CA02 PC03 PC08

Claims (3)

[Claims] 1. A transparent substrate containing at least one selected from the group consisting of a polymer of polyalkylene glycol methacrylate, a polymer of polyalkylene glycol acrylate, and a copolymer of polyalkylene glycol methacrylate and polyalkylene glycol acrylate. A hard surface transparent sheet coated with a silicon dioxide thin film. 2. A polymerization initiator comprising at least one kind of polyfunctional alkoxysilane selected from the group consisting of tetraalkoxysilane and trialkoxysilane, at least one kind selected from the group consisting of polyalkylene glycol methacrylate and polyalkylene glycol acrylate, and a polymerization initiator. The hydrosol solution is applied to a transparent substrate, and simultaneously with or after drying the coating film, at least one member selected from the group consisting of polyalkylene glycol methacrylate and polyalkylene glycol acrylate. A method for producing a hard-surface transparent sheet, comprising performing a polymerization treatment. 3. The method according to claim 2, wherein the polyalkylene glycol methacrylate or the polyalkylene glycol acrylate polyethylene glycol has a molecular weight of 200 to 800.