JPH0831128A - Member for protecting optical disk and optical disk device formed by using the same - Google Patents

Abstract

PURPOSE:To form an optical disk which does not generate errors at the time of writing and reading by lessening the friction between a disk and a cartridge case to suppress generation of worn powder and capturing the worn powder slightly generated at this time by a member for protecting an optical disk. CONSTITUTION:Ultra-high-polymer polyethylene(PE) powder is filled into metal molds and is subjected to compressing after heating at, for example, 130 deg.C to form a preform having porosity 50% and further, the preform is sintered by heating at 160 deg.C and is cooled, by which a round rod-shaped porous body is obtd. The porous body is formed to a thickness, for example, 1007mum by a lathe to a sheet form, by which the porous sheet of the ultra-high polymer PE is obtd. The member 1 for protecting the optical disk is obtd. by sticking the porous sheet of the ultra-high polymer PE on one surface and a separator to the other surface to form a double coated tacky adhesive tape and blanking the tape to an annular shape. The friction of the disk and the cartridge case is lessened and the generation of the worn powder is suppressed. Even the worn powder slightly generated at this time is captured by the member for protecting the optical disk and, therefore, the errors are not generated at the time of writing and reproducing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has excellent adhesiveness, reduces friction between an optical disk and a cartridge case that accommodates the optical disc, suppresses generation of abrasion powder, and captures the generated abrasion powder. The present invention relates to an optical disc protection member having the above and an optical disc device using the same.

[0002]

2. Description of the Related Art Generally, an optical disc has a recording layer and a protective layer sequentially laminated on a resin substrate of acrylic resin, polycarbonate resin, polyolefin resin or the like, and a center hub is joined to the center of the disc. Take the configuration. The optical disc is used as an optical disc device (disc cartridge) housed in a cartridge case from the viewpoint of handling and preventing damage and contamination.

[0003]

However, when an optical disk is housed in a cartridge case to form an optical disk device, abrasion powder is generated due to friction at the contact portion between the cartridge case and the optical disk during transportation of the optical disk device. There is a problem that an error occurs during writing or reading due to the influence. Further, conventionally, in order to reliably prevent damage to the optical disc, it has been practiced to coat the surface of the optical disc with a silicone resin or the like to form a hard coat layer or to stick a polyester film to the surface of the optical disc. There is. This can prevent the optical disc from being damaged, but the friction between the optical disc and the cartridge case becomes large, and the problem of error due to abrasion powder becomes more serious.

Therefore, in order to solve the problem of the abrasion powder, the present inventors have arranged an optical disk protection member made of an ultra-high molecular weight polyethylene non-porous sheet at the contact portion between the optical disk and the cartridge case. Has been proposed (Japanese Patent Laid-Open No. 4-366478). This ultra-high molecular weight polyethylene non-porous sheet has a small friction coefficient and excellent wear resistance, so that the generation of abrasion powder can be suppressed and the occurrence of errors such as when writing an optical disk can be prevented. become. Therefore, this technique proposed by the present inventors has been widely adopted in the field of optical discs.

However, in the above-mentioned ultra-high molecular weight polyethylene non-porous sheet, it is possible to suppress the generation of abrasion powder to some extent, but it is impossible to completely prevent this. Also, with the recent improvement in performance of optical discs, the performance of this ultra-high molecular weight polyethylene non-porous sheet has become insufficient. As a means for further reducing the friction of the ultra-high molecular weight polyethylene non-porous sheet, there is a method of embossing or sandblasting the surface of the sheet to make the surface uneven. However, if these processes are performed, the number of steps is increased, and the manufacturing of the optical disk device becomes complicated. Further, the above-mentioned ultra-high molecular weight polyethylene non-porous sheet also has a problem of poor adhesiveness, and in order to securely fix this sheet to the inner wall of the cartridge case or the like, it is necessary to perform a special treatment.

The present invention has been made in view of the above circumstances, and suppresses the generation of abrasion powder by reducing the contact friction between the optical disk and the cartridge case that accommodates the optical disc, and captures the abrasion powder that has occurred. An object of the present invention is to provide an optical disk protecting member having a function and excellent adhesiveness, and an optical disk device using the same.

[0007]

In order to achieve the above object, the present invention is for protecting an optical disk comprising an ultra high molecular weight polyethylene porous sheet and having a porosity of 20 to 70%. A member is the first gist, and an optical disk device in which an optical disk is housed in a cartridge case, wherein the optical disk and the cartridge case are in contact with each other via the optical disk protection member is a second one. Use as a summary.

[0008]

In order to solve the above problems, the present inventors have conducted a series of studies to select the material of the member for protecting the optical disk and modify it. As a result, if ultra-high molecular weight polyethylene is molded into a porous sheet, and if the porosity of this porous sheet is set to a specific range, the friction coefficient is further reduced compared to the ultra-high molecular weight polyethylene non-porous sheet, and It has been found that the adhesiveness becomes excellent and the abrasion powder is captured. When this ultrahigh molecular weight polyethylene porous sheet is used as a member for protecting an optical disc, and an optical disc device is manufactured using this member,
In the obtained optical disk device, it has been found that the occurrence of an error at the time of writing can be effectively prevented, and the present invention has been reached together with the above findings. According to the present invention, it is possible to provide a high performance optical disk device.

Next, the present invention will be described in detail.

The member for protecting an optical disk of the present invention is formed by molding ultra high molecular weight polyethylene into a porous sheet.

The ultrahigh molecular weight polyethylene porous sheet is made of ultrahigh molecular weight polyethylene.
In general, the molecular weight of polyethylene is about 100,000 or less, whereas the ultrahigh molecular weight polyethylene used in the present invention is
It is over 500,000. It is preferably more than 1 million. The member for protecting an optical disk obtained by using more than 1 million ultra-high molecular weight polyethylene has excellent wear resistance. As such ultra-high molecular weight polyethylene, Hi-Zex Million (trade name, manufactured by Mitsui Petrochemical Industries, Ltd.), Hostalen GUR (trade name, manufactured by Hoechst), and the like are commercially available. In the present invention, the molecular weight means a value measured by a viscosity method.

The above-mentioned ultra-high molecular weight polyethylene porous sheet is prepared by, for example, extracting or sintering a porous body,
This can be obtained by molding into a sheet. Among them, the sintering method (Japanese Patent Publication No. 5-66855) previously proposed by the inventors of the present invention is used from the viewpoint of the reduction of the friction coefficient of the obtained porous sheet and the uniformity of the pores formed. It is preferable. Specifically, it is the method shown below. In addition,
At the time of forming the porous body, a conductive substance such as carbon black may be blended with ultra-high molecular weight polyethylene for the purpose of preventing static electricity.

[Sintering Method] Ultrahigh molecular weight polyethylene powder is filled in a mold, heated at a temperature lower than the melting point of the polyethylene powder, and then pressed to prepare a preform, and the preform is subjected to a reduced pressure atmosphere. Air is removed by leaving it inside, and then it is sintered in a steam atmosphere heated to a temperature above the melting point of polyethylene and then cooled to produce an ultrahigh molecular weight polyethylene porous body.

The above-mentioned sintering method will be described in detail. That is, first, ultrahigh molecular weight polyethylene powder is filled in a mold and heated.

The heating temperature must be lower than the melting point of the ultra high molecular weight polyethylene powder. This heating temperature (X ° C.) is preferably set within the range shown by the following formula. UHPEmp −20 ° C. ≦ X ° C. <UHPEmp UHPEmp: melting point of ultra high molecular weight polyethylene

The heating time is appropriately determined depending on the heating temperature, but is usually in the range of 30 to 60 minutes per 1 cm of the wall thickness of the preform formed in the mold.

After the above heating, the ultra-high molecular weight polyethylene powder filled in the mold is pressed to produce a preform. This pressurization is usually about 0.3-40 kg
It can be performed by a method of adjusting the filling height of the ultra high molecular weight polyethylene powder in the mold with a pressure of / cm ² .

Weight of preform formed in mold (weight of ultra high molecular weight polyethylene powder filled in mold), bottom area of preform (usually the same as bottom area of mold) and preform The following relational expressions hold between the specific gravities (apparent densities) of objects. Weight = bottom area x height x specific gravity (apparent density)

Therefore, the specific gravity (apparent density) of the preform can be determined by setting the filling height of the ultrahigh molecular weight polyethylene powder in the mold by the above-mentioned pressurization. That is, when the same mold is used and the filling weight of the ultrahigh molecular weight polyethylene powder is the same, the higher the filling height, the smaller the specific gravity of the preform.
In the present invention, the specific gravity (apparent density) is about 0.
From the viewpoint of workability, it is preferable to adjust the filling height so as to be in the range of 23 to 0.78 (porosity about 15 to 75%).

The specific gravity (apparent density) of the porous body obtained by this sintering method has a close relationship with the specific gravity (apparent density) of the preform if the other conditions are the same. The higher the specific gravity (apparent density) of the molded product, the higher the specific gravity (apparent density) of the porous body obtained by using it. From this, it can be said that the pressurization is a step of determining the specific gravity (apparent density) of the porous body. When the specific gravity (apparent density) of the preform obtained by the pressurizing step is set within the above-mentioned specific range, the specific gravity (apparent density) is about 0. 28
A porous body having a porosity of about 0.74 (porosity of about 20 to 70%) is obtained. When calculating the porosity from the specific gravity (apparent density) of the preform or porous body, the following formula is used.

A (%) = [1- (B / C)] × 100 A: Porosity B: Specific gravity (apparent density) C: True specific gravity of ultra high molecular weight polyethylene

Next, the preform obtained by the pressurizing step is subjected to deaeration treatment under a reduced pressure atmosphere to eliminate the air in the pores of the preform. Examples of the degassing treatment include a method in which the preform is taken out of the mold, placed in a pressure resistant container and depressurized. The reduced pressure atmosphere is usually in the range of about 0.1 to 10 mmHg.

The degassed preform is then sintered in a steam atmosphere heated above the melting point of the ultrahigh molecular weight polyethylene. During this sintering, the preform is in a degassed state as described above, and the steam is usually pressurized, so that the steam easily penetrates into the preform to quickly transfer heat. Then, the molded product comes to be sintered. As described above, when steam-sintering is performed while maintaining the deaerated state of the preform, heat can be uniformly and quickly transferred to the entire preform, and as a result, pores having a uniform distribution and pore size can be obtained. It is possible to obtain a porous body provided with.
Therefore, in the sintering process using the heated steam, the steam introducing pipe and the valve for opening and closing the introducing pipe are provided in the pressure resistant container, the preform is degassed, and then the depressurized state is released. It is desirable to carry out the method by introducing the heated steam while opening the valve while maintaining the reduced pressure state.

The time required for the above-mentioned sintering is appropriately determined depending on the conditions such as the size of the preform and the sintering temperature, but it is usually about 3 to 6 hours. Since the sintering time in other sintering methods is about 48 to 72 hours, it can be seen that this sintering method is a manufacturing method with high manufacturing efficiency.

After the above-mentioned sintering, the desired porous body can be obtained by cooling. The cooling is preferably carried out by leaving it at room temperature in order to prevent cracking of the porous body due to rapid cooling.

Next, the method of forming the above-mentioned porous body into a sheet is not particularly limited, and for example, cutting can be performed using a lathe or the like. When the optical disk protection member of the present invention is used in an optical disk device, the ultrahigh molecular weight polyethylene porous sheet is generally processed into a flat ring shape. This processing is performed by punching or the like.

The porosity of the ultrahigh molecular weight polyethylene porous sheet of the present invention must be set in the range of 20 to 70%. It is preferably 20 to 50%, and particularly preferably 30 to 50%. That is, when the porosity is less than 20%, the coefficient of friction of the porous sheet becomes high and the adhesiveness becomes poor. vice versa,
This is because if the porosity exceeds 70%, the mechanical strength of the porous sheet decreases and it cannot be put to practical use. This porosity can be adjusted by the specific gravity of the above-mentioned preform, the particle size of the ultrahigh molecular weight polyethylene powder, and the like. In the present invention, the porosity is
It is the ratio of voids to the apparent volume.

The thickness of the ultrahigh molecular weight polyethylene porous sheet of the present invention is usually 30 to 500 μm, preferably 30 to 300 μm, and particularly preferably 50 to 200.
It is in the range of μm. That is, when it is less than 30 μm,
This is because the mechanical strength tends to decrease, and conversely, when it exceeds 500 μm, the clearance with the cartridge case becomes small, and the disk and the cartridge case may come into contact with each other and stable rotation may not be obtained.

As described above, the member for protecting an optical disk of the present invention is made of an ultrahigh molecular weight polyethylene porous sheet having a specific porosity. As described above, by setting the porosity to be in a specific range and the porosity to be in a specific range, the friction coefficient is significantly reduced, and the adhesiveness is improved to a level where it can be practically used. It will have the ability to capture. It can be inferred that the reason why the optical disc protection member of the present invention has the function of capturing wear particles is that wear particles enter the pores of the porous sheet. In the optical disc device using the optical disc protection member having such excellent characteristics, the friction between the optical disc and the cartridge case is extremely small, and the generation of abrasion powder is effectively suppressed, and it slightly occurs. Since the abrasion powder is also captured by the optical disc protection member, the adverse effects of the abrasion powder can be completely eliminated. This is the greatest feature of the present invention.

In order to further reduce the friction coefficient, the ultrahigh molecular weight polyethylene porous sheet may be impregnated with a lubricant such as silicone. In addition, an antistatic agent such as a surfactant may be impregnated for the purpose of preventing electrostatic charge.

Next, an optical disk device using the optical disk protecting member of the present invention will be described. The optical disc device of the present invention is an optical disc device in which an optical disc is housed in a cartridge case, and the optical disc and the cartridge case are in contact with each other through the special optical disc protection member. The method of interposing the member for protecting the optical disk is not particularly limited,
It may be fixed to the optical disk side or the cartridge case side. The method for fixing the member for protecting the optical disk is not particularly limited, and fixing with an adhesive layer,
A fixing method using an adhesive can be used.

The fixing method using the adhesive layer may be, for example, a method of forming an adhesive layer on one surface of the optical disk protecting member. This pressure-sensitive adhesive layer can be formed, for example, by applying a pressure-sensitive adhesive solution and drying it, or by sticking a double-sided pressure-sensitive adhesive tape. The pressure-sensitive adhesive is not particularly limited, and various pressure-sensitive pressure-sensitive adhesives such as silicone-based, acrylic-based and rubber-based pressure-sensitive adhesives can be used. Further, in order to improve the adhesiveness between the adhesive layer and the ultrahigh molecular weight polyethylene porous sheet, the surface of the ultrahigh molecular weight polyethylene porous sheet may be subjected to a modification treatment such as corona discharge. In addition, from the viewpoint of easy handling, a separator may be laminated on the pressure-sensitive adhesive layer. The separator is not particularly limited, but paper treated with silicone resin is preferably used. FIG. 1 shows an optical disk protecting member of the present invention including such an adhesive layer and a separator. In the figure, (a) is a plan view of the optical disk protecting member 1, and (b) is a side view thereof. Further, 1 is an ultrahigh molecular weight polyethylene porous sheet, 2 is an adhesive layer, and 3 is a separator.

As a fixing method using the above adhesive,
For example, there is a method of forming an adhesive layer by applying an adhesive to the optical disc. Examples of this adhesive include acrylic and silicone reactive adhesives.

In the fixing method using the adhesive layer and the fixing method using an adhesive, the fixing method using the adhesive layer is preferable from the viewpoint of ease of fixing work and the like. FIG. 2 shows a side view of an optical disc having an optical disc protection member fixed thereto. In the figure, 1
Is an optical disk protection member, 5 is an optical disk, and 6 is a center hub.

[0035]

INDUSTRIAL APPLICABILITY As described above, the optical disk protecting member of the present invention is made of the ultrahigh molecular weight polyethylene porous sheet having the porosity set in a specific range. This ultra high molecular weight polyethylene porous sheet has an extremely small friction coefficient and has a function of trapping the generated abrasion powder. Therefore, in the optical disk device of the present invention using the optical disk protection member made of this ultra high molecular weight polyethylene porous sheet, the friction between the optical disk and the cartridge case is reduced, and the generation of abrasion powder is suppressed. Even a slight amount of abrasion powder is captured by the optical disc protection member. For this reason,
The optical disk device of the present invention has extremely high performance in which the adverse effects of abrasion powder are completely removed and no error occurs during writing or reading. Since the optical disk protecting member of the present invention is excellent in adhesiveness, it can be used in an optical disk device without any special processing and can contribute to cost reduction of the optical disk device.

Next, examples will be described together with comparative examples.

[0037]

Example 1 Ultra high molecular weight polyethylene powder (molecular weight: 5
1,000,000, melting point: 135 ° C.) is filled in a mold, heated at 130 ° C. and then compressed to prepare a preform having a porosity of 50% (specific gravity: 0.46), which is further heated to 160 ° C. (steam atmosphere). After heating at (middle) for sintering, it was cooled to obtain a rod-shaped porous body (porosity: 47%). This round rod-shaped porous body was cut into a sheet by cutting to a thickness of 100 μm using a lathe to prepare an ultrahigh molecular weight polyethylene porous sheet.

On the other hand, a silicone adhesive (KR101-
10, manufactured by Shin-Etsu Chemical Co., Ltd.) 100 parts by weight (hereinafter abbreviated as “part”), 1.2 parts of benzoyl peroxide, and 100 parts of toluene.
Parts were added to prepare a coating solution. Apply this coating solution to a thickness of 25
A double-sided pressure-sensitive adhesive tape was produced by applying it on both sides of a polyethylene terephthalate film having a thickness of μm and drying it at 130 ° C. for 10 minutes. The thickness of each adhesive layer of this double-sided adhesive tape is 30 μm.

Next, the ultrahigh molecular weight polyethylene porous sheet was attached to one surface of the double-sided pressure-sensitive adhesive tape, and the separator was attached to the other surface. Then, this was punched into a ring shape to obtain an optical disk protection member having a structure as shown in FIG. 1 and a porosity of 47%. In addition, as the separator, a thickness of 50 μm processed with silicone resin
m paper was used.

[0040]

[Example 2] Ultra high molecular weight polyethylene powder (molecular weight: 3
A porous sheet having a porosity of 40% (specific gravity: 0.55) was produced by the same sintering method as in Example 1 using 1,000,000 and a melting point of 135 ° C. Then, this sheet was immersed in a mixed solution of an antistatic agent (Electnon, manufactured by New Fine Chemical Co., Ltd.) and silicone, and then dried to be surface-treated. Then, in the same manner as in Example 1, an optical disk protecting member having a porosity of 40% was manufactured.

[0041]

Example 3 The porosity of the preform was 20% (specific gravity: 0.
74), an optical disk protecting member (porosity: 23%) was produced in the same manner as in Example 1.

[0042]

Example 4 The porosity of the preform was 75% (specific gravity: 0.
23) A member for protecting an optical disk (porosity: 70%) was produced in the same manner as in Example 1 except that the above was adopted.

[0043]

Comparative Example 1 Instead of the ultrahigh molecular weight polyethylene porous sheet, a 100 μm thick non-porous sheet made of ultrahigh molecular weight polyethylene (molecular weight: 2.5 million, melting point 135 ° C.) was used. Except for this, the optical disk protecting member was manufactured in the same manner as in Example 1.

[0044]

Comparative Example 2 A polyethylene terephthalate film was used instead of the ultrahigh molecular weight polyethylene porous sheet.
Except for this, the optical disk protecting member was manufactured in the same manner as in Example 1.

Products of Examples 1 to 4 thus obtained,
The optical disk protection members of Comparative Examples 1 and 2 were examined for wear resistance, friction coefficient, and adhesive force. This result
The results are shown in Table 1 below. The above characteristics were examined according to the following methods.

[Abrasion resistance] JIS K 7204-19
It carried out according to 77. The evaluation of the wear resistance is shown as a comparative value with the value of Example 1 as 1 (reference).

[Friction Coefficient] Using an acrylonitrile-butadiene-styrene copolymer (ABS resin) as a mating material, a sliding speed of 150 mm / min, a circle having a diameter of 12 mm as a contact surface and a load were measured by a Bowden-Leben type friction tester. It was measured under the condition of 200 g.

[Adhesiveness] The adhesive force between the double-faced tape and the sheet surface of the member for protecting an optical disk that contacts the cartridge case was measured at a speed of 300 using a Tensilon universal testing machine.
It was measured under the condition of mm / min.

[0049]

[Table 1]

From Table 1 above, it can be seen that the optical disk protection member of the example product has a low degree of wear, a low coefficient of friction, and an excellent adhesive force. In particular, the optical disk protecting member of Example 2 was impregnated with the slip agent, and thus had a smaller friction coefficient than the other Examples. On the other hand, the optical disc protection member of Comparative Example 1 had a high friction coefficient and a low adhesive force. The optical disk protection member of Comparative Example 2 had a very low degree of wear and a large friction coefficient.

Next, when an optical disk device was manufactured using the optical disk protecting members of the above-mentioned Examples 1 to 4, no error occurred at the time of writing or reading. From this, it is understood that the optical disk device of the present invention has excellent reliability and high performance.

[Brief description of drawings]

1A is a plan view of an embodiment of an optical disk protecting member of the present invention, and FIG. 1B is a side view thereof.

FIG. 2 is a side view showing a state in which the optical disc protection member is fixed to an optical disc.

Claims (4)

[Claims] 1. A member for protecting an optical disk, comprising an ultrahigh molecular weight polyethylene porous sheet and having a porosity set in a range of 20 to 70%. 2. The ultrahigh molecular weight polyethylene porous sheet is an ultrahigh molecular weight polyethylene porous sheet obtained by molding the ultrahigh molecular weight polyethylene porous body produced by the method (A) below into a flat ring-shaped sheet. The member for protecting an optical disc according to claim 1. (A) Ultra-high molecular weight polyethylene powder was filled in a mold, heated at a temperature lower than the melting point of the polyethylene powder, and then pressed to prepare a preform, which was left in a reduced pressure atmosphere. Air is removed, and then sintered in a steam atmosphere heated above the melting point of the polyethylene and then cooled to produce an ultrahigh molecular weight polyethylene porous body. 3. The optical disk protecting member according to claim 1, wherein an adhesive layer is formed on one surface of the ultrahigh molecular weight polyethylene porous sheet. 4. An optical disk device in which an optical disk is housed in a cartridge case, and the optical disk and the cartridge case are provided with the optical disk protection member according to any one of claims 1 to 3. An optical disk device characterized by being in contact.