Patent Application
20050099932
This invention relates to a head for optically or magnetically recording information, reproducing information from and erasing information from an information recording medium. More particularly, it relates to an information recording/reproduction head that can record, reproduce and erase information with an enhanced degree of density and mechanical reliability.
Technological developments are under way for disk type information recording/reproducing systems that typically use magnetic disks and optical disks in order to provide them with a higher capacity and a higher recording density, although image compression technologies remarkably advanced in recent years. Although optical disks allow a relatively high data recording density a higher recording density is desired for them. A smaller light spot can realize a higher data recording density on the optical recording medium. However, the recording density is limited by the diffraction limit of the light spot on the recording medium. When a lens or a far field focusing device is used to focus a light beam onto the surface of a recording medium, the size of the converged light spot at the focal point faces a limit of λ/2 (λ being the wavelength of light) due to diffraction. This is referred to as diffraction limit.
To raise the recording density above the current density level, it is necessary to reduce the size of the light beam emitted to write or read information. Near field optical technologies that exploit the characteristics of the low phase velocity of an evanescent wave have been attracting attention as possible breakthrough in the diffraction limit. These technologies are intended to optically read/write information by means of an optical element that transmits an evanescent wave having a short wavelength through an aperture, which is smaller than the wavelength and formed in a metal film.
Recently, there has been disclosed an optical transmission technology that remarkably raise the transmittance of light being transmitted through an aperture cut through a metal film with a diameter smaller than the wavelength of light, by providing the surface profile of the metal film with projections and recesses that are cyclically arranged near the aperture (Japanese Patent Laid-Open Publication No. 2000-291265). The optical recording system using an optical head having an optical element realized by using a metal film is drawing attention as a system that allows high density recording because it can write information in an area smaller than the wavelength of light.
The aperture 130 has a diameter of d, which is not larger than the wavelength of light that enters the aperture 130. The read/write head 100 is lifted from the optical storage medium 150 by a distance smaller than the diameter of the aperture or held in contact with the optical storage medium 150 when it writes information on or read information from the storage medium. The metal film 122 of the optical element 120 has a cyclic surface topography 140 at least on one of its two surfaces. Typical examples of the cyclic surface topography 140 include one as illustrated in
While optical write/read heads formed by using such an optical element are expected to realize a higher information storage density than ever, they are accompanied by problems that are different from the problems of known optical heads using a far field optical system and adapted to operate with a distance separating the optical head and the storage medium. Examples of the problems of optical heads using such an optical element include that dust and/or scraped particles can enter and fill the micro-aperture and/or the recesses of the cyclic topology formed on the optical element and that the aperture and/or the recesses are scarred to hinder normal recording/reproducing operations because the optical head is lifted only slightly from or held in contact with the storage medium for writing/reading operations and seek operations for tracking signals. These problems are common to both optical disks and magnetic disks. These problems have been discussed frequently particularly in the case of magnetic disk heads adapted to be lifted from or held in contact with the storage medium from the viewpoint that the head that is lifted from or held in contact with the storage medium for operation can crush the storage medium by way of dust and/or scraped particles.
Japanese Patent Laid-Open Publication No. 11-273046 describes a structure, for seizing dust during a seek operation, formed by arranging a step on the lateral surfaces of a magnetic head slider. However, a simple step can attract dust only weakly and hence the attracted dust can easily fall onto the surface of the recording medium and give rise to abrasion and recording/reproduction errors when the slider vibrates. Japanese Patent Laid-Open Publication No. 5-081810 describes a structure formed by arranging a groove on the buoyancy generating surface of a magnetic head slider rail and upwardly tilting the surface linked to the flow-in edge of the groove toward the flow-in edge so as to attract dust to the inclined surface. However, with such a structure, it is not possible to prevent dust from reaching the surface of the slider rail nor is it possible to attract the effect of attracting dust. Japanese Patent Laid-Open Publication No. 4-137286 describes a structure for releasing dust far away from the surface of a recording medium by tapering the front end surface of a magnetic head slider to make it form an acute angle with the guide surface. However, with such a structure formed only by tapering the front end surface of a magnetic head slider, the released dust can, if partially, return and fall on the surface of the recording medium as the slider vibrates Japanese Patent Laid-Open Publication No. 5-159503 discloses a structure formed by arranging a dielectric substance such as ebonite, resin or silicon around a magnetic head slider so as to attract dust by electrostatic force. However, with such an arrangement, the obtained attracting power is small and it is difficult to strongly hold dust. Additionally, the attracting power can fluctuate depending on the environmental conditions and hence is unstable.
In view of the above identified problems of known information recording/reproduction heads for optical or magnetic recording/reproduction that are adapted to be lifted from or held in contact with a recording medium, it is therefore an object of the present invention to provide an information recording/reproduction head that can prevent dust from entering into the gap between the floating slider or the contact slider of the head and a recording medium and from falling onto the recording medium.
The present invention provides, in a first aspect thereof, an information recording/reproduction head for recording information on or reproducing information from a rotary disk, characterized by: a slider adapted to be floated above or held in contact with the disk for traveling, the slider having an organic substance layer, arranged at a surface region thereof in a vicinity of the disk, for attracting dust on the disk so as to collect the dust.
In a preferred embodiment of the information recording/reproduction head of the first aspect of the present invention, the slider has a positive pressure surface for floating thereby or a contact pad for contacting thereby, and a groove, on a lateral surface having an angle with a disk-opposing surface of the positive pressure surface or contact pad, for collecting and holding the dust existing on the disk, the organic substance layer being formed by coating on the groove.
The present invention provides, in a second aspect thereof, an information recording/reproduction head for recording information on or reproducing information from a rotary disk, characterized by: a slider adapted to be held in contact with the disk for traveling, the slider having a lateral surface forming an angle with a disk-opposing surface of a contact pad for the contacting, the lateral surface mounting thereon an organic substance layer for attracting thereon dust existing on the disk so as to collect the dust, wherein a ridge formed by the lateral surface and the disk-opposing surface has a radius of curvature smaller than a value obtained by multiplying a half diameter of particles of the dust existing on the disk and forming clusters by a predetermined constant.
The present invention provides, in a third aspect thereof, an information recording/reproduction head for recording information on or reproducing information from a rotary disk, characterized by: a slider adapted to be held in contact with the disk for traveling, the slider having a contact pad for the contacting, the contact pad having a lateral surface forming an angle with a disk-opposing surface thereof, the lateral surface having thereon a groove for collecting and holding dust existing on the disk, the groove having a layer of an organic substance formed therein for attracting dust for adhesion, wherein a ridge formed by the lateral surface and the disk-opposing surface has a radius of curvature smaller than a value obtained by multiplying a half diameter of particles of the dust existing on the disk and forming clusters by a predetermined constant.
In the information recording/reproduction head of the second and second aspects of the present invention, due to having the configuration as described above, the dust scattering on the recording medium is collected in the groove. The dust collected in the groove can be made to hardly fall back onto the recording medium. The organic substance layer takes a role of holding the dust and anchoring the dust to the slider. Preferably, the organic substance layer should be made to rigidly adhere to the lateral walls of the recessed section of the positive pressure surface and/or that of the contact pads, and exhibit affinity for the dust there and the lubricating oil mixed therewith and also hydrophilicity so that it can prevent crumbs of dust from peeling off from the positive pressure surface and the lateral walls of the contact pads etc. of the slider and falling down therefrom.
The organic substance is expressed by chemical formula of (G-R1)xSi(OR)4-x, where R1, R and x represent a hydrophilic functional group, a hydrocarbon chain an integer selected from 1, 2 and 3, respectively. In addition, G represents a hydrophilic functional group selected from hydrophilic functional groups including OH—(hydroxyl group), NH3—(amino group), HC(—O—)═CH—(glycidoxy group) and —NCO(isocyanate group), R represents a hydrocarbon chain and R represents a reactive functional group selected from reactive functional groups including —CH3, —C2H5 and —H. The hydrogen bond functional group attracts functional groups, existing on the surfaces of dust clusters and along the terminal parts of lubricant with a strong intermolecular force. The reactive functional group gives rise to a chemical reaction with dust and/or lubricant to form a very strong covalent bond. The hydrophilicity that arises due to the hydrogen bond and the chemical reactivity relative to dust provides an effect of binding the organic substance to clusters of dust and lubricant more firmly if compared with hydrocarbons and fluorinated hydrocarbons that are hydrophobic and not hydrophilic.
It is preferable that, among the above heads, the information recording/reproduction head having a contact pad on the slider further include a support spring for supporting the slider, wherein assuming a force by which the support spring is pressed against the slider is W, a distance between a pressure application point at which the support spring presses the slider and a rearmost contact point at which the contact pad contact the disk is L1, a distance between a contact point at which a dust cluster contacts the contact pad and the rearmost contact point is L2 a frictional force applied by the dust cluster to the contact point is Fh, and a variable conversion of A=(WL1/FhL2)2 is made, given B as expressed by the formula of B=2A+1+(4A(A+1))1/2 is the predetermined constant.
Each of all the predetermined constants as described above preferably has a value within a range between 2.6 and 36,000,000. Therefore, if the positive pressure surface or contact pad has a corner having a curvature of radius r which is smaller than the half diameter g of the dust cluster multiplied by B, it is possible to prevent the dust from coming onto the floating surface.
In addition in each of all the information recording/reproduction heads, the disk may be a disk for use in optical recording/reproduction, and the contact pad or the positive pressure surface is provided, on a disk-opposing surface thereof, with an optical element for raising an intensity of light transmitted through the micro-aperture.
In each of all the information recording/reproduction heads as describe above, the disk is preferably a disk for use in magnetic recording/reproduction, and the contact pad or the positive pressure surface is provided, on a disk-opposing surface thereof, with a magnetic recording/reproduction element.
Now, the present invention will be described in greater detail by referring to the accompanying drawings that illustrate preferred embodiments of the present invention.
The optical head 1 has a slider 8 and a support spring. The slider 8 is provided with a rail 10 configuring an air bearing surface for floating the optical head 1 in air above the recording medium 6, with the intervention of the protection film 13 and the lubricating film 14 of the recording medium. In short, the optical head of the present embodiment is a floating type head.
The head of each of the above-described embodiments is additionally provided with grooves or recesses for seizing dust and, preferably, a surface treatment layer is formed in the grooves or the recesses. More specifically, in the case of the floating type slider 20 or the first embodiment, a recess 11 is formed in each piece of the rail 10 of the slider 8, as shown in FIG. 2, and a surface treatment layer 12 is formed on the end facets of each piece of the rail 10 including the recess, as shown in
The recesses and the surface treatment layers take respective roles as described below. As the slider starts running on or above the recording medium, the particles of dust that are scattered on the recording medium are collected in the grooves or the recesses 11. The capacity of the grooves or the recesses is made larger than the volume of the dust. Therefore, the particles of dust collected in the grooves or the recesses can hardly fall back onto the recording medium 6. However, some of them may fall thereon if the slider is subjected to an excessively large acceleration. A surface treatment layer is arranged on each of the recesses in order to prevent the dust from falling. The surface treatment layer 12 takes a role of holding particles of dust and anchoring them to the slider. The surface treatment layer rigidly adheres to the lateral walls of the positive pressure surface or those of each of the contact pads and has affinity for dust and the lubricant that is mixed with the dust and hydrophilicity so that it prevents dust clusters from peeling off and falling from the rail or the lateral walls of the recesses of the contact pads or the similar components.
Preferably, the surface treatment agent that forms the surface treatment layer is expressed by the following chemical formula:
(G-R1)xSi(OR)4-x,
where x represents an integer selected from 1, 2 and 3 and G represents a hydrophilic functional group that may be a hydrogen bond functional group such as OH—(hydroxyl group) or NH3—(amino group) or a chemically reactive functional group such as HC(—O—)═CH—(glycidoxy group) or —NCO(isocyanate group). Hydrogen bond functional groups and the functional groups, which exist on the surface of the dust clusters and at the terminals of the lubricant, attract each other with a strong intermolecular force. Chemically reactive functional groups react with dust and lubricants to form a very strong covalent bond.
The hydrophilicity that arises from the hydrogen bond and the chemical reactivity with dust is quantified by the number of inorganic groups as described in Japanese Patent No. 288490 and provides an effect of binding dust clusters and lubricants to the surface treatment agent more firmly, if compared with hydrocarbons and fluorinated hydrocarbons that are hydrophobic and not hydrophilic. R1 represents a hydrocarbon chain such as —CnH2n— (n being an integer not smaller than 1) and R represents a reactive functional group such as —CH2, —C2H5 or —H that chemically reacts with the slider surface and becomes bonded thereto. The chemical reaction takes place as a result of hydrolysis caused by the moisture adsorbed to the slider or the heat treatment that is conducted at temperature not higher than 300° C. after the application of the surface treatment agent. Then, the SiOR group reacts with water in a manner as expressed by the following formula:
SiOR+H2OSiOH+ROH
and the produced SiOH group reacts with the material M of the slider to produce a bond of SiOM. The reaction becomes less active when the molecular weight of R is too large. In other words, R preferably has a small molecular weight substantially equal to that of —H, —CH3, —C2H5 or —C3H7.
While R1 is the molecular chain of a hydrocarbon group having one or more than one carbon atoms, the number of carbon atoms is preferably not larger than 10 from the viewpoint of solubility to the solvent at the time of application of the surface treatment agent. The —OR is preferably an —OH group that forms an alkoxy group or a silanol group (—SiOH) that reacts with the optically transparent slider material such as quartz or sapphire. The use of a halogen group such as —Cl is not preferable because such a group is corrosive, although highly reactive. The letter x represents an integer that defines the number of functional groups G and OR groups. The affinity of the surface treatment agent for molecules of the lubricant increases as the value of x increases from 1 to 2 or 3, whereas the number of bonds to the recesses decreases at the same time. Therefore, while the use of 2 for x is best in terms of balance therebetween, a satisfactory effect may be obtained by using 1 or 3 for x.
Now, the dynamic conditions that allow dust to enter the gap between the recording medium and the head slider will be discussed below in connection of exemplified contact pads 18.
Each of
Fv=Fh·tan θ (1) and
r=g+g·sin θ (2),
so that consequently the following equation is obtained:
Fv=Fh·(r−g)/(2(r·g)1/2) (3).
On the other hand, assuming that the force by which the support spring is pressed against the contact pad is W while the distance from the corner at the rear and of the contact pad to the pressure application point of the support spring is L1 and the distance from the contact point at the rear end to the corner where the cluster contacts the contact pad is L2 as shown in
Fc=W·L1/L2 (4).
Thus, the cluster pushes up the slider and enters the gap between the contact pad and the optical disk when there arises a combination of r and g that satisfies the conditions under which the force Fc is greater than Fc of the formula (4).
When the following substitutions of
R=r/g and A=(WL1/FhL2)2
are used, the requirement that needs to be met for Fv>Fc is expressed by the following formula:
R<2A+1±(4A(A+1))1/2 (5)
Thus, the dust cluster pushes up the slider and enters the gap between the contact pad and the optical disk when the above requirement is met.
If W is 5 grams and Fh is 1 gram, while L1 is 3 mm and L2 is 1 mm, the ratio R of the half diameter of the dust cluster to the radius of curvature is 902. Thus, when the rail 10 or the contact pad is made to have a corner with a radius of curvature r that is smaller than the half diameter g of the dust cluster multiplied by 902, the dust cluster is prevented from coming onto the floating surface. Dust clusters show a cumulative distribution pattern as shown in
While the use of an optical element formed by using a metal film having an aperture with a diameter smaller than the wavelength of light and a surface profile with projections and recesses that are cyclically arranged near the aperture is described above for the above embodiment, an optical head formed by means of near field optical technologies of using evanescent wave and a metal film having an aperture with a diameter smaller than the wavelength of light but not any surface profile may alternatively be used. Additionally, while the above embodiments are described in connection with an optical head using an optical element, it is apparent that the technological concept of the present invention encompasses the use of a magnetic head.
Thus, as described above, in a floating type or contact type information recording/reproduction head according to the present invention, the slider or each of the contact pads or the rail of the slider is provided at the front end or the rear end and/or the lateral surfaces thereof with a groove or recess cut perpendicularly relative to the surfaces in order to anchor the adhering dust and a surface treatment agent is selectively used to strengthen the bond between the dust on the surface treatment layer and the slider or the contact pads or the rail of the slider in order to prevent dust from falling onto the surface of the recording medium. Additionally, the gap between the slider and the recording medium is so arranged as to prevent dust from entering there. Thus, the dust adhering to the contact pads is physically and chemically held there and prevented from moving and adhering onto the recording medium.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2002-155503 | May 2002 | JP | national |
