JP2010077519A - Method for forming film on lens, and vapor-deposition apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a film on a lens, which precisely controls an electron gun according to characteristics of a vapor-depositing material. <P>SOLUTION: The film-forming method is directed for forming the film on the surface of the lens which is held in a vapor-deposition chamber of a vapor-deposition apparatus by vaporizing and vapor-depositing the vapor-depositing material. In the method, a control section commands a heating section to start heating and output an initial output which has been determined beforehand according to the type of the vapor-depositing material; commands the heating section to gradually increase the output of the heating section by an open loop control; and when the conditions which have been determined beforehand have been satisfied, controls the output of the heating section by a feedback control based on a light quantity value in an optical film thickness measurement section. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an improvement in a method and apparatus for forming a thin film on the surface of a plastic or glass material, and in particular, a technique for forming a thin film with constant optical properties with good reproducibility and forming an antireflection film on a spectacle lens. About.

  In the manufacture of spectacle lenses, there are those to which a multilayer coating technique is applied in which a plurality of thin films are formed on a lens, and optical characteristics such as antireflection and functions such as water repellency are imparted. In particular, it is widely used in products in which a thin film such as an antireflection film is formed on an optical member such as a plastic or glass spectacle lens. The thin film is formed on the optical member by heating and vaporizing (or sublimating) the vapor deposition raw material with an electron gun installed in a chamber of a vacuum vapor deposition apparatus.

As a technique for forming a thin film having a constant optical property with good reproducibility by controlling an electron gun, a technique using an optical film thickness meter is known (for example, Patent Documents 1, 2, and 3). In this vapor deposition apparatus, an optical film that measures the thickness of a thin film using the fact that the amount of transmitted or reflected light when a predetermined film is irradiated with a predetermined light depends on the thickness of the thin film. A thickness meter is used to control the amount of vapor deposition material to fly so that the light amount value of transmission or reflection measured every moment by the optical film thickness meter is close to or equal to the reference light amount value in the thin film formation process.
JP 2001-115260 A JP 2003-202404 A JP 2006-9117 A

  When a transparent inorganic substance is vapor-deposited, if the film formation rate (thin film formation rate) is high, absorption occurs in the transparent thin film formed on the surface of the optical member due to insufficient oxidation of vaporized or sublimated vapor deposition materials. Tend. When the film formation rate is slowed, absorption of the thin film is difficult to occur and the quality of the optical member can be ensured. However, the productivity of the vapor deposition process is lowered, or a defect occurs in the vapor deposition material due to other factors. For this reason, in the above conventional example, the film formation rate at the time of vapor deposition is controlled by controlling the electron gun at the thin film formation rate observed with the optical film thickness meter. The above conventional example is very effective when vapor deposition proceeds to some extent and optical characteristics as a thin film begin to be obtained.

  However, in the above conventional example, when the deposited components are very small before the optical properties appear in the thin film during the deposition (formation of the thin film) at the initial stage of vapor deposition, the vapor deposition rate control at the initial stage of vapor deposition ( There is a risk that the deposition speed control) cannot be performed accurately. This is because the change in reflectance with the film thickness exhibits substantially the same behavior when, for example, a behavior similar to a sine curve is exhibited. In the method of calculating the film thickness by measuring the reflectivity with an optical film thickness meter, the ratio of the change in reflectivity with respect to the film thickness at the extreme inflection point of the sine curve is very small. This is because it becomes difficult to predict. In general, the initial deposition of the multilayer antireflection film starts from an extreme inflection point of the sine curve. When the initial stage corresponds to the extreme value inflection point of the reflectance, it is difficult to predict the laminated state of the film thickness, and the deposition rate in the initial state is increased. In such a state, a situation occurs in which the oxidized state of the formed thin film is deteriorated, and there is a possibility that absorption may occur in the formed film thickness. There was a problem.

  In particular, when film formation control is monitored with an optical film thickness meter, it is difficult to observe the optical characteristics of the thin film at the initial stage of film formation. In some cases, it was particularly difficult to control the electron gun.

  Also, since the required energy of the electron gun differs depending on the state of the source material (evaporation source) that becomes the evaporation source, it is difficult to perform uniform control to determine a predetermined initial value at the initial stage of film formation. It is. For example, when the vapor deposition material is a substance obtained by solidifying powder into a tablet shape, the energy of the electron gun necessary for vapor deposition varies because the state is slightly different depending on the individual difference of the vapor deposition material, even if the same type of vapor deposition material. Even if a plate-shaped vapor deposition material is used, the energy of the electron gun required for vapor deposition differs depending on the crystal state and amorphous state of the plate. Furthermore, there are factors depending on the maintenance of the vapor deposition apparatus, and there may be a deviation between the actual power value (energy) of the electron gun and the indicated value.

  Therefore, since the necessary energy (indicated value) of the electron gun differs depending on the state of the evaporation source serving as the evaporation source, it is difficult to perform uniform control for determining a predetermined initial value at the initial stage of film formation. It was.

  Therefore, the present invention has been made in view of the above problems, and aims to accurately control the electron gun in the initial stage of film formation in accordance with the characteristics of the deposition material, and in particular, a thin film formed on an optical member. The purpose is to stabilize the quality of the film and improve the productivity of the vapor deposition process.

  The present invention is a lens film forming method for forming a film by vaporizing a vapor deposition raw material on a surface of a lens held in a vapor deposition chamber of a vapor deposition apparatus, and depositing the vapor deposition apparatus in the vapor deposition chamber. A heating unit that heats the vapor deposition material, an optical film thickness measurement unit that calculates the film thickness from the amount of surface reflected light of the film formed on the lens, and controls the output of the heating unit A control unit, and the control unit commands the heating unit to set an initial output preset according to the type of the vapor deposition material, and starts the heating unit. The step of acquiring the light amount value of the optical film thickness measurement unit at a set period, the step of instructing the control unit to gradually increase the output of the heating unit by open loop control, and the control unit, Meet preset conditions And when the condition is satisfied, the output of the heating unit is controlled by feedback control based on the light amount value, and the predetermined condition has elapsed since the heating unit was activated. The initial output is a predetermined value that is smaller than an output that reliably vaporizes the vapor deposition material.

  In the present specification, the “output that the vapor deposition raw material is surely vaporized” refers to an output that reaches a temperature exceeding the vaporization point (boiling point and sublimation point) of the vapor deposition material at the pressure in the vapor deposition chamber. The “predetermined value smaller than the vapor deposition material is surely vaporized” means an output that reaches a temperature equal to or slightly lower than the vaporization point (boiling point and sublimation point) of the vapor deposition material. When the vapor deposition proceeds at such an output, the vapor deposition material flies little by little with the vapor pressure and adheres to the substrate, and the film formation proceeds at a slow speed.

  Further, the present invention determines whether or not the control unit satisfies a preset condition, and when the condition is satisfied, heating is performed when the output of the heating unit is controlled by feedback control based on the light amount value. When a predetermined amount of time has elapsed since the start of the unit, if the light amount value is less than or equal to the threshold value, the heating unit is instructed to add the output of the open loop control and the output of the feedback control. Features.

  Note that the output of the feedback control is not limited to a positive output that increases the output, and may be a negative output that decreases the output. When the output of the feedback control is a positive output, the power for calculating the sum with the output by the open loop control is larger than the output of the open loop control. Conversely, when the output of feedback control is a negative output, the sum calculation power with the output by open loop control is lower than the output of open loop control. In other words, if the output by the open loop control calculated from the light quantity information is too small, it is compensated by the positive output of the feedback control, and if the output by the open loop control is too large, the negative output of the feedback control Can be reduced. As a result, film formation can be performed at an appropriate deposition rate.

  According to the present invention, in the initial stage of the vapor deposition process, heating of the vapor deposition raw material is started from an initial output that is slightly smaller than the output at which the vapor deposition raw material is surely vaporized, and after starting the heating unit, a predetermined amount is obtained. Until the time elapses, the output of the heating unit is gradually increased and then the control shifts to feedback control. As a result, vaporization or sublimation starts gradually according to the characteristics of the deposition material, and then the control shifts to feedback control. This makes it possible to accurately control the electron gun at the initial stage of film formation, and stabilize the quality of the thin film. In addition, it is possible to improve the productivity by preventing the deposition process from taking a long time.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows an example in which the present invention is applied to a vacuum deposition apparatus for forming a thin film such as an antireflection film or a water repellent coating on a plastic lens for spectacles. This vacuum deposition apparatus forms an antireflection film or the like by depositing a molded eyeglass lens (hereinafter simply referred to as a lens) with a deposition material (film forming material) in a vacuum deposition chamber.

  In FIG. 1, in a vacuum chamber 1 serving as a film forming chamber, a coat dome 2 that holds a plurality of lenses 2a at the top and a monitor glass 2b for detecting a thin film formation state at a predetermined position is provided. Installed. Below the vacuum chamber 1, a crucible 4 that houses evaporation raw materials (film forming materials) 4 a and 4 b, and an electron gun 3 that evaporates (or sublimates) by applying an electron beam to the vapor deposition raw materials 4 a and 4 b of the crucible 4. , A shutter 5 that selectively blocks evaporated materials from the deposition raw materials 4a and 4b, and a supplied ionized gas (inert gas, oxygen, etc.) to improve the strength and film quality (denseness, etc.) of the deposited thin film ) For generating an ion beam to irradiate the ion beam and a gas generator 15 for filling the vacuum chamber 1 with ionized gas in order to improve the strength and film quality of the deposited thin film. Is provided. The shutter 5 is provided with an actuator (not shown) and is controlled by a control device 12 described later. Further, the vapor deposition raw materials 4a and 4b are different kinds of materials, for example, the vapor deposition raw material 4a is a low refractive index material and the vapor deposition raw material 4b is a high refractive index material. Further, a shutter 141 for protecting the inside of the ion gun 14 can be opened and closed by an actuator (not shown).

  In the vicinity of the upper coat dome 2, a substrate thermometer 6 for measuring the temperature of the lens 2 a as the film formation target held by the coat dome 2 is provided. The substrate thermometer 6 measures the temperature near the lens and indirectly measures the lens temperature. Furthermore, a vacuum gauge 7 for measuring the degree of vacuum (atmospheric pressure) in the vacuum chamber 1 and an exhaust unit 8 for evacuating the vacuum chamber 1 by reducing the pressure are provided. Further, a heater 9 for heating the lens 2 a held on the coat dome 2 is provided. The heater 9 is composed of a halogen heater or the like.

  Further, an optical film thickness meter 10 for measuring the reflectance of the monitor glass 2 b set at a predetermined position of the coat dome 2 is provided above the vacuum chamber 1. The optical film thickness meter 10 is connected to the control device 12 via the film thickness monitor 11, and the optical film thickness meter 10 receives reflected light with respect to the amount of irradiation light as light amount data (light amount value) as will be described later. The light intensity ratio is output. The film thickness is calculated from the amount of reflected light. The configurations of the optical film thickness meter 10 and the film thickness monitor 11 are the same as the configurations of the above-mentioned conventional examples of Japanese Patent Laid-Open Nos. 2001-115260, 2003-202404, and 2006-9117. .

  The control device 12 includes a calculation unit 120 including a CPU, a memory, and a disk device, a reference light amount value data storage unit 13 for feedback control of power supplied to the electron gun 3 during the vapor deposition process, and an initial stage of the vapor deposition process. And an open loop control map 130 that stores a command value to the electron gun 3 for controlling the power supplied to the electron gun 3 in an open loop. Further, the control unit 12 is connected to an input unit 12a configured by a keyboard, a mouse, and the like, and receives commands and inputs from the operator. The control device 12 includes control targets such as the above-described electron gun 3, shutter 5, exhaust unit 8, heater 9, ion gun 14, and gas generator 15, substrate thermometer 6, vacuum gauge 7, optical film thickness. Sensors such as a total of 10 (film thickness monitor 11) are connected, and the control target is controlled based on input from each sensor. The arithmetic unit 120 is loaded with a program for performing a vapor deposition process and is executed by the CPU. Further, the reference light quantity value data storage unit 13 and the open loop control map 130 may be read into the memory of the calculation unit 120 or the disk device.

  That is, the control device 12 controls the exhaust unit 8 based on the information of the vacuum gauge 7 and maintains the inside of the vacuum chamber 1 at a predetermined degree of vacuum (atmospheric pressure). Further, the control device 12 controls the heater 9 based on the information of the substrate thermometer 6 to bring the lens 2a that is the film formation body to a predetermined temperature. Then, the control device 12 has a reference light quantity value data storage unit that changes the light quantity value every time depending on the optical film thickness of the thin film formed on the monitor glass 2 b measured by the optical film thickness meter 10. The power (current and / or voltage) applied to the electron gun 3 is controlled so as to be equal to the value stored in 13. Further, depending on the type of thin film to be formed and the type of vapor deposition materials 4a and 4b to be vaporized (or sublimated), the ion gun 14 is supplied with ionized gas and irradiated with an ion beam. The gas generator 15 supplies a gas corresponding to the type of vapor deposition material, and supplies, for example, oxygen or nitrogen.

  Here, the coat dome 2 is a holding means for holding the lens 2a so that an antireflection film or the like is deposited on the lens 2a. And it is circular so that the several lens 2a can be vapor-deposited simultaneously, and the coat dome 2 has a predetermined curvature so that all the lenses may become the antireflection film of the same quality.

  The electron gun 3 evaporates the vapor deposition raw materials 4a and 4b accommodated in the crucible 4 by heating them to the melting temperature of the vapor deposition raw materials 4a and 4b, and vapor deposits and deposits the vapor deposition raw materials on the lens 2a and the monitor glass 2b. A thin film is formed.

  The crucible 4 is a known container used to hold the vapor deposition materials 4a and 4b. The crucible 4 is cooled or a material having a high thermal conductivity is preferable so that the vapor deposition material is not bumped by the heating of the vapor deposition material by the electron gun 3.

  The shutter 5 is driven by an actuator (not shown) and is controlled to open when deposition is started or closed when deposition is completed, and facilitates control of the thin film. The heater 9 is a heating unit that heats the lens 2a to an appropriate temperature in order to obtain physical properties such as adhesion of a thin film deposited on the lens 2a.

  When the optical film thickness meter 10 irradiates light onto a transparent substrate (monitor glass 2b) having a transparent thin film formed on the surface, the reflected light from the thin film surface and the reflected light from the transparent substrate surface interfere with each other due to the phase difference between them. It uses the phenomenon that causes That is, the phase difference changes depending on the refractive index and optical thickness of the thin film, the state of interference changes, and the amount of reflected light changes depending on the refractive index and optical thickness of the thin film. If the reflected light changes, the transmitted light also inevitably changes. Therefore, the same can be done by measuring the amount of the transmitted light, but the case where the reflected light is used will be described below.

  The optical film thickness meter 10 irradiates the monitor glass 2b held at the center of the coat dome 2 with light of a predetermined wavelength and measures the reflected light. Since it can be considered that the thin film formed on the monitor glass 2b depends on the thin film formed on each lens 2a, information capable of estimating the thin film formed on each lens 2a can be obtained.

<Outline of control>
In the vacuum vapor deposition apparatus of the present invention, as shown in FIG. 4, during the period from the start of the vapor deposition process until a predetermined condition is satisfied (initial stage of the vapor deposition process), the electron gun 3 is subjected to open loop control (initial rate control). When the predetermined condition is satisfied, the output of the electron gun 3 is controlled by feedback control (PID control) to realize the vapor deposition rate in accordance with the characteristics of the vapor deposition material. Furthermore, when conditions related to time, which is a part of the predetermined conditions, are satisfied at the initial stage of the vapor deposition process, the vaporization (or sublimation) of the vapor deposition material is promoted by performing combined control that combines open loop control and feedback control. To do. The feedback control (rate control) is the same as that of the above-mentioned conventional example, Japanese Patent Laid-Open No. 2001-115260, Japanese Patent Laid-Open No. 2003-202404, or Japanese Patent Laid-Open No. 2006-9117. Description is omitted.

  Further, in the present invention, the output of the electron gun 3 that starts open loop control at the initial stage of the vapor deposition process (hereinafter referred to as initial power P0) is the output that the vapor deposition material 4a (or 4b) starts to vaporize (or sublimate). It is set to a value smaller than (hereinafter referred to as vaporization power) and larger than 0, and during the open loop control period, the output commanded to the electron gun 3 is gradually increased from the initial power P0 to form a film. The rate (the formation speed of the thin film formed on the lens 2a) is prevented from becoming excessive and absorption is prevented, and the entire time of the vapor deposition process is prevented from increasing wastefully. In particular, by applying to a sublimation deposition material such as ITO (Indium-Tin Composite Oxide) which is easily absorbed by the thin film of the lens 2a when the film forming rate is increased, ensuring quality and improving productivity. Can do. Details of the vapor deposition process will be described below.

<Setting of initial power P0>
The initial power P0 commanded to the electron gun 3 when starting the vapor deposition process is stored in the open-loop control map 130 in advance for each type of vapor deposition raw material 4a (or 4b), and the vapor deposition process is performed. At this time, the operator selects the input device 12a.

  FIG. 2 is an explanatory diagram showing an example of the open loop control map 130. The open loop control map 130 has one entry for each deposition material, and each entry is configured as follows.

  A vapor deposition raw material 1301 for storing a name or identifier for specifying the type of the vapor deposition raw material, a vaporization power 1302 for storing an output (current value in this example) of the electron gun 3 at which the vapor deposition raw material starts vaporization (or sublimation), and an open Initial power P0 (1303) for storing an output (current value in this example) commanded to the electron gun 3 at the start of loop control (at the start of vapor deposition), and an output to the electron gun 3 increased every predetermined time And an adjustment value ΔP (1304) for storing an increment value (current value in this example) and a light amount value (%) of the optical film thickness meter 10 that ends open loop control and shifts to feedback control are stored. The initial idle time for storing the feedback control start value L1 (1305) and the time from the start time of the vapor deposition process to the start of the feedback control (initial idle time Ti) i and (1306), one of the entry consists of. The open loop control map 130 can store entries for a plurality of vapor deposition materials 4a and 4b.

  The vaporization power, the initial power P0, the adjustment value ΔP, the feedback control start value L1, and the initial idle time Ti are preset by experiments and tests, respectively. For example, when the deposition material 1301 is “A”, the initial power P0 is set to 80% of the vaporization power X, and the deposition material is not clearly vaporized (or sublimated, and so on) immediately after the start of the open loop control. Is set to a value. As described in the previous section, this value is different from the vapor deposition raw material in the form of tablets in the form of tablets. The required output of the electron gun 3 varies. Even if a plate-shaped vapor deposition material is used, the output of the electron gun 3 required for vapor deposition varies depending on the crystal state and amorphous state of the plate even if the same type of vapor deposition material.

  For this reason, even with the same vapor deposition material 4a, there are a vapor deposition material 4a that does not start vaporization when the electron gun 3 is driven with the vaporization power 1302 at the start of open loop control, and a vapor deposition material 4a that starts vaporization rapidly. . In the case of rapid vaporization immediately after the start of the open loop control, as described in the above problem, there is a possibility that absorption due to insufficient oxidation may occur in the thin film formed by the vapor deposition raw material 4a deposited on the lens 2a.

  Therefore, the initial power P0 is set to a clearly lower output than the vapor deposition raw material 4a is surely vaporized, and the output is gradually increased during the open loop control period, so that the film thickness of the thin film deposited on the monitor glass 2b is increased. The state is surely shifted to a state where the optical film thickness meter 10 can measure (feedback control start value L1). As a result, even if the vapor deposition raw material has individual differences in the vaporization start output, it does not cause problems such as absorption in the formed thin film, and prevents the processing time of the entire vapor deposition process from increasing unnecessarily. is there.

  The initial power P0 is smaller than the vaporization power and larger than 0, and is preferably set to a value of 50% or more of the vaporization power, for example.

  Note that the adjustment value ΔP, the feedback control start value L1, and the like may be set to values that do not cause rapid vaporization according to the vaporization characteristics of the vapor deposition raw material 4a as described above. In addition, the initial idle time Ti is also set so that the period during which the command value to the electron gun 3 is increased by the adjustment value ΔP by open loop control for each predetermined cycle, which will be described later, according to the vaporization characteristics of the vapor deposition material 4a. Should be set. That is, during the open loop control period, the command value of the output of the electron gun 3 is gradually increased. Therefore, if the initial idle time Ti is set too long or the feedback control start value L1 is set too high, the vapor deposition material 4a However, the time required for the vapor deposition process also increases. For this reason, it is desirable to set the feedback control start value L1 or the minimum value of the initial idle time Ti that can measure the progress of film formation with the optical film thickness meter 10 in the open loop control map 130 for experiments or the like.

<Details of deposition process>
Next, an example of the control of the vapor deposition process performed by the control device 12 will be described. FIG. 3 is a flowchart showing an example of the control of the electron gun 3 performed by the controller 12 in the vapor deposition process, and is a process executed when a start command is received from the input device 12a.

  In step S1, various parameters used for control by the control device 12 are initialized, and the name or identifier of the vapor deposition material 4a (or 4b, the same applies hereinafter) is received from the input device 12a. Further, the control device 12 sets a predetermined time T1 as a cycle for executing the open loop control in the variable Kt for determining the control cycle. The time T1 is set to 10 msec, for example.

  Also, as a parameter to be initialized, the initial timer Tm1 that measures the time from the start of the vapor deposition process to the end of the open loop control that shifts to the feedback control is reset to 0, and the measurement cycle of the optical film thickness meter 10 is measured. The check timer Tc is reset to 0, the check counter Cc for determining the output update period of the electron gun 3 during the open loop control period is reset to 0, and the FB flag indicating the start of feedback control is reset to 0 To do.

  Next, in step S2, the open loop control map 130 is searched from the name or identifier of the vapor deposition raw material 4a received in step S1, and the initial power P0, adjustment value ΔP, feedback control start value L1, initial idle is searched from the corresponding entry. Time Ti is acquired.

  In step S3, the acquired initial power P0 is set to the electron gun power OP commanded to the electron gun 3 during the open loop control period, and heating of the deposition material 4a by the electron gun 3 is started.

  Next, in step S4, it is determined whether or not the value of the initial timer Tm1 has passed the initial idle time Ti. If it has elapsed, the FB flag for starting feedback control is set to 1 in step S5. On the other hand, if the value of the initial timer Tm1 has not passed the initial idle time Ti, the value of the initial timer Tm1 is updated (time counting) in step S6.

  Next, in step S7, it is determined whether or not the value of the check timer Tc has reached Kt = T1, which is a cycle for acquiring the output of the optical film thickness meter 10. If the value of the check timer Tc has reached the variable Kt, the process proceeds to step S9, and the output (light quantity value) of the optical film thickness meter 10 is read as the film thickness equivalent value of the thin film formed on the lens 2a. On the other hand, if the value of the check timer Tc has not reached the variable Kt, the process proceeds to step S8 to update the value of the check timer Tc, and then returns to step S4 to repeat the above loop.

  In step S10, it is determined whether or not the read light quantity value of the optical film thickness meter 10 exceeds the feedback control start value L1. If the light quantity value of the optical film thickness meter 10 exceeds the feedback control start value L1, the process proceeds to step S20 in order to end the open loop control and shift to feedback control. On the other hand, if the light quantity value of the optical film thickness meter 10 is equal to or less than the feedback control start value L1, the open loop control is continued, and the process proceeds to step S11. This work can also be executed by a method to which multithread processing is applied.

  In step S11, the check timer Tc for reading the output of the optical film thickness meter 10 is reset, and 1 is added to the value of the check counter Cc for determining the output update period of the electron gun 3 during the open loop control period. .

  In step S12, it is determined whether or not the value of the check counter Cc has reached a predetermined value. If the value of the check counter Cc has reached a predetermined value, the output of the electron gun power OP during the open loop control period is updated. It determines with having reached the period to perform, and progresses to step S13. On the other hand, if the value of the check counter Cc has not reached the predetermined value, the process returns to step S4 and the above processing is repeated.

  Here, the predetermined value is set to 500, for example, and in this example, since the value of the check timer Tc is Kt = T1 = 10 msec, the value of the electron gun power OP is updated every 500 × 10 msec = 5 seconds. The

  In step S13, the adjustment value ΔP of the open loop control map 130 corresponding to the deposition material 4a is added to and updated by the value of the electron gun power OP commanded to the electron gun 3 during the open loop control period. A new electron gun power OP that increases the output is set.

  In step S14, the check counter Cc for determining the cycle for updating the electron gun power OP is reset.

  In step S15, it is determined whether or not the FB flag is 1. If the FB flag is 1, it is a complex control period in which the open loop control and the feedback control are used together, and the process proceeds to step S18. On the other hand, if the FB flag is 0, it is during the open loop control period, so the process proceeds to step S16, and the electron gun power OP during the open loop control period is set to the electron gun power P commanded to the electron gun 3. In step S17, the electron gun power P increased by the adjustment value ΔP is commanded to the electron gun 3.

  On the other hand, in step S18 of the composite control period, the electron gun power FBP is obtained by feedback control based on the light amount value of the optical film thickness meter 10. The electron gun power FBP by this feedback control may be obtained by the method disclosed in the conventional example.

  Next, in step S19, the sum of the electron gun power OP during the open loop control period obtained above and the electron gun power FBP by feedback control is set as the electron gun power P during the composite control period. In step 19, if the electron gun power OP is too high, a negative output is applied by the electron gun power FBP, and the electron gun power P becomes lower than the electron gun power OP. When the electron gun power OP is too low, a sex output is added by the electron gun power FBP, and the electron gun power P becomes higher than the electron gun power OP. Then, the summed electron gun power P is output in step S17, and the electron gun 3 is driven.

  After step S20 of the feedback control period, first, in order to change the control cycle to a predetermined value T2 suitable for feedback control in step S20, the predetermined value T2 is set to the variable Kt. The predetermined value T2 is set to 4 seconds, for example. After the next control cycle, the feedback control is repeated each time the value of the check timer Tc reaches the predetermined value T2.

  In step S21, feedback control based on the output (actual light amount) of the optical film thickness meter 10 is performed by the method disclosed in Japanese Patent Application Laid-Open No. 2001-115260 or Japanese Patent Application Laid-Open No. 2006-9117 of the above-described conventional example. In S21, the command value FBP of the electron gun 3 by feedback control is set to the electron gun power P. In the feedback control by the above method, the light amount at time ti-1 (actual time) after the shutter 5 is opened is Li-1 (actual value = actual light amount), and the reference light amount value Ls (= Li-1) is searched from the reference light quantity value data in the reference light quantity value data storage unit 13. If there is no identical value, an approximate value is calculated. Then, a time ts (reference time) corresponding to the light quantity value Ls is calculated from the reference light quantity value data. Next, the light amount value (actual value = actual light amount) corresponding to the time ti after the control interval Δt (seconds) from the actual time ti−1 is set to Li. Further, a reference light amount Ls ′ corresponding to the reference time ts ′ (= ts + Δt) is obtained from the reference data. Further, a light amount value Qi is obtained from the ratio of the change amount of the actual light amount and the change amount of the reference light amount, PID control (proportional, integral, derivative control) is performed on the light amount value Qi, and the electron gun power value for feedback control Determine the FBP.

  Then, after resetting the value of the check timer Tc in step S23, the electron gun power P is commanded to the electron gun 3 in step S17, and the electron gun 3 is controlled by feedback control.

  In step S <b> 24, it is determined whether or not the vapor deposition process termination condition is satisfied. In this determination, for example, the end condition is satisfied when the elapsed time from the start of the vapor deposition process has passed a predetermined time (for example, 12 minutes) or when the light amount value has reached a predetermined value.

  With the above control, the relationship between the light amount value (film thickness equivalent value) of the vapor deposition process and the electron gun power P (command value) is as shown in FIG. FIG. 4 is a graph showing the relationship between the light amount value (film thickness equivalent value), the electron gun power P, and the time when shifting from the open loop control to the feedback control due to the light amount value exceeding the feedback control start value L1. .

  At time Ta, the initial power P0 is commanded to the open-loop control electron gun power OP, the electron gun 3 is activated, and the shutter 5 is opened to start the evaporation process. In the open loop control, the light quantity value of the optical film thickness meter 10 is read every 10 msec with the period Kt = T1, and when the value of the check counter Cc reaches a predetermined value = 500, the adjustment value is set to the electron gun power OP of the open loop control. ΔP is added, and the command value of the electron gun 3 is increased by an adjustment value ΔP which is a predetermined increment value every 5 seconds. The increase of the electron gun power in a cycle of 5 seconds is performed until the light quantity value exceeds the feedback control start value L1 or the value of the initial timer Tm1 reaches the initial idle time. In the illustrated example, the case where the light amount value exceeds the feedback control start value L1 at time Tb, the open loop control is ended, and the control shifts to feedback control is shown.

  In the period of feedback control, the electron gun power FBP of feedback control based on the light amount value of the optical film thickness meter 10 is calculated at a cycle of 4 seconds with the cycle Kt = T2, and commanded to the electron gun 3.

  At the start of the vapor deposition process, the initial power P0 commanded to the electron gun 3 is set to be clearly lower than the power at which the vapor deposition raw material 4a surely starts to vaporize. A large amount of vaporization will not start. That is, even with the same kind of vapor deposition raw material 4a, there is an error in the electron gun power P for starting vaporization due to individual differences, and heating is started at a preset low initial power P0 even for solids that are easily vaporized. In this way, it is possible to prevent absorption from occurring in the transparent thin film formed on the lens 2a by preventing rapid vaporization. For example, in the case of the vapor deposition material “A” shown in FIG. 2, 80% of the standard vaporization power X is set to the initial power P0, thereby preventing rapid vaporization due to individual differences. In the case of a solid that is easily vaporized, the film formation rate is higher than that of a solid that is difficult to vaporize. Therefore, the light amount value exceeds the feedback control start value L1 before the initial idle time Ti is reached, and the feedback control is performed. Can be migrated. For example, even if heating is performed at a preset initial power P0, it is conceivable that the vaporization speed increases due to the error due to the individual difference, but this situation can be avoided by setting the electron gun power FBP by feedback control to a negative output. It can be avoided. Thereby, the output of the electron gun 3 according to the formation speed of the thin film can be controlled.

  On the other hand, in the case of a solid that is difficult to vaporize, the initial power P0 is set to be clearly lower than the electric power at which the vapor deposition raw material 4a normally starts vaporization. Vaporization is not started unless the output of the electron gun 3 is repeatedly increased. For this reason, when waiting for the light quantity value to reach the feedback control start value L1, the time until the end of the vapor deposition process becomes excessive, and the productivity of the vapor deposition process decreases.

  Therefore, the period of only the open loop control is limited to the time when the initial idle time Ti elapses, and the feedback control is started when the film formation is slow even if the output of the electron gun 3 is repeatedly increased by the adjustment value ΔP. Thus, the vaporization of the vapor deposition material 4a can be promoted by correcting the output of the electron gun 3 exceeding the adjustment value ΔP.

  Here, when the feedback control is started after the initial idle time Ti has elapsed, the open loop control is continued until the light quantity value exceeds the FB start value Li, and the combined control period in which the open loop control and the feedback control are used together. And

  In this combined control period, as shown by times Tb to Tc in FIG. 5, the light amount value of the optical film thickness meter 10 is feedback controlled at time Tb when the initial idle time Ti elapses without vaporization of the vapor deposition material 4a. If the start value L1 has not been reached, feedback control is started in addition to open loop control. In the composite control period, as shown in step S19, the summed output of the electron gun power OP by the open loop control and the electron gun power FBP by the feedback control is controlled as a value for commanding the electron gun 3. In the case of a solid that is difficult to vaporize, the output of the electron gun power OP tends to be insufficient, and the electron gun power OP increment value (adjustment value ΔP) may be insufficient. In such a case, at least in an increment value (adjustment value ΔP) of the electron gun power OP by open loop control at every predetermined control cycle (for example, 5 seconds), the electron gun power FBP of feedback control is added with a positive output. As a result, an output equal to or larger than the increment value of the electron gun power OP by the open loop control is added to the electron gun power P. As a result, the output commanded to the electron gun 3 becomes larger than the increment value of the open loop control period as shown in the period of time Tb to Tc in FIG. It becomes possible to do.

  FIG. 6 shows the overall situation of the vapor deposition process by the open loop control, composite control and feedback control. FIG. 6 shows the relationship between the electron gun power P (EB output in the figure) during the vapor deposition process, the film thickness equivalent value (light quantity value) of the thin film formed on the lens 2a, and time.

  At time ta, the electron gun 3 is activated with the initial power P0, and the vapor deposition process is started by open loop control (initial rate control). In the open loop control, the electron gun power P is increased by an adjustment value ΔP every predetermined period (for example, 5 seconds) while monitoring the light amount value of the optical film thickness meter 10. In the open loop control period, the electron gun power P increases substantially monotonically and gradually heats the vapor deposition material 4a. In the entire open loop control period, the electron gun power P is increased by α per unit time. In the illustrated vapor deposition raw material 4a, vaporization of the vapor deposition raw material 4a is very small during the open loop control period, and the light amount value of the optical film thickness meter 10 is slightly increased. For this reason, feedback control is started in addition to open loop control from time Tb when the initial idle time Ti has elapsed before the light quantity value reaches the feedback control start value L1. At time Tc, since the light quantity value of the optical film thickness meter 10 exceeds the feedback control start value L1, the open loop control is terminated and the process proceeds to feedback control. At the time Tc, the thickness of the vapor deposition material 4a is increased, the ratio of the change in the amount of reflected light with respect to the film thickness is increased, and the optical film thickness meter 10 can reliably capture the change in the light amount value of the monitor glass 2b. It becomes possible. In the feedback control period, feedback control of the electron gun power P is performed based on the light amount value of the optical film thickness meter 10 as in the above-described conventional example.

  As described above, in the initial stage of the vapor deposition process, after starting the electron gun 3 with the initial power P0 at which the vapor deposition raw material 4a is not clearly vaporized, the electron gun power P is gradually increased by open loop control. While preventing the vaporization of the raw material 4a from being excessive, it is possible to prevent the vapor deposition processing time from being prolonged.

  The present invention can absorb not only the individual differences of the vapor deposition raw material 4 a but also the change in the characteristics of the vapor deposition process due to the maintenance of the vacuum chamber 1.

  For example, when the maintenance of the electron gun 3 is performed, the actual output of the electron gun 3 with respect to the electron gun power P may fluctuate, and vaporization of the deposition material 4a may start at a value lower than the predicted vaporization power. On the contrary, even if the predicted vaporization power is given to the electron gun 3 after maintenance, vaporization of the vapor deposition raw material 4a may not be started.

  Thus, even when the flight state of the electron beam in the electron gun 3 and the relationship between the efficiency and the output fluctuate due to the maintenance, by applying the present invention, even when the vaporization of the vapor deposition material 4a is started at the initial power P0, When the light quantity value of the optical film thickness meter 10 reaches the feedback control start value Li, the control shifts to feedback control, and it is possible to suppress the film formation rate and prevent the thin film formed on the lens 2a from absorbing. Alternatively, when the actual output decreases with respect to the command value to the electron gun 3, when the initial idle time Ti elapses, the command value to the electron gun 3 is increased during the composite control period to increase the optical film thickness meter 10. Can be increased to the feedback control start value Li, and the vapor deposition processing time can be prevented from becoming excessive.

  In addition, after performing maintenance of the electron gun 3, it is desirable to correct the vaporization power and the initial power P0 of the open loop control map 130 by confirming the preliminary operation.

<Vapor deposition raw material>
When the deposition material is deposited on the lens 2a to form an antireflection film or the like, if the deposition rate (thin film formation rate) is high, the surface of the lens 2a is caused by insufficient oxidation of the vaporized or sublimated deposition material. Absorption tends to occur in the thin film formed. By applying the above-described present invention to the vapor deposition raw material 4a having such a tendency, it is possible to improve the productivity by preventing the vapor deposition processing time from being prolonged while preventing the occurrence of absorption. .

As described above, the following sublimation vapor deposition raw materials are examples of the vapor deposition raw materials that are likely to be absorbed in the thin film formed on the lens 2a due to the high film formation rate.
-A silicon oxide, the mixture of a silicon oxide, a metal, and / or a metal compound, and a chemical bond are mentioned. Among these, silicon oxides such as SiO ₂ may be crystalline or amorphous.
-As a metal compound, a metal oxide, a metal fluoride, and a metal nitride are mentioned.
-As metal oxides, magnesium oxide, calcium oxide, barium oxide, aluminum oxide, titanium oxide, zirconia oxide, sodium oxide, potassium oxide, tin oxide and co-oxidation of tin with other elements And oxides of indium oxide and indium and other elements, magnesium oxide-silicon dioxide cooxide, aluminum oxide-silicon dioxide cooxide (mullite), and the like.
Examples of the metal fluoride include alkaline earth metal fluorides such as magnesium fluoride, calcium fluoride, and barium fluoride, and alkali metal fluorides such as sodium fluoride and potassium fluoride.
-As a metal nitride, aluminum nitride, titanium nitride, silicon nitride, chromium nitride, etc. are mentioned.

  Among the above-mentioned compounds, the sublimation vapor deposition raw material applied to the vapor deposition film imparting optical properties includes silicon oxide, aluminum oxide, zirconium oxide, titanium oxide, titanium nitride, indium oxide, A tin oxide etc. are mentioned.

  Among the above sublimable materials, a deposition material that can be melted once and evaporated (vaporized) depending on the degree of vacuum (atmospheric pressure) and temperature in the deposition chamber 1 and the temperature conditions of the evaporation sources (deposition materials 4a and 4b). There is also. For example, silicon oxide, aluminum oxide, and zirconia oxide can be vapor-deposited after being once melted in an evaporation source depending on setting conditions.

  On the other hand, when producing a thin film having a multilayer structure in which a plurality of deposition raw materials 4a and 4b are alternately deposited, it is difficult to deposit all materials under melting and evaporation conditions. For example, when silicon oxide is melted and the conditions are set, it is difficult to set titanium nitride or the indium-tin composite oxide (ITO) of the present embodiment as melting and evaporating conditions similar to silicon oxide. It is.

  In the sublimation deposition material, the speed of sublimation (deposition) greatly affects the state of the material. Sublimation vapor deposition raw materials are often handled as powders (including tablets in which powders are hardened) that can secure a surface area in order to widen the flying points. On the other hand, it is difficult to keep the surface area uniform due to the diameter, shape, etc. of the particles constituting the powder. As a result, as described above, an event occurs in which the film formation rate during vapor deposition changes every time.

  In the present invention, the film forming speed can be controlled to a desired condition even if it uses the sublimation phenomenon from the powder (it is difficult to keep the film forming speed constant even if vapor deposition is performed under the same conditions).

  Further, regarding the relationship between the change in the light quantity value of the optical film thickness meter 10 and the vapor deposition raw material 4a, the index of the thin film formed is larger than the index (refractive index) of the monitor glass 2b measured by the optical film thickness meter 10. It is preferable to apply the present invention to a higher deposition raw material.

  That is, in the vapor deposition material for forming a thin film having an index higher than that of the monitor glass 2b, the light amount value increases with the progress of film formation (increase in film thickness) from the start of vapor deposition. At this time, if absorption occurs in the thin film formed on the monitor glass 2b, the light quantity value observed by the optical film thickness meter 10 decreases. The light quantity value of the optical film thickness meter 10 is a value obtained by adding the decrease in the light quantity value due to the occurrence of absorption to the increase in the light quantity value due to the increase in the film thickness.

  For this reason, when forming a thin film having a higher index than that of the monitor glass 2b, vaporization of the vapor deposition raw material 4a is started if the increment of the light quantity value of the optical film thickness meter 10 is small or the light quantity value does not increase. It can not be easily determined whether there is little increase in the light amount value due to absorption.

  Therefore, when performing the vapor deposition process with the vapor deposition raw material 4a that forms a thin film having a higher index than the monitor glass 2b, by applying the present invention, the electron gun power P can be controlled by the open loop control from the initial power P0 that is not clearly vaporized. Is gradually increased, and the feedback control is started when the light quantity value exceeds the feedback control start value L1 or the initial idle time Ti elapses, thereby preventing absorption in the formed thin film. Thus, the vapor deposition process can be performed accurately.

  On the other hand, in the vapor deposition process using the vapor deposition raw material that forms a thin film having a lower index than that of the monitor glass 2b, the light amount value decreases with the progress of film formation (increase in film thickness) from the start of vapor deposition. When absorption occurs in the formed thin film, the amount of light observed by the optical film thickness meter 10 decreases. Therefore, if the amount of decrease is excessive, it can be detected that absorption has occurred. The processing can be performed by the feedback control.

  In the above description, the determination of the end condition of the vapor deposition process in step S24 is, for example, an example in which the elapsed time from the start of the vapor deposition process is a predetermined time (for example, 12 minutes), but the open loop shown in FIG. You may set time until a vapor deposition process is complete | finished for every vapor deposition raw material to the control map 130. FIG.

  Moreover, although the example which performs a vapor deposition process in one vacuum chamber 1 was shown in the said embodiment, you may apply this invention to a continuous-type vacuum vapor deposition apparatus.

  As described above, according to the present invention, since it becomes possible to accurately control the electron gun in the initial stage of film formation in accordance with the characteristics of the vapor deposition material, lenses for spectacles and the like having excellent quality and productivity. It can be applied to the manufacturing system.

1 shows an embodiment of the present invention and is a schematic view of a mold vacuum deposition apparatus. Explanatory drawing which shows an example of an open loop control map. The flowchart which shows the flow of control in a vapor deposition process. It is a graph which shows the relationship between the light quantity value (film thickness equivalent value), electron gun power P, and time in the case of shifting from open loop control to feedback control due to the light quantity value exceeding the feedback control start value L1. It is a graph which shows the relationship between the light quantity value (film thickness equivalent value), electron gun power P, and time in the case of shifting from the open loop control to the feedback control through the composite control due to exceeding the initial idle time Ti. Similarly, it is a graph showing the relationship between the light amount value (film thickness equivalent value), the electron gun power P, and the time when shifting from the open loop control to the feedback control due to exceeding the initial idle time Ti.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2a Lens 2b Monitor glass 3 Electron gun 4a, 4b Deposition raw material 12 Controller 14 Ion gun

Claims (12)

A method of forming a lens, wherein a film is formed by vaporizing and evaporating a deposition material on the surface of a lens held in a deposition chamber of a deposition apparatus,
The vapor deposition apparatus includes:
A heating unit disposed in the vapor deposition chamber for heating the vapor deposition material;
An optical film thickness measurement unit capable of predicting the film thickness from the amount of reflected light of the film formed on the lens;
A control unit for controlling the output of the heating unit,
The control unit commands the heating unit a preset initial output according to the type of the vapor deposition material, and starts the heating unit;
The control unit acquires a light amount value of the optical film thickness measurement unit at a preset period;
Commanding the control unit to gradually increase the output of the heating unit by open loop control;
Determining whether or not the control unit satisfies a preset condition, and controlling the output of the heating unit by feedback control based on the light amount value when the condition is satisfied,
The predetermined condition includes that a predetermined time has elapsed since starting the heating unit,
The method for forming a lens according to claim 1, wherein the initial output is a predetermined value smaller than an output for reliably vaporizing the vapor deposition material. The step of instructing the control unit to gradually increase the output of the heating unit by open loop control,
2. The lens film formation according to claim 1, wherein a value obtained by adding an increment value set in advance for each vapor deposition material to the initial output is used as a command value to the heating unit every time the period is reached. Method. The step of determining whether or not the control unit satisfies a preset condition and controlling the output of the heating unit by feedback control based on the light amount value when the condition is satisfied,
When the time elapsed since starting the heating unit has passed a predetermined time, the feedback control is started,
2. The lens film forming method according to claim 1, wherein when the acquired light amount value exceeds a preset threshold value, the open loop control is terminated and the process proceeds to the feedback control. The step of determining whether or not the control unit satisfies a preset condition and controlling the output of the heating unit by feedback control based on the light amount value when the condition is satisfied,
When a predetermined time has elapsed after starting the heating unit, if the light amount value is less than or equal to the threshold value, a value obtained by adding the output by the open loop control and the output by the feedback control is commanded to the heating unit. The method for forming a lens according to claim 3. The optical film thickness measuring unit is
Having a monitor glass to which the vapor deposition material evaporated or sublimated by heating by the heating unit adheres, and measuring the film thickness of the film formed on the monitor glass,
The deposition material is
The method of forming a lens according to claim 1, wherein a refractive index of a film formed on the monitor glass by vaporization or sublimation by heating by the heating unit is larger than a refractive index of the monitor glass. .   The lens deposition method according to claim 5, wherein the vapor deposition material includes an indium-tin composite oxide. A vapor deposition apparatus for generating a film by vaporizing or sublimating a vapor deposition raw material on the surface of a lens held in a vapor deposition chamber,
A heating unit for heating the vapor deposition material;
An optical film thickness measurement unit capable of predicting the film thickness from the amount of reflected light of the film formed on the lens;
A control unit for controlling the output of the heating unit,
The controller is
A film thickness equivalent value measuring unit that acquires a light amount value of the optical film thickness measuring unit at a preset period;
An open loop control unit that commands to gradually increase the output of the heating unit by open loop control;
A feedback control unit for setting the output of the heating unit by feedback control based on the light amount value;
It is determined whether or not a preset condition is satisfied, and when the condition is satisfied, the output of the heating unit is controlled by the feedback control, and when the condition is not satisfied, a switching control unit that continues the open loop control; With
The predetermined condition includes that a predetermined time has elapsed since starting the heating unit,
The initial output is a predetermined value smaller than an output that the vapor deposition material is surely vaporized. The open loop control unit
The vapor deposition apparatus according to claim 7, wherein a value obtained by adding an increment value set in advance for each vapor deposition raw material to the initial output is used as a command value to the heating unit every time the period is reached. The switching control unit
When the time elapsed since starting the heating unit has passed a predetermined time, the feedback control is started,
8. The vapor deposition apparatus according to claim 7, wherein when the acquired light amount value exceeds a preset threshold value, open loop control is terminated and the control shifts to the feedback control. The switching control unit
When the predetermined amount of time has elapsed after starting the heating unit, if the light quantity value is less than or equal to the threshold value, a command is given to the heating unit for the sum of the output from the open loop control and the output from the feedback control. The vapor deposition apparatus according to claim 9. The optical film thickness measuring unit is
Having a monitor glass to which the vapor deposition material evaporated or sublimated by heating by the heating unit adheres, and measuring the film thickness of the film formed on the monitor glass,
The deposition material is
The vapor deposition apparatus according to claim 7, wherein a refractive index of a film formed on the monitor glass by vaporization or sublimation by heating by the heating unit is larger than a refractive index of the monitor glass.   The vapor deposition apparatus according to claim 11, wherein the vapor deposition material includes an indium-tin composite oxide.

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