JPH0359436B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an image forming method in an electrostatic recording device such as an electrophotographic copying machine, and in particular, the present invention relates to an image forming method in an electrostatic recording device such as an electrophotographic copying machine, and in particular, the surface of an image forming member is charged with a background potential. The charged surface is neutralized or charged with the opposite polarity by means such as light irradiation or an electrostatic recording head, and the electrostatic latent image thus formed is applied to the developing sleeve with an alternating current voltage and the same polarity as the background potential. Applying a bias voltage with a DC voltage superimposed thereon, the toner charged to the same polarity as the background potential is ejected from the developer layer on the developing sleeve in a developing area where the developing sleeve and the surface of the image forming body are close to each other. The present invention relates to an image forming method in which development is performed.

[Prior art]

As a typical image forming method as described above, an image forming body having a photoconductor layer on the surface is used,
A laser beam scanner performs spot exposure on the uniformly charged surface of the image forming body to form an electrostatic latent image consisting of low potential dots, and toner charged to the same polarity as the image forming body is deposited on the low potential dots. One example is a method of attaching. This method is compared to an image forming method in which toner charged with the opposite polarity is caused to fly from the developer layer of the developing sleeve and adhere to an electrostatic latent image whose image portion potential is higher than the background potential. In order to cause the toner to adhere to the image forming body against the electrical repulsion from the charging of the image forming body and to prevent fogging, the DC component of the bias voltage applied to the developing sleeve is set close to the background potential; It is also required to increase the amplitude of the alternating current component. Therefore, if the bias voltage during development is applied while the uncharged surface of the image forming body passes through the development area, toner will be unnecessarily attached to the surface of the image forming body, and excess toner will be added to the surface of the image forming body. This may waste energy, increase the burden on the cleaning device, and furthermore, cause toner and the like to scatter, increasing the amount of dirt.

On the other hand, in an image forming method in which toner charged with opposite polarity is attached to an electrostatic latent image whose image partial potential is higher, the electrostatic latent image on the image forming body is The bias voltage is stopped from being applied to the developing sleeve while the surface on which it is not formed passes through the developing area.
It is known from USP3893418 and Japanese Patent Application Laid-Open No. 14266/1983.

However, if this method is adopted as an image forming method in which toner charged to the same polarity as that of the image forming body is attached to the electrostatic latent image, even if toner scattering etc. can be prevented, the electrostatic latent image will not be fully formed. It happens that the image is not developed. Even if a bias voltage is suddenly applied to the developing sleeve when the electrostatic latent image on the image forming body reaches the developing area, it takes time for the bias power supply to stabilize, and the developer on the developing sleeve immediately This is thought to occur because the toner is not transferred from the layer to the image forming body. By applying the same bias voltage during development to the developing sleeve before the electrostatic latent image reaches the developing area, toner will adhere to the image forming element even while the uncharged surface of the image forming element passes through the developing area. This may cause unnecessary toner consumption, increase the load on the cleaning device, or cause toner etc. to scatter, increasing the occurrence of stains.

[Purpose of the invention]

The present invention has been made in order to solve the above-mentioned problems in an image forming method in which toner charged to the same polarity as that of an image forming member is attached to an electrostatic latent image. By applying an appropriate oscillating voltage to the developing sleeve while the non-image-charged surface passes through the developing area, the electrostatic latent image is sufficiently developed without causing toner scattering, etc. This was done by discovering the following.

That is, the present invention provides a method for applying toner charged to the same polarity as that of the image forming member onto the developing sleeve so that the electrostatic latent image can be developed without any trouble and the toner will not be scattered or the burden on the cleaning device will be increased. The object of the present invention is to provide an image forming method in which a developer is caused to fly from a developer layer and adhere to an electrostatic latent image.

[Structure of the invention]

The present invention applies a bias voltage in which an AC voltage and a DC voltage having the same polarity as the background potential of an electrostatic latent image are superimposed to the developing sleeve, so that the developer layer on the developing sleeve has the same polarity as the background potential. In an image forming method in which an electrostatic latent image is developed by flying charged toner, the maximum voltage applied to the developing sleeve is An image forming method characterized in that an oscillating voltage lower than the maximum voltage of the bias voltage is applied, and then the oscillating voltage is changed to the bias voltage, and with this configuration, the above object is achieved. It is something.

〔Example〕

The present invention will be explained below using illustrated examples.

FIG. 1 is a schematic configuration diagram showing an example of a recording apparatus that implements the method of the present invention, FIG. 2 is a partial diagram showing an example of a developing device, and FIGS. 3 to 6 each show the voltage applied to the developing sleeve. Graphs illustrating examples, FIGS. 7 and 8 are circuit diagrams illustrating configuration examples of bias power supplies that apply the voltages shown in FIGS. 3 to 5 and 6, respectively.

The recording device shown in FIG. 1 uses a signal processing device 1 to process image data I obtained from a signal input from a document image sensor, other equipment, data in a data storage unit, etc. )
An image signal composed of converted pixel data is obtained, and a laser beam scanner 2 consisting of a laser, an acousto-optic modulator, a lens device, a rotating polygon mirror, etc. is turned on for each pixel using the pixel data of this binary image.
OFF control, the surface of the photoconductor layer of the image forming body 3, which rotates in the direction of the arrow and is uniformly charged by the charger 4, is image exposed by a laser spot, and the details of the spot exposed portion are shown in Figure 2. A toner image is formed by depositing toner charged to the same polarity as that of the image forming member 3 under an electric field using a developing device 5 as shown in FIG. Then, the formed toner image is transferred to the image forming body 3 in synchronization with the rotation of the image forming body 3.
Recording paper P is fed so as to be in contact with the surface of
The recording paper P on which the toner image has been transferred is separated from the surface of the image forming body 3 by the separator 7, and then the toner image is fixed by the roller fixing device 8. is ejected from the recording device. On the other hand, the surface of the image forming body 3 to which the toner image has been transferred is neutralized by a static eliminator 9, and then residual toner is removed by a cleaning device 10 to complete one image forming process.

In the developing device 5 shown in FIG. 2, a bias voltage is applied by a bias power supply 11 to a developing sleeve 51 made of a non-magnetic material such as aluminum or stainless steel, and an image forming member 3 whose base portion is grounded
An electric field is generated in the development area A between the two. Inside this developing sleeve 51, there are a plurality of N and S on the surface.
A magnet body 52 having magnetic poles is provided. Then, as the developing sleeve 51 stands still or rotates counterclockwise and the magnet body 52 rotates clockwise or stands still, the developer attracted from the developer reservoir 53 to the surface of the developing sleeve 51 by the magnetic force of the magnet body 52 is transferred to the surface of the developing sleeve 51. One or both rotations result in counterclockwise movement. The developer transported in this manner is directed to the image forming body 3 by the layer thickness regulating blade 54.
The toner is regulated to a layer thickness within a range that does not contact the surface of the image forming member 3, and in the development area A, toner flies from the developer layer due to the action of an electric field and develops the electrostatic latent image on the image forming member 3.
Note that it is preferable that the magnet body 52 rotates in that the influence of unevenness of the developer layer is less likely to appear in the development.

The remaining developer layer that has passed through the developing area A is removed from the surface of the developing sleeve 51 by the cleaning blade 55 and returned to the developer reservoir 53. The developer in the developer reservoir 53 is a so-called two-component developer containing a mixture of toner and carrier, and is stirred by the stirring blade 56 so that the toner is charged to the same polarity as that of the image forming member 1. Since the toner is consumed during development, it is replenished from the toner hopper 57 to the developer reservoir 53 by the toner replenishment roller 58.

In order to develop an electrostatic latent image by causing toner charged to the same polarity as that of the image forming member 3 to fly from the developer layer on the developing sleeve 51 in the developing area A, the developing sleeve 51 is provided with the toner of the image forming member 3. A bias voltage in which a DC voltage and an AC voltage having the same polarity as the background potential are superimposed is applied. The bias power supply 11 applies voltages including this bias voltage to the developing sleeve 51 as shown in FIGS. 3 to 6, thereby causing toner scattering and increasing the burden on the cleaning device 10. To ensure that an electrostatic latent image is sufficiently developed without causing any problems.

In FIGS. 3 to 6, T ₀ is the time period during which the uncharged surface of the image forming body 3 passes through the development area A before being charged by the charger 4, and T _v is the time period during which the charger 4 is not charged. T _i is the electrostatic latent image forming surface of the image forming member 3 on which image exposure has occurred, during which the non-image charged surface of the image forming member 3 passes through the developer A. T _v ′ is the time period during which the non-image-charged surface of the image forming body following the electrostatic latent image forming surface passes through the development region A,
T ₀ ' indicates the time period during which the uncharged surface of the image forming body, which has been charged by the charger 4, passes through the development area A. In this case, the time period T ₀ ' becomes the time period T ₀ of the next image recording.

In the example shown in FIG. 3, a DC voltage having a polarity opposite to that of toner charging is applied to the developing sleeve 51 during a time period _T0 that starts with the start of rotation of the image forming body 3.
At T _v , the DC voltage is changed to a DC voltage with a bias voltage during development that is somewhat lower than the charging potential of the image forming member 3, and at the same time, the amplitude of the DC voltage changes from 0 to the amplitude of the AC voltage of the bias voltage during development. A gradually changing alternating current voltage is superimposed on the developing bias voltage to reach the developing bias voltage, and this bias voltage is maintained during time period T _i , and when entering time period T _v ′, the amplitude of the alternating current voltage is first attenuated to 0, Next, the DC voltage is changed to the DC voltage of the first reverse polarity, and the DC voltage is
It is designed to maintain up to T ₀ ′. In this way, when the surface of the image forming body 3 passing through the development area A is not charged, a voltage with the opposite polarity to the toner charge is applied to the developing sleeve 51, so that the surface of the image forming body 3 is not charged with the toner charge. When the developing sleeve 51 is charged to the same polarity, the voltage of the developing sleeve 51 is increased to the DC voltage of the bias voltage during development, and the amplitude gradually increases from 0 until the electrostatic latent image reaches the development area A. By superimposing the alternating current voltage which becomes the alternating voltage of the bias voltage, toner and the like are unnecessarily attached to the image forming body 3 and the cleaning device 10
This prevents an increase in the burden on the developer and an increase in the scattering of toner, etc., reducing the consumption of toner, etc., and also ensures that the developer layer on the developing sleeve 51 is completely formed when the electrostatic latent image reaches the development area A. Since the electrostatic latent image is ready to be developed, an excellent effect of sufficient development can be obtained.

Note that the rotation of the developer layer conveyance of the developing sleeve 51 and the magnet body 52 may be started at any time of the time period T ₀ or T _v , but it is necessary to prevent the scattering of toner, etc.
In order to perform the development evenly, it is most preferable to start before the alternating current voltage of the bias voltage is superimposed on the direct current voltage applied to the developing sleeve 51 during the time period T _v . Further, the rotation of the developer transport may be stopped at any time after the time period T _v ′, but it is performed after the alternating current component that should cause the toner to fly toward the image forming body in the time period T _v ′ has decreased. It is preferable.
This also applies to the following examples.

In the example of FIG. 4, in the time period T ₀ , a DC voltage is applied to the developing sleeve 51 in the same way as in the example of _FIG . An AC voltage that gradually increases up to the AC voltage amplitude of the bias voltage during development is superimposed, and when the amplitude has finished increasing, the DC voltage is changed to the DC voltage of the bias voltage during development, and the resulting bias voltage is is maintained during time period T _i , and when time period T _v is entered, the DC voltage is first changed to the initial DC voltage, contrary to time period T _v , and then the amplitude of the AC voltage is attenuated to 0. return to the initial state,
This state is maintained until the time period T ₀ '. In this example as well, the same effects as in the example of FIG. 3 can be obtained.

In the example shown in FIG. 5, an AC voltage whose amplitude gradually increases from 0 is superimposed during a time period T ₀ ,
This example differs from the example shown in FIG. 4 in that the amplitude of the superimposed AC voltage after development is attenuated to zero after entering the time period T ₀ '. In the example shown in FIG. 5, the same effect as in the example shown in FIG. 4 or 3 can be obtained.

In all the examples shown in FIGS. 3 to 5 described above, _the developing sleeve ₅ is
1, a DC voltage with a polarity opposite to that of the toner charging is applied, but even if this voltage is set to 0, the toner etc. will not scatter and the load on the cleaning device 10 will not increase significantly.

In the example shown in FIG. 6, no voltage is applied to the developing sleeve 51 during the time period _T0 , and when the time period _Tv begins, the toner charge obtained by rectifying the bias voltage during development is applied to the developing sleeve 51. A pulsed voltage of opposite polarity is applied, then the voltage is changed to the bias voltage during development, the bias voltage is maintained during the time period T _i , and the bias voltage is changed to the pulsed voltage again during the time period T _v ′. Then, the application of the pulsed voltage is also stopped to enter the time period T ₀ '. In this example as well, the same effects as in the examples shown in FIGS. 3 to 5 can be obtained.

The application of voltages as shown in FIGS. 3 to 5 is performed by a bias power supply 11 as shown in FIG. 7, and the application of voltages as shown in FIG. This is done by the power supply 11.

That is, in the bias power supply 11 of FIG. 7, when the switch 12 is released from the state shown, a DC voltage of the opposite polarity to that of the toner is applied to the developing sleeve 51, and the voltage dividing contact 13 of the voltage divider is connected from top to bottom. By moving the DC voltage to the DC voltage of the bias voltage during development, move the short-circuit contact 14 of the secondary coil from the bottom to the top while the oscillation circuit is being driven. As a result, an AC voltage whose amplitude changes from 0 to the AC voltage amplitude of the bias voltage during development is superimposed, and the shorting contact 14 and the voltage dividing contact 13 are returned to their original positions in the reverse order of the above. As a result, the voltage application shown in FIG. 3 is performed.

Also, after opening the switch 12, while driving the oscillation circuit, first move the shorting contact 14 from bottom to top, then move the dividing contact 13 from top to bottom, and then after the development is completed, The voltage application in FIGS. 4 and 5 is performed by returning the voltage dividing contact 13 and the shorting contact 14 to their original positions in the reverse order.

In the above, the oscillation circuit is driven by the short-circuit contact 1
You can start at any time before moving 4. Further, the shorting contact 14 may be omitted by changing the amplitude of the AC voltage on the oscillation circuit side. Further, when the applied voltage is set to 0 during the time periods T ₀ and T ₀ ', the upper half of the DC voltage circuit becomes unnecessary, and the switch 12 can also be omitted. Furthermore, if the DC voltage is to be changed in steps without being gradually increased or decreased, the connection between the secondary coil and the DC power source and the ground connection may be made as shown in FIG.

In the bias power supply 11 of FIG. 8, when the oscillation circuit is driven in the state shown and the changeover switch 15 is switched from the a contact to the b contact, a rectified pulse voltage is output to the developing sleeve 51.
Next, when the switch 16 of the rectifier circuit is turned off, the bias voltage during development is outputted, and after the development is completed, the voltage shown in Figure 6 is changed by turning on the switch 16 and switching the changeover switch 15 to the a contact applied.

It is of course preferable that the application of the voltages shown in FIGS. 3 to 6 by the bias power supply 11 be repeated every day for image formation, but it is preferable that the application of the voltages as shown in FIGS. In the case where image formation is performed, the period during which intermediate image formation is performed may be included in the time period T _i . Even in this case, the same effect as described above can be obtained at least for the initial image formation.

The alternating current voltage component and direct current voltage component of the bias voltage during development are determined so that a clear and fog-free toner image can be obtained. ^In order to easily determine such a bias voltage, it is necessary that the two-component developer in the developer reservoir ⁵³ described with reference to FIG. Preferably, magnetic carrier particles are used. As such carrier particles, carrier particles having a resin coating formed on the surface of magnetic particles or carrier particles made of resin particles containing magnetic particles dispersed therein are used. The resistivity of the insulating particles is determined by placing the particles in a container with a cross-sectional area of 0.5 cm ² and tapping them to a thickness of about 1 mm, then applying a load of 1 kg/cm ² on the packed particles. This value is obtained by reading the current value when applying a voltage that generates an electric field of 1000 V/cm between the electrode and the bottom electrode. In addition, in order for development to be carried out clearly and with good resolution, it is preferable that the average particle size of the toner particles in the two-component developer is 20 μm or less, particularly 1 to 10 μm, and the average particle size of the carrier particles is also 5 to 50 μm. It is preferable that there be. The average particle size of these particles is a weight average particle size, and is measured with a Coulter Counter (manufactured by Coulter) or Omnicon Alpha (manufactured by Boshilom). If the average particle size of the toner particles becomes too small, the amount of charge due to friction of a single toner particle becomes small, and the van der Waals force becomes relatively large, making it easier to aggregate and making it difficult to separate and fly. On the other hand, if the average particle size becomes too large, the amount of charge relative to the weight decreases, making it difficult to control flight and reducing resolution. Furthermore, if the average particle size of the carrier particles becomes too small, the force of attraction by the magnetic force of the magnet body 52 becomes weak, but the electrical Coulomb force and Van der Waals force become strong, which causes the carrier particles to become too small. The particles tend to migrate to the surface of the image forming body 3 together with the toner particles, and on the other hand, if the average particle size becomes too large, the developer layer formed on the developing sleeve 51 becomes coarse, making it difficult to make the developer layer thinner. It becomes difficult to form the toner particles uniformly, and the state of adhesion of the toner particles in the developer layer is also uneven, making breakdown and discharge of the voltage applied to the developing sleeve 51 more likely to occur.As a result, toner particle migration and flight control becomes difficult. It becomes difficult.

Furthermore, in order to effectively control toner flight by applying a bias voltage to the developing sleeve 51, it is necessary to increase the gap between the image forming body 3 and the developing sleeve 51 by several times.
It is preferable that the thickness of the developer layer is in the range of 10 to 2000 μm, and therefore the thickness of the developer layer regulated by the layer thickness regulating blade 54 is smaller than that. If the gap in this development zone is made too narrow, the thickness of the developer layer must be made very thin, which makes it impossible to obtain a uniform layer thickness and therefore provides a stable supply of toner particles to the development zone. Not only is this impossible, but also electric discharge is likely to occur between the developing sleeve 51 and the developing body 3, damaging the developer and causing toner particles to scatter. On the other hand, if the gap between the developing areas is made too wide, it becomes difficult to control the flying of toner using the oscillating electric field.

When image formation is performed using the recording apparatus shown in FIGS. 1 and 2 under the above preferable conditions and applying voltages as shown in FIGS. 3 to 6 to the developing sleeve 51, It is possible to reduce the scattering of developer and the burden on the cleaning device 10, and to obtain clear recorded images without fogging.

Next, more specific embodiments of the present invention will be described.

Example 1 The apparatus shown in FIGS. 1 and 2 was used.

The image forming body 3 has a selenium photoreceptor layer on its surface, rotates in the direction of the arrow at a surface speed of 120 mm/sec, and is charged to 500 V by a charger 4. The laser beam scanner 2 forms an electrostatic latent image in the form of 50V dots. The gap between the image forming body 3 and the developing sleeve 51 in the developing area A is 700 μm, the outer diameter of the developing sleeve 51 is 30 mm, and the rotation speed in the left direction is 65 rpm. It is placed in the gap and rotates at 700 rpm in the direction of the arrow. The developer in the developer reservoir 53 is made of an insulating carrier with a resistivity of 10 ¹⁶ Ωmm, which is made by dispersing magnetic powder in a resin with a weight average particle size of about 30 μm, and a positive carrier with a weight average particle size of 14 μm.
A two-component developer mixed with an insulating non-magnetic toner charged to about 20 μC/g is used, and the layer thickness of the developer layer formed on the developing sleeve 51 is regulated to about 500 μm by a layer thickness regulating blade 54.

The bias power supply 11 is connected to the fifth developing sleeve 51.
The voltage was applied as shown in the figure. That is, the bias power supply 11 applies a DC voltage of -150V to the developing sleeve 51 at the same time as the image forming body 3 rotates, and superimposes an AC voltage within the time period _T0 to finally generate an AC voltage of 2kHz, 1kV. The DC voltage component is changed to -150V superimposed voltage, and at the same time as the developing sleeve 51 and the magnet body 52 start rotating as the time period T _v begins, the DC voltage component is changed to _40V. maintains and applies a completely superimposed voltage of 2kHz, 1kV AC voltage and 400V DC voltage, returns the DC voltage component to -150V one second after entering the time period T _v ', and at the same time, the developing sleeve 51 and the rotation of the magnet body 52 is stopped, and
The amplitude of the AC voltage component was attenuated to 0 in time period T ₀ .

Image formation was performed under the above conditions, and the developed toner image was transferred to recording paper P made of plain paper and fixed by roller fixing device 8 with a surface temperature of 140°C.

The recorded image thus obtained was extremely clear with high density and no fog. After recording images on 50,000 sheets of recording paper, we were able to obtain a stable and unchanging recorded image from beginning to end, and no toner was scattered from the gap between the developing device 5 and the image forming body 3. Therefore, the amount of toner collected by the cleaning device 10 was also small.

On the other hand, if the bias voltage is applied to the developing sleeve 51 for the first time immediately before the electrostatic latent image forming surface of the image forming member 3 reaches the developing area A, the leading edge of the recorded image becomes pale, and the image Formation 3
If a complete bias voltage is applied to the developing sleeve 51 before the non-image-charged surface of the developing sleeve 51 reaches the developing area A, not only will the amount of toner collected by the cleaning device 10 significantly increase, but the developing device 5, the amount of toner scattering increased, and the maximum number of sheets of recording paper that could be obtained was 10,000.

Note that the AC component of the bias voltage applied to the developing sleeve 51 during development has a frequency of 100 to 10,000.
Hz, preferably 1000~5000Hz, effective amplitude 200~
At 5000V, there is an effective value of 300~ between the image forming body 3 and
A type that produces an electric field strength of 5000 V/mm is preferably used, and the waveform is not limited to a sine wave, but may be a rectangular wave or a triangular wave. In addition, it is preferable to use a two-component developer as the developer.
A one-component developer known from USP 3893418 and Japanese Patent Application Laid-Open No. 18656/1984 may be used.

〔Effect of the invention〕

According to the image forming method of the present invention, a clear toner image without fogging can be formed using toner charged to the same polarity as that of the image forming member, without scattering the toner or wasting the toner.

The present invention is applicable not only to recording devices that use laser beam scanners but also to recording devices that use multi-needle electrodes and the like. Further, the present invention can also be applied to an image forming method using an image forming body having an insulating layer on a photosensitive layer. Further, the present invention provides a color image recording device having a plurality of developing devices and a color image recording device that superimposes toner images on an image forming body (Japanese Patent Application Nos. 58-184381, 58-183152, and 58-187000). )
It can also be applied to

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a recording apparatus that implements the method of the present invention, FIG. 2 is a partial diagram showing an example of a developing device, and FIGS. 3 to 6 each show the voltage applied to the developing sleeve. Graphs illustrating examples, FIGS. 7 and 8 are circuit diagrams illustrating configuration examples of bias power supplies that apply the voltages shown in FIGS. 3 to 5 and 6, respectively. 2... Laser beam scanner, 3... Image forming body, 4... Charger, 5... Developing device, 51... Developing sleeve, 52... Magnet, 53... Developer reservoir, 54... Layer Thickness regulation blade, A...Development area,
11... Bias power supply, T ₀ , T ₀ '... Time period for the non-charged surface of the image forming member to pass through the developing zone, T _v , T _v '... Time period for the non-image charged surface of the image forming member to pass through the developing zone, T _i ... Time period during which the electrostatic latent image forming surface of the image forming member passes through the development zone.

Claims (1)

[Claims] 1. A bias voltage in which an AC voltage and a DC voltage of the same polarity as the background potential of the electrostatic latent image are superimposed is applied to the developing sleeve to remove the background potential from the developer layer on the developing sleeve. In an image forming method in which an electrostatic latent image is developed by flying toner charged with the same polarity, a maximum voltage is applied to the developing sleeve while the non-image charged surface of the image forming body preceding the electrostatic latent image passes through a development area. An oscillating voltage lower than the maximum voltage of the bias voltage is applied, and then the oscillating voltage is changed to the bias voltage. 2. The image forming method according to claim 1, wherein the oscillating voltage is a voltage having an alternating current component with a smaller amplitude than the alternating current voltage. 3. The image forming method according to claim 1, wherein the oscillating voltage is a voltage obtained by superimposing the alternating current voltage and a direct current voltage of opposite polarity to the background potential. 4. The image forming method according to claim 1, wherein the oscillating voltage is a pulsed voltage having a polarity opposite to that of the background potential obtained by rectifying the bias voltage. 5. The image forming method according to claim 1, wherein the transport drive of the developer layer on the developing sleeve is started while the non-image charged surface of the image forming body passes through a developing area.