JPH01210959A - Heat developing device - Google Patents

Abstract

PURPOSE:To maintain the specified moisture content of a photosensitive material and to stably form an image without being affected by environment and resting time by coating an image forming solvent on the photosensitive material, then subjecting the material to heating development. CONSTITUTION:A coating roller 55 rotates in a direction C and carries over water 70 of the image forming solvent from a tank 72 to form a bead 70A by the water 70 between the roller 55 and the imagewise exposed photosensitive material A when the photosensitive material A is carried to a water coating part 10. Rotation of the roller 55 is then stopped and while the material A is rotated, the water 70 is coated on the rear face thereof. The bead 70A returns by gravity to the tank 72 upon detaching of the rear end of the material A from the roller 55. Thick coating of the bead is thus obviated. The material A is then preferably preheated and subjected to the heating development; thereafter, the material is superposed on image receiving paper and is pressurized to transfer the image to the image receiving paper.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a thermal development device in an image forming apparatus that visualizes an imagewise exposed image by pressure.

<Prior art> An image recording (formation) method that uses a recording material (photosensitive material) whose support is coated with a substance on which an image formed by imagewise exposure is fixed by pressure, and obtains a visible image by applying pressure. Are known.

Examples of recording materials used in such image recording methods include photosensitive materials that utilize microcapsules containing a photosensitive composition, and specifically, a photosensitive material containing a vinyl compound and a photopolymerization initiator precursor. A photosensitive material using a synthetic polymer resin wall capsule has been disclosed (Japanese Unexamined Patent Publication No. 179836/1983).

In this photosensitive material, microcapsules are imagewise cured by exposure to light, then pressure is applied to rupture the uncured microcapsules, and a color image is formed from the released colorant precursor. It has the characteristic of being able to obtain high quality images through extensive processing.

However, this photosensitive material has lower photosensitivity than photosensitive materials using silver halide such as photographic emulsifiers.

Therefore, a new photosensitive material has been disclosed which improves these points and has high photosensitivity and makes it possible to obtain high quality images through simple dry processing (Japanese Patent Laid-Open No. 61-27).
5742). In this light-sensitive material, at least a photosensitive silver halide, a reducing agent, a polymerizable compound, and a color image-forming substance are coated on a support, and at least the polymerizable compound and the color image-forming substance are coated on a support. It is enclosed in a capsule.

An image recording method for recording images using this photosensitive material is disclosed in Japanese Patent Application Laid-Open No. 61-278849. This image recording method first performs imagewise exposure to form a latent image, then develops it using a heating device, and polymerizes the polymerizable compound in the area where the latent image exists to form a high-molecular compound. Harden the capsule. Then, the image-receiving material having an image-receiving layer to which the color image-forming substance can be transferred is stacked and pressurized to rupture at least a portion of the microcapsules in the area where the latent image does not exist, and the color image-forming substance is transferred to the image-receiving material. to obtain an image on an image-receiving material.

Then, using the above-mentioned photosensitive material, this photosensitive material is subjected to imagewise exposure, heat development is performed, and then it is superimposed on an image-receiving material, and this is pressed, and an image is obtained on the image-receiving material by transfer, which is automatically carried out for image recording. An example of the apparatus is shown in Japanese Patent Application No. 1983-51896 filed by the present applicant.

The heat developing device in this case is as shown in FIG.
A heating drum 44 heated to about 150 to 160°C, and a belt support roller 4 in circumferential contact with the heating drum 44.
0.41.42.43 has an endless belt 46 that is passed around the heating drum 44. One example is one in which the photosensitive material is conveyed while being held between the two.

However, when such a thermal development apparatus is used to heat the photosensitive material, the following disadvantages occur due to the small amount of water contained in the photosensitive material. In other words, the water contained in the photosensitive material evaporates and is trapped in areas where the contact pressure between the endless belt and the photosensitive material or the heating drum and the photosensitive material is low, resulting in non-uniform water vapor distribution. This causes wrinkles in the photosensitive material.

Further, since water in a photosensitive material has the function of promoting development, uneven distribution of water (or water vapor) on the surface of the photosensitive material results in uneven development of the photosensitive material, causing image unevenness.

In order to deal with this problem, a method has been proposed in which the photosensitive material is preheated by a preheating means to evaporate water before heat development (Japanese Patent Application No. 298632/1982).

An example of a thermal developing device having such a preheating section is the one shown in FIG. 8.

This device has a heat developing device having the structure shown in FIG. 7 plus a preheating section 11 having roughly a roller 111.

Before the photosensitive material A is sandwiched between the heating drum 44 and the endless belt 46 by the roller 40 and heat development is started, the photosensitive material A is heated to the heating drum 44 in the preheating section 47.
The contact surface with the photosensitive material A is heated, and the water and components contained in the photosensitive material A are evaporated.

When a thermal developing device having such a preheating section is used, the water content of the photosensitive material can be kept below a certain value.

However, since the moisture content of the photosensitive material varies depending on the environment, the time it is left, etc., stable images cannot be obtained simply by keeping the temperature of the preheating section constant.

Therefore, it is conceivable to control the temperature of the preheating section according to the environment. For example, it has been proposed to detect the moisture content of the photosensitive material after preheating and control the temperature of the preheating section based on this detection signal (Japanese Patent Application No. 62-223367).

<Problems to be Solved by the Invention> However, with the above method, it is difficult to precisely control the temperature, etc., and it is not possible to always maintain a constant moisture content suitable for heat development, so that stable images cannot be obtained. That's difficult.

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat developing device that can always produce stable images regardless of environment, standing time, etc.

Means for Solving the Problems> In order to achieve the above objects, the thermal development apparatus of the present invention provides a preheating system for an image forming apparatus that visualizes an image obtained by heating and developing a photosensitive material that has been imagewise exposed under pressure. and a heating and developing section, and before the photosensitive material is preheated in the preheating section, an image forming solvent is applied to the photosensitive material by a coating roller disposed in a tank storing an image forming solvent. It has means for applying by coating.

The thermal development device of the present invention includes a preheating section and a heat development section of an image forming device that visualizes an image obtained by heating and developing an imagewise exposed photosensitive material under pressure,
Before the photosensitive material is preheated in the preheating section, the photosensitive material is provided with means for applying the image forming solvent to the photosensitive material using a coating roller disposed in a tank in which the image forming solvent is stored. .

<Function> The thermal development apparatus of the present invention, before heat-developing the imagewise exposed photosensitive material in the heat-developing section, applies the image-forming solvent to an application roller disposed in a tank that accumulates the image-forming solvent. The photosensitive material is coated with the photosensitive material. That is, the photosensitive material is conveyed onto the coating roller, and when the tip reaches the coating roller, the rotation of the coating roller causes
After lifting the image forming solvent in the tank with the outer periphery of the applicator roller to form a liquid stagnation between the image forming solvent and the photosensitive material, the photosensitive material is conveyed while the applicator roller is stopped rotating and the image forming solvent is removed from the photosensitive material. The image-forming solvent is applied to the substrate.

This application of the image forming solvent is performed before preheating in a thermal developing device having a preheating section.

<Example> This will be explained below with reference to the drawings.

FIG. 1 is a sectional view showing one embodiment of an image forming apparatus equipped with a thermal developing device 1 of the present invention.

As shown in FIG. 1, a housing 12 constituting the image forming apparatus includes a photosensitive material supply section 1 containing a photosensitive material A.
3. An image reading unit 15 that reads image information carried on a document S, a thermal development device 1 of the present invention that performs heat development on the photosensitive material A, and a superposition unit that superimposes the image receiving paper C on the photosensitive material A. 19. A pressure transfer unit 21 that presses the photosensitive material A and the image receiving paper C, a peeling unit 23 that separates the image receiving paper C from the photosensitive material A, and a heating paper C to fix the image and improve the image density. A post-heating device 25 is installed respectively.

housing! A transparent supporting glass plate 14 on which the M document S is placed is arranged on the upper surface of the image reading section 15, and the supporting glass plate 14 is moved over an opening 16 defined on the upper surface of the image reading section 15 by a conveying means (not shown). It is possible to move back and forth in the direction of the arrow.

Note that the image reading section 15 reads the original S through the opening 16.
It includes a light source 18 for illuminating the area and a condensing optical system 20, which are surrounded by a partition wall 22.

In the illustrated example, the document table fJ is a moving type, but a light source moving type may be used.

The photosensitive material supply section 13 is provided in the upper part of the housing 12 and is held in a light-tight manner by a partition wall 26 . A magazine 30 wound with the photosensitive material A is loaded into the photosensitive material supply section 13 via a cover member 28 attached to the upper surface of the housing 12 and which can be freely opened and closed.

A cutter 34 for cutting the photosensitive material A into predetermined lengths is disposed between the photosensitive material supply section 13 and the image reading section 15.

In the illustrated example, the photosensitive material A is in the form of a roll, but it may also be in the form of a cut sheet, and the configuration of the photosensitive material supply section 13 may be appropriately selected.

Furthermore, an exposure opening 36 defined on the bottom of the partition wall 22 surrounding the image reading section 15 faces downstream of the cutter 34 .

The thermal developing device 1 of the present invention is disposed downstream of the image reading section 15, and the photosensitive material A is carried into this thermal developing device 1 via the image reading section 15.

The thermal development apparatus 1 of the present invention includes a means 10 for applying and applying an image forming solvent to a photosensitive material A using a applying roller disposed in a tank storing an image forming solvent, which will be described in detail later; Prior to heat development, photosensitive material A is prepared in advance.
The photosensitive material A is composed of a preheating section 11 that heats the photosensitive material A, and a thermal development section 17 that heats and develops the photosensitive material A after preheating.

In the illustrated example, the preheating section 11 is installed, and although it is more preferable to install the preheating section 11, it does not necessarily have to be installed.

Hereinafter, as will be described later, since the preferred image forming solvent is water, the image forming solvent is water, and the means for applying the image forming solvent by applying it using a coating roller is referred to as the water application section 10.

As shown in FIG. 2, the water application section 10 includes a pair of conveyance rollers 102 and 103 that sandwich the photosensitive material A being conveyed.
A pair of transport rollers 104 and 105 are arranged downstream of these transport rollers 102 and 103 so as to sandwich and transport the photosensitive material A.

These rollers are configured to send the photosensitive material A to the thermal developing section 17 in the direction of the arrow in response to the driving force of a motor (not shown). Furthermore, guide plates 101 are provided between these conveying rollers corresponding to both ends of the photosensitive material A being conveyed.
A.

101B is provided to transport the photosensitive material A to the conveying roller 102.
The paper is guided from between 103 to between transport rollers 104 and 105.

Between the conveyance roller 103 and the conveyance roller 105, a coating roller 55 as a coating member corresponds to the center portion of the back surface (support surface side) of the photosensitive material A. The application roller 55 has its rotating shaft 85 supported by the housing 12 . A motor (both not shown) is connected to the rotating shaft 85 via a gear, and the application roller 55 is rotated in the direction of arrow C by the driving force of this motor.

The coating roller 55 is configured to rotate a predetermined number of times and then stop when the leading end of the photosensitive material A reaches the water coating section 10. This control is performed in advance so that the rotation is synchronized with the conveyance of the photosensitive material A. ing.

Note that the conveyance speed of the photosensitive material A is 20 to 1000111
It should be about 1/S.

A portion of the coating roller 55 is immersed in a tank 72 filled with water 70, which is an image forming solvent.
When the roller 5 rotates, water 70 is brought out on its circumferential surface.

The water 7o taken out by the application roller 55 is transferred to the application roller 55 so that a bead 70A is formed between the water 7o and the photosensitive material A.
The circumferential speed of is set to be the same as the conveyance speed,
When the photosensitive material A is conveyed in this state, the coating water is carried out on the back surface (support surface side) of the photosensitive material A to form a coating film.

Note that during this coating, that is, while the photosensitive material A is moving on the outer periphery of the coating roller 55, the rotation of the coating roller 55 is stopped.

A supply pipe 75 for supplying the water 70 and a discharge pipe 76 for discharging the water 70 in the tank 72 are attached to the tank 72 filled with water 70, and are connected to a pump (not shown).

Therefore, by driving this pump, the water in the tank 72 can be circulated or exchanged as necessary.

Further, an overflow pipe 78 is attached to this tank 72 for discharging excess water 70 filled into this tank 72. This overflow pipe 7
The opening 78A of 8 is arranged at a predetermined height from the bottom 72A of the tank 72, and when the water 70 supplied from the supply vibrator 75 reaches above this opening 78A, the water 70 is transferred to the tank 72. By discharging the water to the outside, the amount of water (water surface height) in the tank 72 can be kept constant.

Note that this water surface is preferably set at a height such that approximately 173 of the application roller 55 is immersed.

In the present invention, the amount of water applied may be 5 to 50 mA per photosensitive material Aim', preferably 10 to 25 mj2. Moreover, the water temperature is about 20 to 30°C.

In the present invention, the image-forming solvent is a solvent required for image formation, and as mentioned above, water is particularly preferable, but other solvents such as low-boiling organic solvents (alcohols, ketones, amides, etc.) can also be used. Alternatively, water or these low-boiling point solvents may be added with various additives such as surfactants, development accelerators, and development stoppers.

In the above embodiment, water is applied from the back side of the photosensitive material A, but as shown in FIG. 4, the water may be applied to the photosensitive layer side of the photosensitive material A.

Such an embodiment is preferable in that water can be applied to the surface of the photosensitive layer.

As shown in FIG. 1, a preheating section 11 and a heat developing section 17 surrounded by a heat-insulating partition wall 38 are disposed downstream of the water application section 10.

The preheating section 11 heats the photosensitive material A after coating with water on a heating drum 44.
The heating drum 44 has an arc of 606 to 180 degrees from just below the roller 111 to just below the roller 40 where heat development starts.

The temperature of the heating drum in the preheating section 11 may be about 120 to 140°C.

In the illustrated example, the preheating section 11 has the above-mentioned configuration, but it may have various other configurations. For example, a heating roller, a heating plate, or a hot air generator provided separately from the heating drum 44 may be used.

The heating and developing section 17 includes a hollow cylindrical heating drum 44 containing a heat source such as a halogen lamp, and belt support rollers 40, 41.
42.43 has an endless belt 46 which is passed over the heating drum 44.
The endless belt 46 is wound around the outer periphery of an arc of 0° to 300°, and the photosensitive material A is sandwiched and conveyed between the endless belt 46 and the heating drum 44.

The temperature of the heating drum 44 in this case may be approximately 130 to 160°C.

The photosensitive material A discharged from the heat developing section 17 is conveyed to the overlapping section 19. The overlapping section 19 has a Y-shaped guide plate 50, and this Y-shaped guide plate 50 has an input path 52a for guiding the photosensitive material A, an input path 52b for guiding the image receiving C described below, and the input path. It is composed of a carry-out path 54 where 52a and 52b merge.

On the other hand, a cassette 56 for storing image-receiving paper C is loaded into a lower corner portion of the housing 12.

In this case, a paper feed roller 58 is disposed at the top of the cassette 56, and the image receiving paper C is transferred to the paper feed roller 58.
is supplied to the carry-in path 52b of the Y-shaped guide plate 50. Note that a manual feed port 60 is defined in the upper part of the cassette 56 in the housing 12;
It is also possible to supply the image-receiving paper C to the carry-in path 52b from there.

In the illustrated example, the image-receiving paper C is in the form of a cut sheet, but it may also be in the form of a roll, in which case it may be configured to be cut as appropriate with a cutter or the like.

A pressure unit 66 including a pressure transfer section 21 and a peeling section 23 is disposed behind the overlapping section 19 .

The pressure transfer section 21 includes a pair of pressure nip rollers 74.80 and a backup roller 96.120 for making the pressure of the pressure nip rollers 74.80 uniform in the axial direction. The pressure nip rollers 74,80 are pressed together with a pressure of approximately 500 kg/cra''.

In the illustrated example, the development and transfer steps are performed separately, but they may be performed simultaneously.

The peeling section 23 includes a guide plate 142, a pair of rollers 32, and a peeling claw 146 having a tip pointing toward the pair of rollers 32λ.
The peeling claw 146 is configured to be rotatably supported by a support plate (not shown) via a support shaft 147.

A waste tray 150 disposed below the photosensitive material supply section 13 is connected to one downstream side of the pressure transfer unit 66 . In this case, the photosensitive material A is carried into the waste tray 150. Further, on the other downstream side of the pressure transfer unit 66, a post-heating device 25 is provided which heats the image receiving paper C onto which the image has been transferred to fix the image and improve the image density.

The post-heating device 25 is composed of a pair of rollers 251 and 252, one of which includes a heating source such as a halogen lamp.

The roller temperature in this case is usually 60 to 120°C. Further, a driving source (not shown) is installed on one of the rollers, so that the rollers 251 and 252 are configured to rotate synchronously.

A take-out tray 152 disposed at a lower corner of the housing 12 is connected downstream of the post-heating device 25, and the image-receiving paper C is led out to this take-out tray 152.

In the image forming apparatus shown in FIG. 1, a photographic material in which a photosensitive material A as a photosensitive element and an image receiving paper C as an image receiving element are provided on separate supports is used as a photographic material. The image receiving element and the image receiving element may be formed on the same support. Furthermore, although an example is taken in which both are peeled off after transfer, a type that does not require peeling may also be used.

Among the recording materials that can generally be used in an image forming apparatus equipped with the thermal development device of the present invention, the following are examples of photosensitive materials.

For example, there is a type of photosensitive material disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 57-179836 in which a polymerizable compound is imagewise cured by imagewise exposure and then pressure is applied to obtain a visible image. This photosensitive material has a synthetic polymer resin wall capsule containing a vinyl compound, a photopolymerization initiator, and a colored precursor supported on a support.

Another example is a type in which a visible image is obtained by applying pressure after preliminary thermal development or wet development of a latent image generated by imagewise exposure.

Examples of such materials include Japanese Patent Application Laid-open No. 6, published by the present applicant.
Publication number 1-278849 or patent application No. 1988-5388
Examples include the material shown in No. 1. Said Japanese Unexamined Patent Publication No. 1986-
The material disclosed in Japanese Patent No. 278849 is a material that is thermally developed and then transferred to an image-receiving material having an image-receiving layer to obtain an image on the image-receiving material. Silver, a reducing agent, a polymerizable compound, and a color image-forming substance are coated, and at least the polymerizable compound and the color image-forming substance are encapsulated in the same microcapsule.

Furthermore, the material disclosed in the above-mentioned Japanese Patent Application No. 61-53881 is for obtaining an image on a photosensitive material without using an image-receiving material. In other words, the image-receiving layer is provided on the photosensitive material itself, and contains silver halide, a reducing agent, a polymerizable compound, and two types of substances that cause a color reaction when in contact with one of the substances that cause a color reaction. and the polymerizable compound is contained in microcapsules,
It has a photosensitive layer on the support, which is present outside the microcapsules in which the material that causes the coloring reaction is a material that contains a polymerizable compound.

The operation of the thermal development apparatus 1 of the present invention will be explained below.

The imagewise exposed photosensitive material A is conveyed to a thermal development apparatus 1 of the present invention as shown in FIG.

First, in the thermal development apparatus 1, the material is transported to the water coating section 10 shown in FIG. 2 or 4.

The application roller 52 attaches the water 70 in the tank 72 to its surface and brings it out, forming a bead 7 between it and the back surface of the photosensitive material A.
0A is formed, and in the embodiment shown in FIG. 2, this is the photosensitive material A.
In the embodiment shown in FIG. 4, it is applied to the side of the photosensitive layer.

The procedure for applying this water 70 to the photosensitive material A will be explained below using the method shown in FIG. 2 as a representative since the embodiments shown in FIG. 2 and FIG. 4 differ only in the coated surface of the photosensitive material A. do.

First, if the photosensitive material A is not present in the water application section 10, the application roller 52 is stopped.

Here, when the leading end of the photosensitive material A is conveyed, the application roller 52 is rotated in the direction of arrow C by the driving force of the motor, and the water 7o is brought out from the tank 72 by adhering to its surface.

The water 7o taken out is applied to the application roller 52 and the photosensitive material A.
A bead 7OA is formed between the two (see Fig. 2).

Next, the rotation of the coating roller 52 is stopped, and while the photosensitive material A is being moved, the water 70 is brought out and coated on the back surface of the photosensitive material A.

When the rear end of the photosensitive material A is removed from the coating roller 52, the excess bead 70A returns to the tank 72 under its own weight, preventing it from being thickly coated on the back side of the photosensitive material A (see FIG. 3). .

The photosensitive material A subjected to water coating in the water coating section 10 is placed in the preheating section 1.
1, and is pressed against the heating drum 44 by the roller 111 and heated.

The temperature in this case is 120-140°C.

The photosensitive material conveyed through the preheating section 11 is conveyed to the heat developing section 17, where it is pressed against the heating drum 44 by the endless belt 46 and heat-developed. The temperature in this case is 130
~160°C.

In the present invention, since water is applied as described above, there is no need to supply extra heat in the preheating section 11 to the heat development section 17, and there is no need to generate more water vapor than necessary. Paper wrinkles do not sometimes occur on the photosensitive material A. Further, since an appropriate amount of water is contained in the photosensitive material A, uneven development does not occur.

above! At Mr. B, the intermittent rotation of the application roller 52 was synchronized with the conveyance of the photosensitive material, but a sensor or the like was installed near the entrance of the water application section 10 to detect the leading or trailing end of the photosensitive material 16. The rotation of the application roller 52 may be controlled by the following steps.

The photosensitive material A heat-developed in the thermal development apparatus 1 of the present invention is carried into the overlapping section 19 and overlapped with the image receiving paper C. Thereafter, the paper is carried into the pressure transfer section 21 and the image is transferred onto the image receiving paper C.

After the transfer, the photosensitive material A and the image receiving paper C are carried into a peeling section 23 where a peeling operation is performed. The peeled image-receiving paper C is carried into the post-heating device 25 and heated, thereby fixing the image and improving the image density. The image-receiving paper C on which the image has been formed in this manner is carried out to the take-out tray 152. On the other hand, the peeled photosensitive material A is carried out to a waste tray 150.

<Effects of the Invention> According to the present invention, since water is applied before heating or heat development when preheating is not used, the amount of water in the photosensitive material can be maintained at an appropriate level regardless of the environment, standing time, etc. This allows you to always obtain stable images.

In order to confirm such an effect, the present inventor conducted various experiments. An example is shown below.

<Experimental example> The photosensitive material and image receiving paper described in Japanese Patent Application No. 18085/1985 were used as photosensitive material A and image receiving paper C, and the image forming apparatus shown in FIG. , 23
Images were obtained under conditions of 60% RH and 30°C, or 80% RH at 30°C. The amount of water applied at this time is 1
5 g/m'', and the water temperature was 25°C.

In addition, the preheating temperature and heat development temperature are each 120°C.
and 150°C.

The characteristic curve at this time is shown in FIG.

Further, in the image forming apparatus shown in FIG.
The same process as above was carried out using an apparatus having the same configuration except that the apparatus was not provided with the apparatus. However, in order to obtain a water content of the photosensitive material that satisfies the environmental conditions, the preheating temperature was set as follows.

15℃, 20%RH condition...100℃23℃
, 60% RH condition...120℃30℃, 80
%RH condition...The characteristic curve at this time is shown in FIG. 6 at 140°C.

In addition, in FIGS. 5 and 6, D represents the image density and E represents the exposure amount.

From the results shown in FIGS. 5 and 6, the effects of the present invention are clear.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of an image forming apparatus equipped with a thermal development device of the present invention. FIGS. 2 and 3 are cross-sectional views showing aspects of the water application section in the heat developing apparatus of the present invention. FIG. 2 shows the state at the start of application, and FIG. 3 shows the state at the end of application. Show things. FIG. 4 is a cross-sectional view showing a different installation position of the water application section in the heat developing apparatus of the present invention. FIG. 5 is a graph showing a characteristic curve of an image obtained by applying the thermal development apparatus of the present invention. FIG. 6 is a graph showing a characteristic curve of an image obtained by applying a conventional thermal development apparatus. FIG. 7 and FIG. 8 are sectional views each showing an aspect of a conventional heat developing device. Explanation of symbols 1... Heat developing device, 10... Water application section, 11... Preheating section, 17... Heat developing section, 44... Heating drum, 6... Endless belt, A. ...Photosensitive material, C...Receiving paper FIG, 3 FIG, 4 FIG, 5 FIG-6 ogE 'FI0.7 F, 168

Claims (1)

[Claims] (1) A thermal development device having a heat development section of an image forming apparatus that visualizes an image obtained by heat development of an imagewise exposed photosensitive material under pressure, wherein the photosensitive material is heated and developed in the heat development section. A thermal development apparatus characterized by comprising means for applying an image forming solvent to the photosensitive material using a coating roller disposed in a tank storing an image forming solvent before heat development. (2) A thermal development device having a preheating section and a heat development section of an image forming apparatus that visualizes an image obtained by heat developing an imagewise exposed photosensitive material under pressure, wherein the photosensitive material is subjected to the preheating. 1. A thermal development apparatus comprising a means for applying an image forming solvent to the photosensitive material using a coating roller disposed in a tank storing an image forming solvent before preheating the photosensitive material.